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We consider the inverse scattering problem of determining the shape of an impenetrable two-dimensional obstacle with a generalized impedance boundary condition from near-field measurements. We prop...

This review reports on some progress in high-frequency diffraction by smooth surfaces. Specific effects related to the special cases of the impedance boundary conditions and the effects that take p...

We show how a Trefftz Discontinuous Galerkin (TDG) method for the displacement form of the Helmholtz equation can be used to approximate problems having a generalized impedance boundary condition (...

A novel series solution is obtained for the scattering problem of waves by a half-plane with different face impedances. The impedance condition is expressed in terms of the sum of Dirichlet and Neumann conditions, multiplied by appropriate coefficients. The scattering problem of plane waves by an interface between two half-planes with different impedances is also investigated. The results are compared with the literature, numerically.

International audience; The simulation of blood flow and pressure in arteries requires outflow boundary conditions that incorporate models of downstream domains. We previously described a coupled multidomain method to couple analytical models of the downstream domains with 3D numerical models of the upstream vasculature. This prior work either included pure resistance boundary conditions or impedance boundary conditions based on assumed periodicity of the solution. However, flow and pressure in arteries are not necessarily periodic in time due to heart rate variability, respiration, complex transitional flow or acute physiological changes. We present herein an approach for prescribing lumped parameter outflow boundary conditions that accommodate transient phenomena. We have applied this method to compute haemodynamic quantities in different physiologically relevant cardiovascular models, including patient-specific examples, to study non-periodic flow phenomena often observed in normal subjects and in patients with acquired or congenital cardiovascular disease. The relevance of using boundary conditions that accommodate transient phenomena compared with boundary conditions that assume periodicity of the solution is discussed.

This paper presents an efficient simulation technology to characterize the Ultra-Wide Band signal propagation between the antennas in close proximity to a human body, where the human body works as a Wireless Body Area Network. The first technique is the hybrid Method of Moments and asymptotic Physical Optics in which the formulation is extended for modeling the dielectric body. The second technique combines the modification of the Multilevel Fast Multipole Algorithm with the Impedance Boundary Condition. These two techniques drastically reduce the computational complexity to model and simulate an electrically very large and complex structure including antennas and human body. Numerical examples showing the effects of the human body on the Ultra-Wide Band signal transmission between two antennas are presented to demonstrate the efficiency of our proposed method.

Applications of fractional operators approach to electromagnetic waves reflection problems are considered. Reflection properties of fractional or intermediate solutions are analyzed. It is shown that this approach is a useful technique for the description of solutions to the reflection problems for some known media in terms of the fractional order and also obtaining boundaries with new features. In this paper intermediate boundaries are modeled with BI slab with a PEC backing and also using anisotropic impedance boundary conditions. The twist-polarizer effect (crosspolarizing reflector) is described in terms of the specific value of the fractional order.

In this paper a least square method is proposed for the solution of the 3-dimensional (3-D) vector parabolic wave equation. This method can correctly incorporate the impedance boundary conditions o...

The modes of electromagnetic wave propagation in a circular tunnel with lossy walls such as concrete are obtained by applying the impedance boundary conditions on the wave solution inside the tunnel. The attenuation coefficients of the lowest order modes are calculated as a function of frequency. The results are found to agree well with the published results using other methods. An equation is proposed to represent the attenuation as a function of frequency and tunnel radius. This work can be easily extended to the case of rectangular tunnel.

Numerical moment-method calculations of the electromagnetic backscattering from experimentally measured wind-roughened water surfaces that were previously made assuming perfectly conducting surfaces have been repeated taking into account the finite conductivity of sea water. The finite conductivity of the scattering medium was treated using impedance boundary conditions. Comparison with the earlier calculations shows that the backscattering drops slightly at horizontal polarization and much more dramatically at vertical polarization when the finite conductivity is considered. At small and moderate incidence angles, the magnitudes of the scattering drops are consistent with that predicted by the two-scale scattering model. The asymmetry in the upwind and downwind looking scattering that results from the non-uniform distribution of the Braggresonant electromagnetically small-scale waves across the larger scale waves is unaffected by the reduced conductivity at horizontal polarization and reduced very slight...

The waves propagating on the surface of an arbitrary convex transparent body are studied by the boundary layer method. When the refraction index of the body is high enough. both creeping and whispering gallery type of wave can propagate. The propagation constant are shown to be the same as for an equivalent body described by an impedance boundary condition. When the refraction index is close to 1, waves of mixed type, looking like creeping outside and whispering gallery inside propagate.

Using a technique borrowed from Idemen [1] and requiring the Fourier transform of the x,y-components of the electric and magnetic fields, we obtain the impedance boundary conditions for electromagnetic plane waves with horizontal, vertical and arbitrary polarization incident on a infinite, smooth, chiral film located at z = 0 and deposited on a metallic substrate. As an application, we discuss the scattering of harmonic plane waves and of a finite beam on such a film.

Luebbers' and Maliuzhinets' solutions for diffraction by a lossy wedge are compared in order to model the urban propagation channel. Derivation, validity criteria and accuracy of impedance boundary conditions (IBCs)-as a main approximation embedded in the Maliuzhinets' solution-are discussed. A modified (a slightly improved) Luebbers diffraction coefficient is proposed. The Uniform Theory of Diffraction (UTD) Maliuzhinets diffraction coefficient is given in a structured form that might facilitate its use. Detailed numerical comparisons of the above-mentioned solutions with method-of-moments solutions using either exact boundary conditions or IBCs are done for canonical configurations.

A spectral-domain-rational-approximation approach is presented for systematic derivation of higher-order impedance boundary conditions for complex stratified coatings, consisting of stacked homogeneous-(bi)anisotropic and (radially) inhomogeneous-isotropic layers, laid on (locally) cylindrical conducting surfaces. Second-order impedance boundary conditions are shown to provide accurate results even when the local curvature radius is a fraction of a wavelength.

The impedance boundary condition is used to obtain the resonant frequency and bandwidth of a circular cylindrical cavity with an imperfectly conducting wall or absorbing lining.

The two-dimensional problems of an E-polarized wave incident on a slightly rough perfectly conducting cylinder and also a cylinder with an impedance boundary condition are considered. Numerical results for a. rectangular cylinder are presented to illustrate the similarities between thesis two cases.

The familiar physical optics (PO) approximation is no longer valid when the perfectly conducting scatterer is coated with dielectric material. This paper reviews several possible PO formulations. By comparing the PO formulation with the moment method solution based on the impedance boundary condition for the case of the coated cone-sphere, a PO formulation using both electric and magnetic currents consistently gives the best numerical results. Comparisons of the exact moment method with the PO formulations using the impedance boundary condition and the PO formulation using the Fresnel reflection coefficient for the case of scattering from the cone-ellipsoid demonstrate that the Fresnel reflection coefficient gives the best numerical results in general.