There has been much interest in studying quasi-periodic events on earthquake models. Here we investigate quasi-periodic events in the avalanche time series on structured earthquake models by the analysis of the autocorrelation function and the fast Fourier transform. For random spatial earthquake models, quasi-periodic events are robust and we obtain a simple rule for a period that is proportional to the choice of unit time and the dissipation of the system. Moreover, computer simulations validate this rule for two-dimensional lattice models and cycle graphs, but our simulation results also show that small-world models, scale-free models, and random rule graphs do not have periodic phenomena. Although the periodicity of avalanche does not depend on the criticality of the system or the average degree of the system or the size of the system, there is evidence that it depends on the time series of the average force of the system.
The interfacial magnetoelectric interaction originating from multi-orbital hopping processes with ferroelectric-associated vector potential is theoretically investigated for complex-oxide composite structures. Large mismatch in the electrical permittivity of the ferroelectric and ferromagnetic materials gives rise to giant anisotropic magnetoelectric effects at their interface. Our study reveals a strong linear dynamic magnetoelectric coupling which genuinely results in electric control of magnetic susceptibility. The constitutive conditions for negative refractive index of multiferroic composites are determined by the analysis of light propagation.
ZnSe as a surface passivation layer in quantum dot-sensitized solar cells plays an important role in preventing charge recombination and thus improves the power conversion efficiency (PCE). However, as a wide bandgap semiconductor, ZnSe cannot efficiently absorb and convert long-wavelength light. Doping transition metal ions into ZnSe semiconductors is an effective way to adjust the band gap, such as manganese ions. In this paper, it is found by the method of density functional theory calculation that the valence band of ZnSe moves upward with manganese ions doping, which leads to acceleration of charge separation, wider light absorption range, and enhancing light harvesting. Finally, by using ZnSe doped with manganese ions as the passivation layer, the TiO2/CdS/CdSe co-sensitized solar cell has a PCE of 6.12%, and the PCE of the solar cell increases by 9% compared with the undoped one (5.62%).
