Improvements in the design of pedestrian facilities have reduced the frequency of crowd accidents, and safety is now generally ensured in well-planned crowd events. However, congestion and ...inefficient use of infrastructures still remain an issue. To guarantee comfort and reduce close contacts between people, there are circumstances when crowd density may have to be reduced well below safety limits. Although research has given a lot of attention to extreme scenarios, methods to improve non-critical conditions have been little explored. In addition, crowd sensing technology is still mostly used for data collection and direct use on crowd management is rare. In this work, we present a system aimed at computing optimal egress time for groups of people leaving a complex facility. We show that, if egress starting time is accurately computed for each group based on actual crowd conditions, density can be greatly reduced without having a large effect on the total egress time of the whole crowd. To show the efficacy of such a system, a small-scale experiment is conducted where all components are tested in a simple scenario. As a result, an increase in total egress time by only 5% allowed to reduce maximum density by 35%.
•In coming decade, the aging rate will dramatically increase in advanced countries.•Focus on the mobility issues where the elderly and young pedestrians are mixed.•Cellular Automata model is created ...with aid of experiments.•The model shows reasonable consistency with the experimental result.•The compatibility of elderly’s safety and young’s mobility is discussed.
The relative weight of the population shifts from younger to elderly in the most of the region on the planet. Current aging rate in the advanced nations varies from 12% to 13% and is expected to increase up to 21–37% in 2050. The increase of aging rate in the society especially in the large city will lead a mobility problem. From a social quality point of view, it is important to achieve the compatibility between safety and mobility respectively for younger and elderly generation. For the purpose of understanding the basic characteristics of the pedestrian dynamics under cohabitation of younger and elderly generation, a Cellular Automata (CA) model is created with the aid of pedestrian experiments. Simulations are carried out to reproduce the experimental results and had shown a good agreement.
First-principles plane wave calculations based on spin-polarized density functional theory (DFT) and generalized gradient approximation (GGA) have been used to study the adsorption of H atoms on ...cubic Er2O3 (001) surface. We identify stable adsorption positions and find that H preferentially adsorbs on top of fourfold-hollow sites and transfers electrons to the surface, resulting in the formations of covalent bonds to the nearest neighboring four oxygen atoms. In the most energetically favorable adsorption sites, It was found that H bonds with O atoms at the cubic Er2O3 (001) surface with an adsorption energy of −295.68kJmol−1 at coverage 1/8ML, and the adsorption energy is inclined to decrease with the increase of H coverage (>1/4ML). In addition, our calculations indicate that the dissociative H atom configurations have adsorption energies that are at least 152.64kJmol−1 greater than the H2 molecule configurations on the surface. These results discussed in the context of erbium oxide slabs are employed to rationalize some processes regarding to the hydrogen isotope permeation behavior of tritium permeation barrier.
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•Evacuation experiments in the presence of wheelchair users are analyzed•Egress time is reduced if wheelchair users are informed on exit type and location•A method to estimate ...decision time is presented•A simulation model for crowds including wheelchair users is presented and validated
This study presents the findings of an evacuation experiment involving a mixed population of able-bodied walking pedestrians and wheelchair users. A simulation model capable of reproducing the results is also introduced. The experiment was designed as a square room having four hidden exits that were different in nature (narrow, wide, sloped, and with stairs). Participants selectively received information allowing them to know the nature of each exit. The conditions under which nobody/everybody knew a priori the configuration of the room were tested alongside the condition where only wheelchair users had access to this information. The results show that evacuation time was greatly reduced when the three wheelchair users (out of 52 participants) were informed of exit location and nature. A further but more limited improvement was seen when all participants received the same information. A more detailed analysis indicates that the smooth motion of wheelchair users has benefits in relation to the surrounding crowd dynamics, highlighting the importance of improving accessibility for disabled people and making available to them information on exit route characteristics. The same results were obtained using the simulation model developed to account for the presence of wheelchair users and employed to investigate more detailed scenarios. More generally, this study suggests that information provision to specific groups of pedestrians could be more efficient and achieve similar results in comparison with trying to reach the largest possible number of pedestrians. The results and the methods presented in this study are particularly relevant to the development of automatic information systems, which are becoming the backbone of large pedestrian facilities.
