瞬时中频测试技术及其在捷变频雷达测试中应用

在介绍瞬时中频测试技术的基础上,介绍利用瞬时中频测试技术对捷变频雷达本振跟踪精度进行测试的原理和方法。重点介绍为提高测量精度而采用内插扩展技术和为克服噪声电平过高而引起测量电路误触发而采用的外闸门技术。

钻杆中频瞬时液相扩散焊机的研制

在石油钻杆瞬时液相扩散焊接技术取得成果的基础上,研制了钻杆中频瞬时液相扩散焊机。该焊机由机械装置(包括夹具装置、顶进装置和基座)、液压系统、中频电源加热系统、控制系统和冷却保护系统组成。工艺试验结果表明,采用钻杆中频瞬时液相扩散焊机制造的钻杆焊接接头变形小、成形美观、接头强度和韧性达到母材水平。

基于肌电信号时频分析的腰背部肌肉功能评价方法研究

肌电信号在评价下腰痛病人背部肌肉功能的研究中得到广泛应用,但是由于肌电信号本身的个体差异很大,往往掩盖被测对象真正的生理差异。本文对采集自腰背部的8通道肌电信号进行研究,对时-频域计算瞬时中频的算法做了改进。并根据正常组和病人组肌电信号的时频谱能量聚集程度不同这一发现提出了一种以能量离散度为指标的区分方法。

A New Transient Impedance-Based Algorithm for Earth Fault Detection in Medium Voltage Networks

This paper presents a new earth-fault detection algorithm for unearthed （isolated） and compensated neutral medium voltage （MV） networks. The proposed algorithm is based on capacitance calculation from transient impedance and dominant transient frequency. The Discrete Fourier Transform （DFT） method is used to determine the dominant transient frequency. The values of voltage and current earth modes are calculated in the period of the dominant transient frequency, then the transient impedance can be determined, from which we can calculate the earth capacitance. The calculated capacitance gives an indication about if the feeder is faulted or not. The algorithm is less dependent on the fault resistance and the faulted feeder parameters; it mainly depends on the background network. The network is simulated by ATP/EMTP program. Several different fault conditions are covered in the simulation process, different fault inception angles, fault locations and fault resistances.