Now showing items 21-40 of 60

• #### Gaussian processes in complex media: new vistas on anomalous diffusion ﻿

(2019-09)
Normal or Brownian diffusion is historically identified by the linear growth in time of the variance and by a Gaussian shape of the displacement distribution. Processes departing from the at least one of the above conditions ...
• #### A generalized Stefan model accounting for system memory and non-locality ﻿

(2020-05)
The Stefan problem, involving the tracking of an evolving phase-change front, is the prototypical example of a moving boundary problem. In basic one- dimensional problems it is well known that the front advances as the ...
• #### Gut microbiota ecology: Biodiversity estimated from hybrid neutral-niche model increases with health status and aging ﻿

(2020-10-30)
In this work we propose an index to estimate the gut microbiota biodiversity using a modeling approach with the aim of describing its relationship with health and aging. The gut microbiota, a complex ecosystem that links ...
• #### A hypothesis about parallelism vs. seriality in dreams ﻿

(2019-10-10)
The current article discusses the hypothesis about parallelism vs. Seriality in dreams. The process of dream building implies the construction of a complex network of closely interrelated sources. On the other hand, the ...
• #### Langevin equation in complex media and anomalous diffusion ﻿

(2018-07-30)
The problem of biological motion is a very intriguing and topical issue. Many efforts are being focused on the development of novel modelling approaches for the description of anomalous diffusion in biological systems, such ...
• #### The M-Wright function as a generalization of the Gaussian density for fractional diffusion processes ﻿

(2013-12-31)
The leading role of a special function of the Wright-type, referred to as M-Wright or Mainardi function, within a parametric class of self-similar stochastic processes with stationary increments, is surveyed. This class ...
• #### Modeling anomalous heat diffusion: Comparing fractional derivative and non-linear diffusivity treatments ﻿

(2018-11)
In the Fourier heat conduction equation, when the flux definition is expressed as the product of a constant diffusivity and the temperature gradient, the characteristic length scale evolves as the square root of time. ...
• #### Modeling non-stationarities in high-frequency financial time series ﻿

(2019-01)
We study tick-by-tick financial returns for the FTSE MIB index of the Italian Stock Exchange (Borsa Italiana). We confirm previously detected non-stationarities. Scaling properties reported before for other high-frequency ...
• #### Modeling of birth-death and diffusion processes in biological complex environments ﻿

(2018-04-20)
This thesis is centered on the theory of stochastic processes and their applications in biological systems characterized by a complex environment. Three case studies have been modeled by the use of the three fundamental ...
• #### Modelling and simulation of wildland fire in the framework of the level set method ﻿

(2016-01-01)
Among the modelling approaches that have been proposed for the simulation of wildfire propagation, two have gained considerable attention in recent years: the one based on a reaction-diffusion equation, and the one based ...
• #### Modelling wildland fire propagation by tracking random fronts ﻿

(2014-12-31)
Abstract. Wildland fire propagation is studied in the liter- ature by two alternative approaches, namely the reaction– diffusion equation and the level-set method. These two ap- proaches are considered alternatives to each ...
• #### Numerical valuation of two-asset options under jump diffusion models using Gauss-Hermite quadrature ﻿

(2017-04-19)
In this work a finite difference approach together with a bivariate Gauss–Hermite quadrature technique is developed for partial integro-differential equations related to option pricing problems on two underlying asset ...
• #### On the merits of sparse surrogates for global sensitivity analysis of multi-scale nonlinear problems: Application to turbulence and fire-spotting model in wildland fire simulators ﻿

(2019-02)
Many nonlinear phenomena, whose numerical simulation is not straightforward, depend on a set of parameters in a way which is not easy to predict beforehand. Wildland fires in presence of strong winds fall into this category, ...
• #### On the propagation of nonlinear transients of temperature and pore pressure in a thin porous boundary layer between two rocks. ﻿

(2019)
The dynamics of transients of fluid-rock temperature, pore pressure, pollutants in porous rocks are of vivid interest for fundamental problems in hydrological, volcanic, hydrocarbon systems, deep oil drilling. This can ...
• #### Quasi-probability Approach for Modelling Local Extinction and Counter-gradient in Turbulent Premixed Combustion ﻿

(2018-05-23)
In opposition to standard probability distributions, quasi-probability distributions can have negative values which highlight nonclassical properties of the corresponding system. In quantum mechanics, such negative values ...
• #### The random diffusivity approach for diffusion in heterogeneous systems ﻿

(2020-12-16)
The two hallmark features of Brownian motion are the linear growth $\langle x^2(t) \rangle = 2 D d t$ of the mean squared displacement (MSD) with diffusion coefficient $D$ in $d$ spatial dimensions, and the Gaussian ...
• #### Random diffusivity from stochastic equations: comparison of two models for Brownian yet non-Gaussian diffusion ﻿

(2018-04)
A considerable number of systems have recently been reported in which Brownian yet non-Gaussian dynamics was observed. These are processes characterised by a linear growth in time of the mean squared displacement, yet the ...
• #### RandomFront 2.3 A physical parametrisation of fire-spotting for operational fire spread models: Implementation in WRF-Sfire and response analysis with LSFire+ ﻿

(2018-12)
Fire-spotting is often responsible for a dangerous flare up in the wildfire and causes secondary ignitions isolated from the primary fire zone leading to perilous situations. The main aim of the present research to provide ...
• #### Reduced description method in the kinetic theory of Brownian motion with active fluctuations ﻿

(2019-09-01)
We develop a microscopic approach to the kinetic theory of many-particle systems with dissipative and potential interactions in presence of active fluctuations. The approach is based on a generalization of Bogolyubov–Peletminskii ...
• #### A renewal model for the emergence of anomalous solute crowding in liposomes ﻿

(2015-12-31)
A fundamental evolutionary step in the onset of living cells is thought to be the spontaneous formation of lipid vesicles (liposomes) in the pre-biotic mixture. Even though it is well known that hydrophobic forces drive ...