Papers by Keyword: Cellular Automaton Model

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Authors: Jie Dong, Xiao Mei Zhang
Abstract: On the basis of Nagel-Schreckenberg model, this paper presents a modified fuzzy cellular automaton model for one-lane highway traffic. An interval type-2 fuzzy logic system is designed to evaluate the randomization parameter of a vehicle based on the spatial headway and speed difference. Some basic qualitative results and the fundamental diagram of our new model are got through computer numerical simulations. The experimental results show that our new model is able to reproduce some of the real macroscopic traffic characteristics such as stop-and-go waves, hysteresis and metastability phenomena.
4423
Authors: Ke Zhao Bai, Li Yang, Jian Huang, Rong Sen Zheng, Hua Kuang
Abstract: Based on the NaSch model, an extended cellular automaton model is proposed to simulate traffic flow by considering the effects of visibility. Under the open boundary condition, the influences of the injection probability, disappearance probability and visibility are discussed. The simulation results show that the injection probability and disappearance probability within a certain range have an important effect on the flux, density and velocity. And traffic jams often occur in poor visibility areas, which can become a road bottleneck. Furthermore, in order to effectively decrease the occurrence of traffic jams, the injection probability and disappearance probability should be set up reasonably.
1782
Authors: Zhen Nan Fu, Shou Mei Xiong
Abstract: A cellular automaton (CA) based model for two-dimensional simulation of the grain morphology of high pressure die casting magnesium alloy was developed. The heterogeneous nucleation, the solute redistribution both in liquid and solid, the interface curvature and the growth anisotropy during solidification were also considered in the model. By fitting the curve of grain density distribution, parameters of continuous nucleation equation based on Gaussian distribution were calculated. The microstructure simulation of step-shape die castings of AM50 magnesium alloy was studied. The metallographic microstructure of the castings at the surface and center of three steps with different initial die temperature was investigated. The simulation results were compared with the experimental results and they were in good agreement on average grain size.
135
Authors: Zhen Nan Fu, Qing Yan Xu, Shou Mei Xiong
Abstract: A cellular automaton (CA)-based model for two-dimensional simulation of the dendritic morphology of magnesium alloys was developed. The model considers solving the solute and heat conservation equations in the modeling domain, including calculation of the solid fraction, the tip velocity, and the solute diffusion process, all of which have significant influence on the dendrite evolution. The microstructure of a step-shape die cast part of AZ91D magnesium alloys was investigated utilizing SEM-EBSD analysis. The microstructure simulation results were compared with the experimental results and they were in good agreement on grain size.
133
Authors: Qing Yan Xu, Bai Cheng Liu, Zuo Jian Liang
Abstract: Dendritic is the most observed microstructure in metallic materials. Traditional Cellular Automaton model can only predict the grain structure and grain size. It is necessary for us to modify the original model to reflect the real shape of dendrite. In the paper, a mathematical model was established to describe the evolution of the dendritic shape, in which the influence of microsegregation and curvature on undercooling was taking into account. In addition, the growth model was proposed based on the minimum free energy principle. Modeling results indicated the proposed models can predict not only grain structure, but also dendritic morphology. Free growth of equiaxed grains and the competitive growth of columnar grains were simulated. The modeling results were also validated with experiments.
3137
Authors: Chen Hsueh Chiang, Chien Tzu Cheng
Abstract: A numerical simulation method is used to analyse the microstructure evolution of 8-mm-diameter brass (70wt%Cu30wt%Zn) rods during the vacuum continuous casting (VCC) process. The macro-and micro-scale coupling method is adopted to develop a temperature field model and a microstructure prediction model. The effects of casting parameters, including casting speed and pouring temperature, on the shape of the solid-liquid (S/L) interface and solidified microstructure are considered. Simulation results show that the casting speed has a large effect on the shape of the S/L interface and grain morphology.
431
Authors: Chang Hai Wei, Yu Huan Wang, Xu Wang
Abstract: Conflicts between left-turning vehicles and pedestrians are common at signalized intersection in most developing countries. A new cellular automaton model is proposed to characterize left-turning traffic flow. New status update rules and driving behavior in affected areas and nonaffected areas are defined. Indexes of density, average speed and volume under different pedestrian violation rates are compared to quantify the impact of conflicts on left-turning traffic flow. Simulation results illustrate that pedestrian violations have a great impact on left-turning traffic flow and capacity of the intersection. Therefore, taking countermeasures will improve vehicle maneuvers, reduce the number of pedestrian accidents and increase the capacity of the intersection.
2053
Authors: Jing Bian, Hong Zhuang, Wei Li
Abstract: It is the key fact for the accuracy of traffic simulation that the cellular automation model of traffic flow could simulate the real hybrid traffic flow. This article shows the method to improve cellular automaton model about two-lane hybrid vehicles based on passive lane-changing, to propose the avoidance rules about the prospective following vehicle, and to suggest the cellular automaton model and evolution rules based on the prospective following vehicle’s avoider. The simulation results show that the erroneous judgment rate for changing lane is the important facts for the state of two-lane hybrid traffic flow, and the accuracy of the simulation is improved in this article.
1627
Authors: Xiao Wei Wei
Abstract: With worsening traffic condition in large and medium-sized cities, it has become one of the most important steps for the urban traffic strategy to solve the traffic problems. Since the urban traffic is a complex system in various factors and huge scale, to establish related mathematical model through computer numerical simulation is a significant solution to the comprehensive problems of complex analysis, decision and planning. At present researches on the problems have been achieved in many foreign countries, but domestic research is not enough, especially in the practical application. The macroscopic traffic flow model and microscopic traffic flow model are described and cellular automaton model, dual channel decision model and car-following model are analyzed in this paper, prediction of the ideal traffic flow and trip distribution is consequently concluded, which deepen the understanding to the traffic flow of various phenomenon intrinsic mechanism and predict most closely to the actual situation of traffic flow, which can make fundamental work for traffic flow simulation and for real-time traffic control[1-3].
237
Authors: Zhen Wang, Feng Zhi Qi, Lu Kai Zhang
Abstract: With the development of public transport, many cities in China have adopted bus lanes as a preferred method to alleviate the problems associated with high traffic demand and congestion. However, especially in the intersections, permanent dedication of one lane in the cases with lower frequency of bus services is very inefficient. We put forward a conversion section the bus lane in the upstream of intersection, in which the status of a given section changes according to the presence or not of a bus in its spatial domain: when a bus is approaching such a section, the status of that lane is changed to bus lane, and after the bus moves out of the section, it becomes open to right-turning vehicles. This measure enables to shorten the travel time of the right turn vehicles by 20%, while the speed of the buses will not be affected.
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