Introduction to Special Section on Tides     

A. D. Rao Professor  T. S. Murty Professor 《Marine Geodesy》2013,36(2-3)

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基于模糊综合评价模型的天津滨海新区湿地生态系统健康评价   总被引：3，自引：0，他引：3  

王秀明  李洪远  孟伟庆 《湿地科学与管理》2010,6(3):19-23

以环渤海地区的天津滨海新区湿地为例,运用模糊综合评价模型对湿地生态系统的健康进行了诊断评价。首先从湿地生态特征、整体功能特征和社会经济3方面选取26个评价指标,构建了天津滨海新区湿地生态系统健康的评价体系。评价等级分为很健康、健康、一般、一般病态、疾病5级,运用定量与定性相结合的方法界定等级。运用模糊综合评价模型对天津滨海新区湿地生态系统健康进行诊断,评价综合得分为0.48,健康水平处于疾病状态,主要表现在水质污染严重和水源保证水平低、景观破碎化、功能退化3个方面。  相似文献   

基于辛算法模拟探地雷达在复杂地电模型中的传播   总被引：2，自引：2，他引：0       下载免费PDF全文

方宏远  林皋 《地球物理学报》2013,56(2):653-659

近年来,探地雷达(GPR)凭借其快速、高效、无破损等特点,已经广泛应用于浅地层目标探测中.数值模拟是研究探地雷达电磁波在地下结构中传播规律的有效手段.辛算法是一种保持Hamilton系统总能量不变的时域数值计算方法.本文提出了基于一阶显式辛分块龙格库塔方法的探地雷达数值模拟方法.通过对比本文算法与时域有限差分方法计算结果可知,在同等计算精度下,本文算法可以节省25%的计算时间.并基于本文算法对两个复杂GPR模型进行正演模拟,得到模拟GPR探测wiggle图,这有助于更好的理解和分析实测雷达数据.  相似文献   

Vulnerability before adaptation: Toward transformative climate action     

Jesse Ribot Associate Professor 《Global Environmental Change》2011,21(4):1160-1162

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Estimation of soil erosion rates in a subtropical mountain watershed using 137Cs radionuclide     

Yu-Jia Chiu  Kang-Tsung Chang  Yi-Chin Chen  Jiunn-Hsing Chao  Hong-Yuan Lee 《Natural Hazards》2011,59(1):271-284

The formulation of watershed management strategies to protect water resources threatened by soil erosion and sedimentation requires a thorough understanding of sediment sources and factors that drive soil movement in the watershed. This paper describes a study of medium-term water-driven soil erosion rates in a mountainous watershed of the Shihmen Reservoir in Taiwan. A total of 60 sampling sites were selected along a hillslope. At each sampling site, the inventory ¹³⁷Cs activity was determined and then calculated with the diffusion and migration model to derive soil erosion rates. The rates are one to two orders of magnitude lower than estimates using the Universal Soil Loss Equation, a soil erosion model often used in Taiwan. Results of multiple regression analysis indicate that the spatial variability of soil erosion rates is associated with the relative position of a sampling site to the nearest ridge and soil bulk densities (r ² = 0.33, p < 0.01). Finally, the patterns of soil redistribution rates on the hillslope follow the ¹³⁷Cs hillslope model as soil erosion increases in the downslope direction. No deposition site is found at footslope because soil deposition is swept away by regular flooding along the stream channel. This study is an important first step in using ¹³⁷Cs as a tracer of soil redistribution in mountainous watersheds of Taiwan.  相似文献   

MODELING UNSTEADY TURBIDITY CURRENTS IN A STEEP NARROW RESERVOIR     

Shaohua Marko HSU  Associate Professor  Dr. Department of Hydraulic Engineering  Feng Chia University  Taichung  Taiwan  China Wei-Sheng YU Environment Section  Agricultural Engineering Research Center  Chungli  Taiwan  China Tzu-Ming LIU Graduate stu 《国际泥沙研究》1997,(3)

1.IN~DUCTIONTurbiditycurrentisoneclassofflowsnameddensitycurrentorgravitycurrent(therHunterRouse(Yih(1980)),whichdePictstheintmsionofheaVyfluidintoalighterone.Usually,thedensitydifferencebetWeentWonuidisrelativelysmallandmixingacrosstheimerfaceoccurs.ThedrivingforceofdensitycurrentsisnotdensitydifferenceitselfbutthedifferenceinspeCmcweights.Turbiditycurrentisnamedwhenthedensitydifferenceisespeciallycausedbysuspendedfinesedimentparticles.Sincesediment-ladenflowcaninteraCtwiththelowerbou…  相似文献   

MODELING SEDIMENT PROCESSES ON SMALL WATERSHEDS:A CONCEPTUAL FRAMEWORK Ⅰ. BROAD SHALLOW FLOW PROCESSE     

Vicente L. LOPES Assistant Professor  School of Renewable Natural Resources  The University of Arizona  Tucson  Arizona  Peter F. FFOLLIOTT Professor  School of Renewable Natural Resources  The University of Arizona 《国际泥沙研究》1992,(3)

A conceptual modeling framework for developing process-based mathematical models of sediment generation, transport, and deposition on broad shallow flow areas is presented. The governing equations relevant to process-based modeling of broad shallow flow sediment processes on small watersheds are presented and the effects of space and time averaging on the predictive equations are described. Starting from the most general one-dimensional, unsteady model of sediment processes, simpler model structures are obtained and the successive simplifications made on the governing equations in order to obtain simpler and less detailed formulations are described. Specific model formulations are given for illustrative purposes and applications of these models to erosion and sediment yield prediction from broad shallow flow areas are shown using sediment data from rainfall simulator plots. In spite of some progress made in the development of process-based erosion and sediment yield models from broad shallow flow areas, further developmental modeling efforts must be based on a clear separation between hydrologic and hydraulic processes, and the soil properties which are significant for each.  相似文献   

ON THE USE OF MOVABLE-BED MODELS FOR RIVER PROBLEMS:A STATE-OF-THE-ART     

M. de Vries G. J. Klaassen  N. Struiksma Professor  Delft University of Technology. The Netherlands.  Delft Hydraulics. The Netherlands. 《国际泥沙研究》1990,(1)

I. INTRODUCTIONMore than a decade ago, under tile auspices of DELFT HYDRAULICS an overview on the use ofmodels for river problems was given (de Vries & van der Zwaard. 1975). Since then a better understanding of morphological processes in rivers has been obtained, their mathematical formulation hasbeen improved and computer facilities have been expended. Scale models and mathematical models arein use. but their field of application is gradually changing. It seems that the better ma…  相似文献   

HYDRODYNAMIC MODELLING OF ESTUARINE CIRCULATION USING A SPLINE METHOD OF FRACTIONAL STEPS     

Pu Wang  R. Kahawita Professor of Mechanics  Lenzhou University  Lanzhou  China. Professor of Civil Ensineering  Ecole Polytechnique de Montreal Canada. 《国际泥沙研究》1990,(1)

I. INTRODUCTIONNumerical models of estuaries incorporating simulation of the density induced circulation are consideredimPOrtant tools in the assessment of their dispersive characteristics. Most models to date have used finite difference approximations to the governing equations (see for example thericke and Hogan, 1977, Blumberg,1 977, Perrels and Karelse, 1978). A numeriCal model of estuarine circulation using a SADI (Spline Alternating Direction implicit) procedure together with a…  相似文献   

IGU Commission on geographical education presents an international symposium     

Professor A. David Hill 《GeoJournal》1990,21(3):303-304

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