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Characterization of plastic flow in two Zr-based bulk metallic glasses

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Science china(Technological sciences) 2006年第4期49卷 414-424页

作者： XING Dongmei1,2. ZHANG Taihua1, LI Weihuo3 & WEI Bingchen3 1. state key {2. of Nonlinear Mechanics (LNM), institute of Mechanics, chinese academy of Sci- ences, beijing 100080, china 2. College of Physics and Electronic Information Science, Tianjin Normal University, Tianjin 300074, china 3. National Microgravity {2., institute of Mechanics, chinese academy of sciences, beijing 100080, china 1. state key {2. of Nonlinear Mechanics (LNM) Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China 2. College of Physics and Electronic Information Science Tianjin Normal University Tianjin 300074 China 3. National Microgravity laboratory Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China

Plastic deformation behaviors of Zr65Al10Ni10Cu15 and Zr52.5Al10Ni10Cu15Be12.5 bulk metallic glasses (BMGs) are studied by using the depth-sensing nanoindentation, microindentation and uniaxial compression. The Be-containing BMG exhibits a signifi- cantly improved overall plastic strain compared with the Be-free alloy during compressive tests. Both BMGs show a loading-rate-dependent serrated flow during nanoindentation measurements, but the Be-containing alloy exhibits a much lower critical loading rate for the disappearance of the serration than the Be-free BMG. The shear band patterns de- veloped during plastic deformation are investigated by microindentation technique, wherein much higher shear band density is found in the Be-containing alloy than in the Be-free alloy, indicating an easier nucleation of shear bands in the former BMG. The dif- ference in the plastic deformation behavior of the two BMGs can be explained by a free volume model.

关键词： Bulk metallic glass, plastic deformation, shear band, nanoindentation.

L curve for spherical triangle region quadtrees

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Science china(Technological sciences) 2004年第3期47卷 265-280页

作者： YUAN Wen1,CHENG Chengqi1,MA Ainai1 & GUAN Xiaojing2.1.institute of remote {2. and Geography Information System,Peking University,beijing 100871,china 2.Centre of state Information,beijing 100045,china Peking Univ Inst Remote Sensing & Geog Informat Syst Beijing 100871 Peoples R China Ctr state Informat Beijing 100045 Peoples R China

The sequence of facets and nodes has a direct influence on the efficiency of access to spherical triangle region quadtree. Based on the labeling schema by Lee, spatial curves both for facets and nodes are proposed and the main algorithms for coordinate translation, node Lsequence generation and visiting nodes are presented. In particular,constant time algorithms for generating node Lsequence are advanced by using bit manipulation operations,which can be easily implemented with hardware. In L curve the distance between three nodes of a facet is mostly limited in a range of small value, thus making fast access possible. Though codes of sibling facets are continuous, the difference between codes of some cousins may occasionally be very large and makes the distance of a few facets also very large, thus greatly increasing the mean node distance and the total traversing distance. Therefore an m cluster of nodes is proposed as a basic storage unit fo n cluster, which should store eery shared node in each,and the distance between three nodes of a facet is limited to a controllagle scope.

关键词： global grid, spherical triangle region quadtree, SQT, QTM, space-filling curve.

A common sense geographic knowledge base for GIR

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Science china(Technological sciences) 2008年第S1期51卷 26-37页

作者： ZHANG Yi,GAO Yong,XUE LuLu,SHEN Si & CHEN KaiChen institute of remote {2. and Geographic Information System,Peking University,beijing 100871,china 1. institute of remote {2. and Geographic Information System Peking University Beijing 100871 China

As background knowledge of geographic information retrieval (GIR),the gazetteers have their limitations. In this paper we propose to develop and implement a com-mon sense geographic knowledge base (CSGKB) instead of the gazetteers. We define that CSGKB is concerned with the representation of geographic knowledge in human brain and the simulation of geographic reasoning in daily life. Traditional geographic information system (GIS) is based on the model of map with its data based on geographic coordinates and its computation based on geometry. However,CSGKB,which is made up of geographic features and relationships and is based on qualitative spatio-temporal reasoning,can be viewed as the direct model of geographic world. This paper also discusses the characters of CSGKB and pre-sents its structure which is composed of knowledge base,inference engine,geo-graphic ontology and learner. The applications using CSGKB include geographic information retrieval (GIR),natural language processing (NLP),named entity rec-ognition (NER),Semantic Web,etc. At present,our work focuses on the design of geographic ontology and the implementation of the CSGKB knowledge base. In this paper we describe the CSGKB ontology structure,top ontology,geographic loca-tion ontology,spatial relationship ontology,and domain ontologies. Finally,we in-troduce the current state of implementation of CSGKB and give an outlook on our future researches.

