Electromagnetic scattering by a straight thin wire

The traveling-wave energy, which multiply diffracts on a straight thin wire, is represented as a sum of terms, each with a distinct physical meaning, that can be individually examined in the time domain. Expressions for each scattering mechanism on a straight thin wire are cast in the form of four basic electromagnetic wave concepts: diffraction, attachment, launch, and reflection. Using the basic mechanisms from P.Ya. Ufimtsev (1962), each of the scattering mechanisms is included into the total scattered field for the straight thin wire. Scattering as a function of angle and frequency is then compared to the moment-method solution. These analytic expressions are then extended to a lossy wire with a simple approximate modification using the propagation velocity on the wire as derived from the Sommerfeld wave on a straight lossy wire. Both the perfectly conducting and lossy wire solutions are compared to moment-method results, and excellent agreement is found. As is common with asymptotic solutions, when the electrical length of wire is smaller than 0.2 λ the results lose accuracy. The expressions modified to approximate the scattering for the lossy thin wire yield excellent agreement even for lossy wires where the wire radius is on the order of skin depth     

Here we go again--and again, and again!

Studies on selected cardiac patients have supported the association between diagonal ear-lobe crease (ELC) sign and coronary artery disease (CAD). The aim of this study was to assess the value of this sign as a predictor of the presence of CAD in the non-cardiac patient population, to see if any association exists between the two and to compare any association with other established risk factors. A significant association exists between ELC and a history of CAD, which is not solely attributable to the increased prevalence of the sign with increasing age. A higher correlation was found between CAD and ELC than between CAD and other risk factors. The sensitivity of the sign was 48%, the specificity 88%, and the positive predictive value 16%. In this population the finding of an ELC is of little clinical value.     

Scattering from three-dimensional cracks

Scattering from three-dimensional cracks is analyzed and measured. The crack geometry is modeled as a rectangular groove in a perfectly conducting surface. The groove forming the crack may be terminated with an open aperture creating a slit in the conducting surface or with an impedance boundary creating a trough. The scattered fields from a crack are analyzed with two types of scattering mechanisms: a component directly related to the scattered fields from a two-dimensional crack, and a traveling-wave component     

The determination of the propagation constant for the travelingwave in an infinite ground plane

The propagation constant for the travelling wave in a trough in an infinite ground plane is examined. The null-field integral is used to determine the electromagnetic field in the trough structure, and pulse basis functions give the distribution of the aperture fields. From this, the propagation constant is solved for, using the Newton-Raphson iterative scheme. Various sizes of geometries are examined. The far-field patterns are calculated and compared with other solutions, thereby validating the integral formulation which subsequently provided the propagation constant. Measurements of two trough geometries are performed to validate the theoretical results