International Journal of Modern Physics C

In this work the motion of a single dislocation in a two-dimensional triangular lattice is studied by using classical Molecular Dynamics method with the Lennard–Jones inter-atomic potential. The dislocation motion is investigated with an interactive simulation program developed to track automatically the movement of lattice defects. Constant strain and constant strain-rate deformations were applied to the system. From constant strain simulations a curve of shear stress versus dislocation velocity is obtained, showing a nonlinear power law relation. An equation of motion for the dislocation is proposed and found to be applicable when the movement of dislocation follows a quasi-static process. Numerical simulations at different strain rates show an elastic-to-plastic transition that modifies the dynamics of the dislocation motion.

Using an approach developed by one of the authors, approximate solutions of the null-Dirichlet problem for the forced Nagumo equation are obtained. It is shown that these solutions are chaotic whatever the values of the control parameter in this equation. It is also shown that in the absence of the external force the solutions are chaotic for negative values of the control parameter. However, these solutions are quasi-periodic for large time scales.

In this paper, an expert system is presented that was developed with the aim to analyze threshold spectra experimentally obtained using backward chaining method of inference. With this way the process of spectra analysis was speeded up and automated. The spectrum usefulness, energy scale calibration, identification of peaks in spectrum, as well as identification of peaks by resonant influence was made possible with this expert system.

The structural properties of carbon nanorods obtained from diamond crystal have been investigated by performing molecular-dynamics computer simulations. Calculations have been realized by using an empirical many-body potential energy function for carbon. Diamond nanorods have been generated from three low-index planes of diamond crystal. It has been found that the average coordination number, cross-section geometry, and surface orientation from which the nanorod is generated play a role in the stability of diamond nanorods under heat treatment. The most stable diamond nanorod has been obtained from the (111) surface.

We studied the statistical distribution of student's performance, which is measured through their marks, in university entrance examination (Vestibular) of UNESP (Universidade Estadual Paulista) with respect to (i) period of study — day versus night period (ii) teaching conditions — private versus public school (iii) economical conditions — high versus low family income. We observed long ubiquitous power law tails in physical and biological sciences in all cases. The mean value increases with better study conditions followed by better teaching and economical conditions. In humanities, the distribution is close to normal distribution with very small tail. This indicates that these power law tails in science subjects are due to the nature of the subjects themselves. Further and better study, teaching and economical conditions are more important for physical and biological sciences in comparison to humanities at this level of study. We explain these statistical distributions through Gradually Truncated Power law distributions. We discuss the possible reason for this peculiar behavior.

We extend the analysis of Ref. 16 showing statistically significant log-periodic corrections to scaling in the moments of the energy dissipation rate in experiments at high Reynolds number (≈ 2500) of three-dimensional fully developed turbulence. First, we develop a simple variant of the canonical averaging method using a rephasing scheme between different samples based on pairwise correlations that confirms Zhou and Sornette's previous results. The second analysis uses a simpler local spectral approach and then performs averages over many local spectra. This yields stronger evidence of the existence of underlying log-periodic undulations, with the detection of more than 20 harmonics of a fundamental logarithmic frequency f = 1.434 ± 0.007 corresponding to the preferred scaling ratio γ = 2.008 ± 0.006.

Based on the computerized symbolic system Maple and a Riccati equation, a new Riccati equation expansion method for constructing nontraveling wave and coefficient functions' soliton-like solutions is presented by a new general ansätz. The proposed method is more powerful than most of the existing tanh methods, the extended tanh-function method, the modified extended tanh-function method, and generalized hyperbolic-function method. By using the method, we not only successfully recovered the previously known formal solutions but could also construct new and more general formal solutions for some nonlinear differential equations. Making use of the method, we study the (2+1)-dimensional Boussinesq equation and obtain rich new families of the exact solutions, including the nontraveling wave and coefficient functions' soliton-like solutions, singular soliton-like solutions, and triangular functions solutions.

Structural, electronic, and vibrational properties of magnesium diboride have been investigated by performing ab initio calculation within DFT level considering full MP2 correlation correction through B3LYP exchange-correlation functional. The structural, electronic, and vibrational properties of MgB₂ triatom have been calculated in its ground state.

Cellular automata (CA) can be considered as discrete dynamical systems exhibiting a rich intrinsic behavior both in space and time. Starting from disordered initial configurations and according to different local evolution rules, CA can evolve into steady states showing regular or complex space–time structures. These structures have been shown to have fractal and multifractal properties. Here, the multifractal properties of linear one-dimensional cellular automata with complex spatio-temporal behaviors are calculated using discrete wavelets transforms.

In this paper we computationally investigate the magnetization for three-dimensional (3D) InAs/GaAs nanorings with different radii in an external magnetic field. Our simulation model includes: (i) the effective mass Hamiltonian in nonparabolic approximation, (ii) the position- and energy-dependent quasi-particle effective mass approximation, (iii) the finite hard wall confinement potential, and (iv) the Ben Daniel–Duke boundary conditions. The nonlinear iterative method is applied to solve the 3D problem. With the developed computer simulator, we find the magnetization for the 3D InAs/GaAs ring is a negative function and oscillates nonperiodically. The oscillation saturates when the applied magnetic filed is increased. This result provides an alternative for the nanoring energy shell structure study and is useful for spintronics applications.

We apply the technique of self-similar exponential approximants based on successive truncations of simple continued exponentials to reconstruct functional laws of the quasi-exponential class from the knowledge of only a few terms of their power series. Comparison with the standard Padé approximants shows that, in general, the self-similar exponential approximants provide significantly better reconstructions.

The present article deals with the critical value p_c of the three-dimensional bootstrap percolation. We will check the behavior of p_c for different lengths of the lattice and additionally we will scale p_c in the limit of an infinite lattice.