International Journal of Modern Physics B

An experimental investigation was conducted to examine the fretting fatigue behavior of physical vapor deposition-coated CrN film deposited on Ti-6Al-4V specimens contacted on both sides with pads of the same material. Behavior against the CrN-coated specimens was characterized through the determination of fretting fatigue strength up to 10⁷ cycles. Fretting damage of specimen surface was characterized by SEM and surface profilometer. The experimental results from the S–N tests indicate that the CrN coating is effective to improve the fretting fatigue strength until about 10⁶ cycles, but over 10⁶ cycles, the strength is lower than that of uncoated specimens. The enhanced fretting fatigue resistance can be attributed to the improved hardness of the CrN film due to change of bias voltage during the film deposition. It has also been concluded that below and about 10⁶ cycles, there is smaller influence of bias voltage on fatigue strength, whereas, over 10⁶ cycles, fatigue strength is clearly changed by bias voltage as well as contact pressure.

We study the alkali-metal-doped fulleride systems based on an impurity model. The bound states are induced by the impurity potential, and the local density of states of the neighboring molecules at the Fermi level is remarkably reduced. We point out that the superconductivity of the whole system will be destroyed when the average distance between the impurities reaches the order of the coherence length. It gives a reasonable explanation to the strange behavior of the transition temperature of the superconducting fullerides.

This paper investigates a synchronous totally asymmetric simple exclusion process (TASEP) with a detachment in a one-dimensional system. In the model, particles can detach irreversibly with probability q from a bulk site which is far away from boundaries. The phase diagram of the model is calculated in the mean-field approach and verified by Monte Carlo simulations. There are five stationary phases in the system. With the increase of q, the regions of the LD/LD and MC/LD phases increase, while the regions of the HD/HD and LD/HD phases decrease. The MC/HD phase corresponds to a critical point.

The seismic properties of a material depend on composition, crystal structure, temperature, pressure and in some cases defect concentrations. Most of the earth is made up of crystals. The elastic properties of crystals depend on orientation and frequency. Thus, the interpretation of seismic data or the extrapolation of laboratory data requires knowledge of crystal or mineral physics, elasticity and thermodynamics. In the present work, we calculated the shear modulus, seismic velocities and Debye temperatures at different high temperature ranges. The temperature dependence of elastic properties such as shear modulus, seismic velocities and Debye temperatures has been measured using Hill's averaging method and other thermodynamic methods for five silicate mantle minerals viz. MgAl₂O₄, Mg₂SiO₄, Fe₂SiO₄, Mn₂SiO₄, and Co₂SiO₄. The results are found to be in good agreement with experimental values.

Both polarons and bipolarons are composite particles with internal structures in nondegenerate conjugated polymers. A bipolaron is a spinless species with charge ±2|e|, while a polaron is a spin-bearing one (spin 1/2, charge ±|e|). Serving as charge carriers, they play an important role in the transport properties of polymer-based optoelectronic devices. By using a nonadiabatic dynamic method, the motion of a bipolaron under an external electric field is theoretically investigated in a conjugated polymer with magnetic impurities. Our results show that a bipolaron can pass through the magnetic impurities, or break down into two polarons with different spins, or be trapped by the magnetic impurities, depending on the width of the impurity region. When the width of the impurity region is comparable to the polaron width, the bipolaron is transformed into two polarons easily. As a polaron and a bipolaron possess different spin characteristics, the decomposition of bipolarons induced by the magnetic impurities may have important effect on the spin polarized transportation.

The coherent entangled state |β, x〉 is proposed in Fock space, which exhibits both the properties of the coherent and entangled states. The |β, x〉 makes up a new quantum mechanical representation, and the completeness relation of |β, x〉 is proved by virtue of the technique of integral within an ordered product of operators. The corresponding Schmidt decomposition of |β, x〉 is investigated. Furthermore, a feasible experimental scheme of |β, x〉 is presented, and generalized P-representation is constructed in the coherent entangled state |β, x〉.

Solution-based chemical method was used to prepare the compound LiCoVO₄. Compound formation was checked by X-ray diffraction (XRD) study and it revealed a cubic unit cell structure with lattice parameter: a = 8.2840 (3) Å. Complex impedance result shows bulk contribution to electrical properties up to 225°C, grain boundary effects for all T ≥ 250°C, and evidence of temperature-dependent electrical relaxation phenomena in the material. The values of activation energy were determined from the Arrhenius plot of DC conductivity versus 10³/T and were equal to ~0.09 eV at 50–200°C and ~0.48 eV at 200–350°C. Complex modulus study indicates non-Debye type (polydispersive) conductivity relaxation in the compound.

