Communications - Scientific Letters of the University of Zilina, 2011 (vol. 13), issue 4
Articles
Static and Dynamic Analysis of Linear Switched Reluctance Machine
Pavol Rafajdus, Peter Sekerak, Lukas Kalamen, Valeria Hrabovcova, Hao Chen
Communications - Scientific Letters of the University of Zilina 2011, 13(4):6-11 | DOI: 10.26552/com.C.2011.4.6-11 
This paper deals with the static and dynamic analysis of the Linear Switched Reluctance Machine (LSRM). The static parameters are investigated by means of Finite Element Method (FEM) for real LSRM and also for its optimized construction topology, where the air gap and mover dimensions are changed. The calculated static parameters are inputs into dynamic mathematical model of the LSRM. This model is simulated under Matlab/Simulink. The output values of the simulation are phase currents, voltages, flux linkages and total force in air gap of real and also optimized LSRM. The results comparison of the real and optimized LSRM is given.
Identification of the Combustion Engine Resistance to Motion Torque Components
Antoni Iskra, Maciej Babiak, Jaroslaw Kaluzny
Communications - Scientific Letters of the University of Zilina 2011, 13(4):12-15 | DOI: 10.26552/com.C.2011.4.12-15
Identification of the combustion engine resistance to motion is necessary in all investigations aimed at limiting frictional losses. Despite many attempts to measure the frictional resistance components, there are still no functional test beds that would allow to take measurements of frictional force or frictional torque in particular units. Most often the mean value of the torque for one or even two full revolutions of the crankshaft is determined. For many reasons it is more convenient to determine the resistance to motion torque of the combustion engine with an external drive but unfortunately, the torque from the external drive is disturbed by...
Flow Modeling in an Evaporator of a Nonconventional Energetic System
Andrej Kovalcik, Emil Toporcer, Vladimir Hlavna
Communications - Scientific Letters of the University of Zilina 2011, 13(4):16-19 | DOI: 10.26552/com.C.2011.4.16-19
An alternative cooling medium (lithium bromide liquid) flows in a cooling jacket of a combustion engine of a nonconventional energetic unit. The paper deals with a flow simulation of the working medium in the vaporization container of a cooling circuit of the nonconventional combustion engine. Consequently evaporation and thermal states at the atmospheric pressure above the nonconventional cooling liquid (solution LiBr - H2O) level in the evaporator are simulated. Limiting conditions for the functionality assurance of the cooling system of the nonconventional combustion engine were found by means of a simulation.
Comparison of Selected Classification Methods in Automatic Speaker Identification
Martin Hric, Michal Chmulík, Roman Jarina
Communications - Scientific Letters of the University of Zilina 2011, 13(4):20-24 | DOI: 10.26552/com.C.2011.4.20-24
This paper presents performance comparison of three different classifiers applied in Automatic SpeakeR Identification: Gaussian Mixture Model (GMM), k Nearest Neighbor algorithm (kNN) and Support Vector Machines (SVM). Each classifier represents different approach to the classification procedure. Mel Frequency Cepstral Coefficients (MFCC) were used as feature vectors in the experiment. Classification precision for each classifier was evaluated on frame and recording level. Experiments were conducted over dataset MobilDat-SK, which was recorded in mobile telecommunication network. Experiment shows promising results for SVM classifier.
Quality of Synthesized Speech: Impact of the Newest Coding Approaches
Miroslava Mrvova, Peter Pocta
Communications - Scientific Letters of the University of Zilina 2011, 13(4):25-31 | DOI: 10.26552/com.C.2011.4.25-31
This contribution deals with the issue of quality of synthesized speech. It introduces principles and approaches of creating this type of speech and basic methods and techniques used to assess the quality of synthesized speech. This article also offers a short overview of relevant experimental studies discussing issues related to this kind of speech and its quality assessment. Finally, it investigates effect of the newest coding approaches (e.g. Speex, iLBC, EVRC-B, etc.) on quality of naturally-produced speech and synthesized speech (generated by diphone and unit-selection synthesizers) predicted by two different objective models and provided by subjective...
Rheological Characteristics of Thermoplastic Polymers after Degradation
Michaela Vojsovicova, Tatiana Liptakova, Viera Zatkalikova
Communications - Scientific Letters of the University of Zilina 2011, 13(4):32-35 | DOI: 10.26552/com.C.2011.4.32-35
Selected rheological properties of thermoplastic polymer materials before and after exposure in different environments were evaluated by Frequency sweep test, which monitors changes in viscoelastic properties of polymers with respect to their molecular structure and their behavior in thermoplastic processes. Samples of tested material were subjected in UV radiation, moist soil with higher concentration of chlorides and solution of n-hexane for exact period. Degradation process resulted in changes of complex dynamic viscosity, storage and loss modulus, changes in molar mass and its distribution.
