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Approximation of dense-n/2.subgraph and table compression problems

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Science china Mathematics 2005年第9期48卷 1223-1233页

作者： XU Dachuan~1 HAN Jiye~2.& DU Dongle~3.1. College of applied Sciences,Beijing university of {2.,Beijing 10002.,china 2. Institute of applied Mathematics,Academy of Mathematics and Systems Science,Chinese Academy of Sciences,Beijing 100080,china 3. Faculty of Administration,university of New Brunswick,P.O.Box 4400,Fredericton,NB E3. 5A3.Canada College of applied Sciences Beijing University of Technology Beijing 100022 China Institute of applied Mathematics Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100080 China Faculty of Administration University of New Brunswick P.O. Box 4400 Fredericton NB E3B 5A3 Canada

We develop improved approximation algorithms for two NP-hard problems: the dense-n/2.subgraph and table *** on SDP relaxation and advanced rounding techniques,we first propose 0. 5982.and 0. 5970-approximation algorithms respec- tively for the dense-n/2.subgraph problem (DSP) and the table compression problem (TCP). Then we improve these bounds to 0. 62.3.and 0. 6708 respectively for DSP and TCP by adding triangle inequalities to strengthen the SDP *** results for TCP beat the 0. 5 bound of a simple greedy algorithm on this problem,and hence answer an open question of Anderson in an affirmative way.

关键词： dense-n/2.subgraph problem(DSP) table compression problem(TCP) SDP approximation ratio

Interfacial Microstructure and Properties of Ti(C, N)/Ni Bonded by Transient Liquid-phase Diffusion

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Journal of Wuhan university of technology(Materials Science) 2009年第3期24卷 432-439页

作者：周世权熊惟皓 school of Mechanical Science and Engineering Huazhong University of Science and Technology Department of Mechanical Engineering University of Waterloo school of Materials Science and Engineering Huazhong University of Science and Technology

Effects of the main process parameters（temperature and time） on microstructure and properties of Ti（C, N）/Ni interface bonded by （Cu＋Nb） interlayer in a vacuum diffusion bonding device were investigated. The interfacial microstructures consisted initially of Ni3.b metallic compound and eutectic of Ni3.b ＋ CuNiss, and finally transformed to （Ti, Nb）（C, N）＋Ni3.b near Ti （C, N） and NiCuss ＋ Ni3.b near Ni when diffusion bonding temperature was 1 52.-1 573.K. It was clear that Cu was a constituent in the transient liquid phase （TLP） into which Ni was dissolved by forming Cu-Ni transition liquid. Nb was dissolved in Cu-Ni transition liquid rapidly. Ti （C, N） conld be wetted by resultant Ni-Nb-Cu transient liquid phase which was followed by a little （Ti, Nb）（C, N） solid solution formed at interface. This increased the interface combining capability. Ultimately the interface shear strength was able to reach 140 MPa. The theoretle analysis and experimental results show that the growth of interfacial reaction layer Ni3.b accords with parabola law, and the activation energy of diffusion reaction is 115.0±0.5 kJ/mol, while the diffusion reaction speed constant is 12.53.mm/s^1/2.

关键词： vacuum diffusion bonding transient liquid phase (TLP) diffusion bonding interlayer activation energy

SrGa_2._4∶Ce blue TFEL in new structure

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Chinese Science Bulletin 1998年第7期43卷 603-605页

作者： XU Chunxiang+1, LOU Zhidong+2. XU Zheng+3.and XU Xurong+3.. National Laboratory of Molecular and Biomolecular Electronics, Southeast university, Nanjing 2.0096,{3. 2. Department of {2. Physics, Tianjin university, Tianjin 3.003.,{3. 3. Institu National Laboratory of Molecular and Biomolecular Electronics Southeast University Nanjina China Department of applied Physics Tianjin University Tianjin China Institute of Photoelectronic technology Northern Jiaotong University Beijing China

SrGa-2.-4∶Ce blue TFEL device with a novel structure was prepared by electron beam evaporation. The dielectric constant of insulator layer in this structure is far less than that in the conventional structure, so the hot-electrons can be accelerated in SiO-2.layers. The stable TFEL with good chromaticity was achieved and the basic characteristics were investigated.

关键词： SrGa-2.-4∶Ce bule TFEL low dielectric constant insulator layer.

On the Symmetry Classes of Functions

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Wuhan university Journal of Natural Sciences 2005年第5期10卷 813-816页

作者： ZHU Ping~1,2. FAN Yun~3.1. school of Mathematics and Statistics, Wuhan university, Wuhan 43.072. Hubei,{2. 2. school of Science, Beijing university of Posts and Telecommunications, Beijing 100876,{2. 3. school of Mathematics and Statistics, Huazhong Normal university, Wuhan 43.079, Hubei,{2. Wuhan university School of Mathematics and Statistics Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***) Beijing university of Posts and Telecommunications School of Science Beijing China (GRID:grid.31880.32) Huazhong Normal university School of Mathematics and Statistics Wuhan Hubei China (GRID:grid.411407.7) (ISNI:***)

Let R be an integral domain of characteristic zero such that the corresponding group rings have block decompositions. We first prove that the submodule consisting of all the R-valued ξi-symmetric functions of several variables is a symmetry class, where ξi is any block character. Then we present a relationship among certain operators introduced for block character. Then we present a relationship among certain operators introduced for block characters. As a consequence, we obtain a decomposition of an arbitrary R-valued function of several variables. Finally, we describe the symmetry property of such summands and determine all the symmetry classes.

