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Influence of frequency on electrical tree initiation in polyethylene

Gaodianya Jishu/High Voltage engineering 2007年第4期33卷 138-142页

作者： Zhou, Yuan-Xiang Wang, Yi-Nan Xing, Xiao-Liang Wang, Yun-Shan Wang, Ning-Hua Liang, Xi-Dong Guan, Zhi-Cheng State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

Treeing degradation in dielectric polymers often leads to insulation failures in electrical equipment. In order to make out the breakdown failures, the tree initiation characteristics of ice-water quenched HDPE under AC voltage in frequencies ranging from 50 Hz to 90 kHz are, studied. It is found that the tree initiation voltages (TIV) change a little when the frequency is from 50 Hz to 1 kHz. When the frequency is higher than 1 kHz, the TIV increases with the increase of frequency before reaching a maximum TIV. While the TIV decreases at first then increases at frequency >10 kHz. There are 7 categories of tree shapes, including branch-like, trunk-like, bosk-like, direct breakdown, bosk-trunk, bosk-breakdown and branch-trunk, appeared in the experiment. The categories of tree shapes manifold with the frequency increasing. The TIV of different categories are different apparently. The breakdown shape shows the highest TIV while the branch-like one shows the lowest TIV. The damage degrees to insulation material are different for different categories. It is also found that as the frequency increases, the dispersion of TIV increases remarkably. Though the polymer shows higher average TIV values as the frequency is larger than 1 kHz, the larger dispersion in higher frequency region indicates that the application of polymer insulators in medium or high frequency area would bring a higher breakdown risk as one can find from the frequent insulation failures in high frequency machines. The influence of frequency on electron accelerating process and fatigue effect aggravation in material under high frequency are considered as main causes of the experiment results.

关键词：聚乙烯电树老化电树起始电树形态频率

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Preparation of TiO films by cathode multi arc ion and its performance

Preparation of TiO films by cathode multi arc ion and its pe...

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International Nano-Optoelectronic Workshop, iNOW

作者： Duojin, Fan Duowang, Fan Chenglong, Wang Lingxiao, Ming Lin, Zhao Hongzhong, Liu Lanzhou Dachen Automatic Control System Co. Ltd. Lanzhou 730070 China MOE Key Lab. of Opto-electronic Technology and Intelligence Control Lanzhou Jiaotong University Lanzhou 730070 China State Key Laboratory for Manufacturing Systems Engineering Xi'an Jiaotong University Xi'an 710049 China

TiO films were prepared by custom-made Cathode Multi Arc Ion equipment. Experimental test results reveal that our equipment can easly deposite big area scale TIO, particle size is in nanometer scale. © 2007 IEEE.

ISBN: (纸本)1424415918

关键词： Particle size

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Synthesis and photocatalytic capability of Cr-TiO2 film

Synthesis and photocatalytic capability of Cr-TiO2 film

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International Nano-Optoelectronic Workshop, iNOW

作者： Xiaojuan, Lu Duowang, Fan Duojin, Fan Hongzhong, Liu School of Automation and Electric Engineering Lanzhou Jiaotong University Lanzhou 730070 China MOE Key Lab. of Opto-electronic Technology and Intelligence Controll Lanzhou Jiaotong University Lanzhou 730070 China Lanzhou Dachen Automatic Control System Co. Ltd. Lanzhou 730070 China State Key Laboratory for Manufacturing Systems Engineering Xi'an Jiaotong University Xi'an 710049 China

A TiO2 catalyst doped by Cr was prepared by the sol-gel method and characterized by UV-2550 and FS. The results revealed that the Cr 6+-doped TiO2 film had the higher photocatalytic activity than pure TiO2 film. ©... 详细信息

ISBN: (纸本)1424415918

关键词： Sol-gel process

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Ventilation conditions and the related symptoms in selected indoor environments in a university

Ventilation conditions and the related symptoms in selected ...

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6th International Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings: Sustainable Built Environment, IAQVEC 2007

作者： You, Yan Bai, Zhipeng Jia, Chunrong Hu, Xinming Ran, Wenting Zhang, Jingjing Yang, Jing State Environ. Protect. Key Lab. of Urban Ambient Air Particulate Matter Pollution Prev. and Control College of Environmental Sciences and Engineering Nankai University Tianjin 300071 China Department of Environmental Health Sciences School of Public Health University of Michigan Ann Arbor MI 48109 United States

