Viscous Regularization of Breaking Faraday Waves

The effect of the viscosity of a liquid on the parameters of standing surface gravity waves in a vertically oscillating rectangular vessel has been experimentally studied. It has been shown for the first time that a 60-fold increase in the viscosity of a working medium as compared to water fundamentally changes the parameters of the second nonlinear wave mode: waves are regularized in the total absence of their breaking. The effect of viscosity on the resonance dependences and process of damping of waves has been studied. The numerical analysis of the dispersion relation for gravity waves has shown that the effects observed in the experiment are due to the presence of short-range perturbations in the cutoff region, where viscous dissipation becomes a dominant factor and short waves are suppressed.     

Computation of the Backscattering Power Density for Rainfall in Millimeter Waves Band

The size distribution and canting angle distribution for non-spherical rain drops are taken into account. Utilizing the Muller matrix, the backscattering power densities are computed at different rain rate and different polarization in millimeter waves band, according the rainfall condition in Xi'an, China. Finally the results obtained are discussed.     

Topological Dark Matter from the Theory of Composite Electroweak Symmetry Breaking

The lightest electroweak baryon as a topological object is investigated by using a general effective Lagrangian of composite electroweak symmetry breaking and the spin-independent electroweak baryon-nucleon scattering cross section is calculated. We explicitly show the masses of the electroweak baryons and the cross section as functions of the Peskin-Takeuchi S parameter and the ratio of the masses of axial-vector and vector composite bosons. We find that it is acceptable to regard the electroweak baryon as a dark matter candidate and the even number of technicolor is favored.     

Topological Dark Matter from the Theory of Composite Electroweak Symmetry Breaking

The lightest electroweak baryon as a topological object is investigated by using a general effective Lagrangian of composite electroweak symmetry breaking and the spin-independent electroweak baryon-nucleon scattering cross section is calculated. We explicitly show the masses of the electroweak baryons and the cross section as functions of the Peskin-Takeuchi S parameter and the ratio of the masses of axial-vector and vector composite bosons. We find that it is acceptable to regard the electroweak baryon as a dark matter candidate and the even number of technicolor is favored.     

K2_SPH方法及二维破碎波的模拟

通过对一些关键技术的改进,特别是自由表面的判断方法和改进的固壁边界条件,使K2_SPH方法能够模拟破碎波问题,完整实现波浪的爬升、翻转、破碎等过程.对大幅液舱晃荡问题的模拟表明,K2_SPH方法较传统SPH方法在波形和压力分布都有明显改进.     

Backscattering of laser light from colloidal silica

Light-scattering experiments gained prominence as potential applications of quantum optics, non-linear optics, and photon localization. The possibility of the realization of lasing action in random media has created much interest in the study of the coherent structure of the backscattered light from disordered media. Backscattering (BS) studies are carried out to analyze the possibilities of photon localization in colloidal silica. The scattering enhancement is best associated with the density of the scatterers. The width of the BS cone and, hence, the mean-free path is related to the concentration of the medium. The dependence of the photon wavelength on the possible characteristics of the scattering is presented.     

Influence of Breaking Waves and Wake Bubbles on Surface-Ship Wake Scattering at Low Grazing Angles

A surface-ship wake model is proposed for calculating the scattering of ship wake from a nonlinear sea surface at a high sea state. Ship waves are simulated based on the Kelvin wave model by the point-source method.A Creamer Ⅱ sea surface based on the Elfouhaily sea spectrum is generated, and breaking waves and foam layer effects are taken into account for the background sea scattering at slight, moderate and high wind speeds.Turbulent bubbles scattering from the ship, which is different from wind-driven bubble breaking, is taken into account with a different concentration distribution using a polynomial fitting function combined with measured data. The surface-ship wake scattering is presented for different wind speeds. Numerical simulations show that ship wake scattering results will be higher when wake bubbles are taken into account. The ship beam is a key parameter that influences the width of the turbulent wake, and results in different scattering characteristics on the scattering image. The wind-induced surface in the presence of breaking waves and whitecaps results in scattering enhancement. This will cause the ship wake signal to be submerged in the back-ground of sea noise, leading to false alarms.     

背散射和饱和效应对双向环形激光场的影响

理论上分析了双向环形气体激光中背散射和饱和效应对光场统计性质的影响，求出了强度相关函数的有效本征值。与实验测量值比较表明，具有背散射的全饱和激光模型与实验吻合得更好，而其它激光模型偏差较大     

Backscattering from different objects in turbulent media

Abstract

The connection between diffraction characteristics of the scatterer and distribution of average backscattered intensity of a spherical wave is considered. In experiments with an ‘infinite’ plane mirror it is shown that the distribution of average backscattered intensity coincides with the correlation function of the intensity fluctuation of a virtual point source located at the mirror and observed from the real source plane. Non-monotonic dependence (with a minimum at the Fresnel number of scattered mirror?1) between the enhancement factor and the size of reflected mirror is observed in experiments.     

