城市干线典型路段速度-流量特性分析

以长春市干线道路的交通流实测数据为依据,绘制了速度-流量的散点图,建立了散点图及边界的线性回归方程,并与Greenshields速度-流量理论模型曲线、高速公路的速度-流量散点图进行了对比,分析了城市道路的速度-流量特性。实际应用表明,该特性分析能为交通管理者确定信号控制策略提供速度-流量依据。

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。

一种改进的Nagel-Schreckenberg模型及速度-流量关系研究

为体现不同车辆在交通流中的差异性,在N agel-Schreckenberg模型的基础上,将减速概率与车辆密度和速度联系起来,提出了一种改进的一维元胞自动机交通流模型,重点研究了平均速度与流量的关系并与实测结果进行了比较,讨论了交通堵塞形成的过程。数值模拟结果表明本文模型在速度-流量关系的描述上要优于N agel-Schreckenberg模型。

基于Van Aerde的城市主干路速度-流量模型研究

速度和流量是道路交通安全管理、事件报警、应急处置重要的基础数据。采用Autoscope视频检测器采集的速度和流量数据作为数据源,进行系统分析,结合其曲线趋势,选择使用Van Aerde经典模型为基础模型,根据交通三参数之间的关系得出速度-流量关系,在此基础上根据交通流在自由流、饱和流、阻塞流状态下的交通特征重新推导,并结合国内城市主干路实际情况进行模型参数标定,进而得出城市主干路的速度-流量关系模型。

市区干道速度-流量散点边界问题研究

由于各种干扰因素的存在,使得市区内的车流在运行时表现出较大的离散性.当流量不变时,车速的波动范围较大,这使得传统的速度-流量模型在对其进行拟合时出现不适用的情况.与以往的研究不同,本文利用霍尔特指数平滑法对速度-流量波动的边界进行了细致的分析,给出了速度-流量散点的上下边界模型.将该模型应用到呼和浩特的主干道交通流分析,发现具有较好的拟合效果.

城市干道路段速度-流量模型及通行能力研究

结合城市干道交通流为间断流的特点,主要研究城市主、次干道交通流速度-流量关系曲线,并采用迭代对分区间法得出各个车道的推荐通行能力值。研究结果可为主、次干道通行能力、服务水平的研究以及交通仿真参数的修订提供理论依据,并为城市交通规划设计、管理及控制提供技术支持。

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。

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。

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。

城市干道交通流速度一流量关系模型研究

为研究适合我国城市干道交通流特点的速度与流量之间的关系,在建立Greenshields模型和Re-Greenshields模型的基础上,结合城市干道交通流为间断流的特点,采用分段建模法建立了G-LN模型。通过拟合判定系数R_(sq)对Greenshields模型和Re-Greenshields模型进行对比,并利用实测数据标准差S对Re-Greenshields模型和G-LN模型进行对比,结果表明:G-LN模型能更好地描述城市干道速度—流量关系。最后分析了模型参数,采用对分区间迭代法计算模型通行能力值。

快速路交通流速度——流量模型研究

主要研究了快速路交通速度-流量关系。在分析了车流运行状态的基础上,结合速度-流量曲线和幂指函数的特点,对传统的幂指函数作了修改,得到了新的速度-流量曲线模型。采用秩相关分析方法给出了自由流速度估计值。实测数据分析结果表明,速度-流量模型拟合的结果较好。

城市干道路段交通流速度——流量关系模型研究

结合城市干道交通流为间断流的特点,主要研究了城市干道交通流速度-流量关系。通过对实测数据的统计分析,分析城市干道路段速度与流量之间的关系,采用分段建模的方法,建立了城市干道速度-流量关系模型,对模型的结果进行了分析。可为通行能力、服务水平的研究以及交通仿真参数的修订提供理论依据,并为城市交通规划设计、管理及控制提供技术支持。