ISBN: (纸本)9784861630705

Limited data are availab.e for understanding indoor environmental quality (IEQ) and the related health effects in schools in China. This paper reports the air exchange rates (AERs) of 50 rooms in a university in Tianjin, China, and explores the relationship between ventilation conditions and symptoms. All of the 50 rooms were visited during June to August, 2006, including 20 dormitories and 5 reading rooms using ceiling fans, 10 old classrooms with split air-conditioners in an old building and 10 new classrooms with air circulation cooling system in a new building, and 5 conference rooms with split air-conditioners. Temperature, relative humidity (RH), and CO2 concentrations were continuously monitored for 12h in each room, and out of the building simultaneously. Occupants in the rooms, all being undergraduates, were investigated by questionnaires regarding time-activity patterns, judgment about IAE in campus and comfortlessness possibly relative to bad ventilation. Room characteristics, ventilation methods and numbers of occupants and their activities were also recorded. AERs were derived from CO2 concentration decay curves obtained when rooms were unoccupied. CO2 concentration, temperature and RH ranged 615-5346 ppm, 18.9-39°C and 30-90%, respectively. Average AERs were 1.2, 1.9, 1.6, 1.1 and 0.7 hr-1 in dormitories, reading rooms, old classrooms, new classrooms and conference rooms, respectively. In dormitories, factors such as outdoor climate conditions, deficiency of building design, room usage and living habits of students, were considered to be essential on ventilation and indoor CO2 concentration. More complaints and symptoms were found in dormitories, classrooms and conference rooms, whose AERs were lowest. CO2 concentrations was highly associated with symptoms such as absence of mind, fidget and headache, regardless of the comfortable temperature (22-28°C) and RH (40-70%) range. In dormitories, AER or CO2 concentrations was not a key factor influencing com

关键词： Ventilation

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Measuring air exchanges rates using continuous CO2 sensors

Measuring air exchanges rates using continuous CO2 sensors

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Symposium on Air Quality Measurement Methods and Technology 2007

作者： Yan, You Zhipeng, Bai Chunrong, Jia Zhaofeng, Wan Wenting, Ran Jingjing, Zhang State Environ. Protect. Key Lab. of Urban Ambient Air Particulate Matter Poll. Prev. and Control College of Environmental Sciences and Engineering Nankai University Tianjin 300071 China Department of Environmental Health Sciences School of Public Health University of Michigan Ann Arbor MI 48109 United States

ISBN: (纸本)9781604239003

Air exchange rate (AER) is a critical parameter for determining indoor air quality and thermal comfort. However, measuring AERs in an effective, real-time, convenient and low-cost way is still a challenge in China. A new AER measuring method using continuous CO2 sensors was validated through both lab.ratory experiments and field studies. controlled lab.ratory simulation tests were conducted in a 1-m3 environmental chamber at different AERs (0.1 10.0 hr-1). AERs were determined using the steady-state method and the decay method based on box model assumptions. Field tests were conducted in four types of environments on campus in during 3-5 weekdays with four sets of sensors coupled with data logger while temperature and relative humidity were determined indoor and outdoor simultaneously. AERs were derived from CO 2 concentration decay curves obtained when rooms were unoccupied. Outdoor climate conditions were also recorded in detail to investigate possible effects on indoor ventilation efficiency. Statistic results indicated that good lab.ratory performance was achieved: duplicate precision was within 10%, differences between the two methods were within 15%, and the measured AERs were 90 -120% of the real AERs. Average AERs were 1.2, 1.9, 1.4, 1.1 and 0.7 hr -1 in dormitories, reading rooms, old classrooms, new classrooms and meeting rooms, respectively. In dormitories, factors such as outdoor climate conditions, deficiency of building design, room usage and living habits of students, were considered to be essential on ventilation and indoor CO 2 concentration. In spite of limitations, this new method, along with mini-sized and easily operational instrumentations which provide sufficient continuous data, demonstrated an effective way to measure AERs in various indoor environments.

关键词： Carbon dioxide

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Model set optimization method for complex plant multi-model control

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IMACS Multiconference on "Computational engineering in Systems Applications", CESA

作者： Jiansheng, Xu Xiong, Hou Yongji, Wang IEEE Department of Control Science and Engineering Huazhong University of Science and Technology Wuhan 430074 China State Key Lab. of National Defense for Aerospace Intelligent Control Beijing 100854 China

ISBN: (纸本)7302139229

In this paper we present a novel model set optimization method that is applicable to the complex systems with large parameters variations and multiple operating modes. The proposed method is based on the multi-model approach to improve the system performance of a complex control system of linear or nonlinear characteristics when it operates at various operating conditions. The multi-model control scheme depends on the multiple representations of a process using different models that generate the control signal needed to make the system follow a prescribed desired trajectory. It uses a set of models-combining the offline identified models and the dynamic model bank with the iterative learning, which guides the adaptation process. The offline models are obtained from the physics or chemistry principles. Dynamic model bank summarizes the parameters of the models that successfully approximate the plant. The model bank can be automatically created and updated and does not call for an initial set of models. By virtue of the iterative learning, we expect to make the models set consist the models which best represented the character of the plant. It uses a soft switching mechanism that provides a smooth transition from an interpolate to a pure hard switching scheme between the models in the model set We also demonstrate the advantage of using this approach on an examples considering control of systems with large parameter variations. Simulation results show that the method proposed in this paper has obvious advantage over the only dynamic model bank, and illustrate the potential of the algorithm of the developed method.

