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1.
The scattering of a spherical wave by a static irregular dielectric surface, separating two subspaces with dielectric constant close to the permittivity of free space, is investigated by the Kirchhoff method. The irregularities of the surface — large-scale with small angles of inclination, and their heights are distributed according to a normal law. Self-shadowing and the set of spots associated with scattering on such a surface are taken into account. The polarization matrix of second moments of the components of the scattered field is calculated. The dependence of the matrix elements on the statistical parameters of a randomly irregular surface are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 7–10, May, 1974.  相似文献   

2.
A thin prolate spheroidal void in an infinite conducting circular cylinder is used to model a broken strand in a wire rope. The rope is excited by an azimuthal magnetic line current which is a model for a thin toroidal coil. The anomalous external fields are computed from the induced electric and magnetic dipole moments of the void. The results have applications to nondestructive testing of wire ropes.  相似文献   

3.
In this paper, polytetrafluoroethylene (PTFE) films are modified using non-equilibrium plasma generated by homogeneous DBD in air at medium pressure, and the results are compared to those treated by using filamentary DBD in air at atmospheric pressure. The surface properties of PTFE films before and after the treatments are studied using contact angle and surface energy measurement, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It is found that the plasma treatments modify the PTFE surface in both morphology and composition. The PTFE films modified in both treatments show a remarkable decrease in water contact and a remarkable increase in surface energy. XPS analysis reveals that oxygen-containing polar groups are introduced onto the PTFE surface, and SEM analysis shows that the surfaces of the films are etched after both the treatments. It is found that homogeneous DBD is more effective in PTFE surface modification than filamentary DBD as it can make the contact angle decline to a lower level by introducing more oxygen-containing groups, and the possible reason for this effect is discussed.  相似文献   

4.
We report on the effect of hexagonal warping on the dynamical conductivity of the surface states of a topological insulator in the presence of nonmagnetic impurities. It is found that the photon energy dependent conductivities are determined by a polarization-function-liked term,  Π2 (q,ω), which contains a velocity term corresponding to the difference of group velocities between the two states due to an electron-impurity scattering. This is different from the conductivity of 2-dimentional electron systems where the conductivity depends on the inverse imaginary part of the dielectric function Im [1/κ(q,ω)]. We present both the real part and imaginary part of the polarization function with different warping strength. It is found that the warping strength can both enhance single particle excitations (SPEs) and suppress the screening effect of electrons. As a result the inverse scattering time is enhanced by up to about two orders of magnitudes. The real part of the longitudinal conductivity of the intra-band process is analog to the case with a conductivity of σ ~ μδ(ω). The broadening of the spectrum in the low energy is not only determined by chemical potential, but also dependent on the warping strength. At higher frequency, the real part of conductivity shows a jump at the threshold photon energy of μ, where the inter-band contribution takes over.  相似文献   

5.
An exact solution of the Boltzmann equation for a binary mixture of colored Maxwell molecules is found. The solution corresponds to a nonequilibrium homogeneous steady state created by a nonconservative external force. Explicit expressions for the moments of the distribution function are obtained. By using information theory, an approximate velocity distribution function is constructed, which is exact in the limits of small and large field strengths. Comparison is made between the exact energy flux and the one obtained from the information theory distribution.  相似文献   

6.
A theoretical investigation is presented of scattering characteristics of a perfectly conducting spherical object placed inside a quasi-optical transmission line of the millimeter and submillimeter waves in the form of a circular hollow dielectric waveguide (HDW). From the analytical expressions obtained, backscattering and extinction cross sections of this object are derived via the excitation coefficient of the dominantHE 11 mode of the circular HDW and the HDW geometrical parameters. The agreement of the results with the corresponding data for the scattering of a plane homogeneous wave is shown.  相似文献   

7.
We describe a systematic investigation on void structures fabricated by femtosecond laser irradiation inside dielectric materials for fabrication of a compact optical circuit. Void shapes fabricated in 5 different dielectric materials were compared and the physical constants determining the void shape were discussed. A long void array is obtainable in a material which has a low critical power for self-focusing. It was also indicated that the coefficient of thermal expansion is a dominant governing factor to fabricate a precise void which has a clear boundary. Furthermore, we propose and design a Mach-Zehnder interferometer in fused silica composed of optical waveguides and photonic crystals to verify practical application of a void array. Simulation results of the optical propagation in a Mach-Zehnder interferometer indicated that the photonic crystals using a void array have potential to fabricate compact optical circuits.  相似文献   

