Registration of terrestrial laser scanner data using imagery     

Khalil  Al-Manasir  Clive S.  Fraser 《The Photogrammetric Record》2006,21(115):255-268

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建筑物立面激光点云的定位     

郭英  卢秀山  王冬 《测绘学院学报》2006,(1)

车载式近景目标3维测量系统,采用激光扫描仪获取建筑物立面点云。激光点云仅具有扫描仪坐标系下的坐标,不便于其他数据融合进行3维建模。文中根据系统的特点和要求,通过建立相应的坐标系,利用已有或优化的坐标转换模型确定坐标系之间的坐标转换关系。依据基准点与载体平台GPS接收机之间同步观测数据将激光点云在扫描仪坐标系下的坐标经过多次坐标转换,得到基准点所在当地坐标系下的坐标。使系统实现了满足精度要求的建筑物立面激光点云的定位工作。  相似文献   

A review and analyses of plumb-line calibration     

José L.  Lerma  Miriam  Cabrelles 《The Photogrammetric Record》2007,22(118):135-150

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X-ray binary unified analysis: pulse/RV application to Vela X1: GP Velorum     

Wilson  & Terrell 《Monthly notices of the Royal Astronomical Society》1998,296(1):33-43

A procedure for simultaneous analysis of multiple kinds of observations is developed for binaries that contain X-ray pulsars. A wide variety of observation types might be included, although we consider only velocity: pulse and light: velocity: pulse cases at present. The model operates with equipotentials and can accommodate non-synchronous rotation and eccentric orbits. The duration condition imposed by observed X-ray eclipses is incorporated as an embedded constraint, so that only solutions consistent with the eclipse duration are found. Relations needed for the method of differential corrections in least-squares solutions are specified, and we apply the Marquardt scheme for improvement of solution convergence. Parameters of Vela X1: GP Velorum are obtained from seven combinations of pulse and radial velocity data. The estimated masses are thereby put into some perspective, especially for the neutron star. The mass of the supergiant ( m  sin³  i ) now ranges only ±5 per cent from the mean of seven results, although the uncertainty in i makes the actual mass range larger. We discuss the determinacy of certain parameters and their historical consistency. For example, the systemic radial velocity differs among spectroscopic data sets by more than 20 km s⁻¹. We show that, contrary to published assertions, the orbital inclinations of high-mass X-ray binaries are essentially indeterminable by the usual methods, although lower limits to inclination may be meaningful for some examples.  相似文献   

High-velocity stars from decay of small stellar systems     

L. G. Kiseleva    J. Colin    B. Dauphole  & P. Eggleton 《Monthly notices of the Royal Astronomical Society》1998,301(3):759-766

In this paper we present numerical results on the decay of small stellar systems under different initial conditions (multiplicity 3 ≤  N  ≤ 10, and various mass spectra, initial velocities and initial configurations). The numerical treatment uses the CHAIN1 code (Mikkola &38; Aarseth). Particular attention is paid to the distribution of high-velocity escapers: we define these as stars with velocity above 30 km s⁻¹. These numerical experiments confirm that small N -body systems are dynamically unstable and produce cascades of escapers in the process of their decay. It is shown that the fraction of stars that escape from small dense stellar systems with an escape velocity greater than 30 km s⁻¹ is ∼1 per cent for all systems treated here. This relatively small fraction must be considered in relation to the rate of star formation in the Galaxy in small groups: this could explain some moderately high-velocity stars observed in the Galactic disc and possibly some young stars with relatively high metallicity in the thick disc.  相似文献   

Stream overflow and dwarf nova eruptions     

M. R. Schreiber  & F. V. Hessman 《Monthly notices of the Royal Astronomical Society》1998,301(3):626-630

We consider the effects of accretion stream overflow on the viscous dynamics of accretion discs in dwarf novae. If the stream from the secondary star is geometrically thick enough, some fraction of its material can flow over and under the disc. The mass and specific angular momentum of the stream are then deposited not only at the point of collision with the outer disc, but also at those radii in the inner disc with geometric heights that are large enough to intercept the residual stream, or near the radius where the disc has the same specific angular momentum as the stream. The overflowing stream can alter the behaviour of heating fronts and cooling fronts in the disc. If the mass fraction of the overflowing stream is of order tens of per cent, the deposition of mass in the inner parts of the disc is sufficient to change the character of the eruption light curves significantly.  相似文献   

