International Journal of Modern Physics B

In this paper, a new cascading failure model is proposed for quantitatively analyzing the railway accident causation. In the model, the loads of nodes are redistributed according to the strength of the causal relationships between the nodes. By analyzing the actual situation of the existing prevention measures, a critical threshold of the load parameter in the model is obtained. To verify the effectiveness of the proposed cascading model, simulation experiments of a train collision accident are performed. The results show that the cascading failure model can describe the cascading process of the railway accident more accurately than the previous models, and can quantitatively analyze the sensitivities and the influence of the causes. In conclusion, this model can assist us to reveal the latent rules of accident causation to reduce the occurrence of railway accidents.

In this paper, we report a study of the effect of a lateral electric field on a quantum-confined exciton in a thin PbS quantum disk. Our approach was performed in the framework of the effective mass theory and adiabatic approximation. The ground state energy and the stark shift were determined by using a variational method with an adequate trial wavefunction, by investigating a 2D oscillator strength under simultaneous consideration of the geometrical confinement and the electric field strength. Our results showed a strong dependence of the exciton binding and the Stark shift on the disk dimensions in both axial and longitudinal directions. On the other hand, our results also showed that the Stark shift’s dependence on the electric field is not purely quadratic but the linear contribution is also important and cannot be neglected, especially when the confinement gets weaker.

Based on a multifractal detrending moving average algorithm (MFDMA), this study uses the fractionally autoregressive integrated moving average process (ARFIMA) to demonstrate the effectiveness of MFDMA in the detection of auto-correlation at different sample lengths and to simulate some artificial time series with the same length as the actual sample interval. We analyze the effect of predictable and unpredictable meteorological disasters on the US and Chinese stock markets and the degree of long memory in different sectors. Furthermore, we conduct a preliminary investigation to determine whether the fluctuations of financial markets caused by meteorological disasters are derived from the normal evolution of the financial system itself or not. We also propose several reasonable recommendations.

We investigate the well-defined measures of measurement-induced nonlocality (MIN) for thermal states of the transverse field XX model, with the addition of three-spin interaction terms being introduced. The results showed that the MINs are very sensitive to system parameters of the chain. The three-spin interactions can serve as flexible parameters for enhancing MINs of the boundary spins, and the maximum enhancement achievable by varying strengths of the three-spin interactions are different for the chain with different number of spins.

By using the first-principles calculations, we studied the effect of carbon (C) on the behaviors of helium (He) in vanadium (V). The results show that C can effectively reduce the solubility of He in bulk V. Compared with defect-free V bulk, the C-vac complex reduces the charge density around it, which makes it act as a trapping center and promotes He nucleation. The maximum number of He atoms trapped by the C-vac complex is five. Furthermore, the interaction between He and the C-vac complex is slightly stronger than that in a C-free vacancy, which indicates that C could increase the trapping ability of vacancy to He atom. Based on the above results, we conclude that C has a certain influence on the dissolution and the trapping behaviors of He in V.

The structural, electronic, optical properties and band offsets of Co₂VGa/GaAs(001) interfaces are discussed within the framework of density functional theory (DFT) using the FP-LAPW method, and the exchange-correlation potential is approximated by GGA. All interface structures are stable in the energy point of view, however the V–Ga/As case is found to be more stable than the others. A remarkable potential difference ($\mathrm{\Delta }$V) appeared in all the interfaces, so the Co₂VGa/GaAs(001) interfaces are good candidates for electron injection. In all the cases, there is no full spin polarization at the Fermi level, but high CBO and ${\mathrm{\Phi }}_p$ coefficients make them promising candidates for spin injection in the transport devices. Optical studies confirm the high metallic treatment of these interfaces as the main electron transitions had occurred in the infrared and visible regions. The real parts of the dielectric function in the x-direction indicate the different behaviors of “Co–Co/As and V–Ga/Ga” and “Co–Co/Ga and V–Ga/As” in the infrared area. In addition, the plasmon frequencies had occurred at high UV energies.

