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51.
We consider the dynamics of the domain-wall kink soliton, in particular we study the zero mode of translation. In the infinitely-thin kink limit, we show that the zero mode is almost completely frozen out, the only remnant being a dynamically constrained four-dimensional mode of a single but arbitrary frequency. In relation to this result, we show that the usual mode expansion for dealing with zero modes - implicit collective coordinates - is not in fact a completely general expansion, and that one must use instead a traditional generalised Fourier analysis. 相似文献
52.
53.
《Communications in Nonlinear Science & Numerical Simulation》2014,19(7):2505-2512
Based on a reactive multiple particle collision method, we construct a mesoscopic dynamics model to simulate chemical system. The validity of the reactive multiple particle collision method under various conditions in a double-feedback bi-stable chemical system is studied. Then, we extend it to simulate diffusion-limited reactions with fast reaction rate in cellular environment. Using the improved method, we observe bi-stable behavior with randomly distributed reactants and spatial domain separation of opposite phases. The particle-based mesoscopic method is computationally efficient, although hydrodynamic interactions and fluctuation are both properly accounted for. Stochastic effects shown to play dominant roles in biochemical dynamics are also considered. The improved method could be used to explore a variety of reactions with disparate scale of reaction rates. 相似文献
54.
Probabilistically induced domain decomposition methods for elliptic boundary-value problems 总被引:1,自引:0,他引:1
Juan A. Acebrn Maria Pia Busico Piero Lanucara Renato Spigler 《Journal of computational physics》2005,210(2):421-438
Monte Carlo as well as quasi-Monte Carlo methods are used to generate only few interfacial values in two-dimensional domains where boundary-value elliptic problems are formulated. This allows for a domain decomposition of the domain. A continuous approximation of the solution is obtained interpolating on such interfaces, and then used as boundary data to split the original problem into fully decoupled subproblems. The numerical treatment can then be continued, implementing any deterministic algorithm on each subdomain. Both, Monte Carlo (or quasi-Monte Carlo) simulations and the domain decomposition strategy allow for exploiting parallel architectures. Scalability and natural fault tolerance are peculiarities of the present algorithm. Examples concern Helmholtz and Poisson equations, whose probabilistic treatment presents additional complications with respect to the case of homogeneous elliptic problems without any potential term and source. 相似文献
55.
56.
This paper is concerned with the Poincaré-Steklov operator that is widely used in domain decomposition methods. It is proved that the inverse of the Poincaré-Steklov operator can be expressed explicitly by an integral operator with a kernel being the Green's function restricted to the interface. As an application, for the discrete Poincaré-Steklov operator with respect to either a line (edge) or a star-shaped web associated with a single vertex point, a preconditioner can be constructed by first imbedding the line as the diameter of a disk, or the web as a union of radii of a disk, and then using the Green's function on the disk. The proposed technique can be effectively used in conjunction with various existing domain decomposition techniques, especially with the methods based on vertex spaces (from multi-subdomain decomposition). Some numerical results are reported.
57.
Xiao-Chuan Cai William D. Gropp David E. Keyes 《Numerical Linear Algebra with Applications》1994,1(5):477-504
In recent years, competitive domain-decomposed preconditioned iterative techniques of Krylov-Schwarz type have been developed for nonsymmetric linear elliptic systems. Such systems arise when convection-diffusion-reaction problems from computational fluid dynamics or heat and mass transfer are linearized for iterative solution. Through domain decomposition, a large problem is divided into many smaller problems whose requirements for coordination can be controlled to allow effective solution on parallel machines. A central question is how to choose these small problems and how to arrange the order of their solution. Different specifications of decomposition and solution order lead to a plethora of algorithms possessing complementary advantages and disadvantages. In this report we compare several methods, including the additive Schwarz algorithm, the classical multiplicative Schwarz algorithm, an accelerated multiplicative Schwarz algorithm, the tile algorithm, the CGK algorithm, the CSPD algorithm, and also the popular global ILU-family of preconditioners, on some nonsymmetric or indefinite elliptic model problems discretized by finite difference methods. The preconditioned problems are solved by the unrestarted GMRES method. A version of the accelerated multiplicative Schwarz method is a consistently good performer. 相似文献
58.
本文介绍了铁电体电畴结构的扫描电子显微镜成像技术。根据畴反差较弱的特点,着重讨论了样品的处理技术及成像参数的选择技巧。实验结果表明:为了避免畴反差被破坏,必须使用较低的入射电子束能量,较大的入射角和快速帧扫描速度。应用这一技术,成功地在OPTON公司生产的DSM950扫描电镜上观察到了锆钛酸铅二元系压电陶瓷材料90°电畴和180°电畴结构花纹,并且当使用高能电子束轰击未镀导电膜的样品时,能观察到电畴的消失过程。 相似文献
59.
Sug-Bong Choe Yoon-Chul Cho Hyuk-Jae Jang Sung-Chul Shin 《Journal of magnetism and magnetic materials》2002,240(1-3):308-310
Activation volumes of the wall-motion and nucleation processes in Co-based multilayer films were characterized from time-resolved domain evolution patterns. These activation volumes were both sensitive to the multilayer structure as well as the film preparation condition. The two activation volumes were generally unequal with each other and the inequality directly influenced on magnetization reversal behavior. 相似文献
60.
We use the lowest possible approximation order, piecewise linear, continuous velocities and piecewise constant pressures to compute solutions to Stokes equation and Darcy's equation, applying an edge stabilization term to avoid locking. We prove that the formulation satisfies the discrete inf-sup condition, we prove an optimal a priori error estimate for both problems. The formulation is then extended to the coupled case using a Nitsche-type weak formulation allowing for different meshes in the two subdomains. Finally, we present some numerical examples verifying the theoretical predictions and showing the flexibility of the coupled approach. 相似文献