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船舶轴系接地装置缺陷与对策
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作者 刘良喜 曾先平 《世界海运》 2020年第12期34-36,共3页
介绍PSC检查中发现的某外轮主机轴系接地装置损坏的缺陷,分析缺陷产生的原因,找出解决问题的方法,结合国际公约和船舶安全管理要求,提出针对性建议,供船舶航运公司和船员参考。
关键词 船舶轴接地装置 PSC检查 航运公司 船员
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低阻抗接地网的设计与施工 被引量:1
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作者 刘浩鑫 《科技与企业》 2012年第14期150-150,共1页
建筑电气施工中为了防止雷击事故的发生,对其技术的要求特别高;而在防雷接地装置中,接地电阻阻值越小,则瞬间内冲击接地电压降就越小,建筑物遭受雷击的危险性就越小。文中介绍了接地系统的作用,分析了共用接地系统的性能和特点,阐述了... 建筑电气施工中为了防止雷击事故的发生,对其技术的要求特别高;而在防雷接地装置中,接地电阻阻值越小,则瞬间内冲击接地电压降就越小,建筑物遭受雷击的危险性就越小。文中介绍了接地系统的作用,分析了共用接地系统的性能和特点,阐述了接地电阻的构成及施工和降阻方法。 展开更多
关键词 防雷 接地系 共用接地系 接地电阻
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PLC控制系统中的抗干扰问题研究
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作者 刘亚楠 李洁 《河南科技》 2011年第3X期44-45,共2页
PLC控制系统可靠性高、价格低且功能齐全,因而应用广泛。在实际应用中,由于现场工作情况的复杂性,PLC控制系统常常会受到干扰。一、PLC控制系统干扰源分析1.来自电源的干扰。PLC系统均由电网供电,由于电网覆盖范围广,受到所有空间电磁... PLC控制系统可靠性高、价格低且功能齐全,因而应用广泛。在实际应用中,由于现场工作情况的复杂性,PLC控制系统常常会受到干扰。一、PLC控制系统干扰源分析1.来自电源的干扰。PLC系统均由电网供电,由于电网覆盖范围广,受到所有空间电磁干扰在线路上的感应电压和电流的影响,尤其是电网内部的变化,通过输电线路传到电源缘边,对PLC系统产生干扰。 展开更多
关键词 抗干扰问题 控制 PLC 统可靠性 感应电压 输电线路 现场工作 电磁干扰 抗干扰措施 接地系
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医用电器设备接地设计初探
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作者 孙晓平 《消费电子》 2014年第2期28-28,共1页
本文从电击对人体的影响及防护措施;屏蔽措施及屏蔽接地系;医用计算机工作接地系统;不接地系统配电方式四个方面论述了医用电器设备接地及不接地配电系统的设计要领。
关键词 医用电器 设备接地 屏蔽 屏蔽接地系 配电 设计
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Importance and Design Requirements of Equipotential Connection in Lightning Protection Engineering
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作者 祝新宇 张影 +1 位作者 钟莉 李金义 《Agricultural Science & Technology》 CAS 2013年第8期1201-1203,1208,共4页
The role played by equipotential connection in lightning protection was summarized in terms of lightning protection,static electricity,electromagnetic shielding,protection from electric shocks,and earth fault protecti... The role played by equipotential connection in lightning protection was summarized in terms of lightning protection,static electricity,electromagnetic shielding,protection from electric shocks,and earth fault protection.In addition,drawbacks of independent grounding and common grounding were concluded.According to standards and researches,such as Building Lightning Protection Design Standard (GB50057-2010),further demands and rules of equipotential connection in lightning protection engineering were proposed,providing references for lightning prevention design,construction and examination by related scientific workers and staffs. 展开更多
关键词 Lightning protection design Equipotential connection Common earthingsystem National standard
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对“全方位思维”的沉思
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作者 邓复群 《江西社会科学》 CSSCI 1991年第1期54-55,共2页
“全方位思维”作为近年来出现的一种思维方式,是针对过去的单向性思维方式而产生的。由于我国长期封建社会经济上的自然经济形式,政治上、思想文化上的专制主义和闭关锁国政策,以及解放后机械地照搬苏联僵化的经济模式和后来的一些“... “全方位思维”作为近年来出现的一种思维方式,是针对过去的单向性思维方式而产生的。由于我国长期封建社会经济上的自然经济形式,政治上、思想文化上的专制主义和闭关锁国政策,以及解放后机械地照搬苏联僵化的经济模式和后来的一些“左”倾错误,使得我们的各项体制自我封闭。 展开更多
关键词 全方位 辩证思维方式 单向性 封建社会经济 接地系 自我封闭 对外开放 复群 貌离神合 非本质联
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Application of DC component to select fault branch in arc suppression coil grounding system 被引量:2
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作者 Zhi-Jie WANG Yan-Wen WANG 《Journal of Coal Science & Engineering(China)》 2013年第3期396-401,共6页
When single phase earth fault occurs in the arc suppression coil grounding system, the amplitude of the transient capacitance current is high and decays fast, but the attenuation of the transient inductance current is... When single phase earth fault occurs in the arc suppression coil grounding system, the amplitude of the transient capacitance current is high and decays fast, but the attenuation of the transient inductance current is much slower. This paper analyses the DC component of fault branch, and has found it is much bigger than that of the normal branches in transient state. All the simulation results obtained from three compensation types, different fault time and different wave cycles show that the DC component of fault branch is much higher than that of those normal branches. These results verify the effectiveness of taking the DC component as the method of fault line selection in the arc suppression coil grounding system. 展开更多
关键词 DC component arc suppression coil fault line selection transient state
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Fault diagnosis in neutral point indirectly grounded system basedon information fusion
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作者 于飞 鞠丽叶 +2 位作者 刘喜梅 崔平远 钟秋海 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2003年第4期434-437,共4页
In neutral point indirectly grounded systems, phase-to-ground fault is putting new demands on fault diagnosis technology. Information fusion is applied to detect the phase-to-ground fault, which integrates several sou... In neutral point indirectly grounded systems, phase-to-ground fault is putting new demands on fault diagnosis technology. Information fusion is applied to detect the phase-to-ground fault, which integrates several sources of information, including line current, line voltage, zero sequence current and voltage, and quintic harmonic wave component. This method is testified through the simulation of Matlab. Simulation results show that the precision and reliability of the detection has been greatly increased. 展开更多
关键词 information fusion fault diagnosis neutral point indirectly grounded system phase-to-ground fault
