检索结果-南通市图书馆

CSEE Journal of Power and Energy Systems 2023年第3期9卷 1227-1234页

作者： Jun Zhao Weijiang Chen kejie li Zihan Teng Ni li Tao Wen Xing Fan State Key Laboratory of Power Grid Environmental Protection China Electric Power Research InstituteWuhan&BeijingChina State Grid Corporation of China BeijingChina School of Electrical Engineering and Automation Hefei University of TechnologyHefeiChina School of Electrical Engineering Xi’an Jiaotong UniversityXi’anChina

The characteristics of conducted disturbances via current transformer(CT)caused by switch operations in 1000 kV UHV substations are studied in this *** the broadband circuit models might have limitations on the stability and accuracy for CT conducted disturbance simulation,a frequencydomain simulation method without circuit synthesis is proposed based on VFTC spectrum and CT transfer *** improve VFTC simulation accuracy,both the bushing radiation loss and frequency-dependent earth impedance are taken into *** characteristics of three types of windings for the 1000 kV GIS CT are ingeniously measured from a combination of fast and slow impulse *** conducted disturbances simulations in UHV Wuhu substation,bushing radiation loss is found to have a suppression effect on the highfrequency response but the effect of frequency-dependent earth impedance can be *** a result,the maximum amplitude of 84.5 A for the conducted disturbance is obtained,thus a fast damped oscillatory wave immunity test with no lower than Level 4 from IEC standard is suggested to test the anti-interference performance of the secondary equipment in UHV substation.

关键词： Conducted disturbance current transformer switch operation simulation UHV substation

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

高铁高架桥箱梁雷击电磁瞬态建模及特性分析

合肥工业大学学报（自然科学版） 2024年第8期47卷 1062-1067,1079页

作者：胡宾向念文李科杰叶维平王立天阳晋合肥工业大学电气与自动化工程学院清华大学电机工程与应用电子技术系中铁电气化勘测设计研究院有限公司北京全路通信信号研究设计院集团有限公司

高速铁路高架桥箱梁是雷击接触网时雷电流的主要泄流通道。由于箱梁是由成百上千根钢筋绑扎而成的复杂鼠笼结构,准确建立其雷击宽频计算模型的难度较大,因此文章基于传输线矩阵法(transmission-line matrix,TLM)建立不同纵向钢筋数量的... 详细信息

高速铁路高架桥箱梁是雷击接触网时雷电流的主要泄流通道。由于箱梁是由成百上千根钢筋绑扎而成的复杂鼠笼结构,准确建立其雷击宽频计算模型的难度较大,因此文章基于传输线矩阵法(transmission-line matrix,TLM)建立不同纵向钢筋数量的箱梁模型,分析其雷击电磁瞬态简化建模的可行性。研究发现:箱梁泄流时,雷电流主要分布在外层纵向钢筋,符合趋肤效应规律;箱梁横截面曲率较大处纵向钢筋为雷击瞬态计算中的关键钢筋,保留该部分纵向钢筋,适当减少曲率较小处的纵向钢筋,可以简化箱梁雷击电磁瞬态模型。箱梁泄流时瞬态电流会在其周围产生瞬态电磁场,威胁轨旁信号设备和线缆端接设备的正常运行,为进一步研究简化纵向钢筋对箱梁周围瞬态电磁环境的影响,基于上述简化建模方法,计算不同纵向钢筋数量桥面电磁场分布及衰减特性,发现箱梁对幅值为100 kA的雷电流泄流时,雷电流注入点30 m范围内的磁场强度超出国家标准规定的电子设备磁场抗扰度,该范围内的桥面电子设备受到严重威胁。

关键词：箱梁简化建模桥面电磁场传输线矩阵法(TLM) 高速铁路

Full-Spectrum Fluoromethyl Sulfonation via Modularized Multicomponent Coupling

在线全文

学校读者我要写书评

暂无评论

CCS Chemistry 2022年第5期4卷 1526-1534页

作者： kejie li Ming Wang Xuefeng Jiang Shanghai Key Laboratory of Green Chemistry and Chemical Process School of Chemistry and Molecular EngineeringEast China Normal UniversityShanghai 200062 State Key Laboratory of Elemento-Organic Chemistry Nankai UniversityTianjin 300071

