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Digitally determining forest inventory units with an ecological classification system

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Science china(Technological sciences) 2006年第z1期49卷 118-127页

作者： TANG Una, WANG Qingli, Guofan Shao, DAI Limin, WANG Shunzhong, LI Xiufen & xu Dong Institute of Applied Ecology, chinese academy of sciences, Shenyang 110016, china Graduate University of chinese academy of sciences, beijing 100101, china Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907, USA 1. Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 China 2. Graduate University of chinese academy of sciences Beijing 100101 China 3. Department of Forestry and Natural Resources Purdue University West Lafayette IN 47907 USA

Management-level forest resource data in china were obtained with a combination of two forest inventories. However, inconsistencies in the spatial attributes of forest data vary between the two inventory types and between two inventories of the same type. The inconsistencies make it inconvenient for long-term forest management planning with digital technologies. Ecological Land Types (ELTs) and Ecological Land Type Phases (ELTPs) have been mapped in selected forestry regions in northeast china, where important forest industries are located. The boundaries of ELTs are determined by geomorphic conditions, which are quantified by Digital Elevation Models (DEM); ELTPs are classified by overlaying ELTs with forest vegetation data layers that are obtained with both remotely sensed and ground data. The ELTPs represent the divisions of land in terms of both natural and human-induced forest conditions, and therefore they are reliable units for forest inventories and management. This paper introduces a case study for digitally determining forest inventory units in Benxi City, Liaoning Province, northeast china. The general objective of the study was to explain how a compatible forest inventory system should be designed and why the compatible forest inventory system was significant to digital forestry in china.

关键词： forest inventory, ecological classification, ELT mapping, ELTP mapping, geographic information systems, forest management.

Estimation of forest volumes by integrating Landsat TM imagery and forest inventory data

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Science china(Technological sciences) 2006年第z1期49卷 54-62页

作者： GU Huiyan, DAI Limin, WU Gang, xu Dong, WANG Shunzhong &WANG Hui Institute of Applied Ecology, chinese academy of sciences, Shenyang 110016, china School of Forestry, Northeast Forestry University, Harbin 150040, china State Key Lab of Systems Ecology, Research Center for Eco-Environmental sciences, chinese academy of sciences, beijing 100085, china Graduate University of chinese academy of sciences, beijing 100039, china 1. Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 China 2. School of Forestry Northeast Forestry University Harbin 150040 China 3. State Key Lab of Systems Ecology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China 4. Graduate University of chinese academy of sciences Beijing 100039 China

Accurate information about forest volumes is essential for forest management planning. The survey interval of the Forest Resource Inventory of china (FRIC) is too long to meet the demand for timely decision-making required for forest protection, management, and utilization. Analysis of satellite imagery provides good potential for more frequent reporting of forest parameters. In this study, we describe an application of the k-nearest neighbors (kNN) method to Landsat TM imagery for improving estimation of forest volumes. Several spectral features were tested and compared in forest volume estimations, including normalized difference vegetation index, environmental vegetation index, and the combination of the spectral features. The combined index resulted in the most accurate volume estimations. The kNN estimator and the combined index were then used in forest volume estimation. The estimation error (RMSE) of the total volume was44.2%, much lower than those for Larix forest (the RMSE was 51.7%) and those for the Korean pine and broadleaved forests (the estimation errors were over 71.7% and 88.19%,respectively). This preliminary study demonstrates the potential of forest volume estimations with remote sensing data to provide useful information for forest management if only limited ground information is available.

关键词： forest inventory, landsat TM, k-nearest neighbors, spectral extraction.

Determination of polychlorinated biphenyl congeners in environmental samples

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Journal of Environmental sciences 1996年第1期8卷 57-65页

作者： Chu Shaogang Yang Chun xu Xiaobai (Research Center for Eco-Environmental sciences,chinese academy of sciences, beijing 100085,china )

A modified separation method has been developed for determinating polychlorinated biphenyl congeners in environmental samples. Direct treatment of extract with concentrated HzSO4 was employed in the first step for removal of lipids and other interfering substances, then a joint column of alumina-silica gel(Ag+) was applied to separate PCBs fraction from HCH, DDT and its analogs. After this separation, the PCBs fraction was analyzed by capillary gas chromatography with ECD detector and confirmed by GC/MS. The recoveries of individual congeners in Aroclor 1254 through the separation are about 79%-84%. The method is very efficient and useful for determination of trace amount of PCB congeners in environmental samples.

关键词： polychlorinated biphenyl capillary gas chromatography environmental samples.

A V-CYCLE MUTIGRID FOR QUADRILATERAL ROTATED Q_1 ELEMENT WITH NUMERICAL INTEGRATION

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Journal of Computational Mathematics 2003年第5期21卷 545-554页

作者： Zhong-ci Shi xue-jun xu(LSEC, Institute of Computational Mathematics, academy of Mathematics and System sciences, chinese academy of sciences, beijing 100080, china) 中科院数学与系统科学院 LSEC CAS 北京 100080

In this paper, a V-cycle multigrid method is presented for quadrilateral rotated elements with numerical integration.

