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Statistical Comparative Analyses of engineering Properties of Microwave and Conventionally Sintered Alumina

MRS Online Proceedings Library 1996年第1期430卷 453-458页

作者： K.R. Binger S.A. Freeman D.J. Grellinger R.F. Cooper J.H. Booske Department of Electrical and Computer Engineering University of Wisconsin - Madison Madison USA Material Science Program University of Wisconsin - Madison Madison USA Department of Material Science and Engineering University of Wisconsin - Madison Madison USA

Processing conditions such as temperature, soak time, and heating rate affect the final density of conventionally-sintered and microwave-sintered ceramics. Of additional importance is the question of whether microwave-sintered ceramics display intrinsically superior macroscopic engineering properties compared with conventionally-sintered control specimens. An analysis using the Yates algorithm indicates that the processing condition which has the largest impact on the density of the specimen is the heating method (microwave vs. conventional). The microwave-sintered specimens resulted in higher densities and higher fracture strengths. However, it was determined that the higher fracture strengths were due to the higher sintered densities rather than a significantly different microstructure.

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Fusion power plants-goals and technological challenges

Fusion power plants-goals and technological challenges

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Intersociety Conference on Energy Conversion engineering (IECEC)

作者： F. Najmabadi Department of Electrical & Computer Engineering and Fusion Energy Research Program University of California San Diego La Jolla CA USA

Fusion is one of a few future power sources with the potential to be both economically acceptable and have attractive safety and environmental characteristics. In addition fusion fuel is inexhaustible, readily available, and affordable. Fusion can be an important option in the energy mix for the future because of environmental, supply, and political difficulties associated with fossil fuels and present-day nuclear power. An overview of the technological requirements for fusion power plants is given and their economic, safety, and environmental features are explored. Conceptual design studies predict that fusion power plants will be capital intensive and will be used as central electric power station. The cost of electricity from these power stations is estimated be comparable to other sources of energy. In addition, by using "low-activation" materials and care in design, fusion safety and environmental advantages (with respect to consequences of accidents, waste-disposal, and air pollution, etc.) can be realized. These advantages of fusion will not, however, be achieved automatically and a significant science and technology development program will be required for their realization.

关键词： Power generation Power generation economics Economic forecasting Environmental economics Fuel economy Fossil fuels Costs Waste materials Air safety Air accidents

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A performance model of space-division ATM switches with input and output queueing

A performance model of space-division ATM switches with inpu...

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Annual Hawaii International Conference on System Sciences (HICSS)

作者： Guogen Zhang W.G. Bulgren V.L. Wallace Computer Science Department University of California Los Angeles Los Angeles CA USA Engineering Management Program University of Kansas Lawrence KS USA Department of Electrical Engineering and Computer Science University of Kansas Lawrence KS USA

An analytic model for the performance evaluation of space-division asynchronous transfer mode (ATM) switches is presented. This model assumes that the switch has a fixed capacity of m, where 1/spl les/m/spl les/N (N is the number of trunks). Other important parameters include arrival rate and buffer sizes. Numerical solutions for the maximum throughput, cell delay, and cell loss probability are given with simulation being utilized in order to validate the analytic model. For independent and identical Bernoulli arrivals, the study shows that the contention processes can be modeled as discrete M/D/m (FIFO or Random) queues, while input queues can be modeled by Geom/G/1 queues, and the output queues are G/sup [X]//D/1 queues. A closed-form approximation for cell delay when m>2 is given. The result shows that the performance of switches with a small capacity can approach that of output queueing. The model and result can be used for switch design analysis and higher layer performance models.

关键词： Asynchronous transfer mode Switches Performance analysis Fabrics Communication switching Queueing analysis Throughput Delay computer science Performance loss

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A nonstationary analysis of bandwidth access control schemes for heterogeneous traffic in B-ISDN

A nonstationary analysis of bandwidth access control schemes...

