检索结果-南通市图书馆

The Kiloparsec-scale Structure of 3C 286

在线全文

学校读者我要写书评

暂无评论

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 Observatory, chinese academy of sciences, Shanghai 200030 national astronomical observatories, chinese academy of sciences, beijing 100012 Shanghai astronomical Observatory 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 286 acquired with the Very Large Array (VLA) at 8.4.and 22.5 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 -120° 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 a22.58.4. 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 a22.58.4.0.88 and a22.58.4.1.79, 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

A Date Recovery System launched for chronological studies in ancient China

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2008年第1期51卷 105-110页

作者： LI Yong national astronomical observatories,chinese {4. of sciences,beijing 100012,China 1. national astronomical observatories Chinese Academy of Sciences Beijing 100012 China

Benefited from the performance of the Xia-Shang-zhou Chronology Project(XSZP) in China and our new astronomical chronology method designed and processed for chinese particular 60-day-cycle Ganzhi(the heavenly stems and earthly branches)date records,we launch a Date Recovery System(DRS)for ancient China. Of high analysis function,this software can recover and convert the complete or incomplete date information originally from Ganzhi style in the historical period of China to the Gregorian Calendar System,which may have wide applications in the area of literary history,archaeology and cultural relic,etc.,and solve the Goldbach Puzzles of chinese *** an example,we give the detailed process for the sculptures on four bronze wares with the Ganzhi data and afterwards employ this software and provide their possible dates corresponding to Gregorian system.

关键词： chronology date ephemeris software

Gamma-ray Bursts: a Probe of Black Holes

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Astronomy and Astrophysics 2001年第6期1卷 487-493页

作者： wei Wang and Yong-Heng Zhao national astronomical observatories,{4., beijing 100012 national astronomical observatories Chinese Academy of Sciences Beijing 100012

There is strong evidence for the existence of black holes (BHs) in some X-ray binaries and in most galactic nuclei based on different types of measurement, but black holes have not been definitely identified for the lack of very firm observational evidence up to now. Because direct evidence for BHs should come from determination of strong gravitational redshift, we expect an object can fall into the region near the BH horizon where radiation can be detected. Therefore the object must be a compact star such as a neutron star (NS), and intense astrophysical processes will release highly energetic radiation that is transient and fast-varying. These characteristics may point to the observed gamma-ray bursts (GRBs). Recent observations of iron lines suggest that afterglows of GRBs show properties similar to those observed in active galactic nuclei (AGNs), implying that the GRBs may originate from intense events related to black holes. A model for GRBs and after-glows is proposed here to obtain the range of gravitational redshifts (zg) of GRBs with known cosmological redshifts. Here, we provide a new method that, with a search for high-energy emission lines (X- or -γ-rays) in GRBs, one can determine the gravitational redshift. We expect zg to be 0.5 or even larger, so we can rule out the possibility of other compact objects such as NSs, and identify the central progenitors of GRBs as black holes.

关键词： black hole physics - accretion accretion disks - gamma rays: burst

A network flow algorithm to position tiles for LAMOST

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2009年第11期9卷 1277-1284页

作者： Guang-wei Li and Gang Zhao national astronomical observatories,{4., beijing 100012, China national astronomical observatories Chinese Academy of Sciences Beijing 100012 China

We introduce the network flow algorithm used by the Sloan Digital Sky Survey （SDSS） into the sky survey of the Large sky Area Multi-Object fiber Spectroscopic Telescope （LAMOST） to position tiles. Because fibers in LAMOST＇s focal plane are distributed uniformly, we cannot use SDSS＇ method directly. To solve this problem, firstly we divide the sky into many small blocks, and we also assume that all the targets that are in the same block have the same position, which is the center of the block. Secondly, we give a value to limit the number of the targets that the LAMOST focal plane can collect in one square degree so that it cannot collect too many targets in one small block. Thirdly, because the network flow algorithm used in this paper is a bipartite network, we do not use the general solution algorithm that was used by SDSS. Instead, we give our new faster solution method for this special network. Compared with the Convergent Mean Shift Algorithm, the network flow algorithm can decrease observation times with improved mean imaging quality. This algorithm also has a very fast running speed. It can distribute millions of targets in a few minutes using a common personal computer.