Modular free-assembly construction of mono-,di-,and tri-fluoromethyl sulfones was comprehensively achieved by a combination of halides,a sulfur dioxide surrogate,and *** industrial raw material thiourea dioxide served as the sulfur dioxide source,combined with readily available fluorocarbon sources such as 2-bromo-2-fluoroacetate and chlorodifluoromethane(ClCF_(2)H,Freon)employed as fluoromethyl ***,four methyl sulfone-containing pharmaceuticals were modified into three types of fluoromethyl sulfones,displaying their great potential for drug discovery via the current *** studies further demonstrated that C-F…H-N interactions between thiourea dioxide and halofluorocarbons play a key role in stabilizing monofluoromethyl electrophiles and difluorocarbene species.

关键词： sulfone trifluoromethyl sulfone difluoromethyl sulfone monofluoromethyl sulfone thiourea dioxide

Dispersion characteristics of switching transients from large‐scale experiments in a 1100 kV gas insulated switchgear circuit

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

High Voltage 2023年第6期8卷 1253-1263页

作者： Zihan Teng Weijiang Chen Jiangong Zhang Baoquan Wan Jun Zhao kejie li Zhenghai liao Zheyuan Gan State Key Laboratory of Power Grid Environmental Protection China Electric Power Research InstituteWuhanChina State Grid Corporation of China BeijingChina School of Electrical Engineering and Automation Hefei University of TechnologyHefeiChina

The switching operation of gas insulated switchgear(GIS)disconnector will produce multiple random spark discharges between the gas gaps of the *** spark discharge can be affected by various random factors,such as trapped charge on the load side,the initial operating phase,gap distance and operating speed of the disconnector,leading to dispersion *** present,some studies have mentioned this dispersion,but its impact is still unclear due to the lack of experimental data,resulting in a deviation between the simulation results and the measured *** this study,thousands of switching operations were carried out based on the 1100 kV full‐scale GIS circuit in Wuhan ultra‐high voltage alternating current Test *** maximal information coeffi-cient analysis,linear regression fitting and other statistical methods were used to discuss the dispersion characteristics of very fast transient overvoltage(VFTO)and transient enclosure voltage(TEV)from large‐scale experimental *** results show that the dispersion of VFTO and TEV in amplitude aspects both increase gradually as the breakdown voltage increases,with the maximum difference of five times of TEV amplitude at normalised breakdown *** terms of frequency characteristics,the dispersion of different fre-quency components in TEV is always greater than that of VFTO,especially for the high‐frequency ***,by comparing the frequency characteristics of TEV at different positions,we notice that the dispersion is almost independent of the spatial po-sition but only determined by the randomness of spark *** discoveries reveal the importance of the dispersion in switching transients and make up for the lack of theoretical understanding of the correlation among them.

关键词： characteristics transient breakdown

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

余伯亮教授辨治周围性面瘫经验总结

光明中医 2024年第18期39卷 3657-3660页

作者：李科杰林海波丘均华余伯亮暨南大学江门市五邑中医院康复科江门市五邑中医院针灸科

介绍全国名老中医专家余伯亮教授辨治周围性面瘫的临床经验。余教授认为此病多以脉络空虚，卫外不固，外感邪气所致，应细察病变部位，在《黄帝内经》刺法理论的指导下，以“多针浅刺”为主，多种刺法相结合的方法；对于顽固久病者，治... 详细信息

介绍全国名老中医专家余伯亮教授辨治周围性面瘫的临床经验。余教授认为此病多以脉络空虚，卫外不固，外感邪气所致，应细察病变部位，在《黄帝内经》刺法理论的指导下，以“多针浅刺”为主，多种刺法相结合的方法；对于顽固久病者，治疗上宜用穴位埋线，取穴以“面五穴”为主，并强调健患同治和颈项论治在此病的重要性，提倡针药结合，以达到内外兼顾的效果，形成一套全面且独具特色的治疗方法。

关键词：口僻周围性面瘫多针浅刺针药结合名医经验

Sensitivity optimization of a monolithic high-shock three-axis piezoresistive accelerometer with single sensing element

