Enhanced Star Formation in Seyfert 2 Galaxies     

Q.-S. Gu  J.-H. Huang  L. Ji 《Astrophysics and Space Science》1998,260(3):389-396

In this paper, we report our preliminary results on enhanced star formation activity in Seyfert 2 galaxies. By re-analysing the Tully-Fisher relation for Whittle's (1992) sample and for a Seyfert 2s' sample selecting from Veron-Cetty and Veron (1996), we find that (1) almost all Seyfert 2 galaxies with circumnuclear star formation have a ratio of far infrared (FIR) to blue luminosities (L_FIR/L_B) to be larger than 1/3; (2) for Seyfert 2 galaxies with L_FIR/L_B > 1/3, the Tuly-Fisher relation is similar to that of the normal spiral galaxies; while for those with L_FIR/L_B ≥ 1/3, they are significantly different from the normal ones, which confirms Whittle's suggestion of enhanced star formation activities in the circumnuclear regions of these Seyfert 2 galaxies. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Inflation in Bianchi type-IX Einstein-Cartan Cosmological Model     

K.H. Kong  P.C.H. Cheung  H.Q. Lu  K.S. Cheng 《Astrophysics and Space Science》1998,260(4):521-529

Within the framework of Einstein-Cartan theory with Weyssenhoff fluid, we investigate an inflation model for an anisotropic Bianchi type-IX cosmological model. The system of field equations is solved numerically and an inflation epoch is achieved. The general condition for the inflation to occur is also discussed. This anisotropic model evolves quickly towards to an isotropic one.  相似文献   

Secular variation of the direction of the ancient geomagnetic field for Loyang region,China     

Q.Y. Wei  T.C. Li  G.Y. Chao  W.S. Chang  S.P. Wang 《Physics of the Earth and Planetary Interiors》1981,25(1):107-112

Curves of the variation of the inclination and declination of the geomagnetic field for the Loyang region during the last 2400 years are presented. An I-D diagram of secular variation, like that for London, has been drawn for Loyang.  相似文献   

Tunneling in rock : Ernest E. Wahlstrom. Elsevier Scientific Publishing Company, Amsterdam, 1973, 250 pp, 121 fig., 22 tables, Dfl. 55,00     

Q. Zruba 《Tectonophysics》1974,22(1-2)

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Contribution of water vapour dimers to clear sky absorption of solar radiation     

PETR CHÝLEK  Q. FU  H. C. W. TSO  D. J. W. GELDART 《地球，A辑:动力气象学与海洋学》1999,51(2):304-313

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A statistical study of Galactic SNRs using the PMN survey     

M. Stupar  M. D. Filipović  Q. A. Parker  G. L. White  T. G. Pannuti  P. A. Jones 《Astrophysics and Space Science》2007,307(4):423-435

The Parkes–MIT–NRAO (PMN) radio survey has been used to generate a quasi all-sky study of Galactic Supernova Remnants (SNRs) at a common frequency of 4.85 GHz (λ=6 cm). We present flux densities estimated for the sample of 110 Southern Galactic SNRs (up to δ=−65°) observed with the Parkes 64-m radio telescope and an additional sample of 54 from the Northern PMN (up to δ=+64°) survey undertaken with the Green Bank 43-m (20 SNRs) and 91-m (34 SNRs) radio telescopes. Out of this total sample of 164 selected SNRs (representing 71% of the currently 231 known SNRs in the Green catalogue) we consider 138 to provide reliable estimates of flux density and surface brightness distribution. This sub-sample represents those SNRs which fall within carefully chosen selection criteria which minimises the effects of the known problems in establishing reliable fluxes from the PMN survey data. Our selection criteria are based on a judicious restriction of source angular size and telescope beam together with careful evaluation of fluxes on a case by case basis. Direct comparison of our new fluxes with independent literature values gives excellent overall agreement. This gives confidence in the newly derived PMN fluxes when the selection criteria are respected. We find a sharp drop off in the flux densities for Galactic SNRs beyond 4 Jy and then a fairly flat distribution from 5 to 9 Jy, a slight decline and a further flat distribution from 9 to 20 Jy though the numbers of SNR in each Jy bin are low. We also re-visit the contentious Σ–D (radio surface brightness–SNRs diameter) relation to determine a new power law index for a sub-sample of shell type SNRs which yields β=−2.2±0.6. This new evaluation of the Σ–D relation, applied to the restricted sample, provides new distance estimates and their Galactic scale height distribution. We find a peak in the SNR distribution between 7–11 kpc with most restricted to ±100 pc Galactic scale height.  相似文献   

Homogenization‐based analysis of anisotropic damage in brittle materials with unilateral effect and interactions between microcracks     

