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31.
Compared with most optimization methods for capacity evaluation, integrating capacity analysis with timetabling can reveal the types of train line plans and operating rules that have a positive influence on improving capacity utilization as well as yielding more accurate analyses. For most capacity analyses and cyclic timetabling methods, the cycle time is a constant (e.g., one or two hours). In this paper, we propose a minimum cycle time calculation (MCTC) model based on the periodic event scheduling problem (PESP) for a given train line plan, which is promising for macroscopic train timetabling and capacity analysis. In accordance with train operating rules, a non-collision constraint and a series of flexible overtaking constraints (FOCs) are constructed based on variations of the original binary variables in the PESP. Because of the complexity of the PESP, an iterative approximation (IA) method for integration with the CPLEX solver is proposed. Finally, two hypothetical cases are considered to analyze railway capacity, and several influencing factors are studied, including train regularity, train speed, line plan specifications (train stops), overtaking and train heterogeneity. The MCTC model and IA method are used to test a real-world case involving the timetable of the Beijing–Shanghai high-speed railway in China. 相似文献
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The increase of public attention, scientific research and political interest in environmental problems associated with transportation has provided the motivation for re-invention of electric vehicles. However the usage of grid-dependent EVs with a high-carbon electricity grid might produce more damage to the environment. This study aims to provide an environmental impact comparison of ICEVs, HEVs and EVs during their usage cycle, by modeling their energy consumption (electricity or fuel) and the supply chains of the supplied energy, (well-to-wheel) based on a life cycle assessment. The results show that running EVs with the existing mixed sources of electrical energy produce larger impacts on the environment 60% of the time; when compared to HEVs. When compared to ICEVs, EVs produce a larger environmental impact on 7 out of 15 environmental impact categories. Overall the environmental impacts of EVs are substantial based on the well-to-wheel analysis. It will continue to be so if no change is made to the methods of electricity generation in the near future. Given that the environmental profile of EVs is linked with the existing national electricity generation mix, the national electricity supply must be made cleaner before the electrification of the urban transport system. 相似文献
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This paper presents a cost scaling based successive approximation algorithm, called ε-BA (ε-optimal bush algorithm), to solve the user equilibrium traffic assignment problem by successively refining ε-optimal flows. As ε reduces to zero, the user equilibrium solution is reached. The proposed method is a variant of bush-based algorithms, and also a variant of the min-mean cycle algorithm to solve the min-cost flow by successive approximation. In ε-BA, the restricted master problem, implying traffic equilibration restricted on a bush, is solved to ε-optimality by cost scaling before bush reconstruction. We show that ε-BA can reduce the number of flow operations substantially in contrast to Dial’s Algorithm B, as the former operates flows on a set of deliberately selected cycles whose mean values are sufficiently small. Further, the bushes can be constructed effectively even if the restricted master problem is not solved to a high level of convergence, by leveraging the ε-optimality condition. As a result, the algorithm can solve a highly precise solution with faster convergence on large-scale networks compared to our implementation of Dial’s Algorithm B. 相似文献
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根据西直沟1#隧道实际工程特点,选取管棚超前支护技术。依据管棚支护的主要机理以及地形地质和荷载情况,采用扇形管棚布置。根据埋深较大时的简化泰沙基公式计算围岩最大压力,并选取管棚参数,对本隧道的施工提供了理论依据,为以后黄土隧道的施工积累了工程实际经验。 相似文献
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张建波 《国防交通工程与技术》2008,6(1):67-69
黄土具有多孔性、密度低、易发生湿陷等特点,在黄土地区修建隧道常会给施工和通车后的安全运行造成影响。结合郑西铁路客运专线隧道施工实践,介绍了在黄土地区修建大跨度铁路隧道的开挖、支护、防排水等施工关键技术,为解决黄土地区大断面隧道施工问题提供了相应经验。 相似文献
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开发了机械式汽车悬架装置试验台闭环控制系统,设计了闭环控制算法,使试验过程中,保证加速度恒定,并通过实验验证了本系统的可行性和正确性,从而使新系统进一步满足汽车悬架特性测试的要求,又降低了研究成本。在软件的开发中,采用VC++6.0语言编制控制系统,使得开发出的系统界面友好,操作方便,功能强大。 相似文献
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随着BIM技术的不断发展,BIM平台在施工全过程的应用逐渐丰富。集成整合平台背后全生命周期的工程数据,并将数据传递至工程建造各个环节当中进行应用,是BIM平台发挥作用的本质。如何在工程的全生命周期收集和整理工程数据库,并传递至各个工作流程中发挥作用,是开展BIM平台建设的重点。以乌鲁木齐市东进场高架道路工程为实例,重点研究BIM平台中工程数据库的建立,分析如何在项目的设计阶段和施工过程中采集工程数据,并将工程数据库应用于项目管理。 相似文献