关键词： geographic information retrieval common sense geographic knowledge base geographic ontology

Comparison of the influence factors on NDVI for CCD camera and WFI imager on CBERS-02

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Science china(Technological sciences) 2005年第S2期48卷 100-115页

作者： YU Tao1,3, LI Xiaoying1,2.3, ZHANG Yong1,2.3, ZHAO Feng1,2.3, GU Xingfa1,3,4, ZHU Li1,2.3, WANG Pengxin5 & MIN Xiangjun6 1. state key {2. of remote sensing Science institute of remote sensing Application, CAS, Bei- jing 100101, china 2. Graduate University of chinese academy of sciences, beijing 100039, china 3. The Center for National Spaceborne Demonstration, beijing 100101, china 4. Institut National de la Recherche Agronomique, Climat Sol Environnement, 84914 Avignon, France 5. College of Information and Electrical Engineering, china Agricultural University, beijing 100083, china 6. china Center for Resource Satellite Data and Application, beijing 100830, china 1. state key {2. of remote sensing Science Institute of Remote Sensing Application CAS 100101 Beijing China 2. The Center for National Spaceborne Demonstration 100101 Beijing China 3. Graduate University of chinese academy of sciences 100039 Beijing China 4. Institut National de la Recherche Agronomique Climat Sol Environnent 84914 Avignon France 5. College of Information and Electrical Engineering China Agricultural University 100083 Beijing China 6. china Center for Resource Satellite Data and Application 100830 Beijing China

CCD and WFI are payloads in the visible light and near infrared bands on CBERS satellites and they have not been applied widely, especially WFI. This article mainly probes into the potential of these two sensors’ application in the vegetation monitoring and analyses the influences of radiometric calibration, atmosphere conditions and sun-observing geometry, etc. on NDVI obtained from these two sensors respectively. In addition it analyses the effect of the spectral response difference of red and near infrared spectral bands in CCD and WFI sensors on NDVI. Results indicate that radiometric calibration is the most important factor on NDVI, which cannot be applied to vegetation monitoring without radiometric calibration. Results also demonstrate that near surface NDVI is different greatly from that of TOA which change with atmosphere conditions. The study shows that NDVI is also affected by the non-lambertian character of surface and the change of the atmospheric path with the observing geometry. And NDVI of WFI is higher than that of CCD. They are very different because of their spectral difference, but they have a good linear relevant relationship.

关键词： CCD WFI NDVI LAI.

Architecture and key technologies of grid geographic information system

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Science china(Technological sciences) 2008年第S1期51卷 102-113页

作者： FANG Yu,HUANG Zhou,CHEN Bin,WU Lun & YIN DaFei institute of remote {2. and Geographic Information System,Peking University,beijing 100871,china institute of remote {2. and Geographic Information System Peking University Beijing 100871 China

The highly efficient and stable collaborative computation platform for geospatial information can be constructed on the basis of Grid computing technology,com-bined with Peer-to-Peer (P2.) computing technology and geospatial database technology. This paper proposed the architecture and key technologies of the Grid GIS (Geographic Information System) incorporated with P2. structure,and corre-spondingly a Grid GIS prototype named Nebula was designed and then imple-mented. Nebula is a suite of middleware for geospatial Grid computing,which could be deployed onto various service nodes in network. Based on Grid protocols and infrastructure,Nebula provides invocation interfaces to users in form of Grid services. By using P2. message based communication mechanism,complex geospatial computation tasks could be accomplished by Nebula in a collaborative way. This paper introduced Nebula's architecture and key modules,and according to experimental data,we discussed the Grid GIS's advantages,application scenar-ios and future directions.

关键词： Grid GIS distributed geospatial computing Peer-to-Peer computing

A semantic geographical knowledge wiki system mashed up with Google Maps

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Science china(Technological sciences) 2010年第S1期53卷 52-60页

作者： GAO Yong,GAO Song,LI RunQiang & LIU Yuinstitute of remote {2. and Geographical Information Systems,Peking University,beijing 100871,china 1. institute of remote {2. and Geographical Information Systems Peking University Beijing 100871 China

A wiki system is a typical Web 2.0 application that provides a bi-directional platform for users to collaborate and share much useful information ***,computers cannot well understand the wiki pages in plain *** user-generated geographical content via wiki systems cannot be manipulated properly and efficiently unless the geographical semantics is explicitly *** this paper,a geographical semantic wiki system,Geo-Wiki,is introduced to solve this ***-Wiki is a semantic geographical knowledge-sharing web system based on geographical ontologies so that computers can parse and storage the multi-source geographical ***,Geo-Wiki mashed up with map services enriches the representation and helps users to find spatial distribution patterns,and thus can serve geospatial decision-making by customizing the Google Maps APIs.

