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Current distribution and stability of LTS/HTS hybrid superconducting conductors

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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 102.06, 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 {2. Chinese Academy of Sciences Beijing China

Current distribution and stability of a hybrid LTS/HTS superconductor, consisting of multifilamentary NbTi/Cu and Bi2.2./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 Bi2.2./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

Study of the circulation theory of the cooling system in vertical evaporative cooling generator

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Science china(Technological sciences) 2006年第3期49卷 358-364页

作者： YU Shunzhou1, CAI Jing2. GUO Chaohong1 & GU Guobiao1 1. institute of electrical {2., chinese academy of sciences, Beijing 100080, china 2. Beijing Changcheng institute of Metrology and Measurement, Beijing 100095, china institute of electrical {2. Chinese Academy of Sciences Beijing China Beijing Changcheng institute of Metrology and Measurement Beijing China

The article briefly states the current development of evaporative cooling generator; its advantages comparing with generators of traditional cooling. Vertical evaporative cooling generator, which adopts Close-Loop-Self-Cycle with no-pump; free convection boil in the hollow stator bar, is one of the great developments in generator design. This article emphasizes the importance of cooling system in generator; expatiates the circulation theory in two aspects, energy; flow;; analyzes the essential reason, motivity; stability of Close-Loop-Self-Cycle. The article points out that the motivity of the circulation is the heat absorbed by coolant. After absorbing heat the coolant will have the ability of doing work because of the phase change. In another words, it is the buoyancy causing by density difference leads to the Close-Loop-Self-Cycle. This conclusion is validated by experimental data.

关键词： vertical evaporative cooling generator, cooling system, circulation theory.

A new transient stability margin based on dynamic security region and its applications

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Science china(Technological sciences) 2008年第6期51卷 751-760页

作者： XUE AnCheng1, 2.& MEI ShengWei1 1 State Key Lab of Power Systems, Department of electrical engineering, Tsinghua University, Beijing 100084,{2. 2.Key Lab of Systems and Control, institute of Systems Science, chinese academy of sciences, Beijing 100190,{2. State Key Lab of Power Systems Department of Electrical Engineering Tsinghua University Beijing China Key Lab of Systems and Control Institute of Systems Science Chinese Academy of Sciences Beijing China

A new transient stability margin is proposed based on a new expression of dynamic security region (DSR) which is developed from the existing expression of DSR. Applications of the DSR based transient stability margin to contingency ranking and screening are discussed. Simulations in the 10-machine 39-bus New England system are performed to show the effectiveness of the proposed DSR based tran-sient stability margin.

关键词： dynamic security region (DSR) transient stability margin contingency screening

Synthesis, characterization and thermostability of barium β-diketonate with tetraethylenepentamine ligand

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Rare Metals 2012年第6期31卷 566-572页

作者： ZHANG Teng, GU Hongwei, DING Fazhu, QU Fei, and DAI Shaotao Key Laboratory of Applied Superconductivity, institute of electrical {2., chinese academy of sciences, Beijing 100190, china Key Laboratory of Applied Superconductivity Institute of Electrical Engineering Chinese Academy of Sciences Beijing China

The metal-organic chemical vapor deposition (MOCVD) technique is a promising process for high-temperature superconductor YBa2.u3O7-δ(YBCO) preparation. In this technique, it is a challenge to obtain barium precursors with high volatility. In addition, the purity, evaporation characteristics and thermostability of adopted precursors in the whole process would decide the quality and reproducible results of YBCO film. In the present report, the barium precursor containing 2.2.6,6-tetramethylheptane-3,5-dionate and tetraethylenepentamine ligands (Ba(TMHD)-tetraen) was synthesized and identified by FTIR, 1H NMR, 13C NMR and ESI-MS spectroscopy. Subsequently the thermal property and the kinetics of decomposition were systematically investigated by combining non-isothermal thermogravimetric analysis methods (TGA), Ozawa, Kissinger and Friedman methods. On the basis of the apparent activation energy of the evaporation process, the thermostability and evaporation characteristics of the precursors were discussed. All results show that Ba(TMHD)-tetraen has higher volatility than Ba(TMHD)2. but it is unstable and highly sensitive to the change of temperature during the whole evaporation process. Therefore, it is very important to choose suitable volatilization technology and conditions for avoiding Ba(TMHD)-tetraen breakdown (or thermal aging) during the MOCVD process.

