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Experimental results and analysis of sparse microwave imaging from spaceborne radar raw data

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Science china(Information sciences) 2012年第8期55卷 1801-1815页

作者： JIANG ChengLong1,2,3,ZHANG BingChen1,2,ZHANG Zhe1,2,3,HONG Wen1,2&WU YiRong1,2 1S cience and Technology on Microwave Imaging Laboratory,beijing 100190,china 2I nstitute of Electronics,chinese academy of sciences,beijing 100190,china 3G raduate university of chinese academy of sciences,beijing 100190,china Science and Technology on Microwave Imaging Laboratory Beijing China Institute of Electronics Chinese Academy of Sciences Beijing China graduate university of chinese academy of sciences Beijing China

Sparse microwave imaging is a novel radar framework aiming to bring revolutions to the microwave imaging according to the theory of sparse signal *** compressive sensing(CS)is introduced to synthetic aperture radar(SAR)imaging in recent years,the current SAR sparse imaging methods have shown their advantages over the traditional matched filtering ***,the requirement for these methods to process the compressed range data results in the increase of the hardware *** the SAR sparse imaging method that directly uses the raw data is *** paper describes the method of SAR sparse imaging with raw data directly,presents the analysis of the signal-to-noise ratio(SNR)in the echo signal by combining the traditional radar equation with the compressive sensing theory,and provides the tests on 2-D simulated SAR *** simulation results demonstrate the validity of the SNR analysis,and the good performance of the proposed method while a large percentage of the raw data is *** experiment with RadarSat-1 raw data is also carried out to show the feasibility of processing the real SAR data via the method proposed in this *** method is helpful for designing new SAR systems.

关键词： sparse microwave imaging synthetic aperture radar(SAR)imaging compressive sensing signalto-noise ratio raw data

Scale effects of leaf area index inversion based on environmental and disaster monitoring satellite data

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Science china Earth sciences 2010年第S1期53卷 92-98页

作者： ZHANG Hao1,LI XiaoWen1,2,CAO ChunXiang1,YANG Hua2,GAO MengXu1,3,ZHENG Sheng1,3,XU Min1,3,XIE DongHui2,JIA HuiCong1,JI Wei1,ZHAO Jian1,3,CHEN Wei1,3 & NI XiLiang1,3 1 State Key Laboratory of Remote Sensing Science,Jointly Sponsored by Institute of Remote Sensing Applications,chinese academy of sciences and beijing Normal university,beijing 100101,china 2 State Key Laboratory of Remote Sensing Science,Jointly Sponsored by beijing Normal university and Institute of Remote Sensing Applications of chinese academy of sciences,beijing 100875,china 3 graduate university of chinese academy of sciences,beijing 100049,china State Key Laboratory of Remote Sensing Science Jointly Sponsored by Institute of Remote Sensing Applications Chinese Academy of Sciences and Beijing Normal University Beijing China State Key Laboratory of Remote Sensing Science Jointly Sponsored by Beijing Normal University and Institute of Remote Sensing Applications of Chinese Academy of Sciences Beijing China graduate university of chinese academy of sciences Beijing China

The spatial distribution of sub-pixel components has an impact on retrieval accuracy,and should be accounted for when inverting a three-dimensional adiative transfer model to retrieve leaf area index(LAI).To investigate this effect,we constructed three realistic scenarios with the same LAI values and other properties,except that the simulated plants had different *** implemented the radiosity method to subsequently produce synthetic bidirectional reflectance factor(BRF) datasets based upon these simulated *** inversion was conducted using these data,which showed that spatial distribution affects retrieval *** inversion was also conducted for LAI based on charge-coupled device(CCD) data from the Environment and Disaster Monitor Satellite(HJ-1),which depicted both forest and drought-resistant crop land *** showed that heterogeneity in coarse-resolution remote sensing data is the main error source in LAI *** spatial distribution of global fractal dimension index,which can be used to describe the area of sub-pixel components and their spatial distribution modes,shows good consistency with the coarse resolution LAI inversion error.