In this research, SrFe${}_{12-x}$Ni${}_x$O${}_{19}$ (x $=$ 0 − 1) hexagonal ferrites were prepared by sol-gel auto-combustion method. Effect of Ni substitution on structural, morphological and magnetic properties of nanoparticles was investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM), respectively. The XRD results confirmed that all samples with x $\le$ 0.5 have single phase M-type strontium ferrite structure, whereas for the SrFe${}_{12-x}$Ni${}_x$O${}_{19}$ samples with x $>$ 0.5, the spinel NiFe₂O₄ phase has also appeared. The lattice parameters and crystallite sizes of the powders were concluded from the XRD data and Williamson–Hall method. Magnetic analyses showed that the coercivity of powders decreased from 5672 Oe to 639 Oe while the saturation magnetization increased from 74 emu/g to 81 emu/g with nickel substitution. The results of this study suggest that the strontium hexaferrites doped with Ni are suitable for applications in high density magnetic recording media as well as microwave devices because of their promising magnetic properties.

Influence of anisotropy on a bending of a magnetic stripe domain wall due to a magnetostatic stray field of a cylindrical magnetic domain (CMD) that is located within the stripe one is under investigation. It is revealed that for a specific set of physical parameters of the domain structure, energy of domain wall bending anisotropy can suppress the bending. An analytical expression for the bending shape is obtained on account of a change of both magnetostatic energy of the configuration and energy of anisotropy of the domain wall.

Tight-binding Hamiltonian on the prismatic pentagonal lattice is exactly solved to obtain the analytic expressions of dispersion relations and eigenvectors. This lattice is made of prismatic pentagon which is different from Cairo pentagon. Six different dispersion relations and total density of states are obtained. Dispersion relations are symmetric about the zero energy at a particular point in the parameter space. Although a large gap is found for the Cairo pentagonal lattice, no gap as well as no Dirac cone is found to appear in the tight-binding band structure for this prismatic pentagonal lattice. Instead, a pair of van Hove singularities has been identified at two different energy values in the band structure.

We focus on the role of heterogeneity on the propagation of firing patterns in feedforward network (FFN). Effects of heterogeneities both in parameters of neuronal excitability and synaptic delays are investigated systematically. Neuronal heterogeneity is found to modulate firing rates and spiking regularity by changing the excitability of the network. Synaptic delays are strongly related with desynchronized and synchronized firing patterns of the FFN, which indicate that synaptic delays may play a significant role in bridging rate coding and temporal coding. Furthermore, quasi-coherence resonance (quasi-CR) phenomenon is observed in the parameter domain of connection probability and delay-heterogeneity. All these phenomena above enable a detailed characterization of neuronal heterogeneity in FFN, which may play an indispensable role in reproducing the important properties of in vivo experiments.

Co(5 nm)/Dy(t${}_{\mathrm{\text{Dy}}}$)/Co(20 nm)/S and Ni(5 nm)/Dy(t${}_{\mathrm{\text{Dy}}}$)/Ni(20 nm)/S trilayer films are prepared by electron-beam sputtering to investigate the influence of dysprosium layer thickness (t${}_{\mathrm{\text{Dy}}}$) and thermal annealing on the crystal structure, magnetoresistance (MR) and magnetic properties of thin films. The thickness of Dy layer changed in the range from 1 nm to 20 nm. The samples annealed for 20 min at 700 K. Electron diffraction patterns reveal that the as-deposited and annealed systems Co/Dy/Co and Ni/Dy/Ni had fcc-Co + hcp-Dy and fcc-Ni + hcp-Dy phase state, respectively. It is also shown that at the t${}_{\mathrm{\text{Dy}}}$ = 15 nm the transition from amorphous to crystalline structures of Dy layer is observed. An increase in the Dy layer thickness results in changes in the MR and magnetic properties of the trilayer systems. It is shown that MR is most thermally stable against annealing to 700 K at t${}_{\mathrm{\text{Dy}}}$ = 15 nm for Co/Dy/Co as well as for Ni/Dy/Ni. For t${}_{\mathrm{\text{Dy}}}$ = 15 nm the, value of MR for both system increases by two times compared to those of pure ferromagnetic (FM) samples. The coercivity (B${}_c$), remanent (M${}_r$) and saturation (M${}_s$) magnetization of the in-plain magnetization hysteresis loops are related to the Dy layer thickness too. The coercivity depends on the FM materials type and diffusion processes at the layer boundary. Accordingly, M${}_r$ and M${}_s$ are reduced with t${}_{\mathrm{\text{Dy}}}$ increasing before and after annealing for both trilayer systems.

