大型车比例对城市道路机动车速度-流量模型的影响分析

交通流组成中的大型车比例是城市道路机动车速度-流量关系建模的重要影响因素,以往研究成果对此考虑不够。以四幅路和三幅路为对象,在大量实测数据基础上采用双因素方差分析法表明机动车流量和大型车比例均对车流速度产生显著影响。由BPR模型拓展得到各类道路速度-流量模型的通用形式,进而利用实测数据从统计学角度进行变量筛选和参数标定,最终建立各类道路不同大型车比例下的机动车速度-流量模型。该模型既可服务于宏观交通流分析,又可以为制定城市道路大型车限行或分流措施等提供参考。

基于速度-流量模型的交通拥堵预警技术研究

随着信息技术的发展,可采集的城市交通数据不断丰富,通过实时采集的速度、流量数据对交通进行研判,在交通拥堵产生前进行预警,可使交通管理者提前采取交通管控措施缓解交通拥堵。基于交通卡口和互联网地图技术采集的速度和流量数据构建交通速度-流量模型,进一步基于模型提出一套交通拥堵预警技术,给出速度和流量的预警参数标定方法,并在实际道路的早、晚高峰时段验证技术成果的正确性。该技术方法可在城市交通采集数据丰富的主干道应用,可辅助交通管理者决策,有效缓解交通拥堵。

冰雪融冻期城市道路行车速度和流量及其关系模型研究

本文将北方冬季的冰雪期分为初冻、冻结和融冻3个时期。在采集了融冻期和非冰雪期城市道路上速度和流量数据的基础上,利用独立样本T检验和方差分析的方法,研究了不同时期速度的差异以及速度和流量在不同车道上的分布特点。在充分分析了融冻期和非冰雪期的速度和流量在时空上的分布后,综合研究这两个时期的速度-流量关系,并且建立了非线性回归模型。通过模型,不仅能了解不同时期的交通流特性,而且还能得到不同时期的道路通行能力,从而为北方城市冬季的道路交通管理和设计做好理论基础。

基于混合交通流的路段非机动车速度-流量关系研究

非机动交通是我国城市交通的一个重要组成部分,除了个别城市,不同规模的城市交通出行方式中,非机动车交通出行占有较大的比重。以大量路段实测数据为基础,运用数理统计方法和spss软件统计分析功能,研究机非物理隔离路段,不同电动自行车混入比例下,自行车、电动自行车、混合非机动车速度-流量关系模型,并将模型应用于实际,即作为道路新建或改建时非机动车道宽度设置的参考依据。

高速公路改扩建施工区通行能力计算模型研究

文章分析高速公路双向四车道两侧拼宽成双向八车道施工控制区各区段的交通特征,发现上游过渡区是施工控制区的瓶颈。根据实测数据,分别建立了基于速度-流量模型和基于影响因素修正模型的通行能力计算方法。研究结果证明这两种方法均可用来计算施工区通行能力值,且与实测数据的相对差值在5%以内,应用这两种方法确定了柳南高速公路改扩建项目半幅封闭施工区上游正常区、上游警告区、上游过渡区、施工作业区的通行能力推荐值分别为:1 712 pcu·h^(-1)·ln^(-1)、1 590 pcu·h^(-1)·ln^(-1)、1 331 pcu·h^(-1)·ln^(-1)、1 361 pcu·h^(-1)·ln^(-1)。

基于交通流理论的道路实际通行能力模型

车道被占用会导致道路横断面通行能力在单位时间内降低,从而影响整个路段的交通状况,造成堵车。针对车道被占用问题,基于2013年全国大学生数学建模竞赛A题所提供的道路交通事故监控视频案例的人工观测数据,以对数关系的流量-速度模型为基础,结合交通工程学理论和通行能力修正系数,导出了道路实际通行能力的计算模型。同时根据交通流理论,建立了一个包含上游流量、事故所处横断面实际通行能力、事故持续时间和堵车排队长度的模型,根据其中任意三个量可求解另外一个量。经检验,模型结果和实际交通情况较吻合,且易于操作,具有一定的实际意义和应用价值。

