International Journal of Modern Physics C

We propose a three-opinion Sznajd model with limited persuasion in which two neighbors still can influence others when the two opinions differ by a small amount. The simulation results show that the initial condition plays a crucial role in the final results and the interaction between people's opinion occurs in the common boundaries of the small districts constituted by the people holding the same opinion. We apply the model to describe the interaction on the attitude toward studying between students in a class or school which is similar with the opinion evolution and give a rough explanation about why a class or school mostly consists of ordinary students.

Galam reshuffling introduced in opinion dynamics models, is investigated under the nearest neighbor Ising model on a square lattice using Monte Carlo simulations. While the corresponding Galam analytical critical temperature T_C≈3.09 [J/k_B] is recovered almost exactly, it is proved to be different from both values, not reshuffled (T_C =2/arcsinh (1)≈2.27 [J/k_B]) and mean-field (T_C =4 [J/k_B]). On this basis, gradual reshuffling is studied as function of 0≤p≤1 where p measures the probability of spin reshuffling after each Monte Carlo step. The variation of T_C as function of p is obtained and exhibits a nonlinear behavior. The simplest Solomon network realization is noted to reproduce Galam p =1 result. Similarly to the critical temperature, critical exponents are found to differ from both, the classical Ising case and the mean field values.

Recently, individual-based models originally used for biological purposes revealed interesting insights into processes of the competition of languages. Within this new field of population dynamics a model considering sexual populations with aging is presented. The agents are situated on a lattice and each one speaks one of two languages or both. The stability and quantitative structure of an interface between two regions, initially speaking different languages, is studied. We find that individuals speaking both languages do not prefer any of these regions and have a different age structure than individuals speaking only one language.

We propose a new topological invariant of unlabeled trees of N nodes. The invariant is a set of N×2 matrices of integers, with ∑_j k^{d_{i, j}} and v_i as the matrix elements, where d_{i, j} are the elements of the distance matrix and v_i denotes ith node's degree and k∈ℕ. To compare the invariant calculated for possibly different graphs, the matrix rows are ordered with respect to the first column, and, if necessary, with respect to the second one. We use the new invariant to evaluate from below the number of topologically different unlabeled trees up to N =17. The results slightly exceed the asymptotic evaluation of Otter.

We study the continuum opinion dynamics of the compromise model of Krause and Hegselmann for a community of mutually interacting agents by solving numerically a rate equation. The opinions are here represented by two-dimensional vectors with real-valued components. We study the situation starting from a uniform probability distribution for the opinion configuration and for different shapes of the confidence range. In all cases, we find that the thresholds for consensus and cluster merging either coincide with their one-dimensional counterparts, or are very close to them. The symmetry of the final opinion configuration, when more clusters survive, is determined by the shape of the opinion space. If the latter is a square, which is the case we consider, the clusters in general occupy the sites of a square lattice, although we sometimes observe interesting deviations from this general pattern, especially near the center of the opinion space.

The C₂₀ cage structure (X@C₂₀; X =Fe, Co, Ni) endohedrally doped with a metal atom has been investigated theoretically by performing molecular-mechanics optimizations, and semi-empirical PM3 level and density functional theory B3LYP/6-31G* level calculations within UHF formalism. Calculations have been performed with different spin configurations for the neutral systems.

We investigate a self-avoiding polymer chain anchored with one end at a hard wall. The chains are modeled using the continuous backbone mass model. The sampling of the conformations is done by molecular dynamics for chains of various sizes. Presented are results for several different interesting situations. We have investigated the pressure that grafted chains of various sizes exert on the wall and find good agreement with the theory, if the theory is extended to the self-avoiding case using the standard scaling laws. Force-elongation simulations are compared to polymer theory and the partition function for a grafted ideal chain is explicitly calculated. Again we find good agreement with the theory.

We introduce a new model that mimics the strong and sudden effects induced by conformity in tightly interacting human societies. Such effects range from mere crowd phenomena to dramatic political turmoil. The model is a modified version of the Ising Hamiltonian. We have studied the properties of this Hamiltonian using both a Metropolis simulation and analytical derivations. Our study shows that increasing the value of the conformity parameter, results in a first order phase transition. As a result a majority of people begin to honestly support the idea that may contradict the moral principles of a normal human beings though each individual would support the moral principle without tight interaction with the society. Thus, above some critical level of conformity our society destabilizes with respect to ideas that might be doubtful. Our model includes, in a simplified way, human diversity with respect to loyalty to the moral principles.

We propose a new version of the spatial model of voting. Platforms of five parties were allowed to evolve in a two-dimensional landscape of political issues so as to get maximal numbers of voters. For a Gaussian landscape the evolution leads to a spatially symmetric state, where the platform centers form a pentagon around the Gaussian peak. For a bimodal landscape the platforms located at different peaks get different numbers of voters.

The stability of α-helices in proteins depends on both their compositions and environments. To see how these two factors match with each other, we selected three typical α-helices from real proteins each of them has different compositions of hydrophobic and hydrophilic amino acids. We simulated the dynamics of the three helices in vacuum and in water using molecular dynamics. The results show that the stabilities of the three α-helices are different in vacuum and in water, which are consistent with their locations in the proteins. We also found some interesting behaviors of these α-helices.

We present the clustering properties of amino acids, which are building blocks of proteins, according to their physico-chemical characters. To classify the 20 kinds of amino acids, we employ a Self-Organizing Map (SOM) analysis for the Miyazawa-Jernigan (MJ) pairwise-contact matrix, the Environment-dependent One-body energy Parameters (EOP) and the one-body energy parameters incorporating the Ramachandran angle information (EOPR) over the EOP in proteins. We provide the new result of the SOM clustering for amino acids based on the EOPR and compare that with those from the MJ and the EOP matrix. All three kinds of energy parameters capture the leading role played by the hydrophobicity and the hydrophilicity of amino acids in protein folding. Our SOM analysis generally illustrates that both the EOP and the EOPR can provide the collective clustering of amino acids by the side chain characteristics and the secondary structure information. However, EOP is better at classifying amino acids according to their side chain characteristics whereas EOPR is better with secondary structure. We show that the EOP and the EOPR matrix manifests more detailed physico-chemical classification of amino acids than those from the MJ matrix, which does not contain a local environmental information of amino acids in the protein structures.

In real traffic, the traffic system is usually composed of different types of vehicles, which have different parameters. How these parameters, especially the lengths of the vehicles, influence the traffic behaviors and transportation capability has seldom been investigated. In this paper, we study the mixed traffic system using the cellular automata traffic flow model. The simulation results show that when the road occupancy rate is large, increasing the fraction of long vehicles can apparently, improve the transportation capability. The influence of slow vehicles fraction on the average velocity of vehicles has been discussed, and it is found that the influences are very different when the difference of vehicle length is considered or not.