利用Smart卡的可撤销匿名性的电子支付系统

本文对文（１）提出的利用Ｓｍａｒｔ卡的电子支付系统进行了改进,提出了一种可撤销用户匿名性的支付系统,一方面,它能有效地保护用户的隐私,另一方面,在银行的协助下,一个可信第三方（委托人）可撤销用户的匿名性。因此可有效地防止钱的伪造、含污和敲诈。     

以左江水利枢纽的建设为契机发展桂西南旅游

左江水利枢纽有其地理优势和自身的旅游价值。以左江水利枢纽的建设为契机，把桂西南４市县的旅游风景区联成一体，成为一环形旅游线路，既可满足旅游者的要求，又可以旅游的发展促进该地区的经济发展，达到帮助老少边贫地区脱贫致富的目的     

The water–food–energy nexus: an introduction to nexus concepts and some conceptual and operational problems

This introduction sets the scene for the special issue compiled by Martin Keulertz, Eckart Woertz and Tony Allan.     

版权贸易发展与出版业“走出去”战略实现

党的十六大确立了文化“走出去”战略,为出版业不断加大“走出去”的力度指明了方向。分析我国版权贸易的现状及特点,探讨我国版权贸易的发展规律及趋势,为促进我国版权贸易的发展特别是促进版权输出开辟了通途。     

中国农业水足迹时空差异和流动格局研究

粮食安全和水资源安全是关系国计民生的重大问题,农业是主要的耗水部门,研究农业生产耗水有利于实现水资源可持续利用。对中国农业水足迹变化趋势和空间差异进行了分析,并构建了优化模型和贸易网络,在此基础上,对各省农产品贸易流动格局进行了分析。分析结果表明:①1961～2011年间,农业水足迹总量持续增长,贡献最大的是畜产品水足迹;人均农业水足迹呈先下降后上升的趋势。②2000年,中国内陆地区,由西北向东南,植物型农产品水足迹含量中的绿水足迹比例逐渐增加。③四川、广东、河南、江苏、山东5个省的农业水足迹消费最高,北京以及沿海等经济发达地区和西北、内蒙古等灌溉密集地区的人均农业水足迹消费较高。④2000年,中国农业水足迹贸易全局节水量为12.6 km~3,国际贸易是主要贡献单位。最后,基于上述研究结果提出了能够促进我国实现农业水资源可持续发展的建议。     

Water temperature as a hindrance,but not limiting factor for the survival of warm water invasive crayfish introduced in cold periods

The success of non-native species establishment depends on various abiotic and biotic factors that determine the outcome of an introduction event. Limiting temperature ranges have been studied for various non-native species; however, such previous assessments of species-specific temperature thresholds may be inadequate. Because several non-native crayfish species prefer warmer water temperatures, introductions were generally assumed to occur during preferable, warmer periods. However, despite the generality, traditionally considered ‘warm-water’ species are gradually appearing in new habitats, which were previously considered too cold for successful establishment. Newly discovered overwintering abilities of these species are likely related to the winter stratification in lentic ecosystems, which maintain tolerable conditions. To understand better the survivability of two such non-native species, red swamp crayfish Procambarus clarkii and marbled crayfish Procambarus virginalis individuals were abruptly subjected to a thermic shock which lowered the water temperature from 20 °C (room temperature) to 6 °C, 4 °C and 2 °C, thus mimicking the release by pet owners during various phases of winter. The survival rate and foraging activity were monitored for up to 98 days. Procambarus clarkii showed a considerable higher survival rate at low temperatures (4 °C, 2 °C) compared to that of P. virginalis with neither sex nor size differences evident. Our findings reveal the ability of warm water invaders to withstand a shock during introduction at low temperature periods without acclimation. Considering these newly discovered shifts in physiological limitations, particularly for the red swamp crayfish, this may indicate a higher threat for areas with colder conditions.     

Virtual Water in Global Food and Water Policy Making: Is There a Need for Rethinking?

