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Search Results: 1 - 10 of 38211 matches for " Mao-Sheng Xiang "
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Relative height accuracy analysis of TanDEM-X system

WANG Bing-nan,XIANG Mao-sheng,

遥感学报 , 2009,
Abstract: According to TanDEM-X satellite program, this paper studies interferometric capabilities of TanDEM-X mission during an orbit period and tries to get the change of relative height error in a global scope. Firstly, based on HILL-equation of the helix formation, effective baseline, including the range and azimuth effective baseline, whichhas a great impacton interferometry is analyzed in detail during an orbit period. Then the influence of baseline decorrelation imposing on interferometric phase error is discussed detailedly, which is themost important influence on relative height error. At lastrelative heightmodel is established and relative heighterrororTanDEM-X system is presented further. The computer simulating result shows the validity ofanalysi
A Bundle Adjustment Calibration Method for Airborne InSAR System Based on Weighting of Feature Points

Han Song-tao,Xiang Mao-sheng,

电子与信息学报 , 2010,
Abstract: Interferometric parameters calibration of InSAR system can acquire both interferometric phase bias and accurate baseline parameters. Then planimetric and vertical accuracies can be improved much. An approach of interferometric calibration over very large areas is presented in this paper. It acquired corresponding points using feature points extraction and optimal matching, then weighted bundle adjustment is induced to realize calibration of each sub-data simultaneously. The calibration parameters are analyzed. Results using airborne data show robust of the algorithm with respect to different terrain type.
Empirical extinction coefficients for the GALEX, SDSS, 2MASS and WISE passbands
Hai-Bo Yuan,Xiao-Wei Liu,Mao-Sheng Xiang
Physics , 2013, DOI: 10.1093/mnras/stt039
Abstract: Using the "standard pair" technique of paring stars of almost nil and high extinction but otherwise of almost identical stellar parameters from the SDSS, and combing the SDSS, GALEX, 2MASS and WISE photometry ranging from the far UV to the mid-IR, we have measured dust reddening in the FUV-NUV, NUV-u, u-g, g-r, r-i, i-z, z-J, J-H, H-Ks, Ks-W1 and W1-W2 colors for thousands of Galactic stars. The measurements, together with the E(B-V) values given by Schlegel et al. (1998), allow us to derive the observed, model-free reddening coefficients for those colors. The results are compared with previous measurements and the predictions of a variety of Galactic reddening laws. We find that 1) The dust reddening map of Schlegel et al. (1998) over-estimates E(B-V) by about 14 per cent, consistent with the recent work of Schlafly et al. (2010) and Schlafly & Finkbeiner (2011); 2) All the new reddening coefficients, except those for NUV-u and u-g, prefer the R(V) = 3.1 Fitzpatrick reddening law rather than the R(V) = 3.1 CCM and O'Donnell (O'Donnell 1994) reddening laws. Using the Ks-band extinction coefficient predicted by the R(V) = 3.1 Fitzpatrick law and the observed reddening coefficients, we have deduced new extinction coefficients for the FUV, NUV, u, g, r, i, z, J, H, W1 and W2 passbands. We recommend that the new reddening and extinction coefficients should be used in the future and an update of the Fitzpatrick reddening law in the UV is probably necessary. We stress however that the FUV- and NUV-band coefficients should be used with caution given their relatively large measurement uncertainties. Finally, potential applications of the "standard pair" technique with the LAMOST Galactic surveys are discussed.
Xe anions in stable Mg-Xe compounds: the mechanism of missing Xe in earth atmosphere
Mao-sheng Miao
Physics , 2013,
Abstract: The reactivity of noble gas elements is important for both fundamental chemistry and geological science. The discovery of the oxidation of Xe extended the doctrinal boundary of chemistry that a complete shell is inert to reaction. The oxidations of Xe by various geological substances have been researched in order to explain the missing Xe in earth atmosphere. Among many proposals, the chemistry mechanisms are straightforward as they identify chemical processes that can capture Xe in earth interior. However, all the mechanisms based on current noble gas chemistry face the same difficulty: the earth lower mantle and core are rich in metals and therefore their chemical environment is reductive. On the other hand, up till now, the opposite chemical inclination, the reductive propensity, i.e. gaining electrons and forming anions, has not been proposed and examined for noble gas elements. In this work, we demonstrate, using first principles calculations and an efficient structure prediction method, that Xe and Kr can form stable MgXe and MgKr compounds under high pressure. These compounds are intermetallic and Xe or Kr is negatively charged. We also find that elevated temperature has large effect in stabilizing MgXe and MgKr compounds. Our results show that the earth has the capability of capturing Xe but not Kr, which is consistent to the depletion of Xe in earth atmosphere. The stability of these compounds suggests that chemical species with completely filled shell may still gain more electrons filling their outer shell in chemical reactions.
Cs in high oxidation states and as a p-block element
Mao-sheng Miao
Physics , 2012, DOI: 10.1038/nchem.1754
Abstract: The major chemical feature of an element is the number of electrons available for forming chemical bonds. A doctrine rooted in the atomic shell model states that the atoms will maintain a complete inner shell while interacting with other atoms. Therefore, group IA elements, for example, are invariably stable in the +1 charge state because the p electrons of their inner shells do not react with other chemical species. This general rule governs our understanding of the structures and reactions of matter and has never been challenged. In this work, we show for the first time that while mixing with fluorine under pressure, Cs atoms will share their 5p electrons and become oxidized to a higher charge state. The formal oxidation state can be as high as +5 within the pressure range of our study (<200 GPa) and stable Cs2+ and Cs3+ compounds can form at lower pressures. While sharing its 5p electrons, Cs behaves like a p-block element forming compounds with molecular, covalent, ionic and metallic features. Considering the pressure range required for the CsFn compounds, the inner shell electrons in other group IA and IIA elements may also bond with F or other chemical species under higher pressure.
Synthesis and Tumor Cytotoxicity of Novel Amide Derivatives of β-Hederin
Yang Liu,Wen-Xiang Lu,Mao-Cai Yan,Yang Yu,Takashi Ikejima,Mao-Sheng Cheng
Molecules , 2010, DOI: 10.3390/molecules15117871
Abstract: Thirteen novel triterpenoid saponins, designed as amide derivatives of the natural cytotoxic saponin β-hederin, were synthesized by a stepwise glycosylation strategy. The in vitro cytotoxic activity of these compounds was evaluated against five different tumor cell lines. Most of the evaluated compounds showed effective inhibitory activity against at least one tumor cell line at micromolar concentrations. The preliminary structure-activity relationships (SAR) indicate that mide derivatization at C-28 resulted in highly cytotoxic derivatives on specific tumor cell lines, and also resulted in an increase in the antitumor selectivity of β-hederin.?
Facile Synthesis of the Naturally Cytotoxic Triterpenoid Saponin Patrinia-Glycoside B-II and Its Conformer
Li Ren,Yong-Xiang Liu,Dan Lv,Mao-Cai Yan,Han Nie,Yang Liu,Mao-Sheng Cheng
Molecules , 2013, DOI: 10.3390/molecules181215193
Abstract: The first chemical synthesis of the natural triterpenoid saponin Patrinia-glycoside B-II, namely oleanolic acid 3- O-α-L-rhamnopyranosyl-(1→2)-[β-D-gluco-pyranosyl-(1→3)]-α-L-arabinopyranoside, has been accomplished in a linear 11-step sequence 11 with 9.4% overall yield. The abnormal 1 C 4 conformation of the arabinose residue was found to occur via conformational fluctuation during preparation of the intermediates. Molecular mechanism and quantum chemistry calculations showed that Patrinia-glycoside B-II and its conformer 1 cannot interconvert under normal conditions. Preliminary structure-activity relationships studies indicated that the 4 C 1 chair conformation of the arabinose residue in the unique α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl disaccharide moiety is one of the chief positive factors responsible for its cytotoxic activity against tumors.
Realization of Outside Calibration Method Based on the Sensitivity Equation for Dual-antenna Airborne Interferometric SAR

