The stability of the planetary three-body problem: Influence of the secular resonances     

Philippe Robutel 《Celestial Mechanics and Dynamical Astronomy》1993,57(1-2):97-98

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图书情报资料工作在测绘教育中的地位与作用     

张春香  陈德云 《地理信息世界》2001,(2)

学校图书馆是图书资料的供应与服务基地 ,其藏书量与藏书类别的多少 ,以及图书馆各专业情报资料源的数量与管理和服务水平 ,是办学条件的重要标志之一 ,因而 ,测绘图书情报资料的信息源建设、测绘科技文献的开发与利用和测绘科技情报资料为师生的服务 ,在测绘教育中有着举足轻重的地位与作用。  相似文献   

Tracing the star stream through M31 using planetary nebula kinematics     

H. R. Merrett  K. Kuijken  M. R. Merrifield  A. J. Romanowsky  N. G. Douglas  N. R. Napolitano  M. Arnaboldi  M. Capaccioli  K. C. Freeman  O. Gerhard  N. W. Evans  M. I. Wilkinson  C. Halliday  T. J. Bridges  D. Carter 《Monthly notices of the Royal Astronomical Society》2003,346(4):L62-L66

We present a possible orbit for the Southern Stream of stars in M31, which connects it to the Northern Spur. Support for this model comes from the dynamics of planetary nebulae (PNe) in the disc of M31: analysis of a new sample of 2611 PNe obtained using the Planetary Nebula Spectrograph reveals ∼20 objects with kinematics inconsistent with the normal components of the galaxy, but which lie at the right positions and velocities to connect the two photometric features via this orbit. The satellite galaxy M32 is coincident with the stream both in position and velocity, adding weight to the hypothesis that the stream comprises its tidal debris.  相似文献   

Energy Of The Universe In Bianchi-Type I Models In MØLler’S Tetrad Theory Of Gravity     

Oktay?Aydo?duEmail author  Mustafa?Salti 《Astrophysics and Space Science》2005,299(3):227-232

In this paper, using the energy definition in MØller’s tetrad theory of gravity we calculate the total energy of the universe in Bianchi-type I cosmological models which includes both the matter and gravitational fields. The total energy is found to be zero and this result agrees with a previous works of Banerjee and Sen who investigated this problem using the general relativity version of the Einstein energy-momentum complex and Xulu who investigated same problem using the general relativity versions of the Landau and lifshitz, Papapetrou and Weinberg’s energy-momentum complexes. The result that total energy of the universe in Bianchi-type I universes is zero supports the viewpoint of Tryon.  相似文献   

2002年12月25日乌恰5.8级地震的长、中、短期跟踪预测和反思     

苏乃秦 《内陆地震》2004,18(3):193-201

在乌恰地区地震活动呈现长期平静异常的背景下,通过多种方法对2002年12月25日乌恰5．8级地震进行了1-3年的中长期预测。应用“模糊地震活动度”和“空区参数法”两种方法进行了1年和半年的中期预测,结合对该地区小震活动动态的分析与震例分析,尤其是预警地震的分析判断,提出了3个月的短期预测意见,较好地预测了这次地震。最后对预测情况进行了正反两个方面的总结和反思,提出了七点看法。  相似文献   

070703天长超级单体龙卷的多普勒雷达典型特征   总被引：10，自引：1，他引：9  

刘娟  朱君鉴  魏德斌  宋子忠  卢海  周红根 《气象》2009,35(10):32-39

主要使用南京多普勒天气雷达资料,分析了2007年7月3日发生在安徽天长和江苏高邮的龙卷风天气,着重分析了中气旋和龙卷涡旋特征(TVS)等产品的典型特征.龙卷发生在飑线回波带的北端强烈发展的超级风暴单体中,回波带前沿存在强烈的水平风切变,使得回波带上不断有中气旋生成.对产生龙卷的超级风暴单体,龙卷发生30min前,雷达给出了中气旋(M)产品,该中气旋持续了7个体扫的时间(42min),在中气旋出现后第5个体扫,雷达给出龙卷涡旋特征(TVS)产品,龙卷涡旋特征持续了3个体扫,综合切变产品也给出了显著的提醒.实地调查结果,龙卷风和第2个TVS同时发生,龙卷风位置与TVS位置对应,但位于TVS的南侧,位于中气旋最大风速圈的南缘.虽然CINRAD/SA雷达的TVS产品有虚警的情况,但结合反射率因子、平均径向速度、中气旋、综合切变等产品的分析,对于龙卷监测和预警会很有帮助的.  相似文献   

