为了改善交通网络运行状况,根据车流密度的差异对宏观路网进行子区划分,提出了面向多个宏观基本图(Macroscopic fundamental diagram,MFD)子区的边界协调控制方法.根据划分的多个子区间邻接关系和流入流出交通流率,建立了路网车流平衡方...为了改善交通网络运行状况,根据车流密度的差异对宏观路网进行子区划分,提出了面向多个宏观基本图(Macroscopic fundamental diagram,MFD)子区的边界协调控制方法.根据划分的多个子区间邻接关系和流入流出交通流率,建立了路网车流平衡方程.通过与最佳累积车辆数进行比较,确定了拥挤度高的子区边界交叉口最佳流入与流出的交通流量;进而建立了以整个路网旅行完成流率最大、平均行程时间和平均延误最小的多目标边界协调优化模型,并通过自适应遗传算法对多目标函数进行求解.以存在4个MFD子区的实际路网为分析对象,对比仿真结果表明所提方法可有效提高路网运行效率、缓解拥堵状况.展开更多
为了解决交通高峰时段城市区域路网过大的交通需求引起的路网通行效率下降以及区域内部交通流分布的异质性产生的道路资源浪费等问题.本文提出了基于区域路网固有属性宏观基本图(Macroscopic fundamental diagram,MFD)的过饱和区域控制...为了解决交通高峰时段城市区域路网过大的交通需求引起的路网通行效率下降以及区域内部交通流分布的异质性产生的道路资源浪费等问题.本文提出了基于区域路网固有属性宏观基本图(Macroscopic fundamental diagram,MFD)的过饱和区域控制优化模型,建立了边界控制信号和内部控制信号目标函数的双层规划优化,进一步设计了基于BP(Back propagation)神经网络的自适应动态规划(Adaptive dynamic programming,ADP)模型,对建立的双层规划区域交通信号进行求解,实例仿真结果验证了本文方法的有效性.通过本文的研究分析,对城市区域交通的需求管控、拥堵政策制定等城市区域交通管理具有一定的指导意义.展开更多
区域边界控制在缓解城市区域交通拥堵方面具有巨大的潜力,但同时容易导致区域边界处形成严重的排队现象。为了解决这一问题,结合高铁站周围路网的交通特性,提出了一种将交通诱导与区域边界控制相结合的基于宏观基本图(Macroscopic Funda...区域边界控制在缓解城市区域交通拥堵方面具有巨大的潜力,但同时容易导致区域边界处形成严重的排队现象。为了解决这一问题,结合高铁站周围路网的交通特性,提出了一种将交通诱导与区域边界控制相结合的基于宏观基本图(Macroscopic Fundamental Diagrams,MFD)的诱导-控制方法。首先,为满足同质性要求,划分路网子区,建立各子区的宏观交通流平衡方程,确定每个子区最佳的车辆数积累;其次,根据各子区的交通状态,实时更新诱导-控制措施,在优先使用交通诱导方式的前提下对高铁站周围路网的交通流进行动态管控;最后,以西安北站周围路网为分析对象,通过仿真分析,对比了无区域边界控制、单一边界控制和诱导-控制三种情况下的管控效果。结果表明,在诱导-控制条件下,区域的平均车速较其他两种情况下分别提高了25.39%和4.61%,平均车辆延误分别减少了28.22%和10.05%,尤其是车辆在落客区的延误明显减少。基于MFD的诱导-控制方法可有效缓解高峰客流时段高铁站周围路网的拥堵,提高客流和车流在高铁站的集散效率。展开更多
A comprehensive, universally valid, elegant and yet simple method to design slender axisymmetric body of minimum wave drag in transonic and supersonic flows is developed. Computational aerodynamics is also used as a t...A comprehensive, universally valid, elegant and yet simple method to design slender axisymmetric body of minimum wave drag in transonic and supersonic flows is developed. Computational aerodynamics is also used as a tool for numerical experiments in gaining physical understanding of the drag mechanism due to the geometry of the aftbody, such as the correlation between wave drag and wave distribution of the aftbody geometry. The method utilizes MFD （modified feasible direction） based optimization program, along with the linear slender body aerodynamics, for its elegance and generic optimization convenience. The efforts are focused on inviscid flow. A practical method of reducing the wave drag of a given body is developed for both bodies with pointed end and with base area, using shock wave generator at a particular location on the aftbody. The results show that the MFD optimization program can be effectively utilized in an aerodynamic optimization problem.展开更多
The macroscopic fundamental diagram（ MFD） is studied to obtain the aggregate behavior of traffic in cities. This paper investigates the existence and the characteristics of different types of daily MFD for the Shang...The macroscopic fundamental diagram（ MFD） is studied to obtain the aggregate behavior of traffic in cities. This paper investigates the existence and the characteristics of different types of daily MFD for the Shanghai urban expressway network. The existence of MFD in the Shanghai urban expressway network is proved based on two weeks＇ data.Moreover, the hysteresis phenomena is present in most days and the network exhibits different hysteresis loops under different traffic situations. The relationship between the