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Czech Technical University in Prague

Acta Polytechnica

Acta Polytechnica 2000

No. (click on selected title and view the annotation)
1 R. Whitford: The Benefits and Costs of Stealth From The Aircraft Designer’s Viewpoint
The reduction or other control of an aircraft’s radar, infrared, visual and acoustic signatures can greatly improve its survival, resulting in improved weapons` effectiveness. Although radar and infrared stealth are important, other aspects of low observability (i.e. acouctic and visual) cannot be ignored. However, this paper, for reasons of brevity, focuses on control of radar and infrared signatures. The topics of: benefits of signature control; contributions of an aircraft to its radar cross section (RCS) and infrared (IR) signature; methods to reduce RCS and IR signature; penalties/costs of signature reduction, in terms of performance, volume, weight and maintenance; and use of radar absorbing materials are addressed. The conclusion is that while signature control is important, there are penalties to be paid. Signature reduction has become yet another factor to be concidered in the series of compromises made during aircraft design trade-offs.
D. Schmitt, A. Strohmayer: Market and Design of a Dedicated Advanced Cargo Aircraft
The development of the European economy requires an efficient transport system. The transportation of goods and freight today is mainly done by surface transport, i.e. road and railways. Air cargo within Europe is in general restricted to mail and parcels. This paper describes the current cargo transport system in Europe and compares road, rail and air transport with respect to energy consumption, land resources required, flexibility and cost of transportation. Based on this comparison, an innovative air cargo transport system will be developed. Three main elements are required for the new system: a specific intermodal cargo airport in every major industrial region of Europe, the design of a new container system and the design of a dedicated large cargo aircraft. A conceptual design for a large cargo aircraft will be shown which can meet the technical and operational requirements arising from the new air transport system.
E. B. Skvortsov: Direct Search in Conceptual Design
The notion Concept implies a set of rules and ideas combining in a common intention actual principles for application, structure and form of a future artificial object. A rational concept is considered as a product of "conceptual design", which is nothing more than a step-by-step research on the possibility of achieving a desired goal. It precedes a full-scale development oriented to the project implementation. The author studies conceptual design as the process of idea evolution involving several s tages (Fig. 1). One of them is considered, for which an effort is made to generate an effective methodology of direct search for a rational concept with due regard for system and other methods.
A. L. Bolsunovsky, N. P. Buzoverya: Transonic Wing Design Using Inverse and Optimization Methods
Presented is an effective procedure for aerodynamic design of transonic wings, based on joint use of fast method for direct calculation and inverse and numerical optimization methods developed by the authors. Each component of the procedure developed is described. Some examples of designing sophisticated advanced configurations are given.
A. L. Bolsunovsky, N. P. Buzoverya, K. S. Nickolaeva: Optimization Procedure for Design of High-lift Airfoils with Specified Stall Behaviour
The description is given of the procedure developed for design of low-speed high-lift airfoils with specified geometric and aerodynamic restrictions, including stall behaviour at high-angle-of-attack regimes. This procedure is based upon joint use of the fast direct solver, the technique of geometry variation and optimization method. The design task is formulated as a nonlinear optimization task with straightforward calculation of Clmax, amax, dCl/da after stall, Dahyst and other airfoil characteristics as objective function and constraint values. The high speed of the direct method permits one to use not only gradient optimization method but also very robust genetic algorithm. No preliminary assumptions are imposed on the type of the airfoil geometry. Smooth local and global shape functions as well as shapes of the known airfoils can be used for geometry variation. A number of design variables is up to 50 and it takes reasonable time to complete optimization cycle even on PS. Typical restrictions concern airfoil thickness, thickness of the trailing part, zero pitching moment etc. Specific restriction for such kind of the optimization task relates to the value of dCl/da after amax, which allows one to control the abruptness of stall. Some examples of using the developed technique for design of high-lift airfoils are given.
D. P. Coldbeck, L. Smrček: Aircraft System Design and Integration
In the 1980's the British aircraft industry changed its approach to the management of projects from a system where a project office would manage a project and rely on a series of specialist departments to support them to a more process oriented method, using systems engineering models, whose most outwardly visible signs were the introduction of multidisciplinary product teams. One of the problems with the old method was that the individual departments often had different priorities and projects would get uneven support. The change in the system was only made possible for complex designs by the electronic distribution of data giving instantaneous access to all involved in the project. In 1997 the Defence and Aerospace Foresight Panel emphasised the need for a system engineering approach if British industry was to remain competitive. The Royal Academy of Engineering recognised that the change in working practices also changed what was required of a chartered engineer and redefined their requirements in 1997 [1]. The result of this is that engineering degree courses are now judged against new criteria with more emphasis placed on the relevance to industry rather than on purely academic content. At the University of Glasgow it was realized that the students ought to be made aware of current working practices and that there ought to be a review to ensure that the degrees give students the skills required by industry. It was decided to produce a one week introduction course in systems engineering for Masters of Engineering (MEng) students to be taught by both university lecturers and practitioners from a range of companies in the aerospace industry with the hope of expanding the course into a module. The reaction of the students was favourable in terms of the content but it seems ironic that the main criticism was that there was not enough discussion involving the students. This paper briefly describes the individual teaching modules and discusses the experiences and lessons learnt from this course with some thoughts on the way it is proposed to develop the course.
M. Millar, L. Smrček: Design of a Data Acquisition System for a Flying Laboratory
The University of Glasgow, Department of Aerospace Engineering has been in possession of a Czech manufactured Remotely Piloted Vehicle (RPV) airframe 1 since 1996. Significant modifications have been made and will continue to be made in order to render the design functional and airworthy. The name ‘Condor’ was chosen as the moniker for the new aircraft. The latest phase of these modifications is the design and implementation of the Condor’s in-flight data acquisition (DAQ) system. The paper will outline the various processes involved and decisions made in the design and implementation of a simple data acquisition system for a RPV. The requirements of the system were first identified, such as those quantities that were deemed essential to the effective operation of the RPV. For example, airspeed, angle of attack, angle of sideslip etc. and the necessary instrumentation for measuring such values chosen and the subsequent signal conditioning needed for the signals to be intelligible to the DAQ Card and computer.
C. Goodchild, J. Watt: Design Failures in Aerospace Electrical Systems(The Identification of Sneak Circuits)
The malfunction or failure of an aircraft electrical system because signal or power flow paths were unintentionally designed into the electrical circuit, is known to be the cause of several major failures of engineering systems. These unintentional signal or power paths are called sneak circuits. The nature of Sneak Circuits was first considered after they had been identified as the cause of some spectacular and expensive rocket failures in the United States space programme. This paper reviews the status of Sneak Circuit Analysis (SCA) and presents a general systematic approach the author has devised to identify sneak circuits during the circuits design phase. The application of the method of SCA is illustrated with a case study. The paper makes a case to take the investigation of an electrical failure or malfunction beyond the identification of a failed component to include a search for possible sneak circuits. The obvious fact that could result from the discovery of a sneak circuit is the shift in legal responsibility from the component manufacturer to the circuit designer.
X. Munduate, F. N. Coton: An Aerodynamic Method for the Preliminary Design of Horizontal Axis Wind Turbines
The present paper describes a method developed to assist in the preliminary aerodynamic design of wind turbines by identifying regions of the rotor disk which are dominated by unsteady and/or three-dimensional effects. The technique is based on a blade element/momentum predictor that has been extended to consider yawed flow and tower shadow effects. In addition, the method tracks temporal changes in blade incidence to identify regions of the rotor disk which are susceptible to dynamic stall. It also monitors and assesses the severity of three-dimensional stall delay and the extent to which this interacts with the regions of unsteadiness. In the paper the capability of the method will be demonstrated by application to the specific test case of the U. S. National Renewable Energy Laboratories (NREL) Combined Experiment turbine.
S. M. Malpede, M. Vezza: Developments of an Interactive Sail Design Method
This paper presents a new tool for performing the integrated design and analysis of a sail. The features of the system are the geometrical definition of a sail shape, using the Bezier surface method, the creation of a finite element model for the non-linear structural analysis and a fluid-dynamic model for the aerodynamic analysis. The system has been developed using MATLAB(r). Recent sail design efforts have been focused on solving the aeroelastic behavior of the sail. The pressure distribution on a sail changes continuously, by virtue of cloth stretch and flexing. The sail shape determines the pressure distribution and, at the same time, the pressure distribution on the sail stretches and flexes the sail material determining its shape. This characteristic non-linear behavior requires iterative solution strategies to obtain the equilibrium configuration and evaluate the forces involved. The aeroelastic problem is tackled by combining structural with aerodynamic analysis. Firstly, pressure loads for a known sail-shape are computed (aerodynamic analysis). Secondly, the sail-shape is analyzed for the obtained external loads (structural analysis). The final solution is obtained by using an iterative analysis process, which involves both aerodynamic and the structural analysis. When the solution converges, it is possible to make design modifications.
J. Vargas, S. Poveda: Concurrent Engineering in Aerospace Industry: How To Achieve Radiofrequency Geometric Specifications in Satellite Antennae
One of the problems that a satellite manufacturing involves is to obtain the geometrical forms and the accurate positions for the different radiofrequency components (reflectors, subreflectors and feeders). CFRP (Carbon Fibber Reinforced Plastics) sandwich structures never are obtained as designed due to the deformations associated to the manufacturing process. So, reflectors, subreflectors and structural components (towers, panels... ) have to be measured in order to include their deviations in the design of the regulation parts. High performance equipment (Co-ordinate Measurement Machines, CAD/CAM Systems and 5 Axis Machine Tool) is used, but it is also necessary to make an integrated and multidisciplinary team. This paper describes how this process was implemented in CASA Space Division during HISPASAT 1C satellite manufacturing program.
D. P. Coiro, M. Madonna: Investigation of Turbulence Effect on Dynamic Behaviour of Aircraft Through Use of JDYNASIM: A Platform Independent Simulation Software
The need of fast and interactive tool to simulate aircraft behaviour is a demand of modern technology. This necessity is more evident when light aircraft and sailplanes are involved. This paper presents an attempt to give simulation possibility almost to everyone through the use of JDynaSim code, written to meet this goal. JDynaSim is an interactive graphic flight simulation code written in JAVA and VRML languages which practically allows everyone to fly the aeroplane under investigation. This is true due to the fact that JAVA is a language born to work under a generic Internet browser (such as Microsoft Explorer or Netscape) and thus it is independent from the operating system under which it is running. Dynamic motion equations are solved by 12 ordinary non-linear differential equations in which the non-linear forces are input in multidimensional matrix form and are interpolated at each time instant. Advancing in time is performed using a 4th order Runge-Kutta integration scheme. Translation equations of motion are written in a flight path axis system while rotational equations are written on body axis system. An on-purpose written pre-processor has to be used to transform forces to appropriate reference system. The code can interactively read mouse and keyboard inputs as well as files with command laws assigned in function of time. There is the possibility to record the interactive session performed and then to repeat the manoeuvre. This paper presents also the code extension for simulating the effect of gusts generated according to classical theories. In particular investigation has been performed to compare results coming from classical theories on aircraft responses to gusts inputs respect to those coming from JDynaSim flight simulator. JDynaSim is available to everybody through Internet at the following URL: www.dpa.unina.it/coiro/
J. Marková, M. Holický: Probabilistic Analysis of Crack Width
Probabilistic analysis of crack width of a reinforced concrete element is based on the formulas accepted in Eurocode 2 and European Model Code 90. Obtained values of reliability index b seem to be satisfactory for the reinforced concrete slab that fulfils requirements for the crack width specified in Eurocode 2. However, the reliability of the slab seems to be insufficient when the European Model Code 90 is considered; reliability index is less than recommended value 1.5 for serviceability limit states indicated in Eurocode 1. Analysis of sensitivity factors of basic variables enables to find out variables significantly affecting the total crack width.
B. Gáti: Investigation of Flight Dynamic of Hang-glider
This paper shows, how the most important parameters of a two-body system like a hang-glider, can be identified. The first step is to develop a simulation program with an acceptable reality model. Such a model involves a lot of constants. I carried out an investigation of sensitivity in order to select the constants that are the most important to specify. The results show that the aerodynamic constant cmq has the most significant effect on a phygoidal oscillation. I have developed an identification program and a measuring system to determine the real value of this constant as well as the hang-glider's other aerodynamical and stability parameters.
J. Ulrych: Analysis of Unsteady Transonic Flow Fields by Means of the Colour Streak Schlieren Method
This article deals with a new approach to the investigation of unsteady transonic flow fields around aerodynamic models and in blade cascades using a schlieren method of flow visualisation. The principle and the application of the Colour Streak Schlieren Method (CSSM) are defined. The characteristic flow field features were observed and analysed around an oscillating NACA 0012 airfoil under the conditions of transonic free stream Mach number (M<FONT face=symbol><SUB>Ą</SUB></FONT>= 0.9), initial angle of attack (<FONT face=symbol>a </FONT>= +4 deg), one amplitude of oscillation (<FONT face=symbol>Da </FONT>= ±3&nbsp;deg), and three frequencies of model oscillation (<EM>f </EM>= 1, 15, 30 Hz). There is a description of the terminal shock wave hysteresis across the investigated area, which was revealed in particular cases. Application possibilities of CSSM and its further development are discussed. Keywords: High-speed aerodynamics, experiment, flow field analysis, transonic flow fields, flow visualisation, Colour Streak Schlieren Method.
2 A. Kudzys, D. Narmontas, L. Vaicekauskas: Probabilistic Durability Analysis in Advanced Engineering Design
Expedience of probabilistic durability concepts and approaches in advanced engineering design of building materials, structural members and systems is considered. Target margin values of structural safety and serviceability indices are analyzed and their draft values are presented. Analytical methods of the cumulative coefficient of correlation and the limit transient action effect for calculation of reliability indices are given. Analysis can be used for probabilistic durability assessment of carrying and enclosure metal, reinforced concrete, wood, plastic, masonry both homogeneous and sandwich or composite structures and some kinds of equipments. Analysis models can be applied in other engineering fields.
A. Kalbáč, R. Černý, P. Přikryl: Optimization of the Vertical Bridgman Method and the Vertical Gradient Method for CdZnTe Single Crystal Production
In designing optimum parameters of advanced crystal growth techniques, computer modeling has become an important tool owing to the fact that computer simulation is much cheaper than many experimental techniques based on the trial and error method. In this paper, the application of computational modeling in the optimization of experimental setups for the production of CdZnTe single crystals from the melt is demonstrated on two characteristic examples, namely on the vertical Bridgman and vertical gradient method. The influence of adjustable parameters on the temperature, concentration and velocity fields, and on the positions and velocities of the moving interface is studied. Finally, the effect of uncertainty in material parameters on computed results is analyzed.
R. Černý, A. Kalbáč, P. Přikryl: Mathematical Modeling of Binary Alloy Solidification
Computational modeling is employed in design and optimization of the preparation process of a two component alloy system with specified composition. A model of binary alloy solidification is formulated using the mass, momentum and energy balances in the liquid and the mass and energy, balances in the solid. The interface between the solid and liquid phases is modeled as a discontinuity surface where the mass, momentum and energy balance conditions are expressed. The numerical solution of the mathematical model is performed using the Galerkin finite element method in a 2-D approximation with the cylindrical symmetry and the moving boundary problem is solved by a front-fixing technique. In a practical application of the computational model, the solidification process of Hg1-xCdxTe is simulated. Moving boundary conditions for temperatures are taken into account, which makes it possible to simulate the Bridgman method of crystal growth for instance. The computational experiments reveal a qualitative agreement of the numerically simulated and experimentally measured concentration fields. The influence of principal parameters of Bridgman growth and of the accuracy of material parameters is studied as well. Concerning the material parameters, the liquid/solid thermal conductivity ratio at the melting temperature is found to be the most important because it can affect the shape of the phase interface significantly, and therefore the temperature and concentration fields as well.
R. Černý, A. Kalbáč: Modeling the Crystallization of Amorphous Silicon Thin Films Using a High Repetition Rate Scanning Laser
An optimum design of experimental setup for the preparation of polycrystalline silicon (pc-Si) films from amorphous layers applicable in the solar cell production is analyzed in the paper. In the computational simulations, the influence of basic characteristic parameters of the experimental procedure on the mechanisms of pc-Si lateral growth is studied. Among these parameters, the energy density of the applied laser and the thickness of the amorphous silicon (a-Si) layer are identified as the most significant. As an optimum solution, the mechanism of pc-Si growth consisting in repeated melting of a part of already crystallized pc-Si layer by the scanning laser is proposed.
J. Toman, R. Černý: The Effect of Mechanical Load on the Thermal Conductivity of Building Materials
The effect of mechanical load on the thermal conductivity of building materials in the design of envelope parts of building structures is studied. A typical building material is chosen in the practical investigation of this effect, namely the cement mortar. It is concluded that in the range of hygroscopic moisture content, lower levels of mechanical load, typically up to 90 % of compressive strength (CS), are not dangerous from the point of view of worsening the designed thermal properties, but in the overhygroscopic region, the load as low as 57 % of CS may be dangerous. The higher levels of loading are found to be always significant because they lead to marked increase of thermal conductivity which is always a negative information for a building designer.
R. Černý, P. Přikryl, G. Ivlev, E. Gatskevich, V. Cháb: Recrystallization of InSb Surfaces Induced by Pulsed Lasers
Pulsed laser processing of InSb wafers for the application in designing high speed infrared detectors is studied both theoretically and experimentally. The recrystallization of InSb surfaces resulting in restoration of the implanted region to a single crystal state is presented as a reasonable alternative to the conventional thermal heating. In the theoretical part, thermal equilibrium and nonequilibrium models of melting, recrystallization and evaporation are formulated to describe transport phenomena in the material induced by laser irradiation. In the experimental part, InSb samples irradiated by the ruby (694 nm, 80ns FWHM), and ArF (193 nm, 10 ns FWHM) lasers are studied using time resolved reflectivity, Auger electron spectroscopy and low energy electron diffraction methods to analyze surface modifications. A comparison of the experimental data with the numerical predictions shows that while for the ruby laser a reasonable agreement in surface melt duration is achieved, the results for the ArF laser differ quite a lot. As a main reason for these differences, the amorphization of the surface is identified.
J. Drchalová, R. Černý, J. Havrda: The Effect of Anisotropy of Building Materials on the Moisture Transfer
The effect of anisotropy of building materials on the moisture transfer in the design of envelope parts of building structures is studied. Two typical fibre containing plate building materials produced in the Czech Republic, Dekalux and Dekalit P, are chosen for the demonstration of this effect. Experimental results show that while for lighter Dekalit P, an order of magnitude difference in the moisture diffusivities k for the two basic orientations, i.e. along and across the plate, is observed, for the heavier Dekalux the differences in k are within the errorbar of the experimental method. As follows from the experimental results, compacting of surface layers of the plates of light fibred materials is very favorable from the point of view of moisture penetration but one should keep in mind that any local damage of the surface layer can result in a considerably faster moisture transfer in the direction along the plate.
P. Hájek: Innovation on RC Waffle and Ribbed Slab Analysis Models
Waffle and ribbed reinforced concrete slabs are widely used in building constructions in view of the flexibility design and structural efficiency. The wide range of reinforced concrete and composite waffle and ribbed slabs has been theoretically analysed and tested from the point of view of structural behaviour within the research performed in the last years. The results of the experimental investigation, supported by theoretical conclusions, have confirmed significantly better structural properties of the composite waffle slabs (composed from RC and ceramic fillers) than the assumptions usually considered in common analysis models. New analysis equivalent models for structural analysis RC and composite waffle and ribbed structures have been developed and compared with the test results. In the paper are presented some generalized conclusions as a basis for the formulation of principles of an optimized design of RC waffle and ribbed slab structures.
J. Pollert: Computer Simulation of Flow in CSO “OK3D Evropská”
During the last 30 years, a number of devices has been developed for dynamic separation of settle able solids in wastewaters. Initially, these separators were used for control of Combined Sewer Overflow (CSO) pollution by retaining the bulk of solids in the underflow, directed to the sewage treatment plant (STP), and allowing combined sewage with reduced pollutant loads to overflow from the sewer systém. This paper is describing CSO “OK 3D Evropská” in Prague 6 on Evropská Street. Inlet to CSO is 3 m diameter tube collecting water from location of Řepy, Vokovice, Liboc and Ruzyně. The outflow throttle pipe is 1.1 m in diameter and continues to central wastewater treatment plant and overflow is ending in Šárecký creek. Šárecký creek flows through the Šárka valley which is environmentally protected area. CSO “OK 3D Evropská" has high overflow crest and probability of the function is 0.44 per year.
P. Bouška, D. Pume: Basic Deformation Parameters of Solid Clay Bricks and Small Masonry Walls
The basic mechanical properties of clay brick masonry and its components were experimentally investigated in the laboratories of the Klokner Institute. The test specimens of masonry materials and the relevant mechanical properties have been identified in solid clay bricks and cement-lime mortar. The aim of the research activity was to study both the deformability of the prevailing type of clay masonry in the existing buildings, i.e. the masonry made from the solid clay units and the lime-cement mortar, and the most important mechanical properties of masonry components.
S. Modrý: Transport of Sulphate Ions into Concrete
Penetration of sulphate ions the cement mortar specimen surface was studied. The sulphate ions diffusion front advances with increasing time, and the content of SO3 in surface layers increases as well. In spite of some experimental problems, electron probe microanalysis seems to be a useful tool for concrete corrosion study.
B. Novotný: Computational Modelling in Development of a Design Procedure for Concrete Road
The computational modelling plays a decisive part in development of a new design procedure for concrete pavement by quantifying impacts of individual design factors. In the present paper, the emphasis is placed on the modelling of a structural response of the jointed concrete pavement as a system of interacting rectangular slabs transferring wheel loads into an elastic layered subgrade. The finite element plate analysis is combined with the assumption of a linear contact stress variation over triangular elements of the contact region division. The linking forces are introduced to model the load transfer across the joints. The unknown contact stress nodal intensities as well as unknown linking forces are determined in an iterative way to fulfil slab/foundation and slab/slab contact conditions. The temperature effects are also considered and space is reserved for modelling of inelastic and additional environmental effects. It is pointed out that pavement design should be based on full data of pavement stressing, in contradiction to procedures accounting only for the axle load induced stresses.
M. Holický, M. Vorlíček: Statistical Techniques for Advanced Design Assisted by Testing
Bayesian approach to determine characteristic and design values of material properties using experimental results is analysed and compared with procedures specified in Eurocode 1, ENV 1991-1. Operational formula for practical application of the statistical technique are derived for various types of probability distributions. Both symmetric and asymmetric theoretical models are considered. Developed numerical tables and practical example indicate that type of distribution is less important than its asymmetry.
I. Vaníček, I. Kazda: Application and Design of Earth Structures from the Reinforced Soils
Paper describes the new problems connected with the proper design of the reinforced soil structures according to Eurocode 7 Geotechnical design. Therefore basic problems of reinforcement are briefly specified together with the influence of construction technology on the behaviour of such structures. Also up to date approach to the design method in the Czech republic are more specified. Finally the program of the new research in this field is described.
M. Vaníček: Limit Design Approach of the Reinforced Soils
Since now the design of slope stability was calculated by means of safety ratio, but nowadays we are going to change this approach to limit states - according to Eurocode 7. For the limit states approach it is necessary to define design values not only of soil properties but also of reinforcing elements. The proposed calculation method of the slope stability using limit states approach was transferred into a computer program SVARG. By this program it is possible to calculate the internal and external stability of reinforced earth structure. The principles of the selected calculation method and examples of stability calculations are presented hereafter.
V. Křístek, M. Škaloud: The Influence of Shear Effects on the Deflections of Steel Box Girder Bridges
It is already well known that the shear lag phenomenon, generated by shear deformations in the flanges of box girders, can result in a very non-uniform distribution, across the flange width, of longitudinal normal stresses, and consequently can then influence girder deflections. The shear lag effects become even more pronounced in cases where flange width increases in relation to girder span. However, in box girders, where the cross-sectional area of webs usually represents a fraction of the total cross sectional area, also shear deformations of webs can significantly affect the magnitudes of girder deflections. Both these phenomena – the shear lag in the flanges and the shear deformations in the webs – become particularly manifest in box girders subjected to considerable shear forces. Such a situation occurs when a box girder bridge is under the action of usual deal and live loads.
P. Kuklík, A. Kuklíková: Nondestructive Strength Grading of Structural Timber
The paper is concerned with the investigation of the use of non-destructive testing methods for the grading of structural timber and for the determination of the performance of structural timber elements. The investigations dealt with the ultrasonic method and the methods of longitudinal and transverse vibrations. The usability of these methods was verified at samples with the structural dimensions. The principle of the work lies in the search for statistic relationships between parameters characterising the timber quality (e.g. bending strength, modulus of elasticity) and magnitudes measured by the above mentioned non-destructive testing methods (e.g. natural frequency, dynamic modulus of elasticity).
3 S. Kudarauskas, J. Vaupšas: Advanced Theory and Application of the Oscillating Synchronous Electrical Motors
This paper considers specific problems of the theory and application of oscillating electrical motors. Classification of electrical machines according to temporal and spatial features of mechanical movement is explained to determine the place of oscillating motors in the whole complex of electrical machines. Here oscillating synchronous motors are described, the main fields of their usage and classification of such motors are defined. The basic (a principle of making equations, their peculiarities) of the theory of oscillating machines are explained in accordance with a general structure of inductive electrical machines. This paper also explains the systems of characteristics of the main motor regime (steady periodic) as principles to make and display functions of a complex argument. The problems of examination and application of oscillating motors and a perspective of such motors are emphasised.
D. J. Murray-Smith: Issues of Model Accuracy and External Validation for Control System Design
Model validation is an important but often neglected aspect of the engineering design process. In the control systems field the accuracy of mathematical models which represent the dynamics of the system being controlled can be of critical importance for design applications in which the overall performance specifications are demanding in terms both of accuracy and speed of response over a wide range of operating conditions. In the past many published reports of engineering design projects which have depended in some way upon complex mathematical or computer models have failed to address questions of model accuracy or to include discussion of the processes used to investigate model limitations. Important exceptions can be found in certain safety-critical areas such as aircraft flight control system design. This paper reviews some of the issues that can arise in the validation of models used for engineering design and makes a number of recommendations both about the processes which should be used in the development and application of mathematical models for engineering design and about the education and training of future engineers.
E. W. McGookin, D. J. Murray-Smith, T. I. Fossen: The Use of Genetic Algorithms for Nonlinear Controller Design
The optimization of nonlinear controller parameters by Genetic Algorithm (GA) is explored in this paper. The type of nonlinear controller that is considered is derived from sliding mode control theory, which is known for its robust properties. The GA technique for optimization has developed from its foundation in Darwinian evolution into a powerful optimization algorithm that can be used for parametric design. Both sliding mode control theory and GA theory are presented. The use of an elite GA for sliding mode controller parameter optimization is illustrated by means of an example which involves the design of a heading controller for a scale model of a supply ship. A GA optimized controller solution is presented. The performance of this controller is illustrated through simulation studies and trials in a model ship water tank facility. These evaluations illustrate that both the sliding mode control law and GA technique are effective design methods for automated design for nonlinear controllers.
F. J. McGibbon: Student Project on the Design, Testing and Development of a Data Acquisition System
This paper discusses in detail an undergraduate student industrial project which forms an integral part the degree of Master of Engineering from the University of Glasgow, Scotland. The host company was Mesit Pristroje spol. s r.o., Uherske Hradiste, Czech Republic co-operating with the Technical University of Brno (VUT Brno), Czech Republic. The project carried out was concerned with a contribution to the design and with the testing and development of a data measurement system designed principally for use in the testing of light aircraft. The system designed in capable of recording static and dynamic measurements up to 1000 Hz, and consists of a piece of hardware interfaced with a personal computer running purposely written software. The paper presents a detailed account of the work carried out by the student together with an explanation of the design of the system. Some possible future developments for the system are also discussed. A description of the European Credit Transfer System (ECTS), used to evaluate the work of a student in a host university or enterprise, is also presented, the project being part of this scheme.
J. Kousal, V. Papež, J. J. Venkrbec, J. Štětina, J. Sedláček: MEE (Materials Engineering for Electronics) - Aim, Tools and Perspectives
New approach to solidification processes based on a combination of mechanical vibrations and on specially introduced magneto-hydrodynamic forces is illustrated on GaSb grown from Ga and Sb solutions. Process is accelerated approximately 20-times compared with “classical” Travelling heater method – solution growth. Up to now, though ingots possess mosaic texture, their transport properties: mH= 3.000 cm2/Vs, p=1.7×1017 at 77 K are slightly better than published results. A schematic arrangement of the growth apparatus for a modified traveling heater method, and of the growth conditions are given. A simple calculation of levitation phenomenon being generated by a controlled MHD forces are presented. There is brought a brief analyses of this phenomenon for an application on the above mentioned processes. Some experimentation attempts are added. Possible perspectives inhering in this peculiar process can also inspire young investigators/scientists.
P. Bečvář, L. Müller, J. Psutka: Classification of Transient Events of Nuclear Reactor Using Hidden Markov Model
This article describes a part of on-line system for a residual life of a pressure vessel shell. In this system there appears a need for determining of a real history of a pressure vessel described as a sequence of so called transient events. Each event (there are 23 events now) is given by its template. It is theoretically necessary to compare data measured in a real history with all possible sequences of transient events. This solution in intractable and that is why a more sophisticated solution had to be used. Because this task is very similar to task of an automatic speech recognition, models and algorithms used to solve speech recognition tasks can be efficiently used to solve our task. Of course there are some different circumstances caused by the fact that the transient events take much longer than words and their number is much smaller than the number of words in speech recognition system's vocabulary. But the inspiration from speech recognition was very useful and the known algorithms rapidly decreased the design time.
V. Smutný, V. Hlaváč, P. Palatka: High Precision Dimensions and Shape Measurements of Small Objects
This paper summarizes the experience with optical gauging of small parts with high accuracy using computer vision technology. The occluding contours of the objects were measured using back illumination. Well known problems of low resolution can be partially overcame by subpixel precision algorithms. The specific problems of high precision measurement (accuracy in range of a few microns) are caused by the presence of dust and fibres on the measured surface and by diffraction and reflection of the light used. First problem can be eliminated by the use of robust methods. The second one can be alleviated by careful design of optics.
P. Mach: Influence of Surface on Quality of Conductive Adhesive Joints
Electrically conductive adhesives are newly developed materials for joining in electronic assembly. Quality of adhesive joints is strongly influenced by quality and materials of joined surfaces. Influence of these parameters on resistance, nonlinearity of current vs. voltage characteristic and thermal aging of adhesive joints were investigated. Three different adhesives offered by three different producers were tested. The joints were prepared on copper and gold surfaces and on copper surface, which was aged at environment of low concentration of SO2. Special resistors with “zero” resistance were assembled using conductive adhesives on substrates with pads mentioned above. It was also found strong influence of material and surface quality of assembled components and conductive tracks on properties of the joints. The joints prepared on gold surface had lower resistance and lower nonlinearity in comparison with joints prepared on copper surface. It was also found that measurement of nonlinearity is a very useful method for investigation of quality of the joints.
S. Hostomský, I. Jelínek: A Formal Design Method
In the first part of this article, there are described two ways out of the design process theory: metamodel as a basic principle of a design process description and non-standard logics as a feasible formal background of the design theory. In the second part, one possibility of the design process description is discussed by means of one type of nonstandard logic – modal logic formalism. A simple example shows some of the properties of our approach.
B. Palán, F. V. Santos, B. Courtois, M. Husák: Microsystems for Space Applications
