The European Physical Journal Plus最新文献

We study the Infeld–Rowlands equation, a nonlinear partial differential equation in three independent variables describing inter alia soliton perturbations for the Ginzburg–Landau equation. First of all, we find a number of invariant modules for the equation under study. These are further employed in order to produce a new class of exact solutions whose generic representatives are not invariant under any Lie point symmetries of the equation  in question. We then proceed to investigate the properties of these solutions.

This paper develops a stochastic SIVR epidemic model with distributed delay to analyze the dynamics of coronavirus spread. We first derive the basic reproduction number and equilibrium points for the deterministic version of the model. For the stochastic model, we establish sufficient conditions for disease persistence using a Lyapunov approach and define a critical threshold (mathcal {R}_0^c), proving the existence of a unique stationary distribution via Khasminskii theory. Moreover, we obtain the exact probability density function around the quasi-equilibrium by solving the associated Fokker–Planck equation. To support intervention planning, we formulate a stochastic optimal control problem with three targeted strategies for susceptible, vaccinated, and infected subpopulations and characterize optimal controls using the stochastic maximum principle. These analytical results clarify key mechanisms driving disease persistence from an epidemiological standpoint. Theoretical findings are validated through numerical simulations, where key parameters are estimated via the Markov chain Monte Carlo method using real-time data.

Interactive hybrid quantum communication plays a crucial role in fulfilling diversity, flexibility and scalability. To address the challenge of large capacity, high success probability and decoherence, we first propose a controlled cyclic and bidirectional communication protocol to achieve the hybrid transmission of arbitrary single-qudit states through selecting a suitable entangled channel and measurement operators. Then, the proposed protocol is generalized to arbitrary multi-qudit states. With the permission of the supervisor, each sender can synchronously teleport an unknown qudit state to her neighbor in the clockwise direction and remotely prepare a known state in the counterclockwise direction with unit success probability. The recipient’s recovery operation is derived from the general expression, which clearly reveals its relationship with the measurement results of the senders and the supervisor. Network coding is ingeniously implemented to decrease the classical communication cost. Moreover, we explore the influence of amplitude damping noise and improve the fidelity by means of weak measurement and environment-assisted measurement. Compared with the existing protocols, our protocols have great advantages in terms of applicability, practicality, resource conservation and so on.

This study investigates the co-doping effects of transition metal (V) and alkali earth metal (Sr) elements on the crystalline structure, surface morphology, optical properties, and photo-sensing performance of ZnO thin films. Thin films of ZnO, ZnO/V, ZnO/Sr, and ZnO/V/Sr were synthesized using the nebulizer spray pyrolysis (NSP) technique. X-ray diffraction analysis confirmed the hexagonal wurtzite structure ZnO structure in all films. The optical band gap energy (E_g) values were determined to be 3.310 ± 0.008 eV for ZnO, 3.301 ± 0.008 eV for ZnO/V, 3.284 ± 0.008 eV for ZnO/Sr, and 3.310 ± 0.008 eV for ZnO/V/Sr. All the deposited thin films were photosensitized to the light. The ZnO/Sr showed the highest performance with a detection (D*) sensitivity of 3.22 × 10⁹ Jones and a photoresponsivity (R) of 1.6 × 10^–2 A/W, measured under a − 4 V bias. This research highlights that doping with transition and alkali earth metal elements is an effective strategy for tailoring the physical properties of semiconducting oxide films.

A wide range of thermal transfer applications from an engineering perspective is greatly beneficial from the thermos-physical characteristics of tri-hybrid nanofluid because the heat transport mainly depends on the thermal conductivity and volume concentrations of nanoparticles. The main focus of the analysis is to discuss the mixed convective stagnation point flow with entropy generation investigation on a Casson tri-hybrid nanofluid caused by a spinning sphere with variable fluid properties numerically. Further, the impact of cross diffusion, heat source, and thermal radiation with convective boundary conditions are taken into consideration in the existing work. In this work, a tri-hybrid nano liquid is formed by suspensions of three dissimilar nanoparticles, such as copper (Cu), silver (Ag), and graphene oxide (GO) with base fluid kerosene oil. The mathematical formulation of the flow model is assembled in the form of partial differential equations (PDEs) and altered into the system of ordinary differential equations (ODEs) by using transformation. The MATLAB bvp4c solver is employed to solve the transformed equations numerically. The graphical changes of various emerging parameters are visualized and discussed thoroughly. It is seen from the graphs that stronger values of the variable viscosity parameter decline the linear velocity of the fluid. In contrast, it shows the reverse trend in the case of angular velocity. Moreover, depreciation in the entropy generation is noted for greater values of magnetic parameter because growing values of magnetic parameter produce the stronger resistance force in the momentum of fluid, as a result, the stronger heat transfer rate produced inside the boundary layer.

