检索结果-南通市图书馆

Chinese Journal of Polymer Science 2002年第5期20卷 431-437页

作者： Zhong-ming Hu Ren-yuan Qian Shou-xi chen Xiao-fang chen Qi-feng Zhou Centre for Molecular Science, Institute of {2. Chinese Academy of Sciences, beijing 100080, china department of Polymer Science & Engineering College of {2. & Molecular Engineering Peking university beijing 100871, china Centre for Molecular Science Institute of Chemistry Chinese Academy of Sciences 北京 100080 department of Polymer Science & Engineering College of Chemistry & Molecular Engineering Peking University 北京 100871

The kinetics of I-->N transition of a side chain nematic polymethacrylate has been studied by small angle depolarized light scattering intensity measurements using a charge coupled device linear image sensor. The polymer shows the transition temperatures K52.79I in degreesC, The H-v scattering intensity T(q,t) during the transition I (at 80.2.egreesC)-->N (at 75.8degreesC) shows that T(q) is independent of q for all t, and during the initial stage (in 6 s) T(t) increases exponentially with t. In the later stage of the transition T(t) approaches a saturation value in 2.min. This experimental result indicates that the I-->N transition of a liquid crystalline polymer is a spinodal type of phase transition mediated by orientation fluctuation.

关键词： side chain nematic polymer isotropic-nematic transition small angle depolarized light scattering

Synchronous estimation of DTM and fractional vegetation cover in forested area from airborne LIDAR height and intensity data

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2008年第S2期51卷 176-187页

作者： BAO YunFei1,2.CAO ChunXiang1,ZHANG Hao1,chen ErXue3,HE QiSheng1,2.HUANG HuaBing1,LI ZengYuan3,LI XiaoWen1,4 & GONG Peng1 1 State Key Laboratory of Remote Sensing Science,jointly sponsored by the Institute for Remote Sensing Applications of Chinese Academy of Sciences and beijing Normal {2.,beijing 100101,china 2.Graduate {2. of the Chinese Academy of Sciences,beijing 100049,china 3 Institute of Forest Resource Information Technique,the Chinese Academy of Forestry,beijing 100091,china 4 Research Center for Remote Sensing and GIS,department of Geography and beijing Key Laboratory for Remote Sensing of Environment and Digital Sites,beijing Normal {2.,beijing 100875,china State Key Laboratory of Remote Sensing Science jointly sponsored by the Institute for Remote Sensing Applications of Chinese Academy of Sciences and Beijing Normal University Beijing China Graduate university of the Chinese Academy of Sciences Beijing China Institute of Forest Resource Information Technique the Chinese Academy of Forestry Beijing China Research Center for Remote Sensing and GIS Department of Geography and Beijing Key Laboratory for Remote Sensing of Environment and Digital Sites Beijing Normal University Beijing China

We proposed a method to separate ground points and vegetation points from discrete return,small footprint airborne laser scanner data,called skewness change *** method,which makes use of intensity of laser scanner data,is especially applicable in steep,and forested *** does not take slope of forested area into account,while other algorithms consider the change of slope in steep forested *** ground points and vegetation points can be used to estimate digital terrain model(DTM) and fractional vegetation cover,respectively.A few vegetation points which were classified into the ground points were removed as noise before the generation of *** method was tested in a test area of 10000 square meters.A LiteMapper -5600 laser system was used and a flight was carried out over a ground of 700―800 *** this tested area,a total number of 1546 field measurement ground points were measured with a total station TOPCON GTS-602.and TOPCON GTS -7002.for validation of DTM and the mean error value is -18.5 cm and the RMSE(root mean square error) is ±2..9 cm.A data trap sizes of 4m in diameter from airborne laser scanner data was selected to compute vegetation fraction *** of fractional vegetation cover was carried out using 15 hemispherical photographs,which are georeferenced to centimeter accuracy by differential *** gap fraction was computed over a range of zenith angles 10° using the gap light analyzer(GLA) from each hemispherical *** R2.for the regression of fractional vegetation cover from these ALS data and the respective field measurements is *** this study presents a method for synchronous estimation of DTM and fractional vegetation cover in forested area from airborne LIDAR height and intensity data.

