Communications - Scientific Letters of the University of Zilina, 2005 (vol. 7), issue 4

Articles

Articles

ARQ Mechanism in HSDPA

Robert Bestak

Communications - Scientific Letters of the University of Zilina 2005, 7(4):5-9 | DOI: 10.26552/com.C.2005.4.5-9  

Two principal features of the MAC-hs protocol include retransmissions of erroneous blocks and in-sequence data delivery to the upper layer. The first function is provided through a HARQ mechanism. The second function is achieved with the help of sliding transmission/receiving window and by using a specific numbering. In this paper, the MAC-hs performance for different sliding window sizes, timer values and number of retransmission attempts are investigated. Simulations show that values of these parameters have to be carefully set up in order to prevent incorrect block discards at the receiver side.

Signification of Depth of Penetration in Eddy Current Non-Destructive Testing

Tomas Marek

Communications - Scientific Letters of the University of Zilina 2005, 7(4):10-13 | DOI: 10.26552/com.C.2005.4.10-13  

Eddy currents are utilized for non-destructive testing of conductive materials. The depth of penetration is a very important parameter as it defines the propagation of the electromagnetic wave as well as of the electromagnetic energy in conductive materials. Limitations of the nondestructive testing using eddy currents are therefore given by the parameter. The paper highlights the signification of the depth of penetration in eddy current non-destructive testing using numerical simulations. A tubular specimen with a defect of a variable depth is inspected using a bobbin type probe and the crack signals are calculated for the purpose. The finite element...

Comparison of Simulation and Experimental Axial Loadings for Hydromechanical Bulge Forming of Copper Cross-Joints

Jacek Chalupczak, Tomasz Milek

Communications - Scientific Letters of the University of Zilina 2005, 7(4):14-17 | DOI: 10.26552/com.C.2005.4.14-17  

Hydromechanical bulging is applied mainly to the series production of hydraulic installation and sanitary facilities including tubes with a changeable diameter, T-pipes and cross-joints. The process consists in placing a tube segment in a die-cavity, pouring some liquid over it and sealing the faces. As a result the liquid pressure rises and the pipe is upset. The basic parameters of the hydromechanical process of bulge forming are: liquid pressure and axial loading. The simulations of hydromechanical bulge forming were performed using MSC Marc software based on the finite element method. The calculation results were compared with the experimental...

Direct Numerical Optimisation of a Fuel Jet Pump Based on a Pseudo-Compressibility Method Using Characteristic Boundary Conditions

Arpad Veress, Jozsef Rohacs, Imre Santa, Tamas Gausz

Communications - Scientific Letters of the University of Zilina 2005, 7(4):18-22 | DOI: 10.26552/com.C.2005.4.18-22  

The paper tries to give an overview of the latest industrial development of the Department of Aircraft and Ships at the Budapest University of Technology and Economics.The numerical investigation presented below based on Chorin's pseudo-compressibility method is used to make the incompressible Euler equations artificially hyperbolic [1]. A less dissipative flux difference splitting method is evolved to solve governing equations. A low cost 4th order Runge-Kutta method is applied for time marching in pseudo space. Both extrapolated and characteristic type boundary conditions are examined and compared with each other in qualitative accuracy and convergence...

A Structure of the Cooling System

Vladimir Hlavna, Dusan Sojcak, Dalibor Barta

Communications - Scientific Letters of the University of Zilina 2005, 7(4):23-26 | DOI: 10.26552/com.C.2005.4.23-26  

Some problems related to energetic flows in a cooling system of the combustion engine equipped with a non-conventional cooling circuit are described in this paper. The verification was carried out on a real diesel tractor engine by exploring the thermal balance. Actually, it is an assessment of the influence of alternative cooling liquid on the engine parameters with a particular attention to the flow of after-expansion energy into the cooling system for its further use. Thermal balance is evaluated by means of a reduced output number related to heat or energy chemically bound in fuel, energy led by the cooling system and energy corresponding to the...

Defectoscopic Susceptibility of Machine Elements

Marian Josko

Communications - Scientific Letters of the University of Zilina 2005, 7(4):27-30 | DOI: 10.26552/com.C.2005.4.27-30  

In the paper defectoscopic susceptibility of machine elements is analyzed. At first, an objective notion is defined and presented in a practical situation. The defectoscopic susceptibility as a feature can be considered and described also as a system consisting of two subsystems and a collection of non-technical factors. The subsystems are defined as a group of many factors. A mathematical structure of selected factors was shown as an example. Some factors of defectoscopic and diagnostic susceptibilities were calculated and gathered for selected parts of a motor vehicle and for air conditioning systems of selected models of cars. The calculated values...

Diagnostics of the Track Substructure Model and Its Practical Use

Libor Izvolt, Jan Kardos, Jan Lelak, Martin Mecar

Communications - Scientific Letters of the University of Zilina 2005, 7(4):31-36 | DOI: 10.26552/com.C.2005.4.31-36  

The paper presents mathematical equations of dependence of deformation resistance (compaction degree) and static/dynamic deformation module of elasticity reached by experimental measurements at laboratory model of scale 1:1 in 2003 and 2004. Recommendations for practice from the point of view of dimensioning and suitability of applied materials into the railway substructure are also presented.

On Dynamics of Certain Economic Models

Lubica Hanustiakova, Rudolf Olach

Communications - Scientific Letters of the University of Zilina 2005, 7(4):37-40 | DOI: 10.26552/com.C.2005.4.37-40  

The article deals with the dynamics of two economic models. The first one is a macroeconomic model about national income and its stability. In the second model the price of a certain commodity is treated. The equilibrium points, periodic points, price cycles and their stability in the market is also observed. The article is interdisciplinary in its nature.

