Model Test on Mechanism of Shear Resistance Borne by Concrete Shear Key and Friction of Element Joint of the Immersed Tunnel北大核心CSCD

By scale model tests, it proves the mechanism mode of shear resistance borne by friction of contact area and concrete shear key in different contact stress states and cushion thicknesses of shear key. The results show that friction plays a significant role on shear resistance of element joint. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

基于联合仿真技术的转缸式斜盘活塞发动机动力学研究

基于Adams和Matlab/Simulink联合仿真技术建立转缸式斜盘活塞发动机的动力学模型,得到发动机关键零部件的速度、加速度、受力以及平衡特性,并利用实际热车试验数据对模型进行验证。仿真结果表明:在满足热强度的前提下,应尽量提高发动机缸内压力,降低发动机转速;后球心圆直径对发动机的运转平稳性影响较大;增加一定的周向位移可提高发动机的机械效率;后球头和后球座之间的摩擦功率最大,需重点考虑润滑和冷却;转缸式斜盘活塞发动机是自平衡的。研究结论可为发动机的工程设计和评估提供重要参考价值。     

Hierarchical perimeter control with guaranteed stability for dynamically coupled heterogeneous urban traffic

Perimeter control based on the Macroscopic Fundamental Diagram (MFD) is widely developed for alleviating or postponing congestion in a protected region. Recent studies reveal that traffic conditions might not be improved if the perimeter control strategies are applied to unstable systems where high demand generates heavy and heterogeneously distributed traffic congestion. Therefore, considering stability of the targeted traffic system is essential, for the sake of developing a feasible and then optimal control strategy. This paper sheds light on this direction. It integrates a stability characterization algorithm of MFD system equations into the Model Predictive Control (MPC) scheme, and features respectively an upper and a lower bound of the feasible control inputs, to guarantee system stability. Firstly, the dynamics of traffic heterogeneity and its effect on the MFD are analyzed, using real data from Guangzhou in China. Piecewise affine functions of average flow are proposed to capture traffic heterogeneity in both regional and subregional MFDs. Secondly, stability of a three-state two-region system is investigated via stable equilibrium and surface boundaries analysis. Finally, a three-layer hierarchical control strategy is introduced for the studied two-region heterogeneous urban networks. The first layer of the controller calculates the stable surface boundaries for the given traffic demands and then determines the bounds of control input (split rate). An MPC approach in the second layer is used to solve an optimization problem with two objectives of minimizing total network delay and maximizing network throughput. Heterogeneity among the subregions is minimized in the last layer by implementing simultaneously a subregional perimeter flow control and an internal flow control. The effectiveness and stability of the proposed control approach are verified by comparison with four existing perimeter control strategies.     

城市交叉口交通拥挤最大排队长度估算模型

文章针对交通波模型应用于城市道路排队长度估算所存在的问题,评述了累计到达-离去模型应用的优势。通过对累计到达-离去模型的三种变形形式的分析比较,选用出其中的一种模型为基础模型进行改进,得到城市交叉口交通拥挤最大排队长度估算模型,并通过VISSIM仿真实验验证了这一改进模型的实用性。     

基于CATIA V6的船体结构模型检查二次开发研究

随着数字化技术的发展,三维设计正成为船舶行业的技术发展方向。基于CATIA V6平台的船体结构三维设计,目前主要应用SFD轻量化模型生成二维图纸对接产品方案设计,应用SDD实体模型对接生产设计。因此在三维建模过程中,为保证二维出图与实体转模的准确性,对船体结构SFD模型进行检查尤为重要。虽然三维模型具有视觉上的直观性,但是在CATIA平台模型检查过程中,由于结构模型构件数量庞大且构件属性信息显示不够直接,应用平台原生功能的模型检查方法效率较低,检查结果不够理想。针对平台原生功能存在的问题,本文探索了二次开发在模型结构检查中的运用。选取船体结构SFD模型中面板加厚方向判定这一典型检查场景为例,通过CAA和EKL混合开发实现了面板加厚方向的批量检查和模型修改,极大提高了模型检查的效率和准确性,实用性高。同时本文也为二次开发应用于船体结构模型检查提供了开发思路和主要技术路线。     

Micro-simulation modelling for traffic safety: A review and potential application to heterogeneous traffic environment

This paper critically reviews micro-simulation modelling applications for traffic safety evaluation with respect to the use of different simulation tools, the application of surrogate safety indicators under different aspects of road environments and crash considerations. General input variables used to develop the models; key parameters for crash prediction; and calibration and validation approaches are explored in the paper. The strengths and weaknesses of used simulation packages for traffic safety evaluation are also pointed out. Moreover, recent advancements in the development and application of traffic safety micro-simulation model for safety assessment are also discussed.Despite having a number of studies, there is still a significant void in the development and application of simulation model to evaluate traffic safety of non-lane based heterogeneous traffic environments that predominate in many developing countries. The paper assessed the potential application of traffic safety micro-simulation model in heterogeneous traffic environments. Finally, a number of potentially fruitful future research directions are highlighted.     

隧道阻塞比对临界风速影响的模型试验研究

分析阻塞比对临界风速的影响,采用1∶20缩尺隧道模型,在火源功率为5.88kW时,对9种不同阻塞比的临界风速进行模型试验研究。结果表明:有车辆阻碍物时临界风速明显降低,并随着阻塞比的增大而减小,且减小比例略小于阻塞比;对临界风速的测量值进行数据拟合得到阻塞比修正系数为0.548,从而提出考虑阻塞比时临界风速的计算公式;对比分析本实验所得与既往研究所得临界风速减小比例与阻塞比的关系,认为火源燃烧面高度、火源位置(火源与阻碍物的相对位置关系、火源在阻碍物内/外部)和车辆侧壁开口面积是导致有车辆阻碍物时临界风速减小比例与阻塞比关系不同的主要因素。     

船舶艉部结构对尾轴振动特性影响研究

船舶大尺度效应造成船体变形大,使船舶轴系和船体之间相互耦合、相互影响问题十分突出。为此,建立了具有非线性油膜力作用的尾轴-油膜-艉部结构耦合系统动力学模型,推导了系统的动力学微分方程并对方程进行求解,分析了不同转速下尾轴的非线性动力学特征,总结了艉部结构系统的固有频率,参振质量,支承刚度,连接刚度对尾轴振动特性的影响。结果表明：考虑艉部结构的影响之后,尾轴-艉部结构耦合系统的振动特性发生了较大的改变,耦合程度受艉部结构固有频率影响较大,尾轴最大振幅随艉部结构参振质量,支承刚度的变化而发生改变。     

新概念汽车模型风洞试验研究

用模型风洞对新概念车在不同横摆角下纵对称面上压力系数、整车气动力和气动力矩的变化以及纵对称面尾部流态分布进行了试验研究。通过和同等试验条件下典型汽车的气动性能对比,由于新概念车良好的外部流线,其气动性能明显优于典型汽车。