Physics, Fluids & Plasmas

Article Mathematics, Applied

A generalized penalty method for a new class of differential inequality system

Ze Yuan, Zijia Peng, Zhenhai Liu, Stanislaw Migorski

Summary: This paper studies a nonlinear system involving a parabolic variational inequality, a history-dependent hemivariational inequality, and differential equation constraints in a Banach space. The unique solvability theorem is derived, and a penalized problem is constructed to obtain an approximating sequence for the nonlinear system. Moreover, the strong convergence of the sequence of approximate solution to the solution of the original system is proved when the penalty parameter converges to zero. Finally, these results are applied to a quasistatic elastic frictional contact problem with heat equation with memory and damage.

COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION (2024)

Article Mathematics, Applied

Optimal control for sampling the transition path process and estimating rates

Jiaxin Yuan, Amar Shah, Channing Bentz, Maria Cameron

Summary: This study focuses on modeling various processes in nature using stochastic differential equations with small white noise. It investigates rare transitions in such systems through transition path theory and proposes a methodology to estimate transition rates and construct effective controllers through the computation of committor functions using neural networks.

COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION (2024)

Article Mathematics, Applied

Traveling waves in a quintic BBM equation under both distributed delay and weak backward diffusion

Feiting Fan, Minzhi Wei

Summary: This paper focuses on the existence of periodic and solitary waves for a quintic Benjamin-Bona-Mahony (BBM) equation with distributed delay and diffused perturbation. By transforming the corresponding traveling wave equation into a three-dimensional dynamical system and applying geometric singular perturbation theory, the existence of periodic and solitary waves are established. The uniqueness of periodic waves and the monotonicity of wave speed are also analyzed.

PHYSICA D-NONLINEAR PHENOMENA (2024)

Article Mathematics, Applied

Dynamics analysis of a diffusive SIRI epidemic system under logistic source and general incidence rate

Wenjie Li, Guodong Li, Jinde Cao, Fei Xu

Summary: This study presents and examines a new diffusive SIRI epidemic model incorporating logistic source and a general incidence rate. Utilizing the construction of Lyapunov functions, the global asymptotic stability of equilibria and the relationship between the basic reproduction number and the local basic reproduction number are thoroughly examined. The persistence and extinction of the infective population are also discussed. Theoretical findings are validated through five illustrative examples.

COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION (2024)

Article Mathematics, Applied

Nonlocal effects on a 1D generalized Ohta-Kawasaki model

Wangbo Luo, Yanxiang Zhao

Summary: We propose a generalized Ohta-Kawasaki model to study the nonlocal effect on pattern formation in binary systems with long-range interactions. In the 1D case, the model displays similar bubble patterns as the standard model, but Fourier analysis reveals that the optimal number of bubbles for the generalized model may have an upper bound.

PHYSICA D-NONLINEAR PHENOMENA (2024)

Article Mathematics, Applied

Modelling and simulations in time-fractional electrodynamics based on control engineering methods

Damian Trofimowicz, Tomasz P. Stefanski, Jacek Gulgowski, Tomasz Talaska

Summary: This paper presents the application of control engineering methods in modeling and simulating signal propagation in time-fractional electrodynamics. By simulating signal propagation in electromagnetic media using Maxwell's equations with fractional-order constitutive relations in the time domain, the equations in time-fractional electrodynamics can be considered as a continuous-time system of state-space equations in control engineering. Analytical solutions are derived for electromagnetic-wave propagation in the time-fractional media based on state-transition matrices, and discrete time zero-order-hold equivalent models are developed and their analytical solutions are derived. The proposed models yield the same results as other reference methods, but are more flexible in terms of the number of simulation scenarios that can be tackled due to the application of the finite-difference scheme.

COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION (2024)

Article Mathematics, Applied

Vibration energy characters study of a soft-core beam system coupled through nonlinear coupling layers

Yuhao Zhao, Fanhao Guo, Deshui Xu

Summary: This study develops a vibration analysis model of a nonlinear coupling-layered soft-core beam system and finds that nonlinear coupling layers are responsible for the nonlinear phenomena in the system. By using reasonable parameters for the nonlinear coupling layers, vibrations in the resonance regions can be reduced and effective control of the vibration energy of the soft-core beam system can be achieved.

COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION (2024)

Article Mathematics, Applied

Latitudinal storm track shift in a reduced two-level model of the atmosphere

Melanie Kobras, Valerio Lucarini, Maarten H. P. Ambaum

Summary: In this study, a minimal dynamical system derived from the classical Phillips two-level model is introduced to investigate the interaction between eddies and mean flow. The study finds that the horizontal shape of the eddies can lead to three distinct dynamical regimes, and these regimes undergo transitions depending on the intensity of external baroclinic forcing. Additionally, the study provides insights into the continuous or discontinuous transitions of atmospheric properties between different regimes.

PHYSICA D-NONLINEAR PHENOMENA (2024)

Article Mathematics, Applied

Inertial power balance system with nonlinear time-derivatives and periodic natural frequencies

Sun-Ho Choi, Hyowon Seo

Summary: In this paper, the asymptotic behavior of a macroscopic power grid system derived from energy conservation is studied. A sufficient condition for the existence of a special solution as well as the stability of the solution are provided.

COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION (2024)

Article Mathematics, Applied

Hamiltonian formulation and symplectic split-operator schemes for time-dependent density-functional-theory equations of electron dynamics in molecules

Francois Mauger, Cristel Chandre, Mette B. Gaarde, Kenneth Lopata, Kenneth J. Schafer

Summary: This study revisits the equations of Kohn-Sham time-dependent density-functional theory (TDDFT) and demonstrates their derivation from a canonical Hamiltonian formalism. By using a geometric description, families of symplectic split-operator schemes are defined to accurately and efficiently simulate the time propagation for specific classes of DFT functionals. Numerical simulations are conducted to illustrate the approach, focusing on the far-from-equilibrium electronic dynamics of a one-dimensional carbon chain. The optimized 4th order scheme is found to provide a good compromise between numerical complexity and accuracy of the simulation.

COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION (2024)

Article Mathematics, Applied

A general theory to estimate Information transfer in nonlinear systems

Carlos A. Pires, David Docquier, Stephane Vannitsem

Summary: This study presents a general theory for computing information transfers in nonlinear stochastic systems driven by deterministic forcings and additive and/or multiplicative noises. It extends the Liang-Kleeman framework of causality inference to nonlinear cases based on information transfer across system variables. The study introduces an effective method called the 'Causal Sensitivity Method' (CSM) for computing the rates of Shannon entropy transfer between selected causal and consequential variables. The CSM method is robust, cheaper, and less data-demanding than traditional methods, and it opens new perspectives on real-world applications.

PHYSICA D-NONLINEAR PHENOMENA (2024)

Article Computer Science, Interdisciplinary Applications

Coupling finite elements of class C1 on composite curved meshes for second order elliptic problems

Ashish Bhole, Herve Guillard, Boniface Nkonga, Francesca Rapetti

Summary: Finite elements of class C-1 are used for computing magnetohydrodynamics instabilities in tokamak plasmas, and isoparametric approximations are employed to align the mesh with the magnetic field line. This numerical framework helps in understanding the operation of existing devices and predicting optimal strategies for the international ITER tokamak. However, a mesh-aligned isoparametric representation encounters issues near critical points of the magnetic field, which can be addressed by combining aligned and unaligned meshes.

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS (2024)

Article Computer Science, Interdisciplinary Applications

Efficient hyperbolic-parabolic models on multi-dimensional unbounded domains using an extended DG approach

Federico Vismara, Tommaso Benacchio

Summary: This paper introduces a method for solving hyperbolic-parabolic problems on multidimensional semi-infinite domains. By dividing the computational domain into bounded and unbounded subdomains and coupling them using numerical fluxes at the interface, accurate numerical solutions are obtained. In addition, computational cost can be reduced by tuning the parameters of the basis functions.

