控制系统故障诊断浅析

简要回顾了故障诊断技术的发展历程,介绍故障诊断的基本概念,着重综述基于模型故障诊断技术和不依赖于模型的智能故障诊断技术特点和发展概况.为未来故障诊断技术的发展提出了一些展望.     

浅析安全策略漏洞防范

随着计算机网络的不断发展,全球信息化已成为人类发展的大趋势。但由于计算机网络具有联结形式多样性、终端分布不均匀性和网络的开放性等特性,致使网络受到偶然或者恶意的原因而遭到破坏、更改、泄露。本文将分别在硬件、软件、协议方面的对常见漏洞进行阐述。     

Analysis of fault tolerant computer systems

In many critical applications of digital systems, fault tolerance has been an essential architectural attribute for achieving high reliability. In recent years, the concept of the performability of such systems has drawn the attention of many researchers. In this paper we develop a general Markov model for fault tolerant computer systems. Various important performance measures, including the performability measures as well as some new performance measures, are treated in a unified manner. Furthermore, general and efficient computational procedures are developed for calculating these performance measures based on the uniformization technique of Keilson. A numerical example is given to illustrate the computational procedures developed.     

高压分压器击穿故障模式分析

通过对高压分压器击穿故障模式的分析和试验研究,发现在抽真空灌注过程中,中空结构的分压器会形成局部低气压,导致分压器击穿。同时,对高压分压器的结构提出了改进设计。     

上海研达调频发射机故障简析

由于我台的上海研达调频发射机使用年数已超过十年之久,并且占据机房发射机的一半数量以上,经常会出现不同状况的发射机故障。文章是对我台研达发射机经常出现的故障的简析,可以帮助我台值班机务员了解发射机并能使其及时倒机,处理发射机故障。     

同步数据接口时钟关系分析

介绍了同步传输常用的技术标准和符合国际规范的同步数据与定时信号关系,根据我国航天测控网中常用通信设备的时钟方式设置,对某国军标中存在的问题进行了探讨,并提出了修改意见。通过对高速数据在不同时钟方式下的传输效果比较,指出了合理选择时钟的重要性,可为实际的工程应用提供参考。     

CT故障的系统化功能化维修分析

设备是医院进行诊断的最主要基础,不过CT设备由于使用的特殊性和设备使用环境的特殊性,其维修管理一向是一个制约CT大规模诊断的关键环节。对于CT医疗设备的操作与运行中常见的设备故障,不但要根据故障进行科学的处理,而且要保障CT医疗设备的最佳工作状态,提高医疗临床的服务质量。CT设备的故障应该还是有规律可循的,因为许多故障是可以进行系统化与功能化预防的。本文为此具体探讨了CT故障诊断中系统化功能化维修思路的建立。     

时钟抖动对射频脉宽调制性能的影响分析

在全数字发信机系统中,射频脉宽调制(RF-PWM)将基带调制信号的幅度与相位信息编码为输出脉冲的宽度和位置。由于数字信号处理器件的非理想特性,其时钟信号的上升沿和下降沿存在抖动误差,影响RF-PWM的输出信号质量。基于3种RF-PWM实现方案,本文通过公式推导确定了时钟抖动引入的非线性失真项,并给出了时钟抖动影响下不同方案输出脉冲信号底噪的数学解析式。最后利用Matlab软件,对不同方案在时钟抖动条件下的基波、奇次谐波和底噪进行仿真验证,结果证明理论推导正确;同时对信号的矢量幅度误差(EVM)和邻信道功率比(ACPR)进行仿真,分析出时钟抖动对信号带内外性能的影响。结果表明,时钟抖动引入的非线性失真主要体现为底噪的抬高;不同RF-PWM实现方案时钟抖动的影响特性各有不同,其中五电平方案对时钟抖动影响具有抑制效果,且随时间分辨力的增大而增大。     

Analysis of vulnerability propagation for the all-optical network based on Bio-PEPA

Wireless Networks - Aiming at the vulnerability propagation of all-optical networks, combining with the characteristics of the all-optical network, a formal modeling and analysis method for...     