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Application of fractal theory in detecting low current faults of power distribution system in coal mines 被引量:5
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作者 LIU Jian-hua LIANG Rui WANG Chong-lin FAN Di-peng 《Mining Science and Technology》 EI CAS 2009年第3期321-325,共5页
Single-phase low current grounding faults areoften seen in power distribution system of coal mines.These faults are difficult to reliably identify.We propose a new method of single-phase ground fault protection based ... Single-phase low current grounding faults areoften seen in power distribution system of coal mines.These faults are difficult to reliably identify.We propose a new method of single-phase ground fault protection based upon a discernible matrix of the fractal dimension associated with line currents.The method builds on existing selective protection methods.Faulted feeders are distinguished using differences in the zero-sequence transient current fractal dimension.The current signals were first processed through a fast Fourier transform and then the characteristics of a faulted line were identified using a discernible matrix.The method of calculation is illustrated.The results show that the method involves simple calculations, is easy to do and is highly accurate.It is, therefore, suitable for distribution networks having different neutral grounding modes. 展开更多
关键词 low current faults zero sequence transient current fractal dimension discernible matrix selective protection
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Dynamically Authorized Role-Based Access Control for Grid Applications
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作者 YAO Hanbing HU Heping LU Zhengding LI Ruixuan 《Geo-Spatial Information Science》 2006年第3期223-228,233,共7页
Grid computing is concerned with the sharing and coordinated use of diverse resources in distributed “virtual organizations”. The heterogeneous, dynamic and multi-domain nature of these environments makes challengin... Grid computing is concerned with the sharing and coordinated use of diverse resources in distributed “virtual organizations”. The heterogeneous, dynamic and multi-domain nature of these environments makes challenging security issues that demand new technical approaches. Despite the recent advances in access control approaches applicable to Grid computing, there remain issues that impede the development of effective access control models for Grid applications. Among them there are the lack of context-based models for access control, and reliance on identity or capability-based access control schemes. An access control scheme that resolve these issues is presented, and a dynamically authorized role-based access control (D-RBAC) model extending the RBAC with context constraints is proposed. The D-RABC mechanisms dynamically grant permissions to users based on a set of contextual information collected from the system and user’s environments, while retaining the advantages of RBAC model. The implementation architecture of D-RBAC for the Grid application is also described. 展开更多
关键词 Grid security RBAC context-based access control
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Research on Common Grounding Electrode Technique in HVDC
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作者 Chenglian MA 《International Journal of Technology Management》 2015年第1期4-6,共3页
This paper discusses the characteristics of DC transmission common system ground electrode type and shared ground electrode, established the mathematical model of two circuit DC systems share ground electrode, analyze... This paper discusses the characteristics of DC transmission common system ground electrode type and shared ground electrode, established the mathematical model of two circuit DC systems share ground electrode, analyze effects of the shared loop ground DC transmission system electrode on the operation of HVDC system size under different operation modes, and compare with the independent ground electrode, ground electrode impact on environment under different operation mode, and the paper finally puts forward some solving measures for the influence of the shared ground electrode on the environment and public ground electrode effects on DC system operation problems. 展开更多
关键词 HVDC ground electrode line protection DC transmission system TRANSIENT
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New One-Way Line for Electric Transmission System 被引量:3
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作者 Michael Bank 《Journal of Energy and Power Engineering》 2012年第8期1320-1327,共8页
There are three well known types of wire lines for transmitting electrical energy or information. The first type is ordinary two wires line (below A-Line). The second type is so-called single-wire line, where ground... There are three well known types of wire lines for transmitting electrical energy or information. The first type is ordinary two wires line (below A-Line). The second type is so-called single-wire line, where ground plays the role instead of second wire. Polyphase systems belong to the third type, three phase system is the most popular among them. The purpose of this article is another attempt to build a one-wired (without ground) system--the transmission of electrical energy. In this paper an original idea of building such a system is justified, the results of simulations and laboratory modeling are presented. It is shown that the proposed method can reduce the cost of electric transmission lines, the losses in them and significantly reduce interferences. 展开更多
关键词 Electrical lines three phase system one line system TRANSFORMER delay line.