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IEEE Annual Joint Conference: INFOCOM, IEEE computer and Communications Societies

作者： Yi Qian D. Tipper D. Medhi Department of Electrical and Computer Engineering Clemson University Clemson SC USA Telecommunications Program Department of Information Science University of Pittsburgh Pittsburgh PA USA Department of Computer Networking University of Missouri Kansas City Kansas City MO USA

We present a comparative analysis of bandwidth access control schemes under nonstationary traffic conditions for heterogeneous circuit-mode traffic offered to a B-ISDN network link. A unified model for analysing the behavior of several bandwidth access control schemes is developed using a Markov process model with acceptance functions. Numerical techniques are used to solve the associated Chapman-Kolmogorov equations and determine the nonstationary behavior. Performance results are given for several common bandwidth access control schemes, namely: complete sharing, complete partitioning, partial sharing, classical trunk reservation, and the probabilistic reservation policy. It is shown that the use of the average arrival rate to estimate the average connection blocking rate may be an underestimate for a system with a time varying arrival process. Also, it is found that a nonstationarity in one traffic class arrival process can impact other stationary traffic classes and the degree of variability depends on the particular access control scheme.

关键词： Bandwidth Access control B-ISDN Traffic control Communication system traffic control Circuits Queueing analysis Markov processes Information analysis Cities and towns

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Measurement of absorption and scattering spectra with oblique incidence reflectometry

Measurement of absorption and scattering spectra with obliqu...

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Biomedical Optical Spectroscopy and Diagnostics, BOSD 1996

作者： Lin, Shao-Pow Wang, Lihong Jacques, Steven L. Tittel, Frank K. Department of Electrical and Computer Engineering Rice University P.O. Box 1892 HoustonTX77251 United States Laser Biology Research Laboratory University of Texas M.D. Anderson Cancer Center Box 17 1515 Holcombe Blvd. HoustonTX77030 United States Bioengineering Program Texas A&M University 234C Zachry Engineering Center College StationTX77843 United States

ISBN: (纸本)1557524270

Fiber optic oblique incidence reflectometry has been demonstrated to be a simple and accurate method for measuring the optical properties, μa and μs', of turbid media such as biological tissues [1,2]. After sampling the spatial distribution of diffuse reflectance of obliquely incident light, we can a) measure the shift in the center of diffuse reflectance, which is proportional to the diffusion coefficient of the medium (D), and b) fit the distribution to a diffusion theory model to determine the effective attenuation coefficient (μeff). μa and μs' can be calculated directly from these two parameters. This paper presents preliminary results that show that both absorption and reduced scattering spectra can be deduced from multi-spectral measurements of the relative diffuse reflectance profile of white light obliquely incident on tissue phantoms. © 1996 Optical Society of America.

关键词： Incident light

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Experimental observation of Coulomb staircase in asymmetric tunnel barrier system

Experimental observation of Coulomb staircase in asymmetric ...

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International Electron Devices Meeting (IEDM)

作者： Y. Matsumoto T. Hanajiri T. Toyabe T. Sugano Department of Electrical and Electronics Engineering Toyo University Kawagoe Saitama Japan Department of Information and Computer Science Toyo University Kawagoe Saitama Japan Frontier Research Program RIKEN Institute of Physical and Chemical Research Wako Saitama Japan

The advantages of single electron devices with asymmetrical tunnel barriers (ATBs), proposed by the authors, over conventional single electron devices with symmetrical tunnel barriers (STBs) are discussed by referring to the features of ATBs and the results of computer simulation of the performance of tunnel-junction-load SET logic and turnstile devices. Experimental observation of a Coulomb staircase and asymmetrical tunnel characteristics in ATBs fabricated with GaAs/AlGaAs heterostructures are also reported.

关键词： Single electron devices Temperature Circuits US Department of Transportation Tunneling Thermal resistance Capacitance computer science Chemical engineering computer simulation

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Room-temperature performance of double-fused 1.54 /spl mu/m vertical-cavity laser

Room-temperature performance of double-fused 1.54 /spl mu/m ...

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Indium Phosphide and Related Materials Conference

作者： D.I. Babic K. Streubel R.P. Mirin J. Piprek N.M. Margalit J.E. Bower E.L. Hu D.E. Mars L. Yang K. Carey Department of Electrical and Computer Engineering University of California Santa Barbara USA Department of Electronics Royal Institute of Technology Stockholm Sweden Materials Science Program University of Delaware Newark USA Hewlett Packard Laboratories Palo Alto CA USA

The progress in understanding wafer-fused vertical-cavity lasers and improvements in fabrication techniques have led to the realization of the first room-temperature continuous-wave operating 1.54-/spl mu/m vertical-cavity lasers. By demonstrating continuous-wave operation at room temperature using vertical-cavity lasers fabricated by two wafer fusion steps, we have shown that wafer fusion is a viable technique. The lasers comprise strain compensated InGaAsP quantum-well active layers sandwiched between two AlGaAs/GaAs quarter-wave mirrors. Characteristics discussed include cavity losses, the gain-current density relationship, and voltage-current characteristics.