Cross-linked polyvinyl alcohol (PVA) graphene oxide (GO) nanocomposites were prepared by simple solution-mixing route and characterized by Raman, UV–visible and fourier transform infrared (FT-IR) spectroscopy analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The XRD pattern and SEM analysis showed significant changes in the nanocomposite structures, and the FT-IR spectroscopy results confirmed the chemical interaction between the GO filler and the PVA matrix. After these morphological characterizations, PVA-GO-based diodes were fabricated and their electrical properties were characterized using current–voltage (I–V) and impedance-voltage-frequency (Z-V-f) measurements at room temperature. Semilogarithmic I–V characteristics of diode showed a good rectifier behavior. The values of C and G/$\omega$ increased with decreasing frequency due to the surface/interface states (N${}_{\mathrm{\text{ss}}}$) which depend on the relaxation time and the frequency of the signal. The voltage, dependent profiles of N${}_{\mathrm{\text{ss}}}$ and series resistance (R${}_{\mathrm{\text{s}}}$) were obtained from the methods of high-low frequency capacitance and Nicollian and Brews, respectively. The obtained values of N${}_{\mathrm{\text{ss}}}$ and R${}_{\mathrm{\text{s}}}$ were attributed to the use of cross-linked PVA-GO interlayer at the Au/n-Si interface.

We consider a one-dimensional photonic crystal (1DPC) composed of double-layered dielectrics. Electric permittivity and magnetic permeability of this crystal depends on the incident electromagnetic wave frequency. We suppose that three level atoms have been added to the second layer of each dielectric and this photonic crystal (PC) has been doped. These atoms can be added to the layer with different rates. In this paper, we have calculated and compared the band structure of the mentioned PC considering the effect of added atoms to the second layer with different rates through the Fresnel coefficients method. We find out that according to the effective medium theory, the electric permittivity of the second layer changes. Also the band structure of PC for both TE and TM polarizations changes, too. The width of bandgaps related to “zero averaged refractive index” and “Bragg” increases. Moreover, new gap branches appear in new frequencies at both TE and TM polarizations. In specific state, two branches of “zero permittivity” gap appear in the PC band structure related to TM polarization. With increasing the amount of the filling rate of total volume with three level atoms, we observe a lot of changes in the PC band structure.

The first-principles calculations based on density functional theory (DFT) have been implemented to investigate the graphene/blue-phosphorus (G/BP) heterostructure as potential anode material for SIBs. The adsorption and diffusion behaviors of sodium (Na) in G/BP heterostructure and the effect of external electric field on Na adsorption have been investigated. The results indicate that G/BP heterostructure with Na adsorption is metallic due to Na incorporation, which is of benefit for electronic conductivity as anode material. The results show that the design of G/BP heterostructure is an efficient scheme to enhance the Na adsorption in G/BP without affecting the high mobility of Na in the G/BP heterostructure surface. The present work demonstrates that the external electric field can effectively modulate the adsorption of Na, and the adsorption behavior of Na is more sensitive to the external electric field when E $>$ 0.10 V Å${}^{-1}$ in G/BP heterostructure. The Mulliken population analysis and DOS calculations have been performed to explore the charge transfer and the interaction between Na and G/BP.