June 2005, Volume 5, Number 2
Summary: 
Martin MACH  Pavel KARBAN  Ivo DOLEŽEL On Some Aspects of Levitation Heating of Metal Bodies [full paper] Levitation induction heating represents the first step of levitation melting, which is an advanced technology used for processing of superclean metals or metal alloys. A workpiece is lifted by the Lorentz forces in time variable magnetic field produced by a system of suitably placed field coils and then heated by the Joule losses. The paper deals with optimization of the heating process from the viewpoint of the velocity of heating the workpiece. Investigated is the influence of its shape (sphere, cylinder, truncated cone) and arrangement of the field coil. The theoretical analysis is supplemented by a series of particular examples and discussion of the results obtained.

Želmíra FERKOVÁ  Ladislav ZBORAY Contribution to Parameter Identification of an Induction Motor by Genetic Algorithms [full paper] The paper presents contribution to parameter identification of an induction motor by genetic algorithms (GA) programme. Its correctness was verified by identification of the model assembled by five rated parameters. Then phase current and speed of the 1.5 kW motor were measured during start by direct connection to mains. Unknown parameters of the mathematical model were identified by GA. Because of varying motor parameters some differences appear among model time responses and real curves. However, certain constant parameters distinct from rated values but ensuring satisfactory matching with measurement may be found. Deviations of time responses were evaluated at measurement of speed, current or both magnitudes. Particular solutions are illustrated by corresponding graphs.

Ján KOLLÁR  Marcel TÓTH Temporal Logic for Pointcut Definitions in AOP [full paper] The aim of this paper is to propose the use of temporal logic in dynamic weaving of advices in aspect oriented programming (AOP), based on process functional paradigm. Namely, temporal logic appears to be well suited tool to design pointcuts whose task is selection of join points throughout source code (static weaving) or program execution (dynamic weaving). Because it is well known that join point model and techniques used for selecting them (pointcuts) are crucial elements of aspect oriented programming, we tried to propose the way of better (at least we think it is better for describing dynamic join points) pointcut formulation in terms of temporal logic. By now we have developed process functional language (PFL), which is simple but yet powerful abstraction used to illustrate mechanisms of programming languages. PFL includes structures and principles supporting functional, imperative and even object oriented and aspect oriented paradigms (which is still under development), so it is multi paradigmatic language. This paper is presenting reflection as a basic property of PFL used as a tool for weaving semantics of aspect code into original code. Code examples in this paper use PFL, but some examples are written also in AspectJ to clarify informal semantics of its operations (particularly cflow operation, since it is used for selecting dynamic join points).

Anton BŘEZINA  Jaroslav POLEC  Andrej VARCHOLA Successive Interpolation/Extrapolation Scheme for Missing Segments Restoration [full paper] This paper introduces a method for restoration of missing arbitrarily shaped image segments using combined discrete orthogonal transforms (DOT). The missing segment texture is successively interpolated/extrapolated using the texture of the correctly decoded segments belonging to the same object, thus having the same texture pattern.

Dragan TASIĆ  Miodrag STOJANOVIĆ Fuzzy Approaches to Distribution Energy Losses Calculation [full paper] Two approaches to calculating distribution energy losses are developed in this paper. The first one is based on the fuzzy load flow, and the other one uses fuzzy clustering technique. The attention at the first approach is devoted to forming the fuzzy numbers that represent loads. Data accessible from the measurements in corresponding substations are considered in this process. Using formed fuzzy loads one fuzzy load flow calculation is made. Results of calculation are fuzzy power losses. Defuzzification gives the deterministic value of average power losses that multiplying with the number of hours for analyzed period gives energy losses. For the second approach, the range of the coefficient that defines fuzziness of clustering is determined, as well as an optimal number of clusters. Analyses shows that the best results are obtained for fuzziness coefficient on the range of 1.12, and the number of clusters up to 20.

Ján MIHALÍK  Radoslav ŠTEFANIŠIN Entropy Coding in Standard Videocodecs [full paper] The paper deals with algorithms of entropy coding in the standard videocodecs H.261,263,264 and MPEG1,2,4 considerably increasing their total data compression. These algorithms are variable length coding by using Huffman codes, arithmetic coding, universal variable length coding, contex based adaptive binary arithmetic coding employing context modeling and binarization of nonbinary symbols. In generally they employ the statistical nonstationary properities of videosignals, which depend on the content of visual scenes.