基于GM(1,1|τ,r)模型的城市道路短时交通流预测

充分考虑城市道路交通系统中交通流存在的延迟性和非线性,本文基于灰色GM(1,1|τ,r)模型对城市道路短时交通流进行建模预测.首先,通过建立城市交通路段上交通流量大于通行能力时的速度-流量关系,得到交通系统延迟时间τ的计算模型.再针对交通流存在的非线性特征,以模型的预测效果最优为目标,建立关于非线性因子的优化模型并利用粒子群算法寻找最佳的非线性参数r.最后对武汉市友谊大道某一路段进行交通实验,将灰色GM(1,1|τ,r)模型的预测结果与灰色GM(1,1)模型和支持向量机进行比较.结果表明,GM(1,1|τ,r)模型的预测精度有明显的提高,能为智能交通系统的管理和控制提供及时可靠的信息资源.

基于模型预测控制含充换储一体站的配电网优化运行

提出一种综合考虑电动汽车充换储一体站与主动配电网的优化调度模型。基于快充用户行驶行为特点、城市道路速度-流量实用模型分别建立快充站和换电站模型,并结合梯级储能集成为一体站模型。在含有风机、光伏、微型燃气轮机和一体站接入的主动配电网中建立优化调度模型,并将模型转化为混合整数二阶锥模型求解。使用基于模型预测控制的多时间尺度优化调度策略实现对配电网日前调度、日内滚动调度和实时反馈校正,减少了分布式电源和负荷的预测误差对配电网运行的影响。以某市公交线路实际道路情况为例,验证了所提出的优化调度策略具有能够满足电动汽车充电负荷需求、抑制功率波动并降低配电网运行维护费用的优势。

Influence of feature size of micro-scale channel on ink flow characteristics

Under the micro-scale condition,feature size of the channel is one of the main factors influencing the fluid flow characteristics. In printing process,ink thickness in the extrusion zone formed by two ink rollers may reach micron scale. Compared with macroscopic fluid,the velocity field and the pressure field of fluid may change when the feature size of fluid channel reaches micron scale. In order to control printing quality,it is necessary to research the influence of feature size on ink flow characteristics in micro scale. This paper analyzes it in theory,and then numerical simulation of an ink flow model with different feature sizes is carried out in no slip condition. The influence of the feature size on the ink flow characteristics and the wall shear force are obtained. Besides,the ink flow model with different feature sizes is simulated numerically in slip condition,and the influence of feature size on ink flow characteristics is obtained. Finally,by comparing and analyzing the above results,it can be concluded that both the ink velocity and pressure at the inlet of the extrusion zone are inversely proportional to the feature sizes whether in slip condition or not. And the ink velocity in slip condition is larger than that without slip,the pressure at the inlet of the extrusion zone is less than that in no slip condition. Within the micro-scale range,the ink velocity difference between the two conditions cannot be ignored. Therefore,it is necessary to consider slip when analyzing the influence of feature size of micro-scale channel on ink flow characteristics.

基于速度—流量关系模型的公路噪声预测方法

车流速度是道路交通噪声预测模型中的重要参数之一,其准确性将直接影响声环境评价的结果。为了解决实际工程应用中车流速度数据获取困难的问题,本文在等效车流量假设和速度相等假设的前提下,推导出一种基于速度—流量模型的公路噪声预测方法。该方法利用了交通工程领域经典的速度—流量关系模型,可根据车流量自动计算车流速度,从而缩减了噪声预测模型中输入参数的数量。其次,实地采集交通流特征数据,采用非线性回归方法标定模型参数。最后,利用同步观测得到的高速公路基本路段上的流量和噪声数据,验证了该方法的有效性,并估计其误差范围。

