Scale‐dependent Poiseuille flow alternatively explains enhanced dispersion in geothermal environments

Fluid flow exerts a critical impact on the convection of thermal energy in geological media, whereas heat transport in turn affects fluid properties, including fluid dynamic viscosity and density. The interplay of flow and heat transport also affects solute transport. To unravel these complex coupled flow, heat, and solute transport processes, here, we present a theory for the idealized scale‐dependent Poiseuille flow model considering a constant temperature gradient (?T) along a single fracture, where fluid dynamic viscosity connects with temperature via an exponential function. The idealized scale‐dependent model is validated based on the solutions from direct numerical simulations. We find that the hydraulic conductivity (K) of the Poiseuille flow either increases or decreases with scales depending on ?T > 0°C/m or ?T < 0°C/m, respectively. Indeed, the degree of changes in K depends on the magnitude of ?T and fracture length. The scale‐dependent model provides an alternative explanation for the well‐known scale‐dependent transport problem, for example, the dispersion coefficient increases with travel distance when ?T > 0°C/m according to the Taylor dispersion theory, because K (or equivalently flux through fractures) scales with fracture length. The proposed theory unravels intertwined interactions between flow and transport processes, which might shed light on understanding many practical geophysical problems, for example, geothermal energy exploration.     

我国震例前兆异常统计特征和应用研究

进行了我国大陆80多个震例(1987～1999年)的前兆异常项数统计, 研究了强震前流体、 形变和电磁三大观测类别的前兆异常项的时空变化属性和综合特征。 着重讨论这3类前兆异常从中期向短临过渡的标记、 可能的场、 源兆、 前兆变化的相关性、 分布的不均匀性及与地震活动的一致性。 在此基础上, 提出综合判定指标并用概率增益的方法对我国大陆强震预测作了一定的应用研究。     

Water-Tank Studies of Separating Flow Over Rough Hills

The present work investigates the lower boundary condition for flows over a steep, rough hill. Simple asymptotic arguments together with the mixing-length hypothesis are used to derive a local analytical solution that is tested against three different flow conditions. In all, 36 velocity profiles are compared with the proposed expression. The experiments were carried out in a water channel and velocity measurements were made through laser Doppler anemometry. The extent of separated flow was made to vary as a function of the roughness and the Reynolds number. The analysis includes regions of attached as well as separated flow. In particular, the solution of Stratford is studied at the points of separation and re-attachment and found to apply equally well in rough walls.     

Struggles over family land? Tree crops,land and labour in Ghana’s Brong-Ahafo region

Agricultural land use in much of Brong-Ahafo region, Ghana has been shifting from the production of food crops towards increased cashew nut cultivation in recent years. This article explores everyday, less visible, gendered and generational struggles over family farms in West Africa, based on qualitative, participatory research in a rural community that is becoming increasingly integrated into the global capitalist system. As a tree crop, cashew was regarded as an individual man’s property to be passed on to his wife and children rather than to extended family members, which differed from the communal land tenure arrangements governing food crop cultivation. The tendency for land, cash crops and income to be controlled by men, despite women’s and young people’s significant labour contributions to family farms, and for women to rely on food crop production for their main source of income and for household food security, means that women and girls are more likely to lose out when cashew plantations are expanded to the detriment of land for food crops. Intergenerational tensions emerged when young people felt that their parents and elders were neglecting their views and concerns. The research provides important insights into gendered and generational power relations regarding land access, property rights and intra-household decision-making processes. Greater dialogue between genders and generations may help to tackle unequal power relations and lead to shared decision-making processes that build the resilience of rural communities.     

背斜-水动力复合油(气)藏油(气)水界面产状

基于Hubbert的油(气)等势面坡度与水头关系的公式和达西定律, 推出了油(气)等势面坡度与水流的渗滤速度的关系式.根据此关系式, 讨论了各种情形水流速度与油气等势面坡度的关系.以此为基础, 认为未被油气充满转折端的背斜-水动力油气藏平面的油水界面由于水流速度大小和方向变化通常应该为曲面; 对被油气充满转折端的背斜-水动力油气藏倾斜的油水界面在不同方向剖面上倾斜不同: 圆柱状背斜横剖面油水界线水平、斜向剖面界线倾向相反, 倾伏背斜的横剖面可能同向倾斜但通常不在同一条倾斜的直线上.      

Easing conservation? Conservation easements, public accountability and neoliberalism

This paper examines the use of conservation easements, with a focus on California. Conservation easements are now the dominant tool used for private land conservation in the United States. Easements are in many ways a paradigmatic neoliberal environmental policy tool. They privatize and re-scale a great deal of land conservation decision-making authority; they are market-based; they provide financial incentives for participation rather than punishment for non-compliance; and they commodify new property rights. However, these neoliberalisms are incorporated in uneven, and sometimes contradictory, ways that emphasize the gulf between neoliberal ideologies and “actually existing neoliberalisms.” Most critically, as a result of extensive public funding and management, conservation easements are not nearly as private (and thus not as neatly neoliberal) as they sometimes seem. Conservation easements are often heralded as a “win–win” land conservation strategy. I argue that the extent to which conservation easements may be construed as win–win solutions depends a great deal on who is included in the calculation of winners and losers. I contend that using and governing easements as if they are private elides complex questions about larger public costs and benefits. This obscures the large number of people and institutions (both state and private) that will likely need to be involved in governing conservation easements in the long term.     

盐湖卤水体系的热力学模型及其应用Ⅰ:在Li+,Na+,K+,Mg2+/Cl-,SO42--H2O体系物理化学方面的应用

在简要介绍如何获得了描述“盐湖卤水体系”Li+ ,Na+ ,K+ ,Mg2 + Cl-,SO42 - H2 O 2 5℃热力学的全部Pitzer参数后 ,详细举例说明了模型在卤水热力学性质预测、含锂盐湖卤水中盐类饱和度、含锂盐湖卤水在2 5℃ 1 0 1 3× 1 0 5Pa下的天然卤水离子缔和状态 (化学模型 )计算等方面的应用     

环台湾岛海域全日分潮的特征和潮汐、潮流的综合性质

用97版POC海洋模式，对环台湾岛海域的全日分潮和整个潮汐，潮流综合特征进行三维数值研究。研究海域全日分潮是由太平洋传入的，且来自台湾岛北部海区传入的潮波穿越海峡。由吕宋海峡传入的全日分潮对维持南海的潮运动起着重要作用。全日分潮最大流同时线分布表层有5个圆流点，其中4个本文首次得到。台湾海峡及其以北海区和台湾东部洋区为不规则半日潮区，台湾东南为全日分潮为主的混合潮区。台湾岛北部为气旋式余流涡旋区，环绕台浅滩为反气旋余流涡旋区，澎湖水道开始的转向流预示着海峡及其邻近海区的涨潮流或落潮流的来临。     

用宽频带辐射能量检验地震能量标度性

本文研究了宽频带辐射能量的能量－频度关系,并试图以此对地震能量标度性假说进行重新检验．结果表明,宽频带辐射能量与其他震级标度之间似乎并不存在一个理想的能量－震级关系,然而至少对所研究的日本和阿拉斯加地区而言,直接针对宽频带辐射能量的频度统计可以得到更好的标度性．