International Journal of Modern Physics C

Among the existing lattice Boltzmann models (LBMs) for compressible flow, the one by Kataoka and Tsutahara [KT model, Phys. Rev. E69, 056702 (2004)] has a simple and rigorous theoretical background. The drawback of this KT model is that it can cause numerical instability if the local Mach number exceeds 1. The precise mechanism of this instability has not yet been clarified. In this paper, we derive entropy functions whose local equilibria are suitable to recover the Euler-like equations in the framework of the lattice Boltzmann method for the KT model. Numerical examples are also given, which are consistent with the above theoretical arguments, and show that the entropy condition is not fully guaranteed in KT model. The negative entropy may be the inherent cause for the nonphysical oscillations in the vicinity of the shock. In contrast to these Karlin's microscopic entropy approach, the corresponding subsidiary entropy condition in the LBM calculation could also be deduced explicitly from the macroscopic version, which provides some insights on the numerical instability of the LBM for shock calculation.

The order parameters and synchronization are numerically investigated in the time delay small-world connected FitzHugh–Nagumo excitable systems. The simulations show that the order parameter continuously decreases with increasing D, the quality of the synchronization worsens for large noise intensity. As the coupling intensity goes up, the quality of the synchronization worsens also, and find that the larger rewiring probability becomes, the larger-order parameter. At the same time, the order parameter goes up, the time delay declines. We obtained the complete phase diagram for a wide range of values of noise intensity D and control parameter g.

Recently, Zhou et al. proposed a quantum secret sharing (QSS) protocol, which provides only 25% qubit efficiency after the processes of the random sampling discussion and the secret derivation. This work proposes an enhancement of Zhou et al.'s protocol. With the technique of the Bell measurement, the improved QSS protocol has 50% qubit efficiency.

Taxi will come to one complete halt during the boarding/alighting period and might produce stop-and-go without passengers, so it often produces traffic interruption on the single-lane system. Tang et al. pointed out that the traffic flow model [Chin. Phys.18, 975 (2009)] can be used to directly describe various micro phenomena resulted by traffic interruption on the single-lane system, if we properly define the traffic interruption probability, so in this paper we adopt this model to study the micro phenomena resulted by taxi on the single-lane system. The numerical results show that this model can describe the effects that taxi has on the trails of each vehicle's motion and the evolutions of the flow and the density on the single-lane system, but that these effects are relevant to the initial conditions of the whole system.

A new stochastic stock price model of stock markets based on the contact process of the statistical physics systems is presented in this paper, where the contact model is a continuous time Markov process, one interpretation of this model is as a model for the spread of an infection. Through this model, the statistical properties of Shanghai Stock Exchange (SSE) and Shenzhen Stock Exchange (SZSE) are studied. In the present paper, the data of SSE Composite Index and the data of SZSE Component Index are analyzed, and the corresponding simulation is made by the computer computation. Further, we investigate the statistical properties, fat-tail phenomena, the power-law distributions, and the long memory of returns for these indices. The techniques of skewness–kurtosis test, Kolmogorov–Smirnov test, and R/S analysis are applied to study the fluctuation characters of the stock price returns.

We present an approximate analytic solution of the Klein–Gordon equation in the presence of equal scalar and vector generalized deformed hyperbolic potential functions by means of parametric generalization of the Nikiforov–Uvarov method. We obtain the approximate bound-state rotational–vibrational (ro–vibrational) energy levels and the corresponding normalized wave functions expressed in terms of the Jacobi polynomial , where μ > -1, ν > -1, and x ∈ [-1, +1] for a spin-zero particle in a closed form. Special cases are studied including the nonrelativistic solutions obtained by appropriate choice of parameters and also the s-wave solutions.

The evacuation process under emergency is studied by means of experiments and simulations, focusing on the influence of the environment information. A revised cellular automaton model in which environment information is considered as "static information" (building structure, spatial distance, etc.) and "dynamic information" (sounds of fire alarm, etc.) is introduced. Two scenarios, including evacuation with and without visibility in a classroom, are studied to investigate the different influence of the two kinds of information on human behavior. The experimental and simulation results demonstrate that:

(1) to intensify the spatial distance information can reduce the evacuation time;

(2) the spatial distance is not the only decisive factor especially in evacuation without visibility because the sound information, which is ignorable in evacuation with visibility, is playing a more important role under this condition;

(3) the intensity of static information can reflect evacuees' familiarity of the environment;

(4) the model can reproduce the experiments well, and the simulation method is useful for further study of the crowd movement simulation.

