The effect of a surface impedance load on the behavior of quasi-Rayleigh waves near a cylindrical cavity

The effect of a surface impedance load on the properties of axisymmetric quasi-Rayleigh waves propagating along the boundaries of a cylindrical cavity is investigated. By solving the problem by means of the impedance method, a dispersion equation for these waves is obtained. It is shown that the equation can be represented as the condition that the determinant of the sum of impedance matrices of the load and the medium is zero. Analysis of this equation allows one to investigate the effect of the surface load on the behavior of quasi-Rayleigh waves and on their critical frequencies. The conditions that should be met by the impedance load for quasi-Rayleigh waves to be absent near the cavity or for one or two such waves to exist are determined. The choice of the load is specified for the propagating quasi-Rayleigh wave to possess preset dispersion properties. The conclusions drawn on the basis of this study are illustrated by several examples of load models that can be implemented in practice.     

弱界面固体附层媒质中的类Rayleigh波

当半无限大固体媒质上有一层固体附加层时表面波是频散的。由界面的“准弹簧”模型,本文导出了有各向同性固体附加层时半无限大各向同性均匀媒质中弱界面情况下的类Rayleigh波的特征方程。文中给出了典型复合结构具有刚性联接界面、滑移联接界面和弱界面时类 Rayleigh波的色散曲线,分析了界面刚度系数对类 Rayleigh波传播速度的影响。数值计算的结果表明选择合适的参数可以由低频超声类Rayleigh进行涂层结构界面特性的无损评价。     

The effect of surface stress on the propagation of Lamb waves

This work investigates the possibility of the propagation of Lamb waves in thin solid layers with external traction free surfaces, in the presence of surface elasticity, inertia and residual stress. It is demonstrated that such waves do exist and that their characteristics can be quite different from their classical counterparts. The governing equations with non-classical boundary conditions involving the bulk and surface stress are solved exactly in the frequency-wavenumber domain. This solution is utilized to compute the Lamb wave modes for different layer thicknesses. An efficient strategy to capture all the modes of Lamb waves within a given frequency window is outlined. It is shown that the effect of surface elasticity and inertia becomes significant with increasing frequency and decreasing layer thickness, where the number of modes participating within a given frequency window is more than that permitted by the classical theory. Further, it is observed that the nature of the Lamb wave modes (in terms of negative dispersion) in the presence of surface stress is similar to what predicted by the nonlocal theory and microstructure based continuum theory.     

The effect of surface waves on the variability of the interference invariant

The effect of sea surface waves on the variability of the interference invariant and on the error in its indication is investigated. To model fully developed waves on the sea surface, the Pierson-Neumann spectrum is used. The acoustic track is chosen to be oriented along the wind direction, which corresponds to the maximal manifestation of normal wave interaction. The effect is considered in both winter and summer conditions in a broad frequency band and in a wide interval of distances. Statistical estimates are obtained for the interference invariant and its measurement error.     

The effect of surface alloying on the surface properties of activated CdSe films

Changes in surface potential, surface conductivity, mobility in a field, and Hall electron mobility in activated CdSe films with a surface alloy of indium are studied. The strong enrichment of charge carriers on the surface is explained by the presence of a positive charge on the surface, neutralizing the negative charge of oxygen atoms, with the latter being neutralized as a result of interaction of metal atoms with oxygen adsorbed on the surface. The possibility of determining the parameters of volume traps and the absolute surface potential of the film by experiments with surface alloying is shown.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 86–90, September, 1972.     

Fdtd simulation for the EMI properties of impedance surface enclosures

An enclosure with impedance interior surfaces is studied using the FDTD method. The FDTD simulation shows a wonderful depression of the resonance-related EMI signals in the impedance surface enclosure.This work was supported by the National Natural Science Fund of China, and by the He Yingdong Education Fund.     

The effect of parametrically excited spin waves on the dispersion and damping of magnetostatic surface waves in ferrite films

This paper describes an experimental study of variations of the dispersion and damping of magnetostatic surface waves in ferrite films, caused by three-and four-magnon interactions with parametric spin waves excited by an auxiliary surface magnetostatic pump wave with frequency f _p. The variations in the dispersion and damping were identified, respectively, with variations Δk″ in the real part and Δk′ in the imaginary part of the wave number of the surface magnetostatic wave. The Δk″ and Δk′ values were determined from the ratio of the changes of the phase increment Δφ and the amplitude increment ΔA of the surface magnetostatic wave to the length L of the nonequilibrium section of the film, where the parametric spin waves exist. It is found that, when three-magnon decay processes are allowed for the pump wave and the surface magnetostatic probe wave, the probe wave can substantially alter the distribution of the parametric spin waves in the film. Zh. éksp. Teor. Fiz. 115, 318–332 (January 1999)     

Fringe waves on an impedance cylinder

Surface diffraction of the plane waves from an impedance cylinder was investigated by the method of physical theory of diffraction (PTD). Physical optics (PO) method was used to gain the uniform scattered fields which are produced by the induced surface currents. Nonuniform currents and scattered fields were obtained by the method of PTD with the assistance of the exact solutions.     

Basic properties of nonlinear surface charge waves at a plasma boundary

The nonlinear properties of surface charges are here analyzed under ideal conditions. We thus deduce a new single equation from the wellknown equations which govern the cold electron plasma motion. Simple formulas that describe the propagation of surface charge perturbations along the plasma boundary are also found.     

The scattering of waves by a periodic surface

The paper derives a general formula for the scattering of electromagnetic (or sound) waves from a periodic, perfectly conducting (or perfectly rigid) surface. No restrictions are imposed on the angle of incidence, the size of the surface or the degree of roughness. Except for the basic Kirchhoff approximation, the method is exact. The results confirm, generalise or correct special cases obtained by more complicated methods.

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