Radiation of surface Stoneley waves by distributed force sources acting at the solid earth-atmosphere interface

Using the Fourier transform, we find an integral solution describing the excitation of seismoacoustic waves in the solid Earth and the atmosphere by time-dependent forces arbitrarily distributed over the interface between the media. The solid Earth and the atmosphere are modeled by an isotropic solid half-space and a homogeneous gaseous half-space, respectively. Depending on the types of the excited surface and bulk waves, classification of the corresponding force distributions is performed. In the case of harmonic sources, an expression for the period-averaged radiated power of the Stoneley wave is obtained. For arbitrary time dependence of the forces, we find an expression describing the the Stoneley-wave energy radiated during the entire time of the source operation. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 7, pp. 624–637, July 2007.     

Excitation of seismoacoustic waves by a harmonic force source acting at the boundary of a liquid layer and an elastic halfspace

A problem on the excitation of seismoacoustic waves in a system of a homogeneous isotropic elastic halfspace covered with a liquid layer is solved in the case of action of a source of point harmonic force on the surface of an elastic medium. Integral expressions are obtained for the radiation powers averaged over a wave period for longitudinal and transverse waves in a solid. Mode excitation is analyzed in detail. Expressions describing parts of the mode powers radiated into a liquid layer and an elastic medium are obtained. Numerical analysis of radiation powers is conducted for spherical longitudinal and transverse waves as well as for the radiation powers of seismoacoustic modes in a solid halfspace and a liquid layer. It is determined that in the conditions characteristic of bottom rocks in the case, where the basin depth is several times and more larger than the sound’s wavelength, about 2/3 of the total power is radiated into a liquid.     

EPR centres at a gas-solid interface induced by a microwave gas plasma

Details are reported for EPR centres induced in various samples after operating a cyclotron resonance type gas discharge inside a vacuum envelope within a microwave cavity. In the case of vacuum crushed GaAs, centres identified as O^?₃ were induced on the surfaces at 100 K. The powder parameters were g₁ = 2.016, g₂ = 2.007 and g₃ = 2.000. For sapphire rods at 80 K, a signal was found similar to that previously observed on gamma-irradiated, oxygen exposed sapphire. The evidence enables identification as O^?₂ on Al in the surfaces, g∥ = 2.040, g⊥ = 2.001. For quartz at 100 K, the major EPR centres were similar to those from gamma irradiated quartz and appeared to be of bulk nature, unaffected by gas pressure and ascribed to plasma activated impurity defect centres.     

Acoustic radiation force acting on elastic and viscoelastic spherical shells placed in a plane standing wave field

The theory of the acoustic radiation force acting on elastic spherical shells suspended in a plane standing wave field is developed in relation to their thickness and the content of their hollow regions. The theory is modified to include the effect of a hysteresis type of absorption of compressional and shear waves in the material. The fluid-loading effect on the acoustic radiation force function Y(st) is analyzed as well. Results of numerical calculations are presented for a number of elastic and viscoelastic materials, with the hollow region filled with water or air. These results show how the damping due to absorption, the change of the interior fluid inside the shells' hollow regions, and the exterior fluid surrounding their structures, affect the acoustic radiation force.     

Measuring the radiation force of megahertz ultrasound acting on a solid spherical scatterer

The paper considers the problem of precise measurement of the acoustic radiation force of an ultrasonic beam on targets in the form of solid spherical scatterers. Using known analytic relations, a numerical model is developed to perform calculations for different sizes of spherical scatterers and arbitrary frequencies of the incident acoustic wave. A novel method is proposed for measuring the radiation force, which is based on the principle of acoustic echolocation. The radiation force is measured experimentally in a wide range of incident wave intensities using two chosen methods differing in the way the location of the target is controlled.     

Theoretical calculation of the acoustic radiation force acting on elastic and viscoelastic cylinders placed in a plane standing or quasistanding wave field

In this work, a new expression of the acoustic radiation force function Yst for solid cylindrical targets, suspended in inviscid fluids in a plane standing wave field, is presented. The case of a plane quasistanding wave field is also considered. Numerical calculations of the radiation force function Yst are performed in a wide range of frequencies for elastic and viscoelastic cylinders and compared to those of rigid cylinders. The fluid-loading effect on the radiation force function curves is also analysed. The results show several features quite different from the rigid cylinder solution.     

固体表面法向力条源的辐射阻抗及各种波型的能量分布

本文主要研究了固体表面法向力条源在各向同性固体中的辐射阻抗和辐射能量。在研究辐射能量时,用辐射导方法求出辐射源的辐射总能量,用远场的声场求出法向力源所辐射的各种波型(表面波、切变波和压缩波)的能量,结果表明:(1)条源的宽度变宽时,压缩波所占的能量比例增加;(2)当条宽在某一个小的范围内取值时,几种波型所占的能量比例几乎相等;(3)对于不同的条源宽度,用辐射导方法求出的总能量等于用声场方法求出的三种波型的能量之和。这不但证明了固体表面法向力条源激发弹性波时能量的守恒,而且也进一步映证了用稳相法得到的远场声场的正确性。     

The radiation impedance and the energy partition among wave fields generated by a normal force strip radiator on isotropic solid surface

I.IntroductionTheacousticbeams'f0cusingandscanninggeneratedbytransducerarraysonso1idsurfacep1ayaveryimportantroleinacousticimagingandultrasonoc1ectronicdevices.InourpreviouSworkt'-'],weinvestigatcdtheproperties0ftheacousticbeams'focusingandscanninga1ongthesymmetricalaxis,acousticfic1ddistributioninthewho1espaceandnearthefocus.Andwealsogaverigoroustheoretica1ana1ysis,numcrica1simu1ationandexperimenta1obscrvation.Butra-diationimpedanceandenergyofthesurfaceradiatorshavenotbeendiscussedyetbynow.…     

