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161.
162.
Jane Bryan Max Munday David Pickernell Annette Roberts 《Maritime Policy and Management》2006,33(4):371-386
The paper seeks to improve the evidence base surrounding regional ports and their economic impact. The paper reveals that industries dependent on the port infrastructure are actually key regional players, often operating in relatively fast growth sectors, and contributing to the economic and social needs of the local economy. The focus in the case element of the paper is the operations of Associated British Ports (ABP) plc in industrial South Wales. In examining the direct and indirect consequences of the port activity the paper adopts an input-output framework of analysis. A better contextualization of the economic impact of ports is shown to be necessary in the devolved policy-making environment in the region. 相似文献
163.
Dennis E. Blumenfeld Lawrence D. Burns J.David Diltz Carlos F. Daganzo 《Transportation Research Part B: Methodological》1985,19(5):361-380
The purpose of this paper is to determine optimal shipping strategies (i.e. routes and shipment sizes) on freight networks by analyzing trade-offs between transportation, inventory, and production set-up costs. Networks involving direct shipping, shipping via a consolidation terminal, and a combination of terminal and direct shipping are considered. This paper makes three main contributions. First, an understanding is provided of the interface between transportation and production set-up costs, and of how these costs both affect inventory. Second, conditions are identified that indicate when networks involving direct shipments between many origins and destinations can be analyzed on a link-by-link basis. Finally, a simple optimization method is developed that simultaneously determines optimal routes and shipment sizes for networks with a consolidation terminal and concave cost functions. This method decomposes the network into separate sub-networks, and determines the optimum analytically without the need for mathematical programming techniques. 相似文献
164.
Governments of all persuasions are increasingly seeking the participation of the private sector in the supply of transport facilities and services. Private sector participation in the financing, construction, operation and maintenance of infrastructure is considered a serious option in a number of countries in the search for ways of providing much needed investment which would otherwise be deferred. This paper considers some economic and financial problems in the private sector provision of major road infrastructure within urban areas. The main issues are attaching prices (i.e. tolls) to the provision of the service, the value of government rights which are being given up either permanently or temporarily, and the identification required by the promoters of the cost of capital which is essential information in establishing the risk. Broader environmental and equity issues are not addressed. If the approach to establishing a private presence in a previously public supply context is handled properly from the outset, the benefits can be significant. Contrarily however, the prospects could be quite undesirable if badly managed, despite the presence of an extended public purse.requests for offprints 相似文献
165.
David L Garrison 《Journal of Marine Systems》1991,2(3-4)
The classic view of the Antarctic pelagic system has suggested that food web dynamics are dominated by the diatom-krill food web link. Recent observations, however, have indicated that this is an oversimplification and that the antarctic food web has a complexity similar to that found in lower latitude systems. More specifically, small particulate feeding protozoans appear to have a much greater importance than was previously assumed.Only a few studies have been sufficiently extensive to characterize the Antarctic pelagic protozoan assemblage. These indicate that heterotrophic flagellates (dinoflagellates and other heterotrophic nanoplankton) and ciliates (mostly non-loricate oligotrichs) dominate the protozooplankton assemblages in surface waters. The combined biomass of protozooplankton has been reported to comprise from < 7 to > 75% of the total nano- and microplankton biomass depending on season and location. Protozoans are also found in sea ice communities where their abundances exceed those typically found in the plankton. Several protozoan species occupy both ice and water habitats, suggesting that seasonally melting sea ice may be the source of ice-edge protozooplankton assemblages.The feeding rates of protozooplankton in Antarctic waters are poorly documented. Consumption estimates based on clearance rates and some preliminary grazing experiments, however, indicate that the protozooplankton should be capable of utilizing a significant proportion of the daily primary and bacterioplankton production. Protozoans may contribute to vertical flux, but present evidence suggests that their contribution will be lower than from other sources. 相似文献
166.
John R. Siddorn J. Icarus Allen Jerry C. Blackford Francis J. Gilbert Jason T. Holt Martin W. Holt Jeff P. Osborne Roger Proctor David K. Mills 《Journal of Marine Systems》2007,65(1-4):417
This paper outlines an approach to complex spatio-temporal marine ecosystem modelling as applied to the North Western European Continental Shelf. The model presented here combines an eddy-permitting (approximately 6 km horizontal resolution) baroclinic model, the Proudman Oceanographic Laboratory Coastal Ocean Modelling System (POLCOMS), with the European Regional Seas Ecosystem Model (ERSEM). This has been run within an operational framework using operationally available high resolution atmospheric and lateral boundary forcing, allowing hindcast and near-real time nowcast simulations to be performed. The modelled surface temperature and chlorophyll distributions are presented, and interannual variations discussed. Validation of both the physical and ecosystem submodels show the system to be effective, whilst highlighting areas where improvements in the system can be made. Distinct regional differences in predictive skill are shown. The system presented is ready for operational implementation to provide products and services for use both scientifically and in coastal zone and shelf seas management activities. A programme of work to update the system is already in place. 相似文献
167.
David L. Greene 《Transportation Research Part B: Methodological》1984,18(1):43-61
A regional, econometric model of heavy truck diesel fuel use is derived based on the theory of production. Input demand functions for new trucks and diesel fuel are specified and estimated. A simple, logistic scrappage model is estimated and used to estimate total heavy truck stocks and diesel-engine heavy truck stocks. Demand equations based on the AIDS almost ideal demand system flexible form cost function are estimated for new heavy truck demand and regional highway diesel fuel demand. New heavy truck demand is found to be elastic with respect to GNP, inelastic with respect to own price, and appears extremely sensitive to short term GNP trends. The short run price elasticity of diesel fuel demand is found to be very small. 相似文献
168.
169.
In contrast to the centralized port-planning framework that is utilized in some industrialized countries, the US relies on a complex and fragmented framework in which responsibility for the planning, development and operation of landside maritime infrastructure rests with State and local governments. It has been argued that the separation of the federal government from port policy was rooted in the port preference clause of the Constitution. This paper is an effort to determine whether the current decentralized port policy in fact stems from the Constitution and, to that end, reviews how over the years the US Supreme Court has construed the port preference clause in the Constitution. It was found that there is no evidence to support the assertion that the port preference clause has restricted the development of Federal port policy. Moreover, the decentralized and fragmented decision-making process that is evident today does not imply the absence of federal impact. Rather, it reflects federal involvement through multiple agencies and regulatory processes and is a conscious effort, consistent with other areas of transport infrastructure development, to retain local decision-making for infrastructure investments. It is concluded by raising the issue whether current federal involvement in ports (that is, existing federal port policy), through dredging, landside transportation improvements or subsidized capital, among other things, needs to be reappraised before a new round of capital intensive investment begins. 相似文献
170.
David T. Hartgen 《Transportation》1974,3(1):45-58
An analogy is developed between individual traveler mode choice decisions and time-dependent product adoption processes in
consumer behaviour. The structure of the adoption sequence is first described conceptually with reference to mode switch ing;
this structure is then used to develop a simple mathematical model of mode switching behaviour over time. Factors to be considered
in interpreting and operationalizing the model are then discussed at some length. The model appears too complex for direct
mathematical solution except in the simplest cases; it may however, be amenable to numerical estimation, given empirical data
on mode switching behaviour over time. 相似文献