Pavel NOVÁK  Jozef JANOŠČÍK The Analysis of Solid Charge Direct Resistance Heating at Different Conditions of Unicity [full paper] The place of generation of technologic heat is important applied criteria for classification of electric heating. According to that, the direct heating is if the heat is generated directly in the heated material, or the indirect heating if material is heated indirectly by the heat generated in conversion element. Possibilities of practical application of both methods are typical for resistant heating. Considering indirect heating, the charge is out of influence of electromagnetic field, this directly does not influence its temperature field. Temperature distribution in the charge volume depends only on its heatphysical properties and conditions of heat exchange on surface, i.e. thermo kinetic processes. Fourier's equation is applied in field solution. Considering direct heating, temperature distribution in the charge volume is more complicated. It is conditioned by interaction of temperature and electromagnetic field, which is generated by the current flowing in the charge. Solution of temperature field in directly heated charge must for that reason respect current density distribution on its crosssection, this leads to applying of heat conduction equation. We introduce its application for different types of temperature fields in the solid charge in this article.

Jozef KÚDELČÍK  Miroslav GUTTEN Analyse of SF6 Properties in Encapsulated Equipments and Its Optimal Utilization with Combination CO2 [full paper] Because of Sulfur Hexafluoride's excellent physical properties and unparalleled dielectric capabilities it has become the single choice for the electrical utility industry worldwide. This inert, nontoxic gas has excellent cooling, insulating, and arc quenching capabilities in potentially high temperature applications such as electrical breakers.

Branislav SOBOTA Bones Visualization in VirtualReality System [full paper] This paper described the morphological simulation of bones for visual frame in the virtual reality system. The paper is divided to three parts. In the first part are described introduction to virtual reality, modelling of bones and fractal geometry. This part also described a method choice for realisation of these problems. As initial tool for solving of this problem, was used Lsystem. Second, main part contained algorithms for generating of bone body and for bone surface. Algorithm for generating of bone body use fractal geometry functions based on Lsystems. Algorithm for generating of bone surface use shrinkwrap method. This process is described as iterative algorithm. The final points set define triangular net of bone surface. By both algorithms is added a possibility of using random parameters values. This feature increased abilities of this process. In the last part are described advantages and disadvantages of this solving. Also are here suggestions for using these bones in virtual models and worlds and examples of outputs from program implementation.

Tomáš PIKULA  Marcel BALÁŽ  Peter TREBATICKÝ  Vladimír LADECKÝ  Robert ŠEVČÍK Testable CryptoCores Using Rijndael Algorithm [full paper] Data security became very crucial topic and for that reason different data encryption algorithms have been developed. They should be parts of complex systems for secure data transfer designed into a single chip. Hardware implementations of a data encryption (decryption) algorithm appear to have a better resistance to attacks. Increasing complexity of electronics systems has made testing one of the most complicated and time consuming problems in system design and production. The microelectronic technologies are driving engineers towards design methodologies called systemonchip (SoC). Predesigned cores with testability blocks are used in the effective SoC design process. The paper presents two testable cores for data encryption that use the AES (Advanced Encryption Standard) algorithm. The first one is the " Memory" version and the second one is the "Composite fields" version . Two types of testability techniques  builtin selftest and wrapper architecture  were applied to the developed and implemented Rijndael cores in XILINX Spartan 3 FPGA. The selftestable core consists of a pseudorandom test pattern generator and control logic, which determines faulty or faultfree behaviour of the core. The core with wrapper allows to access all primary inputs and outputs of the core and a deterministic test set can be applied, and responses can be observed through the wrapper. Both testable encryption cores have been modeled by VHDL and they should be used in a complex secure system.

Marián AMRICH Design and Simulation of Fuzzy Logic Controller for Temperature Control of Temperature Isolated Plant [full paper] Temperature control is widely used in various processes of physical, electronic, chemical, mechanical and biological systems. All these systems are affected by temperature. Some biological processes must be performed in specified temperature range only. For this, controllers are used to keep temperature value on constant level or defined range. A relative new field of SoftComputing area is bringing to us a fuzzy logic approach with specific design procedure by using heuristic information. The paper deals with the influence of fuzzy logic on design of fuzzy based nonlinear controller for simplified temperature isolated plant, combined from temperature isolated room and heating element driven by amplitude of connected voltage from controller through power stage. The design procedure with respect to the quality of stabilization of the system, starting on system identification and continuing with design of firstorder conventional controller and using this setup for fuzzy controller is suggested. This article describes major steps for design of fuzzy PI controller by using human language information which copying linear surface of conventional controller with helpful of defined metarules and uniformly arranged fuzzy sets on inputoutput universe of disclosure. A final design is verified by simulation in MatlabSimulink environment where basic simulation diagram is drawn. It is shown that fuzzy logic based controller is a new approach of control. The cases in which the well tuned fuzzy logic controller in time varying process is more stable and more robust than the conventional approach in plants were observed. But in case when the fuzzy logic controller is tuned incorrectly it can exhibit limit cycle which can decrease lifetime of the actuator.