关键词： LIDAR intensity skewness synchronous DTM fractional vegetation cover

Identification of the Quaternary low gas-saturation reservoirs in the Sanhu area of the Qaidam Basin,china

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2011年第1期8卷 49-54页

作者： Li Xiongyan Li Hongqi Zhou Jinyu He Xu chen Yihan Yu Hongyan State Key Laboratory of Petroleum Resource and Prospecting China University of PetroleumBeijing 102249China Key Laboratory of Earth Prospecting and Information technology China University of PetroleumBeijing 102249China department of Computer Science and technology China University of PetroleumBeijing 102249China Exploration and Development Institute Changqing Petroleum CompanyShaanxi 710021China

Low gas-saturation reservoirs are gas bearing intervals whose gas saturation is less than 47%. They are common in the Quaternary of the Sanhu area in the Qaidam *** to the complex genesis mechanisms and special geological characteristics,the logging curves of low gas-saturation reservoirs are characterized by ambiguity and diversity,namely without significant log response characteristics. Therefore,it is particularly difficult to identify the low gas-saturation reservoirs in the study *** addition,the traditional methods such as using the relations among lithology,electrical property,physical property and gas bearing property,as well as their threshold values,can not effectively identify low gas-saturation *** solve this problem,we adopt the decision tree,support vector machine and rough set methods to establish a predictive model of low gas-saturation reservoirs,which is capable of classifying a mass of multi-dimensional and fuzzy *** to the transparency of learning processes and the understandability of learning results,the predictive model was also revised by absorbing the actual reservoir *** applications indicate that the predictive model is effective in identifying low gas-saturation reservoirs in the study area.

关键词： Sanhu area Qaidam Basin low gas-saturation reservoir decision tree support vector machine rough set predictive model identification

Some invariant properties of ordered information systems under homomorphism

在线全文

学校读者我要写书评

暂无评论

Science china(Information Sciences) 2010年第9期53卷 1816-1825页

作者： WANG ChangZhong1*,chen DeGang2.& HU QingHua3 1department of Mathematics,Bohai {2.,Jinzhou 12.000,china 2.1} of Mathematics and Physics,North china Electric Power {2.,beijing 102.06,china 3Power Engineering,Harbin Institute of technology,Harbin 150001,china department of Mathematics Bohai University Jinzhou China department of Mathematics and Physics North China Electric Power University Beijing China Power Engineering Harbin Institute of Technology Harbin China

In this paper,some properties of ordered information systems under homomorphism are *** concept of a consistent function with respect to dominance relations is first introduced and its properties are ***,some main invariant properties of dominance relations under relation mappings are *** is proven that attribute reductions in the original ordered information system and its image system are equivalent under the condition of *** means of the results,we can get the smaller image system that has the same reducts as a given massive ordered information system.

关键词： consistent function dominance relation ordered information system homomorphism reduction

Paleotemperature changes over the past 3000 years in eastern beijing, china: A reconstraction based on Mg/Sr records in a stalagmite

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2003年第4期48卷 395-400页

作者： MA Zhibang1, LI Hongchun2. XIA Ming1, KU Tehlung2. PENG Zicheng3, chen Yushu4 & ZHANG Zhaofeng3 1. Institute of Geology and Geophysics, Chinese Academy of Sciences, {2. 10002., china 2. department of Earth Sciences, university of Southern California, Los Angeles, CA90089-0740, USA 3. department of Earth and Space Science, university of Science and technology of china, Hefei 2.002., china 4. {2. Foshan Tourist Service Centre, {2. 1012.1, china Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China department of Earth Sciences University of Southern California Los Angeles CA 90089-0740 United States department of Earth and Space Science University of Science and Technology of China Hefei 230026 China beijing Foshan Tourist Service Centre Beijing 101201 China

The Mg/Sr ratio in a stalagmite, which is di-rectly proportional to DMg/Ca, the solid-liquid distribution coefficient of Mg, is proposed as a geochemical thermometer to estimate paleotemperature changes. The paleotempera-ture change in eastern beijing over the past 3000 years has been reconstructed by using this thermometer in the stalag-mite ZFFS-1 from Jingdong Cave. The records can be di-vided into two periods: 3000—2.00 aBP, cool and wet, the air temperature averaging 9.8℃; and 2.00 aBP—present, hot and dry, the air temperature being 1℃ higher than the mean value (11.7℃) of the past 3000 years. During 500—2.0 aBP, the air temperature was about 1.2. lower than that of the present, corresponding to the Little Ice Age in Europe. Like d 18O and d 13C, Mg/Sr (or DMg/Ca) reflects an obviously warming trend of the past 2.0 years. These results are sup-ported by historic records.

