基于CPK的IPSec协议的改进研究

介绍了采用基于组合公钥（CPK）技术的认证原理,提出一种简化或取消第三方CA机构或证明,减少庞大的支持机构和维护量,从而达到简化IPSec协议的实现过程和提高认证效率。     

Part II: Policy instruments for sustainable road transport

Without questioning the fact that to achieve efficiency emitters should pay for the true costs of their actions (a core principle of economic policies such as pollution taxes), we find sufficient evidence in the literature to demonstrate that many other policy instruments can be used in combination with taxes and permits to ensure that the transport needs of the present generation can be met without compromising the ability of future generations to meet any needs of their own.The policies and policy aspects considered in this paper broadly fall into three categories: physical policies, soft policies, and knowledge policies. All three aim to bring about changes in consumers’ and firms’ behaviour, but in different ways. The first category includes policies with a physical infrastructure element: public transport, land use, walking and cycling, road construction, and freight transport. We also consider the particular challenges for mobility in developing countries, and how these may be addressed. Soft policies, on the other hand, are non-tangible aiming to bring about behavioural change by informing actors about the consequences of their transport choices, and potentially persuading them to change their behaviour. These measures include car sharing and car pooling, teleworking and teleshopping, eco-driving, as well as general information and advertising campaigns. Finally, knowledge policies emphasise the important role of investment in research and development for a sustainable model of mobility for the future.The main findings can be summarised as follows.

Physical policies

An increase in the use of public transport, combined with a decrease in the use of private cars, can reduce traffic congestion and, more importantly, carbon dioxide (CO₂) emissions, as public transport generally causes lower CO₂ emissions per passenger kilometre than private cars. Public transport fares are subsidised in most places, which can be justified by economies of scale and by the fact that public transport can reduce total road transport externalities. London, Singapore, Portland and Curitiba are all examples of good practice at government level, having achieved reliable, frequent and integrated public transport.Policies to increase public transport use must be part of an integrated policy. Integrated policy refers to integration across different modes of transport, different government objectives (such as the economy, health and the environment), considering the needs of different social groups, and coordinating action between the relevant government institutions. There is evidence that a lack of coordination can jeopardise the achievement of policy objectives.A sustainable model for transport policy also requires integration with land-use policies. These may be somewhat limited within the bounds of existing cities, but as cities grow and new cities are built, urban planners must put more emphasis on land use for sustainable transport in order to reduce congestion and CO₂ emissions. Sustainable land-use policy can direct urban development towards a form that allows public transport as well as walking and cycling to be at the core of urban mobility.Walking and cycling, which improve general health and produce no tailpipe emissions, constitute an excellent alternative to motorised transport on short-distance trips within towns and cities. The policies which can incentivise walking and cycling include crime reduction to make streets safer, well-maintained and clean pavements, attractive street furniture, safe crossings with shorter waiting times, dedicated cycle paths, showers in offices, and lower speed limits, to name but a few.Road construction and expansion used to be seen as one of the most promising ways to reduce traffic congestion. However, in the mid-1990s, the issue was reassessed and it was found that building and expanding roads, increased, rather than decreased, congestion, and ultimately induced higher levels of travel demand. The reason for this is that the extra capacity reduces the general cost of travelling and the less expensive the travel, the more it will be demanded. Regarding freight modal shift, road transport is much more polluting than rail per tonne-km of goods transported and therefore a shift towards greater use of rail in freight transport is desirable. Inadequate infrastructure is the main obstacle preventing this modal shift taking place.Developing countries face great mobility challenges: rural areas are often extremely poorly connected to transport infrastructure, such that, in contrast to the situation in developed countries, the benefits of road construction can strongly outweigh the total costs (including environmental ones). The main challenge, however, is to develop a solution to the problems arising from the combination of urbanisation and motorisation. Integration of transport and land-use policy will be key to rising to this challenge.

Soft policies

Car sharing and car clubs can also potentially reduce CO₂ emissions, although the aggregate reduction in congestion and emissions has not been measured with an adequate degree of precision in the literature. Teleworking and teleshopping can potentially reduce congestion and also CO₂ emissions. However, the evidence for this reduction is rather mixed, as it is unclear whether these measures lead to overall reductions in road transport.Eco-driving campaigns aim to inform and educate drivers in order to induce them to drive in a fuel-efficient and thus environmentally friendly way. There seems to be some consensus in the literature that eco-driving could lead to reductions in CO₂ emissions of around 10 per cent.Information and education policies have often been advocated as instruments which may affect behavioural change. We find in this paper that these types of measures are necessary, but not sufficient for behavioural change. Advertising and marketing may go a long way in changing peoples’ behaviour. In California, for example, Kahn (2007) finds the “Prius” effect: the Toyota Prius is preferred by consumers relative to other similarly green vehicles, probably due to extensive marketing and celebrity endorsements. Family life changes are also found to trigger changes in behaviour ( [Goodwin, 1989] and [106]). People whose lives are being changed by some important development (birth of a child, retirement, etc) tend to respond more to changes in the relative attractiveness of different transport modes. Advertising campaigns promoting a modal shift towards public transport, for instance, may thus be more successful if targeted at people in the process of important life transitions.

