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Spatio-Temporal Characteristics of Standardized Precipitation Index in the Taihu Basin during 1951-2.00

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Wuhan university Journal of Natural sciences 2009年第6期14卷 518-524页

作者： LIU Xingcai XU Zongxue LIU Bo key laboratory of water and sediment sciences Ministry ofEducation/College of Water Sciences Beijing Normal UniversityBeijing 100875 China

Spatial and temporal characteristics of standardized precipitation index （SPI）, which is widely used for drought/flood monitoring, are investigated in this study. The purpose is to obtain a reasonable primary scheme of zoning on the basis of drought/ wetness conditions in the study area. Spatio-temporal distributions of SPI with the time scales of 3 months and 12.months are investigated with the datasets of precipitation in the Taihu basin during past decades （1951-2.00）. Results indicate that SPI series of 3 months show random fluctuation while that of 12.months behaves like I/f noise. SPI series of 3 months show little trend while that of 12.months show significant trend at several stations. Drought magnitude （DM） is also estimated on the basis of SPI values to assess drought condition. No trend is detected in DMs with time scales of both 3 months and 12.months. Spatial variability of DM is analyzed by mapping the DM with 12.months for extreme drought and wetness, and regional characteristics are analyzed for DM.

关键词： spatio-temporal distribution Taihu basin standardized precipitation index time scale zoning

Sieve M-estimation for semiparametric varying-coefficient partially linear regression model

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Science China Mathematics 2010年第8期53卷 1995-2010页

作者： HU Tao 1,2.& CUI HengJian 1,2.1 School of Mathematical sciences,beijing {2. university,laboratory of Mathematics and Complex Systems,ministry of education,beijing 100875,China 2.School of Mathematical sciences,Capital {2. university,beijing 100048,China 1. School of Mathematical sciences Beijing Normal University Laboratory of Mathematics and Complex Systems Ministry of Education Beijing 100875 China2. School of Mathematical Sciences Capital Normal University Beijing 100048 China

This article considers a semiparametric varying-coefficient partially linear regression *** semiparametric varying-coefficient partially linear regression model which is a generalization of the partially linear regression model and varying-coefficient regression model that allows one to explore the possibly nonlinear effect of a certain covariate on the response variable.A sieve M-estimation method is proposed and the asymptotic properties of the proposed estimators are *** main object is to estimate the nonparametric component and the unknown parameters *** is easier to compute and the required computation burden is much less than the existing two-stage estimation ***,the sieve M-estimation is robust in the presence of outliers if we choose appropriate ρ(·).Under some mild conditions,the estimators are shown to be strongly consistent;the convergence rate of the estimator for the unknown nonparametric component is obtained and the estimator for the unknown parameter is shown to be asymptotically normally *** experiments are carried out to investigate the performance of the proposed method.

关键词： partly linear model varying-coefficient robustness optimal convergence rate asymptotic normality

Quenched moderate deviations principle for random walk in random environment

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Science China Mathematics 2010年第8期53卷 1947-1956页

作者： HONG WenMing 1 & WANG HuaMing 1,2.1 key laboratory of Mathematics and Complex Systems of {2. of {2. & School of Mathematical sciences,beijing normal university,beijing 100875,China 2.Department of Basic Courses,Business college,beijing Union university,beijing 10002.,China 1. key laboratory of Mathematics and Complex Systems of {2. of {2. & School of Mathematical sciences Beijing Normal University Beijing 100875 China2. Department of Basic Courses Business College Beijing Union University Beijing 100025 China

We derive a quenched moderate deviations principle for the one-dimensional nearest random walk in random environment,where the environment is assumed to be stationary and *** approach is based on hitting time decompos... 详细信息

关键词： random walk in random environment moderate deviations principle hitting time

Characteristics of energy dissipation in hyperconcentrated flows

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International Journal of sediment Research 2008年第4期23卷 387-397页

作者： An-ping SHU 1,Qing-quan LIU2.Yu-jun YI 3,and Zhi-dong ZHANG 41 Assoc.Prof.,School of Environment,key laboratory of water and sediment sciences of ministry of {2.,beijing normal university,beijing 100875,China2.Prof.,Institute of Mechanics,Chinese Academy of sciences,beijing 100080,China3 Lecturer,Dr.,School of Environment,beijing normal university,beijing 100875,China4 Graduate student,School of Environment,beijing normal university,beijing 100875,China [a]Assoc. Prof. School of Environment key laboratory of water and sediment sciences of ministry of {2. beijing normal {2. beijing 100875 China [b]Prof. Institute of Mechanics Chinese Academy of sciences beijing 100080 China [c]Lecturer Dr. School of Environment beijing normal {2. beijing 100875 China. The project is supported by the National Natural Science Foundation of China (Grant No. 10672.2.) [d]Graduate student School of Environment beijing normal {2. beijing 100875 China

An equilibrium equation for the turbulence energy in sediment-laden flows was derived on the basis of solid–liquid two-phase flow theory. The equation was simplified for two-dimensional, uniform, steady and fully developed turbulent hyperconcentrated flows. An energy efficiency coefficient of suspended-load motion was obtained from the turbulence energy equation, which is defined as the ratio of the sediment suspension energy to the turbulence energy of the sediment-laden flows. laboratory experiments were conducted to investigate the characteristics of energy dissipation in hyperconcentrated flows. A total of 115 experimental runs were carried out, comprising 70 runs with natural sediments and 45 runs with cinder powder. Effects of sediment concentration on sediment suspension energy and flow resistance were analyzed and the relation between the energy efficiency coefficient of suspended-load motion and sediment concentration was established on the basis of experimental data. Furthermore, the characteristics of energy dissipation in hyperconcentrated flows were identified and described. It was found that the high sediment concentration does not increase the energy dissipation; on the contrary, it decreases flow resistance.

