基于加权Voronoi图的扇区优化研究

管制员的工作负荷是制约空域容量的主要因素.扇区优化的目的则是在符合一定约束条件下平衡管制员的工作负荷,增加容量.文中提出了基于加权Voronoi图的扇区划设方法,确定了管制员工作负荷统计的方法.针对模拟退火算法收敛速度较慢,遗传算法存在早熟收敛的缺陷,使用生长算法与蚁群算法相结合的方法对数学模型进行求解,进而优化Voronoi多边形,最终得到最优扇区边界.仿真结果验证了所提出的扇区优化方法的合理性.     

A two-step outlier removal procedure for surface reconstruction

Outliers in point clouds affect the performance of surface reconstruction directly. Most of outlier removal methods just remove those outliers far away from the real surface and are only applied to handle watertight surface. In this paper, a two-step outlier removal procedure is proposed to filter the point clouds acquired from the gray code and line-shifting technique. The first step is to remove the outliers far away from the real surface. Some feature points are extracted from the point clouds to construct an initial surface. The points with distances to the initial surface greater than a given threshold are removed as distant outliers. The retained points are linked into lines in each structured light sheet using their Voronoi diagrams. Some of lines which are very close to the real surface are removed as near outliers in the second step. The experimental results show that the proposed method is very effective in removing outliers for surface reconstruction. Foundation item: the National Natural Science Foundation of China (No. 30470488)     

Investigating empirical implications of hysteresis in day-to-day travel time variability

Day-to-day travel time variability plays a significant role in travel time reliability. Nowadays, travelers not only seek to minimize their travel time on average, but also value its variation. The variation in the mean and the variance of travel time (across days, for the same departure time) has not been thoroughly investigated. A temporary decrease in capacity (e.g. congestion caused by an active bottleneck) leads to a quite significant difference in the variance of travel time for congestion onset and offset periods. This phenomenon results in hysteresis loops where the departure time periods in congestion offset exhibit a higher travel time variance than the ones in congestion onset with the same mean travel time. The aim of this paper is to identify empirical implications that yield to the hysteresis phenomenon in day-to-day travel times. First, empirical hysteresis loop observations are provided from two different freeway sites. Second, we investigate the potential link with the hysteresis observed in traffic networks on macroscopic fundamental diagram (MFD). Third, we build a piecewise linear function that models the evolution of travel time within the day. This allows us to decompose the problem into its components, e.g. start time of congestion, peak travel time, etc. These components, along with their probability distribution functions, are employed in a Monte Carlo simulation model to investigate their partial effects on the existence of hysteresis. Correlation among critical variables is the most influential factor in this phenomenon, which should be further investigated regarding traffic flow and traffic equilibrium principles.     

单轴转向架焊接构架疲劳强度及模态分析

根据TB/T 2368-2005《动力转向架构架强度试验方法》,采用有限元方法对构架进行强度校核。针对单轴转向架的结构特点,设计了4种超常载荷工况来对构架做静强度评定;设计了9种运营载荷工况,利用Goodman疲劳极限图对构架的疲劳强度进行校核。最后对构架做了模态分析。结果表明构架的强度、刚度均满足车辆运行要求。     

汽油机燃烧循环变动表征参数的探讨

阐述了循环变动对汽油机的动力性、经济性及排放的不利影响 ,进而研究其影响因素。用实测的汽油机相继若干循环的示功图 ,对用缸内压力参数表征循环变动的适应性作出评价。     

道路交通事故再现模拟分析系统的研究

本文研究开发了道路交通事故再现模拟分析系统。基于现实世界中事故形态千差万别的特点，采用人工智能技术、使用不同于其它系统的参数子集建立模型，根据特定事故形态特点进行模型假设。采用虚拟现实技术，以Opengl接口开发了三维动画演示模块，在虚拟世界中演示车辆运动，允许用户改变场景元素。系统中还开发了车辆技术参数数据库。并用此系统对实际的事故进行了模拟分析，与PC－CRASH系统的结果进行了对比，结果基本一致。     

基于BIM的三维地形自动修正和拟合方法

在铁路工程BIM设计中,利用测绘资料生成的三维地形面是BIM设计的基准数据。现有铁路BIM设计软件一般利用已知特征点、线直接生成三角网,由该方法生成的面存在无法反映实际特征以及三角面之间过渡突兀等问题。针对此方法的不足,提出一种基于高斯过程回归模型的三维地形面拟合及修正方法,即利用少量特征点、线拟合三维地形面,也可以在顾及原始曲面三维特征的前提下,利用少量高精度特征点、线进行纠正,得到更高精度的地形面。该方法已应用于京张高铁BIM设计中,为路基、桥梁、隧道、建筑以及站后各专业提供了准确的地形基准,具备良好的实际应用价值。     

七里坪隧道浅埋偏压段支护措施优化研究

文章以改建铁路湘桂线永州至柳州段扩能改造工程七里坪隧道工程实例为依托,考虑了浅埋偏压隧道的地质特性以及围岩受力特征,结合七里坪隧道的支护措施,运用三维离散元软件3DEC对七里坪隧道的锚杆支护方案进行了优化.     

半潜式海洋平台整体结构的三维可靠性分析

本文将半潜式海洋平合模型化为空间刚架结构系统，导出三维刚架梁元在塑性阶段的修正刚度矩阵和等效节点力，并有效地改进了分枝眼界法，开发出通用于平面和立体结构系统的可靠性分析程序，对平台整体结构进行可靠性估算。通过算例，验证了方法和程序的可靠性和通用性。     

新冠肺炎下《汽车三维建模基础》远程竞教结合模式探索

当前严峻的新肺炎疫情下,为实现“停课不停教,停课不停学”的目标,文章提出使用互联网远程教学,并通过广泛流行的大学生机械创新竞赛以及创新创业竞赛,与机械类设计较为紧密的三维设计建模的教学相结合,创造性地探索出新的具有专业特色的远程竞教结合的教学模式,将创新理念融入到教师教学和学生学习与实践当中去。