Modern Physics Letters B

Photoluminescence (PL) spectra, light flux, color temperatures and color coordinates of white light emitting diodes that are based on CaGa₂S₄:Eu${}^{2+}$–CaS:Eu${}^{2+}$ composite solution and industrial phosphor were analyzed. The study was carried out continuously for a 1000 h with two white LEDs which based on an exciting InGaN wavelength of 450 nm with a power of 10 W. Luminous flux and color temperatures were investigated during 200, 400, 600, 800 and 1000 h. All experiments were carried out for both CaGa₂S₄:Eu${}^{2+}$–CaS:Eu${}^{2+}$ and industrial phosphor and comparatively analyzed. Consequently, the application perspectives of CaGa₂S₄:Eu${}^{2+}$–CaS:Eu${}^{2+}$ composite solution in the white LEDs technologies are presented.

The dynamics of a full-scale pipe conveying fluid inside is investigated based on the finite element method (FEM). During the numerical simulation, the Euler–Bernoulli beam equations are used to model the motion of the full-scale pipe while the effect of internal flow is considered. And the semi-empirical time-domain model is applied to simulate the external hydrodynamic forces exerted on the pipe. Then the typical vortex-induced vibration (VIV) characteristics of the full-scale pipe considering both internal and external flows are analyzed. The results show that with the increase of the internal flow velocity, the natural frequencies of the full-scale pipe decrease and the in-line (IL) and cross-flow (CF) dominating modes are increased. Furthermore, the dominating frequencies in both IL and CF directions are not notably changed. And the IL and CF root-mean-square (RMS) values of amplitudes fluctuate at around the stable values due to the stable external hydrodynamic forces. It should be noticed that the IL and CF RMS strain values of the full-scale pipe are increased, especially for high external and internal flow velocities. The maximal RMS strain values in both IL and CF directions appear next to the pipe top, which could have an influence on the motion of the ship on the sea surface.

In this paper, by utilizing a nine-qubit entangled state as a quantum channel, we propose new schemes for symmetric and asymmetric cyclic controlled quantum teleportation (CYCQT). In our proposed schemes, four participants Alice, Bob, Charlie and David teleport their unknown quantum states cyclically among themselves with the help of a controller Eve. No participants can reconstruct the original states sent from the respective senders without the permission of the controller. Also, by considering same nine-qubit entangled state as a quantum channel, we propose a generalized scheme for CYCQT of multi-qubit states. In contrast to the previous CYCQT schemes involving three communicators and a controller, there are four communicators and a controller in the proposed schemes. Also, compared with previous CYCQT schemes, our proposed CYCQT schemes require less consumption of quantum resource and the intrinsic efficiency of the generalized scheme increases with the increase of number of qubits in the information states.

This paper is devoted to the study of a (3 + 1)-dimensional generalized nonlinear evolution equation for the shallow-water waves. The breather solutions with different structures are obtained based on the bilinear form with perturbation parameters. Some new lump solitons are found in the process of studying the degradation behavior of breather solutions, and we also study general lump soliton, lumpoff solution and superposition phenomenon between lump soliton and breather solution. Besides, some theorems about the superposition between lump soliton and $N$-soliton ($N$ is a nonnegative integer) are given. Some examples, including lump-$N$-exponential type, lump-$N$-logarithmic type, higher-order lump-type $N$-soliton, are given to illustrate the correctness of the theorems and corollaries described. Finally, some novel nonlinear phenomena, such as emergence of lump soliton, degeneration of breathers, fission and fusion of lumpoff, superposition of lump-$N$-solitons, etc., are analyzed and simulated.

We investigate a (2 + 1)-dimensional nonlinear Schrodinger equation (NLSE), which describes the spin dynamics of (2 + 1)-dimensional inhomogeneous Heisenberg ferromagnetic spin chain (IHFSC) with bilinear and anisotropic interactions in the semiclassical limit. Miscellaneous new solitons solutions are obtained through the generalized Riccati equation mapping method (GREMM). Moreover, the effects of homogeneity on the soliton propagation and interaction are discussed. The derived structure of the obtain solutions offers a rich platform to better understand the nonlinear dynamics in the ferromagnetic materials.