关键词： HJ-1 leaf area index scale effect spatial distribution

Intrafloral differentiation of stamens in heterantherous flowers

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Journal of Systematics and Evolution 2009年第1期47卷 43-56页

作者： 1,2Zhong-Lai LUO 1,2Lei GU 1Dian-Xiang ZHANG 1(South china Botanical Garden, chinese academy of sciences, Guangzhou 510650, china) 2(graduate university of chinese academy of sciences, beijing 100049, china) South china Botanical Garden Chinese Academy of Sciences Guangzhou 510650 China graduate university of chinese academy of sciences Beijing 100049 China

Flowers that have heteromorphic stamens (heterantherous flowers) have intrigued many researchers ever since the phenomenon was discovered in the 19th century. The morphological differentiation in androecia has been suggested as a reflection of "labor division" in pollination in which one type of stamens attracts pollinators and satisfies their demand for pollen as food and the other satisfies the plant’s need for safe gamete dispersal. The extent and patterns of stamen differentiation differ notably among taxa with heterantherous flowers. Seven species with heteromorphic stamens in three genera were sampled from Leguminosae and Melastomataceae, and the morphological difference of androecia, pollen content, pollen histochemistry and viability, pollen micro-morphology, as well as the main pollinators were examined and compared. Pollen number differs significantly between stamen sets of the same flower in most species investigated, and a correlation of pollen number and anther size was substantiated. Higher pollen viabilities were found in the long (pollinating) stamens of Senna alata (L.) Roxb. and S. bicapsularis (L.) Roxb. Dimorphic pollen exine ornamentation is reported here for the first time in Fordiophyton faberi Stapf. The height of stigma and anther tips of the long stamens in natural conditions was proved to be highly correlated, supporting the hypothesis that they contact similar areas of the pollinator’s body.

关键词： buzz pollination heteranthery labor division pollen micro-morphology pollen number pollination stamen differentiation

Impacts of the Wenchuan Earthquake on the Giant Panda Nature Reserves in china

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Journal of Mountain Science 2010年第2期7卷 197-206页

作者： DENG Xiangzheng JIANG Qunou GE Quansheng YANG LinSheng Institute of Geographic sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China Center for chinese Agricultural Policy Chinese Academy of Sciences Beijing 100101 China graduate university of the chineseacademy of sciences Beijing 100049 China

The Wenchuan Earthquake that occurred in May of 2008 caused damages to large areas of Sichuan,Gansu,and Shaanxi provinces in *** from local governments and related management agencies show that the giant panda nature reserves in the earthquake-hit areas were heavily *** estimates in this paper of the impacts of the earthquake on the giant panda in the earthquake-hit areas were made based on the interpretation of remote sensing images and information collected by field survey.A rapid assessment method was designed to estimate the damages of the earthquake on giant panda *** using visual interpretation methods,we decoded the remote sensing images of the disaster area in the 49 giant panda nature *** results showed that the Wenchuan Earthquake and the succeeding secondary geological disasters caused great damages to the giant panda nature reserves and disturbed the normal life of the giant pandas there (e.g.,landscape fragmentation increased significantly).Undoubtedly,the life of the giant pandas there was ***,although the earthquake caused certain impacts on the giant pandas,it did not really threat their *** so,we still strongly advocate for protection of the giant pandas,and have prioritized a couple of measures to be taken to restore the giant panda nature reserves in the earthquake-hit areas.

关键词： Wenchuan earthquake Remote sensing Giant panda Giant panda nature reserve Rapid assessment method

Reconstructing mean maximum temperature of growing season from the maximum density of the Schrenk Spruce in Yili,Xinjiang,china

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chinese Science Bulletin 2009年第13期54卷 2300-2308页

作者： CHEN Jin1,2,3,WANG LiLi1,4,5,ZHU HaiFeng1 & WU Pu1 1 Institute of Geographic sciences and Natural Resources Research,chinese academy of sciences,beijing 100101,china 2 graduate university of chinese academy of sciences,beijing 100049,china 3 Institute of Vertebrate Paleontology and Paleoanthropology,chinese academy of sciences,beijing 100044,china 4 Institute of Tibetan Plateau Research,chinese academy of sciences,beijing 100085,china 5 Institute of Desert and Meteorology,china Meteorological Administration,ürümqi 830002,china Institute of Geographic sciences and Natural Resources Research Chinese Academy of Sciences Beijing China graduate university of chinese academy of sciences Beijing China Institute of Vertebrate Paleontology and Paleoanthropology Chinese Academy of Sciences Beijing China Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing China Institute of Desert and Meteorology China Meteorological Administration Ürümqi China

