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A virtual reference satellite differential method for relative correction of satellite ephemeris errors

Science china(Physics,Mechanics & Astronomy) 2010年第12期53卷 2300-2306页

作者： CAI ChengLin 1,3 , LI XiaoHui 2,3 & WU HaiTao 2,3 1 Gulin University of Electronic Technology, 541004, china 2 national time service center, chinese academy of sciences, lintong 710600, china 3 Key Laboratory of Precision Navigation and Timing Technology, national time service center, chinese academy of sciences, lintong 710600, china 1. Gulin University of Electronic Technology Gulin 541004 China3. Key Laboratory of Precision Navigation and Timing Technology National Time Service Center Chinese Academy of Sciences Lintong 710600 China2. National Time Service Center Chinese Academy of Sciences Lintong 710600 China

In order to solve the problems that the novel wide area differential method on the satellite clock and ephemeris relative correction (CERC) in the non-geostationary orbit satellite constellation, a virtual reference satellite (VRS) differential principle using relative correction of satellite ephemeris errors is proposed. It is referred to be as the VRS differential principle, and the elaboration is focused on the construction of pseudo-range errors of VRS. Through qualitative analysis, it can be found that the impact of the satellite’s clock and ephemeris errors on positioning can basically be removed and the users’ positioning errors are near zero. Through simulation analysis of the differential performance, it is verified that the differential method is universal in all kinds of satellite navigation systems with geostationary orbit (GEO) constellation, Medium orbit (MEO) constellation or hybrid orbit constellation, and it has insensitivity to abnormal aspects of a satellite ephemeris and clock. Moreover, the real time positioning accuracy of differential users can be maintained within several decimeters after the pseudo-range measurement noise is effectively weakened or eliminated.

关键词： wide area differential method virtual reference satellite (VRS) satellite ephemeris errors satellite clock errors constellation

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The exploration of satellite clock and ephemeris error correction in wide area differential system

The exploration of satellite clock and ephemeris error corre...

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第三届中国卫星导航学术年会

作者： ChengLin CAI 1* XiaoHui LI 2 &HaiTao WU 3 1.Guilin University of Electronic Technology,541004,Guilin,china 2.national time service center,chinese academy of sciences,710600,lintong,china 3.academy of Opto-Electronics,chinese academy of sciences,100094,Beijing,china

Real time principle of wide area differential GPS(WADGPS)uses a generally inverted positioning method of four-dimensional solution of satellite clock and ephemeris *** with the real time single point positioning,positioning accuracy of this method is improved greatly,but the DOP of four-dimensional calculation is up to several hundred,under the error amplification effect of DOP,1 m positioning precision level of WADGPS is difficult to *** overcome the limit of DOP,the feasibility on large and small part decomposition of satellite clock and ephemeris error is analyzed, and optimal differential performances of the exploring two smallness correction methods:Small DOP and no DOP constraint,are analyzed,and they will be the foundation for further exploration.

关键词： wide area differential GPS(WADGPS) DOP satellite clock ephemeris

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Astronomical function and date of the Taosi observatory

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Science china(Physics,Mechanics & Astronomy) 2009年第1期52卷 151-158页

作者： WU JiaBi1, CHEN MeiDong2 & LIU CiYuan3 1 national Astronomical Observatories, chinese academy of sciences, Beijing 100012, china 2 Institute for the History of Natural Science, chinese academy of sciences, Beijing 100010, china 3 national time service center, chinese academy of sciences, Xi’an 710600, china 1. national Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China 2. Institute for the History of Natural Science Chinese Academy of Sciences Beijing 100010 China 3. national time service center Chinese Academy of Sciences Xi’an 710600 China

The Taosi site in Xiangfen County,Shanxi Province,may be the capital of the King Yao. Archeologists recently discovered a large semi-circular stamped-earth platform, II FJT1,which has a clear and definite pounded-earth central core together with a curved wall perforated by twelve gaps. The platform is said to be an ancient observatory used to determine the seasons by watching the sunrise. Each feature of II FJT1 was precisely measured and the data are reproduced in this paper. An astronomical analysis of slots E2 and E12 was carried out using the azimuths of the slots' centerlines and the vertical angle of the mountain ridge opposite, above which the sun rises. The results show that at present the sun is close to the two slots but does not exactly enter them at summer and winter solstice sunrise. Using 14C analysis archeologists dated the site to about 2100 BC. Because of the secular change in the obliquity of the ecliptic,at that date on the summer solstice the half-risen sun would have appeared inside slot E12 just to the right of the centerline,and on the winter solstice the sun would have been exactly on the centerline of slot E2. This result provides compelling proof that II FJT1 is an ancient observatory.

