September 2004, Volume 4, Number 3

DOLEŽEL, I. — KARBAN, P. :
Integral Model of Eddy Currents in Nonmagnetic Structures
BOJKOVIC, Z. — TURÁN, J. — SAMCOVIC, A. — OVSENÍK, Ľ.
Coding, Streaming and Watermarking - Some Principles in Multimedia Signal Processing
MÜHLBACHER, J.
Mechanical Stress of the Gas Turbine Shaft at Generator Failure States
MOJŽIŠ, M. — VOJTKO, J. — ORENDÁČ, M. — HODULÍKOVÁ, A.
Terque Sensor Based on Villari's Phenomenon
ŠKORPIL, J. — DVORSKÝ, E.
Interconnection of Wind Power Stations to the Electric Power Network
BOBER, P. — GIRMAN, M.
Design and Simulation of a Holonic Assembly System
MÜHLBACHER, J. —, NOVÁK, P.
Wind Turbines in the High Voltage Networks of Czech Republic
TURMEZEI, P.
Chalcogenide Materials for Electrochemical Solar Cells
TKÁČ, J.
The Plastic Solar Absorbers and Possibilities of Their Utilization
TOMÁŠEK, M. :
Specification Issues of Communication and Code Mobility
BOKR, J.
Logical Control
Summary:
Ivo DOLEŽEL - Pavel KARBAN
Integral Model of Eddy Currents in Nonmagnetic Structures
[full paper]

Even when most of eddy current problems can succesfully be solved by differential techniques (particularly by the finite element methods), there exists a group of tasks where their application may cause various complications. Mentioned can be presence of geometrically incommensurable subdomains in the investigated area, ignorance of the boundary conditions, movement of some parts in the system etc. In such cases integral models may sometimes prove to be more advantageous. The paper presents the basic integral model of eddy current given by a system of the second-kind Fredholm integral equation and possibilities of using integral schemes of higher order of accuracy. The theoretical considerations are supplemented by two illustrative examples in 2D whose results are discussed and compared with values obtained by other ways


Zoran BOJKOVIC - Jan TURÁN - Andreja SAMCOVIC - Ľuboš OVSENÍK
Coding, Streaming and Watermarking - Some Principles in Multimedia Signal Processing
[full paper]

In this paper, a review of signal processing for networked multimedia is presented. The emphasis is on three important parts of the area, like coding, streaming and watermarking technologies. Multimedia signal (speech, audio, acoustic, image, video, graphics and data) processing is analyzed, as well as perceptual coding of digital audio signals. Another part of the paper seeks to provide watermarking algorithms, and its application in intellectual copyright protection.


Jan MÜHLBACHER
Mechanical Stress of the Gas Turbine Shaft at Generator Failure States
[full paper]

This paper deals with the calculation of the short circuit moment synchronous machine and the influence on reliable operation of the set turbine-generator.


Miroslav MOJŽIŠ - Jozef VOJTKO - Martin ORENDÁČ - Anna HODULÍKOVÁ
Terque Sensor Based on Villari's Phenomenon
[full paper]

The paper describes development and construction of the torque sensor based on Villari's phenomenon (elastomagnetic effect). This paper presents results of the institutional research solved by the Group of Electrical Engineering Theory and Electrical Measurement at the Technical University in Košice. The main task was to create a torque sensor including accessories from homemade materials, experimentally optimize working conditions and to determine metrological properties of the measurement set. The measuring experiment results are evaluated and discussed.


Jan ŠKORPIL - Emil DVORSKÝ
Interconnection of Wind Power Stations to the Electric Power Network
[full paper]

Distributed generation (DG) technologies can provide energy solutions to some customers that are more cost-effective, more environmentally friendly, or provide higher power quality or reliability than conventional solutions. Understanding the wide variety of DG options available in today's changing electric markets can be daunting. Some of these DG technologies offer high efficiency, resulting in low fuel costs, but emit a fair amount of pollutants (CO and NOx); others are environmentally clean but are not currently cost-effective. Still others are well suited for peaking applications but lack durability for continuous output. 
One of the technologies using in DG applications are wind power stations (WPS). The article aims at providing a basic discussion of the relevant issues related to the wind power interconnection in electric distribution system.


