对流电场产生电离层扰动的典型事例

用欧空局ＥＩＳＣＡＴ极光区非相干散射雷达观测资料、南极中山站电离层垂测站和我国１２０°Ｅ电离层站链ｆ０Ｆ２资料，分析了１９９１年５月２～３日一次主要由磁层对流引起的电离层扰动过程。从形态特征上看，它与热层中性大气参与的动力耦合过程明显地不同。对照比较表明，这是一次典型的磁层－电离层电动耦合事例。全球地磁站网资料从另一侧面证实，本文讨论的耦合机制是正确的。     

夏季强沙尘暴内部热力动力特征的个例研究

根据对流体在热低压条件下激发强沙尘暴的机理,并应用Rennó和Ingersoll于1996年提出的热机自然对流理论,对2004年7月12日甘肃省酒泉基准站发生的强沙尘暴内部动力热力结构进行了探讨。结果表明:①在沙尘暴发生前的一小时大气底层处于干热状态,垂直方向巨大的温度梯度有利于干对流发展。②激发强沙尘暴的对流体的切向旋转速度和垂直运动速度的大小,很大程度上决定了沙尘暴的强弱。③利用酒泉站探空资料计算出的沙尘暴对流体的最大切向旋转速度为11.4 m·s-1,垂直运动速度为14.0 m·s-1;地面沙尘暴观测系统记录的平均环境风速仅为5.5 m·s-1,瞬间最大风速只9.3 m·s-1。     

Phase relations of iron and iron–nickel alloys up to 300 GPa: Implications for composition and structure of the Earth's inner core

We have investigated the phase relations of iron and iron–nickel alloys with 18 to 50 wt.% Ni up to over 300 GPa using a laser-heated diamond-anvil cell. The synchrotron X-ray diffraction measurements show the wide stability of hcp-iron up to 301 GPa and 2000 K and 319 GPa and 300 K without phase transition to dhcp, orthorhombic, or bcc phases. On the other hand, the incorporation of nickel has a remarkable effect on expanding the stability field of fcc phase. The geometry of the temperature–composition phase diagram of iron–nickel alloys suggests that the hcp–fcc–liquid triple point is located at 10 to 20 wt.% Ni at the pressure of the inner core boundary. The fcc phase could crystallize depending on the nickel and silicon contents in the Earth's core, both of which are fcc stabilizer.     

Coupled Process Models of Fluid Flow and Heat Transfer in Hydrothermal Systems in Three Dimensions

Geothermal fields and hydrothermal mineral deposits are manifestations of the interaction between heat transfer and fluid flow in the Earth’s crust. Understanding the factors that drive fluid flow is essential for managing geothermal energy production and for understanding the genesis of hydrothermal mineral systems. We provide an overview of fluid flow drivers with a focus on flow driven by heat and hydraulic head. We show how numerical simulations can be used to compare the effect of different flow drivers on hydrothermal mineralisation. We explore the concepts of laminar flow in porous media (Darcy’s law) and the non-dimensional Rayleigh number (Ra) for free thermal convection in the context of fluid flow in hydrothermal systems in three dimensions. We compare models of free thermal convection to hydraulic head driven flow in relation to hydrothermal copper mineralisation at Mount Isa, Australia. Free thermal convection occurs if the permeability of the fault system results in Ra above the critical threshold, whereas a vertical head gradient results in an upward flow field.     

Realistic simulations of stellar surface convection with ANTARES: I. Boundary conditions and model relaxation

We have implemented open boundary conditions into the ANTARES code to increase the realism of our simulations of stellar surface convection. Even though we greatly benefit from the high accuracy of our fifth order numerical scheme (WENO5) the broader stencils needed for the numerical scheme complicate the implementation of boundary conditions. We show that the effective temperature of a numerical simulation cannot be changed by corrections at the lower boundary since the thermal stratification does only change on the Kelvin–Helmholtz time scale. Except for very shallow models this time scale cannot be covered by multidimensional simulations due to the enormous computational requirements. We demonstrate to what extent numerical simulations of stellar surface convection are sensitive to the initial conditions and the boundary conditions. An ill-conceived choice of parameters for the boundary conditions can have a severe impact. Numerical simulations of stellar surface convection will only be (physically) meaningful and realistic if the initial model, the extent and position of the simulation box and the parameters from the boundary conditions are chosen adequately.     

井水温度微动态及其形成机制

介绍了我国地震地下水温度观测概况及已获得的微动态现象, 即水温固体潮、 水温同震效应、 水温前兆异常等, 并对其形成机理做了理论分析。 提出水温微动态形成机理研究应从二个地温梯度、 二个对流、 一个传导、 一个扩散等热系统与热过程去考虑。     

Progress in studies on the structure and physical properties of the mantle in China

The studies on the structure and physical properties of the mantle by Chinese geophysicists from 2003 to 2007 are reviewed in this report. It mainly contains studies on the seismic velocity structure of the mantle,anisotropy of the mantle,mantle discontinuities,mantle convection and the physical properties of mantle. The review concerns mainly the contents,the methods used and the results of the studies. It can be found that new progress in the study on the structure and physical properties of mantle has been made in the last four years in China. In some preexis-tent areas much progress has been made,advanced methods have been adopted,extensive international co-operation has been conducted in many ways,and the scope of the co-operation has gradually expanded. More-over,some new fields appear as well.     

土石坝横向裂缝的土工离心机模型试验研究

岸坡突变所产生的不均匀沉降变形常常是导致土石坝心墙发生横向裂缝的主要原因。使用糯扎渡高心墙堆石坝心墙混合土料进行了模拟心墙发生横向裂缝的土工离心机模型试验。试验中再现了由于岸坡坡度变化导致坝顶发生横向裂缝的现象。采用工程中常用的3种裂缝分析方法：倾度法、Leonards法和有限元应力法对试验结果进行了分析。结果表明,前两种方法仅在测点较多时才是适用的,而有限元应力法对土石坝心墙横向裂缝问题更为有效。     

土石坝心墙水力劈裂的研究进展

简要评述了国内外关于土石坝心墙水力劈裂的研究现状,归纳了土石坝心墙水力劈裂在发生机理、发生条件和影响因素等方面的研究成果。