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| 1 | Orbit determination and time synchronization for a GEO/IGSO satellite navigation constellation with regional tracking network显示文摘Aiming at regional services,the space segment of COMPASS (Phase I) satellite navigation system is a constellation of Geostationary Earth Orbit (GEO),Inclined Geostationary Earth Orbit (IGSO) and Medium Earth Orbit (MEO) satellites.Precise orbit determination (POD) for the satellites is limited by the geographic distribution of regional tracking stations.Independent time synchronization (TS) system is developed to supplement the regional tracking network,and satellite clock errors and orbit data may be obtained by simultaneously processing both tracking data and TS data.Consequently,inconsistency between tracking system and TS system caused by remaining instrumental errors not calibrated may decrease navigation accuracy.On the other hand,POD for the mixed constellation of GEO/IGSO/MEO with the regional tracking network leads to parameter estimations that are highly correlated.Notorious example of correlation is found between GEO's orbital elements and its clock errors.We estimate orbital elements and clock errors for a 3GEO+2IGSO constellation in this study using a multi-satellite precise orbit determination (MPOD) strategy,with which clock error elimination algorithm is applied to separate orbital and clock estimates to improve numerical efficiency.Satellite Laser Ranging (SLR) data are used to evaluate User Ranging Error (URE),which is the orbital error projected on a receiver's line-of-sight direction.Two-way radio-wave time transfer measurements are used to evaluate clock errors.Experimenting with data from the regional tracking network,we conclude that the fitting of code data is better than 1 m in terms of Root-Mean-Square (RMS),and fitting of carrier phase is better than 1 cm.For orbital evaluation,difference between computed receiver-satellite ranging based on estimated orbits and SLR measurements is better than 1 m (RMS).For clock estimates evaluation,2-hour linear-fitting shows that the satellite clock rates are about 1.E-10 s/s,while receiver clock rates are about 1×10 13-1×10 12 s/s.For the 72-hour POD experiment,the average differences between POD satellite clock rates estimates and clock measurements based on TS system are about 1×10 13 s/s,and for receiver clock rates,the differences are about 1×10 15 s/s. | ZHOU ShanShi HU XiaoGong WU Bin LIU Li QU WeiJing GUO Rui HE Feng CAO YueLing Wu XiaoLi ZHU LingFeng SHI Xin TAN HongLi | 2011 | Science China(Physics,Mechanics & Astronomy)2011，54，6： | 44 |
| 2 | Tunable 2D tremella-derived carbon nanosheets with enhanced pseudocapacitance behavior for ultrafast potassium-ion storage显示文摘The sluggish intercalation kinetics of potassium ions in various anode materials severely hinders the practical application of potassium ion batteries(PIBs) in the field of new energy storage. To overcome this difficulty, we developed a green and recyclable molten-salt(MS) strategy using natural tremella as raw material to construct self-N-doped two-dimensional(2D)tremella-derived carbon nanosheets(TCNs), which possesses large specific surface area(SSA), expanded interlayer spacing and rich defects/active sites. Thanks to the unique 2D nanosheet structure and self-N doping, TCNs800 electrode exhibits superior K+storage capacity(386.3 mA h g^(-1) at 0.1 A g^(-1)), ultrafast rate performance(119.7 mA h g^(-1) at 2.0 A g^(-1)) and long-term cycling stability(122.9 mA h g^(-1) with the Coulombic efficiency of near 100% after 1000 cycles). Moreover, detailed electrochemical kinetic analysis shows that the potassium-ion storage mechanism of TCNs800 electrode has enhanced by the pseudocapacitancecontrolled behavior. This work proves an effective green and environmentally friendly MS strategy to prepare 2D biomass nanosheet materials, and provides a reference for exploring excellent electrode materials with pseudocapacitance-controlled behavior. | ZHU LingFeng ZHANG Ze ZHANG Hai WANG Yun LUO JinDi YU Ji QU YaoHui YANG ZhenYu | 2021 | Science China(Technological Sciences)2021，64，9： | 0 |
| 3 | Reversible Data Hiding in Encrypted Images Based on Prediction and Adaptive Classification Scrambling显示文摘Reversible data hiding in encrypted images(RDH-EI)technology is widely used in cloud storage for image privacy protection.In order to improve the embedding capacity of the RDH-EI algorithm and the security of the encrypted images,we proposed a reversible data hiding algorithm for encrypted images based on prediction and adaptive classification scrambling.First,the prediction error image is obtained by a novel prediction method before encryption.Then,the image pixel values are divided into two categories by the threshold range,which is selected adaptively according to the image content.Multiple high-significant bits of pixels within the threshold range are used for embedding data and pixel values outside the threshold range remain unchanged.The optimal threshold selected adaptively ensures the maximum embedding capacity of the algorithm.Moreover,the security of encrypted images can be improved by the combination of XOR encryption and classification scrambling encryption since the embedded data is independent of the pixel position.Experiment results demonstrate that the proposed method has higher embedding capacity compared with the current state-of-the-art methods for images with different texture complexity. | Lingfeng Qu Hongjie He Shanjun Zhang Fan Chen | 2020 | Computers, Materials & Continua2020，，12： | 0 |
| 4 | Overexpression of the LcPIN2 and LtPIN2 Gene in Arabidopsis thaliana Promotes Root Elongation显示文摘The auxin polar transporter,PIN-FORMED 2(PIN2)plays an important role in root development.However,it remains unclear whether PIN2 genes form two Liriodendron species,L.chinense(LcPIN2)and L.tulipifera(LtPIN2),are both involved in root development and whether and to what extent these two genes diverge in function.Here,we cloned and overexpressed LcPIN2 and LtPIN2 in Arabidopsis thaliana wild-type(WT)and Atpin2 mutant.Phylogenetic and sequence analysis showed a small degree of differentiation between these two Liriodendron PIN2 genes.Tissue-specific gene expression analysis indicated that both Liriodendron PIN2 genes were highly expressed in roots,implying a potential role in root development.Finally,heterologous overexpression of LcPIN2 and LtPIN2 in Arabidopsis both significantly increased the root length compared to wild-type and empty vector.Furthermore,the root length defect in Atpin2 was complemented both by LcPIN2 and LtPIN2.However,heterologous overexpression of LcPIN2 and LtPIN2 cannot rescue the defect in root gravitropism of Atpin2 mutants.Taken together,ourfindings unravel PIN2 genes from the magnoliids plant Liriodendron were functionally conserved with AtPIN2 in the dicotyledonous plant Arabidopsis in regard to the regulation of root length,but not root gravitropism.This study also provides a potential target for genetic improvement of the root system in these valuable forest trees Liriodendron. | Zijian Cao Guoxia Xue Lingfeng Hu Haoxian Qu Shuang Liang Jisen Shi Jinhui Chen Zhaodong Hao | 2023 | Phyton-International Journal of Experimental Botany2023，92，8： | 0 |
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