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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 Technology,Beijing 100022,china 2. {3. 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. 6243.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

A trust region algorithm for bilevel programing problems

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Chinese Science Bulletin 1998年第10期43卷 820-824页

作者： LIU Guoshan 1, HAN Jiye 2 and WANG Shouyang 3.1. Department of mathematics, Beijing Normal university, Beijing 100875, china 2. {3. of applied mathematics, Chinese Academy of Sciences, Beijing 100080, china 3. {3. of Systems Science, Chi Department of mathematics Beijing Normal University Beijing China institute of applied mathematics Chinese Academy of Sciences Beijing China institute of Systems Science Chinese Academy of Sciences Beijing China

A trust region algorithm is proposed for solving bilevel programming problems where the lower level programming problem is a strongly convex programming problem with linear constraints. This algorithm is based on a tr... 详细信息

关键词： bilevel programming problem trust region algorithm global convergence.

A low frequency piezoelectric power harvester using a spiral-shaped bimorph

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Science china(Physics,mechanics & Astronomy) 2006年第6期49卷 649-659页

作者： HU Yuantai1,2,HU Hongping2 & YANG Jiashi3.1. institute of mechanics and Sensing Technology,Central South university,Changsha 410083.{3. 2. Department of mechanics,Huazhong university of Science and Technology,Wuhan 43.074,{3. 3. Department of Engineering mechanics,university of Nebraska,Lincoln,NE 68588-0526,USA 1. institute of mechanics and Sensing Technology Central South University Changsha 410083 China 2. Department of mechanics Huazhong University of Science and Technology Wuhan 430074 China 3. Department of Engineering mechanics University of Nebraska Lincoln NE 68588-0526 USA

We propose a spiral-shaped piezoelectric bimorph power harvester operating with coupled flexural and extensional vibration modes for applications to low frequency energy sources. A theoretical analysis is performed and the computational results show that the spiral structure has relatively low operating frequency compared to beam power harvesters of the same size. It is found that to optimize the performance of a piezoelectric spiral-shaped harvester careful design is needed.

关键词： spiral-shaped bimorph,piezoelectric harvester,power density.

Direct CP violation in hadronic B decays

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Science china(Physics,mechanics & Astronomy) 2006年第3期49卷 357-366页

作者： HONG Bihai1,2 & Lü Caidian3.1. Department of Physics, Lishui university, Lishui 3.3.00,china 2. Department of Physics, Shanghai Jiaotong university, Shanghai 20003.,{3. 3. institute of High Energy Physics, Beijing 100049,china Department of Physics Lishui University Lishui 323000 China Department of Physics Shanghai Jiaotong University Shanghai 200030 China institute of High Energy Physics Beijing 100049 China

There are different approaches for the hadronic B decay calculations, recently. In this paper, we upgrade three of them, namely factorization, QCD factorization and the perturbative QCD approach based on kT factorization, using new parameters and full wave functions. Although they get similar results for many of the branching ratios, the direct CP asymmetries predicted by them are different, which can be tested by recent experimental measurements of B factories.

关键词： CP violation hadronic B decay factorization.

An Approximate Solution Technique Depending on an Artificial Parameter: A Special Example

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Communications in Nonlinear Science and Numerical Simulation 1998年第2期3卷 40-45页

作者： Jihuan HE (Shanghai university, Shanghai institute of applied {3. and mechanics, Shanghai 200072, china) Shanghai university Shanghai Institute of Applied Mathematics and Mechanics Shanghai 200072 China

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｔｈｅｌａｓｔｔｗｏｄｅｃａｄｅｓｗｉｔｈｔｈｅｒａｐｉｄｄｅｖｅｌｏｐｍｅｎｔｏｆｎｏｎｌｉｎｅａｒｓｃｉｅｎｃｅ，ｔｈｅｒｅｈａｓａｐｐｅａｒｅｄｅｖｅｒｉｎｃｒｅａｓｉｎｇｉｎｔ... 详细信息

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｔｈｅｌａｓｔｔｗｏｄｅｃａｄｅｓｗｉｔｈｔｈｅｒａｐｉｄｄｅｖｅｌｏｐｍｅｎｔｏｆｎｏｎｌｉｎｅａｒｓｃｉｅｎｃｅ，ｔｈｅｒｅｈａｓａｐｐｅａｒｅｄｅｖｅｒｉｎｃｒｅａｓｉｎｇｉｎｔｅｒｅｓｔｏｆｓｃｉｅｎｔｉｓｔｓ...