CDMA网络中EVDO掉话原因分析

文章主要讨论了在CDMA网络中EVDO的掉话现象,并分析引起掉话的原因,通过对不同原因的分析及定位,找出对应的解决问题的方法,降低掉话率,提升网络质量。     

温州雷神雷达信号瞬断分析

温州大罗山雷神二次雷达已安装运行8年,2012年起偶尔有信号瞬断出现,2015年开始更加频繁,对航空管制造成了一定的影响。文章详细介绍了故障的排除过程,并对之后的运行提出了建议和措施。     

变压器油色谱分析与故障诊断

变压器作为电力设备工作运行的重要基础设备,其实际运行状态直接关系到电力系统运行的可靠性和安全性。文章主要对变压器油色谱分析与故障诊断进行了探究,旨在借助色谱分析方法对变压器故障进行诊断,以此提高变压器日常运行的安全可靠性,为电力系统平稳运行奠定坚实的基础。     

Analysis of DS-CDMA parallel interference cancellation with phaseand timing errors

We consider the use of multistage parallel interference cancellation at the base station of a code-division multiple-access (CDMA) wireless system. Previous work in this area has demonstrated the potential for significant improvements in capacity and near-far resistance. However, most previous work has assumed perfect synchronization with the signals of interest. Practical systems will experience phase jitter and timing errors. We undertake an analysis of the effects of phase and timing errors, obtaining a closed form result for bit-error rate (BER) performance after an arbitrary number of stages of cancellation in an additive white Gaussian noise (AWGN) channel. This result is shown to agree well with simulations. Simulation results are also presented for the important case of frequency selective Rayleigh fading. The results from both analysis and simulations demonstrate that interference cancellation is fairly robust to phase and timing errors     

RBS2000基站隐性故障分析

介绍了基站隐性故障的概念、分类及如何发现和处理隐性障碍的方法.     

Analysis of a passive superconducting fault current limiter

An analysis was carried out to predict the forced response of the equivalent circuit of an innovative superconducting fault current limiter (FCL). The FCL employs two superconducting coils with differing critical currents wound noninductively. The analysis shows that to reduce the voltage drop under normal operating conditions, the coupling coefficient should be kept fairly high (k>0.90). For a given coil configuration (ωL¯=constant), the limiting capability of the device increases with the resistance R of the trigger coil up to a certain value of R, then further increase in R changes very little the limiting capability of the FCL. However, further increase in R can reduce the heat generation rate in the device which will help alleviate the problem of relatively long recovery time. The fault current predicted from estimated values of R compares fairly well with results of an experiment reported in the literature. The discrepancy between the predicted and measured current is due mainly to the uncertainty in the estimated resistance R, because both the purity of Cu and the percentage of Cu in CuNi are not known. By varying the ratio of NbTi-Cu-CuNi in the matrix, the purity of Cu, and the percentage of Cu in CuNi various values of R, can be achieved, which should help to alleviate the problem of excessive Joule heating and recovery time     

Analysis of a serial symbol timing recovery technique employingExclusive-OR circuit

An analysis is presented of the performance of a serial symbol timing recovery (STR) circuit which employs an Exclusive-OR circuit for conventional coherent digital modulated communication systems. The output of the timing circuit is a nearly sinusoidal wave whose zero crossings indicate the appropriate sampling instants for extraction of the data. Assuming that the data pulses entering the timing path are even symmetric, exact analytical expressions for the mean and mean-squared values of the timing wave and for the RMS phase jitter are derived as a function of various system parameters such as channel band limiting, postfiltering, delay element, and power spectral density of noise. Numerical results, also checked by computer simulations, show that considerable improvement can be obtained in jitter performance, in addition to the advantages over other STR techniques of lower cost and simpler hardware implementation     

光纤传输网脆弱性分析与对策研究

光纤传输网具有独特的优势,但也有特殊的脆弱性.随着光纤通信技术的快速发展和广泛应用,光纤传输网的安全性显得越来越重要.文章按照分层的观点,介绍了光纤传输网的安全分层结构,分析了光纤传输网不同层面的脆弱性和所受攻击的类型及方法,并针对各层可能受到的安全威胁, 研究了相关的安全对策.     

基于Wireshark的轨道故障分析与研究

文章提出使用Wireshark工具解决轨道通信中常出现的故障,利用Wireshark的数据包撷取能力分析与排查网络故障的原因,并给出相应的解决方案。实验主要是通过搭建实验环境,模拟实际场景,设计故障点并利用Wireshark工具抓包,分析解决具体故障。实验结果表明,使用Wireshark工具解决轨道通信中常出现的问题,对开辟一条新的故障解决道路具有借鉴意义。