Improved reverse recovery of self-adaptingp emitter efficiency diodes (SPEED)

Contents A fastpnn ⁺ power diode is described, which due to a self-adaptingp emitter efficiency shows an essentially improved reverse recovery behaviour. Thep emitter consists of ap ⁺ region with high injection efficiency and of ap region which has low injection efficiency and densely intersperses thep ⁺ region. The lateral extension of thep ⁺ areas between thep elements and the vertical doping profile of thep region are chosen in such a manner, that the high efficiency of thep ⁺ region becomes effective only at high currents, reducing the forward voltage drop. Up to the normal operative forward current the carrier concentration at the anode side of the base region is smaller than near thenn ⁺ junction. By commutation, this results in a strong reduction of the peak reverse current and a significantly softer reverse current decay compared with standard diodes designed for the same forward and blocking voltages. Modeling calculations as well as measurements on the operation principle and switching behaviour are presented.

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Verbessertes Rückwärtserholungsverhalten von Dioden mit sich selbst anpassenderp-Emitter Efficiency

Übersicht Es wird eine schnellepnn ⁺-Leistungsdiode beschrieben, deren Rückwärtserholungsverhalten (Recovery-Verhalten) infolge einer sich selbst anpassendenp-Emitter Efficiency stark verbessert ist. Diep-Zone besteht aus einemp ⁺-Bereich mit hohem Emitterwirkungsgrad und einemp-Bereich mit niedrigem Injektionsvermögen der denp ⁺-Bereich dicht durchsetzt. Die laterale Ausdehnung derp ⁺-Gebiete zwischen denp-Teillen sowie das vertikale Dotierungsprofil desp-Bereichs werden so, gewählt, daß der hohe Emitterwirkungsgrad desp ⁺-Bereichs erst bei hohen Strömen wirksam wird und die Durchlaßspannung verkleinert. Bis zum üblichen betriebsmäßigen Durchlaßstrom ist die Ladungsträgerkonzentration an der Anodenseite der Basis kleiner als amnn ⁺-Übergang. Dies führt beim Kommutieren zu einer starken Verkleinerung der Rückstromspitze und einem wesentlich weicheren Abfall des Rückstroms (Soft-Recovery-Verhalten) als bei üblichen schnellen Dioden gleicher Durchlaß- und Sperrspannung. Simulationsrechnungen wie auch Meßergebnisse zur Wirkungsweise und zum Schaltverhalten werden vorgestellt.

     

Degradation of PLA and PLA in composites with triacetin and buriti fiber after 600 days in a simulated marine environment

Poly(lactic acid) (PLA), the polymer object of this study, degrades by a biotic process after an abiotic hydrolysis process. Its degradation was evaluated after 600 days of exposure in a simulated marine environment (SME), as buriti fiber‐reinforced composites having triacetin as coupling agent. Composites were obtained by extrusion and films were produced by compression molding. After between 60 and 600 days of exposure, PLA had a weight loss of 2.5%, PLA/T of 1.5%, and 10–12% of weight loss for PLA/B and PLA/B/T, respectively. PLA intercalates reduction, increase, and decrease of its crystallinity attributed to hydrolysis (up to 15 days), impairment of amorphous segments (45 days), and loss of integrity of the matrix (100–600 days), respectively. In the PLA/T composites, triacetin inhibited the diatom colonization process, having its crystallinity values increased after nearly 100 days of exposure with subsequent reduction. For samples with buriti fiber, changes in crystallinity were attributed to absorption of water and exposure of matrix amorphous segments. PLA degradation in a SME is evidently favored by the use of natural fibers since they make easier water access to the matrix and colonization by the protists group, diatoms, showing that the polymer can have reduced post‐use shelf life as composites, with benefits while in use and at the same time post‐use environmental benefits. Triacetin inhibits PLA colonization and degradation up to 45 days after exposure, after which it no longer influences the degradation process. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43290.     

Design and implementation of a vision processing system for awalking machine

A vision processing system for a six-legged walking machine, the adaptive suspension vehicle, is presented. The vision-processing system consists of a laser range-finder, and vision computer, a terrain-elevation map, and a guidance computer. The range-finder measures the distances from itself to the objects in the scene. The specially designed vision computer processes the range data into a terrain-elevation form and stores the information with time data in a terrain-elevation map. With the real-time elevation information in the map, the guidance computer can select the best footholds for the walking machine in order to maneuver over rough terrain     

Verwertung von Natriumsulfat

Utilization of sodium sulphate. Commercial sodium sulphate is usually obtained by crystallization and calcination. Processes for utilizing sodium sulphate that have previously been studied or used are mainly the following methods: electrochemical processes, conversion processes, and reduction processes. At present the first two groups of these three appear more advantageous than the reduction processes, which are technically complex and suffer from the formation of waste gases. The lower energy requirements of the conversion processes offer advantages over electrolytic methods. Only comparative cost estimates for the different processes could help one arrive at a sound evaluation.     

