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Effects of the grain size distribution on the temperature-dependent magnetic susceptibility of magnetite nanoparticles

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Science china Earth sciences 2010年第7期53卷 1071-1078页

作者： ZHAO XiangYu1,2.& liu QingSong1 1 Paleomagnetism and Geochronology Laboratory (SKL-LE), institute of Geology and Geophysics,{2., {2. 10002.,{3. 2.Graduate University of{2., {2. 100049,{3. 1. Paleomagnetism and Geochronology Laboratory (SKL-LE) Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China2. Graduate University of Chinese Academy of Sciences Beijing 100049 China

Magnetite is an important magnetic remanence carrier in natural samples and therefore is of great interest in paleo-, rock-, and environmental magnetism. The magnetic properties of magnetite depend on many factors, e.g., concentration and grain size distribution (GSD). In this study, we theoretically investigated the temperature-dependent susceptibility (TDS) of magnetite nanoparticles with a lognormal GSD. Results show that the TDS is affected highly by the GSD mainly in three aspects. Firstly, the unblocking process becomes smoother with the increase of distribution width, characterizing as a wider Hopkinson peak on the TDS curve. Secondly, the blocking temperature increases with the increase of the median diameter or/and the distribution width. Thirdly, the maximum susceptibility decreases with the increase of distribution width, and has a logarithmic function relation with the standard deviation of the distribution. As a case study, this model was further applied to the thermal products of the chinese loess/paleosol samples to determine the granulometry of newly-formed magnetite upon heating based on TDS curves. The results demonstrate the fidelity and feasibility of this method to determine the GSD of nano-sized magnetic particles.

关键词： Néel theory temperature dependence of susceptibility grain size distribution

Response of remotely sensed Normalized Difference Water Deviation Index to the 2.06 Drought of eastern Sichuan Basin

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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, {2. 100081, china 3.institute of geographic sciences and natural resources research, chinese academy of sciences,{13., china 4 School of Environmental sciences, Peking University, {2. 100871, china 1. School of Water Resource and Hydropower Sichuan University Chengdu 610065 China 2. National Statellite Meteorological Center China Meteorological Administration Beijing 100081 China 3. institute of geographic {2. and {3. resources research Chinese Academy of Sciences Beijing 100101 China 4. School of Environmental sciences Peking University Beijing 100871 China

One of the most serious droughts in last century occurred in eastern Sichuan Basin in the summer of 2.06 (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 2.01―2.06 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 2.06 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

Analysis of Comprehensive Benefits of Transforming Slope Farmland to Terraces on the Loess Plateau:A Case Study of the Yangou Watershed in Northern Shaanxi Province,china

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Journal of Mountain Science 2011年第3期8卷 448-457页

作者： XU Yong YANG Bo TANG Qing liu Guobin liu Puling institute of geographic {2. and {3. resources research CAS Beijing 100101 China Graduate University of chinese academy of sciences Beijing 100049 China institute of Soil and Water Conservation CAS Yangling Shaanxi 712100 China

De-farming slope farmland has been an effective measure in recent years to improve environment and prevent soil and water loss on the Loess *** are different views about the defarming method,and also various de-farming patterns have been put into *** paper takes the Yangou Watershed in Shaanxi Province of china as a case for studying the comprehensive benefits of transforming slope farmland to *** on the day-by-day meteorological data of the Yan'an station in 2.05 and the data of terrain features,soil and land use data of the Yangou Watershed,the impact of transforming slope farmland on terraces were simulated and analyzed in aspects of yield increase and water-soil conservation under different topographic conditions with the aid of software ***,an empirical analysis was applied to study the effects of transforming slope farmland to terraces in the Yangou *** results show that:(1) The bigger the topographic gradient is,the more remarkable benefits it has in yield increase and water-soil conservation.(2. Farmland with slope below 5° could be retained,but farmland with slope above 15° should be converted to forest or grassland as soon as possible.(3. Transforming slope farmland to terraces has the same remarkable effects as the current policy of "Relieving and de-farming" in improving agricultural production conditions,safeguarding food security,raising permanent vegetation coverage rate,and preventing soil and water ***,it is more cost-effective than the policy of "Relieving and de-farming".It's strongly suggested that the policy of transforming slope farmland to terraces be carried out on the Loess Plateau without delay.

关键词： Slope farmland Terrace Comprehensive benefits Yangou Watershed Loess Plateau

Recent glacial retreat in High Asia in china and its impact on water resource in Northwest china

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Science china Earth sciences 2004年第12期47卷 1065-1075页

作者： YAO Tandong 1,2.,wang Youqing 2.,{3. Shiying 2.1 ,PU Jianchen 2.1 ,SHEN Yongping 2.& LU Anxin 2.1 1.{2. of Tibetan Plateau {2.,{3. academy of sciences,{13. 10002.,china 2.Cold and Arid Regions Environmental and Engineering {2. {2.,{3. academy of sciences,Lanzhou 73.000,china 1. chinese academy of sciences Institute of Tibetan Plateau Research 100029 Beijing China 2. chinese academy of sciences Cold and Arid Regions Environmental and Engineering Research Institute 730000 Lanzhou China