An 'outside-in' outburst of Aql X–1     

T. Shahbaz  R. M. Bandyopadhyay  P. A. Charles  R. M. Wagner  P. Muhli  P. Hakala  J. Casares  & J. Greenhill 《Monthly notices of the Royal Astronomical Society》1998,300(4):1035-1040

We present optical spectroscopy and optical and infrared photometry of the neutron star soft X-ray transient Aql X–1 during its X-ray outburst of 1997 August. By modelling the X-ray, optical and IR light curves, we find a 3-d delay between the IR and X-ray rise times, analogous to the UV–optical delay seen in dwarf novae outbursts and black hole X-ray transients. We interpret this delay as the signature of an 'outside-in' outburst, in which a thermal instability in the outer disc propagates inward. This outburst is the first of this type definitively identified in a neutron star X-ray transient.  相似文献   

PSR J1012+5307: younger than it looks?     

L. Burderi  A. R. King  & G. A. Wynn 《Monthly notices of the Royal Astronomical Society》1998,300(4):1127-1130

Lorimer et al. have recently reported that the spin-down age (∼7 × 10⁹ yr) of the low-mass binary pulsar PSR J1012+5307 is much higher than the cooling age (3 × 10⁸ yr) of its white dwarf companion. The proposed solutions for this discrepancy are outlined and discussed. In particular, the revised cooling age estimate proposed by Alberts et al. agrees with data from other low-mass binary pulsar systems if a transition to the 'classical' cooling regime occurs between ∼0.14 and ∼0.28 M_⊙. If this transition is excluded, PSR J1012+5307 seems to have finished its accretion phase far from the spin-up line.  相似文献   

关于数字航测相机像移补偿问题   总被引：3，自引：0，他引：3  

常本义 《测绘学院学报》1998,(2)

航测相机像移补偿有两种方法 :一是在相机的焦平面上 ,使感光平面沿飞行方向 ,在曝光瞬间作一微小位移 ,以改正因摄影平台相对于被摄目标的运动引起的像点位移 ;二是在曝光瞬间 ,使相机作一微小的俯仰角旋转 ,以改正因摄影平台相对于被摄目标的运动引起的像点位移。前者简称为焦平面平移改正法 ,后者可称为俯仰旋转改正法。本文中研究了这两种像移补偿方法的差异和所能达到的精度水平及其适用范围  相似文献   

Gamma-ray bursts from stellar remnants: probing the Universe at high redshift     

Ralph A. M. J. Wijers  Joshua S. Bloom  Jasjeet S. Bagla  & Priyamvada Natarajan 《Monthly notices of the Royal Astronomical Society》1998,294(1):L13-L17

A gamma-ray burst (GRB) releases an amount of energy similar to that of a supernova explosion, which combined with its rapid variability suggests an origin related to neutron stars or black holes. Since these compact stellar remnants form from the most massive stars not long after their birth, GRBs should trace the star formation rate in the Universe; we show that the GRB flux distribution is consistent with this. Because of the strong evolution of the star formation rate with redshift, it follows that the dimmest known bursts have z  ∼ 6, much above the value usually quoted and beyond the most distant quasars. This explains the absence of bright galaxies in well-studied GRB error boxes. The increased distances imply a peak luminosity of 8.3 × 10⁵¹ erg s⁻¹ and a rate density of 0.025 per million years per galaxy. These values are 20 times higher and 150 times lower, respectively, than are implied by fits with non-evolving GRB rates. This means either that GRBs are caused by a much rarer phenomenon than mergers of binary neutron stars, or that their gamma-ray emission is often invisible to us due to beaming. Precise burst locations from optical transients will discriminate between the various models for GRBs from stellar deaths, because the distance between progenitor birth place and burst varies greatly among them. The dimmest GRBs are then the most distant known objects, and may probe the Universe at an age when the first stars were forming.  相似文献