By applying the two efficient mathematical methods particularly with regard to the classical Lie symmetry approach and generalized exponential rational function method, numerous exact solutions are constructed for a (2 + 1)-dimensional Bogoyavlenskii equation, which describes the interaction of Riemann wave propagation along the spatial axes. Moreover, we obtain the infinitesimals, all the possible vector fields, optimal system, and Lie symmetry reductions. The governing Bogoyavlenskii equation is converted into various nonlinear ordinary differential equations through two stages of Lie symmetry reductions. Accordingly, abundant exact closed-form solutions are obtained explicitly in terms of independent arbitrary functions, rational functions, trigonometric functions, and hyperbolic functions with arbitrary free parameters. The dynamical behavior of the resulting soliton solutions is presented through 3D-plots via numerical simulation. Eventually, single solitons, multi-solitons with oscillations, kink wave with breather-type solitons, and single lump-type solitons are obtained. The proposed mathematical techniques are effective, trustworthy, and reliable mathematical tools to work out new exact closed-form solutions of various types of nonlinear evolution equations in mathematical physics and engineering sciences.

The mechanism of plastic deformation under tensile and compressive loading of hexagonal close-packed (HCP)/face-centered cubic (FCC) biphasic titanium (Ti) nanopillars at different temperatures (70 K, 150 K, 300 K and 400 K) and different FCC phase sizes (2 nm, 4 nm, 6 nm and 8 nm) was investigated by molecular dynamics (MD). The plastic deformation is mainly concentrated in the FCC phase during compression loading. The HCP/FCC interface is the main source of $\frac{1}{6}〈\bar{1}\bar{2}1〉$ Shockley partial dislocations. As the temperature increases, the dislocation nucleation rate increases and the surface dislocation source is activated. During tensile loading, it is more likely that the Shockley partial dislocations react with each other in the FCC phase to form Lomer–Cottrell sessile dislocations and stacking fault (SF) nets. When the temperature is reduced to 70 K, tensile twins are formed at the phase interface. The plastic deformation is dominated by twins and $〈\mathrm{\text{c}}+\mathrm{\text{a}}〉$ dislocation slip occurs in the HCP phase. The effect of the FCC phase size on the plastic deformation mechanism of the nanopillar is strong. The FCC phase is transformed into the HCP phase when the FCC phase size in the nanopillar is reduced to 4 nm under compressive loading. However, twin deformation occurs at the HCP/FCC interface when the FCC phase size is reduced to 2 nm under tensile loading.

The conformable derivative and adequate fractional complex transform are implemented to discuss the fractional higher-dimensional Ito equation analytically. The Jacobi elliptic function method and Riccati equation mapping method are successfully used for this purpose. New exact solutions in terms of linear, rational, periodic and hyperbolic functions for the wave amplitude are derived. The obtained solutions are entirely new and can be considered as a generalization of the existing results in the ordinary derivative case. Numerical simulations of some obtained solutions with special choices of free constants and various fractional orders are displayed.

Darboux transformation for the supersymmetric nonisospectral KdV equation is investigated. Based on the Lax pair, we successively construct the one-fold, two-fold and three-fold Darboux tansformations for the supersymmetric nonisospectral KdV equation. Moreover, we present the $n$-fold Darboux transformation in the form of superdeterminant.

Based on the self-consistent mean field theory by considering the next higher harmonics of the superconducting (SC) gap, we discuss the energy and momentum dependence of the electron spectrum in electron-doped cuprate superconductors. By calculation of the electron spectral function, it is shown that the weight of the electron spectrum at the Fermi energy is strongly redistributed by the next higher harmonics of the SC gap in electron-doped cuprate superconductors, especially for the antinodal region. At the antinodal region, the weight of the electron spectrum at the Fermi surface increases with the increase of next higher harmonics term, reaches the maximum at a critical strength, then decreases when the next higher harmonics is larger. Our theoretical results show that the variation of the SC gap with the next higher harmonics can explain the anomalous behavior of the electron spectrum and different angle-resolved photoemission spectroscopy experimental results of different samples of electron-doped cuprate superconductors. Moreover, the magnitude of the SC gap can be suppressed by the next higher harmonics, which may be one of the reasons for the smaller SC gap in electron-doped cuprate superconductors. Obvious topological change happens in the SC gap at a critical strength of the next higher harmonics.

The connected and automated vehicle (CAV) is regarded as an effective way to improve traffic efficiency and safety, which can utilize vehicle-to-vehicle (V2V) communication technology to obtain real-time status information from multiple preceding vehicles. In view of the car-following characteristic of CAV in a V2V communications environment, an extended car-following model AHT-FVD is proposed which takes both average headway and electronic throttle angle difference into account. The stability of this model is examined via linear stability analysis. It is found that the proposed model has a larger stability region than both the full velocity difference (FVD) model and throttle-based FVD (T-FVD) model. Namely, this AHT-FVD model can effectively stabilize traffic flow and alleviate traffic congestion in theory. Moreover, a series of numerical simulations are carried out to explore how average headway together with electronic throttle angle difference influences the stability of traffic flow. Simulation results show that increasing either the average headway weight or the electronic throttle angle difference control signal coefficients can yield higher traffic flow stability. Simulation result is highly consistent with theoretical analysis.

