Radio-wave scattering by two-layer medium with irregular boundaries

Radio-wave scattering by a thin layer with irregular boundaries is examined within the framework of a Kirchhoff approximation. Analytic expressions for the coherent and incoherent components of reflected power are derived and studied for an arbitrary correlation between the irregularities of the boundaries. Conditions under which fading is possible are determined.Scientific-Research Institute of Physics, Rostov University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 35, Nos. 3, 4, pp. 275–284, March–April, 1992.     

An application of the quasipotential method to pion nucleon scattering

The quasipotential method developed in Dubna Laboratory was applied to pion-nucleon scattering processes up to the energies 500 MeV, for obtaining the resonance behaviour of te P₃₃-phase shift. Although numerical calculations have not yet been completed, the existence of a resonance seems very probable.

     

Reflectance of two-layer composite porous media with linear-anisotropic scattering

We report an analysis of the hemispherical reflectance of composite slabs made up of two porous layers. To allow realistic modeling of most porous materials, anisotropic scattering is considered. The reflectance is obtained by using the method of spherical harmonics to solve the equation of transfer. Results from the P-11 approximation are presented for a wide range of governing parameters, including the single-scattering albedos and scattering phase-function coefficients for both porous layers. The effects of anisotropic scattering are illustrated.     

Multi-hybrid method for investigation of EM scattering from inhomogeneous object above a dielectric rough surface

An iterative strategy combining Kirchhoff approximation(KA) with the hybrid finite element-boundary integral(FE-BI) method is presented in this paper to study the interactions between the inhomogeneous object and the underlying rough surface.KA is applied to study scattering from underlying rough surfaces,whereas FE-BI deals with scattering from the above target.Both two methods use updated excitation sources.Huygens equivalence principle and an iterative strategy are employed to consider the multi-scattering effects.This hybrid FE-BI-KA scheme is an improved and generalized version of previous hybrid Kirchhoff approximation-method of moments(KA-MoM).This newly presented hybrid method has the following advantages:(1) the feasibility of modeling multi-scale scattering problems(large scale underlying surface and small scale target);(2) low memory requirement as in hybrid KA-MoM;(3) the ability to deal with scattering from inhomogeneous(including coated or layered) scatterers above rough surfaces.The numerical results are given to evaluate the accuracy of the multi-hybrid technique;the computing time and memory requirements consumed in specific numerical simulation of FE-BI-KA are compared with those of MoM.The convergence performance is analyzed by studying the iteration number variation caused by related parameters.Then bistatic scattering from inhomogeneous object of different configurations above dielectric Gaussian rough surface is calculated and the influences of dielectric compositions and surface roughness on the scattering pattern are discussed.     

Application of a multiregion model to the EM scattering from a rough surface with or without a target above it

An efficient multiregion model is introduced to calculate the electromagnetic scattering from a perfectly electrical conducting(PEC) rough surface with or without a PEC target above it.In the multiregion model,the rough surface is split into multiple regions depending on their position along the rough surface.Two intermediate regions are chosen as the dominant region.If a target is located above the rough surface,the target will also be included in the dominant region.The method of moments(MOM) is only adopted on the dominant region to ensure validity.Hence,the new model can greatly reduce the number of unknowns associated with full MOM analysis.The induced electric currents on the other regions are obtained by approximately considering the mutual coupling between different regions along the rough surface.Compared with the published hybrid method,this new model is not only suitable for EM scattering from a target above a rough surface but also applicable for just rough surfaces.Several numerical simulations are presented to show the validity and efficiency of the multiregion model.     

High-resolution study of quasi-elastic electron scattering from a two-layer system

In large-angle elastic scattering events of keV electrons a significant amount of momentum is transferred from the electron to a nucleus in the target. As a consequence kinetic energy is transferred from the energetic electron to the nucleus, and hence these processes can be referred to as ‘quasi-elastic’. How much energy is transferred depends on the mass of the nucleus. In this paper, we present measurements from a two-layer system (a germanium layer and a carbon layer), and at high energies the quasi-elastic peaks of Ge and C are clearly resolved. It is demonstrated that the sample geometry has a huge effect on the observed relative intensities. It is shown that the intensities are influenced by the elastic scattering cross-section of the atoms in the film, film composition and selective attenuation, due to varying amount of inelastic scattering for layers of the film. However truly quantitative agreement is not obtained.     

Using the perturbation method to compute the electron flux behind a two-layer barrier

The perturbation method is used to compute the electron flux behind a flat two-layer absorber one of whose layers is thin. Analytical expressions relating the fluxes behind two- and one-layer barriers are derived. The theoretical results are compared with experimental data.Translated from Izvestiya VUZ. Fizika, Vol. 11, No. 8, pp. 49–53, August, 1968.     

