International Journal of Modern Physics B

In this paper, an inter-cluster data aggregation based on General Self-Organized Tree-based Energy Balance (GSTEB) routing protocol has been improved by proposing energy efficient protocol under hybrid soft computing. First, finest cluster heads are elected by using enhanced ant colony optimization (ACO) method. After that, information which has been gathered by cluster heads is sent to sink node by applying hybrid soft computing (i.e., hybridization of glow swarm and ACOs). Experimental analysis shows that network lifetime has been improved according to the proposed procedure in contrast with already available procedures.

Crystal structure of ${\mathrm{\text{BaTiO}}}_3$ compound was studied using Atomistix Tool Kit software program at high pressure. It is defined that in this combination, tetragonal–cubic phase transition occurs under high pressure $P\approx 2$ GPa. The character of this phase transition is explained in respect of baric dependence of spontaneous strain. Birch–Murnaghan equation is solved, compression ratio is determined. Results gained by theoretical calculations are compared with experimental values.

The pressure dependence of elastic properties of Mo₂Ga₂C is studied via first-principles calculation. The present investigation shows that differing from other MAX phases, in Mo₂Ga₂C the $C_{33}$ is larger than $C_{11}$, because of the strong Ga–Ga interlayer bonds along $c$-axis. Moreover, under pressure, the $C_{33}$ increases more rapidly, originating from the faster strengthening of Ga–Ga bonds. Interestingly, elastic constants $C_{44}$ soften under high pressure (more than 20 GPa). Especially, the calculated phonon structure demonstrates that transverse acoustic (TA) phonon mode also softens under pressure, implying possible phase transition. The reduction of $C_{44}$ and softening of phonon mode are attributed to significantly weakened Mo–Mo interaction in contrast to the strengthening of Ga–Ga bonds under high pressure. Our present results further indicate that Mo₂Ga₂C is more ductile under pressure.

The structural, electronic, elastic and thermodynamic properties of ${\mathrm{\text{V}}}_2\mathrm{\text{AX}}$ ($\mathrm{\text{A}}=\mathrm{\text{B}}$, Al, Ga, In and TI; $\mathrm{\text{X}}=\mathrm{\text{C}}$ and N) phase have been systematically investigated by the first principles. The optimized lattice parameters are in good agreement with the experimental values and better than the available theoretical data. We calculated the elastic constants $C_{ij}$ and the total density of states, which verified mechanical stability and electronic structural stability, respectively. The other elastic parameters including bulk modulus, shear modulus, Young’s modulus, Cauchy pressure, shear anisotropy factor, linear compressibility coefficients, Pugh’s ratio, Poissons’s ratio, microhardness parameter and machinability index are calculated and discussed in this work. The results show that the compounds we studied are stable in mechanics and are anisotropic materials; the compressibility along $c$-axis is lower than that along $a$-direction except for ${\mathrm{\text{V}}}_2\mathrm{\text{BX}}$ ($\mathrm{\text{X}}=\mathrm{\text{C}}$ and N); the compounds of ${\mathrm{\text{V}}}_2\mathrm{\text{AC}}$ ($\mathrm{\text{A}}=\mathrm{\text{B}},\mathrm{\text{Al}},\mathrm{\text{Ga}},\mathrm{\text{TI}}$) and ${\mathrm{\text{V}}}_2\mathrm{\text{AN}}$ ($\mathrm{\text{A}}=\mathrm{\text{B}},\mathrm{\text{Al}},\mathrm{\text{Ga}}$) are brittle in nature, and ${\mathrm{\text{V}}}_2\mathrm{\text{InN}}$ and V₂TIN are ductile in nature; the shear modulus $G$ limits the mechanical stability of the materials under consideration; the ability to resist shape change and the stiffness of ${\mathrm{\text{V}}}_2\mathrm{\text{AC}}$ are stronger compared with ${\mathrm{\text{V}}}_2\mathrm{\text{AN}}$ when A takes B, Al, Ga, In, TI, respectively. Finally we have estimated the Vickers hardness which shows that the hardness of the ${\mathrm{\text{V}}}_2\mathrm{\text{AX}}$ ($\mathrm{\text{A}}=\mathrm{\text{B}}$, Al, Ga, In, TI) would decrease when C is replaced by N. At last, we investigated the thermodynamic properties of ${\mathrm{\text{V}}}_2\mathrm{\text{AX}}$ by calculating the phonon dispersion, Debye temperature and minimum thermal conductivity. The results show that all structures are dynamical stable and the compounds of ${\mathrm{\text{V}}}_2\mathrm{\text{BC}}$, ${\mathrm{\text{V}}}_2\mathrm{\text{BN}}$, ${\mathrm{\text{V}}}_2\mathrm{\text{AlC}}$ and ${\mathrm{\text{V}}}_2\mathrm{\text{AlN}}$ are candidates for thermal barrier coating (TBC) materials.

In this paper, new exact traveling wave solutions of the $(2+1)$-dimensional Hirota–Maccari system arising in nonlinear optics are successfully obtained by using two methods, namely, Improved $tan(\frac{\mathrm{\Phi }(\rho )}{2})$-expansion method and general projective Riccati equation method. The considered methods have been successfully implemented to find exact traveling wave solutions for nonlinear evaluation equations (NLEE) coming for describing nonlinear optics. The results obtained by these methods are straightforward and concise mathematical tool to set up the exact solutions of NLEE.