基于VISSIM仿真的山区高等级公路雾区限速方法

针对目前山区高等级公路雾区限速理论不能切实反映雾区交通流状态的情况,在完善雾区限速理论的同时,提出了具体的限速方法。首先建立不同大气能见度下驾驶员动态可视距离与车速的关系模型;并以驾驶员的动态可视距离不小于停车视距为条件,得到不同雾况等级下的限速值;其次,考虑到雾区交通量对限速值的影响,基于流量-速度模型,对同一雾况等级根据交通量的大小分级限速;最后,以限速值为变量进行VISSIM仿真对比试验,将车速方差和安全车距达标率作为评价限速值优劣的指标,对雾区限速理论值进行优化;该方法适用于不同交通流状态,可为山区高等级公路雾区交通安全保障方案的制定提供参考。

基于GPS浮动车法的机动车尾气排放量分布特征

以广州市城市干道东风路1902～1903路段为研究对象,根据交通流理论建立了速度-流量模型,采用GPS浮动车速度数据和视频检测流量数据计算了模型的关键参数——阻塞密度,实现了从速度到流量的推算,并采用COPERTⅣ模型计算了不同速度等级下的综合排放因子,通过源强法计算该路段00:01─24:00的小时排放量.对CO,NOx,VOC和PM综合排放因子的速度敏感性分析表明,当平均速度达50 kmh后,随速度的增加综合排放因子下降明显变缓;对小时排放量的分析表明,污染物排放量主要集中在车流量的高峰时段,且与车流密度有很好的线性相关性,相关系数均大于0.90.

尖点突变理论在交通流预测中的应用

运用尖点突变理论从三维空间分析交通流三参数关系 ,并藉此得出我国高速公路通行能力及其速度预测值 .划分稳定流和拥挤流 ,建立符合我国公路交通实际工况下的高速公路速度 -流量模型 ,用实测数据验证了尖点突变理论在交通流预测中应用的可行性 .最后 ,讨论了其应用前景和存在的问题与不足 .

高速公路半幅封闭施工作业区的通行能力

分析了高速公路半幅封闭施工作业区各主要区段的交通特点及其道路通行能力影响因素,在此基础上,提出了基于格林希尔治速度-流量模型的通行能力确定方法和基于运行速度(重点是85%位车速)及道路交通条件修正的通行能力确定方法。应用上述方法计算得出了黑龙江省哈阿高速公路施工作业区上游正常路段、上游警告区及施工区段的实际通行能力值,分别为1 630、1 411、和1 338 pcu.(h.ln)-1。研究结果表明:上述2种方法均可用来确定施工作业区的实际通行能力且计算结果的误差较小,相对误差在0.92%～4.74%之间。

铺设钢板对道路交通运行的影响分析

为保护地下施工作业面或维持路面破损区域车辆的正常通行,工程实践中常采用道路路面临时铺设钢板的措施。在钢板尺寸、铺设位置和类型等特征分析的基础上,研究了临时铺设钢板对城市道路交通流特征参数,如流量、速度、车头时距的影响。进而采用回归分析的方法,引入围挡方式、施工作业区长度、大型车比例和作业区可用车道宽度等变量,构建路面铺设钢板情况下的城市道路速度-流量模型。最后,通过郑州市5处铺设钢板的城市道路实例分析,验证了方法的合理性与可行性。研究结果表明:与正常道路相比,由于钢板厚度与翘曲变形导致的错台及振动作用,铺设钢板的城市道路路段行驶速度降低15%~30%,交通流量降低5%~34%,车头时距增大幅度为8%~61%。由速度-流量模型分析可知,施工作业区长度、钢板设置、大型车比例均对车辆的减速行为影响显著,标准化影响系数分别为-1.06、-0.60和-0.02;另外,当非机动车及行人干扰较小时,双侧施工作业区对道路交通运行起到一定的渠化效应,可减少车辆的并道和换道行为,对交通流运行产生积极影响。

计及充换储一体站的主动配电网鲁棒优化调度

该文提出一种综合考虑电动汽车充换储一体站与主动配电网的两阶段鲁棒优化调度模型。基于多面体不确定集合分别描述电动汽车快充站、风机和光伏模型。针对地理信息系统建立计及网络拓扑结构的交通流量模型,利用电动公交车发车时刻表和线路安排,结合速度-流量实用模型建立电动汽车换电站模型。在风机、光伏、微型燃气轮机和电动汽车充换储一体站接入的主动配电网中,建立两阶段鲁棒优化调度模型并将其转化为混合整数二阶锥模型,采用分层列和约束生成算法对其进行求解。以某地区实际道路情况为例,并结合改进的PG&E69节点系统验证了本文所提方法的优势。

