检索结果-南通市图书馆

How to estimate the effect of an intense meteor shower on human space activities

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2009年第8期52卷 1161-1168页

作者： WU GuangJie national astronomical {2./yunnan observatory,chinese Academy of sciences,kunming 650011,china national astronomical {2./yunnan observatory Chinese Academy of Sciences Kunming 650011 China

In the present age,the potential threat to space projects coming from some intense meteor storms has been ***,the increasing activities of mankind in space for scientific,commercial and military purposes have led to an increase in safety-related problems about the satellites,space stations and *** new techniques for observing meteors and meteor showers have been ***,how to estimate even predict the effect of an intense meteor shower should be further *** initial definition about a meteor storm based on visual observations with a Zenithal Hourly Rate of over one thousand seems insufficient,since it only means a storm or burst of meteors in *** 2.06 the author suggested a synthetical index of the potential threats about intense activities of meteors;however,it is too complex to determine several *** this paper,the author suggests a Special True Number Flux Density(STNFD).Set a certain energy-limit,or a certain electric-charge-limit,and then calculate the number flux *** the comparison between two of the 10 strong meteor showers in recent years it is found that the important factor affecting the space flight security is not only the number of meteoroids,but also their velocities,their average energy and the population index *** show that Giacobinids,even june Bootids,should be one of the most hazardous meteor showers.

关键词： meteors meteorites and tektites spacecraft/atmosphere interactions observation and data reduction techniques

An Efficient High-Resolution Shock-Capturing Scheme for Multi-Dimensional Flows I. Hydrodynamics

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Astronomy and Astrophysics 2006年第6期6卷 680-688页

作者： Cong Yu national astronomical {2. / yunnan astronomical observatory, chinese Academy of sciences, kunming 650011 Graduate School of chinese Academy of sciences, Beijing 100049 Graduate School of chinese Academy of sciences Beijing 100049

Many problems at the forefront of theoretical astrophysics require a treatment of dynamical fluid behavior. We present an efficient high-resolution shock-capturing hydrodynamic scheme designed to study such phenomena. We have implemented a weighted, essentially non-oscillatory （WENO） scheme to fifth order accuracy in space, liLLE approximate Riemann solver is used for the flux computation at cell interface, which does not require spectral decomposition into characteristic waves and so is computationally friendly. For time integration we apply a third order total variation diminishing （TVD） Runge-Kutta scheme. Extensive testing and comparison with schemes that *** characteristic decomposition are carried out demonstrating the ability of our scheme to address challenging open questions in astrophysics.

关键词： accretion - hydrodynamics- method numerical - shock waves

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 {2./yunnan observatory,chinese Academy of sciences,kunming 650011,china Graduate School of chinese Academy of sciences,Beijing 100049,china national astronomical {2./ 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

An Alternative Explanation for a Screw-like Meteoric Train Photographed by Double-Station Observations

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Astronomy and Astrophysics 2007年第6期7卷 814-822页

作者： Guang-Jie Wu1,2.1 national {2. observatories/yunnan observatory,chinese Academy of sciences,kunming 650011 2.Purple Mountain observatory,chinese Academy of sciences,Nanjing 2.0008 Purple Mountain observatory Chinese Academy of Sciences Nanjing 210008

Two-station observation of meteors, especially a meteor trains, provides an effective approach to the measurement of the physical parameters. We have collected four special groups of photographs of meteoric trains taken at two stations during Leonids 2.01. One representative group has been measured and analyzed in detail. An analysis has been reported in our first paper. In this paper, an alternative explanation for the screw-like meteoric train is suggested based on some physical calculations. The results reveal that this train has a screw-like structure and, apparently, spoke beams. The mother meteor of this train may be negatively charged and moves forward along a left-hand screw trajectory under the effect of the geomagnetic field. The spoke beams might be the visual effect of the long time exposure of many particles released from the disintegrated meteoroid.

关键词： meteors meteoroids -- magnetic fields

Avoided crossings between non-radial modes in low mass RGB stars

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2012年第12期12卷 1655-1665页

作者： jun-jun Guo1,2.3,Yan {2.,2.and Xiang-jun Lai1,2.1 national astronomical observatories/yunnan observatory,chinese Academy of sciences, {12.,china 2.key Laboratory for the Structure and Evolution of Celestial Objects,chinese Academy of sciences,{12.,china 3 Graduate University of chinese Academy of sciences,Beijing 100049,china national astronomical {2./yunnan observatory Chinese Academy of Sciences Kunming 650011 China key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China Graduate University of chinese Academy of sciences Beijing 100049 China

Non-radial p modes and g modes appear simultaneously in red giant stars. Their frequencies have different variation rates,causing their frequencies to become close during stellar evolution so that avoided crossings *** separation between regions where acoustic waves and gravity waves propagate for l=1,2.and 3 is different,which results in the coupling efficiency also being *** present the results of numerical computations of the models we *** find that the two kinds of modes for l=2.and 3 need to be closer in frequency in order for a complete exchange to occur,compared to the case for modes with l=*** scaled oscillation frequencies also present better regularity with evolution than modes with l=1. In order to study the effect of the avoided crossings in detail,we set the mode which has the smallest mode inertia to be the p *** plot the two kinds of modes for l =1,2.and 3 in frequency and periodéchelle diagrams and find modes of l=2.and 3 fit the two relations better;they are more equally spaced in frequency and period than modes with l=*** careful observation of the two kinds oféchelle diagrams for l=2.and 3,we still find that some p modes shift a little from being equally spaced in frequency and some g modes,which are close to those p modes in period,shift a little from being equally spaced in ***,we study the relation between the deviation from period being equally spaced and the mode inertia of g modes for different *** g modes of l=1 with a period closer to the p mode have less inertia and the deviation is bigger in the periodéchelle *** deviation is also obvious. However g modes of l=2.and 3 shift a little or have almost no deviation from being equally spaced in period,even though some of them may have strong coupling and close mode inertia like in the p ***,we suggest a possible method for measuring period spacing of g modes precisely using mixed g modes with l=2.and 3 that have fewer observed mixed g m

