Study of vortex breakdown in a stratified fluid

An analysis shows that nonsmooth solutions have to be considered. Weak solutions to the Euler equations describing an incompressible stratified fluid under gravity are defined and studied. The study makes use of a wave energy functional proposed for the nonlinear equations. It is shown that the Euler equations are insufficient for stating a well-posed generalized problem. Additional conditions based on physical considerations are proposed. One condition is energy conservation, and the other is a constraint imposed on the density, which is required for stability. A numerical method is developed that is used to analyze how wave breakdown in a stratified fluid depends on stratification. The numerical results are in satisfactory agreement with experiments.     

NUMERICAL MODELING OF OPTICALLY CONTROLLED DIELECTRIC REASONATORS

To analyze the optically controlled dielectric resonators accurately, an efficient numerical modelling technique is proposed in this paper. By using alternating-direction implicit finite-difference time-domain method and conformal technique, the resonant frequency of a dielectric resonator is calculated. In addition, an optical generation of plasma is used as a possible means of controlling the resonate frequency, and the effect that solid state plasmas have on the resonator’s frequency is described. The numerical results agree very well with measurements in estimation of the optically induced resonator’s frequency-shift.     

Stability of a matrix finite-difference scheme for solving the problem of elastic vibrations

The stability of a matrix finite-difference scheme is analyzed. The scheme is based on central differences and is designed for the differential equation governing the vibrations of an elastic system.     

FDTD Simulation of Electromagnetic Propagation in Magnetized Plasma Using Z Transforms

The electromagnetic propagation through a magnetized plasma slab is studied using the finite-difference time-domain method by means of the z transform The reflection and transmission coefficients of the magnetoactive plasma for the right-hand circularly polarized wave are presented. The comparison of the results of the Z transform and recursive convolution algorithms with analytic values indicates that the Z transform algorithm is more accurate than the recursive convolution algorithm. The Z transform algorithm overcomes the drawback that the recursive algorithm cannot predict the transmission coefficient of the magnetized plasma slab for the right-hand circularly polarized wave in the stop band.     

Application of higher-order flux-limited methods in compositional simulation

A higher-order flux-limited finite-difference scheme has been implemented into a compositional simulator to discretize the convection terms of the component conservation equations and the relative permeability terms of the phase fluxes. Harten's total variation diminishing criteria are imposed directly to the finite-difference equations and the bounds of the flux limiters which are suitable for larger Courant numbers and nonuniform grid systems are obtained. A time-correction technique is applied to increase the time accuracy and improve the stability condition.The scheme has been tested for miscible and immiscible flow problems in one and two dimensions, and the results were compared with those using a third-order method without flux limiting and some available analytical solutions.     

Stress–Strain Analysis of Smooth and Ribbed Shells under Local Loads

Static problems for smooth and discretely reinforced cylindrical shells under local loads and complex boundary conditions are solved. The stress–strain states of the casing and ribs are determined by the technical theory of shells and the Kirchhoff–Clebsch theory of rods, respectively. The reinforcing elements are arranged eccentrically. They are of equal or different stiffness, which is also variable along the length. The problems are solved using the finite-difference method. Theoretical results obtained from a refined mesh are compared with experimental data     

金纳米棒复合体的消光特性

金属纳米颗粒局域表面等离激元共振时能够产生消光和近场增强效应已经成为国内外研究的热点. 应用时域有限差分法对L形纳米棒与普通纳米棒构成的金纳米棒复合体的消光光谱及其近场增强和电流矢量密度分布进行了研究. 计算结果表明, 普通纳米棒和L形纳米棒二聚体的光谱响应与纳米棒间的间距有关, 而金纳米棒复合体的消光光谱可通过调整L形纳米棒与普通纳米棒间的间距、L形纳米棒的臂长度以及普通纳米棒的长度进行调谐. 此外金纳米棒复合体可以分解成L形纳米棒二聚体和普通纳米棒二聚体两个部分, 通过分别改变L形纳米棒的臂长和普通纳米棒的长度, 对比L形纳米棒二聚体和普通纳米棒二聚体间的共振峰位置变化, 可以更直观地了解金纳米棒复合体消光光谱线型的变化. 这些结果可用于指导金纳米棒复合体纳米光子器件的设计, 以满足其在表面增强拉曼散射和生物传感等方面应用.     

Docking small ligands in flexible binding sites

A novel procedure for docking ligands in a flexible binding site is presented. It relies on conjugate gradient minimization, during which nonbonded interactions are gradually switched on. Short Monte Carlo minimization runs are performed on the most promising candidates. Solvation is implicitly taken into account in the evaluation of structures with a continuum model. It is shown that the method is very accurate and can model induced fit in the ligand and the binding site. The docking procedure has been successfully applied to three systems. The first two are the binding of progesterone and 5β-androstane-3,17-dione to the antigen binding fragment of a steroid binding antibody. A comparison of the crystal structures of the free and the two complexed forms reveals that any attempt to model binding must take protein rearrangements into account. Furthermore, the two ligands bind in two different orientations, posing an additional challenge. The third test case is the docking of N^α-(2-naphthyl-sulfonyl-glycyl)-D -para-amidino-phenyl-alanyl-piperidine (NAPAP) to human α-thrombin. In contrast to steroids, NAPAP is a very flexible ligand, and no information of its conformation in the binding site is used. All docking calculations are started from X-ray conformations of proteins with the uncomplexed binding site. For all three systems the best minima in terms of free energy have a root mean square deviation from the X-ray structure smaller than 1.5 Å for the ligand atoms. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 21–37, 1998     

微波脉冲窄缝耦合的数值并行计算

采用时域有限差分方法（FDTD）对微波脉冲与窄缝耦合过程进行了数值模拟计算,分析了数值模拟计算过程中的并行性,给出了相应的并行算法,算法中采用消息合并和计算与通信重叠技术来减少通信阳,分析了算法的通信复杂性,给出了在Alpha工作站上的测试结果。     

Numerical modeling of the transmission dynamics of drug-sensitive and drug-resistant HSV-2

IntroductionThe prevalence of genital herpes infection (caused by HSV-2) in the United States is approximately 22% II]. In developing nations, the infection rate is between 40%A10% I2' 3]. Althoughthere is currently no cure for genital herpes, drug treatment with agents such as acyclovir isknown to significantly relieve symptoms and reduce viral shedding['1. Most cases of HSV-2infections remain untreated in developing nations, and even in the USA only 5%--10% aretreated[4]. Whilst incre…