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IGS产品在GPS时间比对中的应用

天文学报 2004年第4期45卷 428-436页

作者：高玉平中国科学院国家授时中心西安710600

在利用GPS CV(GPS Common View)技术进行高精度时间比对时,电离层和卫星位置误差对观测到的卫星信号的影响是不容忽视的,需要对它进行精确的估计和改正.讨论IGS精密星历和CODE全球总电子含量图(TEC MAPs)在GPS时间传递中的应用.计算结... 详细信息

在利用GPS CV(GPS Common View)技术进行高精度时间比对时,电离层和卫星位置误差对观测到的卫星信号的影响是不容忽视的,需要对它进行精确的估计和改正.讨论IGS精密星历和CODE全球总电子含量图(TEC MAPs)在GPS时间传递中的应用.计算结果表明,采用IGS产品可有效提高单站定时和远距离时间传递的精度.

关键词： IGS GPS 时间比对总电子含量电离层改正观测卫星信号单站星历

Application of GNSS in School Bus Safety Monitoring

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Application of GNSS in School Bus Safety Monitoring

第三届中国卫星导航学术年会

作者： HAN Tao1.2 LU Xiaochun1.2 ZOU Decai1.2 1.National time {1. center Xi’an 71.600 P.R.china 2.Key Laboratory of Precision Navigation and Timing Technology chinese academy of sciences Xi’an 71.600 P.R.china

With the "Regulations of the School Bus Safety（draft）" issued by the State Council at the end of 201.,the management of school bus safety transportation has become a hot *** article puts forward a method of using Global Navigation Satellite System（GNSS）to monitor the school bus *** school bus transport and management system,which is real-time,accurate and efficient,will be built up by integrate satellite positioning technology,information technology,data transmission technology,electronic sensor technology,information processing technology and emergency {1.s ***,the difference between the school bus monitoring and general vehicle monitoring is pointed ***,we find out the main reason is overload of passengers which cause the phenomenon of frequent school bus accident in ***,a School Bus Overloading Monitoring System（School-Bus-OMS）is designed to prevent the phenomenon of overload of *** that,the school bus safety monitoring system which based on GNSS and School-Bus-OMS is ***,a detailed description on the structure,function and rescuing measures of this system are given,and the corresponding mathematical models are established.

关键词： School Bus Safety GNSS Pressure Monitoring Mathematical Modeling

Generation of Broadband Frequency Entangled Biphotons for Quantum Clock Synchronization

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Generation of Broadband Frequency Entangled Biphotons for Qu...

第三届中国卫星导航学术年会

作者： Run-ai Quan 1.,Rui-fang Dong 1.,Fei-yan Hou 1.,Yun Bai 1.2 ,Yu Zhang 1.2 ,Tao Liu 1.,Shou-gang Zhang 1.1.Key Laboratory of time and Frequency Primary Standards,National time service center,chinese academy of Science,Xian,71.600,china 2.Graduate University of chinese academy of Science,Beijing,1.0039,china

Frequency entangled biphotons based on spontaneous parametric down conversion（SPDC）of nonlinear crystal are widely used in Quantum clock synchronization *** time-correlation width of the entangled source determines the accuracy of the attainable synchronization,which relies on the spectral bandwidth of the generated *** theoretically investigate the generation of frequency anti-correlated biphotons from chirped periodically-poled potassium titanyl phosphate（C-PPKTP）.It is demonstrated that an ultra-broadband entangled biphoton source with a width of 857nm was obtained,by using a 1.mm-long crystal with a chirping of 9.7×1. -6 μm -2 , and a cw pumping source with a wavelength of *** corresponding time correlation width is only 3.5fs,which implies feasible clock synchronization accuracy in femtosecond *** further demonstrate that the narrowing of the time-correlation width slows down dramatically by increasing the chirping and the length of the nonlinear crystal, which provides a theoretical instruction for us to trade off between the complexity of the crystal fabrication and the sufficiently narrow time-correlation width.

