基于典型的地月转移轨道和环月轨道,从可见星数、位置精度因子(position dilution of precision,PDOP)和信号的动态特性3个方面系统地仿真分析GNSS在地月空间的可用性。结果表明,地月转移轨道和环月轨道上的接收机载噪比门限设计为12 dB...基于典型的地月转移轨道和环月轨道,从可见星数、位置精度因子(position dilution of precision,PDOP)和信号的动态特性3个方面系统地仿真分析GNSS在地月空间的可用性。结果表明,地月转移轨道和环月轨道上的接收机载噪比门限设计为12 dB-Hz较为合适。在此基础上,提出地月空间航天器在利用GNSS信号方面面临的技术难题。展开更多
The main aim of this paper was to calculate soil organic carbon stock(SOCS) with consideration of the pedogenetic horizons using expert knowledge and GIS-based methods in northeastern China.A novel prediction process ...The main aim of this paper was to calculate soil organic carbon stock(SOCS) with consideration of the pedogenetic horizons using expert knowledge and GIS-based methods in northeastern China.A novel prediction process was presented and was referred to as model-then-calculate with respect to the variable thicknesses of soil horizons(MCV).The model-then-calculate with fixed-thickness(MCF),soil profile statistics(SPS),pedological professional knowledge-based(PKB) and vegetation type-based(Veg) methods were carried out for comparison.With respect to the similar pedological information,nine common layers from topsoil to bedrock were grouped in the MCV.Validation results suggested that the MCV method generated better performance than the other methods considered.For the comparison of polygon based approaches,the Veg method generated better accuracy than both SPS and PKB,as limited soil data were incorporated.Additional prediction of the pedogenetic horizons within MCV benefitted the regional SOCS estimation and provided information for future soil classification and understanding of soil functions.The intermediate product,that is,horizon thickness maps were fluctuant enough and reflected many details in space.The linear mixed model indicated that mean annual air temperature(MAAT) was the most important predictor for the SOCS simulation.The minimal residual of the linear mixed models was achieved in the vegetation type-based model,whereas the maximal residual was fitted in the soil type-based model.About 95% of SOCS could be found in Argosols,Cambosols and Isohumosols.The largest SOCS was found in the croplands with vegetation of Triticum aestivum L.,Sorghum bicolor(L.) Moench,Glycine max(L.) Merr.,Zea mays L.and Setaria italica(L.) P.Beauv.展开更多
目的初步评估探讨核酸筛查模式对献血人群乙型肝炎病毒(hepatitis B virus,HBV)传播残余风险度的影响。方法采用中国大陆执业比对工作组信息管理系统的相关数据,利用NAT单阳性率-窗口期比率数学模型(NAT yield/WP ratio model),对2015—...目的初步评估探讨核酸筛查模式对献血人群乙型肝炎病毒(hepatitis B virus,HBV)传播残余风险度的影响。方法采用中国大陆执业比对工作组信息管理系统的相关数据,利用NAT单阳性率-窗口期比率数学模型(NAT yield/WP ratio model),对2015—2019年度我国18家血液中心的献血人群HBV传播的残余风险度进行趋势分析;同时分析比较2019年18家血液中心的ELISA联合核酸单检/混检(ELISA+ID-NAT/MP-NAT)和ELISA联合核酸混检(ELISA+MP-NAT)2种血液筛查(简称血筛)模式对残余风险度的影响。结果18家血液中心5年的HBV血筛残余风险度总体趋势经趋势卡方检验显示:核酸检测单阳性率趋势χ^(2)=39.42(P<0.01),残余风险度趋势χ^(2)=279.792(P<0.01);ELISA+ID-NAT/MP-NAT和ELISA+MP-NAT 2种不同血筛模式对残余风险度RR的影响差异有显著统计学意义,卡方检验显示χ^(2)=7.4(P<0.01)。结论自2015年我国将核酸检测用于血筛以来,HBV输血传播的残余风险度呈逐年下降趋势,目前主要的2种血筛模式对血液残余风险度有可能造成差别。展开更多
In determining the orbits of low Earth orbit （LEO） satellites using spaceborne GPS, the errors caused by receiver antenna phase center offset （PCO） and phase center variations （PCVs） are gradually becoming a maj...In determining the orbits of low Earth orbit （LEO） satellites using spaceborne GPS, the errors caused by receiver antenna phase center offset （PCO） and phase center variations （PCVs） are gradually becoming a major limiting factor for continued improvements to accuracy. Shiyan 3, a small satellite mission for space technology experimentation and climate exploration, was developed by China and launched on November 5, 2008. The dual-frequency GPS receiver payload delivers 1 Hz data and provides the basis for precise orbit determination within the range of a few centimeters. The antenna PCO and PCV error characteristics and the principles influencing orbit determination are analyzed. The feasibility of PCO and PCV estimation and compensation in different directions is demonstrated through simulation and in-flight tests. The values of receiver antenna PCO and PCVs for Gravity Recovery and Climate Experiment （GRACE） and Shiyan 3 satellites are estimated from one month of data. A large and stable antenna PCO error, reaching up to 10.34 cm in the z-direction, is found with the Shiyan 3 satellite. The PCVs on the Shiyan 3 satellite are estimated and reach up to 3.0 cm, which is slightly larger than that of GRACE satellites. Orbit validation clearly improved with independent k-band ranging （KBR） and satellite laser ranging （SLR） measurements. For GRACE satellites, the average root mean square （RMS） of KBR residuals improved from 1.01 cm to 0.88 cm. For the Shiyan 3 satellite, the average RMS of SLR residuals improved from 4.95 cm to 4.06 cm.展开更多
