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A Novel Dynamic Stretching Solution to Eliminate Saturation Effect in NDVI and Its Application in Drought Monitoring

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Chinese Geographical science 2012年第6期22卷 683-694页

作者： LIU Fang QIN Qiming ZHAN Zhiming school of Earth and space science Peking University Beijing 100871 China Satellite Environment center Ministry of Environmental Protection Beijing 100094 China

The normalized difference vegetation index(NDVI) is one of the key input variables for developing drought ***,the NDVI quickly saturates in high vegetation surfaces,and thus,the generalization of a drought index over different ecosystems becomes a *** paper presents a novel,dynamic stretching algorithm to overcome the saturation effect in NDVI.A scaling transformation function to eliminate saturation effects when the vegetation fraction(VF) is large is *** range adjustment is conducted using three coefficients,namely,the normalization factor(a),the stretching range controlling factor(m),and the stretching size controlling factor(e).The results show that the stretched NDVI(S-NDVI) is more sensitive to vegetation fraction than NDVI when the VF is large,ranging from 0.75 to ***,the saturation effect in NDVI is effectively removed by using the *** analysis suggests that there is a good linear correlation between the S-NDVI and the leaf area index(LAI).At the same time,the proposed S-NDVI significantly reduces or even eliminates the saturation effect over high biomass.A comparative analysis is performed between drought indices derived from NDVI and S-NDVI,*** the experiment,reflectance data from the moderate resolution imaging spectroradiometer(MODIS) products and in-situ observation data from the meteorological sites at a regional scale are *** this study,the coefficient of determination(R2) of the stretched drought index(S-DI) is above 0.5,indicating the reliability of the proposed algorithm with surface soil moisture ***,the S-DI is suggested to be used as a drought index in extended regions,thus regional heterogeneity should be taken into account when applying stretching method.

关键词： drought monitoring saturation effect scaling transformation NDVI MODIS remote sensing

Correlation analysis and partial least square modeling to quantify typical minerals with Chang'E-3 visible and near-infrared imaging spectrometer's ground validation data

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Chinese Journal Of Geochemistry 2014年第1期33卷 86-94页

作者： LIU Bin LIU Jianzhong ZHANG Guangliang LING Zongcheng ZHANG Jiang HE Zhiping YANG Benyong ZOU Yongliao National Astronomical Observatories Chinese Academy of Science graduate University of Chinese Academy of sciences school of space science and Physics Shandong University Shanghai Institute of Technical Physics Chinese Academy of Science Anhui Institute of Optics and Fine Mechanics Chinese Academy of Science

In 2013, Chang'E-3 program will develop lunar mineral resources in-situ detection. A Visible and Near-infrared Imaging Spectrometer(VNIS) has been selected as one payload of CE-3 lunar rover to achieve this goal. It is critical and urgent to evaluate VNIS' spectrum data quality and validate quantification methods for mineral composition before its launch. Ground validation experiment of VNIS was carried out to complete the two goals, by simulating CE-3 lunar rover's detection environment on lunar surface in the laboratory. Based on the hyperspectral reflectance data derived, Correlation analysis and Partial Least Square(CA-PLS) algorithm is applied to predict abundance of four lunar typical minerals(pyroxene, plagioclase, ilmenite and olivine) in their mixture. We firstly selected a set of VNIS' spectral parameters which highly correlated with minerals' abundance by correlation analysis(CA), and then stepwise regression method was used to find out spectral parameters which make the largest contributions to the mineral contents. At last, functions were derived to link minerals' abundance and spectral parameters by partial least square(PLS) algorithm. Not considering the effect of maturity, agglutinate and Fe0, we found that there are wonderful correlations between these four minerals and VNIS' spectral parameters, e.g. the abundance of pyroxene correlates positively with the mixture's absorption depth, the value of absorption depth added as the increasing of pyroxene's abundance. But the abundance of plagioclase correlates negatively with the spectral parameters of band ratio, the value of band ratio would decrease when the abundance of plagioclase increased. Similar to plagioclase, the abundance of ilmenite and olivine has a negative correlation with the mixture's reflectance data, if the abundance of ilmenite or olivine increase, the reflectance values of the mixture will decrease. Through model validation, better estimates of pyroxene, plagioclase and ilmenite's a

关键词：红外成像光谱仪偏最小二乘矿物成分地面验证相关分析模型验证可见光高光谱反射率

Spectral deconvolution analysis on Olivine-Orthopyroxene mixtures with simulated space weathering modifications