Under the impact of climatic warming, the glaciers in the High Asia in china have been retreating continuously with negative glacial mass balance in recent several decades. The retreat became more intensive in the past 10 years. The spatial pattern of the glacial retreat in the High Asia in china is that the smallest magnitude of retreat is in the inland of the Tibetan Plateau, the magnitude increases from the inland to the margin of the Tibetan Plateau, and the largest magnitude at the margin of the Tibetan Plateau. The glacial retreat in the High Asia in china has an important impact on the water resource of the arid regions in Northwest china. This study shows that the glacial retreat in the 1990s has caused an increase of 5.5% in river runoff in Northwest china. In the Tarim River basin, the increase of river runoff is higher than 5.5%.

关键词： High Asia, glacial fluctuation, impact on water resource.

“Greatest lake period” and its palaeo-environment on the Tibetan Plateau

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Journal of geographical sciences 2001年第1期11卷 34-42页

作者： LI Bing-yuan, ZHU Li-ping (institute of geographic {2. and {3. resources research, CAS, beijing 100101, china) institute of geographic {2. and {3. resources research CAS Beijing China

The “greatest lake period” means that the lakes are in the stage of their maximum areas. As the paleo lake shorelines are widely distributed in the lake basins on the Tibetan Plateau, the lake areas during the “greatest lake period” may be inferred by the last highest lake shorelines. They are several, even tens times larger than that at present. According to the analyses of tens of lakes on the Plateau, most dating data fell into the range of 40-2. ka BP, some lasted to 2. ka BP. It was corresponded to the stage 3.of marine isotope and interstitial of last glaciation. The occurrence of maximum areas of lakes marked the very humid period on the Plateau and was also related to the stronger summer monsoon during that period.

关键词： Tibetan Plateau greatest lake period highest lake levels interstitial of last glaciation paleo-monsoon

GIS-Based Assessment of Land Suitability for Optimal Allocation in the Qinling Mountains, china

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Pedosphere 2006年第5期16卷 579-586页

作者： liu Yan-Sui wang Jie-Yong GUO Li-Ying institute of geographic {2. and {3. resources research Chinese Academy of Sciences Beijing 100101 （China） Graduate School of chinese academy of sciences Beijing 100039 （China） College of Tourism and Environmental sciences Shaanxi Normal University Xi＇an 710062 （China）

A GIS-based method was used to assess land suitability in the Qinling Mountains, Shaanxi Province of china through simultaneous consideration of physical features and current land use. Through interpretation of Landsat TM images and extensive field visits the area was modeled into 40 land types in five altitudinal zones (valleys and gullies, hillsides and terraces, foothills, mid-mountain, and sub-alpine mountain). Then, a suitability score was assigned to five physical factors (climate, hydrology, topography, soil, and vegetation). Next, their integrated overall suitability value scores were compared with the observed land cover to determine whether it should be reallocated a new use. Results showed that the five suitability classes of agriculture, forest, grassland, farmland-woodland, and scrub-pasture had altitudinal stratification and a total of 1151 km2.(8.89%) of lands on the northern slopes of the Qinling Mountains had to be reallocated. To achieve this reallocation, 657 km2.of arable land should be reduced, and forest, grassland and scrub-pasture increased by 615 km2. 13. km2.and 405 km2. respectively. Implementation of these recommended land reallocations should help achieve suitable use of land resources and prevent land degradation.

关键词： GIS landforms optimal allocation Qinling Mountains suitability evaluation

Astronomical function and date of the Taosi observatory

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Science china(Physics,Mechanics & Astronomy) 2009年第1期52卷 151-158页

作者： WU JiaBi1, CHEN MeiDong2.& liu CiYuan3.1 National Astronomical Observatories, chinese academy of sciences, {2. 100012.{2. 2.{3. for the History of natural Science, chinese academy of sciences, {2. 100010,{2. 3.National Time Service Center, chinese academy of sciences, Xi’an 710600,{2. 1. National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China 2. institute for the History of natural Science Chinese Academy of Sciences Beijing 100010 China 3. National Time Service Center Chinese Academy of Sciences Xi’an 710600 China

The Taosi site in Xiangfen County,Shanxi Province,may be the capital of the King Yao. Archeologists recently discovered a large semi-circular stamped-earth platform, II FJT1,which has a clear and definite pounded-earth central core together with a curved wall perforated by twelve gaps. The platform is said to be an ancient observatory used to determine the seasons by watching the sunrise. Each feature of II FJT1 was precisely measured and the data are reproduced in this paper. An astronomical analysis of slots E2.and E12.was carried out using the azimuths of the slots' centerlines and the vertical angle of the mountain ridge opposite, above which the sun rises. The results show that at present the sun is close to the two slots but does not exactly enter them at summer and winter solstice sunrise. Using 14C analysis archeologists dated the site to about 2.00 BC. Because of the secular change in the obliquity of the ecliptic,at that date on the summer solstice the half-risen sun would have appeared inside slot E12.just to the right of the centerline,and on the winter solstice the sun would have been exactly on the centerline of slot E2. This result provides compelling proof that II FJT1 is an ancient observatory.

