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Advanced Solid State Lasers, ASSL 2002

作者： Yu, Jirong Braud, Alain Petros, Mulugeta Singh, Upendra N. NASA Langley Research Center Laser System Branch MS 474 HamptonVA23681 United States Science Applications International Corporation 1 Enterprise Parkway HamptonVA23666 United States Science and Technology Corporation 10 Basil Sawyer Drive HamptonVA23666 United States NASA Langley Research Center Electro-optical Control Branch MS 474 HamptonVA23681 United States

An efficient double-pulsed Ho:Tm:YLF 2-μm laser amplifier has been demonstrated. 600 mJ per pulse pair under Q-switch operation is achieved with the gain of 4.4, which represents the highest reported optical-to-optic... 详细信息

ISBN: (纸本)1557526974

关键词： Pulsed lasers

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Efficient double-pulsed Ho amplifier

Efficient double-pulsed Ho amplifier

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Conference on Lasers and electro-Optics (CLEO 2002)

作者： Yu, Jirong Braud, Alain Petros, Mulugeta Singh, Upendra N. NASA Langley Research Center Laser System Branch MS 474 Hampton VA 23681 United States Science Applications Intl. Corp. 1 Enterprise Parkway Hampton VA 23666 United States Science and Technology Corporation 10 Basil Sawyer Drive Hampton VA 23666 United States NASA Langley Research Center Electro-Optical Control Branch MS 474 Hampton VA 23681 United States

ISBN: (纸本)1557527067

A Ho:Tm:YLF 2-μm laser that operated in double pulse fashion was developed. The oscillator and amplifier modules were transversely pumped by GaAlAs diode lasers. Two amplifiers formed a chain to provide necessary gain to the probe beam in a single pass amplification. The laser provided two Q-switched pulses with a single pump pulse. A total of 600 mj of energy was achieved in double pulse operation, and the optical-to-optical efficiency of the amplifier increased to 4.5%, and 61% of the normal mode energy was used.

关键词： Solid state lasers

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Ultrafast energy transfer dynamics between block copolymer and /spl pi/-conjugated polymer

Ultrafast energy transfer dynamics between block copolymer a...

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Pacific Rim Conference on Lasers and electro-Optics (CLEO/Pacific Rim)

作者： Youg Hee Kim Sae Chae Jeoung Donnho Kim Ja-Young Han Hong-Ku Shim National Creative Research Initiatives Center Ultrafast Optical Characteristics Control and Spectroscopy Laboratory Korea Research Institute of Standards and Science Taejon South Korea Department of Chemistry Korea Advanced Institute of Science and Technology Taejon South Korea

The quantum efficiency of the blended polymeric system consisting of poly[2-methoxy-5-(2-ethylhexyloxy)-l,4-phenylenevinylene] (MEH-PPV) and conjugated-nonconjugated multi-block copolymer (CNMBC), poly[l,3-propane-dioxy-1,4-phenylene-1,2-ethylene-(2,5-bis(trimethylsilyl)-1,4 -phenylene)-1,2-ethylene-1,4-phenylene] (DSiPV) is several times higher than that of the constituent polymers, which is explained in terms of the Forster energy transfer theory. But the ultrafast photoexcitation dynamics of MEH-PPV and of the blended polymer consisting of MEH-PPV and DSiPV using the time-resolved fluorescence and femtosecond transient absorption spectroscopic techniques suggests that other mechanisms should be involved. No apparent change in the absorption spectrum of the blended polymer (MEH-FPV:DSiPV=6:4 mass ratio) compared to those of MEH-PPV and DSiPV indicates that neither chemical nor conformational change has occurred upon mixing. Their time-integrated photoluminescence (PL) spectra show that upon blending, the emission from DSiPV disppears while that from MEH-PPV predominates with a slight red-shift of the emission maximum. The red-shifted PL spectrum and the disappearance of the stimulated emission (SE) in the transient absorption spectrum of the blended polymer clearly indicates that two different emissive states play roles in the relaxation process of the primary photoexcitations in MEH-PPV thin films.

关键词： Energy exchange Excitons optical polymers Absorption Charge carrier processes optical control Ultrafast optics Spectroscopy Polymer films electron mobility

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Femtosecond pump-probe investigation on relaxation of photoexcitations and spectral narrowing of photoluminescence for PPV

Femtosecond pump-probe investigation on relaxation of photoe...

