检索结果-内蒙古大学图书馆

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena 1991年第1期9卷 95-110页

作者： M. Tabib‐Azar M. N. Abedin Agostino Abbate P. Das Electrical Engineering and Applied Physics Department Case Western Reserve University Cleveland Ohio 44106 NASA Langley Research Center Nondestructive Measurement Science Branch Hampton Virginia 23665 Electrical Computer and Systems Engineering Department Rensselaer Polytechnic Institute Troy New York 12180‐3950

During the past 20–25 years, the nondestructive surface acoustic wave (SAW) measurement technique has been developed and used to characterize the electrical properties of semiconductor materials and devices. Important semiconductor parameters such as carrier density, type and mobility, interface and fixed oxide charge densities, deep‐level cross section and activation energy, and excess carrier generation and recombination lifetimes are all determined using SAW. In the majority of these experiments, separate medium structure is used where SAW is generated at the surface of a piezoelectric substrate like LiNbO3. SAW in the piezoelectric materials is accompanied by a decaying electric field which interacts with the free carriers of a semiconductor placed nearby. The spatial resolution that is usually achieved in these measurements is on the order of the SAW wavelength or the extrinsic Debye length, whichever is shorter. Variety of semiconductors are characterized using SAW including: silicon, GaAs, AlxGa1−xAs, InAs, GaP, HgxCd1−xTe, CdTe, InP, CdS, and InAs. More recently, high Tc ceramic superconductors have also been studied. The most important aspect of the SAW technique is that it is nondestructive and it has very high sensitivity in studying high resistivity materials. Here, we present a review of the SAW technique discussing its application in quantitative characterization of semiconductor materials and devices.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Operation of harmonic side-drive micromotors studied through gear ratio measurements

Operation of harmonic side-drive micromotors studied through...

引用

International Conference on Solid State Sensors and Actuators (TRANSDUCERS)

作者： M. Mehregany S.M. Phillips E.T. Hsu J.H. Lang Electronics Design Center Department of Electrical Engineering & Applied Physics Case Western Reserve University Cleveland OH USA Laboratory for Electromagnetic & Electronic Systems Department of Electrical Engineering & Computer Science Massachusetts Institute of Technology Cambridge MA USA

The detailed operation of variable capacitance harmonic (or wobble) side-drive micromotors was studied through gear ratio measurements. The gear ratio of the wobble micromotor is affected by wear in the bearing and by rotor slip. Rotor slip is a function of motive torque magnitude, excitation angle, and friction torques. The gear ratio of a wobble micromotor can be expressed as a constant term plus a term that accounts for rotor slip. The constant term is the nominal gear ratio which is equal to the bearing radius divided by the bearing clearance. The rotor slip term is directly proportional to the bushing friction torque and inversely proportional to the square of the excitation voltage. Micromotor operation in air as opposed to nitrogen demonstrates a significantly larger bushing friction torque.< >

关键词： Micromotors Gears Friction Insulators Rotors Contacts Electromagnetic measurements Torque Nitrogen Electric variables measurement

来源：评论

学校读者我要写书评

暂无评论

Raman Scattering in M x C 60 Films (M=K. Rb, Cs;x-0, 3.6)

引用

MRS Online Proceedings Library 1991年第1期247卷 373-378页

作者： Kai-An Wang Ping Zhou Ying Wang J. M. Holden Song-Mn Ren G. T. Hager H. F. Ni P. C. Eklund G. Dresselhaus M. S. Dresselhaus Department of Physics and Astronomy University of Kentucky Lexington USA Center for Applied Energy Research University of Kentucky Lexington USA Francis Bitter National Magnet Laboratory Massachusetts Institute of Technology Cambridge USA Department of Electrical Engineering and Computer Science and Department of Physics Massachusetts Institute of Technology Cambridge USA

The Raman-active modes of solid films of MxC60 (x-0, 6; M=K, Rb, Cs) and K3C60 have been studied experimentally. The mode-activity is dominated by intraball interactions, and the effect of the M + ions on the C60 spectrum is observed to be almost insensitive to the radius or mass of the alkali metal. Tangential modes of solid C60 are observed to soften in M660 by -60 cm-1, which can be attributed to a charge-transfer-induced elongation of the intraball bond lengths, similar to that observed in graphite intercalation compounds. Conversely, the radial modes are found to upshift slightly, indicating that a competing mechanism counteracts the effect of the bond elongation. For K3C60, six Raman lines have been observed in which the lowest frequency mode exhibits a Breit-Wigner-Fano lineshape, indicating a coupling between the lowest frequency Hq-derived intramolecular modes of C60 and a broad Raman-active continuum with the same symmetry lying lower in frequency.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Characterization of semiconductor materials and devices using acoustoelectric voltage measurement