关键词： astro-archeology astro-chronology Taosi culture ancient observatory time service

Quantitative estimation of the shrub canopy LAI from atmosphere-corrected HJ-1 CCD data in Mu Us Sandland

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Science china Earth sciences 2010年第S1期53卷 26-33页

作者： CHEN Wei1,2,CAO ChunXiang1,HE QiSheng1,2,GUO HuaDong3,ZHANG Hao1,2,LI RenQiang4,ZHENG Sheng1,2,XU Min1,2,GAO MengXu1,2,ZHAO Jian1,2,LI Sha1,NI XiLiang1,2,JIA HuiCong1,JI Wei1,TIAN Rong1,2,liu Cheng1,2,ZHAO YuXing5 & LI JingLu6 1 State Key Laboratory of Remote Sensing Science,Jointly Sponsored by the institute of Remote Sensing Applications of chinese academy of sciences and {2. Normal University,{2. 100101,china 2 Graduate University of chinese academy of sciences,{2. 100049,china 3 Center for Earth Observation and Digital Earth,chinese academy of sciences,{2. 100190,china 4 china Key Laboratory of Ecological Network Observation and Modeling,institute of geographical sciences and natural resources {2.},chinese academy of sciences,{2. 100101,china 5 Ordos Forestry Sand Control Science institute,Dongsheng 017000,china 6 Inner Mongolia Biomass Thermoelectricity Limited Company,Wushen 017300,china 1. State Key Laboratory of Remote Sensing Science Jointly Sponsored by the Institute of Remote Sensing Applications of Chinese Academy of Sciences and Beijing Normal University Beijing 100101 China 2. Graduate University of chinese academy of sciences Beijing 100049 China 3. Center for Earth Observation and Digital Earth Chinese Academy of Sciences Beijing 100190 China 4. china Key Laboratory of Ecological Network Observation and Modeling Institute of Geographical Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China 5. Ordos Forestry Sand Control Science institute Dongsheng 017000 China 6. Inner Mongolia Biomass Thermoelectricity Limited Company Wushen 017300 China

The leaf area index(LAI) is an important ecological parameter that characterizes the interface between vegetation canopy and the *** addition,it is used by most process-oriented ecosystem *** paper investigates the potential of HJ-1 CCD data combined with linear spectral unmixing and an inverted geometric-optical model for the retrieval of the shrub LAI in Wushen Banner of Inner Mongolia in the Mu Us ***(Moderate Resolution Atmospheric Radiance and Transmittance Model) was used for atmospheric *** was extracted using the threshold of the normalized difference vegetation index,with which water bodies and farmland were separated,in combination with a vegetation map of the People's Republic of china(1:1000000).Using the geometric-optical model,we derive the per-pixel reflectance as a simple linear combination of two components,namely sunlit background and *** fraction of sunlit background is related to the shrub *** the support of HJ-1 CCD data,we employ linear spectral unmixing to obtain the fraction of sunlit background in an atmospherically corrected HJ *** addition,we use the measured shrub canopy structural parameters for shrub communities to invert the geometric-optical model and retrieve the pixel-based shrub *** total,18 sample plots collected in Wushen Banner of Inner Mongolia are used for *** results of the shrub LAI show good agreement with R2.of 0.817 and a root-mean-squared error of 0.173.

关键词： shrub leaf area index inversion HJ-1 data geometric-optical model MODTRAN Mu Us Sandland

The roles of a decision support system in applying forest ecosystem management in Northeast china

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Science china(Technological sciences) 2006年第z1期49卷 9-18页

作者： DAI Limin, ZHENG Bofu, Guofan Shao & ZHOU Li State Key Lab of Systems Ecology, research Center for Eco-Environmental sciences,{2., {3. 100085, china institute of Applied Ecology,{2., Shenyang 110016, china Department of Forestry and natural resources, Purdue University, West Lafayette, IN 47907, USA Graduate University of{2., beijing 100101, china 1. State Key Lab of Systems Ecology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China2. Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 China3. Department of Forestry and Natural Resources Purdue University West Lafayette IN 47907 USA4. Graduate University of Chinese Academy of Sciences Beijing 100101 China

Forest ecosystems provide a variety of services and forest ecosystem management (FEM) is an effective approach to maximize the services. Because of the complexity of forest ecosystems, the applications of FEM can be facilitated with decision support systems (DSS) that recognize and incorporate ecological and socio-economic variables. With the rapid development of computation and information technologies, DSS have been advanced in many ways. Traditional forest management within a forestry unit in china is planned on a yearly basis. The planning itself remains primarily a verbal concept as there are no quantitative decision-support tools available to translate the concept into forest management actions. For the purposes of FEM at the management level, a forest management DFF, FORESTAR, has been developed under a framework of geographic information system (GIS) and forest models. The paper explained the intelligent modeling mechanisms and demonstrated how the applications of FEM can be strengthened with the applications of FORESTAR.

关键词： forest functions, forested landscapes, forest services, forest models, geographic information systems.