Recent progress in microsystems technologies make them suitable for the space research and development due to their low volume, low mass, low power consumption, leading to reduced mission cost. The most interesting approach is using standard technologies with additional post-processing steps to realize sensors and actuators together with signal processing circuits. This paper summarises some aspects and difficulties of the space environment. The radiation effects in space are described and damage on CMOS structures are explained. Design methodologies for hardening microsystems and MOS based circuits against these effects are presented. Some examples of microsystems examples for space applications fabricated by researches world-wide are given.
J. Vobecký, P. Hazdra, N. Galster: Advanced Design of Lifetime Control for High-power Devices in TCAD Environment
At present, advanced design of high-power devices relies on standard TCAD tools. In spite of their maturity, there are many specific areas these tools do not cover satisfactorily and special approach to device design has to be chosen. One of these areas, namely the device parameter optimization via lifetime engineering, is presented. Optimization of both the static and dynamic parameters of the free-wheeling diode supporting operation of the 4.5 kV Gate Turn-Off thyristor is used as an example.
K. Draxler: Design of Instrument Current Transformer by Means of PC
The principle of design is realization of an instrument current transformer (ICT) with given ratio and burden and with errors which do not exceed given value. It is assumed that the ICT will be realized on a toroidal core made from soft magnetic material so the leakage inductance of secondary winding is negligible. The dependence of apparent permeability and loss angle on the induction is apparent by ICT design. The program makes the calculation of minimum number of ratio windings possible so that the ICT errors do not exceed entered value. The burden and the resistance of secondary winding are respected.
K. Záliš: Using of Expert Systems in Electrodiagnostics of Large Electrical Machines
Several rule-based expert systems were developed for diagnostics of high voltage (HV) insulation systems, especially for the evaluation of partial discharge (PD) activity. Several rule-based expert systems were developed in the cooperation of top diagnostic workplaces of the Czech Republic for this purpose. The IZOLEX expert system evaluates diagnostic measurement data from commonly used off-line diagnostic methods for the diagnostics of HV insulation of rotating machines, non-rotating machines and insulating oils. The CVEX expert system evaluates the PD activity on HV electrical machines and equipment by means of an off-line measurement. The CVEXON expert system is for the evaluation of the discharge activity by on-line measurement and the ALTONEX expert system is the system for on-line monitoring of rotating machines. The complex project for the evaluation of a PD measurement on HV insulation systems has also been made. This complex evaluating system includes two parallel expert systems for the evaluation of a PD activity on HV electrical machines.
J. Vedral, J. Holub: Statistical Method for Testing of Sigma-Delta Converters
Measurement and testing methodology for 2-channel insulated measuring module based S - D on Analog-to-Digital converter AD7710 that has a nominal resolution 16(24) bits is presented. The dependencies of effective resolution on the first notch frequency and gain are given.
J. Fischer: Time Delay and Integration Mode of CCD Linear Image Sensor Operation
This paper is devoted to description, analysis and practical verification of a new method of CCD line sensor control necessary for operation in TDI mode. TDI mode of operation is used when objects observed by CCD sensor move in the direction of line sensor. The results of experiments with test patterns moving with different velocities are discussed. Conclusions and hints applicable for finding velocity of movement are also included in the paper.
V. Benda: Present Problems of Reliability of Power Semiconductor Devices
The paper presents an overview of the main causes of failures of modern switching devices as power MOSFETs, IGBTs, GTOs. The attention is paid to problems of both homogeneity of semiconductor structures and operating conditions, especially at high power devices, which are usually realised as an integration of a high number in parallel connected individual devices. One of the most frequent cause of the device failure is electro-thermally induced stress (especially in the case of power module encapsulations) which can result in thermal fatigue faults in applications with sequential operation mode. A comparison of empirical formulas with experimental results has been done and considerations concerning conditioning reliability of power semiconductor devices have been formulated. In the paper are also discussed some modern trends in controlling devices and the optimum operating conditions of power GTO and IGBT are discussed.
V. Bouda, J. Hampl, J. Kábrt, J. Lipták, F. Novák, V. Pícha, J. Rajman, J. Sedláček: Carbon Circuits in Polymers
Selectively processed areas in polymer layers or foils can form fine carbon circuits of a substantially enhanced conductivity. The state of the CB-particles (and the local plastic’s conductivity) can be changed by the short-range-displacements of the CB-particles that control the internal contacts of the circuit. Several examples of the potentiality of such processing routes are presented. A melt of the CB-plastic in the uni-directional electrical field increases its conductivity rapidly by several orders of magnitude [1]. Cooling down the composite melt into the solid state results in an abrupt decrease of conductivity. The intensity of the conductivity decrease depends on the conditions of the cooling regime [2]. The percolation-like transition can be induced by special processing route of a composite melt that has a lower CB concentration than the theoretical percolation threshold [3].
4 J. E.Vinney, S. Noroozi, P. Sewell, G. N. Blount: The Case for a Case-based Design Assistant
A joint research programme currently being undertaken at Coventry University and the University of the West of England, Bristol, is concerned with developing a useful tool, for the novice or expert designer, which directly supports the conceptual design generation process in the field of mechanical device design. The COnceptual Design ASsistant (CODAS) achieves this by utilising knowledge of past successful solutions and then generating new devices, which can be either novel or routine, that are functionally capable of satisfying the stated device requirements. Case Based Reasoning (CBR) technology is used to store and retrieve past design solutions which are defined in terms of a symbolic representation language. The underlying design model is function based and employs a divergent function to form mapping technique to produce physical embodiments of the proposed functional solutions. The technique has been developed in the field of mechanical device design and is now being developed for use in the prosthetic design field.
S. Salamon, B. Żołtowski: Tightness Tests of Pneumatics Elements of Brake Systems
Comissioning of brake pneumatic elements comprise between others, tightness tests. The presented method of tightness testing, called clase comparison method makes possible to alternative classification: tight – leading and to measure leakages of 1 ncm2/min grade at pressure 0.6 Mpa. The essence of the method and results of investigations of different factors on tightness tests procedure are presented in the work.
H. Williams, R. Masson: Cross Functional Working and Concurrent Engineering – a UK Study
This paper reports on the preliminary results of an investigative study into the implementation of concurrent engineering applied to new product development. Concurrent (or Simultaneous) engineering is the term commonly given to creating new products using multi-disciplined teams of marketing, design, manufacturing and support functions together with supplier and customers. Such techniques have produced robust, low cost quality products in short concept to market times compared to traditional ones. The research investigated design management practice and performance in a number of organisations across a range of industrial sectors in the UK by means of a questionnaire survey. The results identify the current use of a variety of design practices and methodologies such as different organisational structures, the extent of cross-functional working, the use of design and phase reviews and the use of different technologies. They indicate that companies implementing CE are more successful in time to market performance than those who don’t implement CE. Factors most influencing the successful adoption of CE are design and phase reviews, and, to a lesser extent, the use of multifunctional teams and supplier partnerships.
C. Short, G. Cockerham: Human Factor Issues Affecting CAD Implementations
Industrial companies have been implementing Computer Aided Engineering tools for many years with varying degrees of success. In the early implementations considerable emphasis was placed upon the organisational structure necessary to receive and optimise system output. However, it is becoming increasingly clear that any successful CAE implementation has to satisfy three inter-related factors of technology, organisation and human issues. This paper presents the results of an investigation into human factors affecting successful CAD implementation, undertaken through selected case studies and a more general survey of UK industry.
A. Whyte, H. M. Edge, A. AL-Hajj: The Success of Software Support in Engineering: An Emphasis on Process Rather Than Product
There is a need for technological computerized support systems to supplement the structure and process of communication within the multi-disciplinary design team rather than attempt to substitute it. Understanding technological effects on the design process requires focus not on the packages of hardware and software themselves but on the specific roles and social variables that are intrinsic to specialist interaction. The role of inter-professional relationships is important in collaboration towards increasingly technologically complex solutions, and neglect of these relations may lead to the failure of existing information technology systems to support adequately scientific and engineering interaction. Technological influences on the processes of participation come about as a result of design team member choice about what features of technology to use, not from the technology itself. Group dynamics influence choice. Software support systems in isolation, will be unable to instil the crossfertilisation of multi-disciplinary professional objectives required for innovative design. Research is presented that explores the nature of inter-disciplinary relationships in the UK building-design team at the formative stage. The research examines the extent to which the collaborative processes of building-design must be addressed if IT products and moves towards computer-integrated-construction are to succeed in facilitating innovative building and engineering output.
L. F. Silva, M. Lima, C. Couto, J. Coelho, F. N. Ferreira, A. M. Rocha: Mechatronics Approach for a Controlled Actuation of the Presser Foot Mechanism on an Industrial Sewing Machine
This paper describes the study of the research program being carried out on the feeding system of an industrial overlock sewing machine. The results obtained from the presser foot bar displacement and compression force, together with the graphic kinematic analysis, which includes the velocity and acceleration taken from the displacement-time curves of the presser bar, led to further understanding of the feeding system dynamics. This study is providing the basis for the development of a redesigned and optimized fabric feeding system. The new actuation system, based on a proportional force solenoid integrated in the presser foot bar, will be also discussed as an important contribution to achieving a desired dynamic behaviour at high sewing speeds.
S. J. Pickering, D. Lampard, J. Mugglestone: The Use of Computational Fluid Dynamics in the Thermal Design of Rotating Electrical Machines
Thermal constraints impose limitations on the power capability of many electric motors and generators. However, inadequate data on ventilation air flows and convection heat transfer coefficients hamper the design process. Computational fluid dynamics (CFD) presents an opportunity to predict air flow and heat transfer in many situations. However, the complex geometries combined with rotation in the end regions of electric motors and generators present significant difficulties for CFD. An experimental study of air flow and heat transfer in the end region of a 200 kW 2 pole totally enclosed, fan cooled (TEFC) induction motor was carried out. Detailed measurements of heat transfer coefficient around the end windings and frame were made along with measurements of windage loss and airflow at particular locations within the end region. These were compared with a detailed model of the end region using the CFD software Fluent UNS and good agreement was found. The results are presented and the reasons for the difference between the measured values and CFD predictions are discussed. It is concluded that general purpose CFD software is now at a stage of development where it can be used in a design office environment to undertake design analysis of electrical machines.
G. Green: Towards an Integrated Design Evaluation (IDE) Tool
The ability to rapidly evaluate design ideas is an essential element in the goal to increase design productivity. Given the need for companies to produce more innovative products in an increasingly competitive market place it follows that designers have to consider an increased number of design options. Only through the generation of a relatively large number of concept design options along with a rapid and reliable means of evaluating the options will designers be able to increase design productivity whilst identifying and developing new innovative products. This provides designers with a major challenge and requires the provision of design tools and aids. These are likely to be implemented within a computer-based environment. It follows that the theoretical models underpinning them must be shown to be valid, reliable and robust. This paper identifies the evaluation activities within the conceptual phase of the engineering design process and presents theoretical models of evaluation. It then introduces a conceptual structure combining these models into an effective Integrated Design Evaluation (IDE) tool. In addition, this tool has the capacity to retrieve design cases from experience or a formal knowledge base. Two approaches, namely specification-knowledge base and design representation-knowledge base, will be discussed.
S. F. C. F. Teixeira, J. C. F. Teixeira: Modelling Heat Exchangers for Domestic Boilers
In the present paper the thermal behaviour of fin-tube heat exchangers is modeled. Particular attention has been given to the plate fins. The heat fluxes in the fins are described using a finite volume technique to discretize the energy equation. The thermal interactions with the water in the tubes and the surrounding air are treated as external boundaries, using appropriate relationships for forced convection in pipes and flat plates. The numerical results are presented in terms of dimensionless numbers (Fourier, Biot and geometric ratios) which are found to be representative for this particular geometry. Furthermore, the effect of thermal gradients along the fin surface upon the fin efficiency is investigated. Based on a differential model for the heat balances, design charts have been developed for the thermal analysis of heat exchangers.
S. A. MacGregor, L. B. Newnes, J. N. Staniforth, G. R. Kay, M. J. Tobyn, M. D. Horrill, R. C. Lamming, D. W. Hajee: The Use of Computational Fluid Dynamics in the Design of a Pharmaceutical Processor
The use of solid oral dosage such as tablets accounts for approximately 60 % of the total frequency of all pharmaceutical dosage forms. In addition to this 90 % of all drugs supplied are in tablet form even if they are presented in other medicinal forms. During tablet production there are a number of processes that are carried out, in what is essentially a batch process. This work describes the use of computational fluid dynamics (CFD) in the design of a new single vessel pharmaceutical processor. Initially a simple model was developed using the computational code STAR-CD. The results of this were compared with tests carried out in a prototype processor. This provided confidence to develop the design. During the design phases of the work all potential design features have been modeled and the final design choices made on the basis of the CFD results. The initial phases of the work were carried out using single-phase models, however all the recent design work has been carried out using a two-phase flow model.
J. L. Stoyell, P. W. Norman, G. Kane, C. R. Howarth, R. Vaughan: Incorporating Environmental Objectives into the Design Process of Large Made-to-Order Projects. A Case Study of Two Design Teams
Environmetal performance needs to be considered during the conceptual design of Large Made-to-Order products and processes. This paper presents work from a case-study of two such companies based on the study of current practice. Key design activities are modeled using an IDEFO based methodology to investigate opportunities for improvement and to isolate the main barriers against achieving clean design. A system for the transfer of client level environmental objectives to the design team is proposed in order to achieve clean design.
E. Seabra, J. Ferreira da Silva: Design of a Control System for Quality Maintenance on Cutting Edges of Files Production
The file cutting edges are the most important parameter that influence the performance of the filing operation. The practice shows that the most efficient way of generating these cutting edges is by penetration, by blow, of a cutting tool, which creates a plastic deformation on the file body. The penetration depth is probably the most important factor of the final quality of a file. In the existing machines of files manufacturing, this depth is manually adjusted by the operator, using specific mechanism. This means that files are manufactured on an empirical basis, relying on subjective factors, that do not allow to keep constant quality level of the production. In a research work, being developed in the University of Minho, it is intended to eliminate the subjectivity factors by the means of the evolution of the present “all-mechanical” system to a “mechatronic” one. In this paper, which is related with that research work, it presented a study of a round files production machine, regarding the identification, as well as the categorisation, of the operating parameters that affect the cutting edges production. They are, as well, defined and quantified those factors that influence the final quality of a round file.
A. C. Fairlie-Clarke, M. H. Muller: Determinants of Profit as the Criterion for the Evaluation of the Product Development Process
There are three main elements of the product development process that are suitable for evaluation: the means employed, the activities and the outcomes. Most available methods provide an evaluation of the outcomes, but this can only provide retrospective information. There is a need to be able to evaluate an existing or proposed process to determine whether it will successfully meet the objectives of a particular project. This can be done by evaluating the planned activities of the process for their effectiveness in addressing the important issues in the project. These issues are called the “determinants of profit”, and a survey and trials in industry show that they provide an effective criterion against which companies can evaluate the activities of their product development process. The determinants of profit can be divided into enabling determinants, which must be addressed above a threshold value of effectiveness in order to produce a viable product, and differentiating determinants, which provide scope for competitive advantage.
J. Křena, B. Cabrnoch: Development of Aircraft Sandwich Parts
The presented paper shows the design and development process of sandwich parts. A spoiler plate and a main landing gear door are developed. Sandwich parts are made of C/E composite facings and a foam core. FE models have been used for optimization of structures. Emphasis has been placed on deformations of parts under a few load cases. Experimental tests have been used for a verification of structure parts loaded by concentrated forces.
J. Mádl, J. Čermák, M. Vrabec: Computational Techniques in Manufacturing Technology
Manufacturing processes are complex and therefore difficult to plan by software. The present state in computational techniques in manufacturing technology as well as software applications at the Department of Manufacturing Technology of CTU in Prague are discussed in this article. Computational techniques may help to solve many manufacturing problems as such programs in the field of process planning have been developed. However, due to the complexity of manufacturing processes, complete planning of a manufacturing process by software is not possible at present.
D. Hanus: Inlet and Outlet Casings of the Turbojet Engines – Design and Experiment
The paper presents special design method for three-dimensional design of the inlet and outlet channels of the turboprop engines. The method is based on the solution of indirect problem in internal aerodynamics, which is realised by mechanical construction of the flow field between inlet and outlet sections of the designed channel. The flow field is represented by number of flow tubes made of special plastic material, of optimised geometrical shape and their course in the space. The method was applied on the design of inlet channel of the three-shaft turboprop engine Walter M 602 and the aircraft L 610 and on the outlet channel of the two-shaft turboprop engine Walter M 601. Both channels have been manufactured and proved excellent aerodynamic properties. The channels have satisfied the airworthiness requirements and have been certified by the Czech Aviation Administration and by Federal Aviation Administration of the U.S.A. as well. The application of the new outlet channel have contributed to considerable improvement of the performance of the engine of more than 3 % at the same absolute fuel consumption and at 5 °C lower temperature of the gases at the inlet section of the turbine. The mass of the new channel is of 1 kg lower than the original one.
J. Fürst, K. Kozel, J. Horák, M. Vavřincová: Modern Schemes for Computation of Transonic Flows in Internal Aerodynamics
The work deals with numerical solution of steady transonic flows with applications in internal aerodynamics. The problems are described by the system of 2D or 3D Euler or Navier-Stokes equations. Our group developed during last years several central or upwind TVD finite volume methods for computation of transonic flows through a cascade or in a channel using grids of quadrilateral cells or triangular cells. We also developed other (non TVD) schemes e.g. MacCormack scheme or several multistage Runge-Kutta finite volume schemes with applications of some acceleration techniques (multi-grid solution or hierarchical residual averaging). Our aim is to present some comparison of results of flows in internal aerodynamics using TVD schemes or other schemes. One can also compare the influence or artificial viscosity effects especially using TVD schemes.
K. Macek, V. Očenášek, V. Sedláček: Anisotropy and Inhomogeneity in Extrudates of Aluminium Alloys
Anisotropy and inhomogeneity of mechanical properties and texture of microstructure originating in hot extrusion process depend not only on the type of the alloy, state of the billet and extrusion parameters, but also on the shape and size of extrudates. Tensile properties in longitudinal and transversal directions of model extrudates having simple cross-sections have been tested on four types of aluminium alloys. Values of ultimate strength and yield stress in longitudinal direction are higher up to 100 MPa as compared to those in transversal direction, whereas differences in elongation are small. Pronounced anisotropy and inhomogeneity of mechanical properties have been detected in cross-sections of the model extrudates. Quantitative metallography was used for determination of subgrain size, specific number of intermetallic phases, volume fraction of recrystallized grains and for assessment of metallographic texture. Certain implications for the die design based on obtained results are finaly presented.
H. Lauschmann: Textural Analysis of Fatique Crack Surfaces: Image Pre-processing
For the fatique crack history reconstitution, new methods of quantitative microfractography are beeing developed based on the image processing and textural analysis. SEM magnifications between micro- and macrofractography are used. Two image pre-processing operatins were suggested and proved to prepare the crack surface images for analytical treatment: 1. Normalization is used to transform the image to a stationary form. Compared to the generally used equalization, it conserves the shape of brightness distribution and saves the character of the texture. 2. Binarization is used to transform the grayscale image to a system of thick fibres. An objective criterion for the threshold brightness value was found as that resulting into the maximum number of objects. Both methods were succesfully applied together with the following textural analysis.
M. Karlík, J. Siegl, P. Kratochvíl, P. Haušild: Mechanical Properties and Fracture of an Intermetallic Alloy Fe-28Al-4Cr-0.1Ce (at %)
Structure, mechanical properties and fracture of a vacuum cast and hot deformed Fe-28Al-4Cr-0.1Ce (at %) alloy were studied. The material was extruded at 1 140 °C and the samples then annealed in the temperature range from 500 to 800 °C, in the D03 and B2 ordered regions. Mechanical properties were evaluated from Vickers hardness and tensile tests. Structure was examined by optical and electron metallography. Besides coarse Ce bearing particles in the matrix, a Cr-Fe precipitate has also been found, mainly on the grain boundaries. Annealing at 700 and 800 °C leads to recovery of the dislocation structure and to the corresponding decrease of the yield stress. The fracture mechanism depends on the thermal treatment of the alloy and on the test temperature. Micromorphology of fracture surfaces was characterized by different fractographic features, including transgranular cleavage, intergranular decohesion and ductile dimple fracture. Maximum room temperature ductility of 4.3 % was achieved after hot extrusion and annealing for 2 h at 700 °C.
A. Materna, V. Oliva: Computer Simulations of the Fatigue Crack Propagation
The following hypothesis for design of structures based on the damage tolerance philosophy is laid down: the perpendicular fatigue crack growth rate v in a certain point of a curved crack front is given by the local value of stress intensity factor per unit of nominal stress K' and the local triaxiality T which describes the constraint. The relationship v f (K', T) is supposed to be typical for a given loading spectrum and material. Such relationship for a 2024 Al alloy and the flight-simulation spectrum was derived from the fatigue test of the rectangular panel with the central hole and used for three-dimensional simulation of the corner fatigue crack propagation in the model of the wing spar flangeplate. Finite element and boundary element methods were used for these computations. The results of the simulation are in good agreement with the experiment.
5 L. Podolka: Strengthening Beams by Means of CFK Strips
The objective of the investigation described in this paper was to develop a basic set of data required for the application of the strengthening method of bonding CFK strips as reinforcing elements to the existing reinforced concrete structures. In addition on the investigation aimed at establishing the dimensioning data, the work also focused on technical issues related to the design and execution in order to ensure the practical applicability of the method of externally bonded CFK strips. The CFK strips are placed on the bottom side or on the bottom part of the web. The paper also includes the description of variants of tested beams and the evaluation of experimental data, the conclusion, and the outline of elaborated variants.
I. Fořt, F. Ambros, J. Medek: Study of Wear of Pitched Blade Impellers
A study was made of the erosion of blades of pitched blade impellers in a suspension of solid particles in a liquid under a turbulent regime of flow of an agitated charge. The wear of the impeller is described by an analytical approximation in exponential form, and the influence of the pitch angle on the impeller blade wear was studied experimentally. It follows from the results of the experiments made that the wear rate of the pitched blade impellers increases linearly with the decreasing pitch angle within the interval a Î á15°; 45° ń. The proposed form of radial profile of the leading edge of the impeller blade enables us to calculate the surface of the worn blade. This quantity significantly decreases with the length of the period when the blades are affected by the solid particles, and its values calculated according to the suggested profile of the worn blade fit fairly well with the experimentally determined values. The results of the experiments performed are valid for homogeneous distribution of solid particles in an agitated suspension.
J. Matušů, M. Matušů: The Lienhard Interpolation LQ,p -  Method
This paper deals with a generalization of the Lienhard interpolation method from a new point of view. The invariance of the interpolation curve with respect to a change of orientation in the order of supporting points is proved.
J. Fiksa: Some Solutions of Electromagnetic Fields
Solutions of the electromagnetic field by means of potentials under the Lorentz condition are described in this paper. The solution represented by the superposition of TM and TE modes is well known. It is explained why this solution has been exclusively accepted. The possibility of applying the Coulomb gauge is discussed. Due to the noncovariant field requirement, application of the Coulomb condition is unavoidable in quantum theory. In both cases, the longitudinal modes with their possible applications are described.
I. Linkeová: Determination of Tangent Vectors in Construction of Ferguson Interpolation Curves and Surfaces
In technical practice we often need to find an interpolation curve which must go through the given base points. A basis for the calculation of the piecewise interpolation curve is the Ferguson cubic curve, the final shape of which is significantly influenced by the magnitude and the direction of the tangent vectors at the startpoints and endpoints of the individual segments. This article describes a method for calculating tangent vectors at every definition point, which ensures a perfect adaptation of the shape of Ferguson cubic curves to the given configuration of the definition points. This method of determining tangent vectors shows minimal undesirable waving among given points, overshooting in the vicinity of given points is considerably limited, and first-degree continuity is ensured among individual parts of the Ferguson cubic curve. The results are used to create a mathematical model of the given surface. The mathematical model is formed by connecting the Ferguson 12 vector patches. A spherical surface was selected as the testing surface, because it is easy to judge the accuracy of the method by comparing the values of the coordinates of the points on the calculated interpolation surface with the exact analytically calculated values.
B. Novotný: Mechanical properties of Composite Engineering Structures by Multivolume Micromechanical Modelling
Engineering structures often consist of elements having the character of a periodically repeated composite structure. A multivolume micromechanical model based on a representative cell division into r1 × r2 × r3 subcells with different elastic material properties has been used in this paper to derive macromechanical characteristics of the composite construction response to applied load and temperature changes. The multivolume method is based on ensuring the equilibrium of the considered volume on an average basis. In the same (average) way, the continuity conditions of displacements and tractions at the interfaces between subcells and between neighboring representative elements are imposed, resulting in a homogenization procedure that eliminates the discrete nature of the composite model. The details of the method are shown for the case of a concrete block pavement. A parametric study is presented illustrating the influence of joint thickness, joint filling material properties and the quality of bonding between block and filler elements.
P. Brož: Some Micromechanical Aspects of Damage and Fracture
The failure mode is described by means of elasto-plastic fracture mechanics and the main aspects of fatigue crack behaviour are itemized. The crux of the matter is the presentation of the applicability limits of the three substantially different fatigue fracture mechanics equations based on fatigue crack propagation development. In the course of this, the microstructural effects, predominantly crystallographic identification, grain dimension, and second phase structures are considered. For some sorts of FCC polycrystalline metals, the fatigue life and micro-damage heterogeneity are investigated, especially the stage of early plastic fatigue damage initiation while emphasizing slip theory and the localization homogenization technique. An internal damage variable ds is applied to illustrate of the micro-damage of each slip system.
A. Čepek, J. Vondrák: Covariances of Smoothed Observational Data
The method of smoothing observational data in its original form [2–3] did not allow the uncertainties of either the individual smoothed values or their function to be estimated. The present paper, using the same original system of linear equations but a different method for solving them (Cholesky decomposition instead of Gauss elimination), describes an algorithm to compute the covariances of the smoothed data in any selected band. These enable the uncertainties of any function of the smoothed values to be calculated.
J. Kratěna, I. Fořt, O. Brůha, M. Růžička: Dynamic Stress Affecting the Radial Baffle on an Industrial Mixing Unit with a Pitched Blade Impeller
This paper presents a study of dimensioning under fatigue stress of a standard radial baffle in an industrial mixing unit
(T 5 m) with a pitched blade impeller under a turbulent regime of flow of an agitated liquid. The fatigue stress of the radial baffle is calculated from the known experimentally determined distribution of the dynamic pressure affecting the standard radial baffle in a pilot plant agitated system. Asymmetrical distribution of the dynamic pressure along the height of the baffle significantly affects the thickness of the baffle as well as the dimensions of the doublefillet weld fixing the baffle to the vessel wall. Our results are valid for standard pitched blade impellers with four or six inclined blades
(D/T = 1/3, a = 45°) and off-bottom clearances h/T = 0.2, 0.35 and 0.5 pumping liquid downwards in a cylindrical mixing vessel with a flat bottom and four baffles (b/T = 0.1) when the Reynolds number exceeds ten thousand.
P. Hasal, I. Fořt: Macro-instabilities of the Flow Pattern in a Stirred Vessel: Detection and Characterization Using Local Velocity Data
Velocity data obtained by laser Doppler velocimetry (LDV) in a flat-bottomed cylindrical stirred vessel (diameter: 300 mm, filling height: 300 mm, working liquids: water and aqueous glycerine, impeller Reynolds number values (ReM): 750, 1200 and 75000) equipped with four radial baffles and stirred with a pitched blade impeller are analyzed by methods of non-linear analysis. The macro-instability of the flow pattern (MI) was extracted from the experimental data by a combination of the proper orthogonal decomposition (POD) technique and spectral analysis. The relative magnitude of the MI (the fraction of flow total kinetic energy captured by MI) was evaluated and its spatial distribution was determined. The temporal evolution of the MI was constructed from the POD eigenmodes. The chaotic attractors of the macro-instabilities were reconstructed by the method of delays. The embedding dimension was determined by the false nearest neighbor analysis (FNN) method, and the time delay from the first minimum of mutual information. Correlation dimension dc and the largest Lyapunov exponents lmax of the reconstructed attractors were evaluated. The correlation dimension slightly increases with the increasing ReM value. The spatial distribution of dc is quite uniform at all ReM values. The maximum Lyapunov exponent is clearly positive for all analyzed attractors. Spatial distribution of lmax is markedly non-uniform and exhibits irregular variations. Possible applications of nonlinear analysis of local velocity data in mixing processes are mentioned.
K. Záliš: Using Expert Systems in Evaluation of the State of High Voltage Machine Insulation Systems
Expert systems are used for evaluating the actual state and future behavior of insulating systems of high voltage electrical machines and equipment. Several rule-based expert systems have been developed in cooperation with top diagnostic workplaces in the Czech Republic for this purpose. The IZOLEX expert system evaluates diagnostic measurement data from commonly used offline diagnostic methods for the diagnostic of high voltage insulation of rotating machines, non-rotating machines and insulating oils. The CVEX expert system evaluates the discharge activity on high voltage electrical machines and equipment by means of an off-line measurement. The CVEXON expert system is for evaluating the discharge activity by on-line measurement, and the ALTONEX expert system is the expert system for on-line monitoring of rotating machines. These developed expert systems are also used for educating students (in bachelor, master and post-graduate studies) and in courses which are organized for practicing engineers and technicians and for specialists in the electrical power engineering branch. A complex project has recently been set up to evaluate the measurement of partial discharges. Two parallel expert systems for evaluating partial dischatge activity on high voltage electrical machines will work at the same time in this complex evaluating system.
P. Štěpánek: Optimization of Reinforcement of RC Framed Structures
This paper presents the entire formulation of longitudinal reinforcement minimization in a concrete structure of known sections and shape under loading by the normal force and the bending moment. Constraint conditions are given by the conditions of structure reliability in accordance with the relevant codes for ultimate strength and applicability of the sections specified by a designer. Linearization of the non-linear function is described, and possibilities of applying algorithms of linear computing are discussed. The functioning of the process described is demonstrated on a plane frame structure design.
Hamdy K. Elminir, V. Benda, Javed A. Jan: Temperature Distribution in Solar Cells Calculated in Three Dimensional Approach
Field-testing is costly, time consuming and depends heavily on prevailing weather conditions. Adequate security and weather protection must also provide at the test site. Delays can also be caused due to bad weather and system failures. To overcome these problems, a Photovoltaic (PV) array simulation may be used. For system design purpose, the model must reflect the details of the physical process occurring in the cell, to get a closer insight into device operation as well as optimization of particular device parameters. PV cell temperature ratings have a great effect on the main cell performance. Hence, the need for an exact technique to calculate accurately and efficiently the temperature distribution of a PV cell arises, from which we can adjust safe and proper operation at maximum ratings. The Scope of this work is to describe the development of 3D-thermal models, which are used to update the operation temperature, to get a closer insight into the response behavior and to estimate the overall performance.
M. G. Danikas: A Novel Diagnostic Technique to Study the Ageing of Rotating Machine Insulation: The
Rotating machine insulation ageing has been the subject of intensive research over the years. In this paper, model stator bars are investigated with the aid a Partial Discharge (PD) detector. The maximum PD magnitude is recorded as the applied voltage increases and as it decreases. The resulting “hysteresis curve” indicates whether the stator bar is in a “good” or “bad” condition, i.e. it indicates its “state of health”. The proposed method has certain advantages over other methods since it requires only one parameter, i.e. the maximum PD magnitude. It is suggested that the proposed method can be used as a diagnostic tool for assessing the quality and controlling the state of ageing of model stator bars.

