The growth of high quality Si/GaAs superlattices on GaAs substrates using molecular beam epitaxy is described. A typical superlattice structure consisted of ten periods of thin (<5Å) layers of pseudomorphic si...
The growth of high quality Si/GaAs superlattices on GaAs substrates using molecular beam epitaxy is described. A typical superlattice structure consisted of ten periods of thin (<5Å) layers of pseudomorphic silicon alternating with thick GaAs layers; typical GaAs thicknesses range from 100Å to 1850Å. In situ reflection high energy electron diffraction analysis of the structures during growth showed the silicon layers developed a (3 × 1) reconstruction, while the GaAs exhibited a (4×)→(3×)→(3×1)→(2×4) reconstruction sequence. Both observations agree with prior studies of the growth of embedded silicon in GaAs/Si/GaAs heterostructures. X-ray diffraction using the (004) reflection showed sharp and intense satellite peaks (out to 22 orders in one case), indicating a high level of structural quality. Very good agreement has been obtained between observed diffraction patterns and those calculated via dynamical simulation.
This paper describes an effective way of reducing acoustic noise in a motor supplied from an adjustable speed PWM drive. The PWM patterns are selected to eliminate the most acoustically sensitive harmonics in the moto...
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A special neural network topology has been developed that compensates for friction in precision, position controlled mechanisms. A major contribution is that knowledge of the friction's form is used to determine t...
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A special neural network topology has been developed that compensates for friction in precision, position controlled mechanisms. A major contribution is that knowledge of the friction's form is used to determine the neural network's structure. This unique approach solves network sizing and weight initializing problems. The friction model is used for feedforward decoupling of friction-induced torque. The neural network also explicitly incorporates inertia compensation and linear feedback control. Another contribution is a demonstration of the trajectory dependence of static friction compensation with a discrete time controller. The authors include both the theoretical formulation and practical implementation results for the control of a commercial DC motor having a significant amount of static friction.< >
Electric poling at field intensities approaching the dielectric strength of the film is possible with corona poling. Polymeric thin films with large second-order nonlinearities can be created with this poling techniqu...
Electric poling at field intensities approaching the dielectric strength of the film is possible with corona poling. Polymeric thin films with large second-order nonlinearities can be created with this poling technique. In this paper, the corona poling of nonlinear polymeric films at elevated temperatures, processing, characterization and possible ultrashort-pulse applications are reviewed. An experimental technique is presented to measure the electric field during poling of the nonlinear polymeric film. The characterization of orientational order in corona-poled nonlinear polymeric films and the effects associated with the large electric field during poling are discussed. Poled polymeric thin films are uniquely suited for second-order nonlinear optical applications of ultrashort pulses (< 50 fsec) since minimal pulse spreading occurs. The sum-frequency ultrashort-pulse application of nonlinear polymeric thin films and limitations of the thin polymeric films are discussed. Experimental results are presented of a side-chain nonlinear polymer that is ideally suited for ultrashort-pulse applications.
Reports of enhanced sintering rates associated with microwave heating may be due to nonthermal lattice fluctuation statistics. Recent theoretical analyses reviewed in this paper confirm the feasibility of this phenome...
Reports of enhanced sintering rates associated with microwave heating may be due to nonthermal lattice fluctuation statistics. Recent theoretical analyses reviewed in this paper confirm the feasibility of this phenomenon for a wide variety of situations involving very different microwave absorption mechanisms. For materials with weak microwave absorption coefficients, the effect is expected to be uniformly distributed throughout the volume. For strongly absorbing materials, however, the effect is expected to be concentrated near the material surface, with a characteristic exponential penetration depth of Lnt ∼ 10 − 100 μm. An “observable” nonthermal effect depends on the relative magnitude of the microwave electric field strength ¦E¦ and the lattice ion energy relaxation rate γ with the most pronounced effects occurring for larger values of ¦E¦ and smaller values of γ.
Family caregivers of dementia patients experience varying levels of burden (or stress) associated with care giving tasks. Although this burden may lead to negative health effects for caregivers, very few studies have ...
An automated imaging system is described that determines fragment numbers, areas, and size classes of microscopic charcoal in pollen preparations. Charcoal counts made with the scanner are similar to counts made using...
Polar solvents, including dimethylformamide (DMF), have been investigated as anticancer drugs. Their potential usefulness is constrained by hepatotoxic effects. The ability to enhance drug cytotoxicity with ultrasound...
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This paper proposes a new ID-based cryptographic scheme for implementing public-key cryptosystems and signatures. Instead of generating and publishing a public key for each user, the ID-based scheme permits each user ...
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作者：
Iskander, M.F.CAEME Director
Electrical Engineering Department University of Utah Salt Lake City Utah 84112 Dr. Iskander edited two special issues of theJournal of Microwave Power
one on “Electromagnetics and Energy Applications” March 1983 and the other on “Electromagnetic Techniques in Medical Diagnosis and Imaging” September 1983. He authored one book onElectromagnetic Fields and Waves published by Prentice Hall in 1992 he edited theCAEME Software Book
Vol. I 1991 and he coedited a third book onMicrowave Processing of Materials
published by the Materials Research Society in 1991. The holder of seven patents he has contributed 16 chapters to eight research books published more than 90 papers in technical journals and made numerous presentations in technical conferences. In 1983 he received the College of Engineering Outstanding Teaching Award and the College Patent Award for creative innovative and practical invention. In 1984 he was selected by the Utah Section of the IEEE as Engineer of the Year. In 1984 he received the Outstanding Paper Award from the International Microwave Power Institute and in 1985 he received the Curtis W. McGraw ASEE National Research Award for outstanding early achievements by a university faculty member. In 1991 he received the ASEE George Westinghouse National Award for innovation in engineering education. In 1986 Dr. Iskander established the Engineering Clinic Program in the College of Engineering at the University of Utah. Since then the program has attracted more than 45 research projects from 18 companies throughout the United States. He is also the director of the NSF/IEEE Center for Computer Applications in Electromagnetics Education (CAEME). He co-organized symposia on “Microwave Processing of Materials” held in conjunction with Materials Research Society meetings in the Springs of 1990 and 1992 in San Francisco. He also organized several workshops and special sessions in conjunction with IEEE symposia. Dr. Iskander is the editor of the journalComputer Applications i
The National Science Foundation/Institute of electrical and Electronic Engineers (NSF/IEEE) Center for computer Applications in Electromagnetic (EM) Education (CAEME) was funded in early 1990 by the National Science F...
The National Science Foundation/Institute of electrical and Electronic Engineers (NSF/IEEE) Center for computer Applications in Electromagnetic (EM) Education (CAEME) was funded in early 1990 by the National Science Foundation to stimulate and accelerate the use of computers and software tools in EM education. The Center is managed by the Executive Office of IEEE on behalf of the Antennas and Propagation Society. This organizational structure provided avenues for broad participation by universities, professional societies, and corporations in the Center's activities. In two years of operation, CAEME has organized several workshops and special sessions in international meetings, published its first software book, prepared a lesson on “Electromagnetic Waves” using interactive video, and raised over $ 130,000 from university membership, participating societies, and corporate sponsors. This article summarizes CAEME activities, outlines its organizational structure, and briefly describes the contents of its first software book. Future developments are discussed and avenues for participation are outlined.
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