The regional BeiDou Satellite System, or BDS2, broadcasts a differential correction as Equivalent Satellite Clock Correction to correct both orbit and satellite clock errors. For the global BDS, or BDS3, satellite orb...The regional BeiDou Satellite System, or BDS2, broadcasts a differential correction as Equivalent Satellite Clock Correction to correct both orbit and satellite clock errors. For the global BDS, or BDS3, satellite orbit and clock corrections conforming with RTCA standards will be broadcast to authorized users. The hybrid constellation and regional monitoring network pose challenges for the high precision separation of orbit and satellite clock corrections. Three correction models of kinematic,dynamic and Two-way Satellite Time Frequency Transfer(TWSTFT)-based dynamic were studied to estimate the satellite orbit and clock corrections. The correction accuracy of the three models is compared and analyzed based on the BDS observation data. Results show that the accuracies(root mean square, RMS) of dual-frequency real-time positioning for the three models are about 1.76 m, 1.78 m and 2.08 m respectively, which are comparable with the performance of WAAS and EGNOS. With dynamic corrections, the precision of Precise Point Positioning(PPP) experiments may reach about 23 cm after convergence.展开更多
Developing cost-effective electrocatalysts with high activity and stability especially at high current density is of great significance for the large-scale commercial application of electrochemical water splitting to ...Developing cost-effective electrocatalysts with high activity and stability especially at high current density is of great significance for the large-scale commercial application of electrochemical water splitting to hydrogen production but still remains challenging.Herein,we report an effective confinement pyrolysis strategy to fabricate embedded ruthenium-cobalt nanoclusters supported on N-doped porous two-dimensional carbon nanosheets(RuCo@CN).Markedly,the embedded structure can effectively prevent the migration,agglomeration,and leaching of nanoparticles,thus endowing the RuCo@CN catalyst with high stability.To be exact,high stability with up to 650 h can be achieved at high current density(-500 and-1000 mA·cm^(-2)).Besides,the RuCo@CN catalysts also exhibit highly reactive with low overpotentials of only 11mV at-10 mA·cm^(-2).Density functional theory calculations reveal that the introduction of cobalt reduces the decomposition barrier of H_(2)O for RuCo@CN alloy,thus promoting hydrogen evolution reaction.展开更多
基金supported by the National Key Research Program of China as the“Collaborative Precision Positioning Project”(No.2016YFB0501900)the National Natural Science Foundation of China(Grant Nos.41674041,41574029 and 11203059)+2 种基金the Youth Innovation Promotion Association CAS(Grant No.2016242)Shanghai Science and Technology Committee Foundation(Grant No.16511103003)the Shanghai Key Laboratory of Space Navigation and Position Techniques(Grant No.12DZ2273300,ZZXT201701)
文摘The regional BeiDou Satellite System, or BDS2, broadcasts a differential correction as Equivalent Satellite Clock Correction to correct both orbit and satellite clock errors. For the global BDS, or BDS3, satellite orbit and clock corrections conforming with RTCA standards will be broadcast to authorized users. The hybrid constellation and regional monitoring network pose challenges for the high precision separation of orbit and satellite clock corrections. Three correction models of kinematic,dynamic and Two-way Satellite Time Frequency Transfer(TWSTFT)-based dynamic were studied to estimate the satellite orbit and clock corrections. The correction accuracy of the three models is compared and analyzed based on the BDS observation data. Results show that the accuracies(root mean square, RMS) of dual-frequency real-time positioning for the three models are about 1.76 m, 1.78 m and 2.08 m respectively, which are comparable with the performance of WAAS and EGNOS. With dynamic corrections, the precision of Precise Point Positioning(PPP) experiments may reach about 23 cm after convergence.
基金financially supported by the Fundamental Research Funds for the Central Universities (No.D5000220257,D5000220443)the National Natural Science Foundation of China (No.22002120)+2 种基金the Natural Science Foundation of Chongqing,China (No.cstc2020jcyj-msxm X0750)the Guangdong Basic and Applied Basic Research Foundation (No.2019A1515110507)the Key Research and Development Program of Shaanxi (No.2023-YBGY-322)。
文摘Developing cost-effective electrocatalysts with high activity and stability especially at high current density is of great significance for the large-scale commercial application of electrochemical water splitting to hydrogen production but still remains challenging.Herein,we report an effective confinement pyrolysis strategy to fabricate embedded ruthenium-cobalt nanoclusters supported on N-doped porous two-dimensional carbon nanosheets(RuCo@CN).Markedly,the embedded structure can effectively prevent the migration,agglomeration,and leaching of nanoparticles,thus endowing the RuCo@CN catalyst with high stability.To be exact,high stability with up to 650 h can be achieved at high current density(-500 and-1000 mA·cm^(-2)).Besides,the RuCo@CN catalysts also exhibit highly reactive with low overpotentials of only 11mV at-10 mA·cm^(-2).Density functional theory calculations reveal that the introduction of cobalt reduces the decomposition barrier of H_(2)O for RuCo@CN alloy,thus promoting hydrogen evolution reaction.