Acta Polytechnica 2001

No. (click on selected title and view the annotation)
1 A. K. Haghi: Experimental Investigations on Drying of Porous Media Using Infrared Radiation
Increased interest is being shown in infrared drying today because of the environmental and technological advantages offered by this method. In order to assess the advantages of this drying process, extensive trials have been carried out. The objective of this investigation was to study the drying rate of infrared drying. This was achieved with the use of scanning pyrometer and image analysis.
Keywords: infrared dryer, porous media, drying rate, image analysis
A. Prokopska: Application of Morphological Analysis Methodology in Architectural Design
The theory of system and design methodology as the sphere of concepts being objective mode can be applied to a more precise description, analysis and improvement of the methods of the real architectural design process. Lull's art as the primary idea of morphological analysis, has been acknowledged as to an element corresponding with the specificity of architectural design. From the architect's point of view it is worth studying the rules and peculiarities of morphological analysis methodology. In engineering design thus it may be possible to apply the methodology in architectural design. Keywords: design, architecture, engineering, structure, morphology, analysis.
J. Toman, R. Černý: Thermal and Hygric Expansion of High Performance Concrete
The linear thermal expansion coefficient of two types of high performance concrete was measured in the temperature range from 20 °C to 1000 °C, and the linear hygric expansion coefficient was determined in the moisture range from dry material to saturation water content. Comparative methods were applied for measurements of both coefficients. The experimental results show that both the effect of temperature on the values of linear thermal expansion coefficients and the effect of moisture on the values of linear hygric expansion coefficients are very significant and cannot be neglected in practical applications.
Keywords: concrete, linear thermal expansion, linear hygric expansion, moisture, temperature.
J. Toman, R. Černý: Temperature and Moisture Dependence of the Specific Heat of High Performance Concrete
The specific heat of two types of high performance concrete was measured in the temperature range from 20 °C to 1000 °C and in the moisture range from dry material to saturation water content. A nonadiabatic method was chosen instead of classical adiabatic treatments in order to meet the requirements following from the large representative elementary volume of the materials. The measured results reveal a significant temperature effect on the specific heat value. The influence of moisture is less important than the influence of temperature, but is also not negligible.
Keywords: concrete, specific heat, moisture content, temperature.
J. Toman, R. Černý: Thermal Conductivity of High Performance Concrete in Wide Temperature and Moisture Ranges
The thermal conductivity of two types of high performance concrete was measured in the temperature range from 100 °C to 800 °C and in the moisture range from dry material to saturation water content. A transient measuring method based on analysis of the measured temperature fields was chosen for the high temperature measurements, and a commercial hot wire device was employed in room temperature measurements of the effect of moisture on thermal conductivity. The measured results reveal that both temperature and moisture exhibit significant effects on the values of thermal conductivity, and these effects are quite comparable from the point of view of the magnitude of the observed variations.
Keywords: concrete, thermal conductivity, moisture content, temperature.
M. Vognar, Č. Šimáně, D. Chvátil: Faraday Cup for Electron Flux Measurements on the Microtron MT 25
The basic criteria for constructing of an evacuated Faraday cup for precise measurement of 5 to 25 MeV electron beam currents in air from a&nbsp;microtron are established. The Faraday cup, built in the microtron laboratory of the Faculty of Nuclear Sciences and Physical Engineering of CTU Prague, is described together with the electronic chain and its incorporation in the measuring line on the beam. Measures to reduce the backward escape of electrons are explained. The range of currents is from 10-5 to 10-10 A. The diameter of the Al entry window of the Faraday cup is 1.8 cm, and its area is 2.54 cm2. The thickness of the entry window is 0.1 mm.
Keywords: microtron, Faraday cup, electron beams, electron flux measurement
J. Kratěna, I. Fořt, O. Brůha: Dynamic Effect of Discharge Flow of a Rushton Turbine Impeller on a Radial Baffle
This paper presents an analysis of the mutual dynamic relation between the impeller discharge flow of a standard Rushton turbine impeller and a standard radial baffle at the wall of a cylindrical mixing vessel under turbulent regime of flow of an agitated liquid. A portion of the torsional moment of the baffle corresponding to the region of the force interaction of the impeller discharge stream and the baffle is calculated under the assumption of constant angular momentum in the flow region between the impeller and the baffles. This theoretically obtained quantity is compared with the torsional moment of the baffles calculated from the experimentally determined distribution of the peripheral (tangential) component of dynamic pressure along the height of the radial baffle in pilot plant mixing equipment. It follows from the results of our calculations that for both investigated impeller off-bottom clearances the theoretically determined transferred torsional moment of the baffles in the area of interference between the impeller discharge flow and the baffles agrees fairly well with experimentally determined data and, moreover, that more than 2/3 of the transferred torsional moment of the baffles as a whole is located in the above mentioned interference area.
Keywords: Rushton turbine impeller, impeller discharge stream, dynamic pressure.
J. John: Nonlinear Continuous System Identification by Means of Multiple Integration II
This paper presents a new modification of the multiple integration method [1, 2, 3] for continuous nonlinear SISO system identification from measured input - output data. The model structure is changed compared with [1]. This change enables more sophisticated systems to be identified. The resulting MATLAB program is available in [4]. As was stated in [1], there is no need to reach a steady state of the identified system. The algorithm also automatically filters the measured data with respect to low frequency drifts and offsets, and offers the user a potent tool for selecting the frequency range of validity of the obtained model.
Keywords: continuous system identification, multiple integration.
H. M. Abd El-Hady, A. Grünwald, K. Vlčková, J. Zeithammerová: Clinoptilolite in Drinking Water Treatment for Ammonia Removal
In most countries today the removal of ammonium ions from drinking water has become almost a necessity. The natural zeolite clinoptilolite is mined commercially in many parts of the world. It is a selective exchanger for the ammonium cation, and this has prompted its use in water treatment, wastewater treatment, swimming pools and fish farming. The work described in this paper provides dynamic data on cation exchange processes in clinoptilolite involving the NH4+, Ca+2 and Mg+2 cations. We used material of natural origin - clinoptilolite from Nižný Hrabovec in Slovakia (particle-size 3-5 mm). The breakthrough capacity was determined by dynamic laboratory investigations, and we investigated the influence of thermal pretreatment of clinoptilolite and the concentration of regenerant solution (2, 5, and 10% NaCl). The concentrations of ammonium ion inputs in the tap water that we used were 10, 5, and 2 mg NH4+ l-1 and down to levels below 0.5 mg NH4+ l-1. The experimental results show that repeated pretreatment sufficiently improves the zeolite's properties, and the structure of clinoptilolite remains unchanged during the loading and regeneration cycles. Ammonium removal capacities were increased by approximately 40 % and 20 % for heat-treated zeolite samples. There was no difference between the regenerates for 10% and 5% NaCl. We conclude that the use of zeolite is an attractive and promising method for ammonium removal.
Keywords: clinoptilolite, zeolite, ion exchange, ammonia removal, drinking water.
D. Dobrovská: Management of People by Managers with a Technical Background - Research Results
In 1999 and 2000, the Masaryk Institute of Advanced studies of CTU in Prague launched a study of the efficiency of human resource management in Czech enterprises, with emphasis on technically educated managers. About 85 managers, each responsible for 5-250 employees assessed their own HRM activities and attitudes and those of their firm. The following aspects were analysed: evaluating individual management areas, assessing the general management standard of the given company, awareness of the company's personnel management policy, manager's own contribution to formulating the company's personnel management strategy, developing job descriptions, using professional methods of employee selection, promoting employees to the status of manager, periodic assessment of employees, training of staff responsible for assessment, employee remuneration and other motivation tools, etc. Results and data analysis are given in the paper. The managers of the Czech companies reviewed are still involved mainly in operating management, and devote limited time to the conceptual work needed in order to formulate an integral company policy in the area of personnel management. On the basis of this analysis, further training for managers with technical education will be designed and organised by the Masaryk Institute of Advanced Studies.
Keywords: human resource management, effectiveness of personnel management, employee selection, employee assessment, motivation tools, broadening employee skills.
H. M. Abd El-Hady, A. Grünwald, K. Vlčková, J. Zeithammerová: Lewatit S100 in Drinking Water Treatment for Ammonia Removal
Ammonium nitrogen is the most important form of nitrogen that can cause excessive algal growth and stimulate eutrophication in surface water. The purpose of this study is to investigate the possibility of removing ammonium from drinking water by means of an ion exchange process. Polymeric Lewatit S100 material (particle-size 0.3-1.2 mm) was used. The breakthrough capacity was determined by dynamic laboratory investigations and the concentration of regenerant solution (5 and 10 % NaCl) was investigated. The concentration of ammonium ion inputs in the tap water that we used were 10, 5 and 2 mg NH4l-1 and down to levels below 0.5 mg NH4+ l-1. The experimental results show that the breakthrough capacity was very small at ammonium concentration 2 mg NH4+ l-1 compared to its breakthrough capacity at ammonium concentration 10 mg NH4+ l-1. There was no difference between regeneration by 10 and 5 % NaCl. We conclude that the use of Lewatit S100 is an attractive and promising method for ammonium concentration greater than 5 mg NH4+ l-1 and till 10 mg NH4+ l-1.
Keywords: Lewatit S100, ion exchange, ammonia removal, drinking water.
J. Drchalová, J. Poděbradská, J. Maděra, R. Černý: Evaluation of Water Resistance and Diffusion Properties of Paint Materials
A simple method is presented for evaluating the water-proofness quality of paints on lining materials. The method is based on measuring the integral capillarity in dependence on time, and then comparing this value to the value determined for the basic lining material. Measurements of the effective water vapor permeability then provide information on the risk of condensation which may increase after applying the paint. A practical application of the method is performed with four Karlocolor paints on glass concrete substrates. All the Karlocolor paints are found to be very effective materials for driven rain protection. The diffusion properties of all the paints are found to be excellent.
Keywords: water-proofness, diffusion coefficient, paints.
Č. Šimáně, M. Vognar, J. Kříž, V. Němec: A Small Transfer and Distribution System for Liquid Nitrogen
A system for remotely controlled filling of small Dewars with liquid nitrogen from a central storage Dewar vessel is described, consisting of a plunger type pump with an electromechanical driver and electromechanical ball type valves for distribution of liquid nitrogen. The preset nitrogen level in the small Dewars is kept constant by automatic refilling. The delivery is adjustable in steps by frequency change from 2.5 to 25 cm3/s, and delivery height up to 2 meters is assured. Keywords: liquid nitrogen, transfer system, solenoid pump, solenoid valve, automatic level control.
I. Fořt, J. Medek, F. Ambros: Erosion Wear of Axial Flow Impellersin a Solid-liquid Suspension
A study was made of the erosion wear of the blades of pitched blade impellers in a suspension of waste gypsum from a thermal power station (vol. concentration CV = 18.3 %, particle mean diameter d = 0.1 mm, degree of hardness "2.5") and silicious sand (CV = 10 %, d = 0.4 mm, degree of hardness "7.5") in water under a turbulent flow regime of agitated charge when complete homogeneity of the suspension was achieved. Experiments were carried out on pilot plant mixing equipment made of stainless steel (diameter of cylindrical vessel T = 390 mm, diameter of impeller D = 100 mm, impeller off-bottom clearance h = 100 mm) equipped with four wall radial baffles (width b = 39 mm) and an impeller with four inclined plane blades (pitch angle a = 20°, 30°, 45°, relative blade width W/D = 0.2) made either of rolled brass (Brinell hardness 40-50 BH) or of structural steel (Brinell hardness 100-120 BH) always pumping the liquid downwards towards the flat vessel bottom. Two erosion process mechanisms appear, depending on the hardness of the solid particles in the suspension: while the particles of gypsum (lower hardness) generate a uniform sheet erosion over the whole surface of the impeller blade, the particles of silicious sand (higher hardness) generate wear of the leading edge of the impeller blades, together with a reduction of the surface of the worn blade. The hardness of the impeller blade also affects the rate of the erosion process: the higher the hardness of the impeller blade, the lower the wear rate of the blade. This study consists of a description of the kinetics of the erosion process of both mechanisms in dependence on the pitch angle of the tested impellers. While the wear of the leading edge of the blade exhibits a monotonous dependence on the pitch angle, the sheet erosion exhibits the maximum rate within the interval of the pitch angles tested aÎá20°; 45°ń. However, generally the pitch angle a = 45° seems to be the most convenient angle of blade inclination when both investigated mechanisms of the blade erosion process are considered at their minimum rate.
Keywords: pitched blade impeller, erosion wear, solid-liquid suspension.
Č. Šimáně, M. Vognar, D. Chvátil: Some Aspects of Profiling Electron Fields for Irradiation by Scattering on Foils
With the use of formulae derived by Moliere and others the angular distributions of electrons scattered on Al foils have been calculated for electron energies E0 = 10, 15, 20, 22 and 25 MeV. Theoretical results are compared with flux density measurements of 22 MeV electrons, scattered by a 0.16 mm Al foil, with a Faraday cup at distances 100 to 150 cm from the beam exit window, and at distances 110 and 130 cm for electrons scattered by Al foils 0.16, 0.26, 0.36, 0.46 and 0.66 mm in thickness. A strong dependence on the beam aperture, due to the broad beam scattering effects in air, was observed. Semiempirical formulae for beam apertures 1.56 and 4.6 degrees were derived, which reproduce well the experimental results of forward peak electron flux density (electrons × cm-2 ×s -1 × mA-1) for 1 mA of total beam current as functions of the distance from the beam exit window and of the thickness of the Al scattering foils.
Keywords: microtron, electron fields, electron scattering, scattering foils.
M. Kopáčková: Critical Length of a Column in View of Bifurcation Theory
The paper investigates nonlinear eigenvalue problem for a vertical homogeneous rod loaded with its own weight only. The critical length of the rod, for which the rod loses its stability, is found by use of bifurcation theory. Dependence of maximal deflections of the rods on their lengths is given.
Keywords: critical length of column, eigenvalue problem, bifurcation theory, approximation of solution, Bessel function.
2 Ashraf El-Shahat Elsayed, A. Grünwald, D. Dvořák: Pollutant Removal from Highway Runoff Using Retention/Detention Units
Highway runoff contains total suspended solids, hydrocarbons, oil and greases, chloride, and other contaminants that are transported in solution and particulate forms to adjacent floodplains, roadside swales, and retention/detention ponds. Oil and grit chambers represent a type of retention/detention unit used for removing heavy particulates and adsorbed hydrocarbon particulates. Storage/sediment units also represent a type of retention/detention unit used for controlling peak flow and removing suspended solids. The aim of this study is to evaluate the effect of traffic volume and site characteristics on highway runoff quality. The study also aims to evaluate the performance of retention/detention units that collect runoff from the Prague-Brno and Prague-Plzeň highways, Czech Republic. The results of this study indicate no definitive relationship between average daily traffic and concentration of runoff constituents, though the site characteristics have a strong relation to some constituents. The results also show that retention/detention units are effective in treating organic compounds.
Keywords: highway runoff, oil/grit chambers, sedimentation, suspended solids, organic.
Hamdy K. Elminir, U. A. Rahuma, V. Benda: Comparison Between Atmospheric Turbidity Coefficients of Desert and Temperate Climates
Knowledge of the solar radiation available on the earth`s surface is essential for the development of solar energy devices and for estimating of their performance efficiencies. For this purpose it is helpful to study the attenuation of direct normal irradiance by the atmosphere, in terms of fundamental quantities, including optical thickness, relative optical air mass, water vapor content, and aerosol amount. In the present article, we will not deal with cloudy atmospheres because of their great variability in space and time, but will focus our attention on atmospheres characterized by the complete absence of condensed water.
The objectives of this article are to report data on aerosol optical depth and atmospheric turbidity coefficients for a desert climate, and to compare them with those of a temperate climate. Aerosol optical depth, the Linke turbidity factor, TL, and Ångström turbidity coefficients, b, are calculated from measurements of broadband filters at Helwan, Egypt, which has a desert climate. A linear regression model is to be determined between the Linke factor and the Ångström turbidity coefficient. This relation is compared with similar relations reported for a temperate climate [Prague, Czech Republic]. This comparison is made to determine whether a universal relation exists between these two important coefficients, or whether the relation is location dependent.
Keywords: energy demand, environmental management, industrial wastes, sulfur dioxide, carbon dioxide, aerosol optical depth, Linke turbidity factor, Ångström turbidity coefficient.
V. Svoboda, D. Šiktancová: Determining the Permeable Efficiency of Elements in Transport Networks
The transport network is simulated by a directed graph. Its edges are evaluated by length (in linear units or time units), by permeability and by the cost of driving through in a transport unit. Its peaks (nodes) are evaluated in terms of permeability, the time of driving through the node in time units and the cost of driving a transport unit (set) through this node.
For such a conception of the transport network a role of optimisation and disintegration of transport flow was formulated, defined by a number of transport units (transport sets). These units enter the network at the initial node and exit the network (or vanish at the defined node). The aim of optimization was to disintegrate the transport flow so that the permeability was not exceeded in any element of the network (edge, nod), so that the relocation of the defined transport flow was completed in a prearranged time and so that the cost of driving through the transport net between the entry and exit knots was minimal.
Keywords: the transport networks, elements in transport network, disintegration of transport flow in transport networks, permeability of elements in transport network, permeability of networks, determining of the permeability of edges, deterministic and stochastic work regimes, systems of queuing theory, a transcendental equation.
M. Vorel, E. Leidich: Accuracy of Determining Stress Intensity Factors in Some Numerical Programs
At present, there are many programs for numerical analysis of cracks, in particular for determining stress intensity factors. Analyses of a single-edge cracked beam and flat plate with a semielliptical surface crack are presented in this study to examine the accuracy and applicability of the Franc2d and Franc3d programs. Further numerical computations of the MARC program and analytical solutions of stress intensity factors were included to compare the results with each other. For this purpose MARC was equipped with special user procedures. The influence of mesh fineness on the results was also investigated in all programs. The distributions of the stress intensity factors show good agreement in quality. The maximum deviations from the analytical solutions are 9.7 %. With greater numbers of elements programs Franc2d and Franc3d showed some instability, which currently reduces the usefulness and reliability of these promising tools for engineering applications.
Keywords: fracture mechanics, stress intensity factors, numerical programs.
Hamdy K. Elminir, V. Benda, I. Kudláček: Actual Optical and Thermal Performance of Photovoltaic Modules
Field testing is costly, time-consuming and depends heavily on prevailing weather conditions. Adequate security and weather protection must also be provided at the test site. Delays can be caused due to bad weather and system failures. To overcome these problems, a photovoltaic array simulation may be used. In any simulation scheme involving photovoltaic systems, one important choice is the selection of a mathematical model.
In the literature several approaches to the problem have been made. Most procedures designed for this purpose are based on analytical descriptions of the physical mechanisms inside the solar cell that can be represented by a circuit diagram with discrete components, like a two-exponential model. Such simulators have some merits. However, their limited flexibility in readily simulating the influence of solar radiation, temperature and various array parameters is a serious drawback that has been noted. To get more accurate results in predicting the actual performance of photovoltaic modules, the parameters influencing incoming (optical parameters) and outgoing power flow (electrical and thermal parameters) were investigated by simulation and by some verifying experiments, to get a closer insight into the response behavior of this element, and to estimate the overall performance as well as optimization of the parameters.
Keywords: solar radiation, reflection losses, radiation shape factor, radiative surface area, temperature distribution, emissivity, isotropic model, Hay and Klucher's anisotropic models.
Š. Hošková, O. Kapičková, K. Trtík, F. Vodák: Effect of Thermal Cycling on the Strength and Texture of Concrete for Nuclear Safety Structures
The effect of thermal cycling (freezing and thawing) on the texture and strength of two types of concrete is studied:
1. Concrete used for a containment structure at NPP Temelín (Czech Republic) - so-called TEMELÍN concrete.
2. Highly resistant PENLY concrete, which was used as a standard because of its high quality, proved by the research carried out in a European Commission project. The results for the two samples of concrete are compared.
Keywords: Concrete, thermal cycling, texture, strength, porosity.
M. Kalousková, E. Novotná, J. Šejnoha: Reliability - Based Designof Precast Buildings
We present a numerical analysis of a precast structure regarding random properties of the material characteristics of joints, as well as the random character of loading, especially due to temperature impact. Using FEM we compare some of our results with a deterministic nonlinear solution.
Keywords: reliability, precast buildings, joints of panels, two-parameter subgrade, reliability index.
V. Tesař: Two-equation Turbulence Model Similarity Solution of the Axisymmetric Fluid Jet
This paper presents a general, universally valid solution of axisymmetric turbulent submerged jet flow, for which no fully satisfactory solution has been known. What has been available so far are either computational solutions for individual particular cases, lacking universality, or similarity solutions with inadequate turbulence models, some of them based upon assumptions of a speculative character (e.g. constant mixing length across the jet profile). The present approach uses a similarity transformation of the governing equations, which incorporate an advanced turbulence model. The results are shown to be in excellent agreement with available experimental data. The new solution provides a suitable basis for analysis of enigmatic aspects of axisymmetric jets, such as their "spreading anomaly".
Keywords: jet, axisymmetric jet, turbulence, turbulence modelling, two-equation model, similarity solution, fluctuation energy, turbulence dissipation rate, turbulence length scale.
G. Böszörményi, L. Böszörményi: Some Problems of the Integration of Heat Pump Technology into a System of Combined Heat and Electricity Production
The closure of a part of the municipal combined heat and power (CHP) plant of Košice city would result in the loss of 200 MW thermal output within a realtively short period of time. The long term development plan for the Košice district heating system concentrates on solving this problem. Taking into account the extremely high (90 %) dependence of Slovakia on imported energy sources and the desirability of reducing the emission of pollutantst the alternative of supplying of 100 MW thermal output from geothermal sources is attractive. However the indices of economic efficiency for this alternative are unsatisfactory. Cogeneration of electricity and heat in a CHP plant, the most efficient way of supplying heat to Košice at the present time. If as planned, geothermal heat is fed directly into the district heating network the efficiency would be greatly reduced. An excellent solution of this problem would be a new conception, preferring the utilization of geothermal heat in support of a combined electricity and heat production process. The efficiency of geothermal energy utilization could be increased through a special heat pump. This paper deals with several aspects of the design of a heat pump to be integrated into the system of the CHP plant.
Keywords: geothermal energy, ejector, heat pump.
M. Vognar, M. Fišer, Č. Šimáně, D. Chvátil: Filling and Recycling Apparatus of a Cyclotron Target with Enriched Krypton for Production of Radiopharmaceuticals
An apparatus for multiple filling of a cyclotron target with enriched Kr gas is described. The system is based on recycling pressurized gas by cryogenic pumping between the target tube and storage containers. The design and construction makes use of previous experience in the construction and operation of two analogue apparatuses for Xe124 high pressure gas targets, but major modifications have been incorporated, evoked by the different physical properties of Kr, by the character of the nuclear reaction, and by the demand for automation from the side of the end user.
Keywords: generator, Kr gas target, 36K82(p, 2n) 37Rb81 reaction.
3 M. Safan, A. Kohoutková: Influence of Different Drying Conditions on High Strength Concrete Compressive Strength
The influence of different drying conditions on the compressive strength and strength development rates of high strength concrete up to an age of 28 days was evaluated. Two HSC mixes with and without silica fume addition were used to cast cubes of 10 cm size. The cubes were stored in different drying conditions until the age of testing at 3, 7, 28 days.
Keywords: high strength concrete, curing conditions, silica fume, high range water reducers.
J. Kaiser, E. Košťál: Colorimetry and TV Colour Splitting Systems
The colorimetric standard of the present-day television system goes back to the American NTSC system from 1953. In this RGB colorimetric system it is not possible, for basic reasons, to produce a scanning device which will provide signals suitable for controlling any displayed unit. From the very beginning of the television system the scanning device has produced inevitable colour deformation. The range of reproductive colours is not fully utilized either by a contemporary Cathode Ray Tube display unit or by a Liquid Crystal Display. In addition, the range is not sufficient for true reproduction of colours. Specific technical and scientific applications in which colour bears a substantial part of the information (cosmic development, medicine) demand high fidelity colour reproduction. The colour splitting system, working in the RGB colorimetric system, continues to be universally used. This article submits the results of a design for a colour splitting system working in the XYZ colorimetric system (hereafter referred to as the XYZ prism). A way to obtain theoretical spectral reflectances of partial XYZ prism filters is briefly described. These filters are then approximated by real optical interference filters and the geometry of the XYZ prism is established.
Keywords: TV colorimetry, colour splitting system, interferential filters, TV reproduction, colour gamut.
M. Safan, A. Kohoutková: Experiments with Externally Prestressed Continuous Composite Girders
Steel-concrete composite girders have attractive potentials when applied in bridge construction. The serviceability performance of continuous composite girders is becoming more and more a deterministic parameter in the design of this type of structures. An effective method for improving this performance is to apply prestressing to control or completely eliminate concrete deck cracking caused by static and time dependent actions. Little literature has been found addressing the experimental analysis of continuous girders prestressed by means of external deviated tendons. The current research aims to investigate the behavior of a double-span steel composite beam externally prestressed by means of continuous tendons in terms of cracking characteristics, load deflection response, and load carrying capacity. The efficiency of prestressing is evaluated by comparing the results to those of a non-prestressed beam with similar cross sections and spans.
Keywords: composite steel-concrete beams, serviceability, external prestressing, deviated tendons.
A. K. Haghi: Investigation into Airborne Dust ina Wool Textile Mill
Airborne dust samples were gathered from the vicinity of various commonly performed processes in the wool-preparation industry. Samples of airborne wool dust were collected on membrane filters during the processing of wool lots. The chemical composition of the inorganic particles present in the total inspirable and respirable dust fractions was determined with the use of a Scanning Electron Microscope (SEM). The widely differing morphologies of the particles collected raise questions about the validity of trying to correlate minor respiratory symptoms with dust concentrations, as some particle types will penetrate the respiratory system more easily than others. The results are discussed with respect to the sampling methodology used.
Keywords: airborne dust, wool, textile mill, SEM.
Ashraf Fouad Hafez Ismail: Evolved Representation and Computational Creativity
Advances in science and technology have influenced designing activity in architecture throughout its history. Observing the fundamental changes to architectural designing due to the substantial influences of the advent of the computing era, we now witness our design environment gradually changing from conventional pencil and paper to digital multi-media. Although designing is considered to be a unique human activity, there has always been a great dependency on design aid tools. One of the greatest aids to architectural design, amongst the many conventional and widely accepted computational tools, is the computer-aided object modeling and rendering tool, commonly known as a CAD package. But even though conventional modeling tools have provided designers with fast and precise object handling capabilities that were not available in the pencil-and-paper age, they normally show weaknesses and limitations in covering the whole design process.
In any kind of design activity, the design worked on has to be represented in some way. For a human designer, designs are for example represented using models, drawings, or verbal descriptions. If a computer is used for design work, designs are usually represented by groups of pixels (paintbrush programs), lines and shapes (general-purpose CAD programs) or higher-level objects like ‘walls’ and ‘rooms’ (purpose-specific CAD programs).
A human designer usually has a large number of representations available, and can use the representation most suitable for what he or she is working on. Humans can also introduce new representations and thereby represent objects that are not part of the world they experience with their sensory organs, for example vector representations of four and five dimensional objects. In design computing on the other hand, the representation or representations used have to be explicitly defined. Many different representations have been suggested, often optimized for specific design domains or design methods, but each individual computational design system has only one or very few different representations available.
Whatever the choice of the representation, it is likely to influence the outcome of the design process. In any representation, some designs may be more difficult to represent than others, and some designs may not be representable at all.
The same applies if the design process is implemented in a computer program. If a design cannot be represented with a given representation, it cannot be the outcome of a design process using this representation. As is the case for human designers, it is also possible that the representation influences a computational design process such that it is easier for the program to find some designs than others. Depending on the design process used, this might make those designs a more likely outcome of the design process. This is for example the case with stochastic optimization processes, like evolutionary systems and simulated annealing. In these cases, the representation is likely to introduce a bias into the design process.
The selection of the representation is therefore of high importance in the development of a computational design system. Obviously, while choosing the representation the programmer has to ensure that all or as many as possible potentially ‘interesting’ designs can be represented. But it is also generally desirable to minimize the bias introduced by the representation. In contrast to the user-provided design criteria, the bias caused by the representation influences the outcome of the design process in an implicit way which is not obvious to the user, and is difficult to predict and control.
The idea developed in this research is that it is possible to turn the bias caused by the representation into a virtue, by deliberately choosing or modifying the representation to influence the design process in a certain desired way. The resulting ‘focusing’ of the search process is connected to the idea of ‘expansion of search spaces’, a notion used in some definitions of computational creativity. Both ‘focusing’ and ‘expansion of search space’ will be explored in this research.
Keywords: computational creativity, evolved representation, design processes, evolutionary algorithms, search space.
J. Bokr, V. Jáneš: A Logic Object and its State
This paper shows not only that the state of an objecty parameterizes the dyad (stimulus, response) but that it is also the performer of the state transition initiated by the stimulus. Thus, the logic object is a feedback composition of the logic pseudoobject and the static logic object. It is also stated that, without considering the new role of the state, the content of the concept "state" cannot be completely explained. The current intuitive conception of canonical decomposition of an entity is confronted with the exactly introduced decomposition and with the mentioned division of the logic object into a pseudoobject and a static object.
Keywords: logic object, pseudoobject, division, canonic decomposition, delay, state.
Ashraf El-Shahat Elsayed, A. Grünwald, M. Synáčková, M. Slavíček: Modelling of Highway Runoff Quantity and Quality
The stormwater Management Model (SWMM) is a well-known stormwater runoff-simulation model. It is a deterministic, spatially distributed model for calculation of runoff quantity and quality. The aim of this study was to predict highway runoff characteristics using data from different highway catchments. The SWMM was used in the simulation process and the predicted data was verified using monitoring data collected from Prague-Plzeň highway for both total suspended solids and organic compounds. The analyzed data indicated that the simulated TSS, BOD5 concentrations lie within the range of the measured data and both data sets are considered highly polluted with respect to the specification limits. The analyzed data also show that the first flush of runoff is the most polluted, and is responsible for contamination of retention and/or received waters.
Keywords: Stormwater Management Model, highway runoff, quantity, quality, first flush.
Ashraf Fouad Hafez Ismail: Class Representation of Shapes Using Qualitative-codes
This paper introduces our qualitative shape representation formalism that is devised to overcome, as we have argued, the class abstraction problems created by numeric schemes. The numeric shape representation method used in conventional geometric modeling systems reveals difficulties in several aspects of architectural designing. Firstly, numeric schemes strongly require complete and detailed information for any simple task of object modeling. This requirement of information completeness makes it hard to apply numeric schemes to shapes in sketch level drawings that are characteristically ambiguous and have non-specific limitations on shape descriptions. Secondly, Cartesian coordinate-based quantitative shape representation schemes show restrictions in the task of shape comparison and classification that are inevitably involved in abstract concepts related to shape characteristics. One of the reasons why quantitative schemes are difficult to apply to the abstraction of individual shape information into its classes and categories is the uniqueness property, meaning that an individual description in a quantitative scheme should refer to only one object in the domain of representation. A class representation, however, should be able to indicate not only one but also a group of objects sharing common characteristics. Thirdly, it is difficult or inefficient to apply numeric shape representation schemes based on the Cartesian coordinate system to preliminary shape analysis and modeling tasks because of their emphasis on issues, such as detail, completeness, uniqueness and individuality, which can only be accessed in the final stages of designing. Therefore, we face the need for alternative shape representation schemes that can handle class representation of objects in order to manage the shapes in the early stages of designing. We consider shape as a boundary description consisting of a set of connected and closed lines. Moreover, we need to consider non-numeric approaches to overcome the problems caused by quantitative representation approaches.
This paper introduces a qualitative approach to shape representation that is contrasted to conventional numeric techniques. This research is motivated by ideas and methodologies from related studies such as in qualitative formalism ([4], [6], [19], [13], [31]), qualitative abstraction [16], qualitative vector algebra ([7], [32]), qualitative shapes ([18], [23], [21]), and coding theory ([20], [25], [26], [1], [2], [3], [22]). We develop a qualitative shape representation scheme by adopting propitious aspects of the above techniques to suit the need for our shape comparison and analysis tasks. The qualitative shape-encoding scheme converts shapes into systematically constructed qualitative symbols called Q-codes. This paper explains how the Q-code scheme is developed and applied.
Keywords: class representation, shape, qualitative-codes, scheme, properties of qualitative values, linguistic analogy.
A. Grünwald, B. Šťastný, K. Slavíčková, M. Slavíček: Effect of the Distribution System on Drinking Water Quality
The overall objective of this paper is to characterise the main aspects of water quality deterioration in a distribution system. The effect of residence time on chlorine uptake and the formation and evolution of disinfection by-products in distributed drinking water are discussed.
Keywords: drinking water, distribution system, chlorine uptake, THM and HAA formation.
A. K. Haghi: A Mathematical Model of theDrying Process
A convective drying model is proposed which may be used to describe the drying behavior of leather. Using this model, the calculated transient leather temperature agrees well with experimental values. Variations in temperature and moisture content distribution are solved using the finite-difference method. The effects of operation parameters, such as temperature and humidity in the dryer, initial moisture content of the leather, and heat and mass transfer coefficients are examined using the model.
Keywords: convectiv drying model, leather, transient temperature field.
4 S. Vukazich, P. Marek: Structural Design Using Simulation Based Reliability Assessment
The concept of Simulation Based Reliability Assessment (SBRA) for Civil Engineering structures is presented. SBRA uses bounded histograms to represent variable material and geometric properties as well as variable load effects, and makes use of the Monte Carlo technique to perform a probability-based reliability assessment. SBRA represents a departure from the traditional deterministic and semi-probabilistic design procedures applied in codes and as such requires a "re-engineering" of current assessment procedures in accordance with the growing potential of computer and information technology. Three simple examples of how SBRA can be used in Structural Engineering design are presented: 1) the reliability assessment of a steel beam, 2) a truss bar subjected to variable tension and compression, and 3) the pressure on the wall of an elevated water tank due to earthquake load.
Keywords: Structural Engineering, Reliability Assessment, Monte Carlo Method.
F. Schieck, D. Schmitt: Cargo Aircraft Conceptual Design Optimisation Using a Flexible Computer-Based Scaling Approach
In the early design stages of a new aircraft, there is a strong need to broaden the knowledge base of the evolving aircraft project, allowing a profound analysis of the solution concepts and of the design driving requirements. The methodology presented in this paper provides a tool for increasing and improving in an exemplary manner the necessary information on cargo aircraft. By exchanging or adapting a few particular modules of the entire program system, the tool is applicable to a range scale of different aircraft types. In an extended requirement model, performance requirements are represented along with other operational requirements. An aircraft model is introduced in sufficient detail for conceptual design considerations. The computer-aided scaling methodology is explained, which, controlled by an optimisation module, automatically resizes the aircraft model until it optimally satisfies the requirements in terms of a selectable figure of merit. Typical results obtained at the end of the scaling are discussed together with knowledge gained during the process, and an example is given.
Keywords: aircraft conceptual design, aircraft scaling, mass growth factor, aircraft multidisciplinary design optimisation.
A. Strohmayer: Improving Aircraft Design Robustness with Scenario Methods
Compared to other industries, the aerospace sector is characterized by long product cycles in a very complex environment. The aircraft manufacturer has to base his product strategy on a long-term view of risks and opportunities in the transport industry but he cannot predict the development of relevant factors in this market environment with any certainty. In this situation, scenario methods offer a pragmatic way to limit the uncertainties and to work them up methodically, in order to derive recommendations for cost-intensive strategic decisions like for example the go-ahead for a new aircraft concept. By including scenario methods in the aircraft design cycle, the ‘design robustness’ can be improved, i.e. the design is not optimised for a prognosticated operating environment, but can cope with various possible future developments. The paper will explain the three fundamental aspects in applying scenario planning to the aircraft design process: requirement definition, design evaluation and technology identification. For each aspect, methods will be shown, which connect the rather qualitative results of a scenario process with aircraft design, which typically demands a qualitative input.
Keywords: aircraft design, scenario methods, requirements, design evaluation, technology strategy.
J. Marková, M. Holický: Credibility of Design Procedures
Theory of structural reliability enables comprehensive analysis of structural elements with respect to various limit states, and provides valuable insights into the methodology of applied standards. In addition to reliability analysis of the structural element, a new concept of the credibility of theoretical models used to calculate the design value of basic variables is introduced. The presented example of structural verification for limit states of cracking shows that the credibility of commonly applied formulas and reliability of a reinforced concrete slab have a great scatter and are in some cases inadequate.
Keywords: credibility of design procedures, reliability of elements, basic variables, model uncertainties, probability of failure, reliability index.
J. Friedl: Aerodynamic Design of a Tailless Aeroplan
The paper presents an aerodynamic analysis of a one-seat ultralight (UL) tailless aeroplane named L2k, with a very complicated layout. In the first part, an autostable airfoil with a low moment coefficient was chosen as a base for this problem. This airfoil was refined and modified to satisfy the design requirements. The computed aerodynamic characteristics of the airfoils for different Reynolds numbers (Re) were compared with available experimental data. XFOIL code was used to perform the computations. In the second part, a computation of wing characteristics was carried out. All calculated cases were chosen as points on the manoeuvring and gust envelope. The vortex lattice method was used with consideration of fuselage and winglets for very complicated wing geometry. The PMW computer program developed at IAE was used to perform the computations. The computed results were subsequently used for structural and strength analysis and design.
Keywords: aviation, aerodynamics, tailless aeroplane, airfoil, wing.

J. Vacek: Stress Distribution in a Coal Seam before and after Bump Initiation
This paper deals with to the behaviour of open rock that occurs, for example, during longwall mining in coal mines, in deep tunnel, or shaft excavation.
Longwall instability leads to extrusion of rock mass into an open space. This effect is mostly referred to as a bump, or a rock burst. For bumps to occur, the rock has to possess certain particular rock burst properties leading to accumulation of energy and the potential to release this energy. Such materials may be brittle, or the bumps may arise at the interfacial zones of two parts of the rock, that have principally different material properties.
The solution is based on experimental and mathematical modelling. These two methods have to allow the problem to be studied on the basis of three presumptions:
– the solution must be time dependent
– the solution must allow the creation of crack in the rock mass
– the solution must allow an extrusion of rock into an open space (bump effect)
Keywords: rock bursts, bumps, mining, rock mechanics, mathematics and physical modelling.
R. Menzies: Computational Investigation of Flows in Diffusing S-shaped Intakes
This paper examines the flow in a diffusing s-shaped aircraft air intake using computational fluid dynamics (CFD) simulations. Diffusing s-shaped ducts such as the RAE intake model 2129 (M2129) give rise to complex flow patterns that develop as a result of the offset between the intake cowl plane and engine face plane. Euler results compare favourably with experiment and previous calculations for a low mass flow case. For a high mass flow case a converged steady solution was not found and the problem was then simulated using an unsteady flow solver. A choked flow at the intake throat and complex shock reflection system, together with a highly unsteady flow downstream of the first bend, yielded results that did not compare well with previous experimental data. Previous work had also experienced this problem and a modification to the geometry to account for flow separation was required to obtain a steady flow.
RANS results utilising a selection of turbulence models were more satisfactory. The low mass flow case showed good comparison with experiment and previous calculations. A problem of the low mass flow case is the prediction of secondary flow. It was found that the SST turbulence model best predicted this feature. Fully converged high mass flow results were obtained. Once more, SST results proved to match experiment and previous computations the best. Problems with the prediction of the flow in the cowl region of the duct were experienced with the S-A and k-w models. One of the main problems of turbulence closures in intake flows is the transition of the freestream from laminar to turbulent over the intake cowl region. It is likely that the improvement in this prediction using the SST turbulence model will lead to more satisfactory results for both high and low mass flow rates.
Keywords: aerodynamics, computational fluid dynamics, internal flows, turbulence models.
D. Kolman: Analysis of a Thermal Plasma Diamond CVD System
This paper deals with the analysis of a typical engineering system utilizing thermal plasma - a system for Diamond Chemical Vapor Deposition. It defines the system - a slightly overexpanded plasma jet impinging at a downstream -located substrate, outlines the theoretical description of the system - the Navier-Stokes and species conservation equations, and presents key theoretical results on the major and most troublesome factors influencing diamond deposition - velocity and temperature of the jet. Then, the paper demostrates the necessity to shift from a laminar to a turbulent flow description and compares both results to experiments. An explanation of the remaining discrepancy - insufficient velocity drop in the jet - is attempted.
Keywords: modeling, thermal plasma, CVD.
A. Chlupová, J. Heger, A. Vašek: Fatigue Crack Initiation and Early Growth in GLARE 3 Fiber-metal Laminate Subjected to Mixed Tensile and Bending Loading
A special open-hole sheet specimen of GLARE fiber-metal laminate was used to simulate mixed loading similar to the loading of a riveted hole in a real fuselage skin structure. The effect of cyclic tension and secondary bending loading was studied. The notch region was observed through a microscope in order to detect the first fatigue crack initiation during fatigue loading. The number of cycles prior to crack initiation was measured, and the crack growth rate in the surface layer of the laminate was evaluated. The specimens were subjected to fatigue damage investigation in the inner layers of the laminate after termination of the test. A significant effect of secondary bending on fatigue crack initiation and early crack growth was found. The experimental results are discussed in terms of local stress-strain conditions in the notch region evaluated by means of finite element calculation.
Keywords: laminate, composite, fatigue, mixed loading, finite element modeling.

J. Macek, M. Takáts: Involvement of Thermodynamic Cycle Analysis in a Concurrent Approach to Reciprocating Engine Design
A modularised approach to thermodynamic optimisation of new concepts of volumetric combustion engines concerning efficiency and emissions is outlined. Levels of primary analysis using a computerised general-change entropy diagram and detailed multizone, 1 to 3-D finite volume methods are distinguished. The use of inverse algorithms based on the same equations is taken into account.
Keywords: internal combustion engine, thermodynamic optimisation, simulation, configuration design.
D. J. Murray-Smith: The Validation of Computer-based Models in Engineering: Some Lessons from Computing Science
Questions of the quality of computer-based models and the formal processes of model testing, involving internal verification and external validation, are usually given only passing attention in engineering reports and in technical publications. However, such models frequently provide a basis for analysis methods, design calculations or real-time decision-making in complex engineering systems. This paper reviews techniques used for external validation of computer-based models and contrasts the somewhat casual approach which is usually adopted in this field with the more formal approaches to software testing and documentation recommended for large software projects. Both activities require intimate knowledge of the intended application, a systematic approach and considerable expertise and ingenuity in the design of tests. It is concluded that engineering degree courses dealing with modelling techniques and computer simulation should put more emphasis on model limitations, testing and validation.
Keywords: computer-based models, simulation, model limitations, software testing, external validation, software engineering tools.
T. Vyhlídal, P. Zítek: Control System Design Based on a Universal First Order Model with Time Delays
An original modelling approach for SISO systems is presented, based on a first order model with more than one delay in its structure. By means of this model it is possible truly to hit off the properties of systems which are conventionally described by higher order models. The identification method making use of a relay feedback test combined with transient responses of the system has proved to be suitable for assessing the model parameters. With respect to its plain structure the model is well suited to be applied in the framework of an internal model control scheme (IMC). The resultant control algorithm with only one optional parameter is very simple and can easily be implemented, for example by means of a programmable controller (PLC).
Keywords: time delay system, internal model control, system eigenvalues, control parameter setting.
E. Alfaro-Cid, E. W. McGookin, D. J. Murray-Smith: Genetic Algorithm Optimisation of a Ship Navigation System
The optimisation of the PID controllers' gains for separate propulsion and heading control systems of CyberShip I, a scale model of an oil platform supply ship, using Genetic Algorithms is considered. During the initial design process both PID controllers have been manually tuned to improve their performance. However this tuning approach is a tedious and time consuming process. A solution to this problem is the use of optimisation techniques based on Genetic Algorithms to optimise the controllers' gain values. This investigation has been carried out through computer-generated simulations based on a non-linear hydrodynamic model of CyberShip I.
Keywords: Ship control, PID controller, Genetic Algorithm optimisation.
J. Pohl, A. Warell, P. Krus, J.-O. Palmberg: Conceptual Design of a Hydraulic Valve Train System
Variable valve train systems have been brought into focus during recent years as a means to decrease fuel consumption in tomorrow's combustion engines. In this paper an integrated approach, called simulation driven experiments, is utilised in order to aid the development of such highly dynamic systems. Through the use of systematic design methodology, a number of feasible concepts are developed. Critical components are subsequently identified using simulation. In this approach, component behaviour is simulated and validated by measurements on prototype components. These models are unified with complete system models of hydraulically actuated valve trains. In the case of the valve trains systems studied here component models could be validated using comparably simple test set-ups. These models enable the determination of non-critical design parameters in an optimal sense. This results in a number of optimised concepts facilitating an impartial functional concept selection.
Keywords: simulation, simulation based optimisation, conceptual design, valve train system.
C. Munro, P. Krus: Rapid Prediction of Configuration Aerodynamics in the ConceptualDesign Phase
Conceptual aircraft design is characterised by the requirement to analyse a large number of configurations rapidly and cost effectively. For unusual configurations such as those typified by unmanned combat air vehicles (UCAVs) adequately predicting their aerodynamic characteristics through existing empirical methods is fraught with uncertainty. By utilising rapid and low cost experimental tools such as the water tunnel and subscale flight testing it is proposed that the required aerodynamic characteristics can rapidly be acquired with sufficient fidelity for the conceptual design phase. Furthermore, the initial design predictions can to some extent be validated using flight-derived aerodynamic data from subscale flight testing.
Keywords: aircraft design, UAV, water tunnel, flight testing.
M. Holický: Prospects for Advanced Engineering Design Based on Risk Assessment
Current approaches to the design of structures are based on the concept of target probability of failure. This value is, however, often specified on the basis of comparative studies and past experience only. Moreover, the traditional probabilistic approach cannot properly consider gross errors and accidental situations, both of which are becoming more frequent causes of failure. This paper shows that it is useful to supplement a probabilistic design procedure by a risk analysis and assessment, which can take into account the consequences of all unfavourable events. It is anticipated that in the near future advanced engineering design will include criteria of acceptable risks in addition to the traditional probabilistic conditions.
Keywords: reliability, hazard situations, adverse events, costs, risk assessment, Bayessian network, advanced engineering design.
6 T. Ficker, J. Myslín, Z. Podešvová: Non-linear Temperature Profiles
Non-linear temperature profiles caused by temperature-dependent thermal conductivity l(T) of wall materials are discussed. Instead of conventional thermal resistance, modified effective resistance has been introduced.
Keywords: temperature profile in building structures, temperature-dependent thermal conductivity, Fourier's thermal laws.
Abdel-Fattah Attia, P. Horáček: Modeling Nonlinear Systems by a Fuzzy Logic Neural Network Using Genetic Algorithms
The main aim of this work is to optimize the parameters of the constrained membership function of the Fuzzy Logic Neural Network (FLNN). The constraints may be an indirect definition of the search ranges for every membership shape forming parameter based on 2nd order fuzzy set specifications. A particular method widely applicable in solving global optimization problems is introduced. This approach uses a Linear Adapted Genetic Algorithm (LAGA) to optimize the FLNN parameters. In this paper the derivation of a 2nd order fuzzy set is performed for a membership function of Gaussian shape, which is assumed for the neuro-fuzzy approach. The explanation of the optimization method is presented in detail on the basis of two examples.
Keywords: genetic algorithms, fuzzy logic neural network, 2nd order fuzzy sets.
F. I. Younis, A. El-Bassuny Alawy, B. Šimák, M. S. Ella, M. A. Madkour: Stellar Image Interpretation System using Artificial Neural Networks: Unipolar Function Case
An artificial neural network based system for interpreting astronomical images has been developed. The system is based on feed-forward Artificial Neural Networks (ANNs) with error back-propagation learning. Knowledge about images of stars, cosmic ray events and noise found in images is used to prepare two sets of input patterns to train and test our approach. The system has been developed and implemented to scan astronomical digital images in order to segregate stellar images from other entities. It has been coded in C language for users of personal computers. An astronomical image of a star cluster from other objects is undertaken as a test case. The obtained results are found to be in very good agreement with those derived from the DAOPHOTII package, which is widely used in the astronomical community. It is proved that our system is simpler, much faster and more reliable. Moreover, no prior knowledge, or initial data from the frame to be analysed is required.
Keywords: neural networks, knowledge-based system, stellar images, image processing.
M. Badawy, K. Richta: Deriving Triggers from Integrity Constraint Specifications in the Database Management Systems
Supporting integrity constraints is essential for database systems. Integrity constraints are used to ensure that the data in a database complies with rules that have been set to establish accurate and acceptable information for a database. Triggers provide a very powerful and flexible means to realize effective constraint enforcing mechanisms. Implementing triggers based on constraint specifications follows some simple rules that are basically independent of a particular commercial database system. This paper gives these rules, which can be used to derive triggers from constraint specifications. A comparison of advantages of constraints and triggers is also given in this paper.
Keywords: database design, integrity constraints specifications, triggers.
J. Filip: Analytical Model of Modified Traffic Control in an ATM Computer Network
The ABR class of ATM computer networks uses feedback information that is generated by net switches and destination and is sent back to a source of data to control the net load. A modification of the standard traffic management of the ATM network is presented, based on the idea of using RM cells to inform the source about congestion. An analytical model of a net switch is designed and mathematical relations are presented. The probability of queueing is considered. The analytical model of the switch was constructed for the purpose of analysing the network behaviour. It is used for investigating of cells passing through the network. We describe the model below. The submitted analytical results show that this method reduces congestion and improves throughput.
Keywords: Throughput, congestion control, modelling, RM cell, cell refusal.
O. Pokorná, D. Mocková: Models of Financing and Available Financial Resources for Transport Infrastructure Projects
A typical feature of transport infrastructure projects is that they are expensive and take a long time to construct. Transport infrastructure financing has traditionally lain in the public domain. A tightening of many countries' budgets in recent times has led to an exploration of alternative resources for financing transport infrastructures. A variety of models and methods can be used in transport infrastructure project financing. The selection of the appropriate model should be done taking into account not only financial resources but also the distribution of construction and operating risks and the contractual relations between the stakeholders. Keywords: transport infrastructure, project financing, financial resources, models of financing, investments, PPP (Public - Private Partnership)
J. Římal: Measurement of Temperature Fields in Long Span Concrete Bridges
This paper deals with assesing of the influence of climate temperatures on deformations and stresses in a cross section of the Nusle Bridge. The main purpose is to describe the measurement of the thermal fields, to compare measured and computed temperature fields, and to provide a real estimation of the stresses that occur.
Keywords: Nusle bridge in Prague, measurement of thermal fields, calculation of temperature fields, evaluation of stress fields.
L. Böszörményi, G. Böszörményi: A Geothermal Energy Supported Gas-steam Cogeneration Unit as a Possible Replacement for the Old Part of a Municipal CHP Plant (TEKO)
The need for more intensive utilization of local renewable energy sources is indisputable. Under the current economic circumstances their competitiveness in comparison with fossil fuels is rather low, if we do not take into account environmental considerations. Integrating geothermal sources into combined heat and power production in a municipal CHP plant would be an excellent solution to this problem. This concept could lead to an innovative type of power plant - a gas-steam cycle based, geothermal energy supported cogeneration unit.
Keywords: geothermal energy, combined heat and power plant, heat pump, waste heat boiler, district heating network
K. R. Beshay, J. Kratěna, I. Fořt, O. Brůha: Power Input of High-Speed Rotary Impellers
This paper presents the results of an experimental investigation of the power input of pitched blade impellers and standard Rushton turbine impellers in a cylindrical vessel provided with four radial baffles at its wall under a turbulent regime of flow of an agitated liquid. The influence of the geometry of the pitched blade impellers (pitch angle, number of blades) and the off-bottom impeller clearance of both high-speed impellers tested on the impeller power input is determined in two sizes of the cylindrical vessel (0.3 m and 0.8 m diameter of vessel). A strain gauge torquemeter is used in the small vessel and a phase shift mechanical torquemeter is used in the large vessel. All results of the experiments correspond to the condition that the Reynolds number modified for the impeller exceeds ten thousand. The results of this study show that the significant influence of the separating disk thickness of the turbine impeller corresponds fairly well to the empirical equations presented in the literature. Both the influence of the number of impeller blades and the blade pitch angle of the pitched blade impeller were expressed quantitatively by means of the power dependence of the recently published correlations: the higher the pitch angle and the number of blades, the higher the values of the impeller power input. Finally, it follows from results of this study that the impeller off-bottom clearance has a weak influence on the power input of the Rushton turbine impeller, but with decreasing impeller off-bottom clearance the power input of the pitched blade impeller increases significantly.
Keywords: impeller power input, Rushton turbine, pitched blade impeller.
J. Doubek, M. Kreidl: Parasitic Events in Envelope Analysis
Envelope analysis allows fast fault location of individual gearboxes and parts of bearings by repetition frequency determination of the mechanical catch of an amplitude-modulated signal. Systematic faults arise when using envelope analysis on a signal with strong changes. The source of these events is the range of function definition of used in convolution integral definition. This integral is used for Hilbert image calculation of analyzed signal. Overshoots (almost similar to Gibbs events on a synthetic signal using the Fourier series) are result from these faults. Overshoots are caused by parasitic spectral lines in the frequency domain, which can produce faulty diagnostic analysis.
This paper describes systematic arising during faults rising by signal numerical calculation using envelope analysis with Hilbert transform. It goes on to offer a mathematical analysis of these systematic faults.
Keywords: gearbox, bearing, envelope analysis, Hilbert transform, parasitic spectral lines.
I. Fořt, T. Jirout, F. Rieger, R. Allner, R. Sperling: Study of the Blending Efficiency of Pitched Blade Impellers
This paper presents an analysis of the blending efficiency of pitched blade impellers under a turbulent regime of flow of an agitated low viscous liquid. The conductivity method is used to determine of the blending (homogenization) time of miscible liquids in pilot plant mixing equipment with standard radial baffles. For the given homogeneity degree (98 %) a three-blade pitched blade impeller is tested with various off-bottom clearances, vessel/ impeller diameter ratios and various impeller pitch angles.
The experimental results show in accordance with theoretical data from the literature, that the greatest effect on the dimensionless blending time is exhibited by the vessel/ impeller diameter ratio and the impeller pitch angle. The number of total circulations necessary for reaching the chosen homogeneity degree depends on the impeller pitch angle and amounts more than three. Finally, the energetic efficiency of the blending process is calculated. The results of this study show, that the highest energetic efficiency of the three-blade pitched blade impeller appears for the pitch angle a = 24°, the impeller/vessel diameter ratio T/D = 2 and the impeller off-bottom clearance h/D = 1.
Keywords: pitched blade impeller, blending of liquids, degree of homogeneity, turbulent flow.
F. Rieger: Power Characteristics of a Screw Agitator in a Tube
Screw agitators rotating in tubes are very efficient tools for mixing and pumping viscous liquids. The power characteristic of the agitator-tube assembly must be known to enable its power consumption in a given configuration to be calculated. The dimensionless power characteristic is described by Eq. (6). An estimate of power consumption from the power characteristic is schematically shown in Fig. 1. The dependence of the coefficients in Eq. (6) on the Reynolds number is shown in Fig. 5. The power characteristics for selected Reynolds number values are shown in Figs. 6- 9.
Keywords: power, power characteristic, screw agitator, pump.