激光等离子体通道天线的电磁散射特性分析

激光等离子体通道天线被等效为电子在横向旋转、轴向漂移的均匀冷磁化等离子体束,且该等离子体束的横截面为沿轴向不改变的圆形。在考虑离心力、科里奥利力等惯性力的影响下,结合麦克斯韦方程和本构关系,得出了激光等离子体通道天线的散射场。为了简化,计算了一特例,发现了一些有趣的现象。     

Strong scattering of radio waves by a two-layer medium with rough boundaries and inhomogeneous permittivity of the layer

An analytical expression for the two-frequency correlation function of reflected radiation is derived in the framework of the Kirchhoff approximation, assuming that the mean square roughness heights _1,2 of the upper (₁) and lower (₂) boundaries are large compared to the wavelength and taking account of large-scale permittivity fluctuations in the layer. The condition under which p cannot be small when _i ^{2 2} is specified. In particular, it is shown that if the scattering is only at the upper boundary of the layer (when ₁ 0, ₂ = = 0), then this condition is , where m, n=0, 1,.... The potential of the layered medium sounding methods based on the relations obtained is estimated.Institute of Physics, State University, Rostov-on-Don. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 7, pp. 619–630, July, 1995.     

Sound scattering by a resistive and axially symmetric object in a two-layer ocean

An acoustically resistive and axially symmetric object is placed in a two-layer ocean very far from a point source of acoustic waves. The object is either floating in the water layer or buried in the sediment layer. Both layers are homogenous. The size of the object is small when compared to the depth of the water channel. The free surface of the sea is assumed to be soft and the bottom is assumed to be hard. Between the two layers the classical diffraction boundary conditions are taken. An extension of the Deep Water Approximation method [Ergatis P. Radiation, propagation and scattering of acoustic waves in an underwater environment. PhD thesis, University of Patras; 1997 (in Greek)] is being provided to cover the case of resistive scatterers [Colton, D., Kress, R. Integral equation methods in scattering theory. New York: Wiley; 1983].     

Electromagnetic scattering from two-layer rough interfaces in the Kirchhoff approximation

Electromagnetic wave scattering from multilayers consisting of two two-layer Gaussian rough surfaces with lossless media is investigated in the Kirchhoff approximation (KA), with consideration of the shadowing effects. The tapered incident wave is introduced into the classic KA, and the bistatic scattering coefficient is redetermined. The advantage of this method is that it is faster in computation than the exact numerical methods. The numerical results show that the bistatic scattering coefficient calculated in the KA is in good agreement with that obtained by using the method of moment (MOM) over a most angular range, which indicates the validity of the KA proposed in our paper. Finally, the effects of the relative permittivity, the root-mean-square (RMS) height, the correlative length, and the average height between the two interfaces on the bistatic scattering coefficient are discussed in detail.     

磁化铁氧体电磁散射的移位算子FDTD分析

将移位算子（shift operator,SO）-时域有限差分（fintie difference time domain,FDTD）方法推广到外磁场沿任意方向时磁化铁氧体的情形.从磁化铁氧体的相对磁导系数张量和各向异性情形下Maxwell旋度方程出发,推导出外磁场沿任意方向情形下磁化铁氧体电磁散射的SO-FDTD迭代公式.应用该方法计算了磁化铁氧体层、磁化铁氧体球及含磁化铁氧体涂层的Von Karman形雷达罩电磁散射,数值计算结果表明了该算法的正确有效性. 关键词： 磁化铁氧体 FDTD 移位算子法     

Pinning of domain walls in two-layer ferromagnetic nanowire with scattering fields of nanoparticles

The results of a micromagnetic simulation of the pinning-depinning processes of a domain wall (DW) in a rectangular ferromagnetic nanowire (NW) consisting of two magnetic layers with scattering fields of two rectangular two-layer nanoparticles (NPs) located on NW opposite sides and oriented perpendicular to its axis are presented. The features of magnetization reversal of this system in the external magnetic field are studied depending on direction of the magnetic moments of the nanoparticle layers. The value of the depinning field in such a system depends essentially on mutual orientation of NP magnetic moments and NW magnetization. The possibility to realize a magnetic logic cell performing the “conjunction” operation of ternary logic is discussed.     

Experimental modeling the millimeter wave scattering from vegetation canopy

In the paper we present the results of experimental modeling the millimeter wave scattering from elements and fragments of a vegetation canopy. The dependence of amplitude and phase distributions of scattered field in near zone, of back-scattering cross section, and of scattered field distribution in Frenel zone for a fragment of wheat shoots upon the moisture and shape of an individual element is determined.     

Numerical simulation of the EM scattering and Doppler spectrum of a low flying target above dynamic oceanic surface by using the FEM-DDM method

The Doppler (DP) spectrum of a moving target such as a ship, an iceberg or an air-plane above dynamic oceanic surfaces[1—3] is one of the most important subjects for ra-dar oceanic surveillance, target tracking and oceanic remote sensing[4—7]. With the ad-vancement of oceanic remote sensing and radar surveillance, the experimental observa-tion and theoretical modeling of oceanic clutter have been extensively studied, e.g. by using oceanic field measurement, wave tank experiment and some stud…