Improving bus travel time reliability can attract more commuters to use bus transit,and therefore reduces the share of cars and alleviates trafc congestion.This paper formulates a new bus travel time reliability metri...Improving bus travel time reliability can attract more commuters to use bus transit,and therefore reduces the share of cars and alleviates trafc congestion.This paper formulates a new bus travel time reliability metric that jointly considers two stochastic processes:the in-stop waiting process and in-vehicle travel time process,and the bus travel time reliability function is calculated by the convolution of independent events’probabilities.The new reliability metric is defned as the probability when bus travel time is less than a certain threshold and can be used in both conditions with and without bus transfer.Next,Automatic Vehicle Location(AVL)data of the city of Harbin is used to demonstrate the applicability of the proposed method.Results show that factors such as weather,day of the week,departure time,travel distance,and the distance from the boarding stop to the bus departure station can signifcantly afect the travel time reliability.Then,a case with low bus departure frequency is analyzed to show the impact of travelers’arrival distribution on their bus travel time reliability.Further,it is demonstrated that the travel time reliabilities of two bus transfer schemes of the same Origin–Destination(O–D)pair can have signifcantly diferent patterns.Understanding the bus travel time reliability pattern of the alternative bus routes can help passengers to choose a more reliable bus route under diferent conditions.The proposed bus travel time reliability metric is tested to be sensitive to the efect of diferent factors and can be applied in bus route recommendation,bus service evaluation,and optimization.展开更多
In order to describe the behavior of the car under ice and snowfall conditions more realistically,a vehicle following model based on the full velocity difference model is proposed under the premise of considering the ...In order to describe the behavior of the car under ice and snowfall conditions more realistically,a vehicle following model based on the full velocity difference model is proposed under the premise of considering the speed difference and various kinds of ice and snowfall conditions. Under various road conditions,it obtains the critical stability curve of the model,and verifies that the worse the road condition is,the less stable the traffic flow is. In addition,the method of nonlinear analysis is used to obtain the solution of the kink density wave in the space headway under the unstable region. Finally,the conclusions are verified by numerical simulation,that worse road conditions,which means the road surface friction coefficient is small,will lead to greater instability region and worse anti-interference ability of traffic flow,and even cause more congestion and accidents. The conclusions make great contributions to handling the traffic jams and security issues under ice and snowfall conditions.展开更多
全基因组关联分析(genome-wide association studies,GWAS)是研究家畜复杂经济性状和疾病遗传变异的有效方法,GWAS的核心是挖掘遗传变异与目标表型性状间的关系。随着牛全基因组测序工作完成,海量单核苷酸多态性(single nucleotide poly...全基因组关联分析(genome-wide association studies,GWAS)是研究家畜复杂经济性状和疾病遗传变异的有效方法,GWAS的核心是挖掘遗传变异与目标表型性状间的关系。随着牛全基因组测序工作完成,海量单核苷酸多态性(single nucleotide polymorphism,SNP)位点被标记,GWAS越来越多地应用于有关肉牛经济性状相关候选基因的研究。文章综述GWAS的概念、原理、研究方法以及近年来GWAS在肉牛生长性状、肉质性状方面进行的研究,为利用GWAS进行家畜复杂经济性状遗传机制相关研究提供参考,为肉牛育种工作奠定基础。展开更多
基金supported by the National Natural Science Foundation of China(71871075,91846301,71501053)China Postdoctoral Science Foundation(2015M570297)International Postdoctoral Exchange Fellowship(20160076)of China Postdoctoral Council,and CCF-DiDi Big Data Joint Lab.
文摘Improving bus travel time reliability can attract more commuters to use bus transit,and therefore reduces the share of cars and alleviates trafc congestion.This paper formulates a new bus travel time reliability metric that jointly considers two stochastic processes:the in-stop waiting process and in-vehicle travel time process,and the bus travel time reliability function is calculated by the convolution of independent events’probabilities.The new reliability metric is defned as the probability when bus travel time is less than a certain threshold and can be used in both conditions with and without bus transfer.Next,Automatic Vehicle Location(AVL)data of the city of Harbin is used to demonstrate the applicability of the proposed method.Results show that factors such as weather,day of the week,departure time,travel distance,and the distance from the boarding stop to the bus departure station can signifcantly afect the travel time reliability.Then,a case with low bus departure frequency is analyzed to show the impact of travelers’arrival distribution on their bus travel time reliability.Further,it is demonstrated that the travel time reliabilities of two bus transfer schemes of the same Origin–Destination(O–D)pair can have signifcantly diferent patterns.Understanding the bus travel time reliability pattern of the alternative bus routes can help passengers to choose a more reliable bus route under diferent conditions.The proposed bus travel time reliability metric is tested to be sensitive to the efect of diferent factors and can be applied in bus route recommendation,bus service evaluation,and optimization.
基金Sponsored by the National Natural Science Foundation of China(Grant No.71471046,51478151 and 51308165)the Natural Science Foundation of Shandong Province(Grant No.ZR2014GM003 and ZR2013EEQ003)
文摘In order to describe the behavior of the car under ice and snowfall conditions more realistically,a vehicle following model based on the full velocity difference model is proposed under the premise of considering the speed difference and various kinds of ice and snowfall conditions. Under various road conditions,it obtains the critical stability curve of the model,and verifies that the worse the road condition is,the less stable the traffic flow is. In addition,the method of nonlinear analysis is used to obtain the solution of the kink density wave in the space headway under the unstable region. Finally,the conclusions are verified by numerical simulation,that worse road conditions,which means the road surface friction coefficient is small,will lead to greater instability region and worse anti-interference ability of traffic flow,and even cause more congestion and accidents. The conclusions make great contributions to handling the traffic jams and security issues under ice and snowfall conditions.
文摘全基因组关联分析(genome-wide association studies,GWAS)是研究家畜复杂经济性状和疾病遗传变异的有效方法,GWAS的核心是挖掘遗传变异与目标表型性状间的关系。随着牛全基因组测序工作完成,海量单核苷酸多态性(single nucleotide polymorphism,SNP)位点被标记,GWAS越来越多地应用于有关肉牛经济性状相关候选基因的研究。文章综述GWAS的概念、原理、研究方法以及近年来GWAS在肉牛生长性状、肉质性状方面进行的研究,为利用GWAS进行家畜复杂经济性状遗传机制相关研究提供参考,为肉牛育种工作奠定基础。