Acta Polytechnica 2002

No. (click on selected title and view the annotation)
1 J. Barták, M. Hilar, J. Pruška: Numerical Modelling of Overburden Deformations
This paper focuses on the application and verification of mathematical models of the effect of supporting measures on the reduction of overburden deformations. The study of the behaviour of the models is divided into three parts: reduction of the tunnelling effects on the Minorit monastery by means of a jet-grouting curtain; the behaviour of the Hvížďalka backfilled tunnel and a numerical analysis of the supporting measures affecting the tunnel deformations of the Mrázovka tunnel in Prague.
Keywords: numerical modelling, overburden deformations.
T. Ficker, Z. Podešvová: Non-isothermal Diffusion of Water Vapour in Porous Building Materials
Non-isothermal diffusion is analysed using Fick's laws. The exact relations for non-isothermal diffusion flux and partial pressure profiles in porous building materials are derived and discussed.
Keywords: Fick's laws, non-isothermal diffusion, partial pressure profile.
N. Rao, R. Kusumo, A. K. Sinha, M. L. Scott: System Framework for the Design of an Avionics Architecture with Upgrade Potential
The technological growth of ‘avionics systems’ has outpaced the service-life of aircraft, resulting in avionics upgrade as a preferred cost-effective option to new design. Mid-life upgrade of “avionics systems“ by state-of-the-art mission systems has been a challenging engineering task. The complexity of avionics upgrade process is due to the design rigidity of avionics systems architecture. An avionics architecture with growth potential is required to optimise avionics upgrade with state-of-the-art systems. A research program that partially addresses avionics systems upgrade by developing a methodology to design an avionics architecture with in-built growth potential is discussed in this research paper. A ‘system approach’ is adopted to develop a methodology that identifies the design parameters that will facilitate design of an avionics architecture with upgrade potential.
Keywords: avionics systems, avionics upgrade, system approach, avionics architecture.
O. Pokorná, D. Mocková: The Risks of Investments in Transport Infrastructure Projects
Investment decisions should not be taken without an in-depth analysis of the risks. This is an important stage in project preparation and should be performed simultaneously with the planning of the financial operations. Infrastructure development requires that project risks and responsibilities be assigned to the public or private entity that is best able to manage them. The risks and their financial impacts are usually not quantified equally by all parties. Each party views the given risks according to the guarantees provided. These guarantees are related to the form of participation in the project. Keywords: project financing, identification of risks, construction phase risks, start-up and operating phase risks, risk analysis, investment decisions, financial evaluation of the risks.
D. P. Coiro, F. Nicolosi: Design of a Three Surfaces R/C Aircraft Model
Design of a three lifting surfaces radio-controlled model has been carried out at Dipartimento di Progettazione Aeronautica (DPA) by the authors in the last year. The model is intended to be a UAV prototype and is now under construction. The main goal of this small aircraft's design is to check the influence of the canard surface on the aircraft's aerodynamic characteristics and flight behavior, especially at high angles of attack. The aircraft model is also intended to be a flying platform to test sensors, measurement and acquisition systems for research purposes and a valid and low-cost teaching instrument for flight dynamics and flight maneuvering. The aircraft has been designed to fly with and without canard, and all problems relative to aircraft balance and stability have been carefully analyzed and solved. The innovative configuration and the mixed wooden-composite material structure has been obtained with very simple shapes and all the design is focused on realizing a low-cost model.
A complete aerodynamic analysis of the configuration up to high angles of attack and a preliminary aircraft stability and performance prediction will be presented.
Keywords: three surfaces, tri-surfaces, canard, R/C model, design, aerodynamic analysis, performance, stability, upwash, downwash, propeller, wind tunnel test.
M. Kavan: Education for Production and Operations Management
The Department of Mechanical Engineering Enterprise Management at the Faculty of Mechanical Engineering of the Czech Technical University in Prague has its own doctoral programme, and runs postgraduate and master's courses. The Department is engaged in a great deal of research in the field of marketing, financial and mainly operations management. A new Production and Operations Management programme was started in 1997. The programme consists of: Management of Change and the Importance of Innovations, Forecasting and Operations Strategy, Design of Work Systems, Total Quality Management and Inventory Control, Material Requirements Planning and Just-In-Time Systems, Logistics and Practical exercises. The study programme is organised in two stages, winter and summer semesters. The study programme has a strong international orientation. The teaching goal is to prepare students for dealing with real-world settings and implementing the most effective up-to-date practices. The Department aspires to lead in research, and in developing modern concepts and tools. Research is being conducted in the mechanical engineering industry under a grant from the EU LEONARDO programme. We invite you to email with questions or to schedule a visit to the Department at any time.
Keywords: production and operations management, study programme, department of mechanical engineering enterprise management, Czech business and industry, Czech Technical University in Prague, education, lean operations management, Toyota production system.
F. Rieger: Pumping Efficiency of Screw Agitators in a Tube
Most information on pumping efficiency that is available in the literature is limited to the turbulent region (centrifugal pumps). The aim of this paper is to show the effect of the Reynolds number on the pumping efficiency of screw agitators for a wide range of Reynolds number values from creeping to the turbulent flow region. The dependence of pumping efficiency on Reynolds number extends our knowledge about the efficiency of classical impeller pumps restricted usually to the turbulent region.
Keywords: Pumping efficiency, screw agitator.
M. V. Jokl: Thermal Comfort and Optimum Humidity Part 2
The hydrothermal microclimate is the main component in indoor comfort. The optimum hydrothermal level can be ensured by suitable changes in the sources of heat and water vapor within the building, changes in the environment (the interior of the building) and in the people exposed to the conditions inside the building. A change in the heat source and the source of water vapor involves improving the heat - insulating properties and the air permeability of the peripheral walls and especially of the windows. The change in the environment will bring human bodies into balance with the environment. This can be expressed in terms of an optimum or at least an acceptable globe temperature, an adequate proportion of radiant heat within the total amount of heat from the environment (defined by the difference between air and wall temperature), uniform cooling of the human body by the environment, defined a) by the acceptable temperature difference between head and ankles, b) by acceptable temperature variations during a shift (location unchanged), or during movement from one location to another without a change of clothing. Finally, a moisture balance between man and the environment is necessary (defined by acceptable relative air humidity). A change for human beings means a change of clothes which, of course, is limited by social acceptance in summer and by inconvenient heaviness in winter. The principles of optimum heating and cooling, humidification and dehumidification are presented in this paper.
Hydrothermal comfort in an environment depends on heat and humidity flows (heat and water vapors), occurring in a given space in a building interior and affecting the total state of the human organism.
Keywords: thermal comfort, optimum humidity, hygienic standards.
V. Dynda, P. Rydlo: Large-scale File System Design and Architecture
This paper deals with design issues of a global file system, aiming to provide transparent data availability, security against loss and disclosure, and support for mobile and disconnected clients.
First, the paper surveys general challenges and requirements for large-scale file systems, and then the design of particular elementary parts of the proposed file system is presented. This includes the design of the raw system architecture, the design of dynamic file replication with appropriate data consistency, file location and data security.
Our proposed system is called Gaston, and will be referred further in the text under this name or its abbreviation GFS (Gaston File System).
Keywords: file system, replication schema, data protection, consistency, data locating.
M. V. Jokl: Thermal Comfort and Optimum Humidity Part 1
The hydrothermal microclimate is the main component in indoor comfort. The optimum hydrothermal level can be ensured by suitable changes in the sources of heat and water vapor within the building, changes in the environment (the interior of the building) and in the people exposed to the conditions inside the building. A change in the heat source and the source of water vapor involves improving the heat - insulating properties and the air permeability of the peripheral walls and especially of the windows. The change in the environment will bring human bodies into balance with the environment. This can be expressed in terms of an optimum or at least an acceptable globe temperature, an adequate proportion of radiant heat within the total amount of heat from the environment (defined by the difference between air and wall temperature), uniform cooling of the human body by the environment, defined a) by the acceptable temperature difference between head and ankles, b) by acceptable temperature variations during a shift (location unchanged), or during movement from one location to another without a change of clothing. Finally, a moisture balance between man and the environment is necessary (defined by acceptable relative air humidity). A change for human beings means a change of clothes which, of course, is limited by social acceptance in summer and by inconvenient heaviness in winter. The principles of optimum heating and cooling, humidification and dehumidification are presented in this paper.
Hydrothermal comfort in an environment depends on heat and humidity flows (heat and water vapors), occurring in a given space in a building interior and affecting the total state of the human organism.
Keywords: thermal comfort, optimum humidity, hygienic standards.
I. Kršňák, I. Kolcunová: Partial Discharge Measurements in HV Rotating Machines in Dependence on Pressure of Coolant
The influence of the pressure of the coolant used in high voltage rotating machines on partial discharges occurring in stator insulation is discussed in this paper. The first part deals with a theoretical analysis of the topic. The second part deals with the results obtained on a real generator in industrial conditions. Finally, theoretical assumptions and obtained results are compared.
Keywords: partial discharges, stator insulation, high voltage rotating machine, phase resolved partial discharge analysis.
2 M. Bednařík, P. Koníček, M. Červenka: Solution of the Burgers Equation in the Time Domain
This paper deals with a theoretical description of the propagation of a finite amplitude acoustic waves. The theory based on the homogeneous Burgers equation of the second order of accuracy is presented here. This equation takes into account both nonlinear effects and dissipation. The method for solving this equation, using the well-known Cole-Hopf transformation, is presented. Two methods for numerical solution of these equations in the time domain are presented. The first is based on the simple Simpson method, which is suitable for smaller Goldberg numbers. The second uses the more advanced saddle point method, and is appropriate for large Goldberg numbers.
Keywords: Burgers equation, Cole-Hopf transformation, Saddle point method, nonlinearity.
F. Rieger, E. Rzyski: Mixing Suspensions in Slender Tanks
Industrial suspension mixing processes are carried out both in standard tanks (H/D =1) and in the tanks with height H/D > 1. When only one impeller is used in such slender tanks, it may be difficult to produce a suspension of desired homogeneity. Hence it may be necessary to install a larger number of impellers on the shaft.
The aim of this study was to explain the mechanism of suspension formation in slender tanks (H/D = 2) with an increased number of impellers. On the basis of the solid bed height on the tank bottom, the position of the suspension - water interface and the concentration profile of solid particles in the suspension (standard deviation of solid body concentration) the operation of the impellers was estimated and conclusions were drawn on how and at what distance from each other to install them were presented.
The location of the upper, highest impeller appeared to be specially significant. On the basis of this study it is recommended to locate the upper impeller so that its distance from the free liquid surface is less than 0.8 D. It was found that such a position of the highest impeller was also advantageous from the energy point of view.
Keywords: agitation, agitated tank, mixing, suspension.
A. Grünwald, B. Šťastný, K. Slavíčková, M. Slavíček: Formation of Haloforms during Chlorination of Natural Waters
Recent drinking water regulations have lowered the standards for disinfection by-products and have added new disinfection by-products for regulation. Natural organic matter (NOM), mainly humic compounds, plays a major role in the formation of undesirable organic by-products following disinfection of drinking water. Many disinfection by-products have adverse carcinogenic or mutagenic effects on human health. This paper deals with the formation potencial of disinfection by-products in water samples taken from different places in the Flaje catchment.
Keywords: water, chlorination, disinfection by- product formation potential.
M. Kreidl, P. Houfek: Reducing Ultrasonic Signal Noise by Algorithms based on Wavelet Thresholding
Traditional techniques for reducing ultrasonic signal noise are based on the optimum frequency of an acoustic wave, ultrasonic probe construction and low-noise electronic circuits. This paper describes signal processing methods for noise suppression using a wavelet transform. Computer simulations of the proposed testing algorithms are presented.
Keywords: ultrasonic testing, wavelet transform, thresholding of wavelet coefficients, de-noising algorithms.
V. Beran: Optimisation and Just-in-Time
Arranging production activities to fit in with other construction activities is one of the basic ideas of the Just-in-Time approach. In the construction industry it has never been very fully applied. This is a mistake [1]. Construction works, particularly expensive parts of them, are a field where the approach can be and should be applied.
Keywords: Just-in-Time approach, production speeds, production volumes, optimisation savings, dependent capacity expansion, risk of extra costs.
A. K. Haghi: A Mathematical Approach for Evaluation of Surface Topography Parameters
The probability characteristics of surface topography parameters described by the composition of the deterministic component and the homogeneous random normal field were analysed. Formulae for the calculation of the mathematical expectation of the Ras parameter and the evaluation of its variance are given.
Keywords: mathematical approach, surface topography, deterministic component.
V. Tesař: Sampling by Fluidics and Microfluidics
Selecting one from several available fluid samples is a procedure often performed especially in chemical engineering. It is usually done by an array of valves sequentially opened and closed. Not generally known is an advantageous alternative: fluidic sampling units without moving parts. In the absence of complete pipe closure, cross-contamination between samples cannot be ruled out. This is eliminated by arranging for small protective flows that clear the cavities and remove any contaminated fluid. Although this complicates the overall circuit layout, fluidic sampling units with these "guard" flows were successfully built and tested. Recent interest in microchemistry leads to additional problems due very low operating Reynolds numbers. This necessitated the design of microfluidic sampling units based on new operating principles.
Keywords: sampling, fluidics, microfluidics, fluidic valves, flow switching, fluid samples.
M. V. Jokl: The Impact of Odors
The odor microclimate is formed by gaseous airborne components perceived either as an unpleasant smell or as a pleasant smell. Smells enter the building interior partly from outdoors (exhaust fumes - flower fragrance) and partly from indoors (building materials, smoking cigarettes - cosmetics, dishes). They affect the human organism through the olfactory center which is connected to the part of brain that is responsible for controlling people's emotions and sexual feelings: smells therefore participate to a high level in mood formation. The sense of smell diminishes slowly in people over the age of 60, but all female age categories have a better sense of smell than males. Smell is extremely sensitive, e.g., during pregnancy, or if an illness is coming. Bad smells cause a decrease in human performance, loss of concentration, and loss of taste. Sweet smells have a positive impact on human feelings and on human performance. Criteria for odor microclimate appraisal are presented (concentration limits of CO2, TVOC, plf, decipol, decicarbdiox, decitvoc).
Keywords: odors, microenvironment, hygiene, indoor air quality, microclimate.
M. V. Jokl: Optimization of the Odor Microclimate
The odor microclimate is formed by gaseous airborne components perceived either as an unpleasant smell or as a pleasant smell. Smells enter the building interior partly from outdoors (exhaust fumes - flower fragrance) and partly from indoors (building materials, smoking cigarettes - cosmetics, dishes). They affect the human organism through the olfactory center which is connected to the part of brain that is responsible for controlling people's emotions and sexual feelings: smells therefore participate to a high level in mood formation. Sweet smells have a positive impact on human feelings and on human performance. Criteria for odor microclimate appraisal are presented together with ways of improving the odor microclimate (by stopping odors from spreading within a building, ventilation, air filtration, odor removal by plants, deodorization, etc.), including so-called AIR DESIGN.
Keywords: odors, microenvironment, hygiene, indor air quality, microclimate.
S. Usama, B. Šimák: A Low-complexity Wavelet Based Algorithm for Inter-frame Image Prediction
In this paper, a novel multi-resolution variable block size algorithm (MRVBS) is introduced. It is based on: (1) Using the wavelet components of the seven sub-bands from two layers of wavelet pyramid in the lowest resolution; (2) Performing a block matching estimation within a nine-block only in each sub-band of the lower layer; (3) Scaling the estimated motion vectors and using them as a new search center for the finest resolution. The motivation for using the multi-resolution approach is the inherent structure of the wavelet representation. A multi-resolution scheme significantly reduces the searching time, and provides a smooth motion vector field. The approach presented in this paper providing an accurate motion estimate even in the presence of single and mixed noise. As a part of this framework, a comparison of the Full search (FS) algorithm, the three-step search (TSS) algorithm and the new algorithm (MRVBS) is presented. For a small addition in computational complexity over a simple TSS algorithm, the new algorithm achieves good results in the presence of noise.
Keywords: video compression, motion estimation, wavelet transform, multi-resolution.
G. Cooper, G. Thompson: Concept Design and Reliability
The paper outlines an approach to concept design that integrates the development of the design specification with multi-objective concept development. ‘Excursions’ are undertaken to explore particular aspects of the design, e.g., reliability, in order to help create a concept that is strong in the salient design requirements.
The paper then considers reliability as a principal design requirement. Existing reliability evaluation methods are reviewed with respect to their suitability for use in concept design. The paper then describes an approach, an ‘excursion’, that can be used to improve the reliability of a concept. The reliability excursion comprises a systematic method of evaluation and a reliability analysis toolbox. The research reported is an element of a larger concept design activity that itself forms part of a substantial project on integrated product design undertaken at the Polhem Laboratory, Luleå Technical University, Sweden and at UMIST, UK.
Keywords: conceptual design, reliability, approximate analysis tools.
3 P. Hasal, J. Kratěna, I. Fořt: Frequency and Magnitude Analysis of the Macro-instability Related Component of the Tangential Force Affecting Radial Baffles in a Stirred Vessel
Experimental data obtained by measuring the tangential component of force affecting radial baffles in a flat-bottomed cylindrical mixing vessel stirred with pitched blade impellers is analysed. The maximum mean tangential force is detected at the vessel bottom. The mean force value increases somewhat with decreasing impeller off-bottom clearance and is noticeably affected by the number of impeller blades. Spectral analysis of the experimental data clearly demonstrated the presence of its macro-instability (MI) related low-frequency component embedded in the total force at all values of impeller Reynolds number. The dimensionless frequency of the occurrence of the MI force component is independent of stirring speed, position along the baffle, number of impeller blades and liquid viscosity. Its mean value is about 0.074. The relative magnitude (QMI) of the MI-related component of the total force is evaluated by a combination of proper orthogonal decomposition (POD) and spectral analysis. Relative magnitude QMI was analysed in dependence on the frequency of the impeller revolution, the axial position of the measuring point in the vessel, the number of impeller blades, the impeller off-bottom clearance, and liquid viscosity. Higher values of QMI are observed at higher impeller off-bottom clearance height and (generally) QMI decreases slightly with increasing impeller speed. The QMI value decreases in the direction from vessel bottom to liquid level. No evident difference was observed between 4 blade and 6 blade impellers. Liquid viscosity has only a marginal impact on the QMI value.
Keywords: stirred vessel, baffles, tangential force, macro-instability, spectral analysis, proper orthogonal decomposition.
J. Římal: Prague Loretto - Measurements of Moisture Content in Sculptural Group Material
An innovative method of spatial measurement of the moisture distribution in a sculptural group has been developed and verified. This method facilitates monitoring of moisture distribution and, therefore, the condition of the sculptural group in a spatial perspective. The seven-month measurements were in order to take into account all climatic effects influencing the sculpture.These measurements resulted from the practical requirement to provide source material for future conservation interventions to be conducted on the sculptural group in the Prague Loretto.
Keywords: Prague Loretto, measurement of moisture fields, mass transport.
J. Římal: Measurement of Moisture Fields in the Bridge Structure of Charles Bridge
This paper describes measurements of the moisture field of Charles Bridge in Prague. The measurements were scheduled to cover a one-year cycle, including the spring, summer, autumn and winter, in order to monitor the behaviour of the bridge structure over a period of one year.
Keywords: Charles Bridge, measurement of moisture fields, heat and mass transport.
M. Novák, J. Faber, Z. Votruba, V. Přenosil, T. Tichý, P. Svoboda, V. Tatarinov: Reliability of Human Subject - Artificial System Interactions
Main problems related to reliability of interaction between human subject and artificial system (namely of the transportation character) are discussed. The paper consists of three mayor parts:
The first one is devoted to the theoretical backgrounds of the problem from the both theory of system reliability and neurology/psychology views.
Second part presents the discussion of relevant methodologies of the classification and prediction of the reliability decline. The methodology based on EEG pattern analysis is chosen as the appropriate one for the presented task. The key phenomenon of "micro-sleep" is discussed in detail.
The last part presents some latest experimental results in context of presented knowledge. Proposals for the future studies are presented at the end of the presented article. The special interest should be devoted to the analysis and in-time prediction of fatal attention decreases and to the design and construction of the respective on-board applicable warning system.
Keywords: man-system interaction, reliability, attention, vigilance, classification, prediction, EEG analysis, micro-sleep, neuroinformatics.
B. Šulc, J. A. Jan: Non Linear Modelling and Control of Hydraulic Actuators
This paper deals with non-linear modelling and control of a differential hydraulic actuator. The nonlinear state space equations are derived from basic physical laws. They are more powerful than the transfer function in the case of linear models, and they allow the application of an object oriented approach in simulation programs. The effects of all friction forces (static, Coulomb and viscous) have been modelled, and many phenomena that are usually neglected are taken into account, e.g., the static term of friction, the leakage between the two chambers and external space. Proportional Differential (PD) and Fuzzy Logic Controllers (FLC) have been applied in order to make a comparison by means of simulation. Simulation is performed using Matlab/Simulink, and some of the results are compared graphically. FLC is tuned in a such way that it produces a constant control signal close to its maximum (or minimum), where possible. In the case of PD control the occurrence of peaks cannot be avoided. These peaks produce a very high velocity that oversteps the allowed values.
Keywords: modelling, simulation, fluid dynamics, robotics, fuzzy control, proportional-derivative control.
M. V. Jokl: The Danger of Toxic Substances
Toxic (harmful) gases enter building interiors partly from outdoors (sulfur oxides, nitrogen oxides, carbon monoxide, ozone, smog and acid rains), partly originate indoors - as a result of human activity (carbon monoxide, tobacco smoke, nitrogen oxides, ozone, hydrocarbons) and also emanate from building materials (formaldehyde, volatile organic compounds). The human organism is most often exposed to cigarette smoke (especially nonsmokers are endangered, as cigarette smoke devastes the pulmonary and cardiovasculary system) and to smog entering from outdoors, paradoxically during sunny weather. Preventing toxic production is the most effective measure, e.g., by coaxing to coax smokers out of "civilized" areas, by using energy rationally (i.e., conserving energy), to turn to pure fuels and to increase energy production by non-combustion technologies. Besides ventilation and air filtration, the toxic gases can be removed to a remarkable extent by plants (by which decay the substances into nontoxic gases), and by air ionization. Review article.
Keywords: toxic substances, hygienic problem of buildings, health problem within buildings, sick building syndrome.
M. Kreidl, P. Houfek: Using the Correlation Function in Ultrasonic Non-destructive Testing
This paper deals with ultrasonic signal de-noising by means of correlation. It is commonly known that the cross-correlation function shows the statistical dependence between two signals. In ultrasonic inspection, the measured signal is taken as the first signal. The most important aspect of this method is the choice of the second signal. Various types of the second signals can be tried.
Keywords: ultrasonic testing, flaw echo, signal noise reduction, cross-correlation.
A. Čepek: The GNU GaMa Project - Adjustment of Geodetic Networks
The development of Free Software is a well established and successful phenomenon which could hardly exist without the Internet, where groups of programmers scattered all around the world are developing software. The idea of Free Software is highly attractive to talented creative students and can stimulate and support their profesional activities. The GNU GaMa [4] for adjusting of geodetic networks, with input data described in XML, is given here as a concrete example. Free Software [3] (or Open Source) projects need not be limited to software development but can generally cover any professional project based on free information exchange; a suggested example is the planned collection of model geodetic networks described in XML.
Keywords: GNU GaMa, geodetic network adjustment, free software.
M. Jahoda, V. Machoň, L. Vlach, I. Fořt: Macro-instabilities of a Suspension in an Axially Agitated Mixing Tank
This paper deals with an experimental assessment of the occurrence of flow macro-instabilities in a mechanically stirred suspension and visual observation of the origination and extinction of macro-vortices. The mean frequency of the occurrence of macro-instabilities in operational conditions was also observed. The experiments were carried out in a cylindrical vessel with an inner diameter of 0.19 m, and an axial stirrer with six pitched 45° blades (PBT) was used. The diameter of the stirrer was equal to half of the vessel diameter. The mean frequencies of the occurrence of macro-instabilities were determined at the stirrer frequency for just suspended conditions in dependence on solids concentration and impeller clearance (height of the stirrer above the bottom of the vessel).
Two regions of origin of macro-instabilities and one region of extinction were determined visually. It was found that the mean frequency of occurrence of macro-instabilities increases with increasing stirrer frequency at constant concentration of solids. At constant stirrer speed, the frequency of occurrence of macro-instabilities decreases with increasing concentration of solids. At higher concentration of solids, a sharp change toward lower mean frequencies of macro-instabilities was observed.
Keywords: suspension, mixing, macro-instabilities.
B. Teplý: Modelling of Deterioration Effects on Concrete Structures
In order to predict the service life of concrete structures models for deterioration effects are needed. This paper has the form of a survey, listing and describing such analytical models, namely carbonation of concrete, ingress of chlorides, corrosion of reinforcing steel and prestressing tendons. The probabilistic approach is applied.
Keywords: concrete structures, service life, reinforcement, tendons, carbonation, corrosion, chloride ingress.
4 I. Fořt, T. Jirout, R. Sperling, S. Jambere, F. Rieger: Study of Pumping Capacity of Pitched Blade Impellers
A study was made of the pumping capacity of pitched blade impellers in a cylindrical pilot plant vessel with four standard radial baffles at the wall under a turbulent regime of flow. The pumping capacity was calculated from the radial profile of the axial flow, under the assumption of axial symmetry of the discharge flow. The mean velocity was measured using laser Doppler anemometry in a transparent vessel of diameter T = 400 mm, provided with a standard dished bottom. Three and six blade pitched blade impellers (the pitch angle varied within the interval a Îá24°; 45°ń) of impeller/vessel diameter ratio D/T = 0.36, as well as a three blade pitched blade impeller with folded blades of the same diameter, were tested. The calculated results were compared with the results of experiments mentioned in the literature, above all in cylindrical vessels with a flat bottom. Both arrangements of the agitated system were described by the impeller energetic efficiency, i.e, a criterion including in dimensionless form both the impeller energy consumption (impeller power input) and the impeller pumping effect (impeller pumping capacity). It follows from the results obtained with various geometrical configurations that the energetic efficiency of pitched blade impellers is significantly lower for configurations suitable for mixing solid-liquid suspensions (low impeller off bottom clearances) than for blending miscible liquids in mixing (higher impeller off bottom clearances).
Keywords: pitched blade impeller, impeller pumping capacity, turbulent flow, laser Doppler anemometer, impeller energetic efficiency.
P. P. Procházka, M. G. Kugblenu: Application of Discrete Element Methods to the Problem of Rock Bumps
This paper is a continuation of a previous paper by the authors. Applications of two discrete element methods (DEM) to several fields of geotechnics are discussed. The free hexagon element method is considered a powerful discrete element method, and is widely used in mechanics of granular media. It substitutes the methods for solving continuum problems. In order to complete the study, other discrete element methods are discussed. The second method starts with the classical particle flow code (PFC, which uses dynamic equilibrium), but we apply static equilibrium in our case. The second method is called the static particle flow code (SPFC). The numerical experiences and comparison with experimental results from scaled models are discussed.
Keywords: free hexagonal element method, statical PFC, localized damage, occurrence of cracking and bumps during mining or tunneling.
P. P. Procházka, M. G. Kugblenu: Certain Discrete Element Methods in Problems of Fracture Mechanics
In this paper two discrete element methods (DEM) are discussed. The free hexagon element method is considered a powerful discrete element method, which is broadly used in mechanics of granular media. It substitutes the methods for solving continuum problems. The great disadvantage of classical DEM, such as the particle flow code (material properties are characterized by spring stiffness), is that they have to be fed with material properties provided from laboratory tests (Young's modulus, Poisson's ratio, etc.). The problem consists in the fact that the material properties of continuum methods (FEM, BEM) are not mutually consistent with DEM. This is why we utilize the principal idea of DEM, but cover the continuum by hexagonal elastic, or elastic-plastic, elements. In order to complete the study, another one DEM is discussed. The second method starts with the classical particle flow code (PFC - which uses dynamic equilibrium), but applies static equilibrium. The second method is called the static particle flow code (SPFC). The numerical experience and comparison numerical with experimental results from scaled models are discussed in forthcoming paper by both authors.
Keywords: Discrete element methods, free hexagon element method, statical particle flow code.
M. Sýkora: Reliability Analysis of a Steel Frame
A steel frame with haunches is designed according to Eurocodes. The frame is exposed to self-weight, snow, and wind actions. Lateral-torsional buckling appears to represent the most critical criterion, which is considered as a basis for the limit state function. In the reliability analysis, the probabilistic models proposed by the Joint Committee for Structural Safety (JCSS) are used for basic variables. The uncertainty model coefficients take into account the inaccuracy of the resistance model for the haunched girder and the inaccuracy of the action effect model. The time invariant reliability analysis is based on Turkstra's rule for combinations of snow and wind actions. The time variant analysis describes snow and wind actions by jump processes with intermittencies. Assuming a 50-year lifetime, the obtained values of the reliability index b vary within the range from 3.95 up to 5.56. The cross-profile IPE 330 designed according to Eurocodes seems to be adequate. It appears that the time invariant reliability analysis based on Turkstra's rule provides considerably lower values of b than those obtained by the time variant analysis.
Keywords: steel frame, lateral-torsional buckling, reliability, jump processes.
J. Novák: Analysis of Phase Evaluation Algorithms in an Interferometric Method for Static Deformation Measurement
This article describes and analyses an interferometric method for measuring displacements and deformation. The method can be used for a very accurate evaluation of the change in the surface shape of structures used in industry. The paper proposes several multistep phase calculation algorithms and describes an automatic evaluation process using the measurement technique. A complex analysis is also performed of various factors that can have a negative effect on the practical measurement and evaluation process. An analysis is made of the proposed multistep phase calculation algorithms using the proposed error model. It is shown that the resulting phase measurement errors can be effectively reduced by using suitable phase calculation algorithms. The analysis can be applied for a complex comparison of the accuracy and stability of such algorithms.
Keywords: noncontact deformation measurement, phase calculation algorithms, error analysis.
J. Novák: New Phase Shifting Algorithms Insensitive to Linear Phase Shift Errors
This article describes and analyses multistep algorithms for evaluating of the wave field phase in interferometric measurements using the phase shifting technique. New phase shifting algorithms are proposed, with a constant but arbitrary phase shift between captured frames of the intensity of the interference field. The phase evaluation process then does not depend on linear phase shift errors. A big advantage of the described algorithms is their ability to determine the phase shift value at every point of the detector plane. A detailed analysis of these algorithms with respect to main factors that affect interferometric measurements is then carried out. The dependency of these algorithms on phase shift values is also studied several phase calculation algorithms are proposed. These are compared with respect to the resulting phase errors.
Keywords: noncontact deformation measurement, phase calculation algorithms, error analysis.
D. Dobrovská, P. Andres: Technical Teachers and Technical Teacher Education - Research Results
Chartered engineers who are new teachers of technical subjects at various educational institutions receive technical teacher education in the accredited bachelor programme at the Czech Technical University in Prague. This paper presents the results of a recent survey in which engineers expressed their opinions on technical teacher education.
Keywords: teachers of technical subjects, technical teacher education, motivation, non-technical subjects, e-learning.
M. Červenka, M. Bednařík, P. Koníček: Temperature Effects in Acoustic Resonators
This paper deals with problems of nonlinear standing waves in axisymetrically shaped acoustic resonators where a mean temperature is distributed along the axis.
Keywords: nonlinear standing wave, acoustic resonator, temperaturechangeover.
R. Bálek, Z. Šlegrová: A Comparison of Acoustic Field Measurement by a Microphone and by an Optical Interferometric Probe
The objective of this work is to show that our optical method for measuring acoustic pressure is in some way superior to measurement using a microphone. Measurement of the integral acoustic pressure in the air by a laser interferometric probe is compared with measurement using a microphone. We determined the particular harmonic components in the acoustic field in the case of relatively high acoustic power in the ultrasonic frequency range.
Keywords: acousto-optics, ultrasonic light diffraction, heterodyne laser interferometer.
P. Koníček, M. Bednařík, M. Červenka: Propagation of Quasi-plane Nonlinear Waves in Tubes
This paper deals with possibilities of using the generalized Burgers equation and the KZK equation to describe nonlinear waves in circular ducts. A new method for calculating of diffraction effects taking into account boundary layer effects is described. The results of numerical solutions of the model equations are compared. Finally, the limits of validity of the used model equations are discussed with respect to boundary conditions and the radius of the circular duct. The limits of applicability of the KZK equation and the GBE equation for describing nonlinear waves in tubes are discussed.
Keywords: nonlinear acoustics, Khokhlov-Zabolotskaya-Kuznetsov equation, generalized Burgers equation.

Acta Polytechnica 2003

No. (click on selected title and view the annotation)
1 M. Holický, J. Marková: Reliability of Concrete Elements Designed for Alternative Load Combinations Provided in Eurocodes
The basic European standard for design of buildings and other engineering works, EN 1990 "Basis of structural design", provides alternative design procedures, for which national choice is allowed. One of the most important questions concerns three fundamental combinations of actions for persistent and transient design situations in the Ultimate limit states. Simple examples of reinforced concrete elements show, that the alternative load combinations may lead to considerably different reliability levels. Probabilistic methods of structural reliability theory are used to identify characteristic features of each combination and to formulate recommendations. However, further calibration studies are urgently needed in order to prepare National annexes to EN 1990 on time.
Keywords: Eurocodes, combination of actions, partial factors, reinforced concrete beam, column, reliability index.
T. Ficker, Z. Podešvová: Modified Glaser’s Condensation Model
Glaser's condensation scheme with incorporated non-isothermal diffusion is presented and its consequences are studied. Keywords: non-isothermal diffusion, partial pressure profile, condensation in building structures, Glaser's condensation scheme.
L. Böszörményi, G. Böszörményi: Prospects for Geothermal Energy Conversion through a Hybrid Combined Cycle Power Plant
The demand for more intensive utilization of energy sources is getting more important with the forthcoming European Union membership of the Slovak Republic. Lack of resources and poor exploitaition of available resources can be a very difficult problem for energy policy. It is important to use technical solutions to minimize or eliminate this problem. The most beneficial progress could be achieved in the Košice basin where geothermal energy could have effective and multi-purpose use.
Keywords: combined cycle, geothermal energy, heat pump, biomass.
P. Mikeš: Reconstruction of Object Position in X-ray Mammograms
Keywords: reconstruction, decompression, mammography.
V. Beran: Management Processes in Technical-economic Design, Decision-making, Fractals and Market Bubbles
Keywords: decision making, management, cellular automata, fractals, market bubbles, technical economic design, simulations, process and regulation, steering process and management.
M. Toman, P. Procházka: An Algorithm for Investigating the Structure of Material Surfaces
The aim of this paper is to summarize the algorithm and the experience that have been achieved in the investigation of grain structure of surfaces of certain materials, particularly from samples of gold. The main parts of the algorithm to be discussed are:
1. acquisition of input data,
2. localization of grain region,
3. representation of grain size,
4. representation of outputs (postprocessing).
Keywords: investigation of structure of material surfaces, transformation of images, Gaussian low-frequency filter, local equalization, probability distribution of grain size.
T. Ficker: A Short Note on Non-isothermal Diffusion Models
Asymptotic behaviour of the DIAL and DRAL non-isothermal models, derived previously for the diffusion of water vapour through a porous building structure, is studied under the assumption that the initially non-isothermal structure becomes purely isothermal.
Keywords: Isothermal and non-isothermal diffusions, diffusion models, condensation in building structures.
M. Zoriy, F. Černý, D. Palamarchuk, S. Konvičková, I. Hüttel: Measuring the Process Parameters of the IBAD Method
Chromium nitride films are known as good protective layers for against both corrosion and wear. These coatings have been studied in detail during recent years. Their protective capability strongly depends on the deposition conditions. A modern method for preparing chromium nitride is the IBAD (Ion Beam Assisted Deposition) method.
The main parameter determining the composition and properties of the films prepared by the IBAD method is the arrival ratio of impinging nitrogen ions to chromium atoms.
In order to calibrate the ion beam XY-mechanical scanner with a Faraday cup, a detector was designed and constructed. By mathematical processing of the data, the flux of the nitrogen atoms was found. To obtain the flux of the chromium atoms the RBS and Talystep methods were used.
Now, on the basis of this data, we can perform CrNx coatings with controlled composition and properties.
Keywords: IBAD, CrN, CrN2, calibration, electron beam.
D. Palamarchuk, M. Zoriy, J. Gurovič, F. Černý, S. Konvičková, I. Hüttel: DLC Films Deposited by the DC PACVD Method
DLC (Diamond-Like Carbon) coatings have been suggested as protective surface layers against wear. However hard DLC coatings, especially those of greater thickness, have poor adhesion to substrates. We have used several ways to increase the adhesion of DLC coatings prepared by the PACVD (Plasma Assisted Chemical Vapour Deposition) method on steel substrates. One of these is the DC PACVD method for preparing DLC films.
Keywords: DLC, PACVD, microhardness, adhesion.
T. Janda, P. Kuklík, M. Šejnoha: Numerical Implementation of Isotropic Consolidation of Clayey Soils
This paper reports on implementation of several numerical techniques to solve a set of governing equations resulting from simple one dimensional isotropic consolidation of soils that behave according to the Cam clay model. Three different methods of solving the equations of consolidation, namely the collocation method, the finite volume method and the finite element method, are presented. Apart from evaluating their efficiency, which becomes particularly crucial when implementing these techniques in the framework of an optimization problem aimed at tuning the model parameters, a set of parameters of a Cam clay model driving the time dependent response of the soils (deformation dependent variation of the coefficient of permeability and preconsolidation pressure) is also discussed.
Keywords: Cam clay, coefficient of permeability, consolidation, finite volume method, void ratio, genetic algorithm.
V. Tesař: Fluidic Control of Molten Metal Flow
Fluidic devices built from suitable refractory materials can withstand the extreme conditions encountered in flows of molten metals - even those with a high melting point. This paper informs about the hydrodynamic aspects of a recent development of a fluidic controller keeping the metal gravity flow constant. The controller uses a narrow notch weir for generating the control signal and a fluidic vortex valve as the actuator. An unusual feature is the signal transfer between the two components performed also by a molten metal flow. It is even possible to amplify the signal using the liquid metal as the working medium in the amplifier.
Keywords: metallurgy, fluidics, vortex amplifier, jet-deflection amplifier.
T. Ficker, Z. Podešvová: Models for Non-isothermal Steady-State Diffusion in Porous Building Materials
Two models for non-isothermal diffusion of water vapour in building materials have been developed and their numerical outputs compared with a standard isothermal approximation.
Keywords: Fick's laws, non-isothermal diffusion, partial pressure profile.
2 R. Cimbala, I. Kršňák, I. Kolcunová: The Computing of the Influence of a Steady Element on the Polarization Spectrum
This paper describes computation of the influence of a steady current element on the current response of insulation material. The steady element is always present. When the insulation is dry, it can be neglected. When moisture is present, the steady element has to be calculated. A decision can be made after examining the spectrum.
Keywords: polarization spectrum, insulation system, current response, time of stabilization, steady element.
K. Hladká: Tendencies in Spatial Planning in Austria

In Austria there is a federal system, where the power is shared between national (Bund) and regional (Land) governments, with each having autonomy in some spheres, and able to pass laws. Power resides with the national government, although certain responsibilities may be delegated to regional governments. In Austria the national government has no competence in spatial planning, but planning at the national level is undertaken through a joint forum which has advisory powers, and in which the national government and the Länder Austrian are equal partners. At regional level the Austrian Länder play the primary role in spatial planning. The Austrian national government has only limited responsibilities.

Keywords: Austria Conference on Regional Planning (ÖROK), Bund, Land/Länder, ÖSTAT (Austrian Central Statistical Office).

