Space debris poses a serious threat to human space activities and needs to be measured and cataloged. As a new technology for space target surveillance, the measurement accuracy of diffuse reflection laser ranging （D...Space debris poses a serious threat to human space activities and needs to be measured and cataloged. As a new technology for space target surveillance, the measurement accuracy of diffuse reflection laser ranging （DRLR） is much higher than that of microwave radar and optoelectronic measurement. Based on the laser ranging data of space debris from the DRLR system at Shanghai Astronomical Observatory acquired in March-April, 2013, the characteristics and precision of the laser ranging data are analyzed and their applications in orbit determination of space debris are discussed, which is implemented for the first time in China. The experiment indicates that the precision of laser ranging data can reach 39 cm-228 cm. When the data are sufficient enough （four arcs measured over three days）, the orbital accuracy of space debris can be up to 50 m.展开更多
Maintaining the integrity and longevity of structures is essential in many industries,such as aerospace,nuclear,and petroleum.To achieve the cost-effectiveness of large-scale systems in petroleum drilling,a strong emp...Maintaining the integrity and longevity of structures is essential in many industries,such as aerospace,nuclear,and petroleum.To achieve the cost-effectiveness of large-scale systems in petroleum drilling,a strong emphasis on structural durability and monitoring is required.This study focuses on the mechanical vibrations that occur in rotary drilling systems,which have a substantial impact on the structural integrity of drilling equipment.The study specifically investigates axial,torsional,and lateral vibrations,which might lead to negative consequences such as bit-bounce,chaotic whirling,and high-frequency stick-slip.These events not only hinder the efficiency of drilling but also lead to exhaustion and harm to the system’s components since they are difficult to be detected and controlled in real time.The study investigates the dynamic interactions of these vibrations,specifically in their high-frequency modes,usingfield data obtained from measurement while drilling.Thefindings have demonstrated the effect of strong coupling between the high-frequency modes of these vibrations on drilling sys-tem performance.The obtained results highlight the importance of considering the interconnected impacts of these vibrations when designing and implementing robust control systems.Therefore,integrating these compo-nents can increase the durability of drill bits and drill strings,as well as improve the ability to monitor and detect damage.Moreover,by exploiting thesefindings,the assessment of structural resilience in rotary drilling systems can be enhanced.Furthermore,the study demonstrates the capacity of structural health monitoring to improve the quality,dependability,and efficiency of rotary drilling systems in the petroleum industry.展开更多