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Research in Astronomy and Astrophysics 2021年第5期21卷 255-273页

作者： Hui-Jie Han Xiao-Ping Lu Te Jiang Chih-Hao Hsia Ya-Zhou Yang Peng-Fei Zhang Hao Zhang State Key Laboratory of Lunar and Planetary sciences Macao University of Science and TechnologyTaipa 999078MacaoChina Planetary science Institute School of Earth SciencesChina University of GeosciencesWuhan 430074China CNSA Macao center for space Exploration and science Taipa 999078MacaoChina State Key Laboratory of space Weather National Space Science CenterChinese Academy of SciencesBeijing 100190China CAS center for Excellence in Comparative Planetology Hefei 230026China

Olivine and pyroxene are important mineral end-members for studying the surface material compositions of mafic *** profiles of visible and near-infrared spectra of olivine-orthopyroxene mixtures systematically vary with their composition *** our experiments,we combine the RELAB spectral database with new spectral data obtained from some assembled olivine-orthopyroxene *** found that the commonly-used band area ratio(BAR,Cloutis et al.)does not work well on our newly obtained spectral *** investigate this issue,an empirical procedure based on fitted results by a modified Gaussian model is proposed to analyze the spectral *** the new empirical procedure,the endmember abundances can be estimated with a 15%accuracy with some prior mineral absorption *** addition,the mixture samples configured in our experiments are also irradiated by pulsed lasers to simulate and investigate the space weathering *** deconvolution results confirm that low-content olivine on celestial bodies is difficult to measure and ***,the olivine abundance of space weathered materials may be underestimated from remote sensing *** study may be utilized to quantify the spectral relationship of olivine-orthopyroxene mixtures and further reveal their correlation between the spectra of ordinary chondrites and silicate asteroids.

关键词： techniques:spectroscopic instrumentation:spectrographs methods:data analysis minor planets,asteroids:general

Interplanetary Physics Research in China During 2004 - 2005

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空间科学学报 2006年第Z1期26卷 90-96页

作者： WANG Chi WANG Shui State Key Laboratory for space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing 100080 China School of Earth and Space Sciences University of Science and Technology of China

This brief report summarized the latest advances of the interplanetary physics research in China during the period of 2004-2005, made independently by Chinese space physicists and through international collaboration. The report covers all aspects of the interplanetary physics, including theoretical studies, numerical simulation and data analysis.

关键词： Solar wind plasma, Coronal mass ejection, Interplanetary shock, Magnetic cloud

AN EAST ASIAN SUBTROPICAL SUMMER MONSOON INDEX DEFINED BY MOIST POTENTIAL VORTICITY

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Journal of Tropical Meteorology 2011年第1期17卷 11-17页

作者：丛宽毕云 school of Earth and space sciences University of Science and Technology of China

Based on consideration of both thermodynamic and kinetic features of the subtropical summer monsoon in East Asia,a new index is defined by the moist potential vorticity (MPV) for this *** features of the subtropical summer monsoon over 60 years are analyzed using National centers for Environmental Prediction/National center for Atmospheric Research (USA) data from 1948 to *** show that the new index can well reflect the seasonal,interannual,and interdecadal variations of the East Asian subtropical summer *** analysis of the new index and precipitation data from 160 stations in China shows that in high-index years,the summer monsoon is strong,and more rain falls in eastern North China,southwestern China,and along the coast of South China and less rain falls in the Yangtze-Huaihe *** low-index years,the opposite ***,the new index is compared with four established monsoon *** new index is found to have an advantage in representing summer rainfall in the Yangtze-Huaihe ***.

关键词： moist potential vorticity East Asian subtropics summer monsoon index precipitation

Observations of the field-aligned residual flow inside magnetic cloud structure

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science China(Technological sciences) 2009年第9期52卷 2555-2566页

作者： LI HuiJun FENG XueShang ZUO PingBing XIE YanQiong SIGMA Weather Group State Key Laboratory for Space WeatherCenter for Space Science and Applied ResearchChinese Academy of SciencesBeijing 100190China graduate University of the Chinese Academy of sciences Beijing 100039China Institute of Meteorology PLA University of Science and TechnologyNanjing 211101China