K. Slanec, F. Černý, J. Gurovič, V. Chmelík: Modifing the Surface Layers of Mechanical Components
This paper deals with the creation of thin surface layers prepared by the Plasma Assisted Chemical Vapour Deposition Method (PACVD). Polished sample surfaces made of tool steel were used. An investigation of the dependence of layer thickness on process duration was carried out. The structure of the original surface and the structure of the coated surface were evaluated and compared. The microhardness of the surface areas was also measured Keywords: Surface texture parameters, Plasma Assisted Chemical Vapour Deposition, microhardness, chemical composition.
V. Dynda: A Bypass-Ring Scheme for a Fault Tolerant Multicast

We present a fault tolerant scheme for recovery from single or multiple node failures in multi-directional multicast trees. The scheme is based on cyclic structures providing alternative paths to eliminate faulty nodes and reroute the traffic. Our scheme is independent of message source and direction in the tree, provides a basis for on-the-fly repair and can be used as a platform for various strategies for reconnecting tree partitions. It only requires an underlying infrastructure to provide a reliable routing service. Although it is described in the context of a message multicast, the scheme can be used universally in all systems using tree-based overlay networks for communication among components

Keywords: distributed systems, fault tolerance, message multicast, tree-based networks, tree recovery, repair algorithm.

M. Kollár: Measurement of Light Intensity Based on a Flip-flop Sensor
This paper deals with a new type of system for measuring light intensity with the use of a flip-flop sensor controlled by a so-called slow-rise voltage control pulse. A photodiode was used for quantification of the measured light intensity in the structure of the flip-flop. The theoretical considerations are compared with experimental results, and good agreement is reported.
Keywords: measurement, flip-flop sensor, light intensity, equivalent voltage.
H. Achten, J. Jessurun: A Multi-Agent Mah Jong Playing System: Towards Real-Time Recognition of Graphic Units in Graphic Representations

In architectural design, sketching is an important means to explore the first conceptual developments in the design process. It is necessary to understand the conventions of depiction and encoding in sketches and drawings if we want to support the architect in the sketching activity. The theory of graphic units provides a comprehensive list of conventions of depiction and encoding that are widely used among architects. These graphic units form useful building blocks to understand design drawings. We investigate whether it is possible to build a system that can recognize graphic units. The technology we are looking at is multi-agent systems. It was chosen for the following reasons: agents can specialize in graphic units, a multi-agent system can deal with ambiguity through negotiation and conflict resolution, and multi-agent systems function in dynamically changing environments. Currently there is no general approach or technology available for multi-agent systems. Therefore, in our research we first set out to make such a multi-agent system. In order to keep the complexity low, we first aim to make a system that can do something simple: playing Mah Jong solitary. The Mah Jong solitary system shares the following important features with a multi-agent system that can recognize graphic units: (1) specialized agents for moves; (2) negotiation between agents to establish the best move; (3) a dynamically changing environment; and (4) search activity for more advanced strategies. The paper presents the theoretical basis of graphic units and multi-agents systems, followed by a description of the multi-agent framework and its implementation. A number of systems that can play Mah Jong at various degrees of competence and accordingly degrees of complexity of multi-agent system, are distinguished. Finally, the paper demonstrates how the findings are informative for a system that can recognize graphic units.

Keywords: AI, multi-agent systems, games, graphic units, architectural design.

I. Fořt, V. Kreibich, J. Marek: Study of Wear of Pitched Blade Impellers in a Solid-Liquid Suspension
A study was made of the erosion wear of the blades of pitched blade impellers in a suspension of silicious sand (CV = 5 %, =0.325 mm, degree of hardness "7.5") in water under a turbulent flow regime of agitated charge when complete homogeneity of the suspension was achieved. Two aims of the study were defined: the dependence of the rate of the erosion process of the impeller blades on impeller frequency of revolution and on the size of the mixing equipment. Experiments were carried out on pilot plant mixing equipment of two sizes (geometrically similar) made of stainless steel (diameters of cylindrical vessels T1 200 mm and T300 mm, diameters of impellers D100 mm and D66.7 mm, impeller off-bottom clearances h1100 mm and h66.7 mm, respectively) equipped with four radial baffles (width b30 mm, b20 mm, respectively) and an impeller with four inclined plane blades (pitch angle 30°, 45°, relative blade with W/0.2) made of rolled brass (Brinnel hardness 40–50 BM) always pumping the liquid downwards towards the flat vessel bottom. The wear of the impeller was described by an analytical approximation in exponential form with two parameters (the wear rate constant k and the geometrical parameters of the worn blade C) calculated by the least squares method from the experimentally found profile of the worn leading edge of the impeller blades. While the wear rate constant exhibits a monotonous dependence on the pitch angle only, the geometric parameter is dependent both on the pitch angle and in linear form on the impeller tip speed. Thus in the procedure for scaling up the rate of erosion wear of the pitched blade impellers in a suspension of higher solid particle hardness, the decision process parameters are the impeller blade pitch angle and the impeller tip speed.
Keywords: pitched blade impeller, erosion wear, solid-liquid suspension, scaling up procedure.
M. Jiřičková, R. Černý, P. Rovnaníková: Measurement of Moisture Storage Parameters of Building Materials
The moisture storage parameters of three different building materials: calcium silicate, ceramic brick and autoclaved aerated concrete, are determined in the hygroscopic range and overhygroscopic range. Measured sorption isotherms and moisture retention curves are then combined into moisture storage functions using the Kelvin equation. A comparison of measured results with global characteristics of the pore space obtained by mercury intrusion porosimetry shows a reasonable agreement; the median pore radii by volume are well within the interval given by the beginning and the end of the characteristic steep parts of the moisture retention curves.
Keywords: moisture retention curve, sorption isotherm, desorption isotherm, building materials.
V. Beran, J. Frková: Significance of SMEs in the Czech Economy and Supporting SMEs as an Instrument of the Regional Development
SMEs (Small and Medium Enterprises) are important segments of the economic landscape of the Czech Republic, since half of economic production is attributable to SMEs (52.85 %). The role of SMEs in the Czech Republic is the outcome of a long history of economic development and industrialization throughout the 20th century.
Large enterprises prefer to locate their factories according to e range of regional opportunities. Small enterprises are more dependent on business conditions in their region. The transaction costs are relatively high for small firms. These contraints mean that regions without an attractive environment for business need to create acceptable conditions for small businesses, if they are looking for sustainable development.
Keywords: history of SME's, economic Power of SME's, performance indicators, comparison of industrial sectors, value added.
M. Vognar, Č. Šimáně, D. Chvátil: Twenty Years of Microtron Laboratory Activities at CTU in Prague
A concise review is presented of the activities at the Prague microtron laboratory, starting with the construction of the first microtron in the Czechoslovak Republic, covering R&D connected with the design and building of electron accelerators of this type, applications of electron and bremsstrahlung beams and fields in applied radiation dosimetry, in the study of radiation-induced changes of optical and other physical properties of inorganic and organic substances (e.g., scintillation crystals such as PbWO4, optical fibres, semiconductors), for activation analysis of samples, especially from geological mineral ore prospecting (gold ores and others), for radioisotope production ( 123I for medical diagnostic purposes), et cetera. Participation of the microtron laboratory in the education of students of the faculty in various fields of applied dosimetry and other microtron applications is also discussed.
Keywords: microtron design and construction, electron beams, bremsstrahlung,radioisotope production, radiation damage.
T. Ficker, J. Macur: A Note on Normalised Distributions of DC Partial Microdischarges
Statistical distributions (exponential and Pareto) of DC partial microdischarges running within sandwich electrode systems are discussed from the viewpoint of a normalisation procedure which may influence some features of the final distribution.
Keywords: exponential and statistical distributions, partial microdischarges, normalisation procedure.
3 S. Seker, M. E. Aydemir, G. Apaydin: A Simulation Study for Computing the Emissivity of Clouds
In this study, propagation through various distributions of lossy particles in clouds is investigated. Clouds may contain several types of crystal forms which can be modelled in the physical optics scattering region such as thin long cylinders and flat plate. The bistatic scattering patterns and emissivities of various types of clouds are computed for waves of selected polarizations passing through clouds with specified sizes, shapes and distributions. The results are in good agreement with the literature.
Keywords: scattering, emissivity, physical optics, forward scattering theorem.
P. Anderle, L. Smrček, F. N. Coton: Aerodynamic Design and Experimental Investigation of the Sailplane Wing Tip Devices
This paper describes an experimental set-up for the investigation of wing tip devices developed as part of a study into the velocity and vorticity distributions in the flow field behind winglets, using hot-wire anemometry. In this study, effort was focused on gaining a greater understanding of what happens in the region where the winglet joins the wing. The measurements were performed in the Handley-Page wind tunnel of the Department of Aerospace Engineering at the University of Glasgow. In order to carry out measurements with the hot-wire anemometry system, a new traverse mechanism was designed and manufactured. This traverse mechanism was integrated with the other test instrumentation to create a complete measurement chain. The complete system allows fully automated hot wire measurements to be made over a defined area using programmable test parameters.
Keywords: winglet, hot-wire anemometry, traverse mechanism, vorticity.
M. Holický: Risk Assessment in Advanced Engineering Design
Traditional methods for designing of civil engineering structures and other engineering systems are frequently based on the concept of target probability of failure. However, this fundamental quantity is usually specified on the basis of comparative studies and past experience only. Moreover, probabilistic design methods suffer from several deficiencies, including lack of consideration for accidental and other hazard situations and their consequences. Both of these extreme conditions are more and more frequently becoming causes of serious failures and other adverse events. Available experience clearly indicates that probabilistic design procedures may be efficiently supplemented by a risk analysis and assessment, which can take into account various consequences of unfavourable events. It is therefore anticipated that in addition to traditional probabilistic concepts the methods of advanced engineering design will also commonly include criteria for acceptable risks.
Keywords: hazard, risk, assessment, advanced design, structure, engineering system.
I. Horváth: Understanding the Order of Engineering Design Research
Engineering design research manifests as a platform for exploration, description, arrangement, rationalization, and application of design knowledge. What we can see when we are looking at the research into engineering design is an almost chaotically fragmented picture. Is it possible to have a holistic view on the contents and internal relationships of engineering design research? This paper considers teleology, a reflection of a branch of philosophical speculations, as the doctrine of ordering knowledge of engineering design and structuring engineering design research accordingly. Teleology explains that the ultimate reason behind design is to sustain human existence and well being by virtual creation of artifacts and services for society. To this end, knowledge of engineering research is supposed to be transferred from the platform of scientific/theoretical exploration and comprehension to the platform of technical/pragmatic application. This implies a natural streaming of knowledge of engineering design. In order to make the teleological explanation operational, a framework of reasoning has been constructed by adopting the analogy of the source, channel and sink of a stream. To represent the source, channel and sink categories of engineering design knowledge, the author inaugurated nine categories in the framework. It has been hypothesized that the introduced categories are equally valid for research in engineering design as well as for the knowledge of engineering design. Within each category, research domains and trajectories have been defined. The proposed teleology-based framework lends itself to a better understanding of the disciplinary articulation and intrinsic relationships of engineering design research. It is hoped, among other things, to form a basis for a shared understanding, to make the influence of decisions on research programs more transparent, as well as to facilitate organizing subject materials for various design courses.
Keywords: engineering design research, teleology of engineering design, natural stream of knowledge, research categories, research domains, research trajectories.
J. Čermák, G. Gráf: Die Design for Near-Net Shape Forging
This paper discusses the use of conventional forging equipment for the manufacture of precise forging without flash. An analysis is presented of the factors influencing the forging process and the conditions for establishing this technique in a forge based on practical experience at the SKODA Auto forge. The main problem is usually the excess volume of billet material. Three basic forms of die design for overload protection are illustrated and discussed.
Keywords: flashless forging, die design, accommodation space, spring-operated device.
P. Valenta, J. Valentová: Detailed Numerical Modeling of Flood Flow in Floodplains with Complex Geometry
Numerical modeling of flood flow and the evaluation of flood hazards can be based on various numerical models and modeling techniques. One-dimensional (1D), quasi two-dimensional (1,5 D), two-dimensional (2D) or three-dimensional (3D) variants of numerical models can be used. While 3D models are too demanding to be used for flood flow modeling on personal computers, quasi-2D and 2D models can be more widely used to solve even larger practical problems nowadays. Detailed two-dimensional numerical modeling of flood flow in flooded urbanized areas with complex geometry using the 2D depth averaged model is presented in this paper. The governing equations of the model are expressed with a set of depth averaged Reynolds equations consisting of the continuity equation and two momentum equations for the horizontal velocity components. The eddy viscosity, which influences the horizontal turbulent momentum exchange processes, is modeled with the aid of a depth average version of the two-equation k-e turbulence model. The partial differential equations are solved numerically with a control volume method using fine non-orthogonal curvilinear grids and a non-staggered variable arrangement. The applicability and advantages of this modeling approach for simulating the flood flow in floodplains with complex geometry, and in urban areas, are illustrated by the results of a pilot study in Choceň and Ústí nad Orlicí, towns which were severely affected during the 1997 and 1998 floods in the Czech Republic.
Keywords: numerical modeling, modeling of flood flow, control volume method.
G. M. Repici, A. Sorniotti: A General Approach to Study the Reliability of Complex Systems
In recent years new complex systems have been developed in the automotive field to increase safety and comfort. These systems integrate hardware and software to guarantee the best results in vehicle handling and make products competitive on the market.However, the increase in technical details and the utilization and integration of these complicated systems require a high level of dynamic control system reliability. In order to improve this fundamental characteristic methods can be extracted from methods used in the aeronautical field to deal with reliability and these can be integrated into one simplified method for application in the automotive field.Firstly, as a case study, we decided to analyse VDC (the Vehicle Dynamics Control system) by defining a possible approach to reliability techniques. A VDC Fault Tree Analysis represents the first step in this activity: FTA enables us to recognize the critical components in all possible working conditions of a car, including cranking, during 'key-on'-'key-off ' phases, which is particularly critical for the electrical on-board system (because of voltage reduction).By associating FA (Functional Analysis) and FTA results with a good FFA (Functional Failure Analysis), it is possible to define the best architecture for the general system to achieve the aim of a high reliability structure.The paper will show some preliminary results from the application of this methodology, taken from various typical handling conditions from well established test procedures for vehicles.
Keywords: safety, systems reliability, fault tree analysis (FTA), functional analysis (FA), handling, vehicle dynamic control (VDC).
K. Maier: GIS, Information Technology and Spatial Planning
Geographic information systems have been introduced local and regional planning several stages. They have influenced the technique of planning but only to a lesser extent the procedures of planning and the methodology of plan-making. More recently, information technology has challenged the whole concept of planning as an expert-and-government interplay. However, legal frameworks have not reflected the substantial change in the potentials of the technology.Any effort to reflect the new technology will face not only institutional inertia but increasingly also the human capacity of users of planning (i.e., decision-makers, administrators, stakeholders), namely the limited extent of overall IT literacy, which restricts the possible benefits of the technology. The dimension of access to and empowerment in planning may reappear in the context of new technologies, with new professional requirements for planners, beyond the computer, GIS and information technology.
Keywords: geographical information systems, information technology, spatial planning, participation.
J. Mordaka, R. Gentle: The Biomechanics of Gender Difference and Whiplash Injury: Designing Safer Car Seats for Women
Female car users are reported to have a higher incidence of soft tissue neck injuries in low speed rear-end collisions than males, and they apparently take longer to recover. This paper addresses the whiplash problem by developing a biomechanical FEM (Finite Element Method) model of the 50th and the 5th percentile female cervical spines, based on the earlier published male model created at the Nottingham Trent University. This model relies on grafting a detailed biomechanical model of the neck and head onto a standard HYBRID III dummy model. The overall philosophy of the investigation was to see if females responded essentially as scaled down males from the perspective of rear end collisions. It was found that detailed responses varied significantly with gender and it became clear that females cannot be modelled as scaled-down males, thus confirming the need for separate male and female biomechanical models and a revision of car test programmes and regulations which are currently based on the average male. Further investigation is needed to quantify the gender differences and then recommendations can be made for changes to the design of car seats and head restraints in order to reduce the risk of soft tissue injury to women.
Keywords: female, whiplash, rear impact, biomechanics, cervical spine, kinematics.
4 A. González-Betes, R. Martínez-Val: Modeling the Aerodynamics and Performances of a Historic Airplane: the Spanish

The process of modeling the aerodynamics and performances of a historic airplane is very similar to the conceptual and preliminary design phases of a new plane, with the advantage of knowing the configuration and that the airplane was airworthy; thus it is unnecessary to outline and assess many different alternatives. However, the drag polar, the real performances, stability features, etc, are still unknown. For various reasons (in particular because of two World Wars, or the Civil War in the Spanish case) most details of many historical airplanes have been lost.In the present research work, the situation is as follows. In June 1933 the "Cuatro Vientos", a Spanish-built Bréguet XIX Super TR, flew non-stop from Seville to Cuba; a distance of 7500 km (about 4100 nautical miles) in around 40 hours. A few days later, in a far less complicated stage between Havana and Mexico, the airplane was lost with its occupants to a storm in the Yucatan peninsula.The modeling considered in this paper starts by addressing the aerodynamic modifications introduced in the airplane for the extremely long flight. Then, with the help of old and present day aerodynamic data and methods the drag polar is estimated. The available engine data is completed and extrapolated to obtain information on power and fuel consumption. Finally, all this data is integrated to provide a reliable and technically sound reproduction of the Seville-Cuba flight.

Keywords: historic airplanes, airplane performances.

B. Künne, V. Mehlan, A. Langenohl: Heavy Load Rollers in Logistic Systems

Wheels with polyurethane bandages are in common use in logistic systems with friction gear actuation. Many research projects have studied the mechanical construction of these heavy load wheels. The studies have been theoretical as well as experimental. Research interests at the department of machine elements include the wear in the presence of intermediate material on the contact area between the bandage surface and the contact surface on which the wheel rolls off. This problem, which is observed when examining this tribochemical system, has not been studied before. Within this project both one-phase intermediate materials such as sand, water, cutting-cooling-emulsion, metal splinters and two-phase intermediate materials such as sand/water and combinations of the latter were taken into consideration. In addition, the exposure of the bandage hardness, the cross linking agent of the polyurethane, the mechanical stress, and the slip are observed. The analysis of the experimental results indicates that friction gear actuators can be constructed abrasion-optimised, taking into account special interfering effects in the form of intermediate materials in the contact area.

Keywords: wear, polyurethane, heavy load wheel, heavy load rollers, abrasive, tribochemical, hydrolysis, abrasion, intermediate material.

P. Hasal, I. Fořt, J. Kratěna: The Tangential Force Affecting the Radial Baffles in a Stirred Vessel: Analysis of the Macro-instability Related Component

Experimental data obtained by measuring the tangential component of the force affecting radial baffles in a flat-bottomed cylindrical mixing vessel stirred with a Rushton turbine impeller is analysed. Spectral analysis of the experimental data demonstrated the presence of its macro-instability (MI) related low-frequency component embedded in the total force. Two distinct dimensionless frequencies (both directly proportional to the impeller speed of rotation N) of the occurrence of the MI component were detected: a lower frequency of approximately 0.025N and a higher frequency of about 0.085N. The relative magnitude QMI of the MI-related component of the total tangential force was evaluated by a combination of proper orthogonal decomposition (POD) and spectral analysis. The values of magnitude QMI varied in the interval from approximately 0.05 to 0.30. The magnitude QMI takes maximum values at low Reynolds number values (in laminar and transitional regions). In the turbulent region (ReM > 20000) the QMI value is low and practically constant. The dependence of the QMI values on vertical position in the vessel is only marginal. The results suggest that the magnitude of the MI component of the force is significantly influenced by the liquid viscosity and density.

Keywords: stirred vessel, baffles, tangential force, macro-instability, spectral analysis, proper orthogonal decomposition.

T. Vaňura, P. Štěpánek, I. Švaříčková, J. Adámek: Long-term Test Arrangement for Externally Strengthened Reinforced Concrete Elements
Methods for external strengthening of concrete use elements of very high tensional strength glued on to its tensioned surface. These elements may be of metal, carbon fibers (CFRP), glass fibers or others, usually having very good mechanical properties. However, these high-strength elements are normally attached to concrete by epoxy resins. Epoxy resins have a low Young`s modulus and therefore a higher rate of creep may have an influence on the long-term behavior of such external strengthening. In order to verify this idea experimentally a special space-saving arrangement of tests is described in this paper. Panels act as loaded beams but simultaneously as a load for the other panels in a stand. The different load magnitude acting on a different layer of panels should make it possible to study the long-term influence of the degree of shear force on the glue creep. Certainly, the glue creep may be dependent on the type of epoxy resin; therefore several epoxy resin types are included in the tests.
Keywords: carbon fiber (CFRP), glass fiber (GFRP), external strengthening, epoxy-resin creep, test arrangement.
O. Calonius, V. Saikko: Analysis of Relative Motion between Femoral Head and Acetabular Cup and Advances in Computation of the Wear Factor for the Prosthetic Hip Joint
The amount and type of wear produced in the prosthetic hip joint depends on the type of relative motion between the femoral head and the acetabular cup. Wear particles removed from the bearing surfaces of the joint can cause adverse tissue reactions resulting in osteolysis and ultimately in loosening of the fixation of the implant. When designing a simulator for evaluation of prospective materials for artificial hip joints it is important to verify that the type of relative motion at the articulation is similar to that produced in walking, involving continually changing direction of sliding. This paper is an overview of recent research done at Helsinki University of Technology on the analysis of the relationship between relative motion and wear in the prosthetic hip joint.To analyze the relative motion, software for computing tracks, referred to as slide tracks, drawn on the counterface by marker points on the bearing surface was developed and experimentally verified. The overall relative motion of the joint was illustrated by a slide track pattern, produced by many points. The patterns resulting from walking motion and from motion produced in ten contemporary hip simulator types were compared. The slide track computations were not limited to illustrational purposes but offered a basis for computing variations of sliding distances, sliding speeds and direction of sliding during a cycle. This was done for the slide track termed the force track, drawn by the resultant contact force. In addition, the product of the instantaneous load and increment of sliding distance was numerically integrated over a cycle. This track integral of load had so far not been determined for the majority of contemporary hip simulators. The track integral can be used in determining the wear factor, making it possible to compare clinical wear rates with those produced by hip simulators. The computation of the wear factor was subsequently improved by replacing the track integral of the resultant contact force with a surface integral computed as the sum of track integrals of a large number of smaller normal forces obtained by discretizing the contact pressure distribution. The slide track software could also be utilized in the conceptual design of new simulators because it was possible to rapidly investigate the effect of changes to the motion waveform amplitudes or phases, or of omitting certain waveforms to simplify the design of a simulator.The slide track analysis showed that walking motion produced mainly open tracks on the center of contact, implying continually changing direction of sliding. This phenomenon, which is crucial for obtaining the correct wear mechanisms for acetabular cups made of polyethylene, was reproduced by simulators having abduction-adduction motion in addition to flexion-extension motion. In the force track computations involving contemporary simulators with the common femoral head size of 28 mm, the sliding distance per cycle and the force track integral per cycle ranged from 19.7 to 34.3 mm and from 17.4 to 43.5 N m, respectively. The average sliding speed ranged from 19.7 to 49.0 mm/s. The sum of track integrals computed with forces obtained by discretizing the contact pressure distribution reached a substantially higher value than the track integral obtained with the resultant contact force only. This suggests that the wear factor is actually overestimated when computed in the conventional way by dividing the wear rate with the force track integral.
Keywords: prosthetic hip joint, relative motion, slide track, wear simulators, wear factor.
K. Bartušek, E. Gescheidtová: A Magnetic Resonance Measurement Technique for Rapidly Switched Gradient Magnetic Fields in a Magnetic Resonance Tomograph
This paper describes a method for measuring of the gradient magnetic field in Nuclear Magnetic Resonance (NMR) tomography, which is one of the modern medical diagnostic methods. A very important prerequisite for high quality imaging is a gradient magnetic field in the instrument with exactly defined properties. Nuclear magnetic resonance enables us to measure the pulse gradient magnetic field characteristics with high accuracy. These interesting precise methods were designed, realised, and tested at the Institute of Scientific Instruments (ISI) of the Academy of Sciences of the Czech Republic. The first of them was the Instantaneous Frequency (IF) method, which was developed into the Instantaneous Frequency of Spin Echo (IFSE) and the Instantaneous Frequency of Spin Echo Series (IFSES) methods. The above named methods are described in this paper and their a comparison is also presented.
Keywords: nuclear magnetic resonance, gradient magnetic field, magnetic resonance tomography, instantaneous frequency methods, spin echo.
J. Bíla: To Whom Belongs Conceptual Design?

The field of Conceptual Design is very alive and is rapidly developing. This paper investigates the disciplines and domains which substantially form its profile. There are considered disciplines such as Semiotics, Formal Logic, Evolutionary analogies, Qualitative Modelling, Ontologies, Artificial Intelligence and Emergent Synthesis. The answer to the question posed in the title lies nowadays in disciplines related to Cognitive Science.

Keywords: conceptual design, semiotics, ontologies, UML, artificial intelligence.

G. Green: Design Evaluation: Decomposition and State-space Analysis

This paper outlines the increasing demands upon evaluation activity during the engineering design process. In particular, the need to address large numbers of innovative concept options during the conceptual design phase is stressed and a six-step methodology proposed. This methodology combines and integrates techniques of inexact reasoning with the need to combine two basic human approaches to evaluation, namely decomposition and holistic. The holistic evaluation elements comprise fuzzy estimates of probability of achieving Pareto optimal status combined with state-space analysis. An example demonstrates how these methods may converge to provide an appropriate support for human evaluation of emerging designs. It is concluded that the six-step methodology exhibits validity and time reduction in terms of providing an aid to the evaluation of a large number of merging designs and their associated design characteristics.

Keywords: evaluation, decomposition, pareto optimal, inexact reasoning, state-space.

Č. Jarský: On Planning and Managing the Preservation of Historical Buildings
The process of preserving and reconstructing historical buildings poses several specific questions and raises problems which must be solved in the planning and management stage of the building process - from questions of architectural and art-historical significance, via the future purpose of use of the building, links to the surrounding buildings, environmental questions, questions of cost, time analysis, and quality assurance problems. Many of these problems can be solved with the help of a computer model of the course of the rehabilitation and reconstruction of the building created by a construction technology network diagram. The CONTEC integrated project planning, management and quality control system based on these diagrams has been used for bidding, planning and managing the reconstruction process of several significant historical buildings in Prague and other cities.
Keywords: reconstruction, historical buildings, project management, planning, quality assurance, construction technology network diagram.
5 M. Diviš, R. Tichánek, M. Španiel: Heat Transfer Analysis of a Diesel Engine Head
This paper documents the research carried out at the Josef Božek Research Center of Engine and Automotive Engineering dealing with extended numerical stress/deformation analyses of engines parts loaded by heat and mechanical forces. It contains a detailed description of a C/28 series diesel engine head FE model and a discussion of heat transfer analysis tunning and results. The head model consisting of several parts allows a description of contact interaction in both thermal and mechanical analysis.
Keywords: heat transfer analysis, FEM, internal-combustion engine.
B. Jokele, D. K. Fuchs: Reducing Time for the Product Development Process by Evaluation in the Phase of Solution Searching
Less and less time is available for product development process. To prevent product failures and the resulting time intensive and cost intensive iteration steps, some preventive measures must be taken. Within the scope of quality management, FMEA anticipates possible problems concerning product and process properties. Nevertheless, in industrial practice designed products can have failures which were not considered within FMEA. The time pressure is immense, and efforts which do not make a contribution to a successful solution are regarded as lost time.This paper introduces a systematic approach to troubleshooting, with the aim of reducing the time for solution searching by considering the feasibility of ideas at an early stage.
Keywords: troubleshooting, change management, concurrent use of methods.
Tholudin Mat Lazim, Shabudin Mat, Huong Yu Saint: Computational Fluid Dynamic Simulation (CFD) and Experimental Study on Wing-external Store Aerodynamic Interference of a Subsonic Fighter Aircraft

The main objective of the present work is to study the effect of an external store on a subsonic fighter aircraft. Generally most modern fighter aircrafts are designed with an external store installation. In this study, a subsonic fighter aircraft model has been manufactured using a computer numerical control machine for the purpose of studying the effect of the aerodynamic interference of the external store on the flow around the aircraft wing. A computational fluid dynamic (CFD) simulation was also carried out on the same configuration. Both the CFD and the wind tunnel testing were carried out at a Reynolds number 1.86×105 to ensure that the aerodynamic characteristic can certify that the aircraft will not be face any difficulties in its stability and controllability. Both the experiments and the simulation were carried out at the same Reynolds number in order to verify each other. In the CFD simulation, a commercial CFD code was used to simulate the interference and aerodynamic characteristics of the model. Subsequently, the model together with an external store was tested in a low speed wind tunnel with a test section sized 0.45 m×0.45 m. Measured and computed results for the two-dimensional pressure distribution were satisfactorily comparable. There is only a 19 % deviation between pressure distribution measured in wind tunnel testing and the result predicted by the CFD. The result shows that the effect of the external storage is only significant on the lower surface of the wing and almost negligible on the upper surface of the wing. Aerodynamic interference due to the external store was most evident on the lower surface of the wing and almost negligible on the upper surface at a low angle of attack. In addition, the area of influence on the wing surface by the store interference increased as the airspeed increased.

Keywords: computational fluid dynamic (CFD), wind tunnel testing, CFD validation, aerodynamic interference.

H.-P. Geromiller, A. Farschtschi: Numerical Calculation of Electric Fields in Housing Spaces Due to Electromagnetic Radiation from Antennas for Mobile Communication
The influence of electromagnetic radiation from mobile antennas on humans is under discussion in various groups of scientists. This paper deals with the impact of electromagnetic radiation in a housing space. The space is assumed to be bordered by 5 walls of ferroconcrete and a door-window combination on the 6th side, the latter to be electromagnetically transparent. The transparent side of the housing is exposed to an electromagnetic wave. As the source of radiation is considered to be far away from the housing, the radiation is regarded to be from a plane wave. Due to the high signal frequency and ferroconcrete walls, 5 sides of the housing space are considered to be perfect conductors. The electric field inside the housing is calculated numerically by the method of finite differences for different angles of incidence of the radiated electromagnetic wave. The maximum value of the calculated electric field is outlined in a diagram. Keywords: numerical calculation, finite difference, electric fields, mobile communication.
B. Brůžek, E. Leidich: Numerical Simulation of Stresses in Thin-rimmed Spur Gears with Keyway
This paper contains an investigation of the key on a stress distribution in a thin-rimmed spur gear. A stress analysis was carried out by means of the Finite Element Method (FEM). The 2D-FE analysis has helped to find the influence of turning the gearing towards the keyway on the stress in the loaded root of the tooth and in the keyway. 2D and 3D numerical analysis has been used to find mutual influence of every single notch (root of tooth and keyway), influence of thickness of the hub, length of the key and the form of loading. Verification has been carried out through experimental method.
Keywords: gear, keyway, rim thickness.
D. Makovička, J. Král, D. Makovička: Verification of the Wind Response of a Stack Structure
This paper deals with verification analysis of the wind response of a power plant stack structure. Over a period two weeks the actual history of the dynamic response of the structure, and the direction and intensity of the actual wind load was measured, reported and processed with the use of a computer. The resulting data was used to verify the design stage data of the structure, with the natural frequencies and modes assumed by the design and with the dominant effect of other sources on the site. In conclusion the standard requirements are compared with the actual results of measurements and their expansion to the design load.
Keywords: stack structure, wind load, dynamic response, experimental verification.
T. Vyhlídal, P. Zítek: Anisochronic Internal Model Control Design
The features of internal model control (IMC) design based on the first order anisochronic model are investigated in this paper. The structure of the anisochronic model is chosen in order to fit both the dominant pole and the dominant zero of the system dynamics being approximated. Thanks to its fairly plain structure, the model is suitable for use in IMC design. However, use of the anisochronic model in IMC design may result in so-called neutral dynamics of the closed loop. This phenomenon is studied in this paper via analysing the spectra of the closed loop system.
Keywords: internal model control, time delay system, dynamics analysis, system spectrum.
J. Titlestad, T. Fairlie-Clarke, M. Davie, A. Whittaker, S. Grant: Experimental Evaluation of Mountain Bike Suspension Systems
A significant distinction between competitive mountain bikes is whether they have a suspension system. Research studies indicate that a suspension system gives advantages, but it is difficult to quantify the benefits because they depend on so many variables, including the physiology and psychology of the cyclist, the roughness of the track and the design of the suspension system. A laboratory based test rig has been built that allows the number of variables in the system to be reduced and test conditions to be controlled. The test rig simulates regular impacts of the rear wheel with bumps in a rolling road. The physiological variables of oxygen consumption and heart rate were measured, together with speeds and forces at various points in the system. Physiological and mechanical test results both confirm a significant benefit in using a suspension system on the simulated rough track, with oxygen consumption reduced by around 30 % and power transmitted through the pedals reduced by 30 % to 60 %.
Keywords: mountain bike, suspension, dynamics.
H. Cho, B. Oh, C. Jo, K. Lee: Process Design for Hot Forging of Asymmetric to Symmetric Rib-web Shaped Steel

The process design of hot forging, asymmetric to symmetric rib-web shaped steel, which is used for the turnout of express rails has been studied. Owing to the great difference in shape between the initial billet and the final forged product, it is impossible to hot forge the rail in a single stage operation. Therefore, multi stage forging and also die design for each stage are necessary for the production process. The numerical simulation for hot forging of asymmetric shape to symmetric shape was carried out using commercial FEM code, DEFORMTM-2D. Modification of the design and repeated simulation was carried out on the basis of the simulation results. For comparison with the simulation results, a flow analysis experiment using plasticine was also carried out. The results of the flow analysis experiment showed good agreement with those of the simulation.

Keywords: process design, hot forging, asymmetric, symmetric, high speed rail.

J. Ryś, H. Sanecki, A. Trojnacki: Analysis of Gear Wheel-shaft Joint Characterized by Comparable Pitch Diameter and Mounting Diameter
This paper presents the design procedure for a gear wheel-shaft direct frictional joint. The small difference between the operating pitch diameter of the gear and the mounting diameter of the frictional joint is the key feature of the connection. The contact surface of the frictional joint must be placed outside the bottom land of the gear, and the geometry of the joint is limited to the specific type of solutions.

The strength analysis is based on the relation between the torque and statistical load intensity of the gear transmission. Several dimensionless parameters are introduced to simplify the calculations. Stress-strain verifying analysis with respect to combined loading, the condition of appropriate load-carrying capacity of the frictional joint and the fatigue strength of the shaft are applied to obtain the relations between the dimensions of the joint and other parameters. The final engineering solution may then be suggested. The approach is illustrated by a numerical example.

The proposed procedure can be useful in design projects for small, high-powered modern reducers and new-generation geared motors, in particular when manufactured in various series of types.
Keywords: geared motor, gear wheel, frictional joint, strength analysis, fatigue.
I. Jelínek: Modal Logic - a Tool for Design Process Formalisation
In this paper we show the possibility to formalize the design process by means of one type of non-standard logic - modal logic [1]. The type chosen for this study is modal logic S4. The reason for this choice is the ability of this formalism to describe modeling of the individual discrete steps of design, respecting necessity or possibility types of design knowledge. Keywords: modal logic, accessibility relation, design process, formalisation of design process.
6 E. Ritschl, R. Theiner, D. Hanus: Inlet Channel for a Ducted Fan Propulsion System of a Light Aircraft
So-called "cold-jet" propulsion units consist of a piston engine, a blower and the necessary air duct. Till now, all attempts to utilize "cold-jet" propulsion units to maintain the thrust of an airplane have been unsuccessful. Analysis has shown that the main difficulty is the deformation of the flow field at the entry to the blower [1].
Keywords: aircraft, ducted fan, cold-jet, inlet channel, aerodynamics.
M. Valášek, P. Steinbauer, J. Kolář, J. Dvořák: Concurrent Design of Railway Vehicles by Simulation Model Reuse
This paper describes a concurrent design approach to railway vehicle design. Current railway vehicles use many different concepts that are combined into the final design concept. The design support for such systems is based on reusing components from previous design cases. The key part of the railway vehicle design concept is its simulation model. Therefore the support is based on support for reuse of previous simulation models. The simulation models of different railway component concepts are stored using the methodology from the EU CLOCKWORK project. The new concept usually combines stored components.
Keywords: Concurrent engineering, design, reuse, railway vehicles, simulation model.
T. Hagras, J. Janeček: Static vs. Dynamic List-Scheduling Performance Comparison
The problem of efficient task scheduling is one of the most important and most difficult issues in homogeneous computing environments. Finding an optimal solution for a scheduling problem is NP-complete. Therefore, it is necessary to have heuristics to find a reasonably good schedule rather than evaluate all possible schedules. List-scheduling is generally accepted as an attractive approach, since it pairs low complexity with good results. List-scheduling algorithms schedule tasks in order of priority. This priority can be computed either statically (before scheduling) or dynamically (during scheduling). This paper presents the characteristics of the two main static and the two main dynamic list-scheduling algorithms. It also compares their performance in dealing with random generated graphs with various characteristics.

Keywords: list scheduling, compile time scheduling, task graph scheduling, homogeneous computing.
M. V. Jokl: Indoor Air Quality Assessment Based on Human Physiology - Part 1. New Criteria Proposal
Human physiology research makes evident that the Weber-Fechner law applies not only to noise perception but also to the perception of other environmental components. Based on this fact, new decibel units for odor component representing indoor air quality in majority locations have been proposed: decicarbdiox dCd (for carbon dioxide CO2) and decitvoc dTv (for total volatile organic compound TVOC). Equations of these new units have been proved by application of a) experimental relationships between odor intensity (representing odor perception by the human body) and odor concentrations of CO2 and TVOC, b) individually measured CO2 and TVOC levels (concentrations) - from these new decibel units can be calculated and their values compared with decibel units of noise measured in the same locations. The undoubted benefit of using the decibel scale is that it gives much better approximation to human perception of odor intensity compared to the CO2 and TVOC concentration scales.

Keywords: indoor air quality, odors, air changes estimation.

M. V. Jokl: Indoor Air Quality Assessment Based on Human Physiology - Part 2. Limits

In order to evaluate indoor air quality in practice it is necessary to establish limits, or more exactly, tolerable ranges for unadapted and adapted persons. The optimal value overwhelmingly corresponds to PD = 20 %. A better value of PD = 10 % could be prescribed for asthmatics and for persons with increased requirements, i.e. those allergic to the environment and operators in airport control towers and atomic power stations. A worse value PD = 30 % could be accepted as an admissible value. These values differ for unadapted and adapted persons (as introduced by BSR/ASHRAE 62-1989 R). The long-term tolerable value is the end of SBS range (for CO2 it is based on USSR space research, for TVOC on Molhave). The short-term tolerable value is the beginning of the toxic range (for CO2 it is taken from British Guidance Note EH 40/90; for TVOC from Molhave).

Keywords: indoor air quality, odors, air changes estimation.

M. V. Jokl: Indoor Air Quality Assessment Based on Human Physiology - Part 3. Applications

The proposed evaluation system allows something quite new: a) the assessment of the effect of each environmental component (constituent) on the total environment level, b) accurate estimation of air volume for various locations, human occupations and sources of harmful gases. Additional benefits are listed at the conclusion of this part.

Keywords: indoor air quality, odors, air changes estimation.

S. Pekárek: Non-Thermal Plasma Ozone Generation

This paper reviews ozone properties, ozone applications and the mechanism of ozone production in non-thermal plasma. An analysis is made of the influence of a reduced electric field and discharge space temperature on ozone production. The phenomenon of discharge poisoning is also explained. Finally, a modern ozone production system based on dielectric barrier electrical discharge is described.

Keywords: ozone, non-thermal plasma, electrical discharge.

Taha H. S. Abdelaziz, M. Valášek: A Direct Algorithm for Pole Placement by State-derivative Feedback for Single-input Linear Systems

This paper deals with the direct solution of the pole placement problem for single-input linear systems using state-derivative feedback. This pole placement problem is always solvable for any controllable systems if all eigenvalues of the original system are nonzero. Then any arbitrary closed-loop poles can be placed in order to achieve the desired system performance. The solving procedure results in a formula similar to the Ackermann formula. Its derivation is based on the transformation of a linear single-input system into Frobenius canonical form by a special coordinate transformation, then solving the pole placement problem by state derivative feedback. Finally the solution is extended also for single-input time-varying control systems. The simulation results are included to show the effectiveness of the proposed approach.

