Now showing items 6-25 of 35

    • Darrieus-Landau instabilities in the framework of the G-equation 

      Pagnini G.; Trucchia A. (Digital proceedings of the 8th European Combustion Meeting, 18-21 April 2017, Dubrovnik, Croatia, 2017-04)
      We consider a model formulation of the flame front propagation in turbulent premixed combustion based on stochastic fluctuations imposed to the mean flame position. In particular, the mean flame motion is described by ...
    • Effective self-similar expansion for the Gross-Pitaevskii equation 

      Modugno M.; Pagnini G.; Valle-Basagoiti M. A. (Physical Review A, 2018-04)
      We consider an effective scaling approach for the free expansion of a one-dimensional quantum wave packet, consisting in a self-similar evolution to be satisfied on average, i.e., by integrating over the coordinates. A ...
    • Fractional kinetics emerging from ergodicity breaking in random media 

      Molina-García D.; Minh Pham T.; Paradisi P.; Manzo C.; Pagnini G. (Physical Review E, 2016)
      We present a modelling approach for diffusion in a complex medium characterized by a random lengthscale. The resulting stochastic process shows subdiffusion with a behavior in qualitative agreement with single particle ...
    • Fractional relaxation with time-varying coefficient 

      Garra R.; Giusti A.; Mainardi F.; Pagnini G. (Fractional Calculus and Applied Analysis, 2014-12-31)
      From the point of view of the general theory of the hyper-Bessel operators, we consider a particular operator that is suitable to generalize the standard process of relaxation by taking into account both memory effects of ...
    • From G - Equation to Michelson - Sivashinsky Equation in Turbulent Premixed Combustion Modelling 

      Pagnini G. (Proceedings/Extended Abstract Book (6 pages) of the XXXIX Meeting of the Italian Section of the Combustion Institute, Naples, Italy, 2017-06-20)
      It is well known that the Michelson-Sivashinky equation describes hydrodynamic instabilities in turbulent premixed combustion. Here a formulation of the flame front propagation based on the G-equation and on stochastic ...
    • Front Curvature Evolution and Hydrodynamics Instabilities 

      Pagnini G.; Trucchia A. (Proceedings/Extended Abstract Book (6 pages) of the XXXX Meeting of the Italian Section of the Combustion Institute, Rome, Italy, 2017-06-07)
      It is known that hydrodynamic instabilities in turbulent premixed combustion are described by the Michelson-Sivashinsky (MS) equation. A model of the flame front propagation based on the G-equation and on stochastic ...
    • Front propagation in anomalous diffusive media governed by time-fractional diffusion 

      Mentrelli A.; Pagnini G. (Journal of Computational Physics, 2014-12-31)
      In this paper, a multi-dimensional model is proposed to study the propagation of random fronts in media in which anomalous diffusion takes place. The front position is obtained as the weighted mean of fronts calculated by ...
    • Langevin equation in complex media and anomalous diffusion 

      Vitali S.; Sposini V.; Sliusarenko O.; Paradisi P.; Castellani G.; Pagnini G. (Journal of the Royal Society Interface, 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 ...
    • Modeling anomalous heat diffusion: Comparing fractional derivative and non-linear diffusivity treatments 

      Falcini F.; Garra R.; Voller V. (International Journal of Thermal Sciences, 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 

      Ponta L.; Trinh M.; Raberto M.; Scalas E.; Cincotti S. (Physica A: Statistical Mechanics and its Applications, 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 

      Vitali S. (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 

      Mentrelli A.; Pagnini G. (Ricerche di Matematica, 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 

      Pagnini G.; Mentrelli A. (Natural Hazards and Earth System Sciences, 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 

      Fakharany M.; Egorova V.; Company R. (Journal of Computational and Applied Mathematics, 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 ...
    • Quasi-probability Approach for Modelling Local Extinction and Counter-gradient in Turbulent Premixed Combustion 

      Pagnini G.; Trucchia A. (Proceedings/Extended Abstract Book (6 pages) of the XLI Meeting of the Italian Section of the Combustion Institute, 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 ...
    • Random diffusivity from stochastic equations: comparison of two models for Brownian yet non-Gaussian diffusion 

      Sposini V.; Chechkin A. V.; Seno F.; Pagnini G.; Metzler R. (New Journal of Physics, 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+ 

      Trucchia A.; Egorova V.; Butenko A.; Kaur I.; Pagnini G. (Geoscientific Model Development, 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 ...
    • The role of the environment in front propagation 

      Trucchia A.; Pagnini G. (Proceedings of the 18th International Conference on Computational and Mathematical Methods in Science and Engineering, CMMSE 2018 July 9–14, 2018, 2018-07-09)
      In this work we study the role of a complex environment in the propagation of a front with curvature-dependent speed. The motion of the front is split into a drifting part and a fluctuating part. The drifting part is ...
    • Scaling law of diffusivity generated by a noisy telegraph signal with fractal intermittency 

      Paradisi P.; Allegrini P. (Chaos, Solitons and Fractals, 2015-12-31)
      In many complex systems the non-linear cooperative dynamics determine the emergence of self-organized, metastable, structures that are associated with a birth-death process of cooperation. This is found to be described by ...
    • Self-similar stochastic models with stationary increments for symmetric space-time fractional diffusion 

      Pagnini G. (MESA 2014 - 10th IEEE/ASME International Conference on Mechatronic and Embedded Systems and Applications, Conference Proceedings, 2014-12-31)
      An approach to develop stochastic models for studying anomalous diffusion is proposed. In particular, in this approach the stochastic particle trajectory is based on the fractional Brownian motion but, for any realization, ...