城市隧道路段速度–流量特性分析

为确定城市隧道路段及隧道进出口速度和流量关系,研究南京市富贵山隧道进出口的交通流,以隧道进出口交通流实测数据为依据,考虑隧道交通流实际,以20 s为统计间隔,对调查的2 d数据进行处理,将20 s流量换算为标准车小时交通量,速度采用区间平均车速,绘制速度-流量散点图及建立边界回归方程,并对隧道路段及进出口处速度-流量特性进行分析。得到城市隧道路段速度-密度与城市干线典型路段及高速公路路段有明显差异。驾驶员在隧道进口处的自由度较隧道出口处低,隧道路段驾驶员的驾驶自由度较其他路段低,该特性分析可以为城市隧道管理及隧道上游及下游信号控制提供依据。

Characteristics of non-magnetic nanoparticles in magnetically fluidized bed by adding coarse magnets

The fluidization behavior of SiO2, ZnO and TiO2 non-magnetic nanoparticles was investigated in a magnetically fluidized bed （MFB） by adding coarse magnets. The effects of both the amount of coarse magnets and the magnetic field intensity on the fluidization quality of these nanoparticles were investigated. The results show that the coarse magnets added to the bed lead to a reduction in the size of the aggregates formed naturally by the primary nanopartieles. As the macroscopic performances of improved fluidization quality, the bed expansion ratio increases whilst the minimum fluidization velocity decreases with increasing the magnetic field intensity, but for TiO2 nanoparticles there exists a suitable magnetic field intensity of 0.059 6 T. The optimal amounts of coarse magnets for SiO2, ZnO and TiO2 non-magnetic nanoparticles are 40%, 50% and 60% （mass fraction）, respectively. The bed expansion results analyzed by the Richardson-Zaki scaling law show that the exponents depend on both the amount of coarse magnets and the magnetic field intensity.

The Velocity Measurement of Two-phase Flow Based on Particle Swarm Optimization Algorithm and Nonlinear Blind Source Separation

In order to overcome the disturbance of noise,this paper presented a method to measure two-phase flow velocity using particle swarm optimization algorithm,nonlinear blind source separation and cross correlation method.Because of the nonlinear relationship between the output signals of capacitance sensors and fluid in pipeline,nonlinear blind source separation is applied.In nonlinear blind source separation,the odd polynomials of higher order are used to fit the nonlinear transformation function,and the mutual information of separation signals is used as the evaluation function.Then the parameters of polynomial and linear separation matrix can be estimated by mutual information of separation signals and particle swarm optimization algorithm,thus the source signals can be separated from the mixed signals.The two-phase flow signals with noise which are obtained from upstream and downstream sensors are respectively processed by nonlinear blind source separation method so that the noise can be effectively removed.Therefore,based on these noise-suppressed signals,the distinct curves of cross correlation function and the transit times are obtained,and then the velocities of two-phase flow can be accurately calculated.Finally,the simulation experimental results are given.The results have proved that this method can meet the measurement requirements of two-phase flow velocity.

Mass-front velocity of dry granular flows influenced by the angle of the slope to the runout plane and particle size gradation

The mass-front velocities of granular flows results from the joint action of particle size gradations and the underlying surfaces.However,because of the complexity of friction during flow movement,details such as the slope-toe impedance effects and momentum-transfer mechanisms have not been completely explained by theoretical analyses,numerical simulations,or field investigations.To study the mass-front velocity of dry granular flows influenced by the angle of the slope to the runout plane and particle size gradations we conducted model experiments that recorded the motion of rapid and long-runout rockslides or avalanches.Flume tests were conducted using slope angles of 25°,35°,45°,and 55° and three particle size gradations.The resulting mass-front motions consisted of three stages:acceleration,velocity maintenance,and deceleration.The existing methods of velocity prediction could not explain the slowing effect of the slope toe or the momentum-transfer steady velocity stage.When the slope angle increased from 25° to 55°,the mass-front velocities dropped significantly to between 44.4% and59.6% of the peak velocities and energy lossesincreased from 69.1% to 83.7% of the initial,respectively.The velocity maintenance stages occurred after the slope-toe and mass-front velocity fluctuations.During this stage,travel distances increased as the angles increased,but the average velocity was greatest at 45°.At a slope angle of 45°,as the median particle size increased,energy loss around the slope toe decreased,the efficiency of momentum transfer increased,and the distance of the velocity maintenance stage increased.We presented an improved average velocity formula for granular flow and a geometrical model of the energy along the flow line.

