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A preliminary study on vegetation-erosion dynamics and its applications

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Science china Earth Sciences 2005年第5期48卷 689-700页

作者： wang Zhaoyin 1.2 , wang Guangqian 1., li Changzhi 1.& wang Feixin 1.1. department of Hydraulic Engineering, Tsinghua university, Beijing 1.0084, china 2. International Research and Training Center on Erosion and Sedimentation, Beijing 1.0084, china 1. department of Hydrau{1.c Engineering Tsinghua University 100084 Beijing China 2. International Research and Training Center on Erosion and Sedimentation 100084 Beijing China

Vegetation-erosion dynamics is a new interdisciplinary science, studying the laws of evolution of watershed vegetation under the action of various ecological stresses. Introducing a qualitative expression of ecological stresses in this paper, the present authors establish the cou- pled differential equations for the vegetation-erosion process and derive a theoretical solution. The model is applied to the Anjiagou watershed on the Loess Pateau and the Xiaojiang water- shed and its sub-watersheds on the Yunnan Plateau. The calculated results agree well with the vegetation development processes. Abstracted from the differential equations the so-called vegetation-erosion chart is worked out, with which we can predict the development trend of vegetation under no human stresses. It is demonstrated that the erosion control is important for vegetation development and reforestation must be a long-term strategy. On the Yunnan Plateau with relatively high precipitation and temperature, vegetation can be greatly improved if erosion is controlled. On the dry and cold Loess Pateau suffering from high rate of soil erosion, however, vegetation can effectively control erosion but erosion reduction exhibits low effectiveness on vegetation development. Vegetation in the area is not stable and management is always needed to maintain the vegetation.

关键词： vegetation-erosion dynamics, human activities, coupled differential equations, erosion control, vigor ofvegetation.

lipschitz continuity of best approximations and Chebyshev centers

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Chinese Science Bulletin 1998年第3期43卷 185-188页

作者： li Chong {1. wang Xinghua 2 1. Center for Mathematical Sciences, Zhejiang university, Hangzhou 31.027, china 2. department of Mathematics, Hangzhou university, Hangzhou 31.028, china Center for Mathematical Sciences Zhejiang University Hangzhou China department of Mathematics Hangzhou University Hangzhou China

The lipschitz continuity results are given for best approximations and Chebyshev centers. Consequently, the open problem presented by Septycki and Vleck is solved completely.

关键词： best approximation Chebyshev center uniform convexity.

Effect of acid oxidization of carbon nanotube electrode on the capacitances of double layer capacitors

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Science china(Technological Sciences) 2004年第3期47卷 257-264页

作者： li Chensha1.{1. Dazhi1.liANG Tongxiang2,{1. Xiaofeng1.& liANG Ji1.1. department of Mechanical Engineering, Tsinghua university,Beijing 1.0084, china 2. Institute of Nuclear Energy Technology, Tsinghua university,Beijng 1.2201.china Tsinghua Univ Dept Mech Engn Beijing 100084 Peoples R China Tsinghua Univ Inst Nucl Energy Technol Beijing 102201 Peoples R China

Polarizable electrode of electric double layer capacitor was made from carbon nanotubes. The effect of acid oxidation of electrode on the specific capacitance was studied. Oxidation removed the redundant carbon, expanded the pore size and introducedf some kinds of functional groups on the surface of CNTs. The specific capacitance of the electrodes winth organic electrolyte was increased from 21.4 to 49.6 F/g after being oxidized at a volume ratio H2SO4 to HNO3 of 3:1.

关键词： carbon nanotubes, electric double layer capacitor, specific capacitance.

Electroluminescent properties of three ternary europium complexes with different phenanthroline derivatives

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Science china {1. 2004年第4期47卷 326-334页

作者： BIAN Zuqiang1.2, GAO Deqing1. GUAN Min1. XIN Hao1. li Fuyou1. HUANG Chunhui1. {1. Kezhi2 & JIN linpei2 1. State Key Laboratory of Rare Earth Materials chemistry and Applications, Peking university, Beijing 1.0871. china 2. department of chemistry, Beijing Normal university, Beijing 1.0875, china 1. State Key Laboratory of Rare Earth Materials chemistry and App{1.cations Peking University 100871 Beijing China 2. department of {1. Beijing Normal University 100875 Beijing China

