基于改进最优迈步模型的楼梯区域疏散模拟

面对火灾等紧急事件,如何从多层和高层建筑内快速有效地疏散人群是火灾安全研究的一个重要课题。针对楼梯间这一重要疏散场景,考虑行人在台阶与转角平台处的迈步特征差别,在转角平台提出并采用圆形连续场域的生成法和运动规则,构建了一种改进的最优迈步模型。利用该模型重现了NIST进行的疏散演习场景,并从实时疏散人数、总疏散时间和基本图等方面进行了分析。结果表明:模型符合真实楼梯间行人疏散特性,可用于楼梯区域行人流的研究和分析。

基于连续模型的人员疏散仿真分析

行人流连续模型直观地反映人群疏散过程中的疏散特征,本文基于行人流连续模型。研究行人在典型疏散场景下的疏散特征.在COMSOL中建立行人流连续模型及其方程,通过编写MATLAB代码,实现了连续模型及其循环求解框架.利用快速扫描法求解Eikonal方程得到背景场值,在每一步迭代循环中将背景场值作为模型的初始变量导入,调用COMSOL计算模块求解模型的瞬态控制方程.通过两个标准算例,重现了典型的行人流自组织现象,验证了连续模型的合理性.结果表明,本文的疏散仿真分析模型和计算程序是可靠的,疏散仿真分析可以为实际工程中的人员疏散方案的制定以及平面设计与安全布置等方面提供技术支撑.

Pedestrian environment prediction with different types of on-shore building distribution

The aim of this work is to evaluate how the building distribution influences the cooling effect of water bodies. Different turbulence models, including the S-A, SKE, RNG, Realizable, Low-KE and RSM model, were evaluated, and the CFD results were compared with wind tunnel experiment. The effects of the water body were detected by analyzing the water vapor distribution around it. It is found that the RNG model is the most effective model in terms of accuracy and computational economy. Next, the RNG model was used to simulate four waterfront planning cases to predict the wind, thermal and moisture environment in urban areas around urban water bodies. The results indicate that the building distribution, especially the height of the frontal building, has a larger effect on the water vapor dispersion, and indicate that the column-type distribution has a better performance than the enclosed-type distribution.

Influence of driver’s yielding behavior on pedestrian-vehicle conflicts at a two-lane roundabout using fuzzy cellular automata

The roundabouts are widely used in China,some of which have central islands as scenic spots.The crosswalks connecting to the central islands,normally full of pedestrians,have negative impact on roundabout capability and pedestrian safety.Therefore,this study proposes a fuzzy cellular automata(FCA)model to explore the safety and efficiency impacts of pedestrian-vehicle conflicts at a two-lane roundabout.To reason the decision-making process of individual drivers before crosswalks,membership functions in the fuzzy inference system were calibrated with field data conducted in Changsha,China.Using specific indicators of efficiency and safety performance,it was shown that circulating vehicles can move smoothly in low traffic flow,but the roundabout system is prone to the traffic congestion if traffic flow reaches to a certain level.Also,the high yielding rate of drivers has a negative impact on the traffic efficiency but can improve pedestrian safety.Furthermore,a pedestrian restriction measure was deduced for the roundabout crosswalk from the FCA model and national guideline of setting traffic lights.

On the Reproduction Number and a Presentation of Results for Infectious Diseases Models

The classical Kermack-McKendrick homogeneous SIR （susceptible, infected and removed） model is well known, Its general solution is a function of the unique parameter （the reproduction number） that is equal to a mean number of secondary cases produced by a typical infected individual in a completely susceptible population. If the reproduction number is more than one （the threshold value） its value describes an epidemic scope： larger values correspond to more severe epidemics. In the more complex compartment SIR models the population is divided into several non-overlapping groups. It allows us to partly remove assumptions of the classical model. It is well known that for this kind of models, just as for the classical model there is the threshold parameter R0. Usually it is called by the same name--the reproduction number--though the physical meaning of this parameter has changed. The main purpose of the paper is to show that this new parameter is a not unique measure of an epidemic severity for any compartment SIR model. In particular it means that for such models comparison of the severity of two epidemics by simple comparing values of their reproduction numbers is incorrect. For compartment models these statements were proved with the help of the corresponding ODEs analysis. Very popular now individual-based models （IBMs） are more complex in comparison with the compartment ones since they use overlapping groups （school children are members of families also, for example）. In such a case Diekmann＇s calculation method for the reproduction number used in many papers is inapplicable as well as a presentation the simulation results obtained as functions of this parameter.

Simulation model of self-organizing pedestrian movement considering following behavior

A new force is introduced in the social force model （SFM） for computing following behavior in pedestrian counterflow, whereby an individual tries to approach others in the same direction to avoid conflicts with pedestrians from the opposite direction. The force, like a kind of gravitation, is modeled based on the movement state and visual field of the pedestrian, and is added to the classical SFM. The modified model is presented to study the impact of following behavior on the process of lane formation, the conflict, the number of lanes formed, and the traffic efficiency in the simulations. Simulation results show that the following behavior has a significant effect on the phenomenon of lane formation and the traffic efficiency.

Low-Dimensional SIR Epidemic Models with Demographics on Heterogeneous Networks

To investigate the impacts of demographics on the spread of infectious diseases, a susceptib- le-infectious-recovered （SIR） pairwise model on heterogeneous networks is established. This model is reduced by using the probability generating function and moment closure approximations. The basic reproduction number of the low-dimensional model is derived to rely on the recruitment and death rate, the first and second moments of newcomers＇ degree distribution. Sensitivity analysis for the basic reproduction number is performed, which indicates that a larger variance of newcomers＇ degrees can lead to an epidemic outbreak with a smaller transmission rate, and contribute to a slight decrease of the final density of infectious nodes with a larger transmission rate. Besides, stochastic simulations indicate that the low-dimensional model based on the log-normal moment closure assumption can well capture important properties of an epidemic. And the authors discover that a larger recruitment rate can inhibit the spread of disease.

Dynamical analysis of the avian-human influenza epidemic model using multistage analytical method

In this paper, analytical result of avian-human influenza epidemic model has been inves- tigated by applying homotopy analysis method （HAM） and by expanding it to hybrid numeric-analytic method which is known as multistage HAM （MSHAM）. HAM is an algorithm which gives us the approximate solution of the problem in an arrangement of time interims and by modifying it to multistage one. Some advantages such as flexibility of picking the auxiliary linear operator and the auxiliary parameter are emerged, that leads us to achieve some excellent results in this work. Furthermore, in this analyti- cal work, obtained results are compared and reported with numerical ones which were obtained previously from methods such as the Runge-Kutta （RK4） method.