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Sediment transport capacity of hyperconcentrated flow

Science china(Physics,Mechanics & Astronomy) 2008年第8期51卷 961-975页

作者： SHU AnPing1,2.& FEI XiangJun2.1 School of Environment & Key Laboratory of Water and Sediment Sciences,Ministry of Education,beijing Normal university,beijing 100875,china 2.State Key Laboratory of Hydroscience and Engineering,tsinghua university,beijing 100084,china School of Environment & Key Laboratory of Water and Sediment Sciences Ministry of Education Beijing Normal University Beijing 100875 China State Key Laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 China

As one of the most important components of river mechanics,sediment transport capacity of sediment-laden flows has attracted much attention from many researchers working on river mechanics and hydraulic engineering. Based on the time-averaged equation for a turbulent energy equilibrium in solid and liquid two-phase flow,an expression for the efficiency coefficient of suspended load movement was derived for the two-dimensional,steady,uniform,fully-developed turbulent flow. A new structural expression of sediment transport capacity was achieved. Using 115 runs of flume experimental data,which were obtained through two kinds of sediment transport experiments in the state of equilibrium,in combination with the basic rheological and sediment transporting characteristics of hyperconcentrated flow,the main parameters in the structural expression of sediment transport capacity were calibrated,and a new formula of sediment transport capacity for hyperconcentrated flow was developed. A large amount of field data from the Yellow River,Wuding River,and Yangtze River,etc. were adopted to verify the new formula and good agreement was obtained. These results above contribute to an improved theoretical system of river mechanics and a reliable tool for management of rivers carrying high concentration of sediments.

关键词： hyperconcentrated flow turbulent energy equilibrium efficiency coefficient sediment transport capacity

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Parameter identification theory of a complex model based on global optimization method

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Science china(Physics,Mechanics & Astronomy) 2008年第11期51卷 1722-1732页

作者： QU Jie1, JIN QuanLin2.& XU BingYe3 1 College of Automotive Engineering, South china university of Technology, Guangzhou 510640, china 2.beijing research Institute of Mechanical and Electrical Technology, beijing 100083, china 3 Department of Engineering Mechanics, tsinghua university, beijing 100084, china 1. College of Automotive Engineering South China University of Technology Guangzhou 510640 China 2. beijing research Institute of Mechanical and Electrical Technology Beijing 100083 China 3. Department of Engineering Mechanics Tsinghua University Beijing 100084 China

With the development of computer technology and numerical simulation technology, computer aided engineering (CAE) technology has been widely applied to many fields. One of the main obstacles, which hinder the further application of CAE technology, is how to successfully identify the parameters of the selected model. An elementary framework for parameter identification of a complex model is provided in this paper. The framework includes the construction of objective function, the design of the optimization method and the evaluation of the identified results, etc. The parameter identification process is described in this framework, taking the parameter identification of the superplastic constitutive model considering grain growth for Ti-6Al-4V at 92.°C as an example. The objective function is the weighted quadratic sums of the difference between the experimental and computational data for the stress-strain relationship and the grain growth relationship; the designed optimization method is a hybrid global optimization method, which is based on the feature of the objective function and incorporates the strengths of genetic algorithm (GA), the Levenberg-Marquardt algorithm and the augmented Gauss-Newton algorithm. The reliability evaluation of parameter identification result is made through the comparison between the calculated and experimental results and between the theoretical values of the parameters and the identified ones.

关键词： constitutive model parameter identification theory inverse analysis global optimization

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Temperature-controlled ionic liquid dispersive liquid phase microextraction combined with ultra-high-pressure liquid chromatography for the rapid determination of triclosan,triclocarban and methyl-triclosan in aqueous samples

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Science china Chemistry 2010年第12期53卷 2600-2607页

作者： GUO JieHong 1,2.LI XingHong 2.CAO XueLi 1,QU Lei 2.3,HOU DeKun 2.& XU XiaoBai 2.1 School of Chemical and Environmental Engineering,beijing Technology and Business university,beijing 100048,china 2.State Key Laboratory of Environmental Chemistry and Eco-toxicology research center of Eco-Environmental Sciences,Chinese Academy of Sciences,beijing 100085,china 3 Zhengzhou university,Zhengzhou 450001,china 1. School of Chemical and Environmental Engineering Beijing Technology and Business University Beijing 100048 China2. State Key Laboratory of Environmental Chemistry and Eco-toxicology research center of Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China3. Zhengzhou University Zhengzhou 450001 China

