层状各向异性固体媒质的声反射和声透射

本文导出了联系任意对称的各向异性固体层上下界面力学量（位移和应力）的传递矩阵,从而提出了层状固体媒质声反射和声透射的一般模型,作为例子,本文数值计算了金属铝中双层正交对称固体（其间界面呈刚性联接或滑移联接）对声波的反射和透射系数。     

声脉冲在多孔性媒质界面上的反射

本文在理论上分析球面脉冲声波在空气和理想的多孔性媒质界面上的反射问题。在声源为脉冲点源的情形下,给出反射脉冲声波的一般表示式。对以下三种情况做了较详细的分析:（1）声源和接收点在垂直于界面的同一直线上,半无限厚多孔性媒质;（2）声源和接收点在垂直于界面的同一直线上,多孔性媒质层;（3）掠射,半无限厚多孔性媒质。脉冲声波在媒质层上的反射是以声脉冲在媒质层内多次反射和透射来处理的。文中还给出实验结果和理论计算的比较。     

柱状分层固体媒质的声散射

本文评述了各向同性和横向各向同性柱状分层固体声散射理论和实验研究进展 ,介绍了描述圆柱状界面薄层特性的弹簧模型 ,也讨论了该领域中有待进一步研究的一些问题。     

柱状分层固体媒质的声散射

本文评述了各向同性和横向各向同性柱状分层固体声散射理论和实验研究进展介绍了描述圆柱状界面薄层特性的弹簧模型，也讨论了该领域中有待进一步研究的一些问题。     

固体滑移界面的超声评价

为评价固体滑移界面的特性,根据QSM界面模型和粘滞流体的本构方程导出了滑移界面的界面劲度系数及垂直入射到固体滑移界面的超声纵波和SH波的反射系数公式,其中纵波的反射系数与滑移界面层的绝热体积弹性模量、粘滞系数和入射声波的频率有关,而SH波的反射系数与界面层的绝热体积弹性模量和入射波的频率无关。因此,可以用SH波直接评价界面的不同粘滞状态,且不受检测频率的限制。要评价界面的绝热体积弹性模量,则必须增加纵波检测。利用蜂蜜和水模拟不同滑移界面层的声波反射实验验证了上述理论结果。     

层状多孔介质中声反射和透射

本文根据流体饱和多孔介质中声传播的Biot理论和多孔介质界面上的六个边界条件研究了平面声波斜入射于多层水平板状多孔介质时的反射和透射。数值计算了快纵波为入射波时声波频率、入射角等量的变化对能量的反射系数、透射系数的影响。数值计算结果表明,当声波波长与中间介质厚度呈一定比例时,反射系数、透射系数取得极值,入射角、多孔介质的性质对反射系数、透射系数的影响很大。     

固体间界面的物理模型和界面对声波的反射

简要描述了模拟两固体间界面特性的弹簧模型，该模型最早是根据静力学方法提出的，后来用固体间界面薄层的声波反射方法加以改进，从界面弹簧模型可以方便地得到界面外近似边界条件，其中包含界面“弹簧”振子的劲度常数和质量，文章还给出了两相间固体中界面声反射系数的表达式，介绍了测量界面劲度常数的超声反射谱方法。最后讨论了仍关声波与界面相互作用研究领域中最近的一些研究进展。     

光纤孤子在媒质突变界面的反射与透射

本文通过波包慢变假定,准单色近似和径向模式平均法,建立了光纤孤子反射和透射问题的支配方程和边界条件,借助光束传播法,数值模拟孤子在光纤单界面上的反射和透射过程,文中还给出数值实例。 关键词：     

各向同性固体界面非线性反射的实验研究

实验测量了SV波入射到玻璃-空气,玻璃-铁、铜、铝界面上时反射的二次谐波SV波,研究了非线性反射效率与入射角以及材料的线性和非线性特性的关系,发现在某些入射角下,反射的二次谐波会有较大的振幅,报道了实验结果并和理论进行了比较。     

声波垂直入射在两种媒质分界面处的反射和透射

我们知道声波在两个均匀各向同性无限媒质的分界面处垂直入射时,一般有反射波(第一媒质中)和透射波(第二煤质中),而具体情况究竟如何?特别是在分界面处究竟又是怎样呢?本文将作如下分析     

Direct experimental evidence of slip in hexadecane: solid interfaces

The boundary condition for the flow velocity of a Newtonian fluid near a solid wall has been probed experimentally with a novel setup using total internal reflection-fluorescence recovery after photobleaching leading to a resolution from the wall of the order of 80 nm. For hexadecane flowing on a hydrocarbon/lyophobic smooth surface, we give what we think to be the first direct experimental evidence of noticeable slip at the wall. We show that the surface roughness and the strength of the fluid-surface interactions both act on wall slip, in antagonist ways.     

On the role of weak interfaces in blocking slip in nanoscale layered composites

Layered composites of Cu/Nb achieve very high strength levels when the individual layer thicknesses are 1–10?nm, attributable to the interfaces acting as barriers to slip. Atomistic models of Cu/Nb bilayers were used to explore the origins of this resistance. The models clearly show that dislocations placed near an interface experience an attraction toward the interface, regardless of the sign of the Burgers vector or the material in which it is placed. This attraction is caused by shear of the interface induced by the stress field of the dislocation. Furthermore, the dislocation, upon reaching the interface, is absorbed by it in the sense that the core spreads within the interface. We develop a model, using a fractional dislocation approach, which provides an estimate of the strength of the attraction as a function of distance from the interface and also the dependence of the interaction on the type of dislocation. A screw dislocation is much more effective in shearing the interface, and the resulting attractive forces on screws are larger than for edge dislocations.     

On reflection from interfaces with some spatially dispersive metamaterials

Plane-wave reflection from interfaces with single and double wire media is considered. Such media exhibit strong spatial dispersion even at very low frequencies which causes appearance of additional waves. The problem of additional boundary conditions (ABC) in application to wire media is discussed and an ABC-free approach, known in solid state physics, is used. Expressions for the fields and Poynting vectors of refracted waves are derived. The directions and values of the power density flow of refracted waves are found and conservation of the power flow through the interface is checked.     

Zero reflection from layered anisotropic metamaterial structures

Mathematical formulation for analysis of electromagnetic wave scattering from multilayer anisotropic homogeneous metamaterial structures with general tensors is presented. The result is reflection and transmission matrices formulas. Then, closed form formulas are extracted for structures with diagonal tensors. We try to find structures with exact zero reflection for general incident waves. New cases with zero and low reflection are introduced.     

Isothermal slip of a Fermi gas with specular-diffuse reflection from the boundary

A solution of the Kramers problem on isothermal slip of a quantum Fermi gas along a plane solid surface has been obtained. The reflection of molecules from the wall was supposed to be specular-diffuse. A model kinetic equation with the τ-model collision integral and with the collision frequency proportional to the molecular velocity was used. The slip velocity has been analyzed in relation to a parameter representing the ratio of the chemical potential to the product of Boltzmann’s constant by the absolute temperature.     

Non-specular reflection from solid plates and half-spaces

Recent theoretical developments for the reflection effects seen for an ultrasonic bounded beam reflected from a solid surface are presented and a discussion of the implications of these developments is related to the case of reflection from infinite half-spaces and solid plates.