Communications - Scientific Letters of the University of Zilina, 2001 (vol. 3), issue 4
Articles
Evaluation of Pricing Strategies of Elastic Traffic on a Single Communication Link
Peter Fodor, Adam Marquetant
Communications - Scientific Letters of the University of Zilina 2001, 3(4):5-8 | DOI: 10.26552/com.C.2001.4.5-8 
The future integrated service networks supporting multiple traffic classes will require customized admission control and bandwidth sharing strategies, which meet the diverse needs of QoS (Quality of Service)-assured (stream) and best-effort (elastic) services. Recent research results indicate that it is meaningful to exercise call admission control (CAC) even for elastic (best-effort) traffic, because CAC algorithms provide a means to prevent e.g. TCP sessions from excessive throughput degradations [1], [2]. Based on a model of a single link introduced in [2], we evaluate different pricing strategies assigned to elastic calls by determining an optimal...
Control Circuitry for a Partial Series Resonant Converter
Ivan Feno, Eduard Jadron, Pavol Spanik
Communications - Scientific Letters of the University of Zilina 2001, 3(4):9-13 | DOI: 10.26552/com.C.2001.4.9-13
A control circuit for a new high-frequency DC-DC converter, suitable for application in a few kilowatts range, is presented. The converter topology is based on a half bridge series resonant converter, i. e. having only two switches. Resonance occurs only for a part of each switching cycle, and a discrete energy pulse is transferred to the load every half cycle, rendering a variable frequency controller for controlling the output power. The converter features zero-voltage turn-on and snubbed turn-off at reduced current for the switching devices, and zero current commutation of the rectifier diodes, making it suitable for IGBT switches operating at a...
Risk Riskreduction Reductionprinciples
Rastislav Kuliha
Communications - Scientific Letters of the University of Zilina 2001, 3(4):14-18 | DOI: 10.26552/com.C.2001.4.14-18
Various ways are applied for the attestation of a risk degree for a continuous system, with time samples for observation of the state. The neural network has been designed. The parameters of reliability have been calculated for flat power function.
Structural and Morphological Observations on Tungsten Oxide Hydrates Ged to Room Temperature in Alkali Containing Queous Environment
Csaba Balazsi, Judit Pfeifer
Communications - Scientific Letters of the University of Zilina 2001, 3(4):19-25 | DOI: 10.26552/com.C.2001.4.19-25
The room temperature ageing process of tungsten oxide hydrate (H2WO4.H2O) grains prepared by the methods of Freedman [J. Am. Chem. Soc. 81 (1959) 3834.] ([Na]residual 10ppm)) and Zocher and Jacobson [Kolloidchem. Beih. 28-6 (1929) 167.] ([Na]residual 100ppm) has been studied. A comparison between two preparation methods and ageing characteristics is given. It is found that spindle shaped - Zocher type grains have a strong tendency to morphological conversion depending on pH value of surrounding aqueous solution. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) studies have shown that the high structural and morphological...
A Small Punch Test Method Application for the Evaluation of Reactor Pressure Vessel Material Properties Degradation
Jana Vaclavkova, Ludovit Kupca
Communications - Scientific Letters of the University of Zilina 2001, 3(4):26-30 | DOI: 10.26552/com.C.2001.4.26-30
In this paper we describe a new non-standard method for estimation of the reactor pressure vessel (RPV) materials mechanical properties by a small punch (SP) test. The great advantage of the SP test method is a low volume of test samples.Using this method it is possible to obtain the following data of basic mechanical properties: the yield stress and ultimate tensile strength, ductile-brittle transition temperature, the fracture toughness value.This method has been involved in the VÚJE project "New Surveillance Specimen Program for Jaslovské Bohunice V-1 nuclear power plant (NPP)" (NSSP). This paper describes the basic information about a testing procedure,...
Bandwidth Broker Architecture for Diffserv Networks
Octavian Pop, Tamas Mahr, Tímea Dreilinger, Robert Szabo
Communications - Scientific Letters of the University of Zilina 2001, 3(4):31-35 | DOI: 10.26552/com.C.2001.4.31-35
A Bandwidth Broker (BB) is an automated resource manager in the Differentiated Services architecture. It manages Quality of Service resource allocation requests within a single or successive DiffServ domains based on the available resources and on the Service Level Agreements formerly negotiated between the customer and its service provider. If used for multi-domain resource management, BBs negotiate among each other on behalf of the service initiator. Additionally, BBs also participate in transit domain communication by coordinating SLAs across domain boundaries. Various BB architectures have been proposed in the recent years, some of them even have...
