Yang Lizhong

Simulation of bi-direction pedestrian movement using a cellular automata model

A cellular automata model is presented to simulate the bi-direction pedestrian movement. The pedestrian movement is more complex than vehicular flow for the reason that people are more flexible than cars. Some special technique is introduced considering simple human judgment to make the rules more reasonable. Also the custom in the countries where the pedestrian prefer to walk on the right-hand side of the road are highlighted. By using the model to simulate the bi-direction pedestrian movement, the phase transition phenomena in pedestrian counter flow is presented. Furthermore, the introduction of back stepping breaks the deadlock at the relatively low pedestrian density. By studying the critical density of changing from freely moving state to jammed state with different system sizes and different probabilities of back stepping, we find the critical density increases as the probability of back stepping increases at the same system size. And with the increasing system size, the critical density decreases at the same probability of back stepping according to the scope of system size studied in this paper.

Fire situation and fire characteristic analysis based on fire statistics of China

This paper describes the fire situation of China in 1998. Fire statistics data have been analyzed with a view to understand the characteristics of fire accidents, including vocation and location distribution, cause analysis, monthly frequency and frequency of fires by time of day etc. It is revealed that specific work on fire protection should be taken so as to meet the demands of the society. In addition, some of the major fire accidents are also recapitulated briefly. Finally, the study highlights the importance to carry out fire statistics and gives some suggestions.

Modeling Occupant Evacuation using Cellular Automata - Effect of Human Behavior and Building Characteristics on Evacuation

This paper presents a microdiscrete evacuation model which emphasizes the human behavior and is focused on studying the generic properties of occupant evacuation from crowded large, open spaces after a fixed premovement stage. By using Cellular Automata (CA) in developing the rules, the model achieves the advantages of effectively capturing the behavior of occupants at the individual-level while attaining realistic collective level activity. The lively demonstration of the evacuation process offers an easy examination of occupant movement on computer. The studies on some important characteristics in evacuation such as the existence of different velocities of people and the different structure of building offer some key factors affecting evacuation efficiency. By studying on evacuation from a corridor, with and without widen part, we found disordered moving states will badly decrease the evacuation efficiency. It enables us to understand the special phenomena in evacuation and is helpful in performance-based building design.

The effect of socioeconomic factors on fire in china

Fire differs remarkably from other natural disasters because of its close relationship with human behaviors, which are affected by socioeconomic factors. In this article, research on the relationship between socioeconomic factors and fire in China is presented. Correlation analysis shows that in China, socioeconomic factors have a notable influence on fire. But the degree of correlation between them is different from that in other countries. In China, tendency of fire incidence and serious fire situations occur with the development of economy, which is a distinctive characteristic of the relationship between fire and socioeconomic factors. The fire data from China sounds paradoxical between two periods under study and the research indicates that fire rate has a poor relationship with college education, while in developed countries they are revealed as negative correlation. Finally, we discuss how socioeconomic factors influence fire and some predictions made on the fire situation in China.

Experimental Study on Spontaneous Ignition of Wood Exposed to Variable Heat Flux

The ignition of combustible materials is an important process in a fire incident. In this work, an experimental study on the ignition process of wood exposed to a variable heat flux has been carried out. Increasing heat flux is adopted and adjusted to simulate a practical fire environment. The time to ignition, temperature distribution, and mass loss are measured for two species of wood. Both, the increasing rate of incident heat flux and the properties of wood, especially density, obviously affect the results. A conduction model is developed to calculate the surface temperature. A compound ignition criterion is brought out for a variable heat flux.

A modified model of pyrolysis for charring materials in fire

A modified model of pyrolysis for charring materials in fire has been proposed in this paper. In this model some special factors which show the effect on pyrolysis are considered, i.e., heat loss by convection and radiation caused by surface temperature rise and shrinkage of char surface are considered. Experimental device is designed specially for validating the reliability of the model. Effects of density of materials and heat radiation on pyrolysis of materials have also been investigated.

Experimental research on the spatial distribution of toxic gases in the transport of fire smoke

Current assessment models and experimental tests on gas toxicities in a fire hazard are mainly based on the hypothesis that uniform smoke and gas layers exist in the compartment. This study, through experiments conducted in a reduced-scale compartment—corridor model, examines the assumption and explores the characteristics of spatial distribution of toxic gases in smoke transport from a fire hazard. The results suggest that the toxic gases in the upper layer in the corridor are characterized by uniform expansion, while those in the lower layer are not. It has also been found that evolutions of the gases in different layers are not synchronous, while they are identical at the same height where the densities are close. Further analyses indicate that the formation of CO from the deoxidization of O2, CO 2, and the unburned hydrocarbon in the smoke movement delays the time of the maximum concentration.

Analysis of fire and explosion hazards of some hydrocarbon–air mixtures

Hazards caused by leakage of hydrocarbons have long been a problem. In this paper, the critical initiation energy and explosion limits of some hydrocarbon-air mixtures have been measured in confined (rectangle shock tube) and unconfined (plastic bag) condition tests. Two dimensionless parameters are suggested to compare the fire and explosion hazards of different hydrocarbons. Additionally, a series of experiments was performed to determine the influence of chemical additives on the fire and explosion hazards of some hydrocarbon-air mixtures in confined (rectangle shock tube) tests. These results relate directly to flammability and reactivity of hydrocarbon air mixtures. Such measurements are very important for hydrocarbon safety.

Experimental study on characteristics at early stage of fire-measurement and analysis on early development of flame image area

Generally speaking, some characteristics describing the early stage of fire include: heat release, smoke release, flame spread, toxic effluents, melting and dripping. To study these characteristics, an experimental setup must first be established. This paper presents results of experiments and mainly discusses the increase in flame image area of a fire during its early stage. The analysis shows that the flame image area of a fire at an early stage increases continuously, and the increase rule can be described using a geometrical function.

The relationship between smoke concentration some distance down the hallway and the opening of the room of fire origin

The smoke concentration at a distant location down a hallway as a function of different openings of the room of fire origin is considered. A series of tests is reported and the smoke sustaining (residence) time, the concentration peak and the concentration buildup rate are investigated as functions of the size of the opening. The smoke sustaining (residence) time, the most important factor concerning smoke toxicity, is described by a novel concept, wavelength, in this study. Furthermore, it is worth emphasizing that the smoke concentration at the sampling point exhibits a phenomenon of vibration in the case of the smallest opening during the test.