体育馆出口疏散能力的实验研究

为研究出口单位流量与人流时间之间的关系,以某体育馆为例,进行对某一出口常态下的人流观测实验.通过理论计算和建立Cubic回归模型对采集数据进行了统计分析.发现:单位出口流量最大值为2人/(m·s),稳定值为0.8-1.2人/(m·s),最小值为0.2人/(m·s).出口单位流量是人流时间的三次函数.研究结果表明:出口单位流量是随着时间的变化而变化,不是一个定值,而且单位出口流量稳定值分布在初期.本文对性能化防火设计有一定的参考价值.     

危化品企业安全信用内涵的探讨

现代市场经济是信用经济,信用需要用制度来保障.对危化品企业就"信用"与"信用制度"进行了探讨,给出了危化品企业安全信用概念,并简单阐述危化品企业安全信用制度内涵.最后,对建立危化品企业安全信用制度的可能性与必要性进行了分析.     

Review and appraisal of concept of sustainable food production systems

Environmental degradation, competition for resources, increasing food demands, and the integration of agriculture into the international economy threaten the sustainability of many food production systems. Despite these concerns, the concept of sustainable food production systems remains unclear, and recent attempts to appraise sustainability have been hampered by conceptual inconsistencies and the absence of workable definitions. Six perspectives are shown to underpin the concept. Environmental accounting identifies biophysical limits for agriculture. Sustained yield refers to output levels that can be maintained continuously. Carrying capacity defines maximum population levels that can be supported in perpetuity. Production unit viability refers to the capacity of primary producers to remain in agriculture. Product supply and security focuses on the adequacy of food supplies. Equity is concerned with the spatial and temporal distribution of products dervied from resource use. Many studies into sustainable agriculture cover more than one of these perspectives, indicating the concept is complex and embraces issues relating to the biophysical, social, and economic environments. Clarification of the concept would facilitate the development of frameworks and analytical systems for appraising the sustainability of food production systems. LRRC Contribution No. 90–46.     

计算机局域网络保密措施

随着计算机的普及 ,局域网络越来越广为利用 ,但也出现了相应的失密问题。本文从信息及实体两个方面 ,论述了局域网络的保密措施。     

分布式防火墙系统

针对分布式防火墙系统体系结构,从新的网络应用环境出发,指出了传统边界防火墙的缺点;然后提出了分布式防火墙的基本原理,并给出了分布式防火墙的产品,重点分析了分布式防火墙产品中的主机防火墙原理;最后还介绍分布式防火墙对各种问题的解决方案及混合型防火墙的应用实例.     

水资源供需平衡的安全分析

从中国发展的区域基础角度,考察经济核心区和6个大区在未来经济发展中的水资源供需安全问题.在分析中应用一般均衡的分析技术和线性规划逆问题分析技术相结合,研究表明,在未来发展中水资源最紧缺的地区是华北和西北,作为经济核心区的京津唐地区水资源问题最为严重.研究提出,只有结合开源节流和调整产业结构才能保证经济发展中的水资源供应安全.     

More Productivity with Fewer External Inputs: Central American Case Studies of Agroecological Development and their Broader Implications

A study of the impact of two agroecological development programs in central America was conducted in 1994, five years and fifteen years after the programmes had ended. Yields of maize and beans being achieved by those farmers involved in each program were, on the average, more than seven times the yields being achieved at the time of program initiation. Increases in yields and incomes were achieved through the use of a large number of innovations, involving especially soil retention measures, purchased organic matter, intercropped green manure/cover crops, natural pest control, crop diversification and crop rotations. Use of chemical fertilizer was reduced, herbicides avoided almost entirely, and several substitutes for pesticides are now used. These technologies, plus more recent innovations such as microscale water harvesting and precision planting, should enable small farmers around the world to increase productivity enough that the world can avoid major hunger over the next 30 years, without increasing substantially, if at all, the world's use of chemical inputs.     

Delivering on the Promise of Agroforestry

Agroforestry – the traditional practice of growing trees on farms for the benefit of the farm family and for the environment – was brought from the realm of indigenous knowledge into the forefront of agricultural research less than two decades ago. It was promoted widely as a sustainability-enhancing practice that combines the best attributes of forestry and agriculture. Based on principles of natural resource management and process-oriented research, agroforestry is now recognized as an applied science, that is instrumental in assuring food security, reducing poverty and enhancing ecosystem resilience at the scale of thousands of smallholder farmers in the tropics.Trees on farms provide both products and services: they yield food, fuelwood, fodder, timber and medicines, which farm families can use at home or take to market to bring in much-needed cash; they replenish organic matter and nutrient levels in soils and they help control erosion and conserve water. The International Centre for Research in Agroforestry, and its partners, are working to integrate the functions of trees with policy and institutional improvements that aim at facilitating wide-scale adoption by farmers.Two examples described in this paper are replenishing soil fertility in sub-Saharan Africa using short-term improved tree and shrub fallows and the results of agroforestry research to support significant land tenure policy in southeast Asia.Although just one option in sustainable land-use, science-based agroforestry has the potential to produce economically, socially and environmentally sound results for the billions of people who depend on this ancient practice and modern science.     

基于证书权威(CA)中心的时间戳服务系统的实现

介绍了数字签名不具有抗抵赖的问题 ,以及数据抗抵赖在信息安全中的重要性。在对原有的时间戳协议缺乏可靠的身份认证和可信性分析后 ,提出了一种新的基于证书权威 (CA)中心的时间戳服务协议。利用CA中心的信任原理和数字证书的身份认证作用 ,使提供时间戳服务的服务方具备了可靠的身份鉴别和可信性。并利用XML标记对时间戳的数据内容进行描述 ,形成简单、直观的时间戳 ,且无需复杂的编解码过程。通过正确和可信的时间戳可以判定用户数据产生的时间 ,防止用户事后的抵赖行为 ,为网络应用提供更为安全的数据。     

Linking rights and standards: the process of developing "rights-based" minimum standards on food security, nutrition and food aid

This article examines the recent revision of the Sphere Minimum Standards in disaster response relating to food security, nutrition and food aid. It describes how the revision attempted to incorporate the principles of the Humanitarian Charter, as well as relevant human rights principles and values into the Sphere Minimum Standards. The initial aim of the revision was to ensure that the Sphere Minimum Standards better reflected the principles embodied in the Humanitarian Charter. This was later broadened to ensure that key legal standards and principles from human rights and humanitarian law were considered and also incorporated, in part to fill the "protection gap" within the existing standards. In relation to the food security, nutrition and food aid standards, it was agreed by participants in the process that the human right to adequate food and freedom from hunger should be incorporated. In relation to more general principles underlying the Humanitarian Charter, itself drawn largely from human rights and humanitarian law, it was agreed that there was a need to strengthen "protection" elements within the standards and a need to incorporate the basic principles of the right to life with dignity, non-discrimination, impartiality and participation, as well as to explore the relevance of the concept of the progressive realisation of the right to food. The questions raised in linking rights to operational standards required thought, on the one hand, about whether the technical standards reflected a deep understanding of the values expressed within the legal instruments, and whether the existing standards were adequate in relation to those legal rights. On the other hand, it also required reflection on how operational standards like Sphere could give concrete content to human rights, such as the right to food and the right to be free from hunger. However, there remain challenges in examining what a rights-based approach will mean in terms of the role of humanitarian agencies as duty-bearers of rights, given that the primary responsibility rests with state governments. It will also require reflection on the modes and mechanisms of accountability that are brought to bear in ensuring the implementation of the Minimum Standards.