Theory of jam-absorption driving Nishi, Ryosuke; Tomoeda, Akiyasu; Shimura, Kenichiro ...
Transportation research. Part B: methodological,
04/2013, Volume:
50
Journal Article
Peer reviewed
► We make a theoretical framework of a single car’s driving to absorb a traffic jam. ► We represent the time–space points and the velocity of the driving method. ► We clarify the condition of ...absorbing a jam without causing secondary jams. ► We analyze the propagation of compression and expansion waves caused by the driving. ► We propose and analyze an extended driving method with two steps of “slow-in”.
“Can a single car really absorb a traffic jam without making new jams?” In this paper, we focus on this frequently-discussed question, and have succeeded in making a theoretical framework of a driving technique how to absorb a traffic jam by using a minimal microscopic model. Jam-absorption driving comes from Beaty (Beaty, 1998; Beaty, 2013), and it is composed of a sequence of two actions termed the “slow-in” and “fast-out”. The “slow-in” is the action to avoid being captured by a jam and remove it by decelerating and taking a longer headway in advance. The “fast-out” is performed after the “slow-in”, and it is the action to follow the car in front without unnecessary time gaps by accelerating quickly. In our theoretical framework, we have represented the recipe of the actions such as the time–space points and the velocity. Moreover, we have clarified the condition of no secondary jams due to this driving, i.e., the condition that compression and expansion waves caused by this driving meet each other and disappear. Particularly, we have calculated how these waves propagates to the following cars and the point where and when they disappear. Besides, we have analyzed how this point moves in time–space diagrams by varying the timing to start the jam-absorption, and revealed that the pattern of this movement is not constant but changes greatly by the velocity-headway relationships. Furthermore, as a more realistic problem, we have formulated the driving for jam-absorption in two steps of deceleration, which brings rich patterns of collisions among compression and expansion waves.
Pedestrian simulation is a consolidated area of application in which agent-based models are often employed; successful case studies are described in the literature and commercial, off-the-shelf ...simulators are commonly employed by decision makers and consultancy companies. Most state-of-the-art models, however, generally do not consider the explicit representation of pedestrians aggregations (groups) and their implications on the overall system dynamics. This work is aimed at discussing the relevance and significance of this research effort with respect to the need of empirical data about the implication of the presence of groups of pedestrians in different situations (e.g., changing density, spatial configurations of the environment). The article describes an agent-based model encompassing both traditional individual motivations (i.e., tendency to stay away from other pedestrians while moving toward the goal) and a simplified mechanism considering the cohesion effects related to the presence of groups in the crowd. The model is tested in a simple scenario to evaluate the implications of some modeling choices and the presence of groups in the simulated scenario. Moreover, the model is applied in a real-world scenario characterized by the presence of organized groups as an instrument for crowd management. Results are discussed and compared to experimental observations and to data available in the literature.
•Crystal structure plays a critical role in migration barriers of H diffusion in α-Al2O3 and cubic Er2O3.•The diffusivities of hydrogen or deuterium in α-Al2O3 and cubic Er2O3 are 1–3 orders of ...magnitude lower than the corresponding experimental data.•H diffusion in cubic Er2O3 is favorable along the 〈111〉 direction with a small energy of 0.16eV.•High migration barriers of 0.41eV and 1.64eV are required for H diffusion across the Er2O3 planes.
