This work describes the barometric altimetry as virtual constellation applied to the Chinese Area Positioning System (CAPS), which uses the transponders of communication satellites to transfer navigation messages to u...This work describes the barometric altimetry as virtual constellation applied to the Chinese Area Positioning System (CAPS), which uses the transponders of communication satellites to transfer navigation messages to users. Barometric altimetry depends on the relationship of air pressure varying with altitude in the Earth’s atmosphere. Once the air pressure at a location is measured the site altitude can be found. This method is able to enhance and improve the availability of three-dimensional positioning. The difficulty is that the relation between barometric pressure and altitude is variable in different areas and under various weather conditions. Hence, in order to obtain higher accuracy, we need to acquire the real-time air pressure corresponding to an altimetric region’s reference height. On the other hand, the altimetry method will be applied to satellite navigation system, but the greatest difficulty lies in how to get the real-time air pressure value at the reference height in the broad areas overlaid by satellite navigation. We propose an innovational method to solve this problem. It is to collect the real-time air pressures and temperatures of the 1860 known-altitude weather observatories over China and around via satellite communication and to carry out time extrapolation forecast uniformly. To reduce data quantity, we first partition the data and encode them and then broadcast these information via navigation message to CAPS users’ receivers. Upon the interpolations being done in receivers, the reference air pressure and temperature at the receiver’s nearby place is derived. Lastly, combing with the receiver-observed real air pressure and temperature, the site’s altitude can be determined. The work is presented in the following aspects: the calculation principle, formulae, data collection, encoding, prediction, interpolation method, navigation message transmission together with errors causes and analyses. The advantages and shortcomings of the technique are discussed at the end.展开更多
Single nucleotide polymorphisms （SNPs） are the most abundant sequence variations found in plant genomes and are widely used as molecular genetic markers in cultivar identification and genetic diversity studies. The ...Single nucleotide polymorphisms （SNPs） are the most abundant sequence variations found in plant genomes and are widely used as molecular genetic markers in cultivar identification and genetic diversity studies. The objective of this study was to identify SNP markers useful for discrimination of citrus cultivars, since large numbers of expressed sequence tags （ESTs） of sweet orange are available from the National Center for Biotechnology Information （NCBI）. We now have the opportunity to discover SNP markers suitable for determining the haplotypes with which to distinguish very closely related cultivars and to assess genetic diversity within or between related species of citrus. SNPs and small insertions/deletions （Indels） from ESTs of sweet orange and satsuma were identified by the in silico SNP discovery strategy. 55 296 EST sequences of sweet orange and 2 575 of satsuma retrieved from the NCBI repository were mined for potential SNPs. Cleaved amplified polymorphic sequences （CAPS） and sequencing approaches were used to validate putative SNPs in a sample of 30 citrus accessions. A total of 3 348 putative SNPs were identified based on the abundance of sequences and haplotype cosegregation. Of these 3 348 SNPs, the transitions, transversions and Indels ratios were 47.9, 36.1 and 16.0%, respectively. The SNPs occurred on average at a frequency of 1 per 164 bp in the coding region of citrus. 14 SNPs were randomly selected and genotyped according to 30 citrus accessions including 23 accessions of sweet orange; 11 SNPs displayed polymorphism with an average polymorphism information content （PIC） of 0.20 among 30 citrus accessions. The genetic diversity present in sweet orange was low, so the 14 SNP markers failed to discriminate different cultivars of sweet orange, but they did succeed in distinguishing accessions of inter-species of citrus. In this study, SNPs were mined from EST sequences of sweet orange and satsuma, which displayed potential capability as molecular markers to discriminate in展开更多
基于转发式卫星导航定位系统的思路,以与导航定位精度有密切关系的星座的位置精度衰减因子(Position Dilution of Precision,PDOP)在中国区域的分布和变化为主要评判依据,分析讨论由静止通信卫星和倾斜轨道同步通信卫星组成转发式中国...基于转发式卫星导航定位系统的思路,以与导航定位精度有密切关系的星座的位置精度衰减因子(Position Dilution of Precision,PDOP)在中国区域的分布和变化为主要评判依据,分析讨论由静止通信卫星和倾斜轨道同步通信卫星组成转发式中国区域定位系统星座的初步计划.我们重点考虑倾斜轨道同步卫星的3个主要的轨道参数,即轨道倾角、偏心率及升交点赤经的变化对PDOP的影响,通过仿真计算研究了该区域导航定位系统优良星座的布局方案.对多种星座布局分析比较的初步结果表明,设置3颗位于一组使‘8’字形星下点共迹的倾斜轨道同步通信卫星,它们的轨道倾角约为50°,卫星升交点的赤经差为120°,且其星下点轨迹的对称中心处在115°E附近,与4颗或5颗分布于约60°E至165°E轨位处的静止通信卫星组成转发式中国区域卫星定位系统的星座,可以满足对中国陆地和海疆的有效覆盖,可获得相对高精度的导航定位结果.给出了3个相对优秀的星座结构的初步结果,并讨论了有关的问题.展开更多