Calcareous soils are those soils containing layers of carbonate accumulation formed by either secondary accumulation or inheritance of CaCO_3 from calcareous parent materials.These soils are widely distributed in arid...Calcareous soils are those soils containing layers of carbonate accumulation formed by either secondary accumulation or inheritance of CaCO_3 from calcareous parent materials.These soils are widely distributed in arid,semi-arid and even some humid climate environments.However,in the Chinese Soil Taxonomy(CST,3rd version),the soils that contain large amounts of CaCO_3 but do not meet requirements of Aridosols are classified as Hapli-Ustic Cambosols.This group also includes many non-calcareous soils and those soils strongly affected by secondary carbonate accumulation together with quite dissimilar soils in terms of their morphology and properties.This study was conducted to determine calcification patterns and calcic processes occurring in representative pedons of calcareous soils in northwestern Henan Province,China and to classify these soils in CST.A Calcic subgroup was proposed to add within the Hapli-Ustic Cambosols.A diagnostic key was also provided to separate this subgroup from the Typic subgroup.In this way the different calcification degrees of soils were better reflected in the classification,which should lead to more uniform interpretive groups for better soil management.展开更多
文摘基于典型的地月转移轨道和环月轨道,从可见星数、位置精度因子(position dilution of precision,PDOP)和信号的动态特性3个方面系统地仿真分析GNSS在地月空间的可用性。结果表明,地月转移轨道和环月轨道上的接收机载噪比门限设计为12 dB-Hz较为合适。在此基础上,提出地月空间航天器在利用GNSS信号方面面临的技术难题。
基金Under the auspices of Basic Project of State Commission of Science Technology of China(No.2008FY110600)National Natural Science Foundation of China(No.91325301,41401237,41571212,41371224)Field Frontier Program of Institute of Soil Science,Chinese Academy of Sciences(No.ISSASIP1624)
文摘The main aim of this paper was to calculate soil organic carbon stock(SOCS) with consideration of the pedogenetic horizons using expert knowledge and GIS-based methods in northeastern China.A novel prediction process was presented and was referred to as model-then-calculate with respect to the variable thicknesses of soil horizons(MCV).The model-then-calculate with fixed-thickness(MCF),soil profile statistics(SPS),pedological professional knowledge-based(PKB) and vegetation type-based(Veg) methods were carried out for comparison.With respect to the similar pedological information,nine common layers from topsoil to bedrock were grouped in the MCV.Validation results suggested that the MCV method generated better performance than the other methods considered.For the comparison of polygon based approaches,the Veg method generated better accuracy than both SPS and PKB,as limited soil data were incorporated.Additional prediction of the pedogenetic horizons within MCV benefitted the regional SOCS estimation and provided information for future soil classification and understanding of soil functions.The intermediate product,that is,horizon thickness maps were fluctuant enough and reflected many details in space.The linear mixed model indicated that mean annual air temperature(MAAT) was the most important predictor for the SOCS simulation.The minimal residual of the linear mixed models was achieved in the vegetation type-based model,whereas the maximal residual was fitted in the soil type-based model.About 95% of SOCS could be found in Argosols,Cambosols and Isohumosols.The largest SOCS was found in the croplands with vegetation of Triticum aestivum L.,Sorghum bicolor(L.) Moench,Glycine max(L.) Merr.,Zea mays L.and Setaria italica(L.) P.Beauv.
