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Raman Scattering and X-Ray Diffraction Studies of Gallium Nitride Films Grown on (100) Gallium Arsenide

MRS Online Proceedings Library 1994年第1期339卷 503-508页

作者： S. W. Brown S. C. Rand C.-H. Hong D. Pavlidis University of Michigan Applied Physics Program Ann Arbor USA Department of Electrical Engineering and Computer Science University of Michigan Solid State Electronics Laboratory Ann Arbor USA

Raman spectroscopy and x-ray diffraction are used to characterize Gallium Nitride (GaN) films grown on (100) Gallium Arsenide (GaAs) substrates. Reflection X-ray diffraction data from (200) planes of GaAs and cubic GaN are presented. The linewidth of the cubic GaN diffraction peak is shown to be a strong function of the growth temperature. Raman spectra are presented for a series of samples grown at different temperatures. Raman scattering is characterized by strong peaks at 560 cm-1 and at 736 cm-1, corresponding to TO and LO phonon modes of cubic GaN, respectively. An additional, unexplained feature at 768 cm-1 is clearly observed in Raman spectra of c-GaN samples grown at lower temperatures. The polarization dependence of the intensity of the GaN LO phonon mode is presented and compared with the GaAs LO phonon mode to establish the relative orientation of the c-GaN epitaxy on GaAs.

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Wavelength dependence of nanosecond pulsed laser ablation of atherosclerotic coronary artery 2

Wavelength dependence of nanosecond pulsed laser ablation of...

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Medical Applications of Lasers II 1994

作者： Yova, Dido M. Kassis, Kyriakos A. Mouroutis, Theodoros Kavantzas, Nikolaos Agapitos, Emanuel Koutsouris, Dimitrios Serafetinides, Alexander A. National Technical University of Athens Department of Electrical and Computer Engineering Laboratory of Biomedical Engineering and Applied Biophysics Athens15780 Greece Medical School Department of Pathology University of Athens Athens11527 Greece National Technical University of Athens Department of Physics Athens15780 Greece

ISBN: (纸本)9780819416605

Pulsed laser ablation of atheromatous arteries was studied at three wavelengths in the near ultraviolet, visible, and near infrared regions of the spectrum. The experiments were done with an Nd:YAG laser, 9 nsec pulse duration. The wavelength could be fixed at 1064 nm, 532 nm, or 355 nm through KDP crystals. Laser fluences ranged up to 80 J/cm2 and repetition rate was 8 Hz. Ablation fluence thresholds increased with wavelength from UV to the visible region and dropped again near (lambda) equals 1064 nm. Maximum ablation efficiency at 355 nm was measured to be 0.6 mg/J, three times higher than the corresponding value at either 532 or 1064 nm, which was approximately 0.20 mg/J. The results are in good correlation with the optical properties of cardiovascular tissue, assuming that the absorption coefficients are equal to (mu) a approximately equals 24 cm-1 at 355 nm, and (mu) a approximately equals 1.32 cm-1 at 532 or 1064 nm. Corresponding the scattering coefficients assumed to be equal to 8 cm-1 at 355 nm and 20 cm-1 at 532 and 1064 nm. Taking into consideration the composite nature of calcified lesions, the optical properties of cardiovascular tissues, and the different possibilities of the three wavelengths the choice of pulsed Nd:YAG laser with KDP crystals capability seems to be a good choice for angioplasty. © 1994 SPIE.

关键词： Optical properties

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On compacting test sets by addition and removal of test vectors

On compacting test sets by addition and removal of test vect...

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VLSI Test Symposium

作者： S. Kajihara I. Pomeranz K. Kinoshita S.M. Reddy Department of Applied Physics Osaka University Suita Japan Electrical and Computer Engineering Department University of Iowa Iowa IA USA

This paper presents a method of test compaction for stuck-at faults in combinational circuits, that complements previously proposed methods and allows further reduction in test set size in a cost-effective way. A given test set is compacted by generating additional test vectors. Each test vector added allows the removal of two or more test vectors from the existing test set, thus reducing its size. Experimental results for benchmark circuits demonstrate the effectiveness of the method.< >

关键词： Circuit testing Circuit faults Compaction Fault detection Computational modeling physics computing Cities and towns Very large scale integration Flip-flops Combinational circuits

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A unifying view of some training algorithms for multilayer perceptrons with FIR filter synapses

A unifying view of some training algorithms for multilayer p...

