126,357 research outputs found
2D Navier–Stokes equation with cylindrical fractional Brownian noise
No full textWe consider the Navier–Stokes equation on the 2D torus, with a stochastic forcing term which is a cylindrical fractional Wiener noise of Hurst parameter H . Following Albeverio and Ferrario (Ann Probab 32(2):1632–1649, 2004) and Da Prato and Debussche (J Funct Anal 196(1):180–210, 2002) which dealt with the case H = 1/2 , we prove a local existence
and uniqueness result when 7/16< H < 1/2 and a global existence and uniqueness result when 1/2 < H < 1
Sant'Antonio alla Motta fra Otto e Novecento: restauro, scultura, adeguamento liturgico
No full textNel contributo è ricostruita, con l'ausilio di fonti documentarie inedite, la mai sondata storia otto-novecentesca della chiesa di Sant'Antonio alla Motta di Varese, suffraganea della basilica di San Vittore
On a stochastic version of Prouse model in fluid dynamics
No full textAbstractA stochastic version of modified Navier–Stokes equations (introduced by Prouse) is considered in a three-dimensional torus; its main feature is that instead of the linear term −ν△u of the Navier–Stokes equations there is a nonlinear term −△Φ(u)−∇divΦ(u). First, for this equation we prove existence and uniqueness of martingale solutions; then existence of stationary solutions. In the last part of the paper a new model, obtained from Prouse model with the nonlinearity Φ(u)=ν|u|4u, is analysed; for the structure function of this model, some insights towards an expression similar to that obtained by the Kolmogorov 1941 theory of turbulence are presented
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Stationary solutions for stochastic damped navier-stokes equations in R d
No full textWe consider the stochastic damped Navier-Stokes equations in R^d ( d = 2 , 3), assuming that the covariance of the noise is not too regular, so Itô calculus cannot be applied in the space of finite-energy vector fields. We prove the existence of an invariant measure when d =2 and of a stationary solution when d =3
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Invariant Measures for Stochastic Damped 2D Euler Equations
No full textWe study the two-dimensional Euler equations, damped by a linear term and driven by an additive noise. The existence of weak solutions has already been studied; pathwise uniqueness is known for solutions that have vorticity in L∞. In this paper, we prove the Markov property and then the existence of an invariant measure in the space L∞ by means of a Krylov–Bogoliubov’s type method, working with the weak⋆ and the bounded weak⋆ topologies in L∞
Outils expérimentaux pour l’analyse de la perception sociale dans l’aménagement du territoire : représentation cartographique de « paysages de tendance » dans une étude de cas menée en Vénétie (Italie)
No full textAbsolute continuity of the law for the two dimensional stochastic Navier–Stokes equations
No full textWe consider the two dimensional Navier–Stokes equations in vorticity form with a stochastic forcing term given by a Gaussian noise, white in time and colored in space. First, we prove existence and uniqueness of a weak (in the Walsh sense) solution process ξ and we show that, if the initial vorticity ξ_0 is continuous in space, then there exists a space–time continuous version of the solution. In addition we show that the solution ξ (t, x) (evaluated at fixed points in time and space) is locally differentiable in the Malliavin calculus sense and that its image law is absolutely continuous with respect to the Lebesgue measure on R
Stochastic vorticity equation in R2 with not regular noise
No full textWe consider the Navier–Stokes equations in vorticity form in with a white noise forcing term of multiplicative type, whose spatial covariance is not regular enough to apply the Itô calculus in spaces, 1<<∞. We prove the existence of a unique strong (in the probability sense) solution
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