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OSCILLATION CRITERIA FOR NONLINEAR SECOND ORDER ELLIPTIC DIFFERENTIAL EQUATIONS

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Chinese Annals of Mathematics,Series B 1996年第1期17卷 89-102页

作者： ZHANG BINGGEN ZHAO TAO B. S. LALLI (Department of Mathematics, Ocean university of Qingdao, Qingdao 266003, China.)(Department of Mathematics, Arizona State university, U.S.A.)(Departmemt of Mathematics, university of Saskatchewan, canada.) 青岛海洋大学数学系山东青岛 Arizona State university 美国 university of Saskatchewan 加拿大

The second order elliptic differential equations are considered in an exterior domain Ω Rn, n≥2, where p can chang sign. Some new sufficient conditions for the oscillation of solutions of (1.1) and (1.2) are establi... 详细信息

关键词：非线性二次方程椭圆微分方程摆动标准数学分析

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 Technology,Beijing 100022,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 E3B 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 compression. Based on SDP relaxation and advanced rounding techniques, we first propose 0.5982 and 0.5970-approximation algorithms respectively for the dense-n/2-subgraph problem (DSP) and the table compression problem (TCP). Then we improve these bounds to 0.6243 and 0.6708 respectively for DSP and TCP by adding triangle inequalities to strengthen the SDP relaxation. The 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

Flame Retardants in Multimedia in Northeastern Chinese Daling River

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Flame Retardants in Multimedia in Northeastern Chinese Dalin...

Monophyly of the ring-forming group in Diplopoda(Myriapoda,Arthropoda) based on SSU and LSU ribosomal RNA sequences

持久性有机污染物论坛2011暨第六届持久性有机污染物全...

作者： Luo Wang~1,Ye-Qing Sun~1,Hong-Liang Jia~1,Xian-Jie Liu~1,Meng Yang~1,Wen-Jun Hong~1, Yi-Fan Li~(1,2*) (1 International Joint Research Centre for Persistent Toxic Substances(ijrc-pts),Dalian Maritime university,Dalian 116026,China 2Science and Technology Branch,Environment canada,Toronto, Ontario M3H5T4,canada

＜正＞*** Flame retardants are ubiquitous chemical in the environment due to its heavy application,such as electrical wires and cables,computer connectors and plastic roofing materials for more than four *** it can provide protection from fires,environmental concerns have arisen for some of them because of their widespread detection in the environment,persistence in sediment and bioaccumulation in *** of dechloranes in the environment are,however,relatively few. After the discovery of DP in air,sediment and fish samples in 2006 and Dec 602,603 and 604 in

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Progress in Natural Science:Materials International 2009年第10期19卷 1297-1303页

作者： Peiyun Conga,b,Xuhua Xiac,Qun Yanga,a State Key Laboratory of Palaeobiology and Strategraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing 210008,China b Yunnan Key Laboratory for Paleobiology,Yunnan university,Kunming 650091,China c Department of Biology,university of Ottawa,Ont.,canada K1N 6N5 State Key Laboratory of Palaeobiology and Strategraphy Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences Nanjing 210008 China Yunnan Key Laboratory for Paleobiology Yunnan University Kunming 650091 China Department of Biology University of Ottawa Ont. Canada K1N 6N5

Two controversies exist in the phylogeny of the derived millipedes(Diplopoda).The first is whether millipedes with a fusion ring,including Polydesmida,Spirobolida,Spirostreptida and Julida,form a monophyletic group(the ring-forming group).The second concerns the phylogenetic relationship within the three orders of Juliformia,***,Spirostreptida and *** resolve these phylogenetic controversies,we sequenced 18S and 28S rDNA from six millipede orders and retrieved several homologous sequences from *** results give robust support to the monophyly of the ring-forming group based on maximum parsimony methods,max-imum likelihood methods and Bayesian *** monophyly of the ring-forming group suggests that the fusion of segment sclerites might have occurred only once during millipede evolutionary *** also established a sister-group relationship between Spirobol-ida and Spirostreptida within Juliformia after eliminating a short-branch attraction phenomenon,which is consistent with that from the mitochondrial genome analysis.

关键词： Diplopoda Ring-forming group Ribosomal RNA Monophyly Short-branch attraction

INDUCTION PLASMA REACTIVE DEPOSITION OF TUNGSTEN CARBIDE FROM TUNGSTEN METAL POWDER

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Acta Metallurgica Sinica(English Letters) 2001年第5期14卷 352-358页

作者： X.L. Jiang Institute of Surface and Coatings Technology, Central South university, Changsha 410083, China M.I. Boulos Department of Chemical Engineering, university of Sherbrooke, Sherbrooke, J1K 2R1, canada Central South Univ. Changsha 410083 China

Experimental results on the primary carburization reaction between the tungsten powder and methane in the induction plasma, and the secondary carburization of the deposit on substrate at high temperature are reported. Optical microscopy and scanning electron microscopy were used to examine the microstructures of starting tungsten powder, carburized powder, and deposit. X-ray diffraction analysis, thermal gravimetric analysis and microhardness measurement were used to characterize the structures and properties of the powder and the deposit. It is found that the primary carburization reaction in the induction plasma starts from the surface of tungsten particles when the particles are melted. Tungsten particles are partially carburized inside the reactive plasma. Complete carburization is achieved through the secondary carburization reaction of the deposit on substrate at high temperature.

