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A model to compare three alternative forms of public transport - light rail, heavy rail and bus rapid transit - is developed for an urban network with radial lines emanating from the borders to the city centre. The theoretical framework assumes an operation aimed at minimising the total cost associated with public transport service provision, which encompasses both operator and users costs. The decision variables are the number of lines (network density) and the frequency per period for each mode. This approach has no prejudices a priori in respect of whether a specified delivery scenario is aligned with existing modal reputation. Rather, we establish the conditions under which a specific transit mode should be preferred to another in terms of the operator (supply) and user (demand) side offerings. The model is applied using data from Australian cities, suggesting that in most of the scenarios analysed a high standard bus service is the most cost-effective mode, because it provides lower operator costs (infrastructure, rolling stock and operating cost), access time costs (due to a larger number of lines) and waiting time cost (due to larger frequencies of operation). A rail mode, such as light rail or heavy rail, may have a lower total cost only if it is able to run faster than bus rapid transit, and the difference in speed is enough to outweigh the bus advantage on operator cost and access and waiting times. 相似文献
73.
为探索锚泊船偏荡时船与锚链相互作用问题,开展了非均匀条件下锚链静力特性的快速计算研究。采用分段外推-校正方法计算了锚链张力、顶端倾角、悬垂线形状及长度。通过寻找锚链悬垂线最低点位置以及预估顶端倾角的方法来增加求解速度,实现了快速运算。 相似文献
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魏晓江 《筑路机械与施工机械化》2011,28(4):54-56,59
介绍了武广铁路客运专线XXTJV标采用移动模架现场浇筑32m后张预应力双线整孔简支箱梁快速施工技术,采用网络计划技术对移动模架快速制梁施工进行优化管理,达到了连续5孔、每孔11d的施工水平,可为类似工程施工提供一定的经验和指导。 相似文献
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Objective To investigate the histological changes of rapid tooth movement in dogs treated by resistance reduction and distraction osteogenesis, aiming to establish an animal model and further to reveal the remodeling mechanism of rapid tooth movement. Methods A total of 8 local hybrid dogs were selected as subjects for this study. The second pre-molar was extracted on both sides. The experimental side underwent alvelor surgery for resistance reduction and a home-made tooth-borne intraoral distraction device was installed for rapid tooth movement, while for the other side (control side) only tooth-borne intraoral distraction device was used for rapid tooth movement. The longest active force-delivery span was 2 weeks, followed by 6-week retention. The distance between the moved tooth and anchor unit was recorded weekly, and radiography was performed for each side before and after distraction. The surrounding tissues including periodontal ligament and alveolar bone were sectioned for histological analysis. Results The average distance of tooth movement was 3.55mm on the experimental side and 1.11mm on the control side. The rate of tooth movement was notably higher (P<0.01) and no significant apical root resorption was detected by X-ray on the experimental side. The active alvelor bone remodeling was found on the tension and pressure sides. However, there was no significant difference between the experimental side and the control side after the retention period. Conclusion The rate of orthodontic tooth movement can be accelerated through resistance reduction and periodontal distraction without any unfavorable effects but at minimal anchorage loss. 相似文献
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本文结合我国高速铁路客运站的规划和运营管理实际特点,对城市交通接驳能力协调配置问题进行研究.以换乘成本最小为目标,分析城市交通接驳方式分担率,建立铁路与轨道交通、铁路与常规公交的运能合理匹配协调优化模型.并且以北京南站为背景,对城市交通接驳能力匹配方案进行事例模拟分析. 相似文献
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该文阐述了利用由旧路面水泥混凝土块破碎而成的再生骨料,进行再生修补型路用混凝土的性能试验。着重介绍其抗压强度、抗折强度、干缩变形以及抗冻性能的测试。结果表明,所配制的再生早强型和再生快修型混凝土具有较好的力学性能和耐久性能,可用于重交通等级路面的修补。 相似文献