A WH/GSMT-based full-wave analysis for planar transmission linesembedded in multilayered dielectric substrates

A new full-wave analysis method, referred to as the WH/GSMT, is developed to solve multilayered planar transmission line problems. First, the scattering of an obliquely incident parallel plate mode (PPM) by a PEC half plane embedded in a multilayered isotropic dielectric substrate within a PEC parallel plate region is analyzed via the Wiener-Hopf (WH) technique. The solution is then incorporated into the generalized scattering matrix technique (GSMT) to find the (complex) propagation constant and characteristic impedance of the planar transmission lines. The lateral power leakage is taken into account rigorously in the WH/GSMT. Numerical results including the microstrip line, conductor-backed slotline, coupled microstrip lines, and antipodal finlines are presented along with a discussion of the advantages/disadvantages of this method     

A bidirectional vector associative memory architecture with application to neural networks

A bidirectional architecture for associative memory (AM) capable of vector arithmetic operations is proposed. By introducing a pair of masking and tagging mechanisms, the conventional concepts of bit-operations and word-operations in AM have been generalized to row and column operations, respectively. The proposed architecture demonstrates a symmetrical functionality such that associative processing can be performed in both column and row directions. A set of built-in vector arithmetic and logic units (VALU) is designed to perform the basic vector operations, which offers O(max{n, m}) speed-up for vector operations over the conventional AM at an O(n + m) cost for realizing an n × m AM array. As an applicational example, an associative processing implementation for artificial neural networks is presented.     

An eccentrically coated asymmetric antenna applicator forintracavitary hyperthermia treatment of cancer

In this paper a model based on transmission line theory is used to predict the behavior of an eccentrically coated asymmetric antenna applicator for use in intracavitary hyperthermia. Theoretical results for the heating rate (HR) of the applicators are compared to experimental results. The experimental results were obtained at City of Hope National Medical Center using four different 915-MHz applicators, each with a different antenna size and eccentricity of the coating. A parameter delta is defined where delta < 1.0 is a thin wire approximation; delta is primarily a function of the eccentricity of the coating, the antenna diameter, and the coating diameter. It is found that when delta approximately less than 0.5, the theoretical model works well. In particular, it predicts the directivity due to the eccentricity of the coating. However, as this eccentricity is increased or as the antenna diameter is increased (delta approximately greater than 0.6), the model no longer accurately predicts directivity. Thus, the model that can be used to predict the HR profiles for an eccentrically coated asymmetric antenna only when delta approximately less than 0.5.     

High performance thermosets from a curable Diels–Alder polymer possessing benzoxazine groups in the main chain

A high‐molecular‐weight polymer (PBz) possessing reactive benzoxazine groups in the main chain was prepared through the Diels–Alder reaction using bis(3‐furfuryl‐3,4‐dihydro‐2H‐1,3‐benzoxazinyl)isopropane (BPA‐FBz) and bismaleimide (BMI) as monomers. The chemical structure of PBz is characterized with FTIR and ¹H NMR. The polymer PBz was further thermally reacted with a high performance polymer (PBz‐R) through the ring‐opening addition reaction of benzoxazine groups and the addition reaction of maleimide groups. PBz‐R exhibit a high glass transition temperature of 242 °C, good thermal stability, high flame retardancy, high mechanical strength, and great flexibility. Another crosslinked polymer (PBz‐BR) curing from the mixture of BPA‐FBz and BMI was also prepared. The properties of PBz‐BR are also attractive but, however, not as good as what observed with PBz‐R. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6509–6517, 2008     

Preparation of Enamines Catalyzed by Lewis Acids in the Presence of Solid Supports

A simple and effective preparation of enamines from bulky ketones and secondary amines has been achieved with the aid of Lewis acid on various solid supports. The optimized yields were higher than those obtained without the solid support. Factors affecting the yield and regioselectivity of these reactions were also studied. Evidence showed that the reaction proceeded simultaneously in solution and on the solid support.     

A Comparison of Digital Algorithms Used in Computing the Derivative of Left Ventricular Pressure

Five commonly used algorithms for digital differentiation are evaluated to determine how they perform in the presence of 8, 12, and 16 bit quantization noise. The algorithms are compared on the basis of rms error between a model derivative of the left ventricular pressure waveform and the approximate results of each algorithm. Algorithms based on interpolating techniques introduced the least amount of error when 16 bit data were used while algorithms based on least-squares data fit methods performed best on the less accurate 8 bit data. Some of the band-limiting characteristics of the algorithms are also discussed.     

On multiple objective programming problems with set functions

The convexity of a subset of a σ-algebra and the convexity of a set function on a convex subset are defined. Related properties are also examined. A Farkas-Minkowski theorem for set functions is then proved. These results are used to characterize properly efficient solutions for multiple objective programming problems with set functions by associated scalar problems.     

An Internal-Standard Method for Determination of Trace Impurities in Semiconductor Grade Silicon by Neutron Activation Analysis

An internal-standard method^1–4) has been applied for the determination of La, Sb, Au, Cr and Ag in silicon single-crystal by neutron activation analysis using cobalt as an internal-standard element. No chemical separation is required in this case and the precision obtained with the present method is satisfactory.     

The Flow Patterns and Wall Stresses in a Louvered‐Wall Moving Granular Filter Bed of Quartz Sand

The flow patterns and wall stresses in a two‐dimensional louvered moving granular filter bed of quartz sand were investigated. The flow pattern histories of granular solids in the filter bed were recorded using a digital camcorder and a pressure gauge for simultaneously measuring the normal stresses as well as shear stresses of the granular solids. The static wall stress distributions produced by the granular solids were measured, and agreed with a theoretical prediction formed using the differential slice and Runge‐Kutta (order four) methods. The variations in the dynamic wall stresses with time in a moving granular filter bed were obtained and the effect of the louver angle upon the flow patterns and wall stresses was also investigated. Employing the results obtained by stress measurements and image processing, the wall pressure pulsation phenomena in a moving granular filter bed may be further understood. The results reported here provide fundamental information for the design of moving granular filter beds to act as high‐temperature flue gas cleanup filters.