小波去噪和混沌理论应用于输电线缺陷检测

为了解决在利用电磁超声检测高压输电线路缺陷时,回波信号微弱且易被强大的电磁噪声覆盖而难以提取的问题。认真研究了Duffing方程和小波理论。将小波去噪技术和混沌理论结合起来,设计了一种新型微弱信号检测系统。利用MATLAB/Simulink对系统进行了仿真。实验结果证明,此系统能有效检测强电磁背景下的超声信号,进一步降低了系统的输出信噪比,提高了检测性能。     

Steady-state performance of synchronous generators with AC and DCstator connections considering saturation

Synchronous generators with AC and DC stator connections are widely used in systems where simultaneous AC and DC power supplies are needed. For these systems the voltage harmonic distortion of AC voltage, DC voltage ripple and DC voltage varying range are of special interest. Because of the commutation of rectifier and the saturation of magnetic circuit, the accurate calculation of voltage harmonic distortion and DC voltage varying range is comparatively difficult. This paper describes a mathematical model on the basis of multiloop method and FEM, which aims at calculating the steady-state characteristics and the voltage waveforms of AC winding accurately. With this method, the full synergic effects of space harmonics resulting from the magnetic circuit geometry, saliency, saturation, winding layouts, and slotting are included. The calculated results are compared with those of experiments     

威金斯气柜调平钢丝绳断丝原因分析及解决措施

通过威金斯气柜调平钢丝绳损伤机理的分析,经过钢丝绳破断拉力计算,查找钢丝绳断丝的原因,提出了调平钢丝绳的选型。     

Structure and properties of PMN–PT/NZFO laminates and composites

Magnetoelectric (ME) materials of laminated and bulk composites of 0.65Pb(Mg_1/3Nb_2/3)O₃–0.35PbTiO₃ (PMN–PT) and Zn-doped ferrite Ni_0.8Zn_0.2Fe₃O₄ (NZFO) were prepared. The weight ratio of PMN–PT to NZFO in the composites was 5:1. ME coefficients of the laminated and bulk samples at 1.1 kOe magnetic bias were 91 mV/cm Oe and 64 mV/cm Oe, respectively. The ME coefficient of the bulk sample reached 406 mV/cm Oe under a magnetic bias of 0.26 kOe, which was much higher than the reported value in the composite of PZT and nickel ferrite. One of the findings in this study is that a non-uniform distribution of magnetic material in the bulk may lead to enhanced ME effect.     

基于滚铣两步加工的余弦齿廓创成方法研究

基于齿轮啮合原理和数控加工理论,提出一种余弦齿廓滚铣两步加工新方法,即首先利用标准渐开线滚刀滚切出渐开线变位齿轮作为粗加工,并使其加工余量最小;再在此基础上利用立式三轴数控铣床进行铣削成形精加工.建立余弦齿廓滚切加工最小变位系数的数学模型,推导出余弦齿廓铣齿运动的空间转换矩阵,得到三轴数控铣齿成形的通用运动控制模型,分别确定滚齿和铣削的加工刀具选择方法,避免加工过程中出现"过切"及"欠切"现象.最后通过具体实例进行Matlab和Pro/E加工仿真,验证理论模型的正确性和加工方法的可行性.     

Control of the dual mechanical port electrical machine and its applications in hybrid electrical vehicle

This paper deals with the control strategy of the dual mechanical port electrical machine (DMPEM) which is suitable for hybrid electrical vehicles. In particular, it discusses the power management algorithm of the electrical variable transmission (EVT) system based on DMPEM. Also an equivalent circuit of DMPEM has been proposed for the first time, which gives clear physical meanings to all components in the circuit. The power flow of DMPEM under different operating conditions is analyzed from the equivalent circuit. The proposed control strategy is validated on a simulated EVT experiment platform. The result proves its validity. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

清华大学飞轮储能技术研究概况

全面回顾了清华大学在过去17 年内坚持飞轮储能技术研究开发的总体情况。介绍了6 种飞轮储能试验研究系统和工程样机的技术特征,分析了研制过程中遇到的飞轮轴系稳定性、电机设计、充放电控制器调试等关键技术难题,探讨了飞轮储能技术工业化应用开发中应注意的问题。     

氧压酸浸处理锌焙砂中浸渣的新工艺研究

锌焙砂一般采用中性-低酸-高酸三段浸出工序,该工艺在酸浸出中浸渣的过程中,铁也大量浸出进入到溶液中,加重了净化电积前除铁的负担。通过将传统锌湿法冶金工艺与氧压酸浸新工艺相结合,研究了氧压酸浸处理中浸渣的氧气压力、硫酸浓度、温度、浸出时间、粒度、液固比和分散剂等相关因素的影响。实验结果表明该工艺不仅提高了锌的浸出率（〉98％）,降低了铁的浸出率（〈50％）,缩短了生产周期,降低了生产成本,具有良好的经济效益;而且还具有环境友好和资源利用率高等优点,实现了简化工艺和节能减排的目的,为工业化生产提供了参考．     

茂名BOPP专用料的生产与应用

介绍我国双闰伸聚丙烯（ＢＯＰＰ）原料生产及加工行业的现状,明确了ＢＯＰＰ原料市场的开发方向。根据目前原料在加工过程中存在的质量问题。结合上下游生产工艺特点,有针对性地设计原料生产过程控制方案。乎批试生产的ＢＯＰＰ料Ｔ３６Ｆ,经加工厂家应用,产品质量达到国内先进水平。     

内撑式预应力撑杆柱的稳定承载能力试验研究

采用预应力撑杆柱是提高细长型钢柱稳定承载能力的有效方法。本文在分析预应力撑杆柱受力特点的基础上,结合南京图书馆新馆的工程实际,对5根内撑式预应力撑杆柱进行了稳定承载能力模型试验研究,并进行了2根细长形方钢管柱和3根方钢管混凝土柱的模型试验作为对比。重点研究了不同长细比、不同柱截面形式、不同支座约束条件的预应力撑杆柱的稳定承载力。本文的试验与分析结果表明,只要设计合理,内撑式预应力撑杆柱与同尺寸的钢管柱相比具有更高的稳定承载能力,是一种安全、可靠、美观的结构构件。文章还对背景工程内撑式预应力撑杆柱的设计和施工提出了参考建议。