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第三届中国卫星导航学术年会

作者： Wu XiaoLi1Hu XiaoGong2..Wang Gang1*Zhong HuiJuan3&Tang ChengPan2.. Beijing Global Information Center of Application and Exploration, Beijing 100094, china 2. shanghai astronomical observatory,{2., shanghai 200030, china 3. china Defense Science Technology Information Center, Beijing 100142. china

As an important component of a GNSS navigation message, ionospheric delay model parameters are broadcasted for single-frequency users to improve their positioning accuracy. GPS provides daily Klobuchar ionospheric model parameters based on geomagnetic reference frame, while the regional satellite navigation system of Compass broadcasts an eight-parameter ionospheric model generated by processing real data from continuous monitoring stations, which is updated every 2.hours. To evaluate model performance, model predictions are compared against real ionosphere measurements, along with positioning accuracy comparisons. Real data analysis indicates that the Compass ionospheric model provides higher correction precision in middle-latitude regions, but relatively lower correction precision for low-latitude regions where ionosphere possesses much more variability. Thanks to the constellation design of Compass, ionospheric model errors for some receivers manifest a common bias for in-coming GNSS signals from different satellites. Consequently, ionospheric model errors are somehow translated into the receivers’ clock error estimation, while have less influence on the positioning. Given that the chinese global navigation system will still rely on a domestic continuous monitoring network to provide global ionosphere correction service, the applicability of the ionospheric model in regions beyond china’s mainland is studied by applying the regional model to single-frequency positioning experiments of GPS. Real data analysis shows that in the northern hemisphere areas including Asia, Europe and North America, compared with the GPS single-frequency positioning using Klobuchar model for ionospheric delay corrections, the three-dimension position accuracy is improved by 7.8% 35.3% by using the Compass model. But the positioning accuracy in the southern hemisphere is degraded by 9.5%3.5% due to the lack of monitoring stations there.

关键词： ionospheric model regional satellite navigation system model error positioning error

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A Possible Origin of 6.7 GHz Linear Methanol Maser Sources

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chinese Journal of Astronomy and Astrophysics 2001年第5期1卷 389-394页

作者： Ye Xu (shanghai astronomical {2., chinese academy of sciences, shanghai 200030) (Urumqi astronomical {2., chinese academy of sciences, Urumqi 830011) (National astronomical Observatories, chinese academy of sciences, Beijing 100012. E-mail shanghai astronomical {2. Chinese Academy of Sciences Shanghai 200030 []Urumqi Astronomical Observatory Chinese Academy of Sciences Urumqi 830011 []National Astronomical Observatories Chinese Academy of Sciences Beijing 100012

We present a model which explains the observed multi-linear spatial structures with different velocity gradients of the 50-61A+ methanol line at 6.7 GHz. We consider this and other hypotheses and conclude that the met... 详细信息

关键词： masers - stars: circumstellar matter - stars: formation

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The Kiloparsec-scale Structure of 3C 2.6

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chinese Journal of Astronomy and Astrophysics 2004年第1期4卷 28-36页

作者： Tao An, Xiao-Yu Hong and Wei-Hua Wangshanghai astronomical {2., chinese academy of sciences, shanghai 200030 National astronomical Observatories, chinese academy of sciences, Beijing 100012 shanghai astronomical {2. Chinese Academy of Sciences Shanghai 200030 []National Astronomical Observatories Chinese Academy of Sciences Beijing 100012

We present radio images of the compact steep spectrum (CSS) quasar 3C 2.6 acquired with the Very Large Array (VLA) at 8.4 and 2..5 GHz. The source exhibits a two-sided core-jet structure with a bright central component and two extended components one to the east (P.A. 100°) and another to the southwest (P.A. - 116°). From the compact core, an extension runs towards the southwest component up to - 0.7 arcsecond. The emission between the primary central component and the southwest component exhibits a knotty structure. A gradual change of the jet position angles from -135° to -12.° in the inner southwest jet suggests a local bend. The position angle changes of the major eastern components E2.and El suggest that the eastern jet likely follows a curved trace. The bends in the jet trace may be associated with a relativistic precession or some interaction between the jet and the ambient matter. A mean spectral index of a2..58.4- 0.76 (Xv Va) is estimated for the core component. Steep spectra are also obtained for the extended southwest component (2.6', P.A. -116°) and eastern component (0.8', P.A. 100°), with a2..58.4-0.88 and a2..58.4-1.79, respectively. The radio morphologies and spectral index distributions suggest that the core seen in our images is likely to be the beamed inner jet while the real nucleus is dimmed by it beaming away from us.

