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A MODIFIED BISECTION SIMPLEX METHOD FOR LINEAR PROGRAMMING

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Journal of Computational Mathematics 1996年第3期14卷 249-255页

作者： P.Q. Pan(department of Mathematics and mechanics, Southeast university, nanjing china) SOUTHEAST UNIV DEPT MATH & MECHNANJINGPEOPLES R CHINA

In this paper, a modification of the bisection simplex method([7]) is made for more general purpose use. Organized in an alternative simpler form, the modified version exploits information of the optimal value, as does the original bisection method, but no bracket on the optimal value is needed as part of input; in stead, it only requires provision of an estimate b(0) of the optimal value and an estimate of the error bound of b(0) (it is not sensitive to these values though). Moreover, a new, ratio-test-free pivoting rule is proposed, significantly reducing computational cost at each iteration. Our numerical experiments show that the method is very promising, at least for solving linear programming problems of such sizes as those tested.

关键词： Algorithms Simplex method Information economics Method of bisection Error bounds Optimal solutions

Dynamic damage and stress-strain relations of ultra-high performance cementitious composites subjected to repeated impact

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Science china(Technological Sciences) 2010年第6期53卷 1520-1525页

作者： LAI JianZhong1 & SUN Wei2 1 department of Materials Science and engineering,nanjing university of Science and Technology,nanjing 210094,china 2 College of Materials Science and engineering,Southeast university,nanjing 211189,china 1. department of Materials Science and engineering Nanjing University of Science and Technology Nanjing 210094 China2. College of Materials Science and Engineering Southeast University Nanjing 211189 China

Ultra-high performance cementitious composites (UHPCC) were prepared by replacing 60% of cement with ultra-fine industrial waste *** dynamic damage and compressive stress-strain relations of UHPCC were studied using split Hopkinson pressure bar (SHPB).The damage of UHPCC subjected to repeated impact was measured by the ultrasonic pulse velocity *** show that the dynamic damage of UHPCC increases linearly with impact times and the abilities of repeated impact resistance of UHPCC are improved with increasing fiber volume *** stress waves on impact were recorded and the average stress,strain and strain rate of UHPCC were calculated based on the wave propagation *** effects of strain rate,fibers volume fraction and impact times on the stress-strain relations of UHPCC were *** show that the peak stress and elastic modulus decrease while the strain rate and peak strain increase gradually with increasing impact times.

关键词： ultra-high performance cementitious composites (UHPCC) split Hopkinson pressure bar (SHPB) repeated impact damage stress-strain

The reliability of the improved e^N method for the transition prediction of boundary layers on a flat plate

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Science china(Physics,mechanics & Astronomy) 2012年第5期55卷 837-843页

作者： SU CaiHong1,2 1 department of mechanics,Tianjin university,Tianjin 300072,china 2 Tianjin Key Laboratory of Modern engineering mechanics,Tianjin 300072,china 1. department of mechanics Tianjin University Tianjin 300072 China2. Tianjin Key Laboratory of Modern Engineering Mechanics Tianjin 300072 China

The transition criterion in the improved eN method is that transition would occur whenever the velocity amplitude of disturbance reaches 1%-2% of the free stream velocity,while in the conventional eN method,the N factor is an empirical *** this paper the reliability of this key assumption in the improved eN method is checked by results of transition prediction by using the Parabolized Stability Equations(PSE).Transition locations of an incompressible boundary layer and a hypersonic boundary layer at Mach number 6 on a flat plate are predicted by both the improved eN method and the PSE *** from both methods agree fairly well with each other,implying that the transition criterion proposed in the improved eN method is reliable.

关键词： transition prediction boundary layer eN PSE

Development of SOM combustion model for Reynolds-averaged and large-eddy simulation of turbulent combustion and its validation by DNS

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Science china(Technological Sciences) 2008年第8期51卷 1073-1086页

作者： ZHOU LiXing department of engineering mechanics, Tsinghua university, Beijing 100084, china department of engineering mechanics Tsinghua University Beijing 100084 China

The derivation and closure methods of the second-order moment (SOM) combus- tion model are proposed. The application of this model to Reynolds averaged (RANS) and large-eddy simulation (LES) of turbulent swirling diffusion combustion, jet diffusion combustion, and bluff-body stabilized premixed combustion is sum- marized. It is indicated that the SOM model is much better than the eddy-beak-up (EBU) and presumed PDF models widely used in commercial software and engi- neering. The SOM modeling results are close to those obtained using the most accurate but much more complex PDF equation model. Moreover, it can save much more computation time than the PDF equation model. Finally, the SOM model is validated by the direct numerical simulation (DNS) of turbulent reacting channel flows.

关键词： turbulent combustion second-order moment model Reynolds averaged simulation large-eddy simulation

A NEW CLASS OF UNIFORMLY SECOND ORDERACCURATE DIFFRENCE SCHEMES FOR 2D SCALAR CONSERVATION LAWS

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Journal of Computational Mathematics 1997年第4期15卷 311-318页

作者： Juan Cheng(department of Aerodynamics, nanjing university of Aeronautics & Astronautics,nanjing, china)Jia-zun Dai (department of Mathematics, Physics and mechanics, nanjing university of Aeronautics & Astronautics, nanjing, china) 南京航空航天大学空气动力学系江苏南京南京航空航天大学数学系江苏南京

In this paper, concerned with the Cauchy problem for 2D nonlinear hyperbolic conservation laws,we construct a class of uniformly second order accurate finite difference schemes, which are based on the E-schemes. By applying the conver gence theorem of Coquel-Le Floch [1], the family of approximate solutions defined by the scheme is proven to converge to the unique entropy weak L∞-solution. Furthermore, some numerical experiments on the Cauchy problem for the advection equation and the Riemann problem for the 2D Burgers equation are given and the relatively satisfied result is obtained.

