Modern Physics Letters B

Thermal conduction of Frenkel–Kontorova (FK) lattices with a sustained time periodical force is investigated numerically. The occurrence of stochastic resonance and thermal reversal phenomenon is observed, namely, there exist values of the driving frequency at which the heat flux takes its maximum value and directs a reversal of the heat flux for an average zero-temperature difference between the two contacts in a net. The above phenomena are determined by the dynamical parameters of the model, such as the lattice period, the strength of the on-site potential and so on.

CuInSe₂ powders were synthesized by solvothermal method, and then the CuInSe₂/In₂Se₃ bulk samples were fabricated by spark plasma sintering (SPS) technique. To investigate the phase composition, the powders were determined by X-ray diffraction (XRD). The microstructures of the powders and bulk samples were observed by scanning electron microscopy (SEM). The transportation of the electronic properties and thermal conductivity were measured at room temperature to 700 K. According to the results, the CuInSe₂ powders appeared in flower-like patterns which ranged from 3 $\mu$m to 6 $\mu$m. CuInSe₂ powders were synthesized at 180${}^{\circ }$C with a chalcopyrite structure. The Seebeck coefficient increased significantly in composite thermoelectric materials up to $200\mu \mathrm{\text{V}}\cdot {\mathrm{\text{K}}}^{-1}$ at 623 K. The thermal conductivity of the sample significantly decreases from the room temperature to 700 K. The CuInSe₂ bulk composite by solvothermal method achieves the highest ZT value of 0.187 at 700 K.

The master equation formalism is used to describe the possibility for peak population amplitudes of two nonstationary states in a 3-stage linear kinetic system to be endowed with an untraditional physical quantity — competitiveness — established in regard to the differences for the degree of the peak responses to a change in the input rate constants. Calculated coefficients of competitiveness are found to agree with observations of performance for the three optical materials with respect to their reliability in different operating windows. It is concluded that, for a non-equilibrium linear kinetic system, the competitiveness constitutes a common dynamic property of its nonstationary states and, in the case of their directed irreversible evolution, comprises the property of a system’s anti-cooperativity.

A novel high birefringence As₂Se₃-based hexagonal lattice photonic crystal fiber (PCF) is proposed. In the structure, a central defect core and three kinds of elliptical air holes with different major axes length and ellipticity are introduced in the cladding. The finite difference time domain (FDTD) method with perfectly matched layer (PML) absorption boundary conditions are used to simulate the guided modes of the designed PCF. The properties of this PCF are investigated in detail including the birefringence, beat length, dispersion, nonlinearity and polarization mode dispersion in the 2–5 $\mu \mathrm{\text{m}}$ mid-infrared range. The results show that for the optimized structure parameters of $\mathrm{\Lambda }=1.6\mu \mathrm{\text{m}}$, $a=0.4\mu \mathrm{\text{m}}$, $b=0.1\mu \mathrm{\text{m}}$, $a_1=0.6\mu \mathrm{\text{m}}$, $b_1=0.04\mu \mathrm{\text{m}}$, $a_2=0.8\mu \mathrm{\text{m}}$, $b_2=0.06\mu \mathrm{\text{m}}$, the high birefringence of 0.1192 and beat length of 41.93 $\mu \mathrm{\text{m}}$ are obtained. The maximum nonlinearity coefficient of 10,050 w${}^{-1}$km${}^{-1}$ and 15,200 w${}^{-1}$km${}^{-1}$ for x- and y-polarization modes are achieved. The distinctive dispersion is analyzed, which is all-normal in x-polarization direction while it has two zero dispersion points at 3.18 $\mu \mathrm{\text{m}}$ and 3.65 $\mu \mathrm{\text{m}}$ in y-polarization direction. The designed PCF with high birefringence, large nonlinearity and distinctive dispersion will be beneficial for mid-infrared fiber sensing, mid-infrared spectroscopy and nonlinear optics applications.

We introduce a new Hamiltonian model which interpolates between the Jaynes–Cummings model (JCM) and other types of such Hamiltonians. It works with two interpolating parameters, rather than one as traditional. Taking advantage of this greater degree of freedom, we can perform continuous interpolation between the various types of these Hamiltonians. As applications, we discuss a paradox raised in literature and compare the time evolution of the photon statistics obtained in the various interpolating models. The role played by the average excitation in these comparisons is also highlighted.

Polarization is a property of transverse waves that specify the geometrical orientation of the oscillations, and it is of significant importance to control the polarization of waves at the information storage and processing. In this paper, we propose a new type of polarization conversion metasurface based on the $\mathrm{\Phi }$-shaped structure in reflection mode. An ultrawideband cross-polarization conversion is obtained. The simulated results show that this metasurface can rotate the polarized direction of the linearly polarized electromagnetic wave by 90${}^{\circ }$ and the polarization conversion efficiency reaches up to 90% in the ultrawideband from 6.9 GHz to 22.2 GHz. The relative bandwidth is 105%. In addition, the experimental results of polarization conversion efficiency are in good agreement with the simulations. With the advantages of high conversion efficiency, ultrawide operating band and the simple geometric structure, the application of this polarization conversion metasurface structure can be extended to the frequency range of terahertz or even the visible light.