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Pacific Rim Conference on Lasers and electro-Optics (CLEO/Pacific Rim)

作者： Sae Chae Jeoung Yong Hee Kim Dongho Kim Ja-Young Han H.K. Shim National Creative Research Initiatives Center for Ultrafast Optical Characteristics Control and Spectroscopy Laboratory Korea Research Institute of Standards and Science Taejon South Korea Department of Chemistry Korea Advanced Institute of Science and Technology Taejon South Korea

We report femtosecond pump-probe experimental results and emission spectral changes in PPV with a change of excitation power density in order to have a deeper understanding on the primary photoexcitations and the natu... 详细信息

关键词： Ultrafast optics optical pumping Stimulated emission optical control optical films optical polymers Stationary state Bleaching Absorption Excitons

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Capacitive sensing type surface micromachined silicon accelerometer with a stiffness tuning capability

Capacitive sensing type surface micromachined silicon accele...

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IEEE International Conference on Micro electro Mechanical Systems

作者： I.Y. Park C.W. Lee H.S. Jang Y.S. Oh B.J. Ha Research and Development Center Samsung Electro Mechanics Company Limited Suwon South Korea Center for Noise and Vibration Control Department of Mechanical Engineering Korea Advanced Institute of Science and Technology South Korea Microsystems Laboratory Samsung Advanced Institute of Technology South Korea

A novel concept surface micromachined silicon accelerometer which has a stiffness tuning capability to improve the sensor resolution is developed. The stiffness of the sensor structure is reduced by providing an electrostatic negative stiffness. By adopting the stiffness tuning, the initially stiff structure guarantees the stability of the fabrication and the reduced stiffness only along the sensing direction produces the improved resolution. In particular, one of the improved structure of this accelerometer is a branched comb-finger that senses the relative position between the mass and the electrode itself. Maintaining the same capacitance variation, it is able to achieve a larger initial gap between the mass and the electrode which fences the clash problem. The accelerometer has an active size of 650/spl times/530 /spl mu/m/sup 2/, a thickness of polysilicon structure of 7 /spl mu/m, and a proof mass of about 1 /spl mu/g. Experimental results shows that the equivalent noise level of the accelerometer is improved by 30 dB through the stiffness tuning. The accelerometer has a bandwidth of 350 Hz, a linearity of 0.3% FS, and a sensing range of 50 g.

关键词： Silicon Accelerometers electrodes electrostatics Stability Fabrication Capacitance Noise level Bandwidth Linearity

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OPTIMUM FREQUENCY REUSE IN MOBILE TELEPHONY SYSTEMS

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INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS 1995年第3期8卷 185-190页

作者： KAZANTZAKIS, MG DEMESTICHAS, PP ANAGNOSTOU, ME National Technical University of Athens Computer Science Division Department of Electrical and Computer Engineering Heroon Polytechneiou 9 Zografou Athens 15773 Greece Michael G. Kazantzakii was born in Athens Greece in 1962. He received both the Diploma and Ph.D. Degree from the Electrical Engineering Department of the National Technical University of Athens in 1986 and 1992 respectively. During the period 1992–1993 he was a member of the Staff of the Hellenic Navy Research Centre working in the area of underwater acoustics. Since 1994 he has been a researcher at the National Technical University of Athens Department of Electrical Engineering and Computer Science Telecommunications Laboratory. His interests include data mobile and integrated services networks. Panagiotis P. Demestichas was born in Athens Greece in 1967. He received the Diploma in electrical engineering from the National Technical University of Athens (NTUA) Athens in 1993. At present he is a research assistant at NTUA working towards his Ph.D. dissertation. He participated in the BRITE/EURAM-EURATN and in the RACE-TOMQAT and MONET projects. His research interests are in the areas of broadband and mobile networks queueing theory algorithms and complexity theory. He is a Member of the Technical Chamber of Greece. Miltiades E. Anagnostou was born in Athens in 1958. He received the Electrical Engineers Diploma from the National Technical University of Athens (NTUA) in 1981. During the period 1981–1987 he was a teaching assistant at NTUA. In 1987 he received his Ph.D. in the area of computer networks. In 1987–1989 he served the Greek army in the Air Force Research and Development Center. In 1989–1991 he was a Lecturer and since 1991 he has been an Assistant Professor in the Computer Science Division Department of Electrical and Computer Engineering of the NTUA. He teaches courses on modern telecommunications formal specification of protocols stochastic processes and queueing theory. Since 1981 Dr. Anagnostou has been involved

The reason why cellular mobile telephony systems exist is that they allow frequency reuse. Dynamic allocation algorithms improve the network efficiency and the service quality. Dynamic allocation is closely related to the following instantaneous allocation problem: given a number of channels (frequencies), a cell structure and the number of calls to be accommodated in each cell, find the optimum allocation of channels to cells subject to restrictions concerning the distance of cells, where the same frequency can be reused. In this paper we formulate and solve this problem by showing that it can be reduced to a 0-1 programming problem. Finally we present results, and draw subsequent conclusions.