8.
The dependence of the quality of a screened layered spherical resonator on its geometric and electrodynamic parameters is studied in the case of a three-layer dielectric filling on the basis of a mathematical model constructed in the paper.  相似文献   

9.
We report the first measurement of a reduction in the conductivity of liquid sodium due to turbulence in a spherical flow (the beta effect). The sodium is contained in a 0.15 m diameter sphere, typical flow speeds are about 1 m/s, and magnetic Reynold's numbers range from 1 to 8. We find a reduction from the molecular value of the conductivity of about 4%. Results are in rough agreement with simple predictions from mean-field electrodynamics.  相似文献   

10.
张之翔 《大学物理》2011,30(2):22-24
算出了膨胀球面运动时的形状,从而说明光的波前为什么不因为长度收缩而成为椭球面.  相似文献   

11.
In a variety of samples, conductivity is a limiting factor regarding the resolution of dielectric loss peaks of interest. One approach to eliminating the signal that originates from conductivity is the use of insulating layers on one or both electrodes. For the typical case, it is shown that insulation layers add errors rather than improving the situation.  相似文献   

12.
To obtain the eigenmodes of the electromagnetic field at a periodically corrugated metamaterial we consider the analytic extension to the complex plane of the solution to the boundary-value problem for a metamaterial grating. We build a proper Riemann sheet for these eigenmodes and we present numerical examples illustrating their propagation characteristics. Particularly, we pay special attention to regimes corresponding to ideally transparent metamaterials with a negative index of refraction, where the eigenmodes can radiate into the metamaterial medium.  相似文献   

13.
14.
A simple method for determination of effective dielectric constants is proposed that allows a close-spaced two-dimensionally periodic dielectric layer with rectangular elements to be replaced by a homogeneous and anisotropic layer of the same thickness. The method makes it unnecessary to solve the complicated problem of determination of the fields within the elements for calculation of the plane-wave reflection and transmission coefficients in a long-wave approximation, which considerably simplifies the calculations. Comparison with known solutions obtained by rigorous methods for one-dimensionally periodic gratings shows exact agreement of the results. The method is easily extended to magnetodielectric media as well as to multicomponent media, including those whose dielectric constants are functions of the coordinate perpendicular to the layer.Academician A. L. Mints Radio-Engineering Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 36, No. 3-4, pp. 286–294, March–April, 1993.  相似文献   

15.
The effective dielectric constant ∈eff of a medium containing randomly distributed dielectric particles has been analysed by conventional methods: Foldy's approximation, the quasi-crystalline approximation (QCA) and the QCA with coherent potential. These conventional methods, however, have been indicated to become invalid for particles with a high dielectric constant; we have thus presented a new method that is valid for them. This paper compares ∈eff of our method with those of the conventional methods by changing the volume fraction and the dielectric constant of spheres. As a result, our method is shown to be more powerful for the analysis of ∈eff than the conventional methods.  相似文献   

16.
Abstract

The effective dielectric constant ∈eff of a medium containing randomly distributed dielectric particles has been analysed by conventional methods: Foldy's approximation, the quasi-crystalline approximation (QCA) and the QCA with coherent potential. These conventional methods, however, have been indicated to become invalid for particles with a high dielectric constant; we have thus presented a new method that is valid for them. This paper compares ∈eff of our method with those of the conventional methods by changing the volume fraction and the dielectric constant of spheres. As a result, our method is shown to be more powerful for the analysis of ∈eff than the conventional methods.  相似文献   

17.
18.
A new single surface integral equation is derived for light scattering by circular dielectric cylinders. Without adopting the concept of equivalent electric or magnetic surface currents, our formulation is directly derived from coupled-surface integral equations by the property of commutative matrices of Green functions. Further development by such matrix equations leads to only one unknown function for circular dielectric-coated cylinders. In addition, numerical simulations show that even applied to elliptic scatters our equation still gives reasonably good approximate solutions in the sub-wavelength limit.  相似文献   

19.
20.
The electrical conductivity of a liquid dielectric is one of its most important properties; however, it is typically measured in the low-voltage range whereas the features of the current passage processes under the effect of strong electric field remain poorly investigated. The paper presents an experimental technique for rapid measurement of the high-voltage conductivity. The current–voltage characteristics obtained with the voltage modulation by a saw-tooth signal underlie the proposed technique. Some examples are given to demonstrate the importance of its application. The experimental data were complemented with the computer simulation of the corresponding processes.  相似文献   

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