As extraction solvents,ionic liquids have green *** this study,an environmentally benign analytical method termed temperature-controlled ionic liquid dispersive liquid phase microextraction (TIL-DLME) combined with ultra-highpressure liquid chromatography (UHPLC)-tunable ultraviolet detection (TUV) was developed for the pre-concentration and determination of triclosan (TCS),triclocarban (TCC) and methyl-triclosan (M-TCS) in water *** parameters that may affect extraction efficiencies were examined and optimized,including the types and amount of ionic liquids,volume of the diluent,heating temperature,cooling time,salt effect and pH *** the optimum conditions,linearity of the method was observed in the ranges of 0.0100-100 μgL-1 for TCS and M-TCS,and 0.00500-50.0 μgL-1 for TCC with correlation coefficients (r2. > *** limits of detection (LODs) ranged from 1.15 to 5.33 *** in domestic water and TCC in reclaimed water were detected at the concentrations of 1.01 and 0.12. μgL-1,*** spiked recoveries of the three target compounds in reclaimed water,irrigating water,waste water and domestic water samples were obtained in the ranges of 68.4%-71.9%,61.6%-87.8%,58.9%-74.9% and 64.9%-92.4%,*** with the previous dispersive liquid-liquid microextraction method (DLLME) about the determination of TCS,TCC and M-TCS,this method is not only more environmentally friendly but also more sensitive.

关键词： ionic liquid temperature-controlled ionic liquid dispersive liquid phase microextraction UHPLC aqueous samples

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Theoretical analysis of transmission characteristics for all fiber,multi-cavity Fabry-Perot filters based on fiber Bragg gratings

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Science in china(Series F) 2008年第9期51卷 1391-1400页

作者： XU Ou1,2.LU ShaoHua1,2.DONG XiaoWei1,2.LI Bin1,2.NING TiGang1,2.& JIAN ShuiSheng1,2.1 Key Lab of All Optical network & Advanced Telecommunication network of EMC,{2. Jiaotong university,{2. 100044,china 2.Institute of Lightwave Technology,{2. Jiaotong university,{2. 100044,china Key Lab of All Optical network & Advanced Telecommunication network of EMC Beijing Jiaotong University Beijing 100044 China Institute of Lightwave Technology Beijing Jiaotong University Beijing 100044 China

The characteristics of transmission spectra for the all fiber, multi-cavity Fabry- Perot （FP） configuration based on fiber Bragg gratings （FBG） are theoretically analyzed and modeled. The general transmission matrix function for the structure with any number of cavities is derived, and explicit expression of the power trans- mission coefficient for symmetrical two-cavity FP is presented. The general condi- tions for flat-top single resonant peak at the central wavelength in FBG stop band are derived and verified in the numerical simulation section. The transmission peaks of single-cavity and two-cavity FP structures are compared and discussed, and results show that compared to the single-cavity FP, flatness of the top and steepness at the edge of transmission peak can be improved by introducing one more cavity. The resonant transmission peak properties of two-cavity structure are investigated in detail for various values of cavity length and FBGs with different reflection characteristics, and the design guidelines for transmission-type filters are presented. The results show that the steepness of peak slope can be improved by increase of FBG reflectivities, and these kinds of filters can be used as nar- row-band single-channel selectors and multi-channel wavelength de-multiplexing by properly choosing the length of cavities and reflectivities of FBGs.

关键词： fiber Bragg gratings Fabry-Perot cavity transmission-type filter

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Distribution,formation and evolution of sand ridges on the East china Sea shelf

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Science china(Technological Sciences) 2010年第3期53卷 822-828页

作者： ZHAO RenBao 1,2.SUN HaiTao 3,WU YaSheng 3 &ZHAO ChuanFeng 1,2.1MOE Key Laboratory of Petroleum Engineering,china university of Petroleum,{2. 102.49,china 2.Enhanced Oil Recovering research center,china university of Petroleum,{2. 102.49,china 3Faculty of Natural Resource&Information Technology,china university of Petroleum,{2. 102.49,china 1. MOE Key Laboratory of Petroleum Engineering China University of Petroleum Beijing 102249 China2. Enhanced Oil Recovering Research Center China University of Petroleum Beijing 102249 China3. Faculty of Natural Resource & Information Technology China University of Petroleum Beijing 102249 China

Influence of CO2.corrosion on reservoir mineralogical composition,pore structure and their mechanical characteristics was studied using XRD,SEM,rock tri-axial machine and core flow experimental *** was found that the corrosion effect was mainly attributed to rock texture and structure,fluid composition and external dynamical conditions in the experimental *** cores with bedding structures,their bedding surfaces were the preferential corrosion regions,because micro-cracks would evolve at these surfaces in the pressure-releasing ***,for cores with massive structures controlled by stable water environment,the CO2.corrosion would result in pore enlargement and secondary pore *** gas velocity from outlet showed sharp increase in the injection process of CO2.H2. *** could be explained by two changes caused by *** was the opening and closure of *** other was particle *** the corrosion time increased,both tensile strength and compressive strength decreased,which confirmed decrease of cementation *** should also be noted that permeability increase and micro-cracks generation would pose damage to the capacity of CO2.geological storage.

