Ricerc@Sapienza

The transport of nanoparticles in confined geometries plays a crucial role in several technological applications ranging from nanopore sensors to filtration membranes. Here we describe a Brownian approach to simulate the motion of a rigid-body nanoparticle of an arbitrary shape under confinement. A quaternion formulation is used for the nanoparticle orientation, and the corresponding overdamped Langevin equation, completed by the proper fluctuation-dissipation relation, is derived.

Today, biomaterial research on biomimetic mineralization strategies represents a new challenge in the prevention and cure of enamel mineral loss on delicate deciduous teeth. Distinctive assumptions about the origin, the growth, and the functionalization on the biomimetic materials have been recently proposed by scientific research studies in evaluating the different clinical aspects of treating the deciduous tooth. Therefore, appropriate morpho-chemical observations on delivering specific biomaterials to enamel teeth is the most important factor for controlling biomineralization processes.

Diffusion in inhomogeneous materials can be described by both the Fick and Fokker--Planck diffusion equations.
Here, we study a mixed Fick and Fokker--Planck diffusion problem with coefficients rapidly oscillating both in space and time.
We obtain macroscopic models performing the homogenization limit by means of the unfolding technique.

Mixing of a diffusing species entrained in a three-dimensional microfluidic flow-focusing cross-junction is numerically
investigated at low Reynolds numbers, 1 ≤ Re ≤ 150 , for a value of the Schmidt number representative of a small solute
molecule in water, Sc = 103 . Accurate three-dimensional simulations of the steady-state incompressible Navier–Stokes equations
confirm recent results reported in the literature highlighting the occurrence of different qualitative structures of the

Membrane reactors for the production of pure hydrogen are complex systems whose performance is determined by the interplay between transport by convection and dispersion within the packed bed, hydrogen permeation across the membrane, and the reaction kinetics. Much effort has been devoted to the development of simplified models that combine an adequate description of the system, while maintaining a low computational cost.

The formulation of transport models in polymeric systems starting from the theory of stochastic processes possessing finite propagation velocity is here presented. Hyperbolic continuous equations are shown to be derived from Poisson-Kac stochastic processes and the extension to higher dimensions is discussed. We analyze the physical implications of this approach, namely: non-Markovian nature, admissible boundary conditions, breaking of concentration-flux paradigm and extension to nonlinear case.

Considering the dynamics of non-interacting particles randomly moving on a lattice, the occurrence of a discontinuous transition in the values of the lattice parameters (lattice spacing and hopping times) determines the uprisal of two lattice phases. In this letter we show that the hyperbolic hydrodynamic model obtained by enforcing the boundedness of lattice velocities derived in Giona M., Phys.

The concept of stochastic regularity in lattice models corresponds to the physical constraint that the lattice parameters defining particle stochastic motion (specifically, the lattice spacing and the hopping time) attain finite values. This assumption, that is physically well posed, as it corresponds to the existence of bounded mean free path and root mean square velocity, modifies the formulation of the classical hydrodynamic limit for lattice models of particle dynamics, transforming the resulting balance equations for the probability density function from parabolic to hyperbolic.

We exploit prediction capabilities of the moving-boundary model for food isothermal drying proposed in Adrover et al. (2019). We apply the model to two different sets of literature experimental data resulting from the air-drying process of eggplant cylinders (two-dimensional problem) and potatoes slices (three-dimensional problem). These two food materials, both exhibiting non-ideal shrinkage, are characterized by very different “calibration curves“ i.e. different behaviours of volume reduction V/V0as a function of the rescaled moisture content X/X0.

A moving-boundary model is proposed for describing food isothermal drying. The model takes into account
volume reduction of food materials and it is capable to predict sample shrinkage and surface deformation during
the drying process. It can be applied to any sample geometry (discoid, cylindrical, cubic, parallelepiped) and to
any food material since it can take into account that sample volume can decrease of a quantity that can be
smaller, equal or larger than the corresponding volume of removed water.