Showing papers by "Brno University of Technology published in 2000"
TL;DR: In this article, a nonlocal generalization of Weibull theory for structures that are either notched or fail only after the formation of a large crack is extended to predict the probability of failure of unnotched structures that reach the maximum load before a large fracture forms, as is typical of the test of modulus of rupture.
Abstract: The nonlocal generalization of Weibull theory previously developed for structures that are either notched or fail only after the formation of a large crack is extended to predict the probability of failure of unnotched structures that reach the maximum load before a large crack forms, as is typical of the test of modulus of rupture (flexural strength). The probability of material failure at a material point is assumed to be a power function (characterized by the Weibull modulus and scaling parameter) of the average stress in the neighborhood of that point, the size of which is the material characteristic length. This indirectly imposes a spatial correlation. The model describes the deterministic size effect, which is caused by stress redistribution due to strain softening in the boundary layer of cracking with the associated energy release. As a basic check of soundness, it is proposed that for quasibrittle structures much larger than the fracture process zone or the characteristic length of material, the probabilistic model of failure must asymptotically reduce to Weibull theory with the weakest link model. The present theory satisfies this condition, but the classical stochastic finite-element models do not, which renders the use of these models for calculating loads of very small failure probabilities dubious. Numerical applications and comparisons to test results are left for Part II.
113 citations
TL;DR: The nonlocal probabilistic theory developed in Part I is applied in numerical studies of plain concrete beams and is compared to the existing test data on the modulus of rupture.
Abstract: The nonlocal probabilistic theory developed in Part I is applied in numerical studies of plain concrete beams and is compared to the existing test data on the modulus of rupture. For normal size test beams, the deterministic theory is found to dominate and give adequate predictions for the mean. But the present probabilistic theory can further provide the standard deviation and the entire probability distribution (calculated via Latin hypercube sampling). For very large beam sizes, the statistical size effect dominates and the mean prediction approaches asymptotically the classical Weibull size effect. This is contrary to structures failing only after the formation of a large crack, for which the classical Weibull size effect is asymptotically approached for very small structure sizes. Comparison to the existing test data on the modulus of rupture demonstrates good agreement with both the measured means and the scatter breadth.
88 citations
01 Jan 2000
TL;DR: The aim of this paper is to propose the parallel version of this Bayesian Optimization Algorithm, where the optimization time decreases linearly with the number of processors.
Abstract: In the last few years there has been a growing interest in the field of Estimation of Distribution Algorithms (EDAs), where crossover and mutation genetic operators are replaced by probability estimation and sampling techniques. The Bayesian Optimization Algorithm incorporates methods for learning Bayesian networks and uses these to model the promising solutions and generate new ones. The aim of this paper is to propose the parallel version of this algorithm, where the optimization time decreases linearly with the number of processors. During the parallel construction of network, the explicit topological ordering of variables is used to keep the model acyclic. The performance of the optimization process seems to be not affected by this constraint and our version of algorithm was successfully tested for the discrete combinatorial problem represented by graph partitioning as well as for deceptive functions.
54 citations
28 May 2000
TL;DR: The CMOS design of the universal current conveyor with reduced parasitic resistance on the X-terminal is shown and two novel types of invertingCurrent conveyor (ICCI and ICCIII) are defined and modelled.
Abstract: The authors present a novel versatile circuit building block called a universal current conveyor (UCC). The CMOS design of the universal current conveyor with reduced parasitic resistance on the X-terminal is shown. Finally, two novel types of inverting current conveyor (ICCI and ICCIII) are defined and modelled. PSpice simulations of the UCC presented are included.
37 citations
TL;DR: The so-called elementary canonical state models of the third-order piecewise-linear (PWL) dynamical systems, as the simplest ODE equivalents of Chua's equations, are presented and their mutual relations using the linear topological conjugacy are demonstrated.