引用

Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics 1991年第1期9卷 95-110页

作者： Tabib-Azar, M. Abedin, M.N. Abbate, Agostino Das, P. Electrical Engineering and Applied Physics Department Case Western Reserve University Cleveland OH 44106 United States NASA Langley Research Center Nondestructive Measurement Science Branch Hampton VA 23665 United States Electrical Computer and Systems Engineering Department Rensselaer Polytechnic Institute Troy NY 12180-3950 United States

During the past 20-25 years, the nondestructive surface acoustic wave (SAW) measurement technique has been developed and used to characterize the electrical properties of semiconductor materials and devices. Important semiconductor parameters such as carrier density, type and mobility, interface and fixed oxide charge densities, deep-level cross section and activation energy, and excess carrier generation and recombination lifetimes are all determined using SAW. In the majority of these experiments, separate medium structure is used where SAW is generated at the surface of a piezoelectric substrate like LiNbO3 SAW in the piezoelectric materials is accompanied by a decaying electric field which interacts with the free carriers of a semiconductor placed nearby. The spatial resolution that is usually achieved in these measurements is on the order of the SAW wavelength or the extrinsic Debye length, whichever is shorter. Variety of semiconductors are characterized using SA W including: silicon, GaAs, Alx Ga1xAs, InAs, GaP, Hgx Cd1xTe, CdTe, InP, CdS, and InAs. More recently, high Tc ceramic superconductors have also been studied. The most important aspect of the SAW technique is that it is nondestructive and it has very high sensitivity in studying high resistivity materials. Here, we present a review of the SAW technique discussing its application in quantitative characterization of semiconductor materials and devices. © 1991 American Vacuum Society.

关键词： Indium arsenide

来源：评论

学校读者我要写书评

暂无评论

A neural network approach to broadcasting in multihop packet radio networks

A neural network approach to broadcasting in multihop packet...

引用

International Joint Conference on Neural Networks (IJCNN)

作者： N. Funabiki Y. Takefuji K.C. Lee Y.B. Cho T. Kurokawa H. Aiso Department of Electrical Engineering and Applied Physics Case Western Reserve University Cleveland OH USA Systems Engineering Division Sumitomo Metal Industries Limited Japan Department of Computer Science National Defense Academy Yokosuka Kanagawa Japan School of Environmental Information Keio University Fujisawa Kanagawa Japan

A neural network model for broadcasting scheduling in multihop packet radio networks is presented. The problem of broadcast scheduling with a minimum number of time slots is NP-complete. The proposed neural network model finds a broadcasting schedule with a minimal number of time slots, and requires n processing elements for an n-node radio network. Fifteen different radio networks were examined where the neural network model found an m-time-slot solution in O(m) time with n processors.< >

关键词： Neural networks Radio broadcasting Intelligent networks Spread spectrum communication Packet radio networks Radio network Job shop scheduling Mobile communication Processor scheduling Process control

来源：评论

学校读者我要写书评

暂无评论

Single-crystal structural studies of metal–dichloride graphite intercalation compounds

引用

Philosophical Magazine B 1991年第2期64卷

作者： J. S. Speck J. T. Nicholls B. J. Wuensch J. M. Delgado M. S. Dresselhaus H. Miyazak Department of Materials Science and Engineering Department of Physics and Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 USA Materials Department University of California Santa Barbara CA 93106 USA Department of Materials Science and Engineering Department of Physics and Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 USA Cambridge University Cavendish Laboratory Madingley Road Cambridge CB3 0HE UK Department of Materials Science and Engineering Department of Physics and Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 USA Universidad de Los Andes Facultad de Ciencias Departmento de Quimica Merida 5101 Venezuela Department of Materials Science and Engineering Department of Physics and Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 USA Department of Materials Science and Engineering Department of Physics and Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 USA Department of Materials Science and Engineering Department of Physics and Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 USA Department of Applied Physics Tohoku University Sendai Japan