The Distribution System Design Problem Applying Real Settlement Data
Lubos Buzna
Communications - Scientific Letters of the University of Zilina 2001, 3(4):36-40 | DOI: 10.26552/com.C.2001.4.36-40
The complicated way of obtaining true values of entry parameters is a weaker part of distribution system design problem. This paper uses a continuous approximation approach to identify an optimal number of terminals. It is focused on applying real settlement data obtained from close surroundings of towns that are suitable for placing terminals. This more detailed information about settlement is used to obtain a more precise model for continuous approximation. The schemes location procedure is here used for a location of terminals.
Influence of Reinforcement Corrosion on Reliability of Existing Concrete Structures
Peter Kotes, Josef Vican, Jiri Slavik
Communications - Scientific Letters of the University of Zilina 2001, 3(4):41-49 | DOI: 10.26552/com.C.2001.4.41-49
The quality and the durability of the concrete structures are affected by lots of degradation processes. The paper deals with reinforcement corrosion and its influence on the reliability of the existing concrete structures. Two types of passive stage calculation and two types of active stage calculation are considered in this paper. The probabilistic approach is used for the time dependent resistance solution. In conclusion, the change of the failure probability and reliability index of the structure in time influenced by reinforcement corrosion are shown.
Geopotential Model of Earth - Approximation of Earth Shape, Geopotential Model Testing Methods
Robert Tenzer
Communications - Scientific Letters of the University of Zilina 2001, 3(4):50-58 | DOI: 10.26552/com.C.2001.4.50-58
Stokes' geodynamic parameters in the expansion of the gravity potential of the Earth serve for a mathematical and physical description of an outer gravity field of the Earth, the shape and the size of the Earth. In this article, the results from testing of an accuracy of the geopotential model EGM 96 at the territory of Slovakia are published.
Mathematical Apparatus for Error Probability Determination of Block Code Decoders
Maria Franekova
Communications - Scientific Letters of the University of Zilina 2001, 3(4):59-64 | DOI: 10.26552/com.C.2001.4.59-64
This paper deals with safety - related communication in closed transmission systems when block systematic (n, k) safety codes are used. The mathematical apparatus for calculation of probability of undetected sequence error is described for codes, with known and unknown weight structure. The numerical results are valid for a Symmetric Binary Channel when the occurrence of independent errors is assumed.
Evaluation of Adhesive Joints Between Coating and Substrate Using Ultrasonic Spectroscopy
Marian Josko, Marcin Jarmuzek
Communications - Scientific Letters of the University of Zilina 2001, 3(4):65-69 | DOI: 10.26552/com.C.2001.4.65-69
In the paper the theoretical analysis of ultrasonic impulse signal and experimental investigations on some specimens was carried out. The specimens were made of constructional steel on which some coatings of automotive putty and lacquer were layered. In particular, the sensitivity of selected parameters of ultrasonic spectrum on changes of condition of the substrate and bonded materials was studied. It was noticed that irregularities of substrate and the thickness of coatings layered, influence parameters of the ultrasonic signal spectrum.
The Influence of Disintegration Methods on Test Results for Assessment of the Soil Particle Size Distribution
Dana Sitanyiova
Communications - Scientific Letters of the University of Zilina 2001, 3(4):70-79 | DOI: 10.26552/com.C.2001.4.70-79
The article pertinent to the research activity focuses on the hydrometer test performed for assessment of the soil particle size distribution for soils not containing the particles of size over 2 mm. Some stages of the test seem to be problematic, and various laboratories often obtain different test results. The contribution is directed to prove the fact that various methods of particles separation substantially influence the result of a whole hydrometer test and trace how variousseparation methods effect the individual mineral particles together with dispersing agent.
Ecotechnologies for the Reconstructions of Railway Subgrade Construction
Janka Sestakova, Milan Miksik
Communications - Scientific Letters of the University of Zilina 2001, 3(4):80-87 | DOI: 10.26552/com.C.2001.4.80-87
Nowadays the question of the constant stability of the geometry position of the track in connection with modernization of the railway network in our territory is relevant. That is conditioned by the compliance of the rated carrying capacity of the whole subgrade construction. Therefore construction layers are built, which take part in the total increase of its quality. The building and operating work of the railway transport has tobe managed with regard to the protection of the environmental rules. Observing the rules is available by the implementation of recycledmaterials. It's possible to accomplish it by using the technologies, which focus on working...