检定S型短型热电偶的4种不同冷端补偿方法之比较

检定长度在200～700 mm范围内的S型热电偶时,由于参考端温度大都处于室温或者波动的温场之中,需要将参考端温度恒定在0℃或采取修正、补偿等措施进行修正。现采取检定中最常用的4种不同的冷端补偿方法检定同一支S型短型热电偶,对结果进行比较分析,得到这4种不同的冷端补偿方法的优劣性及其准确度排序。结果表明,将参考端应用达到一等标准热电偶准确度水平的同极性热电偶丝延伸至参考端恒温器方法能获得较为理想的补偿效果。     

Silver coated vapor-grown-carbon nanofibers for effective reinforcement of polypropylene-polyaniline

This work utilizes a modification of our process of polymer entrapment in silver to deposit silver crystals on carbon nanofibers at different relative concentrations. The experimental procedure and the characteristics of silver coated nanofibers are presented in detail. The resulting nanofibers are then melt-mixed with a polypropylene-polyaniline blend to form a uniform dispersion that is finally extruded to produce continuous monofilament composites of high axial orientation. The reinforcement effect of the silver coated nanofibers, manifested in the mechanical properties of the monofilament composites, is 3-5 folds higher than that of the pristine nanofibers due to the improved stress transfer mechanism of the former. Additional attractive properties of the new system may result from its anisotropic crystalline structure, enhanced thermal stability, potential electrical conductivity and antibacterial behavior.     

Strain sensing behavior of electrically conductive fibers under large deformation

Electrically conductive fiber/yarn/fabric is one of the promising materials as flexible conductive sensors because of their sensitivity to strain, temperature and humidity. Aiming at developing of effective flexible sensors, this study investigates experimentally the strain sensing behavior of PPy (polypyrrole)-coated Lycra fibers, showing that the electrically resistance of the conductive fibers changes with the deformation of fibers. The variation in electrically resistance is mainly related to the micro-cracks appearing on the fiber surface during deformation. Then, the effects of the characteristic parameters of the micro-cracks are studied statistically by means of image processing functions in MATLAB, and the governing parameters are determined. Based on the results, a model is built to describe the variation of electrical resistance by the parameters of the micro-cracks. The analytical results are compared with the experimental results, showing an acceptable agreement.     

金属氧化物避雷器短路试验(压力释放试验)的重要性分析

为了保证避雷器即使发生故障也不会损坏其他设备或者影响人身安全,短路试验是一项非常重要的试验。由于试验回路电压或容量的关系,在有些短路试验中,避雷器的短路电流第一个峰值达不到要求的试验电流有效值的1.7-2.5倍,通过短路电流的时间往往也不足0.2秒。如果所进行的试验不符合这一要求,将不能真正考验避雷器压力释放装置是否能够起到防爆作用。     

机载电子侦察设备测向性能评估

介绍了短基线时差测向原理,总结分析了影响机载短基线时差测向体制的电子侦察设备测向性能的主要因素,结合工程应用,详细介绍了更科学的评估电子侦察设备测向性能的试飞方法和数据处理方法,并给出了部分实际试飞试验数据的分析评估结果。对机载电子侦察设备靶场试验的测向性能评估具有一定的借鉴意义。     

基于空间状态向量的定子绕组短路辨识

定子绝缘层的瑕疵是电机故障的主要因素.异步电机的检测模型能够检测出少量绕组线圈的短路故障.借助卡尔曼滤波器模型对相电流进行分析,能够准确辨识出微小的短路电流,进而采取有效措施检测故障,防止事故的发生.     

异步电动机轻载起动转子断条故障检测方法

结合笼型异步电机的轻载和起动特性,对笼型异步电动机转子断条故障特征进行了机理仿真与实验分析.在此基础上提出了基于短时傅里叶变换(STFT)的异步电动机转子断条故障检测方法.实例结果表明,该方法是行之有效的.     

新型纳米尺寸MOSFET器件的模拟和设计

在半导体器件的研制过程中,用计算机数值模拟取代测量方法来优化设计器件的性能参数,则器件的调试周期将显著缩短,费用将大幅度降低。本文简述了新型纳米尺寸MOSFET器件模拟的主要物理模型和数值方法,阐述MOSFET相关器件模拟的国内外研究动态,判断其发展趋势和研究方向。     

用薄膜光学理论研究布拉格光纤的传输特性

用薄膜光学的等效导纳方法和阶跃光纤的几何光学理论研究布拉格光纤的传输特性.①设计出了反射率达99.99%包层的厚度、层数;②分析了传输效果随波长、层数、入射角的变化;③得出光束的数值孔径小于0.15时,反射率大干99.99%.这一研究对布拉格光子晶体光纤的实际加工及与阶跃光纤耦合具有重要理论意义.     

短采样宽带信号方位估计快速算法

该文针对短采样宽带信号近似最大似然(AML)方位估计计算量大的问题,将马尔可夫蒙特卡罗方法与近似最大似然方位估计相结合,提出一种基于Gibbs抽样的近似最大似然方位估计新方法(Approximated Maximum Likelihood DOA estimator based on Gibbs Sampling, AMLGS)。研究结果表明,AMLGS方法不但保持了原近似最大似然方位估计方法的优良性能,而且显著减小了计算量。把原方法的计算复杂度从O(LK)减少到O(KJNs)。