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Control design which respects characteristic length scales in smart systems and smart structures

Proceedings of SPIE - The International Society for optical engineering 1999年 3667卷 202-210页

作者： Baillieul, J. Boston Univ Boston United States

Although there is a mature and continually growing body of knowledge concerning the ways in which the dynamics of fluids and solids depend on characteristic length scales, current theories governing control design do not take explicit account of length scales. Recent research has demonstrated the need to take such considerations into account in designing control systems for smart materials and smart structures in which the goal is to employ small-scale actuators and sensors with characteristic length scales in the micron to millimeter range. For many applications, sensors and actuators will need to be separated by considerable distances (in terms of characteristic length scales). Closed loop feedback designs in this setting may involve communications delays, and both the communications channels and the sensors themselves will typically be relatively noisy. Hence traditional approaches to the design of feedback control laws need to be rethought and modified to work effectively in the noisy, nonlinear, bandlimited world of microelectromechanical systems (MEMS). This paper discusses one approach to a robust, length-scale respecting theory of control based on oscillatory actuation. It includes a brief outline of recent developments in the control of mechanical systems using oscillatory actuation, emphasizing the dependence on characteristic length scales. The principal applications with which we are working are micro-pendulum designs, micro-piston actuators for deformable mirrors as well as micro-valves for the control of fluid-structure boundary layer control.

关键词： Intelligent structures

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Computational intelligence in management of ATM networks: a survey of current state of research

Computational intelligence in management of ATM networks: a ...

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Proceedings of the 1999 Applications and Sciences of Neural Networks, Fuzzy Systems, and Evolutionary Computation ii

作者： Sekercioglu, Y.Ahmet Pitsillides, Andreas Vasilakos, Athanasios Swinburne Univ of Technology

Today, a number of researchers are looking at alternative non-analytical control system design and modeling techniques that have the ability to devise effective, robust ATM network management schemes. Such schemes employ artificial neural networks, fuzzy systems and design methods based on evolutionary computation. A summary is given on the current state of ATM network management research employing these techniques. The salient features of the methods employed are reviewed.

关键词： Artificial intelligence

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engineering progress on the fully automated, photon-counting SLR2000 satellite laser ranging station

Engineering progress on the fully automated, photon-counting...

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Conference on Laser Radar Ranging and Atmospheric Lidar Techniques ii

作者： Degnan, JJ NASA Goddard Space Flight Ctr Geosci Technol Off Greenbelt MD 20771 USA

ISBN: (纸本)0819434604

SLR2000 is an autonomous and eyesafe single photon-counting satellite laser ranging station with an expected single shot range precision of about one centimeter and a normal point precision better than 3 mm. The system will provide continuous 24 hour tracking coverage. Replication costs are expected to be roughly an order of magnitude less than that of current manned systems, and the system will be about 75% less expensive to operate and maintain relative to the current manned systems. Computer simulations have predicted a daylight tracking capability to GPS and lower satellites. Computer and hardware simulations have demonstrated the ability of our current correlation range receiver and autotracking algorithms to extract mean signal strengths as small as 0.0001 photoelectrons per pulse from solar background noise during daylight tracking. The initial SLR2000 system concept was developed in 1994 [1], and the technical approach was refined in later years [2]. However, significant funding for the project was not provided by NASA until August 1997. During the first year of funding, prototypes of several "enabling' components, without which the system is not feasible, were successfully developed. These include: (1) a sensitive, high speed, quadrant microchannel plate photomultiplier; (2) a moderate power microlaser transmitter; (3) a "smart" meteorological station; (4) a high speed range gate generator; and (5) a high speed, high resolution event timer. Once the key specifications on these advanced components were largely met and system feasibility had been established, attention then turned to the detailed engineering design and procurement of more conventional elements of the system such as the shelter and protective dome, arcsecond precision tracking mount, telescope, and optical transceiver. The principal challenge during this second phase was to keep prototype fabrication and replication costs as low as possible to meet our cost goals. Prototypes of the various SLR

关键词： Telescopes Prototyping Sensors Space telescopes Receivers Satellites Transmitters Ranging Satellite laser ranging Transceivers

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Large-scale computer generated absorption holograms of 3D objects: Part ii, Practical methodology

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Proceedings of SPIE - The International Society for optical engineering 1999年 3637卷 45-54页

作者： Phillips, Nicholas J. Cameron, Colin D. Dodd, Adrian K. Pain, Douglas A. Sheerin, David T. Slinger, Chris W. De Montfort Univ Leicester United Kingdom

As a support to the advances in theoretical understanding and computational methods, we describe a new laser plotter technique that enables, in principle, an unlimited size of pixel array to be plotted efficiently with a rigorous estimate of duration of the plot run time. developments in laser plotter design are presented that allow the formation of pixellated holographic structures of high precision (c. 1-10 micron pixel dia.) with an accompanying high pixel count (e.g. at least up to, and beyond, 104 per side within a square array). The case of absorption holograms offers an easy route to a good quality result. We can then exploit the many tricks of amplitude holography borrowed from lithographic and holographic experience using ultra-fine grain silver halide materials. The problem of exposure quantization and linearization is addressed in a pragmatic fashion. The central issue of why such holograms can tolerate intrinsic diffraction artifacts within each pixel is considered along with the exposure level quantization - it is difficult to print individual pixels within which the optical density is clinically uniform. We cannot over-estimate the reliability difficulties that can arise in a system designed to print massive arrays of pixels in a serial fashion. The electronic testing involved has to be associated with error-free repeatability and high accompanying switching speeds. This may look easy but it is the major issue that distinguishes serially printed digital holography from the simple one-step parallel process of forming the ordinary hologram.

