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The Amplitude of Mass Fluctuations and Mass Density of the Universe Constrained by Strong Gravitational Lensing

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chinese Journal of Astronomy and Astrophysics 2004年第2期4卷 118-124页

作者： Da-Ming ChenNational Astronomical Observatories, chinese academy of sciences, Beijing 100012 cdm@*** National Astronomical Observatories Chinese Academy of Sciences Beijing 100012

We investigate the linear amplitude of mass fluctuations in the universe, σ8, and the present mass density parameter of the Universe, Ωm, from statistical strong gravitational lensing. We use the two population model of lens halos with fixed cooling mass scale Mc = 3×1013h-1M⊙ to match the observed lensing probabilities, and leave σ8 orΩm as a free parameter to be constrained by the data. Another varying parameter, the equation of state of dark energy ω, and its typical values of -1, -2/3, -1/2 and -1/3 are investigated. We find that σ8 is degenerate with Ωm in a way similar to that suggested by present day cluster abundance as well as cosmic shear lensing measurements: σ8Ω0.6m≈0.33. However, both σ8≤0.7 and Ωm≤0.2 can be safely ruled out, the best fit is when σ8 = 1.0, Ωm = 0.3 and ω= - 1. This result is different from that obtained by Bahcall & Bode, who gave σ8 = 0.98±0.1 and Ωm = 0.17 ±0.05. For σ8 = 1.0, the higher value ofΩm = 0.35 requires ω = -2/3 and Ωm = 0.40 requires ω= -1/2.

关键词： cosmology: theory - cosmological parameters - gravitational lensing

A Note on the Mixing Length Theory and Massive Star Evolution

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chinese Journal of Astronomy and Astrophysics 2001年第1期1卷 50-56页

作者： Li-Cai Deng and Da-Run Xiong ( Beijing Astronomical Observatory, chinese academy of sciences, Beijing 100012 Purple Mountain Observatory, chinese academy of sciences, Nanjing210008 National Astronomical Observatories, chinese academy of sciences, Beij CAS-Peking University Joint Beijing Astrophysical Center Beijing 100871

In this paper, we investigate the problem of supersonic convection caused by the application of the usual Mixing Length Theory (MLT), and give a modification to the original expression of the MLT. In the case of the usual MLT, a zone of supersonic convection exists when the stellar model goes into yellow-red supergiant phase. When the modification is applied, the models of late type supergiants possess shallower convective envelopes for a given temperature compared with the normal formalism of the MLT. Therefore the stellar models made with our new formalism move to lower effective temperature by 100-400 K depending on the luminosity of the star. Such a modification does not affect the convective envelope structure of lower luminosity late type stars, as both expressions of the MLT give the same result. In these stars.

关键词： convection - stars: supergiants - stars: massive stars - stars: evolution

A Possible Origin of 6.7 GHz Linear Methanol Maser Sources

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chinese Journal of Astronomy and Astrophysics 2001年第5期1卷 389-394页

作者： Ye Xu (Shanghai Astronomical Observatory, chinese academy of sciences, Shanghai 200030) (Urumqi Astronomical Observatory, chinese academy of sciences, Urumqi 830011) (National Astronomical Observatories, chinese academy of sciences, Beijing 100012) E-mail Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 []Urumqi Astronomical Observatory Chinese Academy of Sciences Urumqi 830011 []National Astronomical Observatories Chinese Academy of Sciences Beijing 100012

We present a model which explains the observed multi-linear spatial structures with different velocity gradients of the 50-61A+ methanol line at 6.7 GHz. We consider this and other hypotheses and conclude that the met... 详细信息

关键词： masers - stars: circumstellar matter - stars: formation

Wavelet Analysis of the Schwabe Cycle Properties in Solar Activity

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chinese Journal of Astronomy and Astrophysics 2004年第6期4卷 578-582页

作者： Gui-Ming LeNational Astronomical Observatories, chinese academy of sciences, Beijing 100012 Center for Space Science and Applied Research Center, chinese academy of sciences, Beijing 100080 National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 []Center for Space Science and Applied Research Center Chinese Academy of Sciences Beijing 100080

Properties of the Schwabe cycles in solar activity are investigated by using wavelet transform. We study the main range of the Schwabe cycles of the solar activity recorded by relative sunspot numbers, and find that the main range of the Schwabe cycles is the periodic span from 8-year to 14-year. We make the comparison of 11-year’s phase between relative sunspot numbers and sunspot group numbers. The results show that there is some difference between two phases for the interval from 1710 to 1810, while the two phases are almost the same for the interval from 1810 to 1990.

