大型综合枢纽与城市交通体系运行协调性分析

从促进枢纽与城市整体交通相互配合、协调运行的需要出发,分析规划协调、运输组织管理协调以及客运服务要求等多个方面,总结并提出具有普遍适用价值的协调运行对策和建议,为我国综合客运枢纽的运营管理提供参考。     

Environmental standard adoption in Marinas: A spatiotemporal analysis of a special form of maritime transportation hubs

The growth of both commercial and recreational boating has posed significant environmental challenges to waterways. As an effort by the U.S. government and other public service organizations to prevent and mitigate the environmental impact, Clean Marina Programs (CMP) have been developed to encourage marina owners and operators to meet environmental standards and become better stewards of the environment. This study examines the impact of geospatial proximity on the adoption timing and diffusion of a CMP in marinas, a special form of a maritime transportation hub. Drawing upon case study methodology and literature on geography and organizational clusters, we find that the adoption timing of an environmental standard varies with the density of the market within which it is promoted. These results lend support to the notion that firms in close proximity can accelerate standard adoption, hastening information flow about environmental standards through local labor pools, customer interactions, and resources.     

Chemical and mineralogical composition of marine sediments, and relation to their source and transport, Gulf of Carpentaria, Northern Australia

The Gulf of Carpentaria is an epicontinental sea, deeply indented in the north of the Australian continent. A selection of 100 samples of the surficial marine sediments collected on a regional grid were analysed for major chemical elements and mineral phases using wet chemistry, X-ray diffraction, optical and electronic microscopy.The surficial sediments of the Gulf are highly heterogenous and consist of both young and relict mineral and carbonate components. The terrigenous fraction is fluvial in origin and consists mainly of quartz (16–68%), minor feldspars (0–9%) and traces of siderite. The clay species determined include kaolinite, mixed layers of smectite–illite and illite; clays range up to 15% and do not present a clear pattern of distribution. Biologically productive areas of the Gulf, mainly in shallower parts, supply the carbonate component of the sediment. The carbonate material is comprised of aragonite (7–30%), low-Mg (5–30%) and high-Mg calcite (7–28%), and has variable degrees of alteration caused by sediment transport and/or diagenesis. Such processes are partly reflected in the regional distribution of mineral and chemical components throughout the Gulf. The interpretation of the data set was further refined by cluster analysis (Ward's method), which separated eight clusters (provinces) of sedimentary material. The eastern side appears to be the main source of both terrigenous and carbonate sediment, which is inferred to be transported clockwise. During this dispersion, physicochemical and mineralogical changes take place; the sediments become finer grained and characterised by more stable species of carbonates. As a consequence, the center and the northwest sections are clay-rich and contain dominantly low-Mg calcite.Ooids are relict components that have been identified in areas in which they were not mentioned by previous studies, notably in the southeast. These carbonate particles consist of concentric layers of aragonite deposited around a nucleus of angular quartz, most likely of fluvial origin.This study indicates a complex history over a short time frame with sediment supply, biological production and current patterns being the main factors that control the sediment character and its regional distribution within the Gulf.     

广西北部湾港口保税物流腹地经济圈构建研究

广西北部湾港口保税物流群的设立是我国为发展西部地带经济,推动中国-东盟自由贸易区而采取的重要举措。文章结合我国保税物流兴起的背景,介绍了广西北部湾港口保税物流业务分工内容及其对腹地经济区域的辐射作用,分析了广西北部湾港口保税物流腹地经济圈发展存在的问题,提出相应的发展思路和对策。     

北部湾港口建设与整合的思考

交通运输部批准将防城港、钦州港、北海港三港统一归并为广西北部湾港。北部湾港口建设与整合,有利于建设西南出海大通道,加快中国经济融入东盟自由贸易区,开发利用北部湾丰富的资源,促进北部湾经济和城市建设的发展。今后要进一步健全北部湾港口管理体制,发展临港工业,拓展港口腹地,加速与东盟港口对接,加大财政投入,实现北部湾港口群的崛起。     

公铁联运规模效应和枢纽拥挤效应的联动分析

公铁联运最主要的优势就是采用轴辐式网络结构实现规模经济,降低货物的运输成本,货运量越大,规模效应越明显;另一方面,过多的货物在枢纽集结会造成枢纽拥挤,增加货物在枢纽的停留时间,从而降低了公铁联运的竞争力.本文分别采用与流量相关的分段成本函数和M/M/c的排队模型来描述公铁联运的规模效应和拥挤效应,建立了非线性的整数规划模型,用于综合分析规模效应和枢纽拥挤效应对公铁联运的影响.采用混合禁忌搜索算法求解本文的模型,该算法具有较好的收敛效果.最后,分析了铁路服务固定成本、公路运输成本、货物运到期限和枢纽能力对公铁联运竞争力的影响.     

