建材使用固定价格的水利工程施工合同在价格波动时调整策略

在水利水电工程建设与管理实践中,项目法人出于控制投资、节约建设成本等原因,在招投标过程中大量采用固定价格合同,将价格波动带来的风险转嫁给了中标施工承包商,加大了施工承包商的风险,也成为了市场经济活动过程中价格异动导致施工承包商生产经营困难的主要原因之一。在这种情况下,是严格执行合同文件还是应当对原固定价格进行调整,成为工程建设合同管理工作面临的棘手问题,须妥善解决。     

物理创新实验开发应用综述

首先,查阅大量文献,研究国内外创新实验的应用,发现创新实验具有以创新为主、实验器材成本低两个特点.其次,经过前期分析、实验设计、制作、运用、评价等步骤进行创新实验教学.最后,通过对个别案例实验过程进行讨论分析,验证创新实验的重要性.着重介绍了物理创新实验在国内外物理教学中的应用现状,强调了物理创新实验的重要性;又对创新...     

两起变压器轻瓦斯误动原因分析及解决措施

介绍了宁夏电网两起变压器轻瓦斯误动的案例,通过外观检查、点燃试验、色谱分析等试验查找轻瓦斯误动原因,并结合宁夏电网瓦斯继电器运行现状提出相应的解决措施,为宁夏电网主变压器瓦斯继电器安全运行提供借鉴。     

GIS隔离开关温度分布特性的试验研究

气体绝缘组合电器(GIS)为全封闭紧密结构,其内部的隔离开关易于产生机械接触缺陷,在运行电流作用下,一旦隔离开关出现接触不良,将引起温度异常升高,通过温度检测可对GIS隔离开关机械连接状态进行判断。为了获取隔离开关内部动触头温度与设备外壳温度之间的关系,本文基于550 kV GIS开展温升试验,在GIS隔离开关周围布置温度传感器测量温度分布,同时在GIS外壳上进行外部温度的测量,试验研究了不同电流、不同接触电阻下的GIS内部及外部温升规律,结果表明GIS外壳与隔离开关触头的温升存在线性关系,正常情况下顶部外壳温升每上升1 K,对应触头温升提高1.924 K,而故障情况下,对应的触头温升提高2.85 K,并且顶部外壳温度变化范围大,对设备内部温度变化敏感,具有较好的温度辨识性,能更灵敏准确地反映内部触头的温升情况。试验结果分析阐明了GIS内部热源、热量传导路径及温度分布特点,为通过GIS外部温度检测进行内部温度的反演提供了试验基础。     

基于射频偏转腔的束团长度测量系统

本文建立了基于偏转腔的电子束团长度测量系统的模型,揭示了束流和偏转腔参数对测量结果的影响机制,给出了一种束团长度的计算方法。用三维仿真软件CST对腔体建模,得到了最优的单腔腔体尺寸、最优的耦合器尺寸和工作模式场分布,对应的偏转腔系统时间分辨率为182 fs,满足设计要求。用粒子跟踪软件Parmela进行束流动力学模拟,阐明了下游荧光屏上出现束团横向偏移的原因,并验证了理论结果的正确性。     

Research on Nanosecond Pulse Corona Discharge Attenuation

A line-to-plate reactor was set-up in the experimental study on the application of nanosecond pulsed corona discharge plasma technology in environmental pollution control. Investigation on the attenuation and distortion of the amplitude of the pulse wave front and the discharge image as well as the waveform along the corona wire was conducted. The results show that the wave front decreases sharply during the corona discharge along the corona wire. The higher the amplitude of the applied pulse is, the more the amplitude of the wave front decreased. The wave attenuation responds in a lower corona discharge inversely. To get a higher efficiency of the line-to-plate reactor a sharp attenuation of the corona has to be considered in practical design.     

A Test Study of 50% Lightning on Rod-Plane Gap with Impulse Breakdown Voltage Two-Phase Mixture of Gas and Solid Particles

A test study on 50% lightning impulse breakdown voltage in two-phase mixture of gas and solid particles has been carried out in a specially designed discharge cabinet. A mechanical sieve is set up for sifting different solid particles into the discharge space uniformly. The lightning impulse voltage according with international electro-technical commission （IEC） standard is applied to the electrodes inside the discharge cabinet by the rule of up-down method in a total of 40 times. The results showed that the 50% lightning impulse breakdown voltage in two-phase mixture of gas and solid particles has its own features and is much different from that in air.