Ricerc@Sapienza

Recently the authors proposed a model and related analysis on waves in long-range metamaterials. Nonlocal elasticity can be produced by several interacting forces acting between particles at long distance, as Coulomb or magnetic-static forces. The chance of introducing this long-distance forces has a disruptive effect in the elastic dynamics. In fact, classical elasticity is based only upon closest particles interaction in which short range-elastic forces act.

Nonlocal long -range effects are at the base of new phenomena investigated by the authors. In one dimensional systems, this permits the chance of modifying the phase and group velocity of the waveguide, even producing waves transporting energy backwards. In the two-dimensional case a richer scenario is opened. This paper investigates the chance of transporting the energy over a two-dimensional domain through vibrations that can follow a given path. The relationship between the path and the connection template is investigated.

This paper investigates the response of structures including in their constitutive relationship memory effects. The analysis is carried on both by using modal analysis and a wave approach. Memory effects appears by a convolution integral added to conventional differential terms. The dispersion relation for an infinite waveguide is obtained together with the frequency response function for its finite counterpart, with given boundary conditions.

This paper investigates new phenomena in elastic wave propagation in metamaterials, characterised
by long-range interactions. The kind of waves borne in this context unveil wave-stopping,
negative group velocity, instability and hypersonic or superluminal effects, both for instantaneous
and for nonlocal retarded actions. Closed form results are presented and a universal propagation
map synthesizes the expected properties of these materials. Perspectives in physics, engineering and
social dynamics are discussed.

Traveling waves of permanent form with compact support are possible in several nonlinear partial nonlinear differential equations and this, mainly, along two pathways: A pure nonlinearity stronger than quadratic in the higher order gradient terms describing the mathematical model of the phenomena or a special inhomogeneity in quadratic gradient terms of the model. In the present note we perform a rigorous analysis of the mathematical structure of compactification via a generalization of a classical theorem by Weierstrass.

The use of Rayleigh wave ellipticity has gained increasing popularity in recent years for investigating earth structures, especially for near-surface soil characterization. In spite of its widespread application, the sensitivity of the ellipticity function to the soil structure has been rarely explored in a comprehensive and systematic manner. To this end, a new analytical method is presented for computing the sensitivity of Rayleigh wave ellipticity with respect to the structural parameters of a layered elastic half-space.

We propose a one-equation turbulence model based on a modified closure relation for the length scale of turbulence. The proposed model is able to adequately represent the energy dissipation due to the wave breaking and does not need any criterion to a priori locate the wave breaking point and the region in which the turbulence model has to be activated.

The effectiveness of a Metamodel-Embedded Evolution Framework for model parameter identification of a Smoothed Particles Hydrodynamic (SPH) solver, called DualSPHysics, is demonstrated when applied to the generation and propagation of progressive ocean waves. DualSPHysics is an open-source code that provides GP-GPU acceleration, allowing for highly refined simulations. The automatic optimization framework combines the global-convergence capabilities of a Multi-Objective Genetic Algorithm (MOGA) with Response Surface Method (RSM) based on a Kriging approximation.