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91.
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
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西江航道桂平航运枢纽—长洲水利枢纽之间存在约34 km的水位未衔接段,而大藤峡水利枢纽建设选取的江口料场位于长洲枢纽库区回水末端和上游附近滩段。为研究库尾段采砂工程对上游通航水流条件的影响,须同步考虑上游来水和下游库区回水的变化,建立桂平三江口上游黔江河段16 km和桂平枢纽—长洲枢纽约156 km的长河段二维水流数学模型,分析采砂工程对航道通航水流条件的影响。结果表明,采砂工程实施后上游桂平航运枢纽引航道水位降落0.09 m,布岭沙弯道凸岸侧边滩挖除引起主流一定左偏。整体上,除设计流量外,库尾段采砂工程对航道水流条件影响较小。 相似文献
94.
为提出一种适用于隧道初期支护基面找平并且具有一定透水性能的砂浆,将纸纤维加入砂浆试块中对其性能进行改性。通过分析纸纤维的降解原理,并将不同掺量的纸纤维加入砂浆试块中,对其体积密度、吸水率、抗压强度等基本性能指标及微观结构进行测试和分析。由试验结果可知:在碱性环境中,纸纤维具有可降解的性能特点;纸纤维可以使普通砂浆试块的吸水率提升2~3倍,同时也会造成砂浆试块的体积密度和抗压强度降低;对砂浆试块吸水率和抗压强度进行线性拟合后发现其吸水率和抗压强度呈现负相关关系。研究结果表明,通过纸纤维对砂浆进行透水性能的提升是可行的,但是纸纤维掺量对砂浆其他性能的影响还有待进一步研究。 相似文献
95.
Jeom Kee Paik Jae Myung Lee Young II Park Joon Sung Hwang Chang Wook Kim 《Marine Structures》2003,16(8):567-600
Many bulk carrier losses have been reported of late, and one of the possible causes of such casualties is thought to be the structural failure of aging hulls in rough weather. In aging ships, corrosion and fatigue cracks are the two most important factors affecting structural safety and integrity. This paper uses a set of the time-dependent corrosion wastage models for 23 different member locations/categories of bulk carriers previously developed by the authors, based on the available corrosion measurements for existing large bulk carrier structures. Differences due to the location and corrosion severity of every member type are taken into account. The nominal design corrosion values for the primary members are suggested based on the annualized corrosion rates obtained in the present study. The effect of time-variant corrosion wastage on the ultimate hull girder strength as well as the section moduli is studied. The criteria for repair and maintenance of heavily corroded structural members so as to keep the ultimate longitudinal strength at an acceptable level are discussed. Important insights and conclusions developed are summarized. 相似文献
96.
Lidia P. Kostyniuk 《Transportation》2009,36(6):641-642
97.
This paper proposes a non-linear dynamics model for articulated vehicles. This model is able to capture common low-speed behaviours of any articulated vehicles off-highway, such as operating for a corner or roundabout on a cambered or slippery surface. It can be used to assess the low-speed manoeuvrability of articulated vehicles under such manoeuvres and conditions. The vehicle model was validated by comparing its path tracking performance to that of the field tests. 相似文献
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Many French and European cities have developed a bike sharing system since 2005. This policy may be explained in a great part by the success of the Velo??v in Lyon, which contributed to improve the image of cycling in the city. If bicycles, however, appear to find a new place in the city, one can wonder whether this is really due to bike sharing systems? What are the real uses of bicycles in contemporary cities, with or without such a system? To answer these questions, the paper starts with a literature review on bicycle in the city, to draw lessons from recent experiences of bike sharing systems. It then discusses the two cases of Lyon and Lille, which never had a bike sharing system on its own. The evolution of bicycle use is measured with a comparison of household transportation surveys in Lyon (1995 and 1998) and Lille (1998 and 2006). In both cities, the analysis reveals a rise in the proportion of healthiest citizens among urban bikers, as well as a return of bikes in dense areas. Bike sharing systems are part of such tendencies. They support them, but should not become a panacea for policies supporting bike use in the city. 相似文献