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Aging assessment of large generator insulation based on PD measurements

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Progress in Natural Science:materials International 2005年第11期15卷 1035-1043页

作者： YUE Bo, CHEN xiaolin, CHENG Yonghong and xiE Hengkun (State Key Laboratory of Electrical Insulation and Power Equipment, xi'an jiaotong university, xi'an {2., china Graduate school at Shenzhen, Tsinghua university, Shenzhen 518055, china Department of Electrical engineering, Tsinghua university, Beijing 100084, china) State Key Laboratory of Electrical Insulation and Power Equipment Xi''an Jiaotong University Xi''an 710049 China. Graduate school Shenzhen Tsinghua University Shenzhen 518055 China. Department of Electrical engineering Tsinghua University Beijing 100084 China

The statistical parameters of phase resolved partial discharge (PD) distribution and ultra-wideband (UWB) characteristics of PD pulse are proposed for aging assessment of large generator insulation. Multi-stress aging tests of the model generator stator bar specimens were performed and PD measurements were conducted using both digital PD detector with frequency ranging from 40 kHz to 400 kHz and UWB PD detector with bandwidth from 10 MHz to 3 GHz at different aging stages. The test results show that the skewness and UWB frequency characteristics of PD can be taken as the characterization parameters for aging assessment of generator insulation. Furthermore, the measurement results of real generator stator bars show that these methods based on statistical parameters and UWB characteristics of PD are prospective for aging assessment and residual lifetime estimation of large generator stator insulation.

关键词： partial discharge stator insulation multi-stress accelerated aging statistical parameters ultra-wideband aging assessment.

Thermoelastic properties of sandwich materials with pin-reinforced foam cores

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Science china(Technological Sciences) 2008年第12期51卷 2059-2074页

作者： LU TianJian1,LIU Tao2.3 & DENG ZiChen2.4 1 MOE Key Laboratory of Strength and Vibration,school of Aerospace,xi’an jiaotong {2.,xi’an 710049,china 2.Department of engineering Mechanics,Northwestern Polytechnical {2.,xi’an 710072.china 3 Department of engineering,{2. of Cambridge,Cambridge CB2.1PZ,UK 4 State Key Laboratory of Structural Analysis of Industrial Equipment,Dalian {2. of Technology,Dalian 11602.,china MOE Key Laboratory of Strength and Vibration School of Aerospace Xi’an Jiaotong University Xi’an 710049 China Department of engineering Mechanics Northwestern Polytechnical University Xi’an 710072 China Department of engineering University of Cambridge Cambridge CB2 1PZ UK State Key Laboratory of Structural Analysis of Industrial Equipment Dalian University of Technology Dalian 116024 China

Pin-reinforced foam is a novel type of sandwich core materials formed by inserting pins(trusses) into a foam matrix to create a truss-like network reinforced foam *** loading,the pins deform predominantly by local stretching whilst the deformation of foam is governed by local *** paper presents a theoretical study on the thermoelasticity of pin-reinforced foam sandwich *** calculate the effective thermoelastic properties of pin-reinforced foam cores,the energy-based homogenization approach is employed to develop a micromechanics-based model,calibrated by the existing experimental *** is found that the stiffness of the sandwich core is mainly governed by pin reinforcements:the foam matrix contributes little to sandwich *** with traditional foam cores without pin reinforcements,the changes in inplane thermal expansion coefficients are not vigorous as a result of pin reinforcements,while the through-thickness thermal expansion coefficient changes *** is also demonstrated that it is possible to design materials with zero or negative thermal expansion coefficients under such a context.

