Showing papers by "Technical University of Ostrava published in 2002"
TL;DR: A specialization of the augmented Lagrangian-type algorithm of Conn, Gould, and Toint to the solution of strictly convex quadratic programming problems with simple bounds and equality constraints with boundedness of the penalty parameter is achieved.
Abstract: In this paper we discuss a specialization of the augmented Lagrangian-type algorithm of Conn, Gould, and Toint to the solution of strictly convex quadratic programming problems with simple bounds and equality constraints. The new feature of the presented algorithm is the adaptive precision control of the solution of auxiliary problems in the inner loop of the basic algorithm which yields a rate of convergence that does not have any term that accounts for inexact solution of auxiliary problems. Moreover, boundedness of the penalty parameter is achieved for the precision control used. Numerical experiments illustrate the efficiency of the presented algorithm and encourage its usage.
65 citations
TL;DR: It is shown that for small coefficients of friction the discretized problem with Coulomb friction has a unique solution and that this solution is Lipschitzian as a function of a control variable describing the shape of the elastic body.
Abstract: The paper deals with a discretized problem of the shape optimization of elastic bodies in unilateral contact. The aim is to extend existing results to the case of contact problems following the Coulomb friction law. Mathematical modelling of the Coulomb friction problem leads to a quasi-variational inequality. It is shown that for small coefficients of friction the discretized problem with Coulomb friction has a unique solution and that this solution is Lipschitzian as a function of a control variable describing the shape of the elastic body.
The shape optimization problem belongs to a class of so-called mathematical programs with equilibrium constraints (MPECs). The uniqueness of the equilibria for fixed controls enables us to apply the so-called implicit programming approach. Its main idea consists of minimizing a nonsmooth composite function generated by the objective and the (single-valued) control-state mapping. In this paper, the control-state mapping is much more complicated than in most MPECs solved in the literature so far, and the generalization of the relevant results is by no means straightforward. Numerical examples illustrate the efficiency and reliability of the suggested approach.
54 citations
TL;DR: In this article, an iterative process for the numerical realization of contact problems with Coulomb friction is presented, which is based on the method of successive approximations combined with a splitting type approach.
46 citations
TL;DR: In this paper, a new variant of this method is presented, which combines fixed point with block Gauss-Seidel iterations for a sequence of problems with given friction, and results of numerical experiments are given showing that the resulting algorithm may be much faster than the original fixed point method and its efficiency is comparable with the solution of frictionless contact problems.
41 citations
24 Apr 2002
TL;DR: A new algorithm based on measuring the variance of the directions of the gradient of brightness that is better than other known algorithms that are usually used for solving the corners problem.
Abstract: Corners and vertices are important features in images, which are frequently used for scene analysis, stereo matching and object tracking. Many algorithms for detecting the corners have been reported up to now. In this paper, a new algorithm is presented. The algorithm is based on measuring the variance of the directions of the gradient of brightness. The probability of the event that a point belongs to the approximation of a straight segment of the isoline of brightness passing through the point being tested is computed using the technique of Bayesian estimations and used as a weight. The algorithm is presented both from the theoretical and from the practical point of view. The results of tests show that the algorithm is better than other known algorithms that are usually used for solving the problem.
32 citations
22 Nov 2002
TL;DR: The paper presents an overview of techniques and results for equivalence-checking with infinite-state systems and reflects the authors' view on recent development in the area.
Abstract: The paper presents an overview of techniques and results for equivalence-checking with infinite-state systems The selection of presented techniques reflects the authors' view on recent development in the area; the overview of existing results should be up-to-date (as of August 2002)
19 citations
TL;DR: In this article, the authors describe the experience with cold forming of bolts made of micro-alloyed steel, specially designed to enable elimination of thermal treatment, and the results are verified by hardness measurement of produced specimens.
17 citations
TL;DR: In this article, the dependence between the electrical conductance and the vapour concentration for tin dioxide gas sensor is derived based on physical-chemical phenomena and compared with experimental data of good conformity.
Abstract: The dependence between the electrical conductance and the vapour concentration for tin dioxide gas sensor is derived here. The derived formula, based on physical-chemical phenomena, was compared with experimental data of good conformity. This formula can be useful in practical applications including this type of gas sensors.