Analysis of Boundary Conditions for the Simulation of Welding at the Repair of Gas Pipelines with Steel Sleeve
Radoslav Konar, Milos Mician, Anton Hopko
Communications - Scientific Letters of the University of Zilina 2011, 13(4):36-39 | DOI: 10.26552/com.C.2011.4.36-39
Theoretical part of the manuscript deals with basic information about repair of gas pipeline with steel repair sleeves and simulation programme SYSWELD. Experimental part includes analysis of boundary conditions in two-pass fillet welding joint. Results of the analysis will be used for simulation in simulation programme SYSWELD.
Effectivity Analysis of Chosen Numerical Methods for Solution of Mechanical Systems with Uncertain Parameters
Robert Bednar, Milan Saga, Milan Vasko
Communications - Scientific Letters of the University of Zilina 2011, 13(4):40-45 | DOI: 10.26552/com.C.2011.4.40-45
The paper deals with usability and efficiency problem for the chosen solution methods for mechanical systems with structural uncertainties, which are significantly influencing the analysis results and the analysis itself. In the centre of interest will be the chosen approaches and methods. An application of the chosen approaches is presented - the first one, a simple combination of only inf-values or only sup-values; the second one presents full combination of all inf-sup values; the third one uses the optimizing process as a tool for finding out an inf-sup solution and last one is Monte Carlo technique as a comparison tool.
Analysis of the Behaviour of Steel-Concrete Composite Truss
Patricia Duratna, Abdelhamid Bouchair, Jan Bujnak
Communications - Scientific Letters of the University of Zilina 2011, 13(4):46-50 | DOI: 10.26552/com.C.2011.4.46-50
The design specifications of composite truss, included in the American standard (ASCE), are not covered in the European standards (Eurocodes). In this study, to investigate the behaviour of the composite trusses, a finite element model (FEM) is developed using the software CAST3M. The influence of various parameters, such as the diameter of the shear connectors, the degree of connection, the top chord section and the material characteristics on the behaviour of the composite truss and the shear connectors are analyzed. The model shows that the shear connection in the steel-concrete composite truss reduces its deflection by approximately 50 % in comparison...
Simulation Metamodelling of Manufacturing Processes
Silvia Palajova, Milan Gregor
Communications - Scientific Letters of the University of Zilina 2011, 13(4):51-54 | DOI: 10.26552/com.C.2011.4.51-54
This paper deals with models going out of simulation models, so called metamodels. They represent one of the possible ways how to increase effectiveness of simulation optimization, how to reduce the requirements of time-consuming simulation of manufacturing systems and how to make simulation cheaper. The heart of the paper describes steps of a metamodel making process and approximation of a real data using regression analysis and least square method.
Simplification of Marketing Scheme for Business Start-Ups
Jakub Soviar
Communications - Scientific Letters of the University of Zilina 2011, 13(4):55-57 | DOI: 10.26552/com.C.2011.4.55-57
This paper deals with the topic of marketing planning simplification in order to use it for start-ups in the field of small & medium enterprises. There are 11 main question areas which can be used for logical and empiric marketing approaches. These questions are elaborated on the basis of standard marketing planning methods and approaches from the literature given in references.
Supervisors' Assessment According to Bost Method in a Chosen Polish Company
Manuela Konstanciak, Stanisław Borkowski, Marta Jagusiak-Kocik
Communications - Scientific Letters of the University of Zilina 2011, 13(4):58-62 | DOI: 10.26552/com.C.2011.4.58-62
The main subject of the research presented in this paper is assessment of Polish supervisors with use of 4E+1P principle, 12 golden rules and Toyota's principles. This is a part of research conducted within the confines of BOST method, based on the rules of Toyota's system. This test method can be successfully used both in production and service institutions. There are two versions of the survey questionnaire: for supervisors and staff. The questionnaire includes also: the most important areas of improvement, visual control of factors, elements of the manufacturing process, competitive products, assessment of the supervisors and manufacturing processes....
The War on Terror Discourse: The Case of the Second Gulf War
Marek Hampl
Communications - Scientific Letters of the University of Zilina 2011, 13(4):63-66 | DOI: 10.26552/com.C.2011.4.63-66
This paper deals with the notion of discourse as manifested in political text and talk. The theoretical part elaborates the concept of political discourse with special focus on political speeches. Particular attention is also placed on Critical Discourse Analysis, which provides theoretical framework for the study. The subject of the analysis is the discourse of former British Prime Minister Tony Blair during the campaign for the invasion of Iraq in March 2003 and during the initial stages of the military operation itself.
Effect of the Stress State Triaxiality on the Value of Limit Strain of Micro-Void Development in S235JR Steel - Numerical Analysis
Wiktor Wcislik
Communications - Scientific Letters of the University of Zilina 2011, 13(4):67-71 | DOI: 10.26552/com.C.2011.4.67-71
This paper deals with the numerical analysis of plastic deformation and damage development in S235JR steel in complex stress states. The material Gurson Tvergaard Needleman (GTN) model was applied. The analysis was performed for notched bars subjected to tension. An attempt was made to investigate the effect of stress triaxiality on the value of critical strain of voids growth in the GTN model.