目的:应用数据挖掘和网络药理学方法探讨中药熏洗方治疗肛周湿疹的用药规律及机制。方法:检索中国知网、万方、维普、中国生物医学文献数据库2011年1月1日至2020年12月31日关于中药熏洗治疗肛周湿疹的文献;采用中医传承辅助平台V3.0软...目的:应用数据挖掘和网络药理学方法探讨中药熏洗方治疗肛周湿疹的用药规律及机制。方法:检索中国知网、万方、维普、中国生物医学文献数据库2011年1月1日至2020年12月31日关于中药熏洗治疗肛周湿疹的文献;采用中医传承辅助平台V3.0软件对处方用药频次、药性、药味、归经、组方规律、药物核心组合进行分析。通过中药系统药理学数据库与分析平台(traditional Chinese medicine systems pharmacology database and analysis platform,TCMSP)检索用药规律所得苦参汤中8味药物的活性成分及其对应的药物靶点;运用人类基因数据库(the human gene database,GeneCards)获取肛周湿疹的疾病靶点;使用Venny 2.1.0作图工具映射药物与疾病交集靶点,并构建韦恩图;运用STRING数据库及Cytoscape 3.8.2软件构建靶点蛋白-蛋白互作网络(protein-protein interactions,PPI),筛选核心作用靶点,构建“药物-活性成分-作用靶点”网络;应用R语言的clusterProfiler包进行基因本体论(gene ontology,GO)及京都基因与基因组百科全书(kyoto encyclopedia of genes and genomes,KEGG)通路富集分析。结果:共筛选出符合标准的文献386篇,纳入中药处方360首,涉及中药188味;用药频次≥10次的药物共51味,四气分类以寒性为主,五味分类以苦味及辛味为主,药物归经以肝经、胃经及脾经为主;组方规律分析得到高频药对30对,最终演化得到核心组合4个,从用药规律得出苦参汤是治疗肛周湿疹的特效方。共筛选出苦参汤中137个活性成分和224个潜在靶点,与肛周湿疹相关作用靶点24个,经拓扑分析得到3个核心治疗靶点;筛选出槲皮素、木犀草素、山柰酚、金合欢素、苦参碱5个有效活性成分;GO富集分析得到1354个生物学过程、34个细胞组成及71个分子功能;KEGG通路富集分析得到97条信号通路。结论:苦参汤是治疗肛周湿疹的中药古方,苦参汤通过多成分、多靶点、多通路发挥治疗肛周湿疹的作用。展开更多
针对传统文本情感分析获取词向量信息不充分以及情感资源未得到充分利用,导致在判断评论情感极性所依赖的文本信息不足,提出ERNIE-BiGRU-Attention民航旅客评价情感分类模型。首先,应用简单数据增强技术(easy data augmentation,EDA)对...针对传统文本情感分析获取词向量信息不充分以及情感资源未得到充分利用,导致在判断评论情感极性所依赖的文本信息不足,提出ERNIE-BiGRU-Attention民航旅客评价情感分类模型。首先,应用简单数据增强技术(easy data augmentation,EDA)对数据集进行处理。然后基于预训练语言模型(enhanced representation through knowledge integration,ERNIE)对文本进行情感知识提取。在特征提取方面,引入双向门控循环单元(bi-directional gate recurrent unit,BiGRU)与注意力机制。结果表明,该模型在分类上表现优异,综合F 1为0.9759,准确率较对比模型提升0.73%。展开更多
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
Radio frequency signal compatibility is the basis of interoperability of the Satellite eBased Augmentation System(SBAS).SBAS should abide by relative international radio regulations of International Telecommunication ...Radio frequency signal compatibility is the basis of interoperability of the Satellite eBased Augmentation System(SBAS).SBAS should abide by relative international radio regulations of International Telecommunication Union(ITU) and meet the compatibility requirements of radio frequency signal between the Global Navigation Satellite System(GNSS)/SBAS,in order to avoid negative mutual interference.According to ITU Proposal and related reference and assumptions,the paper made simulation of signal receiving maximum power in the Bei Dou Satellite-Based Augmentation System(BDSBAS)global signal coverage.And then,interference of BDSBAS to Global Positioning System(GPS)/WAAS(Wide Area Augmentation System) on L1/L5 bands were calculated and analyzed,with equivalent carrierto-noise ratio as the evaluation parameter.The result shows that the carrier-to-noise ratio decrease of GPS/WAAS caused by BDSBAS B1 C and B2 a signals are extremely lower than inter-system interference of GPS/WAAS,and thus can be ignored in practical applications.Therefore,BDSBAS will not cause the service performance degradation of GPS and WAAS.展开更多
基金Supported by the National Natural Science Foundation of China
文摘Space debris poses a serious threat to human space activities and needs to be measured and cataloged. As a new technology for space target surveillance, the measurement accuracy of diffuse reflection laser ranging （DRLR） is much higher than that of microwave radar and optoelectronic measurement. Based on the laser ranging data of space debris from the DRLR system at Shanghai Astronomical Observatory acquired in March-April, 2013, the characteristics and precision of the laser ranging data are analyzed and their applications in orbit determination of space debris are discussed, which is implemented for the first time in China. The experiment indicates that the precision of laser ranging data can reach 39 cm-228 cm. When the data are sufficient enough （four arcs measured over three days）, the orbital accuracy of space debris can be up to 50 m.
