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排序方式: 共有92条查询结果,搜索用时 15 毫秒
81.
82.
W.Bruce Allen Mohamed M. Mahmoud Douglas McNeil 《Transportation Research Part B: Methodological》1985,19(5):447-456
Reliability of transit time is reputed to be the most important variable influencing freight transport today, according to shipper surveys. Average transit time also plays a major role. A model is developed that shows how a cost-minimizing shipper will adjust its economic order quantity as reliability and/or time in transit changes. Such changes impact on average inventory costs, ordering costs, expected shortage costs and expected excess costs. The model is developed for both discrete and continuous transit time distributions. Reliability is defined as the variance of transit time. A matrix is prepared for some sample data, which shows the minimum cost attainable with each mean/variance of transit time distribution. Comparing across rows and columns of the matrix enables one to show the value (reduction in total cost) obtainable by improving reliability and/or mean transit time. In addition, value can be obtained by improving reliability while increasing average transit time. It is suggested that the model can be used for shippers in negotiating service improvements with carriers and by carriers in negotiating service improvements with shippers. In the former case, the carrier can determine how much they are willing to pay for the improvement, whereas in the latter case, the carriers can determine how much they are able to charge for the improvement. 相似文献
83.
84.
Marc L. Miller 《Coastal management》2013,41(4):309-318
Abstract Natural resource management entities such as the Regional Fishery Management Councils established by the Magnuson Fishery Conservation and Management Act of 1976 depend heavily on science to inform policymakers and to legitimate the policy process. This paper discusses the importance of fishery science to the council system, contrasts the functions of Scientific and Statistical Committees (SSCs) serving the Pacific Fishery Management Council and the New England Fishery Management Council, and remarks on the implications of differences in the display of scientific authority by these SSCs. 相似文献
85.
86.
The adoption of Integrated Urban Models (IUMs) is increasingly being recognized as a tool to support transport policy appraisals in metropolitan areas. In Canada, the ILUTE (Integrated Land Use Transportation Environment) project is an IUM framework currently under development. While model development is undertaken by academics, the implementation of ILUTE is meant to occur within planning organizations thus rendering the success of model application dependent on available resources for modelling and planners’ attitudes towards the role of models. In an attempt to render the ILUTE modelling framework more “policy-sensitive”, a survey was conducted with planners and policy-makers pertaining to the three levels of government (municipal, provincial, and federal) in Canada. The survey collects information with respect to the current evaluation process of transport policy and its associated pitfalls as well as the desired state of policy appraisal and the need for more formal evaluation tools. Results show the presence of numerous challenges working against the proper development, adoption, and refining of models. The most notable of which include a general disbelief in the usefulness of models for decision-making, lack of resources for large-scale modelling exercises, and poor institutional integration among government departments. While local and national planning goals reflect the recent challenges of promoting environmental preservation, reducing social inequities, and improving the quality of life, modelling tools that can assess the impacts of proposed policies on these goals have lagged behind. 相似文献
87.
88.
Douglas K. Fleming 《Maritime Policy and Management》1981,8(4):281-283
The University of Washington recently (1981) established a College of Ocean and Fishery Sciences which incorporates extant programmes in oceanography, fisheries and other marine resource fields. The Institute for Marine Studies (IMS), organized in 1972 and presently directed by Professor Warren Wooster, is one component of the new college. IMS, a multidisciplinary academic and research unit, focuses on the management and policy issues arising from the many different uses of marine and coastal resources. 相似文献
89.
Gerard de Jong Andrew Daly Marits Pieters Stephen Miller Ronald Plasmeijer Frank Hofman 《Transportation》2007,34(4):375-395
This paper provides a review of transport model applications that not only provide a central traffic forecast (or forecasts
for a few scenarios), but also quantify the uncertainty in the traffic forecasts in the form of a confidence interval or related
measures. Both uncertainty that results from using uncertain inputs (e.g. on income) and uncertainty in the model itself are
treated. The paper goes on to describe the methods used and the results obtained for a case study in quantifying uncertainty
in traffic forecasts in The Netherlands.
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Gerard de JongEmail: |
90.
Welfare maximization for bus transit systems with timed transfers and financial constraints 下载免费PDF全文
Conventional and flexible bus services may be combined to better serve regions with a wide range of characteristics. If demand densities and resulting service frequencies are low, the coordination of bus arrivals at transfer stations may significantly reduce passenger transfer times. A method is proposed for integrating, coordinating, and optimizing bus services while considering many‐to‐many travel patterns, demand elasticity, financial constraints, and appropriate service type for various regions. The objective is to maximize welfare, that is, the sum of producer and consumer surplus. The problem is solved with a hybrid optimization method, in which a genetic algorithm with bounded integer variables is selected for solving one of the subproblems. The service types, fares, headways, and service zone sizes are jointly optimized. Sensitivity analyses explore how the choice among conventional and flexible busses depends on the demand, subsidy, and demand elasticity parameters. The results also show that welfare can increase due to coordination, and these increases are found to be higher in cases with high demand or low subsidy. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献