关键词： Multigrid Rotated Q1 elements Numerical integration.

Effects of gravity waves on the distributions of O_3 and OH in the mesopause region

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chinese Science Bulletin 2001年第15期46卷 1265-1268页

作者： xu Jiyao & MA RuipingLaboratory for Space Weather, Center for Space Science and Applied Research, chinese academy of sciences, beijing 100080, china Laboratory of Numeric Study of Heliospheric Physics, chinese academy of sciences, beijing 100080, china Laboratory for Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing China Laboratory of Numeric Study of Heliospheric Physics Chinese Academy of Sciences Beijing China

A dynamical-photochemical model of atmospheric gravity waves is used to study the influences of gravity waves on distributions of atmospheric minor species through transportation and photochemical reactions. We mainly study the effect of gravity waves on the distributions of atmospheric trace gases through the nonlinear photochemical reactions. O3 and OH are taken as examples in this note. The calculations indicate that the effect of gravity waves on the distributions of atmospheric trace gases is mainly through the nonlinear photochemical reactions in the mesopause region. The contribution of the nonlinear photochemical reaction caused by gravity waves can exceed the nonlinear transportation and the eddy diffusion.

关键词： gravity wave photochemical reaction coupling between photochemistry and dynamics.

Environmental awareness and the contemporary society of china——an analysis and an understanding

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Journal of Environmental sciences 1999年第4期11卷 504-509页

作者： xu Song\|ling (Center for Environment and Development, chinese academy of Social sciences, beijing 100732,china) Ctr. for Environment and Development Chinese Academy of Social Sciences Beijing 100732 China

This paper presents an understanding of the relationship between the environmental awareness(EA) and contemporary society of china. The EA of three of the major groups of chinas society, namely intellectuals, government officials, and urban societies are characterized one by one. A number of factors of affecting the EA were investigated in details, the keys among which are the personal level of knowledge and morality, the social and economic development level, environmental codes, environment\|related professional and public regulations, different professional performances. Some policy proposals are finally provided for enhancing the EA of chinas society.

关键词： environmental awareness contemporary society of china sustainable development

SYNTHESIS AND CHARACTERIZATION OF SILAZANE OLIGOMER CONTAINING 1,1,3,3,5,5-HEXAMETHYLCYCLOTRISILAZANE

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chinese Journal of Polymer Science 2000年第5期18卷 449-452页

作者： Cai-hong xu Ning Zhou Ze-min Xie Center for Molecular Science, Institute of Chemistry, chinese academy of sciences, beijing 100080, china chinese Acad Sci Inst Chem Ctr Mol Sci Beijing 100080 Peoples R China

A new silazane oligomer containing cyclotrisilazane was synthesized by KH-catalyzed dehydro-coupling reactions between diphenylsilane and 1,1,3,3,5,5-hexamethylcyclotrisilazane (D-3(N)).

关键词： silazane oligomer diphenylsilane cyclotrisilazane dehydro-coupling reaction

Matrix expression and reachability analysis of finite automata

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控制理论与应用（英文版） 2012年第2期10卷 210-215页

作者： Xiangru xu, Yiguang HONG Key Laboratory of Systems and Control, academy of Mathematics and Systems Science, chinese academy of sciences, beijing 100190, china Key Laboratory of Systems and Control Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing China

In this paper, we propose a matrix-based approach for finite automata and then study the reachability conditions. Both the deterministic and nondeterministic automata are expressed in matrix forms, and the necessary and sufficient conditions on reachability are given using semitensor product of matrices. Our results show that the matrix expression provides an effective computational way for the reachability analysis of finite automata.

关键词： Finite automata Reachability Matrix expression Semitensor product

Temperature variations in the past 6000 years inferred from δ^(18)O of peat cellulose from Hongyuan,china

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chinese Science Bulletin 2002年第18期47卷 1578-1584页

作者： xu Hai, HONG Yetang, LIN Qinghua, HONG Bing, JIANG Hongbo & ZHU YongxuanInstitute of Geochemistry, chinese academy of sciences, Guiyang 550002, china Graduate School of chinese academy of sciences, beijing 100039, china Institute of Geochemistry Chinese Academy of Sciences Guiyang China Graduate School of chinese academy of sciences Beijing China

Trends of the temperature variations recorded in δ18O in Hongyuan peat cellulose are similar to those recorded in δ18O of Jinchuan peat cellulose and in δ18O of Dunde ice core. Climate events have been identified to be globally homogeneous. Two notable climate transition periods have been detected in the past 6000 years, namely 4000 aBP with climate shifting from cold to warm and 1500 aBP with climate shifting from warm to relatively cold. Power spectrum analysis was performed to investigate the periodical signals in the δ18O time series. Typical periodicities of 1200-1087 a, 752 a, 444 a, 325 a, 213 a, 127-123 a, 88 a, 79 a were discovered, indicating an integrated influence on Hongyuan climate from solar, monsoon and ocean activities. Solar forcing has been addressed to be the main driving forcing of Hongyuan climate.

关键词： Hongyuan oxygen isotopic composition peat tempera-ture.