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Nonlinear Refractive Index and Absorption Coefficient of Single-Shell Semiconductor Carbon Nanotube

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wuhan university Journal of Natural Sciences 2003年第3A期8卷 833-836页

作者： Lu Ni,Xiong Gui\|guang  school of physics and technology, wuhan university, wuhan 430072, hubei, china wuhan university School of Physics and Technology Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***)

The nonlinear refractive index and absorption coefficient of single\|shell semiconductor carbon nanotubes(CN s ) are calculated based on the two\|band approximation and Genkin\|Mednis approach. The results of nonlinear refractive index and absorption coefficient reach the order of 10 -8 and 10 -4 cm 2\5W -1 separately, which indicates that CN s have wonderful nonlinear optical properties. Taking into account the temperature effect and overlapping of σ and π orbits, the effect of relaxation term and chiral angle is discussed. The results show that the smaller the relaxation term, the larger the nonlinear absorption coefficient and refractive index. At the same time, CN s with different chiral angles have different results due to their different energy gap.

关键词： nonlinear refractive index nonlinear absorption coefficient relaxation chiral angle

Integrating Audio-Visual Features and Text Information for Story Segmentation of News Video

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wuhan university Journal of Natural Sciences 2003年第4A期8卷 1070-1074页

作者： Liu Hua-yong, zhou Dong-ru  school of Computer,wuhan university,wuhan 430072, hubei, china wuhan university School of Computer Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***)

Video data are composed of multimodal information streams including visual, auditory and textual streams, so an approach of story segmentation for news video using multimodal analysis is described in this paper. The proposed approach detects the topic-caption frames, and integrates them with silence clips detection results, as well as shot segmentation results to locate the news story boundaries. The integration of audio-visual features and text information overcomes the weakness of the approach using only image analysis techniques. On test data with 135 400 frames, when the boundaries between news stories are detected, the accuracy rate 85.8% and the recall rate 97.5% are obtained. The experimental results show the approach is valid and robust.

关键词： news video story segmentation audio-visual features analysis text detection

Electronic Structure of Doped Trans-Polyacetylene

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wuhan university Journal of Natural Sciences 2002年第1期7卷 51-53页

作者： Ren Da-zhi 1,2, Zhuang Wei 2, Wang Jun 2 1. wuhan university Journals Press,wuhan 430072.hubei,china 2. school of physics and technology, wuhan university, wuhan 430072.hubei,china wuhan university Journals Press Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***) wuhan university School of Physics and Technology Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***) wuhan university School of Physics and Technology Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***)

The behavior of electronic structures of doped trans-polyacetylene is revealed by a simple method. (C24H26)+n is used to simulate p-type doped trans-polyacetylene at various doping concentrations. The electronic structure is calculated, by CNDO/2 method. These calculations show that at low doping level, the decrease of electronic energy compensates the increase of elastic energy, thus the bond alternation exists, and the charge carriers are solitons. When doping level is high, the increase of elastic energy is larger than the decrease, of electronic energy, the bond alternation disappears, solitons no longer exist, and polyacetylene is in a metalic state.

关键词： trans polyacetylene CNDO/2 electronic structure doped

Evaluation Method of Web Site Structure Based on Web Structure Mining

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wuhan university Journal of Natural Sciences 2003年第3A期8卷 791-796页

作者： Li Jun\|e 1 , zhou Dong\|ru 2 1. Computer Center,wuhan university, wuhan 430072, hubei, china 2. school of Computer,wuhan university, wuhan 430072, hubei,china wuhan university Computer Center Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***) wuhan university School of Computer Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***)

The structure of Web site became more complex than before. During the design period of a Web site, the lack of model and method results in improper Web structure, which depend on the designer's experience. From the point of view of software engineering, every period in the software life must be evaluated before starting the next period's work. It is very important and essential to search relevant methods for evaluating Web structure before the site is completed. In this work, after studying the related work about the Web structure mining and analyzing the major structure mining methods (Page\|rank and Hub/Authority), a method based on the Page\|rank for Web structure evaluation in design stage is proposed. A Web structure modeling language WSML is designed, and the implement strategies for evaluating system of the Web site structure are given out. Web structure mining has being used mainly in search engines before. It is the first time to employ the Web structure mining technology to evaluate a Web structure in the design period of a Web site. It contributes to the formalization of the design documents for Web site and the improving of software engineering for large scale Web site, and the evaluating system is a practical tool for Web site construction.

关键词： web structure mining page\|rank web structure evaluation modeling language for web structure

Evidence of Positron Trapping into Defects in Zn-Doped GaAs

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wuhan university Journal of Natural Sciences 2003年第4A期8卷 1103-1106页

作者： Wang Zhu, Zheng Zi-yao, Su Ben-fa, Hu Wei-guo school of physics and technology, wuhan university , wuhan 430072, hubei, china wuhan university

The defect properties in as-grown and deformed p-type GaAs with different concentration of dopants and different growth method have investigated by positron lifetime measurement. The result indicates that no positron trapping was observed in LEC-grown Zn-doped p-type GaAs. However, in HB- and FZ-grown Zn-doped GaAs, positron trapping into vacancy type defects was observed. In deformed samples, clusters were formed during deformation. Positron detected shallow positron traps and the dominant shallow positron traps were attributed to Zn acceptors in Zn-doped GaAs.