Modulation instability (MI) in coherently coupled twin-core optical fibers with saturable nonlinearity is investigated. The system is modeled using a modified set of coupled nonlinear Schrodinger equations that incorporate both coherent coupling and nonlinear saturation effects. Linear stability analysis is applied to determine how the dispersion regime, coupling strength, and saturation parameter influence the MI gain spectrum. Our results show that saturation suppresses MI in the normal dispersion regime but enhances it in the anomalous regime. Direct numerical simulations using the split-step Fourier method confirm the analytical predictions, revealing enhanced sideband growth and spectral broadening with increasing saturation. These findings elucidate the competing roles of coherent coupling and saturation in shaping pulse dynamics and provide guidance for the design of coupled fiber systems for controlled nonlinear propagation.

This study examines energy bandgap and thermal properties of mixed nanofluid flow of [KO/SiC + CdTe]^HC passing through solid cone composed of a porous material. We have fabricated microporous-structure thin films from [KO/SiC + CdTe]^HC using a physical vapor deposition (PVD) method. The study has considered existence of heat absorption in porous media and radioactive flow. Silicon carbide [SiC]^NPs and cadmium telluride [CdTe]^NPs are suspended in kerosene oil (KO) to form a hybridized nanofluid. NDsolve in Mathematica software streamlines control equations into ordinary differential equations (ODEs) and computationally resolves them. Effects of various factors, including nanoparticles size, cone angle, heat absorption, radiation, and porosity, are investigated, and results are presented in graphs. We utilize Materials Studio 7.0 software, specifically TDDFT/DMol³ module, to investigate molecular structures and calculate frequencies for both crystal models and individual molecules. We compare DFT-Gaussian09W vibration values with experimental data to assess their structural or optical characteristics. In some cases, results support the relevant numerical findings reported in published research. Adding nanoparticles lowered the energy bandgap from 4.713 to 1.663 eV, and the heat transfer efficiency went up by roughly 30–35%. More porosity made heat distribution better, but thermal radiation made temperature go up but convective efficiency goes down.

The capacity of physics-informed neural networks (PINNs) to handle various nonlinear problems has attracted considerable attention recently. However, because PINNs rely on data points and physical constraint residuals to infer unknowns, they have a number of challenges and limitations, particularly when it comes to addressing complex inverse problems. The solution may be unstable or inaccurate when dealing with sparse or noisy data. In the current study, we propose adaptive weight loss PINNs (AWL-PINNs) to obtain the solution to inverse problems of a nonlinear space-time hyperbolic sine-Gordon equation. AWL-PINNs are an improved PINNs variant that is intended to increase training accuracy and efficiency. In addition, AWL-PINNs are utilized to balance contributions and enhance convergence by modifying the weights upon training according to the amount and rate of change of each loss term. The effectiveness and resilience of this approach are demonstrated through four computational examples. Different parameter identification and boundary control equations are considered among the types of inverse problems available. Two- and three-dimensional figures are displayed to show the dynamics and physical properties of both predicted solutions by the methods and accurate solutions. A comparison was made between AWL-PINN and standard PINN in terms of training and test losses and various error metrics. The tabular and graphical comparison results show that, compared to conventional PINNs, the proposed adaptive weight loss-based deep learning technique performs better in terms of accuracy, robustness, and computational efficiency for solving various inverse problems of nonlinear sine-Gordon equations. Furthermore, AWL-PINNs provide more dependable and repeatable results with less sensitivity to network initialization and data noise, according to statistical error evaluations. Hence, AWL-PINNs are an adaptable and remarkable machine learning tool to effectively handle similar inverse problems of nonlinear physical issues arising in various disciplines.

This work focuses on applying the addendum to Kudryashov’s method to generate the soliton solutions of the perturbed Fokas–Lenells equation with Kudryashov’s law of self-phase modulation having the spatiotemporal dispersion. The presence of self-phase modulation offers a nonlinear intensity-dependent refractive index, while the spatiotemporal dispersion accounts for both temporal and spatial effects in wave propagation. We indicate the dark and bright soliton solutions through the three-dimensional, contour, and two-dimensional portraits. The physical importance of these soliton solutions is discussed, offering a greater understanding of the behavior of nonlinear waves in media characterized by both dispersive and nonlinear effects. Modulation instability (MI) analysis has a crucial role in understanding the dynamics and stability properties of nonlinear models. So, the model under consideration is comprehensively examined to assess its spatiotemporal behavior and identify relevant instability conditions. The findings of this study enhance the broader comprehension of soliton dynamics within nonlinear optical and fluid systems. These insights may have significant implications for the development of advanced communication technologies and further applications across various domains of nonlinear wave theory.