Contrastive Analysis of Working Face Stability in Cases of Climbing Excavation and Horizontal Excavation北大核心CSCD

Restricted by site and construction period of ancillary structure of metro project, climbing excavation is often adopted. In order to determine tunnel face’s stability, the stabilities of working face in the cases of climbing ex- cavation and horizontal excavation were analyzed by theoretical analysis and numerical simulation. With upperbound limit analysis, the affected scope and positions of failure zone were compared; the position of equivalent strain zone and the law of horizontal displacement changes were studied by simulation analysis. The results show that the scope of failure zone caused by climbing excavation was slightly larger than that by horizontal excavation and the po- sition of affected zone is slightly lower than that by horizontal excavation; the horizontal displacement caused by climbing excavation within a scope of 0-1/3 height of tunnel face is slightly larger than that by horizontal excavation while it is slightly smaller beyond the scope of 0-1/3 height of tunnel face; the maximum horizontal displacements in the cases of climbing and horizontal excavation both occur at the place where is 1/3 height of work face and the de- formation of work face in the case of climbing excavation is not larger than that of horizontal excavation; the work face stabilities are mostly the same in the cases of climbing and horizontal excavation without regard to advanced support, and the work face stability is to be guaranteed with proper advanced support. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Unreliable trains and induced rescheduling: implications for cost-benefit analysis

This paper is concerned with the assessment of generalized user cost reductions in the cost-benefit analysis (CBA) of transport policies that aim at reducing unreliability. In particular, we investigate the implications of railway passengers’ anticipating departure behavior when train services were unreliable. A simple model is established to describe and predict such anticipating behavior. Our numerical example shows how travelers’ anticipating departures and scheduling costs depend on the level of unreliability. The possible bias incurred by ignoring the reliability and schedule delay costs reductions in the traditional CBA can be quite substantial. Given our assumptions and parameterization, the underestimation of ignoring these costs could range from 33 to 75% of total generalized user cost reductions.     

A multi-instrumented approach to observing the activity rescheduling decision process

Activity scheduling simulation models represent an emerging and proposing approach to forecasting travel demand. The most significant developmental challenge is the lack of empirical data on how people actually proceed through the scheduling and conflict resolution process. This paper develops a new methodology to collect data about the rescheduling decision process. The data collection involves six stages: preplanned schedule interview, coding of the preplanned schedule, second-by-second Global Positioning System tracking, internet-based prompted recall diary, detection of rescheduling decisions (via comparison of planned versus executed activities), and a final in-depth interview probing the how and why of rescheduling decisions. Each stage of the methodology is described in detail with example results drawn from a pilot study. Key discoveries include: elicitation of multiple preplanned schedule reporting methods (verbal, point-form, calendar); discovery that activity attributes (time, location, involved persons) are planned on significantly different time horizons and include partial elaboration; and provision of new insights into how and why rescheduling decisions are made. A method for automatically tracking rescheduling decisions was also discovered. Overall, the new methodology has potential to contribute to the development of more realistic models of the entire scheduling process, especially rescheduling and conflict resolution sub-models.     

Computer Aided Simulation on Precision Cold Forging of Universal Joint Cross

IntroductionThefiwtee1emenmethod(FEM)playsanextrmelyimPortantroleintheanalysesofengineeringproblems.ForalongtimethismethodhasmainlybeenaPPliedinthelinearfieldandshownitsgreatpower.HoweveealOtofnonlinearengineeringPrOblemsWhichcanneitherbesimPlyreducedtolinearonesnorrCPresentedbylinearlyanalogywhichshallchnsethePfacticalconditionsrelativelymuch,havechallengedfiniteelementmethod(FEM).RecentymuchProgresshasbeenmadebothinthemathematicalandmechanicaltheoryandthecomPulertechnologysothatevent…     

The Effects of Lateral Front Fork Flexibility on the Vibrational Modes of Straight-Running Single-Track Vehicles

By means of a mathematical model the effects of lateral front fork flexibility on the vibrational modes of single-track vehicles have been studied. The analysis performed by Sharp has been used as a starting point. The results have been compared with Roe's empirical findings. The results of the analysis have been translated into practical advice for a more optimal front fork construction.     

African shippers' organizations: the Ghanaian experience

This paper looks at how the Shippers' Council could operate to make shipping cost-effective and to play its role as a servant of trade a servant of the shippers. It looks at the key problems that confront the shipper requiring intervention by a Shippers' Council and surveys how the organization of the Shippers' Council effectively handles problems. The final sections draw conclusions which could contribute to increasing the efficiency of Shippers' Councils, as well as improving the understanding of the Councils as managers of the demand side of shipping.     

机车车辆的主要发展方向

铁路运输拥有系统上的优势,尤其是能源和生态优势,但是,为了能获得社会的更好评价和吸引更多客运量和货运量,重要的就是要在机车车辆制造时保证不断采用新技术方案,以便提高旅客舒适度,降低噪声和振动,保证整个铁路系统电磁兼容性和功能的可靠性.     

The use of equilibrium network models in logistics management: With application to the U.S. coal industry

This paper discusses the use in logistics management of the freight network equilibrium model, developed in Harker and Friesz (1985a, b), called the Generalized Spatial Price Equilibrium Model, or GSPEM. After this discussion, computational techniques for solving this model are presented. The application of GSPEM to the analysis of the U.S. coal economy is then presented and future extensions of this line of research are discussed.     

Cost benefit analysis of urban minibus operations

Earlier work by the Transport Studies Group of the Polytechnic of Central London on minibus development in Britain for the Transport and Road Research Laboratory provided a financial analysis of intensive urban minibus operation. This is taken as the basis for the application of cost-benefit analysis. Unit operating cost savings and passenger benefits are taken into account, using typical demand elasticities derived from earlier work. Particular attention is paid to the problem of evaluating passenger benefits for which waiting time at the roadside is not necessarily an adequate proxy. A direct survey of passenger waiting times indicates that these do not necessarily decrease when a higher-frequency minibus service replaces a conventional bus service but the improved convenience produces an increase in ridership which may be assessed in terms of a demand curve shift to estimate benefits obtained.     

预应力CFRP板加固钢板受拉试验研究

文章对预应力CFRP板双面加固钢板的轴心受拉静力行为进行了试验研究,首先采用一维线弹性理论和三维空间单元有限元模型分析预应力CFRP板双面加固钢板的轴心受拉应力分布,然后对粘贴不同预应力水平CFRP板的加固试件进行轴心受拉试验.结果表明:施加机械锚固装置后,钢板应力水平有很大降低,承载能力相应有很大提高,但刚度提高不大,而且机械锚固装置对保持高承载能力是必须的,应力分布理论值与试验值吻合得很好.试验中还观察到CFRP板高应力条件下很小的蠕变和预应力偏心作用所导致的弯曲应力.短期预应力损失主要由弹性压缩产生,循环荷载下的预应力损失很小.因此总预应力损失可简化计算为短期损失乘以一个安全系数,