横向风作用下高速铁路车桥系统绕流特性分析

基于不可压缩二维雷诺平均N-S方程，采用RING（renormalization group）k-ε两方程湍流模型，对德国ICE（intercity-express）列车和标准简支梁组成的车桥系统在横向风作用下的二维绕流特性进行了分析．计算网格为由三角形非结构网格和四边形结构网格组成的混合网格，采用有限体积法对微分方程进行离散，应用SIMPLE算法解决压强-速度耦合关系．根据高速铁路桥梁带挡风墙的特点，引入空腔流动研究成果对车桥系统的绕流特性进行了理论分析．结果表明，高速铁路桥梁挡风墙的挡风机理在于充分运用了空腔流的旋涡特性．     

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汽车保有量与社会经济的发展有着密切关系，通过建立计量经济学模型寻求汽车保有量和社会经济有关指标的函数关系，可以较为准确地预测一个地区短期内的汽车保有量.本文根据广东省的统计数据，给出建立计量经济学预测模型和进行各项检验的详细过程，并根据模型预测了广东省2004年和2005年的汽车保有量.     

有关超载车辆危害公路桥梁的浅析与思考

总结了超载车辆对各种公路桥梁的危害种类及其原因,并提出一些建议以供思考应用。     

自主水下航行器发展概述

自主水下航行器（AUVs）因其应用于海洋勘探而逐渐成为一个有趣的研究对象。波浪滑翔机是一种行驶于波浪表面的无人滑行器（SUV）,它借助海洋能来推动自己,这对于典型的AUVs所采用的电机供能以及昂贵的锚链系统浮标供
　　能来说,是一种技术上的重大跨越。该文讨论了最有效率的AUVs类型。第一部分为每一种类型的发展历程,第二部分为它们各自的技术特点。此外,波浪滑翔机作为应用于海洋部门的一种新型水下机器人,文中简要地给出它的过去,现在以及未来的发展概述。研究波浪滑翔机的意义在于证明它的效率以及实用性,进而取代诸多的AUVs来实现各种实际应用。而研究结果也表明波浪滑翔机确实可以应用于众多领域。对于海洋检测而言,相比于其他AUVs,波浪滑翔机提供了更廉价,更经济,更环保的作业模式,同时也不需要缆绳、船舶等海上作业服务。     

自主水下机器人下潜困难问题的数值仿真与试验研究

自主水下机器人在近水面运动时,受到文丘里效应产生向上吸力的影响,使得潜器初始下潜困难,近水面的深度保持能力也受到影响。为了研究水下潜器近水面下潜困难问题,文章运用计算流体力学（CFD）软件对某AUV主体周围流场进行近水面数值模拟。模拟结果表明,影响升力和抬头力矩的主要因素是初始的下潜深度和速度。水域试验表明随着初始下潜深度的增加,AUV 的下潜将变得越来越容易,这与模拟结果相一致。     

水下航行体降噪艉翼填角的数值模拟与试验研究

为降低水下航行体噪声,研究了艉翼填角的降噪效果。分析了水下航行体艉翼接合部马蹄涡影响螺旋桨伴流场的特征,认为马蹄涡对水下航行体噪声产生了不利影响。针对某无人水下航行体(UUV)设计了一种艉翼填角,运用CFD方法对该艉翼填角优化螺旋桨伴流场的效果进行了数值模拟,结果显示伴流场轴向速度的周向不均匀度系数下降35%-62%。将艉翼填角应用于该UUV,开展航行辐射噪声测量试验,结果显示艉翼填角使UUV航行噪声总声源级降低3.4 d B,尤其对低频噪声抑制较好。     

Differences in single heavy vehicle crashes at intersections and midblocks

The objective of this research is to identify the factors differentiating between single heavy vehicle collisions at intersections and midblocks by using a binary logit model. Our results show that single vehicle crashes involving heavy vehicle at intersections are more likely to occur on main roads and highways, whereas crashes at midblocks are more likely to occur on divided two‐way roads, roads with special facilities or features (e.g. bridge) and roads with a higher percentage of heavy vehicle traffic. Intersection crashes are also more likely to involve vehicles that are turning left or right, resulting in angle crashes and vehicle overturn, whereas midblock crashes are more likely to involve vehicles on higher posted speed roads. Copyright © 2017 John Wiley & Sons, Ltd.     

Vehicle rollover avoidance by application of gain-scheduled LQR controllers using state observers

Many researches have been conducted in the area of control applied to vehicle dynamics, aiming at reducing the possibility of the occurrence of the type of accident known as rollover. In this research, based on a common nonlinear model and its linearisation, a method for properly selecting matrices for solving the Riccati equation considering different speeds was proposed. The method showed in which ways speed really influences the choice of controller gains. By developing the dynamic equations for the yaw- and roll-coupled motions and modelling of controllers and state observers, it is possible to compare the efficacy of this control strategy using both linear and nonlinear simulations using Matlab. Significant results were obtained regarding the reduction of the rollover coefficient for a double-lane change manoeuvre at different speeds, thus indicating advantages of using this controller in practical cases.     

Quasi steady-state aerodynamic model development for race vehicle simulations

Presented in this paper is a procedure to develop a high fidelity quasi steady-state aerodynamic model for use in race car vehicle dynamic simulations. Developed to fit quasi steady-state wind tunnel data, the aerodynamic model is regressed against three independent variables: front ground clearance, rear ride height, and yaw angle. An initial dual range model is presented and then further refined to reduce the model complexity while maintaining a high level of predictive accuracy. The model complexity reduction decreases the required amount of wind tunnel data thereby reducing wind tunnel testing time and cost. The quasi steady-state aerodynamic model for the pitch moment degree of freedom is systematically developed in this paper. This same procedure can be extended to the other five aerodynamic degrees of freedom to develop a complete six degree of freedom quasi steady-state aerodynamic model for any vehicle.     

Design and validation of a slender guideway for Maglev vehicle by simulation and experiment

Normally, Maglev (magnetic levitation) vehicles run on elevated guideways. The elevated guideway must satisfy various load conditions of the vehicle, and has to be designed to ensure ride quality, while ensuring that the levitation stability of the vehicle is not affected by the deflection of the guideway. However, because the elevated guideways of Maglev vehicles in South Korea and other countries fabricated so far have been based on over-conservative design criteria, the size of the structures has increased. Further, from the cost perspective, they are unfavourable when compared with other light rail transits such as monorail, rubber wheel, and steel wheel automatic guided transit. Therefore, a slender guideway that does have an adverse effect on the levitation stability of the vehicle is required through optimisation of design criteria. In this study, to predict the effect of various design parameters of the guideway on the dynamic behaviour of the vehicle, simulations were carried out using a dynamics model similar to the actual vehicle and guideway, and a limiting value of deflection ratio of the slender guideway to ensure levitation control is proposed. A guideway that meets the requirement as per the proposed limit for deflection ratio was designed and fabricated, and through a driving test of the vehicle, the validity of the slender guideway was verified. From the results, it was confirmed that although some increase in airgap and cabin acceleration was observed with the proposed slender guideway when compared with the conventional guideway, there was no notable adverse effect on the levitation stability and ride quality of the vehicle. Therefore, it can be inferred that the results of this study will become the basis for establishing design criteria for slender guideways of Maglev vehicles in future.