hysteresis phenomena and the inhomogeneity of traffic distribution is verified. The MFDs in the years of 2009 and 2012 are compared. The hysteresis loop still exists in 2012, which further verifies the existence of the hysteresis phenomenon. The direct relationship between the length of the hysteresis loop（ ΔO） and the congestion is proved based on sufficient data. The width of the hysteresis loop, i. e., the drop in network flow（ ΔQ） has no relationship with the congestion, and it varies from day to day under different traffic situations.展开更多
文摘为了改善交通网络运行状况,根据车流密度的差异对宏观路网进行子区划分,提出了面向多个宏观基本图(Macroscopic fundamental diagram,MFD)子区的边界协调控制方法.根据划分的多个子区间邻接关系和流入流出交通流率,建立了路网车流平衡方程.通过与最佳累积车辆数进行比较,确定了拥挤度高的子区边界交叉口最佳流入与流出的交通流量;进而建立了以整个路网旅行完成流率最大、平均行程时间和平均延误最小的多目标边界协调优化模型,并通过自适应遗传算法对多目标函数进行求解.以存在4个MFD子区的实际路网为分析对象,对比仿真结果表明所提方法可有效提高路网运行效率、缓解拥堵状况.
文摘区域边界控制在缓解城市区域交通拥堵方面具有巨大的潜力,但同时容易导致区域边界处形成严重的排队现象。为了解决这一问题,结合高铁站周围路网的交通特性,提出了一种将交通诱导与区域边界控制相结合的基于宏观基本图(Macroscopic Fundamental Diagrams,MFD)的诱导-控制方法。首先,为满足同质性要求,划分路网子区,建立各子区的宏观交通流平衡方程,确定每个子区最佳的车辆数积累;其次,根据各子区的交通状态,实时更新诱导-控制措施,在优先使用交通诱导方式的前提下对高铁站周围路网的交通流进行动态管控;最后,以西安北站周围路网为分析对象,通过仿真分析,对比了无区域边界控制、单一边界控制和诱导-控制三种情况下的管控效果。结果表明,在诱导-控制条件下,区域的平均车速较其他两种情况下分别提高了25.39%和4.61%,平均车辆延误分别减少了28.22%和10.05%,尤其是车辆在落客区的延误明显减少。基于MFD的诱导-控制方法可有效缓解高峰客流时段高铁站周围路网的拥堵,提高客流和车流在高铁站的集散效率。
文摘A comprehensive, universally valid, elegant and yet simple method to design slender axisymmetric body of minimum wave drag in transonic and supersonic flows is developed. Computational aerodynamics is also used as a tool for numerical experiments in gaining physical understanding of the drag mechanism due to the geometry of the aftbody, such as the correlation between wave drag and wave distribution of the aftbody geometry. The method utilizes MFD （modified feasible direction） based optimization program, along with the linear slender body aerodynamics, for its elegance and generic optimization convenience. The efforts are focused on inviscid flow. A practical method of reducing the wave drag of a given body is developed for both bodies with pointed end and with base area, using shock wave generator at a particular location on the aftbody. The results show that the MFD optimization program can be effectively utilized in an aerodynamic optimization problem.
基金The National Natural Science Foundation of China(No.51238008)
文摘The macroscopic fundamental diagram（ MFD） is studied to obtain the aggregate behavior of traffic in cities. This paper investigates the existence and the characteristics of different types of daily MFD for the Shanghai urban expressway network. The existence of MFD in the Shanghai urban expressway network is proved based on two weeks＇ data.Moreover, the hysteresis phenomena is present in most days and the network exhibits different hysteresis loops under different traffic situations. The relationship between the hysteresis phenomena and the inhomogeneity of traffic distribution is verified. The MFDs in the years of 2009 and 2012 are compared. The hysteresis loop still exists in 2012, which further verifies the existence of the hysteresis phenomenon. The direct relationship between the length of the hysteresis loop（ ΔO） and the congestion is proved based on sufficient data. The width of the hysteresis loop, i. e., the drop in network flow（ ΔQ） has no relationship with the congestion, and it varies from day to day under different traffic situations.
