Solution of problem of electromagnetic waves scattering on inhomogeneously layered scatterers using pattern equation method

In this paper, the pattern equation method (PEM) is used to solve the problems of electromagnetic waves scattering by inhomogeneously layered scatterers. The numerical algorithm based on PEM for multilayered scatterers of arbitrary geometry is developed. The numerical results are presented for magneto-dielectric objects coated with magneto-dielectric materials to demonstrate the stability, accuracy, and efficiency of the proposed method. A comparison of the results obtained by the present method and by the other methods are shown and the limits of applicability of method are outlined.     

Scattering of electromagnetic waves by a perfectly conducting body with a chiral coating

We propose a numerical method for solving problems of electromagnetic scattering in the resonance spectrum of frequencies by a 3D ideally conducting arbitrary-shaped body covered by a homogeneous chiral coating. A program package for calculating the characteristics of the scattered field and checking the accuracy of the obtained solution based on the above method is described briefly. Some results of numerical calculations are given, which are useful for a study of the influence of “chirality” on the scattering properties of absorbing coatings. Siberian Physical-and-Technical Institute at Tomsk State University, Tomsk, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 4, pp. 495–506, April, 1998.     

Defects in the in situ synthesized TiB2/Fe composite coatings during PTA process

The in situ synthesized TiB₂/Fe composite coatings were deposited by the plasma transferred-arc (PTA) powder surfacing process. The macro and micro defects in the TiB₂/Fe composite coatings were investigated in this paper. It is found that heat input plays an important role in macro defects in the coatings. Only when the energy density and total heat input are appropriate will nice forming with few macro defects be obtained. As micro defects in the coatings, slag inclusions (C, Al₂O₃) and cracks often appear together. And it is found that slag inclusions and cracks tend to appear with a low dilution rate of the coatings, and their tendency decreases as the dilution rate increases.     

Relativistic theory of tunnel and multiphoton ionization of atoms in a strong laser field

Relativistic generalization is developed for the semiclassical theory of tunnel and multiphoton ionization of atoms and ions in the field of an intense electromagnetic wave (Keldysh theory). The cases of linear, circular, and elliptic polarizations of radiation are considered. For arbitrary values of the adiabaticity parameter γ, the exponential factor in the ionization rate for a relativistic bound state is calculated. For low-frequency laser radiation , an asymptotically exact formula for the tunnel ionization rate for the atomic s level is obtained including the Coulomb, spin, and adiabatic corrections and the preexponential factor. The ionization rate for the ground level of a hydrogen-like atom (ion) with Z ? 100 is calculated as a function of the laser radiation intensity. The range of applicability is determined for nonrelativistic ionization theory. The imaginary time method is used in the calculations.     

Photon electrodynamics and photon structure as a bunch of one of many possible states of electromagnetic field

Fundamental laws of conservation are used to show that electromagnetic field is generally represented (even in vacuum at ρ = 0 and j = 0) using four vectors D, E, B, and H with different equations of state (material equations) that are linear for electromagnetic waves and nonlinear for photons and particles. An equation that describes different states of electromagnetic field (i.e., different but not arbitrary relationships of field vectors E, H, D, and B) is derived. It is shown that electromagnetic wave and photon are different states of electromagnetic field that exhibit different dependences of energy density on field vectors. Partial analytical solutions are obtained for a photon (spatially localized bunch of electromagnetic field energy) that propagates at a velocity of light along a single (as distinct from electromagnetic wave) direction.     

Absorption and generation of electromagnetic waves by structural inhomogeneities of solid

The integrability conditions of the electromagnetic field equations in a continuum with defects and their wave solutions are found. The following dislocation effects on the electromagnetic wave propagation in a continuous medium are investigated: the change in the direction of the electromagnetic wave propagation in a continuous medium; the rotation of the polarization plane of electromagnetic field wave in a continuous medium; the excitation of longitudinal components of the electromagnetic wave in a continuous medium and the change in the electromagnetic wave intensity related to this phenomenon. The energy balance equation for the electromagnetic field in a continuum with a stationary distribution of dislocation is found and it is shown that an electromagnetic wave excites exciton modes localized at dislocations in the solid.     

Combined laser calorimetry and surface thermal lens technique for optical coating characterization

A combined laser calorimetry (LC) and surface thermal lens (STL) technique with a continuous-wave (cw) modulated excitation is developed for characterizing the absorption properties of optical coatings. LC and STL signals are simultaneously obtained with highly reflective coating samples irradiated at 1064 nm. With a modulated irradiation power of 2.6 W, the limits of absorptance detection for the LC and STL signals are approximately 1.2×10^-6 and 0.5×10^-6, respectively. The influences of different excitation parameters (modulation frequency, excitation-beam power and irradiation time) on the absorptance measurements are experimentally analyzed. The applicability of the combined LC and STL technique to the investigation of the laser-induced absorption changes of optical coatings in an absolute absorptance scale is demonstrated. PACS 42.87.-d; 78.20.-e     

Theoretical analysis of optical properties of dielectric coatings dependence on substrate subsurface defects