Axisymmetry Breaking to Travelling Waves in the Cylinder with Partially Heated Sidewall

The transition from an axisymmetric stationary flow to three-dimensional time-dependent flows is carefully studied in a vertical cylinder partially heated from the side, with the aspect ratio A = 2 and Prandtl number Pτ=0.021. The flow develops from the steady toroidal pattern beyond the first instability threshold, breaks the axisymmetric state at a Rayleigh number near 2000, and transits to standing or travelling azimuthal waves. A new result is observed that a slightly unstable flow pattern of standing waves exists and will transit to stable travelling waves after a long time evolution. The onset of oscillations is associated with a supercritical Hopf bifurcation in a system with O（2） symmetry.     

Plane Waves Propagating in Gases Composed of Composite Particles

The quantum discrete kinetic equations are solved to study the propagation of plane waves in a system of composite particles with hard-sphere interactions and the filling factor (ν) being 1/2. We compare the dispersion relations thus obtained by the relevant Pauli-blocking parameter B which describes the different-statistics particles for the quantum analog of the discrete Boltzmann system when B is positive (Bose gases), zero (Boltzmann gases), and negative (Fermi Gases). We found, as the effective magnetic field being zero (ν = 1/2 using the composite fermion formulation), the electric field effect will induce anomalous dispersion relations.     

Backscattering of light from a dielectric layer on a reflecting substrate

Scattering of light from rough dielectric films is studied experimentally. It is shown that the interference pattern of the scattered field depends critically on the power spectrum of the roughness, especially on its long-scale component. When the height of roughness is small compared with the wavelength, the backscattering peak (if it exists) is due to the interference of the singly scattered fields; hence the properties of the backscattered peak are rather unusual. In particular, the width of the peak is determined by the thickness of the film and is independent of the parameters of disorder. The intensity of the peak increases with an increase of the rms height of the surface roughness and becomes independent of the rms when the roughness is of the order of the wavelength.     

Effects of Periodic Boundary Condition on Traffic Waves

In this paper, we use the speed-gradient model proposed by Jiang et al. [Transp. Res. B 36 （2002） 405] to study the effect of boundary condition on shock and rarefaction wave. Our numerical results show that this model can reproduce the evolution of the two traffic waves, which further proves that this model can be used to perfectly explore the consequences caused by various boundary conditions.     

混合模拟方法模拟电子在固体表面的背散射

将电子输运的直接模拟方法和压缩历史方法相结合,建立能量为50 eV~1 GeV范围的电子在介质中输运的混合模拟蒙特卡罗方法.通过调整散射角参数和损失能量参数控制单次碰撞发生的次数,输运过程中单次碰撞采用直接模拟,在两次直接碰撞之间使用压缩历史方法模拟发生的多次小碰撞过程.利用该方法模拟电子在固体表面的背散射过程,探讨不同计算参数对计算效率和结果的影响,计算不同能量电子在固体表面的背散射系数和出射电子能量分布,计算结果与实验数据符合较好.     

Diffuse Backscattering Mueller Matrices Patterns from Turbid Media

We present experimental measurements and theory of the diffusely backscattered Mueller matrix patterns that arise from illuminating a turbid medium with a polarized laser beam. Our technique employs polarized light from a He-Ne laser (λ=632.8nm) focused onto the surface of the scattering medium. A surface area of approximately 2×2 cm² centred on the light input point is imaged through polarization analysis optics onto a CCD camera. The Mueller matrix is reconstructed by 49 intensity measurements with various orientations of polarizer and analyser. The measured Mueller matrix of polystyrene spheres is compared with the theory result of incoherent scattering of light by spheres. It shows that the azimuthal patterns of the Mueller matrix are determined by the symmetry of the turbid media and the shape of scattering particles. The result is further proved by experiments with polystyrene spheres of different concentrations in de-ionized water.     

Dynamical Effects of Gravitational Shock Waves

Gravitational shock waves are defined in the framework of space-times with distribution-valued curvature tensors. Then different kinds of motion in the presence of a gravitational shock wave are investigated. In an earlier paper the same investigation was carried out for an ordinary gravitational discontinuity wave. Discontinuity effects due to gravitational shock waves are compared to those due to ordinary waves.