Influence of the Choice of Core-Envelope Transition Point on the Binary Merger of Two Main-sequence Components     

Xue-Fei Chen  Zhan-Wen HanNational Astronomical Observatories  Yunnan Observatory  Chinese Academy of Sciences. Kunming  Graduate School of the Chinese Academy of Sciences  Beijing 《中国天文和天体物理学报》2005,5(1):65-76

We have studied the influence of different choices of core-envelope transition point on the final merger of contact binaries with two main-sequence components. A binary of 1.00 + 0.90M⊙ with an initial orbital period of 0.35d is examined. The mass fraction of the primary mixed with the matter of the secondary, qmix, determined by the chosen core-envelope transition point, ranges from 0.04 to 1.00 in our analysis. If as qmix< 0.8, none of the  相似文献   

Non‐equilibrium concepts lead to a unified explanation of the formation of chondrules and chondrites     

Milton BLANDER  Arthur D. PELTON  In‐Ho JUNG  Richard WEBER 《Meteoritics & planetary science》2004,39(12):1897-1910

Abstract— Calculations of the formation of seven types of chondrules in Semarkona from a gas of solar composition were performed with the FACT computer program to predict the chemistries of oxides (including silicates), developed by the authors and their colleagues. The constrained equilibrium theory was used in the calculations with two nucleation constraints suggested by nucleation theory. The first constraint was the blocking of Fe and other metal gaseous atoms from condensing to form solids or liquids because of very high surface free energies and high surface tensions of the solid and liquid metals, respectively. The second constraint was the blocking of the condensation of solids and the formation of metastable liquid oxides (including silicates) well below their liquidus temperatures. Our laboratory experiments suggested subcooling of type IIA chondrule compositions of 400 degrees or more below the liquidus temperature. The blocking of iron leads to a supersaturation of Fe atoms, so that the partial pressure of Fe (p_Fe) is larger than the partial pressure at equilibrium (p_Fe(eq)). The supersaturation ratio S = p_Fe/p_Fe(eq) becomes larger than 1 and increases rapidly with a decrease in temperature. This drives the reaction Fe + H₂O ? H₂ + FeO to the right. With S = 100, the activity of FeO in the liquid droplet is 100 times as large as the value at equilibrium. The FeO activities are a function of temperature and provide relative average temperatures of the crystallization of chondrules. Our calculations for the LL3.0 chondrite Semarkona and our study of some non‐equilibrium effects lead to accurate representations of the compositions of chondrules of types IA, IAB, IB, IIA, IIAB, IIB, and CC. Our concepts readily explain both the variety of FeO concentrations in the different chondrule types and the entire process of chondrule formation. Our theory is unified and could possibly explain the formation of chondrules in all chondritic meteorites as well as provide a simple explanation for the complex chemistries of chondrites, and especially for type 3 chondrites.  相似文献   

地壳对海洋潮汐的响应   总被引：2，自引：2，他引：0  

郑文衡  王乘  何振  牛安福 《大地测量与地球动力学》2002,22(2):41-46

应用三维动态有限元方法研究了中国北部地区的地壳对邻近的渤海与黄海海平面变化的响应。虽然此应力场过于微弱不足以引发地震，但发现应力集中的位置及应力场变化较大的位置恰好与某些现代地震的震中一致。这一结果表明研究地壳对广泛分布的载荷的响应对研究区域地震构造是有帮助的。  相似文献   

青藏块体东北缘断层形变与中强地震   总被引：7，自引：4，他引：3  

陈兵  江在森  马文静  黎凯武  薛富平 《大地测量与地球动力学》2002,22(4):49-55

对祁连山－海原断裂带近期断层形变特征进行了初步研究，发现多场地，大范围的断层活动异常是中等强度地震发生的显著背景，并且往往与大陆地震活动的阶段性总体状况相呼应；区域形变存在明显的特征量，包括特征形态和特征时间，同一场地在不同地震前的异常特征具有重复性，但会受到背景差异显著的不同地震的影响，目前形变状况表明研究区仍具有发生中强地震的地壳运动背景。  相似文献   

Strong Tides in 1964 and 1982     

Dianyou Chen  Xuexiang Yang  Qiyuan Qiao 《东北亚地学研究》2003,(1)

1StrongtideandastronomicalconditionsPartial solar eclipse occurred 4 times in 1964, 1982 and 2000 respectively. Time interval is about 3 Saros periods (one Saros period is 18 years and 10.33～11.33 days). Total lunar eclipse occurred 2 times in 1964 and 2000 respectively and 3 times in 1982. However, there was no lunar eclipse in 1966, 1984 and 2002. It seems that they had similar astro-nomical conditions and the best was in 1982. The studies about the effect of tide on the global climate…  相似文献   

A THREE-DIMENSIONAL ELASTIC NESTED-GRID MESO-(β-γ)SCALE ATMOSPHERIC MODEL——PARTI:MODEL DESCRIPTION          下载免费PDF全文

刘玉宝  周秀骥  胡志晋 《Acta Meteorologica Sinica》1993,(3)

A three-dimensional elastic nonhydrostatic mesoscale(β-γ)model with nested-grid is presented.It uses a set of fullequations in terrain-following coordinates as its basic dynamic frame,which is solved with a time-splitting algorithmfor acoustic and gravity waves.The model physical parameterization includes a K-theory subgrid eddy mixing for cloudand free atmosphere,a bulk planetary boundary layer parameterization,and three types of sofisticated cloudmicrophysics schemes with double-parameters for hail-bearing clouds,warm clouds and snowing clouds respectively.The model is designed to be used flexibly for simulations of a variety of meso-and small-scale atmospheric processes,and can be improved as a regional and local operational NWP system in future.  相似文献   

βCephei变星的脉动不稳定带的研究(英文)     

