检索结果-南通市图书馆

A Difference Scheme for the Coupled KdV equation

在线全文

学校读者我要写书评

暂无评论

Communications in Nonlinear Science and Numerical Simulation 1999年第1期4卷 60-63页

作者： Shaohong ZHU (Department of Mathematics, Tianjin Normal University, Tianjin 300074, China) e-mail: zsh@*** Department of Mathematics Tianjin Normal University Tianjin 300074 China

In this paper, a difference scheme for the periodic initial-boundary problem of the coupled KdV equation is given. The scheme keeps the first two conserved quantities which the differential equation possesses. The catch-ran iterative method is used to solve the difference equations. The numerical simulation exhibits the existence of two-soliton solutions.

关键词： coupled KdV equation conserved quantity catch-ran iterative method

State of the Art and Perspectives of Hydroforming of Tubes and Sheets

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2001年第3期17卷 321-324页

作者： F. Vollertsen Department for Metal Forming Technologies, University Paderborn, Paderborn, Germany e-mail: fv@luf.upb.de Univ Gesamthsch Paderborn Dept Metal Forming Technol D-4790 Paderborn Germany

Hollow parts of high accuracy and high strength can be produced by forming methods using liquid media. Hydroforming of tubes has reached a high standard for small parts (volume some 1000 cm3) and is further developed for larger parts (volume some 10.000 cm3). Processes for hydraulic sheet metal forming are sometimes used for small parts from single sheets These pro-cesses are currently under intensive investigation, which is also true for the processing of double layered sheets Single sheets can be formed using membranes which separate the workpiece and the liquid. This results in interesting possibilities for a part and process integration in one step The forming performance of aluminum alloys can be enhanced by using a heated liquid media when forming without membranes.

关键词： State of the Art and Perspectives of Hydroforming of Tubes and Sheets

Hardening of Thermal Photons Through Inverse Compton Scattering in Strong Magnetic Fields

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2001年第5期1卷 411-420页

作者： YiXu Hong－HuaXu DepartmentofPhysics ShanghaiJiaotongUniversityShanghai200030 DepartmentofPhysics ShanghaiJiaotongUni

A new spectrum function is obtained by use of the Compton scattering cross section in the laboratory frame derived earlier. This spectrum function, besides some modifications in the coefficients of the resonant term, contains also a non-resonant term which is inversely proportional to the square of the magnetic field. Based on this spectrum function, the hardening of thermal photons through inverse Compton scattering by relativistic electron beams on the surface of a strongly magnetized neutron star is investigated. Two new features are found. First, there is a maximum scattered photon energy for a given resonant scattering, beyond which resonance disappears. This maximum depends on the electron energy and the magnetic field, but is independent of the incident photon energy. Second, beyond each resonant scattering, there is a high-energy tail, resulting from non-resonant scattering. It is also found that all the tails have a common upper limit which is the highest scattered photon energy for the given incident photon and electron energies. These two new features are absent in the Monte Carlo simulations and therefore, may have physical implications for y-ray emissions.

关键词： stars: neutron star magnetic fields - scattering - gamma rays

Flow of Viscous Oil in the Volute of a Centrifugal Pump

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2002年第1期11卷 10-15页

作者： Wen-Guang LI (Hydraulic Machinery Division, Gansu University of Technology, Lanzhou 730050, China e-mail: Liwg@***) Hydraulic Machinery Division Gansu University of Technology Lanzhou China

The flows of water as well as viscous oil in the three rectangular sections of the volute of a centrifugal pump are measured by using a two-dimensional laser Doppler velocimetry(LDV) in the best efficiency and part-loading points, respectively. The results show that the magnitude of tangential component of absolute velocity is one order larger than that of radial component. There are spiral motions in the sections of the volute. The angular momentum of liquid in the volute isn’t conservative and the viscosity of liquid is larger, this situation is more severe. The flow of water or viscous oil in the volute is diffused in both best efficiency point and part-loading points. The diffusion of the flow is weakened while pumping the viscous oil.

关键词： centrifugal pump volute flow measurement viscosity LDV.

Initial Magnetization Curve and Hardening Mechanism in the Nanocomposite Nd_8Fe_(85)Nb_1B_6 Ribbon

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2001年第3期17卷 311-313页

作者： Yandong GAO, Shaoqing ZHANG and Bocao LIU Beijing Institute of Aeronautical Materials, Beijing 100095, China e-mail: ydgao@*** Beijing Inst Aeronaut Mat Beijing 100095 Peoples R China