Age and metallicity of compact stellar systems in Virgo and Fornax     

P. Firth  E. A. Evstigneeva  M. J. Drinkwater 《Monthly notices of the Royal Astronomical Society》2009,394(4):1801-1811

From high signal-to-noise ratio GMOS-N and AAOmega spectra, we have measured line-strength indices in the Lick/IDS system for several luminous and spatially dispersed compact stellar systems (CSSs) located in the Virgo and Fornax galaxy clusters. We estimate their [α/Fe] ratios, ages and metallicities using a simple (single-burst) stellar population model. We confirm that the Virgo core region luminous CSSs (     ) contain ancient stellar populations with subsolar total metallicities, suggesting that they comprise the bright tail of M87's GC distribution. The two Virgo intracluster globular clusters have ages and metallicities consistent with the cluster core CSSs. Two Fornax luminous CSSs also have ancient stellar populations but are at the upper end of the Virgo CSS metallicity range, while the third (UCD3) appears to be relatively young, metal-rich and with a core + halo radial profile. Our results suggest that Fornax may contain an extra population of luminous CSSs formed more recently than the ancient GC-like systems found in both clusters.  相似文献   

Old stellar population synthesis： new age and mass estimates for Mayall Ⅱ = G1     

Jun Ma  ;Richard de Grijs  ;Zhou Fan  ;Soo-Chang Rey  ;Zhen-Yu Wu  ;Xu Zhou  ;Jiang-Hua Wu  ;Zhao-Ji Jiang  ;Jian-Sheng Chen  ;Kyungsook Lee  ;Sangmo Tony Sohn 《天体物理学报》2009,(6):641-652

Mayall Ⅱ = G1 is one of the most luminous globular clusters （GCs） in M31. Here, we determine its age and mass by comparing multicolor photometry with theoretical stellar population synthesis models. Based on far- and near-ultraviolet GALEX photometry, broad-band UBVRI, and infrared JHKs 2MASS data, we construct the most extensive spectral energy distribution of G 1 to date, spanning the wavelength range from 1538 to 20 000A. A quantitative comparison with a variety of simple stellar population （SSP） models yields a mean age which is consistent with G1 being among the oldest building blocks of M31 and having formed within ～1.7 Gyr after the Big Bang. Irrespective of the SSP model or stellar initial mass function adopted, the resulting mass estimates （of order 10^7M⊙） indicate that GI is one of the most massive GCs in the Local Group. However, we speculate that the cluster＇s exceptionally high mass suggests that it may not be a genuine GC. Our results also suggest that G1 may contain, on average, （1.65±0.63） × 10^2L⊙ far-ultraviolet-bright, hot, extreme horizontal-branch stars, depending on the adopted SSP model. In addition, we demonstrate that extensive multi-passband photometry coupled with SSP analysis enables one to obtain age estimates for old SSPs that have similar accuracies as those from integrated spectroscopy or resolved stellar photometry, provided that some of the free parameters can be constrained independently.  相似文献   

浅谈测绘的社会作用   总被引：4，自引：2，他引：2  

石如文 《测绘与空间地理信息》2005,28(2):40-41

人类社会已进入了崭新的信息化时代,测绘在经济建设和社会发展中起着非常重要的作用,测绘行业要努力为社会主义现代化建设提供测绘保障。  相似文献   

Globular clusters in the outer halo of M31: the survey     

A. P. Huxor  N. R. Tanvir  A. M. N. Ferguson  M. J. Irwin  R. Ibata  T. Bridges  G. F. Lewis 《Monthly notices of the Royal Astronomical Society》2008,385(4):1989-1997

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