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Retrieving crop leaf area index by assimilation of MODIS data into a crop growth model

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science china Earth sciences 2010年第5期53卷 721-730页

作者： WANG DongWei1,2,3. WANG JinDi1,2 & LIANG ShunLin4 1 State Key Laboratory of Remote Sensing science, Jointly Sponsored by beijing Normal University and Institute of Remote Sensing Applications, CAS, beijing 100875,{3. 2 School of Geography, beijing Key Laboratory of Environmental Remote Sensing and Digital City, beijing Normal University, beijing 100875,{3. 3.Haihe River Water Conservancy Commission, Tianjin 3.0170,{3. 4 Department of Geography, University of Maryland, college Park, MD 20742, USA 1. State Key Laboratory of Remote Sensing science Jointly Sponsored by Beijing Normal University and Institute of Remote Sensing Applications CAS Beijing 100875 China2. School of Geography Beijing Key Laboratory of Environmental Remote Sensing and Digital City Beijing Normal University Beijing 100875 China3. Haihe River Water Conservancy Commission Tianjin 300170 China4. Department of Geography University of Maryland College Park MD 20742 USA

Leaf area index (LAI) is an important parameter in monitoring crop growth. One of the methods for retrieving LAI from remotely sensed observations is through inversion of canopy reflectance models. Many model inversion methods fail to account for variable LAI values at different crop growth stages. In this research, we use the crop growth model to describe the LAI changes with crop growth, and consider a priori LAI values at different crop growth stages as constraint information. The key approach of this research is to assimilate multiple canopy reflectance values observed at different growth stages and a priori LAI values into a coupled crop growth and radiative transfer model sequentially using a variational data assimilation algorithm. Adjoint method is used to minimize the cost function. Any other information source can be easily incorporated into the inversion cost function. The validation results show that the time series of MODIS canopy reflectance can greatly reduce the uncertainty of the inverted LAI values. Compared with MODIS LAI product at Changping and Shunyi Counties of beijing, this method has significantly improved the estimated LAI temporal profile.

关键词： inversion leaf area index crop growth model time series MODIS

Developing land use scenario dynamics model by the integration of system dynamics model and cellular automata model

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science china Earth sciences 2005年第11期48卷 1979-1989页

作者： HE Chunyang, SHI Peijun, CHEN Jin, Li Xiaobing, PAN Yaozhong, LI Jing, LI Yuechen & LI Jinggang Key Laboratory of Environmental Change and Natural Disaster, Ministry of Education of china, beijing Normal University college of Resources {3. & Technology, beijing Normal University, beijing 100875, china 1. Key Laboratory of Environmental Change and Natural Disaster Ministry of Education of China Beijing Normal University China 2. college of Resources science & Technology Beijing Normal University 100875 Beijing China

Modeling land use scenario changes and its potential impacts on the structure and function of the ecosystem in the typical regions are helpful to understanding the interactive mechanism between land use system and ecological system. A Land Use Scenario Dynamics (LUSD) model by the integration of System Dynamics (SD) model and Cellular Automata (CA) model is developed with land use scenario changes in northern china in the next 20 years simulated in this paper. The basic idea of LUSD model is to simulate the land use scenario de-mands by using SD model at first, then allocate the land use scenario patterns at the local scale with the considerations of land use suitability, inheritance ability and neighborhood effect by using CA model to satisfy the balance between land use scenario demands and supply. The application of LUSD model in northern china suggests that the model has the ability to reflect the complex behavior of land use system at different scales to some extent and is a useful tool for assessing the potential impacts of land use system on ecological system. In addition, the simulated results also indicate that obvious land use changes will take place in the farming-pastoral zone of northern china in the next 20 years with cultivated land and urban land being the most active land use types.

关键词： system dynamics, cellular automata, scenario, land use, model

Threshold proxy quantum signature scheme with threshold shared verification

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science china(Physics,Mechanics & Astronomy) 2008年第8期51卷 1079-1088页

作者： YANG YuGuang1,3.4 & WEN QiaoYan2 1 college of Computer science and Technology,beijing University of Technology,beijing 100124,china 2 State Key Laboratory of Networking and Switching Technology,beijing University of Posts and Tele-communications,beijing 100876,china 3.State Key Laboratory of Integrated Services Network,Xidian University,Xi’an 710071,china 4 State Key Laboratory of information Security(Graduate University of Chinese Academy of sciences) ,beijing 100049,china 1. college of Computer science and Technology Beijing University of Technology Beijing 100124 China 3. State Key Laboratory of Integrated Services Network Xidian University Xi’an 710071 China 4. State Key Laboratory of information Security (Graduate University of Chinese Academy of sciences) Beijing 100049 China 2. State Key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications Beijing 100876 China

A threshold proxy quantum signature scheme with threshold shared verification is proposed. An original signer could authorize a group as its proxy signers. Then only t or more of n persons in the proxy group can generate the proxy signature on behalf of the original signer and any t-1 or fewer ones cannot do that. When the proxy signature needs to be verified,any t or more of n persons belonging to the verification group can verify the message and any t-1 or fewer ones cannot verify the validity of the proxy signature.

