检索结果-南通市图书馆

Eco-Environmental Vulnerability Evaluation in the Yellow River Basin,china

在线全文

学校读者我要写书评

暂无评论

Pedosphere 2008年第2期18卷 171-182页

作者： WANG Si-Yuan LIU Jing-Shi YANG Cun-jian Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100085 （China） Institute of Electronics Chinese Academy of Sciences Beijing 100080 （China） Centre of RS and GIS Applications Sichuan Normal University Chengdu 610066 （China）

Using remote sensing(RS)data and geographical information system(GIS),eco-environmental vulnerability and its changes were analyzed for the Yellow River Basin,*** objective of this study was to improve our understanding of eco-environmental changes so that a strategy of sustainable land use could be *** environmental numerical model was developed using spatial principal component analysis(SPCA)*** model contains twelve factors that include variables of land use,soil erosion,topography,climate,and *** this model,synthetic eco- environmental vulnerability index(SEVI)was computed for 1.90 and 2.00 for the Yellow River *** SEVI was classified into six levels,potential,slight,light,medium,heavy,and very heavy,following the natural breaks classification. The eco-environmental vulnerability distribution and its changes over the ten years from 1.90 to 2.00 were analyzed and the driving factors of eco-environmental changes were *** results show that the eco-environmental vulnerability in the study area was at medium level,and the eco-environmental quality had been gradually improved on the ***,the eco-environmental quality had become worse over the ten years in some *** the study area,population growth,vegetation degradation,and governmental policies for eco-environmental protection were found to be the major factors that caused the eco-environmental changes over the ten years.

关键词： eco-environmental vulnerability geographic information system (GIS) remote sensing (RS) spatial principal component analysis Yellow River Basin

Scattered Rural Settlements and Development of Mountainous Regions in Western Sichuan,china

在线全文

学校读者我要写书评

暂无评论

Wuhan University Journal of Natural sciences 2007年第4期12卷 737-742页

作者： gao Yanjun CHEN Guojie SHEN Maoying Key Laboratory of Mountain Hazards and Surface Process Chinese Academy of Sciences/Institute of Mountain Hazards and Environment Chinese Academy of Sciences Chengdu 610041 Sichuan China Graduate University of chinese academy of sciences Beijing 100049 China Sichuan academy of Social {1. Chengdu 610072 Sichuan China

Making rural settlements of Mountainous Regions in Western Sichuan as the study objects and using symbolic statistical methods, then combining the case study of Daofu County, the paper analyzes the negative impact of the scattered rural settlements on infrastructure construction, farmers＇ income increase and mountain ecological reconstruction in mountainous regions of western Sichuan. The results indicate that economic density is positively related to both rural settlements density （R^2.0.73） and rural population density （R^2.0.77）, and it is the same for relationship between towns density and rural settlements density （R^2.0.88） and between towns density and economic density （R^2.0.71., and the scattered distribution pattern of the rural settlements and shortage of economic centers is a major factor to the lagged socioeconomic development. On the eco-economic zoning to Daofu County, the paper indicates the spatial distribution model and the industrial development model of the rural settlements need to be changed, and rural population should be concentrated in larger rural settlements with development of off-farm industries while infrastructure construction is to reinforced.

关键词： mountainous regions in western Sichuan rural settlement scattered distribution development

Exact Convergence Rate of the Local Limit Theorem for a Branching Random Walk in Zd with a Random Environment in Time

在线全文

学校读者我要写书评

暂无评论

chinese Annals of Mathematics,Series B 2024年第5期 805-822页

作者： jian-xin LIU Zhi-qiang {1. School of Mathematical sciences Beijing Normal University Laboratory of Mathematics and Complex Systems (Ministry of Education) School of Mathematical Sciences Beijing Normal University

Abstract Consider a branching random walk with a random environment in time in the d-dimensional integer *** branching mechanism is governed by a supercritical branching process,and the particles perform a lazy random walk with an independent,non-identical increment *** A?Zd,let Z_n（A） be the number of offsprings of generation n located in *** exact convergence rate of the local limit theorem for the counting measure Zn（·） is *** partially extends the previous results for a simple branching random walk derived by gao （2.1.,*** Appl.）.

