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Wareing CJ 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2008,366(1884):4429-4440
Since being named 'wonderful' in the seventeenth century for its peculiar brightness variability, Mira A has been the subject of extensive research and become the prototype for a whole class of 'Mira' variable stars. The primary star in a binary system, Mira A is reaching the end of its life and currently undergoing an extended period of enhanced mass loss. Recent observations have revealed a surrounding arc-like structure and a stream of material stretching 12 light years away in opposition to the arc. In this article, I review recent modelling of this cometary appearance as a bow shock with an accompanying tail of material ram pressure stripped from the head of the bow shock, place Mira in an evolutionary context, predict its future with reference to the similar star R Hya and planetary nebula Sh 2-188, and speculate some avenues of research both on Mira itself and on other 'Mira-like' stars with bow shocks and tails. I also discuss the implications of this discovery for our own star, the Sun. 相似文献
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嵊州,地处浙江东部,这里气候温和,四面环山,群山众谷,林木茂密,得天独厚的自然条件,孕育出一朵独特的工艺之花--嵊州根雕. 相似文献
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油墨的吸收性是印刷质较短的时间尺度上分析油墨与纸张的接触过程,从而建立模型.探讨油墨吸收性对印刷质量的影响,并提出解决办法. 相似文献
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Journal of Superconductivity and Novel Magnetism - The magnetic moment of a spherical superconductor that is located on the axis of the external axisymmetric magnetic field is found. It is proved... 相似文献
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When an unknown (target) probability density function (pdf) is to be reconstructed from its moments with the aid of a multiparametric (or semi-parametric) representation model, a large number of constraints (moment equations) is needed, usually larger than the unknown parameters. However, there is a strong belief, expressed by various authors, see Fasino D, Inglese G (Rendiconti dell' Istituto di Matematica dell' Università di Trieste XXVIII (1996) 183], and French JB [In: Dalton BJ, et al., Theory and application of moments problems in many-fermion systems (1979) 1], that most of the information defining a compactly supported pdf is usually contained in its first few moments. In addition, numerical experimentation has shown [Probab Engng Mech 17 (2002) 273] that the variation of the reconstructed pdf when higher-order moments vary within the recursively defined moment bounds, is weak, becoming insignificant as the moment order N increases. Based on these observations, we propose a method for extending a set of given moments, in cases that they are insufficient for solving the Hausdorff moment problem using a multiparametric model. Additional moments, compatible with the given ones, are obtained by exploiting upper and lower moment bounds. Then, two sequences of ‘dual’ (upper and lower) approximant pdfs are constructed, along with an easily realizable criterion of mutual convergence. The numerical performance and consistency of the solution algorithm have been illustrated for unimodal and bimodal pdfs. 相似文献