防止噪声引起的电子设备误动作——最为重要的是降低接地系统的阻抗(上)

本文用具体实例说明如何防止电子设备由外界噪声引起的误动作。对噪声加以分类,并说明了与某些电磁波(Electromagnetic compatibility)的兼容性。文中还提出了减少接地系统的阻抗、改进滤波电路及其组装方法、布线方法以及接地方法等。其中降低接地系统的阻抗是防止噪声干扰的根本措施。     

小电流接地系统选线注入信号的频率分析

注入信号法是广泛应用于小电流接地系统单相接地故障的选线方法,实际应用中由于接地故障电阻大,容易发生选线失败的现象。文章通过分析注入信号法的基本原理及注入信号的流通路径,借助Matlab仿真,研究了注入信号频率对选线效果的影响,得出了降低注入信号的频率可以减小非故障线路对信号电流的分流作用、提高注入法的适用范围和选线准确率的结论。     

通信网恶意代码攻击效果评估研究

网络攻击效果评估的目的是对网络攻击行为所能达到的攻击效果进行综合评判,从而发现网络中的薄弱点。文中提出了一个网络攻击与效果评估系统：首先恶意代码控制系统框架制定攻击策略对目标系统进行攻击;接着对网络攻击进行破坏能力预估,采用层次分析法定义指标,利用Delphi法确定指标权重,最后通过加权法综合效果评估值。三次攻击实验的实测结果表明该系统可以量化实际的网络攻击效果,从而准确评价网络攻击所达到的破坏程度。     

航天器综合测试中的接地技术研究

航天器综合测试中,航天器及地面测试系统的正确接地是航天器安全保证和抑制干扰的关键环节之一,有必要对其进行正确的认识;介绍了接地系统的构成和作用,论述了正确接地方法的重要性以及基本的接地要求,详细描述了航天器综合测试环境中测试场地和供电系统的接地布局,分析了航天器本身及测试仪器设备、电缆的接地特点,给出了航天器与地面测试设备接地系统的正确连接原则,提出消除接地干扰的建议,并且制定了切实可行的安全保证措施。     

基于组合波工程化测量消除引线互感的接地阻抗测量方法

摘要: 以正弦波电流为激励信号测量接地网接地阻抗时,由于电压线、电流线之间不可避免的存在平行共线,由此产生的互感耦合会导致接地阻抗测量结果偏高,影响接地网安全性能评估。为解决此问题,提出了一种基于组合波工程化测量消除引线互感的接地阻抗测量方法,用方波电流测量接地阻抗电阻分量,用正弦波测量接地阻抗模值,在测量现场通过改变平行共线距离获得不同互感耦合强度的测量值,解析剔除互感耦合分量后,获得准确的接地阻抗测量值。在110kV变电站现场通过夹角法、反向法测量,并与土壤分层的接地网模型仿真结果对比,组合波工程化测量结果与接地阻抗仿真值误差仅为1%。     

智能化楼宇的电气保护形式与接地措施

通过对几种供电接地系统的介绍 ,分析适合智能化楼宇的供电接地系统 ,较为详尽地阐述了各种接地系统的接地措施 ,并对适用于智能化楼宇的电气保护与接地方法提出了建议。     

架空明线信道参数的简易测试

本文对明线阻抗测试中的阻抗电桥法与其它几种简易方法结合实测数据进行了分析对比;对信道幅频特性的测试给出了实测结果,并做了简要讨论。     

高可靠性1394总线传输线缆阻抗特性测试研究

面向新一代飞机的1394总线应用中,传输线缆作为总线传输介质,影响总线的传输特性。为满足新型机载1394线缆的高可靠性要求,本文对1394线缆的结构及差分阻抗进行了理论分析,提出了1394线缆的测试设备及测试环境,采用专用设备对1394线缆的差分阻抗进行了测试,测试结果表明,被测1394线缆满足线缆阻抗特性指标。在测试结论的支撑下,规范了1394线缆阻抗特性测试指标。为高可靠性1394线缆传输提供了理论依据及测试实验数据,为1394线缆的选型及应用奠定了基础,对构建整个1394总线具有指导意义并进而指导整个系统设计。     

高可靠性1394总线传输线缆阻抗特性测试研究

面向新一代飞机的1394总线应用中,传输线缆作为总线传输介质,影响总线的传输特性。为满足新型机载1394线缆的高可靠性要求,文中对1394线缆的结构及差分阻抗进行了理论分析,提出了1394线缆的测试设备及测试环境,采用专用设备对1394线缆的差分阻抗进行了测试,测试结果表明,被测1394线缆满足线缆阻抗特性指标。在测试结论的支撑下,规范了1394线缆阻抗特性测试指标。为高可靠性1394线缆传输提供了理论依据及测试实验数据,为1394线缆的选型及应用奠定了基础,对构建整个1394总线具有指导意义并进而指导整个系统设计。     

浅谈综合布线系统接地设计

综合布线系统作为建筑智能化不可缺少的基础设施,其接地系统的好坏将直接影响到综合布线系统的运行质量,故而显得尤为重要。本文介绍了综合布线系统接地的结构及设计要求,并提出在接地设计中应注意的几个问题。     

