GEO-slope/w和不平衡推力法联合确定公路碎石土路堑边坡下滑力设计值

碎石土高边坡是路基工程中一种常见的特殊路基,对于需要加固的不稳定路堑高边坡,潜在不稳定面的确定是最重要也是首要的问题,提出采用GEO slope/w搜索潜在不稳定面并对不稳定面进行修正,利用修正后的不稳定面作为边坡加固的潜在不稳定面,按照不平衡推力法计算边坡的设计下滑力的方法加以解决。     

Learning aircraft operational factors to improve aircraft climb prediction: A large scale multi-airport study

Ground-based aircraft trajectory prediction is a major concern in air traffic control and management. A safe and efficient prediction is a prerequisite to the implementation of new automated tools.In current operations, trajectory prediction is computed using a physical model. It models the forces acting on the aircraft to predict the successive points of the future trajectory. Using such a model requires knowledge of the aircraft state (mass) and aircraft intent (thrust law, speed intent). Most of this information is not available to ground-based systems.This paper focuses on the climb phase. We improve the trajectory prediction accuracy by predicting some of the unknown point-mass model parameters. These unknown parameters are the mass and the speed intent. This study relies on ADS-B data coming from The OpenSky Network. It contains the climbing segments of the year 2017 detected by this sensor network. The 11 most frequent aircraft types are studied. The obtained data set contains millions of climbing segments from all over the world. The climbing segments are not filtered according to their altitude. Predictive models returning the missing parameters are learned from this data set, using a Machine Learning method. The trained models are tested on the two last months of the year and compared with a baseline method (BADA used with the mean parameters computed on the first ten months). Compared with this baseline, the Machine Learning approach reduce the RMSE on the altitude by 48% on average on a 10 min horizon prediction. The RMSE on the speed is reduced by 25% on average. The trajectory prediction is also improved for small climbing segments. Using only information available before the considered aircraft take-off, the Machine Learning method can predict the unknown parameters, reducing the RMSE on the altitude by 25% on average.The data set and the Machine Learning code are publicly available.     

船体低阶湿模态计算方法对比研究

以某豪华游轮船体为研究对象,针对船体梁的低阶湿模态特性,将虚质量法应用于船体低阶湿模态计算,并与基于Lewis经验公式的附加质量法进行了对比分析。结果显示两种方法前四阶船体湿模态相差均在4.5%以内,特别是船体首阶湿模态相差仅0.3%。但附加质量法计算附连水质量过程复杂,且高阶模态计算偏差大。虚质量法计算过程简单,计算结果准确可靠,并且可在一次计算中得到船体前几阶低阶湿模态。本文使用的计算方法适用于船体低阶湿模态计算,对工程实际问题有一定的参考价值。     

城市轨道交通列车运行延误及其传播特点的仿真研究

城市轨道交通系统具有列车运行间隔小、站间距离短、车站线路布置比较简单等特点，一旦列车发生运行延误，其传播的速度快、影响范围大。本文在分析城市轨道交通列车运行延误发生的随机性特征的基础上，指出城市轨道交通列车运行延误具有直接性、快速性和双向性的特点以及基于这些特点的列车运行延误传播的两种表现形式，然后运用系统仿真的理论与方法，建立了基于列车运行图的城市轨道交通列车运行延误的仿真模型，通过设计合理的列车运行延误统计指标和仿真分析方案，以某城市轨道交通线路为背景进行仿真分析。通过仿真分析发现，列车运行延误及其传播主要与能力利用率、缓冲时间、备车数量以及辅助线数量等因素有关，并且这些参数之间应该保持一定的合理匹配关系。     

Disturbance compensation with a torque controllable steering system

Via a conventional steering system the driver perceives desired and disturbing effects such as road feedback and resonance effects, respectively. They appear with overlapping frequency spectra within the driver's steering torque. This paper introduces a control algorithm that is suppressing periodic disturbances without affecting useful steering road feedback attributes as well as regular power assistance characteristic. This is realised by an integrated torque actuator within the steering column in conjunction with a conventional Hydraulic-assisted Power Steering (HPS) system.     

