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Dielectric Properties and Breakdown of the Gate Oxide in the MOS Structure

Author(s): Ladislav Harmatha,Peter Valent,Juraj Racko / Language(s): English Issue: 2/2010

The article treats the methodology of measuring the breakdown voltage on Si-based MOS structures. Identification of defects in the thin gate oxide is performed using the Weibull statistical analysis. By comparing the current and capacitance measurements on MOS structures we determined the influence of the defect charge in the oxide upon the parameters characterizing the breakdown. A higher occurrence of defects was correlated with elevated values of the flat band voltages. This verifies the hypothesis of an increased destruction of MOS structures caused by electrically active defects arising in the course of thermic oxidation and pre-oxidation treatment of the surface of silicon.

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A Theoretical Study of the Temperature Sensor Based on the LP01-LP02 Intermodal Interference in Optical Fiber with a Liquid Core

Author(s): Ivan Martincek,Dusan Pudis / Language(s): English Issue: 2/2010

We theoretically propose the temperature sensor based on optical fiber consisting of fused silica and core of 2.5 μm radius filled in with toluene. In such an optical fiber the intermodal interference of modes LP01-LP02 shows a characteristic dependence of the equalization wavelength λ0 on temperature. The optical fiber sensor was theoretically investigated in the temperature range of 0-40 °C, where the equalization wavelength λ0 for modes LP01-LP02 changes from 1284.2 nm to 844.1 nm. Such considerable wavelength change with temperature favors this sensor for temperature measurements with sensitivity better than 0.1 °C.

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Low-Coherence Interferometry for Measurement of Properties of Optical Components

Author(s): Daniel Kacik,Norbert Tarjanyi,Ivan Turek / Language(s): English Issue: 2/2010

We present a modification of the interferometric method for the measurement of refractive index or thickness of optical devices using an easily aligned, almost all-fiber Michelson interferometer. Applicability of the method is demonstrated by the chromatic dispersion measurement of photonic crystal fiber sample. The birefringence of the optical device based on LiNbO3 obtained from the measurement of refractive indices is demonstrated and its value is determined for two different crystal samples. It is also shown that when the thickness of, for example, photopolymer material is known the refractive index of the device can be determined. The described method can be a practical tool for laboratories with the need of inexpensive and easily built setup for measurement of refractive index or thickness of optical devices even in a broad spectral range.

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Silicon Nitride Based Non-Volatile Memory Structures with Embedded Si or Ge Nanocrystals

Author(s): Zsolt J. Horvath,P. Basa,T. Jaszi,György Molnár,A. I. Kovalev,D. L. Wainstein,T. Gerlai,P. Turmezei / Language(s): English Issue: 2/2010

Memory structures with an embedded sheet of separated Si or Ge nanocrystals were prepared by low pressure chemical vapour deposition using a Si3N4 control and SiO2 tunnel layers. It was obtained that a properly located layer of semiconductor nanocrystals can improve both the charging and retention behaviour of the MNOS structures simultaneously. Memory window width of above 6 V and retention time of 272 years was achieved for charging pulses of 15 V, 10 ms.

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Analysis of Complex Time Function of Converter Output Quantities Using Complex Fourier Transform/Series

Author(s): Maria Zaskalicka,Pavel Zaskalicky,Mariana Benova,Mahmud Ali Rzig Abdalmula,Branislav Dobrucky / Language(s): English Issue: 1/2010

The paper deals with the complex- and discrete Fourier transform which has been considered for both three- and two phase orthogonal voltages and currents of systems. The investigated systems are power electronic converters supplying alternating current motors. Output voltages of them are strongly non-harmonic ones, so they must be pulse-modulated due to requested nearly sinusoidal currents with low total harmonic distortion. Modelling and simulation experiment results of half-bridge matrix converter for both steady- and transient states are given under substitution of the equivalence scheme of the electric motor by resistive-inductive load and back induced voltage. The results worked-out in the paper confirm a very good time-waveform of the phase current and results of analysis can be used for fair power design of the systems.

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Better Confidence Intervals for a Binomial Proportion

Author(s): Ivana Pobocikova / Language(s): English Issue: 1/2010

Interval estimation of a binomial proportion is one of the basic problems in statistics. In technical practice a binomial proportion is often used in statistical quality control. The standard Wald interval and the exact Clopper-Pearson interval are the most common and frequently used intervals. They are presented in the majority of statistical literature. It is known that the Wald interval performs poorly and this interval should not be used. In this paper we recommend the alternatives of confidence intervals that have a better performance and are appropriate for practical use. We compare the performance of six alternatives of confidence intervals for a binomial proportion: the Wald interval, the Clopper-Pearson interval, the Wilson score interval, the Wilson score interval with continuity correction, the Agresti-Coull interval and the Jeffreys interval in terms of the coverage probability, the interval length and the root mean square error.