关键词：北京京东溶洞石笋 Mg/Sr记录古气温测年 3000年

Human multi-drug resistant hepatocellular carcinoma induced in nude mice by B-ultrasonographically-directed orthotopic implantation:a new experimental model

在线全文

学校读者我要写书评

暂无评论

Hepatobiliary & Pancreatic Diseases International 2007年第4期6卷 393-398页

作者： Lei Ding,Xiao-Ping chen,Zhi-Wei Zhang,Kai Jing and Wan-Guang Zhang Hepatic Surgery Center,Affiliated Tongji Hospital,Tongji Medical College,Huazhong university of Science and {2.,Wuhan 430030,china department of Oncology Center,beijing Shijitan Hospital,beijing 100038,china Hepatic Surgery Center Affiliated Tongji Hospital Tongji Medical College Huazhong University of Science and Technology Wuhan 430030 China. dinglei1005@***

BACKGROUND:Present studies on the reversal of multi-drug resistance(MDR) are almost entirely limited to in vitro systems,and are seldom carried out in vivo. In order to study MDR under the in vivo situation,a MDR cell strain was used to establish a model in nude mice via orthotopic implantation directed by B-ultrasonography. This model is expected to provide a good platform for evaluating strategies to reverse the phenomenon of primary hepatocellular carcinoma(HCC) MDR. METHODS:An orthotopic MDR1 hepatoma was obtained by injecting the cell lines HepG2.and HepG2.ADM subserosally into the liver of nude mice(10 control and 2. MDR mice). The injections were made under B-ultrasonographic direction. Ultrasonography and laparotomy were used to assess tumor growth,and the long chain PCR technique was applied to sequence the MDR1 gene from multi-drug resistant human HCC cells,HepG2.ADM,and corresponding implanted tumor tissues. Furthermore,MDR1 mRNA and P-gp protein expression were evaluated by reverse transcriptase-polymerase chain reaction(RT-PCR),Western blotting,and immunohistochemical methods. RESULTS:The success rates of tumor implantation and induction of MDR were 100%(30/30) and 95%(19/2.),respectively. The 3.8kbp MDR1 gene band was detected from the HepG2.ADM cell line and the correspondingimplanted tumor tissues,and the MDR1 gene sequence coincided with that reported in GenBank. The expressions of MDR1 mRNA and P-gp protein in MDR mice were significantly higher than those in the control group. There was a significant difference in P-gp protein expression between MDR and control mice. CONCLUSION:A MDR model has been successfully established in nude mice via orthotopic implantation of multi-drug resistant human HCC cells directed by ultrasonography.

关键词： nude mice orthotopic implantation carcinoma,hepatocellular drug resistance,multiple

Atomistic simulation of rare earth-transition intermetallic compounds derived from CaCu5 type

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2003年第5期 21-26页

作者： chen Nanxian, LU Yao, SHEN Jiang and WU Yu (1. Institute of Applied Physics, beijing {2. of Science and technology, beijing 100083, china 2. department of Physics, Ts-inghua {2., beijing 100084, china) Institute of Applied Physics，beijing university of Science and {2.，beijing 100083，china department of Physics，Tsinghua university，{2. 100084，china Institute of Applied Physics，beijing university of Science and {2.，beijing 100083，china

The rare earth(R)-transition metal(M) compounds are important subjects of new functional materials. In this paper, first we review the transformation relations between R-M compounds (Rn-mM5n + 2.) derived from CaCu5 type structure, and discuss their validity and limitations. Then we calculate the lattice parameters and crystal structures of five binary compounds, SmFe5, Sm2.e17 (H), Sm2.e17(R), SmFe12.t), and Sm3Fe2. by energy minimization. With above results, we get the vector transformation matrix in reciprocal space in comparison with the traditional transformation matrix and analyze the reason for their similarity and difference. Finally, we discuss the stable effect of the third elements Cr, Ti to Sm3Fe2.- The third elements also change the lattice parameters and the materials X-rays diffraction pattern. The tradition matrix cannot reflect these differences.

关键词： R-M compounds derived from CaCus type structure transformation relation interatomic potential.

Superconductivity of small metal grains

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(Physics,Mechanics & Astronomy) 2005年第4期48卷 431-441页

作者： ZHENG Renrong1 chen Zhiqian2.& ZHU Shunquan1,3 1. department of Physics, Shanghai Normal {2., Shanghai 2.02.4, china 2. department of Physics, Southwest Normal {2., Chongqing 400715, china 3. department of Computer and Electric technology, Shanghai Business School, Shanghai 2.1400, china department of Physics Shanghai Normal University Shanghai China department of Physics Southwest Normal University Chongqing China department of Computer and Electric technology Shanghai Business School Shanghai China