Macro modeling and analysis of traffic flow with road width

The macro modeling and the solution of traffic flow with road width were investigated.Firstly,a new macro model with the consideration of road width was proposed.Secondly,the effects of road width on uniform flow and small perturbation were studied.The analytical and numerical results show that widening (shrinking) road can enhance (reduce) the equilibrium speed and flow,and the increments (decrements) will increase with the absolute value of road width gradient.In addition,the numerical results illustrate that the new model can describe the effects of road width on the evolutions of uniform flow and small perturbation.

A Simple Lumped Mass Model to Describe Velocity of Granular Flows in a Large Flume

This paper presents a lumped mass model to describe the run-out and velocity of a series of large flume tests,which was carried out to investigate some propagation mechanisms involved in rapid,dry,dense granular flows and energy transformation when the flows encountered obstacles and reoriented their movement directions.Comparisons between predicted and measured results show that the trend of predicted velocities was basically matched with that of measured ones.Careful scrutiny of test videos reveals that subsequent particles with a higher velocity collided with slowed fronts to make them accelerate. However,this simple model cannot reflect collisions between particles because it treated released materials as a rigid block.Thus,the predicted velocity was somewhat lower than the measured velocity in most cases.When the flow changed its direction due to the variation in slope inclination,the model predicted a decrease in velocity.The predicted decrease in velocity was less than the measured one within a reasonable range of 10% or less.For some cases in which a convexity was introduced,the model also predicted the same trend of velocities as measured in the tests.The velocity increased greatly after the materials took a ballistic trajectory from the vertex of the convexity,and reduced dramatically when they finally made contact with the base of the lower slope.The difference between prediced and measured decrease in velocity was estimated to be about 5% due to the landing.Therefore,the simple lumped mass model based on the energy approach could roughly predict the run-out and velocity of granular flows,although it neglected internal deformation,intergranular collision and friction.

Experimental investigation of vortex-induced vibrations of long free spans near seabed

There are many experimental studies dedicated to determining the effect of the proximity of a plane boundary on the vortex-induced vibration (VIV) of submarine pipeline spans, but they all only concerned the first mode VIV motion of the pipe. In this paper, a pipe model, 16 mm in diameter, 2.6 m in length and with a mass ratio (mass/displaced mass) of 4.30, was tested in a current tank. The reduced velocity was in the range of 0-16.7 and gap ratios at the pipe ends were 4.0, 6.0 and 8.0. The response of the model was measured using optical fiber strain gauges. Results of response amplitude and frequency were presented and the transition from the first dominant mode to the second one was shown. In the tests, it was found that the response amplitude experienced a continuous transition between the two modes, but the dramatic increase in the response frequency appeared with the shift in dominant mode from the first mode to the second one as the flow velocity increased. As the gap ratio decreased, the shift in the dominant mode took place at a higher reduced velocity.

Numerical Simulation of Flow in Centrifugal Pump with Complex Impeller

Based on the Navier-Stokes equations and the Spalart-Allmaras turbulence model,three dimensional turbulent flow fields in centrifugal pump with long-mid-short blade complex impeller are calculated and analyzed numerically.The relative velocity and pressure distributions in the flowpart are obtained.It is found that the flow in the passage of the complex impeller is unsymmetrical due to the joint action between volute and impeller.The back-flow region is at inlet of long-blade suction side,near middle part of long-blade pressure side and outlet of short-blade suction side.The flow near volute throat is affected greatly by volute.The relative velocity is large and it is easy to bring back flow at outlet of the complex impeller near volute throat.The static and total pressure rise uniformly from inlet to outlet in the impeller.At impeller outlet,the pressure periodically decreases from pressure side to suction side,and then the static pressure sharply rise near the throat.The experimental results show that the back flow in the impeller has an important influence on the performance of pump.