Azhar A. Rizvi

Corrections to "asymptotic solutions for the scattered fields of plane wave by a cylindrical obstacle buried in a dielectric half-space"

The purpose of this communication is to point out multiple errors in a previously published work and to present the erroneous parts of the work in an error free form. The typographical errors cause serious problems in the understanding of this interesting and stimulating work. It is also observed that the plots given in the published paper also contain errors. Some accurate plots are given for the same data as given in the pre- viously published work. The plots given in this communication agree very well with the corresponding method of moments results. Efforts are also made to extend previous work by evaluating the far-zone scattered field in the lower dielectric half-space. The problem of scattering of electromagnetic waves from an obstacle buried in dielectric half-space geometry has been under- taken by many authors. The work by Hongo and Hamamura 1 is most interesting and stimulating among all of these. Unfortu- nately, there are many typographical errors in the published paper. Some of these typographical errors cause serious problems in the understanding of their work. In this communication, their work is presented in an error-free form so that interested readers can easily understand Hongo and Hamamuras important work. Efforts are also made to extend their work to calculate the far-zone scat- tered field expression in region below the buried obstacle. For convenience, equations and figures in this communication are la- beled with same equation and figure numbers as given in work by Hongo and Hamamura and only erroneous parts of the paper are discussed. It is important to note that, field plots given in that paper 1 cannot be reproduced by either using erroneous far-zone field expression which is given in the published paper or far-zone field expression given in this communication. Therefore, it is concluded that the field plots given in the paper1 also contain errors. Far-zone field expression is plotted for the same data as given in the paper1 for the case of a perfectly conducting circular cylinder using the field expression given in this communication.

Low Contrast Circular Cylinder Buried in a Grounded Dielectric Layer

Scattering of obliquely incident, perpendicularly polarized plane wave by a dielectric circular cylinder, which is buried in a grounded dielectric layer has been considered. Dielectric cylinder has low dielectric contrast from the host grounded dielectric layer. The solution to the problem has been obtained by using a perturbation technique. Unperturbed fields are calculated inside the grounded dielectric layer, when it contains no inhomogeneity. Buried low contrast dielectric cylinder has been considered as perturbation in the dielectric layer. First order perturbed fields outside the grounded dielectric layer due to the dielectric cylinder are calculated in the far-zone.

Free-space wavelength-multiplexed optical scanner

A wavelength-multiplexed optical scanning scheme is proposed for deflecting a free-space optical beam by selection of the wavelength of the light incident on a wavelength-dispersive optical element. With fast tunable lasers or optical filters, this scanner features microsecond domain scan setting speeds and large- diameter apertures of several centimeters or more for subdegree angular scans. Analysis performed indicates an optimum scan range for a given diffraction order and grating period. Limitations include beam-spreading effects based on the varying scanner aperture sizes and the instantaneous information bandwidth of the data-carrying laser beam.

Scattering of Electromagnetic Waves from a Deeply Buried Circular Cylinder

Utilizing an approximate induced current distribution, the far-zone scattered fields from a perfectly conducting, circular cylinder, which is deeply buried in a dielectric half-space are evaluated. Interpretation of these scattered fields is presented in terms of ray optics. Important scattering parameters, i.e., far-zone field patterns, 3dB beamwidth, scattering width and total scattered power are evaluated. It is found that monostatic scattering width of circular cylinder, which is deeply buried in a dielectric half-space configuration, is related to monostatic scattering width of circular cylinder in a homogeneous medium via dielectric constant times the fourth power of Fresnel transmission coefficient. Behaviour of the total scattered power as a function of depth is found to be oscillatory around a mean value which is the total power scattered from a cylinder in homogeneous medium.

