软基土体中的真空度测试

采用理论分析与现场实测相结合的办法,研究真空预压时使用传统真空度测头测量软基土体中真空度的不足之处,并指出使用孔隙水压力测头测量真空度的可取之处。     

移动交通检测系统中探测车的样本数量

基于各国移动交通检测系统中探测车样本数量问题的研究现状,分析了现有成果存在的不足。在考虑探测车速度、计算时间间隔、数据精度要求等因素基础上,针对交通流密度均匀分布和非均匀分布两种情况,利用数理统计方法建立了道路网上探测车样本数量的双层模型。结果表明:当计算时间间隔为5 min时,若道路网上交通流密度均匀分布,则探测车比例至少为5.0%;若道路网上交通流密度非均匀分布,则探测车比例至少为7.0%。     

“BOT＋EPC”模式下公路工程概算编制问题分析

＂BOT＋EPC＂作为高速公路建设领域的一种新模式,对设计概算编制深度和精度提出更高要求。结合重庆新千公里高速公路建设实践,指出传统意义上两阶段初步设计概算与新型建设模式不协调的一面。从高速公路建设管理的角度,指出公路建设模式变化催生设计概算编制随之调整,强调新模式下概算编制中应着重注意的若干问题。     

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以切换定位技术作为手机探测车的定位技术,针对切换定位技术低定位精度的特征,对手机探测车异常切换位置修正问题进行了研究．根据问题描述,提出一个两阶段手机探测车异常切换位置修正方法,分别为异常切换路段速度修正和异常切换位置重置．在第一阶段中,结合桥接切换路段构建一个双层数据融合模型,对异常切换路段速度修正值进行求解．在第二阶段中,采用遗传算法求解异常切换位置重置问题得到异常切换位置修正结果．通过实证数据,评估分析了基于本文修正方法计算得到的手机探测车切换路段速度估计绝对误差,与原始数据比较表明,本文提出的方法是可行有效的,可以应用于道路交通信息提取的研究中．     

Property Analysis of Urban Road Travel Time

To estimate arterial link traffic condition based on probe vehicles, it is necessary to investigate the fluctuation characteristics of road travel time with traffic condition. On the basis of micro traffic simulation model, this paper analyzes the fluctuation of road travel time with traffic condition, and examines whether the mean travel time can reflect the variation of traffic conditions including free flow, congestion to traffic jam. As a conclusion, (1) mean link travel time can be used to identify free flow, congestion, and traffic jam; (2) mean link travel time divides congestion condition, but cannot subdivide free flow condition; (3) in the condition of congestion, travel time is distributed as a two-peak mode, and the average travel time is difficult to be estimated by small size sample.     

水平管降膜厚度分布特性及对传热的影响

为了解水平管降膜流动状况,基于气液两相界面的物理特性,在外径为20～32 mm、管间距为10～40mm、雷诺数为150 ～ 800的范围内,应用电导探针法,实验研究了液膜沿水平管周向分布特性,获得了液膜在10°～170°周向范围内的分布参数,分析了这些分布参数对水平管局部传热的影响.结果表明:Nusselt公式对圆管下半周液膜厚度的预测值明显偏大,在不同工况下,最薄液膜出现在周向角为90° ～ 115°的区域内;液膜厚度随管间距的增加而减小,随雷诺数的增加而增大,管径变化对其影响很小;粗糙管壁可以薄化液膜,传热管结垢区域容易引起液膜破裂,导致“干斑”现象发生.     

实时分布式地图匹配系统的设计与实现

在智能交通系统的基础上,设计实现了基于实时浮动车数据的分布式地图匹配系统.分布式架构的应用旨在提高系统数据接收和处理的实时性.同时提出了一种基于道路网格和最短路径的快速地图匹配算法,通过网格划分确定候选路段,根据二次网格划分、GPS角度和数量对候选路段权重进行修正,并利用最短路径算法寻求最符合路径,在保证处理效率的同时匹配的精度也有所提升.仿真实验选用三台匹配处理节点,经验证,完成大连市1000辆出租车约130万个GPS点的地图匹配用时为1分37秒,算法的平均正确匹配率为93.3％.实验结果满足实际智能交通系统的基本要求.     

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在讨论探测车样本数量统计需求的基拙上，提出了一种基于探测车技术的路段平均速度自适应加权指数平滑佑计模型，模型中加权系数随着跟踪误差大小和路段上探测车数量的变化而自适应调整，并利用VISSIM仿真数据验证了该模型。结果表明：在路段上探测车占交通流比例随时间变化且不能充分满足统计要求的情况下，相对传统的算术平均方法，基于指数平滑的路段平均速度佑计能够有效提高估计精度，并且可有效减小由路段上探测车数量变化而引起的速度佑计方差。     

Outsourced probe data effectiveness on signalized arterials*

ABSTRACT

This paper presents results of an I-95 Corridor Coalition sponsored project to assess the ability of outsourced vehicle probe data to provide accurate travel time on signalized roadways for the purposes of real-time operations as well as performance measures. The quality of outsourced probe data on freeways has led many departments of transportation to consider such data for arterial performance monitoring. From April 2013 through June of 2014, the University of Maryland Center for Advanced Transportation Technology gathered travel times from several arterial corridors within the mid-Atlantic region using Bluetooth traffic monitoring (BTM) equipment, and compared these travel times with the data reported to the I95 Vehicle Probe Project (VPP) from an outsourced probe data vendor. The analysis consisted of several methodologies: (1) a traditional analysis that used precision and bias speed metrics; (2) a slowdown analysis that quantified the percentage of significant traffic disruptions accurately captured in the VPP data; (3) a sampled distribution method that uses overlay methods to enhance and analyze recurring congestion patterns. (4) Last, the BTM and VPP data from each 24-hour period of data collection were reviewed by the research team to assess the extent to which VPP captured the nature of the traffic flow. Based on the analysis, probe data is recommended only on arterial roadways with signal densities (measured in signals per mile) up to one, and it should be tested and used with caution for signal densities between one and two, and is not recommended when signal density exceeds two.     

X波段4单元矩形径向线馈电螺旋阵的设计

为探索高功率高增益天线的实现途径,提出并设计了一种矩形径向线馈电螺旋阵.阐述了矩形径向线馈电螺旋阵的工作原理,对辐射单元、耦合探针和馈电系统进行了详细设计,进而得到一个X波段4单元阵列天线模型.对该模型进行的数值模拟结果表明,在8.5~10.3 GHz的频带范围内,天线反射系数小于0.1,增益大于12 dB,轴向轴比值小于1.9.