Modeling of terminal ring structures for high-voltage power MOSFETs

To achieve a high blocking voltage, a power MOSFET is often guarded with multiple floating field limiting rings (MFFLRs) to re-distribute the electric field for extending the breakdown voltage. However, this high-voltage protecting structure occupies a significant silicon area of the power MOSFET. The breakdown field of a floating ring depends on the junction curvature, sizes of the rings and the spacing between the rings. A good design can reduce the total silicon area of the MOSFET transistor by optimizing the floating ring design through modeling. The conventional approach was based on the classical breakdown field model originally developed for the low-voltage p–n junction which has limited precision in the medium to high electric field range. In this work, a precise fitting model for the MFFLR structure with high junction breakdown voltage is proposed. Measurement results of the breakdown voltage of the MOSFETs for the MFFLR structure are presented.     

Designing crease patterns for polyhedra by composing right frusta

We propose an original and novel algorithm for the automatic development of crease patterns for certain polyhedra with discrete rotational symmetry by composing right frusta. Unlike existing algorithms, the folded product will conform to the surface of the target polyhedron without external flaps. The crease patterns of frusta are drawn first and then composed by the algorithm to draw the crease pattern of the rotationally symmetric polyhedron. The composition is performed by splitting creases that were folded on pleats from frustum crease patterns. A CAD program has been written to implement the algorithm automatically, allowing users to specify a target polyhedron and generate a crease pattern that folds into it.     

Resistance Microwelding of Ti-55.8?wt?pct Ni Nitinol Wires and the Effects of Pseudoelasticity

Nitinol has revolutionized many traditional engineering designs with its unique properties that include pseudoelasticity and the shape-memory effect (SME). However, the general lack of understanding on welding Nitinol limits its full potential in practical applications. The current study examined the microstructure and mechanical properties of resistance microwelded (RMW) Ni-rich Nitinol wires at different applied currents. The results revealed a solid-state bonding mechanism that consisted of six main stages, including (1) cold collapse, (2) dynamic recrystallization, (3) interfacial melting, (4) squeeze out, (5) excessive flash, and (6) surface melting. The joint strength and fracture mechanism were linked closely to the metallurgical properties of the welds. Through differential scanning calorimetry (DSC) testing, it was found that the weld metal underwent phase transformation at lower temperatures compared with the base material. Also, the pseudoelastic property of Nitinol was found to have a large effect on the contact resistance during the onset of welding current. Compression tests with varying temperatures confirmed distinct differences in displacement (i.e., cold collapse) under the welding load of 5?kg-f caused by changes in the thermodynamic stability of the austenite phase. Both the dynamic resistance and displacement measurements were found to be significantly different during the RMW of Nitinol crossed wires compared with welding 316 low-vacuum melted (LVM) stainless steel (SS) crossed wires.     

Predictor-corrector type multi-rate sample hold for continuous estimated outputs

A novel predictor-corrector hold (PCH) that yields continuous estimates for all instances is proposed for multi-rate control systems. The principle, characteristic, and performance of the PCH are analyzed. Through a comparison with other conventional holds, the efficacy of the proposed PCH is validated.     

集成电路电磁兼容测试PCB设计

PCB设计为集成电路电磁兼容测试过程中的一个重要环节,对测试结果的精确度有很大影响,并且与常规PCB设计又有比较大的差异.为提高集成电路电磁兼容测试数据的精准度,基于ICEMC测试标准中对PCB设计的要求,对测试PCB设计中的问题进行了研究分析及解决方法验证,给出了三种屏蔽方法设计方案,明确了过孔间距约束的计算方法,提出去耦电容选型原则及I/0负载匹配方法.通过典型测试案例,从PCB结构设计、布局及布线三个方面进行了详细阐述.旨在为IC研发人员和电磁兼容检测人员提供指导和参考.     

Analysis of the Chirped Super Moiré Gratings Based on Acousto-Optical Superlattices

There are multiple passbands in a chirped Bragg grating based on acousto-optic superlattice. The structure can be regarded as an acousto-induced super Moiré grating (AI-SMG). The analysis shows that the passbands of the AI-SMG are produced by several pairs of neighboring chirped gratings. With suitable structure parameters selected, the passbands can be non-larenzian-shape, narrow flat-top, with ripple less than 0.5dB and steep slope. The devices can be used as tunable narrow-band multichannel transmission filters. This analysis is useful for the designs and applications of the devices.     

Magnetohydrodynamic flow in a rectangular duct with suction and injection

Summary The effects of suction or injection on an incompressible laminar flow in a rectangular duct with nonconducting walls in the presence of an imposed transverse magnetic field are examined. Analytical solutions are obtained for the velocity and magnetic field, which are useful for obtaining the current density and electric field strength.     

On the interplay of cell thickness and optimum period of silicon thin‐film solar cells: light trapping and plasmonic losses

Light trapping and photon management in honeycomb‐textured microcrystalline silicon solar cells are investigated experimentally and by modeling of the manufacturing process and the optical wave propagation. The solar cells on honeycomb‐textured substrates exhibit short circuit current densities exceeding 30 mA/cm² and energy conversion efficiencies of up to 11.0%. By controlling the fabrication process, the period and height of the honeycomb‐textured substrates are varied. The influence of the honeycomb substrate morphology on the interfaces of the individual solar cell layers and the quantum efficiency is determined. The optical wave propagation is calculated using 3D finite difference time domain simulations. A very good agreement between the optical simulation and experimental results is obtained. Strategies are discussed on how to increase the short circuit current density beyond 30 mA/cm². In particular, the influence of plasmonic losses of the textured silver (Ag) reflector on the short circuit current and quantum efficiency of the solar cell is discussed. Finally, solar cell structures with reduced plasmonic losses are proposed. Copyright © 2015 John Wiley & Sons, Ltd.     

A study of construction mediator tactics—Part II: The contingent use of tactics

Mediation is a dynamic process. A mediator facilitates a settlement through the appropriate use of tactics that adapt and respond to the situational factors as the mediation progresses. This is described as the contingent use of tactics and is one of the prerequisites for mediation success. Having a better understanding of this contingent use of tactics is crucial to the practicing construction mediators as well as researchers. In the first of the companion papers, principal component factor analyses were employed to develop taxonomies for the three mediation dimensions; dispute sources, mediator tactics and mediation outcomes. Part II of the companion papers presents a study on the contingent use of mediator tactics in relation to the dispute sources and mediation outcomes. To achieve this objective, factor scales for the three mediation dimensions were first derived. Moderated multiple regressions (MMR) was then performed on these factor scales to detect the contingent effect of tactics on outcomes respective to the dispute sources. By examining the changes in the R²$R^2$ values of the moderated regression equations, the effectiveness of tactics in bringing about the desired outcomes were investigated. The tactics of Trust Building and Reality Test were found to be the most versatile tactics. These reaffirm the industry belief that disputes are in fact problems that can be solved if pragmatic and sensible approaches are taken instead of the entrenched confrontational attitude. More significantly, the exercise of such approaches can only be possible in a trusting environment. These findings also add strength to the current endeavors in co-operative contracting as in partnering and strategic alliances.