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Ngila Mwase† 《运输评论》2013,33(3):191-206
Zambia has attempted to reduce her excessive transport dependency on her traditional transport routes via South Africa and the former Portugese colonies. The costly construction of the Tanzania‐Zambia Railway (TAZARA) was part of this diversification strategy. This article examines the nature, extent and direction of Zambian traffic, including its historical evolution. It explores further the place of TAZARA among the various routes to Mozambican, Angolan and South African ports, and the ensuing actual and potential competition. Future traffic patterns will be influenced not only by the direct and service‐oriented costs of the different lines, but also by the region's volatile and uncertain political climate. 相似文献
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Robert E. Paaswell 《Transportation》1973,2(4):351-371
An examination of current population statistics shows that in the U.S. more than half of the population is without immediate access to a car, and in the U.K. more than three-fifths of the population is without access to a car. This phenomenon has been accentuated by national investment in both countries in major highway programs. The term carless refers to more than just households that own no cars. It extends, in households with cars to those without licenses (old and young), the handicapped, and even the licensed drivers who have no access to the family car when it is in use elsewhere (e.g. at work). The most severely effected are those in urban areas and especially the urban poor. Transportation expenses are limited for the poor when other family expenditures (food, shelter) take a high priority. Once the work trip has been satisfied, money for other trips, for the poor, is not always available. One solution to cost-free travel is pedestrianism (walking), but this too is difficult in urban areas where the pedestrian has been overlooked in favor of the car. Solutions to problems of the carless include dial-a-ride, better public transit, and better design of urban form. 相似文献
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针对海中箱梁现浇施工中的工程量大、工期紧迫、悬臂法施工不能满足工期要求和施工难度大等问题,文章结合青岛海湾大桥箱梁现浇施工实践,介绍以钢管桩支撑作为承载基础,采用贝雷梁与碗扣式支架相结合的支架,成功地解决现浇箱梁施工难题的方法。 相似文献
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Mark Greer 《Transportation Research Part A: Policy and Practice》2009,43(9-10):779-789
Data envelopment analysis is used to evaluate the technical efficiencies of a number of major passenger airlines in the United States at transforming their inputs (labor, fuel and fleet-wide seating capacity) into available seat-miles. A tobit regression model is then used to identify the underlying drivers of airline efficiency, as measured by the data envelopment analysis efficiency score. The impact of unionization on airline efficiency is found to be statistically insignificant, controlling for the influences of other hypothesized determinants of airline efficiency: the average age of an airline’s fleet, the average size of its aircraft, its average stage length, the extent to which the airline relies of hubbing within its route structure, the percent of its passenger enplanements that are international, and whether the airline is a legacy carrier. The statistically significant drivers of airline efficiency, at a ten percent level of significance, are average aircraft size, average stage length and the extent to which the airline relies on hubbing and connecting flights within its route structure. The stage length variable is not significant at a five percent level of significance, however. An increase in average aircraft size or in average stage length enhances an airline’s efficiency whereas an increase in hubbing reduces it. 相似文献
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复合式TBM在重庆地铁实践中的关键技术研究 总被引:4,自引:0,他引:4
文章通过复合式TBM在重庆轨道交通六号线工程中的应用实践,对复合式TBM的特点及其工程适应性进行了分析;对衬砌断面及其支护参数的设计、超深竖井及其支护参数的设计,以及复合式TBM穿越建筑物的施工微扰动控制设计等几大关键技术方案进行了详细阐述;明确了设计方案的合理性与先进性. 相似文献