Peter BOBER - Michal GIRMAN
Design and Simulation of a Holonic Assembly System
[full paper]

This paper defines an overall structure and behaviour of components of a holonic assembly system. The required properties of the holonic assembly system are autonomy and possibility of automatic reconfiguration in case of failures and relocations of individual elements - holons. The assembly system consists of input buffer, transportation, and universal assembly stations. Rule based distributed scheduling is used for assembly task planning. Desired properties are achieved by mutual interaction of holons. Designed structure and scheduling rules are verified by simulation. The proposed scheduling rule gives good output rate already for 10 tasks available at a time as compared to quasi optimal output rate when all 200 work orders were scheduled at once.


Jan MÜHLBACHER - Pavel NOVÁK
Wind Turbines in the High Voltage Networks of Czech Republic
[full paper]

It has been generated a lot of gigawatthours from new wind farms all over the world in the last years. Otherwise, there appeared problems with connection and operation associated with this "boom" of wind power. Questions like voltage changes, flicker, harmonic currents, behaviour during network disturbances and regulation of reactive power are presently discussed.
The purpose of this article is to show possibilities of wind power in Czech Republic, with aspects of integration to the high voltage networks. The rules for operation of transmission and distribution lines are determined by Energy Regulatory Office. According to these rules, which include the connecting conditions and evaluation of wind turbine grid impacts, is made an evaluation of small wind farm grid connection.



Péter TURMEZEI
Chalcogenide Materials for Electrochemical Solar Cells
[full paper]

The problem of electrical energy storage can possibly be solved with the help of electrochemical solar cells, which are suitable to generate either electrical energy or hydrogen gas under special conditions. The greatest problem of the electrochemical solar cell technology is to find novel materials which have appropriate properties for electrochemical energy conversion. In this work Cd4GeSe6, a novel material for electrochemical solar cells, will be presented.


Ján TKÁČ
The Plastic Solar Absorbers and Possibilities of Their Utilization
[full paper]

Utilization of solar energy becomes the more topical. The most spread application is heating the water. This contribution deals with construction of plastic solar collector-absorber for low temperature utilization, especially for heating the water in swimming pools. This collector has a set construction. It enables the creation of required absorbing area on the surface of the ground without bearing constructions, and also the free movement of persons on the absorber surface. These solar absorbers also enable the other non-conventional possibilities of utilization. Carried-out measurements shown that solar absorbers are the most effective possibility of utilization of solar energy at present.


Martin TOMÁŠEK
Specification Issues of Communication and Code Mobility
[full paper]

Presented process calculus for agent communication and mobility can be used to express distributed systems based on agent technology and mobile code applications in general. Agents are abstraction of the functional part of the system architecture and they are modeled as process terms. Agent actions model interactions within the distributed system: local/remote communication and mobility. Places are abstraction of the computational environment where the agents are evaluated and where interactions take place. Distributed system is modeled as a parallel composition of places where each place is evolving asynchronously. Formal operational semantics defines rules to describe behavior within the distributed system and provides a guideline for implementations. Via a series of examples we show that mobile code applications can be naturally modeled.


Josef BOKR
Logical Control
[full paper]

The paper deals with logic control technological devices. An impossibility of Glushkov¢s and Bellman¢s concepcions of logic control is shown and thus the new idea is proposed.


 

Publisher

    Faculty of Electrical Engineering and Informatics, Technical University of Košice, Slovak Republic

    Reg. No.: EV 2921/09,
    thematic group B1,
    ISSN 1335-8243
    The editorial board assumes no responsibility for damages suffered due to use of acts, methods, products, instructions for use or other ideas published by the article authors whatsoever.
EAN 9771335824005