关键词： methods data analysis -- methods statistical

The Two Mini-lobes of the CSO OQ208——VLBI Observations at 5 GHz and 8.4.GHz

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Astronomy and Astrophysics 2003年第6期3卷 505-512页

作者： wei-Hua Wang, Xiao-Yu Hong and Tao AnShanghai astronomical Observatory, chinese academy of sciences, Shanghai 200030 national astronomical observatories, chinese academy of sciences, beijing 100012 Shanghai astronomical Observatory Chinese Academy of Sciences Shanghai 200030 []National Astronomical Observatories Chinese Academy of Sciences Beijing 100012

We present the results of VLBI observations at 5 GHz and 8.4.GHz of the compact symmetric object (CSO) OQ208. Images taken on four epochs at 5GHz and one at 8.4.Hz show that the parsec radio structure of the source consists of two mini-lobes, both of them are resolved into two hot-spots. We note that the component D is stronger than the component C in the south-west region at 5 GHz, indicating that component D is less free-free absorbed than C at low frequency. On the basis of the separation of components A and D, a proper motion of 0.032±0.02 mas yrbetween the two mini-lobes is estimated. This value is about half the previous estimates based on the separation of components A and C with 8.4.GHz VLBI data. The reason for the decrease in the expansion velocity is discussed.

关键词： galaxies: individual (Mkn 668 OQ208) - galaxies: active

Detectability of rotation-powered pulsars in future hard X-ray surveys

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2009年第11期9卷 1241-1258页

作者： wei Wang national astronomical observatories Chinese Academy of Sciences Beijing 100012 China

Recent INTEGRAL/IBIS hard X-ray surveys have detected about 10 young pulsars. We show hard X-ray properties of these 10 young pulsars, which have a luminosity of 10^33 - 10^37 erg s^-1 and a photon index of 1.6-2.1 in the energy range of 20-100 keV. The correlation between X-ray luminosity and spin-down power of Lx ∝ Lsd^1.31 suggests that the hard X-ray emission in rotation-powered pulsars is dominated by the pulsar wind nebula （PWN） component. Assuming spectral properties are similar in 20-100keV and 2-10 keV for both the pulsar and PWN components, the hard X-ray luminosity and flux of 39 known young X-ray pulsars and 8 millisecond pulsars are obtained, and a correlation of Lx ∝ Lsd^1.5 is derived. About 20 known young X-ray pulsars and 1 millisecond pulsars could be detected with future INTEGRAL and HXMT surveys. We also carry out Monte Carlo simulations of hard X-ray pulsars in the Galaxy and the Gould Belt, assuming values for the pulsar birth rate, initial position, proper motion velocity, period, and magnetic field distribution and evolution based on observational statistics and the Lx - Lsd reltions：Lx ∝Lsd^1.31 and Lx∝Lsd^1.5 More than 4. young pulsars （mostly in the Galactic plane） could be detected after ten years of INTEGRAL surveys and the launch of HXMT. So, the young pulsars would be a significant part of the hard X-ray source population in the sky, and will contribute to unidentified hard X-ray sources in present and future hard X-ray surveys by INTEGRAL and HXMT.

关键词： pulsars general -- stars neutron -- X-rays stars -- radiation mechanisms nontherrnal

A Test on Different Types of the Time Curve of Hardness Ratio of Gamma-Ray Bursts based on the Curvature Effect

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Astronomy and Astrophysics 2008年第4期8卷 451-464页

作者： Lan-wei Jia national astronomical observatories/Yunnan Observatory,{4. academy of sciences,Kunming 650011,China Graduate School of chinese academy of sciences,beijing 10004.,China national astronomical observatories/ Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China and Graduate School of chinese academy of sciences Beijing 100049 China