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Experimental Behavior of Jurik's Nearest Point Approach Algorithm for Linear Programming

Author(s): Ondrej Such / Language(s): English Issue: 1/2010

T. Jurik recently proposed a new algorithm for solving linear programming problems. The algorithm is iterative, finding points on the boundary of the problem's convex polyhedron. Global convergence of the algorithm is an open question. Jurik benchmarked the performance of the algorithm on standard sets of linear optimization problems, and the algorithm was on par with commonly used ones, and sometimes beating the simplex method by a wide margin. In this note we concentrate on testing local behavior of the algorithm near a vertex in the three dimensional Euclidean space. Our experiments indicate that the behavior of the algorithm is mostly very fast, but there appear to be cases where its behavior is worse than the simplex method.

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Design of Compression Members for Durability

Author(s): Jozef Vican,Marian Sykora / Language(s): English Issue: 4/2009

General principles of structural elements design for durability and their application in the case of compression members are presented in this paper. The degradation effects of material deterioration due to corrosion cause the loss of member resistance, but the limit states method does not directly reflects design and verification allowing for failures caused by material deterioration. The time-dependent loss of compression member resistance was computed for specific corrosion models to express the time-dependent approximation function taking into account effects of corrosion degradation. Then, the design member resistance could be obtained using buckling member resistance multiplied by a time-dependent function considering corrosion degradation effects within the member lifetime.

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Analysis of Factors Influencing Microstructure and Mechanical Properties of Austempered Ductile Iron

Author(s): Alan Vasko / Language(s): English Issue: 4/2009

The paper deals with some factors influencing microstructure and mechanical properties of austempered ductile iron (ADI). Final structure and properties of ADI are obtained by exactly controlled process of heat treatment of nodular cast iron. The influence of conditions of isothermal heat treatment on microstructure and mechanical properties of austempered ductile iron, especially different temperature of isothermal transformation of austenite and different holding time at this temperature, is shown in the paper.

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Properties of Strain-Gauge Load Cells Applied for Stator Reaction Measurement

Author(s): Lubomir Miklanek / Language(s): English Issue: 4/2009

This contribution deals with experience with the measurement of the stator reaction of the dynamometer using load cells. Originally, the stator reaction had been measured using a balance mechanism. Within the framework of the author's research, it was necessary to improve the accuracy of torque measurement of the dynamometer. To accomplish this requirement, the old balance mechanism was replaced by a strain-gauge load cell. Two various types of the load cells were applied in order to arrange the measuring range to the expecting range of values of the torque. During the calibration, hysteresis in voltage output of the both applied load cells was observed. The maximal value of the hysteresis was about 0.5 % of the measured range of both of the load cells. Moreover, a certain temporary-plasticity of both of the load cells occurred.

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General Vectorization of Line Objects in Drawn Maps

Author(s): Peter Tarabek / Language(s): English Issue: 4/2009

Drawn maps consist of multiple object types. The most important are line objects which represent infrastructure. Attributes of these objects are essential for many tasks but in raster format they provide only low level information. Vectorization must be used to obtain vector data. In this paper general vectorization process consisting of five stages is proposed. For these stages short discussion and basic recommendations are given and some proper methods are presented.

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A Multi Label Algorithm for K Shortest Paths Problem

Author(s): Stanislav Paluch / Language(s): English Issue: 3/2009

The paper presents an algorithm for computing k shortest walks or k shortest paths in a directed graph G (V, A). The proposed algorithm can be applied for solving the k shortest paths problem in an undirected graph G (V, E), too, by transforming the graph G (V,E) to the digraph G(V, A) where the arc set A contains a couple of arcs (u,v), (v,u) for every edge {u,v} E.

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Parallel Backtracking Algorithm for Hamiltonian Path Search

Author(s): Karol Grondzak,Penka Martincova / Language(s): English Issue: 3/2009

The speed of calculations is a common problem to tackle in many areas of scientific research and real life. This paper presents an implementation of a parallel backtracking algorithm. The performance of the proposed algorithm is demonstrated on the problem of Hamiltonian Path search. Obtained results exhibit significant improvement of the parallel algorithm over the sequential one. Different aspects of parallelization of backtracking algorithm are studied and presented.

