检索结果-南通市图书馆

DC ice-melting model for wet-growth icing conductor and its experimental investigation

Science china(Technological Sciences) 2010年第12期53卷 3248-3257页

作者： FAN SongHai1,2, JIANG XingLiang1, SHU LiChun1, SUN CaiXin1 & WANG DaXing1,2 1 State Key Laboratory of power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400044, china 2 sichuan {3. power Test and research institute, chengdu 610072, china State Key Laboratory of power Transmission Equipment & System Security and New Technology Chongqing University Chongqing China sichuan electric power Test and {3. institute Chengdu China

Icicles are often formed under the downside surface of conductor in the wet growth icing of overhead power line. When the ice deposit around overhead power line is molten by Joule heat produced by current, the pattern of heat transfer of ice deposit with icicles is dissimilar to that without icicle, so the ice-melting model for the columnar icing conductor cannot be applied to icicle-shaped icing conductor. According to the heat-transfer characteristic of the icicle-shaped icing conductor, this paper puts forward a DC ice-melting model for the icicle-shaped icing conductor. Because this full model includes three-dimensional heat-transfer and interface movement, which cannot be solved in closed form, a finite element scheme in space-domain and a finite difference scheme in time-domain are employed to discretize the governing equations. Firstly the whole ice-melting process on the icicle-shaped icing conductor is simulated by this model. Then the simulated results are validated by ice-melting experiments in the artificial chamber. The study from the model and the experiments shows that the size and length of icicle as well as the space between the adjacent icicles are factors to affect ice-melting. With the shorter icicle space, the bigger icicle size and the longer icicle-length, the surface of ice layer is enlarged and then more heat is taken away by the convection and radiation, so the ice melting time will get longer.

关键词： power line icing ice storm ice melting icicle

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Effects of Annealing Temperature on the electrical Conductivity and Mechanical Property of Cu-Te Alloys

引用

Journal of Wuhan University of Technology(Materials Science) 2007年第1期22卷 88-90页

作者：朱达川 Metallic Material Department College of Material Science and Engineering Sichuan University

The effects of annealing temperatre on the electrical conducitivity and mechanical property of Cu-Te alloys were studied via an AG-10TA electronic universal machine, an SB223. digital electric bridge, SEM, EDS and XPS. The results show the electrical conductivity increases while the tensile strength fluctuates when the annealing temperature becomes higher because the recrystallization occurs during the annealing process, leading to the density of dislocation decreasing, grain size growing up, but the second phase precipitating sufficiently and simultaneously.

关键词： Cu-Te alloys annealing temperature recrystallization

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Characteristics of the Lower Yellow River channel shrinkage and its discriminant parameters

引用

Science china(Technological Sciences) 2010年第5期53卷 1374-1386页

作者： HU ChunHong1 & ZHANG GuoGang2 1 china institute of Water Resources and Hydropower {3.,Beijing 10003.,china 2 Guangdong electric power Design institute,Guangzhou 510663.china china institute of Water Resources and Hydropower {3. Beijing China Guangdong electric power Design institute Guangzhou China

This paper analyzes the changing trends of the Lower Yellow River(LYR) transverse profile parameters and their aberrance points by the time series analysis *** results show that there has been a trend of changes in the LYR channel transverse profile parameters since the *** main river channel has a tendency of shrinkage year by year and the trend will be continued in the *** main features of the LYR channel shrinkage are remarkable reductions of bankfull dis-charges and bankfull areas,corresponding decreases of bankfull widths,average bankfull water depths and maximal bankfull water depths,as well as increases of bankfull water levels and width-depth ratios *** discriminant parameters for threshold of the LYR main channel shrinkage were put *** indicates that the LYR main channel began to shrink in the 1970s and has entered into a serious phase of channel shrinkage since the *** incompatible index of discharged water-sediment processes of the Sanmenxia Reservoir was introduced,which revealed that there was a trend of increasing in the incompatibility between water flow and sediment *** relations between the LYR main channel shrinkage parameters and discharged water-sediment processes of the Sanmenxia Reservoir were founded,which indicate that the LYR main channel shrinkage can be mitigated and improved through the regulation of discharged water-sediment processes of the reservoir,especially through the regulation of water-sediment incompatible *** LYR channel for water and sediment transportation can be restored and maintained.