关键词： Iterative methods

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A variable-length encoding method to prevent the error propagation effect in video communication

A variable-length encoding method to prevent the error propa...

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作者： Ma, Linhua Chang, Yilin Liu, Jun Du, Xinmin State Key Lab. of Integrated Service Networks Xidian University Xi'an China KongJun Engineering Institute Xi'an China Xi'an Satellite Control Center Xi'an China

A novel variable-length code (VLC). called alternate VLC (AVLC), is proposed, which employs two types of VLC to encode source symbols alternately. Its advantage is that it can not only stop the symbol error propagation effect, but also correct symbol insertion errors and symbol deletion errors, which is very important in video communication. Copyright © 2006 The Institute of Electronics, Information and Communication Engineers.

关键词： Encoding (symbols)

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An axial-beam piezoresistive accelerometer for high-performance crash detection of automotive industry

An axial-beam piezoresistive accelerometer for high-performa...

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2006 5th IEEE Conference on Sensors

作者： Dong, Peitao Xinxin, Li Yuelin, Wang Songlin, Feng Shengyi, Li State Key Lab. of Transducer Technology Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai 200050 China College of Mechatronics Engineering and Automation National University of Defense Technology Changsha 410073 China

ISBN: (纸本)1424403766

A high-performance piezoresistive accelerometer is developed for crash assessment of automobiles. For meeting the technical requirements, a novel sensor scheme is used that features both high sensitivity and high dynamic characteristics (including high resonant frequency and precise damping ratio). A three-beam seismic mass structure is proposed with the combination of a comb damper. Considering the demand in low-cost volume production, standard silicon wafers (instead of SOI wafers) are used here for micro-fabrication of the sensors. Double-sided deep RIE is processed for the micromechanical structure that is combined with the piezoresistive integration process. Test results show that the normalized sensitivity of the accelerometer is measured as 0.11mv/g/5v within the full-range of 2000g. The resonance frequency is 31KHz, with the band of ±5% variation in sensitivity wider than 5kHz. 15000g shocking test has been implemented to the packaged device, resulting in safe survival. © 2006 IEEE.

关键词： Silicon wafers

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Risk-based study on under voltage load shedding schemes

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical engineering 2006年第19期26卷 18-22页

作者： Dai, Jian-Feng Zhu, Ling-Zhi Zhou, Shuang-Xi Lu, Zong-Xiang State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

A risk based method is proposed to design under voltage load shedding (UVLS) scheme. Different with traditional methods, the proposed one employs a series of risk indices, which are obtained based on a full-scale contingencies analysis, to determine the operating parameters of load shedding. According to this method, the load bus, in which the UVLS can exert itself with the highest efficiency to prevent voltage collapse, is selected as the first candidate to execute load shedding. And the amount of loads to be shed is identified though a relationship between risk values and shedding amount. The selection of shedding time conforms to the principle that the compound risk brought by failed shedding and unexpected shedding must be the minimum. Experiments conducted for IEEE 39-bus system reveal that the proposed method redound to identify the location, amount and time of load shedding more accurately and reasonably due to taking into account a great deal of uncertain factors.

关键词： Electric load shedding

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Study on probability of voltage instability based on the stochastic characteristic of load margin index

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical engineering 2006年第13期26卷 26-30页

作者： Dai, Jian-Feng Wang, Hai-Chao Zhou, Shuang-Xi Lu, Zong-Xiang Zhu, Ling-Zhi State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

In order to make up the deficiency of traditional analytical method used in the research of voltage stability problem, we need to know the probability information concerned with voltage instability. Therefore, this paper proposes a method to calculate the probability of voltage instability based on the stochastic characteristic of load margin index. This method firstly determines the stochastic characteristic of load margin index through an analysis about the randomicity of parameters which tie up with the tracing of critical point in continue power flow computation, and then figures out the probability of voltage instability by using moment and cumulate method. Owing to take into account more uncertain factors' influence on the voltage stability, the result acquired by this method is much more accurate and reasonable. A numerical simulation based on IEEE 39-bus system reveals that the proposed method works properly.

关键词： Electric power systems

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