A model for refractive index of stratified dielectric substrate was put forward according to theories of inhomogeneous coatings. The substrate was divided into surface layer, subsurface layer and bulk layer along the normal direction of its surface. Both the surface layer (separated into N₁ sublayers of uniform thickness) and subsurface layer (separated into N₂ sublayers of uniform thickness), whose refractive indices have different statistical distributions, are equivalent to inhomogeneous coatings, respectively. And theoretical deduction was carried out by employing characteristic matrix method of optical coatings. An example of mathematical calculation for optical properties of dielectric coatings had been presented. The computing results indicate that substrate subsurface defects can bring about additional bulk scattering and change propagation characteristic in thin film and substrate. Therefore, reflectance, reflective phase shift and phase difference of an assembly of coatings and substrate deviate from ideal conditions. The model will provide some beneficial theory directions for improving optical properties of dielectric coatings via substrate surface modification.     

Generalized surface current method in the macroscopic theory of diffraction radiation

The surface current method known in the theory of electromagnetic waves diffraction has been generalized to be applied to the problems of diffraction radiation generated by a charged particle moving nearby an ideally-conducting screen in vacuum. An expression for induced surface current density leading to the exact results in the theory of transition radiation has been derived, and by using this expression several exact solutions of diffraction radiation problems are found. Limits of applicability for the earlier known models based on the surface current conception are indicated. Properties of radiation from a semi-plane and from a slit in cylinder are investigated at the various distances to observer.     

Electromagnetic probing of the underlying surface and of the upper ground layer for the purpose of their monitoring and diagnostics

A short review is given of theoretical work carried out under the author on the problem of the electromagnetic probing of the underlying surface and the upper ground layer, including regions containing local and extended natural and artificial inhomogeneities. This work mainly involves electromagnetic boundary problems for homogeneous and inhomogeneous media when they are excited by electromagnetic sources of various types. Considerable attention is devoted to approximate methods for solving these problems. In the case of low-frequency probe fields the solutions are obtained taking account of the weak magnetic properties of soil. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 62–75, August, 1998.     

微波强耦合论

在本文中,作者尝试从耦合波的观点来研究电磁波通过两边有导电屏的长槽(即槽耦合波导系统)的衍射问题,提出一个实际求解这个边值问题的、建立在明皙物理概念上的理论。应用这个理论的观点,研究耦合波导问题,就和研究单一波导问题一样,能够采取相同的数学途径,这个途径就是正交函数的展开理论。这样,从来都是用不同方法来处理的两类波导传输问题,现在就能用统一的、联系的观点来分析。为了就明这个理论的具体应用,作者分析了用来完成矩形波导主波和低衰减圆电波之间功率转换的长槽定向耦合器,得出了一系列的计算基本参数的原始公式。文末指出了本文所提理论和方法的若干进一步应用。     

Electromagnetic emission of mobile dislocation segments in an ionic crystal

The problem of electromagnetic emission of an edge dislocation segment moving in an ionic lattice with a NaCl-type structure is considered. The proposed mechanism of electromagnetic emission is associated with the appearance of macroscopic alternating polarization currents along the extraplane edge of the edge dislocation in the course of its motion between adjacent valleys of the Peierls relief. The relationships for electro-magnetic radiation fields of an arbitrarily moving segment are derived, and the problem of electromagnetic emission of a segment that executes harmonic oscillations in the field of an external quasi-stationary elastic wave with a frequency (where l is the segment length and c is the velocity of sound) is treated in detail. The power of the emitted electromagnetic signal and the “acoustoelectromagnetic transformation” coefficient (the ratio between the electromagnetic radiation power and the mechanical power required for setting the segment in motion) are determined.     

On the scattering of torsional elastic waves from axisymmetric defects in coated pipes

Long range ultrasonic testing is now a well established method for examining in-service degradation in pipelines. In order to protect pipelines from the surrounding environment it is common for viscoelastic coatings to be applied to the outer surface. These coatings are, however, known to impact on the ability of long range ultrasonic techniques to locate degradation, or defects, within a coated pipe. The coating dissipates sound energy travelling along the pipe, attenuating both the incident and reflected signals making responses from defects difficult to detect. This article aims to investigate the influence of a viscoelastic coating on the ability of long range ultrasonic testing to detect a defect in an axisymmetric pipe. The article focuses on understanding the behaviour of the fundamental torsional mode and quantifying the effect of bitumen coatings on reflection coefficients generated by axisymmetric defects. Reflection coefficients are measured experimentally for coated and uncoated pipes and compared to theoretical predictions generated using numerical mode matching and a hybrid finite element technique. Good agreement between prediction and measurement is observed for uncoated pipes, and it is shown that the theoretical methods presented here are fast and efficient making them suitable for studying long pipe runs. However, when studying coated pipes agreement between theory and prediction is observed to be poor for predictions based on those bulk acoustic properties currently reported in the literature for bitumen. Good agreement is observed only after conducting a parametric study to identify more appropriate values for the bulk acoustic properties. Furthermore, the reflection coefficients obtained for the fundamental torsional mode in a coated pipe show that significant sound attenuation is present over relatively short lengths of coating, thus quantifying those problems commonly encountered with the use of long range ultrasonic testing on coated pipes in the field.     

