1,721,036 research outputs found
Hausdorff moment problem and Maximum Entropy: On the existence conditions
No full textDifferent existence conditions of the Maximum Entropy solution to finite Hausdorff moment problem have been formulated in literature. Through a counterexample we prove that the most cited one is uncorrect. We do not bound ourselves to a crude counterexample, as we think that a detailed explanation is of interest by itself. It clarifies the difference existing between the finite and infinite Hausdorff moment problem existence conditions
Recurrence Time Distributions: A Discussion
No full textSome theoretical properties implied by "Predictable Modele" are enlighted and diecussed. In particular
the aspects of interest in short-time prediction are shown.
A few italian zones are analyzed. Results obtained in previous paper are prensented: the residual
uncertainties are discussed here, especially about the "tail" values of dietributions.
Because of the poor phyical knawledge the acceptabiity of a model is rather debatable. A comparison
with maximum entropy densities estimation and with bayesian non parametric inference gives useful
suggestions about the acceptability
Stochasticity thresholds in a lattice field theory
No full textSi considera un sistema di oscillatori con un accoppiamento che è suggerito, per approssimazione reticolare, da un semplice modello di interesse nella teoria relativistica dei campi classica e quantistica, e se ne dà una stima numerica delle soglie di stocasticità. I risultati trovati sono qualitativamente in accordo con quelli già noti per sistemi di oscillatori accoppiati che vengono tipicamente considerati nell'ambito dei fondamenti dinamici della meccanica statistica, come il modello di Fermi-Pasta-Ulam.We consider a system of oscillators with a coupling which is suggested, through lattice approximation, by a simple model of interest in classical and quantum-relativistic field theory, and give a numerical estimate of its stochasticity thresholds. The results found are qualitatively in agreement with those already known for systems of coupled oscillators which are typically considered in the framework of the dynamical foundations of statistical mechanics, such as the Fermi-Pasta-Ulam model. © 1980 Società Italiana di Fisica
Spectral-domain decomposition methods for the solution of acoustic and elastic wave equations
No full textA new spectral-domain decomposition method is presented for acoustic and elastodynamic wave propagation in 2-D heterogeneous media. Starting from a variational formulation of the problem, two different approaches are proposed for the spatial discretization: a mixed Fourier-Legendre and a full Legendre collocation. The matching conditions at subdomain interfaces are carefully analyzed, and the stability and efficiency of time-advancing schemes are investigated. The numerical validation with some significant test cases illustrates the accuracy, flexibility, and robustness of our methods. These allow the treatment of complex geometries and heterogeneous media while retaining spectral accuracy
Generalized Galerkin approximations of elastic waves with absorbing boundary conditions
No full textFor the propagation of elastic waves in unbounded domains, absorbing boundary conditions (ABCs) at the fictitious numerical boundaries have been proposed. In this paper we focus on both first-and second-order ABCs in the framework of variational (weak) approximations, like those stemming from Galerkin method (or its variants) for finite element or spectral approximations [1]. In particular, we recover first order conditions as natural (or Neumann) conditions, whereas we propose a penalty residual method for the treatment of second order ABCs. The time discretization is based on implicit backward finite differences, whereas we use spectral Legendre collocation methods set in a variational form for the spatial discretization (treatment of finite element or spectral element approximations is completely similar). Numerical experiments exhibit that the present formulation of second-order ABCs improves the one based on first-order ABCs with regard to both the reduction of the total energy in the computational domain, and the Fourier spectrum of the displacement field at selected points of the elastic medium. A stability analysis is developed for the variational problem in the continuous case both for first-and second-order ABCs, A suitable treatment of ABCs at corners is also proposed. © 1998 Elsevier Science S.A. All rights reserved
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
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