关键词： stars:oscillations-stars:red giants

The relationship of extended radio power and broad emission line luminosity in blazars

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2010年第S1期53卷 240-243页

作者： liU HongTao & Bai JinMing national {2. observatories/yunnan observatory,chinese Academy of sciences,kunming 650011,china chinese Acad Sci Yunnan Observ Natl Astron Observ Kunming 650011 Peoples R China

The relationship between broad line luminosity LBLR and extended radio power PE is *** the log PE-log LBLR diagram,FSRQs populate the region of higher luminosity relative to BL Lacs,and FR II BL Lacs are between FSRQs and FR I BL *** these blazars,there is a significant correlation between LBLR and *** regression line scales as PE ∝ L0B.L87R ± *** slope of this scaling relation is consistent with that derived from the simple theoretical ***,the unification of BL Lacs and FRSQs into a single population finds a statistical basis,and a disk-jet symbiosis in blazars is *** II BL Lacs are probably at an intermediate stage in the sequence from FSRQs to BL Lacs with FR I BL Lacs at the end of this sequence.

关键词： accretion black hole physics BL Laceratae objects:general galaxies:nuclei quasars:general

Studies of solar flares and CMEs related to the space solar missions in the future

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2009年第11期52卷 1646-1654页

作者： liN jun1,2. {2. astronomical observatories/yunnan astronomical observatory, chinese Academy of sciences, kunming 650011, china 2.Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02.38, USA national astronomical {2./yunnan astronomical observatory Chinese Academy of Sciences Kunming 650011 China Harvard-Smithsonian Center for Astrophysics 60 Garden Street Cambridge MA 02138 USA

Solar eruptions and the related processes involve magnetic fields and plasma flows of various scales in both time and space. These processes include the convective motions of the mass and magnetic field in the photosphere, evolutions of magnetic fields in both the chromosphere and the corona prior to and during the disruption of magnetic fields in response to the photospheric motions. These evolutions constitute a whole process of transporting the magnetic energy and the helicity from the photosphere to the corona, and then to interplanetary space. The present work, on the basis of a solar eruption model, discusses these processes, and the related questions, unanswerable at present, but could be the scientific objectives of the space solar missions in the future.

关键词： solar eruptions magnetic field energy conversion magnetic reconnection current sheet

RT Leonis Minoris:an Unstable W Ursae Majoris System with a Spotted Component

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6期4卷 553-562页

作者： Yu-Lan Yang and Qing-Yao liunational {2. observatories, yunnan observatory, chinese Academy of sciences,kunming 650011 United Laboratory of Optical Astronomy, chinese Academy of sciences national astronomical {2. Yunnan Observatory Chinese Academy of Sciences Kunming 650011 []United Laboratory of Optical Astronomy Chinese Academy of Sciences

Complete BV light curves of the W UMa type binary RT LMi are presented. From the observations, four times of minimum light were determined. Based on the new times of minimum light and those collected from the literature, changes in the orbital period of the system were found and analyzed with Kalimeris et al.'s method. The result shows that the orbital period possibly oscillates with a cycle of about 64 years and an amplitude of 1.2.× 10-6 days. The present CCD photometric observations reveal that the light curves are obviously asymmetrical, and show a positive O'Connell effect, while the light curves obtained in 1982.exhibit a negative O'Connell effect. The present light curves were analyzed by means of the latest version of the Wilson-Devinney code, which was also used to correct the photometric effects, including the distortion on the radial-velocity curves obtained by Rucinski et al. The following absolute dimensions have been derived: MI -1.2. ±0.08 M⊙, M2.= 0.48 ±0.06 M⊙, R1 = 1.2. ±0.06 R⊙, R2.= 0.83 ±0.05 R⊙, L1 = 1.88±0.12.L⊙, L2.= 0.77±0.08 L⊙, and A = 2.64±0.02.R⊙. The asymmetry of the light curves can be explained by a model with a cool spot on the secondary component. The orbital period modulation can be reproduced by a magnetic activity cycle model of the secondary component with ΔJ = 5.6 × 1046 g cm2.s-1, ΔΩ/Ω = 8.8 × 10-4, and B = 5.1 × 103 G.

关键词： star: contact binary - star: individuals: RT LMi - star: magnetic activity

The Chemical Classification of the AGB Star IRAS 17515-2.07

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 551-554页

作者： Pei-Sheng Chen and Pin Zhang1national astronomical {2., yunnan observatory, chinese Academy of sciences, kunming 650011 2.osmic Ray Institute, yunnan University, kunming 650091 Cosmic Ray Institute Yunnan University Kunming 650091

The chemical classification of IRAS 17515-2.07 has been debated for a longtime. Up to now there are two contenders, oxygen-rich or carbon-rich. We believe that IRAS17515-2.07 is an oxygen-rich source: because (ⅰ) it shows the silicate self-absorbed emission; (ⅱ)in the near infrared-IRAS diagram it is located in the oxygen-rich object region and (ⅲ)particularly, it has detected SiO maser emission.

关键词： stars: AGB stars: chemical classification stars: maser infrared: stars