Hybrid-directional planning: improving improvement heuristics for scheduling resource-constrained projects

The resource-constrained project scheduling problem (RCPSP) has been of a continuing interest and challenge for researchers and practitioners since its advent. The formidable computational requirements of the RCPSP have resulted in numerous attempts to develop heuristic procedures, leading to the interest in improvement heuristics. Traditionally, such heuristics constructed a schedule by the scheme of forward, backward, or bidirectional planning directions. In this paper, we introduce a hybrid-directional planning that can make all improvement heuristics (e.g., meta-heuristics) more effective in solving the RCPSP. To validate its effectiveness, the proposed scheme is incorporated into three popular meta-heuristics, including genetic algorithm, simulated annealing, and Tabu search. A comprehensive numerical investigation shows that the performance of such meta-heuristics is significantly increased by using the hybrid-directional planning, which indicates that such a hybrid planning direction will hopefully encourage researchers and practitioners to apply it to different improvement heuristics for solving the RCPSP.     

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.

     

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     

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.     

Multi-heuristic desirability ant colony system heuristic for non-permutation flowshop scheduling problems

Ant colony optimization (ACO) is a novel intelligent meta-heuristic originating from the foraging behavior of ants. An efficient heuristic of ACO is the ant colony system (ACS). This study presents a multi-heuristic desirability ACS heuristic for the non-permutation flowshop scheduling problem, and verifies the effectiveness of the proposed heuristic by performing computational experiments on a well-known non-permutation flowshop benchmark problem set. Over three-quarters of the solutions to these experiments are superior to the current best solutions in relevant literature. Since the proposed heuristic is comprehensible and effective, this study successfully explores the excellent potential of ACO for solving non-permutation flowshop scheduling problems.     

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.     

The formation of quantum dot structures in 30-pair InGaN/GaN multiple quantum wells after proper thermal annealing treatment

This study systematically investigates the relation between strain energy and quantum dot (QD) formation for 30- pair InGaN/GaN multiple quantum wells (QW) by means of atomic force microscopy and high-resolution transmission electron microscopy. The results show that a higher number of quantum wells induce a higher strain energy and higher density of V-shaped defects, which increases the number of non-radiative centers. However, after thermal annealing, the strain energy accumulated from stacking faults is released and leads to the formation of a QDs structure. The strain energy around the quantum dot structure was calculated using by the NCEM Phase Extensions to the Digital Micrograph. The zone of higher strain energy was observed, which proves that the strain energy is the driving force for the formation of quantum dot structures.     

Applying PSO-based BPN for predicting the yield rate of DRAM modules produced using defective ICs

Dynamic random access memory (DRAM) modules are an important component of electronic equipment, impacting the quality, performance, and price of the final product. A typical DRAM module is composed of DRAM integrated circuits (ICs). DRAM ICs of higher quality can be used to produce DRAM modules of higher quality. However, high-quality DRAM ICs are more costly. Some DRAM module manufacturers purchase batches of DRAM ICs containing defective units and then have the batch tested in order to select DRAM ICs for production of DRAM modules. This type of DRAM module is suitable only for products not intended for work in harsh environments or being sold in lower price markets. Due to the lower quality of the DRAM ICs, the actual quality of the DRAM module is not easily predicted. Predicting the yield rate of the DRAM module is thus an important issue for DRAM module manufacturers who purchase DRAM ICs of lower quality. This study uses a back-propagation neural network (BPN) to predict the yield rate of the DRAM modules produced using defective DRAM ICs. BPN is a very capable method and has been successfully applied across many fields. However, network parameters and input features differ depending on the application. Thus, a particle swarm optimization approach is proposed to obtain suitable parameters for the BPN and to select beneficial subsets of features which result in a better prediction of the DRAM module yield rate. The experimental results showed that it outperforms traditional stepwise regression analysis.     

A new simple and reliable method to form a textured Si surface forthe fabrication of a tunnel oxide film

In this work, a textured Si surface was formed with a new simple and reliable method for tunnel oxide fabrication. First, a thin poly-Si layer (12 nm thick) was deposited on Si surface and a 30-nm thick dry oxide film was then grown in O₂ ambient. This oxide film was served as a sacrificial oxide. The poly-Si film and Si substrate were both oxidized during thermal oxidization. After stripping this sacrificial oxide, a textured Si surface was obtained. Tunnel oxide grown on this textured Si surface has asymmetrical J-E characteristics, less interface states generation and better reliability (larger Q_bd ) as compared to those of normal oxide