A network was characterized by its viscoelastic properties. The viscoelastic property indicates the deformations or changes in the shape and in the internal structure during the evolution of a network. The change in the direction of motion was taken as elastic deformation and the change in the vertical direction as viscous deformation. These deformations were related to the change of geometry of internal structure and of shape. Thus it was possible to characterize a network by its storage and loss moduli. The change of the structure of a network during its evolution changes also its entropy. However entropy depends on the number of microstates of an already existing framework. As examples, two different systems (i) New York Stock Exchange and (ii) a melody were studied for their viscoelastic properties. The change of viscous property was compared with the change of different types of entropies such as configurational entropy, crossing entropy, and topological entropy. This last entropy was introduced and explained in the text. It was found out that there is no direct correspondence between the increase of entropy and the increase of viscous property of a network although they sometimes correlate with each other.

The spin-1 Ising Blume–Emery–Griffiths (BEG) model has been simulated using a cellular automaton (CA) algorithm improved from the Creutz cellular automaton (CCA) for a face-centered-cubic (fcc) lattice. The ground state diagram (k, d) of the fcc BEG model has ferromagnetic (F), quadrupolar (Q), and staggered quadrupolar (SQ) structure regions. The simulations have been made in the SQ region for the parameter values in the intervals -24 ≤ d = D/J < 0 and -3 ≤ k = K/J ≤ 0. The phase diagrams on the (kT_C/J, d) and the (kT_C/J, k) planes have been obtained through k = -3 and d = -4 lines, respectively. The SQ region separates into five regions (A₃ B(a), A₃ B(f), AB (type-I), AB (type-II), and AB₃(f)) which have the different stoichiometric Cu–Au type structures.

A weak harmonic parametric excitation with random phase has been introduced to tame chaotic arrays. It has been shown that when the amplitude of random phase properly increases, two different kinds of chaotic arrays, unsynchronized and synchronized, can be controlled by the criterion of top Lyapunov exponent. The Lyapunov exponent was computed based on Khasminskii's formulation and the extension of Wedig's algorithm for linear stochastic systems. In particular, it was found that with stronger coupling the synchronized chaotic arrays are more controllable than the unsynchronized ones. The bifurcation analysis, the spatiotemporal evolution, and the Poincaré map were carried out to confirm the results of the top Lyapunov exponent on the dynamical behavior of control stability. Excellent agreement was found between these results.

There are numerous examples of societies with extremely stable mix of contrasting opinions. We argue that this stability is a result of an interplay between society network topology adjustment and opinion changing processes. To support this position we present a computer model of opinion formation based on some novel assumptions, designed to bring the model closer to social reality. In our model, the agents, in addition to changing their opinions due to influence of the rest of society and external propaganda, have the ability to modify their social network, forming links with agents sharing the same opinions and cutting the links with those they disagree with. To improve the model further we divide the agents into "fanatics" and "opportunists," depending on how easy it is to change their opinions. The simulations show significant differences compared to traditional models, where network links are static. In particular, for the dynamical model where inter-agent links are adjustable, the final network structure and opinion distribution is shown to resemble real world observations, such as social structures and persistence of minority groups even when most of the society is against them and the propaganda is strong.

This study investigates numerically the effect of asymmetric sinusoidal oscillating motion on the propulsion performance of a pitching foil and attempts to gain insight in whether the low thrust generated by pure pitching could be improved by asymmetric motion. The propulsion performance and flow structure are explored by solving the unsteady Navier–Stokes equations. Computations are conducted for a range of oscillation frequency, pitching amplitude, and asymmetry. The results show that the higher asymmetry can induce the stronger reverse Von Karman vortex in the wake, which in turn leads to the increased thrust. However, the propulsion efficiency reduces as increasing asymmetry. Computed results are further adopted to shed insight into the mechanism of thrust enhancement.