Stochastic Lattice gas Cellular Automata Model for Epidemics

The aim of this study was to develop and explore a stochastic lattice gas cellular automata （LGCA） model for epidemics. A computer program was development in order to implement the model. An irregular grid of cells was used. A susceptible-infected-recovered （SIR） scheme was represented. Stochasticity was generated by Monte Carlo method. Dynamics of model was explored by numerical simulations. Model achieves to represent the typical SIR prevalence curve. Performed simulations also show how infection, mobility and distribution of infected individuals may influence the dynamics of propagation. This simple theoretical model might be a basis for developing more realistic designs.

A cellular automata framework for porous electrode reconstruction and reaction-diffusion simulation

Due to the high charge transfer efficiency compared to that of non-porous materials,porous electrodes with larger surface area and thinner solid pore walls have been widely applied in the lithium-ion battery field.Since the capacity and charge-discharge efficiency of batteries are closely related to the microstructure of porous materials,a conceptually simple and computationally efficient cellular automata(CA)framework is proposed to reconstruct the porous electrode structure and simulate the reactiondiffusion process under the irregular solid-liquid boundary in this work.This framework is consisted of an electrode generating model and a reaction-diffusion model.Electrode structures with specific geometric properties,i.e.,porosity,surface area,size distribution,and eccentricity distribution can be constructed by the electrode generating model.The reaction-diffusion model is exemplified by solving the Fick's diffusion problem and simulating the cyclic voltammetry(CV)process.The discharging process in the lithium-ion battery are simulated through combining the above two CA models,and the simulation results are consistent with the well-known pseudo-two-dimensional(P2D)model.In addition,a set of electrodes with different microstructures are constructed and their reaction efficiencies are evaluated.The results indicate that there is an optimum combination of porosity and particle size for discharge efficiency.This framework is a promising one for studying the effect of electrode microstructure on battery performance due to its fully synchronous computation way,easy handled boundary conditions,and free of convergence concerns.

A cellular automata model of epidemics of a heterogeneous susceptibility

In this paper we present a model with spatial heterogeneity based on cellular automata （CA）. In the model we consider the relevant heterogeneity of host （susceptible） mixing and the natural birth rate. We divide the susceptible population into three groups according to the immunity of each individual based on the classical susceptible-infectedremoved （SIR） epidemic models, and consider the spread of an infectious disease transmitted by direct contact among humans and vectors that have not an incubation period to become infectious. We test the local stability and instability of the disease-free equilibrium by the spectrum radii of Jacobian. The simulation shows that the structure of the nearest neighbour size of the cell （or the degree of the scale-free networks） plays a very important role in the spread properties of infectious disease. The positive equilibrium of the infections versus the neighbour size follows the third power law if an endemic equilibrium point exists. Finally, we analyse the feature of the infection waves for the homogeneity and heterogeneous cases respectively.

Study on Simulation of Foreshock Activity Properties before Strong Earthquake Using Heterogeneous Cellular Automata Models

Three different degrees of heterogeneous fault models are simulated by using 2-D random dynamic cellular automata models for analyzing macroscopic behaviors of seismic activity evolution influenced by heterogeneity of fault structures. The results show that the heterogeneities of fault structures can influence evolution properties of the foreshock activity and rupture process, such as the mediate heterogeneous and less heterogeneous structures, which show relatively higher ASR rates and more significant seismic gaps before main shocks. Besides, stress drop distribution ranges of the foreshock events when approaching a main shock show more homogenous (narrower) than that of the foreshock events far from a main shock. So the heterogeneity of fault structures plays an important role in strong earthquake preparation processes.

An extended cellular automata model with modified floor field for evacuation

The floor field model has been widely used in evacuation simulation research based on cellular automata model. However, conventional methods of setting floor field will lead to highly insufficient utilization of the exit area when people gather on one side of the exit. In this study, an extended cellular automata model with modified floor field is proposed to solve this problem. Additionally, a congestion judgment mechanism is integrated in our model, whereby people can synthetically judge the degree of congestion and distance in front of them to determine whether they need to change another exit to evacuate or not. We contrasted the simulation results of the conventional floor field model, the extended model proposed in this paper, and Pathfinder software in a same scenario. It is demonstrated that this extended model can ameliorate the problem of insufficient utilization of the exit area and the trajectory of pedestrian movement and the crowd shape of pedestrians in front of exit in this new model are more realistic than those of the other two models. The findings have implications for modeling pedestrian evacuation.

