Search results for "volte"

Low frequency gray-body factors and infrared divergences: rigorous results

2015

Formal solutions to the mode equations for both spherically symmetric black holes and Bose-Einstein condensate acoustic black holes are obtained by writing the spatial part of the mode equation as a linear Volterra integral equation of the second kind. The solutions work for a massless minimally coupled scalar field in the s-wave or zero angular momentum sector for a spherically symmetric black hole and in the longitudinal sector of a 1D Bose-Einstein condensate acoustic black hole. These solutions are used to obtain in a rigorous way analytic expressions for the scattering coefficients and gray-body factors in the zero frequency limit. They are also used to study the infrared behaviors of …

Timbrel vaults in Sicily: analysis of a little-known construction technique

2016

La ricerca di alternative al legno per la realizzazione di orizzontamenti ha condotto ad approfondimenti e sperimentazioni sulle strutture voltate, con risultati di grande originalità in grado di coniugare economia e leggerezza senza perdere in sicurezza; vengono qui analizzate le volte siciliane costituite da più fogli di mattoni sottili uniti con gesso (volte realine secondo la definizione locale). Già ampiamente documentata nella Spagna tardo-medievale, la tecnica venne introdotta saltuariamente in Sicilia a partire dalla fine del XV secolo, ed assunse un ruolo importante dalla metà del XVIII. Attraverso l’analisi diretta e delle documentazioni relative ai maggiori cantieri e dai prezzia…

Hyers-Ulam Stability of a Nonlinear Volterra Integral Equation on Time Scales

2020

We study Hyers-Ulam stability of a nonlinear Volterra integral equation on unbounded time scales. Sufficient conditions are obtained based on the Banach fixed point theorem and Bielecki type norm.

Spectral Approach to Equivalent Statistical Quadratization and Cubicization Methods for Nonlinear Oscillators

2003

Random vibrations of nonlinear systems subjected to Gaussian input are investigated by a technique based on statistical quadratization, and cubicization. In this context, and depending on the nature of the given nonlinearity, statistics of the stationary response are obtained via an equivalent system with a polynomial nonlinearity of either quadratic or cubic order, which can be solved by the Volterra series method. The Volterra series response is expanded in a trigonometric Fourier series over an adequately long interval T, and exact expressions are derived for the Fourier coefficients of the second- and third-order response in terms of the Fourier coefficients of the first-order, Gaussian…

On the translation of the three fundamental problems of elastic equilibrium of anisotropic bodies into systems of Fredholm first kind integral equati…

1972

Environmental Metal Pollution Considered as Noise: Effects on the Spatial Distribution of Benthic Foraminifera in two Coastal Marine Areas of Sicily …

2008

We analyze the spatial distributions of two groups of benthic foraminifera (Adelosina spp. + Quinqueloculina spp. and Elphidium spp.), along Sicilian coast, and their correlation with six different heavy metals, responsible for the pollution. Samples were collected inside the Gulf of Palermo, which has a high level of pollution due to heavy metals, and along the coast of Lampedusa island (Sicily Channel, Southern Mediterranean), which is characterized by unpolluted sea waters. Because of the environmental pollution we find: (i) an anticorrelated spatial behaviour between the two groups of benthic foraminifera analyzed; (ii) an anticorrelated (correlated) spatial behaviour between the first …

«Per non dar moto alle fabriche»: l'ingegnere regio Scipione Basta e la costruzione della cappella Roano nel duomo di Monreale

2015

«PER NON DAR MOTO ALLE FABBRICHE»: THE ROYAL ENGINEER SCIPIONE BASTA AND THE CONSTRUCTION OF THE ROANO CHAPEL IN THE CATHEDRAL OF MONREALE. In December 1686 the Royal Engineer Scipione Basta, a personality still largely to be investigated but which seems to portend a specific expertise in techno-constructive issues and in particular in structural reinforcement, was appointed by the Viceroyal Government to draw up a technical report concerning some delicate constructive aspects of the project of the architect fra Giovanni da Monreale for the chapel commissioned by the archbishop Roano for the cathedral. Due to the particular configuration of the building to be constructed –a domed octagonal …

Existence and uniqueness of nontrivial collocation solutions of implicitly linear homogeneous Volterra integral equations

2011

We analyze collocation methods for nonlinear homogeneous Volterra-Hammerstein integral equations with non-Lipschitz nonlinearity. We present different kinds of existence and uniqueness of nontrivial collocation solutions and we give conditions for such existence and uniqueness in some cases. Finally we illustrate these methods with an example of a collocation problem, and we give some examples of collocation problems that do not fit in the cases studied previously.

Intracrystalline Diffusion of Benzene in Ga-Silicate

1991

Abstract The sorption kinetics of benzene in large Ga-MFI crystals was investigated under constant volume- variable pressure conditions. A complete analysis of the uptake curves has been performed using solution of a nonlinear Volterra equation which describes the interaction of uptake process with the apparatus. Within the time scale of uptake measurements (10 3 -10 4 s) the uptake curves were found to be consistent with the solution of the second Fick's law. Corrected diffusion coefficients were found to be essentially independent of loading within the loading range investigated and in contrast to the system benzene-HNaZSM-5 [1,2] their temperature dependence is much stronger.

Non-Lipschitz Homogeneous Volterra Integral Equations

2018

In this chapter we introduce a class of nonlinear Volterra integral equations (VIEs) which have certain properties that deviate from the standard results in the field of integral equations. Such equations arise from various problems in shock wave propagation with nonlinear flux conditions. The basic equation we will consider is the nonlinear homogeneous Hammerstein–Volterra integral equation of convolution type $$\displaystyle u(t) = \int _0^t k(t-s) g(u(s))\,\mathrm {d}s. $$ When g(0) = 0, this equation has function u ≡ 0 as a solution (trivial solution). It is interesting to determine whether there exists a nontrivial solution or not. Classical results on integral equations are not to be …