关键词： sun sunspot sun activity method data analysis

A TRUST REGION METHOD FOR SOLVING DISTRIBUTED PARAMETER IDENTIFICATION PROBLEMS

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Journal of Computational Mathematics 2003年第6期21卷 759-772页

作者： Yan-fei Wang Ya-xiang Yuan(LSEC, ICMSEC, academy of Mathematics and System sciences, chinese academy of sciences,Beijing 100080, China) LSEC ICMSEC Academy of Mathematics and System Sciences Chinese Academy of Sciences Beijing 100080 China

This paper is concerned with the ill-posed problems of identifying a parameter in an elliptic equation which appears in many applications in science and industry. Its solution is obtained by applying trust region method to a nonlinear least squares error problem. Trust region method has long been a popular method for well-posed problems. This paper indicates that it is also suitable for ill-posed problems. Numerical experiment is given to compare the trust region method with the Tikhonov regularization method. It seems that the trust region method is more promising.

关键词： Parameter identification Ill-posed problems Trust region.

CONSTRUCTION OF A PRECONDITIONER FOR DOMAIN DECOMPOSITION METHODS WITH POLYNOMIAL LAGRANGIAN MULTIPLIERS

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Journal of Computational Mathematics 2001年第2期19卷 213-224页

作者： Qi-ya Hu (Institute of Computational Mathematics, academy of Mathematics and Systems sciences, chinese academy of sciences, Beijing 100080, China) Guo-ping Liang Jin-zhao Liu (Institute of Mathematics, academy of Mathematics and Systems sciences, chinese 中科院计算数学与工程计算数学所北京 100080 中科院数学所北京 100080

In this paper we consider domain decomposition methods with polynomial Lagrangian multipliers to two-dimentional elliptic problems, and construct a kind of simple preconditioners for the corresponding interface equation. It will be shown that condition number of the resulting preconditioned interface matrix is almost optimal (namelys it has only logarithmic growth with dimension of the local interface space).

关键词： Domain Decomposition Non-matching grids Lagrangian multipliers Preconditioner Condition number.

An Efficient High-Resolution Shock-Capturing Scheme for Multi-Dimensional Flows I. Hydrodynamics

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chinese Journal of Astronomy and Astrophysics 2006年第6期6卷 680-688页

作者： Cong Yu National Astronomical Observatories / Yunnan Astronomical Observatory, chinese academy of sciences, Kunming 650011 Graduate School of chinese academy of sciences, Beijing 100049 Graduate School of chinese academy of sciences Beijing 100049

Many problems at the forefront of theoretical astrophysics require a treatment of dynamical fluid behavior. We present an efficient high-resolution shock-capturing hydrodynamic scheme designed to study such phenomena. We have implemented a weighted, essentially non-oscillatory （WENO） scheme to fifth order accuracy in space, lILLE approximate Riemann solver is used for the flux computation at cell interface, which does not require spectral decomposition into characteristic waves and so is computationally friendly. For time integration we apply a third order total variation diminishing （TVD） Runge-Kutta scheme. Extensive testing and comparison with schemes that *** characteristic decomposition are carried out demonstrating the ability of our scheme to address challenging open questions in astrophysics.

关键词： accretion - hydrodynamics- method numerical - shock waves

Investigation of a New Exsolved Cu-Fe-S Phase in“Abnormal Sphalerite”

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Acta Geologica Sinica(English Edition) 1991年第1期65卷 27-36,110-111页

作者： Li Jiuling Wang Su Institute of Mineral Deposits, chinese academy of Geolgical sciences,Beijing Beijing Laboratory of Electron Microscopy, chinese academy of sciences, Beijing Institute of Mineral Deposits Chinese Academy of Geolgical Sciences Beijing China

A new exsolved copper-iron-sulfur phase in sphalerite has been found in the Dajing cassiterite- sulfidecopper-silver-tin deposit, Inner Mongolia, China. After investigating the optical properties, chemical composi-tion, crystal structure and exsolved Characters of the exsolved phase, the authors present important evidencefor its being a new exsolved copper-iron-sulfur phase mineral. Its formation mechenism is discussed in consider-ing heating experiments, phase equilibrium data and the geology of the deposit.

关键词： Ph Fe Abnormal Sphalerite Cu

Vertical Scale Parameter Estimates for 48 Non-edge-on Spiral Galaxies

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chinese Journal of Astronomy and Astrophysics 2003年第6期3卷 499-504页

作者： Jun MaNational Astronomical Observatories, chinese academy of sciences, Beijing 100012 National Astronomical Observatories CAS NAOC Beijing 100012 China

In the first paper of this series, we directly studied the mathematicalforms, symmetry of spiral structure, and the projection of galactic discs on the images, andmeasured the pitch angles of the spiral arms and inclination angles of the galactic discs for 60spiral galaxies. In this second paper, we estimate the vertical scale parameters of 48 non-edge-onspiral galaxies based on the method proposed by Peng et al. and on the results given in Paper I. Aswe know, for edge-on disc galaxies we can obtain the vertical scale parameter from the photometry,once a mathematical form is specified for the vertical light distribution. For non-edge-on galaxies,some other methods have to be used. The statistical result was that the vertical scale parameter iscomparable for edge-on and non-edge-on galaxies, although it is obtained from two very differentmethods.

关键词： galaxies: spiral galaxies galaxies: vertical scale parameter