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A MULTIGRID METHOD FOR NONLINEAR PARABOLIC PROBLEMS

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Journal of Computational Mathematics 1996年第4期14卷 363-382页

作者： x.J. Yu(Laborutory of Computational Physics, Institute of applied Physics and ComputationalMathematics, beijing, china) INST APPL PHYS & COMPUTAT MATH LAB COMPUTAT PHYSBEIJINGPEOPLES R CHINA

The multigrid algorithm in [13. is developed for solving nonlinear parabolic equations arising from the finite element discretization. The computational cost of the algorithm is approximate O(NkN) where N-k is the dim... 详细信息

关键词： Th Math A MULTIGRID METHOD FOR NONLINEAR PARABOLIC PROBLEMS UC

Existence of Exactly n+1 Simple 4-Periodic Solutions of the Differential Delay Equation x(t)=-f(x(t-1))

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Acta Mathematica Sinica,English Series 1994年第1期10卷 80-87页

作者： Ge Weigao Department of applied Mathematics beijing Institute of Technology beijing,100081{3. 1. Department of applied Mathematics Beijing Institute of Technology 100081 Beijing China

By discussing the zeros of *** we give in this paper a criterion for the existence of exactly n+1 simple 4-periodic solutions of the differential delay equation x(T)= -f(x(t-1)).

关键词： Existence of Exactly n+1 Simple 4-Periodic Solutions of the Differential Delay Equation x t-1

A Fundamental Inequality for Meromorphic Functions in an Angular Domain and Its Application

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Acta Mathematica Sinica,English Series 1994年第3期10卷 308-314页

作者： Zhang Xuelian Department of applied Mathematics beijing Institute of Technology beijing,100081{3. 1. Department of applied Mathematics Beijing Institute of Technology 100081 Beijing China

This paper is to study the characteristic functions of meromorphic functions for an angular *** show an inequality which is similar to the inequality in the second fundamental theorem of Nevranlinna,and estimate its *... 详细信息

关键词： inequality Borel Domain angular directions false suppose establishing latter enough

Changes of decay rates of radioactive ^(111)In and ^(3.)P induced by mechanic motion

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Science china Chemistry 2007年第2期50卷 170-174页

作者： HE YuJian1,QI Fei2 & QI ShengChu3.1 College of Chemistry and Chemical Engineering,Graduate University of Chinese Academy of Sciences,beijing 100049,china 2 No. 1,Gravenhurst Court,Gaithersburg,Md 20878,USA 3.Department of applied Chemistry,Peking University,beijing 100871,china 1. College of Chemistry and Chemical Engineering Graduate University of Chinese Academy of Sciences Beijing 100049 China 2. No. 1 Gravenhurst Court Gaithersburg Md 20878 USA 3. Department of applied Chemistry Peking University Beijing 100871 China

The changes of decay rates of radionuclide 111In(electron capture) and 3.P(β decay) induced by exter-nal mechanic motion are studied. The results indicate that,in the external circular rotation in clockwise and anticlockwise centrifuge on Northern Hemisphere(radius 8 cm,2000 r/min) ,the half life of 111In compared with the referred(2.83.d) is decreased at 2.83. and increased at 1.77%,respectively;the half life of 3.P compared with the referred(14.29 d) is decreased at 3.78% and increased at 1.75%,respec-tively. When the clockwise and anticlockwise rotations increase to 4000 r/min,the half life of 111In is decreased at 11.3.% and increased at 6.3.%,respectively;the half life of 3.P is decreased at 10.08% and increased at 4.3.%,respectively. When the circular rotation is removed,the decay rates of 111In and 3.P return back to the referred,respectively. It is found that the external circular rotations in clockwise and anticlockwise centrifuge selectively increased and decreased the decay rates of 111In and 3.P,respec-tively,and the effects are strongly dependent on the strength of circular rotation. It is suggested that these effects may be caused by the chiral interaction.

关键词： circular rotation helical motion 111In 3.P decay rate chirality

Mechanism of Cathode Process of B(Ⅲ) in LiF-NaF-KBF_4 Meltby Electrochemical Titration Technique

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International Journal of Minerals,Metallurgy and Materials 1998年第4期12卷 203-207页

作者： Qingrong Shi Xindong Wang Lianyu Yuan Shuzhen Duan(applied Science School, University of Science and Technology beijing, beijing 100083.{3.) applied Science School University of Science and Technology Beijing Beijing 100083 China

The mechanism of cathode process of B(Ⅲ) at molybdenum and platinum electrodes in LiF-NaF-KBF4melt was studied and the transferred electron number of the reaction was calculated by means of cyclic *** effect of adsorption of electroactive component on the electrochemical response (e. g., the voltammetric i─Ecurves) was analyzed and discussed. The 'electrochemical spectra' for linear sweep voltammetry was used to elucidate the electrode reaction accompanied by a following transform process. The results show that the reduction ofB(Ⅲ) to B(0) proceeds in reversible one step three-electron reaction and the cathode process of B(Ⅲ) is affected byproduct adsorbed strongly at the electrode surface. It is assumed that the reduction and deposition of B(Ⅲ) at molybdenum and platinum electrodes proceed in two kinds of mechanism： (1) B(Ⅲ)＋ 3. = Bads→ B (surface diffusiondeposition mechanism) and (2) B(Ⅲ) ＋ 3. = B (direct deposition mechanism).