关键词： Computer generated holography

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Revisions to the JDL data fusion model

Revisions to the JDL data fusion model

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Conference on Sensor Fusion - Architectures, Algorithms, and Applications iiI

作者： Steinberg, AN Bowman, CL White, FE ERIM Int Inc Arlington VA 22209 USA

ISBN: (纸本)0819431931

The Data Fusion Model maintained by the Joint Directors of Laboratories (JDL) Data Fusion Group is the most widely-used method for categorizing data fusion-related functions. This paper discusses the current effort to revise and expand this model to facilitate the cost-effective development, acquisition, integration and operation of multi-sensor/multi-source systems. Data fusion involves combining information - in the broadest sense - to estimate or predict the state of some aspect of the universe. These may be represented in terms of attributive and relational states. If the job is to estimate the state of a people (or any other sentient beings), it can be useful to include consideration of informational and perceptual stares in addition to the physical state. Developing cost-effective multi-source information systems requires a method for specifying data fusion processing and control functions, interfaces, and associated databases. The lack of common engineering standards for data fusion systems has been a major impediment to integration and re-use of available technology: current developments do nor lend themselves to objective evaluation, comparison or re-use. This paper reports on proposed revisions and expansions of the JDL Data Fusion model to remedy some of these deficiencies. This involves broadening the functional model and related taxonomy beyond the original military focus, and integrating the Data Fusion Tree Architecture model for system description, design and development.

关键词： Data fusion Data modeling Systems modeling Standards development Data processing Sensors Algorithm development Data analysis Systems engineering Signal detection

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Advances in cathodes for high current RF photoinjectors

Advances in cathodes for high current RF photoinjectors

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Proceedings of the 1999 Free-Electron Laser Challenges ii

作者： Dowell, David H. Boeing Space & Communications Group Seattle United States

There is considerable interest in using RF photocathode guns and injectors in a variety of applications for electron sources. Unfortunately, the short operating time of the cathode and the complicated laser needed to drive the cathode limits these devices to the research laboratory. However, recent developments in cathode research indicate the possibility of a robust, long-lived cathode with high sensitivity at visible wavelengths. The combination of coating with a protective layer and operating at an elevated temperature could significantly increase the lifetime of cesium-antimony cathodes. This paper reviews the cathode quantum efficiencies and lifetimes observed in RF guns, discusses the drive laser issues and describes recent advances in both metal and cesium-based cathodes.

关键词： Photocathodes

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Experimental investigation of ion beam transport in a laser initiated high current discharge channel

Experimental investigation of ion beam transport in a laser ...

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The 26th IEEE International Conference on Plasma Science (ICOPS99)

作者： Tauschwitz, A. Niemann, C. Penache, D. Presura, R. Gesellschaft fuer Schwerionenforschung GSI Darmstadt Germany

The space charge and current neutralized beam focusing and transport in gas discharge plasmas is under investigation since a number of years. Paralleled by engineering design work of a modified HILIFE ii reactor with discharge channel based final beam transport, and by experimental investigations of laser initiated high current discharges at the Lawrence Berkeley National Laboratory (LBNL), the ion optical properties of such a channel will be studied for the first time with a heavy ion beam at GSI. The experiment uses the heavy ion beam of the GSI-UNILAC linear accelerator with a typical ion energy of 11.4 MeV/amu.

关键词： Laser produced plasmas

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Recent developments in hybrid mirror technology for the Next Generation Space Telescope

Recent developments in hybrid mirror technology for the Next...

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Proceedings of the 1999 18th Congress of the International Commission for Optics (ICO XViiI): Optics for the Next Millennium

作者： Dodson, Kelly J. Mehle, Greg V. Kasl, Eldon P. Composite Optics Inc San Diego CA United States

The objective of this paper is to report the recent developments in lightweight mirror technology at Composite Optics, Incorporated (COI). The developments are a result of the activities being conducted in support of the Next Generation Space Telescope (NGST) Program. The sponsors of these efforts are the NASA Marshall and Goddard Space Flight Centers. The requirements, design approach, performance, and the technology status for the program are summarized. The emergence of composite materials provides exciting potential for nontraditional, accurate, lightweight, stable, stiff, and high strength mirrors. This evolving technology promises significant improvement in reducing weight, cost and cycle time for future infrared, visible, and x-ray systems. Customers currently embracing composite mirror technology for radiometric use are already reaping substantial system performance benefits. Other customers interested in LIDAR, IR, visible, and grazing incidence x-ray applications are eagerly awaiting successful completion of current technology development and demonstration efforts.

关键词： Mirrors

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Control design which respects characteristic length scales in smart systems and smart structures

Control design which respects characteristic length scales i...

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Proceedings of the 1999 Smart Structures and Materials - Mathematics and Control in Smart Structures

作者： Baillieul, J. Boston Univ Boston MA United States

关键词： Intelligent structures

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optical systems for high-resolution digital still cameras

Proceedings of SPIE - The International Society for Optical ...

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Proceedings of SPIE - The International Society for optical engineering 1999年 3737卷 202-213页

作者： Schuster, Norbert Rollei Fototechnic Braunschweig Braunschweig Germany

Starting from the minimum pixel number 1 k×1.3 k for the high resolution digital photography, the camera development is dominated by the progress of matrices. Basic relations for the lens adaptation (focal length, aperture, resolution) to actual detector developments are presented. Resolution losses by color interpolation and by optical low pass filters in the one shot photography are quantified by special MTFs. Relations for the admissible blur circle, defining the depth of field in the digital photography, are deducted. Consequences of the lens adaptation to matrix proprieties are presented by several examples. Further developments in the semiprofessional digital still photography with nonchangeable lenses, in the digital use of classic SLR-cameras and in the professional digital still photography with bellows cameras are presented. New viewfinder concepts are discussed.

关键词： optical systems

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