高原人群出行拥挤感知与调适行为研究

为缓解高原城市节日期间部分路段人流过于密集的状况，对高原人群出行过程中的拥挤感知和调适行为进行研究。首先，在对高原人群高度自由走行速度、生理尺寸进行测定的基础上，采用连续人群流动模型分别对高原人群拥挤临界密度、人群运动速度减小时的人群密度和人群停滞状态时的最大密度进行测算，进而标定高原人群最大忍受密度为8.5人/m2。然后，选取雪顿节期间八廓南街人流短时间内高度聚集的状况进行拥挤状况评估，结果显示该路段人群密度为8.34人/m2，接近高原人群最大忍受密度，因此判定八廓南街存在拥挤事故风险。最后，依据基于层次分析法的高原人群拥挤感知影响因素分析结论，提出相应的调适行为措施，力求维护民族宗教节日期间高原城市公众正常的出行秩序。     

基于改进密度聚类算法的交通事故地点聚类研究

交通事故特征受地域分布影响显著，本文对交通事故特征进行优化聚类研究.基于 2019年无锡市交通事故数据，调用开放地图接口地理编码解算事故地点经纬度，使用密度聚类算法对事故地点与事故原因进行密度聚类.传统的密度聚类算法依赖距离阈值和样本数阈值的准确输入，为解决这一局限，建立一种自适应搜索距离阈值和样本数阈值的密度聚类模型，并与原始聚类模型进行对比.结果表明，优化算法在参数确定上更加智能，对簇的划分更加准确，对噪声点的识别更加合理.通过机器学习中轮廓系数计算方法计算模型得分，证明了该算法在城市道路交通事故地理位置聚类中的适用性.     

基于概率密度演化的斜拉索多级变幅时变疲劳可靠度分析

拉索是斜拉桥的主要受力构件,在车辆、风等交变荷载作用下易发生多级变幅疲劳损伤,而经典可靠度方法预测多级变幅时变疲劳可靠度难度大且计算效率低。针对这一问题,提出一种高效的多级变幅斜拉索时变疲劳可靠度预测方法。基于Miner累积损伤理论,建立同时考虑荷载和材料随机性的变幅疲劳损伤概率演化模型;构建应力幅出现频率指标,解决多级变幅疲劳损伤演化过程中偏微分方程难以确定问题,通过概率密度演化方法精确计算多级变幅时变疲劳可靠度,并采用五级变幅材料试验数据和某桥梁斜拉索的模拟数据验证所提方法的可行性。结果表明:所提方法的计算效率远高于蒙特卡洛方法;在小概率失效时,其计算精度高于蒙特卡洛方法。     

The identification and empirical characterization of vehicular (Lagrangian) fundamental diagrams in multilane traffic flow

Traditional macroscopic traffic flow modeling framework adopts the spatial–temporal coordinate system to analyze traffic flow dynamics. With such modeling and analysis paradigm, complications arise for traffic flow data collected from mobile sensors such as probe vehicles equipped with mobile phones, Bluetooth, and Global Positioning System devices. The vehicle‐based measurement technologies call for new modeling thoughts that address the unique features of moving measurements and explore their full potential. In this paper, we look into the concept of vehicular fundamental diagram (VFD) and discuss its engineering implications. VFD corresponds to a conventional fundamental diagram (FD) in the kinematic wave (KW) theory that adopts space–time coordinates. Similar to the regular FD in the KW theory, VFD encapsulates all traffic flow dynamics. In this paper, to demonstrate the full potential of VFD in interpreting multilane traffic flow dynamics, we generalize the classical Edie's formula and propose a direct approach of reconstructing VFD from traffic measurements in the vehicular coordinates. A smoothing algorithm is proposed to effectively reduce the nonphysical fluctuation of traffic states calculated from multilane vehicle trajectories. As an example, we apply the proposed methodology to explore the next‐generation simulation datasets and identify the existence and forms of shock waves in different coordinate systems. Our findings provide empirical justifications and further insight for the Lagrangian traffic flow theory and models when applied in practice. Copyright © 2015 John Wiley & Sons, Ltd.     

疏浚监控系统原理及校验方法*

耙吸式挖泥船与绞吸式挖泥船的疏浚监控系统的校验工作与施工生产是密不可分的。为提高挖泥船的疏浚监控系统校验工作的准确性和合理性，对耙吸挖泥船与绞吸挖泥船部分无溯源施工设备原理及校验方法进行分析，如绞刀深度原理及校验方法、耙臂下放深度原理及校验方法；并对部分主要施工设备原理及校验方法进行分析，如密度计原理及校验方法、流速计原理及校验方法。结合实际校验的工作经验，验证施工关键设备校验后调整方法的可行性及校验结果的可靠性，得出提高两种挖泥船校验工作质量和效率的方法，提高了施工准确度和生产效率，使疏浚项目加快顺利完成。     

Aggregating mobile object trajectories: cumulative time geographic density estimation for GPS data

We present new approaches that expand upon the time geographic density estimation (TGDE) framework previously employed to estimate potential path trees. In the past, TGDE metrics have identified possible locations an individual moving object may have passed between, given known origin and destination points. This paper utilizes a new form of TGDE to investigate taxicab GPS traces over a specified time horizon with position ‘gaps’. To this end, we propose a new extension to the TGDE framework, TGDE-C, which is used to determine the cumulative TGDE values for a group of GPS traces, at a given location. These metrics are applied to multiple taxis and allow for time of day analysis. Additionally, we combine these new extensions with existing TGDE metrics that allow us to determine how accessible individual or groups of vehicles are to urban opportunities.     

Impact of regional population density on walking behavior

Land use can influence walking (measured by the number of steps) and so the health of people. This paper presents the result of empirical research on the impact of regional population densities (inhabitants per inhabitable area) on the number of steps (all steps, both outdoors and indoors). With data collected from almost 11,000 respondents in 148 Japanese regions, we estimate polynomial regression models, the total number of steps being the dependent variable and densities being the main independent variable. Regional population density significantly affects the number of steps after controlling for individual and household attributes. The estimated population density that maximizes the number of steps is around 11,000?persons/km². Increasing densities, up to levels of around 11,000?inhabitants/km², could increase walking and consequently the health of inhabitants. The population density elasticity of the number of steps is 0.046–0.049 in a simple log linear regression model without a peak.     

一种改进的Jakes’信道模型及仿真

由于无线通信环境中存在的诸多不确定因素以及其在现代无线通信系统中的重要作用，合理的无线信道成为通信系统仿真研究的重要目的。确立信道仿真模型的目的就是为了尽可能的得到实际信道的统计特性，该文针对Jakes提出的信道模型，通过仿真来分析其局限性，并参考其中的谐波叠加（sum of sinusoids，SOS）法，来建立一种采用了随机分支增益、随机初始相位和有条件的随机多普勒频率改进的信道模型。     

光面爆破技术在城市地铁隧道施工中的应用

文章从光面爆破机理、光面爆破技术中各主要参数的确定,以及光面爆破在实际工程中的应用几个方面出发,以深圳地铁安-侨区间隧道硬岩段施工为例,研究分析了如何利用光面爆破技术来提高城市地铁浅埋暗挖法的光爆效果,特别是近距离穿越重要建(构)筑物时如何有效进行光面爆破。     

Moiré条纹密度对条纹图噪声及相位混频的影响

分析了Moiré条纹密度对条纹图噪声及相位混频的影响,提出了一种调整Moiré条纹密度的方法以有效减少条纹图噪声与包裹相位图噪声,并消除条纹过密产生的相位混频。试验测量表明,该方法能够获得可靠的测量结果,具有较好的测量精度。