500 kV 开关弹簧机构支架螺栓断裂的原因分析及处理

HPL500B2型弹簧机构支架(BA)螺栓断裂可能导致开关分合闸失败,对其原因进行分析,发现BA螺栓由于预紧固力矩过大,接近其扭断力矩,使得作用在BA螺栓上的力偏高,BA螺栓安全系数仅为12%,安全系数较低。列出BA螺栓更换步骤及注意事项,并详细介绍分闸、合闸弹簧调整步骤,为类似事件的处理提供参考。     

3D Simulation Research on Urea-SCR DeNO<em>x Catalyst for Diesel Engine

In order to reduce oxides of nitrogen (NOx) emanated from a diesel eng ine, a comprehensive urea selective catalyst reduction (SCR) DeNOx catalys t was modeled in which numerical simulations were used as a complementary tool f or the experimental investigations to make the design decisions, and hence short en the development process. In this approach, relevant conversion reactions were studied in 1D model, and the parameters obtained in this way were transferred t o 3D simulations. According to the results ...     

二进制粒子群算法中V型转换函数的应用分析

二进制粒子群算法(BPSO)由于规则简单、参数设置较少等优点被广泛应用到各领域,但是其具有过强的全局搜索能力,缺乏局部的搜索能力等缺陷。针对BPSO存在的缺陷很多文献提出了改进方法,但是针对转换函数的改进较少。通过定义粒子间的距离来分析出BPSO所存在的缺陷,从而进一步分析BPSO中S型转换函数的缺点,并且有针对性地提出更符合BPSO要求的V型转换函数。实验结果表明,所提V型转换函数能克服原始BPSO的缺陷,相比S型转换函数以及现有文献所提的V型转换函数更能提升算法的性能,得到更高的分类准确率。     

Ultrasonic testing and microscopic analysis on concrete under sulfate attack and cyclic environment

The damage process of concrete exposed to sodium sulfate attack and drying-wetting cycles was investigated. The water to binder（W/B） ratio and the concentration of sulfate solution were taken as variable parameters. Through the experiment, visual change, relative dynamic modulus of elasticity（RDME） and the surface damage layer thickness of concrete were measured.Furthermore, SEM and thermal analysis were used to investigate the changing of microstructure and corrosion products of concrete.The test results show that the ultrasonic velocity is related to the damage layer of concrete. It approves that an increase in damage layer thickness reduces the compactness and the ultrasonic velocity. The deterioration degree of concrete could be estimated effectively by measuring the surface damage layer and the RDME of concrete. It is also found that the content of gypsum in concrete is less than that of ettringite in test, and some gypsum is checked only after a certain corrosion extent. When the concrete is with high W/B ratio or exposed to high concentration of sulfate solution, the content of ettringite first increases and then decreases with corrosion time. However, the content of gypsum increases at a steady rate. The content of corrosion products does not correspond well with the observations of RDME change, and extensive amount of corrosion products can be formed before obvious damage occurs.     

对称式双电位扩展键盘设计

本设计是基于MCU的一款高效率键盘输入系统。通过对分立按键和普通二极管的合理布局,实现了一种利用N个双向I/O端口确定N2＋N个键值的键盘电路设计。实验证明,该键盘电路结构简单、抗干扰能力强、稳定性好,具有很高的使用价值。     

正则表达式匹配引擎性能分析

正则表达式具有强大的描述能力,在计算机领域,正则表达式匹配技术应用十分广泛。目前,已经有多个正则表达式匹配引擎,在实际应用中,对于不同的匹配规则集和正则语法,不同的匹配引擎会有不同的性能表现。本文通过对PCRE、Greta、Boost、RE2四种常用正则表达式匹配引擎的性能测试,给出在不用的正则语法情况下的匹配速度,并深入分析不同坏境下适用的正则表达式匹配引擎。对实际系统设计中正则表达式库的选择有指导意义。     

一起500kV变压器典型事故原因分析

对某电厂一起500 kV变压器由于高压线圈股间短路,逐步发展为匝间短路,从而引起高低压线圈短路、低压侧避雷器爆炸的事故原因进行了详细的分析,为防止类似事故的发生提供了借鉴。     

钢纤维混凝土抗冻性能试验研究

为了研究钢纤维混凝土的抗冻性能,采用快冻法进行了0%、0.5%、1.0%、1.5%、2.0%五种不同钢纤维掺量的混凝土在水中和3.5%氯化钠溶液中冻融试验。通过分析冻融循环次数和钢纤维体积率对钢纤维混凝土冻融后质量损失、劈裂强度损失和相对动弹性模量变化的影响,分析了冻融环境下钢纤维对混凝土的增强机理。并且用压汞法和SEM从微观上研究了钢纤维混凝土的孔径分布特征,讨论了微观结构对其抗冻性能的影响。研究表明,在冻融循环作用下掺入适量的钢纤维能够减小混凝土内部的孔隙率、增加密实度,有效阻止混凝土内部微裂缝的产生与发展,提高混凝土的抗冻性能。钢纤维掺量对混凝土抗冻性影响显著,掺量为1.5%时,钢纤维对混凝土抗冻性能改善效果最好。     

FPGA实现的正则表达式匹配性能分析

分析出影响FPGA实现的正则表达式匹配性能的关键因素是正则表达式匹配性能优化的前提.首先由L7-Filter各个规则的性能测试结果分析出低主频规则有别于其它高主频规则的三个特征.其后通过设计多个字符组串联而成的特殊正则表达式测试模型去验证这三个特征对基于FPGA的正则表达式自动机性能的影响程度.得出如下结论:基于FPGA的正则表达式自动机的主频随字符组宽度的增长而迅速下降,随字符组串联数目的增长而缓慢下降;星号(*)或问号(?)重复语法对字符组规则主频的影响大于加号(+)重复语法对字符组规则主频的影响.最后将基于字符组的结论推广至更普遍的大量字符“或(Ⅰ)”操作的层面.