检索结果-南通市图书馆

On the siltation of the middle Yangtze River

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china earth sciences 2004年第5期47卷 463-480页

作者： YIN Hongfu1, CHEN Guojin2, LI Chang抋n1 & WEI Yuan3.1. school of earth sciences,{3., Wuhan 43.074, china 2. Hydrogeological Team, Hubei Bureau of Geology and Mineral resources, Jingzhou 43.100, china 3. Geological Survey of Jiangxi Province, Nanchang 3.0201, china school of earth sciences China University of Geosciences Wuhan 430074 China Hydrogeological Team Hubei Bureau of Geol./Mineral Rsrc. Jingzhou 434100 China Geological Survey of Jiangxi Prov. Nanchang 330201 China

About 5.2×108 t/a of silts from the upper reach of the Yangtze River are transported through Yichang into the middle Yangtze River. The middle Yangtze itself and its tributaries yield ca. 0.8×108 t silts annually. Of this total 6×108 t/a input of silts, ca. 1.2×108 t/a are deposited within the river artery and lakes, while ca 4.83.108 t/a are at first transported into the lower reach through Datong, and then either deposited along the river and the Yangtze Delta, or output into the sea. Along the middle Yangtze River silting generally exceeds scouring, but the spatial and temporal distributions of scour-and-fill, as well as its distribution in the river valley transections, are uneven. Along the Yichang-Chenglingji and Jiujiang-Datong Segments of the middle Yangtze, scouring exceeds or equals silting. Silting mainly occurs along the Luoshan-Wuhan-Huangshi Segments with Wuhan as the pivotal point, as well as in the Dongting and Poyang Lakes. Even in these silting-dominated areas, there are times and parts of segments that scouring prevails. As to the transections, generally the river channel of main stream is scouring-dominated, forming V-shaped sections to a depth of 203. m or more, whereas the floodplains and bar islands are silting-dominated, forming wide and relatively high flats, which are often artificially transformed into protected embankments. Because the Jingjiang Levee separates the Jianghan Plain from Yangtze to the south, little has been deposited in that plain except a few sediments from the Han River—a tributary of the middle Yangtze. This factor plus the tectonic sag of that plain has made the altitude of plain surface several meters lower than that of the levee in most of the areas. Sil-tation along the Luoshan-Wuhan-Huangshi Segments has resulted in the elevation of flood level in this and upstream segments. River channel scouring plus floodplain silting have caused the transections of the middle Yangtze valley typically with deep channel and height

关键词： the middle Yangtze, scour-and-fill, siltation, silt utilization.

Response of remotely sensed Normalized Difference Water Deviation Index to the 2006 Drought of eastern Sichuan Basin

在线全文

学校读者我要写书评

暂无评论

Science china earth sciences 2008年第5期51卷 748-758页

作者： ZHANG WenJiang1, LU QiFeng2, GAO ZhiQiang3.& PENG Jian4 1 school of Water Resource and Hydropower, Sichuan university, Chengdu 610065, china 2 National Satellite Meteorological Center, china Meteorological Administration, beijing 100081, china 3.Institute of Geographic sciences and Natural resources Research, Chinese Academy of sciences, beijing 100101, china 4 school of Environmental sciences, Peking university, beijing 100871, china school of Water Resource and Hydropower Sichuan University Chengdu China National Statellite Meteorological Center China Meteorological Administration Beijing China Institute of Geographic sciences and Natural resources Research Chinese Academy of Sciences Beijing China school of Environmental sciences Peking University Beijing China

One of the most serious droughts in last century occurred in eastern Sichuan Basin in the summer of 2006 (hereinafter called the Drought). The response of Moderate Resolution Imaging Spectroradiometer (MODIS, boarding on NASA satellites of Terra and Aqua) to the Drought was analyzed in order to reach one practicable monitoring solution for regional soil moisture. Temporal process and spatial extension of the Drought were firstly estimated with ground meteorological and hydrological observations. Then, for the whole region of Sichuan and Chongqing, the remotely sensed Normalized Difference Water In- dex (NDWI) for the summers of 2001―2006 were calculated based on 8-day composite MODIS products, which were further used to construct a new water index (Normalized Difference Water Deviation Index, NDWDI) to examine the sensitivity of remote sensing in the Drought. The study showed that the NDWDI is more sensitive to regional drought than other absolute-soil-moisture-based indices. With the new index, the study extracted the spatial-temporal characteristics of the 2006 Drought, and explored its developing and withdrawing processes, which agreed with related statistics. Compared with ground method of drought observation, the NDWDI-based remote sensing solution of this paper is more pref- erable and practicable in that the local soil properties of water consumption and supply are implicitly taken into account, and the spatial representativity limit of ground observation is circumvented to a degree as satellite remotely senses the earth surface in a way of two-dimensional pixel matrix. So, the NDWDI-based method can be used to monitor regional soil water stress situation more practically and efficiently.