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Distribution of Large Volume Image Data Using the Mixed Mode of Java Servlet and COM on Web
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作者 WANGMi ZHUXinyan +1 位作者 PANJun CHENNengcheng 《Geo-Spatial Information Science》 2004年第3期167-173,共7页
This paper reports some researches on distribution of large volume image data using techniques of the Mixed Mode of Java Servlet and COM on Web. The architecture and key technologies are discussed in detail. The web d... This paper reports some researches on distribution of large volume image data using techniques of the Mixed Mode of Java Servlet and COM on Web. The architecture and key technologies are discussed in detail. The web distribution system of image is implemented and the system is tested by the application instances. At last, the advantages and disadvantages for this web image distribution mode are analyzed. 展开更多
关键词 seamless image database WEB GIS connection pool COM &. DCOM
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Coordinated scheduling model for intermodal transit hubs based on GI/M^K/1 queuing system
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作者 贾洪飞 曹雄赳 杨丽丽 《Journal of Central South University》 SCIE EI CAS CSCD 2015年第8期3247-3256,共10页
Coordinated scheduling of multimode plays a pivotal role in the rapid gathering and dissipating of passengers in transport hubs. Based on the survey data, the whole-day reaching time distribution at transfer points of... Coordinated scheduling of multimode plays a pivotal role in the rapid gathering and dissipating of passengers in transport hubs. Based on the survey data, the whole-day reaching time distribution at transfer points of passengers from the dominant mode to the connecting mode was achieved. A GI/M K/1 bulk service queuing system was constituted by putting the passengers' reaching time distribution as the input and the connecting mode as the service institution. Through queuing theory, the relationship between average queuing length under steady-state and headway of the connecting mode was achieved. By putting the minimum total cost of system as optimization objective, the headway as decision variable, a coordinated scheduling model of multimode in intermodal transit hubs was established. At last, a dynamic scheduling strategy was generated to cope with the unexpected changes of the dominant mode. The instance analysis indicates that this model can significantly reduce passengers' queuing time by approximately 17% with no apparently increase in departure frequency, which provides a useful solution for the coordinated scheduling of different transport modes in hubs. 展开更多
关键词 traffic engineering coordinated scheduling queuing theory intermodal transit hub HEADWAY
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An Improved Direction Relation Detection Model for Spatial Objects
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作者 FENGYucai YIBaolin 《Geo-Spatial Information Science》 2004年第4期297-302,共6页
Direction is a common spatial concept that is used in our daily life. It is frequently used as a selection condition in spatial queries. As a result, it is important for spatial databases to provide a mechanism for mo... Direction is a common spatial concept that is used in our daily life. It is frequently used as a selection condition in spatial queries. As a result, it is important for spatial databases to provide a mechanism for modeling and processing direction queries and reasoning. Depending on the direction relation matrix, an inverted direction relation matrix and the concept of direction pre- dominance are proposed to improve the detection of direction relation between objects. Direction predicates of spatial systems are also extended. These techniques can improve the veracity of direction queries and reasoning. Experiments show excellent efficiency and performance in view of direction queries. 展开更多
关键词 spatial databases geographic information systemst direction relations direction relation matrix
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A Study on Neutral Point Earthed Method of Power System
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作者 Feigao Li Yanhua Meng Shaobing Shi 《International Journal of Technology Management》 2013年第3期5-7,共3页
This paper mainly is study on power system working state with neutral point different grounded methods, when the power system is normal working and the single-phase grounding. And further analysis of the different ope... This paper mainly is study on power system working state with neutral point different grounded methods, when the power system is normal working and the single-phase grounding. And further analysis of the different operating modes of voltage and current relationships, expounds the different operation occasions and characteristics. 展开更多
关键词 power system neutral point grounded methods