关键词：

Nematode Faunal Response to Grassland Degradation in Horqin Sandy Land

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Pedosphere 2007年第5期17卷 611-618页

作者： LIANG Wen-Ju ZHONG Shuang HUA jian-Feng CAO Cheng-You jianG Yong Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 （China） College of sciences Northeastern University Shenyang 110004 （China） Graduate School of the chinese academy of sciences Beijing 100049 （China）

The responses of soil nematode communities to grassland degradation were studied under undegraded grassland (UG), degraded grassland (DG),and improved grassland (IG),in Horqin Sandy Land,Inner Mongolia,Northeast *** samples were collected at depths of 0-1.,1.-2.,and 2.-30 *** organic carbon (TOC) and total nitrogen (TN) exhibited positive effects on the total number of nematodes and trophic *** treatment effects were found in the total number of nematodes,plant parasites,and *** taken in the improved grassland could improve the number of omnivore-predators,especially in the deeper soil *** richness was lower in the DG treatment than in the IG and UG *** food web structure index (SI) was significantly higher in the UG and IG treatments than in the DG treatment.A higher SI suggested a food web with more trophic linkages and relatively healthy ecosystems.

关键词： functional groups grassland degradation Horqin Sandy Land soil nematodes

Optimal representation of multivariate functions or data in visualizable low-dimensional spaces

在线全文

学校读者我要写书评

暂无评论

chinese Science Bulletin 2001年第16期46卷 1337-1345页

作者： SONG jian {1. {2. of Engineering, beijing 1.0038, china chinese {1. of Engineering Beijing China

It is intended to find the best representation of high-dimensional functions or multivariate data in L2.W) with fewest number of terms, each of them is a combination of one-variable function. A system of nonlinear integral equations has been derived as an eigenvalue problem of gradient operator in the said space. It proved that the complete set of eigenfunctions generated by the gradient operator constitutes anorthonormal system, and any function of L2.W) can beexpanded with fewest terms and exponential rapidity of convergence. It is also proved as a corollary, thegreatest eigenvalue of the integral operators hasmultiplicity 1.if the dimension of the underlying space nn = 2. 4 and 6.

关键词： nonlinear integral equations gradient operators eigenvalues orthonormal system of eigenfunctions optimal approximation.

Uncovering the electrooxidation behavior of 5-hydroxymethylfurfural on Ni/Co electrodes

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2024年第5期92卷 1-7页

作者： Shilin Fan Bin Zhu Xiao Yu Yang gao Weiping Xie Yong Yang {1. Zhang Chunlin Chen Ningbo Institute of Materials Technology&Engineering Chinese Academy of SciencesNingbo 315201ZhejiangChina University of chinese academy of sciences Beijing 100049China

Biomass,derived from plant photosynthesis that captures carbon dioxide to form carbohydrates,offers vast renewable *** electrooxidation of biomass,coupled with the hydrogen evolution reaction,enables the simultaneous production of biomass-based plastic monomers and green hydrogen,attracting significant scholarly ***,ambiguity remains regarding the adsorption mechanism at the catalyst surface(Langmuir-Hinshelwood or Eley-Rideal)and the adsorbed substrate *** address this,we prepared a Ni/Co electrode for the electrooxidation of 5-hydroxymethylfurfural(HMF)into 2.5-furandicarboxylic acid(FDCA)through a corrosion reaction and electro-reduction *** conversion reached 1.0.00%,FDCA yield reached 96.82.,and Faradic efficiency(FE)reached 92.1.%.Meaningfully,utilizing in-situ spectroscopy and electrochemical methods,this work provided valuable insights into active sites and catalyst surface adsorption.

关键词： Electrocatalysis Electrochemistry 2.5-Furandicarboxylicacid 5-Hydroxymethylfurfural Biomass

Observation constraints of the hard X-ray modulation telescope HXMT

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2010年第S1期53卷 31-35页

作者： LU Yu1.2.ZHANG WenZhao3,QU JinLu1.SONG LiMing1.gao {1.3,ZHANG HongMei4 & OU Ge4 1.Key Laboratory of Particle Astrophysics,Institute of High Energy Physics,{1. {2. of sciences,beijing 1.0049,china 2.Graduate University of{12.,beijing 1.0049,china 3 Department of Astronomy,beijing Normal University,beijing 1.0875,china 4 Computing Center,Institute of High Energy Physics,{1. {2. of sciences,beijing 1.0049,china Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing China Graduate University of chinese academy of sciences Beijing China Department of Astronomy Beijing Normal University Beijing China Computing Center Institute of High Energy Physics Chinese Academy of Sciences Beijing China

The hard X-ray modulation telescope HXMT is a low orbit X-ray space telescope whose main science goals are to accomplish a hard X-ray all sky survey and to study timing and spectral characteristics of X-ray *** has three kinds of science instruments:the high energy X-ray detector(HE),the medium energy X-ray detector(ME) and the low energy X-ray detector(LE).The observation schedule of HXMT is a key to achieving the science goal of HXMT,and the analysis of the observation constraints is one of the first tasks in making the observation *** paper analyzes how the observation constraints influence the sky visibility and the visible time distribution of X-ray sources and discusses the schedule strategy with regard to the observation constraints.

