Narrow Results

The influence of information on the pedestrian in crowd dispersion process is investigated under the open boundary condition on the square lattice by the use of the lattice gas model of biased random walkers without the back step. It is found that the jamming phenomenon occurs when the total entrance density is small in spite of influence of information. The mean velocity 〈v〉_ped of the walkers moving remains a constant via a small fluctuation for the small total entrance density, but for the large total entrance density, the 〈v〉_ped increases from 0 to 1. The mean velocity 〈v〉_inf of information spreading increases from 0 to 1, and then decreases to 0. The critical density decreases with increasing the size W of the system. When the size of the system is small, the platform appears because of asymmetry in propagation of information.

Pedestrian behavioral modeling is an important topic to reproduce rich pedestrian dynamics phenomena. In this paper, a modified lattice gas model is proposed to simulate pedestrian counter flow under periodic boundary conditions by considering the variable transition probability, which can quantitatively describe complex human subconscious behaviors and distinguish the individual and common characteristics of pedestrians. Four types of walkers are involved in the model, and their dynamical characteristics are discussed in some complex situations. The simulation results show that the presented model can reproduce some essential features of pedestrian counter flows, such as the lane formation, segregation effect and phase separation. For the mixed pedestrian flows, the comparison between the subconscious behaviors of obeying the traffic rules and those of breaking the traffic rules indicates that the former could effectively reduce the occurrence of jam cluster. In addition, it is found that with increase of the strength of drift D₁, the jam transition threshold decreases. Finally, the simulation results are compared with our previous study (see Ref. 32). It is shown that the mean velocity and the mean flow are always larger at the free moving phase, and the underlying mechanism is discussed in detail.

To propose method that can optimize the movement efficiency of passengers in the railway station and then guarantee the personal security under emergency case, we did experimental and modeling research on the movement behavior and characteristics of the passengers in a railway station. Observation experiments were conducted to analyze the process of passengers catching trains and leaving the station, through which, the phenomena of lane changing and dislocation were found in a straight channel, and seven categories of baggage were also identified in the crowd. Analysis shows that personal speed would rise as the increasing size of the baggage. A modified lattice gas model focus on the passengers carrying baggage was further built to study passengers movement characteristics. Using this model, the effect of pause probability of passengers and the effect of channel width on movement efficiency were analyzed, according to which, a management strategy to promote the flow rate of crowd in railway station was proposed. This study may be useful to study on evacuation of the railway station, control of the passengers and formulate pre-proposal on emergency evacuation.

Analyzing the pedestrian subconscious behavior and walking environment in the passage, right-moving preference subconscious strength and overtaking subconscious strength are introduced into the pedestrian simulation model which is based on lattice gas model. Two pedestrian subconscious behavior simulation models, which are distinguished by whether considering pedestrian flow ratio of two directions or not, are established respectively. With the platform of MATLAB software, the simulations of pedestrian counter flow subconscious behavior are realized. The simulations indicate that compared with the pedestrian subconscious behavior simulation model without considering the pedestrian flow ratio of two directions, the model that considers the pedestrian flow ratio of two directions is better in simulating the pedestrian subconscious behavior.

A Monte Carlo simulation of the dynamics of diffusion process is presented in the framework of the lattice gas model. The considered lattice is of square geometry with lateral interaction energy between diffusive adsorbates. The paper is entirely devoted to first J_FN and second J_SN neighboring repulsive interactions with the ratio R=J_SN/J_FN in the [0, 1] interval. It is shown that repulsive second neighboring interaction allows emergency of new ordered phases at the coverages theta = 1/4 and 3/4 and induces anisotropy when R is greater than the magnitude 0.5. The present situation is similar to that of Sadiq and Binder, Surf. Sci.128, 350 (1985) except for the choice of transition probability. Particular attention is given to both the behavior of the tracer diffusion coefficient and to the static of the half-full lattice for which a complete phase diagram is derived from calculation of the apparent activation energy. Our dynamic calculations suggest that in the temperature range examined, the jump algorithm gives rise to acceptable results, even its criticable normalization factor.

By using established statistical thermodynamic theory of adsorbate-induced surface stress of adsorption monolayer on metal surface, the surface stress Δg in the self-assembly of alkanethiols on Au(111) surface has been calculated. The quantitative relations of the surface stress Δg with the length N of the alkyl chain of the molecule and with the coverage θ of molecules on Au(111) have been theoretically studied, respectively. The calculated results agree with Berger et al.'s experiment. The qualitative discrepancy between the theory and experiment on the sign of the surface stress has been resolved. Among various components of the adsorbate–adsorbate interaction energies in the adlayer, the substrate-mediated interaction is significant for the adsorbate-induced surface stress, which shows that indirect contribution of the adsorption energy of alkanethiols through the substrate-mediated interaction is very important.

The electronic states of silver halides and sodium halides are calculated by the DV-Xα cluster method to get more microscopic evidence for the p-d hybridization in noble metal halides. It is found that both components of anti-bonding and bonding exist in the diagram of overlap population for AgX (X=halogen) and these two components are made up of the 4d band of Ag⁺ and the p band of halogen ion, which form the p-d hybridization. Next a computer simulation by a molecular dynamics method has been performed to a model material which is composed of accumulating two different fluoride conductors: ···BaF₂-CaF₂-BaF₂-CaF₂···. It is obtained that the diffusion coefficient and ionic conductivity of F ions in the layered fluoride conductors increases with decreasing periods, which coincide with experiments. Lastly the dynamical correlation between diffusing cations and tetrahedra of the anion bcc sublattice in an α-AgI is studied using a molecular-dynamics method. When a silver ion is approaching the boundary surface of an empty tetrahedron(TH), the boundary plane area of the TH increases to faciliate the uptake of a silver ion. THs repeat contraction and expansion with motion of mobile silver ions. The ionic conductivity in superionic conductors with two kinds of mobile ions is investigated by general formulation of multicomponent lattice gas model in one dimension. The Hamiltonian includes a weak hopping term for its interacting-ion system. It is shown that the mixing of correlational two kinds of mobile ions leads to a decrease of the ionic conductivity, compared with the case of excluding the inter-ionic interaction.