基金Supported by the National Basic Research Program of China (Grant No. 2007CB815500)the National High Technology Research and Development Program (Grant No. 2004AA105030)+1 种基金the Pilot Project of the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KGCX1-21)the National Natural Science Foundation of China (Grant No. 10453001)
文摘This work describes the barometric altimetry as virtual constellation applied to the Chinese Area Positioning System (CAPS), which uses the transponders of communication satellites to transfer navigation messages to users. Barometric altimetry depends on the relationship of air pressure varying with altitude in the Earth’s atmosphere. Once the air pressure at a location is measured the site altitude can be found. This method is able to enhance and improve the availability of three-dimensional positioning. The difficulty is that the relation between barometric pressure and altitude is variable in different areas and under various weather conditions. Hence, in order to obtain higher accuracy, we need to acquire the real-time air pressure corresponding to an altimetric region’s reference height. On the other hand, the altimetry method will be applied to satellite navigation system, but the greatest difficulty lies in how to get the real-time air pressure value at the reference height in the broad areas overlaid by satellite navigation. We propose an innovational method to solve this problem. It is to collect the real-time air pressures and temperatures of the 1860 known-altitude weather observatories over China and around via satellite communication and to carry out time extrapolation forecast uniformly. To reduce data quantity, we first partition the data and encode them and then broadcast these information via navigation message to CAPS users’ receivers. Upon the interpolations being done in receivers, the reference air pressure and temperature at the receiver’s nearby place is derived. Lastly, combing with the receiver-observed real air pressure and temperature, the site’s altitude can be determined. The work is presented in the following aspects: the calculation principle, formulae, data collection, encoding, prediction, interpolation method, navigation message transmission together with errors causes and analyses. The advantages and shortcomings of the technique are discussed at the end.
基金supported by the National Natural Science Foundation of China(2006BAD13B06-1-4)the Natural Science Foundation of Chongqing,China (CSTC,2007BB1343)
文摘Single nucleotide polymorphisms （SNPs） are the most abundant sequence variations found in plant genomes and are widely used as molecular genetic markers in cultivar identification and genetic diversity studies. The objective of this study was to identify SNP markers useful for discrimination of citrus cultivars, since large numbers of expressed sequence tags （ESTs） of sweet orange are available from the National Center for Biotechnology Information （NCBI）. We now have the opportunity to discover SNP markers suitable for determining the haplotypes with which to distinguish very closely related cultivars and to assess genetic diversity within or between related species of citrus. SNPs and small insertions/deletions （Indels） from ESTs of sweet orange and satsuma were identified by the in silico SNP discovery strategy. 55 296 EST sequences of sweet orange and 2 575 of satsuma retrieved from the NCBI repository were mined for potential SNPs. Cleaved amplified polymorphic sequences （CAPS） and sequencing approaches were used to validate putative SNPs in a sample of 30 citrus accessions. A total of 3 348 putative SNPs were identified based on the abundance of sequences and haplotype cosegregation. Of these 3 348 SNPs, the transitions, transversions and Indels ratios were 47.9, 36.1 and 16.0%, respectively. The SNPs occurred on average at a frequency of 1 per 164 bp in the coding region of citrus. 14 SNPs were randomly selected and genotyped according to 30 citrus accessions including 23 accessions of sweet orange; 11 SNPs displayed polymorphism with an average polymorphism information content （PIC） of 0.20 among 30 citrus accessions. The genetic diversity present in sweet orange was low, so the 14 SNP markers failed to discriminate different cultivars of sweet orange, but they did succeed in distinguishing accessions of inter-species of citrus. In this study, SNPs were mined from EST sequences of sweet orange and satsuma, which displayed potential capability as molecular markers to discriminate in
文摘基于转发式卫星导航定位系统的思路,以与导航定位精度有密切关系的星座的位置精度衰减因子(Position Dilution of Precision,PDOP)在中国区域的分布和变化为主要评判依据,分析讨论由静止通信卫星和倾斜轨道同步通信卫星组成转发式中国区域定位系统星座的初步计划.我们重点考虑倾斜轨道同步卫星的3个主要的轨道参数,即轨道倾角、偏心率及升交点赤经的变化对PDOP的影响,通过仿真计算研究了该区域导航定位系统优良星座的布局方案.对多种星座布局分析比较的初步结果表明,设置3颗位于一组使‘8’字形星下点共迹的倾斜轨道同步通信卫星,它们的轨道倾角约为50°,卫星升交点的赤经差为120°,且其星下点轨迹的对称中心处在115°E附近,与4颗或5颗分布于约60°E至165°E轨位处的静止通信卫星组成转发式中国区域卫星定位系统的星座,可以满足对中国陆地和海疆的有效覆盖,可获得相对高精度的导航定位结果.给出了3个相对优秀的星座结构的初步结果,并讨论了有关的问题.