17 citations
16 Sep 2002
TL;DR: The results of the tests show that the new algorithm for detecting the corners is better than the other known algorithms that are usually used for solving the problem.
Abstract: The corners and vertices are important features in images, which are frequently used for scene analysis, stereo matching and object tracking. Many algorithms for detecting the corners have been developed up to now. In this paper, a new and efficient algorithm is presented. The probability of the event that a point belongs to the approximation of the straight segment of the isoline of brightness containing the corner candidate being tested is determined using the technique of Bayesian estimations, and then used for computing the angle between the segments. The results of the tests show that, in the sense of the successfulness of detection, the new algorithm is better than the other known algorithms that are usually used for solving the problem.
14 citations
29 Oct 2002
TL;DR: This paper introduces a geometric framework for indexing and querying XML data conceived in this way, and uses the UB-tree forindexing the vector spaces and the M-treefor indexing the metric spaces.
Abstract: Using the terminology usual in databases, it is possible to view XML as a language for data modeling. To retrieve XML data from XML databases, several query languages have been proposed. The common feature of such languages is the use of regular path expressions. They enable the user to navigate through arbitrary long paths in XML data. If we considered a path content as a vector of path elements, we would be able to model XML paths as points within a multidimensional vector space. This paper introduces a geometric framework for indexing and querying XML data conceived in this way. In consequence, we can use certain data structures for indexing multidimensional points (objects). We use the UB-tree for indexing the vector spaces and the M-tree for indexing the metric spaces. The data structures for indexing the vector spaces lead rather to exact matching queries while the structures for indexing the metric spaces allow us to provide the similarity queries.
10 citations
08 Apr 2002
TL;DR: It is shown that the membership problem for any relation subsuming bisimilarity and subsumed by simulation preorder is DP-hard (even) for one-counter nets (where the counter cannot be tested for zero).
Abstract: We present a general method for proving DP-hardness of equivalence-checking problems on one-counter automata. For this we show a reduction of the Sat-Unsat problem to the truth problem for a fragment of (Presburger) arithmetic. The fragment contains only special formulas with one free variable, and is particularly apt for transforming to simulation-like equivalences on one-counter automata. In this way we show that the membership problem for any relation subsuming bisimilarity and subsumed by simulation preorder is DP-hard (even) for one-counter nets (where the counter cannot be tested for zero). We also show DP-hardness for deciding simulation between one-counter automata and finite-state systems (in both directions).
01 Jan 2002
TL;DR: The possibility of disposing of selected kinds of industrial waste into abandoned mines, or into the exploited parts of active mines, belongs at present to topical problems in the Czech Republic as mentioned in this paper.
Abstract: The possibility of disposing of selected kinds of industrial waste into abandoned mines, or into the exploited parts of active mines, belongs at present to topical problems in the Czech Republic. In the Czech part of the Lower Silesian Basin, the mining activities have stopped in 1995 and the mines are now under a process of liquidation. Mine workings in both the Odolov and Katefina Mines were simply flooded and their shafts were filled by sorted rock material. The first negative impacts on groundwater quality were documented for this method of liquidation. The Mine Jan Sverma Mine was liquidated instead by filling of the mine workings with a floated self-solidifying ash mixture. Finally the mine workings were sealed with the fill that had the hydraulic properties of impermeable rocks. All the mines considered represent independent geo-hydrodynamic systems without connection with other hydro-geological structures in the study area. The hydro-geological problems of the two liquidation methods are assessed in this contribution.
TL;DR: In this article, a theoretical model of magnetooptical binary grating with cylindrical microdots is presented, where the anisotropy of permittivity is induced by external magnetic field.
Abstract: We present theoretical model of magnetooptical binary grating with cylindrical microdots, where the anisotropy of permittivity is induced by external magnetic field. Rigorous coupled wave method is applied to grating multilayer with periodical ordering. In particular, Kerr rotation versus grating fill factor dependence is studied and obtained results are compared to experimental ones.
TL;DR: In this paper, a comparison of experimental data obtained by Kerr microscopy with micro-magnetic simulation based on the lattice spin Hamiltonian is presented, which is motivated by the idea of the development of a 2D magnetic field detector.