关键词： carbon dioxide geological storage mineralization enhanced oil recovery corrosion

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An introduction to tsinghua Cloud

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Science china(Information Sciences) 2010年第7期53卷 1481-1486页

作者： ZHENG WeiMin1,2.1Department of Computer Science and Technology, tsinghua university, beijing 100084, {2. 2.3} National Laboratory for Information Science and Technology, beijing 100084, {2. 1. Department of Computer Science and Technology Tsinghua University Beijing 100084 China2. Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China

Cloud computing has become a trend that draws attention from both academia and industry all over the world. This paper unveils details of tsinghua Cloud, a comprehensive solution for cloud computing developed by Tsing... 详细信息

关键词： cloud computing distributed file system virtual computing environment data sharing

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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 Ministry of Education, 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 Ministry of Education, 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 Ministry of Education 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 Ministry of Education 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

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Analysis of coupling from core mode to counter-propagating radiation modes in tilted fiber Bragg gratings

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Science china(Information Sciences) 2010年第5期53卷 1078-1088页

作者： LU ShaoHua 1,2., XU Ou 1,2., FENG SuChun 1,2., DONG XiaoWei 1,2., PEI Li 1,2.& JIAN ShuiSheng 1,2.1 Key Laboratory of All Optical network & Advanced Telecommunication network of EMC, {2. Jiaotong university, {2. 100044, china 2.Institute of Lightwave Technology, {2. Jiaotong university, {2. 100044, china 1. Key Laboratory of All Optical network & Advanced Telecommunication network of EMC Beijing Jiaotong University Beijing 100044 China2. Institute of Lightwave Technology Beijing Jiaotong University Beijing 100044 China

Radiation-mode coupling is stronger and more efficient in tilted fiber Bragg gratings than in other fiber gratings; it has good advantage in such fields as optical communication and optical sensors. A simplified coupled-mode theory (CMT) approach is proposed for what we believe to be the first time, whose validity is demonstrated by comparing its simulation results with that of the complete CMT equations. With the simplified CMT approach, a theoretical spectral analysis of coupling from core mode to counter-propagating radiation modes in reflective tilted fiber Bragg gratings is presented. The influence of grating length, refractive index modulation amplitude and tilt angle is exhaustively investigated on the transmission spectrum characteristics. The different dependences between s-polarized and p-polarized radiation-mode coupling on grating tilt angle are discussed, and the coupling strength of 45 -tilted gratings shows the greatest polarization dependence with the limitation of backward-propagating radiation-mode coupling.

关键词： fiber optics tilted fiber Bragg gratings coupled-mode theory radiation-mode coupling

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Investigating spatial distribution of tourist attractions’inlinks: A case study of three mountains

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Science china(Technological Sciences) 2010年第S1期53卷 126-133页

作者： ZHANG Yi 1,QI LiNa 2.YANG AnRan 1,SHI Lei 1 & XU Li 1 1 Institute of RS and GIS,Peking university,beijing 100871,{2. 2.center for Recreation and Tourism research,Peking university,beijing 100871,{2. Peking Univ Inst RS & GIS Beijing 100871 Peoples R China Peking Univ Ctr Recreat & Tourism Res Beijing 100871 Peoples R China

In hyperlink analysis,most researchers focus on interpreting hyperlink counts,they seldom concern themselves enough about the significance of spatial distribution of *** this paper,we argue that not only can the inlink count to a tourist attraction’s official website reflect its attractiveness,but also the spatial distribution of its inlinks can reflect the distribution of its tourist source *** mountains in Anhui Province,china,are chosen for the case ***,the correlation between the spatial distributions of an attraction’s tourist source markets and its official website’s inlinks is ***,the tourism indexes such as the spatial concentration index(SCI)and the attraction radius(AR),which are calculated by inlinks,are compared to the real indexes based on tourist ***,the detailed discussion and analysis are presented and an improved model,which is used to calculate the distribution of inlinks,is proposed.

关键词： tourist attractiveness hyperlink analysis spatial distribution of hyperlinks tourist source market

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Adjoint method for the optimum planning of industrial pollutant sources

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Science china Earth Sciences 2005年第8期48卷 1270-1279页

作者： LIU Feng1,2. HU Fei2.& ZHU Jiang2.1. College of Environmental Sciences, Peking university, beijing 100871, {2. 2. LAPC, Institute of Atmospheric Physics, Chinese Academy of Sciences, beijing 10002., {2. 1. College of Environmental Sciences Peking University 100871 Beijing China 2. LAPC Institute of Atmospheric Physics Chinese Academy of Sciences 100029 Beijing China

The optimum planning of industrial pollutant sources, which optimizes the economic object without violating environmental constraints, is an important and hard task to be conquered. In this paper, an adjoint method is developed to solve the problem. The penalty function is in-troduced to deal with the environmental inequality constraints, and Lagrange function is con-structed to derive the adjoint equation and the gradient of the object function. In this means, the gradient of the object function can be calculated by solving the adjoint equation, and the infor-mation from the gradient is used to make the object function descend and approach to an optimal solution after some iterations. A two-dimensional, simplified model is used for numerical experi-ments. The theoretical derivations are verified by the results of the experiments. Furthermore, the adjoint method is shown to be of excellent convergence and efficiency, which is adaptive to the fast development of air quality numerical models and super computers.

关键词： optimum planning, industrial pollutant sources, adjoint equation, penalty function, gradient.

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