用多变量时间序列相关模型预测矿井涌水量   总被引：3，自引：0，他引：3  

杨永国  谢克俊 《煤田地质与勘探》1995,23(6):38-42

运用多变量时间序列分析方法，建立了南桐煤矿二井的涌水量与降雨量之间的相关模型，并将其用于矿井涌水量的预测，结果表明，南桐二井涌水量与降雨量呈滞后一个月、三个月和三年的关系，预测结果与实测值对比分析表明，本模型的预测结果精度较高。  相似文献   

大青沟国家自然保护区地面苔藓植物分布格局   总被引：1，自引：1，他引：0  

田桂泉  韩淑美  苏日古嘎 《中国沙漠》2018,38(3):545-552

用双向指示种分析（TWINSPAN）、除趋势对应分析（DCA）和典范对应分析（CCA）研究了大青沟国家自然保护区32个样地36种地面生苔藓植物分布格局。TWINSPAN和DCA分析结果显示,地面生苔藓植物群落可以分成双色真藓（Bryum bicolor）-小石藓（Weissia controversa）群落、西伯利亚瘤冠苔（Mannia sibirica）+小石藓（Weissia controversa）群落、密叶绢藓短柄变种（Entodon compressus var.zikaiwiensis）-密叶绢藓（Entodon compressus）+反扭藓（Timmiella anomala）群落、绒叶青藓（Brachythecium velutinum）-鳞叶藓（Taxiphyllum taxirameum）+尖叶匐灯藓（Plagiomnium cuspidatum）群落和地钱（Marchantia polymorpha）+曲肋薄网藓（Leptodictyum humile）-鳞叶藓（Taxiphyllum taxirameum）-柳叶藓（Amblystegium serpens）+平肋提灯藓（Mnium laevinerve）群落5组,对应分布在羊草（Leymus chinensis）草地、西伯利亚杏（Prunus sibirica）灌丛、大果榆（Ulmus macrocarpa）林、蒙古栎（Quercus mongolica）林和水曲柳（Fraxinus mandschuria）林。CCA分析结果显示,影响苔藓植物分布的主要因子有土壤水分、乔木盖度、空气湿度、凋落物盖度、草本层盖度等。  相似文献   

Evidence for pole switching in the magnetic cataclysmic variable BY Camelopardalis     

Paul A. Mason  Gavin Ramsay  Ivan Andronov  Sergey Kolesnikov  Nickolay Shakhovskoy  & Elana Pavlenko 《Monthly notices of the Royal Astronomical Society》1998,295(3):511-518

An analysis of X-ray and optical light curves of the magnetic cataclysmic variable (MCV) BY Cam is presented. This system is one of three MCVs in which the spin period of the white dwarf and the binary orbital period differ by ∼1 per cent. As such these 'BY Cam' stars are important objects with which to probe the field structure of the magnetic white dwarf and ultimately the nature of synchronization of AM Her binaries. We confirm asynchronous rotation of the magnetic white dwarf with respect to the binary. We find evidence that the accretion stream accretes directly on to the white dwarf as in AM Her systems, but further, the stream impacts on to different magnetic poles over the course of the beat period. We present evidence that the optical and hard X-ray light curves modulate in phase, but together they are out of phase with the soft X-ray light curve. We confirm the spin down of the white dwarf which is expected to lead to the synchronization of the spin and orbital periods of BY Cam.  相似文献   

Radiation-driven winds from luminous accretion discs     

Daniel Proga  James M. Stone  & Janet E. Drew 《Monthly notices of the Royal Astronomical Society》1998,295(3):595-617

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Large-amplitude periodic variations in the angular diameter of R Leonis     

D. Burns  J. E. Baldwin  R. C. Boysen  C. A. Haniff  P. R. Lawson  C. D. Mackay  J. Rogers  T. R. Scott  D. St.-Jacques  P. J. Warner  D. M. A. Wilson  & J. S. Young 《Monthly notices of the Royal Astronomical Society》1998,297(2):462-466

We report the first direct detection of long-term periodic diameter variations in a Mira variable. Angular diameter measurements of the 313-d period variable R Leonis at 833 nm and 940 nm obtained between 1996 February and 1997 June using the Cambridge Optical Aperture Synthesis Telescope (COAST) and the William Herschel Telescope (WHT) show a cyclic modulation of the apparent stellar diameter by approximately 35 per cent. The agreement between these new data and archival measurements from 1992 January suggests coherence in the modulation over a 5-yr period. Our data are consistent with recent models which suggest that, in photometric bands with only weak to moderate molecular contamination, periodic variations in stellar diameter of order 50 per cent can be maintained. The measurements indicate that the apparent stellar diameter was largest at visual phase 0.5 and that any phase shifts between the visual light curve and those at 833 and 940 nm were at most 0.05. The large offset (∼ 0.25) between the phase of the observed diameter maximum and that predicted for the photospheric continuum diameter variations suggests that our observations are more sensitive to the changing temperature structure of the outer atmosphere than to the deeper continuum-forming layers.  相似文献   

An averaging method to study the motion of lunar artificial satellites II: Averaging and Applications     

