Data fusion algorithm for macroscopic fundamental diagram estimation

A promising framework that describes traffic conditions in urban networks is the macroscopic fundamental diagram (MFD), relating average flow and average density in a relatively homogeneous urban network. It has been shown that the MFD can be used, for example, for traffic access control. However, an implementation requires an accurate estimation of the MFD with the available data sources.Most scientific literature has considered the estimation of MFDs based on either loop detector data (LDD) or floating car data (FCD). In this paper, however, we propose a methodology for estimating the MFD based on both data sources simultaneously. To that end, we have defined a fusion algorithm that separates the urban network into two sub-networks, one with loop detectors and one without. The LDD and the FCD are then fused taking into account the accuracy and network coverage of each data type. Simulations of an abstract grid network and the network of the city of Zurich show that the fusion algorithm always reduces the estimation error significantly with respect to an estimation where only one data source is used. This holds true, even when we account for the fact that the probe penetration rate of FCD needs to be estimated with loop detectors, hence it might also include some errors depending on the number of loop detectors, especially when probe vehicles are not homogeneously distributed within the network.     

A data fusion approach for real-time traffic state estimation in urban signalized links

Real-time estimation of the traffic state in urban signalized links is valuable information for modern traffic control and management. In recent years, with the development of in-vehicle and communication technologies, connected vehicle data has been increasingly used in literature and practice. In this work, a novel data fusion approach is proposed for the high-resolution (second-by-second) estimation of queue length, vehicle accumulation, and outflow in urban signalized links. Required data includes input flow from a fixed detector at the upstream end of the link as well as location and speed of the connected vehicles. A probability-based approach is derived to compensate the error associated with low penetration rates while estimating the queue tail location, which renders the proposed methodology more robust to varying penetration rates of connected vehicles. A well-defined nonlinear function based on traffic flow theory is developed to attain the number of vehicles inside the queue based on queue tail location and average speed of connected vehicles. The overall scheme is thoroughly tested and demonstrated in a realistic microscopic simulation environment for three types of links with different penetration rates of connected vehicles. In order to test the efficiency of the proposed methodology in case that data are available at higher sampling times, the estimation procedure is also demonstrated for different time resolutions. The results demonstrate the efficiency and accuracy of the approach for high-resolution estimation, even in the presence of measurement noise.     

海上油气平台可燃气体探测器的布置、选型、安装和维护

在海上平台油气生产中，有效地利用可燃气体探测器来检测海上生产设备的泄漏状况，并及时采取相应的保护措施，是保证油气生产和人身安全的重要一环。但目前对海上油气平台可燃气体探测器工程设计的系统研究却鲜见于国内外的工程文献中，针对这一现状，在研究国内外现有规范和标准以及工程设计经验的基础上，通过分析可能产生泄漏的工艺设备、可燃气体性质和外部环境等因素来确定可燃气体探测器的物理位置，同时完成可燃气体探测器的选型，并根据现场的工作环境合理安装可燃气体探测器，最后总结探测器使用维护中需要注意的问题。对可燃气体探测器的布置、选型、安装和维护的系统总结和分析研究为海上平台火气系统的设计提供了技术支持，从而进一步保障海上油气平台的生产安全。     

道岔外锁闭装置在线探伤仪的研制

道岔外锁闭装置是重要的信号基础设备,直接关系到铁路运输的安全。介绍了一种外锁闭装置在线探伤仪,采用超声波探伤原理,能够实现外锁闭装置在线探伤,可智能选择预置探点并判定结果,是电务维护人员对在用外锁闭装置进行在线无损检测的专用工具。     

隧道火灾探测器的应用与测试技术

概述了国内外目前常见的几种隧道火灾探测器的工作原理和应用现状,归纳了他们在实际应用中的普遍优势、常见问题和存在缺陷。在介绍感温火灾探测器产品检测方法的基础上,结合传统工程检测方法和工程现场情况,对高速公路隧道火灾探测器的检验方法和思路进行了一定的创新和开拓,介绍了可应用于隧道火灾探测器工程现场检测的新方法,探讨了简单易行的检测方案,确保检测内容能够真实反映系统运行情况。现场实际应用表明,这些方法具有实用和推广价值,希望能对隧道火灾探测器的初期选型、后期维护以及工程检测过程有所帮助。     

基于CCD的增压锅炉火焰温度及辐射率检测

为实现对炉内火焰温度分布进行实时监测和有效控制以提高锅炉运行的可靠性和经济性,通过接口与密封装置,将3支彩色火焰图像探测器分别布置在增压锅炉前后墙的观火孔内,通过专业采集软件采集炉内火焰图像并保存至计算机中,运用图像处理技术以及基于双色法的火焰温度检测方法得到火焰的辐射温度和辐射率分布图像,实测结果与数值模拟结果吻合较好。不同负荷下试验表明:辐射温度与过热蒸汽温度、烟气压差和燃油压力的变化趋势表现很好的一致性,辐射率的变化趋势则与之相反。     

基于数据融合的路段行程时间估计

基于检测器数据的路段行程时间估计通常具有精度不高和可靠性差的特点。论文引入了自适应式卡尔曼滤波,采用K近邻法寻找相似的交通流状态来标定状态转移系数,建立了基于固定型检测器数据和移动型检测器数据的路段行程时间估计融合模型。实际数据的验证结果是,平均相对误差为9.52%,相对误差的标准差为8.92%。研究表明,与基于移动检测器数据的估计方法相比较,该方法极大地改善了估计精度和可靠性,还具有收敛速度快、对初值不敏感、参数少等特点。     

基于图像识别与追踪技术的高速公路交通事件有效检测范围

针对视频交通事件检测器的有效检测范围目前在行业内产生的广泛争议,结合摄像机安装高度、安装角度、摄像机性能指标,通过理论计算和试验验证,得到视频交通事件检测系统对相关交通事件的合理检测范围,从而为高速公路全程视频监控系统外场监控摄像机的布设间距、布设方式提供数据支持,实现高速公路全程无盲区智能化监控识别。计算结果表明,对于小汽车停驶等交通事件,其有效检测距离大于1 000 m的传统说法是不准确的,目前的技术水平很难达到,其合理检测距离应该在500 m左右,试验数据验证了这一说法,但视频交通事件检测系统的有效检测距离后续会随着摄像机性能的不断增强而有所提高,从而满足高速公路监控系统不断提高的监控需求。     

非常态下城市道路交通检测器布局优化方法

为了使城市道路上布设的交通检测器能够实时、准确地提供路网动态交通流信息,并最大程度地节约经济成本,通过仿真对交通异常事件下城市道路交通流量和车辆延误进行了估计,并利用模糊聚类分析法、回归分析法和车辆延误估计模型,研究了路网在非常态下的检测器空间位置以及空间密度的布局优化方法;通过一个算例,对提出的检测器布局优化方法进行了验证分析,并得出了算例中检测器布局的优化方案。结果表明:所提出的检测器布局优化方法是可行的。     

在线水洗在混凝土制作中的应用

鉴于采用在线式水洗生产混凝土的方式以其良好的效果受到业界的好评,在分析离线式水洗工作流程及其不足的基础上,现结合现场施工的实际情况,介绍了在线水洗在混凝土搅拌站中的应用及其优点,指出采用在线水洗所生产的水泥混凝土的质量有很大提高,同时减少了施工3-．序,节约了施工时间,具有良好的经济效益,因而值得推广应用。