关键词： galaxy: quasar: individual - radio continuum: VLA

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CO observations of massive star forming regions at different evolutionary phases

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Science china(Physics,Mechanics & Astronomy) 2006年第5期49卷 626-640页

作者： CHEN Xi1,2. XU Ye1,3, SHEN Zhiqiang1,3 & LI Jingjing1,2.1. shanghai astronomical {2., chinese academy of sciences, shanghai 200030, china 2. Graduate School of the chinese academy of sciences, Beijing 100034, china 3. Joint Institute for Galaxy and Cosmology, shanghai astronomical {2. and the University of Science and Technology of china, shanghai 200030, china shanghai astronomical {2. Chinese Academy of Sciences Shanghai 200030 China Graduate School of the chinese academy of sciences Beijing 100034 China Joint Institute for Galaxy Cosmology Shanghai Astronomical Observatory the University of Science Technology of china Shanghai 200030 China

The 12.O (J=1-0), 13CO (J=1-0) and C18O (J=1-0) emissions in 9 massive star forming regions, which are believed to be at different stages of massive star formation, were mapped with the 13.7 m millimeter wave telescope at Qinghai Station of Purple Mountain observatory. Of the observed 9 sources, 13CO cores were detected in seven of them, and C18O cores in five of them. And only two sources associated with C18O cores and H2. masers showed the extended structures and strong outflows. This is the first detection of outflow associated with IRAS 2.566+582. in the observing field of S152.S153. The physical parameters of cores and outflows for these sources, derived from Local Thermal Equilibrium (LTE) analysis, are presented. These observing results suggest that the C18O cores will only appear when the gas density is high enough and the probability to have an outflow is very high when the clumps show the C18O and H2. maser simulta- neously.

关键词： star formation cloud core outflow H2. maser

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Decomposition of the X-ray waveform of soft gamma-ray repeaters during giant flares

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Science china(Physics,Mechanics & Astronomy) 2010年第S1期53卷 249-251页

作者： XING Yi & YU WenFei shanghai astronomical {2.,chinese academy of sciences,shanghai 200030,china chinese Acad Sci Shanghai Astron Observ Shanghai 200030 Peoples R China

We have analyzed the observations of SGR 1806-2. and SGR 1900+14 during giant flares made with the Rossi X-ray Timing *** have studied the pulsating tail after the initial spike and decomposed the pulse waveform into separate components of *** found evidence for phase shifts of those *** is probably due to rapid geometrical changes in the magnetic field of the neutron star during giant *** phase shifts could be used to constrain the geometry of the magnetic field.

关键词： soft gamma-repeaters giant flare waveform decomposition

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Polynomial regression calculation of the Earth's position based on millisecond pulsar timing

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Research in Astronomy and Astrophysics 2012年第2期12卷 219-234页

作者： Feng Tian 1,2.Zheng-Hong Tang 1,Qing-Zeng Yan 1,2.and Yong Yu 11 shanghai astronomical {2.,chinese academy of sciences,shanghai 200030,china 2.Graduate University of chinese academy of sciences,Beijing 100049,china shanghai astronomical {2. Chinese Academy of Sciences Shanghai 200030 China Graduate University of chinese academy of sciences Beijing 100049 China

Prior to achieving high precision navigation of a spacecraft using X-ray observations, a pulsar rotation model must be built and analysis of the precise posi- tion of the Earth should be performed using ground pulsar timing observations. We can simulate time-of-arrival ground observation data close to actual observed values before using pulsar timing observation data. Considering the correlation between the Earth＇s position and its short arc section of an orbit, we use polynomial regression to build the correlation. Regression coefficients can be calculated using the least square method, and a coordinate component series can also be obtained; that is, we can calcu- late Earth＇s position in the Barycentric Celestial Reference System according to pulse arrival time data and a precise pulsar rotation model. In order to set appropriate param- eters before the actual timing observations for Earth positioning, we can calculate the influence of the spatial distribution of pulsars on errors in the positioning result and the influence of error source variation on positioning by simulation. It is significant that the threshold values of the observation and systematic errors can be established before an actual observation occurs; namely, we can determine the observation mode with small errors and reject the observed data with big errors, thus improving the positioning result.