The crystal structures of CoCl2-, MnCl2-, NiCl2-, and CuCl2-graphite intercalation compounds (GICs) have been studied with single crystal X-ray diffraction methods. The first three intercalates maintain their pristine in-plane CdCl2structure after *** intercalate layers in stage 1 CoCl2-, MnCl2-, NiCl2-GICs stack in an ordered αβTγαβTγ rhombohedral sequence. Additionally, the carbon layers in stage 1 CoCl2-GIC stack in an ordered ABC rhombohedral sequence. For CoCl2-, MnCl2-, and NiCl2,-GICs the intercalate and carbon in-plane lattices exhibit rotational epitaxy. The epitaxy angle is either near 0° or 30°, depending on the intercalate. Current models for rotational epitaxy do not explain the observed rotation angles. The CuCl2layers have the periodicity of a centred rectangular net and stack, in the stage 1 GIC, in an ordered αβTαβTαβT sequence. The intercalate in stage 1 CuCl2-GIC forms a metrically face centred orthorhombic lattice; however, the symmetry of the intercalate structure is monoclinic. The intercalate interlayer interaction is attenuated by the intervening carbon layers, so that the stacking of the intercalate layers in all of the stage 2 compounds is uncorrelated.

关键词：

来源：评论

学校读者我要写书评

暂无评论

MAGNETOHYDRODYNAMIC SUBMARINE PROPULSION SYSTEMS

引用

NAVAL ENGINEERS JOURNAL 1991年第3期103卷 141-157页

作者： SWALLOM, DW SADOVNIK, I GIBBS, JS GUROL, H NGUYEN, LV VANDENBERGH, HH Daniel W. Swallomis the director of military power systems at Avco Research Laboratory Inc. a subsidiary of Textron Inc. in Everett Mass. Dr. Swallom received his B.S. M.S. and Ph.D. degrees in mechanical engineering from the University of Iowa Iowa City Iowa in 1969 1970 and 1972 respectively. He has authored numerous papers in the areas of power propulsion and plasma physics and currently is a member of the Aerospace Power Systems Technical Committee of the AIAA. Dr. Swallom has directed various programs for the development of advanced power generation systems lightweight power conditioning systems and advanced propulsion systems for marine applications. His previous experience includes work with Odin International Corporation Maxwell Laboratories Inc. Argonne National Laboratory and the Air Force Aero Propulsion Laboratory. Currently Dr. Swallom is directing the technical efforts to apply magnetohydrodynamic principles to a variety of propulsion and power applications for various marine vehicles and power system requirements respectively. Isaac Sadovnikis a principal research engineer in the Energy Technology Office at Avco Research Laboratory Inc. a subsidiary of Textron Inc. He received his B.S. in engineering (1974) B.S. in physics (1975) M.S. in aeronautics and astronautics (1976) and Ph.D. in physics of fluids (1981) at the Massachusetts Institute of Technology. Dr. Sadovnik has been involved in research work funded by DARPA concerning the use of magnetohydrodynamics for underwater propulsion. He has built theoretical models that predict the hydrodynamic behavior of seawater flow through magnetohydrodynamic ducts and their interaction with the rest of the vehicle (thrust and drag produced). In addition Dr. Sadovnik has been involved in research investigations geared toward the NASP program concerning the use of magnetohydrodynamic combustion-driven accelerator channels. Prior to joining Avco Dr. Sadovnik was a research assistant at MIT where he conducted experimental and

Magnetohydrodynamic propulsion systems for submarines offer several significant advantages over conventional propeller propulsion systems. These advantages include the potential for greater stealth characteristics, increased maneuverability, enhanced survivability, elimination of cavitation limits, greater payload capability, and the addition of a significant emergency propulsion system. These advantages can be obtained with a magnetohydrodynamic propulsion system that is neutrally bouyant and can operate with the existing submarine propulsion system power plant. A thorough investigation of magnetohydrodynamic propulsion systems for submarine applications has been completed. During the investigation, a number of geometric configurations were examined. Each of these configurations and mounting concepts was optimized for maximum performance for a generic attack class submarine. The optimization considered each thruster individually by determining the optimum operating characteristics for each one and accepting only those thrusters that result in a neutrally buoyant propulsion system. The results of this detailed optimization study show that the segmented, annular thruster is the concept with the highest performance levels and greatest efficiency and offers the greatest potential for a practical magnetohydrodynamic propulsion system for attack class submarines. The optimization study results were used to develop a specific point design for a segmented, annular magnetohydrodynamic thruster for an attack class submarine. The design point case has shown that this thruster may be able to provide the necessary thrust to propel an attack class submarine at the required velocity with the potential for a substantial acoustic signature reduction within the constraints of the existing submarine power plant and the maintenance of neutral buoyancy. This innovative magnetohydrodynamic propulsion system offers an approach for submarine propulsion that can be an important contributio