Abstract: This contribution is motivated by the idea of the development of a 2D magnetic field detector. A potential application is in material evaluation - micro-crack detection using stray field sensing. Another motivation is the general study of interactions betwtween individual magnetic elements which can act as magnetic tunnel junction (NITJ) electrodes in MRAM (magnetic random access memory) array or magneto-static logic elements. The structure is studied by magneto-optic (MO) methods including MO diffraction measurement awl Kerr microscopy. At the end of this paper will be presented a comparison of experimental data obtained by Kerr microscopy with micro-magnetic simulation based on the lattice spin Hamiltonian
01 Jan 2002
TL;DR: A survey of the methods used for determining nitrogen in water technology can be found in this article, where the most frequently used methods are discussed: amoniakalni dusik, dusicnany, Dusitany, celkový a organický dusika.
Abstract: By the survey presented in this paper the methods used for determining nitrogen in water technology are described. There are the several nitrogen forms which are important for water treatment and must be routinely analysed: ammonia, nitrates, nitrites, and total and organic nitrogen. The list of analytical procedures is not complete and it is focused at the most frequently used methods. The paper is intended to inform, in short, technologists and/or other people responsible for water treatment technology about the upto-date analytical procedures and their application. Preferably, the standardized methods are mentioned. Abstrakt V přispěvku je uveden přehled analytických metod, ktere se pouivaji v technologii vody ke stanoveni dusikatých sloucenin. Jejich výcet neni uplný a omezuje se na nejcastěji pouivane postupy pro stanoveni těch forem dusiku, ktere jsou z hlediska technologických procesů důleite: amoniakalni dusik, dusicnany, dusitany, celkový a organický dusik. Clanek si klade za cil informovat technology a ostatni pracovniky o soucasných postupech a jejich principech. Přednostně jsou uvedeny metody, ktere jsou normalizovane.
01 Jan 2002
TL;DR: This paper deals about the possibility of actual technologies, which use the dynamic HTML pages, especially ASP (Active Server Pages) technology, and their use for the designing systems support and demonstrates actual capabilities of Internet information technologies.
Abstract: This paper deals about the possibility of actual technologies, which use the dynamic HTML pages, especially ASP (Active Server Pages) technology, and their use for the designing systems support. Authors start at their long-time experiences with the web- oriented information systems building, as well as the designing process support. There are the exercises "Databank of control systems devices" and "The steel manual" shown in the paper and demonstrate actual capabilities of Internet information technologies. Database applications allow sophisticated data selection, editing and presentation on Internet with help of a thin front-end application like web browser.
01 Jan 2002
TL;DR: Fuzzy methodology is applied and fuzzy simple additive weighting method type model is designed, which means financial indices, weights are fuzzy terms and the aspect of non-fixed preciousness of data is included.
Abstract: The ranking of the companies according to financial characteristics is a crucial problem of the financial decision-making. Paper describes an approach to the multiple attribute financial level evaluation. Conditions of financial decision-making are supposed to be only vaguely determined. Fuzzy methodology is applied and fuzzy simple additive weighting method type model is designed. It means financial indices, weights are fuzzy terms and the aspect of non-fixed preciousness of data is included. Fuzzy sets of T-number types, extension principle, e-cut methodology are used. Methodology of ranking companies is suggested. The simplified illustrative example is introduced.
TL;DR: In this paper, a method for quantifying probability of brittle fracture in low-alloyed steels is presented. But the method is limited to the case of Ni-Cr steel.
Abstract: This paper presents a method for quantifying probability of brittle fracture in low alloy steels. The proposed method shows how the probability of brittle fracture varies with stress intensity factor, temperature, deformation characteristics and microstructural parameters of low-alloyed steel. Application of this method on Ni-Cr steel demonstrated very good agreement of predicted temperature dependence of scatter in brittle fracture toughness with experimental results. The method enables also to calculate characteristic distance as a radial dimension from the crack tip where microcrack initiation is most probable. The characteristic distance of investigated Ni-Cr steel was found to decrease with increasing temperature. Microstructural mechanisms of initiation and propagation of brittle fracture were identified from results of fractography analysis. The proposed procedure represents a foundation for systematic control of relationship between stress-strain behaviors, toughness and reliability of steel engineering parts.
