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[en] This study investigates the effects of guide-based guidance on the pedestrian evacuation under limited visibility via the simulations based on an extended social force model. The results show that the effects of guides on the pedestrian evacuation under limited visibility are dual, and related to the neighbor density within the visual field. On the one hand, in many cases, the effects of guides are positive, particularly when the neighbor density within the visual field is moderate; in this case, a few guides can already assist the evacuation effectively and efficiently. However, when the neighbor density within the visual field is particularly small or large, the effects of guides may be adverse and make the evacuation time longer. Our results not only provide a new insight into the effects of guides on the pedestrian evacuation under limited visibility, but also give some practical suggestions as to how to assign guides to assist the evacuation under different evacuation conditions. - Highlights: • Extended social force model is used to simulate guided pedestrian evacuation. • Effects of guides on pedestrian evacuation under limited visibility are dual. • Effects of guides on pedestrian evacuation under limited visibility are related to neighbor density within visual field.
[en] A modified cellular automata model is proposed to simulate the pedestrian evacuation behavior in a room with multiple exits by considering the reserve capacity of the exit. The main idea is motivated by the original concept of minority game, which means less congested exits may be preferentially chosen together with the floor fields. The model outperforms previous ones under the condition in which pedestrians are distributed heterogeneously. Simulation results show that wise exit choosing with the consideration of reserve capacity may reduce the evacuation time apparently, which is more realistic. Furthermore, the impacts of the room geometry and parameter settings are investigated extensively.
[en] Due to a procedural error in construction of Figs. 8 and 9, listed minimum speeds to beat the tsunami wave in areas of Seaside seaward of Neawanna Creek are too high. The two figures should be replaced by the new figures below.
[en] This paper investigates the effect of the pedestrian density in building on the evacuation dynamic with simulation method. In the simulations, both the visibility in building and the exit limit of building are taken into account. The simulation results show that the effect of the pedestrian density in building on the evacuation dynamics is dual. On the one hand, when the visibility in building is very large, the increased pedestrian density plays a negative effect. On the other hand, when the visibility in building is very small, the increased pedestrian density can play a positive effect. The simulation results also show that when both the exit width and visibility are very small, the varying of evacuation time with regard to the pedestrian density is non-monotonous and presents a U-shaped tendency. That is, in this case, too large or too small pedestrian density in building is disadvantageous to the evacuation process. Our findings provide a new insight about the effect of the pedestrian density in building on the evacuation dynamic. - Highlights: • Pedestrian density inside buildings has dual effects on evacuation. • Increased pedestrian density has a negative effect in cases of increased visibility. • Increased pedestrian density has a positive effect in cases of decreased visibility.
[en] The faster-is-slower effect (FIS), which means that crowd at a high enough velocity could significantly increase the evacuation time to escape through an exit, is an interesting phenomenon in pedestrian dynamics. Such phenomenon had been studied widely and has been experimentally verified in different systems of discrete particles flowing through a centre exit. To experimentally validate this phenomenon by using people under high pressure is difficult due to ethical issues. A mouse, similar to a human, is a kind of self-driven and soft body creature with competitive behaviour under stressed conditions. Therefore, mice are used to escape through an exit at a corner. A number of repeated tests are conducted and the average escape time per mouse at different levels of stimulus are analysed. The escape times do not increase obviously with the level of stimulus for the corner exit, which is contrary to the experiment with the center exit. The experimental results show that the FIS effect is not necessary a universal law for any discrete system. The observation could help the design of buildings by relocating their exits to the corner in rooms to avoid the formation of FIS effect. (paper: interdisciplinary statistical mechanics)
[en] The Fukushima Daiichi accident highlighted the difficulty in making good decisions regarding post-accident actions for the protection of members of the public. Discussions are continuing between the authorities and the residents about ‘how safe is safe’. Although governmental officials have argued that 20 mSv per year is a safe level of exposure, many residents have expressed strong doubts, and one of their major concerns is the greater health risk of radiation exposure for children. For settling this controversy, the author has demonstrated risk projections for cancer mortality of female children (0 to 18 years old) resulting from four different levels of radiocaesium deposits on the ground. The results showed that, for female children, the cumulative lifetime attributable risk of cancer mortality due to 18-years external radiation exposure from radiocaesium in soil would be 0.9% for 134Cs and 2.4% for 137Cs for an initial annual dose of 20 mGy/year; when the initial dose was 5 mGy/year, the cumulative lifetime cancer risk would be 0.2% and 0.6% for 134Cs and 137Cs, respectively. These results indicate the critical importance of accurate information about the composition and behavior of major radionuclides released to the environment, as well as precise dose monitoring and risk coefficients, for proper decision-making regarding protective actions for members of the public.
[en] A mixed strategy of the exit selection in a pedestrian evacuation simulation with multi-exits is constructed by fusing the distance-based and time-based strategies through a cognitive coefficient, in order to reduce the evacuation imbalance caused by the asymmetry of exits or pedestrian layout, to find a critical density to distinguish whether the strategy of exit selection takes effect or not, and to analyze the exit selection results with different cognitive coefficients. The strategy of exit selection is embedded in the computation of the shortest estimated distance in a dynamic parameter model, in which the concept of a jam area layer and the procedure of step-by-step expending are introduced. Simulation results indicate the characteristics of evacuation time gradually varying against cognitive coefficient and the effectiveness of reducing evacuation imbalance caused by the asymmetry of pedestrian or exit layout. It is found that there is a critical density to distinguish whether a pedestrian jam occurs in the evacuation and whether an exit selection strategy is in effect. It is also shown that the strategy of exit selection has no effect on the evacuation process in the no-effect phase with a low density, and that evacuation time and exit selection are dependent on the cognitive coefficient and pedestrian initial density in the in-effect phase with a high density. (general)
[en] By means of game theory, the effect of compassion mechanism on the evacuation dynamics of pedestrians from a room is studied based on a cellular automaton model. Pedestrians can choose to cooperate or defect in a snowdrift game during the movement. With the compassion mechanism, pedestrians share their payoff to the poorest peer when several pedestrians compete for the same empty cell. Simulation results show that the escape time grows with fear degree r of the snowdrift game, and the compassion mechanism will have a different effect on the system compared with the situation of a spatial game with fixed population. By payoff redistribution, the compassion can help the minor strategy to survive. When the fear degree r is large, the compassion can sustain the cooperative behavior, and spontaneously decreases the escape time. When the fear degree r is small, the compassion will decrease the cooperation frequency, and slightly increase the escape time. The phenomenon is explained by the evolution and competition of defectors and cooperators in the system. Finally, the effect of initial cooperator proportion, the effect of two exits, and the effect of “Richest-Following” strategy, and the effect of initial density are also discussed. (paper)
[en] The rescue organisation in case of catastrophic situation is based on known principles: creation of medical buffer structures between hazard spot where injured people are being collected and rear hospitals, triage of victims as urgent casualties. We will propose computer aid in order to value the time used to prepare and evacuate all the victims from the site, knowing inventory of available means, waiting periods and lengths of intervention, types and number of victims. Thus, it is possible to optimize the former organisation, qualitatively and quantitatively to improve efficiency in rescuing operations. (author)