关键词： Ship Propulsion

来源：评论

学校读者我要写书评

暂无评论

Identification in H∞: the continuous-time case

Identification in H∞: the continuous-time case

引用

American Control Conference (ACC)

作者： A. J. Helmicki C. A. Jacobson C. N. Nett Georgia Institute of Technology School of Applied and Engineering Physics Atlanta GA USA Department of Electrical and Computer Engineering Northeastern University Boston MA USA

In this paper recent results obtained by the authors for control-oriented identification of stable, discrete-time systems are extended to stable, strictly proper, continuous-time systems. The required a priori information consists of a lower bound on the relative stability, an upper bound on the "steady state" gain, and an upper bound on the rate of "roll-off" of the unknown system. The required experimental information consists of a finite number of possibly corrupt frequency response estimates for the unknown system. Given this information an algorithm is developed which yields both a continuous-time identified model and an explicit bound on the H ∞ norm of the model error. Like its discrete-time counterpart, this algorithm is a nonlinear function of the data used and is robustly convergent with respect to the a priori system information given.

关键词： Upper bound System identification Frequency estimation Control systems Stability Steady-state Frequency response Jacobian matrices Robustness Robust control

来源：评论

学校读者我要写书评

暂无评论

computer-SYSTEM ARCHITECTURE CONCEPTS FOR FUTURE COMBAT SYSTEMS

引用

NAVAL ENGINEERS JOURNAL 1990年第3期102卷 43-62页

作者： ZITZMAN, LH FALATKO, SM PAPACH, JL Dr. Lewis H. Zitzman:is the group supervisor of the Advanced Systems Design Group Fleet Systems Department The Johns Hopkins University Applied Physics Laboratory (JHU/APL). He has been employed at JHU/APL since 1972 performing applied research in computer science and in investigating and applying advanced computer technologies to Navy shipboard systems. He is currently chairman of Aegis Computer Architecture Data Bus and Fiber Optics Working Group from which many concepts for this paper were generated. Dr. Zitzman received his B.S. degree in physics from Brigham Young University in 1963 and his M.S. and Ph.D. degrees in physics from the University of Illinois in 1967 and 1972 respectively. Stephen M. Falatko:was a senior engineering analyst in the Combat Systems Engineering Department Comptek Research Incorporated for the majority of this effort. He is currently employed at ManTech Services Corporation. During his eight-year career first at The Johns Hopkins University Applied Physics Laboratory and currently with ManTech Mr. Falatko's work has centered around the development of requirements and specifications for future Navy systems and the application of advanced technology to Navy command and control systems. He is a member of both the Computer Architecture Fiber Optics and Data Bus Working Group and the Aegis Fiber Optics Working Group. Mr. Falatko received his B.S. degree in aerospace engineering with high distinction from the University of Virginia in 1982 and his M.S. degree in applied physics from The Johns Hopkins University in 1985. Mr. Falatko is a member of Tau Beta Pi Sigma Gamma Tau the American Society of Naval Engineers and the U.S. Naval Institute. Janet L. Papach:is a section leader and senior engineering analyst in the Combat Systems Engineering Department Comptek Research Incorporated. She has ten years' experience as an analyst supporting NavSea Spa War and the U.S. Department of State. She currently participates in working group efforts under Aegis Combat System Doctrin