In this paper, we use the Replica-Exchange Wang–Landau (REWL) technique to study the behavior of the two-point correlation function of the site diluted classical anisotropic Heisenberg (AH) model in two dimensions. The model has a topological Berezinskii–Kosterlitz–Thouless (BKT) transition for any dilution down to the percolation threshold, ${\rho }_{\mathrm{\text{th}}}\approx 0.59275$. Contrary to earlier results that predict the exponent of the correlation function, $\eta$, to decay linearly to zero as a function of temperature, we found that it decreases with temperature to a finite value ${\eta }_0$ at $T\to 0$ for any dilution ${\rho }_{\mathrm{\text{th}}}\le \rho \le 1$.

In this paper, we present the construction of the rational solutions to the nonlocal nonlinear Schrödinger equation by the bilinear method and KP reduction method. The solutions are given in determinant form, the first- and second-order rational solutions are analyzed for their dynamic behaviors.

Label propagation algorithm (LPA) attracts wide attention in community detection field for its near linear time complexity in large scale network. However, the algorithm adopts a random selection scheme in label updating strategy, which results in unstable division and poor accuracy. In this paper, five different indicators of node similarity are introduced based on network local information to distinguish nodes and a new label updating method is proposed. When there are multiple maximum neighbor labels in the propagation process, the maximum label corresponding to the most similar node is selected for updating instead of a random one. Five different forms of improved LPA are proposed which are named as SAL-LPA, SOR-LPA, JAC-LPA, SOR-LPA, HDI-LPA and HPI-LPA. The experiment results on real-world and artificial benchmark networks show that the improved LPA greatly improves the performance of the original algorithm, among which HPI-LPA is the best.

We present a simple method for enhancing the bandwidth and absorptivity of metamaterial perfect absorber (MPA)-formed disk resonators. Utilizing low-conductivity polymer and near-field coupling of multi-band resonances, a 6.8 GHz broadband MPA is achieved with absorption over 90%. The proposed MPA also shows polarization-independent absorption behavior. Furthermore, the structural design is useful for making broadband MPA and can be applied to higher frequencies with a simple configuration.

A realistic interaction potential model (RIPM) has been formulated to theoretically predict the pressure-induced phase transition, elastic properties and thermophysical properties of AlAs and AlSb, including temperature effect (300 K). This model exhibits a better agreement with the available experimental rather than theoretical data for obtained calculations of phase transition pressures and volume collapses. We have achieved elastic moduli, anisotropy factor, Poisson’s ratio, Kleinman parameter, on the basis of the calculated elastic constants. Apparently, this is the first time when thermophysical properties of these compounds are explored at temperature effect by using a single model. Our results are justified by available measured and other reported data which support the validity of our model.

A composite mechanoluminescent layer has been produced on the surface of polymethylmethacrylate by liquid-phase embedding of ${\mathrm{\text{SrAl}}}_2{\mathrm{\text{O}}}_4:({\mathrm{\text{Eu}}}^{2+},{\mathrm{\text{Dy}}}^{3+})$ phosphor microparticles into the polymethylmethacrylate surface layer. The photoluminescence and mechanoluminescence of the obtained layer have been investigated. The mechanoluminescence was excited by the short acoustic pulses and by the dynamic pressure of the stylus sliding over the mechanoluminescent layer surface. A possible mechanism of mechanoluminescence excitation is under discussion. The produced composite layer is shown to exhibit high efficiency of “mechano-optical” transformation.

Perfect acoustic absorption is an important issue for a lot of applications. In this paper, a rigidly backed poroelastic plate with periodic elliptic inclusions is proposed to achieve perfect acoustic absorption at low frequencies by using the finite element method (FEM) with the porous material considered as fluid and solid materials. The absorption of the acoustic energy in such a composite plate resulting from viscous and thermal losses is enhanced by the resonances of the inclusions and energy trapping between the upper part of the poroelastic plate and the inclusion at low frequencies. The influence of the geometry, the incidence angle and the material properties on the absorption coefficient are investigated in detail. Our results show that increasing the major axis of the inclusion, the first absorption peak is pushed to lower frequencies and its value is first increased upto one and then it is decreased. The major axis is the most important parameter to tune the absorption peak, when the thickness is not changed. Once the major axis is determined, perfect acoustic absorption persists even if other parameters are changed. The reported results pave the way for the design of absorption devices which could be used to solve the major issue of noise control.

This paper investigates the ($2+1$)-dimensional Heisenberg ferromagnetic spin chain (HMF) model. The model describes the nonlinear spin dynamics of HMF. By adopting the modified $F$-Expansion and projective Riccati equation methods, we report the dark, combined dark-bright and envelope optical solitons, complexitons singular solutions of the equation along with the conditions that must be satisfied for solitons to exist. The physical structure of the obtained solutions are shown by graphic illustration in order to give a better understanding on the dynamics of optical solitons.

Applying surface piezoelectricity theory and plane wave expansion (PWE) method to the model of Kirchhoff plate, the calculation method of band structure of a piezoelectric phononic crystal (PC) nanoplate with surface effects is proposed and formalized. In order to investigate the bandgap properties of first order in the nanoplate in detail, the corresponding influence rules of thermo-electro-mechanical coupling fields, surface effects and geometric parameters on bandgaps are studied. During the researches, temperature variation, electrical voltage and external axial force are picked as the influencing parameters corresponding to thermo-electro-mechanical coupling fields. Residual surface stress and material intrinsic length are chosen as the influencing parameter related to surface effects. Lattice constant, radius of PZT-4 hole and thickness of nanoplate are picked as the influencing parameters of geometric parameters. All the results are expected to be helpful for the design of micro and nanodevices based on piezoelectric periodic nanoplates.