Abstract: The so-called elementary canonical state models of the third-order piecewise-linear (PWL) dynamical systems, as the simplest ODE equivalents of Chua's equations, are presented. Their mutual relations using the linear topological conjugacy are demonstrated in order to show in detail that Chua's equations and their canonical ODE equivalents represent various forms of qualitatively equivalent models of third-order dynamical systems. New geometrical aspects of the corresponding transformations together with examples of typical chaotic attractors in the stereoscopic view, give the possibility of a deeper insight into the third-order system dynamics.
33 citations
TL;DR: In this paper, the authors proposed a new mass method of measurement of small flow of two-phase media, where the solid particles are carried by a carrying gas (air) and the method exploits the fact that the solid particle being carried by flowing air impacting a properly formed obstacle generates an acoustic surface wave (acoustic emission).
Abstract: This paper is concerned with a new mass method of measurement of small flow of two-phase media, where the solid particles are carried by a carrying gas (air). The method exploits the fact that the solid particles being carried by a flowing air impacting a properly formed obstacle generates an acoustic surface wave (acoustic emission). The acoustic signal is indicated by the aid of a high sensitive transducer, which converts the acoustic signal to an electric one. The magnitude of the electric signal is proportional to the (average) mass of particles having a constant (unified) velocity. In general, in this way we get the information about the magnitude of particles being measured and about their quantity. The electric output signal of the transducer is processed in the electric section of the meter, using up-to-date electrical devices that are able to carry out amplitude or frequency analyses of the signal and performs its another processing. We may use the same idea of the particle sensing, but with two obstacles in the flow channel, to create a cross-correlation velocity flowmeter.
17 citations
TL;DR: Two different speaker modeling approaches, based on multilayer perceptrons (MLPs) and on Gaussian mixture models (GMMs) are studied, and the MLP-based segmental systems have performance comparable to that of the global MLPs, and in the mismatched train-test conditions slightly better results are obtained with the segmental MLP system.
16 citations
TL;DR: In this article, a colorimetric interferomentry has been applied to the study of EHD lubrication of point contacts under pure rolling conditions to obtain lubricant film shapes with high accuracy and resolution.
Abstract: Colorimetric interferomentry has been applied to the study of EHD lubrication of point contacts under pure rolling conditions to obtain lubricant film shapes with high accuracy and resolution. An RGB CCD camera together with an extensive image processing software has enabled real time evaluation of chromatic interferograms. The classical numerical isothermal solution of EHD lubrication of point contacts has been used for the comparison with three-dimensional representations of film thickness distributions obtained from experiments. A good agreement was found between experimental and numerical EHD film shapes by comparing lubricant film profiles and positions of minimum film thickness. Both experimental results and numerical solution confirm the ratio between central and minimum film thickness to change significantly with operating conditions.
15 citations
01 Jan 2000
TL;DR: This article tries to identify some common high-level problems of this area from a higher perspective and then to outline a possible solution, showing an example with the definition of data interfaces for respective KDD steps using XML.
Abstract: In recent years, the XML language has been receiving much interest among IT community. It has many nice properties that make it a great candidate for representation of different kinds of data. In this paper we will propose an XML framework for the domain of knowledge discovery in databases. This is not a specification document; this article tries to be a compendium of ideas and remarks concerning the broad area of knowledge discovery in databases (KDD). It tries to identify some common high-level problems of this area from a higher perspective and then to outline a possible solution, showing an example with the definition of data interfaces for respective KDD steps using XML.
15 citations
03 Apr 2000
TL;DR: This paper deals with hierarchical, multiple fieldbus-based architectures using four case studies that present some concepts reusable in developing the interconnections of intelligent sensors and actuators using NBIP-ASI, ASI, and two different Bitbus-NBIP hierarchical coupling structures.