The argument that economies that face acute water scarcity problems can and should meet their water demand for food through cereal imports from water-rich countries; and that virtual water trade can be used to achieve water securities has become dominant in global water discussions. Analysis of country level data on renewable freshwater availability and net virtual water trade of 146 nations across the world shows that a country's virtual water trade is not determined by its water situation. Some countries have the advantage of high “economic efficiency” in food production and have surplus water, but resort to food import, whereas some water scarce countries achieve high virtual water trade balances. Further analysis with a set of 131 countries showed that virtual water trade increased with increase in gross cropped area. This is because of two reasons: First, when access to arable land increases, the ability to utilize available blue water for irrigation increases. Second, increasing access to arable land improves the access to water held in the soil profile as “free good”, a factor not taken into account in assessing water availability. Hence, many of the humid, water-rich countries will not be in a position to produce surplus food and feed the water scarce nations; and virtual water often flows out of water-poor, land rich countries to land-poor water-rich countries. This means that “distribution of scarcity” and “global water use efficiency”, are goals that are difficult to achieve through virtual water trade in a practical sense. For a water-poor, but land rich country, virtual water import offer little scope as a sound water management strategy as what is often achieved through virtual water trade is improved “global land use efficiency”. The important policy inferences emerging from the analyses are two: First, assessing the food security challenges posed to nations in future purely from a water resource perspective provides a distorted view of the food security scenario. National policies on food security should take into account “access to arable land” apart from water availability. Second, analysis of water challenges posed by nations purely from the point of view of renewable water availability and aggregate demands will be dangerous. Access to water in the soil profile, which is determined by access to arable land, would be an important determinant of effective water availability.     

The contribution of chevon from Africa to global meat production

Africa's goat population increased by 75% between 1980 and 2005 and constitutes 30% of the world goat population. Although Africa produces about 20% of the world's chevon, its share of world chevon market has been declining. Exports from Africa represent less than 5% of the total world trade. Most goats are raised by smallholder farmers for subsistence and trading in informal markets. The world renowned Boer, Kalahari Red and Savanna goats are meat breeds that were developed in South Africa. Information on most African goat breeds is scanty, but there seems to be large variations in the breed characteristics, which suggests a potential for selective breeding for more and meat breeds. Recommendations for enhancing goat production in Africa include, prioritizing research and technology transfer on meat goat production, development of more chevon breeds, devising methods to enhance the quality of African chevon through pre- and post-harvest interventions, and improved support from government institutions and policy.     

调水工程受水区增量水权转换模式创新与设计

结合南水北调受水区典型城市东营市经济社会发展格局以及水资源配置布局,提出统一配置、综合定价,定向供给、独立核算,水权转换、市场竞价的增量水权利用的模式;进一步重点针对水权转换模式,初步构建包括利益相关方界定、信息管理、交易定价、交易协调、合约管理等内容的增量水权利用机制,设计水权交易平台,就平台性质界定、水权来源、利益相关方责任、准入要求、转让期限等内容进行探讨。结合水权交易模式设计,实现政府行政调控和市场经济调节相结合,优化水资源配置、推进区域水资源节约集约利用,缓解东营市黄河以南南水北调东线水利用不足、黄河以北产业发展用水短缺约束局面。     

基于ELES模型的城镇居民生活用水水价支付能力研究——以北京市为例

本文从支付能力的角度,根据计量经济学的需求函数理论,以我国城镇居民消费支出结构数据为基础,提出了应用扩展线性支出系统(ELES)模型,分析城镇居民生活用水水价支付能力。以北京市为例,采用1998～2004年截面数据资料,计算分析了不同时期居民用水需求与水费支出水平、居民用水的边际消费倾向、需求收入弹性以及不同收入户的用水基本需求等,以此定量研究了北京市城镇居民生活用水水价的支付能力。研究结果表明:平均收入水平下,居民对水价具有一定的支付能力,其基本用水需求均能得到满足;可支配收入增长对居民用水需求的影响不大;北京市生活用水水价还有上调的空间,但低收入户的水价支付能力有限,是重点考虑的对象。