关键词： geo-ontology semantic wiki mashup Google Maps

On MSDT inversion with multi-angle remote sensing data

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Science china Earth sciences 2007年第3期50卷 422-429页

作者： FENG XiaoMing1,2.& ZHAO YingShi1 1 College of Resources and Environment, Graduate University of the chinese academy of sciences, beijing 100049,{2. 2.3}, chinese academy of sciences, beijing 100101,{2. 1. College of Resources and Environment Graduate University of the Chinese Academy of Sciences Beijing 100049 China 2. institute of remote sensing applications Chinese Academy of Sciences Beijing 100101 China

With the wavelet transform, image of multi-angle remote sensing is decomposed into multi-resolution. With data of each resolution, we try target-based multi-stages inversion, taking the inversion result of coarse resolution as the prior information of the next inversion. The result gets finer and finer until the resolution of satellite observation. In this way, the target-based multi-stages inversion can be used in remote sensing inversion of large-scaled coverage. With MISR data, we inverse structure parameters of vegetation in semiarid grassland of the Inner Mongolia Autonomous Region. The result proves that this way is efficient.

关键词： target-based multi-stages inversion multi-angle remote sensing wavelet transform

Focal plane wave-front sensing algorithm for high-contrast imaging

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Science china(Physics,Mechanics & Astronomy) 2009年第8期52卷 1284-1288页

作者： DOU JiangPei1,2.3,REN DeQing1,2.4,ZHU YongTian1,2.& ZHANG Xi1,2.3 1 National Astronomical Observatories/Nanjing institute of Astronomical Optics & Technology,chinese {2. of sciences,Nanjing 2.0042.china 2.key laboratory of Astronomical Optics & Technology,Nanjing institute of Astronomical Optics & Technology,chinese {2. of sciences,Nanjing 2.0042.china 3 Graduate University of{12.,beijing 100049,china 4 Physics & Astronomy Department,California state University Northridge,18111 Nordhoff Street,Northridge,California 91330-82.8,USA National Astronomical Observatories/Nanjing institute of Astronomical Optics & Technology Chinese Academy of Sciences Nanjing 210042 China key laboratory of Astronomical Optics & Technology Nanjing Institute of Astronomical Optics & Technology Chinese Academy of Sciences Nanjing 210042 China Graduate University of chinese academy of sciences Beijing 100049 China Physics & Astronomy Department California State University Northridge 18111 Nordhoff Street Northridge California 91330-8268 USA

High-contrast imaging provided by a coronagraph is critical for the direction imaging of the Earth-like planet orbiting its bright parent star.A major limitation for such direct imaging is the speckle noise that is induced from the wave-front error of an optical *** derive an algorithm for the wave-front measurement directly from 3 focal plane *** 3 images are achieved through a deformable mirror to provide specific phases for the optics *** introduce an extra amplitude modulation on one deformable mirror configuration to create an uncorrelated wave-front,which is a critical procedure for wave-front *** simulation shows that the reconstructed wave-front is consistent with the original wave-front theoretically,which indicates that such an algorithm is a promising technique for the wave-front measurement for the high-contrast imaging.

关键词： high-contrast imaging multi-image algorithm speckle nulling technique wave-front sensing

Multi-channel SAR imaging based on distributed compressive sensing

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Science china(Information sciences) 2012年第2期55卷 245-259页

作者： LIN YueGuan1,2.3,ZHANG BingChen1,2.JIANG Hai1,2.3,HONG Wen1,2.& WU YiRong1,2.1National key laboratory of Science and Technology on Microwave Imaging,{2. 100190,china 2.4} of Electronics,chinese academy of sciences,{2. 100190,china 3Graduate University of chinese academy of sciences,{2. 100049,china 1. National key laboratory of Science and Technology on Microwave Imaging Beijing 100190 China2. Institute of Electronics Chinese Academy of Sciences Beijing 100190 China3. Graduate University of Chinese Academy of Sciences Beijing 100049 China

The rapid development of compressive sensing(CS)shows that it is possible to recover a sparse signal from very limited *** aperture radar(SAR)imaging based on CS can reconstruct the target scene with a reduced number of collected samples by solving an optimization *** multi-channel SAR imaging based on CS,each channel requires sufficient samples for separate imaging and the total number of samples could still be *** propose an imaging algorithm based on distributed compressive sensing(DCS)that reconstructs scenes jointly under multiple ***-channel SAR imaging based on DCS not only exploits the sparsity of the target scene,but also exploits the correlation among *** requires significantly fewer samples than multi-channel SAR imaging based on *** multiple channels offer different sampling rates,DCS joint processing can reconstruct target scenes with a much more flexible allocation of the number of measurements offered by each channel than that used in separate CS processing.

关键词： synthetic aperture radar multi-channel synthetic aperture radar compressive sensing distributed compressive sensing