Abstract: This paper deals with hierarchical, multiple fieldbus-based architectures using four case studies that present some concepts reusable in developing the interconnections of intelligent sensors and actuators. The single-master, low-level fieldbusses considered involve (1) ASI (Actuator-Sensor-Interface), which is an example of a lowest-level industrial interconnection; (2) NBIP (Nine-Bit Inter-processor Protocol), which is an example of a special purpose link-layer protocol for microcontrollers; and (3) Bitbus, which is an example of well-established fieldbus utilized for almost 20 years in various applications. The paper begins with classification issues; particularly, coupling architectures are treated both from the viewpoint of more classical interconnections of wide-area and local-area networks, and from the viewpoint of fieldbus domain. Next part introduces the ASI and NBIP protocols while the well-known Bitbus is reviewed in applications. To offer more complex insight, implementation tools-developed particularly to support low-level fieldbus interconnecting experiments-are also mentioned. Four case studies demonstrating consequently NBIP-ASI, ASI-ASI, and two different Bitbus-NBIP hierarchical coupling structures create the kernel of the paper. Finally, brief notes about origins, results, and current targets of the project conclude the contribution.
15 citations
28 May 2000
TL;DR: A fast computational method for the numerical inversion of two-dimensional Laplace transforms (2D-NILT) is described, improved significantly using an /spl epsiv/-algorithm to give precision to the result.
Abstract: The paper describes a fast computational method for the numerical inversion of two-dimensional Laplace transforms (2D-NILT). The numerical procedure is basically that based on FFT algorithms (Brancik and Valsa, 1998), but it is improved significantly using an /spl epsiv/-algorithm to give precision to the result. Compared with the original method, the procedure under consideration enables the error to be decreased by a few orders. The method has been programmed and verified using the universal mathematical language Matlab.
TL;DR: The photoluminescence in polysilanes during the change from linear one-dimensional (1D) Si chain to amorphous three-dimensional Si network was studied in this article.
TL;DR: In this article, an ion associates of anionic monodentate PGM complexes with low and high-molecular mass ammonium cations give satisfactory results in ion interaction HPLC on reversed phase silica in the presence of CH3CN or CH3OH modifiers.
Abstract: Various platinum group metals (PGMs) can be separated in the form of complexes with monodentate ligands, ion associates or chelates by high performance liquid chromatography (HPLC) or capillary zone electrophoresis (CZE). Ion associates of anionic monodentate PGM complexes with low and high-molecular-mass ammonium cations give satisfactory results in ion interaction HPLC on reversed phase silica in the presence of CH3CN or CH3OH modifiers. PGM chelates often show considerable shortcomings due to kinetic hindrance during their formation and must be formed prior to HPLC application. Capillary zone electrophoresis (CZE) brings some new aspects to the separation of PGMs in addition to increasing separation speed and miniaturization of the system. Both methods can be successfully used for the treatment of platinum anti-cancer drugs, their organic impurities, hydrolytic products or metabolites in body fluids. Representative examples are discussed in this paper.
TL;DR: In this article, the non-crystalline ordered phthalocyanine (Pc) films made by vacuum sublimation were used in organic field effect transistors (OFETs).
Abstract: The non-crystalline ordered phthalocyanine (Pc) films made by vacuum sublimation were used in organic field-effect transistors (OFETs). The spectroscopic method of temperature-modulated field-effect (TM-FE) was used for measurement of films properties and optimization of their parameters The mobility of the phthalocyanine film increased by several orders of magnitude by ordering in stacks, parallel to the substrate. This was achieved by choosing proper substrate temperature, temperature anneal and the final thickness of the films. The achieved results are: on–off current ratio 107 and the hole mobility μh=3×10−4 cm2 V−1 s−1.
TL;DR: In this article, two colorimetric interferometry techniques for the determination of elastohydrodynamic lubricant film thickness and shape in model contacts were reported. But these techniques are limited in accuracy and resolution to several nanometers and the relationship between the central and minimum thickness and rolling speed in the very thin film thickness regime was not studied.
Abstract: Recently, we reported two novel experimental techniques for the determination of elastohydrodynamic lubricant film thickness and shape in model contacts based on colorimetric interferometry. This approach successfully overcomes two major limitations of conventional optical interferometry – accuracy and resolution. This paper presents the next stage in the development of these two techniques. The use of spacer layer has enabled to extend the film thickness measurement range down to several nanometers so that the relationship between the central and minimum film thickness and rolling speed in the very thin film thickness regime could be studied. The measurement techniques also produced information about film thickness profiles across lubricated contact and three-dimensional maps of film thickness.
