Fracture void structure: implications for flow, transport and deformation

 This review focuses on studies of flow, transport and deformation processes at a scale of a single discontinuity. The paper provides an evaluation of: (1) various methods suggested for geometrical characterization of void structure; and (2) theoretical and practical problems arising from significant differences between the actual geometry of fracture void structure and its parallel plate representation. The use of an equivalent aperture concept is shown to be seriously misleading in: (a) evaluation of flow regime, and hence selection of appropriate flow laws; (b) correlating tracer and hydraulic tests, and assessment of solute transport properties; and (c) relating hydraulic and mechanical apertures, and predicting influence of stress perturbation and deformability. Received: 2 August 1999 · Accepted: 30 November 1999     

Cashing Out,Cashing In: Rural change on the south coast of Western Australia

Over the past century the cultural and physical landscape of the Shire of Denmark on the south coast of Western Australia has been transformed by successive waves of in-migrants. The paper examines the period since the early 1970s when alternative lifestylers and early retirees, attracted by the district's natural beauty and low land prices, began moving in and acquiring former Group Settlement holdings. The activities of these and subsequent 'alternatives' and 'cashed out' early retirees settling in the district have raised the marketability of the Shire's cultural capital. These changes have occurred in association with broader processes of rural restructuring and changing notions of 'rurality'. Increasingly, Denmark's cultural and physical landscape has become a highly marketable product for consumption by Perth's affluent middle classes. In recent years land prices have risen rapidly as speculators and financiers seek to 'cash in' on the 'cashed out' society. The paper explores these issues and relates them to broader processes of economic and social change occurring at the national and international levels.     

暴雨与非暴雨过程涡散场能量收支特征

选取云南暴雨和非暴雨两类天气过程，分别应用人选上支方程计算了暴雨区面积－时间平均参量收以各项量值，给出了对流层整层和上（２００－４００ｈＰａ）中（４００－６００ｈＰａ）下（６００－８００ｈＰａ）各层涡散场动能源汇特征，同时还指出了两类天气在动能制造、能量转换等方面存在的较差异，尤其是两类天气的大多数能量收支磺符号相反     

Carbon flux in the northwest Mediterranean estimated from microbial production

Spring profiles of microbial production derived from the dark incorporation of tritiated leucine and tritiated thymidine in the northwest Mediterranean show an exponential decline with depth. Assuming this to represent a steady-state balance between microbial respiration and the downward flux of carbon, the downward flux is estimated as (1−/)p/b, where p is the microbial production, their gross growth efficiency and b the coefficient of exponential decline with depth. Summer profiles, ranging over about 3° of latitude and 4° of longitude, were well fitted by a two-component exponential decline, suggesting two distinct microbial substrates. Values of b for the more rapidly declining component varied between 0.01 and 0.06 m⁻¹ according to location. In the case of the slower component, b was estimated as 0.002 m⁻¹, and did not vary significantly over the region. Estimated fluxes of carbon at the surface are 123–335 mg m⁻² d⁻¹ for the fast and 95 mg m⁻² d⁻¹ for the slow component. Below about 200 m, carbon flux is dominated by the slow component. Flux estimates are compatible with flux estimates from sediment traps in the same region. The observed changes between the spring and summer profiles, combined with the horizontal homogeneity of the summer profiles below 200 m, are consistent with a downward transport of about 5–10 m d^–1, implying a significant dispersive component to the observed fluxes.     

渤海悬浮颗粒物三维输运模式的研究 Ⅱ.模拟结果

利用本文Ⅰ给出的悬浮物输运的三维动力数值模式，在渤海中进行了两种情形下的模拟。首先模拟了黄河排出的细颗粒物在渤海中的运动，结果表明，这些颗粒物大部分将滞留在渤海内，而且其分布与气象条件有密切关系。另外对大风情况下悬浮物的输运进行了模拟，结果显示，大风到来时海水中的悬浮物浓度急剧上升，海底侵蚀增强，而风停止时，悬浮物浓度经过一段时间延迟后，会恢复到正常状态。这与实际观测的趋势是一致的，表明用本模式研究悬浮物的输运是可行的。     