关键词： MOCVD barium precursor synthesis thermostability

ON THE OBSERVABILITY AND DETECTABILITY OF LINEAR STOCHASTIC SYSTEMS WITH MARKOV JUMPS AND MULTIPLICATIVE NOISE

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Journal of Systems Science & Complexity 2010年第1期23卷 102-115页

作者： Yuanhua NI Weihai ZHANG Haitao FANG Key Laboratory of Systems and Control Institute of Systems Science Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China. College of Information and electrical engineering Shandong University of Science and Technology Qingdao China.

This paper presents the notions of exact observability and exact detectability for Markov jump linear stochastic systems of Ito type with multiplieative noise （for short, MJLSS）. Stochastic Popov-Belevith-Hautus （PBH） Criterions for exact observability and exact detectability are respectively obtained. As an application, stochastic H2.H∞ control for such MJLSS is discussed under exact detectability.

关键词： Exact detectability exact observability Markov jump systems multiplicative noise PBH Criterion stochastic H2.H∞ control.

Preparation and characterization of PZT thick film enhanced by ZnO nanowhiskers for MEMS piezoelectric generators

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Progress in Natural Science:Materials International 2011年第2期21卷 159-163页

作者： Zhong-xia DUAN~1,Guo-qin YU~2.Jun-biao LIU~1,Jun LIU~2.Xiao-wen DONG~2.Li HAN~1,Peng-yun JIN~1 1.institute of electrical {2.,chinese academy of sciences,Beijing 100190,china 2.Shanghai Municipal Electric Power Company,Shanghai 2.002.,china institute of electrical {2. Chinese Academy of Sciences Beijing 100190 China Shanghai Municipal Electric Power Company Shanghai 200025 China

A hybrid sol-gel route which was used to fabricate PZT thick film for MEMS piezoelectric generators was investigated. （100）-oriented Pb(Zr0.52.i0.48)O3thick films enhanced by ZnO nanowhiskers（ZnOw） were successfully prepared on Pt/Cr/SiO2.Si substrates via spin-coating ZnOwsuspension and PZT *** influences of film thickness on the microstructure and electrical properties of composite thick film were *** results show that PZT composite thick films have（100）-oriented perovskite *** results show that,the surface of as-prepared（100）-oriented PZT piezoelectric composite thick film is smooth,compact and crack-free,and the cross section is *** composite thick films exhibit good ferroelectric,dielectric and piezoelectric properties.2.urn-thick（100）-oriented PZT piezoelectric composite thick film has the remnant polarization intensity and coercive field of 6.7μC/cm2.nd 92.5 kV/cm,the dielectric constant and dielectric dissipation of 1 431 and 0.44,respectively,and piezoelectric constant d33is calculated to be 151.0 pC/*** composite thick film is good to meet the use of MEMS piezoelectric generators.