Keywords: pole placement, state-derivative feedback, linear single-input systems, feedback stabilization.

Acta Polytechnica 2004

No. (click on selected title and view the annotation)
1 Farag Ibrahim Younis Elnagahy, B. Šimák: Wavelet-Based Embedded Rate Scalable Still Image Coders: A review

Embedded scalable image coding algorithms based on the wavelet transform have received considerable attention lately in academia and in industry in terms of both coding algorithms and standards activity. In addition to providing a very good coding performance, the embedded coder has the property that the bit stream can be truncated at any point and still decodes a reasonably good image. In this paper we present some state-of-the-art wavelet-based embedded rate scalable still image coders. In addition, the JPEG2000 still image compression standard is presented.

Keywords: JPEG2000, embedded image coding, grayscale, color, scalable, progressive, compression, discrete wavelet transform.

T. Brandejský: Implementation of Component-based Simulation Support Tool for Conceptual Design

Presented paper speaks about the problem of conceptual design stage simulation support. Simulation support is a very useful part of conceptual design system due to capability to verify ideas in early design stages. The problem excluding classical simulation tools is lack of information about designed device, is inconsistency and uncertainty. Thus specialised tool must be developed. The component-oriented editor of component descriptions and models is presented. This tool enables to describe components not only in terms of algebraic equations, but also by fuzzy rules. The problem of dynamic work with uncertainty representation during simulation and design processes is also solved. Presented tool also differentiates from standard tools like Mathematica or Matlab in its ability to work with component-based models, where each component is described from many aspects and only few of them are valid in concrete use. The tool must be able to select relations relevant in concrete simulation task and omit the rest.

Keywords: component-based simulation, conceptual design, mixed uncertainty description, heterogeneous model, dynamic uncertainty representation selection.

A. El-Bassuny Alawy, F. I. Y. Elnagahy, A. A. Haroon, Y. A. Azzam, B. Šimák: Stellar Image Interpretation System Using Artificial Neural Networks: II - Bi-polar Function Case

A supervised Artificial Neural Network (ANN) based system is being developed employing the Bi-polar function for identifying stellar images in CCD frames. It is based on feed-forward artificial neural networks with error back-propagation learning. It has been coded in C language. The learning process was performed on a 341 input pattern set, while a similar set was used for testing. The present approach has been applied on a CCD frame of the open star cluster M67. The results obtained have been discussed and compared with those derived in our previous work employing the Uni-polar function and by a package known in the astronomical community (DAOPHOT-II). Full agreement was found between the present approach, that of Elnagahy et al, and the standard astronomical data for the cluster. It has been shown that the developed technique resembles that of the Uni-Polar function, possessing a simple, much faster yet reliable approach. Moreover, neither prior knowledge on, nor initial data from, the frame to be analysed is required, as it is for DAOPHOT-II.

Keywords: neural networks, knowledge-based system, stellar images, image processing.

I. H. Tuncer, M. Kay: Optimization of Flapping Airfoils for Maximum Thrust and Propulsive Efficiency

A numerical optimization algorithm based on the steepest decent along the variation of the optimization function is implemented for maximizing the thrust and/or propulsive efficiency of a single flapping airfoil. Unsteady, low speed laminar flows are computed using a Navier-Stokes solver on moving overset grids. The flapping motion of the airfoil is described by a combined sinusoidal plunge and pitching motion. Optimization parameters are taken to be the amplitudes of the plunge and pitching motions, and the phase shift between them. Computations are performed in parallel in a work station cluster. The numerical simulations show that high thrust values may be obtained at the expense of reduced efficiency. For high efficiency in thrust generation, the induced angle of attack of the airfoil is reduced and large scale vortex formations at the leading edge are prevented.

Keywords: optimization, flapping airfoils, unsteady aerodynamics, moving overset grids.

L. Végh: The Psychological Image of Realistic Physical Quantities.The Psychological Speed of Aging

The article is dealing with psychological images of real physical quantities, such as time, length, etc. and with their interrelationship in general and in the scientific field in particular. It has been shown that the importance of the above is reflected by the possibility to influence or reshape, within certain limits, positively or negatively, the psychological images of real values, so as to meet the outlined or desired expectation. As shown, one of the possible practical application of the above phenomenon is the possibility to positively influence the speed of aging.This problem has been demonstrated in the article analytically, as well as graphically.

Keywords: real values, psychological image, biological vs. psychological age, psychological speed of aging.

B. A. Belyaev, A. A. Leksikov, S. G. Ovchinnikov, I. Kraus, A. S. Parshin: Magnetic Technique for Nondestructive Evaluation of Residual Stresses

A technique has been designed for measuring planar components of stray fields from ferromagnetic samples placed in a constant magnetizing field. The technique is based on recording the field of magnetization reversal of a thin magnetic film with the small coercive force being the sensor device of a microwave detector. The possibility of measuring the deformation inhomogeneities caused by mechanical treatment when manufacturing products from ferromagnetic materials is demonstrated. The results of the magnetic measurements agree with the data from X-ray diffraction analysis.

Keywords: ferromagnetic resonance, thin magnetic films, microvawe scanning spectrometer, residual stress

A. Noriega Ponce, A. Aguado Behar, A. Ordaz Hernández, V. Rauch Sitar: Neural Networks for Self-tuning Control Systems

In this paper, we presented a self-tuning control algorithm based on a three layers perceptron type neural network. The proposed algorithm is advantageous in the sense that practically a previous training of the net is not required and some changes in the set-point are generally enough to adjust the learning coefficient. Optionally, it is possible to introduce a self-tuning mechanism of the learning coefficient although by the moment it is not possible to give final conclusions about this possibility. The proposed algorithm has the special feature that the regulation error instead of the net output error is retropropagated for the weighting coefficients modifications.

Keywords: neural networks, feedforward, back-propagation, networks, self-tuning control.

T. Zadražil, F. Vodák, O. Kapičková: Effect of Temperature and Age of Concrete on Strength - Porosity Relation

The compressive strengths of unsealed samples of concrete at the age of 180 days and have been measured at temperatures 20 °C, 300 °C, 600 °C and 900 °C. All of tests were performed for cold material. We compared our results with those obtained in [10] for the same type of concrete (age 28, resp. 90 days and measured at temperature ranging from 20 °C to 280 °C). Dependencies of compressive strength and porosity were correlated together and compared for the samples of age 28, 90 and 180 days. Behaviour of concrete of the age 90, resp. 180 days confirms generally accepted hypothesis that with increasing porosity strength of the concrete decreases. It has to be stressed out, howerer, that concrete samples of the age 28 days exhibit totally opposite dependency.

Keywords: compressive strength, temperature dependency, porosity.

V. Sopko, K. Trtík, F. Vodák: Influence of Gamma Irradiation on Concrete Strength

Aging of concrete due to gamma irradiation. Strength of concrete are in a good correspondency with already known results.

Keywords: concrete, gamma irradiation, strength.

Č. Šimáně, M. Vognar, D. Chvátil: The System for Control and Stabilization of the Beam Position in the Microtron MT-25 in Prague
A method of control the beam position at crucial points of the transport system and for the stabilization of its output position has been proposed and preliminary tested. The method is based on secondary electron emission from a thin metallic wire probe induced by electrons from the 25 MeV microtron. It was demonstrated, that magnetic field of the order of 0.2 T and parallel to the wire probe in front of the orifice of the extraction channel in the acceleration space, does not prevent the functioning of the method. A strong parasitic effect of secondary electron emission from the material of the channel and its support construction was found, leading to the inversion of the electron current polarity from the wire. This effect can be to great extent eliminated by negative electric potential bias relative to the channel. At the electron output current of 1 mA the secondary emission current from the wire probe of 0.3 mm diameter is of the order of several nA. Two electromechanical systems were designed for the removal of the probes from the beam path, to avoid the deterioration of the electron beam quality by scattering. Electronic schemes used for remote measurement of small probe currents, suppressing the influence of strong electromagnetic noise, are described. For stabilization of the output beam position two wire probes situated in air close to the Al output window were used. These probes having been placed at the periphery of the beam did not deteriorate the beam quality. The difference of their emission currents was used as an error signal to control the magnetic field of the last dipole, which kept the beam in the center of the output window. Keywords: microtron, electron transport, beam detection, beam position stabilization, secondary electron emission.
2 D. J. Murray-Smith: Biological Systems Thinking for Control Engineering Design
Artificial neural networks and genetic algorithms are often quoted in discussions about the contribution of biological systems thinking to engineering design. This paper reviews work on the neuromuscular system, a field in which biological systems thinking could make specific contributions to the development and design of automatic control systems for mechatronics and robotics applications. The paper suggests some specific areas in which a better understanding of this biological control system could be expected to contribute to control engineering design methods in the future. Particular emphasis is given to the nonlinear nature of elements within the neuromuscular system and to processes of neural signal processing, sensing and system adaptivity. Aspects of the biological system that are of particular significance for engineering control systems include sensor fusion, sensor redundancy and parallelism, together with advanced forms of signal processing for adaptive and learning control.
Keywords: biology, control systems, design, neuro-muscular system.
Tholudin Mat Lazim, Shabudin Mat, Huong Yu Saint: Computational Fluid Dynamic Simulation (CFD) and Experimental Study on Wing-external Store Aerodynamic Interferenceof a Subsonic Fighter Aircraft

The main objective of the present work is to study the effect of an external store to a subsonic fighter aircraft. Generally most modern fighter aircraft is designed with an external store installation. In this project a subsonic fighter aircraft model has been manufactured using a&nbsp;computer numerical control machine for the purpose of studying the effect of the external store aerodynamic interference on the flow around the aircraft wing. A computational fluid dynamic (CFD) and wind tunnel testing experiments have been carried out to ensure the aerodynamic characteristic of the model then certified the aircraft will not facing any difficulties in stability and controllability. In the CFD experiment, commercial CFD code is used to simulate the interference and aerodynamic characteristics of the model. Subsequently, the model together with an external store was tested in a low speed wind tunnel with test section sized 0.45 m × 0.45 m. Result in the two-dimensional pressure distribution obtained by both experiments are comparable. There is only 12 % deviation in pressure distribution found in wind tunnel testing compared to the result predicted by the CFD. The result shows that the effect of the external storage is only significant at the lower surface of the wing and almost negligible at the upper surface of the wing. Aerodynamic interference is due to the external storage were mostly evidence on a lower surface of the wing and almost negligible on the upper surface at low angle of attack. In addition, the area of influence on the wing surface by store interference increased as the airspeed increase.
Keywords: computational fluid dynamic (CFD), wind tunnel testing, validation, aerodynamic interference.

K. Sibilski: Dynamics of Micro-Air-Vehicle with Flapping Wings
Small (approximately 6 inch long, or hand-held) reconnaissance micro air vehicles (MAVs) will fly inside buildings, and require hover for observation, and agility at low speeds to move in confined spaces. For this flight envelope insect-like flapping wings seem to be an optimal mode of flying. Investigation of the aerodynamics of flapping wing MAVs is very challenging. The problem involves complex unsteady, viscous flow (mainly laminar), with the moving wing generating vortices and interacting with them. At this early stage of research only a preliminary insight into the nature of the little known aerodynamics of MAVs has been obtained. This paper describes computational models for simulation of the controlled motion of a microelectromechanical flying insect - entomopter. The design of software simulation for entomopter flight (SSEF) is presented. In particular, we will estimate the flight control algorithms and performance for a Micromechanical Flying Insect (MFI), a 80–100 mm (wingtip-to-wingtip) device capable of sustained autonomous flight. The SSEF is an end-to-end tool composed of several modular blocks which model the wing aerodynamics and dynamics, the body dynamics, and in the future, the environment perception, control algorithms, the actuators dynamics, and the visual and inertial sensors. We present the current state of the art of its implementation, and preliminary results.
Keywords: micromechanical flying insect, entomopter aerodynamics, entomopter dynamics, insect flight, software simulator, insect aerodynamics, insect dynamics.
M. Ota, I. Jelínek: The Role of CAD in Enterprise Integration Process
This article deals with the problem of the mutual influence between software systems used in enterprise environment and enterprise integration processes. The position of CAD data and CAx systems in the integrated environment of manufacturing enterprises is clarified. As a consequence, the key role of CAx systems used in those companies is emphasized. It is noted that the integration of CAD data is nowadays only on a secondary level, via primarily integrated PDM systems. This limitation is a reason why we are developing a unified communication model focused on product-oriented data. Our approach is based on Internet technologies, so we believe that is independent enough. The proposed system of communication is based on a simple request-replay dialogue. The structure of this model is open and extensible, but we assume supervision supported by an Internet portal.
Keywords: CAD, Enterprise Information Systems, Internet Portals, PDM.
A. V. Petrov, Y. G. Stepanov, M. V. Shmakov: Development of a Technique and Method of Testing Aircraft Models with Turboprop Engine Simulators in a Small-scale Wind Tunnel - Results of Tests
This report presents the results of experimental investigations into the interaction between the propellers (Ps) and the airframe of a twin-engine, twin-boom light transport aircraft with a Ő-shaped tail. An analysis was performed of the forces and moments acting on the aircraft with rotating Ps. The main features of the methodology for windtunnel testing of an aircraft model with running Ps in TsAGI`s T-102 wind tunnel are outlined.The effect of 6-blade Ps slipstreams on the longitudinal and lateral aerodynamic characteristics as well as the effectiveness of the control surfaces was studied on the aircraft model in cruise and takeoff/landing configurations. The tests were conducted at flow velocities of VĄ= 20 to 50 m/s in the ranges of angles of attack a = -6 to 20 deg, sideslip angles of b = -16 to 16 deg and blade loading coefficient of B=0 to 2.8. For the aircraft of unusual layout studied, an increase in blowing intensity is shown to result in decreasing longitudinal static stability and significant asymmetry of the directional stability characteristics associated with the interaction between the Ps slipstreams of the same (left-hand) rotation and the empennage.
Keywords: windtunnel testing, propeller slipstream, engine failure, test methodology.
R. W. Vroom, E. J. J. van Breemen, W. F. van der Vegte: Developing a Conceptual Design Engineering Toolbox and its Tools
In order to develop a successful product, a design engineer needs to pay attention to all relevant aspects of that product. Many tools are available, software, books, websites, and commercial services. To unlock these potentially useful sources of knowledge, we are developing C-DET, a toolbox for conceptual design engineering. The idea of C-DET is that designers are supported by a system that provides them with a knowledge portal on one hand, and a system to store their current work on the other. The knowledge portal is to help the designer to find the most appropriate sites, experts, tools etc. at a short notice. Such a toolbox offers opportunities to incorporate extra functionalities to support the design engineering work. One of these functionalities could be to help the designer to reach a balanced comprehension in his work. Furthermore C-DET enables researchers in the area of design engineering and design engineers themselves to find each other or their work earlier and more easily. Newly developed design tools that can be used by design engineers but have not yet been developed up to a commercial level could be linked to by C-DET. In this way these tools can be evaluated in an early stage by design engineers who would like to use them. This paper describes the first prototypes of C-DET, an example of the development of a design tool that enables designers to forecast the use process and an example of the future functionalities of C-DET such as balanced comprehension.
Keywords: toolbox, conceptual design engineering, development process, use process forecast, balanced comprehension.
M. Valášek, P. Steinbauer, Z. Šika, Z. Zdráhal: Knowledge Support of Simulation Model Reuse
This describes the knowledge support for engineering design based on virtual modelling and simulation. These are the results of the EC Clockwork project. A typical and important step in the development of a simulation model is the phase of reusing. Virtual modelling and simulation often use the components of previous models. The usual problem is that the only remaining part of the previous simulation models is the model itself. However, a large amount of knowledge and intermediate models have been used, developed and then lost. A special methodology and special tools have therefore been developed on support of storing, retrieving and reusing the knowledge from previous simulation models. The knowledge support includes informal knowledge, formal knowledge and intermediate engineering models. This paper describes the overall methodology and tools, using the example of developing a simulation model of Trijoint, a new machine tool.
Keywords: Simulation model, reuse, knowledge management, machine tool.

M. Studničková: The Effect of Pedestrian Traffic on the Dynamic Behavior of Footbridges
The dynamic response of a footbridge depends namely on the natural frequencies of the structure in vertical, in horizontal and in torsion. If any of the frequencies in vertical is in the range 1.0 Hz to 3.0 Hz, the dynamic response from moving people can be significant. In this case it is necessary to calculate vibrations taking into account both serviceability and ultimate limit states. The same problem arises when any of the frequencies in horizontal (transversal) or in torsion are in the range 0.5 Hz to 1.5 Hz. Such frequencies haveare found namely in footbridges with larger spans or cable-stayed and suspension footbridges.A unique cable-stayed footbridge with prestressed concrete was dynamically analyzed and the dynamic response to simulated pedestrian loading was calculated. The calculated effects were compared with the pedestrian comfort criteria for serviceability limit states. These criteria are defined in terms of maximum acceptable acceleration of the bridge deck.
Keywords: vibrations, footbridge, dynamic actions due to pedestrians, acceptance criteria, response, serviceability.
P. Fošumpaur, L. Satrapa: Control of Systems of Reservoirs with the Use of Risk Analysis
A system of reservoirs is usually defined as a system of water management elements, that are mutually linked by inner and outer connections in a purpose-built complex. Combined elements consist of reservoirs, river sections, dams, weirs, hydropower plants, water treatment plants and other hydraulic structures. These elements also include the rainfall system, the run-off system, the ground water system, etc. A system of reservoirs serves many purposes, which result from the basic functions of water reservoirs: storage, flood control and environmental functions. Most reservoirs serve several purposes at the same time. They are so called multi-purposes reservoirs. Optimum design and control of a system of reservoirs depends strongly on identifying the particular purposes. In order to assess these purposes and to evaluate the appropriate set of criteria, risk analysis can be used. Design and control of water reservoir functions is consequently solved with the use of multi-objective optimisation. This paper deals with the use of the risk analysis to determine criteria for controlling the system. This approach is tested on a case study of the Pastviny dam in the Czech Republic.
Keywords: risk analysis, system of reservoirs, multi-objective optimisation, water supply, hydropower plant, fuzzy logic.
V. Zagursky, I. Zarumba, A. Riekstinsh: A coding and On-Line Transmitting System
A distributed data acquisition system is proposed. It provides parallel and simultaneous coding and on-line transmission of signals. This system has higher accuracy of measurements and performance in sampling and transmission than known analogs.

V. Zagursky, A. Riekstinsh: Speech Signal Recovery in Communication Networks
Interpolation approaches to the shape recovery of a speech signal in transmission over packet switched communications networks are proposed. The samples of signal fragments are mixed and transmitted in correspondence with standard procedure for packet-switched transmission. After reception a reverse permutation is made. In the case of packet losses missing samples are separated by several samples of the source signal. Correlation properties of the signal are used for the recovery samples due to first- and second-order non-adaptive and adaptive interpolation. For the loss of 25 % packets and second order adaptive interpolation a 2- 4 % error distribution range has been achieved.
J. Čulík: Simulation of Scoliosis Treatment Using a Brace
Ivo Mařík M.D. has treated many child patients with scoliosis at the "Centre for Locomotor Defects", Olšanská 7, 130 00 Prague 3. The author has cooperated with him, and composed the computer program for the spine stress state under brace effects and for simulating scoliosis treatment. The program simulates the spinal curve remodelling in time for a specific child patients, and the algorithm for stress state calculation and treatment simulation is given.Orthopaedists in the Czech Republic use Cheneau-type or Cerny-type corrective braces. The brace exerts force effects on the skeleton of a child. The brace is made individually for each patient, in the following way: first, a negative plaster form of the child`s trunk is made, and then the positive plaster form is created. The orthopaedist determines the places where brace has to load the patient`s trunk, and the plaster form deepened in these places on the basis of his advice. The laminate brace made according to this plaster form constricts the child`s trunk (like a tight shoe).This paper shows how the stress state is determined in vertebrae and in inter-vertebral discs, and the solution of spinal curvature correction under brace force effects for a specific child patient. The project aims to find the dependence of the activation and velocity of spinal curvature correction in the spinal stress state for many patients. The paper shows the computing algorithms for spinal deformations and the stress state under brace force effects, and a simulation of spinal curvature correction.Spinal curvature is determined according to measured values on an X-ray of a patient before a brace is applied. The stress state in the spine and the spinal deformation are investigated by the finite element method as beam (spine) in an elastic ground (soft tissue). Two algorithms are used. The first algorithm deals with the spine above and below the soft tissues, and it is loaded by given displacements of the trunk surface. The second algorithm determines from the X-ray of a patient with and without a brace the spine deformation and the spine stress state, and the necessary trunk surface displacement is determined from this deformation.The calculation algorithm and parameters were compared with contest of treatment. The trunk surface load was checked by sensor that plates were placed into the braces to measure the load values between the brace and the surface of the child. The simulation program assesses the spinal curvature correction according to the spinal curvature type, the spinal stress state and the period of time for which the brace will be applied.
Keywords: biomechanics, simulation of treatment, scoliosis, spine stress state, spine remodelling.
J. Dušek, M. Dostálek: Image Analysis of Eccentric Photorefraction
This article deals with image and data analysis of the recorded video-sequences of strabistic infants. It describes a unique noninvasive measuring system based on two measuring methods (position of I. Purkynje image with relation to the centre of the lens and eccentric photorefraction) for infants. The whole process is divided into three steps. The aim of the first step is to obtain video sequences on our special system (Eye Movement Analyser). Image analysis of the recorded sequences is performed in order to obtain curves of basic eye reactions (accommodation and convergence). The last step is to calibrate of these curves to corresponding units (diopter and degrees of movement).
Keywords: eccentric photorefraction, purkynje images, strabismus, image analysis.
D. J. Telfer, J. W. Spencer, G. R. Jones, J. E. Humphries: A Novel Approach to Power Circuit Breaker Design for Replacement of SF6
This contribution explores the role of PTFE ablation in enhancing current interruption for various background gases in high voltage circuit breakers. An assessment of the current interruption capability has been made in terms of the arcing duration and the contact gap length at which critical arc extinction is achieved. These observations are supported by measurements of the magnitude of extinction and re-ignition voltage peaks. Most previous and other current experimental work on gas filled circuit breaker design follows conventional wisdom in investigating arcing behaviours at elevated gas pressures (usually up to 6 bar). But in this work we concentrate on the effects of using low gas pressures (less than 1 bar) in the presence of a close-fitting shield of ablatant polymer material (PTFE) that surrounds the electrode assembly of an experimental high power circuit breaker. We demonstrate that for several different gases, arc extinction capability compares well under these conditions with SF6, suggesting that SF6 could be replaced entirely in this novel system by more environmentally friendly gases. Moreover, the critical contact gap lengths at extinction are only slightly greater than when using SF6 at 6 bar. Weight loss measurements from the ablatant shield suggest that a chemical puffer action is the most likely mechanism for achieving the observed arc extinctions in this system.
Keywords: circuit breaker, power distribution, SF6 replacement, arc-induced ablation, anti-pollution.
J. Murín, M. Kropáč, R. Fric: Numerical Analysis of the Temperature Field in Luminaires
This paper contains a calculation of the thermal field caused by electro-heat in lighting devices. After specifying the heat sources, a thermal analysis is make using the finite element method and the equivalent thermal scheme method. The calculated results have been verified experimentally.
Keywords: thermal analysis, luminaire, choke coil, heat loss, surface temperature, finite element method.
S. Nikolovski, T. Barić: Computer Aided Design of Transformer Station Grounding System Using CDEGS Software
This paper presents a computer-aided design of a transformer station grounding system. Fault conditions in a transformer station can produce huge damage to transformer station equipment if the grounding system is not designed properly. A well designed grounding system is a very important part of the project for transformer station design as a whole. This paper analyses a procedure for transformer grounding system design and spatial distribution of touch and step voltage on the ground surface level, using the CDEGS (Current Distribution Electromagnetic Interference Grounding and Soil Structure Analysis) software. Spatial distribution is needed for checking and finding dangerous step and touch voltages above and around the transformer station. Apparent earth resistivity data is measured and analyzed using the RESAP module of the CDEGS software. Because of the very high current flow into the grounding system during a single line to ground fault or a three phase fault in the transformer station, very high and dangerous potentials can be induced on the metallic structures including the fence, which can cause dangerous situations for people and animals near the station and for the personnel inside the station. The PLOT module of CDEGS is used to view the results of the scalar potential, step and touch voltage on the surface. Graphic displays include equipotent contour lines and potential profiles (gradients) in 3D and 2D perspective and apparent soil resistivity (Wm) versus inter electrode spacing (m). The results of alternative grid designs may be displayed simultaneously for the purpose of comparison. Keywords: computer-aided design, substation, grounding grid, soil, safety, touch and step voltage.
T. Bányai: Recycling and Networking
In recent years, the notion that for environmental and legislative reasons improvements The national environmental policies and practice, including recycling strategies, are desirable and in many cases might be economically beneficial has been gaining ground. Although according to recent surveys the state of the environment in Hungary is in line with average values of the European Union, the main challenge for the country is to achieve sustainability in economic, environmental and technological terms. With a view to accession to the European Union, a harmonisation strategy must be worked out and implemented. This harmonisation strategy includes not only legislative aspects, but also social, technological, financial and logistic considerations.Because of the high logistic costs of achieving closed loop recycling systems, the author focuses on logistic aspects and tasks of the improvement phases and concentrates on the possibilities of networking and co-operation. The paper describes some possible alternative solutions for co-operative recycling processes, to improve the following logistic parameters: delivery times, accuracy of supply, running times, utilization of capacities, stock quantities, flexibility, transparency of the system, high forwarding capability, quality of product. The logistic aspects of co-operation will be analysed from the viewpoint of a closed loop economy.
Keywords: co-operation, logistics, networking, optimisation, recycling.
P. Chudý: Response of a Light Aircraft Under Gust Loads
This project presents work performed by the Institute of Aerospace Engineering, Brno University of Technology. The primary purpose of this work was to estimate the aeroelastic response of a light aircraft under gust loads. In the past, the gust response has been investigated using the Pratt - Walker formula. This formula is derived from the response of a rigid airplane to a discrete gust. However, the Pratt-Walker formula does not capture either the stochastic nature of continuous turbulence or the effects of structural flexibility. The analysis described here was performed using the advanced FEM software package MSC Nastran.
Keywords: gust load, finite element, aeroelasticity, frequency response, continuous turbulence.
S. Slavík: Preliminary Determination of Propeller Aerodynamic Characteristics for Small Aeroplanes
This paper deals with preliminary determination of propeller thrust and power coefficients depending on the advance ratio by means of some representative geometric parameters of the blade at a specific radius: propeller blade chord and blade angle setting at 70 % of the top radius, airfoil thickness at the radius near the tip and the position of the maximum blade width. A rough estimation of the non-linear influence of propeller blades number is included.The published method is based on Lock`s model of the characteristic section and the Bull-Bennett lift and drag propeller blade curves. Lock`s integral decomposition factors and the loss factor were modified by the evolution of the experimental propeller characteristics. The numerical-obtained factors were smoothed and expressed in the form of analytical functions depending on the geometric propeller blade parameters and the advance ratio.
Keywords: propeller, propeller aerodynamics, thrust coefficient, power coefficient, propeller efficiency, propeller design.
3 J. Ulrych: Analysis of Unsteady Transonic Flow Fields by Means of the Colour Streak Schlieren Method

This article deals with a new approach to the investigation of unsteady transonic flow fields around aerodynamic models and in blade cascades using a schlieren method of flow visualisation. The principle and the application of the Colour Streak Schlieren Method (CSSM) are defined. The characteristic flow field features were observed and analysed around an oscillating NACA 0012 airfoil under the conditions of transonic free stream Mach number (MĄ= 0.9), initial angle of attack (a = +4 deg), one amplitude of oscillation (Da = ±3 deg), and three frequencies of model oscillation (f = 1, 15, 30 Hz). There is a description of the terminal shock wave hysteresis across the investigated area, which was revealed in particular cases. Application possibilities of CSSM and its further development are discussed.

Keywords: High-speed aerodynamics, experiment, flow field analysis, transonic flow fields, flow visualisation, Colour Streak Schlieren Method.

F. M. Catalano: On the Effects of an Installed Propeller Slipstream on Wing Aerodynamic Characteristics
This work presents an experimental study of the effect of an installed propeller slipstream on a wing boundary layer. The main objective was to analyse through wind tunnel experiments the effect of the propeller slipstream on the wing boundary layer characteristics such as: laminar flow extension and transition, laminar separation bubbles and reattachment and turbulent separation. Two propeller/wing configurations were studied: pusher and tractor. Experimental work was performed using two different models: a two-dimensional wing with a central cylindrical nacelle for the tractor configuration, and a simple two-dimensional wing with a downstream propeller for the pusher tests. The relative position between propeller and wing could be changed in the pusher model, and a total of 7 positions were analysed. For the tractor tests the relative propeller/wing was fixed, but three different propellers: two, three and four bladed were tested. Measurements included pressure distribution, hot wire anemometry and boundary layer characteristics by flow visualisation. The results showed that the pusher propeller inflow affects the wing characteristics by changing the lift, drag, and also delays the boundary layer transition and separation. These effects are highly dependent on the relative position of the wing/propeller. On the other hand, the tractor propeller slipstream induces transition and its effect is dependent on the number of blades.
Keywords: Wing /propeller interference, propeller slipstream, boundary layer.
J. Heger: Finite Element Modelling of Mechanical Phenomena Connected to the Technological Process of Continuous Casting of Steel
A finite element method algorithm is presented that enables numerical simulation of real phenomena that take place during an industrial process of continuous casting of steel. The algorithm takes into account all known kinds of nonlinearities: material nonlinearity connected to the nonlinear temperature dependence of material properties, large deformations from the process of material forming and contacts between the slab and rollers of the strand. Received results describe the sensitivity of the product to crack initiation, not only during the process of continuous casting itself but also in the finished and cooled slab.
Keywords: Continuous casting, steel slab, numerical simulation, finite element method, nonlinearity, large deformations, contact, crack initiation.
T. Mareš: Controlling Laminate Plate Elastic Behavior
This paper aims to express the relation of a measure of laminate plate stiffness with respect to the fiber orientation of its plies. The inverse of the scalar product of the lateral displacement of the central plane and lateral loading of the plate is the measure of laminate plate stiffness. In the case of a simply supported rectangular laminate plate this measure of stiffness is maximized, and the optimum orientation of its plies is searched.
Keywords: mechanical properties, laminate, plate, composites.
V. Bauma, M. Valášek, Z. Šika: Design and Properties of Octaslide Redundant Parallel Kinematics
This paper describes the conceptual design process of OCTASLIDE redundant parallel kinematics for a machine tool. Redundantly actuated parallel kinematics is a recently developed new concept for machine tools. It enables all mechanical properties of machine tools to be improved several times simultaneously. This is particularly demonstrated on the design of the OCTASLIDE. This is a concept of a five-axis machine tool centre. The paper describes the critical initial design phases and the accessible mechanical properties. The design process has follow the newly developed design methodology for parallel kinematics machines.
Keywords: parallel kinematics, redundant actuation, five axes, machine tool, dexterity, stiffness.
Z. Maléř, S. Slavík, T. Marczi, M. Růžička: Common Mathematical Model of Fatigue Characteristics
This paper presents a new common mathematical model which is able to describe fatigue characteristics in the whole necessary range by one equation only:
log N = A(R) + B(R)×logSa 
where A(R) = AR2+BR+C and B(R)=DR2+AR+F.
This model was verified by five sets of fatigue data taken from the literature and by our own three additional original fatigue sets. The fatigue data usually described the region of N = 104 to 3×106 and stress ratio of R = -2 to 0.5. In all these cases the proposed model described fatigue results with small scatter. Studying this model, following knowledge was obtained:     
- the parameter "stress ratio R" was a good physical characteristic     
- the proposed model provided a good description of the eight collections of fatigue test results by one equation only     
- the scatter of the results through the whole scope is only a little greater than that round the individual S/N curve     
- using this model while testing may reduce the number of test samples and shorten the test time     
- as the proposed model represents a common form of the S/N curve, it may be used for processing uniform objective fatigue life results, which may enable mutual comparison of fatigue characteristics.
Keywords: fatigue characteristics, mathematical model, stress ratio R.
J. I. Leinonen: Superior Properties of Ultra-fine-grained Steels
A description of the improved mechanical properties obtained in ultra-fine-grained steels up to now will be presented in this paper, and some potential applications of these new generation steels will be described. In addition, the principle and implementation of a novel hot rolling process developed by the author will be introduced. This novel Thermomechanical Nonrecrystallisation Control Process (TNCP) has been shown to give an ultra-fine ferrite (uff) structure with grain sizes of 2 to 3mm in various test steels, thus resulting in super-toughness. Charpy V impact test results suggest that some of these steels could still be tough at temperatures lower than -100 °C. This novel process, TNCP, is one potential candidate for the commercial production of superior ultra-fine-grained steels in the future.
Keywords: ultra-fine-grained steel, super-toughness, yield strength, fatigue strength, TNCP.
M. Polášek, J. Macek, O. Vítek, K. Kozel: Integration of CFD Methods into Concurrent Design of Internal Combustion Engine
This paper describes patterns of algorithms for different innovative levels of design at parametric, configuration and conceptual levels. They can be applied to Computer-aided Engine Design (CED). Data structures, process simulation hierarchy, engine simulation modules and the requirements for further development are described. An example of advanced thermodynamics modeling of combustion engines is included.
Keywords: Internal combustion engine, simulation, CAD, CFD, combustion, knock.
N. Matsuki, H. Tokunaga, H. Sawada: A Component-based Software Development and Execution Framework for CAx Applications
Digitalization of the manufacturing process and technologies is regarded as the key to increased competitive ability. The MZ-Platform infrastructure is a component-based software development framework, designed for supporting enterprises to enhance digitalized technologies using software tools and CAx components in a self-innovative way. In the paper we show the algorithm, system architecture, and a CAx application example on MZ-Platform. We also propose a new parametric data structure based on MZ-Platform.
Keywords: component-based development, CAD, parametric modeling.
M. Horák: Nanoelectronic Device Structures at Terahertz Frequency
Potential barriers of different types (rectangular, triangle, parabolic) with a dc-bias and a small ac-signal in the THz-frequency band are investigated in this paper. The height of the potential barrier is modulated by the high frequency signal. If electrons penetrate through the barrier they can emit or absorb usually one or even more energy quanta, thus the electron wave function behind the barrier is a superposition of different harmonics. The time-dependent Schrödinger equation is solved to obtain the reflection and transmission amplitudes and the barrier transmittance corresponding to the harmonics. The electronic current density is calculated according to the Tsu-Esaki formula. If the harmonics of the electron current density are known, the complex admittance and other electrical parameters of the structure can be found. Keywords: Nanoelectronic, terahertz, potential barrier, transmittance, Schrödinger equation.
H.-P. Geromiller, A. Farschtschi: Numerical Calculation of Electric Fields in Housing Spaces due to Electromagnetic Radiation from Antennas for Mobile Communication
The influence of electromagnetic radiation from mobile antennas on humans is under discussion in various group of scientists. This paper deals with the impact of electromagnetic radiation in housing spaces. The space is assumed to be bordered by 5 walls of ferroconcrete and a door-window combination on the 6th side, the latter to be electromagnetic transparent. The transparent side of the housing is exposed to an electromagnetic wave. As the source of radiation is considered to be far away from the housing, the radiation is regarded as a plane wave. Due to the high signal frequency and the ferroconcrete walls, 5 sides of the housing space are considered to be perfect conductors. The electric field inside the housing is calculated numerically by the method of finite differences for different angles of incidence of the radiated electromagnetic wave. The maximum value of the calculated electric field is outlined in a diagram.
Keywords: numerical calculation, finite difference, electric fields, mobile communication.
G. Green, G. Mamtani: An Integrated Decision Making Model for Evaluation of Concept Design
The Conceptual design phase generates various design concepts and these are then evaluated in order to identify the 'Best’ concept. Identifying the Best concept is important because much of the product life cycle cost is decided in this phase. Various evaluation techniques are performed so as to aid decision-making. Different criteria are weighted against concepts for the comparison. This paper describes the research being carried out at the University of Glasgow on design evaluation. It presents the Application of fuzzy logic for design evaluation and proposes an integrated decision-making model for design evaluation. This is a part of research project that aims at developing a computer tool for evaluation process to aid decision-making. Keywords: Concept design, design evaluation, fuzzy logic.
P. Chudý, K. Fiľakovský, J. Friedl: Aerodynamic Analysis of Turboprop Engine Air Intake
The objective of this paper is to present CFD computation of a LET L-410 engine nacelle equipped with a Walter M-601E turboprop engine. The main purpose is to estimate the air intake fluid characteristics of different air intake geometries. The results of these computations are part of an optimisation process focused on increasing the performance and reducing the losses in the ‘engine - nacelle` system. A problem with flow separation in the input section was observed. This project is supported by Ministry of Industry and Trade of the Czech Republic. Keywords: aerodynamic, CFD, turboprop engine, air intake.
E. Jurun, I. Veza: Developing Model for Supply Chain Management - the Case of Croatia
This paper describes a model of supply chain management (SCM). It explains overall supply chain issues, strategic importance of SCM, supply chain strategies and an example of mathematical formulation. A supply chain is a global network of organizations that cooperate to improve the flows of material and information between suppliers and customers at the lowest cost and the highest speed. The objective of a supply chain is customer satisfaction. At the strategic level, a supply chain can be considered as being composed of five activities: buy, make, move, store and sell. Each activity is a module. The set of modules, along with its links, constitutes a model of the supply chain. Our paper presents some insights into the supply chain strategies of companies in Croatia. The major goal of this paper is to show a model for supply chain management in mathematical terms, with an example of mathematical formulation.
Keywords: supply chain, supply chain management, system modeling, logistic system, supply chain strategies.
4 A. Farouk, L. Lamboj, J. Kos: A Numerical Model to Predict Matric Suction Inside Unsaturated Soils
The objective of this research is to introduce a numerical simulation model to predict approximate values of the matric suction inside unsaturated soils that have low water contents. The proposed model can be used to predict the relationship between the water content and the matric suction of a studied soil to construct the soil-water characteristic curve. In addition, the model can be utilized to combine the predicted matric suction with the soil parameters obtained experimentally, which enables us to explain how matric suction can affect the behaviour of unsaturated soils, without the need to utilize advanced measuring devices or special testing techniques. The model has given good results, especially when studying coarse-grained soils.
Keywords: Unsaturated soil, matric suction, surface tension, soil-water characteristic curve.
A. Farouk, L. Lamboj, J. Kos: Influence of Matric Suction on the Shear Strength Behaviour of Unsaturated Sand

As a part of the effort made to understand the behaviour of unsaturated soils, this work studies the shear strength characteristics of a cohesionless unsaturated soil. Generally, the determination of the shear strength of unsaturated soils is a great challenge to geotechnical engineers, both in terms of understanding it and the effort necessary to determine it. Matric suction is one of the stress state variables that control the shear strength of unsaturated soils. Therefore, the main aim of this study is to investigate the effect of matric suction on the shear strength characteristic of sand known commercially as Sand PR33. The shear strength behaviour of unsaturated sand is studied in this work using the constant water content triaxial test method with measurements of matric suction during the shearing stage. The tests were performed using the axis translation technique in such a way that the pore-air pressure was controlled while the pore-water pressure was measured during all tests.

Keywords: Unsaturated, suction, sand, triaxial, shear strength, axis translation technique.