关键词： Lower Yellow River time series analysis main river channel shrinkage discriminant parameters of channel shrinkage water-sediment incompatible index

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Computational theory of cavitating flows for hydraulic turbomachinery with consideration of influence of water quality

引用

Science china(Technological Sciences) 2010年第12期53卷 3341-3348页

作者： WANG Lei1,2 & CHANG JinShi2 1 Huadian electric power research {3., Hangzhou 3.003., china 2 College of Water Conservancy and Civil Engineering, china Agricultural University, Beijing 100083. china Huadian electric power research {3. Hangzhou China College of Water Conservancy and Civil Engineering China Agricultural University Beijing China

Previously it was assumed that the pressure within the cavity or on the cavity surface remained constant and the vapor pressure of clean water at 20°C and 0 m altitude was utilized as the computational boundary for cavitating flows in hydraulic turbomachinery. Cavitation was confused with vaporization, and the effect of water quality on cavitation pressure characteristics was not taken into account. In recent years, lots of experiments of cavitation pressure characteristics of different water qualities including different sand concentrations of sand water and different altitudes of clean water have been performed by the authors, and the important influences of water quality on cavitation pressure characteristic have been validated. Thus the water quality should be involved in the cavitating flows computation. In the present paper, the effect of water quality on the cavitation pressure characteristic is analyzed and the computational method and theory of cavitating flows for hydraulic turbomachinery that considers the influence of water quality are proposed. The theory is suitable for both the potential flow method and the two-phase flow method for cavitating flows simulation. Finally, the validation results for cavitating flows in a hydraulic tur- bine indicate the significant influences of water quality on the cavitating flow performance.

关键词： cavitating flows cavitation pressure water quality hydraulic turbomachinery

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

The influence of the sand-dust environment on air-gap breakdown discharge characteristics of the plate-to-plate electrode

引用

Science china(Physics,Mechanics & Astronomy) 2010年第3期53卷 458-464页

作者： HE Bo1, ZHANG Gang1, CHEN BangFa1, GAO NaiKui1, LI YaoZhong2, PENG ZongRen1 & JIN HaiYun1 1 State Key Laboratory of electrical Insulation and power Equipment, Xi’an Jiaotong University, Xi’an 710049, china 2 Xinjiang electric power research institute, Urumqi 83.011, china State Key Laboratory of electrical Insulation and power Equipment Xi’an Jiaotong University Xi’an China Xinjiang electric power research {3. Urumqi China

The experiments of plane-plane gap discharge was carried out in an environment of artificial sandstorm. By comparing and analyzing the differences in gap breakdown voltage between the sand & dust environment and clean air, some problems were investigated, such as effects of wind speed and particle concentration on the breakdown voltage, differences of gap discharge characteristics between the dust & sand medium and the clean air medium. The results showed that compared with the clean air environment, the dust & sand environment had a decreased gap breakdown voltage. The longer the gap distance, the greater the voltage drop; the breakdown voltage decreased with the increase of particle concentration in flow. With the increase of wind speed, the breakdown voltage decreased at the beginning and rose afterwards. The results of the paper may helpful for further research regarding the unidentified flashover and external insulation characteristics of the HV power grid in the dust & sand environment.

关键词： external insulation air-gap breakdown sand-dust flow simulation experiment

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Preparation and Magnetic Properties of Mn-Zn Ferrites by the Co-precipitation Method

引用

Journal of Wuhan University of Technology(Materials Science) 2009年第6期24卷 875-878页

作者：李雪张俊喜 School of Environmental and Chemical Engineering Shanghai University Electrochemical research Group Shanghai University of Electric PowerKey Laboratory of State Power Corporation of China

Mn-Zn ferrites （Mn1-xZnxFe2O4） with different compositions were prepared by the coprecipitation method, and the influences of such synthesis conditions as pH value, composition and volume ratio （R） of the mixed solution and NH4HCO3.solution on their microstructures and magnetic properties were discussed. The samples were characterized by X-ray diffraction （XRD） and magnetization measurement instrument. Lattice parameters and average crystalline size of the synthesized materials were calculated from the corresponding XRD patterns with the related software Jade.5. For samples of different pH values, only one phase was found when pH values were 7.0, 8.0 and 9.0. The sample with pH value of 7.0 exhibited the highest saturation magnetic induction, the lowest coercive force, and crystallized best. For samples of different R values with pH value of 7.0, only one phase was observed in all samples, and the sample with R value of 2.3.exhibited the highest saturation magnetic induction and the lowest coercive force. The composition has mainly afected the magnetic properties, and the saturation magnetic induction increases with the increase of the content of Zn （x）, but decreases when x is beyond 0.6. The trend of coercive force is on the contrary. However, no magnetism is exhibited when the x value is up to 0.8.

关键词： co-precipitation method microstructure magnetic property Mn-Zn ferrite

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

基于阴极再循环的燃料电池系统建模与动态性能分析

引用

同济大学学报（自然科学版） 2024年第4期52卷 619-627页

作者：刘泽许思传同济大学汽车学院上海201804

阴极再循环通过调节电堆进气中的氧分压和水蒸气分压特别适合解决车用燃料电池系统在低怠速工况下的缺水和高电势问题。建立了一个带阴极再循环功能的燃料电池非线性系统控制模型,使用阴极再循环泵将阴极出口的气体引回到空压机出口实... 详细信息

阴极再循环通过调节电堆进气中的氧分压和水蒸气分压特别适合解决车用燃料电池系统在低怠速工况下的缺水和高电势问题。建立了一个带阴极再循环功能的燃料电池非线性系统控制模型,使用阴极再循环泵将阴极出口的气体引回到空压机出口实现了进气加湿和氧分压调节。该模型可捕捉由阴极再循环带来的一系列动态响应。结果表明,阴极再循环可以极大地改善小电流密度下的进气湿度,随着阴极再循环比的增加,加湿动态响应加快;氧分压调节的动态响应较慢,但通过合理的阴极再循环策略仍能将小电流密度下的高电势限制在0.8V以下。通过抑制小电流密度下的电压,实现了50%的怠速功率降幅。

