延长煤矿矿灯使用寿命的一种实用型电路设计

研究延长煤矿矿灯使用寿命的一种实用型矿灯充电保护器设计，针对如何限制矿灯过度充电和充电电流过大造成的矿灯损坏设计了双比较器电路。并就其原理和工作过程进行了探讨。     

Anti-chloride permeability and anti-chloride corrodibility of a green high performance concrete admixture in concrete

1. Introduction In order to meet the demands of developing west zone of China and utilization of urban underground space, tunnel construction is increasingly paid more attention to in China. As is known, concrete is the main building material used in civil engineering, which is always affected and eroded by various ions in underground water, so the durability of concrete structure which is the main part of tunnels and underground projects, has been a hot subject for investigation in civil engi…     

基于校企合作的光纤通信教学改革举措

光纤通信课程是一门理论性强、知识点较多的专业课。结合教学实践与课程特点,以校企合作为平台,对该课程教学方法进行探讨,通过激发学生学习兴趣,对课程内容进行调整,与企业共建实验室,师资培训与交流,成立项目梯队等措施改善教学效果。     

Quantifying and visualizing change: Strain monitoring of tapestries with digital image correlation

A three-year research project at the University of Southampton (2007–2010) investigated whether monitoring techniques commonly used by engineers to assess the strength and durability of materials could be usefully applied to inform the condition assessment of historic tapestries. To date it has not been possible to obtain an objective picture of the overall condition of a tapestry; the study investigated whether it is possible to identify precursors of structural damage. The two techniques, digital image correlation (DIC) and optical fibre sensors, were used to monitor a representative wool fabric, specially woven tapestry samples, a newly woven tapestry, and historic tapestries, both in the laboratory and in situ in a historic house. This study first sets out to answer the question: can DIC be used to monitor and visualize strain in historic tapestries? It is shown that DIC can be used successfully. Secondly, it discusses the map function, a novel development which allowed the monitoring equipment to be moved, so that it could be used in situ in a historic house. Thirdly, it provides further details of the experimental work using optical fibre sensors to confirm the accuracy of the DIC technique.     

玻璃化温度测试在干式变压器浇注中的应用

介绍了环氧树脂的玻璃化温度测试实验,提出将玻璃化温度测试应用于干式变压器的浇注过程中。通过对玻璃化温度曲线的分析,判断其固化情况,及时了解干式变压器的浇注情况。对比玻璃化温度结果可以判断出浇注原料配比的值,从而了解设备情况,控制产品质量。     

应用于低中频Zigbee收发机的5-GHz恒定带宽频率综合器（英文）

设计并实现了一个应用于ZigBee收发机的全集成整数N频率综合器.频率综合器中采用了稳定环路带宽技术,使频率综合器的环路带宽在压控振荡器（VCO）的整个输出频率范围内恒定不变,从而维持了频率综合器的相位噪声最优值与环路稳定性.频率综合器的同相与正交信号（IQ）由VCO输出端的除2分频器产生.该频率综合器采用0.18μm RF CMOS工艺技术制造,芯片面积约1.7mm2.频率综合器采用在晶圆测试的方式进行了测试.在1.8V电源电压下,频率综合器不包括输出缓冲所消耗的总功率为28.8mW.频率综合器在2.405GHz载波1及3MHz频偏处测得相位噪声分别为-110和-122dBc/Hz.频率综合器在2MHz频偏处测得的参考杂散为-48.2dBc.测得的建立时间约为160μs.     

基于ANSYS/Maxwell的感应滤波配电变压器设计与实验研究北大核心

该文提出了一种适用于低压配电网系统下的新型感应滤波配电变压器设计方法,并将其应用于综合性创新实验的教学案例中。在感应滤波配电变压器的设计中,将感应滤波技术应用于采用Ddy联结组别的配电变压器中。通过建立电路数学模型,推导阀侧产生的谐波电流与网侧电流之间的关系,揭示感应滤波配电变压器的滤波特性。该文采用ANSYS/Maxwell软件建立新型变压器的3D模型,在模型上通过仿真能量法对比工程磁路法,验证变压器绕组间短路阻抗满足技术要求;并通过磁路耦合添加滤波支路,监测变压器的网侧电流,验证其可以有效滤除电网谐波污染。最后通过实验验证了所设计的变压器的正确性和有效性,进一步激发了学生的学习兴趣和创新热情。     

时频信息融合的电弧故障识别及仿真实验北大核心

为保证实验室用电安全,针对实验室电弧故障,提出一种时频信息融合的电弧故障识别方法并模拟验证。首先分别搭建模型模拟并联与串联电弧,然后在PSCAD/EMTDC中搭建三相五线制实验室用电系统模拟实验室用电电弧,最后针对难以辨识的串联电弧故障,依据突变理论融合时频信息,与阈值进行比较判断故障,并依据多类型负载实验室用电仿真系统进行验证。结果表明该方法可行性高且故障识别率达90%以上。将电弧故障辨识方法以及仿真实验用于教学有助于增强学生实验室安全用电意识,加深学生对相关电路原理、信号处理和故障辨识相关知识的理解,培养学生分析和解决实际电气问题的能力。