This paper sets forth computer systems architecture concepts for the combat system of the 2010–2030 timeframe that satisfy the needs of the next generation of surface combatants. It builds upon the current Aegis computer systems architecture, expanding that architecture while preserving, and adhering to, the Aegis fundamental principle of thorough systems engineering, dedicated to maintaining a well integrated, highly reliable, and easily operable combat system. The implementation of these proposed computer systems concepts in a coherent architecture would support the future battle force capable combat system and allow the expansion necessary to accommodate evolutionary changes in both the threat environment and the technology then available to effectively counter that threat. Changes to the current Aegis computer architecture must be carefully and effectively managed such that the fleet will retain its combat readiness capability at all times. This paper describes a possible transition approach for evolving the current Aegis computer architecture to a general architecture for the future. The proposed computer systems architecture concepts encompass the use of combinations of physically distributed, microprocessor-based computers, collocated with the equipment they support or embedded within the equipment itself. They draw heavily on widely used and available industry standards, including instruction set architectures (ISAs), backplane busses, microprocessors, computer programming languages and development environments, and local area networks (LANs). In this proposal, LANs, based on fiber optics, will provide the interconnection to support system expandability, redundancy, and higher data throughput rates. A system of cross connected LANs will support a high level of combat system integration, spanning the major warfare areas, and will facilitate the coordination and development of a coherent multi-warfare tactical picture supporting the future combatant command st

关键词： computer Architecture

来源：评论

学校读者我要写书评

暂无评论

THE COMMAND SUPPORT AT-SEA EXPERIMENT

引用

NAVAL ENGINEERS JOURNAL 1990年第3期102卷 25-36页

作者： BUSCHER, DJ SUNDAY, DM David J. Buscher:is an electrical engineer on the Principal Professional Staff of the Fleet Systems Department of The Johns Hopkins University Applied Physics Laboratory. He earned his BS degree in electrical engineering from Villanova University in 1967 an MSEE degree from the University of Maryland in 1972 and an MS degree in technical management from The Johns Hopkins University in 1985. He was the lead engineer on the Command Support At-Sea Experiment Project. He started his career in 1967 with the U.S. Army Harry Diamond Laboratory working on computer and communications projects. During this time he worked in Vietnam with the United States Army Vietnam Science Advisor Office. Since joining JHU/APL in 1978 he has worked on a variety of projects associated with computer graphics hospital patient information systems computer networks autonomous underwater vehicles and satellite communications. He is currently assistant group supervisor of the Computer Systems Group. Daniel M. Sunday:is a mathematician on the Principal Professional Staff of the Fleet Systems Department of The Johns Hopkins University Applied Physics Laboratory. He earned his Ph.D. in mathematics from the University of Minnesota in 1971 and did postdoctoral research on neural networks at the University of California at Berkeley. Since joining JHU/APL in 1980 Dr. Sunday has worked as a designer and developer of software systems with emphasis on medical imaging interactive graphics natural language interfaces and software standards. He was the network designer for the Headquarters Integrated Office System (HIOS) Network for the Army at the Pentagon. He is currently the lead software engineer on the Command Support At-Sea Experiment Project.

The Command Support At-Sea Experiment (CS@SE) provides experimental advanced graphics display systems consisting of large screen color displays and operator console color displays in the combat information center (CIC) of an Aegis cruiser and in the tactical flag command center (TFCC) of an aircraft carrier. CS@SE systems are designed to prototype potential command support capabilities in an at-sea environment to validate and refine requirements for planned production system upgrades. These systems use sophisticated color graphics techniques to provide real-time tactical displays that improve the availability of information to an operator by reducing clutter through the use of color, area fill, transparen overlays and intensity coding of track symbols. Interfaces wen developed with the Aegis Display System (ADS), Shipboarc Gridlock System with Auto-correlation (SGS/AC), Flag Dats Display System (FDDS) and Tomahawk Engagement Planning and Exercise Evaluation System (TEPEE) that provided the data for the presentation of a tactical display. Display elements included both real-time and over-the-horizon (OTH) surface track data, velocity leaders, tags, uncertainty ellipses, and history trails. The display also included filled land masses, country boundaries, commercial airways, cities, graphics overlays (i.e., operational areas), weapon system missile performance contours, and engagement plans. This paper describes the experiment, its installation and integration into the shipboard environments of an Aegis cruiser (USS Leyte Gulf ) and an aircraft carrier (USS America , its usage by the ships companies and embarked staffs, and the experiment result! and findings. Key conclusions of the experiment are: 1 Advanced graphics color displays can significantly enhance the ability of the warfighter to assimilate a complex tactical display. 2 Both ships reported a requirement for a correlated OTH and real-time track display with the ability to clearly differentiate the two types

关键词： computer Graphics

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：