27 Aug 2000
TL;DR: The paper tries to establish the uniform design concept for evolvable hardware based applications by presenting a component "evolvable pixel predictor" as a demo example.
Abstract: The paper tries to establish the uniform design concept for evolvable hardware based applications. Evolvable circuit is understood as a system component with ability to evolve. As demo example, a component "evolvable pixel predictor" is presented.
TL;DR: In this article, thin plasmon polymer films were deposited from a mixture of dichloro(methyl)phenylsilane (DCMPS) vapour and gaseous hydrogen in a capacitive coupling deposition system on pieces of silicon wafers.
Abstract: Thin plasma polymer films were deposited from a mixture of dichloro(methyl)phenylsilane (DCMPS) vapour and gaseous hydrogen in a r.f. (13.56 MHz) capacitive coupling deposition system on pieces of silicon wafers. Some samples were annealed in vacuum at the temperature ranging from 450 to 700°C. Chemical composition, structure and surface morphology of annealed samples and those stored in air at room temperature were studied by FTIR, XPS, SEM, and optical microscopy. Thermal stability and a decomposition of the plasma polymer with increasing temperature were characterized by thermogravimetry together with mass spectrometry. The plasma polymer was stable up to a temperature of 300°C. Above that temperature the material started to decompose together with additional cross-linking due to incorporation of extra oxygen atoms forming new siloxane bonds. The plasma polymer was tough at room temperature but much more brittle at elevated temperatures.
01 Jan 2000
TL;DR: In this article, a low temperature plasma technology is used for surface modification of reinforcements, which is able to prepare controlled interphases, which can lead to higher strength and higher toughness of the specific composite system.
Abstract: A development of high-performance composites is tightly bound with a designing of composite interphases. The interphase is a region intermediate to the fibre and the matrix which are in a contact. In fact this region includes the fibre coating and a part of the matrix affected by the presence of the coated fibre. Theoretical and experimental studies have showed that the properties of fibre reinforced composites are given by the coating material with its thickness and modulus, by the interaction at interfaces with the fibre and the matrix, and by the reinforcement and matrix materials. Therefore, sophisticated interphases can lead to higher strength and higher toughness of the specific composite system. Low temperature plasma technology is the new technique used for surface modification of reinforcements. This technology is able to prepare controlled interphases. Actual possibilities and achievements of the plasma technology are outlined.
TL;DR: In this article, the authors presented the application of self-tuning digital PID controllers for process control modelled by δ - models, where the process is identified by the regression (ARX) model using the recursive least squares method (RLSM) with LD decomposition and applied directional forgetting.
TL;DR: The protein sequence and structure of metal centres demonstrate the relationship of NOR to the family of terminal oxidases, and the binuclear Fe−Fe reaction centre, consisting of antiferromagnetically coupled hæm B and nonhæm iron, is analogous to Fe−Cu centre of terminal oxidation.
Abstract: The review briefly summarizes current knowledge of the bacterial nitric-oxide reductase (NOR). This membrane enzyme consists of two subunits, the smaller one contains haem C and the larger one two haems B and nonhaem iron. The protein sequence and structure of metal centres demonstrate the relationship of NOR to the family of terminal oxidases. The binuclear Fe−Fe reaction centre, consisting of antiferromagnetically coupled haem B and nonhaem iron, is analogous to Fe−Cu centre of terminal oxidases. The data on the structure and function of NOR and terminal oxidases suggest that all these enzymes are closely evolutionally related. The catalytic properties are determined most of all by the relatively high toxicity of nitric oxide as a substrate and the resulting strong need to maintain its concentration at nanomolar levels. A kinetic model of the action of the enzyme comprises substrate inhibition. NOR does not conserve the free energy of nitric oxide reduction because it does not work as a proton pump and, moreover, the protons coming into the reaction are taken from periplasm,i.e. they do not cross the membrane.
TL;DR: In this paper, a simplified method based on an integral measurement of intensity of the optical emission spectrum by a semiconductor photodetector in the nitrogen afterglow at low temperatures was proposed and realized in practice.
