Design of a wideband microstrip antenna and the use of artificial neural networks in parameter calculation

This paper deals with the design of a multi-slot hole-coupled microstrip antenna on a substrate of 2 mm thickness that gives multi-frequency (wideband) characteristics. The Method of Moments (MoM)-based IE3D software was used to simulate the results for return loss, VSWR, the Smith chart, and the radiation patterns. A tunnel-based artificial neural network (ANN) was also developed to calculate the radiation patterns of the antenna. The radiation patterns were measured experimentally at 10.5 GHz and 12 GHz. The experimental results were in good agreement with the simulated results from IE3D and those of the artificial neural network. A new method of using a genetic algorithm (GA) in an artificial neural network is also discussed. This new method was used to calculate the resonant frequency of a single-shorting-post microstrip antenna. The resonant frequency calculated using the genetic-algorithm-coupled artificial neural network was compared with the analytical and experimental results. The results obtained were in very good agreement with the experimental results.     

Terahertz characterisation of building materials

To obtain realistic models for propagation channels in future pico-cellular indoor terahertz communication systems it is necessary to know the reflective properties of building materials found in a typical office environment. The angular dependent reflection coefficients of different building materials were determined using terahertz time-domain spectroscopy in transmission geometry and Fresnel's equations. This approach is more efficient than a set of measurements in reflection geometry for different angles. Verification of the method with a set of such reflection measurements shows an excellent agreement.     

An efficient nonlinear circuit simulation technique

This paper proposes a novel method for the analysis and simulation of integrated circuits (ICs) with the potential to greatly shorten the IC design cycle. The circuits are assumed to be subjected to input signals that have widely separated rates of variation, e.g., in communication systems, an RF carrier modulated by a low-frequency information signal. The proposed technique involves two stages. Initially, a particular order result for the circuit response is obtained using a multiresolution collocation scheme involving cubic spline wavelet decomposition. A more accurate solution is then obtained by adding another layer to the wavelet series approximation. However, the novel technique presented here enables the reuse of results acquired in the first stage to obtain the second-stage result. Therefore, vast gains in efficiency are obtained. Furthermore, a nonlinear model-order reduction technique can readily be used in both stages making the calculations even more efficient. Results will highlight the efficacy of the proposed approach     

Learning through multimedia

The creation of multimedia composition tools for young learners is addressed. The factors to consider in designing composing tools are discussed. Such a set of tools, called the Multimedia Works software environment, is described. It consists of three programs: Media Space, a multimedia database and research program; Multimedia Works Composer, a storyboarding and presentation program; and Video Light Table, a direct manipulation video-clip editor. The use of student participation in developing the tools is also described. Some problems that are being worked on are examined     

A logical approach to program analysis

This paper describesMicroScope, a framework for developing analysis tools for Lisp programs. MicroScope uses a knowledge-intensive approach for program representation and analysis. The analysis tools share a common object oriented program database, and a common Prolog inference engine. The use of Prolog and a declarative representation for programs permits sharing of information, and provides high bandwidth communication between diverse analysis tools. It also supports program specification and debugging activities in the same framework. Extensions to Prolog to support analysis are described, and two tools, theCritic and theExpector, are presented.This work supported in part by Hewlett-Packard Company, the National Science foundation Under Grant Number MCS81-21750 and the Defense Advanced Research Projects Agency under contract number DAAK11-84-K-0017.     

A cathode readout gas sampling calorimeter with conductive plastic tubes

We constructed and tested a prototype gas sampling electromagnetic calorimeter of the Pb-proportional tube sandwich type. The calorimeter uses conductive plastic tubes and cathode pad readout with a tower structure which resulted in reasonable energy and spatial resolutions for electrons in the momentum range 0.5–4.0 GeV/c; $\text{σ}{}_{\mathrm{E}}\text{E =}\text{21\%}\text{(E(}\text{GeV}\text{)}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{, σ}{}_{\mathrm{x}}\text{= 6}\text{mm}\text{(at 3 GeV}$/c). This paper describes the test and the performance studied under various conditions.     

Analytical pyrolysis as a tool for the study of plastic coals

The technique of analytical pyrolysis has been used to characterize 40 similar mid-rank western Kentucky coals of widely differing ASTM Gieseler plasticity. Certain pyrolysis/g.c. variables were shown to correlate well with both ASTM Gieseler and isothermal plasticity. Highly plastic coals were shown to exhibit certain characteristic peaks in the 450 °C pyrogram which were absent in the pyrogram of the non-plastic coals. Two coals, representing the two extremes in plasticity, were selected for further study. After extraction with solvents such as DMF the characteristic peaks were absent in the 450 °C pyrogram of the extraction residue of the highly plastic coal. These peaks were also shown to decrease with increasing severity of air oxidation of the plastic coal. This technique appears to be a useful tool for the analysis of mid-rank plastic coals and supports the view that the substances contained in the bitumen fraction of these coals are involved in the development of the plastic state.     

Acrylonitrile-based copolymers: Synthesis,characterization, and formation of ultrafiltration membranes utilized for the immobilization of proteins

Various high molecular weight copolymers of acrylonitrile and a vinyl comonomer containing an aryl amine, a pyridine, or an aliphatic hydroxyl group were synthesized via slurry polymerization techniques so as to contain from 1 to 15 mol % functional comonomer. The comonomer content was quantitated by ultraviolet absorbance, base titration of acid polymer salts, and/or relative chemical reactivity with trichloro-s-triazine. Thin films were cast from copolymer solutions, coagulated into unsupported ultrafiltration membrances, and characterized with respect to both water permeability and pore size distribution. Analysis by size exclusion chromatography of the membrane permeate of a pool of dextran fractions yielded a continuous distribution curve for membrane pore size over the range 1.5 to 70 nm. The ultrafiltration membranes were used for protein immobilization after appropriate chemical activation. The three distinct types of functional copolymers gave comparable results for α-chymotrypsin, with protein weight loadings of 6–12% and 40–65% retention of enzymatic specific activity.     

Low backmixing in multistage agitated contactors used as reactors

The objective of the study was to test the validity of an available backmix correlation in the low backmix regime required by multistage agitated contactors used as reactors. The correlation was found to be inapplicable, and new equation forms were developed to fit the new experimental data. Keys to low backmix rates are a small annular area around the shaft compared to the column cross-sectional area and an extended annular path length.