Selective Idling: Experiments in Transport Layer Energy Conservation

In this paper we consider the potential of using an aggressive form of energy conservation for mobile computing environments. The estimators for the round-trip time and round-trip time variance used by TCP are used to direct the transceiver of a mobile node to idle over extended periods of time when packet activity is not anticipated. In addition, we consider data link layer extensions that provide additional control information allowing the mobile to be further selective as to when to idle and when to activate the network interface device. Simulations are conducted to examine the performance of the proposed scheme under various levels of congestion in the fixed part of the network, from completely unloaded to fully congested. The simulations reveal that the technique is promising but its effectiveness depends crucially on the control of the maximum window size used by TCP and on accurate knowledge of the congestion conditions in the network.     

玻璃幕墙传热系数计算方法及工程应用

在研究玻璃幕墙热传递特点的基础上,基于一维稳态热传导理论,以中空玻璃为例建立了玻璃系统传热系数计算模型;基于二维稳态热传导理论和有限单元法,采用三节点三角形单元对二维温度场进行了离散,推导了单元热传导矩阵和温度载荷列阵,并推导了热对流、热流密度、辐射以及各种边界条件耦合作用下对单元热传导矩阵和温度载荷列阵的修正公式,建立了玻璃幕墙框及附加线传热系数计算模型。利用Visual C++和ObjectARX对AutoCAD进行了二次开发,研发了玻璃幕墙传热系数计算软件TJCW,并通过算例与LBNL系列软件计算结果进行比较,验证了所编软件的正确性和有效性。最后对某工程实例中玻璃幕墙传热系数进行了节能验算。研究结果表明:建立的传热系数计算模型能够正确的计算玻璃幕墙传热系数,基于该计算模型开发出的软件能够应用于实际工程的节能分析和计算中。     

The future sustainability of water supply in Kuwait

Abstract

The main natural source of water available in Kuwait is the brackish groundwater located in the Kuwait Group and the Dammam aquifers, where the salinity ranges from 4300 to 10200 mg/l and from 2500 to 10000 mg/l, respectively. Limited fresh groundwater resources in Al‐Rawdhatain and Umm Al‐Aish fields, which have a salinity of 359 ‐1737 mg/l, are also available. Most of the groundwater in Kuwait is used for irrigation, domestic purposes, small‐scale industries and for blending with distilled water. Because rainfall is seasonal and less than annual evaporation, the recharge of the groundwater from rainfall is negligible. The objective of this paper is to assess the different water resources in Kuwait in order to make an integrated management plan and to focus on future sustainability. Generally, in the State of Kuwait, there is increasing pressure on the natural water resources because of the exploitation of the aquifers at a rate exceeding that of both the groundwater recharge and population growth (from 1.4 million in 1980 to 2.55 million in 2003). This has lead to the observed decline in groundwater level and to the deterioration of water quality. In the early 1950s, a plan was endorsed in Kuwait to establish seawater desalination plants. By 2005, six desalination plants have been established, with a total capacity of distillation units of 1434.72 ×103 m³/d (315.6 MIGD). However, the gross maximum consumption for the year 2003 reached a value of 1440.17 ×103 m³/d (316.8 MIGD), which is higher than the total capacity of the available distillation units. Given the limitation of conventional water and the shortages of non‐conventional water, along with the increasing population, Kuwait must consider the recycling of wastewater for irrigation, industrial or any other unrestricted non‐potable purpose.     

The deep waters of land reform: land,water and conservation area claims in Limpopo Province,Olifants Basin,South Africa

Through investigating the reactions of commercial farmers to land and water reforms in the Trichardtsdal-Ofcolaco area, Limpopo Province, Olifants Basin, South Africa, from 1997 to 2006, it is shown that water claims are key to land redistribution processes, and that commercial farmers make strategic use of arguments for nature conservation and ecological stewardship to defend their claims to water. Given these observations, caution is warranted with respect to the implementation of land and water reforms as separate policy packages; it may be more effective to design water and conservation policies as an integral part of land reform programmes.     

Integrated Water Resources Management in the Republic of Uzbekistan

Abstract

The Uzbek socio-economic structure is characterized by the transition from a centrally-planned to a market-orientated economy, with a shifting from agricultural production to industrial development. However, the agricultural sector continues to play a significant role in a general economy of the country. The major water sector strategy is to decrease the dependence of agricultural production on climate by introducing advanced irrigation techniques and water saving methods to achieve future sustainable socio-economic development and environmental protection. Water management policy should be flexible enough to adapt to new demands. The regulation of consumption through demand management tools, such as appropriate pricing policies, has recently received greater attention in Uzbekistan. The main thesis of this paper is that allocation of water resources cannot be separated from ecological and economic considerations. The establishment of development objectives and the identification of constraints are also discussed. In the coming years, special attention will need to be paid to the control of water pollution and land salinization, water resources conservation, and acknowledging that actions to increase water productivity are as important as finding additional sources of water.     

亭子口水利枢纽工程环境保护实践

嘉陵江亭子口水利枢纽地处川北革命老区,生态环境较好,环境保护要求高;移民按照国务院471号令实施.工程建设遵循国家环境保护的基本国策,确立了建设“绿色工程”的环保目标,按照本项目的特点,科学规划,创新管理模式,采取过硬措施,满足环保投资,使环境保护与枢纽工程同时规划、同时建设、同时投入使用,见到了实效.     

以节水和水资源优化配置为目标的水权交易机制设计

对无交易机制、市场交易机制和政府主导交易机制3 种状态下水权交易的资源配置效率和节水效果进行了分析与比较。首先运用简单的个体决策模型来分析比较无交易机制状态和市场交易机制状态下的资源配置效率和节水效果;其次运用两阶段博弈模型分析政府主导交易机制下的个体最优决策所导致的资源配置效率和节水效果。分析结果表明在参与人目标收益最大化约束前提下,市场交易机制只能实现水资源的优化配置却不能促进节水,而政府主导交易机制在实现水资源优化配置上更有效率,而且在一定条件下可能促进节水。最后通过数值模拟演示了上述分析结构,并运用美国加州和德州的水权交易数据进一步验证了本文结论。     

水土保持在治理北京空气可吸入颗粒物PM2.5工作中的作用及思考

随着国家工业化、城镇化、现代化发展步伐的加快,统筹生态系统、经济系统和社会管理系统协调发展的任务更加艰巨,水土保持作为研究水、土两大生态基础资源,推进构建由水资源、土地资源和植被资源共同组成的区域或流域生态系统良性演进的学科,在落实科学发展的征程上作用将更大、任务将更艰巨、意义将更深远.通过分析空气中PM2.5的成因,指出了北京治理PM2.5面临的严峻挑战,提出了发挥水土保持作用治理PM2.5的微观、中观、宏观思路.     

Flux limiters fourth and sixth order high resolution method for hyperbolic conservation laws

This paper presents new fourth and six order accurate explicit finite difference scheme for hyperbolic conservation laws. The technique of obtaining high resolution, total variation non increasing oscillation free and explicit scalar difference scheme is derived by adding multi-limiters of antidiffusive flux to a first order scheme.