01 Jan 2002
TL;DR: In this article, the authors deal with the problem of car random burst shaking while its engine is running at idle and present how to use newly developed measurement methods and data processing tools.
Abstract: The paper deals with the problem of car random burst shaking while its engine is running at idle. The disturbing vibration is excited by non-uniform engine rotational frequency that is transferred to the car body vibration and finally to passengers. Having in mind that the car structure is linear, it is possible to estimate the regression linear model for transferring vibration at individual frequencies. The paper presents how to use newly developed measurement methods and data processing tools.
01 Jan 2002
TL;DR: A new formal method of navigation through query result based on an original idea of concept order structure, which exploits the concept lattices theory and the fuzzy set theory to uncover significant concepts without the need of user scaling.
Abstract: Query in Information Retrieval produces some amount of relevant results. Consecutively, there is a need for some qualitative clas- sification of these particular results in such way the user is able to un- derstand. In this article we introduce a new formal method of navigation through query result. This navigation method is based on an original idea of concept order structure, which exploits the concept lattices theory and the fuzzy set theory. So far, user must provide a subjective factor - at- tribute scaling. Our method helps to uncover significant concepts without the need of user scaling.
01 Jan 2002
TL;DR: In this article, a method for quantifying probability of brittle fracture in low-alloyed steels is presented, which shows how the probability of fracture varies with stress intensity factor, temperature, deformation characteristics and microstructural parameters of low alloy steels and enables also to calculate characteristic distance as a radial dimension from the crack tip where microcrack initiation is most probable.
Abstract: This paper presents a method for quantifying probability of brittle fracture in low alloy steels. The proposed method shows how the probability of brittle fracture varies with stress intensity factor, temperature, deformation characteristics and microstructural parameters of low-alloyed steel. Application of this method on Ni-Cr steel demonstrated very good agreement of predicted temperature dependence of scatter in brittle fracture toughness values with experimental results. The method enables also to calculate characteristic distance as a radial dimension from the crack tip where microcrack initiation is the most probable. The characteristic distance of investigated Ni-Cr steel was found to decrease with increasing temperature. Microstructural mechanisms of initiation and propagation of brittle fracture were identified from results of fractography analysis. The proposed procedure represents a foundation for systematic control of relationship between stress-strain behaviours, toughness and reliability of steel engineering parts
01 Jan 2002
01 Jan 2002
TL;DR: The paper refers to using information technologies at the lowest level of control applications - in direct control - and describes the reasons for using Intranet/Internet in HMI/SCADA systems and explains thin and fat client functions.
Abstract: The paper gives main information about using information technologies in a control system. The term of information technology is being defined according to fundamental requirements coming from the everyday operation of a company. There is also a review of the recent state of the art of process data visualization and monitoring in industrial control systems. The paper refers to using information technologies at the lowest level of control applications - in direct control. Then, it further describes the reasons for using Intranet/Internet in HMI/SCADA systems and explains thin and fat client functions. This work has been supported by MSMT 272300012 granted project.
01 Jan 2002
TL;DR: Possibility of monitoring manufacturing hall and photos scanned processing with objective to identify chosen technological entities and indicate their position in time and can be supplied with artificial intelligence elements.
Abstract: The paper deals with possibilities of monitoring manufacturing hall and photos scanned processing with objective to identify chosen technological entities and indicate their position in time. Algorithmes that exploites sensitive colour and shape discrimination enable entity allocation to selected groups. The algorithmes can be supplied with artificial intelligence elements.
01 Jan 2002
TL;DR: In this paper, a comparison of methodology for determination of the flow stress based on results of plastometric hot torsion test is performed, and significant differences in the course of stress are demonstrated, and in particular the determination of flow stress maximum point.
Abstract: In the paper is performed a comparison of methodology for determination of the flow stress based on results of plastometric hot torsion test. As basis for calculations were taken the registered values of torque moment in the function of a number of torsions obtained during torsion test of tool steel. The torsion tests were executed at torsion plastometer in the Department of Mechanics and Plastic Working Technology at Silesian Technical University in Katowice, in the range of temperatures 850 – 1050 °C and twist rate 10 – 500 rpm. There were demonstrated significant differences in the course of stress – strain curves, and in particular the determination of flow stress maximum point.