International Journal of Modern Physics B

Graphene oxide colloid has been widely used in the synthesis of various graphene-based materials. Graphene oxide sheets, with a low bending rigidity, can be folded when assembled in aqueous phase. A simple but industrial scalable way, aerosol processing, can be used to fabricate folded graphene-based materials. These folded materials can carry various cargo materials and be used in different applications such as time-controlled drug release, medical imaging enhancement, catalyst support and energy related areas. The aerosol synthesis of folded graphene-based materials can also be easily extended to fabricate hybrid nanomaterials without any complicated chemistries.

In this paper, the transmission and absorption properties of nonsymmetrical cavity structure with metal material have been studied through transfer matrix method and electromagnetic (EM) field simulations. The absorption is found to be dependent on the cavity resonance effect. For a nonsymmetrical structure, the EM wave can be totally absorbed from one incidence direction, at the same time the EM wave is totally reflected from the opposite incidence direction. The reasons of the nonreciprocal absorption are analyzed in detail.

In this paper, we theoretically investigate the band structures of Lamb wave in one-dimensional radial phononic crystal (PC) slabs composed of a series of alternating strips of epoxy and aluminum. The dispersion relations, the power transmission spectra and the displacement fields of the eigenmodes are calculated by using the finite element method based on two-dimensional axial symmetry models in cylindrical coordinates. The axial symmetry model is validated by three-dimensional finite element model in Cartesian coordinates. Numerical results show that the proposed radial PC slabs can yield several complete band gaps with a variable bandwidth exist for elastic waves. Furthermore, the effects of the filling fraction and the slab thickness on the band gaps are further explored numerically. It is worth observing that, with the increase of the filling fraction, both the lower and upper edges of the band gaps are simultaneously shifted to higher frequency, which results from the enhancement interaction between the rigid resonance of the scatterer and the matrix. The slab thickness is the key parameter for the existence and the width of complete band gaps in the radial PC slabs. These properties of Lamb waves in the radial PC plates can potentially be applied to optimize band gaps, generate filters and design acoustic devices in the rotary machines and structures.

The pressure dependent changes in transition temperature (T_c) of alkali doped C₆₀ superconductor has been studied theoretically considering the combination of phonon mediated mechanism and high energy electronic interaction mechanism. The latter mechanism involves bond polarization in interaction with conduction electrons. The expression for T_c, isotope effect coefficient (α) and (dT_c/dP)_P has been obtained to explain the observed experimental results of alkali doped C₆₀. A good agreement has been found in experimental (T_c) and (dT_c/dP)_{P = 0} values and calculated values.

Using the theories of complex networks and gravitational field, we study the dynamic routing process under the framework of node gravitational field, define the equation of gravitation of travel path to data package and introduce two parameters α and γ for adjusting the dependences of transmission data on the unblocked degree of node, the transmission capacity of node and the path length. Based on the path's attraction, a gravitational field routing strategy under node connection ability constraint is proposed with considering the affect of node aggregation ability to transport process, and a parameter is used to adjust the control strength of routing process to node aggregation ability. In order to clarify the efficiency of suggested method, we introduce an order parameter η to measure the throughput of the network by the critical value of phase transition from free state to congestion state, and analyze the distribution of betweenness centrality and traffic jam. Simulation results show that, compared with the traditional shortest path routing strategy, our method greatly improve the throughput of a network, balance the network traffic load and most of the network nodes are used efficiently. Moreover, the network throughput is maximized under μ = -1, and the transmission performance of the algorithm is independent of the values of α and γ, which indicate the routing strategy is stable and reliable.

We analytically investigate the thermal entanglement of three-mixed-spin (1/2, 1, 1/2) XXZ model with the DM interaction under an external magnetic field B. Two different cases are considered: one subsystem (1/2, 1/2) consists of two spin-1/2 fermions and the other subsystem (1/2, 1) contains a spin-1/2 fermion and a spin-1 boson. It is shown that the DM interaction parameter D, the external magnetic field strength B and coupling constant J have different effects on Fermi and mixed Fermi–Bose systems. All of the factors mentioned above can be utilized to control entanglement switch of any two particles in mixed spins model.

The local atomic and electronic structure of La_0.5Sr_0.5MnO₃ was investigated at different annealing temperatures (T_A) by X-ray absorption spectroscopy (XAS) and photoemission spectroscopy (XPS). The extended X-ray absorption fine structure indicates that the MnO₆ octahedral distortion is reduced by increasing T_A. The chemical shift for the sample with T_A = 1350°C measured by XPS of Mn 2p core level demonstrates the increasing of Mn³⁺ ions content. From the deconvolution of valence band photoemission spectra, the number of e_g electron is also proved to increase with increasing T_A. It is also demonstrated that there is a strongest hybridization between O 2p and surrounding atomic orbital states in sample with T_A = 1350°C, which is consistent with valence band photoemission.

To study the mechanical, spin polarized electronic and magnetic behavior of TmX(X = Cu, Ag), full-potential linear augmented plane wave plus local orbital method has been used. The lattice parameter (a₀), bulk modulus (B₀) and its first-order pressure derivative have been calculated using optimization method. Mechanical properties have been studied in terms of elastic constants (C_ij), Young's modulus (Y), shear modulus (G) and Poisson's ratio (v) at ambient temperature and pressure which are found to be consistent with available experimental/theoretical values. Electronic properties have been investigated in terms of band structure and density of state histograms for spin up and spin down channel. Electronic and magnetic behavior of TmX shows that studied materials are metallic ferromagnets with high spin polarization in which Tm-f state electrons are contributed mainly.

The stability and collective excitations of binary Bose–Einstein condensates with cubic and quintic nonlinearities in variable anharmonic optical lattices are investigated. By using the variational approach, the influences of the quintic nonlinearities and the shape of the external potential on the stability are discussed in details. It is found that the quintic intraspecies and interspecies interatomic interactions profoundly affect the stability criterion and collective excitations of the system. The shape dependent potential form that characterizes the optical lattice deeply alters the stability regions. Direct numerical simulations of the mean-field coupled Gross–Pitaevskii equation describing the system agree well with the analytical predictions.

Based on the time-dependent Ginzburg–Landau equations, we study numerically the vortex configuration and motion in mesoscopic superconducting cylinders. We find that the effects of the geometric symmetry of the system and the noncircular multiply-connected boundaries can significantly influence the steady vortex states and the vortex matter moving. For the square cylindrical loops, the vortices can enter the superconducting region in multiples of 2 and the vortex configuration exhibits the axial symmetry along the square diagonal. Moreover, the vortex dynamics behavior exhibits more complications due to the existed centered hole, which can lead to the vortex entering from different edges and exiting into the hole at the phase transitions.