1,721,016 research outputs found
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
Análisis comparativo de estrategias numéricas para problemas aeroespaciales de control óptimo
No full textLa teoría de optimización se ha venido desarrollando desde el siglo XVII desde el llamado problema de la braquistócrona planteado por Bernoulli, sin embargo, ha sido hasta la mitad del siglo XX que se ha comenzado a implementar en problemas de aeronáutica y aeroespaciales. Ya que fue a mediados de este siglo que se desarrollaron las importantes contribuciones de Pontryagin (con el Principio del Mínimo) y Bellman (en optimización mediante programación no lineal), lo cual permitió el desarrollo de la teoría de control óptimo basada en el cálculo de variaciones. A partir de entonces y paralelamente al desarrollo del control óptimo se ha desarrollado una serie de métodos numéricos que buscan obtener la solución aproximada a un problema ya que en la mayoría de los casos no es posible encontrar soluciones analíticas debido a la complejidad de los modelos matemáticos que describen el proceso. Existen tres principales enfoques o también llamados métodos para plantear los problemas de control óptimo, los cuales son el método directo, el método indirecto y la programación no lineal. Los principales enfoques utilizados actualmente son el método indirecto y el método directo. Dependiendo del enfoque que se desee implementar en un problema de control óptimo se contará con una serie de alternativas numéricas para dar con una solución aproximada al problema. Actualmente existen líneas de investigación dedicadas a mejorar las técnicas numéricas o investigar bajo qué circunstancias funcionan mejor los principales dos enfoques para los problemas de control óptimo. Este trabajo busca comparar dos técnicas aplicadas en problemas aeroespaciales, por un lado está el método de colocación implementado en BVP4C de Matlab y por otro el método pseudo espectral implementado en DIDO en Matlab. Ambos métodos convergieron a soluciones validas en los problemas planteados, presentando diferencias en cuanto a precisión, tiempo de corrida, razón de convergencia y sensibilidad a la estimación inicial. De este trabajo se desprende que el método de colocación es más rápido en tiempo de corrida, pero presenta alta sensibilidad a la estimación inicial lo cual no es raro para cualquier método numérico empleado bajo el enfoque indirecto de control óptimo
Improving the efficiency of algebraic subspace clustering through randomized low-rank matrix approximations
No full textIn many research areas, such as computer vision, image processing, pattern recognition,
or systems identification, the segmentation of heterogeneous high-dimensional data sets is
one of the most common and important tasks. Based on the subspace clustering approach,
the Generalized Principal Component Analysis (GPCA) is an algebraic-geometric method
that attempts to perform this task. However, due to GPCA requires performing matrix
decompositions whose computational cost is cubic with respect to the size of the matrix (in
the worst case), the data segmentation becomes expensive when such size is very large.
Consequently, the present thesis work is intended to support our initial hypothesis: it
is possible to find matrix decompositions via randomized schemes that not only reduce
the computational costs, but also they maintain the effectiveness of their results. This
allows GPCA to manipulate both large and heterogeneous high-dimensional data sets, and
thus GPCA can enter into domains where its applicability has been partially or totally
restricted
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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