关键词： sandwich panel pin reinforcement analytical solutions homogenization thermoelasticity thermal expansion

Inferring playback rate and rate resets of P2. video streaming transmissions by piecewise line envelope approximation

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The Journal of china Universities of Posts and Telecommunications 2009年第2期16卷 58-62,79页

作者： LI Chun-xi CHEN Chang-jia school of Electronics and Information engineering,Beijing {2. university,Beijing 100044,china [a]school of Electronics and Information engineering Beijing jiaotong university Beijing 100044 china

Conventionally, P2. video is regarded as CBR traffic. However, our measurements have shown that the rate reset cannot be neglected in a practical IPTV system because each rate reset often leads to performance degradation. Thus, addressing the problem of inferring playback rate and rate reset in a P2. video system is significant. In this article, an algorithm termed piecewise linear envelope approximation （PLEA） is proposed, in which a follow-up time is introduced to smooth rate fluctuations in a small time scale and to adapt rate jumps in a large time scale automatically. With the PLEA algorithm, discontinuity introduced by blind segmentations adopted by current methods is avoided. Furthermore, unlike existing algorithms in which both segmentation and combinations are performed in multiple runs, only a single computation path is involved in the PLEA algorithm. This makes PLEA algorithm amenable to implementation of low complexity by either software or hardware. Both theoretical analysis and experiment based on measured data show that the PLEA outperforms existing algorithms based on segmentation.

关键词： P2. video playback rate rate reset convex hull linear program

The Core and Coritivity off a System (IV)——Relations between a System and Its Complement

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Journal of Systems engineering and Electronics 1993年第2期4卷 28-34页

作者： Wang Yingluo, Xu Jin and xi YouminManagement school, xi’an jiaotong university,{2., china

The coritivity, h(G), of a connected graph G, is defined by h(G) = max{ω(G-S)-|S|: S∈C(G)}, where ω(G) denotes the number of components of a graph G, C(G) denotes the collection of cut-sets of G. In this paper, the notion of complementary coritivity is proposed, and the relations between coritivity and its complement are studied, for example, two bounds, Nordaus-Gaddum problems and some foundational properties etc.

关键词： Coritivity of a system Complementary coritivity Bounds Nordhaus-Gaddhum problem.

ANALYTICAL AND NUMERICAL SOLUTIONS FOR THE FLOW IN MICROTUBE WITH THREE-DIMENSIONAL CORRUGATED SURFACE,PART 1:STEADY FLOW

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Journal of Hydrodynamics 2010年第5期22卷 647-656页

作者： WANG Hao-li YANG Meng WANG Yuan College of Metrological Technology and engineering China Jiliang University Hangzhou 310018China Department of Fluid engineering School of Energy and Power Engineering Xi＇an Jiaotong University Xi＇an710049 China

The influences of three-dimensional corrugated wall on the fully-developed steady no-slip flows in microtube are studied by analytical and numerical methods in this article. Detailed analytical solutions for the space-averaged equations and the numerical method for the solutions of the disturbance equations are given. An iterative arithm of coupled equations with respect to space-averaged velocities and disturbance velocities is suggested. The study shows that a three-dimensional subsidiary stress layer exists in the near-wall region. The relative roughness, wavenumber and Reynolds number are three important parameters influencing the subsidiary stresses and the space-averaged pressure drop. The space-averaged pressure drop subject to an invariable flow rate mainly depends on the position of datum surface. When the datum surface is taken at the balance position of wall function, the value of pressure drop is determined by the dynamic characteristics of the flow.

关键词： microtube three-dimensional corrugated surface space-averaged method subsidiary stress

INTELLIGENT INTEGRATION CONTROL OF ROTATING DISK VIBRATION

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Chinese Journal of Mechanical engineering 2001年第4期14卷 330-335页

作者： Qiu Jinbo,Huang xieqing,Wang Daqing (school of Mechanical engineering,{2.) 西安交通大学陕西

The rotating disk is a basic machine part that is u sed widely in industry. The motion equation is transformed into the dynamic equa tion in real modal space. The personating intelligent integration is introduced to improve the existing control method. These modes that affect the transverse vibration mainly are included to simulate the vibration of rotating disk, and two methods are applied separately on condition that the sensor and the ac tuator are collocated and non collocated. The results obtained by all sided si mulations show that the new method can obtain better control effect, especially when the sensor and the actuator are non collocated.