关键词： Sichuan Basin drought Normalized Difference Water Deviation Index response of remote sensing regional scale

Uniqueness and local stability for the inverse scattering problem of determining the cavity

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2005年第8期48卷 1113-1123页

作者： FENG Lixin & MA Fuming LMAM, school of Mathematical sciences, Peking university, {3. 100871, china school of Mathematical sciences, Heilongjiang university, Harbin 150080, china school of Mathematical sciences, Jilin university, Changchun 13.012, china LMAM School of Mathematical Sciences Peking University Beijing China school of Mathematical sciences Heilongjiang University Harbin China school of Mathematical sciences Jilin University Changchun China

Considering a time-harmonic electromagnetic plane wave incident on an arbitrarily shaped open cavity embedded in infinite ground plane, the physical process is modelled by Maxwell's equations. We investigate the inverse problem of determining the shape of the open cavity from the information of the measured scattered field. Results on the uniqueness and the local stability of the inverse problem in the 2-dimensional TM (transverse magnetic) polarization are proved in this paper.

关键词： uniqueness, stability, Maxwell's equations, inverse scattering problem.

Molecular mechanism of dehydrin in response to environmental stress in plant

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2007年第3期17卷 237-246页

作者： ZHANG Yuxiu , WANG Zi and XU Jin (Department of Bioengineering, school of Chemical and Environmental Engineering, china university of Mining and Technology ({3.), beijing 100083, china Department of Biology, Graduate university of Chinese Academy of sciences, {3. 100049, china) Department of Bioengineering School of Chemical and Environmental Engineering China University of Mining and Technology (Beijing) Beijing 100083 China Department of Biology Graduate University Chinese Academy of Sciences Beijing 100049 China

Dehydrins, known as the D-11 subgroup of late embryogenesis abundant (LEA) protein, are an immunologically distinct family of proteins, which typically accumulate in desiccation-tolerant seed embryo or in vegetative tissues in response to various environmental stresses such as drought, salinity and freezing. The existence of conservative sequences designated as K, S, and Y segments is a structural feature of dehydrins, and the K segment found in all dehydrins represents a highly conserved 15 amino acid motif (EKKGIMDKIKEKLPG) and forms an amphiphilicα-helix. According to the arrangement of these domains and clustering analysis, dehydrins are subdivided into 5 subtypes: YnSK, Kn, KnS, SKn and YnK. Different types of dehydrins are induced by different environmental stress in plants. Study results showed that dehydrins might play important protective roles under abiotic stress via a number of different mechanisms, including improving or protecting enzyme activities by the cryoprotective activity in responding to freeze/thaw or dehydration; stabilizing vesicles or other endomembrane structures by function as the membrane stabilizer during freeze induced dehydration, and preventing the membrane system from the oxidative damage induced by reactive oxygen radicals as the radical scavenger. Here, the gene expression and molecular mechanisms of dehydrin in response to stress in plants are discussed.

关键词： dehydrin stress mechanism.

Re-Os(ICP-MS)dating of the massive sulfide ores from the Jinchuan Ni-Cu-PGE deposit

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china earth sciences 2005年第10期48卷 1672-1677页

作者： YANG Gang1,2, DU Andao1, LU Jiren3. QU Wenjun1 & CHEN Jiangfeng2 1. National Research Center of Geoanalysis, beijing 10003., china 2. Laboratory for earth Material Cycling, {3. of earth and Space sciences, university of Science and Technology of china, Hefei 23.026, china 3. Institute of Mineral Resource, Chinese Academy of Geological sciences, beijing 10003., china National Research Center of Geoanalysis university of Science and Technology of china Chinese Academy of Geological sciences

Massive sulfide ore from the Jinchuan Ni-Cu-PGE deposit was dated by Re-Os technique using Carius Tube digestion, Os distillation, Re extraction by acetone and ICP-MS measurement. An isochron giving an age of 83. ± 3. Ma, initial 187Os/188Os ratio of 0.279 ± 0.018 (MSWD = 1.7) and γOs = 13. ± 15 is obtained. The Re-Os age obtained agrees, within analytical uncertainties, with previous SHRIMP zircon U-Pb age of 827 ± 8 Ma (n=5, MSWD = 4.3.. The result suggests that the deposit was formed at Neoproterozoic and that the formation of the Jinchuan Ni-Cu-PGE sulfide deposit may be closely related to the plume activity, which were attributed to the breakup of the Rodinia supercontinent. The high γOs of the massive ores sug-gests that crustal material was involved in the formation of the Jinchuan deposit, however, the quantity of the added crustal material is less than 10%.

关键词： Jinchuan Ni-Cu-PGE deposit, Re-Os dating, ICP-MS.