ZHANG Wei,XIANG Mao-sheng,WU Yi-rong,

遥感技术与应用 , 2009,
Abstract: The outside calibration for the Dual-antenna Airborne InSAR was researched by 3D reconstruction model.The error model based on sensitivity equations was educed by differentiating InSAR imaging equations based on adopting Sensitivity Equations.Then the biases of interferometric parameters were solved by several accurate Ground Control Points(GCPs). The calibrated interferometric parameters were calculated by iteration method.And the accurate Digital Elevation Model (DEM) was reconstructed.A set of InSAR data was adopted to do calibration experiments,which was derived by the Airborne InSAR system researched independently by Institute of Electronics,Chinese Academy of Sciences.The experimental results show that this algorithm is efficient.
Studies on outside Calibration Method Based on the Boresight Model for Dual-antenna Airborne Interferometric SAR

ZHANG Wei,XIANG Mao-sheng,WU Yi-rong,

遥感技术与应用 , 2008,
Abstract: Based on the boresight model for the Dual\|antenna Airborne InSAR,the outside calibration was researched by adopting sensitivity equations.The error model based on sensitivity equations was educed by differentiating InSAR imaging equations.Then the biases of interferometric parameters were solved by several accurate Ground Control Points(GCPs). The calibrated interferometric parameters were calculated by iteration method.And the accurate Digital Elevation Model (DEM) was reconstructed.Then the ground points were oriented.A set of InSAR data was adopted to do calibration experiments,which was derived by the Airborne InSAR system researched independently by Institute Of Electronics,Chinese Academy Of Sciences.The experimental results show that this algorithm is efficient.
A Block Positioning Method for Airborne InSAR System

Mao Yong-fei Xiang Mao-sheng Wei Li-deng,

电子与信息学报 , 2012,
Abstract: Positioning method aims to get the geographical coordinates of each pixel in SAR images. It is necessary to calibrate the parameters of the positioning model to increase precision. This paper presents a method based on sensitivity equations to calibrate the positioning model by linearizing the position errors. Then a method of joint calibration of the positioning model over large areas including several scenes is proposed, and it can achieve the positioning of large areas with few Ground Control Points (GCPs) by using Corresponding Points (CPs) between adjoining scenes. The results show that with few GCPs the accuracy of this method is better than polynomial ortho-rectification model and range-Doppler model.
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