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS (2024)

Article Mathematics, Applied

Inverse scattering transform for the integrable fractional derivative nonlinear Schrödinger equation

Ling An, Liming Ling, Xiaoen Zhang

Summary: In this paper, an integrable fractional derivative nonlinear Schrodinger equation is proposed and a reconstruction formula of the solution is obtained by constructing an appropriate Riemann-Hilbert problem. The explicit fractional N-soliton solution and the rigorous verification of the fractional one-soliton solution are presented.

PHYSICA D-NONLINEAR PHENOMENA (2024)

Article Mathematics, Applied

Dynamical inquest of refuge and bubbling issues in an interacting species system

Gourav Mandal, Lakshmi Narayan Guin, Santabrata Chakravarty

Summary: The ecological framework investigates the dynamical complexity of a system influenced by prey refuge and alternative food sources for predators. This study provides a thorough investigation of the stability-instability phenomena, system parameters sensitivity, and the occurrence of bifurcations. The bubbling phenomenon, which indicates a change in the amplitudes of successive cycles, is observed in the current two-dimensional continuous system. The controlling system parameter for the bubbling phenomena is found to be the most sensitive. The prediction and identification of bifurcations in the dynamical system are crucial for theoretical and field researchers.

COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION (2024)

Article Mathematics, Applied

Normalized fractional gradient flow for nonlinear Schrödinger/Gross-Pitaevskii equations

Xavier Antoine, Jeremie Gaidamour, Emmanuel Lorin

Summary: This paper is interested in computing the ground state of nonlinear Schrodinger/Gross-Pitaevskii equations using gradient flow type methods. The authors derived and analyzed Fractional Normalized Gradient Flow methods, which involve fractional derivatives and generalize the well-known Normalized Gradient Flow method proposed by Bao and Du in 2004. Several experiments are proposed to illustrate the convergence properties of the developed algorithms.

COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION (2024)

Article Mathematics, Applied

Cauchy matrix structure and solutions of the spin-1 Gross-Pitaevskii equations

Shangshuai Li, Da-jun Zhang

Summary: In this paper, the Cauchy matrix structure of the spin-1 Gross-Pitaevskii equations is investigated. A 2 x 2 matrix nonlinear Schrodinger equation is derived using the Cauchy matrix approach, serving as an unreduced model for the spin-1 BEC system with explicit solutions. Suitable constraints are provided to obtain reductions for the classical and nonlocal spin-1 GP equations and their solutions, including one-soliton solution, two-soliton solution, and double-pole solution.

COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION (2024)

Article Mathematics, Applied

A new cutting plane method for lexicographic multi-objective integer linear programming

Marco Cococcioni, Alessandro Cudazzo, Lorenzo Fiaschi, Massimo Pappalardo, Yaroslav D. Sergeyev

Summary: This work presents a new cutting plane method for lexicographic multi-objective integer linear programming. The method reformulates the problem into one with a single scalar objective function involving Grossone, and introduces a novel cutting plane named Gross-based Objective Function Cutting Plane. Furthermore, by combining different cutting planes, an algorithm called Gross-based Cutting Plane is proposed, which has been proven to find the optimal solution of the problem.

COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION (2024)

Article Mathematics, Applied

A new kind of double phase elliptic inclusions with logarithmic perturbation terms I: Existence and extremality results

Yongjian Liu, Yasi Lu, Calogero Vetro

Summary: This paper introduces a new double phase elliptic inclusion problem (DPEI) involving a nonlinear and nonhomogeneous partial differential operator. It establishes the existence and extremality results to the elliptic inclusion problem and provides definitions for weak solutions, subsolutions, and supersolutions.

COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION (2024)

Article Thermodynamics

Coupled motion characteristic of standard flag and inverted flag in tandem arrangement

Pingping Shen, Weiguo Zhao, Hongjun Zhang, Zhengdao Wang, Hui Yang, Yikun Wei

Summary: In this paper, the dynamics of flow-induced flutter of standard and inverted flags in tandem arrangement were experimentally studied. The critical velocity of the tandem flags was found to be decreased due to the flow perturbation between them, leading to a broader range of flag flapping velocities. The hysteresis loop of the tandem standard flag was significantly reduced, indicating improved performance in practical applications.

EXPERIMENTAL THERMAL AND FLUID SCIENCE (2024)