关键词： Math A NEW CLASS OF UNIFORMLY SECOND ORDERACCURATE DIFFRENCE SCHEMES FOR 2D SCALAR CONSERVATION LAWS high Ph

A new sequential learning algorithm for RBF neural networks

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Science china(Technological Sciences) 2004年第4期47卷 447-460页

作者： YANG Ge1, LV Jianhong1 & LIU Zhiyuan2 1. department of Power engineering, Southeast university, nanjing 210096, china 2. department of Power engineering, nanjing Institute of Technology, nanjing 210013, china 1. department of Power engineering Southeast University 210096 Nanjing China 2. department of Power engineering Nanjing Institute of Technology 210013 Nanjing China

Due to their inherent imperfections, it is hard to use the static neural networks for nonlinear time-varying process modeling and prediction, and the minimal resource allocation network (MRAN) is difficult to be realized for its too many regulation parameters. A new sequential learning algorithm for radial basis function (RBF) neural networks based on local projection named Local Projection Network (LPN) is proposed in this paper. The results of validation for several benchmark problems with the new algorithm show that the presented LPN not only has the same level as M-RAN in network size and precision of the outputs, but also has fewer regulation parameters and is more predictable.

关键词： radial basis functions, local projection network, minimal resource allocation network, learning algorithm.

Some variational principles in electroelastic media under finite deformation

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Science china(Physics,mechanics & Astronomy) 2008年第9期51卷 1390-1402页

作者： KUANG ZhenBang department of engineering mechanics,Shanghai Jiaotong university,Shanghai 200240,china department of engineering mechanics Shanghai Jiaotong University Shanghai 200240 China

It is proposed that the universal thermodynamic energy variational principle is in-cluded in the first law of thermodynamics. Some variational principles in the elec-troelastic media under finite deformation are derived from this universal thermo-dynamic variational principle. It is suggested that in the general electroelastic analysis the environment should be considered together with the discussed elec-troelastic medium. For the variational principle of nonlinear electroelastic media the variation of the electric potential is coupled with the virtual displacement,and the variation of the initial volume should be considered. The Maxwell stress in the initial configuration is naturally derived from this variational principle and it is unique in the second order precision.

关键词： first law of thermodynamics variational principle the electroelastic media the governing equation

The complex variable reproducing kernel particle method for elasto-plasticity problems

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Science china(Physics,mechanics & Astronomy) 2010年第5期53卷 954-965页

作者： CHEN Li1 & CHENG YuMin2 1 department of engineering mechanics,Chang’an university,Xi’an 710064,china 2 Shanghai Institute of Applied Mathematics and mechanics,Shanghai university,Shanghai 200072,china 1. department of engineering mechanics Chang’an University Xi’an 710064 China2. Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 China

On the basis of reproducing kernel particle method(RKPM),using complex variable theory,the complex variable reproducing kernel particle method(CVRKPM) is discussed in this *** advantage of the CVRKPM is that the correction function of a two-dimensional problem is formed with one-dimensional basis function when the shape function is *** the CVRKPM is applied to solve two-dimensional elasto-plasticity *** Galerkin weak form is employed to obtain the discretized system equation,the penalty method is used to apply the essential boundary *** then,the CVRKPM for two-dimensional elasto-plasticity problems is formed,the corresponding formulae are obtained,and the Newton-Raphson method is used in the numerical *** numerical examples are given to show that this method in this paper is effective for elasto-plasticity analysis.

关键词： meshless method reproducing kernel particle method(RKPM) complex variable reproducing kernel particle method(CVRKPM) correction function elasto-plasticity

Preparation and performances of bulk porous Al foams impregnated with phase-change-materials for thermal storage

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Progress in Natural Science:Materials International 2012年第5期22卷 440-444页

作者： Jinghua Jiang a,b,Yingying Zhu b,Aibin Ma a,b,Donghui Yang b,c,Fumin Lu b,Jianqing Chen b,Jun Shi b,Dan Song a,b a National engineering Research Center of Water Resources Efficient Utilization and engineering Safety,hohai university,nanjing 210098,china b College of mechanics and Materials,hohai university,nanjing 210098,china c department of Mechanical and Aerospace engineering,North Carolina State university,Raleigh,NC 27695-7919,USA [a] National engineering Research Center of Water Resources Efficient Utilization and engineering Safety Hohai University Nanjing 210098 China [b] College of mechanics and Materials Hohai University Nanjing 210098 China [c] department of Mechanical and Aerospace engineering North Carolina State University Raleigh NC 27695-7919 USA

Shape-stabilized phase change materials(PCMs) exhibit desirable thermal storage properties and are used for energy conservation *** study is focused on the preparation and thermal-/dynamic-mechanical properties of the bulk porous Al foams impregnated with organic PCMs such as paraffins and stearic *** results indicated that the new shape-stabilized PCMs composites could be produced by a simple and eco-friendly constant-pressure impregnation *** filling fraction of PCMs was approximately more than 80% for the impregnated samples with vacuuming or without *** shape-stabilized PCMs/Al-foam composites exhibited considerable latent thermal storage potential for good interface,desirable phase-change temperature range and latent heat values(72.9kJ/kg for the paraffin/Al-foam composite and 66.7kJ/kg for the stearic acid/Al-foam composite).Moreover,the impregnation of PCMs improved the dynamic-compression yield strength,durability and resistance to oxidation of Al foams and made its ideal energy-saving materials.

关键词： Phase change materials Porous Al foams Composites Thermal storage Dynamic mechanical properties