Gas exsolution and flow during supersaturated water injection in porous media: I. Pore network modeling

Degassing and in situ development of a mobile gas saturation take place when an aqueous phase saturated with gas at a pressure higher than the subsurface pressure is injected in water-saturated porous media. In the first part of this work, a pore network model is used to study the key physical aspects of this novel and hitherto unexplored way of introducing a gas phase in the subsurface. Following heterogeneous nucleation, growth of gas phase clusters driven by convective diffusion of solute from the bulk aqueous phase, is shown to result in a ramified pattern of gas-occupied pores, which is controlled by capillary and buoyancy forces. The interplay between mass transfer and immiscible displacement processes, namely gas cluster coalescence, mobilization under the action of buoyancy forces and fragmentation resulting from capillary instabilities, is seen to favour the propagation of a stable gas saturation front. Pore network model predictions of the macroscopic mass transfer rate coefficient are in fair agreement with a recently published empirical correlation.     

Void fraction measurements and scale effects in breaking waves in freshwater and seawater

This paper follows from the work of Blenkinsopp and Chaplin (2007) and describes detailed measurements of the time-varying distribution of void fractions generated by breaking waves in freshwater, artificial seawater and natural seawater under laboratory conditions, along with flow visualisation of the entrainment process. The measurements were made with highly sensitive optical fibre phase detection probes and the results demonstrate that although an additional population of fine (d < 0.3 mm) bubbles existed in the seawater cases, the total volume and distribution of entrained air, and the spatial and temporal evolution of the bubble plumes were very similar in all three water types. The influence of water type may be relatively insignificant, but a numerical bubble tracking model shows that the effect of scale is an important consideration when modelling the post-entrainment evolution of breaker-entrained bubble plumes. Consequently the results suggest that while the use of freshwater in laboratory models of oceanic processes can be considered valid in most situations, the effect of scale may impact interpretation of the results.     

基于地震信息的大屏可视化技术研究与应用

为提高指挥大屏信息读取效率,更好地进行防震减灾工作,对指挥大屏地震信息可视化开展了一系列研究,详细探讨了基于地震信息的指挥大屏可视化内容,包括大屏布局、设计思想、颜色搭配、文字表达、图标设计、交互显示与整体展示效果等方面,对地震应急信息的准确完备、快速传递、清晰表达和高效处理有一定提高。     

应用系统内部行为审计模型的构建

计算机系统内部安全和系统外部安全是计算机系统安全体系中的两个重要组成部分.从系统内部安全出发,为应用程序内部的安全手段提出一种行为审计模型,用以监督和记录系统操作者的行为,为检查可疑活动提供有利证据.     

一种实现局域网内屏幕共享的新方法

介绍了一种基于事件驱动和多播的实现局域网内屏幕共享的新方法,通过与原有的定时截取和广播发送数据的方式的比较,可以得出结论,新方法不仅减少了对CAI教学课件教师端和未参加教学的网内终端的资源占用,而且使跨网教学更加灵活.     

Faster-than-light motion in quasars

Over the past fifteen years, observations of some quasars with the techniques of very-long-baseline interferometry have shown that the angular separation between pairs of radio-emitting regions in their cores is increasing year after year. If the quasars are indeed as far away as implied by Hubble’s law, then these angular motions translate into linear speeds several times the speed of light. Several theoretical scenarios have been proposed to show that the observed motions are illusory. The leading contender in this field — the relativistic beam model — and an alternative offered by the concept of a gravitational screen are described and compared in the light of recent observational data.     

Transient discharges from marine hydrocarbon seeps: spatial and temporal variability

Marine hydrocarbon gas emissions at an intense, 20-m-deep seep in the Santa Barbara Channel, California were studied with a network of three turbine seep-tents and repeated seabed mapping. The tents observed two gas ejection events that are interpreted as due to blockage of constrictions in fractures and subsequent blow-through. Seabed mapping suggests that very large transient emission events occur, are related to tar, and are temporally and spatially variable. Transient emissions have the potential to more efficiently transport methane to the atmosphere than steady-state emissions. We present an electrical model analog of subsurface seepage useful for seepage flux interpretation. The model predicts that variations in resistance at one vent shifts some of its flux to other connected vents, and that the shift is not zero-sum, i.e., a resistance change at one vent causes a flow change for the overall fracture system.     

广东省基础地理信息数据库设计的关键技术

介绍广东省基础地理信息数据库设计的关键技术，包括软、硬件及网络环境、系统体系结构、系统运行模式、数据库的组织结构、系统的功能等方面的技术，为同行业的数据库建设提供参考。     

中断服务程序的驻留与应用

中断是计算机系统工作中的重要过程。本文介绍了设置新的中断向量和中断服务程序驻留的方法,并以建立屏幕电子表为例,予以详细说明。     

Vesicle layering in solidified intrusive magma bodies: a newly recognized type of igneous structure

 We report a novel type of layering structure in igneous rocks. The layering structure in the Ogi picrite sill in Sado Island, Japan, is spatially periodic, and appears to be caused by the variation in vesicle volume fraction. The gas phase forming the vesicles apparently exsolved from the interstitial melt at the final stage of solidification of the magma body. We call this type of layering caused by periodic vesiculation in the solidifying magma body "vesicle layering." The presence of vesicle layering in other basic igneous bodies (pillow lava at Ogi and dolerite sill at Atsumi, Japan) implies that it may be a fairly common igneous feature. The width of individual layers slightly, but regularly, increases with distance from the upper contact. The layering plane is perpendicular to the long axes of columnar joints, regardless of gravitational direction, suggesting that the formation of vesicles is mainly controlled by the temperature distribution in the cooling magma body. We propose a model of formation of vesicle layering which is basically the same as that for Liesegang rings. The interplay between the diffusion of heat and magmatic volatiles in melt, and the sudden vesiculation upon supersaturation, both play important roles. Received: 15 February 1996 / Accepted: 24 June 1996