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Negative refraction in two-dimensional photonic crystals

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Progress in Natural Science:Materials International 2006年第10期16卷 1027-1032页

作者： REN Xiaobin, REN Kun, FENG Zhifang, FENG Shuai and REN cheng ( School of Physics Science and Information Technology, Liaocheng University, Liaocheng 252059, China beijing National Laboratory for Condensed Matter Physics, institute of Physics, chinese academy of sciences, {3. 100080, China) [a]School of physics Science and Information Techonolgy Liaocheng University Liaocheng China [b]beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing China

Recent progress made in research on negative refraction in two-dimensional photonic crystals is reviewed. Special attentions are paid to the research results of our group. We explore the underlying mechanism governing the occurrence of negative refraction in periodic and quasiperiodic photonic crystals. These results may be useful references for the application of photonic crystals. The perspectives of future research on negative refraction are briefly predicted.

关键词： negative refraction photonic crystals superlens subwavelength imaging equifreqnency surface.

Urban effects and summer thunderstorms in a tropical cyclone affected situation over Guangzhou city

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Science China Earth sciences 2007年第12期50卷 1867-1876页

作者： MENG WeiGuang1,3.YAN Jinghua1 & hu HaiBo2 1 institute of Tropical and Marine Meteorology,{3. Meteorological Administration(CMA),Guangzhou 510080,China 2 institute of Urban Meteorology,CMA,beijing 100089,China 3.State Key Laboratory of Severe Weather,{3. academy of Meteorological sciences,beijing 100081,China 1. institute of Tropical and Marine Meteorology Chinese Meteorological Administration (CMA) Guangzhou 510080 China 3. State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences Beijing 100081 China 2. institute of Urban Meteorology CMA Beijing 100089 China

With data mainly from Guangzhou mesonet Automatic Weather Stations(AWS),Guangzhou Doppler Radar and satellite TBB data,characteristics and evolution of the urban heat island(UHI) over Guang-zhou City were analyzed in a tropical cyclone affected situation for early August *** particular,two thunderstorms occurring during this period respectively at the night of 4 August and in the afternoon of 7 August were investigated to study the relationships between the development of thunderstorms and the *** showed that two thunderstorms were associated with the UHI *** induced local air convergence and initiated the thunderstorm *** cases showed a general agreement in time and space for the locations of maximum UHI,convergence,convection,and *** was found to be more favorable to developing in time periods and locations with stronger intensity of *** also showed that,due to the urban effects,both thunderstorms got strengthened when moving over Guangzhou City,with maximum radar echoes observed right over the urban area and precipitation located within the *** these features reveal that two thunderstorms were urban-induced storms.

关键词： summer thunderstorms, urban heat islands (UHI), urban effects, tropical cyclone

Modeling of Hillslope Runoff and Soil Erosion at Rainfall Events Using Cellular Automata Approach

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Pedosphere 2009年第6期19卷 711-718页

作者： MA Ting ZHOU cheng-hu CAI Qiang-Guo State Key Laboratory of Resources and Environmental Information System Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 (China) Graduate University of the chinese academy of sciences Beijing 100049 (China)

A novel quantitative cellular automata (CA) model that simulates and predicts hillslope runoff and soil erosion caused by rainfall events was developed by integrating the local interaction rules and the hillslope surface hydraulic processes. In this CA model, the hillslope surface was subdivided into a series of discrete spatial cells with the same geometric features. At each time step, water and sediment were transported between two adjacent spatial cells. The flow direction was determined by a combination of water surface slope and stochastic assignment. The amounts of interchanged water and sediment were computed using the Chezy-Manning formula and the empirical sediment transport equation. The water and sediment discharged from the open boundary cells were considered as the runoff and the sediment yields over the entire hillslope surface. Two hillslope soil erosion experiments under simulated rainfall events were carried out. Cumulative runoff and sediment yields were measured, respectively. Then, the CA model was applied to simulate the water and soil erosion for these two experiments. Analysis of simulation results indicated that the size of the spatial cell, hydraulic parameters, and the setting of time step and iteration times had a large impact on the model accuracy. The comparison of the simulated and measured data suggested that the CA model was an applicable alternate for simulating the hillslope water flow and soil erosion.