Cellular automata modeling of pedestrian＇s crossing dynamics

Cellular automata modeling techniques and the characteristics of mixed traffic flow were used to derive the 2-dimensional model presented here for simulation of pedestrian’s crossing dynamics. A conception of “stop point” is introduced to deal with traffic obstacles and resolve conflicts among pedestrians or between pedestrians and the other vehicles on the crosswalk. The model can be easily extended, is very efficient for simulation of pedestrian’s crossing dy- namics, can be integrated into traffic simulation software, and has been proved feasible by simulation experiments.

A cellular automata model with probability infection and spatial dispersion

In this article, we have proposed an epidemic model based on the probability cellular automata theory. The essential mathematical features are analysed with the help of stability theory. We have given an alternative modelling approach for the spatiotemporal system which is more realistic from the practical point of view. A discrete and spatiotemporal approach is shown by using cellular automata theory. It is interesting to note that both the size of the endemic equilibrium and the density of the individuals increase with the increase of the neighbourhood size and infection rate, but the infections decrease with the increase of the recovery rate. The stability of the system around the positive interior equilibrium has been shown by using a suitable Lyapunov function. Finally, experimental data simulation for SARS disease in China in 2003 and a brief discussion are given.

Cellular Automata Models of Traffic Behavior in Presence of Speed Breaking Structures

In this article, we study traffic flow in the presence of speed breaking structures. The speed breakers are typically used to reduce the local speed of vehicles near certain institutions such as schools and hospitals. Through a cellular automata model we study the impact of such structures on giobal traffic characteristics. The simulation results indicate that the presence of speed breakers could reduce the global flow under moderate global densities. However, under low and high global density traffic regime the presence of speed breakers does not have an impact on the global flow. Further the speed limit enforced by the speed breaker creates a phase distinction. For a given global density and slowdown probability, as the speed limit enforced by the speed breaker increases, the traffic moves from the reduced flow phase to maximum flow phase. This underlines the importance of proper design of these structures to avoid undesired flow restrictions.

Numerical study on photoresist etching processes based on a cellular automata model

For the three-dimensional (3-D) numerical study of photoresist etching processes, the 2-D dynamic cellular automata (CA) model has been successfully extended to a 3-D dynamic CA model. Only the boundary cells will be processed in the 3-D dy-namic CA model and the structure of “if-else” description in the simulation pro-gram is avoided to speed up the simulation. The 3-D dynamic CA model has found to be stable, fast and accurate for the numerical study of photoresist etching processes. The exposure simulation, post-exposure bake (PEB) simulation and etching simulation are integrated together to further investigate the performances of the CA model. Simulation results have been compared with the available ex-perimental results and the simulations show good agreement with the available experiments.

Photolithography Process Simulation for Integrated Circuits and Microelectromechanical System Fabrication

Simulations of photoresist etching,aerial image,exposure,and post-bake processes are integrated to obtain a photolithography process simulation for microelectromechanical system（MEMS） and integrated circuit（IC） fabrication based on three-dimensional （3D） cellular automata（CA）. The simulation results agree well with available experimental results. This indicates that the 3D dynamic CA model for the photoresist etching simulation and the 3D CA model for the post-bake simulation could be useful for the monolithic simulation of various lithography processes. This is determined to be useful for the device-sized fabrication process simulation of IC and MEMS.