T. Ficker: Multifractal Image Analysis of Electrostatic Surface Microdischarges
The multifractal image analysis of Lichtenberg figures has confirrmed a self- similar arrangement of surface streamers belonging to the special case of electrostatic separation discharges propagating along a surface of polymeric dielectrics.
Keywords: Microdischarges, random processes, multifractals, electrets.
T. Ficker, V. Kapička, J. Macur, P. Slavíček, P. Benešovský: Fractality of Electrostatic Microdischarges on the Surface of Polymers
Ramified Lichtenberg figures caused by electrostatic microdischarges on the surface of polymeric polyethylene terephthalate have been studied. They occurred in consequence of the previous electret forming of the polymeric sheets and were initiated in the air gap between the grounded electrode and the polymeric sheets. Multifractal image analysis was used to determine the fractal dimensions of the Lichtenberg patterns in dependence on the loading voltages used for electret forming.
Keywords: Electrostatic microdischarges, Lichtenberg figures, multifractal formalism, fractal dimension, electret saturated states.
P. Jiroušek: Programming a Logical Control Method by a Parallel Process
This paper deals with the development of the problem oriented language PRIMAS for use in program control. It is based on virtual parallelism of the controlling program to make its hierarchical structure transparent. The author has also worked on the compiler and the control process simulator. This system enables verification of the control algorithm when there is no controlled machine and no control system. The PRIMAS language, compiler and simulator were developed and applied to real tasks, in the course of work on the author`s PhD dissertation.
Keywords: Higher program language, logic control, modelling and simulating.
M. Audy, M. Šejnoha: Effect of Boundary Constraints in the Formulation of the Partition of Unity Method: One-dimensional Setting
The paper examines an effect of boundary constraints applied to the enhanced degrees of freedom of partition of unity based discontinuous elements. To highlight the present issue the problem is studied in a one-dimensional setting. In particular, an example of a one-dimensional bar element crossed by a set of discontinuities having a finite elastic stiffness clearly shows a need for proper approximation of the displacement field within a discontinuous element in order to correctly represent the structural response. While the discontinuous elements with boundary constraints applied to the enhanced degrees of freedom display an unrealistic dependence of the global response on the locations of the discontinuities, the discontinuous elements with complete approximation of the discontinuous part of the displacement field provide the expected global response independent of the locations of the discontinuities.
Keywords: Strong discontinuity approach, Partition of unity method (PUM), Boundary constraints.
J. Kratěna, I. Fořt: Study of the Discharge Stream from a Standard Rushton turbine impeller
The discharge stream from a standard Rushton turbine impeller exhibits special flow properties different from the characteristics of the velocity field in other parts of the volume of an agitated liquid in a cylindrical baffled vessel, e.g. two prevailing components of the mean velocity (radial and tangential), high rate of turbulent energy dissipation and anisotropy of turbulence in this region. At the same time, the discharge stream plays an important role in mixing operations, above all in liquid-liquid and gas-liquid systems.This paper deals with theoretical and experimental studies of the velocity field and flow of angular momentum in a discharge stream from a standard Rushton turbine impeller in a cylindrical baffled flat bottomed vessel under turbulent regime of flow of an agitated liquid with emphasis on describing the ensemble averaged values over the whole interval of the tangential coordinate around the vessel perimeter.
Keywords: Rushton turbine impeller, discharge stream, turbulent flow, velocity field.
J. Brož, I. Fořt, R. Sperling, S. Jambere, M. Heiser, F. Rieger: Pumping Capacity of Pitched Blade Impellers in a Tall Vessel with a Draught Tube

A study was made of the pumping capacity of pitched blade impellers (two, three, four, five and six blade pitched blade impellers with pitch angles a = 35° and 45°) coaxially located in a cylindrical pilot plant vessel with cylindrical draught tube provided with a standard dished bottom. The draught tube was equipped with four equally spaced radial baffles above the impeller pumping liquid upwards towards the liquid surface. In all investigated cases the liquid aspect ratio H/T=1.2–1.5, the draught tube / vessel diameter ratios DT /T = 0.2 and 0.4 and the impeller / draught tube diameter ratio D/DT = 0.875. The pumping capacity of the impeller was calculated from the radial profile of the axial component of the mean velocity in the draught tube below the impeller at such an axial distance from the impeller that the rotor does not affect the vorticity of the flow. The mean velocity was measured using a laser Doppler anemometer with forward scatter mode in a transparent draught tube and a transparent vessel of diameter T = 400 mm. Two series of experiments were performed, both of them under a turbulent regime of flow of the agitated liquid. First, the optimum height of the dished bottom was sought, and then the dependences of the dimensionless flow rate criterion and the impeller power number on the number of impellerblades were determined for both pitch angles tested under conditions of optimum ratio HT/DT. It follows from the results of the experiments that the optimum ratio HT/DT = 0.25 when the cross sectional areas of the horizontal flow around the bottom and the vertical inflow to the draught tube are the same. For all the tested pitched blade impellers the impeller power number when a = 45° exceeds the value of this quantity when pitch angle a = 35°, while the flow rate number when a = 35° exceeds this quantity when a = 45°. On the other hand, the absolute values of the impeller power number when the draught tube was introduced correspond fairly well to the dimensionless impeller power input measured in a system without a draught tube. However, the absolute values of the flow rate number found in the former system are significantly lower than the dimensionless impeller pumping capacity determined in the latter system. The hydraulic efficiency of pitched blade impellers N3Qp/Po for the investigated geometry of the agitated systems does not depend on the number of impeller blades, but it is significantly lower than the quantity determined in an agitated system with a dished bottom but without the draught tube.

Keywords: pitched blade impeller, impeller pumping capacity, draught tube, laser Doppler anemometer, turbulent flow.

T. H. S. Abdelaziz, M. Valášek: Eigenstructure Assignment by State-derivative and Partial Output-derivative Feedback for Linear Time-invariant Control Systems
This paper introduces a parametric approach for solving the problem of eigenstructure assignment via state-derivative feedback for linear control time-invariant systems. This problem is always solvable for any controllable systems if the open-loop system matrix is nonsingular. In this work, the parametric solution to the feedback gain matrix is introduced that describes the available degrees of freedom offered by the state-derivative feedback in selecting the associated eigenvectors from an admissible class. These freedoms can be utilized to improve the robustness of the closed-loop system. Finally, the eigenstructure assignment problem via partial output-derivative feedback is introduced. Numerical examples are included to show the effectiveness of the proposed approach.
Keywords: Eigenstructure assignment, state-derivative feedback, output-derivative feedback, linear systems, feedback stabilization, parametrization.
V. Matz, M. Kreidl, R. Šmíd: Signal-to-Noise Ratio Improvement based on the Discrete Wavelet Transform in Ultrasonic Defectoscopy
In ultrasonic testing it is very important to recognize the fault echoes buried in a noisy signal. The fault echo characterizes a flaw in the material. An important requirement on ultrasonic signal filtering is zero-time shift, because the position of ultrasonic echoes is essential. This requirement is accomplished using the discrete wavelet transform (DWT), which is used for reducing the signal-to-noise ratio. This paper evaluates the quality of filtering using the discrete wavelet transform. Additional computer simulations of the proposed algorithms are presented.
Keywords: ultrasonic testing, discrete wavelet transform, de-noising algorithms.

Acta Polytechnica 2005

No. (click on selected title and view the annotation)
1 J. Skokánek: Deformation Stress State of Elastic Bodies
The theory of the deformation stress state is based on the actual corpuscular structure of matter characterized in terms of mechanics by the fact that an increase in the distance of two adjacent atoms is accompanied by the origin of an attractive force and a reduction in their distance by the origin of a repulsive force. These forces differ significantly from the classical internal forces, which are the forces of the mechanics of perfectly solid bodies. These express the equilibrium of forces with reference to the given area within the loaded body, and have no direct deformation effect. This paper defines the quantities of the deformation stress state - the deformation force and the deformation stress - the direct manifestation of which is a deformation. The author introduces the term of deformation stress state theory (DSS theory) to the field of the theory of elasticity dealing with the stress state of deformable bodies. The quantities and the equations of this theory also form the basis for the formulation of the theory of failure, which makes it possible to determine reliably the safety margin and the strength of a multiaxially loaded body from the stress state described by the static quantities (stress tensor) and uniaxial strength.
Keywords: deformation force, deformation stress, effective stress, effective strength, proportionality principle.
A. Čepek, J. Pytel: A Progress Report on Numerical Solutions of Least Squares Adjustment in GNU Project Gama
GNU project Gama for adjustment of geodetic networks is presented. Numerical solution of Least Squares Adjustment in the project is based on Singular Value Decomposition (SVD) and General Orthogonalization Algorithm (GSO). Both algorithms enable solution of singular systems resulting from adjustment of free geodetic networks.
Keywords: geodesy, least square adjustment, local geodetic network.
O. Brůha, T. Brůha: Heating and Cooling Anomaly of a Rotating Body
This paper deals with an effect which appears when heating or cooling a rotating body. No external forces acting on the body are supposed. Due to thermal expansion, the moment of inertia of the body varies together with the temperature changes. In agreement with the principle of conservation of angular momentum [1], the angular momentum is constant. This results in angular velocity changes and subsequently in kinetic energy changes. Also the stress energy varies together with the changes in thermal dimension. To satisfy the principle of energy conservation we have to suppose that the changes in kinetic and stress energy are compensated by the changes in internal energy, which is correlated with temperature changes of the body. This means that the rules for the heating or cooling process of a rotating body are not the same as those for a body at rest. This idea, applied to a cylinder rotating around its geometric axis under specific parameters, has been mathematically treated. As a result, the difference between the final temperature of the rotating cylinder and the temperature of the cylinder at rest has been found.
Keywords: angular momentum, energy conservation, rotating body, thermal expansion.
A. Almarimi, J. Pokorný: Schema Management for Data Integration: A Short Survey

Schema management is a basic problem in many database application domains such as data integration systems. Users need to access and manipulate data from several databases. In this context, in order to integrate data from distributed heterogeneous database sources, data integration systems demand the resolution of several issues that arise in managing schemas. In this paper, we present a brief survey of the problem of schema matching which is used for solving problems of schema integration processing. Moreover, we propose a technique for integrating and querying distributed heterogeneous XML schemas.
Keywords: schema matching, schema integration, data integration.

S. Usama, M. Montaser, O. Ahmed: A Complexity and Quality Evaluation of Block Based Motion Estimation Algorithms
Motion estimation is a method, by which temporal redundancies are reduced, which is an important aspect of video compression algorithms. In this paper we present a comparison among some of the well-known block based motion estimation algorithms. A performance evaluation of these algorithms is proposed to decide the best algorithm from the point of view of complexity and quality for noise-free video sequences and also for noisy video sequences.
Keywords: motion estimation, block matching, quality evaluation, complexity evaluation.
P. Tesárek, J. Pavlík, R. Černý: Comparison of the Capacitance Method and the Microwave Impulse Method for Determination of Moisture Profiles in Building Materials
A comparison of the capacitance method and the microwave impulse method for the determination of moisture profiles in three typical porous building materials is presented in this paper. The basic principles of the measuring methods are given. The calibration process is described in detail. On the basis of the measured results, it can be concluded that the capacitance method provides better accuracy in the range of lower moisture content than to the microwave impulse method, which is more accurate for the highest values of moisture content.
Keywords: Moisture profiles, capacitance method, microwave impulse method, building materials.
J. Hodač: 3D Information System of Historical Site - Proposal and Realisation of a Functional Prototype
The development of methods for 3D data acquisition, together with progress in information technologies raises the question of creating and using 3D models and 3D information systems (IS) of historical sites and buildings. This paper presents the current state of the "Live Theatre" project. The theme of the project is the proposal and realisation of a 3D IS of the baroque theatre at Český Krumlov castle (UNESCO site).The project is divided into three main stages - creation of a 3D model, proposal of a conception for a 3D IS, and realisation of a functional prototype. 3D data was acquired by means of photogrammetric and surveying methods. An accurate 3D model (photo-realistic, textured) was built up with MicroStation CAD system. The proposal of a conception of a 3D IS was the main outcome of the author`s dissertation. The essential feature of the proposed conception is the creation of subsystems targeted on three spheres - management, research and presentation of the site. The functionality of each subsystem is connected with its related sphere; however, each subsystem uses the same database. The present stage of the project involves making a functional prototype (with sample data). During this stage we are working on several basic technological topics. At present we are concerned with 3D data, its formats, format conversions (e.g. DGN Ţ VRML) and its connection to other types of data. After that, we will be seeking a convenient technical solution based on network technologies (Internet) and an appropriate layout for the data (database). The project is being carried out in close co-operation with the administration of the castle and some other partners. This stage of the project will be completed in December 2005.A functional prototype and the information acquired by testing it will form the basis for the final proposal of a complex IS of a historical site. The final proposal and appropriate technology will be the outcome of the project. The realisation of a complex 3D IS will then follow. The results will be exploitable both for site management and for organisations working in the area of presenting historical sites and creating multimedia shows.
Keywords: cultural heritage, 3D information sciences, system, project, proposal, development, virtual reality, Internet/web.
D. Lemák, J. Studnička: Influence of Ring Stiffeners on a Steel Cylindrical Shell
Shell structures are usually formed from concrete, steel and nowadays also from many others materials. Steel is typically used in the structures of chimneys, reservoirs, silos, pipelines, etc. Unlike concrete shells, steel shells are regularly stiffened with the help of longitudinal and/or ring stiffeners.The authors of this paper investigated steel cylindrical shells and their stiffening with the use of ring stiffeners. The more complete the stiffening, the more closely the shell will act to beam theory, and the calculations will be much easier. However, this would make realization of the structure more expensive and more laborious. The target of the study is to find the limits of ring stiffeners for cylindrical shells. Adequate stiffeners will eliminate semi-bending action of the shells in such way that the shell structures can be analyzed with the use of numerical models of the struts (e.g., by beam theory) without significant divergences from reality. Recommendations are made for the design of ring stiffeners, especially for the distances between stiffeners and for their bending stiffness.
Keywords: shell, cylindrical shell, chimney, steel structure, wind load, ring stiffener, distance of stiffeners, stiffness of ring stiffener, design.
2 H. Kubátová: Modeling by Petri Nets
One specific model of a digital system in different types of Petri nets is presented. The formal definitions of the basic (black-and-white) Petri net, a place/transition net (P/T net), an arc-constant coloured Petri net (ac-CPN) and a coloured Petri net (CPN) are presented and explained on the basis of this example. Real models of dining philosophers, a producer-consumer system and railway tracks are described.
Keywords: Petri nets, formal models, hardware, digital design, Field Programmable Gate Array (FPGA), PNML, VHDL, Finite State Machine (FSM)
J. Bokr, V. Jáneš: Realization of Logical Circuits with Majority Logical Function as Symmetrical Function
The paper deals with the "production" and design of symmetrical functions, particularly aimed at the design of circuits with majority elements, which lead to interesting solutions of logical structures. The solutions are presented in several examples, which show the applicability of the procedures to the design of FPGA morphology on chips.
Keywords: Shannon extension development, Hamming weight, derivation of Boolean function, symmetrical and majority function.
M. Bečvář, P. Štukjunger: Fixed-Point Arithmetic in FPGA
Arithmetic operations are among the most frequently-used operations in contemporary digital integrated circuits. Various structures have been designed, utilizing different features of IC architectures. Nevertheless, there are very few studies that consider the design of arithmetic operations in Field Programmable Gate Arrays (FPGAs), a re-programmable type of digital integrated circuit. This text compares the results achieved when implementation of basic fixed-point arithmetic units in FPGA.
Keywords: arithmetic, fixed-point, FPGA.
M. Šoch, R. Lórencz: Solving Inverse Kinematics - A New Approach to the Extended Jacobian Technique
This paper presents a brief summary of current numerical algorithms for solving the Inverse Kinematics problem. Then a new approach based on the Extended Jacobian technique is compared with the current Jacobian Inversion method. The presented method is intended for use in the field of computer graphics for animation of articulated structures.
Keywords: inverse kinematics, Jacobian inversion, extended Jacobian technique.
J. Bokr, V. Jáneš: Trivial Logic Arrays
This paper deals with matrix modelling of trivial logic arrays (PLA, PAL, ROM) and the design of the above array as structural models of static and dynamic logic objects.
Keywords: cartesian product of matrices, PLA, PAL, ROM, canonical decomposition, states coding, states coding of Miller or Liu, substitute input variable.
S. Korbel, V. Jáneš: Implementation of a Microcode-controlled State Machine and Simulator in AVR Microcontrollers (MICoSS)
This paper describes the design of a microcode-controlled state machine and its software implementation in Atmel AVR microcontrollers. In particular, ATmega103 and ATmega128 microcontrollers are used. This design is closely related to the software implementation of a simulator in AVR microcontrollers. This simulator communicates with the designed state machine and presents a complete design environment for microcode development and debugging. These two devices can be interconnected by a flat cable and linked to a computer through a serial or USB interface.Both devices share the control software that allows us to create and edit microprograms and to control the whole state machine. It is possible to start, cancel or step through the execution of the microprograms. The operator can also observe the current state of the state machine. The second part of the control software enables the operator to create and compile simulating programs. The control software communicates with both devices using commands. All the results of this communication are well arranged in dialog boxes and windows.
Keywords: state machine, microcontroller, microprogramming, software implementation of a simulator.
P. Fišer, H. Kubátová: Pseudorandom Testing - A Study of the Effect of the Generator Type
The test pattern generator produces test vectors that are applied to the tested circuit during pseudo-random testing of combinational circuits. The nature of the generator thus directly influences the fault coverage achieved. In this paper we discuss the influence of the type of pseudo-random pattern generator on stuck-at fault coverage. Linear feedback shift registers (LFSRs) are mostly used as test pattern generators, and the generating polynomial is primitive to ensure the maximum period. We have shown that it is not necessary to use primitive polynomials, and moreover that their using is even undesirable in most cases. This fact is documented by statistical graphs. The necessity of the proper choice of a generating polynomial and an LFSR seed is shown here, by designing a mixed-mode BIST for the ISCAS benchmarks.An alternative to LFSRs are cellular automata (CA). We study the effectiveness of CA when used as pseudo-random pattern generators. The observations are documented by statistical results.
Keywords: built-in self-test, diagnostics, testability, LFSR, test pattern generators, column-matching.
J. Schmidt, M. Novotný: Scalable Normal Basis Arithmetic Unit for Elliptic Curve Cryptography

The design of a scalable arithmetic unit for operations over elements of GF(2m) represented in normal basis is presented. The unit is applicable in public-key cryptography. It comprises a pipelined Massey-Omura multiplier and a shifter. We equipped the multiplier with additional data paths to enable easy implementation of both multiplication and inversion in a single arithmetic unit. We discuss optimum design of the shifter with respect to the inversion algorithm and multiplier performance. The functionality of the multiplier/inverter has been tested by simulation and implemented in Xilinx Virtex FPGA. We present implementation data for various digit widths which exhibit a time minimum for digit width D=15.                                         Keywords: finite fields, normal base, multiplication, inversion, arithmetic unit.

J. Buček, J. Hlaváč, M. Matušková, R. Lórencz: Cost-Effective Architectures for RC5 Brute Force Cracking
In this paper, we discuss the options for brute-force cracking of the RC5 block cipher, that is, for revealing the unknown secret key, given a sample ciphertext and a portion of the corresponding plaintext. First, we summarize the methods employed by the current cracking efforts. Then, we present two hardware architectures for finding the secret key using the "brute force" method. We implement the hardware in FPGA and ASIC and, based on the results, we discuss the cost and time needed to crack the cipher using today`s technology and suggest a minimum key length that can be considered secure.
Keywords: RC5 cipher, decryption, brute-force cracking, FPGA, ASIC.
3 H. Song, B. Eynard, P. Lafon, L. Roucoules: Towards Integration of CAx Systems and a Multiple-View Product Modeller in Mechanical Design
This paper deals with the development of an integration framework and its implementation for the connexion of CAx systems and multiple-view product modelling. The integration framework is presented regarding its conceptual level and the implementation level is described currently with the connexion of a functional modeller, a multiple-view product modeller, an optimisation module and a CAD system. The integration between the multiple-view product modeller and CATIA V5 based on the STEP standard is described in detail. Finally, the presented works are discussed and future research developments are suggested.
Keywords: concurrent engineering, integrated design, CAx system, product modelling, STEP.
R. Tichánek, M. Španiel, M. Diviš: Structural Stress Analysis of an Engine Cylinder Head
This paper deals with a structural stress analysis of the cylinder head assembly of the C/28 series engine. A detailed FE model was created for this purpose. The FE model consists of the main parts of the cylinder head assembly, and it includes a description of the thermal and mechanical loads and the contact interaction between their parts. The model considers the temperature dependency of the heat transfer coefficient on wall temperature in cooling passages. The paper presents a comparison of computed and measured temperature. The analysis was carried out using the FE program ABAQUS.
Keywords: structural stress analysis, FEM, internal-combustion engine.
M. M. A. Bicak, H. T. Belek, A. Göksenli: Vibration Damping of a New Ionic Liquid under Electric Field Effect
Ionic liquids are recently-developed smart materials that are not well known by mechanical engineers. They are of great interest due to their non-volatility, viscosity and extremely high electrical conductivity. Up to now, no reports have appeared on their rheological properties under magnetic or electrical fields.In this work, we study the electro-rheological behaviour of a newly presented ionic liquid (2-hydroxyethylammonium formate).Our experiments show that the ionic liquid is not sensitive to magnetic fields. Nevertheless, resonably high damping ratios (42.8%) have been attained under relatively low electric fields (0.6 kVcm-1).
Keywords: damping characteristics, ionic liquid, electrorheological fluid.
M. Valášek, V. Bauma, Z. Šika: Study of Concepts of Parallel Kinematics Machines for Advanced Manufacturing
This paper deals with possible new concepts for machine tools based on parallel kinematics for advanced manufacturing. Parallel kinematics machines (PKM) enable the mechanical properties of manufacturing machines to be improved. This has been proven by several new machine tool concepts. However, this potential can be and must be increased by applying the principle of redundant actuation. This paper deals with the extension of the concepts of redundantly actuated parallel kinematics structures for five-sided five-axis machine tools and for a free-forming sheet metal forming machine. The design principles of previous successful PKMs are summarized and new concepts are proposed. The most important requirement criteria are summarized. The proposed concepts are qualitatively and initially quantitatively evaluated according to these criteria.
Keywords: parallel kinematics, machine tools, metal forming machines, conceptual design.
J. K. Tan: Elicitation of Preference Structure in Engineering Design
Engineering design processes, which inherently involve multiple, often conflicting criteria, can be broadly classified into synthesis and analysis processes. Multiple Criteria Decision Making addresses synthesis and analysis processes through multiple objective optimisation to generate sets of efficient design solutions (i.e. on Pareto surfaces) and multiple attribute decision making to analyse and select the most preferred design solution(s). MCDM, therefore, has been widely used in all fields of engineering design; for example it has been applied to such diverse areas as naval battle ships criteria analysis/selection and product appearance design. Given a list of design alternatives with multiple conflicting criteria, preferences often determine the final selection of a particular set of design alternative(s). Preferences may also be used to drive the design/design optimisation processes. Various methods have been proposed to model preference structure, for example simple weights, multiple attribute utility theory, pairwise comparison, etc. Preference structure is often non-linear, discontinuous and complex. An Artificial Neural Network (ANN) learning-based preference elicitation method is presented in this paper. ANNs efficiently model the non-linearity, complexity and discontinuity nature of any given preference structure. A case study is presented to illustrate the learning-based approach to preference structure elicitation.
Keywords: engineering design, multiple criteria decision making, preference structure.
H.-A. Crostack, M. Höfling, J. Liangsiri: Simulation in Quality Management - An Approach to Improve Inspection Planning
Production is a multi-step process involving many different articles produced in different jobs by various machining stations. Quality inspection has to be integrated in the production sequence in order to ensure the conformance of the products. The interactions between manufacturing processes and inspections are very complex since three aspects (quality, cost, and time) should all be considered at the same time while determining the suitable inspection strategy. Therefore, a simulation approach was introduced to solve this problem.The simulator called QUINTE [the QUINTE simulator has been developed at the University of Dortmund in the course of two research projects funded by the German Federal Ministry of Economics and Labour (BMWA: Bundesministerium für Wirtschaft und Arbeit), the&nbsp;Arbeitsgemeinschaft industrieller Forschungsvereinigungen (AiF), Cologne/Germany and the Forschungsgemeinschaft Qualität, Frankfurt a.M./Germany] was developed to simulate the machining as well as the inspection. It can be used to investigate and evaluate the inspection strategies in manufacturing processes. The investigation into the application of QUINTE simulator in industry was carried out at two pilot companies. The results show the validity of this simulator. An attempt to run QUINTE in a user-friendly environment, i.e., the commercial simulation software - Arena(R) is also described in this paper.
Keywords: simulation, quality, inspection strategies, manufacturing process.
NOTATION: QUINTE Qualität in der Teilefertigung (Quality in the manufacturing process)
J. Ríos, J. V. Jiménez, J. Pérez, A. Vizán, J. L. Menéndez, F. Más: KBE Application for the Design and Manufacture of HSM Fixtures
The design of machining fixtures for aeronautical parts is strongly based in the knowledge of the fixture designer, and it comprises certain repetitive tasks. An analysis of the design process allows us to state its suitability for developing Knowledge Based Engineering (KBE) applications in order to capture the knowledge, and to systematize and automate the designs.This work justifies the importance of fixtures for High Speed Milling (HSM), and explains the development of a KBE application to automate the design and manufacturing of such elements. The application is the outcome of a project carried out in collaboration with the company EADS.In the development process, a specific methodology was used in order to represent the knowledge in a semi-structured way and to document the information needed to define the system. The developed KBE application is independent of the parts design system. This makes it necessary to use an interface to input the part geometry into the KBE application, where it is analyzed in order to extract the relevant information for the fixture design process. The results obtained from the application come in three different ways: raw material drawings, fixture 3D solid models, and text files (Bill Of Materials - BOM, and Numerical Control - NC programs). All the results are exported to other applications for use in other tasks. The designer interacts with the application through an ad hoc interface, where he is asked to select or input some data and where the results are also visualized. The prototype KBE application has been carried out in the ICAD development environment and the main interface is with the CAD/CAM system CATIA V4.
Keywords: KBE, ICAD, HSM fixtures design.
G. Mullineux, B. Hicks, T. Medland: Constraint-Aided Product Design
The importance of supporting the early stages of design is widely accepted. In particular, the development of supportive tools and methods for modelling and analysis of evolving design solutions present a difficult challenge. One reason for this is the need to model both the product design and the design knowledge from which the design is created. There are a number of limitations with many existing techniques and an alternative approach that deals with the design constraints themselves is presented. Dealing directly with the constraints affords a more generalised approach that represents the process by which a product is designed. This enables modelling and reasoning about a product from an often abstract and evolving set of requirements. The constraint methodology is an iterative process where the design requirements are elaborated, the constraint rules altered, design ideas generated and tested as functional structures. The incorporation of direct search techniques to solve the constrained problem enables different solutions to be explored and allows the determination of ‘best compromises` for related constraints. A constraint modelling environment is discussed and two example cases are used to demonstrate the potential of a constraint-aided approach for supporting important issues such as the design of product variants and product families.
Keywords: constraint modelling, design knowledge, synthesis, product design, product families.
R. Humble, H. Millward, A. Mumby, R. Price: The Design and Development of Enhanced Thermal Desorption Products
This research study is based on a knowledge-transfer collaboration between The National Centre for Product Design and Development Research (PDR) and Markes International Ltd. The aim of the two-year collaboration has been to implement design tools and techniques for the development of enhanced thermal desorption products. Thermal desorption is a highly-specialised technique for the analysis of trace-level volatile organic compounds. This technique allows minute quantities of these compounds to be measured; however, there is an increasing demand from customers for greater sensitivity over a wider range of applications, which means new design methodologies need to be evaluated. The thermal desorption process combines a number of disparate chemical, thermal and mechanical disciplines, and the major design constraints arise from the need to cycle the sample through extremes in temperature. Following the implementation of a comprehensive product design specification, detailed design solutions have been developed using the latest 3D CAD techniques. The impact of the advanced design techniques is assessed in terms of improved product performance and reduced development times, and the wider implications of new product development within small companies are highlighted.
Keywords: thermal desorption, product design, SME.
B.-R. Hoehn, K. Steingroever, M. Jaros: Modelling a New Product Model on the Basis of an Existing STEP Application Protocol
During the last years a great range of computer aided tools has been generated to support the development process of various products. The goal of a continuous data flow, needed for high efficiency, requires powerful standards for the data exchange. At the FZG (Gear Research Centre) of the Technical University of Munich there was a need for a common gear data format for data exchange between gear calculation programs. The STEP standard ISO 10303 was developed for this type of purpose, but a suitable definition of gear data was still missing, even in the Application Protocol AP 214, developed for the design process in the automotive industry. The creation of a new STEP Application Protocol or the extension of existing protocol would be a very time consumpting normative process. So a new method was introduced by FZG. Some very general definitions of an Application Protocol (here AP 214) were used to determine rules for an exact specification of the required kind of data. In this case a product model for gear units was defined based on elements of the AP 214. Therefore no change of the Application Protocol is necessary. Meanwhile the product model for gear units has been published as a VDMA paper and successfully introduced for data exchange within the German gear industry associated with FVA (German Research Organisation for Gears and Transmissions). This method can also be adopted for other applications not yet sufficiently defined by STEP.
Keywords: data exchange, product model, gear data, STEP.
C. Alkin, C. E. Imrak, H. Kocabas: Solid Modeling and Finite Element Analysis of an Overhead Crane Bridge
The design of an overhead crane bridge with a double box girder has been investigated and a case study of a crane with 35 ton capacity and 13 m span length has been conducted. In the initial phase of the case study, conventional design calculations proposed by F. E. M Rules and DIN standards were performed to verify the stress and deflection levels. The crane design was modeled using both solids and surfaces. Finite element meshes with 4-node tetrahedral and 4-node quadrilateral shell elements were generated from the solid and shell models, respectively. After a comparison of the finite element analyses, the conventional calculations and performance of the existing crane, the analysis with quadratic shell elements was found to give the most realistic results. As a result of this study, a design optimization method for an overhead crane is proposed.
Keywords: overhead crane, finite element method, solid modeling, box girder.
J. Novotný, J. Nožička, J. Adamec, L. Nováková: Measurement of Two Phase Flow
This paper presents the results of experiments with moist wet steam. The aim of the experiment was to measure the velocity of the growth of a condensing nucleus in wet steam dependent on the velocity of condensation. For the experiments in wet steam an experimental setup was designed and constructed, which generated superheated steam at lowered pressure and a temperature of 50 °C. Low pressure and temperature of the hot vapour was chosen in order to minimize the risk of accidental disruption of the wall. The size of the condensing nucleus was measured by the method of Interferometric Particle Imaging (IPI). The IPI method is a technique for determining the particle size of transparent and spherical particles based on calculating the fringes captured on a CCD array. The number of fringes depends on the particle size and on the optical configuration. The experimental setup used is identical with the setup for measuring flow by the stereo PIV method. The only difference is the use of a special camera mount comprising a transparent mirror and enabling both cameras to be focused to one point. We present the results of the development of the growth of a condensing nucleus and histograms of the sizes of all measured particles depending on position and condensation velocity.
Keywords: two phase flow, condensation, wet steam, IPI measurement.
D. P. Coiro, A. De Marco, F. Nicolosi, S. Melone, F. Montella: Dynamic Behaviour of the Patented Kobold Tidal Current Turbine: Numerical and Experimental Aspects
This paper provides a summary of the work done at DPA on numerical and experimental investigations of a novel patented vertical axis and variable pitching blades hydro turbine designed to harness energy from marine tidal currents. Ponte di Archimede S.p.A. Company, located in Messina, Italy, owns the patented KOBOLD turbine that is moored in the Messina Strait, between the mainland and Sicily. The turbine has a rotor with a diameter of 6 meters, three vertical blades of 5 meters span with a 0.4 m chord ad hoc designed curved airfoil, producing high lift with no cavitation. The rated power is 160 kW with 3.5 m/s current speed, which means 25% global system efficiency. The VAWT and VAWT_DYN computer codes, based on Double Multiple Steamtube, have been developed to predict the steady and dynamic performances of a cycloturbine with fixed or self-acting variable pitch straight-blades. A theoretical analysis and a numerical prediction of the turbine performances as well as experimental test results on both a model and the real scale turbine will be presented and discussed.
Keywords: vertical-axis-hydro-turbine, variable pitch, Double-Multiple-Streamtube, tidal currents, tidal energy.
P. Fošumpaur, F. Čihák: Design and Optimization of a Turbine Intake Structure
The appropriate design of the turbine intake structure of a hydropower plant is based on assumptions about its suitable function, and the design will increase the total efficiency of operation. This paper deals with optimal design of the turbine structure of run-of-river hydropower plants. The study focuses mainly on optimization of the hydropower plant location with respect to the original river banks, and on the optimal design of a separating pier between the weir and the power plant. The optimal design of the turbine intake was determined with the use of 2-D mathematical modelling. A case study is performed for the optimal design of a turbine intake structure on the Nemen river in Belarus.
Keywords: run-of-river hydropower plant, turbine intake, 2-D modelling, optimization.
M. Macdonald, J. Rhodes: Finite Element Modelling of Cold Formed Stainless Steel Columns
This paper describes the results obtained from a finite element investigation into the load capacity of column members of lipped channel cross-section, cold formed from Type 304 stainless steel, subjected to concentric and eccentric compression loading. The main aims of this investigation were to determine the effects which the non-linearity of the stress-strain behaviour of the material would have on the column behaviour under concentric or eccentric loading. Stress-strain curves derived from tests and design codes are incorporated into non-linear finite element analyses of eccentrically loaded columns and the results obtained are compared with those obtained on the basis of experiments on stainless steel channel columns with the same properties and dimensions. Comparisons of the finite element results and the test results are also made with existing design specifications and conclusions are drawn on the basis of the comparisons.
Keywords: finite elements, stainless steel, cold forming.
M. Holický: Fuzzy Optimisation of Structural Performance
Structural performance has become a fundamental concept in advanced engineering design in construction. Basic criteria concerning the action effects and imposed performance requirements are analysed assuming two types of uncertainties: randomness and vagueness. The natural randomness of the action effect is handled by commonly used methods of the theory of probability. The vagueness of performance requirements due to indistinct or imprecise specification and perception is analysed using the basic tools of the theory of fuzzy sets. Both types of uncertainties are considered to define fuzzy probabilistic measures of structural performance, the damage function and fuzzy probability of failure. Fuzzy probabilistic optimisation of vibration constraints indicates that the limiting values recommended for the acceleration of building structures may be uneconomical. Further research should focus on verifying of the input theoretical models using available experimental data.
Keywords: performance requirements, randomness, fuzziness, optimisation.
4 P. Zítek, T. Vyhlídal: Model Based Control of Moisture Sorption in a Historical Interior
This paper deals with a novel scheme for microclimate control in historical exhibition rooms, inhibiting moisture sorption phenomena that are inadmissible from the preventive conservation point of view. The impact of air humidity is the most significant harmful exposure for a great deal of the cultural heritage deposited in remote historical buildings. Leaving the interior temperature to run almost its spontaneous yearly cycle, the proposed non-linear model-based control protects exhibits from harmful variations in moisture content by compensating the temperature drifts with an adequate adjustment of the air humidity. Already implemented in a medieval interior since 1999, the proposed microclimate control has proved capable of permanently maintaining constant a desirable moisture content in organic or porous materials in the interior of a building.
Keywords: equilibrium moisture sorption, humidity control, non-linear cascade control.
D. Telfer, J. Spencer: Properties and Performance of a New Compact HF Aerial Design for Multi-Band Operation
This work is an extension to that of Telfer and Austin [1] in that here a balanced feed embodiment of an inwardly-inclined folded dual monopole aerial is presented and discussed in terms of its improved performance over the original configuration. This includes greater control of the stability of the far-field (FF) lobe pattern with operating frequency, and a considerably extended frequency range (3:1 ratio) over which Near Vertical Incidence Skywave (NVIS) propagation in the high frequency (HF) bands can be exploited. Furthermore, the FF lobe patterns at frequencies >2× the fundamental design frequency are such that advantage can be taken of conventional non-NVIS horizontal propagation at those frequencies using the same aerial. At the fundamental frequency, compactness of design and robustness of its NVIS FF pattern to orientation make the novel balanced aerial design a convenient replacement for a full-length low dipole in cluttered environments. The paper also presents a vehicle-mounted version for medium range operation within HF skip distances. Applications highlighted include stations for remote monitoring of environmental measurements in difficult or hostile terrain.
Keywords: aerial, antenna, multi-band, NVIS, HF, environmental monitoring.
A. J. Mitchell, E. W. McGookin, D. J. Murray-Smith: Implementation of Sliding Mode Observer Based Reconfiguration in an Autonomous Underwater Vehicle
This paper looks at the implementation of a Sliding Mode Observer (SMO) based Reconfiguration algorithm to deal with sensor faults within the context of navigation controllers for Autonomous Underwater Vehicle (AUV). In this paper the reconfigurability aspects are considered for the heading controller. Simulation responses are used to illustrate that the Sliding Mode Observer is able to give state information to the controller when there is a fault in the AUV`s sensor package. Comparisons are made between the Sliding Mode Controller with and without reconfigurability for a number of different sensor failures, e.g. bias errors in or the complete loss of the heading data, and the robustness of the Sliding Mode Observer is investigated through the introduction of disturbances into the system.
Keywords: autonomous underwater vehicles, sliding-mode control, fault tolerance, reconfiguration, sliding mode observers, environmental disturbances.
J. A. Walker, C. Cossar, T. J. E. Miller: Simulation and Analysis of Magnetisation Characteristics of Interior Permanent Magnet Motors
Modern permanent magnet (PM) synchronous brushless machines often have magnetic circuits in which the patterns of saturation are complex and highly variable with the position of the rotor. The classical phasor diagram theory of operation relies on the assumption of sinusoidal variation of flux-linkage with rotor position, and neglects the non-linear effects that arise in different operating states. The finite element method is a useful tool for detailed magnetic analysis, but it is important to verify simulation results by direct measurement of the magnetic characteristics of the motor, in terms of "magnetisation curves" of current and flux-linkage. This paper presents results from finite element simulations to determine the magnetisation in a split-phase interior permanent magnet (IPM) motor. Investigation has been made to determine the effects of the rotor geometry on the synchronous reactances and airgap flux distribution. Comparisons are made with a second IPM motor with a different rotor configuration.
Keywords: permanent magnet, finite element method, flux-linkage measurement, rotor bridges.