Abstract: On the basis of spectroscopical measurements, a method for the determination of hydrocarbon concentration has been proposed and realized in practice This simplified method is based on an integral measurement of intensity of the optical emission spectrum by a semiconductor photodetector in the nitrogen afterglow at low temperatures The advantage of the proposed method is its technical simplicity and the economy of the measuring equipment We used a photodiode BPW34B with increased sensitivity in the spectral range 300-400 nm as a detector The detection limit of our method is in the order of 109 carbon atoms in pure nitrogen A kinetic model of the energy transfer processes during the afterglow of pure nitrogen with hydrocarbon traces is given It can successfully explain the observed results and also provides a good explanation of the quenching of nitrogen `pink afterglow' by hydrocarbon traces The value of the rate coefficient of the main afterglow reaction N2(X,1Σg+,v≥12) + CN(X 2Σ)→N2(X 1Σg+) + CN(B 2Σ+) was predetermined about 12×10-11 cm3 s-1 at room temperature The method was used for the determination of polymeric material degradation at low pressures
TL;DR: The implementation principle of a virtual evolvable machine on top of a normal FPGA is described, in this way, the current FPGAs can implementevolvable circuit.
16 Jul 2000
TL;DR: The goal of this article is to present the conception of the solution and some new ideas for the fuzzy control of GA parameters by virtue of the behavior of some GA characteristics.
Abstract: Applications of genetic algorithms (GA) for optimisation problems are widely known as well as their advantages and disadvantages compared with classical numerical methods. In practical tests, GA appears a robust method with a broad range of applications. The determination of GA parameters could be complicated. Therefore for some real-life applications, several empirical observations of an experienced expert are needed to define these parameters. This fact degrades the applicability of a GA for most of the real-world problems and users. Therefore, this article discusses some possibilities with setting GA parameters. The setting method of GA parameters is based on the fuzzy control of values of GA parameters. The feedback for the fuzzy control of GA parameters is realized by virtue of the behavior of some GA characteristics. The goal of this article is to present the conception of the solution and some new ideas.
TL;DR: A digital adaptive PID controller algorithm, which contained on-line identification, is presented, which can be implemented on all controller design methods, which are based on the knowledge of the ultimate values, such as the well-known Ziegler-Nichols (Z-N) method.
03 Jul 2000
TL;DR: Different approaches to configuration, reconfiguration and fault tolerance implementation of two-dimensional cellular system are described.
Abstract: Recently, hardware researchers have promptly begun to investigate alternative computational principles to the conventional ones. The main signs of these principles are inspiration in biology and their direct hardware implementation. Evolvable hardware, cellular computing or embryonic electronics are the most important examples. This paper describes different approaches to configuration, reconfiguration and fault tolerance implementation of two-dimensional cellular system. Simplicity of the cell, vast parallelism, and the connection locality are considered as the design restrictions.
TL;DR: A self – tuning PID controller algorithm derived that is suitable for the automatic setting of analog and digital PID controllers for deterministic processes or the adaptive control of stochastic and nonlinear processes.
01 Dec 2000
01 Jan 2000
TL;DR: This paper deals with the analysis of musical effects, the design of algorithms for simulating these effects, and their realization on both digital signal processors and the PC platform in the form of plug-in modules for the DirectX environment.
Abstract: For quite some time in the area of commercial utilization of digital audio effects, efforts have emerged to create simulate by software analog effects and effect processors This paper deals with the analysis of musical effects, the design of algorithms for simulating these effects, and their realization on both digital signal processors and the PC platform in the form of plug-in modules for the DirectX environment. It also deals with the problem of controlling the effect parameters and with subjective testing of algorithms, and it examines the fidelity of simulated effects as compared with the original.
TL;DR: Simulation results verifying the correctness of the model are provided and mathematical model derived using the Euler-Newton method of free bodies dynamics of SSMR is described.
TL;DR: In this paper, the design of simple controllers for stable and also unstable time-delay systems using polynomial approach is presented based on various approximations of the time delay.