停车诱导信息系统条件下的城市交通网络SUE配流模型及算法

停车诱导信息系统(Parking Guidance Information System,PGIS)被认为是改善城市交通拥挤的一项有效技术,不同的PGIS市场占有率对道路交通的影响是不同的。文章将出行者分成两类:使用PGIS和不使用PGIS,考虑了PGIS对出行者道路和停车选择行为的影响以及PGIS的市场占有率,构造了随机用户均衡模型来描述PGIS条件下的道路和停车选择问题,设计了相应的算法。最后,通过一个算例对模型及算法进行了验证。     

Situation and prospects of shipboard integrated power system reconfiguration technology北大核心CSCD

当前,船舶综合电力系统(IPS)正朝着复杂化、模块化、自动化方向发展,研究快速、稳定、能够应对各种突发状况的船舶综合电力系统重构技术对保障船舶安全和可靠航行具有重要意义。首先,综述当前国内外在船舶综合电力系统重构技术方面的研究进展,讨论集中式重构和分布式重构的特点,并对数学优化算法、启发式算法、人工智能算法等进行归纳总结;然后,分析面对多重并发故障时重构技术所面临的困难与挑战,提出需重点关注混杂系统建模和分层分布式重构框架的建立;最后,从重构模型建立、算法优化、分布式架构等方面对未来船舶综合电力系统重构的发展提出设想和建议。     

Minnows And Sharks - Survival Of The Fittest

The Brazilian ship financing system has some unique features. The funds made available to finance the construction and acquisition of ships are sourced from a tax on import and cabotage freight, payable by the shippers. For Brazilian flagged ships, a portion of the tax generated can be used for the payment of loan instalments. This paper analyses the impact of the tax on the economy as a whole, and discusses the distribution of the tax burden between the shipowner and the shipper, taking into account the maritime transport demand elasticities in Brazil. The paper also analyses the effectiveness of the financing system in reducing the capital cost to shipowner, and the distortion effects produced by the utilization of the tax in loan repayments. The conclusion is that there are important distortions that may threaten the recovery of the maritime industry in Brazil.     

An Institutional Model for Comanagement of Coastal Resources in Fiji

In light of increasingly depleted coastal resources under the current management structure, this article explores the institutional arrangements that would be necessary in Fiji to create and implement a viable comanagement regime that would devolve some of the responsibility for management to the communities. Based on the literature concerning institutions for comanagement and the present situation and the institutional management structure in Fiji, it is recommended that government act as the catalyst by putting forth an enabling policy framework for comanagement that formally recognizes customary marine tenure. Such a policy should allow communities to derive bylaws from local rules, through shared management and technical assistance at the provincial level. At this same administrative level, planning units are recommended to coordinate government management of activities in the coastal zone.     

Rehabilitating the Mangrove Resources of Cogtong Bay,Philippines: A Comanagement Perspective

The local management of mangrove resources in Cogtong Bay, Philippines, dates back to the 1940s and 1950s when some families informally designated mangrove areas under their care and management. The 1960s and 1970s saw several exogenous events that led to the progressive denudation of mangrove stands and the decline in fish catch per fishing trip. This article draws attention to the forces that prompted coastal villages and external agents to collaborate with the national and local government units in resource rehabilitation. It also assesses the performance of a coastal resources comanagement project at Cogtong Bay.     

Shorelines management: The French approach

Although France does not have a specific law dealing with shorelines management, various policies and policy instruments exist which enable a certain amount of control over the shoreline development process. This article discusses the various institutional arrangements in France as they relate to (1) problems of marine pollution, (2) the control of land‐based pressures for shoreline use and development, and (3) the creation of a new shorelands trust. The role of existing institutions, such as the six river basin agencies, is also discussed.     

Weaving marine food webs from end to end under global change

Marine food web dynamics are determined by interactions within and between species and between species and their environment. Global change directly affects abiotic conditions and living organisms, impinging on all trophic levels in food webs. Different groups of marine researchers traditionally study different aspects of these changes. However, over medium to long time scales perturbations affecting food webs need to be considered across the full range from nutrients to top predators. Studies of end-to-end marine food webs not only span organism sizes and trophic levels, but should also help align multidisciplinary research to common goals and perspectives. Topics are described that bridge disciplinary gaps and are needed to develop new understanding of the reciprocal impacts of global change on marine food webs and ocean biogeochemistry. These include (1) the effects of nutrients on biomass and production, (2) the effects of varying element ratios on food web structure and food quality, (3) bulk flows of energy and material in food webs and their efficiencies of transfer, (4) the ecological effects of species richness and the roles of microbial organisms, (5) the role of feeding behaviour in food web dynamics and trophic controls, (6) the spatial dynamics of communities and links between different food webs, (7) the combined effects of body size and behaviour in determining dynamics of food webs, and (8) the extent to which the ability of marine organisms (and communities) to adapt will influence food web dynamics. An overriding issue that influences all topics concerns the time and space scales of ecosystem variability. Threads link different nodes of information among various topics, emphasizing the importance of tackling food web studies with a variety of modelling approaches and through a combination of field and experimental studies with a strong comparative approach.     

美国铁路车钩缓冲装置的发展(待续)

介绍美国铁路车钩缓冲装置的发展过程、结构特点及运用情况。     

Near surface deformation of rails and wheels in a curve and during acceleration and braking

A hierarchical concept for describing the rolling/sliding contact of a wheel on a rail is proposed, which is developed to model the near surface deformation of the contacting partners depending on the vehicle system dynamics. In principal the vehicle dynamics simulation delivers the input for a static finite element model for the elastic-plastic rolling/sliding contact investigation. To include also more realistic rough surfaces in the calculations, which is absolutely necessary to predict the highly deformed surface layer as observed in wheels and rails, a further refinement of the mesh is necessary and performed. The output values of the static finite element model are now boundary conditions for the finite element micro-model. The results of this micro-model correspond well with the micro-structural investigations of wheel and rail surfaces.