Analytical representation of the surface wave generated by an antenna at the interface between two homogeneous media

Theoretical approach to the solution of georadiolocation (inverse) problem of reconstructing the antenna current and the permittivity of the underlying surface, based on the measurements of the field propagating along the Earth℉s surface, is proposed. An expression for the tangential component of the electric field of the surface wave from a transmitting antenna lying in the plane of discontinuity of two homogeneous media is expressed in terms of the Laplace function Ŵ(q, ζ) of two complex arguments for any discontinuity parameters. The function Ŵ(q, ζ) is presented as series, which make it possible to calculate rapidly the values of Ŵ(q, ζ) and investigate its analytic properties. The inverse Laplace transform is performed by integrating the function Ŵ(q, ζ) over closed contours. The corresponding integrals are proper in this case, due to which the calculation time greatly decreases in comparison with the Fourier transform. When the permittivity dispersion can be neglected, the tangential component of the surface wave is algebraically expressed in terms of the function Ŵ(q, ζ). This circumstance allows one to decrease the time for calculating the surface wave at a specified point to several milliseconds and determine both the current through the transmitting antenna and the permittivity of the underlying surface for a few seconds.     

Excitation of surface wave beams at the interface between linear and nonlinear media

The spatial evolution of quasi-optical electromagnetic-wave beams propagating in the vicinity of an interface between linear and nonlinear media is studied. It is demonstrated that three-dimensional nonlinear surface beams can efficiently be excited by Gaussian beams of optimal shape, incident onto the nonlinear interface at angles exceeding the total internal reflection angle, and that giant nonlinear Goos-Hänchen effect can result from this process.     

Ponderomotive nongradient force acting on a relativistic particle crossing an inhomogeneous electromagnetic wave

The ponderomotive force acting on a relativistic charged particle crossing an inhomogeneous electromagnetic wave is investigated numerically and analytically. The initial velocity of the particle is perpendicular to the electric field vector of the wave and to the direction of its propagation. The wave has zero gradient in the direction of propagation and is inhomogeneous in both transverse directions. It is shown that the ponderomotive force acting on the particle is parallel to the wave vector. The magnitude of the force is determined not only by the extent of wave inhomogeneity in the direction of the translational motion of particle, but also by its inhomogeneity in the transverse direction. It is found that the trajectory of a particle is determined by the action of ponderomotive forces as well as by its drift in a nonuniform field.     

Frequency dependence of the acoustic radiation force acting on absorbing cylindrical shells

The frequency dependence of the radiation force function Y(p) for absorbing cylindrical shells suspended in an inviscid fluid in a plane incident sound field is analysed, in relation to the thickness and the content of their interior hollow region. The theory is modified to include the effect of hysteresis type absorption of compressional and shear waves in the material. The results of numerical calculations are presented for two viscoelastic (lucite and phenolic polymer) materials, with the hollow region filled with water or air indicating how damping and change of the interior fluid inside the shell's hollow region affect the acoustic radiation force. The acoustic radiation force acting on cylindrical lucite shells immersed in a high density fluid (in this case mercury) and filled with water in their hollow region, is also studied.     

Generation of the third harmonic of a surface wave in a semiconductor-metal delay structure

Khar'kov State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiiofizika, Vol. 34, No. 6, pp. 724–728, June, 1991.     

Generation of coherent radiation at 61.6 nm by fifth harmonic conversion of radiation from a XeCl laser

Fifth harmonic conversion of radiation from a XeCl laser in Ar and Kr, generating radiation at 61.6 nm, is reported. Fifth power law variation of the generated energy with the pump energy is observed. The effects of continuum absorption are observed in the width of the phase matching peak in Ar.     

Adaptative lensing driven by the radiation pressure of a continuous-wave laser wave upon a near-critical liquid liquid interface

The bending of a liquid interface by the radiation pressure of a cw laser wave is generally weak. To strongly enhance the coupling, we investigate lensing in a near-critical phase-separated liquid mixture. By continuously tuning the softness of the meniscus by varying the temperature, we observed huge stationary interface deformations at low beam power that led to an important variation of the resultant soft lensing. We also illustrate the crucial role played by temperature in this process to demonstrate its potential use in lens adaptation.     

P波入射下固固界面的二阶谐波场特性

应用二阶势理论研究了P波入射到固-固界面情况下的二阶谐波场。运用变动参数法求解二阶非齐次势函数方程的边值问题,数值计算了二阶谐波位移与入射角的关系,结果表明当入射角到达某个角度时,二阶谐波场的位移会急剧增大。同时,当入射角度为θ_w时,特解位移趋近无限大的有关现象依然出现,关于边界面的影响也做了讨论。     

Theoretical and numerical calculation of the acoustic radiation force acting on a circular rigid cylinder near a flat wall in a standing wave excitation in an ideal fluid

The acoustic radiation force acting on a cylinder near a flat wall in a standing wave is calculated by analytical methods and numerical simulations. An exact theoretical solution is presented as well as an approximate solution. The approximate solution is in algebraic form and quite easy to compute. The numerical simulation is based on FVM (Finite Volume Method) on unstructured triangular meshes. The exact theoretical, approximate and numerical solutions are compared with each other and good agreements are obtained. Furthermore, the effects of the flat wall are investigated in detail by the three methods.