摘要:

There are many boundary integral formulations for the problem of electromagnetic scattering from and transmission into a homogeneous material body. The only formulations which give a unique solution at all frequencies are those which involve both electric and magnetic equivalent currents, and satisfy boundary conditions on both tangential E and tangential H. Formulations which involve only electric (or magnetic) equivalent currents, and those which involve boundary conditions on only tangential E (or tangential H) are singular at frequencies corresponding to the resonant frequencies of a resonator formed by a perfect conductor covering the surface of the body and filled with the material exterior to the body in the original problem.

ISSN:0920-5071    

DOI:10.1163/156939389X00016

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The complex source point method converts an omnidirectional source diffraction solution into a beam solution by an appropriate choice of complex source coordinates. In so doing shadow and reflection boundary singularities of the geometrical theory of diffraction become non-singular, in general. Thus the suggestion that, for certain parameters, transition region functions are unnecessary. Here numerical results from uniform and asymptotic solutions for beam diffraction by half-planes and wedges indicate this is so only if diffraction is negligible. Convenient uniform expressions are shown to provide accurate far field values for all parameters.

ISSN:0920-5071    

DOI:10.1163/156939389X00025

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

High frequency wave propagation in inhomogeneous media is often treated using the geometrical optics technique. Near caustics, this approach requires modification. One such modification is the Lagrange Manifold formalism. Transport equations associated with the Lagrange Manifold formalism valid near caustics in several media of geophysical interest are developed. Some energy and polarization considerations at caustics are also discussed.

ISSN:0920-5071    

DOI:10.1163/156939389X00034

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In this paper, the polarizability and dipole moment of different types of small inhomogeneous inclusions are solved. From the dipole moment, the effective permittivity of a dielectric mixture that contains these kinds of inclusions are solved. Two ways to approach the exact solution are presented: the external and internal field solutions. For cases where an inclusion does not possess sharp boundaries, a variational approach appears most efficient. A stationary functional for the polarizability is derived which can be used to calculate accurate estimates for the dipole moment with simple trial functions. Results are shown for multilayer inclusions, and inhomogeneous inclusions with linear, parabolic, and Gaussian permittivity profiles.

ISSN:0920-5071    

DOI:10.1163/156939389X00043

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Earth terrains are modeled by a two-layer configuration to investigate the polarimetric scattering properties of the remotely sensed media. The scattering layer is an anisotropic random medium characterized by a three-dimensional correlation function with lateral and vertical correlation lengths and variances. Based on the wave theory under Born approximations, this model is applied to derive the fully polarimetric backscattering coefficients of the Mueller and covariance matrices. A single scattering process is considered and all the multiple reflections at the boundaries are taken into account. For an anisotropic random medium with optic axis tilted off the vertical axis, the corresponding Mueller and covariance matrices do not contain any zero elements. To account for the azimuthal randomness in the growth direction of leaves in tree and grass fields, an averaging scheme is applied to obtain the backscattering coefficients. In this case, the Mueller matrix contains eight zero elements and the covariance matrix has four zero elements, and the cross polarization term σvhdoes not vanish. Theoretical predictions are matched with experimental data for sea ice and vegetation fields.

ISSN:0920-5071    

DOI:10.1163/156939389X00052

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939389X00061

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor