Communications - Scientific Letters of the University of Zilina, 2007 (vol. 9), issue 4
Articles
QoS Issues in Complex-Based High Altitude Platform Communication Systems
Konstantinos Birkos, Theofilos Chrysikos, Stavros Kotsopoulos
Communications - Scientific Letters of the University of Zilina 2007, 9(4):5-9 | DOI: 10.26552/com.C.2007.4.5-9 
The use of High Altitude Platforms is a promising solution towards the integration of different wireless networks. Complex-based High Altitude Platform communication systems can offer high quality wireless services combined with enhanced bandwidth efficiency. Inter-system handover and power control are major factors affecting the provided quality of service. The impact of these factors under strong fading environments is studied in the present work.
Analysis of Input Impedance of the Traction Vehicle with DC Chopper as a Function of Operation Mode
Adam Szel±g, Marcin Steczek
Communications - Scientific Letters of the University of Zilina 2007, 9(4):10-13 | DOI: 10.26552/com.C.2007.4.10-13
A problem of analysis of the input impedance of a converter traction vehicle is presented in the paper. The value of input impedance of a traction vehicle has significant influence of compatibility between track circuits and traction vehicles. The model of chopper controlled DC series motor vehicle was implemented as a simulation model including all significant parameters of the whole system: substation-catenary-input filter-chopper. Exemplary results of analysis of the specific locomotive EM10 are included. The results both of analytical and simulation approach for low frequency input impedance computations were compared.
Velocity Vector Control of a Linear Permanent Magnet Synchronous Motor
Vladimir Vavrus, Jan Vittek, Michal Malek
Communications - Scientific Letters of the University of Zilina 2007, 9(4):14-19 | DOI: 10.26552/com.C.2007.4.14-19
The paper presents a design of vector control algorithm for electric drive employing a linear permanent magnet synchronous motor (LPMSM). For simulation and further experimental verification it was necessary to formulate a mathematical model of the LPMSM. This model was derived from a standard mathematical model of a rotary PMSM and then exploited to verify vector control of the machine. The presented simulation results are used to control the LPMSM drive system with maximum efficiency.
Integrating Ecological Components in Kilometre-Based Road Toll Systems
Marcus Einbock, Gudrun Stranner
Communications - Scientific Letters of the University of Zilina 2007, 9(4):20-24 | DOI: 10.26552/com.C.2007.4.20-24
Some member states of the European Union (e.g. Germany, the Czech Republic) have already included ecological components in their pricing systems of kilometre-based road tolls for road freight transport on the motorway-net. This means that vehicles with very modern emission standards have to pay less per kilometre in contrast to older trucks with a higher volume of exhaust-emissions. Austria implemented a kilometre-based road toll system in 2004, but without an ecological component. The goal of the paper is to evaluate the effects of considering EURO emission standards in the price systems of road tolls in Austria with the help of the scenario technique....
Modelling the Ultrasonic Diagnosis of Adhesive Bonds
Marian Josko
Communications - Scientific Letters of the University of Zilina 2007, 9(4):25-29 | DOI: 10.26552/com.C.2007.4.25-29
In the paper, the conception of modelling the diagnosis of adhesive bonds by ultrasonic method is presented. Two complementary models of bonds diagnosis are presented and discussed. The models proposed reduce an evaluation of coating adherence to assessment of condition of bond between coating and substrate. The models are connected with period of production of adhesive bonds (so called control diagnostic) and with the operational or maintenance period of its existence (operational diagnostic).
Equation of the Standard EN 12195-1 Stipulates Unreasonable Demands for Cargo Securing
Juraj Jagelcak
Communications - Scientific Letters of the University of Zilina 2007, 9(4):30-33 | DOI: 10.26552/com.C.2007.4.30-33
Cargo securing is a factor influencing safety and quality of transport considerably. In this paper the problem of calculation of over top lashing to prevent tipping is mentioned. "European standard EN 12195-1 Load Restraint Assemblies. Safety. Part 1: Calculation of lashing forces" stipulates unreasonable demand for number of over top lashings to prevent tipping of load. The calculation of number of lashings gives infinite results for certain lashing angles. The reason can be found in equation (8) of the standard.
The Effects of Referential Questions in the EFL Classroom
Martina Siposova
Communications - Scientific Letters of the University of Zilina 2007, 9(4):34-37 | DOI: 10.26552/com.C.2007.4.34-37
The article deals with complexity and importance of asking questions in the foreign language classroom. Since questions are one of the most essential teaching tools, teachers use them quite frequently during their lessons. The importance of referential questions, which are often referred to as "genuine or real" questions, lies in the fact that they have highly positive influence on the learning process. The qualitative study reported here shows that the impact of referential questions on university students can be characterised as constructive (i.e. effective and creative), leading to constructive conversation in the language seminars.