Three ternary Eu(III) complexes with general formula of Eu(DBM)3LN (DBM = dibenzoylmethanate, and LN (N = 1.3 ) stand for three different 1.1.-phenanthroline derivatives) have been synthesized for vacuum deposition films-based electroluminescent devices. The complex Eu(DBM)3L3 (L3 = 2-phenyl-3-[3-(carbazol-9-yl)propyl]imidazo[4,5-f]1.1.-phenan-throline) was designed with an effort to combine the electron-transporting phenanthroline platform and the hole-transporting carbazole group into one molecule expecting to improve both electron and hole transporting properties simultaneously. The results show that the variation of the neutral ligands in Eu(III) mixed ligand complexes is a simple and effective approach to the improvement in the thermal stability, PL and EL properties of materials. A double-layer device with the configuration of ITO/TPD (50 nm)/Eu(DBM)3L3 (50 nm)/Mg0.9Ag0.1.(200 nm)/Ag (1.0 nm) exhibited Eu(III)-based pure red emission with a maximum brightness of 561.cd/m2 at 1. V, and an onset driving voltage of 8 V. A device with the configuration of ITO/TPD (50 nm)/[Eu(DBM)3L3 (5 nm):BCP (5 nm)]4/BCP (20 nm)/AIQ (1. nm) Mg0.9Ag0.9 (1.0 nm)/Ag (1.0 nm) gave high efficient and pure red light emission with a luminance of 1.1. cd/m2. Keywords dibenzoylmethane - electroluminescence - lanthanide - N ligands

关键词： dibenzoylmethane electroluminescence lanthanide N ligands

Recurrence spectra of He atoms in strong external fields

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Science china(Physics,Mechanics & Astronomy) 2004年第4期47卷 477-484页

作者： liN Shenglu1. li Hongyun1. wang Dehua2, ZHAO Wenli1.& GAO Feng1.1. department of Physics, Shandong Normal university, Jinan 25001., china 2. department of Mathematics and Physics, Shandong Institute of Architecture and Engineering, Jinan 25001., china 1. department of Physics Shandong Normal University 250014 Jinan China 2. department of Mathematics and Physics Shandong Institute of Architecture and Engineering 250014 Jinan China

By employing a model potential including the electron exchange energy, we extend the semiclassical closed orbit theory to study the multielectron atoms. Using special region-splitting consistent and iterative method, we figure out the closed orbits in the corresponding classical system and calculate the recurrence spectra of triplet helium atoms in parallel electric and magnetic fields at scaled energy ε=?0.03,n≈40,n=0. The core-scattering effects have been taken into account, which lead to more peaks in the spectra. It has also been confirmed by means of the direct comparison between the spectral portrait in such a plot and those of hydrogen case. In order to compare the theoretic results with experiment, we investigate the closed orbits and recurrence spectra of helium atoms for the similar exchange potential but applied only by single electric field at scaled energy ε=?2.7 case. The spectra are in good agreement with the experimental observation. We conclude that our model is correct and it is necessary to consider the exchange effect for determining the photoabsorption spectra of multielectron atoms in strong external fields.

关键词： exchange potential, recurrence spectra, semiclassical closed orbit theory, core-scattering.

The influence of laser pulse on the photoabsorption spectra of li atom in strong external field

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Science china(Physics,Mechanics & Astronomy) 2006年第2期49卷 178-186页

作者： wang Dehua1.& {1.N Shenglu2 1. School of Physics and Electronic Engineering, Yantai Normal university, Yantai 264025, china 2. department of Physics, Shandong Normal university, Jinan 25001., china 1. School of Physics and Electronic Engineering Yantai Normal University Yantai 264025 China 2. department of Physics Shandong Normal University Jinan 250014 China

Using the time-dependent perturbation theory and the calculation formula of the single- and double-pulse absorption spectra of the atom in strong external fields, we calculate the single- and double-pulse absorption spectra of li atom in strong magnetic field for different pulse widths. The results show that a pulse of some width can reduce the contribution of the short period closed orbits and eliminate the contribution of the long period orbits. Compared with the single-pulse absorption spectra, we found that for some phase differences, the double-pulse laser absorption spectra are strengthened; while for others, they are reduced. Therefore, we can use the pulse laser to control the oscillation of the absorption spectra and obtain the optimization object.

关键词： laser pulse closed orbit absorption spectra.

