Cost-optimized switched reluctance motor drive with bipolar currents

The manufacturing cost of switched reluctance motors (SRM) are low due to concentrated stator windings and extremely simple and robust rotor construction, having neither permanent magnets nor the rotor windings. Therefore, the SRM drives have been considered as a promising solution for cost-critical applications where the electronic speed control is needed, such as the appliance drives, HVAC blowers and compressors, drives in commercial and residential buildings and similar. One of the reasons that hindered the SRM drives expansion was the lack of standardized power converters produced in volume. Advantageous SRM power converter topologies have been proposed over the years, however, some of them were utilizing a large number of discrete power components, while the others were leading to a poor utilization of the DC-bus voltage. In this article, a novel SRM drive is proposed, entirely based on standard industrial inverter modules, fully utilizing bus voltage. Besides, due to the pulse polarity alteration, the dwell period can be arbitrarily chosen and can freely overlap defluxing interval in the adjacent phase. Therefore, the applicable voltage reaches theoretical maximum for the given bus voltage, extending in such way the torque-speed region up to the motor-related limits. Proposed topology is functional in the four quadrants and in the field weakening as well. This article includes the operation principles of the proposed solution and continues with practical application on a three-phase SRM. Also, design considerations and experimental results are included, as well as the consideration of the drive cost.     

Improving network security using genetic algorithm approach

With the expansion of Internet and its importance, the types and number of the attacks have also grown making intrusion detection an increasingly important technique. In this work we have realized a misuse detection system based on genetic algorithm (GA) approach. For evolving and testing new rules for intrusion detection the KDD99Cup training and testing dataset were used. To be able to process network data in real time, we have deployed principal component analysis (PCA) to extract the most important features of the data. In that way we were able to keep the high level of detection rates of attacks while speeding up the processing of the data.     

Influence of the type and degree of alteration of andesite and dacite on the quality and life of asphaltic concrete

This report deals with the influence of alteration processes in andesite and dacite with special reference to those alterations and characteristics of stone having the greatest influence on the quality of asphaltic concrete mixes. Using andesites and dacites with extremely different properties for standard asphaltic mixes has proved that quality of the mixes very much depends on the quality of the stone aggregate used. Properties of stone aggregate of different degree and type of alteration have a significant influence on the rheological characteristics of bitumen. Therefore, special attention has been paid to this influence.     

An in-depth analysis of Raman and near-infrared chemical images of common pharmaceutical tablets

This study reports on the application of Raman and near-infrared (NIR) imaging techniques for determining the spatial distribution of all (five) components in a common type of pharmaceutical tablet manufactured in two different ways. Multivariate chemical images were produced as principal component (PC) scores, while univariate images were produced by using the most unique spectra selected by the orthogonal projection approach (OPA), a searching algorithm. Multivariate Raman images were obtained for all five components in both tablets, while only two or three components could be imaged with the NIR instrument. Very interesting PC results are reported that in effect cast doubt on the effectiveness of the established criteria for determining signal-related PCs in the Raman data. PCA has been found to be indispensable for imaging the minor components using the Raman data. Significant similarity between the multivariate and univariate chemical images has been noted despite there being considerable spectral overlap within the Raman and, especially, within the NIR mapping data sets. Gray-scale images are carefully thresholded, which allowed for quantitative comparison of the obtained binarized images. A thorough discussion is given on the problems and approximations needed for producing composite images.     

Blackberry seed extracts and isolated polyphenolic compounds showing protective effect on human lymphocytes DNA

The tentative identification of seed extracts from 3 cultivars of blackberry (blackberry seed extracts [BSEs]) constituents was performed by LC/UV/MS technique. The identified compounds belonged to ellagitannins, galic acid derivatives, and ellagic acid derivatives. Two ellagitannins, Lambertianin C and Sanguiniin H-6, and an ellagic acid derivative, 4-α-L-arabinofuranosylellagic acid, were isolated using semipreparative High-performance liquid chromatography. The structure elucidations were based on high resolution-mass spectrometry and nuclear magnetic resonance studies. The BSEs and 3 isolated pure compounds were tested for in vitro protective effect on chromosome aberrations in peripheral human lymphocytes using cytochalasin-B blocked micronucleus (MN) assay. The frequency of MN was scored in binucleated cells, and nuclear proliferation index was calculated. Among the tested extracts, the seeds of cv. Thornfree at concentration of 1 μg/mL exhibit the most prominent effect decreasing the frequency of MN by 62.4%, when compared with the controls cell cultures. Antioxidant potential of pure ellagitannins cannot explain the strong effect of BSEs. The assumption was that better antioxidant effect of BSEs result from synergistic effects of individual compounds contained in the extracts and/or some minor components possessed strong activity. PraCTICAL APPLICATION: Our results provide evidence of protective effects of BSEs and isolated pure compounds on cytogenetic damages in human lymphocytes. Thus, BSEs could exert beneficial effects in quite a few diseases, because many of the biological actions have been attributed to their antioxidant properties.     

A Model for Explosive Reactive Armor Interaction with Shaped Charge Jet

Study of interaction of explosive reactive armor (ERA) with shaped charge jet is the basis for evaluation of the effectiveness of ERA. The physically based theoretical model of this interaction is given. It is incorporated in the NERA computer code. The influences of backward moving plate and forward moving plate thickness, explosive layer thickness, jet attack angle, and distance between ERA and main armor are investigated. The comprehensive analysis of a longitudinal point of impact effect on ERA efficiency, based on NERA code calculations, is presented. Computational results of NERA code are compared with experimental data. The computational and experimental results of penetration in the steel armour target are in good agreement. The developed code enables optimization of explosive reactive armor characteristics.     

An improvement in the calculation of the magnetic field for an arbitrary geometry coil with rectangular cross section

Hong Lei, Lian‐Ze Wang and Zi‐Niu Wu presented new simple and convenient solutions of the magnetic field for an arbitrary geometry coil with rectangular cross section. They treated two types of basic forms: the trapezoidal prism segment and curved prism segment. The curved prism segment has been divided into a series of small trapezoidal prism segments with the same cross section and its magnetic field is a vector sum of the individual fields created by each small trapezoidal prism conductor. For one trapezoidal prism conductor the magnetic field is obtained by 1‐D integrals using Romberg numerical integration. In this paper, we give a completely analytical solution of these 1‐D integrals that considerably saves the computational time especially in the computation of the magnetic field nearby the conductor surface, at the conductor surface and inside the conductor. From obtained analytical expressions the treatment of singularities can be easily done. Also, we tested four types of numerical integration (Gaussian, Romberg, Simpson and Lobatto) to find the most convenient singularity treatment of 1‐D integrals. These obtained results are compared with those obtained analytically so that one can understand the advantage of the proposed approach. The paper points out on the accuracy and the computational cost. Copyright © 2005 John Wiley & Sons, Ltd.     

Aeroelastic applications of the Connection Machine

This paper describes the implementation of a dynamical systems approach to aeroelastic analysis using the Connection Machine model 2 (CM-2). Through numerical simulation, the regions of harmonic and chaotic behavior in the δ,R_x (velocity, in-plane load) plane have been examined in detail. These regions are of interest in evaluation of the fatigue life of fluttering plates. The CM-2 computer architecture allows the removal of many of the previous simplifying and limiting assumptions regarding the prediction of the stability regions maps. Owing to its high-speed prediction capability, the CM-2, with framebuffer, offers 'real-time' display of the solution as it evolves during the prediction process. This feature gives insight into the fundamental way in which the solution evolves. This is essential in defining the scenarios describing roads to chaotic behavior of the dissipative dynamical systems.