田斌 《紫金山天文台台刊》2003,(2)

在本文中我们对两种不同的 βCephei变星的理论脉动不稳定带作了比较。它们具有明显的不同之处。为了确定这种变星的脉动不稳定带的轮廓 ,我们根据 4 9颗 βCephei变星的观测资料作了统计研究。在从样本星的色指数 (B -V) ,(U -B)和视差得到它们的有效温度和光度之后 ,我们发现在赫罗图上它们大多数是位于主序带内的。而且这些样本星的质量都位于 7M⊙ 到 30M⊙ 之间。和理论模型的比较表明我们提出的具有光度上边界和红蓝边界的 βCephei变星的理论脉动不稳定带跟观测吻合得更好  相似文献   

Magnetic susceptibility variations of the Edicaran cap carbonates in the Yangtze platform and their implications for paleoclimate     

吴怀春  张世红  蒋干清  李海燕 《中国海洋湖沼学报》2005,(3)

1 INTRODUCTION One of the most intriguing phenomena in the late Neoproterozoic (~750 to 543 Ma) is the globa occurrence of thin carbonates that directly overlie glacial deposits in almost every continent (Kennedy 1996; Hoffman et al., 1998; Hoffman and Schrag 2002; Brasier and Shields, 2000; James et al., 2001 Jiang et al., 2003; Nogueira et al., 2003). These “cap carbonates”, commonly several to tens of meters thick, have attracted enormous interests because o their unusually negati…  相似文献   

An Atomic Force Microscopy study of the growth of calcite in the presence of sodium sulfate   总被引：1，自引：0，他引：1  

Aikaterini I. Vavouraki  Christine V. Putnis  Andrew Putnis  Petros G. Koutsoukos   《Chemical Geology》2008,253(3-4):243-251

In situ atomic force microscopy (AFM) has been used to compare the growth of pure calcite and the growth of calcite in the presence of sulfate ions from aqueous solutions at a constant value of supersaturation (S.I. = 0.89) with respect to calcite. The effect of sulfate ions on calcite growth rates is determined and a potential incorporation of sulfate ions is identified in the calcite during growth. Solutions supersaturated with respect to calcite with solution concentration ratio of one and a constant pH of 10.2, were prepared and sulfate was added as Na₂SO₄ aqueous solution. The solution composition was readjusted in order to keep the supersaturation and pH constant. PHREEQC was used to determine relevant solution concentrations. In situ AFM experiments of calcite growth were performed using a fluid cell and flowing solutions passed over a freshly cleaved calcite surface. Growth rates were determined from the closure of the rhombohedral etch pits induced by initial dissolution with pure water. The spreading rate of 2-dimensional nuclei was also measured. At low concentrations of sulfate (≤ 0.5 mM), no effect on the growth rate of the calcite was observed. At higher concentrations (2 to 3 mM) of sulfate, the growth rate increased, possibly because a higher concentration of calcium and carbonate was necessary to maintain the supersaturation constant. At much higher concentrations of additional sulfate (up to 60 mM) the growth rate of the calcite was substantially decreased, despite the fact that a further increase of calcium and carbonate was required. The morphology of 2-dimensional growth nuclei became increasingly elongated with increasing sulfate content. Measurements of step height showed that newly grown steps were approximately 1 Å higher when grown in high sulfate concentrations, compared to steps grown in sulfate-free solutions. At sulfate concentrations above 5 mM the growth mechanism changes from layer growth to surface roughening. These observations suggest that the new growth has incorporated sulfate into the calcite surface.  相似文献   

青藏高原西部赛利普中新世火山岩源区:地球化学及Sr-Nd同位素制约   总被引：11，自引：6，他引：5  

王保弟  许继峰  张兴国  陈建林  康志强  董彦辉 《岩石学报》2008,24(2)

青藏高原拉萨地块西部赛利普地区新生代火山岩依据主量元素可划分为超钾质、钾质和钙碱性系列,主要的岩石类型为粗面安山岩、粗面岩,一个超钾质岩石的40Ar-39Ar年龄为17.58Ma,指示出火山活动为中新世.超钾质、钾质和钙碱性火山岩都显示出富集LREE及LILE(Th、U)、亏损HFSE(Nb、Ta、Ti)的特征.超钾质火山岩具有较高的K2O(6.31%～8.55%)、MgO(6.75%～8.96%)、Cr(270.7×10-6～460.4×10-6)、Ni(142.3×10-6～233.9×10-6)含量,较高的(87Sr/86Sr)i(0.71883～0.72732)和较低的εNd(-14.78～-15.37),指示可能起源于一个前期亏损并经后期俯冲作用改造的富钾的方辉橄榄岩富集地幔源区.钾质火山岩具有比超钾质火山岩低的K2O、MgO、Cr、Ni含量以及高的Ba、Sr含量,初始87Sr/86Sr为0.71553～0.71628,初始143Nd/144Nd为0.51197～0.51198,在空间上与超钾质火山岩共生,可能是前者母岩浆的演化产物.钙碱性火山岩具有较高的Sr(881.7×10-6～1309.2×10-6)、Sr/Y比值(50～108)和较低的Y(12.05×10-6～18.02×10-6),明显亏损重稀土Yb(0.93×10-6～1.30×10-6),类似于典型的埃达克质岩成分特征但相对高钾,并具有相对低的(87Sr/86Sr);(0.70928～0.71374)以及高的εNd(-7.90～-10.91),指示起源于富钾增厚下地壳物质的部分熔融.区域上拉萨地块超钾质岩、钾质岩与N-S向地堑系在空间上共存、时间上相吻合,由此本文认为拉萨地块中新世钾质.超钾质岩和南北向地堑系的形成可能与中新世早期北向俯冲的印度大陆岩石圈断离有关.  相似文献