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Development of distributed time-variant gain model for nonlinear hydrological systems

Science China Earth Sciences 2005年第6期48卷 713-723页

作者： XIA Jun1, 2, WANG Gangsheng1, TAN Ge1, YE Aizhong2 & G. H. Huang3 1. Key Laboratory of Water Cycle & Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China 2. State Key Laboratory of Water Resources & Hydropower Engineering Sciences, Wuhan University, Wuhan 430072, China 3. Faculty of Engineering, University of Regina, 3737 Wascana Parkway, Regina, Sask., S4S 0A2, Canada Correspondence should be addressed to Xia Jun Key Laboratory of Water Cycle & Related Land Surface Processes Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing China State Key Laboratory of Water Resources & Hydropower Engineering Sciences Wuhan University Wuhan China Faculty of Engineering University of Regina Sask Canada

In this paper, a rainfall-runoff modeling system is developed based on a nonlinear Volterra functional series and a hydrological conceptual modeling approach. Two models, i.e. the time-variant gain model (TVGM) and the distributed time-variant gain model (DTVGM) that are built on the platform of Digital Elevation Model (DEM), Remote Sensing (RS) and Unit Hydro-logical Process were proposed. The developed DTVGM model was applied to two cases in the Heihe River Basin that is located in the arid and semiarid region of northwestern China and the Chaobai River basin located in the semihumid region of northern China. The results indicate that, in addition to the classic dynamic differential approach to describe nonlinear processes in hy-drological systems, it is possible to study such complex processes through the proposed sys-tematic approach to identify prominent hydrological relations. The DTVGM, coupling the advan-tages of both nonlinear and distributed hydrological models, can simulate variant hydrological processes under different environment conditions. Satisfactory results were obtained in fore-casting the time-space variations of hydrological processes and the relationships between land use/cover change and surface runoff variation.

关键词： hydrological process, nonlinearity, time-variant gain model, distributed hydrological model.

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A numerical simulation of nonlinear propagation of gravity wave packet in three-dimension compressible atmosphere

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Science China(Technological Sciences) 2002年第3期45卷 306-313页

作者：吴少平易帆 Wuhan Institute of Physics and Mathematics Chinese Academy of Sciences Wuhan China Department of Physics Huazhong Normal University Wuhan China Department of Radio Science and Technology Wuhan University Wuhan China

By using FICE scheme, a numerical simulation of nonlinear propagation of gravity wave packet in three-dimension compressible atmosphere is presented. The whole nonlinear propagation process of the gravity wave packet is shown; the basic characteristics of nonlinear propagation and the influence of the ambient winds on the propagation are analyzed. The results show that FICE scheme can be extended in three-dimension by which the calculation is steady and kept for a long time; the increase of wave amplitude is faster than the exponential increase according to the linear gravity theory; nonlinear propagation makes the horizontal perturbation velocity increase greatly which can lead to enhancement of the local ambient winds; the propagation path and the propagation velocity of energy are different from the results expected by the linear gravity waves theory, the nonlinearity causes the change in propagation characteristics of gravity wave; the ambient winds alter the propagation path and group velocity of gravity wave.

关键词： gravity wave, nonlinearity, FICE scheme, simulation.

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Unconventional Hamilton-type variational principles for nonlinear coupled thermoelastodynamics

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Science China Mathematics 2002年第6期45卷 783-794页

作者：罗恩黄伟江邝君尚罗志国 Dept. of Appl. Mechanics and Eng. Zhongshan University Guangzhou 510275 China Department of Civil Engineering Hong Kong Univ. of Sci. and Technol. Hong Kong Hong Kong

According to the basic idea of classical yin-yang complementarity and modern dual-complementarity, in a simple and unified new way proposed by Luo, the unconventional Hamilton-type variational principles for geometrically nonlinear coupled thermoelastodynamics can be established systematically. The new unconventional Hamilton-type variational principle can fully characterize the initial-boundaty-value problem of this dynamics. In this paper, an important integral relation is given, which can be considered as the expression of the generalized principle of virtual work for geometrically nonlinear coupled thermodynamics. Based on this relation, it is possible not only to obtain the principle of virtual work in geometrically nonlinear coupled thermodynamics, but also to derive systematically the complementary functionals for eight-field, six-field, four-field and two-field unconventional Hamilton-type variational principles by the generalized Legendre transformations given in this paper. Furthermore, with this approach, the intrinsic relationship among various principles can be explained clearly.

关键词： unconventional Hamilton-type variational principle, geometric nonlinearity, coupled thermoelasto dynamics, dual-complementary relation, initial- boundary-value problem.