Distributed Database Systems in the Dynamic Networks Environment
Jan Janech, Tomas Baca
Communications - Scientific Letters of the University of Zilina 2011, 13(4):72-77 | DOI: 10.26552/com.C.2011.4.72-77
This article describes a new architecture of a distributed database system, which is designed especially for the dynamic networks environment. Problems with the architecture of a traditional distributed database system are explained, and a solution is offered. The architecture introduced in this article does not intend to be a universal database system. It is a specialized solution for the implementation of distributed database systems in the dynamic networks environment.
Company in Crisis
Lucia Vrablova, Milan Gregor
Communications - Scientific Letters of the University of Zilina 2011, 13(4):78-81 | DOI: 10.26552/com.C.2011.4.78-81
This paper deals with corporate crisis. It draws attention to the failing firm strategy in times of crisis. The corporate crisis is an important part of business life cycle. Proper crisis management is necessary for the survival of a competitive fight and staying on the market.
Chinese Economic Success - Inspiration for Economy, Policy and Security
Milos Ondrusek
Communications - Scientific Letters of the University of Zilina 2011, 13(4):82-86 | DOI: 10.26552/com.C.2011.4.82-86
This paper focuses on the recent changes in global economic relations and increase of China's importance in global politics, security and economy. It describes the changes in China's security, economic, political strategy and its influence to its own development and empowering its position in international economic, political and security relations. The implications for the EU security management are described, too.
Application of Univariate Time Series Theory to Passenger Demand Forecasting
Ondrej Cyprich
Communications - Scientific Letters of the University of Zilina 2011, 13(4):87-91 | DOI: 10.26552/com.C.2011.4.87-91
The methods, which are used for the purpose of passenger demand forecasting by Slovak transportation companies at the present time, are considerably simplified, and what is more, they are not already considered to be accurate. These limitations might be caused by insufficient research in this area over last years. Purpose of this paper is to identify a statistical model of passenger demand for suburban bus transport which satisfies the statistical significance of its parameters and randomness of its residuals. Three different methodologies - exponential smoothing, multiple linear regression and autoregressive models were used in order to identify more...
Verification of The Water Transport Parameter - Moisture Storage Function of Autoclaved Aerated Concrete - Approximately Calculated from a Small Set of Measured Characteristic Values
Pavol Durica, Marian Vertal
Communications - Scientific Letters of the University of Zilina 2011, 13(4):92-97 | DOI: 10.26552/com.C.2011.4.92-97
The aim of the paper is to determine the moisture transport parameters for selected type of autoclaved aerated concrete using fly ash order to carry out the numerical analysis of the hygrothermal performance of selected building structures in real conditions. The moisture storage function (sorption, suction) and the liquid water transport coefficient are taken into consideration. Obtaining knowledge of these parameters involves a series of laboratory measurements and tests. Applying those parameters into modern calculation methods (WUFI) we will be able to analyse annual hygrothermal performance of porous concrete wall constructions in climatic conditions...
Construction of High-Speed Tracks
Stanislav Hodas
Communications - Scientific Letters of the University of Zilina 2011, 13(4):98-101 | DOI: 10.26552/com.C.2011.4.98-101
The current situation and conditions of construction of high speed tracks (HST) in the Slovak Republic and the comparison with the situation abroad. The speed of train sets and the track quality for high speed trains. The dynamics of railway running. The speeds of the HST trains are limited by the respective track state. The tilting train set wagons - increasing the new levels of speeds in railway curves. The time comparison of the high speed trains to air and road transport "from city centre to city centre". The required conditions and parameters of construction of high speed tracks up to Vmax 200-240 km.h1 within the track modernizations.
The Cohesion or Dilation Effect on the Shear Strength of Granitic Residual Soil
Luis J. Andrade Pais, L. M. Ferreira Gomes, Isabel Falorca, Paulo M. Carvalho, Victor P. Cavaleiro
Communications - Scientific Letters of the University of Zilina 2011, 13(4):102-108 | DOI: 10.26552/com.C.2011.4.102-108
The paper reports laboratory investigations carried out in granitic residual soil from Covilha, to evaluate the stress-strain-dilatancy behaviour to provide a new model. Some soil tests are intended only to classify soil into broad groups. Other tests are done to examine the mechanical behaviour of soils and particularly to investigate their strength and deformation during loading. Drained and undrained triaxial tests were performed to study soil fabric effects on the mechanical behaviour of a granitic residual soil. It was revealed that the dilatancy of the saturated soil contributes to shear stress and strength at lower confining pressures. The cohesion...
Toxic Properties of Plastics in Fire and Their Impact on the Environment and Human Health
Martin Hrinko, Katerina Orlikova
Communications - Scientific Letters of the University of Zilina 2011, 13(4):109-114 | DOI: 10.26552/com.C.2011.4.109-114
The article describes and analyses toxic substances produced during a combustion of plastics which affect human health. Accidents and emergencies resulting from the combustion of plastic materials occur very often during the industrial production and technological processes. The authors illustrate this fact using the most recent example - the fire in the manufacturing and logistics premises in Chropyne, the Czech Republic, during which the professional as well as volunteer firefighters and the specialized fire rescue service units were employed.