关键词： quantum signature threshold proxy quantum group signature threshold shared verification

Threshold quantum secret sharing between multi-party and multi-party

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science china(Physics,Mechanics & Astronomy) 2008年第9期51卷 1308-1315页

作者： YANG YuGuang1,2,3.& WEN QiaoYan4 1 college of Computer science and Technology,beijing University of Technology,beijing 100124,china 2 State Key Laboratory of Integrated Services Network,Xidian University,Xi’an 710071,china 3.State Key Laboratory of information Security (Graduate University of Chinese Academy of sciences),beijing 100049,china 4 State Key Laboratory of Networking and Switching Technology,beijing University of Posts and Tele-communications,beijing 100876,china college of Computer science and Technology Beijing University of Technology Beijing 100124 China State Key Laboratory of Integrated Services Network Xidian University Xi’an 710071 China State Key Laboratory of information Security (Graduate University of Chinese Academy of sciences) Beijing 100049 China State Key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications Beijing 100876 China

A threshold quantum secret sharing (TQSS) scheme between multi-party and multi-party was proposed using a sequence of single photons,which is useful and efficient when the parties of communication are not all present. We described the process of this TQSS scheme and discussed its security. It was shown that entan-glement is not necessary for quantum secret sharing. Moreover,the theoretic effi-ciency was improved to approach 100% as almost all the instances can be used for generating the private key,and each photon can carry one bit of information. This protocol is feasible with the present-day technique.

关键词： threshold quantum secret sharing quantum cryptography single photon multi-party and multi-party

An efficient quantum secret sharing protocol with orthogonal product states

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science china(Physics,Mechanics & Astronomy) 2007年第3期50卷 331-338页

作者： YANG YuGuang1,2, WEN QiaoYan3.& ZHU FuChen4 1 School of Computer, beijing University of Technology, beijing 100022, china 2 State Key Laboratory of {3. Security, Graduate University of Chinese Academy of sciences, beijing 100022, china 3.School of science, beijing University of Posts and Telecommunications, beijing 100876, china 4 National Key Laboratory for Modern Communications, Chengdu 610041, china 1. School of Computer Beijing University of Technology Beijing 100022 China 2. State Key Laboratory of information Security Graduate University of Chinese Academy of Sciences Beijing 100022 China 3. School of science Beijing University of Posts and Telecommunications Beijing 100876 China 4. National Key Laboratory for Modern Communications Chengdu 610041 China

An efficient quantum secret sharing protocol with orthogonal product states in the 3.3.Hilbert space is presented. The particles in the orthogonal product states form two particle sequences. One sequence is sent to Bob and the other is sent to Charlie after rearranging the particle orders. With the help of Alice, Bob and Charlie make the corresponding local measurement to obtain the information of the or- thogonal product states prepared. This protocol has many distinct features such as great capacity and high efficiency.

关键词： quantum secret sharing orthogonal product state orthogonal measurement

Synchronization of Digital Chaos in Secure Communication Systems

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Journal of University of science and Technology beijing 2001年第4期8卷 299-305页

作者： Geng Zhao, Deling Zheng, ShaojunHuang 1)college of Electric science and Technology beijing. beijing 100070, china 2)information Engineering School, University of science and Technology beijing. beijing 100083. china Coll Elect Sci & Technol beijing Beijing 100070 Peoples R China Univ Sci & Technol beijing Informat Engn Sch Beijing 100083 Peoples R China

The theories of synchronization based on secure communications using digital chaos are presented. A new synchronous method-cycles-interval Pulse drive is developed and realized. Experimental results show it is available, and in order to reduce synchronous noise, a method using model references solves the ratio of signal power to noise power, so the secure communication system can be realized.

关键词： digital chaotic synchronization cycles-interval pulses drive synchronous noise model reference

Spatio-temporal pattern analysis of single-trial EEG signals recorded during visual object recognition

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science china(information sciences) 2011年第12期54卷 2519-2527页

作者： WANG ChangMing 1 , HU XiaoPing 3., YAO Li 1,2 , XIONG Shi 2 & ZHANG JiaCai 2 1 National Key Laboratory of Cognitive Neuroscience and Learning, beijing Normal University, beijing 100875,{3. 2 college of information science and Technology, beijing Normal University, beijing 100875,{3. 3.Biomedical Imaging Technology Center, Emory University/Georgia Institute of Technology, Atlanta 3.3.2, USA 1. National Key Laboratory of Cognitive Neuroscience and Learning Beijing Normal University Beijing 100875 China3. Biomedical Imaging Technology Center Emory University/Georgia Institute of Technology Atlanta 30322 USA2. College of Information Science and Technology Beijing Normal University Beijing 100875 China