The melt-spun Nd8Fe85Nb1B6 ribbon was prepared by the single roller method with the tangential speed of 20 m/s. A mixture of Nd2Fe14B and alpha -Fe phases with the average crystalline grain size of about 20 nm was found to exist in the as-quenched ribbons. The initial magnetization curve of the nanocomposite Nd8Fe85Nb1B6 ribbon can be divided into four sections by the inflection points on it. The magnetically hardening mechanism corresponding to each section was investigated. The initial susceptibility of the Nd8Fe85Nb1B6 ribbon is higher than that of the Nd15Fe85B9 powder, which may be attributed to the reversible magnetization rotation in the central region not influenced by the exchange-coupling effect within the alpha -Fe grains. The above-mentioned magnetization rotation leads to the formation of equilibrium 180 deg. domain walls at the boundaries of the alpha -Fe grains. With the increase of applied field, these domain walls are compressed reversibly towards the Nd2Fe14B grains and eventually invade into them. The irreversible movement of the domain walls in the Nd2Fe14B grains accounts for the steepest growth of magnetization with the applied field. Finally, the magnetically inhomogeneous 'core regions' are formed in the Nd2Fe14B grains, and the magnetization rotation in these 'core regions' indicates the end of the whole initial saturation process.

关键词： Fe Nb1B6 Ribbon Nd

A tool model for predicting atmospheric chemical kinetics with sensitivity analysis

在线全文

学校读者我要写书评

暂无评论

Journal of environmental Sciences 2001年第1期13卷 79-86页

作者： SHeN Ji (Research Center for eco\|environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.e\|mail:shenji@***) Research Center for eco-environmental Sciences Chinese Academy of Sciences Beijing 100085 China. shenji@***

A package(a tool model) for program of predicting atmospheric chemical kinetics with sensitivity analysis is presented. The new direct method of calculating the first order sensitivity coefficients using sparse matrix technology to chemical kinetics is included in the tool model, it is only necessary to triangularize the matrix related to the Jacobian matrix of the model equation. The Gear type procedure is used to integrate a model equation and its coupled auxiliary sensitivity coefficient equations. The FORTRAN subroutines of the model equation, the sensitivity coefficient equations, and their Jacobian analytical expressions are generated automatically from a chemical mechanism. The kinetic representation for the model equation and its sensitivity coefficient equations, and their Jacobian matrix is presented. Various FORTRAN subroutines in packages, such as SLODe, modified MA28, Gear package, with which the program runs in conjunction are recommended. The photo\|oxidation of dimethyl disulfide is used for illustration.

关键词： atmospheric chemical model chemical kinetics sensitivity analysis

Do Globular Clusters Harbor Black Holes?

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2001年第4期1卷 291-295页

作者： Xian-Zhong Zheng (National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012)e-mail:zxz@*** National Astronomical Observatories Chinese Academy of Sciences Beijing 100012

It has been firmly established that there exists a tight correlation be- tween the mass of the central black hole and velocity dispersion (or luminosity) in elliptical galaxies, 'pseudobulges' and bulges of galaxies, although the nature of this correlation still remains nuclear. We explore the possibility of extrapolating such a correlation to less massive, spherical systems like globular clusters. In particular, motivated by the apparent success in the globular cluster M15, we present an estimate of the central black hole mass for a number of globular clusters with available velocity dispersion data.

关键词： black hole physics-globular clusters: general - galaxies: general

The Blow-up Rate for a System of Heat equations with Neumann Boundary Conditions

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,english Series 1999年第4期15卷 549-554页

作者： Zhigui Lin Department of Mathematics,Yangzhou University,Yangzhou 225002,P.R.China e-mail:zglin68@hotmail.comChunhong Xie Department of Mathematics,Nanjing University,Nanjing 210093,P.R. China e-mail:algebra@*** Department of Mathematics Yangzhou University Yangzhou P. R. China Department of Mathematics Nanjing University Nanjing P. R. China

This paper deals with the blow-up properties of solutions to a system of heat equations u_t=Δ_u,v_t=Δv in B_R×(0,T) with the Neumann boundary conditions u/η=e^v,v/η=e^u on S_R×[0,T).The exact blow-up rates are *... 详细信息

关键词： System of heat equations Neumann boundary conditions Blow-up rate Blow-up set

The effect of Material Properties on StressState Near the Ply Interface of Laminates

在线全文

学校读者我要写书评

暂无评论

Communications in Nonlinear Science and Numerical Simulation 1999年第2期4卷 118-122页

作者： Wei FeNG(Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai 200072,China)e-mail: glliu@*** Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 China

In this paper, the attention is restricted to the cases of symmetric angleply laminates. The stress distributions are studied at the ply level with an emphasison the interface effect in the central region of symmetric composite laminates. It hasbeen discovered that the numerical distributions of stresses in angle-ply laminates arequite different from the results by the classical laminate theory. There are in-plane stressconcentrations near ply interface in the interior region of laminated composites due to theabrupt change of fiber orientation. Because interlaminar stresses and thus delaminationcan arise in any gradient stress field in a laminated composite, there exist interlaminarstresses near the ply interface in the interior region. The effects of the material propertieson the concentration of in-plane stress are also discussed.

关键词： laminate stress concentration material property