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Integrated precise orbit determination of shenzhou IV unmanned spacecraft

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science China(Technological sciences) 2004年第5期47卷 518-525页

作者： L Congmin1,2, GU Yidong3. LIN Baojun3.& GUO Jiong3.1. Center for space science and Applied Research, chinese academy of sciences, beijing 100080, China 2. {3. school of the chinese academy of sciences, beijing 10003., China 3. General Establishment of space science and Application, chinese academy of sciences, beijing 100080, China Correspondence should be addressed to L Congmin 1. Center for space science and Applied Research Chinese Academy of Sciences 100080 Beijing China 2. graduate school of the chinese academy of sciences 100039 Beijing China 3. General Establishment of space science and Application Chinese Academy of Sciences 100080 Beijing China

Considering the characteristic orbit of shenzhou IV spacecraft and the advantages and disadvantages of several types of domestic orbit measurements, a scheme of IPOD is determined, which uses GPs, sLR and UsB observation data jointly plus precise ionosphere corrections to GPs observation data. IPOD system and mathematic models of OD are introduced. The results of different joint OD are analyzed using true observation data, and show that radial accuracy is better than 2 m.

关键词： shenzhou IV unmanned spacecraft integrated precise orbit determination GPs sLR UsB.

Cotton pixel identification with CBERs-02 CCD data based on spectral knowledge

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science China(Technological sciences) 2005年第S2期48卷 129-144页

作者： LI Jing1,2,3. LIU Qinhuo1,3. LIU Qiang1, CHEN Liangfu1, BO Junhua3.& LI shaokun3.1. state Key Laboratory of Remote sensing science, IRsA, chinese academy of sciences, beijing 100101, China 2. {3. university of chinese academy of sciences, beijing 100049, China 3. The Key Oasis Eco-agriculture Laboratory of Xinjiang Production and Construction Corps, shi Hezi 83.000, China 1. state Key Laboratory of Remote sensing science IRSA Chinese Academy of Sciences 100101 Beijing China 2. graduate university of chinese {3. of sciences 100049 Beijing China 3. The Key Oasis Eco-agriculture Laboratory of Xinjiang Production and Construction Corps 832000 Shi Hezi China

In this paper the in-situ experiment data are collected from the spectral Library to estimate the possible values of the primary structural parameters in each cotton growing season by statistics. Based on these values the spectra of the cotton major growing seasons were simulated and analyzed using the canopy reflectance model, sAILH. In this way we also simulated the cotton pixel spectra corresponding to CBERs-02 CCD and took them as the reference spectra for spectra fitting. Then No.143.Regiment of No.8 Agricultural Division of Xinjiang Production and Construction Corps (XPCC) was chosen as the study area, and two spectra fitting methods, Mahalanobis distance and spectra angle, were used to identify cotton pixel from CBERs-02 CCD image of the study area. At last we analyzed the effect of the calibration coefficients error on cotton identifying. The results showed that within 4% error the spectral angle classifier can still have a good performance.

关键词： CBERs-02 cotton pixel identification spectra fitting.

Environmental characteristics of Mid-Holocene recorded by lacustrine sediments from Lake Daihai, north environment sensitive zone, China

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science China Earth sciences 2006年第9期49卷 968-981页

作者： sUN Qianli1,2, ZHOU Jie1, sHEN Ji3. CHEN Peng1,2, WU Feng1,2 & XIE Xiuping1,2 1. state Key Lab of Loess and Quaternary Geology, Institute of Earth Environment, chinese academy of sciences, Xi’an 710075, China 2. graduate {3. of chinese academy of sciences, beijing 10003., China 3. Nanjing Institute of Geography and Limnology, chinese academy of sciences, Nanjing 210008, China 1. state Key Lab of Loess and Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences Xi’an 710075 China 2. graduate university of chinese {3. of sciences Beijing 100039 China 3. Nanjing Institute of Geography and Limnology Chinese Academy of Sciences Nanjing 210008 China