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Minimal Total Area Convex Set Partitioning Problem

Author(s): Štefan Pesko / Language(s): English Issue: 3/2009

The linear binary model for finding set partitioning of the points in the plane is studied. We present heuristic which generates partitioning of points to clusters for a given number of seeds with searched seeds of clusters in a plane. For this cluster the convex hulls are constructed via Graham's scan algorithm. This approach is demonstrated on the real instance of Florida area with 235 points for 10 and 13 clusters.

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A Contour Approach to Thinning Algorithms

Author(s): Peter Tarabek / Language(s): English Issue: 3/2009

Thinning algorithms are widely used in many image processing tasks. Many thinning algorithms were proposed but they usually tend to process all image pixels in every iteration. Two approaches to contour thinning are described and a short discussion about their features is given. These approaches can be implemented as sequential or parallel algorithms with different deletion rules. Results of comparison and analysis are presented in this paper.

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Algorithm for Generating Text Descriptions of Bit Calendars

Author(s): Hynek Bachraty,Emil Krsak,Marek Tavac / Language(s): English Issue: 3/2009

The article deals with the problematics of generating calendar text descriptions based on their bit map. We introduce the description of the algorithm we have designed, its basic ideas and parts. We also present the results of testing the successfulness of the algorithm before it is primarily used.

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Effect of Short Saffil Fibres and SIC Particles on Mechanical Properties of Magnesium Alloys

Author(s): Zuzanka Trojanova,Zoltan Szaraz,V. Gartnerova / Language(s): English Issue: 1/2009

The high temperature mechanical behaviour of composites with the AZ91 and AS21 magnesium alloys matrix, reinforced with short Saffil fibres and SiC particles were investigated. Samples were deformed in compression in the temperature range from room temperature to 300 °C. The yield stress and the maximum stress of true stress-true strain curves decrease with increasing temperature. Light and electron microscopy were used for study of the microstructure of composites. Possible hardening and softening mechanisms are discussed. The increased dislocation density and the shear stress at reinforcing phase/matrix interfaces were found as the most important contributions to the strengthening.

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Fatigue Lifetime of 7075 Aluminium Alloy from Ultimate Tensile Strength to Permanent Fatigue Limit

Author(s): Josef Zapletal,Stanislav Vechet,Jan Kohout,Petr Liskutin / Language(s): English Issue: 1/2009

The aim of this paper is to study fatigue behaviour of 7075 aluminium alloy at room temperature for both important directions (longitudinal as well as transversal) with respect to the direction of forming. Smooth test bars were subjected to symmetrical push-pull loading at stresses which cover the whole range of lifetime from UTS to permanent fatigue limit. The results are presented above all as S-N curves fitted using suitable regression functions which lead to precise and reliable determination of fatigue limits.

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Fatigue Resistance of High-Thickness Al-Alloy Sheets after Water Jet Cutting

Author(s): Ivo Cerny,Dagmar Mikulova / Language(s): English Issue: 1/2009

Water jet cutting is a useful advanced technology of separating materials with a great industrial potential due to high cutting speed, precision, shape repeatability and possibilities to be performed automatically with a computer control. It is well known, however, that fatigue properties are particularly strongly affected by surface conditions and quality of surface layer. Water jet cutting was applied to Al-alloy sheets of fairly high thickness, namely 50.8 mm. Fatigue resistance of water cut specimens and failure mechanisms were investigated and compared with those studied using a reference batch of specimens manufactured by fine milling. Character of surface damage caused by water jet cutting resulted in a considerable reduction of fatigue strength in comparison with milled surface. The results are discussed considering microscopic analysis of surface and subsurface conditions of fatigue crack initiation.

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Fatigue Properties of Steel with Increased Atmospheric Corrosion Resistance

Author(s): Marian Bursak,Otakar Bokuvka / Language(s): English Issue: 1/2009

The paper deals with the influence of cyclic loading (tension-compression, bending and torsion) on the course of the fatigue life and the fatigue limit of advanced low-alloyed strip steel with increased atmospheric corrosion resistance. The tested steel shows, besides very good mechanical properties (Re>380 MPa, A5>30%), also very good fatigue resistance and its fatigue limit/ultimate tensile strength ratio is above 0.5. These properties are provided by a favourable fine-grained structure of the tested steel.

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