Daniel Steichen 《Celestial Mechanics and Dynamical Astronomy》1998,68(3):225-247

On this, the second part of a two part study (Steichen, 1998) we further develop a semi-analytical theory for a lunar artificial satellite. This theory is obtained by averaging analytically the Hamiltonian function over period up to a month. The averaged equations are then numerically integrated. The solution is free from singularities at e = 0 and I = 0 and is not expanded in powers of these variables. In the last section, the analytic work is applied to characteristic examples to validate the method used. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Accretion disc outbursts: a new version of an old model   总被引：1，自引：0，他引：1  

Jean-Marie Hameury  Kristen Menou  Guillaume Dubus  Jean-Pierre Lasota  & Jean-Marc Huré 《Monthly notices of the Royal Astronomical Society》1998,298(4):1048-1060

We have developed 1D time-dependent numerical models of accretion discs, using an adaptive grid technique and an implicit numerical scheme, in which the disc size is allowed to vary with time. The code fully resolves the cooling and heating fronts propagating in the disc. We show that models in which the radius of the outer edge of the disc is fixed produce incorrect results, from which probably incorrect conclusions about the viscosity law have been inferred. In particular we show that outside-in outbursts are possible when a standard bimodal behaviour of the Shakura–Sunyaev viscosity parameter α is used. We also discuss to what extent insufficient grid resolution has limited the predictive power of previous models. We find that the global properties (magnitudes, etc.) of transient discs can be addressed by codes using a high, but reasonable, number of fixed grid points. However, the study of the detailed physical properties of the transition fronts generally requires resolutions which are out of reach of fixed grid codes. It appears that most time-dependent models of accretion discs published in the literature have been limited by resolution effects, improper outer boundary conditions, or both.  相似文献   

Mapping the β Cephei instability strip: photometric variability of stars in the central part of the Cygnus OB2 association     

A. Pigulski  & Z. Ko&#;aczkowski 《Monthly notices of the Royal Astronomical Society》1998,298(3):753-762

The central part of the Cygnus OB2 association was searched for the presence of short-period hot pulsators. Out of 16 O-type stars in the field, five turned out to be variable. None of the O-type variables showed short-period variations characteristic for the β Cephei-type stars. However, two β Cephei stars were found among the early B-type members of the association. Their pulsation periods are too long to be in agreement with the average association age. We note that the discrepancy can be explained by non-coeval star formation, which was already suggested by other authors from the investigation of the colour–magnitude diagrams of the association.   We found 29 new variables in all fields searched by us. About half of these are Cygnus OB2 members. By means of Hα photometry, we confirmed the presence of Hα emission in two stars and found one new Be star. A weak Hα emission is probably present in all observed O-type supergiants and giants. We also give the new BVRI Hα photometry for almost 300 stars. This multicolour photometry is used to determine a dereddened colour–magnitude diagram for the association and make a reddening map of the observed field. The extinction in the field, expressed as the total absorption in the Johnson V filter, A _v , ranges from 4.1 to 7.0 mag; the average A _V amounts to 5.8 mag. One O-type star is probably a background object.  相似文献   

Evidence for a rotational velocity field about the white dwarf of V347 Puppis     

M. D. Still  D. A. H. Buckley  & M. A. Garlick 《Monthly notices of the Royal Astronomical Society》1998,299(2):545-553

We present time-resolved optical spectroscopy of the deeply eclipsing nova-like binary V347 Pup, which provides evidence for a rotational velocity field in the low-excitation lines, as expected from accretion disc emission. The low-excitation line profiles are a composite of the disc and the irradiated inner-face of the donor star. This picture is remarkably simple compared to the other members of the eclipsing nova-like family. Unsatisfactory radial velocity solutions for the accreting object provided by standard methods encourage us to apply a technique developed to measure stellar motion from tomographic reconstructions of the time-dependent line profiles. We find some evidence for a spiral pattern over the disc and for disc-overflow accretion. If the emission distribution proves to be a long-term feature, V347 Pup will provide an opportunity to study disc kinematics with greater confidence than allowed by the other eclipsing nova-like objects.  相似文献   

A frequency analysis of the p-mode pulsations of the Ap SrEu(Cr) star HD 119027     

Peter Martinez  C. Koen  & D. J. Sullivan 《Monthly notices of the Royal Astronomical Society》1998,300(1):188-192

We present new high-speed, multisite photometric observations of the rapidly oscillating Ap star HD 119027 acquired over seven nights during 1996. A frequency analysis of these observations reveals the presence of oscillations at 1835, 1875, 1888, 1913, 1940, 1942 and (possibly) 1953 μHz. These frequencies are consistent with a spacing of either 13 or 26 μHz, depending on the reality of the oscillations at 1875 and 1953 μHz. The data in hand do not permit us to discriminate between the two possible spacings. If the smaller value of the spacing is correct, it suggests that HD 119027 is outside the main-sequence band. Two of the frequencies listed above are separated by only 1.95 μHz, suggesting that they are modes of ( n ,ℓ) and ( n  − 1, ℓ + 2), which in roAp stars is a quantity governed by the internal magnetic field.  相似文献