关键词： quantum clock synchronization broadband entanglement C-PPKTP spontaneous parametric down conversion

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用状态空间模型递推模拟振荡器噪声

时间频率学报 2003年第1期26卷 54-60页

作者：李孝辉边玉敬中国科学院国家授时中心

对振荡器的五种噪声之间的关系作了介绍 ,并对相位时间信号的状态空间模型的基本理论作了描述。在此基础上导出了五种噪声的递推模拟方法。最后模拟了这五种噪声并分析了它们的功率谱。结果表明 ,功率谱符合这几种噪声的定义。

关键词：模拟振荡器噪声

Reliability-aware automatic composition approach for web services

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Science china(Information {1.) 2012年第4期55卷 921-937页

作者： LI Mu 1.2,LI Bo 1.2 & HUAI JinPeng 1.2 1.State Key Laboratory of Software Development Environment,Beihang University,Beijing 1.01.1.china 2 School of Computer Science and Engineering,Beihang University,Beijing 1.01.1.china 1. State Key Laboratory of Software Development Environment Beihang University Beijing 100191 China2. School of Computer Science and Engineering Beihang University Beijing 100191 China

In this paper,we study the reliability-aware synthesis problem for composing available services automatically and guaranteeing that the composed result satisfies the specification,such as temporal constraints of functionality and reliability,{1.ed on a synthesis model for mediator of web services composition (CSM).This approach focuses on handling attributes and state relations,and permitting users and services to operate over them,i.e.,read /write their data values and compare them according to a dense state *** show that the reliability-aware synthesis problem for the specification is EXPtime-complete and we give an exponential-time algorithm (CSM-NSA) which for a given formula ψ and a synthesis model,synthesizes available services in the library satisfying ψ over the synthesis model (if they exist) or responds with "not satisfiable" (otherwise).The specification ψ is a fragment of PCTL (probabilistic computation tree logic),obtained from "ordinary" CTL (computation tree logic) by replacing the EX,AX,EU and AU operation with their quantitative counterparts X >p,X =1.U >p,and U =1.*** opposed to NSA,we provide a more effective algorithm to replace the NSA algorithm called CSM-HSA (heuristic synthesis algorithm).Though HSA is an incomplete algorithm,the answer is *** experiments show that the HSA algorithm solves the problem of reliability-aware service synthesis effectively and efficiently.

关键词： reliability web services synthesis problem synthesis model heuristic algorithm

A user-space file system for on-demand legacy desktop software

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Science china(Information {1.) 2011年第6期54卷 1142-1150页

作者： ZHANG YouHui 1.2 , SU GeLin 1.2 & ZHENG WeiMin 1.2 1.Department of Computer Science and Technology, Tsinghua University, Beijing 1.0084, china 2 Tsinghua National Laboratory for Information Science and Technology, Tsinghua University, Beijing 1.0084, china 1. Department of Computer Science and Technology Tsinghua University Beijing 100084 China2. Tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing 100084 China

Some user-level virtualization technologies have been used to convert legacy software (like the existing Windows desktop applications) into the on-demand software without any modification. To give the client a friendly and compatible method to access on-demand legacy software across the Internet, this paper presents a clientend file system for this usage case. It is a Windows user-space file system based on the cloud storage (where the on-demand software is stored), which converts the local file system accesses into remote visits. Quite a few optimizations are adopted and adjusted to suit the file-access-pattern of on-demand software, including the local cache, metadata/data/software prefetch and content-addressable storage (CAS), to decrease the number of remote visits and/or to overlap IO (input/output) operations with software execution. Detailed access-pattern analyses are also presented. This file system has been implemented and tests show that it is practical for much daily-used software-a local cache of limited size can provide up to 80% hit ratio and the corresponding overhead of running-time is about 37%. Owing to this method, on any compatible and networked computer, a user can use his/her personalized software conveniently although it does not exist on the local host.

