南京长江三桥深水基础钢套箱施工

深水基础施工是大桥施工的重点,如何合理地选择其施工方案是保证大桥按期顺利完成、降低工程造价的关键。本文介绍了长江三桥钢围堰施工方案的比选及其施工要点,以供参考。     

Feasibility of localizing in vivo micro-devices with electromagnetic methods

In order to measure the location of medical micro-devices in the gastrointestinal tract, electromagnetic methods were developed considering the magnetic permeability of human bodies. Two varieties of electromagnetic localization methods have been implemented： one uses direct current（DC） to generate the electromagnetic field, and the other uses alternating current （AC）. The two varieties of the localization principle were analyzed and relevant experiments were made. The experiments show that the alternating electromagnetic method acquires higher accuracy, higher stability and wider measurement range.     

Connecting e-hailing to mass transit platform: Analysis of relative spatial position

This paper analyzes and compares two different relative spatial position (RSP) designs in an integrated e-hailing/fixed-route transit system: a zone-based design that operates e-hailing vehicles within a zone, and a line-based design that operates e-hailing vehicles along a fixed-route transit line and with a stable headway. To conduct a meaningful comparison, the optimal design problems for both systems are formulated using a same analytical framework based on the continuous approximation approach. A comprehensive numerical experiment is performed to compare various cost components corresponding to the optimal designs, and a discrete-event simulation model is developed to validate the analysis. The analytical and simulation results agree with each other well, with a discrepancy in the total system cost less than 5% in most test scenarios. These results also suggest that the line-based system consistently outperforms the zone-based system in terms of both agency and user costs, for all scenarios tested. Compared to the zone-based design, the line-based design features a sparser fixed-route network (resulting in larger stop spacing) but a higher dispatching frequency. It is concluded that the higher efficiency of the line-based design is likely derived from the strategy of operating e-hailing vehicles with a more regular route/headway structure and allowing ride-sharing.     

Estimation of wheel–rail friction for vehicle certification

In certification of new rail vehicles with respect to running characteristics, a wide variety of operating conditions needs to be considered. However, in associated test runs the wheel–rail friction condition is difficult to handle because the friction coefficient needs to be fairly high and the friction is also generally hard to assess. This is an issue that has been studied in the European project DynoTRAIN and part of the results is presented in this paper. More specifically, an algorithm for estimating the wheel–rail friction coefficient at vehicle certification tests is proposed. Owing to lack of some measurement results, the algorithm here is evaluated in a simulation environment which is also an important step towards practical implementation. A quality measure of the friction estimate is suggested in terms of estimated wheel–rail spin and total creep. It is concluded that, tentatively, the total creep should exceed 0.006 and the spin should be less than 1.0 m^?1 for the algorithm to give a good friction estimate. Sensitivity analysis is carried out to imitate measurement errors, but should be expanded in further work.     

跨海钢混结合梁斜拉桥边跨施工方案研究

福厦客专安海湾特大桥主桥为国内首座跨海高速铁路结合箱形截面梁斜拉桥,该桥主桥采用(40+135+300+135+40)m双塔双索面斜拉桥跨越安海湾航道。本文结合桥址处水浅、滩涂发育,潮汐明显,周围养殖密布等影响因素,对边跨钢箱梁进行了悬臂拼装施工、高位支架滑移施工、高位支架顶推施工等多方案比选,同时针对顶推方案又从顶推过程是否设置前导梁,是否一次性带桥面板上桥及实施中所用工装设备、顶推支架进行了综合比选,重点对无导梁不带板顶推施工方案进行了介绍,为以后类似工程施工提供借鉴。     

基于中国人体驾乘姿态的汽车人机空间布置研究

合理的人机空间布置对汽车的舒适性与安全性至关重要,人体驾乘姿态是汽车人机空间布置的依据。文章设计试验,扫描得到500样本分别在8辆车中的驾乘姿态数据,对数据进行统计分析,建立驾驶员座椅适宜线方程与中国人体2D模板,基于标杆车进行验证,结果显示,方程及模板精度较高,符合中国人体驾乘特征。该研究为汽车人机空间布置提供理论依据,为研发适合中国人驾乘的车辆提供支撑,对建立中国汽车人机设计体系具有重要意义。     

基于双轴速率转台的IMU440惯性测量单元快速标定方法与实验

在捷联惯导系统中,惯性器件的确定性误差是系统误差的主要原因之一。为了提高惯导系统的输出精度,必须对这一误差加以补偿。以美国Crossbow公司开发的IMU440惯性测量单元为对象进行了快速标定实验,建立了陀螺仪和加速度计的误差模型方程,提出了用于辨识陀螺仪和加速度计误差模型参数的速率和位置标定法,根据两种标定方法得到了IMU440惯性测量单元的误差模型,最后对误差模型进行了校验。实验结果表明,误差补偿后的惯性器件输出值可以很好地接近理想输出值,大大降低了捷联惯导系统的输出误差。     

基于运动学特性的双横臂悬架硬点位置优化

利用空间机构运动学和数值计算的方法对双横臂独立悬架系统进行了运动学分析,以悬架运动学特性设计曲线为优化目标,对悬架硬点的布置位置进行了优化。结果表明,按照优化后的硬点位置计算出的悬架运动学特性曲线与设计曲线基本一致,因此利用该方法可以快速实现对悬架硬点结构的优化布置,提高车辆性能。     

特长公路隧道平导通风方案研究及优化

为了给特长单洞双向公路隧道提供经济合理的通风方案和设计参数,结合四川绵茂公路篮家岩隧道通风设计实际工程,综合考虑篮家岩隧道的工程地质条件、环境保护等制约因素的影响,选择了有利于救援和隧道修建的半横向平导通风方案.在平导通风方案中,根据隧道纵坡线形,计算分析后确定风压中性点,合理组织风流,并为特长单洞双向公路隧道提供了可...     

混合动力汽车制动踏板位移传感器的故障诊断

混合动力汽车的怠速停机、制动能量回馈等功能都需要制动踏板位移信号作为输入判定条件,因此有必要对制动踏板位移传感器信号的有效性进行监控,以正确识别其工作是否正常。如果不正常,那么是哪种失效方式?针对具体的失效方式采用相应的故障处理方式,以保证混合动力系统工作稳定。本文系统地介绍了荣威750BSG混合动力汽车制动踏板位移传感器的短路、断路、合理性和零点漂移等故障的诊断方法,提供了一整套针对制动踏板系统的安全监控方法。