Unsteady mass outflow from Wolf-Rayet stars

We show that hydrostatically equilibrium models for the thin photospheres of helium stars based on new opacities κ_R (OPAL and OP) can be constructed only for masses M<5M _⊙. The parameter Г=κL/4πGMc, defined as the ratio of light pressure to gravity, exceeds a critical value of 1.0 for larger masses, which must result in mass outflow under light pressure. This mass limit matches the observed lower limit for the masses of Wolf-Rayet stars (M _WR>5M _⊙)), which is an additional argument that the Wolf-Rayet stellar cores are actually helium stars. By solving the equation of radiative transfer in extended atmospheres, we construct a semiempirical model for a WN5 star (M _WN5=10M _⊙)) with a helium core and an expanding envelope, whose physical and geometric parameters are known mainly from light-curve solution for the eclipsing binary V444 Cyg (WN5+06): outflow rate $\dot M \approx 1.0 \times 10^{ - 5} M_ \odot yr^{ - 1} $ , terminal velocity V _∞≈2000 km s^?1, and expanding-envelope optical depth τ_env≈25. The temperature at the outer boundary of the photosphere of a helium star surrounded by such an envelope is approximately 130 kK higher than that in the absence of an envelope, being T _ph≈240 kK. Because of the high temperatures, the absorption coefficients at the corresponding photospheric levels are smaller than those in models with no envelope; therefore, the photosphere turns out to be in hydrostatic equilibrium and stable against light pressure (Г_max≈0.9). As a way out of this conflicting situation (an expanding envelope together with a hydrostatically equilibrium photosphere), we propose a model of discrete mass outflow, which is also supported by the observed cloudy structure of the envelopes in this type of stars. To quantitatively estimate parameters of the nonuniform outflow model requires detailed gas-dynamical calculations.     

不同温压下岩石弹性波速度、衰减及各向异性与组构的关系

结合岩石组构分析 ,阐述了岩石弹性波传播速度和衰减以及它们的各向异性与岩石组构之间的关系。在不同温压条件下对具有很强晶格优选方位的岩石样品的研究表明 ,随着围压的增加 ,波速和Q值均增大 ,但是在相互正交的 3个方向上 (垂直或平行于层理面及线理方向 )增大的速度并不相同 ,这与微裂隙的逐渐闭合密切相关。观测到的波速和Q值的各向异性具有不同的形成机理 ,波速各向异性主要与定向分布的微裂隙和主要矿物的晶格优选方位等构造因素有关 ;高围压下Q值各向异性与速度各向异性正好相反 ,可能是由于定向排列的矿物晶体沿不同方向其边界之间接触程度不同造成的。对岩石组构的研究不仅可以揭示岩体的变形机制、变形的动力学过程及其有关的热力学信息 ,还可以对宏观岩石的各种物理性质 ,尤其是力学特性 ,从微观机理上加以解释。文中特别强调了岩石组构分析对研究岩石物理性质的各向异性具有十分重要的意义。     

我国中、新生代盆地砂岩型铀矿沉积环境研究概述①

分析我国砂岩型铀矿沉积环境研究领域现状及研究意义、含铀碎屑沉积建造类型及其沉积特征、砂岩型铀矿成矿有利相位，并提出砂岩型铀矿沉积环境研究应该注意的几个问题。     

河南省禹州市地质灾害与防治预案

禹州市是河南省地质灾害大市。通过对该市地质灾害的表现形式、形成条件、诱发因素及其危险性的初步评估,提出了地质灾害的防治建议和预案,制定了近、中、远三期具体治理规划和达到的目标,并举出实例来说明建立预警系统和制定防治预案的可行性。     

Seasonal variations and mechanism for environmental control of NEE of CO_2 concerning the Potentilla fruticosa in alpine shrub meadow of Qinghai-Tibet Plateau

The study by the eddy covariance technique in the alpine shrub meadow of the Qing-hai-Tibet Plateau in 2003 and 2004 showed that the net ecosystem carbon dioxide exchange (NEE) exhibited noticeable diurnal and annual variations, with more distinct daily changes during the warmer seasons. The CO2 emission of the shrub ecosystem culminated in April and September while the CO2 absorption capacity reached a maximum in July and August. The absorbed carbon dioxide during the two consecutive years was 231.4 and 274.8 g CO2·m-2 respectively, yielding an average of 253.1 gCO2·m-2 per year: that accounts for a large proportion of absorbed CO2 in the region. Obviously, the diurnal carbon flux was negatively related to temperature, radiation and other atmospheric factors. Still, minute discrepancies in kurtosis and duration of carbon emission/absorption were detected between 2003 and 2004. It was found that the CO2 flux in the daytime was similarly affected by photosynthetic photon flux density in both years. Temperature appears to be the most important determinant of CO2 flux: specifically, the high temperature during the plant growing season inhibits the carbon absorption capacity. One potential explanation is that soil respiration is enhanced under such condition. Analysis of biomass revealed that the annual net carbon fixed capacity of aboveground and belowground biomass was 544.0 in 2003 and 559.4 g Cm"2 in 2004, which coincided with the NEE absorption capacity (63.1 g C·m-2 in 2003 and 74.9 g C·m-2 in 2004) in the corresponding plant growing season.     

北京城市规划区水源热泵系统应用适宜性分区

鉴于北京市水源热泵系统应用过程中存在地下水水资源因不能完全回灌造成浪费及运行效率未能充分发挥等问题,本文针对水源热泵系统运行过程中地下水的抽灌模式,根据北京规划市区的水文地质条件,对水源热泵系统应用的适宜性进行了分区,为水源热泵技术因地制宜、合理有序应用提供了科学的思路。     

三维质点追踪模型及其在胶南海域的应用

在已建立的变边界河口、陆架、海洋模型(ECOM)的基础上添加一个变边界质点追踪模块,研究胶东半岛南海域的物质输运特征,讨论了三维空间中,水质点在潮流作用下的迁移特点.该模型在近海海洋环境管理上具有实用价值.     

回归分析方法在地震科学应用中的问题与探讨

分析了回归分析方法在地震科学应用中存在的问题,提出了按变量之间的物理关系进行分类回归的新观点。针对实际地震问题给出了具体的分类方案,从理论上论述了不同类型问题采用不同的回归方法的必要性。通过对实际地震问题分析,剖析了现有回归分析方法的优缺点和适用条件。在此基础上,对不同类型统计问题如何选用适当的回归分析方法提出了合理的建议。     

麦棉套作主要虫害发生与气象条件的关系

根据危害棉花最重的棉蚜、棉红蜘蛛、棉铃虫和棉盲蝽象4大害虫的生物学特性、发生时段的气候条件和麦棉套种棉田生态因素,分析了4大害虫大发生的原因及预测预报,并提出了防治措施。     

中国石油战略选区重点目标油气地质条件分析及勘探建议

首先,分析了中国石油天然气股份有限公司优选出的3个战略选区重点目标,即河套盆地、塔里木东南坳陷和羌塘盆地的油气资源条件,认为这3个目标都具有资源量大、资源丰度较高的特点,具有开展战略选区的油气资源基础.其次,论述了3个目标的储盖组合和油气显示情况,指出每个地区虽然具有不同的特点,但都具有基本的油气成藏条件和较好的勘探前景.最后,在分析3个目标存在的主要问题的基础上,提出了相应的勘探工作建议.