We analyzed a sample of 66 gamma-ray bursts （GRBs） and statistically confirmed the prediction on the time curve of the hardness ratio of GRBs made by Qin et al. based on the curvature effect. In their analysis, GRB pulses are divided into three types according to the shape of their raw hardness ratio （RHR） time curves, defined as to include the background counts to the signal counts, so as to make use of counts within small time intervals. Of the three types, very hard sources exhibit a perfect pulse-like profile （type 1）, hard bursts possess a pulse-like profile with a dip in the decay phase （type 2）, and soft bursts show no pulse-like profile but have only a dipped profile （type 3）. In terms of the conventional hardness ratio, type 3 sources are indeed generally softer than those of type 1 and type 2, in agreement with the prediction. We found that the minimum value of RHR is sensitive in distinguishing the different types. We propose that GRB pulses can be classified according to the minimum value of RHR and that the different type sources may be connected with different strengths of the shock or/and the magnetic field.

关键词： gamma-rays burst -- gamma-rays observations - methods statistical

Spectral Properties of Anomalous X-ray Pulsars

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Astronomy and Astrophysics 2003年第6期3卷 543-550页

作者： Ye Lu, wei Wang and Yong-Heng Zhaonational astronomical observatories,{4., beijing 100012 national astronomical observatories CAS NAOC Beijing 100012 China

We examine the spectra of the persistent emission from anomalous X-ray pulsars (AXPs) and their variation with the spin-down rate . Based on an accretion-powered model, the influences of both the magnetic field and the mass accretion rate on the spectral properties of AXPs are addressed. We then investigate the relation between the spectral property of AXPs and mass accretion rate . The result shows that there exists a linear correlation between the photon index and the mass accretion rate: the spectral hardness increases with increasing . A possible emission mechanism for the explanation of the spectral properties of AXPs is also discussed.

关键词： pulsars: general stars: neutron X-rays: stars accretion: accretion disks

Phase field modeling of ferroelastic variant switching in yttria-stabilized t'zirconia with strain gradient elasticity and interface tension

在线全文

学校读者我要写书评

暂无评论

Science China(Technological sciences) 2024年第5期67卷 1443-1457页

作者： zhou QianQian wei YueGuang zhou YiChun YANG Li College of Engineering BIC-ESATPeking UniversityBeijing100871China School of Advanced Materials and Nanotechnology Xidian UniversityXi’an710126China Frontier Research Center of Thin Films and Coatings for Device Applications Academy of Advanced Interdisciplinary ResearchXidian UniversityXi’an710126China

The 6–8 wt%yttria-stabilized zirconia with a tetragonal structure(t’-YSZ)is extensively employed in thermal barrier *** exceptional fracture toughness of t’-YSZ can be attributed to its distinctive ferroelastic toughening *** and interface tension play a critical role in ferroelastic variant switching at the micro-and *** paper presents an original thermodynamically consistent phase field(PF)theory for analyzing ferroelastic variant switching at the micro-and nano-scale of t’-*** theory incorporates strain gradient elasticity using higher-order elastic energy and interface tension tensor via geometric nonlinearity to represent biaxial tension resulting from interface ***,a mixed-type formulation is employed to implement the higher-order theory through the finite element *** an interface in equilibrium,the effects of strain gradient elasticity result in a more uniform distribution of stresses,whereas the presence of interface tension tensor significantly amplifies the stress magnitude at the *** introduction of an interface tension tensor increases the maximum value of stress at the interface by a factor of 4.to *** nucleation and evolution of variants at a pre-existing crack tip in a mono-phase t’-YSZ have also been *** strain gradient elasticity is capable of capturing the size effect of ferroelastic variant switching associated with microstructures in ***,when the grain size approaches that of the specimen,the critical load required for variant switching at the crack tip increases,resulting in greater dissipation of elastic energy during ferroelastic variant ***,the interface tension accelerates the evolution of *** presented framework exhibits significant potential in modeling ferroelastic variant switching at the micro-and nano-scale.

关键词： thermodynamics strain gradient elasticity interface tension phase field method ferroelastic variant switching