Antonio Montano 🪄

Training effect in exchange-bias systems consists of a variation in coercivity and symmetry between the first reversal after field cooling and the following loops. It has been shown, in the frame of a two-dimensional coherent-rotation approach, that training might be explained in terms of an initial noncollinear arrangement of the antiferromagnetic spins after field cooling, which relaxes to a collinear arrangement during the first reversal [A. Hoffmann, Phys. Rev. Lett. 93, 097203 (2004)]. In… Visualizza altro

Training effect in exchange-bias systems consists of a variation in coercivity and symmetry between the first reversal after field cooling and the following loops. It has been shown, in the frame of a two-dimensional coherent-rotation approach, that training might be explained in terms of an initial noncollinear arrangement of the antiferromagnetic spins after field cooling, which relaxes to a collinear arrangement during the first reversal [A. Hoffmann, Phys. Rev. Lett. 93, 097203 (2004)]. In this paper, we extend the model to three dimensions, by numerically solving the Landau-Lifshitz-Gilbert equation describing the precession motion of magnetic moments. We are thus able to discuss the validity of Hoffmann’s model within a three-dimensional approach, with parameter values similar to those in the original publication, and to enlighten the role of out-of-plane anisotropies and Gilbert damping in determining the occurrence of training. Moreover, when realistic values are considered for the magnetocrystalline anisotropy of the system, we find that no training is reproduced within our extended model, suggesting that symmetry-driven irreversibilities might not be as relevant as previously believed for training effect. Meno dettagli

A model of a rowing scull has been developed, comprising the full motion in the symmetry plane and the interaction with the hydrodynamics. A particular emphasis has been given to the energy dissipation due to the secondary movements activated by the motion of the rowers and the intermittent forcing terms. Numerical simulations show the effectiveness of the proposed procedure.

In this article, we devise a simulation tool of the dynamics of a tethered buoy, which is a mooring system consisting of a rigid floating body (buoy) connected by an elastic cable (mooring line) to the bottom of the fluid environment. The accuracy and robustness of the overall solution algorithm are based on an appropriate choice of three main ingredients. The first ingredient is the use of a novel mixed finite element formulation for the mooring line, which allows a robust modeling of the… Visualizza altro

In this article, we devise a simulation tool of the dynamics of a tethered buoy, which is a mooring system consisting of a rigid floating body (buoy) connected by an elastic cable (mooring line) to the bottom of the fluid environment. The accuracy and robustness of the overall solution algorithm are based on an appropriate choice of three main ingredients. The first ingredient is the use of a novel mixed finite element formulation for the mooring line, which allows a robust modeling of the cable even in the limit of an infinite value of the Young modulus. The second ingredient is the use of quaternions in the equations of motion of the floating body, instead of Euler angles, which avoids angle singularities in the presence of large rotations. The third ingredient is the use of an implicit method (Backward Euler) for time discretization, in conjunction with a damped Newton method for the solution of the resulting nonlinear system, which avoids computational inefficiency of explicit time integration schemes in the presence of quasi-inextensible cables and a fine spatial grid size. The physical soundness of the mooring system model and the accuracy and robustness of the proposed numerical procedure are validated in the study of a tethered buoy operating under static and dynamic industrial-like working conditions. Meno dettagli