By using reactive magnetron sputtering system, titanium dioxide thin films were fabricated onto quartz substrate, and then modified by Ge and Si atoms that were introduced with ion implantation method. XRD, AFM, XPS, and UV-vis were used to characterize these films, and X-ray photoelectron spectroscopy (XPS) was adopted to examine the atomic chemical states of implanted titanium dioxide thin films. The results show that there are Ge and silicon oxides precipitations in TiO₂ matrices. The implanted Ge + Si thin film exhibits an intense absorption band within visible region, which will further benefit its practical applications.

The luminescence mechanisms of a potential scintillation crystal YBa₃B₉O₁₈ were investigated by experimental methods. As a first step, the optical band gap energy E_g was estimated to be 7.3 eV from the optical absorption spectrum and vacuum ultraviolet excited luminescence spectra. The X-ray photoelectron spectroscopy measured in the valence region coincided with the first principle energy band calculation. Based on the analysis of valence band structure and vacuum ultraviolet excited luminescence spectra the origins of emission bands of YBa₃B₉O₁₈ were studied. The intrinsic luminescence of YBa₃B₉O₁₈ was attributed to the radiative decay of self-trapped excitons. The elucidation of the luminescence mechanism provides a physical picture on the property-structure correlation and may help to accelerate the applications of the potential scintillation crystal.

In the present paper, the microstructure and tensile properties of Al–Mg–Si alloy irradiated with 2 MeV protons for 5, 10, 20, and 40 mins at 300 K are investigated. The microstructure of irradiated specimens, observed using metallurgical microscope, shows that aspirates are emitted out from the surface of irradiated specimens, which take the form of clusters and/or precipitates with increase of exposure time. The tensile behavior of irradiated specimens was investigated using universal testing machine and compared with that of unirradiated one. The yield stress, ultimate tensile stress and % elongations remain unchanged after 5 and 10 mins of irradiation. However with an increase of irradiation time up to 20 mins, an increase in yield stress, ultimate tensile stress and decrease in % elongation was observed. With further increase of exposure time to 40 mins, the increase in yield stress and decrease in plasticity became more prominent. The results of stress relaxation tests performed during the tensile deformation have also been presented. The XRD analysis reveals that the microstructural changes controlling the tensile properties in irradiated samples appear to be physical rather than chemical.

In this paper, the condition of completely nearest-neighbor couplings is introduced into the coupled Hindmarsh–Rose neurons in two-dimensional arrays. It is found that the stable rotating spiral wave can be developed and the transition of spiral wave in the coupled Hindmarsh–Rose neurons are investigated. The factor of synchronization is defined to investigate the development and instability of the spiral wave. Furthermore, the external injected current, coupling coefficients and other decisive bifurcation parameter r and χ, are endowed with different values to study the transition of spiral wave by analyzing the factor of synchronization and the snapshots of the activator. It is found that the critical sudden change points in the curve for factor of synchronization often indicates sudden transition of spiral wave, the instability or death of the spiral wave. The snapshots are also plotted to confirm the results from the curve of the factor of synchronization. Finally, the noise-induced instability and chaotic logistic map-induced instability of spiral wave are investigated and discussed.

The electronic transport through a mesoscopic confining region coupled to two spin-orbit coupling semiconductor leads is studied. We mainly focus on how the transport behaviors are affected by the Rashba spin-orbit interaction (SOI), which has been neglected in the previous theoretical papers but indeed exists in the semiconductor leads from the recent experimental results. By using Landauer–Büttiker formula and the non-equilibrium Green's function method, the linear conductance of this device is obtained. The numerical results exhibit that the conductance are similar for the two cases of the absence and the presence of the SOI. It means that the SOI in the leads does not qualitatively affects the transport behaviors. However, in detail, the peaks of the conductance are widened and enhanced by the SOI. In some specific cases, the widening and the enhancement could be very strong.

The effect of nonlinear interactions in a crystal on the polariton behavior has been investigated. A new mode in the photonic band gap in LiNbO₃ is obtained, as suggested by some recent literature. This mode is shown to be almost dispersionless, which may find application in optical communication. The Raman scattering and parametric amplification are interpreted in terms of a dielectric function, which includes nonlinearity. The scattering efficiency is shown to be a consequence of the photonic band gap. The nonlinearity is shown to lead to a soft mode-like behavior in polar crystals.

The indentation simulation of the nanocrystalline Ni is carried out by molecular dynamics technique (MD) to study the mechanical behavior at nanometer scales. The sphere indenter is used, and simulation sample with three grains and two grain boundaries is adopted. The strength of nanocrystalline is studied as indenter is set at grain boundary and grain, respectively. Some defects such as dislocations or slipping deformation are observed. It is found that dislocations are emitted from the grain boundary or the sample surface. The temperature distribution of local region around indenter is analyzed and it can explain our MD simulation results.