Object discrimination is a fundamental cognitive function for human brains. In this study, we utilized an analysis approach for single-trial electroencephalography (EEG) to analyze the spatio-temporal activation patterns of visual objects processing in human brains, and attempted to apply it to discriminate different visual objects. The spatial patterns were respectively extracted from scalp EEG and the reconstructed cortical sources, while the experiment participants were perceiving 4 different categories of visual objects (faces, buildings, cats and cars). By classifying the patterns extracted from single-trial EEG, the presented visual objects could be discriminated by a computer, and the classification accuracies may provide a quantitative index to evaluate the spatial differences of the brain activations related to different visual objects. Our results demonstrated that the spatial patterns on both the scalp and the sources levels resulted in higher classification accuracies than chance rate. We also examined the classification results using temporally non-overlapping time intervals of different event-related potential (ERP) components. The temporal changes of classification accuracies may reflect the temporal distribution of the discriminative information in the EEG responses. The present pattern extraction and classification methods may compose a computational model for single-trial EEG data analysis in investigations of the spatio-temporal activation patterns for object recognition. These spatio-temporal patterns in EEG may be useful to identifying the discriminative spatial areas and time stages to improve the accuracies and efficiencies of object discrimination. In addition, investigating and utilizing humans'cognitive mechanisms of object recognition may improve computers' processing efficiency of visual information.

关键词： EEG spatio-temporal pattern object recognition single-trial analysis visual information processing

A high-resolution late Pleistocene record of pollen vegetation and climate change from Jingning, NW china

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science china Earth sciences 2006年第2期49卷 154-162页

作者： LI Chunhai12, TANG Lingyu1, FENG Zhaodong3.4, ZHANG Hucai2, WANG Weiguo3.& AN Chenbang3.1. Nanjing Institute of Geology and Palaeontology, Chinese Academy of sciences, Nanjing 210008, china 2. Nanjng Institute of Geography and Limnology, Chinese Academy of sciences, Nanjing 210008, china 3. Environment and Resources college, Lanzhou University, Lanzhou 73.000, china 4. beijing Normal University, beijing 100875, china 1. Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences Nanjing 210008 China 2. Nanjng Institute of Geography and Limnology Chinese Academy of Sciences Nanjing 210008 China 3. Environment and Resources college Lanzhou University Lanzhou 730000 China 4. beijing Normal University Beijing 100875 China

With the support of 18 AMS-14C data, a high-resolution pollen record from the Suancigou section at Jingning, Gansu Province was established. Our results showed that the vegetation ex-perienced a series of changes characterized by the alternative growth and decline of forest and steppe components during the period from 44.2 to 11 ka B.P. in the Jingning area. Over the period of 44―29 ka B.P. (MIS3., coniferous forests were flourishing, indicating a humid climate with the tem-perature being lower than that of the present. Since 23.ka B.P., the vegetation was dominated by steppe-desert steppe under a cold and dry condition, and entered the Last Glacial Maximum domi-nated by desert steppe. Several periods of the marked decrease in the arborous pollen content in Suancigou well corresponded to the North Atlantic Heinrich events, especially to Heinrich event 3. further supporting that the Heinrich events were well reflected by the pollen record in the Loess Pla-teau as well.

关键词： Western Loess Plateau, pollen record, climatic change, late Pleistocene.

Bursting of Morris-Lecar neuronal model with current-feedback control

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science china(Technological sciences) 2009年第3期52卷 771-781页

作者： DUAN LiXia1, LU QiShao2 & CHENG DaiZhan3.1 college of science, North china University of Technology, {3. 100144, china 2 School of science, {3. University of Aeronautics and Astronautics, {3. 100191, china 3.Institute of Systems science, Chinese Academy of sciences, {3. 100190, china college of science North China University of Technology Beijing 100144 China School of science Beijing University of Aeronautics and Astronautics Beijing 100191 China Institute of Systems science Chinese Academy of Sciences Beijing 100190 China

The Morris-Lecar (ML) neuronal model with current-feedback control is considered as a typical fast-slow dynamical system to study the combined influences of the reversal potential VCa of Ca2+ and the feedback current I on the generation and transition of different bursting oscillations. Two-parameter bifurcation analysis of the fast subsystem is performed in the parameter (I, VCa)-plane at first. Three important codimension-2 bifurcation points and some codimension-1 bifurcation curves are obtained which enable one to determine the parameter regions for different types of bursting. Next, we further divide the control parameter (V0, VCa)-plane into five different bursting regions, namely, the "fold/fold" bursting region R1, the "fold/Hopf" bursting region R2, the "fold/homoclinic" bursting region R3. the "subHopf/homoclinic" bursting region R4 and the "subHopf/subHopf" bursting region R5, as well as a silence region R6. Codimension-1 and -2 bifurcations are responsible for explanation of transition mechanisms between different types of bursting. The results are instructive for further understanding the dynamical behavior and mechanisms of complex firing activities and information processing in biological nervous systems.

关键词： neuron bursting bifurcation fast-slow dynamics analysis codimension