In this paper,we report two MC events observed by WIND spacecraft with good examples of fieldaligned residual flow inside the MC structure. For both events,the co-moving frames are determined through the deHoffman-Teller (HT) analysis and the axial orientations are inferred by the newly developed minimal residue (MR) method. The nature coordinate system for both events are constructed with velocity of the HT frame and the inferred MC axis,the field and flow remaining in the HT frame are analyzed at this coordinate system. As a result,we find that the residual flows in the co-moving HT frame of the two MC events are almost anti-parallel to the helical magnetic field. We speculate that the field-aligned residual flows are large scale coherent hydrodynamic vortices co-moving with the MCs at the supersonic speed near 1 AU. data analyses show that the event in slow ambient solar wind is expanding at 1 AU and another one in fast solar wind does not show apparent expansion. Proton behaviors for both events are quasi-isothermal. Accelerated HT analysis shows that both events have no suitable HT frame with constant accelerations,which suggests that both events may be moving at the constant speed near 1 AU under the assumptions of the HT analysis. For both events,the ratio of the dynamic pressure to the magnetic pressure is larger than that of the thermal pressure to magnetic pressure,which suggests that the dynamic effects due to the plasma flows remaining in the co-moving HT frame are more important than the thermal effects in the study of MC evolution and propagation.

关键词： interplanetary medium solar wind magnetic cloud (MC) Sun:coronal mass ejections (CMEs)

Dark Matter Particle Explorer observations of high-energy cosmic ray electrons plus positrons and their physical implications

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science China(Physics,Mechanics & Astronomy) 2018年第10期61卷 2-13页

作者： Qiang Yuan Lei Feng Key Laboratory of Dark Matter and space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210008China school of Astronomy and space science University of Science and Technology of ChinaHefei 230026China center for High Energy Physics Peking UniversityBeijing 100871China

The DArk Matter Particle Explorer （DAMPE） is a satellite-borne, high-energy particle and 3,-ray detector, which is dedicated to indirectly detecting particle dark matter and studying high-energy astrophysics. The first results about precise measurement of the cosmic ray electron plus positron spectrum between 25 GeV and 4.6 TeV were published recently. The DAMPE spectrum reveals an interesting spectral softening arount 0.9 TeV and a tentative peak around 1.4 TeV. These results have inspired extensive discussion. The detector of DAMPE, the data analysis, and the first results are introduced. In particular, the physical interpretations of the DAMPE data are reviewed.

关键词： dark matter cosmic rays electrons plus positrons pulsars

Atomic Spin Polarization Controllability analysis:A Novel Controllability Determination Method for Spin-Exchange Relaxation-Free Co-Magnetometers

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IEEE/CAA Journal of Automatica Sinica 2022年第4期9卷 699-708页

作者： Zhuo Wang Sixun Liu Ruigang Wang Linlin Yuan Jiong Huang Yueyang Zhai Sheng Zou IEEE the Research Institute for Frontier science the Beijing Advanced Innovation center for Big data-Based Precision Medicine Beihang University the school of Instrumentation and Optoelectronic Engineering Beihang University the Research Institute of Frontier science Beihang University

This paper investigates the atomic spin polarization controllability of spin-exchange relaxation-free co-magnetometers(SERFCMs).This is the first work in the field of controllability analysis for the atomic spin ensembles systems,whose dynamic behaviors of spin polarization are described by the Bloch *** on the Bloch equations,a state-space model of the atomic spin polarization for SERFCM is first established,which belongs to a particular class of nonlinear *** this class of nonlinear systems,a novel determination method for the global state controllability is proposed and ***,this method is implemented in the process of controllability analysis on the atomic spin polarization of an actual ***,a theoretically feasible and reasonable solution of the control input is proposed under some physical constraints,with whose limitation of realistic conditions,the controller design can be accomplished more practically and more ***,the simulation results demonstrate the feasibility and validation of the proposed controllability determination method.

关键词： Atomic spin polarization Bloch equations controllability determination nonlinear state-space model spin-exchange relaxation-free co-magnetometer(SERFCM)

Heliosphereic Physics Research in China: 2002-2003

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空间科学学报 2004年第Z1期24卷 102-115页

作者： WANG Chi FENG Xueshang WANG Shui center for space science and Applied Research The Chinese Academy of Sciences Beijing 100080 China Center for Space Science and Applied Research The Chinese Academy of Sciences Beijing 100080 China School of Earth and Space Sciences University of Science and Technology of China Hefei 230026 China

This brief report summarized the latest advances of the heliospheric physics research in China during the period of 2002-2003, made independently by Chinese space physicists and through international collaboration. The report covers all aspects of the heliospheric physics, including theoretical studies, numerical simulation and data analysis.

关键词： Solar wind plasma, Coronal mass ejection, Interplanetary shock,Magnetic cloud