关键词： Hyperconcentrated flows Turbulence energy Efficiency coefficient Energy dissipation

Redevelopment of liftoff rates of saltating sand grains based on a simple optimization model

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Science China Earth sciences 2010年第4期53卷 568-574页

作者： CHENG Hong & ZOU XueYong State key laboratory of Earth Surface Processes and Resource Ecology,{2. {2. university,{2. 100875,China MOE Engineering Center of Desertification and Blown-sand Control,{2. {2. university,{2. 100875,China key laboratory of Environmental Change and Natural Disaster of the ministry of education of China,{2. {2. university,{2. 100875,China 1. State key laboratory of Earth Surface Processes and Resource Ecology Beijing Normal University Beijing 100875 China2. MOE Engineering Center of Desertification and Blown-sand Control Beijing Normal University Beijing 100875 China3. Key Laboratory of Environmental Change and Natural Disaster of the Ministry of Education of China Beijing Normal University Beijing 100875 China

This paper is a redevelopment result of liftoff rates of saltating sand grains based on our previous *** sand flow is a complex multi-phase flow because of a special two-phase gas-solid flow near ground *** extensive research on the movement of blowing sand,no model fully characterizes aeolian sand flow,and large differences often exist between simulations of aeolian sand movement and field *** key problem is a few of sufficient research on liftoff rates of saltating sand grains(also called the number of liftoff sand grains per unit time and per unit bed area).It is necessary to re-search in advance liftoff rates of saltating sand *** redeveloped liftoff rates of saltating sand grains by establishing an optimization model based on the flux of aeolian sand flow at different heights of the sampler in wind tunnel and the simulated capture of saltating sand grains by different heights of the sampler that are from different liftoff position(distance from the sampler) in order to revise previous inversion condition of liftoff rates of saltating sand *** rates increased rapidly with increasing wind *** frictional wind velocities of u=0.67,0.77,0.82.0.83,and 0.87 m s-1,liftoff rates were 3840,954502.52.5114,5499407,and 76962.1 sand grain s-1 m-2.*** rates could be expressed as the square of the instantaneous frictional wind velocity and a constant(0.663) that differs from the critical(threshold) frictional wind velocity at which saltation *** our results require additional experimental validation and the simple optimization model must be improved,they nonetheless provide a strong basis for future research.

关键词： liftoff rates of saltating sand grains optimization model wind tunnel two-phase gas-solid flow

APPLICATION OF SWAT MODEL IN THE UPSTREAM waterSHED OF THE LUOHE RIVER

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Chinese Geographical Science 2003年第4期13卷 334-339页

作者： ZHANG Xue-song, HAO Fang-hua, CHENG Hong-guang, LI Dao-feng (State key laboratory of {2. Environment Simulation,Institute of Environmental {2., beijing normal university,beijing 100875,P. R. China) State key laboratory of {2. Environment Simulation Institute of Environmental Sciences Beijing Normal University Beijing 100875 P. R. China

In the Huanghe (Yellow) River basin,soil erosion is a serious problem,while runoff and sediment yield simulation has not been extensively studied on the basis of GIS (Geographic Information System) and distributed hydrological model. GIS-based SWAT (Soil and water Assessment Tool) model was used to simulate runoff and sediment in the Huanghe River basin. The objective of this paper is to examine the applicability of SWAT model in a large river basin with high sediment runoff modulus,which could reach 770t/(km2.a). A two-stage "Brute Force" optimization procedure was used to calibrate the parameters with the observed monthly flow and sediment data from 1992.to 1997,and with input parameters set during the calibration process without any change the model was validated with 1998-1999’s observed data. Coefficient of examination (R2. and Nash-Suttcliffe simulation efficiency (Ens) were used to evaluate model prediction. The evaluation coefficients for simulated flow and sediment,and observed flow and sediment were all above 0.7,which shows that SWAT model could be a useful tool for water resources and soil conservation planning in the Huanghe River basin.