J. Bíla, M. Tlapák: Ontologies and Formation Spaces for Conceptual ReDesign of Systems
This paper discusses ontologies, methods for developing them and languages for representing them. A special ontology for computational support of the Conceptual ReDesign Process (CRDP) is introduced with a simple illustrative example of an application. The ontology denoted as Global context (GLB) combines features of general semantic networks and features of UML language. The ontology is task-oriented and domain-oriented, and contains three basic strata - GLBExpl (stratum of Explanation), GLBFAct (stratum of Fields of Activities) and GLBEnv (stratum of Environment), with their sub-strata. The ontology has been developed to represent functions of systems and their components in CRDP. The main difference between this ontology and ontologies which have been developed to identify functions (the semantic details in those ontologies must be as deep as possible) is in the style of the description of the functions. In the proposed ontology, Formation Spaces were used as lower semantic categories the semantic deepness of which is variable and depends on the actual solution approach of a specialised Conceptual Designer. Keywords: ontologies, conceptual redesign, fields of activities, principles, UML.
C. Peebles, C. Bil, L. Drack: Intelligent Data Storage and Retrieval for Design Optimisation - an Overview
This paper documents the findings of a literature review conducted by the Sir Lawrence Wackett Centre for Aerospace Design Technology at RMIT University. The review investigates aspects of a proposed system for intelligent design optimisation. Such a system would be capable of efficiently storing (and compressing if required) a range of types of design data into an intelligent database. This database would be accessed by the system during subsequent design processes, allowing for search of relevant design data for re-use in later designs, allowing it to become very efficient in reducing the time for later designs as the database grows in size. Extensive research has been performed, in both theoretical aspects of the project, and practical examples of current similar systems. This research covers the areas of database systems, database queries, representation and compression of design data, geometric representation and heuristic methods for design applications.
Keywords: database architectures, design optimisation, configuration control, data access and retrieval.
R. E. Crosbie, N. G. Hingorani: High-Speed Real-Time Simulators for Engineering Design
The use of computer simulations is now an established technique in engineering design. Many of these simulations are used to predict the expected behavior of systems that are not yet built, or of existing systems in modes of operation, such as catastrophic failure, in which it is not feasible to test the real system. Another use of computer simulations is for training and testing purposes in which the simulation is interfaced to real hardware, software and/or a human operator and is required to operate in real-time. Examples are plant simulators for operator training or simulated environments for testing hardware or software components. The primary requirement of a real-time simulation is that it must complete all the calculations necessary to update the simulator outputs as well as all the necessary data I/O within the allotted frame time. Many real-time simulations use frame times in the range of a few milliseconds and greater.There is an increasing number of applications, for example in power electronics and automotive systems, in which much shorter frame rates are required. This paper reviews some of these applications and the approaches to real-time simulation that can achieve frame times in the range 5 to 100 microseconds.
Keywords: computer simulation, real-time, engineering design, digital signal processors.
T. S. Ericsen: Physics Based Design, the Future of Modeling and Simulation
This paper discusses the expanding role of modeling and simulation in the design and development of electrical power systems. The concepts of physics-based design and building blocks are introduced to show how complex systems may be simplified. However, the detail and complexity of tomorrow’s systems are beyond today’s tools. Computing power has increased to the point where physics-based design is possible. The aim of this paper is to discus the issues and opportunities for modeling and simulation in advanced system design.
Keywords: modeling, simulation, power electronics, power electronic building blocks, PEBB, electric power systems, advance marine electric power systems, naval electric power systems.
M. Hrouzek: Feedback Control in an Atomic Force Microscope Used as a Nano-Manipulator
This paper offers a concise survey of the most commonly used feedback loops for atomic force microscopes. In addition it proposes feedback control loops in order to minimize the effect of thermal noise on measurements of weak forces, and to improve the manipulability of the AFM. Growing requirements to study and fabricate systems of ever-shrinking size mean that ever-increasing performance of instruments like atomic force microscopes (AFM) is needed. A typical AFM consists of a micro-cantilever with a sharp tip, a sample positioning system, a detection system and a control system. Present day commercial AFMs use a standard PI controller to position the micro-cantilever tip at a desired distance from the sample. There is still a need for studies showing the optimal way to tune these controllers in order to achieve high closed-loop positioning performance. The choice of other controller structures, more suitable for dealing with the robustness/performance compromise can also be a solution.
Keywords: automatic control, atomic force microscopy, thermal noise.

D. P. Coiro, A. de Marco, F. Nicolosi, N. Genito, S. Figliolia: Design of a Low-Cost Easy-to-Fly STOL Ultralight Aircraft in Composite Material
The paper deals with the design of an aircraft, starting from a market survey, the conceptual design loop and the preliminary choice of dimensions, and leading to the detailed design of efficient high-lift systems and a low-drag fuselage shape. Technological challenges regarding the design of low-cost systems for flap/slat retraction and a simple wing folding system are highlighted. Aiming at an efficient optimization algorithm, we developed a new integration technique between CAD, aerodynamic and structural numerical calculation. Examples deriving from this new approach are presented.
Keywords: STOL, preliminary design.
G. Avanzini, S. D’Angelo, G. de Matteis: Design and Development of the Engine Unit for a Twin-Rotor Unmanned Aerial Vehicle
Advanced computer-aided technologies played a crucial role in the design of an unconventional Uninhabited Aerial Vehicle (UAV), developed at the Turin Technical University and the University of Rome "La Sapienza". The engine unit of the vehicle is made of a complex system of three two stroke piston engines coupled with two counter-rotating three-bladed rotors, controlled by rotary PWM servos. The focus of the present paper lies on the enabling technologies exploited in the framework of activities aimed at designing a suitable and reliable engine system, capable of performing the complex tasks required for operating the proposed rotorcraft. The synergic use of advanced computational tools for estimating the aerodynamic performance of the vehicle, solid modeling for mechanical components design, and rapid prototyping techniques for control system logic synthesis and implementation will be presented.
Keywords: uninhabited aerial vehicle, computational fluid dynamics, solid modeling, rapid prototyping.
D. J. McGeoch, E. W. McGookin, S. S. Houston: Sliding Mode Implementation of an Attitude Command Flight Control System for a Helicopter in Hover
This paper presents an investigation into the design of a flight control system, using a decoupled non-linear sliding mode control structure, designed using a linearised, 9th order representation of the dynamics of a PUMA helicopter in hover. The controllers are then tested upon a higher order, non-linear helicopter model, called RASCAL. This design approach is used for attitude command flight control implementation and the control performance is assessed in the terms of handling qualities through the Aeronautical Design Standards for Rotorcraft (ADS-33). In this context a linearised approximation of the helicopter system is used to design an SMC control scheme. These controllers have been found to yield a system that satisfies the Level 1 handling qualities set out by ADS-33.
Keywords: helicopter, sliding mode control, hover, handling qualities, ADS-33E-PRF, response types.
V. Zanic, P. Prebeg: Primary Response Assessment Method for Concept Design of Monotonous Thin-Walled Structures
A concept design methodology for monotonous, tapered thin-walled structures (wing/fuselage/ship/bridge) is presented including modules for: model generation; loads; primary (longitudinal) and secondary (transverse) strength calculations; structural feasibility (buckling/fatigue/ultimate strength criteria); design optimization modules based on ES/GA/FFE; graphics. A method for primary strength calculation is presented in detail. It provides the dominant response field for design feasibility assessment. Bending and torsion of the structure are modelled with the accuracy required for concept design. A ‘2.5D-FEM’ model is developed by coupling a 1D-FEM model along the ‘monotonity’ axis and a 2D-FEM model(s) transverse to it. The shear flow and stiffness characteristics of the cross-section for bending and pure/restrained torsion are given, based upon the warping field of the cross-section. Examples: aircraft wing and ship hull.
Keywords: thin-walled structures, shear flow, FEM, concept design.
R. Poul, D. Hanus: Composite Axial Flow Propulsor for Small Aircraft
This work focuses on the design of an axial flow ducted fan driven by a reciprocating engine. The solution minimizes the turbulization of the flow around the aircraft. The fan has a rotor - stator configuration. Due to the need for low weight of the fan, a carbon/epoxy composite material was chosen for the blades and the driving shaft.The fan is designed for optimal isentropic efficiency and free vortex flow. A stress analysis of the rotor blade was performed using the Finite Element Method. The skin of the blade is calculated as a laminate and the foam core as a solid. A static and dynamic analysis were made. The RTM technology is compared with other technologies and is described in detail.
Keywords: axial flow fan design, ducted fan, composite blades.
P. Kaňovský, L. Smrcek, C. Goodchild: Simulation of UAV Systems
The study described in this paper deals with the issue of a design tool for the&nbsp;autopilot of an Unmanned Aerial Vehicle (UAV) and the selection of the airdata and inertial system sensors. This project was processed in cooperation with VTUL a PVO o.z. [1]. The feature that distinguishes the autopilot requirements of a UAV (Figs. 1, 7, 8) from the flight systems of conventional manned aircraft is the paradox of controlling a high bandwidth dynamical system using sensors that are in harmony with the low cost low weight objectives that UAV designs are often expected to achieve. The principal function of the autopilot is flight stability, which establishes the UAV as a stable airborne platform that can operate at a precisely defined height. The main sensor for providing this height information is a&nbsp;barometric altimeter. The solution to the UAV autopilot design was realised with simulations using the facilities of MatlabŇ and in particular SimulinkŇ[2].
Keywords: autopilot, modelling, Sojka, tools, UAV
5 M. Dostál, J. Zymák, M. Valach: Physical and Numerical Difficulties in Computer Modelling of Pellet-Cladding Contact Problems for Burned-Up Fuel
The importance of fuel reliability is growing due to the deregulated electricity market and the demands on operability and availability to the electricity grid of nuclear units. Under these conditions of fuel exploitation, the problems of PCMI (Pellet-Cladding Mechanical Interaction) are very important from the point of view of fuel rod integrity and reliability. Severe loading is thermophysically and mechanically expressed as a greater probability of cladding failure especially during power maneuvering. We have to be able to make a realistic prediction of safety margins, which is very difficult by using computer simulation methods. NRI (Nuclear Research Institute) has recently been engaged in developing 2D and 3D FEM (Finite Element Method) based models dealing with this problem. The latest effort in this field has been to validate 2D r-z models developed in the COSMOS/M system against calculations using the FEMAXI-V code. This paper presents a preliminary comparison between classical FEM based integral code calculations and new models that are still under development. The problem has not been definitely solved. The presented data is of a preliminary nature, and several difficult problems remain to be solved.
Keywords: PCMI, FEM, contact, pellet, cladding.
H. Filipská, K. Štamberg: Mathematical Modeling of a Cs(I) – Sr(II) – Bentonite – Magnetite Sorption System, Simulating the Processes Taking Place in a Deep Geological Repository
The derivation of mathematical models of systems consisting of Cs(I) or Sr(II) and of bentonite (B), magnetite (M) or their mixtures (B+M) are described. The paper deals especially with modeling of the protonation and sorption processes occurring on the functional groups of the solid phase, namely on so called edge sites and layer sites. The two types of sites have different properties and, as a result, three types of Surface Complexation Models (SCM) are used for edge sites, viz. two electrostatic SCMs: the Constant Capacitance Model (CCM) and the Diffusion Double Layer Model (DLM), and one without electrostatic correction: the Chemical Model (CEM). The processes taking place on the layer sites are described by means of the Ion Exchange Model (IExM). In the course of modeling, the speciation of the given metal in the liquid (aqueous) phase has to be taken into account. In principle, the model of protonation or sorption processes is based on the reactions occurring in the aqueous phase and on the surface of the solid phase, and comprises not only the equations of the equilibrium constants of the individual reactions, but also the mass and charge balance equations. The algorithm of the numerical solution is compatible with FAMULUS 3.5 (a Czech software product quite extensively used at Czech universities in the last decade, the bookcase codes of which are utilized).
Keywords: cesium, strontium, bentonite, magnetite, surface sorption, ion exchange, protonation, titration, mathematical modeling.
P. Baláži: Various Properties of Sturmian Words
This overview paper is devoted to Sturmian words. The first part summarizes different characterizations of Sturmian words. Besides the well known theorem of Hedlund and Morse it also includes recent results on the characterization of Sturmian words using return words or palindromes. The second part deals with substitution invariant Sturmian words, where we present our recent results. We generalize one-sided Sturmian words using the cut-and-project scheme and give a full characterization of substitution invariant Sturmian words.
Keywords: Sturmian words, mechanical words, 2-interval exchange map, palindromes, return words, substitutions.
P. Ambrož: Non-Standard Numeration Systems
We study some properties of non-standard numeration systems with an irrational base b > 1, based on the so-called beta-expansions of real numbers [1]. We discuss two important properties of these systems, namely the Finiteness property, stating whether the set of finite expansions in a given system forms a ring, and then the problem of fractional digits arising under arithmetic operations with integers in a given system. Then we introduce another way of irrational representation of numbers, slightly different from classical beta-expansions. Here we restrict ourselves to one irrational base – the golden mean – and we study the Finiteness property again.
Keywords: numeration system, beta expansion, tau-adic expansion.
H. Lavička, F. Slanina: A Model of the Distribution of Wealth in Society
A model of the distribution of wealth in society will be presented. The model is based on an agent-based Monte Carlo simulation where interaction (exchange of wealth) is allowed along the edges of a small-world network. The interaction is like inelastic scattering and it is characterized by two constants. Simulations of the model show that the distribution behaves as a power-law and it agrees with results of Pareto.
Keywords: Pareto`s law, economics, scattering.
J. Novotný, M. Štefaňák, V. Košt`ák: Multi-Particle Universal Processes
We generalize bipartite universal processes to the subclass of multi-particle universal processes from one to N particles. We show how the general statement for a multi-particle universal process can be constructed. The one-parameter family of processes generating totally anti-symmetric states has been generalized to a multi-particle regime and its entanglement properties have been studied. A view is given on the complete positivity and the possible physical realization of universal processes.
Keywords: universal processes, quantum entanglement, complete positivity.
P. Novotný, J. Hrivnák: On Orbits of the Ring Znm under Action of the Group SL(m, Zn)
We consider the action of the finite matrix group SL(m,Zn) on the ring Znm. We determine orbits of this action for n arbitrary natural number. It is a generalization of the task which was studied by A. A. Kirillov for m = 2 and n prime number. Keywords: ring, finite group.
L. Thinová, A. Fronka, D. Milka: Personal Dosimetry Enhancement for Underground Workplaces
Personal dosimetry for underground workers mainly concerns measurement of the concentration of radon (and its daughters) and the correct application of the data in dose calculation, using a biokinetic model for lung dosimetry. A conservative approach for estimating the potential dose in caves (or underground) is based on solid state alpha track detector measurements. The obtained dataset is converted into an annual effective dose in agreement with the ICRP recommendations using the "cave factor", the value of which depends on the spectrum of aerosol particles, or on the proportional representation of the unattached and the attached fraction and on the equilibrium factor. The main difference between apartments and caves is the absence of aerosol sources, high humidity, low ventilation rate and the uneven surface in caves. A more precisely determined dose value would have a significant impact on radon remedies or on restricting the time workers stay underground. In order to determine how the effective dose is calculated, it is necessary to divide these areas into distinct categories by the following measuring procedures: continual radon measurement (to capture the differences in EERC between working hours and night-time, and also between daily and seasonal radon concentration variations); regular measurements of radon and its daughters to estimate the equilibrium factor and the presence of 218Po; regular indoor air flow measurements to study the location of the radon supply and its transfer among individual areas of the cave; natural radioactive element content evaluation in subsoils and in water inside/outside, a study of the radon sources in the cave; aerosol particle-size spectrum measurements to determine the free fraction; monitoring the behaviour of guides and workers to record the actual time spent in the cave, in relation to the continuously monitored levels of Rn concentration.
Keywords: radon concentration, underground, cave, effective dose, aerosol particles.
T. Čechák, L. Musílek, T. Trojek, I. Kopecká: Application of X-Ray Fluorescence Analysis in Investigations of Historical Monuments
Nuclear techniques and other techniques using ionising radiation represent a valuable tool in non-destructive diagnostics applied to archaeological finds and objects of arts, namely for determining the composition of materials used in the production of artefacts. X-ray fluorescence analysis, both in its energy form and in its wave dispersive form, is one of the most widespread methods using ionising radiation to study the elemental composition of materials. It is frequently used for studies of various cultural and historic relicts and objects of art. This work summarizes the authors` experience with X-ray fluorescence analysis in investigating historical frescos namely by means of portable provide spectroscopic devices. The results of these measurements information on the composition of the pigments, enable the comparison of processes used in the fabrication of pigments by individual artists, and in many cases offer information on how to repair the damaged parts.
Keywords: X-ray Fluorescence Analysis, Si(Li) detectors, portable spectrometers, energy dispersive analysis, fresco paintings, 55Fe, 238Pu.
6 J. R. Tippetts, V. Tesař: Flow Visualisation by Condensing Steam - an Unusual Method Applied to Development of a Low Reynolds Number Fluidic Selector Valve
A visualization method so far not mentioned in the literature has been recently developed by the authors as a useful validation supplement to numerical flowfield computations in the design of microfluidic devices. The method is based upon water vapour condensation on device channel walls. It is extremely easy to set up with minimum expense - and yet it is very reliable. As an application example, the paper shows the method used in study of properties of a microfluidic valve intended for switching gaseous sample flows in a microfluidic selector sampling unit. A scaled-up model of the valve was built, as usual, in transparent acrylic material, making possible observation and photo-recording of the deposition and subsequent drying of the condensed droplets. The scaling-up slowed down the time scale enough for investigating the transition processes which takes place as the flow in the valve is switched on and off.
Keywords: flow visualization, condensing steam, microfluidics, valves.
V. Tesař: Time-Mean Helicity Distribution in Turbulent Swirling Jets
Helicity offers an alternative approach to investigations of the structure of turbulent flows. Knowledge of the spatial distribution of the time-mean component of helicity is the starting point. Yet very little is known even about basic cases in which Helicity plays important role, such as the case of a swirling jet. This is the subject of the present investigations, based mainly on numerical flowfield computations. The region of significantly large time-mean helicity density is found only in a rather small region reaching to several nozzle diameters downstream from the exit. The most important result is the similarity of the helicity density profiles.
Keywords: helicity, chirality, jets, swirling flows, swirl generator, supercirculation.
T. H. S. Abdelaziz, M. Valášek: A Complete Parametric Solutions of Eigenstructure Assignment by State-Derivative Feedback for Linear Control Systems
In this paper we introduce a complete parametric approach for solving the problem of eigenstructure assignment via state-derivative feedback for linear systems. This problem is always solvable for any controllable systems iff the open-loop system matrix is nonsingular. In this work, two parametric solutions to the feedback gain matrix are introduced that describe the available degrees of freedom offered by the state-derivative feedback in selecting the associated eigenvectors from an admissible class. These freedoms can be utilized to improve robustness of the closed-loop system. Accordingly, the sensitivity of the assigned eigenvalues to perturbations in the system and gain matrix is minimized. Numerical examples are included to show the effectiveness of the proposed approach.
Keywords: eigenstructure assignment, state-derivative feedback, linear control systems, feedback stabilization, parametrization.
V. Dynda: Generic Platform for Failure Recovery in Survivable Trees
Failure recovery is a fundamental task of the dependable systems needed to achieve fault-tolerant communications, smooth operation of system components and a comfortable user interface. Tree topologies are fragile, yet they are quite popular structures in computer systems. The term survivable tree denotes the capability of the tree network to deliver messages even in the presence of failures. In this paper, we analyze the characteristics of large-scale overlay survivable trees and identify the requirements for general-purpose failure recovery mechanisms in such an environment. We outline a generic failure recovery platform for preplanned tree restoration which meets those requirements, and we focus primarily on its completeness and correctness properties. The platform is based on bypass rings and it uses a bypass routing algorithm to ensure completeness, and specialized leader election to guarantee correctness. The platform supports multiple, on-line and on-the-fly recovery, provides an optional level of fault-tolerance, protection selectivity and optimization capability. It is independent of the the protected tree type (regarding traffic direction, number of sources, etc.) and forms a basis for application-specific fragment reconnection.
Keywords: fault tolerance, failure recovery, tree restoration, distributed algorithms.
P. Večeř, M. Kreidl, R. Šmíd: Condition Indicators for Gearbox Condition Monitoring Systems
Condition monitoring systems for manual transmissions based on vibration diagnostics are widely applied in industry. The systems deal with various condition indicators, most of which are focused on a specific type of gearbox fault. Frequently used condition indicators (CIs) are described in this paper. The ability of a selected condition indicator to describe the degree of gearing wear was tested using vibration signals acquired during durability testing of manual transmission with helical gears.
Keywords: damage detection, condition monitoring, condition indicators, transmissions, vibration.
T. Ficker: On Deterministic Chaos in Microdischarge Phenomena
Time series of pulsating microdischarges were analysed. The results showed that deterministic chaos is present in these series. The estimated values of the correlation coefficients indicated a strong chaotic discharge behaviour.
Keywords: microdischarges, deterministic chaos, fractals.
E. Čermáková: Magnetization of Steel Building Materials and Structures in the Natural Geomagnetic Field
This paper presents the physical basis of the magnetic properties of ferromagnetic materials and shows their relationships with external geomagnetic field. It graphically processes the experimental data detected by an HMR magnetometer. Taking into account the natural geomagnetic field under the effects of steel U profiles, variations of the natural geomagnetic field in a steel structure building are indicated and the potential existence of Sick Building Syndrome (SBS) in these types of buildings is pointed out.
Keywords: experiment, geomagnetic fields, magnetometer, Sick Building Syndrome, U profile.
P. Kubalík, H. Kubátová: Parity Codes Used for On-Line Testing in FPGA
This paper deals with on-line error detection in digital circuits implemented in FPGAs. Error detection codes have been used to ensure the self-checking property. The adopted fault model is discussed. A fault in a given combinational circuit must be detected and signalized at the time of its appearance and before further distribution of errors. Hence safe operation of the designed system is guaranteed. The check bits generator and the checker were added to the original combinational circuit to detect an error during normal circuit operation. This concurrent error detection ensures the Totally Self-Checking property. Combinational circuit benchmarks have been used in this work in order to compute the quality of the proposed codes. The description of the benchmarks is based on equations and tables. All of our experimental results are obtained by XILINX FPGA implementation EDA tools. A possible TSC structure consisting of several TSC blocks is presented.
Keywords: on-line testing, self-checking, error detection code, fault, error, FPGA.
L. Mervart, A. Čepek: Geoinformatics Study at the Czech Technical University in Prague
At the CTU in Prague, there is a long tradition of master degree courses in geodesy, geodetic surveying and cartography. Taking into account the fast development of information technologies in recent decades, we decided to prepare a new study program that would combine computer science with a background of geodetic and cartographic know-how. Apart from other sources, our plans were inspired and influenced by the Review of Education Needs, a report prepared by Stig Enemark (Prague 1998), and by our experience from several Virtual Academy workshops.We have decided to call this program "Geoinformatics" to emphasize the role of computer technologies in collecting, analyzing and exploiting information about our planet. Within this presentation we will explain the basic ideas behind our new study program and emphasize the features that distinguish it from classical geodetic or cartographic programs. We will mention the connection between our new study program and several geodetic and software projects running at our institute - software development for real-time GPS applications, cooperation with the Astronomical Institute, University of Berne, on the development of so-called Bernese GPS Software, the GNU project Gama for adjustment of geodetic networks, etc.
Keywords: key education, curricula, geoinformation, software development.

Acta Polytechnica 2006

No. (click on selected title and view the annotation)
1 J. Bokr, V. Jáneš: State of a Logical Object
The paper deals with the state and performance of a logical object on a state-differentiating level and with the so called determinization of a finite - automaton model. Keywords: logical object, state, state transition, finite automaton.
B. Kuhlenkoetter: Development of a Robot System for Advanced High Quality Manufacturing Processes

Grinding and polishing are standard operations in material processing which are nowadays automated with the help of industrial robots in order to relieve human labour and optimize the profitability of production. However, it is expensive to adapt present systems to the production of other part geometries and operation cycles, and therefore adaptations are economically applicable only for large batch sizes.This project develops an "intelligent" robot system that obtains sensory skills due to the linkage of innovative robot technology and image processing systems via new software. With this system even the smallest error on highly-polished, mirror-like surfaces can be detected objectively and reproducibly. In addition, the system will be capable of establishing an optimum error compensation strategy dependent on the error data, as well as generating and realizing operating programmes. For this purpose it is given a manual-learning skill. A new offline-programming and simulating system for exacting operation processes makes it easier to set up, change and optimize robot programmes, thus making it useful for the operator.
Keywords: flexible manufacturing systems, materials handling and robotics, quality systems.
Selected paper from the 4th International Conference on Advanced Engineering Design (AED 2004), which was held in Glasgow from 5 to 8 September 2004.

G. Mamtani, G. Green: Reliability Risk Evaluation during the Conceptual Design Phase
Systematic evaluations of concept designs involve considering a range of criteria. Interaction with industry supports the view that reliability is a major criterion among those considered in product design. Although there are few methods to predict reliability in the initial phases of design, most of them are only applicable to adaptive designs. In this paper, we introduce the concept of relative reliability risk assessment for original designs, where information availability is less, to calculate reliability. We consider the function structures of the product under consideration and apply the analytic hierarchy process using verbal assessments for relative measurements. The weight assigning technique used is the entropy method. A final value of R3I (Relative Reliability Risk Index) is calculated and the idea of concept functionality graphs is presented. This method is applied on the example of seat suspensions for an off highway vehicle and the results are discussed. The findings help to sort out the concepts that are relatively strong in terms of reliability.
Keywords: reliability, concept design.
Selected paper from the 4th International Conference on Advanced Engineering Design (AED 2004), which was held in Glasgow from 5 to 8 September 2004.
B. Rehák: Design of a Predictive Hierarchical Controller Using FEMLAB
A hierarchical controller with two levels is proposed. One level is based on dynamic optimization while the second is responsible for tracking the optimal trajectory and rejecting disturbances. Its implementation using the FEMLAB system is described. Some simulations are presented at the end of the paper, together with an evaluation of the performance.
Keywords: hierarchical control, boundary-value problem, dynamical optimization, FEMLAB.
O. Drahovzal: Company Value, Real Options and Financial Leverage
This paper deals with determining of the value of companies and financial leverage. The author tries to find the optimum debt ratio for selected companies in the Czech Republic. The method of yield option extension is used for evaluating a company. The DCFC method was selected as the yield method, due to its simplicity. The dynamic model used allows us to make changes in the debt ratio with recalculations of all parameters that depend on it. The assessment is made from two points of view: Firstly, the maximum of the total amount of financial resources, and, secondly, the maximum of the inverse sums of the ROE index and the ratio of equity to the value of the company. The values of the total debt ratio and the long-term debt ratio are shown as results.
Keywords: evaluation, real options, financial leverage.
M. A. A. Saafan: Shear Strengthening of Reinforced Concrete Beams Using GFRP Wraps
The objective of the experimental work described in this paper was to investigate the efficiency of GFRP composites in strengthening simply supported reinforced concrete beams designed with insufficient shear capacity. Using the hand lay-up technique, successive layers of a woven fiberglass fabric were bonded along the shear span to increase the shear capacity and to avoid catastrophic premature failure modes. The strengthened beams were fabricated with no web reinforcement to explore the efficiency of the proposed strengthening technique using the results of control beams with closed stirrups as a web reinforcement. The test results of 18 beams are reported, addressing the influence of different shear strengthening schemes and variable longitudinal reinforcement ratios on the structural behavior. The results indicated that significant increases in the shear strength and improvements in the overall structural behavior of beams with insufficient shear capacity could be achieved by proper application of GFRP wraps.
Keywords: strengthening, shear capacity, GFRP, polyester, fiberglass, wrapping.
J. Pekař, J. Štecha: Identification and Predictive Control by p-norm Minimization
Real time system parameter estimation from the set of input-output data is usually solved by minimization of quadratic norm errors of system equations - known in the literature as least squares (LS) or its modification as total least squares (TLS) or mixed LS and TLS. It is known that the utilization of the p-norm (1Łp<2) instead of the quadratic norm suppresses the wrong measurements (outliers) in the data. This property is shown for different norms, and it is shown that the influence of outliers is suppressed if p®1. Also optimal predictive control utilizing p-norm minimization of the criterion is developed, and the simulation results show the properties of such control. Keywords: identification, predictive control, p-norm, ARX model, iteratively reweighted least squares, linear programming.
V. Tesař: Similarity Solutions of Jet Development Mixing Layers Using Algebraic and 1-Equation Turbulence Models
Mixing layers are formed between two parallel fluid streams having different velocities. One of the velocities may be zero, as is the usual case of the mixing layer that surrounds, immediately downstream from the nozzle, the core of a developing jet issuing into stagnant surroundings. Earlier - but so far not properly published - experimental evidence shows a remarkably weak effect of transversal curvature, making the present solution applicable with acceptable precision to description of developing round jets. This paper presents solutions of a planar mixing layer by a similarity transformation, which reduces the problem to solving ordinary differential equations. Two solutions are investigated: one based on an algebraic model and the other using the 1-equation model of turbulence. They are compared with recent results of PIV measurements of a developing jet.
Keywords: similarity of shear flows, mixing layer, turbulence models, algebraic model, one-equation model, submerged jets.
J. Bokr, V. Jáneš: Logical Structural Models with Multiplexors
The paper deals with the use of multiplexors in designing logical structural models.. The applications can be preferably used in designing morphology on EFGA chips and other programmable structures. Illustrative examples are included.
Keywords: Boolean function, Artjuchov- Shalyto extension, Shannon extension, Boolean function decomposition, multiplexor.
2 I. Šimeček: A Simple Cache Emulator for Evaluating Cache Behavior for SMP Systems
Every modern CPU uses a complex memory hierarchy, which consists of multiple cache memory levels. It is very difficult to predict the behavior of this hierarchy for a given program (for details see [1, 2]). The situation is even worse for systems with a shared memory. The most important example is the case of SMP (symmetric multiprocessing) systems [3]. The importance of these systems is growing due to the multi-core feature of the newest CPUs.The Cache Emulator (CE) can simulate the behavior of caches inside an SMP system and compute the number of cache misses during a computation. All measurements are done in the "off-line" mode on a single CPU. The CE uses its own emulated cache memory for an exact simulation. This means that no other CPU activity influences the behavior of the CE. This work extends the Cache Analyzer introduced in [4].
Keywords: cache hierarchy, cache emulator, symmetric multiprocessing, MESI protocol.
H. F. Soliman, A.-F. Attia, M. Hellal, M. A. L. Badr: Power System Stabilizer Driven by an Adaptive Fuzzy Set for Better Dynamic Performance
This paper presents a novel application of a fuzzy logic controller (FLC) driven by an adaptive fuzzy set (AFS) for a power system stabilizer (PSS).The proposed FLC, driven by AFS, is compared with a classical FLC, driven by a fixed fuzzy set (FFS). Both FLC algorithms use the speed error and its rate of change as input vectors. A single generator equipped with FLC-PSS and connected to an infinite bus bar through double transmission lines is considered. Both FLCs, using AFS and FFS, are simulated and tested when the system is subjected to different step changes in the reference value. The simulation results of the proposed FLC, using the adaptive fuzzy set, give a better dynamic response of the overall system by improving the damping coefficient and decreasing the rise time and settling time compared with classical FLC using FFS. The proposed FLC using AFS also reduces the computational time of the FLC as the number of rules is reduced.
Keywords: fuzzy controller: static and adapted fuzzy sets and power system stabilizer.
A.-F. Attia, H. Soliman, M. Sabry: Genetic Algorithm Based Control System Design of a Self-Excited Induction Generator
This paper presents an application of the genetic algorithm (GA) for optimizing controller gains of the Self-Excited Induction Generator (SEIG) driven by the Wind Energy Conversion Scheme (WECS). The proposed genetic algorithm is introduced to adapt the integral gains of the conventional controllers of the active and reactive control loop of the system under study, where GA calculates the optimum value for the gains of the variables based on the best dynamic performance and a domain search of the integral gains. The proposed genetic algorithm is used to regulate the terminal voltage or reactive power control, by adjusting the self excitation, and to control the mechanical input power or active power control by adapting the blade angle of WECS, in order to adjust the stator frequency. The GA is used for optimizing these gains, for an active and reactive power loop, by solving the related optimization problem. The simulation results show a better dynamic performance using the GA than using the conventional PI controller for active and reactive control.
Keywords: genetic algorithms, conventional controllers, self-excited induction generator.
P. Brož: Some Effects on Fatigue Strength
It has been widely known for some time that the mean stress affects the fatigue strength of steel. This is distinctly evident when working with non-welded or stress-relieved welded details. Some consequences of this influence are revealed when evaluating the stress history, or when counting the cycles.In this paper, decisive influences on the plain fatigue limits or strengths are indicated, when applying a mean stress, together with the effects of both combined stress and anisotropy and the minimum stress required to grow a crack of a given length and depth.
Keywords: alternating stress, mean load, notched and cracked specimen, notched fatigue data, reversed direct stress, stress ratio.
P. Pecherková, I. Nagy: Mixture Based Outlier Filtration

Success/failure of adaptive control algorithms - especially those designed using the Linear Quadratic Gaussian criterion - depends on the quality of the process data used for model identification. One of the most harmful types of process data corruptions are outliers, i.e. ‘wrong data’ lying far away from the range of real data. The presence of outliers in the data negatively affects an estimation of the dynamics of the system. This effect is magnified when the outliers are grouped into blocks. In this paper, we propose an algorithm for outlier detection and removal. It is based on modelling the corrupted data by a two-component probabilistic mixture. The first component of the mixture models uncorrupted process data, while the second models outliers. When the outlier component is detected to be active, a prediction from the uncorrupted data component is computed and used as a reconstruction of the observed data. The resulting reconstruction filter is compared to standard methods on simulated and real data. The filter exhibits excellent properties, especially in the case of blocks of outliers.
Keywords: data filtration, system modelling, mixture models, Bayesian estimation, prediction.

A. Dočekal, M. Kreidl, R. Šmíd: System for 3D Visualization of Flaws for Eddy Current Inspection
This paper presents a novel method for 3D visualization of flaws detected during Eddy Current (EC) inspection. The EC data was acquired using an automated scanning system equipped with precise eddy current probe positioning. The method was tested on a single frequency instrument with an absolute probe. The EC inspection procedure is implemented statically by registering the operating point of the instrument at each equidistant point on a tested object.The paper describes a data processing method based on the Fourier transform enabling 3D visualization of flaws. This three-dimensional image of the result of a scan enables the position of flaws to be determined, and the size and bevel (angle to the surface) of each detected flaw to be estimated. This research investigated flaws rising from the surface of the tested object, and flaw depth was not evaluated in this work. This method of visualization is simple to implement and is currently targeted for application in EC scanning devices.
Keywords: Eddy Current (EC), visualization, modified Fourier descriptors.
L. Kalvoda, J. Aubrecht, R. Klepáček: Fiber Optic Detection of Ammonia Gas
Bathochromic shifts accompanying the formation of several bivalent metallic complexes containing 5-(4’-dimethylaminophenylimino) quinolin-8-one (L1), and 7-chlore-5(4’-diethylamino-2-methylphenylimino) quinolin-8-one (L2) ligands in ethanol solutions were evaluated by VIS-NIR spectroscopy. The [L1-Cu-L1] sulphide complex was selected as a reagent for further tests on optical fibres. Samples of multimode siloxane-clad fused-silica fibre were sensitized by diffusing an ethanol/chloroform solution of the dye into the cladding polymer, and tested by VIS-NIR optical spectroscopy (12 cm long fibre sections), and optical time domain reflectometry (OTDR; 20 ns laser pulses, wavelength 850 nm, 120 m long fibre sensitized within the interval 104–110 m). A well-resolved absorption band of the reagent could be identified in the absorption spectra of the fibres. After exposure to dry ammonia/nitrogen gas with increasing ammonia concentration
(0–4000 ppm), the short fibre samples showed subsequent decay of NIR optical absorption; saturation was observed for higher ammonia levels. The concentration resolution r»50 ppm and forward response time t90»30 sec were obtained within the interval 0–1000 ppm. The OTDR courses showed an enhancement of the back-scattered light intensity coming from the sensitized region after diffusion of the initial reagent, and decay after exposure to concentrated ammonia/nitrogen gas (10000 ppm).
Keywords: chemical sensors, ammonia sensors, optical fibres.
M. Popovac: Reconstruction of the Old Bridge of Mostar
The Old Bridge of Mostar was built in 1566 by Hajrudin, a student of Kodza Mimar Sinan, the greatest Ottoman architect. It is a stone bridge of very slender and elegant shapes: its profile and its skyline are so thin and so high over the river waters that it is hard to believe that such a structure could be made out of huge stone blocks. The Bridge was destroyed in November 1993 by shelling during the recent war events. Its reconstruction was one of the biggest and most complicated projects involving UNESCO, The World Bank and many local and international experts. The task was to build a New Old Bridge – precisely the same in all details as the Old one. After many studies, tests and shape determinations, the project was completed and the actual reconstruction work could begin. Ancient techniques and methods, original materials and a perfectly reconstructed shape gave this Bridge its new life in post-war Mostar.
Keywords: old, bridge, Mostar, Maja, Popovac, Bosnia, Herzegovina, reconstruction, UNESCO, World Bank.
3 P. Brož: Metal Fatigue Features
This paper presents a summary of fatigue, crack initiation and growth, and fractographic findings for metal materials. The purpose of this paper is to consolidate and summarize some aspects of the fatigue of materials and structures.
Keywords: fracture surface, fracture toughness, macro-and microscopic appearance, microcrack, slip band, small cracks, striation, subgrain, transcrystalline.
I. Šimeček: Performance Aspects of Sparse Matrix-Vector Multiplication
Sparse matrix-vector multiplication (shortly SpM×V) is an important building block in algorithms solving sparse systems of linear equations, e.g., FEM. Due to matrix sparsity, the memory access patterns are irregular and utilization of the cache can suffer from low spatial or temporal locality. Approaches to improve the performance of SpM×V are based on matrix reordering and register blocking [1, 2], sometimes combined with software-pipelining [3]. Due to its overhead, register blocking achieves good speedups only for a large number of executions of SpM×V with the same matrix A.We have investigated the impact of two simple SW transformation techniques (software-pipelining and loop unrolling) on the performance of SpM×V, and have compared it with several implementation modifications aimed at reducing computational and memory complexity and improving the spatial locality. We investigate performance gains of these modifications on four CPU platforms.
Keywords: sparse matrix-vector multiplication, code restructuring, loop unrolling, software pipelining, cache hierarchy.
F. Rieger: Determination of Rheological Parameters from Measurements on a Viscometer with Coaxial Cylinders
The paper deals with measurements of non-Newtonian fluids on a viscometer with coaxial cylinders. The procedure for determining the rheological model parameters is recommended for power-law fluids and Bingham plastics.
Keywords: viscometer with coaxial cylinders, power-law fluids, Bingham plastics.
I. Baroňák, M. Vozňák: CaC in ATM - the Diffuse Method
Connection Admission Control is an element in the of preclusive mechanisms of ATM management. Its main task is to prevent overloading of the network and to ensure the required quality of service. This means that it has to predict the service of the network and according to its state it can manage both existing and new connections. This paper deals with the diffuse method, a CAC method that enables us to obtain the required results. Keywords: ATM, QoS, CaC - the diffuse method.
M.-F. Robbe: A Porosity Method to Describe Complex 3D-Structures Theory and Application to an Explosion
A theoretical method was developed to be able to describe the influence of structures of complex shape on a transient fluid flow without meshing the structures. Structures are considered as solid pores inside the fluid and act as an obstacle for the flow. The method was specifically adapted to fast transient cases.The porosity method was applied to the simulation of a Hypothetical Core Disruptive Accident in a small-scale replica of a Liquid Metal Fast Breeder Reactor. A 2D-axisymmetrical simulation of the MARS test was performed with the EUROPLEXUS code. Whereas the central internal structures of the mock-up could be described with a classical shell model, the influence of the 3D peripheral structures was taken into account with the porosity method.
Keywords: porosity method, homogenization, nuclear reactor, explosion, fluid-structure coupling.
M. Lidmila, L. Horníček, H. Krejčiříková, P. Tyc: Problems in Different Measuring and Assessment the Modulus of Deformation Using the Czech and German Methodologies
Comparative laboratory and in-situ measurements were used to establish the relationships between the static moduli of deformation calculated under the ČD methodology and the DB methodology. The measurements proved that the moduli of deformation determined in accordance with the two methodologies cannot be substituted for each other.
Keywords: Modul of deformation, conventional Trans-European System, the substructure, Classification of Soils, the earth subgrade, the fixed track section, the corridor track, rubber plates, granulated gravel, the correlation coefficient.