Railway planning in developing countries: a case study of Colombia

This paper describes a study of possible network changes for the Colombian railway system. A cost model is developed and the variation of costs with traffic density and with gradient is analysed and found to be different from that expected from experience in developed countries. The evaluation of network changes is carried out by a form of systems analysis in which two new lines and many closures are examined. Closures are evaluated by means of social cost benefit analysis incorporating a consumers’ surplus approach. The study recommends fairly radical changes to the present network configuration, these involving the construction of one new line and the closure of several existing ones.     

基于显式积分技术求解大变形橡胶减振元件非线性准静态刚度的方法

将实验测试时间作为计算的加载时间,能够得到与试验等效的橡胶件准静态刚度曲线;金属部件的模拟采用不影响计算时间步长的刚体单元代替可变形的有限单元,可将计算时间缩短20倍;质量缩放因子取2.3×109,泊松比取0.495,对橡胶件的体积可压缩性进行软化,以达到缩短计算时间和保证计算精度的目的;设置橡胶材料的黏性,能够抑制求解过程中出现的数值振荡现象.仿真计算分析与实验结果表明:与隐式积分技术相比,采用显式积分技术能够使大变形工况下橡胶减振元件非线性准静态刚度仿真计算的收敛性提高30％,而动能与内能之比仅为1.5％;在橡胶件垂向压缩量为0～30mm时,采用显式积分技术得到的仿真计算结果与实验结果基本吻合,误差仅为5.5％.研究结果表明,显式积分技术适合用于橡胶件开发过程中对其大变形工况下准静态刚度的仿真计算.     

The effectiveness of differential pricing on route choice

The use of differential pricing as a means of traffic management has been advocated by specialists in the field of transport for quite some time. Because of technical and political reasons, a full-scale pricing scheme for the use of road space has yet to be introduced. Applying the principle to a highly automatic rail system, however, is technologically much more feasible. The Mass Transit Railway Corporation of Hong Kong has implemented a so-called revenue neutral peal pricing policy after the completion of a second cross-harbour route- the East Harbour Crossing — in May, 1990. Passengers travelling from Kowloon to the central business district (including Jordon and Tsim Sha Tsui on the Kowloon side and stations from Sheung Wan to Causeway Bay on the Island side) during the morning peak hour are confronted with the following choice: either (i) make use of the Nathan Road Corridor and pay 80 cents on top of normal face; or (ii) take the less congested but in general longer route via the East Harbour Crossing and get a 80 cents discount. The present paper attempts to analyse the effectiveness of this differential pricing policy in diverting passengers from the overcrowded section to the less heavily utilized route. A personal interview survey comprising a total of 1094 successful cases was conducted for this purpose. The logit regression model was employed to analyse the route choice. It is found that income, habit and journey time are the most important variables determining the route choice. The effect of cost or fare difference, although large in terms of magnitude, is only marginally significant in the statistical sense. It is suggested that efforts to change the passengers' habit and measures to shorten the train transfer time at the Quarry Bay Station for the East harbour Crossing users would be more effective in achieving this end. This is especially the case given the current political development in Hong King which renders further enlargement of the price difference a highly difficult proposition.     

城市公共自行车高峰期需求不均衡的调度优化研究

通过对城市公共自行车系统自行车高峰期需求不均衡的使用状况进行研究,讨论公共自行车车辆调度优化,研究车辆路径问题。构建车辆优化调度模型,并设计禁忌搜索算法对模型进行求解,得出公共自行车需求高峰期车辆调度路径,最后构造算例对调度路径进行算例分析。研究结果表明:该模型具有一定的实用价值,可以实现城市公共自行车高峰期需求不均衡的车辆调度优化。     

从杨丽娟事件看介入式报道的不当对大学生等青少年群体媒介素养的影响

文章回顾了在杨丽娟事件中媒体的介入性报道的种种失误表现,指出了介入性报道对事件的演进过程和悲剧性结局的不当干预作用和影响。文章认为,媒体在使用介入性报道时,必须谨慎小心,坚持新闻报道的客观公正原则,选择正确的报道方法,以期对当代大学生等青少年群体媒介素养有积极的影响。