基于元胞自动机的高速公路主线同侧连续入口间距研究

针对高速公路主线同侧连续入口处车辆行驶安全与通行效率问题,对高速公路主线同侧连续入口间距进行了研究。通过建立元胞自动机仿真模型,分析了主线与匝道设计速度的差异以及高速公路主线匝道连续入口间距各部分长度对交通冲突率、平均拥堵车辆数和平均速度的影响;提出了不同主线与匝道设计速度组合下的主线同侧连续匝道入口间距推荐值;并对不同间距组合下的工况进行了仿真对比分析。研究结果表明:当主线与匝道设计速度的差异较大时,现有规范中的高速公路主线同侧连续入口间距难以满足交通安全与通行效率要求;相比采用规范中的一般值,采用文中推荐值时的主线车辆平均速度由81.39 km/h上升到95.29 km/h,匝道车辆冲突率由0.0335次/(km·veh)下降到0.0256次/(km·veh),匝道车辆平均拥堵数由0.0077 veh/s下降到0.0022 veh/s,提高了车辆通行效率,降低了车辆发生事故的风险。

基于改进NaSch模型的网联异质交通流特性分析

为研究智能网联环境下异质交通流演变规律,设计典型场景驾驶模拟实验,采集传统车辆(human driven vehicle,HDV)与智能网联车辆(connected vehicle,CV)驾驶行为特征指标,对异质交通流关键参数进行分析和标定;构建考虑HDV与CV驾驶行为差异的异质交通流元胞自动机模型;并基于改进的NaSch模型进行仿真实验,解析智能网联环境下交通流基本图,分析异质交通流特性。研究结果表明:较于HDV,CV驾驶员捕捉道路信息和反应时间提升约11.4%;自由流状态下,CV车速比HDV车速提升了7.4%,且同一车速下安全跟驰距离缩短了18.2%;随着CV所占比例由20%增至80%,交通流基本图显示交通流平均车速显著提升,交通流率增加,时空轨迹图显示局部拥堵状况明显改善。

面向灾害蔓延仿真的元胞自动机通用模型

为模拟灾害蔓延而建立的元胞自动机模型种类繁多,但尚无一种通用的建模方法。基于此提出了一种面向灾害蔓延仿真的元胞自动机通用模型。首先,通过解析灾害蔓延机理和理论模型,根据灾害动态发展变化过程的相似性,将灾害蔓延分解为灾害量集、时空邻域集、判定规则集、更新规则集4个部分;其次,采用元胞自动机的建模方法将4个部分重新组合,构建灾害蔓延的元胞自动机参数计算仿真模型;最后,利用所提方法改进了A.Ohgai的城市火灾蔓延模型,并进行了实例验证分析。研究结果表明:所提模型只需输入环境数据和灾害起始扰动,就能得到灾害模型中的各项动态参数,可为多种灾害蔓延仿真提供通用建模方法和实现模式。

考虑车辆异质性的堵塞交通流模型研究

为研究交通事故对高速公路交通流的影响,以双车道安全距离元胞自动机模型为基础引入强行变道规则,建立了考虑车辆异质性的高速公路车辆堵塞模型。利用MATLAB数值模拟高速公路异质交通流,分析不同交通密度情况下的交通事故持续时间以及重载货车占比对高速公路堵塞交通流的影响。研究表明:交通事故持续时间及重载货车占比均对高速公路堵塞交通流具有显著影响;当车辆密度大于4veh/km小于80veh/km时,交通事故持续时间对交通流有着显著影响,且持续时间越长对交通流的影响越大;当车辆密度小于30veh/km时,重载货车占比对交通流有着显著的影响,并且占比越大对交通流影响越大。

深圳河流域城市洪涝风险分析

日益严峻的城市洪涝灾害严重威胁着城市安全和可持续发展,准确评估城市洪涝风险对于保护人民群众生命财产安全至关重要。本研究基于元胞自动机洪水模拟模型构建深圳河流域洪涝仿真模型,采用综合主观层次分析法和客观权重赋权法的博弈论组合赋权法对各指标赋权,评估和预测不同降雨情景下深圳河流域城市洪涝风险。结果表明:深圳河流域城市洪涝高风险区存在典型的时空差异,随着暴雨重现期的增加,面积占比从2年一遇的0.20%增加到100年一遇的0.82%;中低风险区面积占比从2年一遇的67.4%减少到100年一遇的64.7%。研究结果可有效识别深圳河流域洪涝风险分布,为完善深圳河流域洪涝综合防治体系,提升城市洪涝防御能力和韧性提供借鉴与参考。