关键词： Rotating disk Distributed parameter Gyroscopic system Active control Intelligent integration

Glacial debris flow susceptibility mapping based on combined models in the Parlung Tsangpo Basin,china

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Journal of Mountain Science 2024年第4期21卷 1231-1245页

作者： ZHOU Yonghao HU xiewen xi Chuanjie WEN Hong CAO xichao JIN Tao ZHOU Ruichen ZHANG Yu GONG Xueqiang Faculty of Geosciences and engineering Southwest Jiaotong UniversityChengdu 611756China school of Architecture and Civil engineering Xihua UniversityChengdu 610039China

Machine learning(ML)-based prediction models for mapping hazard(e.g.,landslide and debris flow)susceptibility have been widely developed in recent ***,in some specific areas,ML models have limited application because of the uncertainties in identifying negative *** Parlung Tsangpo Basin exemplifies a region prone to recurrent glacial debris flows(GDFs)and is characterized by a prominent landform featuring deep *** the limitations of the ML model,we developed and compared two combined statistical models(FA-WE and FA-IC)based on factor analysis(FA),weight of evidence(WE),and the information content(IC)*** final GDF susceptibility maps were generated by selecting 8 most important static factors and considering the influence of *** results show that the FA-IC model has the best *** areas with a very high susceptibility to GDFs are primarily located in the narrow valley section upstream,on both sides of the valley in the middle and downstream of the Parlung Tsangpo River,and in the narrow valley section of each *** areas encompass 86 gullies and are characterized as"narrow and steep".

关键词： Parlung Tsangpo Basin Glacial debris flow Factor analysis Susceptibility mapping Weight of evidence Information content method.

AOD estimation in WSN localization system with synthetic aperture technique

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Science china(Information Sciences) 2012年第10期55卷 2216-2225页

作者： WANG WenJie,YAO BoBin & YIN QinYe MOE Key Lab for Intelligent Networks and Network Security,school of Electronic and Information engineering,xi’an {2. university,xi’an 710049,china 1. MOE Key Lab for Intelligent Networks and Network Security School of Electronic and Information Engineering Xi’an Jiaotong University Xi’an 710049 China

Angel of departure(AOD) based distributed localization scheme in wireless sensor networks allows the single antenna sensor node to estimate its own AOD information by an equivalent antenna array for further position ***,the condition that the number of antennas at the multi-antenna agent/anchor node should be larger than the number of multipath signal components(MPCs) constrains its actual *** this paper,we provide a more practical approach to achieve AOD information estimation under multipath *** that the sensor node can not identify the line of sight(LOS) signal component due to the insufficient degree of freedom,which is determined by the above limiting condition,we introduce a synthetic aperture technique with the aid of a fast moving multi-antenna agent/anchor *** operation greatly enlarges the degree of freedom of the equivalent antenna array constructed at sensor node end but without requiring other extra physical antennas equipped at agent/anchor node or sensor node end,which means that it relaxes the limiting ***,the AOD information of LOS signal component can be estimated and extracted successfully in complex multipath *** analysis proves the effectiveness of our proposed synthetic aperture technique and numerical simulations show great performance improvement.

关键词： angle of departure degree of freedom synthetic aperture wireless sensor networks

ON-LINE STATE PREDICTION OF ENGINES BASED ON FLAT NEURAL NETWORK

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Chinese Journal of Mechanical engineering 2001年第1期14卷 51-56页

作者： xi Gang Zhang Jianwu Chen Li school of Mechanical engineering, Shanghai {2. university 上海交通大学机械工程学院上海

A flat neural network is designed for the on line state prediction of engine. To reduce the computational cost of weight matrix, a fast recursive algorithm is derived according to the pseudoinverse formula of a partition matrix. Furthermore, the forgetting factor approach is introduced to improve predictive accuracy and robustness of the model. The experiment results indicate that the improved neural network is of good accuracy and strong robustness in prediction, and can apply for the on line prediction of nonlinear multi input multi output systems like vehicle engines.

关键词： Engine model Neural network On line prediction Nonlinear system