Venture Capital in Central and Eastern Europe - Slovakian Case

Magdalena Markiewicz

Communications - Scientific Letters of the University of Zilina 2005, 7(4):41-46 | DOI: 10.26552/com.C.2005.4.41-46  

Financing business at the very first stage or expanding it, together with active participation in creating strategies of management, marketing, sales and other fields, may be done by venture capital funds and venture investors. They offer capital, know-how, expertise and assistance and are ready to take significantly higher risk for the average period of 5-7 years. Venture investments are especially effective in stock-oriented markets, due to an opportunity of easy disinvestment through public offering, or in emerging markets, where they meet prospects of very high rates of return. Private equity and venture capital investments may highly support the...

Electronic Toll Collection at Parking Areas

Rastislav Pirnik, Jiri Zahradnik, Ales Janota, Peter Ciganek

Communications - Scientific Letters of the University of Zilina 2005, 7(4):47-51 | DOI: 10.26552/com.C.2005.4.47-51  

The paper presents an object-oriented modeling of electronic toll collection in transport applications, deals with designing of a use case diagram, class diagram, sequence diagram, and state chart. The modelling of parking system activities by the UML language (Unified Modeling Language) creates suitable and effective environment for team members communication, simplifies software design process, and unifies principles and techniques used for documentation creation.

Limits of the Multiplier Adjustment Approach to Capacitated Location Problem

Lydia Gabrisova

Communications - Scientific Letters of the University of Zilina 2005, 7(4):52-55 | DOI: 10.26552/com.C.2005.4.52-55  

This contribution deals with a distribution system design problem, in which the located facilities satisfy all customer demands under limited abilities. The objective is to minimize the total costs, including both fixed charges and service costs. A special approach based on Lagrangean relaxation will be discussed here for its ability to cope with limited capacities of located facilities. Using the Lagrangean relaxation, the model of the original problem is rearranged to a model, which can be solved by exact algorithms for considerably large size. The capacities of the located facilities bring serious difficulties concerning solving technique, in the...

Analysis of Cooperative Unions' Development Case Study: Poland

Joanna Bednarz

Communications - Scientific Letters of the University of Zilina 2005, 7(4):56-58 | DOI: 10.26552/com.C.2005.4.56-58  

Cooperative unions in Poland are self-aid communities acting on the market of financial services. They gather people connected by the same working place or membership in the same community or professional group, who save together and lend money one another. They play an important economic role in Poland because of the fact that they are servicing people who because of their unfavourable or unstable financial condition could not be clients of commercial banks, and in this way would be denied the access to certain financial services, mainly to credits. In the presented article the quick development of the cooperative unions in Poland is presented.

Legendre Polynomials Used for the Approximation of Cylindrical Surfaces

Dariusz Janecki, Krzysztof Stępien

Communications - Scientific Letters of the University of Zilina 2005, 7(4):59-61 | DOI: 10.26552/com.C.2005.4.59-61  

The paper deals with a concept of application of orthogonal Legendre polynomials for the approximation of cylindrical surfaces. It presents fundamentals of a mathematical model of such approximation. The theoretical considerations are supported by the results of the experimental verification of the developed concept.

The Development of Strategic Management

Mariana Strenitzerova

Communications - Scientific Letters of the University of Zilina 2005, 7(4):62-65 | DOI: 10.26552/com.C.2005.4.62-65  

The top managers agree on the fact that the development of new strategies is their most important task. However, up to what extent do the time and means expended on the more or less formalized strategic processes really lead to a better efficiency and productivity of the firm? It was dominant task of the study of the German counselling firm The Galileo Consulting Group in cooperation with the European Business School in Oestrich-Winkel. Interactive strategic modelling is a method of an individualizing instrumentarium by means of which it is possible to depict interactively various variant of future actions.

Radio Resource Allocation in Mobile Communication Systems

Andrej Husar, Peter Cepel, Peter Brida, Vladimir Wieser

Communications - Scientific Letters of the University of Zilina 2005, 7(4):66-68 | DOI: 10.26552/com.C.2005.4.66-68  

In the article we deal with two types of Call Admission Control Schemes (Reservation-based CAC scheme and Probability-based CAC scheme) and we made simulations in Matlab environment. Both types of these transmission schemes belong to homogeneous type of radio resource management applications. Only voice application belongs here (traditional wireless networks) and each call demands the same amount of bandwidth (channel, frequency or time slots). Both schemes are compared and evaluated at the end of the article.

Illnesses and Diseases: Article or Not? That's Question!

Marta Kadorova, Zuzana Ondrackova

Communications - Scientific Letters of the University of Zilina 2005, 7(4):69-78 | DOI: 10.26552/com.C.2005.4.69-78  

The paper analyses the use of articles with the names of illnesses, diseases and disorders in the English language. The paper is divided into three parts. The first one summarizes rules about the articles and illnesses in prescriptive grammar books. The second one contains a table which aims to present the list of illnesses, diseases and disorders with corresponding articles. The final one focuses on the results of the research which was based on the comparison of the theoretical background and the actual use of articles with the names of illnesses, diseases and disorders in The Family Medical Reference Book.

Lute Music in the Area of Contemporary Slovakia in the Period of Renaissance Jean Baptista Besard - Thesaurus Harmonicus

Michal Hottmar

Communications - Scientific Letters of the University of Zilina 2005, 7(4):79-81 | DOI: 10.26552/com.C.2005.4.79-81  

The article analyses the issue of occurrence of lute music, its repertoire, players, and composers connected with the area of Slovakia in the age of humanism.