关键词： symmetry class strict symmetry class blockcharacter ξi-symmetric function block idempotent

Effects of binders on the performance of electric double-layer capacitors of carbon nanotube electrodes

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Progress in Natural Science:Materials International 2005年第5期15卷 453-457页

作者： LI Chensha1*, WANG Dazhi1, ZHANG Baoyou2. WANG Xiaofeng1, CAO Maosheng3. and LIANG Ji1(1. Department of Mechanical Engineering, Tsinghua university, Beijing 100084, china 2. Center for Analysis and Measurement, Harbin Institute of {2., Harbin 150001, china 3. school of Material Science and Engineering, Tsinghua university, Beijing 100084, china) Department of Mechanical Engineering Tsinghua University Beijing 100084 China Center for Analysis and Measurement Harbin Institute of Technology Harbin 150001 China school of Material Science and Engineering Tsinghua University Beijing 100084 China

Polarizable electrodes of electric double layer capacitor (EDLCs) were made from carbon nanotubes. Effects of different binders, which are phenolic resin (PF) and polytetrafluoroethylene (PTFE), on the properties of polarizable electrodes are studied. Results indicate that the microstructure, pore size distribution and specific capacitance of the electrodes with PTFE binder are superior to those electrodes with PF binder after carbonization. The suitable binder (PTFE) for carbon nanotubes electrodes is proposed.

关键词： carbon nanotubes electric double-layer capacitors phenolic resin polytetrafluoroethylene.

A study of two-dimensional magnetic polaron

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Science china(Physics,Mechanics & Astronomy) 2006年第4期49卷 421-429页

作者： LIU Tao1, ZHANG Huaihong1, FENG Mang1,2.& WANG Kelin1,3.1. school of Science, Southwest university of Science and {2., Mianyang 62.010, china 2. Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 43.070, china 3. Department of Modern Physics, university of Science and {2. of china, Hefei 2.002., china school of Science Southwest University of Science technology Mianyang 621010 China Wuhan Institute of Physics Mathematics Chinese Academy of Sciences Wuhan 430070 China Department of Modern Physics University of Science technology of china Hefei 230026 China

By using the variational method and anneal simulation, we study in this paper the self-trapped magnetic polaron (STMP) in two-dimensional anti-ferromagnetic material and the bound magnetic polaron (BMP) in ferromagnetic material. Schwinger angular momentum theory is applied to changing the problem into a coupling problem of carriers and two types of Bosons. Our calculation shows that there are single-peak and multi-peak structures in the two-dimensional STMP. For the ferromagnetic material, the properties of the two-dimensional BMP are almost the same as that in one-dimensional case; but for the anti-ferromagnetic material, the two-dimensional STMP structure is much richer than the one-dimensional case.

关键词： self-trapped magnetic polaron, bound magnetic polaron, impurity potential, anti-ferromagnet.

Comprehensive evaluation of mechanism of "chimney effect" using principles of magnetism, geochemistry and mineralogy

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Chinese Science Bulletin 1998年第9期43卷 743-748页

作者： LIU Qingsheng 1, CHENG Tongjin 2.and LIU Shugen 3.1. Department of applied Geophysics, china {2. of Geosciences, Wuhan 43.074, china 2. Center of Petroleum Geochemistry, china National Star Petroleum Corporation, Hefei 2.002., china 3. The St Department of applied Geophysics China University of Geosciences Wuhan China Center of Petroleum Geochemistry China National Star Petroleum Corporation Hefei China The State Key Laboratory of Oil/Gas Reservoir Geology and Exploitation of china Chengdu Institute of Technology Chengdu China

Study of forming mechanism of "chimney-effect" (CE) has important significance for basic theory and applications of non-seismic geophysical and geochemical methods locating oil/gas reservoirs. The theoretical basis of comprehensive evaluation of mechanism of CE using principles of magnetism, geochemistry and mineralogy has been reviewed, with the problems to be solved: (ⅰ) study for the relationship between process of oil/gas migration and geochemical field; (ⅱ) analysis of genesis of magnetic, geochemical and mineralogical anomaly; (ⅲ) interpretation of surface soil magnetism and geochemical anomaly combined with seismic data.

关键词： chimney effect (CE) hydrocarbon microseepage oil/gas accumulation.

Thermodynamic Analysis of the Preparation Process of EB-PVD SiC Coating

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Journal of Wuhan university of technology(Materials Science) 2009年第3期24卷 363-366页

作者：易剑 school of Mechatronics Engineering Taizhou University Laser Processing Center Tianjin Polytechnic University Center for Composite Materials Harbin Institute of Technology

The process of preparing SiC coating by electron beam-physical vapor deposition （EB-PVD） was discussed from viewpoint of thermodynamis. Results show that within the temperature range of 2.700-3.3.0 K, the ratio of SiC in the SiC coating doesn＇t change much and keeps around 0.7. Purity of the as-deposited SiC coating is not high. To improve the purity of the SiC coating, the SiC ingot is required to not be, necessary in full density but be fine-grained.

关键词： thermodynamics SiC coating EB-PVD ratio of SiC purity

Parabolic equation of the m-Laplacian with nonlinear boundary condition

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Chinese Science Bulletin 1998年第11期43卷 905-908页

作者： WANG Shu+ 1, 2. WANG Mingxin 3. XIE Chunhong 1 1. Department of Mathematics, Nanjing university, Nanjing 2.0093.{3. 2. Department of Mathematics, Henan university, Kaifeng 475001,{3. 3. Department of applied Mathematics, Southeast university, Department of Mathernntics Nanjing University Nanjing China Department of Mathematics Henan University Kaifeng China Department of applied Mathematics Southeast University Nanjing China

The existence and nonexistence of global positive weak solutions of parabolic equation of the m-Laplician with nonlinear boundary condition are dealt with. The necessary and sufficient conditions on the existence of a... 详细信息

关键词： nonlinear boundary condition parabolic equation of m-Laplacian global solution blow-up.