International Journal of Modern Physics B

The conditions of local Lorentz invariance (LLI) breakdown, obtained during neutron emission from a sonicated cylindrical bar of AISI 304 steel, were reproduced in a system made of a mole of mercury. After 3 min, a part of the liquid transformed into solid state material, in which isotopes were found with both higher and lower atomic mass with respect to the starting material. Changes in the atomic weight without production of gamma radiation and radionuclides are made possible by deformed space–time reactions.

Controlling neurons to generate a desired or normal spiking behavior is the fundamental building block of the treatment of many neurologic diseases. The objective of this work is to develop a novel control method–closed-loop proportional integral (PI)-type iterative learning control (ILC) algorithm to control the spiking behavior in model neurons. In order to verify the feasibility and effectiveness of the proposed method, two single-compartment standard models of different neuronal excitability are specifically considered: Hodgkin–Huxley (HH) model for class 1 neural excitability and Morris–Lecar (ML) model for class 2 neural excitability. ILC has remarkable advantages for the repetitive processes in nature. To further highlight the superiority of the proposed method, the performances of the iterative learning controller are compared to those of classical PI controller. Either in the classical PI control or in the PI control combined with ILC, appropriate background noises are added in neuron models to approach the problem under more realistic biophysical conditions. Simulation results show that the controller performances are more favorable when ILC is considered, no matter which neuronal excitability the neuron belongs to and no matter what kind of firing pattern the desired trajectory belongs to. The error between real and desired output is much smaller under ILC control signal, which suggests ILC of neuron’s spiking behavior is more accurate.

This paper proposes a new full velocity difference model considering the driver’s heterogeneity of the disturbance risk preference for car-following theory to investigate the effects of the driver’s heterogeneity of the disturbance risk preference on traffic flow instability when the driver reacts to the relative velocity. We obtain traffic flow instability condition and the calculation method of the unstable region headway range and the probability of traffic congestion caused by a small disturbance. The analysis shows that has important effects the driver’s heterogeneity of the disturbance risk preference on traffic flow instability: (1) traffic flow instability is independent of the absolute size of the driver’s disturbance risk preference coefficient and depends on the ratio of the preceding vehicle driver’s disturbance risk preference coefficient to the following vehicle driver’s disturbance risk preference coefficient; (2) the smaller the ratio of the preceding vehicle driver’s disturbance risk preference coefficient to the following vehicle driver’s disturbance risk preference coefficient, the smaller traffic flow instability and vice versa. It provides some viable ideas to suppress traffic congestion.

We study the linear stability and collision characteristics of the solitons of the Bose–Einstein condensates (BECs) trapped in two barrier potentials. It is shown that the soliton obtained at the top of the barrier potential is stable. Especially, when the two barrier potentials are considered as the output source of the dark solitons, the collision spots and pattern (such as chase, head-on or localization and through collision) of two solitons may be manipulated by the height of the barrier potential.

On the basis of first principles calculations, we have calculated the elastic properties, stress–strain relations, ideal tensile strengths, ideal shear strengths, and the ideal compressed strengths of Al and Al₃Mg. The stress–strain relations of Al₃Mg are strikingly similar to those of Al, indicating that the crystal structure appears to be more important than the identity of the individual atoms during uniaxial deformation. Al₃Mg is found to have larger moduli and higher strengths than Al but less ductile than Al. So Al₃Mg is expected to be a harder material, consistent with its exploitation in Al precipitate-hardening mechanisms. The calculated elastic properties, tensile strengths and shear strengths of Al are consistent with experimental values or previous theoretical results. We also use another method (molecular dynamics (MD) simulations) to recalculate elastic constants, ideal tensile and compressed strength of Al₃Mg for checking and comparing. We find that the results obtained by the two methods agree well with each other. The failure modes under uniaxial $〈100〉$ tension are also explored for Al and Al₃Mg. Our calculations confirm that Al fail by shear and predict that Al₃Mg also fail by shear.