Proportional delay is a class of unbounded time-varying delay. A class of bidirectional associative memory (BAM) memristive neural networks with multiple proportional delays is concerned in this paper. First, we propose the model of BAM memristive neural networks with multiple proportional delays and stochastic perturbations. Furthermore, by choosing suitable nonlinear variable transformations, the BAM memristive neural networks with multiple proportional delays can be transformed into the BAM memristive neural networks with constant delays. Based on the drive-response system concept, differential inclusions theory and Lyapunov stability theory, some anti-synchronization criteria are obtained. Finally, the effectiveness of proposed criteria are demonstrated through numerical examples.

A single-patterned five-band terahertz metamaterial absorber based on simple metal–dielectric–metal sandwich structure is investigated and demonstrated. The numerical simulations reveal the different dependence of the absorption ability on the incident polarization angle, dielectric layer, and structural dimensions of the single pattern. The extracted electric field distribution indicates that the five-band near-perfect absorption performance (average over 98%) mainly originates from the combination of LC, dipole, quadrupole, and high-order resonance. The researches on magnetic field and power loss density distributions further reveal the absorption mechanism. Moreover, additional resonance mode can be excited to form a six-band high-performance absorber only by adjusting some geometric dimensions of the single pattern with multiple resonance modes. The simple method provides us a very good idea to implement a super multi-band absorber. The proposed absorbers here can be applied in massive related fields, such as metamaterial sensors, thermal radiation, and imaging system.

The equation of motion for a particle moving in complex space is obtained and then solved. The interaction between the real and imaginary components of motion can produce what can be regarded as a wave motion in real space. The formation of interference patterns and polarization of a matter wave can be accounted for by the particle’s motion in complex space. The deterministic particle view of a free particle can then be reconciled with its dual probabilistic wave picture but the formulation is entirely in complex space.

The plasmon resonances of individual aluminum nanoparticles are investigated by electron energy-loss spectroscopy (EELS) in scanning transmission electron microscope (STEM). Surface plasmon mode and bulk plasmon mode of Al nanoparticles are clearly characterized in the EEL spectra. Discrete dipole approximation (DDA) calculations show that as the particle diameter increases from 20 nm to 100 nm, the plasmon resonance shifts to lower energy and higher mode of surface plasmon arises when the diameter reaches 60 nm and larger.

In this paper, two-dimensional thermoelastic analysis of a functionally graded nanoshell is presented based on nonlocal elasticity theory. To formulate this problem, first-order shear deformation theory (FSDT) is used for axial and radial deformations simultaneously. Material properties are assumed to be mixture of ceramic and metal based on a power law distribution. Principle of virtual work is used for derivation of the governing equations. The analytical approach is presented based on eigenvalue and eigenvector method to derive four unknown functions including radial and axial displacements and rotations along the longitudinal direction. In addition, the influence of nonlocal and in-homogeneous index parameter is studied on the responses of the system. Two-dimensional results are presented along the radial and longitudinal directions.

Microbubble drag reduction on the axisymmetric body is experimentally investigated in the turbulent water tunnel. Microbubbles are created by injecting compressed air through the porous medium with various average pore sizes. The morphology of microbubble flow and the size distribution of microbubble are observed by the high-speed visualization system. Drag measurements are obtained by the balance which is presented as the function of void ratio. The results show that when the air injection flow rate is high, uniformly dispersed microbubble flow is coalesced into an air layer with the larger increment rate of drag reduction ratio. The diameter distributions of microbubble under various conditions are submitted to normal distribution. Microbubble drag reduction can be divided into three distinguishable regions in which the drag reduction ratio experiences increase stage, rapid increase stage and stability stage, respectively, corresponding to the various morphologies of microbubble flow. Moreover, drag reduction ratio increases with the decreasing pore sizes of porous medium at the identical void ratio in the area of low speeds, while the effect of pore sizes on drag reduction is reduced gradually until it disappears with the increasing free stream speeds, which indicates that smaller microbubbles have better efficiency in drag reduction. This research results help to improve the understanding of microbubble drag reduction and provides helpful references for practical applications.

This study focused on the corrosion protection performance of plasma polymerized HMDSO thin films in two different corrosive medias, 0.3M NaCl and 0.3M H₂SO₄. The pp-HMDSO thin films were deposited on steel substrates for electrochemical tests using the potentiodynamic polarization technique, they were deposited also on aluminum and silicon substrates to investigate their resistance to corrosion, through the analysis of the degradation of microhardness and morphology, respectively, after immersion of the substrates for one week in the corrosive media. The results showed promising corrosion protection properties of the pp-HMDSO thin films.

Considering the effect of headway changes with memory, an improved continuum model of traffic flow is proposed in this paper. By means of linear stability theory, the new model’s linear stability with the effect of headway changes with memory is obtained. Through nonlinear analysis, the KdV–Burgers equation is derived to describe the propagating behavior of traffic density wave near the neutral stability line. Numerical simulation is carried out to study the improved traffic flow model, which explores how the headway changes with memory affected each car’s velocity, density and energy consumption. Numerical results show that when considering the effects of headway changes with memory, the traffic jams can be suppressed efficiently. Furthermore, research results demonstrate that the effect of headway changes with memory can avoid the disadvantage of historical information, which will improve the stability of traffic flow and minimize car energy consumption.