共查询到20条相似文献,搜索用时 15 毫秒
1.
A simple and exactly soluble model is presented for a two-electron capture process accompanied by a large lattice relaxation. The model is a system of two interacting electrons in a deformable lattice with a single donor-type impurity. It is demonstrated that the model has the following two advantages. First, it exhibits a larger lattice relaxation for the binding of the second electron than for the first. Second, it enables us to discuss possible magnetic behaviors of the impurity in the ground state. 相似文献
2.
Lattice Boltzmann Method is recently developed within numerical schemes for simulating a variety of physical systems. In this paper a new lattice Bhatnagar-Gross-Krook (LBGK) model for two-dimensional incompressible magnetohydrodynamics (IMHD) is presented. The model is an extension of a hydrodynamics lattice BGK model with 9 velocities on a square lattice, resulting in a model with 17 velocities. Most of the existing LBGK models for MHD can be viewed as compressible schemes to simulate incompressible flows. The compressible effect might lead to some undesirable errors in numerical simulations. In our model the compressible effect has been overcome successfully. The model is then applied to the Hartmann flow, giving reasonable results. 相似文献
3.
MA Chang-Feng SHI Bao-Chang CHEN Xing-Wang 《理论物理通讯》2005,44(5):917-920
Lattice Boltzmann Method is recently developed within numerical schemes for simulating a variety of physical systems. In this paper a new lattice.Bhatnagar-Gross-Krook (LBGK) model for two-dimensional incompressible magnetohydrodynamics (IMHD) is presented. The model is an extension of a hydrodynamics lattice BGK model with 9 velocities on a square lattice, resulting in a model with 17 velocities. Most of the existing LBGK models for MHD can be viewed as compressible schemes to simulate incompressible flows. The compressible effect might lead to some undesirable errors in numerical simulations. In our model the compressible effect has been overcome successfully. The model is then applied to the Hartmann flow, giving reasonable results. 相似文献
4.
The novel lattice hydrodynamic model is presented by incorporating the “backward looking” effect. The stability condition for the the model is obtained using the linear stability theory. The result shows that considering one following site in vehicle motion leads to the stabilization of the system compared with the original lattice hydrodynamic model and the cooperative driving lattice hydrodynamic model. The Korteweg-de Vries (KdV, for short) equation near the neutral stability line is derived by using the reductive perturbation method to show the traffic jam which is proved to be described by KdV soliton solution obtained from the KdV equation. The simulation result is consistent with the nonlinear analysis. 相似文献
5.
REN Hongwu FANG Zhujie 《Chinese Journal of Lasers》1999,8(6):525-530
1 Introduction Opticaltomographyprovidesanalternativetechnologytoprobebreastcancerandmonitorhumantissue’sfunctionalparameternoninvasively[1,2].Photonmigrationintissueplaysakeyroleinopticaltomography.Recently,alatticerandomwalkmodel[3,4]isemployedtod… 相似文献
6.
A lattice random walk model based on particles scattering on discrete lattice of homogenous space is introduced. The discrete Green's function (DFG) for two-dimensional and three-dimensional lattice random walk of photon is found and proved by mathematical induction. The convolution theorem of photon lattice random walk is presented. They can be used with the method of images to calculate the photon density distribution in semi-infinite and finite slab homogenous turbid media such as tissue. 相似文献
7.
H. Jex 《Zeitschrift für Physik B Condensed Matter》1986,63(1):91-95
A one-dimensional lattice model of a solid-solid interface is presented within which it is possible to calculate the transmission and reflection amplitudes of lattice vibrations at the interface. The model is applied for acoustic and optic phonons with arbitrary wavelength from the Brillouin zone. General expressions for the coefficients of power transmission and power reflection are evaluated. The reciprocity theorem is proved and applications of numerical results are discussed. 相似文献
8.
Dirk Kehrwald 《Journal of statistical physics》2005,121(1-2):223-237
It is shown how shear-thinning flow can be simulated without the need for numerical differentiation by following a lattice
Boltzmann approach. The basic idea of is to combine the Cross model of viscosity with a 3D multiple relaxation time lattice
Boltzmann method and to extract the required velocity derivatives from intrinsic quantities of the lattice Boltzmann scheme.