To understand the microscopic mechanism of H diffusion in tritium permeation barrier (TPB), we have explored the energetics and mobility of neutral hydrogen in α-Al2O3 with hexagonal structure as well as sequioxide Er2O3 with cubic bixbyite structure using first-principles density-functional calculations. The comparison of the most energetically favorable H interstitial positions between α-Al2O3 and Er2O3 shows that crystal structure plays a critical role in determining migration barriers. Combining static and molecular-dynamics calculations with nudged elastic band method, we derive the temperature-dependent diffusivity of hydrogen or deuterium in α-Al2O3 and Er2O3 as D(T)=(2.37×10−7m2/s) exp (−1.25eV/kT) and D(T)=(1.72×10−7m2/s) exp (−1.64eV/kT), 1–3 orders of magnitude lower than the corresponding experimental data. The migration barrier for H diffusion between the planes defined by Er2O3 units along the 〈111〉 direction is found to be very small at 0.16eV, while higher migration barriers of 0.41eV and 1.64eV are found for the diffusion across the planes. These results indicate that H diffusion in Er2O3 is favorable along the 〈111〉 direction. Quantum effects on H diffusion through α-Al2O3 and Er2O3 are discussed.
New generations of computer-based simulations of pedestrian crowd dynamics are aimed at improving both scientific knowledge about such complex social phenomena and practical use of the results for ...more efficient, safer management of pedestrian circulation dynamics in urban scenarios. Within this twofold framework, the validation of the developed models with field data plays a central role, and the acquisition of empirical evidence about human behavior during locomotion is mandatory. An empirical investigation of pedestrian personal space (i.e., the area surrounding an individual while walking and into which strangers cannot intrude without causing discomfort) is reported. The investigation was developed in an ad hoc experimental setting to collect meaningful data (e.g., measurements of the front zone of personal space under static and moving conditions). The main results are presented to illustrate both the adopted experimental setting and the related data-collection method. These results represent an innovative contribution toward defining a metric for the characterization of spatial interactions among pedestrians and allowing the validation of simulation models dedicated to the study of the dynamic behavior of pedestrian crowd phenomena.
To understand the microscopic mechanism of H diffusion in tritium permeation barrier (TPB), we have explored the energetics and mobility of neutral hydrogen in I--Al2O3 with hexagonal structure as ...well as sequioxide Er2O3 with cubic bixbyite structure using first-principles density-functional calculations. The comparison of the most energetically favorable H interstitial positions between I--Al2O3 and Er2O3 shows that crystal structure plays a critical role in determining migration barriers. Combining static and molecular-dynamics calculations with nudged elastic band method, we derive the temperature-dependent diffusivity of hydrogen or deuterium in I--Al2O3 and Er2O3 as D(T) = (2.37 A 10a7 m2/s) exp (a1.25 eV/kT) and D(T) = (1.72 A 10a7 m2/s) exp (a1.64 eV/kT), 1a3 orders of magnitude lower than the corresponding experimental data. The migration barrier for H diffusion between the planes defined by Er2O3 units along the a1 1 1a direction is found to be very small at 0.16 eV, while higher migration barriers of 0.41 eV and 1.64 eV are found for the diffusion across the planes. These results indicate that H diffusion in Er2O3 is favorable along the a1 1 1a direction. Quantum effects on H diffusion through I--Al2O3 and Er2O3 are discussed.
First-principles plane wave calculations based on spin-polarized density functional theory (DFT) and generalized gradient approximation (GGA) have been used to study the adsorption of H atoms on ...cubic Er sub(2)O sub(3) (001) surface. We identify stable adsorption positions and find that H preferentially adsorbs on top of fourfold-hollow sites and transfers electrons to the surface, resulting in the formations of covalent bonds to the nearest neighboring four oxygen atoms. In the most energetically favorable adsorption sites. It was found that H bonds with O atoms at the cubic Er sub(2)O sub(3) (001) surface with an adsorption energy of -295.68 kj mol super(-1) at coverage 1/8 ML, and the adsorption energy is inclined to decrease with the increase of H coverage (>1/4 ML). In addition, our calculations indicate that the dissociative H atom configurations have adsorption energies that are at least 152.64 kj mol super(-1) greater than the H sub(2) molecule configurations on the surface. These results discussed in the context of erbium oxide slabs are employed to rationalize some processes regarding to the hydrogen isotope permeation behavior of tritium permeation barrier.
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