Water masses and cyclonic circulation in Bay of La Paz, Gulf of California, during June 1998

The Bay of La Paz, a coastal and shallow basin of the Gulf of California (depth<420 m), exchanges mixed-layer waters with the Gulf of California predominantly through Boca Grande (Big Mouth), in the northeastern part of the bay. Equatorial Surface Water (ESW) flows from the gulf to the bay; once there, due to evaporation processes, this water increases its salinity above 35.00, therefore becoming Gulf of California Water (GCW) Mass. During June 1998, the baroclinic circulation in the bay was dominated by a cyclonic gyre. The hydrographic dome, related to this gyre, is depicted until approximately 150-m depth. However, the vertical mixing of water between the mixed-layer and the ones below practically does not occur because of the development of a sharp pycnocline. This fact and the isolation of the bottom of the bay by a bathymetric sill (approximately 250-m depth) at Boca Grande induce low oxygen content, particularly in the bottom-waters (O₂<0.1 ml/l). Chlorophyll values are higher and with larger vertical fluctuations within the Bay of La Paz than outside.     

The reliable hub-and-spoke design problem: Models and algorithms

Hub-and-spoke structure is widely adopted in industry, especially in transportation and telecommunications applications. Although hub-and-spoke paradigm demonstrates significant advantages in improving network connectivity with less number of routes and saving operating cost, the failure of hubs and reactive disruption management could lead to substantial recovery cost to the operators. Thus, we propose a set of reliable hub-and-spoke network design models, where the selection of backup hubs and alternative routes are taken into consideration to proactively handle hub disruptions. To solve these nonlinear mixed integer formulations for reliable network design problems, Lagrangian relaxation and Branch-and-Bound methods are developed to efficiently obtain optimal solutions. Numerical experiments are conducted with respect to real data to demonstrate algorithm performance and to show that the resulting hub-and-spoke networks are more resilient to hub unavailability.     

Congestion spill effects of Heathrow and Frankfurt airports on connection traffic in European and Gulf hub airports

We develop two stage fixed-effects single-spill and double-spill models for congestion connection spills of London Heathrow and Frankfurt airports on 9 hub airports in Europe and the Gulf. Our panel data covers connection traffic from 1997 to 2013 for Heathrow and 1997 to 2011 for Frankfurt. The single-spill results support strongly that the connection spills from Heathrow’s capacity limitations do strengthen competing hub airports of major alliance groups and to a lesser degree one Gulf hub. The double-spill model for Heathrow and Frankfurt shows nearly asymmetric overall spill characteristics between the two airports. Our results underline the influence of airline network strategies on congestion spills as European airline networks are shaped by alliances and umbrella mergers. Thus, the airline network perspective in airport capacity expansion decisions needs to play a greater role, as indicated by our asymmetric results for overall spill effects between Heathrow and Frankfurt airports.     

Coastal and Ocean Science-Based Decision-Making in the Gulf of California: Lessons and Opportunities for Improvement

The Gulf of California hosts astounding biodiversity that supports numerous economic activities in the region. These activities, and emerging threats, are placing pressure on the region's ecosystems. Government and civil society are working to address threats through several conservation and management mechanisms. Nevertheless, the use and incorporation of scientific information—a key component for creating effective and durable management—is still deficient. This article presents the concept of science integration and discusses the findings of a study that assesses the regional landscape, existing institutional arrangements, and capacity for using science to inform policy and management decisions. It also explores the current use of science within fisheries policy and management and the capacity of the National Network of Information and Research of Fisheries and Aquaculture (RENIIPA) and the State Fisheries and Aquaculture Councils, two mechanisms in the region. Finally, it shares lessons learned and offers recommendations on how the region can strengthen science-based decision-making. Results indicate that while there are some actors in the Gulf of California producing relevant science, there is varying capacity of intermediary groups connecting producers with users of science, or mechanisms in place to ensure that science is being utilized in decision-making processes. Moreover, despite having a well-developed landscape of producers and intermediaries and mechanisms in place for fisheries management in the region, effective science integration is not occurring.