关键词： hillslope surface hydraulic parameters sediment simulation water

The universal fuzzy logical framework of neural circuits and its application in modeling primary visual cortex

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Science China(Life sciences) 2008年第10期51卷 902-912页

作者： hu Hong1, LI Su2, WANG YunJiu2, QI XiangLin2 & SHI ZhongZhi1 1 Key Laboratory of Intelligent Information Processing, institute of Computing Technology, chinese {3. of {3., beijing 100080, China 2 Laboratory of Visual Information Processing, institute of Biophysics, chinese {3. of {3., beijing 100101, China 1. Key Laboratory of Intelligent Information Processing Institute of Computing Technology Chinese Academy of Sciences Beijing 100080 China 2. Laboratory of Visual Information Processing Institute of Biophysics Chinese Academy of Sciences Beijing 100101 China

Analytical study of large-scale nonlinear neural circuits is a difficult task. Here we analyze the function of neural systems by probing the fuzzy logical framework of the neural cells' dynamical equations. Al- though there is a close relation between the theories of fuzzy logical systems and neural systems and many papers investigate this subject, most investigations focus on finding new functions of neural systems by hybridizing fuzzy logical and neural system. In this paper, the fuzzy logical framework of neural cells is used to understand the nonlinear dynamic attributes of a common neural system by abstracting the fuzzy logical framework of a neural cell. Our analysis enables the educated design of network models for classes of computation. As an example, a recurrent network model of the primary visual cortex has been built and tested using this approach.

关键词： nonlinear dynamical system fuzzy logic visual cortex

Period-doubling bifurcations of the thermocapillary convection in a floating half zone

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Science China(Physics,Mechanics & Astronomy) 2010年第9期53卷 1681-1686页

作者： AA Yan,LI Kai,TANG ZeMei,CAO Zhonghua & hu WenRui National Microgravity Laboratory,institute of Mechanics,{3. academy of {3.,beijing 100190,China 1. National Microgravity Laboratory Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China

This study experimentally explored the fine structures of the successive period-doubling bifurcations of the time-dependent thermocapillary convection in a floating half zone of 10 cSt silicone oil with the diameter d0=3.00 mm and the aspect ratio A=l/d0=0.72 in terrestrial *** onset of time-dependent thermocapillary convection predominated in this experimental configuration and its subsequent evolution were experimentally detected through the local temperature *** experimental results revealed a sequence of period-doubling bifurcations of the time-dependent thermocapillary convection,similar in some way to one of the routes to chaos for buoyant natural *** critical frequencies and the corresponding fractal frequencies were extracted through the real-time analysis of the frequency spectra by Fast-Fourier-Transfor-mation(FFT).The projections of the trajectory onto the reconstructed phase-space were also ***,the experimentally predicted Feigenbaum constants were quite close to the theoretical asymptotic value of 4.669 [Feigenbaum M *** Lett A,1979,74:3.5-3.8].

关键词： thermocapillary convection bifurcation transition to turbulence

Truncation Analysis for the Derivative Schrodinger Equation

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Acta Mathematica Sinica,English Series 2002年第1期18卷 137-146页

作者： XU Peng cheng CHANG Qian Shun GUO Bo Ling academy of Mathematics and System {3.. {3. academy of {3.. beijing 100080. P. R. China institute of Applied Physics and Computational Mathematics. P. O. Box 8009. beijing 100080. P. R. China academy of Mathematics and System sciences Chinese Academy of Sciences Beijing 100080 P. R. China institute of Applied Physics and Computational Mathematics 8009 Beijing 10080 P. R. China

The truncation equation for the derivative nonlinear Schrodinger equation has been dis- cussed in this paper. The existence of a special heteroclinic orbit has been found by using geometrical singular perturbation the... 详细信息

关键词： Derivative nonlinear Schrodinger equation Geometric singular perturbation theory Melnikov's technique

Late Mesozoic Exhumation of the huangling Massif:Constraints on the Evolution of the Middle Yangtze River

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Acta Geologica Sinica(English Edition) 2024年第1期98卷 250-264页

作者： SU Jianchao LIN Xu LI Chang’an Jolivet MARC WU Lin cheng Feng DENG Bin WU Zhonghai CHEN Xiaokang hu chengwei School of Geography and Information Engineering China University of GeosciencesWuhan 430074China College of Civil Engineering and Architecture China Three Gorges UniversityYichangHubei 443002China Géosciences Rennes CNRS-UMR6118Univ RennesRennesFrance State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBejing 100029China Key Laboratory of Orogenic Belts and Crustal Evolution Ministry of EducationSchool of Earth and Space SciencesPeking UniversityBeijing 100871China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation/chengdu University of Technology Chengdu 100871China institute of Geological Mechanics Chinese Academy of Geological ScienceBeijing 100081China

