A complete N-body model of the old open cluster M67     

Jarrod R. Hurley  Onno R. Pols  Sverre J. Aarseth  Christopher A. Tout 《Monthly notices of the Royal Astronomical Society》2005,363(1):293-314

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数据仓库技术在GSM网络预警系统中的应用     

孔珏  李志蜀  杨正海 《成都信息工程学院学报》2005,20(6):690-694

随着信息技术的发展，越来越多的组织机构需要能够更好的利用他们使用过的数据。由于操作型数据库是面向任务的，存放在这种数据库中的数据易变、不稳定，对企业决策过程支持力度不够。数据仓库中的数据是为查询分析特别构建的，数据仓库的目标是更有效的利用组织机构中已有的数据，辅助决策过程。结合TMN（电信管理网）的实际情况，讨论数据仓库技术以及OLAP分析模式在电信管理系统中的一个应用。  相似文献   

Molecular cloud regulated star formation in galaxies     

C. M. Booth  Tom Theuns  Takashi Okamoto 《Monthly notices of the Royal Astronomical Society》2007,376(4):1588-1610

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Star clusters with primordial binaries – III. Dynamical interaction between binaries and an intermediate-mass black hole     

Michele Trenti  Eliani Ardi  Shin Mineshige  Piet Hut 《Monthly notices of the Royal Astronomical Society》2007,374(3):857-866

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The minimum mass ratio of W UMa-type binary systems     

B. Arbutina 《Monthly notices of the Royal Astronomical Society》2007,377(4):1635-1637

When the total angular momentum of a binary system   J _tot= J _orb+ J _spin  is at a certain critical (minimum) value, a tidal instability occurs which eventually forces the stars to merge into a single, rapidly rotating object. The instability occurs when   J _orb= 3 J _spin  , which in the case of contact binaries corresponds to a minimum mass ratio   q _min≈  0.071–0.078. The minimum mass ratio is obtained under the assumption that stellar radii are fixed and independent. This is not the case with contact binaries where, according to the Roche model, we have   R ₂= R ₂( R ₁, a , q )  . By finding a new criterion for contact binaries, which arises from  d J _tot= 0  , and assuming   k ²₁≠ k ²₂  for the component's dimensionless gyration radii, a theoretical lower limit   q _min= 0.094–0.109  for overcontact degree   f = 0–1  is obtained.  相似文献   

Environmental influences on the morphology and dynamics of group-sized haloes     

Cinthia Ragone-Figueroa  Manolis Plionis 《Monthly notices of the Royal Astronomical Society》2007,377(4):1785-1794

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Redshift-space limits of bound structures     

Rolando Dünner  reas Reisenegger  rés Meza †  Pablo A. Araya  Hernán Quintana 《Monthly notices of the Royal Astronomical Society》2007,376(4):1577-1587

An exponentially expanding Universe, possibly governed by a cosmological constant, forces gravitationally bound structures to become more and more isolated, eventually becoming causally disconnected from each other and forming so-called 'island universes'. This new scenario reformulates the question about which will be the largest structures that will remain gravitationally bound, together with requiring a systematic tool that can be used to recognize the limits and mass of these structures from observational data, namely redshift surveys of galaxies. Here we present a method, based on the spherical collapse model and N -body simulations, by which we can estimate the limits of bound structures as observed in redshift space. The method is based on a theoretical criterion presented in a previous paper that determines the mean density contrast that a spherical shell must have in order to be marginally bound to the massive structure within it. Understanding the kinematics of the system, we translated the real-space limiting conditions of this 'critical' shell to redshift space, producing a projected velocity envelope that only depends on the density profile of the structure. From it we created a redshift-space version of the density contrast that we called 'density estimator', which can be calibrated from N -body simulations for a reasonable projected velocity envelope template, and used to estimate the limits and mass of a structure only from its redshift-space coordinates.  相似文献   

Regular motions in double bars – I. Double-frequency orbits and loops     

Witold Maciejewski  E. Athanassoula 《Monthly notices of the Royal Astronomical Society》2007,380(3):999-1008

Bars in galaxies are mainly supported by particles trapped around stable periodic orbits. These orbits represent oscillatory motion with only one frequency, which is the bar driving frequency, and miss free oscillations. We show that a similar situation takes place in double bars: particles get trapped around parent orbits, which in this case represent oscillatory motion with two frequencies of driving by the two bars, and which also lack free oscillations. Thus the parent orbits, which constitute the backbone of an oscillating potential of two independently rotating bars, are the double-frequency orbits. These orbits do not close in any reference frame, but they map on to closed curves called loops. Trajectories trapped around the parent double-frequency orbit map on to a set of points confined within a ring surrounding the loop.  相似文献   

Erratum: Effective collision strengths for ground-state and 2s²2p–2s2p² fine-structure transitions in C ii     

《Monthly notices of the Royal Astronomical Society》2006,373(2):879-880

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Microlensing in dark matter haloes     

Janne Holopainen  Chris Flynn  Alexander Knebe  Stuart P. Gill  Brad K. Gibson 《Monthly notices of the Royal Astronomical Society》2006,368(3):1209-1222

Using eight dark matter haloes extracted from fully self-consistent cosmological N -body simulations, we perform microlensing experiments. A hypothetical observer is placed at a distance of 8.5 kpc from the centre of the halo measuring optical depths, event durations and event rates towards the direction of the Large Magellanic Cloud. We simulate 1600 microlensing experiments for each halo. Assuming that the whole halo consists of massive astronomical compact halo objects (MACHOs),   f = 1.0  , and a single MACHO mass is   m _M= 1.0 M_⊙  , the simulations yield mean values of  τ= 4.7^+5.0_−2.2× 10⁻⁷  and  Γ= 1.6^+1.3_−0.6× 10⁻⁶  events star⁻¹ yr⁻¹. We find that triaxiality and substructure can have major effects on the measured values so that τ and Γ values of up to three times the mean can be found. If we fit our values of τ and Γ to the MACHO collaboration observations, we find   f = 0.23^+0.15_−0.13  and   m _M= 0.44^+0.24_−0.16  . Five out of the eight haloes under investigation produce f and m _M values mainly concentrated within these bounds.  相似文献