关键词： Carburizing Deposition Methane Powder metals Tungsten Tungsten carbide

Two-dimensional investigation of forced bubble oscillation under microgravity

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Progress in Natural Science:Materials International 2003年第12期 9-14页

作者： HONG Ruoyu 1 and Masahiro KAWAJI 2(1. Department of Chemistry and Chemical Engineering, Soochow university, Suzhou 215006, China 2. Department of Chemical Engineering and Applied Chemistry, university of Toronto, Toronto ON M5S 3E5, canada) Department of Chemistry and Chemical Engineering Soochow University Suzhou 215006 China Department of Chemical Engineering and Applied Chemistry University of Toronto Toronto ON M5S 3E5 Canada

Recent referential studies of fluid interfaces subjected to small vibration under microgravity conditions are reviewed. An experimental investigation was carried out aboard the American Space Shuttle Discovery . Two dimensional (2 D) modeling and simulation were conducted to further understand the experimental results. The oscillation of a bubble in fluid under surface tension is governed by the incompressible Navier Stokes equations. The SIMPLEC algorithm was used to solve the partial differential equations on an Eulerian mesh in a 2 D coordinate. Free surfaces were represented with the volume of fluid (VOF) obtained by solving a kinematic equation. Surface tension was modeled via a continuous surface force (CSF) algorithm that ensures robustness and accuracy. A new surface reconstruction scheme, alternative phase integration (API) scheme, was adopted to solve the kinematic equation, and was compared with referential schemes. Numerical computations were conducted to simulate the transient behavior of an oscillating gas bubble in mineral oil under different conditions. The bubble positions and shapes under different external vibrations were obtained numerically. The computed bubble oscillation amplitudes were compared with experimental data.

关键词： Navier Stokes (N S) equations volume of fluid (VOF) microgravity bubble oscillation.

CRITERION　OF　STOCHASTIC　LAYER　NEAR　A　PLANAR　HOMOCLINIC　ORBIT　OF　NONLINEAR　DYNAMICAL　SYSTEM

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Journal of Hydrodynamics 1995年第2期7卷 35-50页

作者： Albert C. J. Luo(Department of Mechanical & Industrial Engineering university of Manitoba. Winnipeg, Manitoba, R3T 2N2,canada) Univ of Manitoba Winnipeg Canada

A new analytic method is developed for nonlinear dynamical system, to investigate the mathematical structure and physical characteristics of the stochastic layer near a homoclinic or heteroclinic orbit. This method is based on the subharmonic resonant condition and an energy increment along the separatrix of the system. The critical conditions for the disappearance of stochastic layer are presented, which are associated with all control parameters of the system including initial conditions, excitation frequencies excitatiom amplitudes ***, using this method, we analyze two simple nonlinear dynamical systems, namely,Duffing-Holmes's equation and a forced planar pendulum. As their stochastic layers begin to disappear, their critical amplitudes are also obtained for the given excitation frequency and other chosen parameters. By means of these conditions, we carry out numerical simulations for the two simple models. Their stochastic layer will be shown using Poincare mapping section. Our theoretical results are subeequently shown to be in a good agreement with numerical simulations.

关键词： nonlinear dynamical system stochastic layer numerical simulation

Variations in Wear Resistance of a Novel Triboalloy Pseudoelastic TiNi Alloy-with Respect to its Pseudoelasticity and Hardness

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Journal of Materials Science & Technology 2001年第1期17卷 45-46页

作者： D.Y.Li and X.Ma Dept. of Chemical and Materials Engineering, university of Alberta, Edmonton, Alberta, canada T6G 2G6 Dep. of Chem. Univ. of Alberta Edmonton Canada

It has recently been found that TiNt shape memory alloy has another attractive property; high resistance to wear. The wear resistance of this alloy benefits from its pseudoelasticity (PE). It has, however, been noticed that other mechanical properties also affect the wear resistance, especially the hardness. Research was conducted to investigate the correlation between the wear resistance and both the PE and hardness. It has been demonstrated that when the PE is high, lower hardness leads to higher wear resistance.

关键词： TiNi Variations in Wear Resistance of a Novel Triboalloy Pseudoelastic TiNi Alloy-with Respect to its Pseudoelasticity and Hardness

Molecular and quantum mechanical studies on the monomer recognition of a highly-regular b-helical antifreeze protein

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Science China Chemistry 2004年第1期47卷 34-40页

作者： YANG Zuoyin, JIA Zongchao, LIU Ruozhuang & CHEN GuangjuDepartment of Chemistry, Beijing Normal university, Beijing 100875, China Faculty of Science, Beijing university of Chemical Technology, Beijing 100029, China Department of Biochemistry, Queen’s university, Kingston, Ontario K7L 3N6, canada Department of Chemistry Beijing Normal University Beijing China Faculty of Science Beijing University of Chemical Technology Beijing China Department of Biochemistry Queenś University Kingston Canada

The possible interaction models for an antifreeze protein from Tenebrio molitar (TmAFP) have been systematically studied using the methods of molecular mechanics, molecular dynamics and quantum chemistry. It is hoped that these approaches would provide insights into the nature of interaction between protein monomers through sampling a number of interaction possibilities and evaluating their interaction energies between two monomers in the course of recognition. The results derived from the molecular mechanics indicate that monomer's β-sheets would be involved in interaction area and the side chains on two β-faces can match each other at the two-dimensional level. The results from molecular mechanics and ONIOM methods show that the strongest interaction energy could be gained through the formation of H-bonds when the two β-sheets are involved in the interaction model. Furthermore, the calculation of DFT and analysis of van der Waals bond charge density confirm further that recognition between the two TCTs mainly depends on inter-molecular hydroxyls. Therefore, our results demonstrate that during the course of interaction the most favorable association of TmAFPs is via their β-sheets.

关键词： antifreeze protein, recognition, dynamics simulation, molecular mechanics, quantum chemistry.