关键词： HXMT observation constraints sky visibility

A novel integrated step-feed biofilm process for the treatment of decentralized domestic wastewater in rural areas of china

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental sciences 2010年第3期22卷 321-327页

作者： Hanwen Liang, Min gao, Junxin Liu, Yuansong Wei, Xuesong Guo Research Center for Eco-Environmental {1.,{2., {2. 1.0085, china. Research Center for Eco-Environmental sciences Chinese Academy of Sciences Beijing 100085 Chin

For wastewater treatment in rural areas, a novel three-stage step-feed wastewater treatment system, combined with a drop-aeration biofilm process, was tested in the laboratory to investigate its performance in removing suspended solids （SS）, chemical oxygen demand （COD）, NH4＋-N, total nitrogen （TN）, and total phosphorus （TP）. The removal rates of SS, COD and NH4＋-N were 90%, 80%, and 90% in efluent concentrations less than 1. mg/L, 50 mg/L and 8 mg/L, respectively. The TP removal rate was less satisfactory. The C/N ratio in the raw wastewater was often less than 3.5, and the removal efficiency of TN was therefore limited. A carbon-release batch experiment was carried out to measure the feasibility of enhancing denitrification at low influent C/N ratios. The result showed that the C/N could be over 9.0 in the supernatant. Polymerase chain reaction denaturing gradient gel electrophoresis technology was used to reveal the changes in the bacterial community during different stages of the integrated step-feed biofilm process. The results showed that banding patterns and the distribution of dominant bands for the same experimental period in different aerobic zones were similar. Phylogenetic analysis indicated that lanes 1., 1. and 1., which presented three aerobic zones at the same operation period, had the closest phylogenetic relationship among the lanes.

关键词： step-feed biofilm removal efficiency PCR-DGGE C/N ratio

Zircon SHRIMP U-Pb dating for the Cangshuipu volcanic rocks and its implications for the lower boundary age of the Nanhua strata in South china

在线全文

学校读者我要写书评

暂无评论

Science Bulletin 2003年第16期48卷 1663-1669页

作者： WANG jian1, LI Xianhua2. DUAN Taizhong3, LIU Dunyi4, SONG Biao4, LI Zhongxiong1. & {1. Yonghua5 1. Chengdu Institute of Geology and Mineral Resources,{1. Geologi-cal Survey, Chengdu 61.082.{1. 2. Guangzhou Institute of Geochemistry, chinese academy of sciences, Guangzhou 51.640,{1. 3. Colorado School of Mines, Golden, CO 80401.1.87, USA (Present address: Marathon Oil Company, Houston, TX 77056-2.2., USA) 4. Institute of Geology, {12. academy of Geological sciences, Bei-jing 1.0037,{1. 5. Graduate School of the {12. academy of Geological sciences, {1.} 1.0037,{1. Correspondence should be addressed to Wang {1.} (e-mail: {1.}wang@ ***) Chengdu Institute of Geology and Mineral Resources China Geological Survey Chengdu 610082 China Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou 510640 China Colorado School of Mines Golden CO 80401-1887 USA Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China Graduate School of the chinese {1. of Geological {2. Beijing 100037 China

The continental volcanic rocks and volcaniclas-tic sedimentary conglomerates of the Cangshuipu Formation occur well in Yiyang of Hunan Province, consisting of a wedge-shaped succession of Neoproterozoic strata that over-lie with high-angle unconformity the flysch turbidites of the Lengjiaxi Group in the Upper Mesoproterozoic Eonothem. SHRIMP zircon U-Pb dating gives a weighted mean age of 81. 1. Ma for the dacitic volcanic agglomerates from the lowest part of the volcanic rocks in the Cangshuipu Forma-tion. This age is younger than previously reported values of 92.0}933 Ma for the volcanic rocks from the Cangshuipu Formation. Our new dating represents the lower boundary age of the Neoproterozoic System in the studied area. The younger age for the Cangshuipu volcanic rocks is supported by the following observations: （1. Lower Neoproterozoic strata （81.—1.00 Ma） are missing in the studied area; （2. the Nanhua rift system was initiated at about 82. Ma; and （3） an age of82. Ma may be taken as the lower boundary tim-ing of the Nanhua System （even Neoproterozoic） in South china.

关键词： Zicon U-Pb dating Neoproterozoic volcanics rift basin Nanhua System.