To study the historical temperature variation in Yili of Xinjiang,the tree-ring chronologies of maximum density(MXD) and tree-ring width(TRW) were established with the Schrenk Spruce(Picea schrenkiana *** Mey) collected from six sites to analyze the characteristics and ability of response to climate *** results suggest that the MXD chronology of the Schrenk Spruce from different sampling sites responded to climate change well and were positively correlated with the mean maximum temperature and the mean temperature from April to August in the study *** mean maximum temperature anomaly from April to August,spanning the years from 1848 to 2000,was reconstructed by three MXD chronologies which were selected by stepwise *** reconstructed function was stable and explained 56.2% of the *** reconstructed results indicated a cold span of 153 years in spring and summer from the beginning of the 1950s to the beginning of the 1970s in the Yili *** strongly increasing tendency was detected in the mean maximum temperature anomaly from April to August during this reconstructed period.

关键词：平均最高气温伊犁谷地最大密度云杉胡杨生长季节新疆树木年轮宽度

Birthrates and delay times of Type Ia supernovae

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Science china(Physics,Mechanics & Astronomy) 2010年第3期53卷 586-590页

作者： WANG Bo1,2,3, LIU ZhengWei1,2,3, HAN YunKun1,2,3, LEI ZhenXin1,2,3, LUO YangPing1,2,3 & HAN ZhanWen1,2 1National Astronomical Observatories/Yunnan Observatory, chinese academy of sciences, Kunming 650011, china 2Key Laboratory for the Structure and Evolution of Celestial Objects, chinese academy of sciences, Kunming 650011, china 3graduate university of chinese academy of sciences, beijing 100049, china National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming China graduate university of chinese academy of sciences Beijing China

Type Ia supernovae (SNe Ia) play an important role in diverse areas of astrophysics, from the chemical evolution of galaxies to observational cosmology. However, the nature of the progenitors of SNe Ia is still unclear. In this paper, according to a detailed binary population synthesis study, we obtained SN Ia birthrates and delay times from different progenitor models, and compared them with observations. We find that the Galactic SN Ia birthrate from the double-degenerate (DD) model is close to those inferred from observations, while the birthrate from the single-degenerate (SD) model accounts for only about 1/2-2/3 of the observations. If a single starburst is assumed, the distribution of the delay times of SNe Ia from the SD model is a weak bimodality, where the WD + He channel contributes to the SNe Ia with delay times shorter than 100 Myr, and the WD + MS and WD + RG channels to those with age longer than 1 Gyr.

关键词： binaries: close stars: evolution supernovae: general white dwarfs

A one-dimensional heat transfer model of the Antarctic Ice Sheet and modeling of snow temperatures at Dome A, the summit of Antarctic Plateau

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Science china Earth sciences 2010年第5期53卷 763-772页

作者： CHEN BaiLian1,3, ZHANG RenHe2, SUN ShuFen1, BIAN LinGen2, XIAO CunDe4,2 & ZHANG TingJun5 1 Institute of Atmospheric Physics, chinese academy of sciences, beijing 100029, china 2 chinese academy of Meteorological sciences, beijing 100081, china 3 graduate university of chinese academy of sciences, beijing 100049, china 4 Cold and Arid Regions Environmental and Engineering Research Institute, chinese academy of sciences, Lanzhou 730000, china 5 The National Snow and Ice Data Center, university of Colorado, Boulder, CO 80309-0449, USA Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China graduate university of chinese academy of sciences Beijing China chinese academy of Meteorological sciences Beijing China Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou China The National Snow and Ice Data Center University of Colorado Boulder USA

A vertical one-dimensional numerical model for heat transferring within the near-surface snow layer of the Antarctic Ice Sheet was developed based on simplified parameterizations of associated physical processes for the atmosphere, radiation, and snow/ice systems. Using the meteorological data of an automatic weather station (AWS) at Dome A (80°22′S, 70°22′E), we applied the model to simulate the seasonal temperature variation within a depth of 20 m. Comparison of modeled results with observed snow temperatures at 4 measurement depths (0.1, 1, 3, 10 m) shows good agreement and consistent seasonal variations. The model results reveal the vertical temperature structure within the near-surface snow layer and its seasonal variance with more details than those by limited measurements. Analyses on the model outputs of the surface energy fluxes show that: 1) the surface energy balance at Dome A is characterized by the compensation between negative net radiation and the positive sensible fluxes, and 2) the sensible heat is on average transported from the atmosphere to the snow, and has an evident increase in spring. The results are considered well representative for the highest interior Antarctic Plateau.

