On the penetration of a hot diapir through a strongly temperature-dependent viscosity medium     

Stephen F. Daly  Arthur Raefsky 《Geophysical Journal International》1985,83(3):657-681

Summary. The ascent of a hot spherical body through a fluid with a strongly temperature-dependent viscosity has been studied using an axisymmetric finite element method. Numerical solutions range over Peclet numbers of 10⁻¹– 10³ from constant viscosity up to viscosity variations of 10⁵. Both rigid and stress-free boundary conditions were applied at the surface of the sphere. The dependence of drag on viscosity variation was shown to have no dependence on the stress boundary condition except for a Stokes flow scaling factor. A Nusselt number parameterization based on the stress-free constant viscosity functional dependence on the Peclet number scaled by a parameter depending on the viscosity structure fits both stress-free and rigid boundary condition data above viscosity variations of 100. The temperature scale height was determined as a function of sphere radius. For the simple physical model studied in this paper pre-heating is required to reduce the ambient viscosity of the country rock to less than 10²² cm² s⁻¹ in order for a 10 km diapir to penetrate a distance of several radii.  相似文献   

研究Chandler摆动的一个随机激发模型   总被引：1，自引：0，他引：1  

黄淑亚  廖新浩  朱元兰 《天文学报》2001,42(3):259-265

基于同运动激发了Chandler摆动的假设，提出一个研究Chandler摆动的随机非线性模型，它是由一个随机性阶梯函数和一个具有阻尼的线性谐振子的Euler中心差分格式混合而成，研究此模型中各个参数与Chandler摆动振幅的关系，通过对基于实测资料获得的有效大气角动量时间序列的统计分析，初步发现其中含有随机噪声成份，它可以激发目前观测到的Chandler摆动振幅的28－40％，最后，对Chandler摆胡机激发的假设作了一些讨论。  相似文献   

植物地球化学测量法在秦巴地区寻找金矿中的应用     

王平  王波  刘金成  汪振洋  胡西顺 《地球科学与环境学报》1995,(2)

在植被发育的秦巴地区，应用植物地球化学测量法寻找金矿取得了初步的研究成果，用来找金矿的有效指示植物有：槲、栎、板栗（雄株）和马桑等。这些植物作为找矿标志，可明显指示出位于厚覆盖层之下的金矿体。据此，可圈定出找金的有利地段．  相似文献   

延安市区斜坡稳定性两级模糊综合评判     

张骏  倪万魁  冯希杰 《地球科学与环境学报》1990,(1)

本文采用两级模糊综合评判方法,在对延安市区斜坡稳定性进行定性分析和评价的基础上,选取主要影响因素作为评价指标并将其定量化,然后按不稳定、次不稳定、基本稳定和稳定等四个级别进行了延安市区斜坡稳定性两级模糊综合评判。评判结果较好地反映了市区斜坡带的实际稳定程度。该方法清晰易用,能使较多的影响因素参与评判,是进行斜坡稳定性定量化研究的一个有效途径。  相似文献   

Study of the radon concentrations in drinking water from three main cities of Shaanxi Province,China     

Lu?XinweiEmail author  Zhang?Xiaolan 《Environmental Geology》2004,45(8):1082-1086

This paper presents the results of radon concentration measurements in the drinking water from the municipal water supply system and private wells of Xian, Xianyang and Baoji city of Shaanxi province of China. The measurements were carried out on 38 samples. Radon levels in drinking water in Xian, Xianyang and Baoji were found to be 5.78, 13.04 and 15.01 k Bq m^–3, respectively. The AM radon concentration of private well water from Xianyang and Baoji is 28.84 k Bq m^–3 and 38.85 k Bq m^–3, respectively, which is 2.56 times and 3.14 times as high as that of tap water radon, respectively. The radiation risk of radon in water would be due to degassing and not due to drinking water. The domestic use of showers, humidifiers, and cooking, washing up, laundering, etc. may lead to an additional increase of the radon concentration in the indoor air. The observed radon concentration in drinking water from three main cities of Shaanxi Province can contribute to a 4.86 to 32.63% increase in indoor radon concentration and can cause 0.068±0.016 mSv y^–1 to 0.177±0.045 mSv y^–1 extra annual effective dose to males, 0.060±0.014 mSv y^–1 to 0.155±0.039 mSv y^–1 to females. The mean annual effective dose equivalents to males and females of Xianyang and Baoji from well water account for 25.94 to 39.75% of environmental radon and radon daughters annual effective dose equivalents. The radon concentrations in the well water from Xianyang and Baoji will bring a definite additional risk to the population.  相似文献   