Electromagnetic Scattering from a Random Cylinder by Moments Method

A mathematical model of random cylinder is given to facilitate realization of a single random cylinder and study its electromagnetic scattering properties. The proposed model is very versatile as cylinders with cross sections varying from circular to rough (noise like) can be easily generated. Statistical properties of the radius of random cylinder are analytically determined. Electromagnetic field scattered from a smooth random cylinder is obtained using Moments Method. Ensemble averages of the scattered field in all directions and total scattering cross section are obtained. The optical theorem test shows that the solution obtained in this paper is better than the earlier proposed solutions.

Scattering from a Cylindrical Object Buried in a Geometry with Parallel Plane Interfaces

The present invention describes package units for medical purposes, in particular for receiving and/or storing sterilizable preparations for parenteral uses or dialysis solutions, comprising a container having at least one discharge spout and consisting of polyamide 66 or a laminate of polyamide 66 sheet and polyolefin sheet, the polyolefin sheet being disposed on the side facing the liquid to be stored and the sheet of polyamide 66 being disposed on the outside and the two sheets being bonded together in usual manner by means of an adhesive. The package units may further comprise an inner container or an outer container. The package unit is made in that a container having at least one discharge spout is made from polyamide 66 or the aforementioned laminate, said container filled with the liquid to be stored, then sealed and sterilized and possibly subsequently surrounded after cooling and drying with an outer container of polymeric material. Package units according to the invention may also be made in that from a polymeric material an inner container having at least one discharge spout is made, said container filled with the liquid to be stored, sealed, then surrounded with an outer container of polyamide 66 or a laminate of polyamide 66 sheet and polyolefin sheet, the polyolefin sheet being disposed at the side of the laminate facing the inner container and the sheet of polyamide 66 of the laminate representing the outer sheet, and thereafter sterilized.

Scattering of electromagnetic plane wave from a low contrast circular cylinder buried in non-integer dimensional Half Space

The objective of this paper is to study ‘scattering of electromagnetic waves from a dielectric circular cylinder buried in non-integer dimensional dielectric half-space’. To achieve this objective first two auxiliary problems are solved. The problem of reflection and transmission of electromagnetic waves for an interface between two dielectric mediums is studied first. The dimension normal to the interface is non-integer. Secondly, radiated fields from a buried current carrying line source in an non-integer dimensional half-space have been derived. By using the results of these auxiliary problems, scattering from a low contrast dielectric cylinder buried in non-integer dimensional half-space is studied using perturbation technique. Special cases are also considered when one of the two or both half-spaces are taken to be of integer dimension

Random Errors Modelling and Their Effects Upon RCS for an Artificial Object Containing Thin Long PEC Needles

The scattering of electromagnetic plane wave from an artiflcial object containing thin long perfectly conducting needles embedded in a homogeneous background material is characterized by parameters like positioning, orientations and lengths of needles. Firstly, models of random errors in positioning and orientation of perfectly conducting needles are proposed. Secondly, their efiects upon ensemble averaged RCS is analyzed. It is investigated theoretically that increasing error in positioning and orientation of conducting needles reduces ensemble averaged RCS.

Analysis of single server queueing systems with heavy tail distributions

Heavy tail distributions serve as better models in todays high speed communication networks, where the traffic is heterogeneous in nature. It has been asserted that these distributions do not have closed form for their Laplace transforms, hence classical queueing models can not be applied. A little is known about exact solutions of queueing systems with heavy tail distributions. In this paper it has been shown that the exact expressions for the Laplace transforms of some heavy tail distributions can be obtained with little attempt and these expressions offer exact analysis of queueing systems using classical queueing models. A simulator has been developed to verify the analytical results

Fractional Solutions for the Helmholtz's Equation in a Multilayered Geometry

A generalized fractional order integral operator is derived that relates the one and two dimensional Greens function for a geometry with parallel plane interfaces. It is found that order of the operator is independent of the geometry while lower limit and operational variable are functions of the geometry. Utilizing the general fractional order operator, it is possible to calculate the fractional solutions for Helmholtzs equation in a geometry with parallel plane interfaces. A generalized expression is proposed for far-zone fractional solution in a geometry with parallel plane interfaces.