关键词： Vertical cavity surface emitting lasers Mirrors Optical pulse generation Absorption Pulse measurements Quantum well lasers Doping Temperature Propagation losses Size measurement

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Performance Analysis of Service Transmission in the ATM Environment using a Distributed Simulator

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International Journal of Modelling & Simulation 1996年第1期16卷 30-30页

作者： Koutroubinas, S. Antonakopoulos, T. Stavroulopoulos, C. Makios, V. Laboratory of Electromagnetics Electrical Engineering Department University of Patras 26500 Patras Greece School of Electrical Engineering University of Patras Patras Greece European Economic Community Laboratory of Electromagnetics University of Patras Video Mail Services Technical Chamber of Greece Communications Group Electrical Engineering Department University of Patras Program Committee IEEE Intl. Workshop Rapid Syst. P. Commun. and Computer Societies IEEE Technical University Munich Germany Max Planck Inst. for Plasmaphisics Technical University Munich Germany Max Planck Inst. for Plasmaphisics Munich Germany Department of Electronics Carleton University Ottawa Ont. Canada Carleton University Electromagnetics Laboratory Electrical Engineering Department University of Patras Greece IEEE Canadian Association of Physicist German Physical Society VDE Greek Technical Chamber

This paper presents a distributed simulator for performance analysis of various applications in the asynchronous transfer mode (ATM) environment. The simulator is used to determine how the quality of a service, either synchronous or asynchronous, is affected when it is transmitted through an ATM network under various traffic conditions. The simulator has been implemented in a distributed Unix environment using network and operating system functions and simulates the three lower layers of B-ISDN. It has been based on the time-driven approach, and is modular and expandable because it uses standard operating system calls for adapting new applications and services to the simulator environment. The paper presents performance analysis results of constant and variable bit rate services, as well as experimental results on compressed and uncompressed image transmissions.

关键词： ATM B-ISDN Performance analysis Simulation

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Book reviews

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Minds and Machines 1996年第2期6卷 239-285页

作者： Abbott, Barbara Herskovits, Annette Peterson, Philip L. Mele, Alfred R. Cole, David J. Crevier, Daniel Pelletier, Francis Jeffry Berkeley, Istvan S. N. Kitts, Brendan J. Brown, Mike Paliouras, George Department of Linguistics and Languages Michigan State University East Lansing USA Department of Philosophy Michigan State University East Lansing USA Program in Applied Linguistics Boston University Boston USA Department of Philosophy Syracuse University Syracuse USA Department of Philosophy Davidson College Davidson USA Department of Philosophy University of Minnesota Duluth USA Department of Electrical Engineering École de Technologie Supérieure Université du Québec Montréal Canada Department of Philosophy University of Alberta Edmonton Canada Department of Computing Science University of Alberta Edmonton Canada Biological Computation Project University of Alberta Edmonton Canada Center for Complex Systems Brandeis University Waltham USA Department of Computer Science University of Manchester Manchester U.K.

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Performance of a muscle-like “leaky” pneumatic actuator powered by modulated air pulses

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Journal of Field Robotics 1996年第6期13卷

作者： Jan H. Cocatre-Zilgien Fred Delcomyn John M. Hart Department of Entomology University of Illinois Urbana IL 61801 Department of Entomology Neuroscience Program University of Illinois Urbana IL 61801 Department of Electrical and Computer Engineering University of Illinois Urbana IL 61801

There is current interest in the development of legged robotic devices inspired by biological walking systems. We have developed an actuator for this type of device that closely emulates the performance of muscle. The actuator is a “leaky” single-effect air cylinder controlled through a 3-way valve that either permits charging the cylinder with compressed air or opens it to the atmosphere. To emulate muscular activation with trains of identical nerve impulses that vary in frequency, we controlled the pressure in the cylinder through pulse frequency modulation. To allow a comparison between our cylinder and muscle, we evaluated the open loop performance of the cylinder and valve system in isometric (no motion) and linear isotonic (constant load) conditions. We demonstrate that this mode of activation of the cylinder makes its behavior quite close to that of muscle. Furthermore, our cylinder/valve system generated twice the tension developed by muscle of the same cross-sectional area, with half its power-to-weight ratio. © 1996 John Wiley & Sons, Inc.

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