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Frontiers in Optics, FiO 2003

作者： Shimshi, L. Ishaaya, A.A. Davidson, N. Friesem, A.A. Hasman, E. Dept. of Physics of Complex Systems Weizmann Institute of Science Rehovot76100 Israel Optical Engineering Laboratory Faculty of Mechanical Engineering Technion - Israel Institute of Technology Haifa32000 Israel

Second harmonic generation can be highly efficient with a laser operating with a single high order mode. A 90% increase in output power was obtained with a Q-Switch Nd:YAG laser when it was operating with TEM01 rather... 详细信息

ISBN: (纸本)1557527598

关键词： Harmonic generation

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Overview of the South China Sea Monsoon Experiment

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Advances in Atmospheric sciences 2004年第3期21卷 343-360页

作者：丁一汇李崇银柳艳菊 National Climate Center China Meteorological Administration Beijing 100081 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 National Climate Center China Meteorological Administration Beijing 100081 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid DynamicsInstitute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029he present paper gives an overview of the key project " South China Sea Monsoon Experiment (SCSMEX)" operated by the Ministry of Science and Technology of China during the period of 1996-2001. The SCSMEX is a joint atmospheric and oceanic field experiment which aims to better understand the onset maintenance and variability of the summer monsoon over the South China Sea (SCS). It is a large-scale international effort with many participating countries and regions cooperatively involved in this experiment. With the field observation in May-August 1998 a large amount of meteorological and oceanic data was acquired which provides excellent datasets for the study of the SCS monsoon and the East Asian monsoon and their interaction with the ocean. The preliminary research achievements are as follows. (1) The earliest onset of the Asian monsoon over the SCS and Indo-China Peninsula has been well documented. Prom the viewpoint of the synoptic process its onset is closely related to the early rapid development of a twin cyclone to the east of Sri Lanka. The conceptual modei of the SCS monsoon onset in 1998 was put forward. The 50-year time series of the SCS monsoon onset date was also made. (2) Two major modes namely the 30-60-day and 10-20-day oscillations were ascertained. The influences of the abnormal SCS monsoon on the precipitation over eastern China and its modes were identifled. A strong (weak) monsoon over the SCS usually leads to less (more) precipitation over the middle and lower reaches of the Yangtze River

The present paper gives an overview of the key project ' South China Sea Monsoon Experiment (SCSMEX)' operated by the Ministry of science and technology of China during the period of 1996-2001. The SCSMEX is a joint atmospheric and oceanic field experiment which aims to better understand the onset, maintenance, and variability of the summer monsoon over the South China Sea (SCS). It is a large-scale international effort with many participating countries and regions cooperatively involved in this experiment. With the field observation in May-August 1998, a large amount of meteorological and oceanic data was acquired, which provides excellent datasets for the study of the SCS monsoon and the East Asian monsoon and their interaction with the ocean. The preliminary research achievements are as follows. (1) The earliest onset of the Asian monsoon over the SCS and Indo-China Peninsula has been well documented. Prom the viewpoint of the synoptic process, its onset is closely related to the early rapid development of a twin cyclone to the east of Sri Lanka. The conceptual modei of the SCS monsoon onset in 1998 was put forward. The 50-year time series of the SCS monsoon onset date was also made. (2) Two major modes, namely the 30-60-day and 10-20-day oscillations were ascertained. The influences of the abnormal SCS monsoon on the precipitation over eastern China and its modes were identifled. A strong (weak) monsoon over the SCS usually leads to less (more) precipitation over the middle and lower reaches of the Yangtze River basin, and more (less) precipitation in North China. (3) During the monsoon onset over the SCS, a wide variety of organized mesoscale convective systems (MCSs) were observed by a Doppler radar array deployed over the northern SCS. The relationship between large-scale circulations and MCSs during the monsoon onset process in 1998 was clearly revealed. It was suggested that there is a kind of positive feedback mechanism between large-scale circulations and

关键词： field experiment South China Sea monsoon low frequency oscillation (LFO) meso scale convective systems (MSCs) air-sea interaction numerical simulation

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Effect of phase errors on laser mode selection with binary phase elements

Effect of phase errors on laser mode selection with binary p...

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Conference on Lasers and Electro-Optics Europe (CLEO EUROPE)

作者： G. Machavariani A.A. Ishaaya N. Davidson A.A. Friesem S. Blit E. Hasman Department of Physics of Complex Systems Weizmann Institute of Science Rehovot Israel Optical Engineering Laboratory Faculty of Mechanical Etigineering Tecknion-Israel Ituritute of Technology Haifa Israel

We present numerical and experimental investigations to determine the effect of such surface height deviations of the intra-cavity binary phase elements inserted into an Nd-YAG laser and the selection of the Laguerre-... 详细信息

关键词： Laser modes Mirrors Degradation Thermal lensing Apertures Q factor Laser theory Lenses Optical coupling Optical resonators

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Compact and simple configurations for converting laser beam distributions

Compact and simple configurations for converting laser beam ...