In this paper, we study the modulational instability (MI) in a biexciton molecular chain taking into account the saturable nonlinearity effects (SNE). Under the adiabatic approximation, the biexciton system is reduced to two coupled nonlinear Schrödinger equations. We perform the linear stability analysis of continuous wave solutions of the coupled system. This analysis reveals that the MI gain is deeply influenced by the SNE. Indeed, the gain spectrum decreases when increasing the saturable nonlinearity parameters. The numerical simulations reveal that the system exhibits incoherent periodic array of patterns and we also observe train of pulses due to the SNE.

The exact solutions of the complete Dirac equation for fermions moving in ideal Aharonov–Bohm rings are used for deriving the exact expressions of the relativistic partial currents. It is shown that as in the nonrelativistic case, these currents can be related to the derivative of the fermion energy with respect to the flux parameter. A specific relativistic effect is the saturation of the partial currents for high values of the total angular momentum. Based on this property, the total relativistic persistent current at T = 0 is evaluated giving its analytical expression and showing how this depends on the ring parameters.

First principle calculations are performed to investigate the electronic structure, structural phase stability, optical and vibrational properties of double perovskite oxide semiconductors namely Ba₂ScMO₆ (M = Nb, Ta) in the cubic symmetry using WIEN2k. In order to study the ground state properties of these compounds, the total energies are calculated as a function of reduced volumes and fitted with Brich Murnaghan equation. The estimated ground state parameters are comparable with the available experimental data. Calculations of electronic band structure on these compounds reveal that both Ba₂ScNbO₆ and Ba₂ScTaO₆ exhibit a semiconducting behavior with a direct energy gap of 2.78 and 3.15 eV, respectively. To explore the optical transitions in these compounds, the real and imaginary parts of the dielectric function, refractive index, extinction coefficient, reflectivity, optical absorption coefficient, real part of optical conductivity and the energy-loss function are calculated at ambient pressure and analyzed. The collective Raman active modes of the atoms of these materials are also calculated in order to understand the structural stability of these compounds.

The transmittance and reflectance of cuprous oxide (Cu₂O) thin film deposited on quartz substrate were measured by a spectrophotometer. Use the optical dielectric model combining the Forouhi–Bloomer model with modified Drude model (FBM+MDM), the optical constants, as well as the thickness of Cu₂O film were attained from its measured transmittance data. Moreover, by means of the TFCalc software, the reflectance and transmittance were calculated conversely from the optical constants (n, k) and the thickness of the Cu₂O film. It was found that the calculated reflectance and transmittance were in good agreement with the measured ones. So the optical dielectric model, namely FBM+MDM, is suitable for Cu₂O thin film.

We report on photoreflectance anisotropy (PRA) spectroscopy of InGaAs/AlAs/AlAsSb coupled double quantum wells (CDQWs) with extremely thin coupling AlAs barriers grown by molecular beam epitaxy (MBE), with no intentional doping. By probing the in-plane interfacial optical anisotropies (OAs), it is shown that PRA spectroscopy has the ability to detect and distinguish semiconductor layers with quantum dimensions, as the anisotropic photoreflectance (PR) signal stems entirely from buried quantum wells (QWs). In order to account for the experimental PRA spectra, a theoretical model at k = 0, based on a linear electro-optic effect through a piezoelectric shear strain, has been employed to quantify the internal electric fields across the QWs. The dimensionalities of the PR lineshapes were tested by using reciprocal (Fourier) space analysis. Such a complementary test is used in order to correctly employ the PRA model developed here.

Molecular dynamics (MD) simulations of the melting and transport properties in liquid states of platinum for the pressure range (50–200 GPa) are reported. The melting curve of platinum is consistent with previous ab initio MD simulation results and the first-principles melting curve. Calculated results for the pressure dependence of fusion entropy and fusion volume show that the fusion entropy and the fusion volume decrease with increasing pressure, and the ratio of the fusion volume to fusion entropy roughly reproduces the melting slope, which has a moderate decrease along the melting line. The Arrhenius law well describes the temperature dependence of self-diffusion coefficients and viscosity under high pressure, and the diffusion activation energy decreases with increasing pressure, while the viscosity activation energy increases with increasing pressure. In addition, the entropy-scaling law, proposed by Rosenfeld under ambient pressure, still holds well for liquid Pt under high pressure conditions.