Iron oxide nanopowder synthesized by electroerosion dispersion (EED) – Properties and potential for microwave applications

Magnetic nanoparticles (MNP) have attracted considerable interest in many fields of research and applied science due to their impressive properties. In the past, especially biomedical problems have promoted the development of MNPs. For technical applications e.g. wastewater treatment and absorption of electromagnetic waves, the existing synthesis approaches are too expensive and/or the producible quantities are too low. In this work we present a method for simple preparation of size-controlled magnetic iron oxide nanoparticles by electroerosion dispersion (EED) of carbon steel in water. We describe the synthesis method, the laboratory installation and discuss the structural, chemical and electromagnetic properties of the synthetized EED powders as well as their applicability for microwave absorption compared to other available ferrite powders.     

In-situ SEM observations of ultrasonic cavitation erosion behavior of HVOF-sprayed coatings

Several typical high-velocity oxy-fuel (HVOF)-sprayed coatings, including WC-10Co4Cr coatings, Co-based coatings, WC-10Co4Cr/Co-based composite coatings, and Fe-based amorphous/nanocrystalline coatings were fabricated, and their cavitation behavior was evaluated in deionized water. Further, in-situ SEM surface observations were used to understand the microstructure of tested coatings. The results show that cavitation erosion initially occurred at pre-existing defects in the coatings. Meanwhile, it was found that cavitation erosion damage of the WC-10Co4Cr/Co-based composite coating, which contained a hard reinforcing phase (WC-10Co4Cr phase) and a soft matrix phase (Co-based phase), preferentially occurred at or around pores and microcracks in the reinforcement, rather than in the defect free matrix. This suggested that defects were a critical contributing factor to cavitation damage of the composite coatings. Furthermore, a mechanism was suggested to explicate the cavitation behavior of composite coatings. The approach of using in-situ SEM surface observations proved to be useful for the analysis of the cavitation mechanism of engineering materials and protective coatings.     

Two-photon processes in scattering on a short-range potential

In the first nonvanishing order of perturbation theory for the interaction with electromagnetic radiation, accurate expressions are obtained for the cross sections of two-photon processes in scattering on a potential. The conditions of applicability of the dipole approximation in interactions with a laser field in scattering problems are investigated. The results obtained are compared with the well-known Bunkin and Federov formula for induced multiphoton bremsstrahlung.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 92–95, April, 1984.     

电子与太阳电磁射线综合辐照对Teflon FEP/Al光学性能的影响

 在30keV的电子、质子单独辐照及电子与太阳电磁射线综合辐照作用下，对Teflon FEP/Al第二表面镜光学性能的演化进行了研究。试验结果表明，在相同辐照通量与能量乘积的情况下，电子与质子单独辐照后Teflon FEP/Al涂层材料的太阳吸收比变化相同，故可用电子与太阳电磁射线综合辐照简化地面模拟加速试验。Teflon FEP/Al光学性能退化动力学曲线可描述成加速系数与辐照时间乘积（称为当量辐照时间）的指数函数形式。在当量辐照时间相同的情况下，太阳吸收比的变化与加速系数无关。     

Parametric study of uniformly polarized stochastic electromagnetic beam and its imaging

A parametric study is performed in investigating the stochastic electromagnetic beam generated by a uniformly polarized electromagnetic Gaussian Schell-model source and passing through ABCD optical systems. Through theoretical analysis, the requirement is derived that the uniformly polarized electromagnetic field can be obtained at the output plane of the imaging optical system. Furthermore, the general imaging formula of the stochastic electromagnetic beam is derived. Numerical examples are also presented to illustrate the application.     

Exact travelling solutions for some nonlinear physical models by ( <Emphasis Type="Italic">G</Emphasis>′/ <Emphasis Type="Italic">G</Emphasis>)-expansion method

In this paper, we establish exact solutions for some special nonlinear partial differential equations. The (G′/G)-expansion method is used to construct travelling wave solutions of the two-dimensional sine-Gordon equation, Dodd–Bullough–Mikhailov and Schrödinger–KdV equations, which appear in many fields such as, solid-state physics, nonlinear optics, fluid dynamics, fluid flow, quantum field theory, electromagnetic waves and so on. In this method we take the advantage of general solutions of second-order linear ordinary differential equation (LODE) to solve many nonlinear evolution equations effectively. The (G′/G)-expansion method is direct, concise and elementary and can be used with a wider applicability for handling many nonlinear wave equations.     

计算机机箱关键部位感应电压统计特性分析

通过基于随机矩阵理论的耦合模型,对不同频段电磁波环境中计算机机箱关键部位感应电压的统计分布进行了理论和实验分析,实验测量结果与理论分析结果非常一致。给出了随机耦合模型应用的简单例子,验证了随机耦合模型在宽频带电磁环境下系统级效应分析和预测的适用性。为电子设备(尤其大型的具有非平行面封装腔体电子设备)电磁环境效应分析提供了一种方法。