工程勘察方案中"V"字型布孔原则的探讨     

祁乐凤  毛群芳 《上海国土资源》2004,(2):26-28

文章从对有关规范中孔间距规定的理解出发,对“V”字型布孔的合理性和局限性提出了讨论。  相似文献   

Effect and mechanism of stresses on rock permeability at different scales   总被引：1，自引：0，他引：1  

YIN Shangxian  WANG Shangxu 《中国科学D辑(英文版)》2006,49(7):714-723

1 Introduction Unlike general solids, rocks are porous materialswhich include different scales of pores, such as pores, cracks, fractures, capillary and disfigurement in the crystal, tiny pores and cracks between crystal grains at micro-scale, in which the fluid is water, oil or gas. Thedifferences between rocks and solids can be seen in two aspects, one is stresses bearing states. Solids are only subjected to external stresses, while rocks are subjected to external stresses σ ij (i, j=1,2,3)…  相似文献   

The Transition Between the Scale Domains of Ray and Effective Medium Theory and Anisotropy: Numerical Models   总被引：1，自引：0，他引：1  

Yinbin Liu  Douglas R. Schmitt 《Pure and Applied Geophysics》2006,163(7):1327-1349

The anisotropy of a periodically layered isotropic medium is numerically modeled in order to study the effect of the scale of heterogeneity on seismic observations. An important motivation is to delineate the wavelength ranges over which a pulse propagating obliquely through the structure will be described by either ray (short wavelength) or effective medium (long wavelength) theory. The same band-limited pulse is propagated obliquely at a variety of incidence angles through a compositionally uniform layered structure as a function of the layer thicknesses. The resulting seismograms display similar behavior to that encountered for normal incidence including the effects of stop- and pass-bands. Velocities determined from time picks on these seismograms show a large difference in velocities between the long and short wavelength limits as has been previously demonstrated for normal incidence propagation. The bulk of the transition between these two limits is independent of incidence angle and occurs when the ratio between the wavelength and the layering thickness is near a value of 10. Two more geologically reasonable models show that these effects are diminished with smaller contrasts between the layers.  相似文献   

Lower mantle dynamics with the post-perovskite phase change, radiative thermal conductivity, temperature- and depth-dependent viscosity     

Ctirad Matyska  David A. Yuen 《Physics of the Earth and Planetary Interiors》2006,154(2):196-207

The new post-perovskite phase near the core-mantle boundary has important ramifications on lower mantle dynamics. We have investigated the dynamical impact arising from the interaction of temperature- and depth-dependent viscosity with radiative thermal conductivity, up to a lateral viscosity contrast of 10⁴, on both the ascending and descending flows in the presence of both the endothermic phase change at 670 km depth and an exothermic post-perovskite transition at 2650 km depth. The phase boundaries are approximated as localized zones. We have employed a two-dimensional Cartesian model, using a box with an aspect-ratio of 10, within the framework of the extended Boussinesq approximation. Our results for temperature- and depth-dependent viscosity corroborate the previous results for depth-dependent viscosity in that a sufficiently strong radiative thermal conductivity plays an important role for sustaining superplumes in the lower mantle, once the post-perovskite phase change is brought into play. This aspect is especially emphasized, when the radiative thermal conductivity is restricted only to the post-perovskite phase. These results revealed a greater degree of asymmetry is produced in the vertical flow structures of the mantle by the phase transitions. Mass and heat transfer between the upper and lower mantle will deviate substantially from the traditional whole-mantle convection model. Streamlines revealed that an overall complete communication between the top and lower mantle is difficult to be achieved.  相似文献   

温宿县水稻春播期间气象条件分析     

李凤琴  刘海蓉  全学荣  刘进新 《沙漠与绿洲气象(新疆气象)》2006,29(6):19-20,23

依据温宿县34a的气象资料,着重分析了温宿县水稻春播期间的气象条件,并提出了相应的对策建议。  相似文献