关键词： perturbation methods homotopy Duffing equation nonlinearity

Virtual multi-dimensional internal bonds model and its application in simulation of rock mass

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Science china(Technological Sciences) 2008年第2期51卷 192-201页

作者： ZHANG ZhenNan1,2 & GE XiuRun3.4 1 Department of Civil Engineering,Shanghai university,Shanghai 200072,china 2 Shanghai {3. of applied mathematics and mechanics,Shanghai university,Shanghai 200072, china 3.{3. of Geotechnical Engineering,Shanghai Jiao Tong university,Shanghai 20003.,china 4 {3. of Rock and Soil mechanics,Chinese Academy of Sciences,Wuhan 43.071,china 1. Department of Civil Engineering Shanghai University Shanghai 200072 China 2. Shanghai institute of applied mathematics and {3. Shanghai University Shanghai 200072 China 3. institute of Geotechnical Engineering Shanghai Jiao Tong University Shanghai 200030 China 4. institute of Rock and Soil mechanics Chinese Academy of Sciences Wuhan 430071 China

VMIB (virtual multi-dimensional internal bonds) is a multiscale mechanical model developed from the VIB (virtual internal bond) theory. In VIB theory,the solid mate-rial is considered to consist of random-distributed material particles in microscale. These particles are connected with normal bonds. The macro constitutive relation is derived from the cohesive law between particles. However,in VMIB,the micro particles are connected with both normal and shear bonds. The macro constitutive relation is derived in terms of bond stiffness coefficients. It has been theoretically certified that there exists a corresponding relationship between the two bond stiffness coefficients and the two macro material constants,i.e. the Young’s modulus and Poisson ratio. This corresponding relationship suggests that it should be necessary and sufficient to simultaneously account for the normal and shear interactions between particles. Due to the fact that the fracture criterion is directly incorporated into the constitutive relation,both VIB and VMIB present many advantages in simulating fractures of materials. In the damage model of rock mass,a damage tensor is usually defined to describe the distribution of cracks. The damage value in one direction determines the relative stiffness of rock mass in this direction. In VMIB solid,the relative distribution density of micro bonds in one direction determines the relative macro stiffness of the material in this direction. The effects of the damage value and the relative distribution density of bonds are consistent. To simulate the failure behavior of rock mass with VMIB,the presented paper sets up a quantitative relationship between the damage tensor and the rela-tive distribution density of bonds. Comparison of the theoretical and the experi-mental results shows that VMIB model can represent the effect of distributed cracks on rock mass with this relationship. The presented work provides a founda-tion for further simulating fracture behavior

关键词： VMIB (virtual multi-dimensional internal bonds) rock mass VIB (virtual internal bonds) multi-cracked body numerical simulation

Weakly nonlinear stability of ultra-thin slipping films

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Progress in Natural Science:Materials International 2005年第9期15卷 827-831页

作者： HU Guohui(Shanghai institute of applied mathematics and {3., Shanghai university, Shanghai 200072, china) Shanghai institute of applied mathematics and {3. Shanghai University Shanghai 200072 China

A weakly nonlinear theory is presented to study the effects of slippage on the stability of the ultra-thin polymer films. The nonlinear mathematical model is constructed for perturbations of small finite amplitude based on hydrodynamic equations with the long wave approximation. Results reveal that the nonlinearity always accelerates the rupture of the films. The influences of the slip length, film thickness, and initial amplitude of perturbations on the rupture of the films are investigated.

关键词： ultra-thin film weakly nonlinear theory hydrodynamic stability rupture of thin film.

A New Cellular Automaton Model for TrafficFlow

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Communications in Nonlinear Science and Numerical Simulation 1999年第4期4卷 264-267页

作者： Yongtao HU(Shanghai institute of applied mathematics and {3., Shanghai university,Shanghai 200072, china) Shanghai institute of applied mathematics and {3. Shanghai University Shanghai 200072 China

IntroductionCellularautomaton(CA)***,thesemodelSareremaxkable***]introdu... 详细信息

IntroductionCellularautomaton(CA)***,thesemodelSareremaxkable***]introdu...

关键词： traffic model transportation simulation cellular automata

SrGa_2S_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 210096, china 2. Department of applied Physics, Tianjin university, Tianjin 3.003., china 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-2S-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-2S-4∶Ce bule TFEL low dielectric constant insulator layer.