Enhancing the capacitances of electric double layer capacitors based on carbon nanotube electrodes by carbon dioxide activation and acid oxidization

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Science china(Technological Sciences) 2010年第5期53卷 1234-1239页

作者： li ChenSha1.2,QIAO YingJie1.WU JianJun2,{1. DaZhi2 & YUAN DianBo2 1.department of Materials Science,harbin Engineering university,harbin 1.0001.china 2 department of Mechanical Engineering,Tsinghua university,Beijing 1.0084,china 1. department of Materials Science Harbin Engineering University Harbin 150001 China2. Department of Mechanical Engineering Tsinghua University Beijing 100084 China

Polarizable electrodes of electric double layer capacitors(EDLCs) were made from carbon nanotubes(CNTs).Effect of carbon dioxide activation together with acid oxidation for the electrodes on the characteristics and performances of electrodes and EDLCs was *** dioxide activation changed the microstructure of the electrodes,increased the effective surface area of CNTs and optimized the distribution of apertures of the *** oxidization modified the surface characteristics of *** on the polarizable electrodes treated by carbon dioxide activation and acid oxidization,the performances of EDLCs were greatly *** specific capacitance of the electrodes with organic electrolyte was increased from 21.8 F/g to 60.4 F/g.

关键词： carbon nanotube electric double layer capacitor scan electron microscopy

Chinese Jingdezhen blue and white imperial porcelain

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Science china(Technological Sciences) 2004年第3期47卷 366-375页

作者： WU Juan1. li Jiazhi1. DENG Zequn1.& {1. Changsui2 1. Laboratory of Ancient Ceramics, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, china 2. department of History of Science and Archaeometry, university of Science and Technology of china, Hefei 230026, china Chinese Acad Sci Shanghai Inst Ceram Lab Ancient Ceram Shanghai 200050 Peoples R China Univ Sci & Technol china Dept Hist Sci Archaeometry Hefei 230026 Peoples R China

Jingdezhen blue and white imperial porcelain specimens from the Yuan, Ming and Qing dynasties have been systematically analyzed using a nondestructive test method—— energy dispersive X-ray fluorescence analysis (EDXRF). The derived data of major and trace element compositions have been treated by correspondence analysis. The variation laws of the composition patterns for Jingdezhen blue and white imperial porcelain in different historical periods owing to the change in raw materials, recipe and technology have been discussed, and a time model related to variation of element composition has been preliminarily established, It would be helpful for scientific dating of Jingdezhen blue and white imperial porcelain, and even for the studies on the whole field of identification of ancient ceramics.

关键词： energy dispersive X-ray fluorescence analysis, blue and white imperial porcelain, correspondence analysis.

Potential control of horseradish peroxidase immobilization on gold electrode

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中国科学：化学英文版 2004年第2期47卷 134-141页

作者： GE Cunwang1.2, YU Wei1. {1. Changan1. wang Nanping2 & GU Ning1.1. Key Laboratory of Molecular and Biomolecular Electronics (Southeast university), Ministry of Education, Research Center for Nano-scale Science and Technology, Southeast university, Nanjing 21.096, china 2. department of chemistry, Nantong Teachers College, Nantong 226007, china 1. Key Laboratory of Molecular and Biomolecular Electronics (Southeast university) Ministry of Education Research Center for Nano-scale Science and Technology Southeast University 210096 Nanjing China 2. department of {1. Nantong Teachers College 226007 Nantong China

A new approach based on potential control was firstly used for the immobilization of horseradish peroxidase (HRP) as the model protein. The self-assembly monolayer (SAM) was prepared with 2-aminoethanethiol (AET) on the gold electrode. The charge on HRP was adjusted by means of the acidity of the phosphate buffer solution (PBS) for dissolving the HRP. The in-fluence of electric potential on HRP immobilization was investigated by means of colorimetric immunoassay of enzyme-substrate interaction (CIESI) using an automatic plate reader. The HRP modified electrodes were characterized with X-ray photoelectron spectroscopy (XPS) as well as atomic force microscope (AFM) on template-stripped gold surface. The potential for maximum immobilization of HRP was near the zero charge potential. The result indicates that controlled potential can affect the course of HRP immobilization without the loss of enzymic activity. It is of great significance for the control of biomolecular self-assembly and the intrinsic electric device.

关键词： electric potential control, horseradish peroxidase, immobilization, gold electrode, self-assembly.