Names of Historical Geographical Places and Articles Used with Them
Marta Kadorova, Zuzana Ondrackova
Communications - Scientific Letters of the University of Zilina 2007, 9(4):38-43 | DOI: 10.26552/com.C.2007.4.38-43
The paper analyses the use of articles with the names of historical geographical places and related issues (focused on prehistoric and ancient times) in the English language. The paper is divided into three parts. The first one summarizes general rules for the use of articles with geographical names in prescriptive English grammar books. The second part contains a table which aims to present the list of the historical geographical names with corresponding articles. The final one concentrates on the analysis of the actual use of articles with the historical geographical names as found in the following books on history: The Concise History Encyclopaedia...
Evaluation of Comfort for Passengers of Railway Vehicles
Juraj Gerlici, Tomas Lack, Zuzana Ondrova
Communications - Scientific Letters of the University of Zilina 2007, 9(4):44-49 | DOI: 10.26552/com.C.2007.4.44-49
The passenger's complex sensation felt during the application of oscillations and/or inertia forces, via the whole-body transmission is defined and evaluated with the help of comfort indexes such as a mean comfort; mean permanent sensation evaluated according to the measurement procedures for the indexes, and comfort on curve transition, discomfort due to a perceived curve entry or reverse transmission, or comfort on discrete events - discomfort, due to a perceived transient oscillation on a straight track, curves and curve transitions. In the text the authors deal with mean comfort evaluation and its qualification with the help of the Comfort Indexes.
Using Proximity Technology for Localization in Wireless Sensor Networks
Peter Brida, Martin Matula, Jan Duha
Communications - Scientific Letters of the University of Zilina 2007, 9(4):50-54 | DOI: 10.26552/com.C.2007.4.50-54
The localization in wireless sensor networks is very important for function of the network (routing…). The objective of the localization process is to determine the position of device (sensor, node) from the information acquired from the reference devices. These devices of course know their location. The aim of the paper is to give a survey of two proximity based location techniques performance. The results of basic proximity based localization techniques are compared with modified (enhanced) proximity technique. It does not belong to the most accurate techniques, but on the other hand, it is a low cost alternative to more expensive techniques.
Analysis of Vibration When Application of Progressive Grinding Wheels
Jana Steiningerova, Miroslav Neslusan, Stefan Nemeth
Communications - Scientific Letters of the University of Zilina 2007, 9(4):55-58 | DOI: 10.26552/com.C.2007.4.55-58
This investigation was undertaken to compare the performance of grinding wheels containing newly developed "seeded gel" aluminum oxide abrasive with the wheels containing conventional monocrystalline aluminum oxide. The experiments were carried out on the surface grinder BPH 20 over a wide range of removal rates with two grinding wheels on hardened bearing-steel specimens. It was found that the wheels containing "seeded gel" abrasive required less grinding power and gave higher grinding stability than monocrystalline abrasive wheels of the same grade with better surface waviness. The potential improvement in productivity using the "seeded gel" abrasive...
Dealing with Key Terms in Risk Analysis and Phenomenon of Uncertainty in this Process
Katarina Holla
Communications - Scientific Letters of the University of Zilina 2007, 9(4):59-61 | DOI: 10.26552/com.C.2007.4.59-61
Unifying key terms in crisis management is one of the main vague field when performing risk analysis. Differences between terms and their definitions should eventuate into problems with communication in this area. I will mention a causal relationship between danger, treat and risk and I will try to integrate them into the surrounding of technological processes. In the next paragraph I will be dealing with risk analysis which should be characterized as a systematic use of available information to determine how often specified events may occur and the magnitude of their likely consequences. Therefore the wide range of uncertainty will occur when performing...
Analysis and Evaluation of the Knowledge Management
Dana Stredakova
Communications - Scientific Letters of the University of Zilina 2007, 9(4):62-65 | DOI: 10.26552/com.C.2007.4.62-65
There is a huge amount of knowledge in any organization. People at all levels have accumulated knowledge about what customers want, about how best to design products and processes, about what has worked in the past and what has not. A company that can collect all that knowledge and share it between employees will have a huge advantage over an organization that never discovers what its people know. Organizations must pay much more attention to the incentives that key workers have to share knowledge, and not focus only on developing the mechanisms that enable them to do so.
A Dynamic Messenger Problem
Jan Fabry
Communications - Scientific Letters of the University of Zilina 2007, 9(4):66-69 | DOI: 10.26552/com.C.2007.4.66-69
Messenger services provide customers to deliver their package from a specific origin to a specific destination. Real situations require the fast messenger's reaction to the on-line customer's request. While it is not possible to change the planned route in static distribution problems, a dynamic version enables a dispatcher the integration of a new request to existing route for optimization. The mathematical models proposed in the paper are based on the Miller-Tucker-Zemlin's formulation of Traveling Salesman Problem. Because of NP hardness of the problem it is impossible for most real problems to find the optimal solution in acceptable time. Heuristic...