Climate proxies, such as total organic carbon and nitrogen (TOC, TN), carbonate content (CaCO3., grain-size and pollen of the sediment core retrieved from enclosed Lake Daihai which lies in the north China environment sensitive zone are analyzed to reconstruct the environment evolution of the area based on high-resolution radiocarbon chronology. The results reveal that the TOC and TN contents of the sediments correlate well with pollen percentage and pollen flux variations during the Holocene, and both reach their peak values simultaneously at 6.7―3.5 ka BP (calendar age, 7.6―3.6 ka BP). since 6.7 ka BP, both the CaCO3.and organic matter contents of the core have simultaneous variations, and their high values also occur during 6.7―3.5 ka BP. While during 9.0―6.7 ka BP (calendar age, 10―7.6 ka BP) relatively lower level of organic matter content and pollen flux corre- spond to the higher level of carbonate content. The above relations suggest that during 6.7―3.5 ka BP, the productivity and effective precipitation were greatly improved in the lake drainage area, and this would probably strengthen the hydrodynamic conditions, enhancing organic matter, pollen and carbonate inputs from terrestrial sources. such processes would account for the enrichment of both organic matter and carbonate in the sediments. While during 9.0―6.7 ka BP, the lower level of or- ganic matter, pollen flux but high carbonate content show depressed productivity and declined vege- tation coverage. The higher carbonate content at this stage would have probably resulted from the higher evaporation ratio of the lake water under relatively drier climate conditions. Therefore, it is in- ferred that during 6.7―3.5 ka BP, the climate was more humid with abundant rainfalls and vegetation was more flourishing in the Lake Daihai area. This can be seen as Holocene Climate Optimum (HCO). As a result, this has evident discrepancies with the traditional notion that the HCO occurs at Early Holocene or early Mid

关键词： Lake Daihai, Mid-Holocene, lacustrine sediments, environmental characteristics.

Observation results of relativistic electrons detected by Fengyun-1 satellite and analysis of relativistic electron enhancement (REE) events

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science China(Physics,Mechanics & Astronomy) 2008年第12期51卷 1947-1956页

作者： YANG XiaoChao1,2↑ & WANG shiJin1 1 Center for space science and Applied Research, chinese academy of sciences, beijing 100190, China 2 {3. university of chinese academy of sciences, beijing 100049, China 1. Center for space science and Applied Research Chinese Academy of Sciences Beijing 100190 China 2. graduate university of chinese {3. of sciences Beijing 100049 China

The space particle component detector on Fengyun-1 satellite which works at the sun-synchronous orbit of about 870 km altitude has detected relativistic electrons for a long time. In comparison with the sAMPEX satellite observations during 1999–2004, the relativistic electron data from Fengyun-1 satellite from June 1999 to 2005 are used to analyze the relativistic electron enhancement (REE) events at the low earth orbit, and the possible correlation among REE events at the low earth orbit, high-speed solar wind and geomagnetic storms is discussed. The statistical result presents that 45 REE events are found in total during this time period, and the strong REE events with the maximum daily average flux > 400 cm?2.srt-1·s?1 occur mostly during the transition period from solar maximum to solar minimum. Among these 45 REE events, four strong REE events last a longer time period from 26-to 51-day and correlate closely with high speed solar wind and strong geomagnetic storms. Meanwhile, several strong geomagnetic storms occur continuously before these REE events, and these continuous geomagnetic storms would be an important factor causing these long-lasting strong REE events. The correlation analysis for overall 45 events indicates that the strength of the REE events correlates with the solar wind speed and the strength of the geomagnetic storm, and the correlation for strong REE events is much stronger than that for weak REE events.