关键词： positron annihilation defect semiconductor deformation p-type GaAs

Weak martingale Hardy spaces and weak atomic decompositions

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Science china Mathematics 2006年第7期49卷 912-921页

作者： HOU Youliang & REN Yanbo school of Mathematics and Statistics, wuhan university, wuhan 430072, china Department of Mathematics & physics, Henan university of Science and technology, Luoyang 471003, china 1. school of Mathematics and Statistics Wuhan University Wuhan 430072 China 2. Department of Mathematics & physics Henan University of Science and Technology Luoyang 471003 China

In this paper we define some weak martingale Hardy spaces and three kinds of weak atoms. They are the counterparts of martingale Hardy spaces and atoms in the classical martingale Hp-theory. And then three atomic decomposition theorems for martingales in weak martingale Hardy spaces are proved. With the help of the weak atomic decompositions of martingale, a sufficient condition for a sublinear operator defined on the weak martingale Hardy spaces to be bounded is given. Using the sufficient condition, we obtain a series of martingale inequalities with respect to the weak Lp-norm, the inequalities of weak (p ,p)-type and some continuous imbedding relationships between various weak martingale Hardy spaces. These inequalities are the weak versions of the basic inequalities in the classical martingale Hp-theory.

关键词： martingale, weak Hardy space, weak atom, atomic decomposition.

Photoluminescence of ZnO Nanorods Grown by Hydrothermal Method on Si Substrate

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wuhan university Journal of Natural Sciences 2009年第5期14卷 415-418页

作者： HU Ming,ZHANG Xia,MENG Xianquan school of physics and technology,wuhan university,wuhan 430072.hubei,china school of physics and technology Wuhan University Wuhan 430072 Hubei China

ZnO nanorods were grown on Si substrate by hydrothermal method under various reaction time （12, 24, and 36 h）, Zn^2＋ concentrations （0.01, 0.02, and 0.05 mol/L） and reaction temperatures （70-95 ~C）. Their photoluminescence （PL） tests were taken at room temperature. Nanorods grown under longer reaction times or higher temperatures can emit stronger UV light and depressed green light, suggesting better crystallization of ZnO nanorods. Higher Zn^2＋ concentration results in stronger green band emitting, whereas the UV peak is depressed with the Zn^2＋ concentration over 0.02 mol/L. This indicates that excessive interstitial Zn defects may be introduced into the nanorods in Zn-rich environment.

关键词： ZnO nanorods hydrothermal method photoluminescence

Ferroelectric properties of Bi_(3.4)Ho_(0.6)Ti_3O_(12) thin films prepared by sol-gel method

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Science china(Technological Sciences) 2008年第9期51卷 1439-1444页

作者： FU ChengJu1, HUANG ZhiXiong1, LI Jie2 & GUO DongYun3 1 school of Materials Science and technology, wuhan university of technology, wuhan 430070, china 2 school of Mechanical Engineering, Chongqing university of Science and technology, Chongqing 400050, china 3 Department of physics, wuhan university, wuhan 430072, china school of Materials Science and technology Wuhan University of Technology Wuhan 430070 China school of Mechanical Engineering Chongqing University of Science and Technology Chongqing 400050 China Department of physics Wuhan University Wuhan 430072 China

We have prepared the Ho-substituted bismuth titanate (Bi3.4Ho0.6Ti3O12, BHT) thin films on Pt/Ti/SiO2/Si substrates using sol-gel method. The crystal structure and morphology of the films were characterized using X-ray diffraction and atomic force microscopy. The BHT film shows a single phase of Bi-layered Aurivillius structure and dense microstructure. The 2Pr and 2Ec of the 600-nm-thick BHT film were 38.4 μC/cm2 and 376.1 kV/cm, respectively at applied electric field 500 kV/cm. The dielectric constant and dielectric loss are about 310 and 0.015 at a frequency of 1 MHz, respectively. The Pr value decreased to 93% of its pre-fatigue values after 4.46×109 switching cycles at 1 MHz frenquency, and the BHT film shows good in-sulating behavior according to the test of leakage current.

关键词： Bi3.4Ho0.6Ti3O12 thin film sol-gel method ferroelectric property fatigue dielectric constant

Phylogeny Constructed by Using Diversity Increment

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wuhan university Journal of Natural Sciences 2003年第S1期8卷 303-306页

作者： Shi Feng, Li Na-na, Li Yuan-xiang, zhou Huai-beischool of Mathematics and Statistics, wuhan university, wuhan 430072.hubei,chinaAdvanced Research Center for Science and technology, wuhan university, wuhan 430072, hubei,chinaState Key Laboratory of Software Engineering, wuhan university, wuhan 430072.hubei,china wuhan university School of Mathematics and Statistics Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***) wuhan university Advanced Research Center for Science and Technology Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***) wuhan university State Key Laboratory of Software Engineering Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***) wuhan university Advanced Research Center for Science and Technology Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***) wuhan university State Key Laboratory of Software Engineering Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***)

A new approach based on the concept of the diversity increment is applied to reconstruct a phylogeny. The phylogeny of the Eutherian orders use concatenated H-stran-ded amino acid sequences, and the result is consiste... 详细信息

关键词： diversity indicator phylogeny distance