文摘Maintaining the integrity and longevity of structures is essential in many industries,such as aerospace,nuclear,and petroleum.To achieve the cost-effectiveness of large-scale systems in petroleum drilling,a strong emphasis on structural durability and monitoring is required.This study focuses on the mechanical vibrations that occur in rotary drilling systems,which have a substantial impact on the structural integrity of drilling equipment.The study specifically investigates axial,torsional,and lateral vibrations,which might lead to negative consequences such as bit-bounce,chaotic whirling,and high-frequency stick-slip.These events not only hinder the efficiency of drilling but also lead to exhaustion and harm to the system’s components since they are difficult to be detected and controlled in real time.The study investigates the dynamic interactions of these vibrations,specifically in their high-frequency modes,usingfield data obtained from measurement while drilling.Thefindings have demonstrated the effect of strong coupling between the high-frequency modes of these vibrations on drilling sys-tem performance.The obtained results highlight the importance of considering the interconnected impacts of these vibrations when designing and implementing robust control systems.Therefore,integrating these compo-nents can increase the durability of drill bits and drill strings,as well as improve the ability to monitor and detect damage.Moreover,by exploiting thesefindings,the assessment of structural resilience in rotary drilling systems can be enhanced.Furthermore,the study demonstrates the capacity of structural health monitoring to improve the quality,dependability,and efficiency of rotary drilling systems in the petroleum industry.
文摘目的:应用数据挖掘和网络药理学方法探讨中药熏洗方治疗肛周湿疹的用药规律及机制。方法:检索中国知网、万方、维普、中国生物医学文献数据库2011年1月1日至2020年12月31日关于中药熏洗治疗肛周湿疹的文献;采用中医传承辅助平台V3.0软件对处方用药频次、药性、药味、归经、组方规律、药物核心组合进行分析。通过中药系统药理学数据库与分析平台(traditional Chinese medicine systems pharmacology database and analysis platform,TCMSP)检索用药规律所得苦参汤中8味药物的活性成分及其对应的药物靶点;运用人类基因数据库(the human gene database,GeneCards)获取肛周湿疹的疾病靶点;使用Venny 2.1.0作图工具映射药物与疾病交集靶点,并构建韦恩图;运用STRING数据库及Cytoscape 3.8.2软件构建靶点蛋白-蛋白互作网络(protein-protein interactions,PPI),筛选核心作用靶点,构建“药物-活性成分-作用靶点”网络;应用R语言的clusterProfiler包进行基因本体论(gene ontology,GO)及京都基因与基因组百科全书(kyoto encyclopedia of genes and genomes,KEGG)通路富集分析。结果:共筛选出符合标准的文献386篇,纳入中药处方360首,涉及中药188味;用药频次≥10次的药物共51味,四气分类以寒性为主,五味分类以苦味及辛味为主,药物归经以肝经、胃经及脾经为主;组方规律分析得到高频药对30对,最终演化得到核心组合4个,从用药规律得出苦参汤是治疗肛周湿疹的特效方。共筛选出苦参汤中137个活性成分和224个潜在靶点,与肛周湿疹相关作用靶点24个,经拓扑分析得到3个核心治疗靶点;筛选出槲皮素、木犀草素、山柰酚、金合欢素、苦参碱5个有效活性成分;GO富集分析得到1354个生物学过程、34个细胞组成及71个分子功能;KEGG通路富集分析得到97条信号通路。结论:苦参汤是治疗肛周湿疹的中药古方,苦参汤通过多成分、多靶点、多通路发挥治疗肛周湿疹的作用。
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supported in part by the National Natural Science Foundation of China (Grant Nos.42074044 and 41974041)in part by “Young Talent Lifting Project” of China Association for Science and Technology (Grant No.2019QNRC001)。
文摘Radio frequency signal compatibility is the basis of interoperability of the Satellite eBased Augmentation System(SBAS).SBAS should abide by relative international radio regulations of International Telecommunication Union(ITU) and meet the compatibility requirements of radio frequency signal between the Global Navigation Satellite System(GNSS)/SBAS,in order to avoid negative mutual interference.According to ITU Proposal and related reference and assumptions,the paper made simulation of signal receiving maximum power in the Bei Dou Satellite-Based Augmentation System(BDSBAS)global signal coverage.And then,interference of BDSBAS to Global Positioning System(GPS)/WAAS(Wide Area Augmentation System) on L1/L5 bands were calculated and analyzed,with equivalent carrierto-noise ratio as the evaluation parameter.The result shows that the carrier-to-noise ratio decrease of GPS/WAAS caused by BDSBAS B1 C and B2 a signals are extremely lower than inter-system interference of GPS/WAAS,and thus can be ignored in practical applications.Therefore,BDSBAS will not cause the service performance degradation of GPS and WAAS.