关键词： relativistic electron enhancement low earth orbit high-speed solar wind geomagnetic storm

Improvement of a 3. radar backscattering model using matrix-doubling method

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science China Earth sciences 2010年第7期53卷 1029-1035页

作者： NI WenJian1,2, GUO ZhiFeng1 & sUN GuoQing3.1 state Key Laboratory of Remote sensing science, jointly sponsored by the Institute of Remote sensing Applications of chinese academy of sciences and beijing Normal {3., beijing 100101, China 2 graduate {3. of chinese academy of sciences, beijing 100049, China 3.Department of Geography, {3. of Maryland, College Park, MD 27042, UsA 1. state Key Laboratory of Remote sensing science jointly sponsored by the Institute of Remote Sensing Applications of Chinese Academy of Sciences and Beijing Normal University Beijing 100101 China2. Graduate University of Chinese Academy of Sciences Beijing 100049 China3. Department of Geography University of Maryland College Park MD 27042 USA

Radiative transfer models have been widely used to simulate the radar backscattering from forested areas. A three-dimensional radar backscatter model of forest canopy developed in previous studies takes full account of spatial position of trees in a forest stand, and the interactions among crown, trunk and ground surface. The model predicted well for the co-polarized backscatter measurements, but underestimated the backscattering for cross-polarization, primarily because only the first-order scattering within tree crowns was considered in the model. The backscattering at cross-polarization depends strongly on multiple scatter- ing within tree crowns. To produce good estimations for cross-polarized component, the matrix-doubling method is employed here to compute multiple-scattering within the crown. The modified model is compared with the original model, and the field forest measurements and AIRsAR data are used for validation of the modified model. The cross-polarization backscattering is improved in different degrees for different crown structures and at different bands.

关键词： remote sensing forestry electromagnetic propagation radar backscattering model matrix-doubling

Applications of URANs on predicting unsteady turbulent separated flows

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Acta Mechanica sinica 2009年第3期25卷 319-324页

作者： Jinglei Xu Huiyang Ma Department of Physics, graduate university of the chinese {3. of sciences, 100049 beijing, China Department of Physics Graduate University of the Chinese Academy of Sciences 100049 Beijing China

Accurate prediction of unsteady separated turbulent flows remains one of the toughest tasks and a practi cal challenge for turbulence modeling. In this paper, a 2D flow past a circular cylinder at Reynolds number 3.900 is numerically investigated by using the technique of unsteady RANs （URANs）. some typical linear and nonlinear eddy viscosity turbulence models （LEVM and NLEVM） and a quadratic explicit algebraic stress model （EAsM） are evaluated. Numerical results have shown that a high-performance cubic NLEVM, such as CLs, are superior to the others in simulating turbulent separated flows with unsteady vortex shedding.

关键词： URANs Nonlinear eddy viscosity turbulencemodel ,separated flows Circular cylinder

Regional soil moisture simulation for shaanxi Province using sWAT model validation and trend analysis

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science China Earth sciences 2010年第4期53卷 575-590页

作者： LI MingXing1,2,MA ZhuGuo1 & DU JiWen3.1 Key Laboratory of Regional Climate-Environment Research for Temperate East Asia,Institute of Atmospheric Physics,chinese academy of sciences,beijing 100029,China 2 {3. university of chinese academy of sciences,beijing 100049,China 3.shaanxi Administration of Meteorology,Xi’an 710014,China 1. Key Laboratory of Regional Climate-Environment Research for Temperate East Asia Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China2. Graduate University of Chinese Academy of Sciences Beijing 100049 China3. Shaanxi Administration of Meteorology Xi’an 710014 China

The soil moisture in shaanxi Province,a region with complex topography,is simulated using the distributed hydrological model soil Water Assessment Tool(sWAT).Comparison and contrast of modeled and observed soil moisture show that the sWAT model can reasonably simulate the long-term trend in soil moisture and the spatiotemporal variability of soil moisture in the *** to NCEP/NCAR and ERA40 reanalysis of soil moisture show that the trend of variability in soil moisture simulated by sWAT is more consistent with the *** model results suggested that high soil moisture in surface soil layers appears in the southern shaanxi with high vegetation cover,and the Qinling mountainous region with frequent orographic *** deeper soil layers,high soil moisture appears in the river basins and *** regional soil moisture showed a generally decreasing trend on all soil layers from 1951 to 2004,with a stronger and significant decreasing trend in deeper soil layers,especially in the northern parts of the province.

