煤矿井下直流杂散电流的研究

杂散电流所造成的电机车钢轨及其附近的埋地管线的腐蚀、人身触电和对通信系统的干扰等问题日益凸显出来。文章通过建立电机车简单的单边供电模型,在合理的假设前提下推导出了杂散电流的计算公式,并应用Matlab仿真软件对推导出的公式进行仿真分析。仿真分析结果表明:在单边供电的区间内,随着距电机车距离的增大,杂散电流先增大后减小,在供电区间的中点达到最大;过渡电阻和轨道纵向电阻率对杂散电流泄漏影响很大;供电距离和供电电流对杂散电流的影响次之。     

矿井直流杂散电流分布规律的仿真研究

根据井下直流机车回流通路的特点,建立了杂散电流传输网络有限单元模型,提出了直流杂散电流和接触电压分布的数值计算模型;结合仿真计算的结果,对影响杂散电流和接触电压分布的参数进行了比较和讨论,为系统设计提供了理论基础。     

分布式轨道交通杂散电流监测模型研究

为了保障城市轨道交通的安全,对腐蚀轨道附近建筑中钢筋的杂散电流的检测和防护已成为必然.复杂的环境使杂散电流难于直接检测,为此本文深入杂散电流腐蚀的机理,运用电路理论推导杂散电流分布的理论公式,建立离散的供电理论模型.根据杂散电流的分布规律,分析了影响杂散电流的各个参数,设计了基于供电区间的有效的分布式轨道交通杂散电流监测模型.     

矿井供电电缆绝缘电阻不对称对交流杂散电流分布的影响

在分析矿井交流杂散电流产生机理的基础上,以某矿井交流供电系统为研究对象,结合交流杂散电流可能流通的路径,搭建了矿井交流杂散电流模型,并采用Matlab/Simulink软件进行仿真分析,研究了高低压电缆绝缘电阻在不同不平衡系数下交流杂散电流的分布规律。研究结果表明:当高压或低压电缆绝缘电阻发生不对称后,因其产生的交流杂散电流主要分布在绝缘电阻不对称区间内的屏蔽层/地线芯、金属网等结构上;当整条电缆绝缘电阻不对称时,交流杂散电流在返回电网的回流路径中不断增大;随着电缆绝缘电阻不平衡系数的增大,流经屏蔽层/地线芯、金属网及各接地极的交流杂散电流有效值均增大。     

基于分布式传感器的地铁过渡电阻测量方法

地铁过渡电阻是影响杂散电流泄露的重要因素之一,准确测量过渡电阻可以及时了解地铁回流系统的老化程度,对于杂散电流的防治有很大的意义.提出了一种可以在线测量地铁过渡电阻的方法,将列车运行时的回流电流作为外部测试电源,利用区间中的传感器采集区间内轨道电压和排流网极化电压,得出轨道到排流网的电压,再根据两个区间的轨道电流求出泄...     

分布式轨道交通杂散电流监测系统设计与实现

基于供电区间的杂散电流分布规律研究,设计传感器,并采用现场总线网络获取分布在区间各监测点的传感器数据,按照分布式模型处理并在线分析杂散电流的影响。通过SCADA对单个或多条线路各个区域的整体监测,实时显示杂散电流的分布,智能分析积累数据,指导轨道绝缘维护。实践验证分布式监测系统具有监测准确、可靠性高、成本低等优点。     

轨道交通杂散电流腐蚀的监测及防护研究

南京港华燃气公司发现马群区域天然气高压管道上有强烈干扰的杂散电流存在,大大超过了行业规范《SY/T0017-2006埋地钢质管道直流排流保护技术标准》规定,该规定中提出当管道任意点的管地电位正向偏移均值大于100mV时,必须采取排流保护或其他防护措施,结合常规技术杂散电流防护存在的不足,提出了新型的监测及防护方法。本研究设计的方案采用了杂散电流补偿的方法,避免杂散电流对天然气高压管道的杂波干扰,通过设计出一套监测与防护系统,在系统中加入与地铁供电电流大小相等、方向相反的补偿电流,进而减小或抵消在特定区间内产生的杂散电流。试验结果表明,本文设计的方法大大减少了杂散电流,符合燃气管道相关标准,大大提高了轨道交通的安全性。     