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Statistical distribution of nonlinear random wave height

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Science China Earth Sciences 2006年第4期49卷 443-448页

作者： HOU Yijun1, GUO Peifang1,2, SONG Guiting1,2, SONG Jinbao1, YIN Baoshu1 & ZHAO Xixi1,2 1. Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China 2. Graduate University of the Chinese Academy of Sciences, Beijing 100039, China Institute of Oceanology Chinese Academy of Sciences Qingdao China Graduate University of the Chinese Academy of Sciences Beijing China

A statistical model of random wave is developed using Stokes wave theory of water wave dynamics. A new nonlinear probability distribution function of wave height is presented. The results indicate that wave steepness not only could be a parameter of the distribution function of wave height but also could reflect the degree of wave height distribution deviation from the Rayleigh distribution. The new wave height distribution overcomes the problem of Rayleigh distribution that the prediction of big wave is overestimated and the general wave is underestimated. The prediction of small probability wave height value of new distribution is also smaller than that of Rayleigh distribution. Wave height data taken from East China Normal University are used to verify the new distribution. The results in- dicate that the new distribution fits the measurements much better than the Rayleigh distribution.

关键词： Random ocean wave, nonlinearity, wave height distribution.

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A reduced-order method for estimating the stability region of power systems with saturated controls

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Science China(Technological Sciences) 2007年第5期50卷 585-605页

作者： GAN DeQiang XIN HuanHai QIU JiaJu HAN ZhenXiang Department of Electrical Engineering Zhejiang University Hangzhou 310027 China Department of Electrical Engineering Zhejiang University Hangzhou 310027 China Department of Electrical Engineering Zhejiang University Hangzhou 310027 China Department of Electrical Engineering Zhejiang University Hangzhou 310027 China

In a modern power system, there is often large difference in the decay speeds of transients. This could lead to numerical problems such as heavy simulation burden and singularity when the traditional methods are used to estimate the stability re- gion of such a dynamic system with saturation nonlinearities. To overcome these problems, a reduced-order method, based on the singular perturbation theory, is suggested to estimate the stability region of a singular system with saturation nonlinearities. In the reduced-order method, a low-order linear dynamic system with saturation nonlinearities is constructed to estimate the stability region of the primary high-order system so that the singularity is eliminated and the estimation process is simplified. In addition, the analytical foundation of the reduction method is proven and the method is validated using a test power system with 3 buses and 5 machines.

关键词： saturation nonlinearity, power system stabilizer, linear matrix inequality, singular perturbation method, reduced-order method

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Theoretical analysis of thermal/electric-filed poling silica glass

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Science China(Technological Sciences) 2002年第6期45卷 646-653页

作者：刘雪明郑小平郭奕理张汉一李艳和 Department of Electronic Engineering Tsinghua University Beijing 100084 China

Based on the experimental results, three basic conclusions are summarized for the thermal/electric-field poling (TEFP) silica materials, with which the second-order nonlinear optical coefficient in the bulk silica glass after TEFP is calculated, and relationships between the coefficient and the applied voltage V 0 in the poling process and the thickness of the nonlinear layer created from the poling are obtained. Theoretical results show that the second-order susceptibility χ(2) and the second-harmonic efficiency η in the poled bulk glass are proportional to √V 0 and V 0 2 , respectively; χ(2)～0.2?1.6 pm/V for the bulk glass after the typical TEFP; χ(2) decreases with an increase in the poling time after the TEFP silica glass approximately reaches the steady state. Theoretical results are well consistent with the experimental reports.

关键词： silica, second-order nonlinearity, thermal/electric-field poling, carrier.

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High Nonlinear Optic Activity Chromophore-Design and Synthesis

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合成化学 2004年第Z1期12卷 7-7页

作者： He Mingqian Thomas M. Leslie Corning Incorporated SP-FR-6 Corning NY 14831 USACorning Incorporated SP-FR-6 Corning NY 14831 USA

Chromophores are the center piece of second order nonlinear optical (NLO) *** common chromophore consists of a Donor-Bridge-Acceptor structure. Donors and acceptors are connected by a bridge and together they make a fully conjugated system. Based on our previously synthesized novelacceptors [1], we have synthesized a large number of high electro-optic chromophores. In this paper, we report four general types of chromophore that *** during the last few years in our laboratory. Due to The general nature of our chromophore's structure it is best described as:In these structures, R2 and R3 are different groups or a spiro ring junction. Since they are connected to the chromophore with an SP3 hybridized carbon at the furan ring, they are both out of the plane of the conjugated chromophore system. This unique design greatly increases the chromophore's solubility and processability. We believe this design also prevents the highly dipolar,flat chromophores from achieving - stacking resulting on easier poling and a higher EO *** poling results proved our hypothesis with a world record 70 pm/V EO coefficient has been obtained at 1550nm in this class of chromophores.

关键词： Synthesis, chromophores, nonlinearity, optical materials, poling, EO coefficient

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