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901.
能源在集装箱港口企业总成本中占有相当比重,抓好集装箱港口能源管理工作十分重要。提出了分解能源消耗指标的做法。并在分解基础上,对能源消耗进行内部分析和外部分析,有效地降低运营成本。 相似文献
902.
903.
高寒隧道保温设计研究及热工计算方法初探 总被引:1,自引:0,他引:1
目前国内高寒隧道研究成果还不能完全满足隧道设计要求,文章借鉴我国建设部房建行业和日本国铁的研究成果,提出了适用于季节性冻土隧道洞口保温段长度、衬砌保温及水沟保温的设计计算方法。 相似文献
904.
905.
对中低速磁悬浮轨道梁设计和试验进行系统阐述。研究表明:中低速磁悬浮轨道梁适宜采用单箱单室后张预应力混凝土简支梁,强度计算不是轨道梁的控制因素,但是截面扭矩很大;刚度和动力性能成为中低速磁悬浮轨道梁的设计控制因素,通过试验,给出刚度和自振频率限值。专门研制的拉力调高钢支座能保证轨道梁横向稳定,预制架设方法是最适宜的施工方法。 相似文献
906.
Michiel C.J. Bliemer John M. Rose 《Transportation Research Part A: Policy and Practice》2011,45(1):63-79
Discrete choice experiments are conducted in the transport field to obtain data for investigating travel behaviour and derived measures such as the value of travel time savings. The multinomial logit (MNL) and other more advanced discrete choice models (e.g., the mixed MNL model) have often been estimated on data from stated choice experiments and applied for planning and policy purposes. Determining efficient underlying experimental designs for these studies has become an increasingly important stream of research, in which the objective is to generate stated choice tasks that maximize the collected information, yielding more reliable parameter estimates. These theoretical advances have not been rigorously tested in practice, such that claims on whether the theoretical efficiency gains translate into practice cannot be made. Using an extensive empirical study of air travel choice behaviour, this paper presents for the first time results of different stated choice experimental design approaches, in which respective estimation results are compared. We show that D-efficient designs keep their promise in lowering standard errors in estimating, thereby requiring smaller sample sizes, ceteris paribus, compared to a more traditional orthogonal design. The parameter estimates found using an orthogonal design or an efficient design turn out to be statistically different in several cases, mainly attributed to more or less dominant alternatives existing in the orthogonal design. Furthermore, we found that small designs with a limited number of choice tasks performs just as good (or even better) than a large design. Finally, we show that theoretically predicted sample sizes using the so-called S-estimates provide a good lower bound. This paper will enable practitioners in better understanding the potential benefits of efficient designs, and enables policy makers to make decisions based on more reliable parameter estimates. 相似文献
907.
Multi-objective optimization of a road diet network design 总被引:1,自引:0,他引:1
Keemin Sohn 《Transportation Research Part A: Policy and Practice》2011,45(6):499-511
The present study focuses on the development of a model for the optimal design of a road diet plan within a transportation network, and is based on rigorous mathematical models. In most metropolitan areas, there is insufficient road space to dedicate a portion exclusively for cyclists without negatively affecting existing motorists. Thus, it is crucial to find an efficient way to implement a road diet plan that both maximizes the utility for cyclists and minimizes the negative effect on motorists. A network design problem (NDP), which is usually used to find the best option for providing extra road capacity, is adapted here to derive the best solution for limiting road capacity. The resultant NDP for a road diet (NDPRD) takes a bi-level form. The upper-level problem of the NDPRD is established as one of multi-objective optimization. The lower-level problem accommodates user equilibrium (UE) trip assignment with fixed and variable mode-shares. For the fixed mode-share model, the upper-level problem minimizes the total travel time of both cyclists and motorists. For the variable mode-share model, the upper-level problem includes minimization of both the automobile travel share and the average travel time per unit distance for motorists who keep using automobiles after the implementation of a road diet. A multi-objective genetic algorithm (MOGA) is mobilized to solve the proposed problem. The results of a case study, based on a test network, guarantee a robust approximate Pareto optimal front. The possibility that the proposed methodology could be adopted in the design of a road diet plan in a real transportation network is confirmed. 相似文献
908.
Joseph Y.J. Chow Amelia C. Regan 《Transportation Research Part A: Policy and Practice》2011,45(8):765-778
A real option portfolio management framework is proposed to make use of an adaptive network design problem developed using stochastic dynamic programming methodologies. The framework is extended from Smit’s and Trigeorgis’ option portfolio framework to incorporate network synergies. The adaptive planning framework is defined and tested on a case study with time series origin-destination demand data. Historically, OD time series data is costly to obtain, and there has not been much need for it because most transportation models use a single time-invariant estimate based on deterministic forecasting of demand. Despite the high cost and institutional barriers of obtaining abundant OD time series data, we illustrate how having higher fidelity data along with an adaptive planning framework can result in a number of improved management strategies. An insertion heuristic is adopted to run the lower bound adaptive network design problem for a coarse Iran network with 834 nodes, 1121 links, and 10 years of time series data for 71,795 OD pairs. 相似文献
909.
在建的钱江隧道是高速公路项目钱江通道及接线工程下穿钱塘江的控制性工程,隧址位于钱塘江人海口,工程地质条件及河段水文条件复杂.隧道过江段采用盾构法施工,隧道直径为15.0 m,是目前世界上最大的盾构法隧道.文章详细介绍了钱江隧道工程的建设环境、建设标准,以及隧道平面、纵断面及横断面布置等总体设计方案,并对超大直径盾构隧道结构及防水、盾构浅埋下穿河流、软土地层深基坑、盾构段立体化平行作业及综合防灾系统等关键技术进行了阐述. 相似文献
910.
空隙率的大小对大空隙沥青混合料的渗透性及力学性能具有很大影响,透水铺面应根据用途选择合适的空隙率,在一定的水头(降雨强度)下利用空隙模型确定的目标空隙率进行混合料配合比设计.结果表明,空隙模型确定的目标空隙率可为混合料的配合比设计提供理论指导,提高了传统设计方法的工作效率和准确性. 相似文献