谐振接地系统单相接地故障仿真分析

针对谐振接地系统发生单相接地故障时因故障线路电流很小且方向不确定而导致选线难度大的问题,从理论上分析了谐振接地系统发生单相接地故障时的零序电压、零序电流变化规律;在Matlab软件中建立了小电流接地系统仿真模型,并分别对中性点不接地系统、全补偿谐振接地系统、过补偿谐振接地系统、欠补偿谐振接地系统进行了仿真分析,仿真结果与理论分析结果一致,进而得出结论:发生单相接地故障时,中性点不接地系统可选用基于幅值和方向等稳态分量的选线方法,谐振接地系统不可选用该种选线方法,但两种系统可选用同一种基于暂态分量的选线方法。     

Grounding computational engines

Integrating the processing of sensory information and natural language is not a homogeneous enterprise, and there are different proposals from both connectionism and symbolic AI on how to proceed. This paper considers one problematic part of the enterprise, what we call the internalist trap for the systems of symbolic AI and connectionism. Two kinds of computational mechanism are discussed, the Syntactic engine of symbolic AI and the more novel Spatial engine of connectionism, and the different solutions to the internalist trap that each machine requires is explored. What emerges from our discussion is the relative paucity of the representational resources available to the Syntactic engine, in comparison to those available to the Spatial engine. This inequality is important, because it is precisely these resources that, we argue, are crucial in hooking atomic representations to the world. That is, whilst it is possible for both kinds of computational engine to be hooked up to the world, it is only the Spatial engine which possesses the requisite resources in and of itself.     

新型智能接地网接地电阻测量装置的研究

接地电阻值是发电厂、变电站接地系统的重要技术指标。本文回顾了传统的接地电阻测量方法，介绍了变电站接地网接地电阻智能测量装置的组成、工作原理和特点。该装置可以缩短测量引线的长度，而且测量所需电流小，大大提高了测量的准确性与便捷性。     

斜接地极降低矩形地网接地电阻研究

基于CDEGS软件建立仿真计算模型,分析斜接地极敷设位置、角度、长度、根数等不同时,降低不同面积接地网的接地电阻的效果和特征,进而优化斜接地极的布置方式.     

DCS系统接地应用

根据对陕西锌业有限公司商洛炼锌厂20万t烟气制酸装置DCS系统的设计、安装及应用经验,对DCS系统的接地进行探讨。     

防雷设计系统中的接地分析

针对防雷设计中通信设备和电子设备的防雷接地,根据国家标准要求从外部防雷装置中接地体的选用、有效降低接地电阻的大小和选择合适的联合接地方式等三个方面阐述了合理接地的问题;通过对布线、屏蔽和接地方式,空间磁场对通信线路的电磁感应影响情况和降阻剂对接地电阻的影响实验,总结了能够保护电子设备的安全布线和接地方式。     

接地抗干扰技术的探讨

接地技术是抑制噪声和防止干扰的重要手段之一。对几种常见的接地方式分别做了介绍,列出了其优缺点。在此基础上,详细阐述了A／D转换器、屏蔽线、平衡电路和PCB板的接地抗干扰的方法,以及电子设备在设计地线和接地点时应考虑的主要问题。     

Grounding symbols into perceptions

This paper deals with symbol formation, from a cognitive point of view, through a connectionist model. To give an idea of our aim, let us consider the metaphor of learning to play tennis. Two knowledge forms are involved:

- implicit knowledge, e.g. sensori-motor associations; this knowledge is subsymbolic

- explicit knowledge, e.g. a teacher giving verbal advice, which makes use of symbols.

Learned knowledge consists of a combination of subsymbolic and symbolic items. More than a juxtaposition, this combination involves grounding symbols into a subsymbolic substratum. This leads us to connectionist modelling which is considered as the common framework for both kinds of knowledge.     

Grounding soft systems research

This paper suggests that Checkland's soft systems methodology (SSM) may, in certain instances, yield improved results if used in combination with Glaser and Strauss's grounded theory (GT). In order to facilitate the conjunctive use of these two qualitative approaches to social phenomena, GT is first re-interpreted through the perception filter of systems thinking. The two techniques are then subjected to analysis in terms of their ontological, epistemological and research design assumptions, from which it is concluded that there are no insurmountable barriers to their combined use. A further series of potential objections to grounding soft systems research as proposed in this paper are then raised and dealt with. Finally, it is concluded that while grounding soft systems research is in theory at least highly intuitively appealing, empirical research using the techniques in the way recommended here is required before the utility of the proposal can be ascertained with any degree of certainty.     

Grounding language in perception

This paper describes an implemented computer program that recognizes the occurrence of simple spatial motion events in simulated video input. The program receives an animated line-drawing as input and produces as output a semantic representation of the events occurring in that animation. This paper suggests that the notions ofsupport, contact, andattachment are crucial to specifying many simple spatial motion event types and presents a logical notation for describing classes of events that incorporates such notions as primitives. It then suggests that the truth values of such primitives can be recovered from perceptual input by a process of counterfactual simulation, predicting the effect of hypothetical changes to the world on the immediate future. Finally, it suggests that such counterfactual simulation is performed using knowledge of naive physical constraints such assubstantiality, continuity, gravity, andground plane. This paper describes the algorithms that incorporate these ideas in the program and illustrates the operation of the program on sample input.