This paper focuses on the simulation analysis of stripe formation and dynamic features of intersecting pedestrian flows.The intersecting flows consist of two streams of pedestrians and each pedestrian stream has a des...This paper focuses on the simulation analysis of stripe formation and dynamic features of intersecting pedestrian flows.The intersecting flows consist of two streams of pedestrians and each pedestrian stream has a desired walking direction.The model adopted in the simulations is the social force model, which can reproduce the self-organization phenomena successfully. Three scenarios of different cross angles are established. The simulations confirm the empirical observations that there is a stripe formation when two streams of pedestrians intersect and the direction of the stripes is perpendicular to the sum of the directional vectors of the two streams. It can be concluded from the numerical simulation results that smaller cross angle results in higher mean speed and lower level of speed fluctuation. Moreover, the detailed pictures of pedestrians＇ moving behavior at intersections are given as well.展开更多
DC stray current can cause severe corrosion on buried pipelines.In this study,firstly,we deduced the equation of DC stray current interference on pipelines.Next,the cathode boundary condition was discretized with pipe...DC stray current can cause severe corrosion on buried pipelines.In this study,firstly,we deduced the equation of DC stray current interference on pipelines.Next,the cathode boundary condition was discretized with pipe elements,and corresponding experiments were designed to validate the mathematical model.Finally,the numerical simulation program BEASY was used to study the corrosion effect of DC stray current that an auxiliary anode bed generated in an impressed current cathodic protection system.The effects of crossing angle,crossing distance,distance of the two pipelines,anode output current,depth,and soil resistivity were investigated.Our results indicate that pipeline crossing substantially affects the corrosion potential of both protected and unprotected pipelines.Pipeline crossing angles,crossing distances,and anode depths,our results suggest,have no significant influence.Decreasing anode output current or soil resistivity reduces pipeline corrosion gradually.A reduction of corrosion also occurs when the distance between two parallel pipelines increases.展开更多
Rapid advances in vehicle automation and communication technologies enable connected autonomous vehicles(CAVs)to cross intersections cooperatively,which could significantly improve traffic throughput and safety at int...Rapid advances in vehicle automation and communication technologies enable connected autonomous vehicles(CAVs)to cross intersections cooperatively,which could significantly improve traffic throughput and safety at intersections.Virtual platooning,designed upon car‐following behavior,is one of the promising control methods to promote cooperative intersection crossing of CAVs.Nevertheless,demand variation raises safety and stability concerns when CAVs adopt a virtual platooning control approach.Along this line,this study proposes an adaptive vehicle control method to facilitate the formation of a virtual platoon and the cooperative crossing of CAVs,factoring demand variations at an isolated intersection.This study derives the stability conditions of virtual CAV platoons depending on the time‐varying traffic demand.Based on the derived stability conditions,an optimization model is proposed to adaptively control CAVs dynamics by balancing approaching traffic mobility and safety to enhance the reliability of cooperative crossing at intersections.The simulation results show that,compared to the nonadaptive control,our proposed method can increase the intersection throughput by 18.2%.Also,time‐to‐collision results highlight the advantages of the proposed adaptive control in securing traffic safety.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61233001)the Fundamental Research Funds for the Central Universities,China(Grant No.2017JBM014)
文摘This paper focuses on the simulation analysis of stripe formation and dynamic features of intersecting pedestrian flows.The intersecting flows consist of two streams of pedestrians and each pedestrian stream has a desired walking direction.The model adopted in the simulations is the social force model, which can reproduce the self-organization phenomena successfully. Three scenarios of different cross angles are established. The simulations confirm the empirical observations that there is a stripe formation when two streams of pedestrians intersect and the direction of the stripes is perpendicular to the sum of the directional vectors of the two streams. It can be concluded from the numerical simulation results that smaller cross angle results in higher mean speed and lower level of speed fluctuation. Moreover, the detailed pictures of pedestrians＇ moving behavior at intersections are given as well.
文摘DC stray current can cause severe corrosion on buried pipelines.In this study,firstly,we deduced the equation of DC stray current interference on pipelines.Next,the cathode boundary condition was discretized with pipe elements,and corresponding experiments were designed to validate the mathematical model.Finally,the numerical simulation program BEASY was used to study the corrosion effect of DC stray current that an auxiliary anode bed generated in an impressed current cathodic protection system.The effects of crossing angle,crossing distance,distance of the two pipelines,anode output current,depth,and soil resistivity were investigated.Our results indicate that pipeline crossing substantially affects the corrosion potential of both protected and unprotected pipelines.Pipeline crossing angles,crossing distances,and anode depths,our results suggest,have no significant influence.Decreasing anode output current or soil resistivity reduces pipeline corrosion gradually.A reduction of corrosion also occurs when the distance between two parallel pipelines increases.
基金US National Science Foundation,Grant/Award Number:CMMI‐2047793。
文摘Rapid advances in vehicle automation and communication technologies enable connected autonomous vehicles(CAVs)to cross intersections cooperatively,which could significantly improve traffic throughput and safety at intersections.Virtual platooning,designed upon car‐following behavior,is one of the promising control methods to promote cooperative intersection crossing of CAVs.Nevertheless,demand variation raises safety and stability concerns when CAVs adopt a virtual platooning control approach.Along this line,this study proposes an adaptive vehicle control method to facilitate the formation of a virtual platoon and the cooperative crossing of CAVs,factoring demand variations at an isolated intersection.This study derives the stability conditions of virtual CAV platoons depending on the time‐varying traffic demand.Based on the derived stability conditions,an optimization model is proposed to adaptively control CAVs dynamics by balancing approaching traffic mobility and safety to enhance the reliability of cooperative crossing at intersections.The simulation results show that,compared to the nonadaptive control,our proposed method can increase the intersection throughput by 18.2%.Also,time‐to‐collision results highlight the advantages of the proposed adaptive control in securing traffic safety.
