S. González García

Extension of Berenger's PML for bi-isotropic media

An extension of Berengers perfectly matched layer (PML) absorbing boundary conditions to adapt bi-isotropic media is formulated. The method is developed under simple algebraic conditions and validated with the finite-difference time-domain method (FDTD).

Extension of Berenger's absorbing boundary conditions to match dielectric anisotropic media

The authors propose an extension of Berengers perfectly matched layer (PML) absorbing boundary conditions (ABCs) to achieve a perfect matching of waves propagating in anisotropic media. Although the procedure to obtain the matching conditions is valid for any kind of anisotropic material, it has been validated with a lossless two-dimensional uniaxial medium, in which the optical axis is not contained in its plane section. The finite difference time domain method, with an alternative scheme for anisotropic media, is used to simulate the problem and to obtain the numerical reflection coefficient.

Time domain analysis of thin-wire antennas over lossy ground using the reflection-coefficient approximation

This paper presents a procedure to extend the methods of moments in time domain for the transient analysis of thin-wire antennas to include those cases where the antennas are located over a lossy half-space. This extended technique is based on the reflection coefficient (RC) approach, which approximates the fields incident on the ground interface as plane waves and calculates the time domain RC using the inverse Fourier transform of Fresnel equations. The implementation presented in this paper uses general expressions for the RC which extend its range of applicability to lossy grounds, and is proven to be accurate and fast for antennas located not too near to the ground. The resulting general purpose procedure, able to treat arbitrarily oriented thin-wire antennas, is appropriate for all kind of half-spaces, including lossy cases, and it has turned out to be as computationally fast solving the problem of an arbitrary ground as dealing with a perfect electric conductor ground plane. Results show a numerical validation of the method for different half-spaces, paying special attention to the influence of the antenna to ground distance in the accuracy of the results.

A time-domain near- to far-field transformation for FDTD in two dimensions

This paper proposes an algorithm based on the equi alence principle to calculate, straightforwardly in the time domain, the transient far field response of a two-dimensional structure. The algorithm implementation in ol es the numerical e aluation of a time integral along the nearto far-field con ersion contour of the equi alent currents at the ( ) Huygens surface, obtained with the finite-difference time-domain FDTD method. 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 427 432, 2000.

Generalization of Berenger's absorbing boundary conditions for 3-D magnetic and dielectric anisotropic media

A general method is deeloped which extends Berengers () ( ) perfect matching layer PML absorbing boundary conditions ABCs to achiee a perfect matching of waes propagating in 3-D magnetic and r or dielectric anisotropic media. The method isalidated with the finite-difference time-domain method. Q 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 126)130, 1998.

A New Hybrid Method Combining the ADI-FDTD and the MOMTD Techniques

This paper describes a new hybrid technique, combining the alternating direction implicit finite difference time domain (ADI-FDTD) method and the method of moments in the time domain (MoMTD) to analyze problems involving thin-wire antennas close to inhomogeneous dielectric bodies. The unconditionally stable ADI-FDTD formulation presents computational advantages over the explicit Yee FDTD scheme in cases that require a fine mesh to accurately model their electromagnetic characteristics. The hybrid procedure has been found stable in the examples analyzed so far, which was not always the case in the previous approach based on the classical Yee FDTD.This paper describes a new hybrid technique, combining the alternating direction implicit finite difference time domain (ADI-FDTD) method and the method of moments in the time domain (MoMTD) to analyze problems involving thin-wire antennas close to inhomogeneous dielectric bodies. The unconditionally stable ADI-FDTD formulation presents computational advantages over the explicit Yee FDTD scheme in cases that require a fine mesh to accurately model their electromagnetic characteristics. The hybrid procedure has been found stable in the examples analyzed so far, which was not always the case in the previous approach based on the classical Yee FDTD.

A UNIFIED LOOK AT BERENGER'S PML FOR GENERAL ANISOTROPIC MEDIA

The recently proposed general material-independent per- () fectly matched layer GMIPML and extended perfectly matched layer () EPML techniques sere to adapt general dielectric and magnetic anisotropic media. Perfect matching is achieed both by the former, based on a straight generalization of Berengers PML using a D and B formulation, and by the latter using an E and H formulation. In this paper, a general theory enclosing both formulations is proposed. 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 28:414 416, 2001.

A Resistively Loaded Thin-Wire Antenna for Mine Detection

This paper shows that, using genetic algorithms to calculate the resistive load distribution along a wire antenna, in order to optimize its broadband characteristics, it is possible to obtain better results in detecting land mines using a GPR, than when the antenna is loaded with the Wu–King resistive profile.

Uranyl complexes of α-carboxypolymethylenediaminetetra-acetic acids

Abstract The uranyl complexes of N,N,N′,N′-tetrakis(carboxymethyl)-2,3-diaminopropionic acid, N,N,N′,N′-tetrakis(carboxymethyl)diaminobutyric acid, N,N,N′,N′-tetrakis(carboxymethyl)ornithine and N,N,N′,N′-tetrakiscarboxymethyl)lysine have been studied by potentiometry, with computer evaluation of the titration data by the MINIQUAD program. Stability constants of the 1:1 and 2:1 metal:ligand chelates have been determined as well as the hydrolysis and polymerization constants at 25° in 0.1M potassium nitrate. Results are compared with those obtained for the uranyl complexes of the corresponding members of the series of the polymethylenediaminetetra-acetic acids.

Time-domain hybrid methods to solve complex electromagnetic problems

This communication describes the FDTD-FETDMoMTD and the ADI-FDTD/MoMTD time-domain hybrid techniques. They are applied to analyze complex electromagnetic problems such as those involving thin-wire antennas radiating in the presence of arbitrary objects. The methods combines the ability of the FDTD to deal with arbitrary material properties, the versatility of the FETD to accurately model curved geometries, that of the MoMTD to analyze thin-wire structures, or that of the ADIFDTD formulation of not imposing conditions on the duration of the temporal interval. Attention is paid to the algorithms that connects the different techniques. Representative numerical results are given and discussed