关键词： MOBILE TELEPHONY FREQUENCY ALLOCATION UMTS

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Analytic modeling of staring infrared systems with multidimensional matched filters

Analytic modeling of staring infrared systems with multidime...

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Infrared Systems and Components II 1988

作者： Scribner, D.A. Longmire, M.S. Kruer, M.R. Electro-optical Technology Branch Optical Science Division Naval Research Laboratory WashingtonDC20375 United States Western Kentucky University Department of Physics and Astronomy Bowling GreenKY42101 United States

Methods are discussed for analytic modeling of staring autonomous infrared systems for use in point-source detection. Our analysis generally reviews frequency domain methods that can be used from a system engineering perspective to conceptually design an infrared sensor and predict its performance in conjunction with a multidimensional matched filter to perform either temporal, spatial or spatio-temporal (3-D) image processing. Specifically we will be concerned with point-source targets that have a unique temporal behavior and are embedded in background clutter. Both the signal and the clutter can have some level of apparent motion associated with them in terms of a fixed velocity. The modeling process is fully parametric and can include all salient features of a time-dependent target, stochastic background, atmospheric propagation, optical system and staring infrared detector array. We show that this modeling technique lends itself very well to parametric analysis that is often very useful in design trade-offs and optimization studies. An example is given that deals with moving target detection, temporal filtering, spatial filtering, and spatio-temporal filtering. © 1988 SPIE. All rights reserved.

关键词： Matched filters

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Some advantages of using scatter plate interferometer in testing aspheric surfaces

Some advantages of using scatter plate interferometer in tes...

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Optics and the Information Age

作者： Su, Der-Chin Honda, Toshio Tsujiuchi, Jumpei Institute of Electro-Optical Engineering National Chiao Tung University 1001 Ta-Hsueh Road Hsin-Chu Taiwan Imaging Science and Engineering Laboratory Tokyo Institute of Technology 4259 Nagatsuda Midori-Ku Yokohama 227 Japan

The scatter plate interferometer a simple structure and is very conventient for measuring the surface errors of a concave mirror. In this interferometer, unlike all the others, there is no one-to-one point correlation between the mirror to be tested and the scatter plate which acts as a beam splitter. Using this feature, we show that a scatter plate interferometer is more stable than any other interferometer. In addition, a new convenient method, which can realize the null test of aspheric surfaces, is proposed by some modifications of optical setup, without using any special optical elements.

关键词： Interferometers

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Applications of Holography 1

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1000年

作者： Euval S. Barrekette Winston E. Kock Teruji Ose Jumpei Tsujiuchi George W. Stroke

ISBN: (数字)9781468419054

ISBN: (纸本)9781468419078

Holography has matured over the years since it was first invented by Dennis Gabor and further developed by many workers during the last decade. With some applications a commercial reality and many more continually appearing, it is now possible to compile a volume devoted to the applications of holography. This book consists primarily of papers presented at the second U.S. Japan Seminar on holography, held in Washington, D.C., from October 20-27, 1969, under the auspices of the National Academy of sciences, National science Foundation, and the Japanese Society for the Promotion of science. In addition to most of the papers presented at the seminar, several others are included because they cover important applications which are appropriate to this volume. Attendance at the seminar was limited to ten delegates from each country; these delegates being chosen so as to permit the seminar to include as wide a range of subjects as possible, with each delegate being recognized as an authority in his particular field of holography. In addition, Dr. Gilbert Devey (Program 'Director for Engineering Systems for the National science Foundation, and the one most responsible for making the seminar possible), Professor Wolf F.

关键词： science, Humanities and Social sciences, multidisciplinary

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Simple Precise Time Signal Delivery over Fiber Link Scheme

Simple Precise Time Signal Delivery over Fiber Link Scheme

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第五届中国卫星导航学术年会

作者： Yitang Dai Zhongle Wu Tianpeng Ren Feifei Yin Kun Xu Jintong Lin Geshi Tang State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications Beijing 100876 China Science and Technology on Aerospace Flight Dynamics Laboratory Beijing 100094 China Beijing Aerospace Control Center Beijing 100094 China

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