Relationship Between Embedding Depth and Residual Stress in the cBN Grain of Monolayer Brazed Abrasive Tools

The relationship between the embedding depth and the residual stress in the brazed cBN grains is analyzed experimentally in order to optimize the embedding depth of grains in the monolayer brazed abrasive tools. It is found that the residual stress is stable without remarkable gradient in the core zones of the brazed grains. However, the stress distribution gradient is rather great in the regions such as both ends of the central axis, the margin region of the central plane in the cBN grains, and the margin region of the section plane between the grains and the filler top. The maximum tensile stress in the margin zone of the brazed cBN grains has the most important influence on the mechanical property of the grains. The embedding depth is accordingly optimized at 30-40% of the total height of cBN grain.     

基于可靠性的配电网规划思路和方法 讲座六 可靠性与费用的关系

规划人员在考虑配电网应具有良好的可靠性时,面临的主要挑战是如何处理可靠性与费用的关系。基于可靠性规划最终的问题就是要在定额资金的范围内获得尽可能高的供电可靠性,或以尽可能少的费用获得特定水平的供电可靠性。重点介绍了基于成本效益的可靠性改进方法(CERI),是能有效处理可靠性与费用关系的一种方法,该方法简单实用、无需建模和复杂计算。介绍了可靠性的投资分配的基本概念以及CERI的6个基本步骤,最后给出了一个应用示例。     

选区激光熔化成型悬垂结构的计算机辅助工艺参数优化

为了提高选区激光熔化(SLM)成型悬垂结构的质量,从调节成型方向和能量输入入手研究悬垂结构的计算机辅助工艺参数优化。以减小零件模型整体难成型悬垂面的面积为目标,以零件模型非成型方向的两个旋转角度为优化变量,建立成型方向的优化模型,并基于遗传算法实现优化模型参数的求解。通过遍历零件模型中的所有三角面片,建立倾斜角静态查找表,并在成型时查表实现能量输入的实时调节。实验结果表明,经成型方向优化,零件模型难成型悬垂面的面积从555.12mm2减小为16.211mm2,所需支撑数量明显减少;成型后所得零件无明显悬垂物和翘曲变形,成型质量明显改善。     

多晶体材料微构件尺度效应的实验和模型研究

归纳了微电子机械系统中多晶体材料微构件在微塑性加工和应用中其力学性能所表现出来的尺度效应及其多种尺寸关联的主要特征,介绍了微构件外形几何尺寸和材料内部微结构尺寸对其弹、塑性力学性能尺度效应耦合影响的实验和模型研究的主要进展。重点总结并分析了多晶体材料微构件越小越强和越小越弱两种类型尺度效应的研究方法以及测试、影响因素及微观机理初步分析的结果。结论是:微构件内、外尺寸的耦合关联影响控制了尺度效应和与其相对应的材料内在特征长度,今后如能进一步探明微构件外形结构尺寸、晶粒尺寸和材料内在特征长度与其性能异变之间的制约关系,基于晶体学和高阶理论建立较全面、系统的力学分析模型,将有可能揭示微构件多晶材料内在特征长度的微结构控制的机理,进而实现通过调控材料的微结构控制微构件的宏观力学性能。     

Zinc-Modified ZSM-5 Nanozeolites Synthesized by the Seed-Induced Method: Interrelation of Their Textural,Acidic, and Catalytic Properties in DME Conversion to Hydrocarbons

The effect of the method of introduction of zinc cations and the zinc content in a nanocrystalline zeolite of the ZSM-5 type on the physicochemical and catalytic properties of the material in DME conversion to a mixture of liquid synthetic hydrocarbons has been studied. Zinc is introduced into the catalysts both during the zeolite synthesis and the ion exchange (Zn _n Al _m NZ5 and ZnNZ5, respectively). The use of nanocrystalline Zn _n Al _m NZ5 zeolites provides the formation of a mixture of liquid hydrocarbons with a high selectivity of no less than 90%; the liquid hydrocarbons contain more than 70% of isoparaffins and a small amount of aromatic compounds. An increase in the zinc loading of the Zn _n Al _m NZ5 zeolite from 0.9 to ~3% leads to an increase in the methanol content in the aqueous phase of the liquid product, an increase in the selectivity for liquid hydrocarbons, and a slight increase in the concentration of aromatic and unsaturated hydrocarbons in the mixture. In the presence of the ZnNZ5/Al₂O₃ catalyst with Zn introduced by ion exchange, the methanol content in the aqueous phase and the aromatics content in the liquid hydrocarbon mixture are significantly higher. The Zn _n Al _m NZ5 nanozeolites are characterized by a more developed external surface, a higher concentration of mesopores, and higher acidity.     

微波器件失效率快速试验方法研究

介绍了微波低噪声GaAs FET恒定应力加速寿命试验结果,沟道温度T_(ch)为145℃时,平均寿命MTTF为9.64×10~6h,最主要的失效模式是源漏饱和电流I_(DSS)退化降低。建立了表征GaAs FET稳定性的敏感参数I_(DSS)的退化模型InP=a+blnt,分析了I_(DSS)退化与温度应力的加速关系。提出了快速推断器件可靠性的建议。     

非平面接地静磁表面波延迟线的优化设计＊

本文改进了非平面接地静磁表面波延迟线器件模型,并首次采用递归二次规划对器件结构进行了优化设计,为静磁波器件设计提供了新途径。     

Donor–acceptor copolymers based on benzo[1,2-b:4,5-b′]dithiophene and pyrene-fused phenazine for high-performance polymer solar cells

Two novel donor–acceptor (D–A)-type conjugated polymers of PTTPPz-BDT and PTTPPz-BDTT were successfully synthesized by Stille coupling polymerization, in which 7,8-dialkoxy benzo[1,2-b:4,5-b′]dithiophene (BDT) and 7,8-bithienyl benzo[1,2-b:4,5-b′]dithiophene (BDTT) were used as donor units, thiophene and pyrene-fused phenazine (PPz) were employed as π-bridges and acceptor units, respectively. High carrier mobilities, broad absorption spectra, narrow optical band gaps, and low HOMO energy levels were observed for both polymers. Furthermore, high-efficiency photovoltaic performance with power conversion efficiency (PCE) over 4.25% was exhibited in their polymer solar cells (PSCs) using [6,6]-phenyl-C₇₁-butyric-acid-methyl-ester (PC₇₁BM) as acceptor. The maximum PCE of 4.86% with short-circuit current density of 11.10 mA cm⁻² and fill factor of 62.5% was obtained in the PTTPPz-BDTT based cell. These results indicate that incorporating large planar PPz moiety into D–A-type copolymer is an efficient approach to improve photovoltaic performance for PSCs.     

High-brightness AlGaInP 573-nm light-emitting diode with a chirpedmultiquantum barrier

A novel chirped multiquantum barrier (CMQB) structure was used for AlGaInP light-emitting devices. We have theoretically studied the blocking efficiency of the CMQB structure and found that the CMQB structure is more effective in blocking the electron wave than the conventional uniform multiquantum barrier (UMQB) structure. AlGaInP light emitting diodes (LEDs) with the CMQB structure and the UMQB structure were both fabricated and compared. It was found that the luminescence intensity of the AlGaInP CMQB LED is larger and the intensity distribution of the AlGaInP CMQB LED is more uniform than the AlGaInP UMQB LED. The intensity-current measurement also shows that the electroluminescence intensity of the AlGaInP CMQB LED starts to saturate at a higher injection current