地铁站台乘客候车区域选择行为分析与建模

在城市轨道交通运营高峰时段,轨道交通站台受大客流冲击,极易出现乘客候车分布不均现象,导致乘客上下车效率低下、秩序混乱等问题。针对乘客进入站台后的候车区域选择行为特性进行分析,从乘客、站台、环境3个方面提出乘客候车区域选择行为影响因素,并对行为影响因素进行重要度排序。基于关键影响因素,构建候车区域吸引力模型,建立基于元胞自动机的站台乘客候车区域选择行为仿真模型。分析客流到达率、乘客到各候车区域距离、各区域乘客聚集度、排队空间影响系数与候车区域利用率的关系。挖掘不同因素影响对站台候车区域利用率的影响机理,以支撑站台候车引导策略的制定和客流的精细化组织。

铝硅合金微观组织数值模拟的研究现状及发展趋势

随着计算材料的发展,数值模拟技术已在铝硅合金凝固过程微观组织的研究中发挥了重要作用。本文就数值模拟技术应用于铝硅合金凝固过程微观组织的形成过程,综述了模拟铝硅合金微观组织形成过程必要的形核与生长模型;着重描述了广泛应用于模拟铝硅合金微观组织形成过程的方法,如元胞自动机法和相场法;最后展望了未来铝硅合金数值模拟技术的发展趋势。

基于FLUS模型的武汉市未来土地利用时空格局演变模拟

FLUS模型耦合了人类活动与自然因素综合作用,可以模拟预测多种类型土地利用变化,是目前模拟土地利用变化的一种较完善的模拟框架。本文以武汉市为研究区,基于过去一段时期的土地利用变化数据,应用FLUS模型的自上而下灰色马尔科夫预测模块对未来土地利用数量结构进行预测,应用自下而上的耦合神经网络的元胞自动机模块模拟土地利用空间格局的综合演变。结果表明:(1)选取坡度、距市中心距离、距重点镇中心距离、距高速路距离、距主干道距离、距主要河流距离自然环境区位因子作为土地利用变化空间驱动因子,FLUS模型模拟总精度为85.23%,综合Kappa系数为0.770 8,模型模拟结果可靠。(2)2050年武汉市土地利用结构以建设用地、耕地和水域为主,分别占总面积的41%、33%、19%,林地约占6%,草地与未利用地的比例较低。(3)从空间布局看,武汉市建设用地的增长基本呈现同心圆式增长,在发展前期,在发展中心主城区的同时,以卫星城的模式发展周边小城镇。随着中心城区逐渐饱和,远期转向摊大饼式发展,建设用地的扩张侵占了耕地、林地、水域和草地。

基于元胞自动机的传染病传播模型研究

从复杂适应系统的观点,通过建立元胞自动机模型的方法模拟疾病传播这个复杂的过程.并对SARS地传播过程成功地进行了模拟。同时以此为基础针对可能对传染病产生影响的几种因素作了具体地考察,如人员的移动、及时就医等,考察这些因素对控制传染病达到稳定的具体影响,并给出一些控制这类问题的建议。

基于灰色模型-元胞自动机模型的佛山市土地利用情景模拟分析

通过模拟土地利用变化情景,了解土地利用变化趋势,可为制定科学的土地利用管理策略提供支持,根据近年来建设用地扩张在佛山市土地利用类型变化中占主导地位的特点,选择灰色模型作为数量模型,元胞自动机模型作为空间模型,设定3种建设用地扩张情景:适度约束、中度约束和强力约束,结合数量模型和空间模型的优点,模拟2015年土地利用空间布局。研究结果表明:在设定的3种建设用地扩张情景下,建设用地增加的面积分别为278.3、216.5和154.6km2,相应来源于耕地的比率分别为42.28%、48.38%和55.96%,说明耕地仍然是建设用地增加的主要来源,也即耕地保护和经济发展的矛盾将会进一步增大,可为政府和土地管理部门制定政策提供一定的参考,从而采取更有针对性的措施。