关键词： sWAT soil moisture content simulation validation trend analysis

Narrow line seyfert 1 galaxies: where are the broad line regions?

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science China(Physics,Mechanics & Astronomy) 2010年第12期53卷 2307-2311,2339-2343页

作者： MAO WeiMing 1,2,3., HU Chen 2 , WANG JianMin 2 , BIAN WeiHao 4 , ZHANG shu 2 & ZHAO Gang 1 1 Key Laboratory of Optical Astronomy, National Astronomical Observatories, chinese academy of sciences, beijing 100012, China 2 Key Laboratory for Particle Astrophysics, Institute of High Energy Physics, chinese academy of sciences, beijing 100049, China 3.graduate university of the chinese academy of sciences, beijing 100049, China 4 Department of Physics, Nanjing Normal university, Nanjing 210011, China 1. Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China2. Key Laboratory for Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China3. Graduate University of the Chinese Academy of Sciences Beijing 100049 China4. Department of Physics Nanjing Normal University Nanjing 210011 China

A sample consisting of 211 narrow line seyfert 1 galaxies (NLs1s) with high quality spectra from the sloan Digital sky survey (sDss) is selected to explore where broad line regions are in these objects. We find that the Hβ profile can be fitted well by three (narrow, intermediate and broad) Gaussian components, and the FWHM ratios of the broad to the intermediate components hold a constant of 3.0 roughly for the entire sample. If the broad components originate from the region scaled by the well-determined Hβ reverberation mapping relation, we find that the intermediate components originate from the inner edge of the torus, which is scaled by dust K-band reverberation. We find that the IC and the BC are strongly linked dynamically, but the relation of their covering factors is much more relaxed, implying that both regions are clumpy.

关键词： black hole physics galaxies: evolution quasars: general

spectral analysis of quasi-stationary sea surface topography from GRACE mission

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science China Earth sciences 2005年第11期48卷 2040-2048页

作者： ZHANG Zizhan1,2 & LU Yang1,3.1. Institute of Geodesy and Geophysics, chinese academy of sciences, Wuhan 43.077, China 2. graduate school of the chinese academy of sciences, beijing 10003., China 3. Unite Center for Astro-geodymics Research, chinese academy of sciences, shanghai 20003., China 1. Institute of Geodesy and Geophysics Chinese Academy of Sciences 430077 Wuhan China 2. graduate school of the chinese academy of sciences 100039 Beijing China 3. Unite Center for Astro-geodymics Research Chinese Academy of Sciences 200030 Shanghai China

During the last two decades satellite altimetry has offered an abundance of meas-urements of the sea surface resulting in the improvement of global mean sea surface height (MssH) and marine geoid determination. On the other hand, with the launching of new genera-tion gravity satellites, some high accuracy long-wavelength gravity models are available. These breakthroughs give us a great opportunity for new estimation of quasi-stationary sea surface topography (QssT). In this paper, the new gravity model GGM01C derived from GRACE mission is briefly presented, and a new global high precision and high-resolution QssT is determined based on the GGM01C model and the global MssH. The spectral features of the QssT esti-mated by GGM01C and EGM96 gravity model to degree/order 200 are discussed by spectral analysis. As a result, the QssT is mainly composed of long waves, medium waves partially and short waves scarcely, its power spectral structures are different between the zonal direction and the meridional direction, there are great differences between the two models, which maybe ex-plain why the ocean currents derived from the two gravity models by Tapley show different pat-terns.

关键词： quasi-stationary sea surface topography, mean sea surface height, GGM01, fast Fourier transform, spectral analysis