Communications - Scientific Letters of the University of Zilina, 2004 (vol. 6), issue 1
Articles
Manufacture and Compositional Analysis of Silicon Nitride Composites with Different Carbon Additions
Csaba Balazsi, Ferenc Weber, Zsolt Kasztovszky
Communications - Scientific Letters of the University of Zilina 2004, 6(1):5-9 | DOI: 10.26552/com.C.2004.1.5-9 
Carbon black and graphite nano/micrograins and sintering additives (Al2O3 and Y2O3) were added to silicon nitride starting powder. These mixtures were mechanochemically activated several hours in a planetary type alumina ball-mill in order to achieve a homogenous mass. As an alternative to nano- and micrograins, carbon fibres were added to carbon free silicon nitride batches. After dry pressing of rectangular bars sinter-HIP was applied. Structural, morphological and compositional analyses were performed on as-prepared samples. Bending strength and elastic modulus were found to be influenced by amount of carbon black and graphite introduced in silicon...
Shape Memory Alloy - Modern Smart Material for Various Applications
Grzegorz Kłapyta
Communications - Scientific Letters of the University of Zilina 2004, 6(1):10-14 | DOI: 10.26552/com.C.2004.1.10-14
The article deals with modern materials - Shape Memory Alloys. The author presents short history of its discovery and its particular properties. One-way and two-way shape memory effects are illustrated and explained. Advantages and disadvantages of SMA are listed and possibilities of usage are discussed. There are also given some interesting applications in various fields of life illustrated by pictures and photos gathered from Internet sites.
Influence of Heat Treatment on the Microstructure and Composition of Plasma Sprayed Coatings
Wojciech Zorawski, Rafal Chatys
Communications - Scientific Letters of the University of Zilina 2004, 6(1):15-18 | DOI: 10.26552/com.C.2004.1.15-18
Plasma sprayed coatings have been used in various industries for a number of purposes. To increase their mechanical properties, different methods of thermal treatment are being applied. This work is concerned with composite coatings obtained by plasma spraying of the Al2O33TiO2 and NiO powders (50 % and 50 % by weight), which were then reduced at an atmosphere of dissociated ammonia. Their chemical composition and morphology were determined by means of the EDS microprobe and the Joel 5400 scanning microscope respectively. It has been reported that the process of reduction contributes to the homogeneity of the coating, and that the modified structure...
Adaptive Fuelling of the SI Engine
Mirosław Wendeker
Communications - Scientific Letters of the University of Zilina 2004, 6(1):19-25 | DOI: 10.26552/com.C.2004.1.19-25
The paper presents some investigations concerning implementation of the adaptive control methods for the control of the fuel injection in an automotive gasoline engine. As quality index the difference between a current emission level and the level obtained during the stoichiometric combustion was chosen. Stoichiometric mixture provides maximal conversion ratio of the catalytic converter. The paper presents mathematical procedures of the direct adaptive control, based on the adaptive algorithms, which use competitive estimators. Theoretical analysis was supplied with the results of computer simulation of the single point gasoline injection engine model.
Influence of the Wheels on the Automobile Dynamics
Rastislav Istenik, Dalibor Barta, Wladyslaw Mucha
Communications - Scientific Letters of the University of Zilina 2004, 6(1):26-28 | DOI: 10.26552/com.C.2004.1.26-28
The analysis of the vehicle dynamics with various types of wheels (R13, R14, R15) in two shifting modes and at the driving on a horizontal plane, at downhill- and uphill- driving as well as with different vehicle total mass is described in this paper.
Dynamic Air Traffic Control Wake Vortex Safety and Capacity System
Peter Choroba
Communications - Scientific Letters of the University of Zilina 2004, 6(1):29-33 | DOI: 10.26552/com.C.2004.1.29-33
International regulations require aircraft to be separated in approach phase of flight by up to six nautical miles (11.12 km) due to the potential hazard caused by the swirling air left in their wakes. This 'wake vortex' is now the subject of intense worldwide research to understand the nature of the phenomenon and find ways of making air travel safer while reducing congestion around airports. "With the world airline fleet expected to double in size over the next 15 years and the giant A380 entering service in 2005, solutions to the wake-vortex problem cannot come too soon for the aerospace industry and therefore there is a strong need for developing...
Handover Latencies in BCMP Networks
Gergely Biczok, Kristof Fodor, Balazs Kovacs
Communications - Scientific Letters of the University of Zilina 2004, 6(1):34-37 | DOI: 10.26552/com.C.2004.1.34-37
In this article, we give a short overview on wireless access networks and the BRAIN Candidate Mobility Protocol (BCMP). The two different handover mechanisms of BCMP are introduced. With the help of standard network tools and an own measurement program, latencies caused by both kinds of handovers were examined. We show that latency values are largely hardware-dependent and that by an adequate hardware configuration, BCMP provides smooth and fast handovers. This makes BCMP suitable for using with real-time applications, such as packetswitched voice or video.
Development and DSP Implementation of Ann-Based VPWM in a Voltage Source Inverter
Martin Kuchar, Pavel Brandstetter
Communications - Scientific Letters of the University of Zilina 2004, 6(1):38-41 | DOI: 10.26552/com.C.2004.1.38-41
This paper deals with development, simulation and DSP implementation of space vector modulator based on artificial neural network. The modulator is designed for a voltage source inverter utilization. In the contribution an explanation of presented ANN-based VSI-VPWM is described. Main features and advantages of the used algorithm are summarized too. The entire AC electrical drive consists of a frequency converter, induction motor and microprocessor control system. In the paper a description of the control system with TMS 320C40 DSP is also given. A very important part of the development is simulation, because it is necessary to verify rightness of...