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Tony H. Grubesic Fangwu Wei 《Transportation Research Part A: Policy and Practice》2012,46(10):1562-1573
Essential Air Service (EAS) is a federally funded program in the United States that provides connecting, commercial air service between rural communities and their nearest large or medium commercial hub airport. During fiscal year 2010, $170 million dollars were spent to provide this service to 107 communities in the US. However, with significant variations in subsidies to each airport (ranging from $427,757 to $3,082,403) and marked differences in passengers served, there are serious concerns regarding the overall efficiency of the EAS program. The purpose of this paper is to use data envelopment analysis integrated in a geographic information system for evaluating service efficiencies at the community level. Policy implications and strategies to improve the EAS program are discussed. 相似文献
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新老路基结合部处治技术 总被引:3,自引:0,他引:3
新老路基结合部处治技术课题组 《西部交通科技》2006,(4)
文章分析了路基拓宽工程的主要方式和工程技术问题,提出了新老路基不协调变形的计算方法和路面结构对路基不协调变形的力学响应模式,通过建立基于不协调变形控制的路基拓宽设计理论和方法,系统地提出不同条件下的新老路基结合部处治技术及其施工控制方法,为公路路基拓宽工程的设计与施工提供了科学依据。 相似文献
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结合苏州太湖大道改造工程阳山西路隧道基坑工程,文章分析了紧邻有轨电车高架桥基坑施工时存在的风险及相应安全保证措施,研究了各主要施工工序的控制要点,并对施工期间可能出现的风险提出了针对性的应急措施,不仅可以确保基坑的安全和稳定,而且将基坑施工对高架桥的影响降到最低,安全保障措施可供类似工程参考。 相似文献
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S. Erlander 《Transportation Research Part B: Methodological》1979,13(3):259-267
We consider a model which combines gravity model trip distribution and equilibrium assignment. This model contains a free parameter which must be fixed using supplementary information, that is, the model must be calibrated. It is natural to ask which supplementary information is sufficient to determine the free parameter. We show here that under very weak hypotheses each of the quantities, the entropy H or the total assignment cost F, is alone sufficient to determine the free parameter. In contrast, it is shown by means of a counterexample that even under very strong hypotheses, the total cost C is not sufficient. 相似文献
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受汶川地震的影响,经过断层带的公路隧道在施工时更容易出现大的塌方事故.为避免造成人员伤亡和经济损失,本文以广甘高速公路杨家山隧道右洞桩号K22+624段塌方为工程背景,采用现场地质描述分析、地质雷达探测,以及编写程序的正演模拟相结合,对汶川地震过后断层带对隧道塌方的影响进行研究.结果表明,在震后断层带的影响范围内,围岩整体特性发生突变,雷达波形图中会形成强烈的反射波信号,经过后期处理,能够得到较为清晰的波形异常图,从而推测出掌子面前方可能出现塌方的情况.文章最后对地质雷达探测加以正演模拟,可有效地指导整个隧道施工过程,并取得较好的经济收益. 相似文献
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盾构始发和到达安全掘进控制技术是困扰盾构隧道施工的主要难题之一。盾构进出洞施工中,面临掌子面失稳、土体坍塌、涌水涌砂、地表沉陷、盾构"抬头及磕头"等诸多施工风险。本文从基坑及隧道的破坏模式,塑性区分布范围出发,通过有限差分法针对易受扰动的浅埋砂层地层盾构始发段进行了研究,为加固区范围大小的选择提供了依据。研究表明,在不采取加固措施时,基坑开挖后隧道始发段的竖向位移、拱底的隆起和最大纵向挤出变形量均过大,显示基坑将发生坍塌等破坏。当盾构始发段主要加固措施为旋喷桩,加固后的土体的物理参数得到了显著的提升。本文在此基础上得出了旋喷桩的合理加固区域。 相似文献
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广州地铁六号线东山口站为国内首例在周边环境复杂条件下实施"先隧后站、盾构隧道扩挖"修建地铁车站的工程。文章介绍了该站左线站台隧道在盾构隧道的基础上扩挖形成地铁车站的主要修建技术及施工特点和难点。实践证明,采用盾构与明(暗)挖法相结合修建地铁车站的施工技术,是城市繁华地区修建地铁车站有效解决区间盾构隧道与车站施工相互干扰难题的重要途径。 相似文献
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《Transportation Research Part A: Policy and Practice》2006,40(9):776-791
This paper describes important aspects of the design of the Athletes transportation system for the Athens 2004 Olympic Games. The unique characteristics of this network include the close dependence of the vehicle schedules on the competition and training program, the requirement for 100% service reliability, as well as the requirement for full system monitoring and control. In this paper we present methods for the development of service specifications, estimation of the bus fleet size, the design of the network’s organization and management system, and corresponding critical implementation issues. All these issues are relevant to the design and management of bus transport systems for large events. 相似文献