Plate subduction leads to complex exhumation processes on *** huangling Massif lies at the northern margin of the South China *** the huangling Massif was exhumed as a watershed of the middle reaches of the Paleo-Yangtze River during the Mesozoic remains under *** examined the exhumation history of the huangling Massif based on six granite bedrock samples,using apatite fission track(AFT)and apatite and zircon(U-Th)/He(AHe and ZHe)*** samples yielded ages of 157–13. Ma(ZHe),119–106 Ma(AFT),and 114–72 Ma(AHe),*** modeling revealed that three phases of rapid cooling occurred during the Late Jurassic–Early Cretaceous,late Early Cretaceous,and Late *** exhumation processes led to the high topographic relief responsible for the emergence of the huangling *** integrated of our new data with published sedimentological records suggests that the huangling Massif might have been the watershed of the middle reaches of the Paleo-Yangtze River since the *** that time,the rivers flowed westward into the Sichuan Basin and eastward into the Jianghan *** subduction of the Pacific Plate beneath the Asian continent in the Mesozoic deeply influenced the geomorphic evolution of the South China Block.

关键词： apatite zircon (U-Th)/He fission track huangling Massif Yangtze River

Resurvey After 20 Years:Updating the Distribution,Population,and Potential Threats of the Chinting Alpine Toad

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Asian Herpetological Research 2024年第2期15卷 73-81页

作者： Yuezheng FAN Qingfeng CHEN Yuwen cheng Kaicheng TANG Ling SUN Yonghao huANG Lan ZHAO Dong LIANG Xiaoyi WANG Junhua hu chengdu institute of Biology Chinese Academy of SciencesChengdu 610041SichuanChina University of chinese academy of sciences Beijing 100049China The State-owned Forest Farm of Hongya County Meishan 620360SichuanChina Sichuan Mt.Emei Forest Ecosystem National Observation and Research Station Leshan 614201SichuanChina

Considering the increased anthropogenic impacts,species with a limited range and low detectability often lack fundamental information and conservation actions,placing them at a high risk of *** Chinting alpine toad Scutiger chintingensis is a rare mountain amphibian endemic to the eastern margin of the Qinghai-Xizang Plateau in *** its whole distribution range,only three known populations(Wolong,Emei,and Wawu)exist and no recent population status report has been documented for this species over the past two *** 2020 to 2023.we investigated the species distribution,and assessed the risk factors for the main *** recorded this species in all distribution areas,and updated a new distribution site with a lower elevation *** relative population density was 0.024±0.012 ind./m^(2)on Mount Emei,whereas only 0.008±0.017 ind./m^(2)on Mount *** significant difference was observed in the number of individuals between the two populations;however,the relative population density was significantly *** and waste discharge resulting from the construction of scenic areas,as well as disturbances from tourism,were the primary anthropogenic factors that influenced the survival of this *** results provide the updated information on the distribution and population status of the Chinting alpine toad,and suggest that unrecorded populations,as well as a wider elevation range,may exist for this *** findings emphasise the importance of timely updates of species distribution and population information and offer a basis for the future conservation of endangered amphibians.

关键词： distribution endemic amphibian population size Scutiger chintingensis threat factor

Automatic real-time SLAM relocalization based on a hierarchical bipartite graph model

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Science China(Information sciences) 2012年第12期55卷 2841-2848页

作者： DONG QiuLei ,GU ZhaoPeng & hu ZhanYi National Laboratory of Pattern Recognition(NLPR),institute of Automation,chinese {3. of {3.,beijing 100190,China 1. National Laboratory of Pattern Recognition (NLPR) Institute of Automation Chinese Academy of Sciences Beijing 100190 China

The need to increase the robustness of a real-time monocular SLAM system raises the important problem of relocalization;namely,how to automatically recover a SLAM system after tracking *** address this problem by proposing a real-time relocalization algorithm based on a hierarchical bipartite graph *** the SLAM system is lost,we use the latter model to find sufficient correspondences between the detected image and stored map features,thus achieving efficient,real-time *** model accounts for both temporal and spatial *** results on both synthetic and real data support the effectiveness of the proposed algorithm.

关键词： monocular SLAM real-time relocalization hierarchical bipartite graph model