散料研磨工艺对工件表面质量及材料去除率的影响

通过实验探讨了散料研磨过程中磨料种类、磨料粒度和研磨剂装入量等工艺参数对工件表面质量和材料去除率的影响.实验结果表明,随磨料粒度的增大,工件表面粗糙度值、残余应力和材料去除率增大;采用相同粒度磨料研磨,磨料的硬度越高,工件表面残余应力和材料去除率越大.硬度高、脆性大的磨料,可有效减小研磨表面粗糙度值;随研磨剂装入量的增大,表面残余应力减小.对工件表面粗糙度和材料去除率而言,研磨剂装入量有一最佳值,装入量过小或过大,均会降低工件表面质量和研磨效率.     

应用于PWM转换器的高性能误差放大器

基于整个环路稳定性的分析,提出一种高性能误差放大器,该电路与芯片外围的反激式应用电路一起完成负反馈调节.基于700V BCD工艺,对该电路的应用芯片进行仿真和流片.测试结果表明,该电路产生的动态阻抗为18Ω,PWM增益为-25.3%/mA,满足工程应用要求,实现系统稳定输出.     

Facile synthesis of near-monodisperse Ag@Ni core-shell nanoparticles and their application for catalytic generation of hydrogen

Magnetically recyclable Ag-Ni core-shell nanoparticles have been fabricated via a simple one-pot synthetic route using oleylamine both as solvent and reducing agent and triphenylphosphine as a surfactant. As characterized by transmission electron microscopy (TEM), the as-synthesized Ag-Ni core-shell nanoparticles exhibit a very narrow size distribution with a typical size of 14.9 ± 1.2 nm and a tunable shell thickness. UV-vis absorption spectroscopy study shows that the formation of a Ni shell on Ag core can damp the surface plasmon resonance (SPR) of the Ag core and lead to a red-shifted SPR absorption peak. Magnetic measurement indicates that all the as-synthesized Ag-Ni core-shell nanoparticles are superparamagnetic at room temperature, and their blocking temperatures can be controlled by modulating the shell thickness. The as-synthesized Ag-Ni core-shell nanoparticles exhibit excellent catalytic properties for the generation of H(2) from dehydrogenation of sodium borohydride in aqueous solutions. The hydrogen generation rate of Ag-Ni core-shell nanoparticles is found to be much higher than that of Ag and Ni nanoparticles of a similar size, and the calculated activation energy for hydrogen generation is lower than that of many bimetallic catalysts. The strategy employed here can also be extended to other noble-magnetic metal systems.     

液晶显示器NVIS高亮LED背光源研究

提出了一种满足液晶显示器NVIS的高亮LED背光设计方法。介绍了白灯LED+OGB LED背光阵列优化设计,降低混光距离比、提高均匀度的方法,并通过试差法,对配色后测量结果进行分析,求出最佳配色方案;模拟与实验结果表明,该设计方法完全能够满足夜航要求。     

桥梁型式对40 m简支梁磁浮车致动力响应的影响

为研究不同型式的40 m简支梁在中低速磁浮列车作用下的动力响应及影响机理,基于40 m简支梁梁轨一体方案和梁上梁方案两种型式,考虑PID主动悬浮控制,采用模态综合理论,建立精细的中低速磁浮列车—简支梁系统动力相互作用理论模型,并基于长沙磁浮试验进行可靠性验证。对两种型式的40 m简支梁在低速磁浮列车作用下的动力响应进行分析及对比,探讨不同桥梁型式对系统耦合振动的影响机理。结果表明：相比于梁上梁方案,梁轨一体方案的竖向动挠度更大、加速度更小,车体竖向位移更大、加速度相近,梁上梁方案更优;桥梁型式对主动悬浮控制系统的影响较微弱;梁上梁方案中简支梁存在丰富的高频局部振动模态,会增大桥梁变形和桥梁、车体的振动优势频率;桥梁型式的不同会通过波长效应、局部振动等影响磁浮列车—轨道—桥梁系统的耦合振动。     

纳米陶瓷TiO_2的制备和特性

本文论述了用惰性气体原位加压（ＩＧＣ）法制备纳米级ＴｉＯ２粉体，并探讨了几种烧结方法中的工艺参数影响，研究了纳米晶的特性和超塑性机理     

Synthesis and characterization of polyurethane/polybenzoxazine‐based interpenetrating polymer networks (IPNs)

Sequential interpenetrating polymer networks (IPNs), based on polyurethane and polybenzoxazine, were synthesized. Fourier Transform infrared spectrometry was employed to monitor the formation kinetics, which indicated that only physical bonding existed in the resulting IPNs. Morphological investigations revealed a lightly phase separation behaviour in all of the IPNs studied. © 2003 Society of Chemical Industry     

南水北调调蓄工程经济性的探讨

用于调节南水北调工程来水的有两类水库，在这两类水库中，一类为已建水库，位于南水北调中线以西较高位置，叫做“高库”，例如黄壁庄水库；另一类为拟建水库，位于中线以东平原洼地，也叫“低库”，以大浪淀水库为例．技术经济指标分析表明，第一类水库的供水成本明显小于后者，故得出如下结论：利用某些已建“高库”的闲置库容调节南水北调来水可能是经济的．     

Alternative to the effective transmittance approach for the calculation of polychromatic transmittances in rapid transmittance models

Many current rapid transmittance algorithms, specifically the Optical Path Transmittance (OPTRAN), are based on use of effective transmittances to account for the effects of polychromatic radiation on the transmittance calculations. We document how OPTRAN was modified by replacing the effective transmittance concept with a correction term. Use of the correction term solves some numerical problems that were associated with use of effective transmittances, greatly reduces the line-by-line computational burden, and allows for the efficient inclusion of more gases. This correction method can easily be applied to any other fast models that use the effective transmittance approach.     

西方古代剧场建筑设计中的声学因素(四)——18,19世纪法国“启蒙时期”剧场设计中的声学因素

介绍了法国"启蒙时期"的建筑思潮,讲述了"新古典主义"时期法国剧场建筑的特点,并对法国波尔多大剧院、贝桑松剧场以及鲁保对景象厅剧场的设计方案进行了详细说明。在剧场建筑设计中"新古典主义"与"巴洛克"两种风格的相互批判又相互渗透中,汇成了折中的风格,在建筑中最明显地表现在法国巴黎国家大剧院的建筑上。这是一座在法国引以为荣的剧场建筑,详细介绍了该建筑的规模、布局及特点,该建筑充分地显示了"科学和民主"的鲜明倾向。