风洞模型激光攻角测量

给出一种用于风洞飞机模型攻角测量的方法.采用对称双光束交叠照射角传感器,风洞实验测角范围由40°增加到76°;利用电子处理器计数干涉条纹,测角精度可达0.005°.     

一种群签名方案的安全缺陷及其改进

最近Lee和Chang提出了一种基于离散对数的高效群签名方案。然而,该方案不能抵御伪造攻击,同时不具有不可链接性的特点。敖青云等人提出一种改进的方案,希望能克服Lee-Chang方案的不足。本文首先指出了敖青云等人提出的群签名方案仍然是不安全的,基于Tseng方案,提出了一种改进的群签名方案,并对其安全性进行了简要分析。     

A three-stage evacuation decision-making and behavior model for the onset of an attack

Pedestrian behavior models have successfully reproduced human movement in many situations. However, few studies focus on modeling human behavior in the context of terrorist attacks. Terrorist attacks commonly occur in crowded public areas and result in a large number of casualties. This paper proposes a three-stage model to reproduce a series of complex behaviors and decision-making processes at the onset of an attack, when pedestrians generally do not have clear targets and have to deal with fuzzy information from the attack. The first stage of the model builds a Bayesian belief network to represent the pedestrians’ initial judgment of the threat and their evacuation decisions. The second stage focuses on pedestrians’ global assessment of the situation through an analogy with diffusion processes. The third stage uses a cost function to reproduce the trade-offs of distance, safety, and emotional impact when considering a path to take. The model is validated using a video from the November 2015 Paris attack. The behavioral characteristics and trajectories of three pedestrians extracted from the video are reproduced by the simulation results based on the model. The research can be used to set rules when performing risk analysis and strategic defensive resource allocation of terrorist attacks using agent-based simulation methods.     

基于图像识别的轮轨冲角测量系统研究

为了解决机车车辆运行过程中轮轨冲角的连续测量问题,研究基于运动图像识别的轮轨冲角测量原理,提出轮轨冲角测量方法。运用该方法研制了由图像采集系统、同步采集控制系统、图像处理软件等组成的轮轨冲角测量系统,通过连续测量转向架侧架与轨道的夹角和轮对与侧架的夹角计算轮轨冲角。应用该测量方法对DF8B三轴径向转向架机车进行实车线路试验,测得该车径向机构锁定和不锁定两种状态下通过250 m半径曲线时的第一轴和第三轴轮轨冲角变化曲线。     

大攻角下超大跨度斜拉桥颤振性能节段模型风洞试验

为了研究一座1 400 m跨径流线型闭口箱梁断面斜拉桥的颤振性能,根据其风致静力失稳或颤振前主梁最大有效风攻角已接近±10°的特点,通过弹簧悬挂节段模型试验,开展了大攻角下桥梁颤振性能研究。试验发现,在4°~10°风攻角下,高风速时模型均出现了弯扭耦合程度较弱的自限幅非线性颤振现象;而在其他攻角下,高风速时模型则表现为常规的发散型弯扭耦合颤振。研究发现,经典的线性颤振理论无法适用于研究试验中大攻角下出现的非线性颤振现象。因此,采用了一种简化的非线性半经验数学模型来表示非线性颤振中的自激扭矩,并从试验模型颤振位移时程中识别得到了模型参数。基于这一非线性自激力模型,通过试验测得的位移信号来构造自激扭矩时程,再利用自激扭矩的做功时程来识别各个气动参数。之后,利用其中的部分气动参数构造气动阻尼,并基于结构阻尼系数与气动线性阻尼系数之和为零的判断条件,提出了一种针对非线性颤振现象的临界风速确定方法,同时将线性和非线性颤振的起振判断条件进行了很好的统一。研究结果表明,利用这一方法求得的颤振临界风速与风洞试验中出现的现象基本吻合。     

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.     

桥梁断面静三分力系数的CFD计算分析

利用流体分析软件Fluent计算了不同桥梁断面型式在中等雷诺数时和不同攻角下的阻力系数和升力系数。文中选用6类不同桥梁断面型式进行了计算分析。通过计算得出的阻力、升力系数随攻角的变化对比以及风场压力云图直观反映,初步分析了各类断面在静风作用下三分力系数值的特性。计算结果表明,钝体断面其阻力系数的变化形式相似,而上下不对称开口会造成其升力系数的变化;而流线型断面,其阻力系数与钝体断面截然不同,与攻角有直接的关系,实际应用需要多注意。     

武广客运专线边坡支护结构中锚固体抗腐蚀性的技术措施

针对边坡支护结构中锚固体腐蚀是引起结构破坏失效的重要因素,其主要表现为锚固用水泥砂浆灌浆不足、浆体自干燥收缩裂缝大、抗环境水侵蚀能力差等方面。以武广客运专线为研究背景,针对锚固体易出现的腐蚀情况和特点设计试验,考察锚固用水泥砂浆的流动性、匀质性、自收缩性能及抗硫酸盐侵蚀性能等因素,提出改善锚固体抗腐蚀性能的技术措施。结果表明:粉煤灰、矿渣等矿物掺合料和新型外加剂KS-Ⅰ能够有效提高水泥砂浆的工作性能和抗侵蚀能力,满足工程应用的需要。试验结果为武广客运专线锚固结构防腐设计提供了依据,并可为类似设计提供技术储备。     

不同纵摇轴位置下的二维柔性鳍推进性能与流场特性研究

利用FLUENT软件数值计算了二维柔性鳍作升沉纵摇运动时的推力系数及推进效率,探讨了修正Bose变形方程、均匀载荷和非均匀载荷悬臂梁变形方程等三种柔性模式下纵摇轴位置对摆动鳍推进性能的影响,其中纵摇轴在尾缘处能够获得更大的推力,而最高的推进效率分别对应修正Bose模式下纵摇轴距首缘1／3弦长处和悬臂梁柔性变形模型下纵摇轴距首缘2／3弦长处．同时计算分析了斯特劳哈尔数、最大攻角等参数对柔性鳍水动力性能的影响,建立了最大推力系数和最高推进效率所对应的参数区间,其中低St数的最高推进效率发生在低αmax,高St数的最高推进效率发生在高αmax．     

航母编队舰载机防空体系打击联盟问题研究

针对作战体系网络化发展新趋势,构建了舰载机防空体系网络模型。分析了网络化作战资源的组织形式,提出打击联盟概念。对打击联盟形成问题进行形式化描述,并建立了问题的数学模型。根据舰载机防空作战背景,深入研究了模型的约束条件,并对模型的特征进行分析,为后续研究打击联盟形成问题的具体实现提供理论基础。