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Conference on Lasers and Electro-Optics Europe (CLEO EUROPE)

作者： G. Machavariani A.A. Ishaaya N. Davidson A.A. Friesem E. Hasman Department of Physics of Complex Systems Weizmann Institute of Science Rehovot Israel Optical Engineering Laboratory Faculty of Mechanical Engineering Technion-Israel Institute of Technology Haifa Israel

In this paper, we present a relatively simple and practical approach for efficiently conversing of a single high-order mode intensity distribution to a nearly Gaussian distribution. It is based on dividing the high-order mode distribution into equal parts that are then combined together coherently. Experimentally we implement this approach with single interferometric elements, whose surfaces are specially coated. With single interferometric element, the interferometric stability is significantly improved and the complexity of alignment is reduced.

关键词： Laser beams Coatings Laser theory Optical interferometry Laser modes Gaussian distribution Polarization Laboratories Stability Optical pulses

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Robust strictly positive real synthesis of polynomial segments for discrete time systems

Robust strictly positive real synthesis of polynomial segmen...

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IEEE Conference on Decision and Control

作者： Wensheng Yu Long Wang Yong Xiang Laboratory of Complex Systems and Intelligence Science Institute of Automation Chinese Academy and Sciences Beijing China Center for Systems and Control Department of Mechanics and Engineering Science Peking University Beijing China School of Engineering and Technology Deakin University Geelong VIC Australia

ISBN: (纸本)0780379241

By using the result of robust strictly positive real synthesis of polynomial segments for continuous time systems, it is proved that, for any two n-th order polynomials a(z) and b(z), the Schur stability of their convex combination is necessary and sufficient for the existence of an n-th order polynomial c(z) such that c(z)/a(z) and c(z)/b(z) are both strictly positive real. We also provide the construction method of c(z). Illustrative examples are provided to show the effectiveness of this method.

关键词： Robustness Polynomials Discrete time systems Continuous time systems Robust stability Control system synthesis Transfer functions Research and development Laboratories Intelligent systems

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Human systems integration and advanced technology in engineering department workload and manpower reduction

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NAVAL ENGINEERS JOURNAL 2003年第1期115卷 57-65页

作者： Lively, KA Seman, AJ Kirkpatrick, M KENNETH A. LIVELY graduated from the University of Colorado with a BS in applied mathematics and an MS in mathematics in 1976 and from the Massachusetts Institute of Technology with an MS in electrical engineering and the degree ocean engineer in naval architecture and marine engineering in 1984. He retired from the U.S. Navy in 1989 after 23 years of service. Assignments included electrical officer on the USS Constellation (CV 64) project engineer for the DDG 51 machinery control system (NAVSEA) and DDG 51 Technical Director (NAVSEA). He was vice president of the PDI Division of Bird-Johnson Company from July 1989 to November 1998 where he managed various gas turbine and machinery controls related development projects. He joined Anteon Corporation's Systems Engineering Group as senior controls engineer in December 1998 where he provided technical support to the integrated power systems program (NAVSEA PMS 510) and managed the Office of Naval Research Afloat Laboratory. DR. MARK KIRKPATRICK is currently an independent consultant in human factors and work-load/manning analysis and modeling. He holds a Ph.D. degree in experimental psychology from The Ohio State University and has 34 years of experience in applied human factors. From 1982 through 2000 Dr. Kirkpatrick served as the senior vice president of Carlow International. Prior to joining Carlow in 1982 Dr. Kirkpatrick served as a member of the technical staff at North American Rockwell's Missiles Division and as a project director and vice president for Essex Corporation. His areas of expertise include workload simulation task analysis operator-in-the-loop simulation human performance experimentation statistical analysis and human factors T&E. He has directed and/or participated in human factors projects for the U.S. Navy U.S. Army NASA Department of Transportation the U.S. Nuclear Regulatory Commission and private industry. ANTHONY J. SEMAN III is the technical manager for the reduced ship's crew by virtual presence (RSVP) advanced technology d

Aboard current ships, such as the DDG 51, engineering control and damage control activities are manpower intensive. It is anticipated that, for future combatants, the workload demand arising from operation of systems under conditions of normal steaming and during casualty response will need to be markedly reduced via automated monitoring, autonomous control, and other technology initiatives. Current DDG 51 class ships can be considered as a manpower baseline and under Condition III typical engineering control involves seven to eight watchstanders at manned stations in the Central Control Station, the engine rooms and other machinery spaces. In contrast to this manning level, initiatives such as DD 21 and the integrated engineering plant (IEP) envision a partnership between the operator and the automation system, with more and more of the operator's functions being shifted to the automation system as manning levels decrease. This paper describes some human systems integration studies of workload demand reduction and, consequently, manning reduction that can be achieved due to application of several advanced technology concepts. Advanced system concept studies in relation to workload demand are described and reviewed including. Piecemeal applications of diverse automation and remote control technology concepts to selected high driver tasks in current DDG 51 activities. Development of the reduced ship's crew by virtual presence system that will provide automated monitoring and display to operators of machinery health, compartment conditions, and personnel health. The IEP envisions the machinery control system as a provider of resources that are used by various consumers around the ship. Resource needs and consumer priorities are at all times dependent upon the ship's current mission and the availability of equipment pawnbrokers.

