Communications - Scientific Letters of the University of Zilina, 1999 (vol. 1), issue 2
Articles
Comparing dual access approaches for exact solution of location problems
Jaroslav Janacek, Johanna Kovacikova
Communications - Scientific Letters of the University of Zilina 1999, 1(2):4-8 | DOI: 10.26552/com.C.1999.2.4-8 
The paper deals with exact solution of two uncapacitated location problems. The location problem consists in placing some facilities of unrestricted capacity in the formed network. The facility can have various natures. It could be aservice centre, whose location can be done at anode of the network, or it can be adirect train, which can be placed into a transport plan. In comparison with the former case, this facility has the nature of a graph edge.The key-stone of the computational success of the often used branch and bound method is the lower bound tightness. This paper, reports numerical experiments with the dual access approach used for the solution...
Trackage modelling and algorithms for finding the shortest train route
Antonin Kavicka, Ludmila Janosikova
Communications - Scientific Letters of the University of Zilina 1999, 1(2):9-21 | DOI: 10.26552/com.C.1999.2.9-21
This paper deals with two models of track network in a railway station and algorithms for finding the shortest train route. In the first model - a weighted digraph - two vertices represent a track or a switch track. Edges of a digraph are understood as the possible transitions between tracks. In the second model - a non-oriented edge weighted graph - the edges represent tracks and the vertices match the connections between tracks. Algorithms for finding a shortest route were designed and verified for both models. These algorithms respect rules for the movement of rail vehicles, as well as their length and the occupation of tracks by other rolling stock.
Comparison of dynamic methods of road pavement evenness evaluation
Martin Decky
Communications - Scientific Letters of the University of Zilina 1999, 1(2):22-32 | DOI: 10.26552/com.C.1999.2.22-32
The paper presents the review of dynamic methods of road pavement evenness evaluation used in the Slovak Republic. The principles of assessment by parameters C and IRI (International Roughness Index) are detailed here. The measuring set called the Single-Wheel Vehicle of the University of Žilina (JP VŠDS), which appreciates parameter C has been designed on the DMS (double-mass measuring set) dynamic principle. The design of this system pavement assessment in term of longitudinal unevenness was realised for a consideration stationary random process. The conclusion of our paper is devoted to the comparison of longitudinal unevenness evaluated by our...
The effectiveness of given financial resources for the additional Thermal insulation of buildings
Karol Potocek
Communications - Scientific Letters of the University of Zilina 1999, 1(2):33-39 | DOI: 10.26552/com.C.1999.2.33-39
Current development of material base and technology enables different ways to improve heat-insulating properties of existing packing constructions of the building. Particular ways are different among themselves concerning the service life. This contribution deals with the appreciation of additional thermal insulation while taking into account the return of financial expenses in the relation to its service life. Basic calculation formulas and their graphical illustration (which gauges economical effectiveness) are presented.
The evaluation of the appropriateness of railway subgrade restoration With an unconventional material
Janka Gombitová
Communications - Scientific Letters of the University of Zilina 1999, 1(2):40-44 | DOI: 10.26552/com.C.1999.2.40-44
This paper deals with the results achieved during the testing of a new geosynthetic reinforcing material - GEOWEB, which was used for the restoration of railway subgrade. Conventionally used materials are no longer sufficient for reconstruction works within the modernisation of railway tracks and stations.
Another perspective on the forecasting of economic processes
Mária Mičeková
Communications - Scientific Letters of the University of Zilina 1999, 1(2):45-51 | DOI: 10.26552/com.C.1999.2.45-51
This article describes methods used from dynamic systems theory in solving the tasks of forecasting economic processes. The possibility of using theoretical methods in forecasting is demonstrated with the example of the prediction regarding the development of the rate of exchange between the USD and the SK.
Nonlinear least squares method
Jaromír Máca, Bohus Leitner
Communications - Scientific Letters of the University of Zilina 1999, 1(2):52-58 | DOI: 10.26552/com.C.1999.2.52-58
The paper deals with a comparison of linear and nonlinear least squares approximation. Its aim is to show that the well known transformations of nonlinear dependencies on linear dependencies do not always give exact results. Therefore, the only right possibility of approximation of nonlinear functions is to use one of nonlinear least squares procedures. The Levenberg - Marquardt compromise seems to be by far the best one.
Mechanical properties of advanced mg alloys
Pavel Lukáč, Zuzanka Trojanová, Peter Palček
Communications - Scientific Letters of the University of Zilina 1999, 1(2):59-63 | DOI: 10.26552/com.C.1999.2.59-63
This paper describes the tensile strength of Mg alloys determined at room temperature and creep. The deformation mechanisms are discussed.
New possibilities for machined surface quality improvements
Karol Vasilko
Communications - Scientific Letters of the University of Zilina 1999, 1(2):64-69 | DOI: 10.26552/com.C.1999.2.64-69
The main relationships governing the machining processinclude the relationship between the roughness of the machined surface, the feed and the curvature radius of the tool tip expressed by the approximate equation: Ry f2/8r ε . According to this equation, an increase of the feed increases the capacity of the surface roughness, according to aparabolic law. This fact prevents large increases in the productivity of machining. There are certain reserves in increasing the curvature radius of the tip which is present in the denominator. However, very large increase of the tip diameter increases the length of the cutting edge in engagement and causes...
Architecture of the slovak air traffic management system in relation to the european system
Karel Havel
Communications - Scientific Letters of the University of Zilina 1999, 1(2):70-79 | DOI: 10.26552/com.C.1999.2.70-79
This paper outlines an overall CNS/ATM architecture, its components flow between (common functional architecture) and functional blocks allocation to the organisational units (system architecture). It does not represent the final architecture but defines the technical framework for the harmonisation and integration efforts. It is the baseline for the specification work for implementation in 2001-2005 in the framework of the EATCHIP Work Programme, serves as an information source for local planning actions by the national administration, serves, at a lower level of decomposition, as a framework for detailed architecture work, and is a baseline for the...