1,721,096 research outputs found
Discontinuous Galerkin approximation of the Maxwell eigenproblem
Full text linkA theoretical framework for the analysis of discontinuous Galerkin
approximations of the Maxwell eigenproblem with discontinuous coefficients is
presented. Necessary and sufficient conditions for a spurious-free
approximation are established, and it is shown that, at least on conformal
meshes, basically all the discontinuous Galerkin methods in the literature
actually fit into this framework. Relations with the classical theory for
conforming approximations are also discussed
A fast algorithm for determining the propagation path of multiple diffracted rays
No full textWe present a fast algorithm for path computation of multiple diffracted rays relevant to ray tracing techniques. The focus is on double diffracted rays, but generalizations are also mentioned. The novelty of our approach is in the use of an analytical geometry procedure which permits to re-write the problem as a simple nonlinear equation. This procedure permits a convergence analysis of the algorithms involved in the numerical resolution of such nonlinear equation. Moreover, we also indicate how to choose the iteration starting point to obtain convergence of the (locally convergent) Newton method. As in previous works, explicit solutions are obtained in the relevant cases of parallel or incident diffraction edges. © 2007 IEEE
IsoGeometric Analysis: A New Paradigm in the Numerical Approximation of PDEs Cetraro, Italy 2012 Preface
No full textA plastic optical fiber sensor for vibration measurements
No full textAn innovative low-cost, intensity-based optical sensing system to measure vibrations is presented. The developed system uses a cheap setup based on plastic optical fibers and non-demanding data processing to measure the amplitude of vibrations, independently from the vibrating surface reflectivity. Moreover the proposed approach is able to operate at much higher frequencies than most of currently available setups. Preliminary measurement campaigns using multicolored vibrating surfaces have been carried-out to assess the performance of the syste
Apparatus for multipoint Thomson scattering measurements in the ETA BETA II Reverse Field Pinch experiment
No full textA multipoint Thomson scattering apparatus under development for the measurement of spatial Te and ne profiles in the ETA-BETA II reverse field pinch experiment is described. The apparatus is based upon the two-channel analysis method already adopted in the TFR tokamak. The 90°scattered light is collected simultaneously from seven spatial positions along a plasma diameter by means of high-efficiency, quartz, fiber-optic light guides. The detection system consists of a set of high aperture (f/2.4), plane grating, Littrow spectrometers developed to match the high throughput of the collection optics. These instruments employ photomultipliers with a GaAs photocathode (quantum efficiency approximately-equal-to 20%, λ=700 nm) and have a stray light rejection ratio of 3×10-4. Laboratory tests and preliminary measurements in ETA-BETA II have shown good sensitivity and a S/N ratio sufficient to diagnose plasmas with n e≥1013 cm-3
Moment equations for the mixed formulation of the Hodge Laplacian with stochastic loading term
Full text linkWe study the mixed formulation of the stochastic Hodge-Laplace problem defined on an n-dimensional domain D (n≥ 1), with random forcing term. In particular, we focus on the magnetostatic problem and on the Darcy problem in the three-dimensional case. We derive and analyse the moment equations, that is, the deterministic equations solved by the mth moment (m≥ 1) of the unique stochastic solution of the stochastic problem. We find stable tensor product finite element discretizations, both full and sparse, and provide optimal order-of-convergence estimates. In particular, we prove the inf-sup condition for sparse tensor product finite element spaces
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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