关键词： Naval warfare

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High-order mode selection in q-switched Nd:YAG lasers

High-order mode selection in q-switched Nd:YAG lasers

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Conference on Lasers and Electro-Optics (CLEO 2002)

作者： Ishaaya, A.A. Davidson, N. Machavariani, G. Friesem, A.A. Hasman, E. Dept. of Physics of Complex Systems Weizmann Institute of Science Rehovot 76100 Israel Optical Engineering Laboratory Faculty of Mechanical Engineering Technion-Israel Inst. of Technology Haifa Israel

ISBN: (纸本)1557527067

An efficient high-order mode selection in a Q-switched Nd:YAG laser was demonstrated using various intracavity phase elements. The laser consisted of a stable plano-concave resonator, a flashpump pumped 5 mm diameter Nd:YAG rod, and a Q-switch scheme. The scheme comprised of a polarizer-electrooptical crystal waveplate, and an aperture to limit the number of high order modes. Results indicated that high gain and short pulse duration have minor effect on the laser configuration operating with a high-order mode.

关键词： Neodymium lasers

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Efficient formation of pure helical beams from a Gaussian beam

Efficient formation of pure helical beams from a Gaussian be...

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Conference on Lasers and Electro-Optics (CLEO 2002)

作者： Machavariani, Galina Davidson, N. Friesem, A.A. Ishaaya, A.A. Blit, S. Hasman, E. Dept. of Physics of Complex Systems Weizmann Institute of Science Rehovot 76100 Israel Optical Engineering Laboratory Faculty of Mechanical Engineering Technion-Israel Inst. of Technology Haifa Israel

ISBN: (纸本)1557527067

Formation of pure helical beams from a Gaussian beam using spiral phase elements (SPE) was studied. Beam quality factor M2 for helical beams, which were obtained by passing Gaussian and shifted-Gaussian beams through different SPEs, was calculated. Results indicated that the M2 values for incident shifted-Gaussian beams were nearly identical to pure modes. Large values of M2 were obtained for incident Gaussian beams.

关键词： Laser beams

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Geometric fractal growth model for scale-free networks

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Physical Review E 2002年第5期65卷 056101-056101页

作者： S. Jung S. Kim B. Kahng Nonlinear and Complex Systems Laboratory Department of Physics Pohang University of Science and Technology Pohang Kyongbuk 790-784 Korea School of Physics and Center for Theoretical Physics Seoul National University Seoul 151-747 Korea

We introduce a deterministic model for scale-free networks, whose degree distribution follows a power law with the exponent γ. At each time step, each vertex generates its offspring, whose number is proportional to the degree of that vertex with proportionality constant m−1 (m>1). We consider the two cases: First, each offspring is connected to its parent vertex only, forming a tree structure. Second, it is connected to both its parent and grandparent vertices, forming a loop structure. We find that both models exhibit power-law behaviors in their degree distributions with the exponent γ=1+ln(2m−1)/lnm. Thus, by tuning m, the degree exponent can be adjusted in the range, 2<γ<3. We also solve analytically a mean shortest-path distance d between two vertices for the tree structure, showing the small-world behavior, that is, d∼lnN/lnk¯, where N is system size, and k¯ is the mean degree. Finally, we consider the case that the number of offspring is the same for all vertices, and find that the degree distribution exhibits an exponential-decay behavior.

关键词： .time step connected follows tree vertices system size Tuning analytically degree distribution loop structure Geometric fractal growth deterministic model offspring grandparent degree exponent

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ROBUST CONGESTION CONTROL IN HIGH SPEED COMMUNICATION NETWORKS: A MODEL PREDICTIVE CONTROL APPROACH

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IFAC Proceedings Volumes 2002年第1期35卷 103-108页

作者： Hua O. Wang Yongru Gu Huajing Fang Laboratory for Intelligent and Nonlinear Control (LINC) Department of Electrical and Computer Engineering Duke University Durham NC 27708-0291 USA Center for Nonlinear and Complex Systems Department of Control Science and Engineering Huazhong University of Science and Technology Wuhan 430074 China

In this paper, the design of explicit rate-based congestion control in high speed communication networks is considered. At a bottleneck node, there are multiple best-effort sources competing with other high priority cross traffic sources. The goal of congestion control is to achieve high link utilization, low packet loss, low delay, and fairness among the best-effort sources. In this paper, the high priority traffic is described by an autoregressive integrated moving average (ARIMA) process. To deal with the propagation delays associated with the best-effort sources, model predictive control, particularly, generalized predictive control, techniques are proposed to solve the congestion problem here. It is demonstrated that the proposed controller performs well and is robust to delay uncertainties. In addition, in a multiple-nodes configuration, the controller provides max-min fairness.

关键词： Communication control applications Model-based control Predictive control Communication networks Time delay Robustness

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