文摘目的初步评估探讨核酸筛查模式对献血人群乙型肝炎病毒(hepatitis B virus,HBV)传播残余风险度的影响。方法采用中国大陆执业比对工作组信息管理系统的相关数据,利用NAT单阳性率-窗口期比率数学模型(NAT yield/WP ratio model),对2015—2019年度我国18家血液中心的献血人群HBV传播的残余风险度进行趋势分析;同时分析比较2019年18家血液中心的ELISA联合核酸单检/混检(ELISA+ID-NAT/MP-NAT)和ELISA联合核酸混检(ELISA+MP-NAT)2种血液筛查(简称血筛)模式对残余风险度的影响。结果18家血液中心5年的HBV血筛残余风险度总体趋势经趋势卡方检验显示:核酸检测单阳性率趋势χ^(2)=39.42(P<0.01),残余风险度趋势χ^(2)=279.792(P<0.01);ELISA+ID-NAT/MP-NAT和ELISA+MP-NAT 2种不同血筛模式对残余风险度RR的影响差异有显著统计学意义,卡方检验显示χ^(2)=7.4(P<0.01)。结论自2015年我国将核酸检测用于血筛以来,HBV输血传播的残余风险度呈逐年下降趋势,目前主要的2种血筛模式对血液残余风险度有可能造成差别。
基金co-supported by the National Natural Science Foundation of China (Nos.61370013 and 91438202)the High Resolution Earth Observation System Major Special Project Youth Innovation Foundation of China (No.GFZX04060103)
文摘In determining the orbits of low Earth orbit （LEO） satellites using spaceborne GPS, the errors caused by receiver antenna phase center offset （PCO） and phase center variations （PCVs） are gradually becoming a major limiting factor for continued improvements to accuracy. Shiyan 3, a small satellite mission for space technology experimentation and climate exploration, was developed by China and launched on November 5, 2008. The dual-frequency GPS receiver payload delivers 1 Hz data and provides the basis for precise orbit determination within the range of a few centimeters. The antenna PCO and PCV error characteristics and the principles influencing orbit determination are analyzed. The feasibility of PCO and PCV estimation and compensation in different directions is demonstrated through simulation and in-flight tests. The values of receiver antenna PCO and PCVs for Gravity Recovery and Climate Experiment （GRACE） and Shiyan 3 satellites are estimated from one month of data. A large and stable antenna PCO error, reaching up to 10.34 cm in the z-direction, is found with the Shiyan 3 satellite. The PCVs on the Shiyan 3 satellite are estimated and reach up to 3.0 cm, which is slightly larger than that of GRACE satellites. Orbit validation clearly improved with independent k-band ranging （KBR） and satellite laser ranging （SLR） measurements. For GRACE satellites, the average root mean square （RMS） of KBR residuals improved from 1.01 cm to 0.88 cm. For the Shiyan 3 satellite, the average RMS of SLR residuals improved from 4.95 cm to 4.06 cm.
基金supported by the National Basic Research Program(973 Program) of China(No.2008FY110600)the National Natural Science Foundation of China(No.41371226)
文摘Calcareous soils are those soils containing layers of carbonate accumulation formed by either secondary accumulation or inheritance of CaCO_3 from calcareous parent materials.These soils are widely distributed in arid,semi-arid and even some humid climate environments.However,in the Chinese Soil Taxonomy(CST,3rd version),the soils that contain large amounts of CaCO_3 but do not meet requirements of Aridosols are classified as Hapli-Ustic Cambosols.This group also includes many non-calcareous soils and those soils strongly affected by secondary carbonate accumulation together with quite dissimilar soils in terms of their morphology and properties.This study was conducted to determine calcification patterns and calcic processes occurring in representative pedons of calcareous soils in northwestern Henan Province,China and to classify these soils in CST.A Calcic subgroup was proposed to add within the Hapli-Ustic Cambosols.A diagnostic key was also provided to separate this subgroup from the Typic subgroup.In this way the different calcification degrees of soils were better reflected in the classification,which should lead to more uniform interpretive groups for better soil management.