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Fault location of two-parallel transmission line for double phase-to-earth fault using one-terminal data
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作者 张庆超 段晖 +1 位作者 耿超 宋文南 《Journal of Zhejiang University Science》 CSCD 2003年第5期520-525,共6页
An accurate algorithm for fault location of double phase-to-earth fault on transmission line of direct ground neutral system is presented. The algorithm, which employs the faulted phase network and zero-sequence netwo... An accurate algorithm for fault location of double phase-to-earth fault on transmission line of direct ground neutral system is presented. The algorithm, which employs the faulted phase network and zero-sequence network as fault-location model in which the source impedance at the remote end is not involved, ef-fectively eliminates the effect of load flow and fault resistance on the accuracy of fault location. The algorithm achieves accurate location by measuring only one local end data and is used in a procedure that provides automatic determination of faulted types and phases, and does not require the engineer to specify them. Simulation results showed the effectiveness of the algorithm under the condition of double phase-to-earth fault. 展开更多
关键词 Fault location Transmission line Double phas e-to-earth fault
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Mathematical Modelling for Assessing Integrity of Power Systems Grounding Devices
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作者 Yury Chikarov Tek Tjing Lie Nirmal-Kumar Nair 《Journal of Energy and Power Engineering》 2012年第7期1097-1105,共9页
This paper presents the development of a new technique to monitor the operating conditions of a grounding device of high voltage apparatus and systems without any diggings and forced outages. The model is based on the... This paper presents the development of a new technique to monitor the operating conditions of a grounding device of high voltage apparatus and systems without any diggings and forced outages. The model is based on the evaluation of the magnetic field distribution along the current-carrying horizontal element when it has been deteriorated or broken. A mathematical model which can be used to analyze and evaluate the integrity of the grounding device has been developed. Computer simulation studies were conducted to validate the effectiveness of the proposed model. 展开更多
关键词 Grounding devices horizontal elements eat'thing.
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Departure from Indigenous Land Use System and the Consequential Impacts: A Case of Cuvelai Basin, North-Central Namibia
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作者 Johanna Ngula Niipele lsak Kaholongo Kaholongo Joseph Njunge 《Journal of Environmental Science and Engineering(A)》 2015年第3期143-153,共11页
The Cuvelai Basin of north-central Namibia consists of unique seasonal wetlands made up of shallow pans locally known as Iishana (Oshana, singular) which form ephemeral network systems. The basin has relatively fert... The Cuvelai Basin of north-central Namibia consists of unique seasonal wetlands made up of shallow pans locally known as Iishana (Oshana, singular) which form ephemeral network systems. The basin has relatively fertile soils encouraging human settlements. More than 40% of the country's population resides in the basin. Early settlers in the basin utilized indigenous knowledge to develop land use systems that were in harmony with biophysical characteristics of the area. Over the years, there has been a departure from these indigenous land use systems resulting in land management problems. A desktop study coupled with field observations was conducted to describe the indigenous land use systems of the Owambo people living in the basin, and to determine factors behind the departure and consequential impacts of this departure on sustainability of land uses. Possible ways of preventing erosion of this indigenous knowledge were given attention. The paper recommends that the Owamboindigenous land management system needs to be embedded within government policies and regulations and should be strictly enforced. There is also a need for designing strategic basin management plans that are a combination of both scientific and indigenous knowledge. 展开更多
关键词 Cuvelai Basin Owambo people indigenous land use system sustainable development.
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某船柴油机主轴承损坏故障分析 被引量:2
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作者 李瑞民 陈昶 +1 位作者 匡加勇 王连海 《航海技术》 2016年第3期61-62,共2页
0引言 某船柴油机型号为MAN B&W 7S60MC-C,2014年发生柴油机主轴承损坏故障,经检修,确认故障为静电腐蚀所致,维修周期长达半年,延误船期并造成较大损失。同时,由于修理工艺的不同,柴油机No.1主轴承异于其他主轴承,加装有监控设备,增... 0引言 某船柴油机型号为MAN B&W 7S60MC-C,2014年发生柴油机主轴承损坏故障,经检修,确认故障为静电腐蚀所致,维修周期长达半年,延误船期并造成较大损失。同时,由于修理工艺的不同,柴油机No.1主轴承异于其他主轴承,加装有监控设备,增加管理难度。 展开更多
关键词 轴承损坏 故障分析 电腐蚀 修理工艺 维修周期 主轴承 艉轴 接地装置 白合金轴承 接地保护装置
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