A transportation land use model for rural areas

This paper examines the interaction of transportation and land use in rural areas. The spatial distribution of employment and population is complicated by many factors such as accessibility, income variance, prices, geographical characteristics, and government intervention. This analysis attempts, by using twostage least squares, to isolate the impact on employment and household density of changing transportation cost as measured by accessibility. The results indicate that the accessibility measure used in this study is a sensitive transmitter of changes in a transportation system. The accessibility coefficient derived from a reduced-form equation was used to forecast the impact of a transportation change.The author would like to thank Charles Floyd and Paul Wendt for their helpful comments, and Michael Rowan for his computational work on the accessibility matrix.     

Comparative investigation of plain and silver impregnated activated carbons for the removal of cyanide from basic aqueous solutions in the batch process

Purolite AC-20 and Norit RB 0.8CC activated carbons impregnated with AgNO₃ were used for the removal of CN^– and Ag–CN complex from model wastewater. The formed Ag⁰ centers were approved by scanning electron microscopy micrographs and X-ray powder diffraction data. The degree of Ag⁰ participating in CN^– sorption varied from 100 to 45% on AC-20/Ag and from 100 to 73% on RB 0.8CC/Ag, by varying [CN^–]/[Ag] in the initial solution from 2.0 to 19.2. The Freundlich isotherm and Fleming kinetic models were consistent with the experimental data. The K_F values for the CN^– adsorption on AC-20/Ag and RB 0.8CC/Ag increased by a factor of 1.2 and 1.5, but they lowered for Ag–CN adsorption by a factor of 4.1 and 2.1, respectively, as compared to that of plain activated carbons. The removal of 90% cyanides is appropriate by combining two batches from activated carbon: impregnated, mainly for the removal of CN^–, and plain, removing the rest of Ag–CN.     

改进输配电系统接线以改善电能质量的评估

电能质量问题已经引起全球许多电力公司的重视。特别是当今制造业中广泛应用的自动化系统中的电子设备对供电质量提出了更高的要求 ,因此电能质量问题成为电力公司计划与设计及供电系统运行中的关键。在一个互连系统中 ,当有故障发生时 ,来自故障相的故障电流将会引起网络其它正常部分的电压下降。一旦故障排除 ,根据网络的阻抗水平 ,系统电压将即刻恢复到它的正常状态。这种电压的突然下降和随后的迅速恢复就被称作电压骤降。电压骤降是当今电能质量干扰中最常见的几种类型之一。引起电压骤降的最典型的原因是电力系统上发生短路、大电动机…     

Synthesis and structural investigations on aluminium-free Ti-Beta/SBA-15 composite

An aluminium-free Ti-Beta/SBA-15 composite material was prepared by the post-synthesis incipient wetness-deposition of different amounts of Ti-Beta nanoparticles solution on the SBA-15 matrix. The presence of crystalline nanoparticles in the solution, used for impregnation on SBA-15, was confirmed by HRTEM measurements. The hexagonal arrangement of the mesopores of SBA-15 was proven by XRD and TEM measurements. The presence and the deposition of Ti-incorporated zeolitic nanoparticles on the mesopore walls of SBA-15 were proven by nitrogen sorption analysis, IR spectroscopy and TG analysis. The X-ray absorption spectroscopy analysis of local environment of titanium incorporated in the new composite material showed that the product contained five fold coordinated framework titanium. These Ti sites can be oxidation titanium sites.     

AN LMI APPROACH TO ROBUST H∞ CONTROL FOR UNCERTAIN CONTINUOUS‐TIME SYSTEMS

This paper investigates the problems of robust H∞ control for uncertain continuous‐time systems with time‐varying, norm‐bounded uncertainties in all system matrices. Necessary and sufficient conditions for the above problems are proposed. All conditions are represented in the form of linear matrix inequalities (LMIs). The robust H∞ controller can be easily designed from the solutions of the LMI conditions. Unlike earlier works, the proposed method does not involve any parameter tuning. Thus the robust H∞ optimization control problem, which has not been discussed in earlier reports, can be dealt with using this newly proposed method.