关键词： Antarctic Ice Sheet near-surface layer energy transfer numerical model

Avoided crossings between non-radial modes in low mass RGB stars

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Research in Astronomy and Astrophysics 2012年第12期12卷 1655-1665页

作者： Jun-Jun Guo1,2,3,Yan Li1,2 and Xiang-Jun Lai1,2 1 National Astronomical Observatories/Yunnan Observatory,chinese academy of sciences, Kunming 650011,china 2 Key Laboratory for the Structure and Evolution of Celestial Objects,chinese academy of sciences,Kunming 650011,china 3 graduate university of chinese academy of sciences,beijing 100049,china National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China graduate university of chinese academy of sciences Beijing 100049 China

Non-radial p modes and g modes appear simultaneously in red giant stars. Their frequencies have different variation rates,causing their frequencies to become close during stellar evolution so that avoided crossings *** separation between regions where acoustic waves and gravity waves propagate for l=1,2 and 3 is different,which results in the coupling efficiency also being *** present the results of numerical computations of the models we *** find that the two kinds of modes for l=2 and 3 need to be closer in frequency in order for a complete exchange to occur,compared to the case for modes with l=*** scaled oscillation frequencies also present better regularity with evolution than modes with l=1. In order to study the effect of the avoided crossings in detail,we set the mode which has the smallest mode inertia to be the p *** plot the two kinds of modes for l =1,2 and 3 in frequency and periodéchelle diagrams and find modes of l=2 and 3 fit the two relations better;they are more equally spaced in frequency and period than modes with l=*** careful observation of the two kinds oféchelle diagrams for l=2 and 3,we still find that some p modes shift a little from being equally spaced in frequency and some g modes,which are close to those p modes in period,shift a little from being equally spaced in ***,we study the relation between the deviation from period being equally spaced and the mode inertia of g modes for different *** g modes of l=1 with a period closer to the p mode have less inertia and the deviation is bigger in the periodéchelle *** deviation is also obvious. However g modes of l=2 and 3 shift a little or have almost no deviation from being equally spaced in period,even though some of them may have strong coupling and close mode inertia like in the p ***,we suggest a possible method for measuring period spacing of g modes precisely using mixed g modes with l=2 and 3 that have fewer observed mixed g m

关键词： stars:oscillations-stars:red giants

Growth characteristics and response to climate change of Larix Miller tree-ring in china

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Science china Earth sciences 2010年第6期53卷 871-879页

作者： SUN Yu1,4, WANG LiLi1,2,3, CHEN Jin5, DUAN JianPing1,4, SHAO XueMei1,2 & CHEN KeLong6 1 Institute of Geographic sciences and Natural Resources Research, chinese academy of sciences, beijing 100101, china 2 Institute of Tibetan Plateau Research, chinese academy of sciences, beijing 100085, china 3 Institute of Desert and Meteorology, china Meteorological Administration, Urumqi 830002, china 4 graduate university of chinese academy of sciences, beijing 100049, china 5 Institute of Vertebrate Paleontology and Paleoanthropology, chinese academy of sciences, beijing 100044, china 6 School of Life and Geography sciences, Qinghai Normal university, Xining 810008, china Institute of Geographic sciences and Natural Resources Research Chinese Academy of Sciences Beijing China graduate university of chinese academy of sciences Beijing China Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing China Institute of Desert and Meteorology China Meteorological Administration Urumqi China Institute of Vertebrate Paleontology and Paleoanthropology Chinese Academy of Sciences Beijing China School of Life and Geography sciences Qinghai Normal University Xining China

As one of the earliest species used in dendrochronological studies, Larix responds sensitively to climate change. In this study, nine larch species and one variety from eleven sites were collected to study the growth characteristics of tree-ring width using dendrochronological methods. Ten residual tree-ring chronologies were developed to analyze their relationships with regional standardized anomaly series by Pearson’s correlation analysis. The results suggest that most of the chronologies had significantly positive correlations with the mean temperature and mean maximum temperature in May. The spring temperature evidently limited the radial growth of the larch species without precipitation control. The largest mean tree-ring width was found in Himalayan Larch in Jilong, whereas Master Larch in Si’er reflected the smallest mean value. Both species presented little climate information in this study. chinese, Potanin, and Tibetan larches are significantly correlated with climate change, implying a huge potential for climate history reconstruction. The elevation of the sampling sites appears to be an important condition for tree-ring growth of larches responding to climate factors.

关键词： Larix Miller tree-ring climate change mean temperature in May