Computational results are presented for a simple benchmark and for the simulation of liquid composite moulding. 相似文献
9.
A three-company econophysics model for competing multi-agent systems in a triangular lattice is analyzed using mean field theory for its phase diagram. Interpretations for the temperature, spin density and lattice structures are presented. Suggestions for the use of this model for econophysics in the context of multi-agent systems are made. 相似文献
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11.
A lattice random walk model based on walkers wandering on discrete lattice of scattering space by discrete spatial and temporal step is presented. The scattering matrix and linking matrix of the lattice random walk are given for the scattering and absorption processes in homogenous and inhomogeneous turbid media. All the results obey the principle of causality. 相似文献
12.
REN Hongwu FANG Zujie 《Chinese Journal of Lasers》1999,8(4):327-333
Introduction Opticaltomographyusingnearinfraredlighttoextractinteriorabnormalitiesinformationattractsmanyresearchinterestsinbiomedicaloptics[1],becauseitprovidesanalternativepotentialmodalitytoprobebreastcancerandmonitorbrainandmuscleoxygenationnon… 相似文献
13.
Morikazu Toda 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2004,80(10):445
In this article a brief review of the theory of one-dimensional nonlinear lattice is presented. Special attension is paid for the lattice of particles with exponential interaction between nearest neighbors (the Toda lattice). The historical exposition of findings of the model system, basic equations of motion, special solutions, and the general method of solutions are given as chronologically as possible. Some reference to the Korteweg-de Vries equation is also given. The article consists of three parts. Firstly, the idea of dual system is presented. It is shown that the roles of masses and springs of a harmonic linear chain can be exchanged under certain condition without changing the eigenfrequencies. Secondly, the idea is applied to the anharmonic lattice and an integrable lattice with exponential interaction force between adjacent particles is obtained. Special solutions to the equations of motion and general method of solution are shown. In the last part, some studies on the Yang-Yang’s thermodynamic formalism is given. 相似文献
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15.
《Physics letters. [Part B]》1988,201(3):340-344
A chiral invariant lattice fermion action which solves the species-doubling problem of Dirac fermions on a lattice for (even) dimensions of space-time less than eight is presented. The decoupling of replica fermions requires to give up rotational and gauge symmetry in the regularization procedure. The corresponding lattice Schwinger model reproduces all the results of the continuum theory. 相似文献
16.
17.
Longhi S 《Physical review letters》2006,97(11):110402
An exactly-solvable model for the decay of a metastable state coupled to a semi-infinite, tight-binding lattice, showing large deviations from exponential decay in the strong coupling regime, is presented. An optical realization of the lattice model, based on discrete diffraction in a semi-infinite array of tunneling-coupled optical waveguides, is proposed to test nonexponential decay and for the observation of an optical analog of the quantum Zeno effect. 相似文献
18.
Efficient, nonlinearly stable entropic lattice Boltzmann models for computational fluid dynamics are presented. A new method of fast evaluation of equilibria to machine precision is proposed. Analytical solution is found for the collision step which guarantees stability and thermodynamic consistency of the scheme. As an example, a novel 15-velocity lattice Boltzmann model is derived and validated with a simulation of a three-dimensional backward-facing step flow. 相似文献
19.
We consider two-flavor asymmetric QCD combined with a low-energy effective model inspired by chiral perturbation theory and lattice data to investigate the effects of masses, isospin and baryon number on the pressure and the deconfinement phase transition. Remarkable agreement with lattice results is found for the critical temperature behavior. Further analyses of the cold, dense case and the influence of quark mass asymmetry are also presented. 相似文献
20.
多孔介质中高Péclet数和大黏性比下混溶流体的流动和扩散广泛存在于二氧化碳驱油、化工生产等工业过程中.用数值方法对该问题进行研究时,关键在于如何正确描述高Péclet数和大黏性比下多孔介质内流体的行为.为此,提出了一种基于多松弛模型和格子动理模型的耦合格子Boltzmann模型.通过Chapman-Enskog分析,证明该模型能有效求解不可压Navier-Stokes方程和对流扩散方程.数值结果表明,该模型不仅具有二阶精度和良好的稳健性,而且对于高Péclet数和大黏性比的问题具有良好的数值稳定性,为模拟此类问题提供了有效工具. 相似文献