关键词： autonomous positioning - millisecond pulsar - pulsar timing - re-gression analysis

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The relation between black hole masses and Lorentz factors of the jet components in blazars

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Research in Astronomy and Astrophysics 2009年第3期9卷 293-301页

作者： Ming Zhou1,2.3 and Xin-Wu Cao1,2.1 shanghai astronomical {2., chinese academy of sciences, shanghai 200030, china 2.Joint Institute for Galaxy and Cosmology (JOINGC) of SHAO and USMC, shanghai 200030, china 3 Graduate School of the chinese academy of sciences, Beijing 100049, china shanghai astronomical {2. Chinese Academy of Sciences Shanghai 200030 China Joint Institute for Galaxy and Cosmology (JOINGC) of SHAO and USMC Shanghai 200030 China Graduate School of the chinese academy of sciences Beijing 100049 China

We explore the relationship between black hole mass (MBH) and the motion of the jet components for a sample of blazars. The Very Long Baseline Array (VLBA) 2.cm Survey and its continuation: Monitoring of Jets in active galactic nuclei (AGNs) with VLBA Experiments (MOJAVE) have observed 2.8 radio-loud AGNs, of which 146 blazars have reliable measurements of their apparent velocities of the jet components. We calculate the minimal Lorentz factors for these sources from their measured apparent velocities, and their black hole masses are estimated with their broad-line widths. A sig- nificant intrinsic correlation is found between black hole masses and the minimal Lorentz factors of the jet components. The Eddington ratio is only weakly correlated with the min- imal Lorentz factor, which may imply that the Blandford-Znajek (BZ) mechanism may dominate over the Blandford-Payne (BP) mechanism for the jet acceleration (at least) in blazars.

关键词： black hole physics — galaxies: active — galaxies: jets — galaxies: nuclei

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Entropy of Dilatonic Black Hole due to Arbitrary Spin Fields

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chinese Journal of Astronomy and Astrophysics 2001年第4期1卷 357-364页

作者： You-Gen Shen and Chang-Jun Gao (shanghai astronomical {2., chinese academy of sciences, shanghai 200030 National astronomical Observatories, chinese academy of sciences, Beijing 100012.Institute of Theoretical Physics, chinese academy of Scienc Institute of Theoretical Physics Chinese Academy of Sciences Beijing 100080

Using the membrane model based on the brick-wall model, we calculate the free energy and entropy of dilatonic black hole due to arbitrary spin fields. The result shows that the entropy of scalar field and the entropy ... 详细信息

关键词： black hole physics - entropy - spin

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Some developments of hot accretion flow theory in the past ten years

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Science china(Physics,Mechanics & Astronomy) 2010年第S1期53卷 24-30页

作者： YUAN Feng Key Laboratory for Research in Galaxies and Cosmology,shanghai astronomical {2.,chinese academy of sciences,shanghai 200030,china 1. Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China

The hot accretion flow model was re-discovered in 1994 by Narayan and *** theoretical works have been conducted and significant progresses have been *** this paper,we review several developments in the past ten *** mainly includes the finding of outflow and convection and its dynamical effect on inflow;the direct electron heating by viscous dissipation;the effect of large scale toroidal magnetic fields in the inner region of the accretion flow;and the effect of global Compton *** observational applications are also introduced very briefly.

关键词： flow Some developments of hot accretion flow theory in the past ten years

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Entropy of three-dimensional BTZ black holes

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中国科学：物理学、力学、天文学英文版 2004年第3期47卷 277-283页

作者： GAO Changjun1,2.& SHEN Yougen1,2.3,4 1.shanghai astronomical {2.,chinese academy of sciences,shanghai 200030,china(mailing address) 2.National astronomical Observatories,chinese academy of sciences,Beijing 100012.china 3.Institute of Theoretical Physics,chinese academy of sciences,Beijing 100080,china 4.shanghai United Center for Astrophysics,shanghai 2.02.4,china 1. shanghai astronomical {2. Chinese Academy of Sciences 200030 Shanghai China 2. National astronomical Observatories Chinese Academy of Sciences 100012 Beijing China 3. Institute of Theoretical Physics Chinese Academy of Sciences 100080 Beijing China 4. shanghai United Center for Astrophysics 200234 Shanghai China

The entropies of scalar field and neutrino field are calculated in the background of three-dimensional BTZ black hole. Considering statistical physics,we propose not to consider the superraradiant modes for bosons (Fermion fields do not display supperradiance).In fact,the nonsuperradiant modes do contribute exactly the area entropy for both bosons and fermions. The result shows that the neutrino field entropy is 3/2.times the scalar one.

关键词： BTZ black holes, entropy, supperradiant modes.

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