关键词：车用燃料电池系统阴极再循环面向控制建模动态性能

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Current distribution and stability of LTS/HTS hybrid superconducting conductors

引用

Science china(Technological Sciences) 2010年第7期53卷 2000-2007页

作者： GUAN XiaoJin1,2, WANG YinShun1 & ZHOU WeiWei3.1 Key Laboratory of HV and EMC Beijing, North china electric power University, Beijing 102206, china 2 Department of Physics, Baoding University, Baoding 071000, china 3.institute of electrical Engineering, Chinese Academy of Sciences, Beijing 100190, china Key Laboratory of HV and EMC Beijing North China Electric Power University Beijing China Department of Physics Baoding University Baoding China institute of electrical Engineering Chinese Academy of Sciences Beijing China

Current distribution and stability of a hybrid LTS/HTS superconductor, consisting of multifilamentary NbTi/Cu and Bi2223.Ag tapes, were numerically analyzed according to power-law models. The results showed that most of current passed through the LTS and the current increased in the HTS with temperature rise when the transport current was below the critical current of the hybrid conductor. The quench propagation velocity of the hybrid conductor was smaller but its minimum quench energy was larger than those of LTS conductors, indicating that the stability of the hybrid superconducting conductor was effectively improved and a high engineering current density was simultaneously achieved. Finally, a hybrid sample, made by soldering Bi2223.Ag tape onto NbTi/Cu conductor, was prepared and tested successfully at helium temperature. The experimental results qualitatively agreed with the simulated ones.

关键词： distribution hybrid conductor minimum quench energy quench propagation velocity n value stability

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

APPLYING PPE MODEL BASED ON RAGA TO CLASSIFYAND EVALUATE SOIL GRADE

引用

Chinese Geographical Science 2002年第2期12卷 136-141页

作者： FU Qiang1,2, LU Tie guang2, FU Hong2(1. College of Hydraulic power, sichuan University, chengdu 610065, P.R.{3. 2. Northeast Agricultural University, Harbin 15003., P. R. china) College of Hydraulic power Sichuan University Chengdu P. R. China Northeast Agricultural University Harbin P. R. China

The research of soil classification and soil grade evaluation is often based on fuzzy theory. So, the traditional method has an inevitable problem about weight matrix which given by some experts, and the final result can be influenced by artificial factors. The essentials of fuzzy synthetically judge is to handle the data of high dimension. That is to reducing the dimension number. The weight matrix in fuzzy theory is corresponding to low dimension projection value of each index. But we can′t define whether the weight matrix given by experts is the best projection value or not. So, the authors apply a new technique of falling dimension named projection pursuit to soil study, through using the improved real coding based accelerating genetic algorithm to optimize the projection direction. Thus, it can transfer multi dimension data into one dimension data, through searching for the optimum projection direction to realize the soil classification and its grade evaluation. The method can avoid the artificial disturbance, and acquire preferably effect. Thus, the paper provides a new method to the research of soil classification and grade evaluation.

关键词： RAGA PPE soil classification soil evaluation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Ecological hydraulic radius model to calculate instream flow requirements for transporting sediment in the western water transfer region

引用

Science china(Technological Sciences) 2009年第11期52卷 3401-3405页

作者： MEN BaoHui1 & LIU ChangMing2 1 Renewable Energy institute, North china electric {3. University, Beijing 102206, china 2 Key Laboratory of Water Cycle and Related Land Surface Process, institute of Geographical Sciences and Natural Resources research, Chinese Academy of Sciences, Beijing 100101, china Renewable Energy institute North China Electric Power University Beijing China Key Laboratory of Water Cycle and Related Land Surface Process Institute of Geographical Sciences and Natural Resources Research Chinese Academy of Sciences Beijing China

Transporting sediment is a natural function of the river. To maintain the normal evolution of the river certain amount of water flow is required, which is called the instream flow requirements for transporting sediment (IFRTS). We defined the permitting flow velocity by the conception of IFRTS, and also put forward the ecological hydraulic radius model (EHRM) to estimate IFRTS. The calculating process of EHRM is explained by the example of Daofu Hydrological Station on Xianshui branch of Yalong River in the west line first-stage construction of South-North Water Transfer Project. The result shows that the IFRTS occupied 29.7%―59.5% of annual mean discharge in flood season, the average of IFRTS was about 100.2 m3.s during 1966―1987, it is close to the IFRTS 90 m3.s calculated by IFRTS conception. Hence, it is feasible to use EHRM to calculate IFRTS.

关键词： ecological hydraulic radius model (EHRM) instream flow requirements for transporting sediment (IFRTS) permitting flow velocity ecological hydraulic radius for transporting sediment

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：