Search results for "Matematica"

Phase transition and lambda-line in liquid helium

2013

A hydrodynamical model describing the superfluid phase transition of 4He close to $\lambda$-line is presented. In the work, which generalizes a phase field model of lambda transition previously formulated by the same authors, the independent fields are the density, the temperature, the velocity, the heat flux and a scalar function $f$, linked to the modulus of the wave-function $\psi$, solution of the Ginzburg-Landau equation. In this framework, the heat flux is given by a modified Maxwell-Cattaneo equation. The restrictions on the constitutive quantities are obtained from the entropy principle, using the Liu method of Lagrange multipliers. A maximum theorem is proved that allows the model …

Local uniqueness of the solutions for a singularly perturbed nonlinear nonautonomous transmission problem

2020

Abstract We consider the Laplace equation in a domain of R n , n ≥ 3 , with a small inclusion of size ϵ . On the boundary of the inclusion we define a nonlinear nonautonomous transmission condition. For ϵ small enough one can prove that the problem has solutions. In this paper, we study the local uniqueness of such solutions.

Inversion formulae for the integral transform on a locally compact zero-dimensional group

2009

Abstract Generalized inversion formulae for multiplicative integral transform with a kernel defined by characters of a locally compact zero-dimensional abelian group are obtained using a Kurzweil-Henstock type integral.

Brain-predicted age difference score is related to specific cognitive functions: A multi-site replication analysis

2021

Abstract Brain-predicted age difference scores are calculated by subtracting chronological age from ‘brain’ age. Positive scores reflect accelerated ageing and are associated with increased mortality risk and poorer physical function. To date, however, the relationship between brain-predicted age difference scores and specific cognitive functions has not been systematically examined. First, applying machine learning to 1,359 T1-weighted MRI scans, we predicted the relationship between chronological age and voxel-wise grey matter data. This model was then applied to MRI data from three independent datasets, significantly predicting chronological age: Dokuz Eylul University (n=175), the Cogni…

Didactics of mathematics and architecture: the golden ratio in la Lonja de Valencia

2016

[EN] This paper has a twofold purpose. First, to structure and relate a teaching experience on the tutoring of a graduation work in Mathematics made in the University of Valencia. The main property of the didactic purpose involved in the project is that it deals with the geometric properties of a landmark building of the city of Valencia. Our aim is to analyze the process of formulation, firming up, documentation and elaboration of the work that was followed during this experience. Second, to analyze the methodology used to obtain and valuate the results that come from one of the fundamental parts of this work: the harmonic decomposition of the building named Lonja de la Seda in Valencia

Integration by parts for the Lr Henstock-Kurzweil integral

2015

Musial and Sagher [4] described a Henstock-Kurzweil type integral that integrates Lr-derivatives. In this article, we develop a product rule for the Lr-derivative and then an integration by parts formula.

Luigi Cremona's Years in Bologna: From Research to Social Commitment

2012

Luigi Cremona (1830-1903), unanimously considered to be the man who laid the foundations of the prestigious Italian school of Algebraic Geometry, was active at the University of Bologna from October 1860,when assigned by the Minister Terenzio Mamiani (1799-1885) to cover the Chair of Higher Geometry, until September 1867 when Francesco Brioschi (1824-1897) called it to the Politecnico di Milano. The "Bolognese years" were Cremona's richest and most significant in terms of scientific production,and, at the same time, were the years when he puts the basis for its most important interventions in the social and political life of the "newborn" kingdom of Italy. In this article we present these d…

A generalized Degn–Harrison reaction–diffusion system: Asymptotic stability and non-existence results

2021

Abstract In this paper we study the Degn–Harrison system with a generalized reaction term. Once proved the global existence and boundedness of a unique solution, we address the asymptotic behavior of the system. The conditions for the global asymptotic stability of the steady state solution are derived using the appropriate techniques based on the eigen-analysis, the Poincare–Bendixson theorem and the direct Lyapunov method. Numerical simulations are also shown to corroborate the asymptotic stability predictions. Moreover, we determine the constraints on the size of the reactor and the diffusion coefficient such that the system does not admit non-constant positive steady state solutions.

A personality mathematical model of placebo with or without deception: an application of the Self-Regulation Therapy

2019

A DERIVATION OF THE VLASOV-NAVIER-STOKES MODEL FOR AEROSOL FLOWS FROM KINETIC THEORY

2016

This article proposes a derivation of the Vlasov-Navier-Stokes system for spray/aerosol flows. The distribution function of the dispersed phase is governed by a Vlasov-equation, while the velocity field of the propellant satisfies the Navier-Stokes equations for incompressible fluids. The dynamics of the dispersed phase and of the propellant are coupled through the drag force exerted by the propellant on the dispersed phase. We present a formal derivation of this model from a multiphase Boltzmann system for a binary gaseous mixture, involving the droplets/dust particles in the dispersed phase as one species, and the gas molecules as the other species. Under suitable assumptions on the colli…