Q. Z. Zhu  D. Kondo  J. F. Shao 《国际地质力学数值与分析法杂志》2009,33(6):749-772

This paper is devoted to micromechanical modeling of induced anisotropic damage in brittle geomaterials. The formulation of the model is based on a proper homogenization procedure by taking into account unilateral effects and interactions between microcracks. The homogenization procedure is developed in the framework of Eshelby's inclusion solution and Ponte‐Castaneda and Willis (J. Mech. Phys. Solids 1995; 43 :1919–1951) estimate. The homogenization technique is combined with the thermodynamics framework at microscopic level for the determination of damage evolution law. A rigorous crack opening–closure transition condition is established and an energy‐release‐rate‐based damage criterion is proposed. Computational aspects on the implementation of micromechanical model are also discussed. The proposed model is evaluated by comparing numerical predictions with experimental data for various laboratory tests on concrete. Parametric studies on unilateral effects and influences of microcracks interactions are finally performed and analyzed. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Vertical dynamic response of a rigid foundation embedded in a poroelastic soil layer     

Y. Q. Cai  X. Q. Hu  C. J. Xu  Z. S. Hong 《国际地质力学数值与分析法杂志》2009,33(11):1363-1388

A simplified analytical method is presented for the vertical dynamic analysis of a rigid, massive, cylindrical foundation embedded in a poroelastic soil layer. The foundation is subjected to a time‐harmonic vertical loading and is perfectly bonded to the surrounding soil in the vertical direction. The soil underlying the foundation base is represented by a single‐layered poroelastic soil based on rigid bedrock while the soil at the side of the foundation is modeled as an independent poroelastic layer composed of a series of infinitesimally thin layers. The behavior of the soil is governed by Biot's poroelastodynamic theory and its governing equations are solved by the use of Hankel integral transform. The contact surface between the foundation base and the soil is smooth and fully permeable. The dynamic interaction problem is solved following standard numerical procedures. The accuracy of the present solution is verified by comparisons with the well‐known solutions obtained from other approaches for both the elastodynamic interaction problem and poroelastodynamic interaction problem. Numerical results for the vertical dynamic impedance and response factor of the foundation are presented to demonstrate the influence of nondimensional frequency of excitation, soil layer thickness, poroelastic material parameters, depth ratio and mass ratio on the dynamic response of a rigid foundation embedded in a poroelastic soil layer. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Absolute Magnitudes of Be Stars Based on Hipparcos Parallaxes     

P. Zhang  C. Q. Liu  P. S. Chen 《Astrophysics and Space Science》2006,306(3):113-128

The absolute visual magnitudes of 457 Be stars are determined from Hipparcos parallaxes, subsequently the mean absolute visual magnitudes of Be stars for luminosity classes III, IV and V are obtained. The new Mv calibration is compared with existing calibrations. It is found that Be stars are generally brighter than B stars of the corresponding spectral types, and that there is no direct correlation between absolute magnitudes and the stellar rotational velocity, these results are in agreement with some earlier results. A new and interesting result is that there is no direct correlation between near infrared excess and absolute visual magnitudes for Be stars. Moreover, possible biases, such as the Malmquist bias and the Lutz–Kelker bias, are also discussed.  相似文献   

Orientation of Galaxies in the Local Supercluster: A Review     

F. X. Hu  G. X. Wu  G. X. Song  Q. R. Yuan  S. Okamura 《Astrophysics and Space Science》2006,302(1-4):43-59

The progress of the studies on the orientation of galaxies in the Local Supercluster (LSC) is reviewed and a summary of recent results is given. Following a brief introduction of the LSC, we describe the results of early studies based on two-dimensional analysis, which were mostly not conclusive. We describe next the three-dimensional analysis, which is used widely today. Difficulties and systematic effects are explained and the importance of selection effects is described. Then, results based on the new method and modern databases are given, which are summarized as follows. When the LSC is seen as a whole, galaxy planes tend to align perpendicular to the LSC plane with lenticulars showing the most pronounced tendency. Projections onto the LSC plane of the spin vectors of Virgo cluster member galaxies, and to some extent, those of the total LSC galaxies, tend to point to the Virgo cluster center. This tendency is more pronounced for lenticulars than for spirals. It is suggested that ‘field’ galaxies, i.e., those which do not belong to groups with more than three members, may be better objects than other galaxies to probe the information at the early epoch of the LSC formation through the analysis of galaxy orientations. Field lenticulars show a pronounced anisotropic distribution of spin vectors in the sense that they lay their spin vectors parallel to the LSC plane while field spirals show an isotropic spin-vector distribution.  相似文献