地理学在全球变化研究中的学科地位及重要作用

分析了当前全球变化研究的主要特点,指出地理学在全球变化研究中将发挥日益重要的作用。提出了地理学在全球变化研究中应着重开展研究的4个方面的重点科学问题。     

Sulfur distribution and transport studies in East Asia using eulerian model

A three-dimensional regional Eulerian model of sulfur deposition and transport is developed. Processes treated in the model include emission, transport, diffusion, gas-phase and aqueous-phase chemical process, dry deposition, rainout and washout or sulfur. A “looking up table” method is provided to deal with the gas-phase chemical process including sulfur transfer. Dry-depositon velocity considers the influence of underlying surface, wind, degree of stabil-ity by parameterization. Model calculated values reasonably agrees with observation. Distribution of sulfur deposi-tion and transport in East Asia are also analyzed in this paper. Some amount of sulfur emission of different countries transport across boundaries, but the main origin of sulfur deposition in each country in East Asia is from itself. Furthermore, some transport paths on different layers and outlet or inlet zones are found. According to sulfur bal?ance and budget we concluded that sulfur outlets are bigger than inlets across boundary and emissions are more than deposition in most places of East Asia.     

Subseabed disposal of radioactive waste: effects of consolidational fluid flow

Subseabed disposal of radioactive waste applies a multiple-barrier concept with the sediment being the most important barrier for preventing a release of nuclides into the biosphere. While many investigations have been carried out to analyze the risk potential in this type of disposal, the effects of sediment consolidation and associated fluid flow have not fully been taken into consideration. Here, possible effects of consolidational fluid flow in the penetrator disposal option and possible consequences to the transport of nuclides in the sediment are analyzed. Results of numerical experiments demonstrate that consolidation contributes to the transport of radioactive nuclides released from containers buried in the sediment and to the release of nuclides at the sediment-water interface. Both depend on geological conditions and to a large extent on possible alterations of hydraulic conductivity i of the sediment in the vicinity of the entry path of a penetrator.Symbols c concentration ml m^–3 - c _a concentration of adsorbed solute mg kg^–1 (relative to dry weight of sorbing substance) - c _in solute concentration of source q mg m^–3 - c ₀ initial concentration mg m^–3 - ID dispersion tensorm ²s^–1 - ID ^* diffusion tensor m²s^–1 - D coefficient of dispersion m²s^–1 - d ₀ coefficient of molecular diffusion m²s^–1 - d coefficient of effective diffusion m²s^–1 - g gravity m²s^–1 - h piezometric pressure m - k hydraulic conductivity m²s^–1 - m mass kg - p pressure Pa - q source/sink m³s^–1 - S ₀ specific surface m²m^–3 - t time s - v velocity m s^–1 - x, z cartesian coordinates m - compressibiliy of sediment m²N^–1 - _L longitudinal dispersivity m - effective porosity (decimal fraction) - density kg m^–3 - _s density of sediment kg m^–3 - _w density of water kg m^–3 - decay constant per s - kinematic viscosity m²s^–1     

Mobilising generosity, framing geopolitics: Narrating crisis in the homeland through diasporic media

This paper provides an account of the humanitarian interventions enacted by the Croatian–American diaspora during the secessionist conflicts in Yugoslavia during the 1990s. Whilst undeniably an act of generosity towards ‘distant strangers’, actions such as these also represent a much more complex reality – they are an outcome of a complex set of relations and processes, in which the ethical choices of individuals become bound up with nationalist ideologies, geopolitical questions and, crucially, knowledge and understanding of distant events. In particular, this paper considers the ways in which generosity is mobilised through the framing of Balkan geopolitics through diasporic media. In so doing, it becomes possible to deepen the dialogue between work on geography and ethics on the one hand, and critical geopolitics on the other. In particular, the paper argues that due attention needs to be paid to the ways in which such ‘networks of concern’ are constructed in a variety of banal and mundane ways.     

关于美中基础地理信息产品及其分发模式的思考

作为当今经济和科技最发达的国家,美国在基础地理信息产品建设和分发服务方面是代表世界最先进水平的国家之一,其丰富的基础地理信息系列产品、优秀的网络分发服务系统、完善的数据共享和更新策略等都值得我们学习和借鉴。本文介绍了美国基础地理信息产品的种类、发展及其分发服务模式,并根据我国的实际情况,在相关方面提出了几点建议。