DSP Implementation and Simulation of IM Drive Using Fuzzy Logic
Libor Stepanec, Pavel Brandstetter
Communications - Scientific Letters of the University of Zilina 2004, 6(1):42-45 | DOI: 10.26552/com.C.2004.1.42-45
This paper deals with vector-controlled induction motor drive, which uses fuzzy logic as a part of artificial intelligence. There are three phases: development, simulation and DSP implementation, which are discussed in this paper. In the first part of the paper fuzzy logic and development of the given problem are described. Next, there is a description of the used control structure. Important simulations were realised, which confirm the rightness of proposed structure and good behaviour of developed fuzzy controller. The simulation results are also given. In the end part of the paper, there are presented a control system with DSP TMS 320C40 and experimental...
Individual and Sectional Communication Systems in Management and Development of Human Potential
Martina Blaskova
Communications - Scientific Letters of the University of Zilina 2004, 6(1):46-49 | DOI: 10.26552/com.C.2004.1.46-49
The article deals with identification of communication systems existing inside the organization: individual, group and organizational. The article deals with possibility to perceive human potential management and development processes as communicational processes, it means, the processes, which we can understand through prism of communication. The quality of basic communicational skills using (active listening, assertivity, empathy and persuasion) is an important condition of permanent growth of human potential management and development system.
Human Factor in Decision-Making in Simulation Model of Transportation System and Approaches to Its Modelling
Michal Zarnay
Communications - Scientific Letters of the University of Zilina 2004, 6(1):50-53 | DOI: 10.26552/com.C.2004.1.50-53
The article deals with human factor in decision-making in simulation model of transportation system. It points to the difference between the management in reality and in a model, where it is more difficult to represent the human thinking. The consequence of this is a higher probability of deadlock appearances that can be developed after operation has deflected from the plan. The effort to minimize the operation deviations leads to processing larger amount of information and to more complicated decision-making algorithms, which makes the simulation model more complicated and slower. The task of the developer is to set the level of details in the decision-making...
Change Management: The People Dimension of Change
Mariana Strenitzerova
Communications - Scientific Letters of the University of Zilina 2004, 6(1):54-57 | DOI: 10.26552/com.C.2004.1.54-57
Change management is the process, tools and techniques to effectively manage people and the associated human resource issues that surface when implementing business changes. Change management as a field of study finds its roots in two areas: business process improvement and psychology. The ADKAR model for change management as the diagnostic tool helps employees understand where they are in the change process. A manager can use this tool to identify gaps in his change management process and to provide effective coaching for his employees.
Theory and Measurements of Bitumen Binders Adhesion to Aggregate
Eva Remisova
Communications - Scientific Letters of the University of Zilina 2004, 6(1):58-63 | DOI: 10.26552/com.C.2004.1.58-63
The pavement as unit is able to perform services, provided that we ensure good synergy of layers and especially good adhesion between used materials. Adhesion knowledge allows to design suitable technology by preventing defects and to ensure service ability and life of pavement.In the paper there is a theoretical analysis of problem of bitumen binders adhesion to aggregate, basic methodologies to evaluate this property and specific results achieved at measuring by the method STN 65 7089 and EN 12272-3. At the same time the results are compared from the type of aggregate point of view as one of the most important factors that influenced adhesion.
Static and Dynamic Tests of the Railway Subgrade Construction Model
Jan Lelak, Dusan Slavik, Martin Mecar
Communications - Scientific Letters of the University of Zilina 2004, 6(1):64-67 | DOI: 10.26552/com.C.2004.1.64-67
The presented paper deals with the research of railway subgrade construction. The purpose was to compare static and dynamic modulus of deformation namely on two different railway subgrade constructions. The effect of reinforcing geosynthetics was found out as well, when a different type of reinforcing geosynthetics was used.
The Eigenvalue Approximations of the Laplace Operator Defined on a Domain with Strongly Deformed Boundary
Slavka Tkacova
Communications - Scientific Letters of the University of Zilina 2004, 6(1):68-71 | DOI: 10.26552/com.C.2004.1.68-71
In this paper the eigenvalue approximations of the Laplace operator defined on a domain with strongly deformed boundary are presented. Because the exact eigenfunctions exhibit complicated behaviour in the vicinity of singular points of the used conformal mapping, the B-spline trial functions are used in order to improve the quality of the eigenfunction approximations near the singular points.
Tests of Deformation and Tensions in Reinforced Non-Cohesive Soil Layer
Andrzej Surowiecki, Edward Hutnik
Communications - Scientific Letters of the University of Zilina 2004, 6(1):72-76 | DOI: 10.26552/com.C.2004.1.72-76
The paper describes the results of laboratory testing of vertical deformations, horizontal pressure and vertical tensions on the close contact between reinforced non-cohesive soil layer and single-parameter subsoil. In particular, the diagrams of deformations and vertical tensions have been presented in the function of static load and reinforcement parameters. The following parameters have been also formulated: pattern to the calculation of coefficient of vertical tensions remittance and condition of equilibrium tensions in the reinforced soil model.