Speed aware self-adapting and reconfigurable routing mechanism in MANET

A self-adapting and reconfigurable routing mechanism is proposed according to the average moving speed of the nodes in mobile ad hoc network （MANET）. This mechanism is based on the perception of moving speed and a predesigned selection metric to choose the optimal routing protocol. The routing evaluation and selection metric is derived by OPNET simulations. AODV and OLSR are used as the example to show the process of this mechanism with the moving speed varying. The routing protocol can be configured without central configuration and human management. Besides, the overhead of the mechanism is reasonable and doesnot affect the quality of service （QoS） of the traffic in the network. Results show that the optimal routing protocol can be configured adaptively according to the speed so that better performance than end-to-end delay and packet delivery ratio. a specific protocol can be obtained in terms of

Optimum control strategy for all-variable speed chiller plant

The optimum control strategy and the saving potential of all variable chiller plant under the conditions of changing building cooling load and cooling water supply temperature were investigated. Based on a simulation model of water source chiller plant established in dynamic transient simulation program (TRNSYS),the four-variable quadratic orthogonal regression experiments were carried out by taking cooling load,cooling water supply temperature,cooling water flow rate and chilled water flow rate as variables,and the fitting formulas expressing the relationships between the total energy consumption of chiller plant with the four selected parameters was obtained. With the SAS statistical software and MATHEMATICA mathematical software,the optimal chilled water flow rate and cooling water flow rate which result in the minimum total energy consumption were determined under continuously varying cooling load and cooling water supply temperature. With regard to a chiller plant serving an office building in Shanghai,the total energy consumptions under different control strategies were computed in terms of the forecasting function of cooling load and water source temperature. The results show that applying the optimal control strategy to the chiller plant can bring a saving of 23.27% in power compared with the corresponding conventional variable speed plant,indicating that the optimal control strategy can improve the energy efficiency of chiller plant.

Downlink SINR and Rate Distribution of Ultra-Dense Het Nets with Burst Traffic

SINR distribution and rate overage distribution are crucial for optimization of deployment of Ultra-dense Het Nets.Most existing literatures assume that BSs have full queues and full-buffer traffic.In fact,due to ultra-dense deployment of small cells,traffic in small cell varies dramatically in time and space domains.Hence,it is more practical to investigate scenario with burst traffic.In this paper,we consider a two-tier non-uniform ultra-dense Het Net with burst traffic,where macro BSs are located according to Poisson Point Process(PPP),and pico BSs are located according to Poisson Hole Process(PHP).The closed-form expressions of SINR distribution and rate distribution are derived,and then validated through simulation.Our study shows that different from the result of full buffer case,the SINR distribution and rate distribution of users depend on the average transmission probabilities of BSs in burst traffic case.

Detailed string stability analysis for bi-directional optimal velocity model

The class of bi-directional optimal velocity models can describe the bi-directional looking effect that usually exists in the reality and is even enhanced with the development of the connected vehicle technologies. Its combined string stability condition can be obtained through the method of the ring-road based string stability analysis. However, the partial string stability about traffic fluctuation propagated backward or forward was neglected, which will be analyzed in detail in this work by the method of transfer function and its H∞ norm from the viewpoint of control theory. Then, through comparing the conditions of combined and partial string stabilities, their relationships can make traffic flow be divided into three distinguishable regions, displaying various combined and partial string stability performance. Finally, the numerical experiments verify the theoretical results and find that the final displaying string stability or instability performance results from the accumulated and offset effects of traffic fluctuations propagated from different directions.