Knowledge policies

Research and Development is crucial for developing sustainable and low-carbon transport for the future, and it is essential that governments provide incentives to undertake R&D, so that new low-carbon technologies in the transport sector can be demonstrated and applied at a large scale.Finally, we consider the issue of policy combination and integration. There is evidence that the combination and integration of policies can lead to positive side-effects and synergies. Policy integration is crucial in order to rise to the challenges we face in moving towards a sustainable mobility model. We conclude that classical economic policies may be successfully combined with a number of policy measures discussed in this paper in order to achieve sustainability in transport.     

消防水炮在小型高速船舶上的应用实例

水上火灾具有起火快，易蔓延，难扑救等特点，如能在起火初期尽快将消防人员送达起火处了解火情并进行初期扑救，往往能对扑救工作起到事半功倍的效果。将消防水炮和高速艇相结合，是满足上述需求的一个解决方案。主要介绍了消防水炮在小型艇上的应用实例，采用恰当功率的水炮泵，优化选取的进水口、尽量短而直的管路是该艇水炮设计的技术特点。通过对该具体项目的实施及故障进行分析，简要阐述了水炮设备在小型船舶上使用的可行性及应用前景。     

浅谈水库除险加固问题及治理对策

病险水库除险加固的投资不足、前期工作深度不够、项目管理不规范及未能建立良性循环的管理体制是影响其加固进度及质量的主要原因。本文探讨了解决这些问题的办法。     

中国城市公交和车辆技术的创新发展

本文对中国城市公交和车辆技术的创新发展最新成果进行了介绍,论述了中国城市公交和车辆技术的发展方向及发展前景。     

Predicting Stakeholder Support for Fishery Policies

Fisheries management has been used to address declining fisheries and threats to livelihood and food security. Past research suggests that public support for fishery policies is a necessary component for sustaining the long-term success of fisheries management. This study predicted public support by examining fishers’ perspectives on co-management and fish catch since the establishment of marine protected areas (MPAs), a commonly employed fisheries management tool. Data were obtained from onsite surveys (n = 505) with fishers from three municipalities in Cebu, Philippines: Oslob, Santander, and Samboan. Structural path analyses revealed that beliefs about co-management and fish catch predicted support for fishery policies (R² = 59%). Separate path analyses for each municipality showed that co-management had greater influence in predicting public support for fishery policies in Oslob and Santander. Fish catch was a better predictor for public support for fishery policies in Samboan. Results can help local governments, non-governmental organizations, and fishery managers to prioritize, plan, and improve fisheries management in municipal waters.     

Rail and multi-modal transport

This paper elaborates on the definitions of inter and multi-modal transport, as well as their differences in terms of performance. A survey of the barriers, both internal and external, to an efficient intermodal transport is included followed by an analysis of the advantages and disadvantages of combining rail transport with the other transport modes. Transhipment technologies for efficient freight service and some examples of freight rail corridors between sea and inland terminals are presented. The integration between air and rail transport is discussed and the potential synergies between air and high-speed rail services are emphasised. The paper concludes with a discussion on energy use for sustainable rail performance.     

MMAS in Belize

This article is part of a special issue that provides insight into global conservation science by analyzing a 5-year, $12.5 million global marine conservation science and policy program. In this article, we summarize the development of the program in Belize, which concentrated its effort in the southern portion of the country. The marine managed areas that developed in Belize took a variety of different forms, and involved a number of different government and private sector agencies and organizations.     

基于状态迁移的网络安全联动策略模型

针对网络安全联动系统中安全策略结构日益复杂,数量不断增多所带来的策略冲突、效率低下、冗余等问题,文章采用形式化分析的方法对安全联动防卫策略的完备性、一致性和冗余性进行了定义及分析,提出了一种基于状态迁移的网络安全联动策略模型。该模型由实体、状态、服务三层构成,通过状态迁移过程分析实体之间的关系,并由服务层提供构造、检测等分析组件确保系统稳定运行。该模型实现了策略从生成、应用到失效的全生命周期管理。     

Fuel price elasticities for single-unit truck operations in the United States

This paper provides fuel price elasticity estimates for single-unit truck activity, where single-unit trucks are defined as vehicles on a single frame with either (1) at least two axles and six tires; or (2) a gross vehicle weight greater than 10,000 lb. Using data from 1980 to 2012, this paper applies first-difference and error correction models and finds that single-unit truck activity is sensitive to certain macroeconomic and infrastructure factors (gross domestic product, lane miles expansion, and housing construction), but is not sensitive to diesel fuel prices. These results suggest that fuel price elasticities of single unit truck activity are inelastic. These results may be used by policymakers in considering policies that have a direct impact on fuel prices, or policies whose effects may be equivalent to fuel price adjustments.