关键词： astro-archeology astro-chronology Taosi culture ancient observatory time service

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An analysis of the wide area differential method of geostationary orbit satellites

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Science china(Physics,Mechanics & Astronomy) 2009年第2期52卷 310-314页

作者： CAI ChengLin1,2,3?, LI XiaoHui1 & WU HaiTao1 1 national time service center, chinese academy of sciences, lintong 710600, china 2 Hunan Institute of Humanities, Science and Technology, Loudi 417000, china 3 Graduate University of chinese academy of sciences, Beijing 100049, china 1. national time service center Chinese Academy of Sciences Lintong 710600 China 2. Hunan Institute of Humanities Science and Technology Loudi 417000 China 3. Graduate University of chinese academy of sciences Beijing 100049 China

This work aims to obtain a wide area differential method for geostationary orbit (GEO) constellation. A comparison between the dilution of precision (DOP) of four-dimensional (4D) calculation including sa- tellite clock errors and ephemeris errors and that of three-dimensional (3D) calculation only including ephemeris errors with the inverse positioning theory of GPS shows the conclusion that all the 3D PDOPs are greatly reduced. Based on this, a basic idea of correcting satellite clock errors and ephem- eris errors apart is put forward, and moreover, a specific method of separation is proposed. Satellite clock errors are separated in a master station with time synchronization, and all the remaining pseu- do-range errors after the satellite clock errors have been deducted are used to work out ephemeris corrections of all GEO satellites. By a comparative analysis of user positioning accuracy before and after differential, the wide area differential method is verified to be quite valid for GEO constellation.

关键词： geostationary orbitsatellite dilution of precision satellite ephemeris errors satellite clock errors wide area differential method

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A study on volunteer augmentation navigation technology

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Science china(Physics,Mechanics & Astronomy) 2011年第6期54卷 1029-1034页

作者： WU HaiTao 1,2,LU XiaoChun 1,2,ZOU DeCai 1,2 & HAN Tao 1,2 1 national time service center,chinese academy of sciences,Xi’an 710600,china 2 Key Laboratory of Precision Navigation and Timing Technology,chinese academy of sciences,Xi’an 710600,china 1. national time service center Chinese Academy of Sciences Xi’an 710600 China2. Key Laboratory of Precision Navigation and Timing Technology Chinese Academy of Sciences Xi’an 710600 China

Navigation augmentation technology is one of the most common methods to increase the continuity,reliability and integrity of the global satellite navigation *** concept of volunteer augmentation navigation (VNA) is proposed and the elements and topological structure of VNA are also analyzed in this *** study focuses on the neural network model that volunteers and ordinary users use modern communication information network to exchange self-organizing *** neural cell model of Volunteer Augmentation Navigation using shared information is *** interactive general relative positioning is *** basic theories and methods of volunteer augmentation navigation are formed on the basis of the above-mentioned *** study of realization mechanism of volunteer augmentation technology helps to form a relatively integral architecture of volunteer augmentation navigation.A user self-service satellite navigation augmentation which combines information exchange and navigation services may strengthen the continuity,reliability and integrity of the navigation *** volunteer augmentation navigation theory proposed in this paper improves the traditional satellite navigation application model and expands the connotation and denotation of satellite navigation augmentation methods.

