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Title: Interaction of a Current-Carrying Coil with a Slot in a Conducting Plate: A Problem of Eddy-Current Nondestructive Evaluation
Abstract: Eddy-current methods are often used in the nondestructive evaluation of conducting structures. In the simplest procedure, a current-carrying coil is scanned over the conducting workpiece, inducing eddy-currents into the structure. If there is a defect (which could be a crack, or some other conducting anomaly), then the driving-point impedance of the coil changes slightly. The variation of the change in impedance with position of the probe coil is, in some sense, a signature of the defect.
Author(s): H. A. Sabbagh, L. D. Sabbagh
File Type: Journal Paper
Issue:Volume: 5      Number: 3      Year: 1990
Download Link:Click here to download PDF     File Size: 179 KB

Title: Calculating the Currents Induced on Wires Attached to Opposite Sides of a Thin Plate
Abstract: This configuration represents a class of electromagnetic radiation modeling problems that arise when attempting to predict the level of electromagnetic interference from table-top computing devices [1]. The method used to analyze this configuration must be able to model electrically small, thin plates with wires attached to opposite sides of the plate. The amplitude of the current at the base of the long wire is the parameter that must be calculated. This parameter was chosen because it is relatively easy to measure and because there is a high degree of correlation between this current and the radiated field strength.
Author(s): T.H. Hubing
File Type: Journal Paper
Issue:Volume: 5      Number: 3      Year: 1990
Download Link:Click here to download PDF     File Size: 190 KB

Title: Magnetic Diffusion in One Dimension
Abstract: Electromagnetic systems for which conduction currents are the only source of magnetic field can be characterized by Maxwell's equations using the magnetoquasistatic form of Ampere's law, where time varying D-vector is neglected over a surface of fixed identity [1]. The differential equation governing the magnetic field in these applications takes on the familiar parabolic form that often denotes a diffusion process.
Author(s): D.A. Torrey, P.L. Levin, R.Pl. Langevin
File Type: Journal Paper
Issue:Volume: 5      Number: 3      Year: 1990
Download Link:Click here to download PDF     File Size: 189 KB

Title: Induction Heating Problems for 2-D Vectgor Electromagnetic Code Validations
Abstract: Four problems in induction heating of lossy and non-lossy media are posed. The first consists of a simple two-region geometry which is amenable to analytic solution. Two possible boundary conditions are suggested, one of which requires the coupling of interior and exterior solutions (thus making a three region problem). The next two problems are "spin-offs" of the first where the geometry is modified in simple ways. We have found that while these alternate geometries are quite harmless in appearance, they nonetheless produce some very interesting and complex solutions which can be quite non-intuitive, especially when lossy and non-lossy media occur in combination. The final problem is an irregularly-shaped set of lossy regions placed inside a cylindrical induction heater. It is intended to be representative of induction heating of biological tissue as a cancer therapy. Some sample solutions are provided.
Author(s): K.D. Paulsen, D.R. Lynch
File Type: Journal Paper
Issue:Volume: 5      Number: 3      Year: 1990
Download Link:Click here to download PDF     File Size: 791 KB

Title: 5:1 Dipole Benchmark Case
Abstract: Incident field is resolved into azimuthal modes, m-0, 1, and 2 modes are used. Multipole sources are located at nine equally spaced points along the axis of the dipole, and the code solves for 166 source coefficients by matching the boundary condition in the least-squares sense. This solution is a comromise between accuracy and running time. The RMS error in the tangential E-field is 0.024 volts, which is 32 dB below the incident field, and 49 dB below the peak E-field normal to the surface. The scattered field is believed to be accurate to plus or minus 0.003 dB.
Author(s): A.C. Ludwig
File Type: Journal Paper
Issue:Volume: 5      Number: 3      Year: 1990
Download Link:Click here to download PDF     File Size: 1087 KB

Title: 6 Types of Canonical Problems Based on One Geometrical Model
Abstract: Six canonical problems are hereafter proposed, which represent different types of EMF problems with bodies in the size of wavelength. These are lossy and coated bodies radiated by a plane wave and conductive and lossy bodies radiated either by a concentrated or by a more distributed near field source. All cases are based on the same geometrically simple body of revolution. These canonical problems can therefore be used as benchmarks for the applicability and efficiency for both BOR as well as full 3D codes and only very simple input and output routines are required. The problems have been solved with the MMP3D program package. Tabular field values in sensitive points and an estimation of accuracy are given in the data sheet to each case. It was attempted to "optimize" the compromise between running time and accuracy.
Author(s): N. Kuster
File Type: Journal Paper
Issue:Volume: 5      Number: 3      Year: 1990
Download Link:Click here to download PDF     File Size: 1418 KB

Title: Scattering by a Right-Angled Penetrable Wedge: A Stable Hybrid Solution (TM Case)
Abstract: The problem of electromagnetic scattering by a dielectric wedge of interior wedge angle pi/2 has been solved by the hybrid technique combining the Method of Moments (MOM) and Geometrical Theory of Diffraction (GTD) for TM polarization. Pulse functions are used around the edge of the wedge and GTD fields are matched at a distance from the edge on both sides [1]. This substantially reduces the number of MOM current samples to be used. The variation of amplitude and phase of the surface current density has been determined for different values of parameters on both walls. The stability of the matrix solution has been tested. The behaviour of the numerical diffraction coefficient has been discussed. The solution for the scattering from a perfectly conducting wedge is obtained when the relative dielectric constant is equated to a large value (typically, 1000). The attractive feature of this method is that it calls for much less computer memory and also processing time.
Author(s): A.K. Bhattacharyya
File Type: Journal Paper
Issue:Volume: 5      Number: 3      Year: 1990
Download Link:Click here to download PDF     File Size: 463 KB

Title: Transient Scattering from a Perfectly Conducting Cube
Abstract: We consider the transient scattering of an electromagnetic pulse from a perfectly conducting unit cube. Solutions are obtained by means of time marching methods applied to both the Magnetic Field Integral Equation (MFIE) and the Electric Field Integral Equation (EFIE). The MFIE is solved using the method outlined in [1], with a finite difference discretisation of time derivative as described in [3] used to ensure stability of the time marching solutions.
Author(s): B.P. Rynne, P.D. Smith
File Type: Journal Paper
Issue:Volume: 5      Number: 3      Year: 1990
Download Link:Click here to download PDF     File Size: 256 KB

Title: Canonical Two-Dimensional Inverse Scattering Problem
Abstract: The following twodimensional electromagnetic TE- or TM-scattering problem is considered: A circular cylindrical scatterer with cross-section in the xy-plane and infinitely long in z-direction is embedded in vacuum and is composed of 3 circular cylindrical concentric layers (n=3) with radii…
Author(s): K.J. Langenberg, H. Chaloupka
File Type: Journal Paper
Issue:Volume: 5      Number: 3      Year: 1990
Download Link:Click here to download PDF     File Size: 90 KB