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IEEE Workshop on Neural Networks for Signal Processing

作者： A. Back E.A. Wan S. Lawrence Ah Chung Tsoi Department of Electrical and Computer Engineering University of Queensland Saint Lucia QLD Australia Department of Electrical Engineering and Applied Physics Oregon Graduate Institute of Science and Technology Portland OR USA

Concerns neural network architectures for modelling time-dependent signals. A number of algorithms have been published for multilayer perceptrons with synapses described by finite impulse response (FIR) and infinite impulse response (IIR) filters (the latter case is also known as locally recurrent globally feedforward networks). The derivations of these algorithms have used different approaches in calculating the gradients, and in this paper we present a short, but unifying account of how these different algorithms compare for the FIR case, both in derivation, and performance. A new algorithm is subsequently presented. In this paper, results are compared for the Mackey-Glass chaotic time series (1977) against a number of other methods including a standard multilayer perceptron, and a local approximation method.< >

关键词： Multilayer perceptrons Finite impulse response filter Neurons Neural networks Multi-layer neural network Nonhomogeneous media Digital filters Delay effects physics Approximation methods

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A unified model for predicting the electrical, mechanical and thermal characteristics of stranded overhead-line conductors

A unified model for predicting the electrical, mechanical an...

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Canadian Conference on electrical and computer engineering (CCECE)

作者： Filipovic-Gledja Morgan Findlay Department of Electrical and Computer Engineering McMaster University Hamilton ONT Canada Division of Applied Physics CSIRO Lindfield NSW Australia

Four separate models have been developed during the past thirty years to account for the electrical, mechanical and thermal aspects of the behavior of stranded overhead conductors. Each model contains a number of variables, and some of these variables are common to two or more of the models. Hence, the design of overhead line conductors is usually undertaken in a rather piecemeal fashion. This paper describes the unified model, which incorporates electromagnetic, mechanical, and radial and steady-state thermal models. An example is given of the design of an ACSR conductor.< >

关键词： Power transmission lines Power transmission mechanical factors Power cable thermal factors Aluminum power conductors Stranded conductors

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Ampacity of aerial bundled cables

Ampacity of aerial bundled cables

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Canadian Conference on electrical and computer engineering (CCECE)

作者： Morgan Power Research Laboratory Department of Electrical and Computer Engineering McMaster University Hamilton ONT Canada Division of Applied Physics CSIRO Lindfield Australia

Problems associated with the proximity of buildings and trees and the clashing of bare conductors have stimulated the world-wide trend towards the use of insulated conductors (cables) for the overhead distribution of electric power. An IEC Guide, Publication 287-2, proposes a method for determining the current-carrying capacity of a single core or cable in still air, but does not include multicore cables or cables in moving air. This paper summarises recent work on the heat transfer from single and multi-core cables in conditions of natural or forced convection. It is shown that certain assumptions in the IEC Guide are incorrect, and a method is proposed for determining the ampacity of overhead cables under various atmospheric conditions.< >

关键词： Power distribution lines Power cable thermal factors IEC Bundle conductors

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Structural Characterization of Nanocrystalline Mo and W Carbide and Nitride Catalysts Produced by Co 2 Laser Pyrolysis

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MRS Online Proceedings Library 1994年第1期368卷 69-74页

作者： Xiang-Xin Bi K. Das Chowdhury R. Ochoa W. T. Lee S. Bandow M. S. Dresselhaus P. C. Eklund Department of Electrical Engineering and Computer Science MIT Cambridge USA Department of Materials Science and Engineering MIT Cambridge USA Center for Applied Energy Research University of Kentucky Lexington USA Instrument Center Institute for Molecular Science Okazaki Japan Department of Physics MIT Cambridge USA