关键词： boron ions cathode process cyclic voltammetry fluoride melt

Application and Comparison of SST Model in Numerical Simulation of the Axial Compressors

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Journal of Thermal Science 2010年第4期19卷 300-309页

作者： YIN Song~1,JIN Donghai~2,GUI Xingmin~3.and ZHU Fang Aero-Engines Simulation Research Center,School of Jet Propulsion,beijing University of Aeronautics and Astronautics, beijing,100191,china Aero-Engines Simulation Research Center School of Jet Propulsion Beijing University of Aeronautics and Astronautics Beijing China

The shear-stress transport(SST)turbulence model is incorporated into Navier-Stokes equations to simulate a turbomachinery flowfield.A staggered finite volume method is used to make the mean flow equations and turbulence model equations strongly coupled and enhance the stability of the numerical *** implicit treatment of the source terms is applied to the SST model.A steady state solution is obtained using five-stage Runge-Kutta time-stepping scheme with local time stepping and residual smoothing to accelerate convergence. The wall distance d,a key parameter in the SST model,is solved by a partial differential *** validations of the code are conducted on rotor 3.,wp11 at design and off-design conditions by comparison with measurements and the Spalart-Allmaras(SA)turbulence *** flow within the tip is calculated with a multi-block grid.

关键词： SST model staggered finite volume method turbomachinery simulation multi-block grid

Complex conforming Delaunay triangulation

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Science china(Information Sciences) 2010年第6期53卷 1130-1140页

作者： MENG XianHai 1, LI JiGang 1, YANG Qin 1, CAI Qiang 2 & CHEN QiMing 3.1 NLSDE, School of Computer Science and Engineering, BeiHang University, beijing 100083. china 2 School of Computer Sciences, beijing Technology and Business University, beijing 10003., china 3.School of Mechanical Engineering and Automation, BeiHang University, beijing 100083. china 1. NLSDE School of Computer Science and Engineering BeiHang University Beijing 100083 China2. School of Computer Sciences Beijing Technology and Business University Beijing 100037 China3. School of Mechanical Engineering and Automation BeiHang University Beijing 100083 China

A novel algorithm of conforming Delaunay triangulation for curved geometry is presented in the paper.A progress has been made for the problem puzzled Delaunay refinement where curved constraints cannot be accepted as input *** algorithm is based on a new sufficient condition for the existence of constraints in *** requires computing only the intersection between constraints and Voronoi edges or faces instead of the circum-sphere of curved *** the termination of the algorithm when small input angles exist in constraints, a weighted method is applied to ensure that the algorithm can terminate under any *** two-dimensional and three-dimensional results are also *** is shown that the algorithm has the capability of dealing with both linear and nonlinear constraints in a consistent way, without the need of maintaining triangular meshes on face constraints.

关键词： mesh generation Delaunay triangulation conforming curved constraints tetrahedralization weight

Structure and Formative Mechanism of Black Patina on Bronze Mirrors

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International Journal of Minerals,Metallurgy and Materials 1998年第3期12卷 147-155页

作者： Zhaozeng Ma Ling Du Xiulan Yin Lianji Jin Chunying Fang(applied Science School, University of Science and Technology beijing, beijing 100083.{3.) applied Science School University of Science and Technology Beijing Beijing 100083 China

The formation of the black patina induced by soil humic asid under different conditions was studied, theblack, grey and brown colored shiny surfaces prepared in laboratory were analyzed. As a result the formation oftin-rich shiny black surface on bronze mirrors is the product of soil corrosion of the bronze mirrors. The patina isformed by reection between the alloy and the humic acid in soil, and leaching of copper and lead oxides through along period time when the mirrors were buried under the ground leaving a dense compact corrosion-resistant layerconsisted predominantly of stannic oxide microcrystal.

关键词： black patina on ancient bronze mirror humic acid soil corrosion, SnO_2 microcrystal

Surface Nanocrystallization of Magnesium Alloy AZ91D by High-Energy Shot Peening

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Journal of Wuhan University of Technology(Materials Science) 2009年第4期24卷 515-519页

作者：张津 School of Materials Science & Engineering University of Science and Technology Beijing College of Materials Science & Engineering Chongqing University of Technology

High-energy shot peening （HESP）, a method to produce severe plastic deformation by high velocity flying balls, was applied on die cast magnesium alloy AZ91D. Effects of surface nanocrystallization by HESP and heat treatment at different temperatures were investigated. The mi- crostructure evolution was conducted using X-ray diffraction （XRD） and field emission scanning electronic microscopy （FESEM）. The hardness was measured by microhardness tester. The experimental results show that surface nanocrystrallization of AZ91D obtained by HESP would lead to the increase of microhardness. Low temperature heated at 100℃ for 1 h do not change the property obviously. However, both the microstructure and microhardness vary greatly after heat treatment at 400℃ for 1 h.

关键词： AZ91 D surface nanocrystallization HESP microhardnss corrosion resistance