The influence of time dependence on the model which consists of two qubits interacting with a two-mode electromagnetic field of the parametric amplifier type is investigated. The analytical solution of the wave function is obtained. The quantum Fisher information, entanglement and population inversion for a time-dependent system are analyzed. The photon statistics of a single-mode are quantified by the evolution of the Mandel parameter. Our results showed that there exists a positive relationship between the time-dependent parameter and entanglement. In other words, the time-dependent parameter due to the degree of entanglement is increased. Also, the quantum quantifier is strongly affected by the time-dependent coupling parameter in the absence and presence of the detuning parameter. This enables new parameters to control the degree of entanglement and quantum Fisher information, especially in quantum communication.

A stochastic dynamic model of a Kaplan turbine is established in this paper during the transient process. When the Kaplan turbine operates with fluctuating load, the synergistic relationship between the guide vanes and blades experiences random fluctuation resulting from the mechanical, hydraulic and signal factors. To study the effect of stochastic fluctuations of the synergistic relationship, Chebyshev polynomial approximation method is adopted to analyze the stochastic dynamic characteristics of the Kaplan turbine during the transient process. Using Chebyshev polynomial approximation, the stochastic model of the Kaplan turbine is simplified to its equivalent deterministic model, and the stochastic dynamic characteristics of the model are investigated in the transient process. The effects of stochastic intensity on the dynamic behaviors of the Kaplan turbine are analyzed by means of numerical simulation. Moreover, the influences of PID parameters on the stochastic dynamic characteristics of the Kaplan turbine are studied through bifurcation diagrams. Analysis of stochastic characteristics and dynamic behaviors suggests that transient performance improvement can be obtained by controlling the synergistic stochastic intensity and PID parameters.

In this paper, the investigation is conducted on a (2 + 1)-dimensional extended Boiti–Leon–Manna–Pempinelli equation for an incompressible fluid. Via the Riemann theta function, periodic-wave solutions are derived, and breather-wave solutions are constructed with the aid of the extended homoclinic test approach. Based on the polynomial expansion method, several traveling-wave solutions are derived. Besides, we observe that the amplitude of the breather keeps unchanged during the propagation and the traveling wave which is kink shaped propagates stably. Furthermore, we analyze the transition between the periodic-wave and soliton solutions, which implies that the periodic-wave solutions tend to the soliton solutions via a limiting procedure.

A nonlinear Partially-Averaged Navier–Stokes model with near-wall correction is developed for separated turbulent flow simulations. The periodic hills flow is simulated to validate the new model and the results are compared with the standard $k-𝜀$ model, MPANS model, MSST PNAS model, standard $k-𝜀$ PANS model, and experimental/LES results. It is found that the new model shows better performance in the prediction of both mean velocity and turbulent statistics compared to the other models. From the prediction of the near-wall friction coefficient of periodic hills flow, the new model shows good resolution in the near-wall region by considering the near-wall damping function to turbulent viscosity, gradient production term, and turbulence scale correction term for the near-wall region. From the analysis of anisotropy-invariant and sub-filtered stress (SFS), it can be found that the nonlinear term is necessary for prediction accuracy improvement in turbulent flow simulation with strong separation.

The time–frequency analysis by smooth Pseudo-Wigner-Ville distribution (SPWVD) is utilized for the double-line laser ultrasonic signal processing, and the effective detection of the metal surface defect is achieved. The double-line source laser is adopted for achieving more defects information. The simulation model by using finite element method is established in a steel plate with three typical metal surface defects (i.e. crack, air hole and surface scratch) in detail. Besides, in order to improve the time resolution and frequency resolution of the signal, the SPWVD method is mainly used. In addition, the deep learning defect classification model based on VGG convolutional neural network (CNN) is set up, also, the data enhancement method is adopted to extend training data and improve the defects detection properties. The results show that, for different types of metal surface defects with sub-millimeter size, the classification accuracy of crack, air holes and scratch surface are 94.6%, 94% and 94.6%, respectively. The SPWVD and CNN algorithm for processing the laser ultrasonic signal and defects classification supplies a useful way to get the defect information, which is helpful for the ultrasonic signal processing and material evaluation.