1,720,988 research outputs found
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
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∞
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
Ergodic results for the stochastic nonlinear Schrödinger equation with large damping
Full text linkWe study a nonlinear Schrödinger equation with a linear damping, i.e. a zero-order dissipation, and an additive noise. Working in R^d with d _ < 3 we we prove the uniqueness of the invariant measure when the damping coefficient is sufficiently large
Absolute continuity of the law for the two dimensional stochastic Navier–Stokes equations
Full text linkWe 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
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
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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