关键词： volunteer augmentation navigation self-organizing information exchange interactive general relative positioning

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Performance and Application of Double-layered Microcapsule Corrosion Inhibitors

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Journal of Wuhan University of Technology(Materials Science) 2024年第4期39卷 845-853页

作者：余海燕 WANG Yingxiang WANG Ruizhi HU lintong WANG Tianlei School of Materials Science and Engineering Tianjin Chengjian UniversityTianjin 300384China Tianjin Key Laboratory of Building Green Functional Materials Tianjin Chengjian UniversityTianjin 300384China

Double-layered microcapsule corrosion inhibitors were developed by sodium monofluorophosphate as the core material,polymethyl methacrylate as the inner wall material,and polyvinyl alcohol as the outer wall material combining the solvent evaporation method and spray drying *** protection by the outer capsule wall was used to prolong the service life of the corrosion *** dispersion,encapsulation,thermal stability of microcapsules,and the degradation rate of capsule wall in concrete pore solution were analyzed by ultra-deep field microscopy,scanning electron microscopy,thermal analyzer,and sodium ion release rate *** microcapsules were incorporated into mortar samples containing steel reinforcement,and the effects of double-layered microcapsule corrosion inhibitors on the performance of the cement matrix and the actual corrosion-inhibiting effect were *** experimental results show that the double-layered microcapsules have a moderate particle size and uniform distribution,and the capsules were completely *** microcapsules as a whole have good thermal stability below 230 ℃.The monolayer membrane structure microcapsules completely broke within 1 day in the simulated concrete pore solution,and the double-layer membrane structure prolonged the service life of the microcapsules to 80 days in the simulated concrete pore solution before the core material was completely *** mortar samples containing steel reinforcement incorporated with the double-layered microcapsule corrosion inhibitors still maintained a higher corrosion potential than the monolayer microcapsule corrosion inhibitors control group at 60 *** incorporation of double-layered microcapsules into the cement matrix has no significant adverse effect on the setting time and early strength.

关键词： corrosion inhibitors microcapsule double-layer structure potentiodynamic polarization curve

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Teleconnection between the Indian summer monsoon onset and the Meiyu over the Yangtze River Valley

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Science china Earth sciences 2008年第7期51卷 1021-1035页

作者： LIU YunYun1,2,3 & DING YiHui2 1 chinese academy of Meteorological sciences, Beijing 100081, china 2 national Climate center, Beijing 100081, china 3 Graduate University of chinese academy of sciences, Beijing 100049, china 1. chinese academy of Meteorological sciences Beijing 100081 China 2. national Climate center Beijing 100081 China 3. Graduate University of chinese academy of sciences Beijing 100049 China

Based on the Indian and chinese precipitation data and the NCEP-NCAR reanalysis circulation data, the relationship between the Indian summer monsoon (ISM) onset and the Meiyu over the Yangtze River Valley has been discussed by the methods of correlation analysis and composite analysis. The results show that the date of ISM onset over Kerala in the southwestern coast of the Indian Peninsula is about two weeks earlier than the beginning of the Meiyu over the Yangtze River Valley. After the outbreak of ISM, the teleconnection mode sets up from the western coast of India via the Bay of Bengal (BOB) to the Yangtze River Valley and southern Japan. It is different both in time and space from the telecon- nection mode which is from the northwest of India via the Tibetan Plateau to northern china. The for- mer mode is defined as the "south" teleconnection of the Asian summer monsoon, forming in the pe- riod of ISM onset; while the latter mode is called the "north" teleconnection, mainly occurring in the Asian monsoon culminant period. During the process of the "south" teleconnection’s formation, the Asian monsoon circulation has experienced a series of important changes: ISM onset, the northward movement of the south Asia high (SAH), the onset vortex occurrence, the eastward extension of the stronger tropical westerly belt, and the northeastward jump of the western Pacific subtropical high (WPSH), etc. Consequently, since ISM sets up over Kerala, the whole Asian continent is covered by the upper SAH after about two weeks, while in the mid- and lower troposphere, a strong wind belt forms from the Arabian Sea via the southern India, BOB and the South china Sea (SCS), then along the western flank of WPSH, to the Yangtze River Valley and southern Japan. With the northward moving of the subtropical jet streams, the upper westerly jet stream and the low level jet have been coupled ver- tically over east Asia, while the Yangtze River Valley happens to locate in the ascending motion

关键词： Indian summer monsoon (ISM) the Meiyu over the Yangtze River Valley teleconnection mode

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Simulations for terrestrial planets formation

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Science china(Physics,Mechanics & Astronomy) 2009年第5期52卷 794-803页