Using both XRD and HRTEM lattice imaging, we have shown that CO2 laser pyrolysis (LP) produces nanoscale transition metal carbide and nitride catalysts, including cubic Mo2C, Mo2N, and W2N, which possess highly crystalline structures in their as-synthesized form In contrast, LP-produced W2C in its hexagonal phase is disordered. Clear lattice expansion, induced by the small crystallite size of the nanoparticles has been observed for LP-produced Mo2C particles, which have a typical crystallite size of 2 nm. No carbon coating was observed in HRTEM for LP-produced Mo2C particles. Furthermore, Mo=N and Mo=C bonding in Mo2N and Mo2C, respectively, were identified by an XPS measurement, which also reveals the presence of a thin oxide layer formed on the particle surface during the passivation process. Finally, the average crystallite sizes determined from HRTEM and XRD are in good agreement, indicating that the line broadening observed in XRD is due to the small crystallite size of the nanoparticles.

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An Efficient Network Analyser Based on Linear Array Architecture

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Parallel Algorithms and Applications 1994年第1-2期2卷 139-147页

作者： Metallinos, S.N. Reisis, D.I. Stassinopoulos, G.I. Division of Computer Science Department of Electrical Engineering National Technical University of Athens Athens 15773 Zographou Greece Division of Computer Science Department of Electrical Engineering National Technical University of Athens Division of Applied Physics University of Athens Athens 15773 Zographou United States

In this paper we present an array based network analyzer for Broadband Integrated Services Digital Networks. The analyzer is laid as a linear array processor. We describe the implementation of the analyzer’s functions on the array processor. Apart the real-time application, the importance of this study becomes more apparent by the fact that, the resulting design can be implemented on configurable gate array and be attached to a microprocessor. Nevertheless, it is also possible to use the analyser array in combination with commercially available hardware to debug the network equipment in the development phase. © 1994, Taylor & Francis Group, LLC. All rights reserved.

关键词： Broadband networks Linear arrays Network analyzer String matching

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Adaptive multiuser detection in dispersive channels with array observations

Adaptive multiuser detection in dispersive channels with arr...

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Asilomar Conference on Signals, Systems & computers

作者： S.D. Gray J.C. Preisig D. Brady MITRE Corporation Bedford MA USA Department of Applied Ocean Physics and Engr Woods Hole Oceanographic Institution Woods Hole MA USA Department of Electrical and Computer Engineering Northeastern University Boston MA USA

We present a multiuser receiver which is capable of operating in time-variant channels with severe multipath. For each active user, the receiver consists of a multi-input, single-output filter followed by a single-user adaptive equalizer. The array processing filter is chosen to maximize an averaged performance metric which measures reduction in the interference from multiple asynchronous cochannel users and the reduction in intersymbol interference caused by time spreading of the transmitted signal. The single-user adaptive equalizer that follows the array processing filter eliminates the remaining intersymbol interference prior to hard symbol decisions. Receiver performance is demonstrated using data obtained from two acoustic channels where two cochannel users are transmitting in shallow-water at 18 and 30 nautical miles from the receiver array.< >

关键词： Multiuser detection Dispersion Adaptive arrays Intersymbol interference Adaptive filters Adaptive equalizers Array signal processing Time measurement Signal processing Acoustic arrays

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Microscopic spallation process and its potential role in laser-Tissue ablation 5

Microscopic spallation process and its potential role in las...

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Laser-Tissue Interaction V;and Ultraviolet Radiation Hazards 1994

作者： Dingus, R.S. Curran, D.R. Oraevsky, A.A. Jacques, S.L. Applied Theoretical Physics Division Los Alamos National Laboratory Los AlamosNM87545 United States Shk Physics and Geophysics Department Poulter Laboratory SRI International 333.Ravenswood Avenue Menlo ParkCA94025 United States Departrnent of Electrical and Computer Engineering Rice University HoustonTX77251 United States Laser Biology Research Lab UT/M. D. Anderson Cancer Center 1515 Holcombe Boulevard HoustonTX77030 United States

Research is being performed at several locations in consideration of learning the value of the front surface spallation process for tissue ablation. The experimental results are illustrating complicated features associated with the microscopic behavior of materials during the spallation process. This paper summarizes the current understanding of the spallation process in various materials and presents an interpretation of recent laser-Tissue interaction experiments. © 1994 Proceedings of SPIE - The International Society for Optical engineering. All rights reserved.

关键词： Tissue

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