1,721,095 research outputs found
Data-Driven Kernel Designs for Optimized Greedy Schemes: A Machine Learning Perspective
Full text linkThanks to their easy implementation via radial basis functions (RBFs), meshfree
kernel methods have proved to be an effective tool for, e.g., scattered data interpolation, PDE collocation, and classification and regression tasks. Their accuracy might depend on a length scale
hyperparameter, which is often tuned via cross-validation schemes. Here we leverage approaches
and tools from the machine learning community to introduce two-layered kernel machines, which
generalize the classical RBF approaches that rely on a single hyperparameter. Indeed, the proposed
learning strategy returns a kernel that is optimized not only in the Euclidean directions, but that
further incorporates kernel rotations. The kernel optimization is shown to be robust by using recently improved calculations of cross-validation scores. Finally, the use of greedy approaches, and
specifically of the vectorial kernel orthogonal greedy algorithm (VKOGA), allows us to construct
an optimized basis that adapts to the data. Beyond a rigorous analysis on the convergence of the
so-constructed two-layered (2L)-KOGA, its benefits are highlighted on both synthesized and real
benchmark dataset
Spectral filtering for the resolution of the Gibbs phenomenon in MPI applications
Full text linkPolynomial interpolation on the node points of Lissajous curves using Chebyshev series is an e effective
way for a fast image reconstruction in Magnetic Particle Imaging. Due to the nature of spectral methods, a
Gibbs phenomenon occurs in the reconstructed image if the underlying function has discontinuities. A possible
solution for this problem are spectral filtering methods acting on the coefficients of the interpolating polynomial.
In this work, after a description of the Gibbs phenomenon in two dimensions, we present an adaptive spectral
filtering process for the resolution of this phenomenon and for an improved approximation of the underlying
function or image. In this adaptive filtering technique, the spectral filter depends on the distance of a spatial
point to the nearest discontinuity. We show the effectiveness of this filtering approach in theory, in numerical
simulations as well as in the application in Magnetic Particle Imaging
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
Short-Circuit Calculations in LV Cold Ironing Systems: Characteristic Currents Method CCM and IEC Method
No full textThis paper presents the calculation procedure of short
circuits adopting the CCM “Characteristic Currents Method”.
In a previous paper by the author Parise, the CCM has been
upgraded with the introduction of "characteristic"
countercurrents and the generalization of the Kirchhoff laws.
For illustrating the calculation procedure, the selected case study
deals with a low voltage cold ironing system where multiple ships
are allowed to operate simultaneously on one shore power
transformer and, so, a comparison has been developed between
the IEC approach of the short-circuit calculation and the CCM
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
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