航空重力测量中数字滤波器的设计与应用     

李姗姗 《测绘学院学报》1999,(2)

根据航空重力测量的要求以及滤波器的性能特点, 选择设计了适用于航空重力测量中ＧＰＳ高精度确定垂直扰动加速度的ＦＩＲ 低通滤波器和ＦＩＲ 低通微分器。并通过模拟数据的检测, 证明所设计的滤波器质量令人满意。  相似文献   

Resonant tidal excitations of rotating neutron stars in coalescing binaries     

Wynn C. G. Ho  Dong Lai 《Monthly notices of the Royal Astronomical Society》1999,308(1):153-166

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Secular instability of g-modes in rotating neutron stars     

Dong Lai 《Monthly notices of the Royal Astronomical Society》1999,307(4):1001-1007

Gravitational radiation tends to drive gravity modes in rotating neutron stars to become unstable. For an inviscid star, the instability sets in when the rotation frequency is about 0.7 times the corresponding mode frequency of the non-rotating star. Neutron stars with spin frequencies ≳100 Hz are susceptible to this instability, with a growth time of the order of years. However, it is likely that viscous dissipation suppresses the instability except for a narrow range of temperatures around 10⁹ K. We also show that the viscosity-driven instability of g-modes is absent.  相似文献   

The imprint of the equation of state on the axial w-modes of oscillating neutron stars     

Omar Benhar  Emanuele Berti  Valeria Ferrari 《Monthly notices of the Royal Astronomical Society》1999,310(3):797-803

We discuss the dependence of the pulsation frequencies of the axial quasi-normal modes of a non-rotating neutron star upon the equation of state describing the star interior. The continued fraction method has been used to compute the complex frequencies for a set of equations of state based on different physical assumptions and spanning a wide range of stiffness. The numerical results show that axial gravitational waves carry relevant information on both the structure of neutron star matter and the nature of the hadronic interactions.  相似文献   

The shape of 'dark matter' haloes of disc galaxies according to MOND     

Mordehai Milgrom 《Monthly notices of the Royal Astronomical Society》2001,326(4):1261-1264

Analyses of halo shapes for disc galaxies are said to give conflicting results. I point out that the modified dynamics (MOND) predicts for disc galaxies a distribution of fictitious dark matter that comprises two components: a pure disc and a rounder halo. The former dominates the true disc in regions of small accelerations, where it controls the z -dynamics in the disc (disc flaring etc.); it has a finite total mass. It also dominates the round component near the centre where the geometry is nearly planar. The second component controls motions far from the plane, has a total enclosed mass that diverges linearly with radius, and determines the rotation curve at large radii. Its ellipticity may be appreciable at small radii but vanishes asymptotically. This prediction of MOND differs from what one expects from galaxy formation scenarios with dark matter. Analyses to date, which, as they do, assume one component – usually with a constant ellipticity – perforce give conflicting results for the best value of ellipticity, depending on whether they probe the disc or the sphere, small radii or large ones.  相似文献   

Confrontation of MOdified Newtonian Dynamics with the rotation curves of early-type disc galaxies     

R. H. Sanders  E. Noordermeer 《Monthly notices of the Royal Astronomical Society》2007,379(2):702-710

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直接推导摄动运动方程的一种方法     

冯和生  李语强 《天文学报》2007,48(1):54-59

提出一种直接推导摄动运动方程的方法,也就是以矢量的微分运算为工具直接推导二体问题意义下的瞬时椭圆如何在摄动力三分力的作用下轨道根数发生的变化,推导过程几何图像清晰,力学意义明确．特别是对ω、M两根数的推导,比传统的方法更简洁、直观．  相似文献   

Erratum: The structure of superposed Weyl fields     

O. Semerák  T. Zellerin  M. &#;á&#;ek 《Monthly notices of the Royal Astronomical Society》2001,322(1):207-208

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Market areas – a methodological reflection on their boundaries     

Günter Löffler 《GeoJournal》1998,45(4):265-272

According to a classical definition the size of a market area results from the spatial range of the demanded and/or supplied goods and services. Distance-sales-relations or price-sales-relations produce overlapping and interconnecting sales cones with fuzzy limits in space. Thus the problem consists in identifying boundaries or edges of boundaries which result from the intensity of (spatial) spending power flows or spatial consumer shopping behaviour defining a system of functional regions. They can be estimated empirically by surveys or by mathematical models. In the former case the customer flows or spending power flows themselves are empirically recorded, in the latter they are determined from structure data of the supply and demand locations taking the distance barrier into consideration. The methods and their variants are described, their strengths and weaknesses discussed and possible areas of application presented. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

On radiating stellar collapse with shear     

Kesh S. Govinder  Megan Govender  & Roy Maartens 《Monthly notices of the Royal Astronomical Society》1998,299(3):809-810

Relativistic models of radiating stellar collapse with shear require careful checking of all the equations and quantities involved. We illustrate this by showing that, in a recently proposed model, the metric ansatz is in fact too restrictive to allow any radial evolution to occur, and only tangential evolution is possible. Furthermore, the assumption of pressure isotropy is shown to reduce the model to the static case without radiation or shear.  相似文献