作者： ZHANG Niu 1,2 &JI JiangHui 2,3 1Graduate University of chinese academy of sciences,Beijing 100049,china 2Purple Mountain Observatory,chinese academy of sciences,Nanjing 210008,china 3 national Astronomical Observatories,chinese academy of sciences,Beijing 100012,china Graduate University of chinese academy of sciences Beijing 100049 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China national Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

In this paper,the formation of terrestrial planets in the late stage of planetary formation is investigated using the two-planet *** that time,the protostar formed for about 3 Ma and the gas disk *** the model,the perturbations from Jupiter and Saturn are *** of the mass of outer planet,and the initial eccentricities and inclinations of embryos and planetesimals are also *** results show that,terrestrial planets are formed in 50 Ma,and the accretion rate is about 60%-80%.In each simulation,3-4 terrestrial planets are formed inside"Jupiter"with masses of 0.15 -3.6M⊕.In the 0.5-4 AU,when the eccentricities of planetesimals are excited,planetesimals are able to accrete material from wide radial *** plenty of water material of the terrestrial planet in the Habitable Zone may be transferred from the farther places by this *** could also happen a few times between two major planets only if the outer planet has a moderate mass and the small terrestrial planet could survive at some resonances over time scale of 10 8 *** one of our simulations,commensurability of the orbital periods of planets is very ***,a librating-circulating 3:2 configuration of mean motion resonance is found.

关键词： astrophysics exoplanet planetary formation n-body simulation

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What does the Sun tell and hint now?

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Research in Astronomy and Astrophysics 2009年第9期9卷 959-965页

作者： Ke-Jun Li1,2 1 national Astronomical Observatories /Yunnan Observatory,chinese academy of sciences,Kunming 650011,china 2 Key Laboratory of Solar Activity,national Astronomical Observatories,chinese academy of sciences,Beijing 100012,china national Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Key Laboratory of Solar Activity National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

Some historical records, which have held since the beginning of modern solar activity cycles, are being broken by the present Sun： cycle 23 records the longest cycle length and fall time; latitudes of high-latitude sunspots belonging to a new cycle around the minimum time of the cycle are statistically the lowest at present, compared with those of other cycles; there are only one or no sunspots in a month appearing at high latitudes for 58 months, which is the first time that such a long duration has been observed. The solar dynamo is believed to be slowing down due to：（1） the minimum smoothed monthly mean sunspot number is the smallest since cycle 16 onwards, and even probably among all modern solar cycles; and （2） once the time interval between the first observations of two neighboring sunspot groups is larger than 14 d, it should be approximately regarded as an observation of no sunspots on the visible solar disk, called a spotless event. Spotless events occur with the highest frequency around the minimum time of cycle 24, and the longest spotless event also appears around the minimum time for observations of the Sun since cycle 16. Cycle 24 is expected to have the lowest level of sunspot activity from cycle 16 onwards and even probably for all of the modern solar cycles.

关键词： Sun: activity -- Sun: general -- sunspots

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Modeling earthquake indexes derived from the earthquake warning system upon the planet earth

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Science china(Physics,Mechanics & Astronomy) 2010年第12期53卷 2293-2299页

作者： LI Yong national Astronomical Observatories, chinese academy of sciences, Beijing 100012, china 1. national Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

By studying the correlation between historical earthquake data and the distributional characteristics of parameters of solid earth tides in the earthquake epicenter, we are able to design a forecasting function of earthquake probability. We put forward a design method for the Earthquake Warning System. The model could theoretically simulate and be used to predict the probability of strong earthquakes that could occur anywhere at any time. In addition, the system could also conveniently obtain global or partial Modeling Earthquake Indexes to finally combine the precise pointing prediction and forecast of partial indexes. The literature quotes global data values, provided by NEIC, of 1544 M ≥ 6.5 earthquakes. It also gives examples of instantaneous earthquake indexes of the whole world and Taiwan Region on 1st January 2010, UT=0:00 and the average earthquake index near the Taiwan Region. According to the 10-year pointing prediction of strong earthquakes in San Francisco, the literature provides the average earthquake index on 24th June 2015 (± 15 days), in its neighborhood.

关键词： earthquake earthquake warning system astrogeodynamics index

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