关键词： luohe river watershed SWAT model sediment flow

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基于条件异方差分析的水文时序模型及其应用

系统工程理论与实践 2009年第11期29卷 19-30页

作者：王红瑞高雄常晋源左恒北京师范大学水科学研究院-水沙科学教育部重点实验室北京100875 北京师范大学数学科学学院北京100875

针对条件异方差现象在水文过程的时序研究中常被忽略的情况,建立了水文过程时间序列分析和预测模型.首先,利用Census X12.解水文时序,由其得到的周期项与趋势项分别建立相应的条件异方差模型;其次,对于分解序列后得到的残差项,建立基... 详细信息

针对条件异方差现象在水文过程的时序研究中常被忽略的情况,建立了水文过程时间序列分析和预测模型.首先,利用Census X12.解水文时序,由其得到的周期项与趋势项分别建立相应的条件异方差模型;其次,对于分解序列后得到的残差项,建立基于BX数据生成的灰色Markov预测模型;再次,将三个模型进行耦合,编制了算法流程,由此提出了一种基于条件异方差的水文时序分析与预测模型;最后以河南省淮河流域的鲇鱼山水文站1975-1999年逐月的径流量为例进行了应用验证.研究结果表明:提出的模型从预测效果来看,总的平均偏差只有17.42.,其精度要明显高于常规的水文时序分析中ARCH和ARMA(1,1)等传统方法.

关键词：时间序列分解条件异方差模型灰色BX数据生成法灰色Markov预测模型鲇鱼山水文站

Eco-environmental water requirement for wetlands in Huang-Huai-Hai Area, China

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Progress in Natural Science:Materials International 2002年第11期 43-50页

作者： GUI Baoshan and YANG Zhifeng(1. Institute of Environmental sciences, beijing normal university State {2. Joint {2. of Environmental Simulation and Pollution Control, beijing 100875, China 2. Institute of water sciences, beijing normal university {2. {2. for water and sediment sciences, ministry of education, beijing 100875, China) Institute of Environmental sciences，beijing {2. university State key Joint laboratory of Environmental Simulation and Pollution Control，{2. {2.，China Institute of Environmental sciences，beijing {2. university State key Joint laboratory of Environmental Simulation and Pollution Control，{2. {2.，China Institute of water sciences Beijing Normal University key laboratory for {2. and {2.

Based on the related literature and the analysis of the relationship between wetland ecosystem and hydroperiod, the estimating and classifying methods of eco-environmental water requirement for wetlands are established. The data collected from Huang-Huai-Hai Area are from the electronic map (1:2.0000) of China National Topographical Database of 1997 and the historical statistics since the 1980s. The results indicate that the minimum eco-environmental water requirement for wetlands is 16.98 × 10 m and the optimal one is 38.38 × 109 m3 in the studied area. For the five wetland nature reserves covered in the area, the values are 1. 47 × 109 m3 and 3. 31 × 109 m3 respectively. The comparisons of the mentioned minimum water requirement with the status water use, which is 17.05 × 109 m3 for wetland ecosystem (1997 as the status year), suggest that the water use has not met the minimum eco-environmental water requirement in the Haihe and Huanghe Basins of the studied area. However, the status water use gu

关键词： eco-environmental water requirement wetlands Huang-Huai-Hai Area.

Anomalous magnetotransport in LaMn_(1-x)Te_xO_3

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Science China(Physics,Mechanics & Astronomy) 2009年第7期52卷 987-992页

作者： TAN GuoTai1,2. CHEN ZhengHao3 & ZHANG XiaoZhong4,5 1 key laboratory of Beam Technology & Materials Modification of the {2. of {2., Institute of Low Energy Nuclear Physics, beijing normal university, beijing 100875, China 2.beijing Radiation Center, beijing 100875, China 3 laboratory of Optical Physics, Institute of Physics, Chinese Academy of sciences, beijing 100080, China 4 key laboratory of Advanced Materials of the {2. of {2., Department of Materials Science and Engineering, Tsinghua university, beijing 100084, China 5 beijing National Center for Electron Microscopy, Tsinghua university, beijing 100084, China 1. key laboratory of Beam Technology & Materials Modification of the {2. of {2. Institute of Low Energy Nuclear Physics Beijing Normal University Beijing 100875 China 2. beijing Radiation Center Beijing 100875 China 3. laboratory of Optical Physics Institute of Physics Chinese Academy of Sciences Beijing 100080 China 4. key laboratory of Advanced Materials of the {2. of {2. Department of Materials Science and Engineering Tsinghua University Beijing 100084 China 5. beijing National Center for Electron Microscopy Tsinghua University Beijing 100084 China

The LaMn1-xTexO3+δ (x=0.1, 0.2. 0.3) were synthesized using solid-state reaction method for the first time. X-ray photoemission spectrum (XPS) shows that in the samples the Te ions have a valence of Te4+, and Mn3+ ions are partly converted into Mn2. and Mn4+ due to the excess oxygen and Te doping. The magnetotransport associated with Mn2., Mn3+ and Mn4+ was investigated. The experimental results show that the samples are insulator at 0 T when the amount of Mn3+ is much larger or less than the sum of Mn2. and Mn4+; by contrast, the samples display metal to insulator transition with increasing temperature when the amount of Mn3+ is close to the sum of Mn2. and Mn4+. These anomalous magnetotransport behaviors were analyzed in the frame of the double-exchange (DE) mechanism.

关键词： colossal magnetoresistance La-Te-Mn-O magnetotransport