International Journal of Modern Physics C

Molecular dynamics simulations technique is used to study the consolidation of two nanoparticles of Cu element. We have studied sintering processes of two nanoparticles at different temperatures. Two model systems with 4 and 10 nm diameter of particles are selected to study the sintering process of the two nanoparticles. Orientation effects on the physical properties of consolidation of two nanoparticles with respect to each other are investigated. Temperature effects on the consolidation of two nanoparticles are also studied. The order of the values obtained in the simulation for the constant volume heat capacity and latent heat of fusion is good agreement with the bulk results. Moreover, we have investigated the size effects on the consolidation of two different sizes of nanoparticles, that is, one particle of diameter with 10 nm is fixed while the other one is changing from 1 to 10 nm. Melting temperatures of the copper nanoparticles are found to be decreased as the size of the particle decreases. It is found that simulation results are compatible with the other theoretical calculations.

In this work, we study the effects of scale-free topology and congestion on load distribution. Congestion effect can be described by link cost functions, which map link flows into travel times. Two different kinds of link's practical capacity (it is similar to link's capacity for transport) which is a parameter in link cost functions, i.e., uniform case and nonuniform case, are investigated. After introducing the effect of congestion, load distribution is typically discussed in Barábasi–Albert and Goh scale-free networks. In the uniform case, for Barábasi–Albert scale-free networks, we recover a power-law behavior for load distribution with a larger exponent, as compared with the distribution of betweenness centrality; for Goh scale-free networks, we also recover a power-law behavior and its exponent approaches to the exponent of degree distribution. While in the nonuniform case, the power-law behavior for load distribution may not always be conserved in both Barábasi–Albert and Goh scale-free networks. That is to say, different kinds of load distributions are obtained under different conditions. It may shed some light to study traffic dynamics on scale-free networks.

In this paper, the cellular automata models for motorized vehicle flow and that for bicycle flow are combined to modeling the interactions between the right-turning motorized vehicle and the driving ahead bicycle at intersection. We introduce the probability that the cross point is taken up by the same kind of vehicle during two successive time steps to describe the complex behaviors when conflict happens. The flux of both motorized vehicle and bicycle depending on the inflow rates are investigated and the spatiotemporal diagrams are also presented to show different traffic states as the inflow rates change. The simulation results show that the model can describe the interactions between motorized vehicle and bicycle. It makes foundations for future research on mixed traffic flow.

We have studied the influence of the distribution of bimodal bonds on the phase transition in two-dimensional 8-state Potts model by the recently proposed Wang–Landau (WL) and the Swendsen–Wang (SW) algorithm. All simulations and measurements are done for r = 0.5. Physical quantities such as energy density and specific heat are evaluated at all temperatures. We have also obtained the probability distributions of the energy in order to monitor the transitions. We have observed that some cases of the periodically arranged bond distributions show a single peak, and some cases show double or triple peaks in the specific heat. Besides, it seems that the appearing of these peaks in the specific heat relates to a blocking procedure for periodicity. When the number of interaction pairs between the bimodal bonds is increased on the lattice with the blocking procedure, one can observe a single peak, otherwise, one can observe a double or triple peaks in the specific heat. From the point of view of simulation methods, the WL algorithm also works efficiently in the simulation of the system for a periodically arranged bond distribution as well as the SW algorithm.

The stability and controllability of asymmetric complex dynamical networks are investigated in detail based on eigenvalue analysis. Pinning control is suggested to stabilize the homogenous stationary state of the whole coupled network. The complicated coupled problem is reduced to two independent problems: clarifying the stable regions of the coupled network and specifying the eigenvalue distribution of the asymmetric coupling and control matrices. The dependence of the controllability on both pinning density and pinning strength is studied.

A free and fair press is an essential condition for democracy. In many western countries, the media production, distribution, ownership, and funding are dominated by corporations, and therefore governed by the idea of maximizing profits for the investors making freedom and fairness of the press very questionable. There exist, however, a number of political activists who, by writing books and articles, and giving talks, are fighting to free the media from the influence of big corporations. This paper presents a simple cellular automaton model of this struggle.

This paper presents an algorithm, which computes the number of anti-red bonds in a simple cubic lattice (site percolation) for different sizes and densities. Our interest was the fractal dimension of anti-red bonds at the percolation threshold. The value is found to be 1.18 ± 0.01. Two different theories proposed by Conigilio resp. Gouyet suggested a fractal dimension of 1.25 resp. 0.9. Thus, we can exclude the theory of Gouyet and are consistent with the one by Coniglio.

This study incorporates bulk dissipation described by a losing probability f into a modified Manna model on an L × L square lattice. The crossover behavior between bulk and boundary dissipation is investigated using the characteristic lengths produced by bulk dissipation. The toppling number N_n and area N_a are studied. For a probability distribution of N_s, where s = n or a, the scaling form including the finite-size scaling (f = 0) and the critical scaling (L → ∞) are determined. Subsequently, this paper investigates the joint probability distribution and provides the scaling relation between the toppling number and area.

In this paper, we propose a spreading activation approach for collaborative filtering (SA-CF). By using the opinion spreading process, the similarity between any users can be obtained. The algorithm has remarkably higher accuracy than the standard collaborative filtering using the Pearson correlation. Furthermore, we introduce a free parameter β to regulate the contributions of objects to user–user correlations. The numerical results indicate that decreasing the influence of popular objects can further improve the algorithmic accuracy and personality. We argue that a better algorithm should simultaneously require less computation and generate higher accuracy. Accordingly, we further propose an algorithm involving only the top-N similar neighbors for each target user, which has both less computational complexity and higher algorithmic accuracy.

The Geometric Random Inner Product (GRIP) is a recently developed test method for randomness. As a relatively new method, its properties, weaknesses, and strengths are not well documented. In this paper, we provide a rigorous discussion of what the GRIP test measures, and point out specific classes of defects that it is able to diagnose. Our findings show that the GRIP test successfully detects series that have regularities in their first- or second-order differences, such as the Weyl and nested Weyl sequences. We compare and contrast the GRIP test to some of the existing conventional methods and show that it is particularly successful in diagnosing deficient random number generators with bad lattice structures and short periods. We also present an application of the GRIP test to the decimal digits of π.

Numerical schemes that are implemented by interpolation of exact solutions to a differential equation naturally preserve geometric properties of the differential equation. The solution interpolation method can be used for development of a new class of geometric integrators, which generally show better performances than standard method both quantitatively and qualitatively. Several examples including a linear convection equation and a nonlinear heat equation are included.

Recently, there are many methods for constructing multi-wing/multi-scroll or hyperchaotic attractors; however, it has been noticed that the attractors with both multi-wing topological structure and hyperchaotic characteristic rarely exist. A new chaotic system, obtained by making the change on coordinate to the Hu chaotic system, can generate very complex attractors with four-wing topological structure and three positive Lyapunov exponents over a wide range of parameters. The influence of parameters varying to system dynamics is analyzed, computer simulations and bifurcation analysis is also verified in this paper.