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2009年第19期54卷 3600-3607页

作者： SONG Ping li QingZhou li kejie School of Aerospace Science and Engineering Beijing Institute of Technology Beijing 100081 China

There exist several difficulties in the design of monolithic high-shock three-axis accelerometer, such as high g overload, transverse overload and the cross coupling in three dimensions, etc. It is necessary to optimize the sensitivity to improve the performance of the accelerometer. For the monolithic high-shock three-axis accelerometer, the complexity of the sensitivity optimization is that it should consider not only the sensitivity difference between different axes but also the elimination of cross-coupling outputs, together with the natural frequency, structural integrity and high g overload. In this paper, the optimization process for decreasing the difference of the sensitivities between different axes of a monolithic high-shock three-axis piezoresistive accelerometer with single sensing element is established. The optimization is conducted in the condition of 100000 g acceleration by two methods-the method based on the optimization module of ANSYS and the ACO (ant colony optimization) method. The comparison between un-optimized and optimized models proves the efficiency of the optimization methods. In addition, the optimization results show that the ACO method combined with the FEA (finite element analysis) is much more efficient than the method based on the optimization module of ANSYS for the structural optimization problem. And the ACO method can be widely used in the optimization problem of the sensing elements with complicated structure.

关键词：单片电路最佳化设计研究 ACO

Adsorption Performance of Sliding Wall-Climbing Robot

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2010年第6期23卷 733-741页

作者： li Jun GAO Xueshan FAN Ningjun li kejie JIANG Zhihong JIANG Zhijian School of Mechatronical Engineering Beijing Institute of Technology Beijing 100081 China School of Electric and Information Engineering Beijing University of Civil Engineering and Architecture Beo＇ing 100044 China

Sliding wall-climbing robot （SWCR） is applied worldwide for its continuous motion, however, considerable air leakage causes two problems： great power consumption and big noise, and they constraint the robot＇s comprehensive performance. So far, effective theoretical model is still lacked to solve the problems. The concept of SWCR＇s adsorption performance is presented, and the techniques of improving utilization rate of given adsorption force and utilization rate of power are studied respectively to improve SWCR＇s adsorption performance. The effect of locomotion mechanism selection and seal＇s pressure allocation upon utilization rate of given adsorption force is discussed, and the theoretical way for relevant parameters optimization are provided. The directions for improving utilization rate of power are pointed out based on the detail analysis results of suction system＇s thermodynamics and hydrodynamics. On this condition, a design method for SWCR-specific impeller is presented, which shows how the impeller＇s key parameters impact its aerodynamic performance with the aid of computational fluid dynamics （CFD） simulations. The robot prototype, BIT Climber, is developed, and its functions such as mobility, adaptability on wall surface, payload, obstacle ability and wall surface inspection are tested. Through the experiments for the adhesion performance of the robot adsorption system on the normal wall surface, at the impeller＇s rated rotating speed, the total adsorption force can reach 237.2 N, the average effective negative pressure is 3.02 kPa and the design error is 3.8% only, which indicates a high efficiency. Furthermore, it is found that the robot suction system＇s static pressure efficiency reaches 84% and utilization rate of adsorption force 81% by the experiment. This thermodynamics model and SWCR-specific impeller design method can effectively improve SWCR＇s adsorption performance and expand this robot applicability on the various walls. A sliding wall-climbing

关键词： wall-climbing robot adsorption performance centrifugal impeller CFD simulation

Reliability improvement of gas discharge tube by suppressing the formation of short-circuit pathways

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2022年第3期24卷 138-151页

作者： lingyun CHENG Nianwen XIANG kejie li Weijiang CHEN Kai BIAN Jin YANG Zongqi XU Congying HAN Hongyang GU Chun YANG Heifei University of Technology Hefei 230009People's Republic of China Institute of Energy Hefei Comprehensive National Science CenterHefei 230031People's Republic of China State Grid Corporation of China Beijing 100031People's Republic of China Beijing National Railway Research&Design Institute of Signal&Communication Group Co. Ltd.Beijing 100070People's Republic of China