关键词： PZT thick film ZnO nanowhisker electrical properties piezoelectric generator

Salient region detection and segmentation for general object recognition and image understanding

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Science china(Information sciences) 2011年第12期54卷 2481-2490页

作者： HUANG TieJun 1 , TIAN YongHong 1 , LI Jia 2.& YU HaoNan 11 National engineering Laboratory for Video Technology, School of electrical engineering and Computer Science, Peking University, Beijing 100871, china 2.Key Laboratory of Intelligent Information Processing, institute of Computing Technology, chinese academy of sciences, Beijing 100190, china National engineering Laboratory for Video Technology School of Electrical Engineering and Computer Science Peking University Beijing China Key Laboratory of Intelligent Information Processing Institute of Computing Technology Chinese Academy of Sciences Beijing China

General object recognition and image understanding is recognized as a dramatic goal for computer vision and multimedia retrieval. In spite of the great efforts devoted in the last two decades, it still remains an open problem. In this paper, we propose a selective attention-driven model for general image understanding, named GORIUM (general object recognition and image understanding model). The key idea of our model is to discover recurring visual objects by selective attention modeling and pairwise local invariant features matching on a large image set in an unsupervised manner. Towards this end, it can be formulated as a four-layer bottom-up model, i.e., salient region detection, object segmentation, automatic object discovering and visual dictionary construction. By exploiting multi-task learning methods to model visual saliency simultaneously with the bottom-up and top-down factors, the lowest layer can effectively detect salient objects in an image. The second layer exploits a simple yet effective learning approach to generate two complementary maps from several raw saliency maps, which then can be utilized to segment the salient objects precisely from a complex scene. For the third layer, we have also implemented an unsupervised approach to automatically discover general objects from large image set by pairwise matching with local invariant features. Afterwards, visual dictionary construction can be implemented by using many state-of-the-art algorithms and tools available nowadays.

关键词： object recognition image understanding visual saliency salient object segmentation visual dictionary

New technique to control in situ oxygen fugacity in water-free high-pressure system──Using Cu-O as an example

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chinese Science Bulletin 1998年第16期43卷 1353-1358页

作者： LI Heping 1, XIE Hongsen 1, GUO Jie 1, ZHANG Yueming 1,XU Zuming 1 and XU Ji’an 2.1. institute of Geochemistry, chinese academy of sciences, Guiyang 550002.{2. 2. institute of Earth sciences, Taiwan 1152.,{2. institute of Geochemistry Chinese Academy of Sciences Guiyang China institute of Earth sciences Taiwan China

Through inserting a solid oxygen-specific electrolyte (YSZ) inside and exerting an electrical power of direct current outside between the sample and oxygen reservoir (an solid oxygen buffer), oxygen was driven by the power from the cathodic electrode area into the positive electrode area at high temperature and high pressure. In this way, the oxygen fugacity in the sample was in situ controlled independently of temperature and pressure. By using Cu-O system as an example, this technique was proved to be successful.

关键词： in situ control of oxygen fugacity water-free system high temperature and high pressure.

Effect of As Interstitial Diffusionon on the Properties of Undoped Semi-insulating LECGaAs

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Rare Metals 2001年第3期20卷 187-191页

作者： Ruixia Yang, Fuqiang Zhang, Nuofu Chen 1) Hebei University of Technology, Tianjin 300130, china 2. institute of Semiconductors,{2., Beijing 100083, china 河北工业大学天津 300130 中科院半导体所北京 100083

Annealing was carried out at 950 and 112. degreesC under various As pressure for undoped (ND) semi-insulating (SI) LECGaAs. The effects of annealing on native defects and electrical properties were investigated. Experimental results indicate that, after an annealing at 950 degreesC for 14 h under low As pressure, the Hall mobility decreases and the resistivity increases dramatically for the samples. These changes in electrical properties are due to the generation of intrinsic acceptor defects, and the generation of the intrinsic acceptor defects originates from the outdiffusion of As interstitial at high temperature. The generation of the intrinsic defects and these changes in electrical properties can be suppressed by increasing the applied As pressure during annealing. The concentration of the main donor defect E12.(AsGaVGa) can be decreased by about one order of magnitude by an evacuated annealing at 112. degreesC for 2.8 h followed by a fast cooling. The decrease in E12.concentration can also be suppressed by increasing the As pressure during annealing.

关键词： semi-insulating GaAs intrinsic acceptor defects As interstitial indiffusion As pressure annealing