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Search Results: 1 - 10 of 7692 matches for " Claudio Floris "
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Numeric Solution of the Fokker-Planck-Kolmogorov Equation  [PDF]
Claudio Floris
Engineering (ENG) , 2013, DOI: 10.4236/eng.2013.512119

The solution of an n-dimensional stochastic differential equation driven by Gaussian white noises is a Markov vector. In this way, the transition joint probability density function (JPDF) of this vector is given by a deterministic parabolic partial differential equation, the so-called Fokker-Planck-Kolmogorov (FPK) equation. There exist few exact solutions of this equation so that the analyst must resort to approximate or numerical procedures. The finite element method (FE) is among the latter, and is reviewed in this paper. Suitable computer codes are written for the two fundamental versions of the FE method, the Bubnov-Galerkin and the Petrov-Galerkin method. In order to reduce the computational effort, which is to reduce the number of nodal points, the following refinements to the method are proposed: 1) exponential (Gaussian) weighting functions different from the shape functions are tested; 2) quadratic and cubic splines are used to interpolate the nodal values that are known in a limited number of points. In the applications, the transient state is studied for first order systems only, while for second order systems, the steady-state JPDF is determined, and it is compared with exact solutions or with simulative solutions: a very good agreement is found.

Random Response of a Strongly Nonlinear Oscillator with Internal and External Excitations  [PDF]
Claudio Floris
Journal of Applied Mathematics and Physics (JAMP) , 2019, DOI: 10.4236/jamp.2019.72025
Abstract: A second order oscillator with nonlinear restoring force and nonlinear damping is considered: it is subject to both external and internal (parametric) excitations of Gaussian white noise type. The nonlinearities are chosen in such a way that the associated Fokker-Planck-Kolmogorov equation is solvable in the steady state. Different choices of some system parameters give rise to different and interesting shapes of the joint probability density function of the response, which in some cases appears to be multimodal. The problem of the determination of the power spectral density of the response is also addressed by using the true statistical linearization method.
Stochastic Stability of Damped Mathieu Oscillator Parametrically Excited by a Gaussian Noise
Claudio Floris
Mathematical Problems in Engineering , 2012, DOI: 10.1155/2012/375913
Abstract: This paper analyzes the stochastic stability of a damped Mathieu oscillator subjected to a parametric excitation of the form of a stationary Gaussian process, which may be both white and coloured. By applying deterministic and stochastic averaging, two Itô’s differential equations are retrieved. Reference is made to stochastic stability in moments. The differential equations ruling the response statistical moment evolution are written by means of Itô’s differential rule. A necessary and sufficient condition of stability in the moments of order r is that the matrix of the coefficients of the ODE system ruling them has negative real eigenvalues and complex eigenvalues with negative real parts. Because of the linearity of the system the stability of the first two moments is the strongest condition of stability. In the case of the first moments (averages), critical values of the parameters are expressed analytically, while for the second moments the search for the critical values is made numerically. Some graphs are presented for representative cases.
On the Effects of Different Interpretations of Stochastic Differential Equations  [PDF]
Claudio Floris
Applied Mathematics (AM) , 2019, DOI: 10.4236/am.2019.1011063
Abstract: This paper addresses the problem of the interpretation of the stochastic differential equations (SDE). Even if from a theoretical point of view, there are infinite ways of interpreting them, in practice only Stratonovich’s and Itô’s interpretations and the kinetic form are important. Restricting the attention to the first two, they give rise to two different Fokker-Planck-Kolmogorov equations for the transition probability density function (PDF) of the solution. According to Stratonovich’s interpretation, there is one more term in the drift, which is not present in the physical equation, the so-called spurious drift. This term is not present in Itô’s interpretation so that the transition PDF’s of the two interpretations are different. Several examples are shown in which the two solutions are strongly different. Thus, caution is needed when a physical phenomenon is modelled by a SDE. However, the meaning of the spurious drift remains unclear.
Palmar Intertriradial Ridge Counts in Sardinians  [PDF]
Giovanni Floris
Advances in Anthropology (AA) , 2015, DOI: 10.4236/aa.2015.53012
Abstract: Palmar intertriradial ridge counts (a-b, b-c, c-d, a-d) in 260 males and 260 females of Sardinian origin were considered. Bilateral and sex differences, correlation coefficients, skewness and kurtosis of the four distributions and an index of asymmetry were calculated. There are no sex differences, ridge counts show positive and almost always significant correlations. The a-d ridge count shows a normal distribution in both sexes.
Palmar Dermatoglyphics of Corsicans and Comparison with Those of Sardinians  [PDF]
G. Floris, C. M. Calò
Advances in Anthropology (AA) , 2018, DOI: 10.4236/aa.2018.84014
Abstract: We report on five dermatoglyphic traits recorded on palm prints in sample of Sardinians and Corsicans. The two populations are very similar but not identical.
Een natie van verwijfde moederskindjes, Wagneraanbidders en heldhaftige Romeinen. Vier publicaties over de Italiaanse cultuurpolitiek na het Risorgimento
Floris Meens
Incontri : Rivista Europea di Studi Italiani , 2013,
Tomo II: La valutazione come riferimento per la pianificazione: Cagliari e il suo contesto - Cagliari: da capitale del Mediterraneo a capitale nel Mediterraneo
Emilio Floris
Aestimum , 2003,
Hadron yields and the phase diagram of strongly interacting matter
Michele Floris
Physics , 2014, DOI: 10.1016/j.nuclphysa.2014.09.002
Abstract: This paper presents a brief review of the interpretation of measurements of hadron yields in hadronic interactions within the framework of thermal models, over a broad energy range (from SIS to LHC energies, $\sqrt{s_{NN}} \simeq$ 2.5 GeV -- 5 TeV). Recent experimental results and theoretical developments are reported, with an emphasis on topics discussed during the Quark Matter 2014 conference.
Fundamental divisors on Fano varieties of index n-3
Enrica Floris
Mathematics , 2010,
Abstract: Let X be a Fano manifold of dimension n and index n-3. Kawamata proved the non vanishing of the global sections of the fundamental divisor in the case n=4. Moreover he proved that if Y is a general element of the fundamental system then Y has at most canonical singularities. We prove a generalization of this result in arbitrary dimension.
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