After cumulative discharge of gas discharge tube(GDT),it is easy to form a short circuit pathway between the two electrodes,which increases the failure risk and causes severe influences on the protected *** reduce the failure risk of GDT and improve cumulative discharge times before failure,this work aims to suppress the formation of two short-circuit pathways by optimizing the tube wall structure,the electrode materials and the electrode structure.A total of five improved GDT samples are designed by focusing on the insulation resistance change that occurs after the improvement;then,by combining these designs with the microscopic morphology changes inside the cavity and the differences in deposition composition,the reasons for the differences in the GDT failure risk are also *** experimental results show that compared with GDT of traditional structure and material,the method of adding grooves at both ends of the tube wall can effectively block the deposition pathway of the tube wall,and the cumulative discharge time before device failure is increased by 149%.On this basis,when the iron-nickel electrode is replaced with a tungsten-copper electrode,the difference in the electrode’s surface splash characteristics further extends the discharge time before failure by 183%.In addition,when compared with the traditional electrode structure,the method of adding an annular structure at the electrode edge to block the splashing pathway for the particles on the electrode surface shows no positive effect,and the cumulative discharge time before the failure of the two structures is reduced by 22.8%and 49.7%,*** these improved structures,the samples with grooves at both ends of the tube wall and tungsten-copper as their electrode material have the lowest failure risk.

关键词： gas discharge tube short-circuit failure tube wall groove tungsten-copper electrode failure risk

Effects of yttrium on microstructure and mechanical properties of Mg-6Al magnesium alloy

在线全文

学校读者我要写书评

暂无评论

China Foundry 2010年第4期7卷 362-366页

作者： Ren Wenliang li Quan＇an li Jianhong li kejie Zhang Xingyuan School of Material Science and Engineering Henan University of Science and Technology Luoyang 471003 China School of Material Science and Engineering Xi＇an University of Technology Xi＇an 710048 China

Since Y has a great solid solubility in magnesium alloys, it helps enhancing the heat-resistant property of magnesium alloys. The effects of Y on microstructures and mechanical properties of Mg-6Al alloy have been studied in this work. The results show that Y addition refines grains of Mg-6Al alloy, and reduces the amount of the Mg 17 Al 12 phase. At the same time, the high melting-point Al 2 Y phase particles are formed. According to the mathematical model of the two-dimensional lattice misfit proposed by Braffit, it is believed that the Al 2 Y particles can serve as the nucleation sites for α-Mg. After T6 treatment, both elongation and ultimate tensile strength of Mg-6Al alloy at the room temperature and high-temperature increased firstly and then decreased, with increasing Y addition. The peak mechanical properties were achieved in the Mg-6Al-1.2Y alloy system. Y addition appears to change the fracture characteristic of Mg-6Al alloy. With 1.2wt%Y, the fracture surface of the alloy showed a lot of dimples and tearing ridges which connected the microscopic dimples and the fracture is mixed fracture of quasi-cleavage and ductile fracture.

关键词： yttrium Mg-6Al alloy microstructure mechanical properties

Microstructure and mechanical properties of Mg-6Al magnesium alloy with yttrium and neodymium

在线全文

学校读者我要写书评

暂无评论

China Foundry 2009年第2期6卷 124-128页

作者： Chen Jun li Quanan li Jianghong li Xiaofeng li kejie Zhang Xingyuan School of Material Science and Engineering Henan University of Science and Technology Luoyang 471003 China

The effects of rare earth(RE) elements Y and Nd on the microstructure and mechanical properties of Mg-6Al magnesium alloy were *** results show that a proper level of RE elements can obviously ref ine the microstructure of Mg-6Al magnesium alloys,reduce the quantity of β-Mg17Al12 phase and form Al2Y and Al2Nd *** combined addition of Y and Nd dramatically enhances the tensile strength of the alloys in the temperature range of 20-175℃.When the content of RE elements is up to 1.8%,the values of tensile strength at room temperature and at 150℃ simultaneously reach their maximum of 253 MPa and 196 MPa,*** main mechanisms of enhancement in the mechanical properties of Mg-6Al alloy with Y and Nd are the grain ref ining strengthening and the dispersion strengthening.

关键词： Y Nd Mg-6Al magnesium alloy microstructure elevated mechanical properties