The formulas of the energy gap and superconducting critical temperature appropriate for systems with both odd and even number of electrons are derived; the bases of the derivations are BCS theory and energy level statistics. Numerical results qualitatively agree with the experimental phenomena. i.e., the superconductivity of small metallic grains will first enhance then decrease to zero when the grain are getting smaller and smaller. The calculations indicate that the above phenomena happen in the metallic grains belonging to Gaussian Orthogonal Ensemble (GOE) and Gaussian Unitary ensemble (GUE) with zero spin; The superconductivity of small metallic grains in Gaussian Symplectic Ensemble (GSE) will monotonically decrease to zero with the decreasing of the grain size. The analyses suggest that the superconductivity enhancements come from pairing and the balance of the strengths between spin-orbital coupling and external magnetic field. In order to take the latter into account, it is necessary to include the level statistics given by Random Matrix Theory (RMT) in describing small metallic grains.

关键词： size effect, superconductivity enhancements, small metallic grains.

High-throughput real-time assay based on molecular beacons for HIV-1 integrase 3'-processing reaction

在线全文

学校读者我要写书评

暂无评论

Acta Pharmacologica Sinica 2007年第6期28卷 811-817页

作者： Hong-qiu HE~2.Xiao-hui MA~(2.4),Bin LIU~2.Xiao-yi ZHANG~2.Wei-zu chen~2.Cun-xin WANG~(2.3),Shao-hui chenG~(2.3)~2.College of Life Science and Bioengineering,{2. university of technology,{2. 10002.,china College of Life Science and Bioengineering Beijing University of Technology Beijing China department of Pharmacentical and Biomedical Sciences University of Georgia Athens USA

Aim:To develop a high-throughput real-time assay based on molecular beaconsto monitor the integrase 3’-processing reaction in vitro and apply it to ***:The recombinant human immunodeficiency virus (HIV)-1integrase (IN) is incubated with a 38 mer oligonucleotide substrate,a sequenceidentical to the U5 end of HIV-1 long terminal repeats (LTR).Based on the fluores-cence properties of molecular beacons,the substrate is designed to form a stem-loop structure labeled with a fluorophore at the 5’ end and a quencher at the 3’ *** cleaves the terminal 3’-dinucleotide containing the quencher,resulting in anincrease in fluorescence which can be monitored on a *** this assay,tests were performed to investigate the effects of substrates,enzyme and the metal ion concentrations on the IN activity and optimal param-eters were ***,2.IN inhibitors were employed to test the perfor-mance of this assay in antiviral compound ***:The fluorescentintensity of the reaction mixture varies linearly with time and is proportional to thevelocity of the 3’-processing *** were performed and the results showedthat the optimal rate was obtained for a reaction mixture containing 50 mg/L recom-binant HIV-1 IN,400 nmol/L substrate,and 10 mmol/L Mn2..The IN 3’-processingreaction under the optimal conditions showed a more than 18-fold increase in thefluorescence intensity compared to the enzyme-free *** IC50values ofthe IN inhibitors obtained in our assay were similar to the values obtained from aradiolabeled substrate ***:Our results demonstrated that this is afast,reliable,and sensitive method to monitor HIV IN 3’-processing reaction andthat it can be used for inhibitor screening.

关键词： HIV integrase 3’-processing molecular beacons

Synergistic Effect in Mixed Capillary Gas Chromatographic Stationap Phases Containing Heptakis(2.3,6-tri-o-pentyl)-β-cyclodextrin and Dibenzo-18-crown-6

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Chemical Letters 1999年第3期10卷 223-226页

作者： Li Ming YUAN Ruo Nong FU Xue Xian chen Shi Hong GUl Rong Ji DAI (chemistry {2. of Yunnan Normal university.Kunming 650092.({2. of Chemical Engineering.beijing institute of technology,beijing 100081)(Solar Energy Research Institute ofyunna chemistry department Yunnan Normal University Kunming 650092 China department of Chemical Engineering Beijing Institute of Technology Beijing 100081 China Solar Energy Research Institute Yunnan Normal University Kunming 650092 China

used－silical capillary columns containing heptakis（2.3、6－tri－o－pentyl）-β-cyclodextrinand dibenzo-18-crown-6 were *** studying the selectivity of mixed stationary phases forsome solute *** well as comparing with the heptakis（2.3、6-tri-O-pentyl）-β-cyclodextrin and thedibenzo-18-crown-6 used as individual stationary phase、the synergistic effects were *** effects were affected by the column *** ratio and linear velocity of carrier gas．

关键词： Gas chromatography mixed stationary phase synergistic effect heptakis(2.3.6-tri-o-pentyl)-β-cyclodextrin dibenzo-18-crown-6