基于预充电过程的牵引变流器支撑电容器参数辨识方法

支撑电容器是牵引变流器的关键部件之一,起着稳定直流侧电压的作用。支撑电容器若长期处于高温、高压的环境,其等效串联电阻会逐渐增大,电容器的性能会逐渐衰退,从而影响变流器的可靠性。根据电容器的健康状态采取不同的维修策略,可以提高牵引系统的安全性和可维护性。为此,文章针对机车牵引变流器提出一种基于预充电过程的支撑电容器参数辨识方法,以实现对支撑电容器的失效预警。其不需要增加传感器,而是利用机车每次启动预充电过程的中间电压以及二次侧电流信号,根据支撑电容器等效电路建立参数的辨识模型;与传统的基于梯度下降的参数辨识算法不同,文章采用遗传算法在参数变化区间内搜索最优值进行等效串联电阻的辨识,以提高参数辨识的可靠性。在不同噪声情况下进行仿真实验并通过模拟机车预充电过程进行物理实验,结果显示,辨识误差均在±3%以内,验证了所提出方法的有效性。     

煤矿井下机车运输监控系统轨道传感器的研究

煤矿井下机车在运行过程中会产生大量的直流磁场,直流磁场会给机车监控系统中的轨道传感器带来干扰,导致错误输出。文章分析并计算了导轨直流磁场对电感式轨道传感器的干扰,并对电感式轨道传感器的设计进行了改进,将轨道传感器线圈与机车导轨磁场设计成互相垂直的,并给出了线圈宽度的计算公式。该方案有效降低了直流磁场对轨道传感器的影响,提高了轨道传感器的抗干扰能力,同时增大了轨道传感器的有效检测距离。     

硅微陀螺仪驱动信号提取端口噪声分析

建立了硅微陀螺仪驱动模态的接口模型,设计了驱动速度信号敏感接口电路,分析表明合理的参数选择基本消除了接口模型中寄生电阻电容导致信号衰减.建立了接口电路的噪声模型,推导了各噪声源导致输出噪声电压公式.仿真和试验表明,由运算放大器的噪声电压和噪声电流,及上置直流偏置电阻R1所产生的噪声功率较大.因此,减小前置运算放大器的输入噪声电压、噪声电流以及寄生电容CPP或者增大直流偏置电阻R1可以有效抑制上述噪声的影响.     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

基于QTE的蒙古文显示机制研究与实现

蒙古语言是中国蒙古族使用的通用语言,由于蒙古文区别于其他文字的书写方式和其自身变形机制等特点,在很多通用的文字处理引擎中都不被支持。在嵌入式产品开发与应用领域中Linux加QTE已经成为流行方式。该文给出了一种在QTE环境上实现基于标准Unicode的蒙古文点阵显示和变形算法, 并自定义了支持蒙古文的QTE组件,扩展了QTE功能,为在Linux加QTE方式的嵌入式体系结构中处理蒙古文提供了一种解决方法。     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

基于AD9626的模拟信号采集存储卡设计

自然界的绝大部分信号都是以模拟的形式存在,因此模拟信号的采集转换存储在数字时代十分关键。文章讨论了在雷达信号处理领域基于AD9626的AD采集存储卡的设计原理、硬件结构和程序设计与芯片配置等问题,为今后相关领域的研究提供了可参考的方案。     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

A human-computer interface for non-computer specialists

The COM teleconferencing system was designed to be easy to use for both beginners and people with much computer experience. A number of design choices in organizing the human-computer interface were considered very carefully. These design problems are not unique for teleconferencing applications, but will appear in many other developments of human-computer interfaces for non-computer specialists. This report discusses naming conventions, menu format, user commands, help facility and the treatment of ‘type ahead’ from the users.