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煤矿井下直流杂散电流的研究 总被引:1,自引:1,他引:0
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。 相似文献
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《工矿自动化》2019,(2):65-69
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。 相似文献
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分布式轨道交通杂散电流监测系统设计与实现 总被引:1,自引:0,他引:1
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。 相似文献
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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。 相似文献
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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。 相似文献
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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. 相似文献
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S. Shaw 《Journal of Computer Assisted Learning》1993,9(2):93-99
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. 相似文献
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European Community policy and the market 总被引:1,自引:0,他引:1
C. Lloyd 《Journal of Computer Assisted Learning》1993,9(2):86-91
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. 相似文献
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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。 相似文献
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Wayne O’Brien Author Vitae 《Journal of Systems and Software》2008,81(11):1997-2013
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. 相似文献
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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. 相似文献
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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 相似文献
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David Poole 《Computational Intelligence》1989,5(2):97-110
Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given. 相似文献
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Watts S. Humphrey 《Annals of Software Engineering》2002,14(1-4):39-72
This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)SM and Team Software Process (TSP){SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical. 相似文献
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基于复小波噪声方差显著修正的SAR图像去噪 总被引:4,自引:1,他引:3
提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。 相似文献
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R. NOSS 《Journal of Computer Assisted Learning》1987,3(1):2-12
Abstract This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development. 相似文献