关键词： on-demand software software as a service user-space file system cloud storage

Interoperability Feasibility Analysis between Beidou and GPS

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Interoperability Feasibility Analysis between Beidou and GPS

第三届中国卫星导航学术年会

作者： LU Xiaochun 1.2 LU Jun 3 WANG Xue 1.2 BAI Yan 1.2 4 HAN Tao 1.2 * 1. National time {1. center Xi’an 71.600 P.R.china 2. Key Laboratory of Precision Navigation and Timing Technology chinese academy of sciences Xi’an 71.600 P.R.china 3. Beijing Institute of Tracking and Telecommunications Technology No.26 Beiqing road Haidian district Beijing china 4. Graduate School of the chinese academy of Science Beijing 1.0040 P.R.china

Interoperability has become a focus of Global Navigation Satellite System （GNSS） and a development aspect, and incurs much focus among the world. For the purpose of maximum benefit, a series of interoperability researches and cooperation are putting forward. In this paper, according to the development of Beidou and GPS, we analyzed the interoperability feasibility between them as three phases. First of all, we introduced the signal plane of Beidou and GPS, separated their interoperability into three phases. After that, we analyzed the signal performance and service performance during each phases. Finally, based on the analyzing results, we offer a reference for Beidou signal design.

关键词： Interoperability signal performance service performance GDOP

System time offset based RAIM in combined GPS/Beidou navigation system

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System time offset based RAIM in combined GPS/Beidou navigat...

第三届中国卫星导航学术年会

作者： XU LongXia1.2,3*1. LI XiaoHui1.2, XUE YanRong1.2,3, CAI ChengLin4& GUO MeiJun1.3 1.ational time {1. center, chinese academy of sciences, Xi’an 71.600, china 2Key Laboratory of Precision Navigation and Timing Technology, chinese academy of sciences, Xi’an 71.600, china 3Graduate University of chinese academy of sciences, Beijing 1.0039, china 4Guilin University of Electronic Technology, Guilin, 541.04, china

Compatibility and interoperability of GNSS （Global Navigation Satellite System） are becoming the main trend of future navigation. However, each navigation system has a time scale. When users positioning with not only one system, the time offset between them must be considered. There are several ways to acquire system time offsets. By adding unknown variables in the combined position equation to solve this variable is the commonly used way. For positioning with multi-constellations, system time offsets are some kind of burden which must be taken into account. This paper takes full use of the obtained offsets and proposes a new fault detection method for RAIM （Receiver Autonomous Integrity Monitoring）. Simulations are made to estimate the ability of this new method. This new method takes the high stability of system time offsets of GPS/Beidou system and applies it to assistant fault detection. This method has no additional requirements for navigation system and is fit for applied in receivers. It can be expected this method will be one means of RAIM for Beidou navigation system when integrated with other GNSS in future.

关键词： Compatibility and Interoperability time Offset Receiver Autonomous Integrity Monitoring Fault Detection.

3D building modeling,organization and application in digital city system

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中国科学：技术科学英文版 2010年第S1期53卷 134-142页

作者： YANG Xue 1.WENG JingNong 1.2,XIA YuBin 2,WU Lun 3 & SUI ZhengWei 3 1.College of Software,Beihang University,Beijing 1.01.1.china 2 College of Computer,Beihang University,Beijing 1.01.1.china 3 Institute of Remote Sensing and GIS,Peking University,Beijing 1.0871.china Beihang Univ Coll Software Beijing 100191 Peoples R China Beihang Univ Coll Comp Beijing 100191 Peoples R China Peking Univ Inst Remote Sensing & GIS Beijing 100871 Peoples R China

The real world is a three-dimensional(3D)space requiring that 3D geospatial information applications be developed in alignment with the observer’s visual and perceptive ***,3D building model data are required in a wide range of areas such as urban planning,environmental protection,real estate management and emergency *** the same time,the development of Web {1.[LU1.technologies allows the possibility of the widely distributed 3D geospatial data on the web.3D city building model with its related information is an important part in the construction of a digital city system,and has become a staple resource on the web *** view of the hierarchical representation of a 3D building model,an abstract of a 3D building model based on structure details is studied,and a novel representation approach named 3D transparent building hierarchical model is presented in this *** approach fully uses both the existing 3D modeling technologies and CAD constructing mapping *** the spatial relationship description,structural components inside a building can be represented and integrated as hierarchical models in a unified 3D *** addition,based on the characteristics of the 3D building model data,a {1.-oriented architecture and Web {1. technologies for 3D city building models are *** aim of the approach is that 3D city building models can be used as a kind of data resource {1. on the web,and can also exist independently in various different web applications.

关键词： 3D modeling 3D transparent building hierarchical models china Star web services