The new interpretation of support vector machines on statistical learning theory

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2010年第1期53卷 151-164页

作者： ZHANG ChunHua 1 , TIAN YingJie 2 & DENG NaiYang 3.1 school of Information, Renmin university of china, {3. 100872, china 2 Research Center on Fictitious Economy and Data Science, Chinese Academy of sciences, {3. 100080, china 3.College of Science, china Agricultural university, beijing 100083, china school of Information Renmin University of China Beijing China Research Center on Fictitious Economy and Data Science Chinese Academy of Sciences Beijing China College of Science China Agricultural University Beijing China

This paper is concerned with the theoretical foundation of support vector machines (SVMs). The purpose is to develop further an exact relationship between SVMs and the statistical learning theory (SLT). As a representative, the standard C-support vector classification (C-SVC) is considered here. More precisely, we show that the decision function obtained by C-SVC is just one of the decision functions obtained by solving the optimization problem derived directly from the structural risk minimization principle. In addition, an interesting meaning of the parameter C in C-SVC is given by showing that C corresponds to the size of the decision function candidate set in the structural risk minimization principle.

关键词： C-support vector classification the minimization principle of the structural risk KKT conditions

Node ordinal encoded genetic algorithm for the optimal allocation of water resources

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2005年第5期15卷 448-452页

作者： YANG Xiaohua1*, YANG Zhifeng 1,2, SHEN Zhenyao1 and LI Jianqiang3.1. State Key Laboratory of Water Environment Simulation, school of Environment, beijing Normal university, beijing 100875, china 2. Key Laboratory for Water and Sediment sciences Ministry of Education, school of Environment, beijing Normal university, beijing 100875, china 3. Water resources and Hydropower Planning and Design General Institute, MWR, beijing 100011, china) State Key Lab. of Water Environ. Simulation Sch. of Environ. Beijing Normal Univ. Beijing 100875 China Key Lab. for Water and Sediment Sci. Min. of Edu. Sch. of Environ. Beijing Normal Univ. Beijing 100875 China Water resources and Hydropower Planning and Design General Inst. MWR Beijing 100011 China

A new method, node ordinal encoded genetic algorithm (NOEGA), is proposed for solving water resources optimal allocation problems, in which the capacity of water resources is split into a number of smaller parts so that successive operations can be overlapped. Our objective is to maximize the whole benefit function. To overcome the “dimensionality and algorithm complexity curse” while searching for solutions and looking for an optimal solution, the operations of one-point crossover operator, gene exchange operator, gene random operator, gene shift operator and node ordinal strings are established. It is proved to be an effective optimal method in searching for global solutions. The NOEGA does not need a diversity of initial population, and it does not have the problem of immature convergence. The results of two cases show that using NOEGA to solve the optimal allocation model is very efficient and robust. In addition, the algorithm complexity of NOEGA is discussed.

关键词： water resources optimal allocation node ordinal code genetic algorithm.

The Crustal Shortening and Reconstruction of the Main Terranes Through Mesozoic-Cenozoic in Qinghai-Tibet Plateau

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

地学前缘 2009年第S1期16卷 270-271页

作者： Meifeng Shi~(1,2),Yalin Li~2,Ke Cao~2 1.Chengdu Institute of Geology and Mineral resources,Chengdu 610082,china. 2.school of {3. sciences and resources,china university of geosciences(beijing),beijing 100083,china

It is one of hot issues in Tibetan research that is to study the mode,process and kinetics of the crustal shortening during *** this paper, on the basis of systematic collection,analysis and research of the existing data and results from Himalayas,Lhasa and Qiangtang terranes,we conducted the balanced cross-section *** the north Qiangtang,the line-balanced cross-section

关键词： Qinghai-Tibet Plateau crustal shortening shortening value terrane

A　New　Mid　Early　Pleistocene　Mammalian　FaunaDiscovered　in　Choukoutien，china　and　Its　Application　in　Biostratigraphy

在线全文

学校读者我要写书评

暂无评论

Journal of earth Science 1995年第1期14卷 41-47,120页

作者： Cheng Jie(Department of Geology and Mineral resources, china university of geosciences,beijing {3.)Cao Boxun(Faculty of earth sciences, china university of geosciences,Wuhan 43.074)Tian MingZhong(Department of Geology and Mineral resources, china Unive

This paper deals with a new Early Pleistocene micromammalian fauna found in Choukonden (Zhoukoudian) and its application in *** new locality (east cave ), discovered in 1985,is located on the north slope of the Taipingshan Hill, about 2 km northeast of the Loc.1 in Choukoutien and is about 140-150m in altitude. At this locality,abundant fossil mammals are found in thick cave-fissure deposit. This fauna comprises 3.mammalian taxa. Based on the comparison of the fauna, as Well as the sporo-pollen, climate events and paleomagnetic polarity section with those in other areas,we come to the conclusion that the sediments (Taipingshan Formation) in east cave were formed during the Period about from 1.67 Ma B. P. to 0.97 Ma B. P., and the fauna is about 1.20 Ma B. P. in ags.

关键词： mid Early Pleistocene micromammalian fauna biostratigraphy Choukoutien.