1,720,980 research outputs found
GAUSS QUADRATURE FOR LINEAR FUNCTIONALS AND NEW SEQUENCE TRANSFORMATIONS
Full text linkThis thesis is divided into two parts. In the first one we present an extension of the Gauss quadrature formula for the approximation of the quasi definite linear functionals. This extension is obtained using the orthogonal polynomials theory and, in particular, using the relation between sequences of these polynomials and some matrices called Jacobi matrices. We call this proposed formula n-weight Gauss quadrature and we show that it satisfies all the main properties of the “classical” formula, which we call n-node Gauss quadrature. Furthermore, we show that the proposed quadrature can be computed by the non-Hermitian Lanczos algorithm, in the same way in which the n-node Gauss quadrature can be computed by the Hermitian Lanczos algorithm. In the last chapter of the first part we present some preliminary results about possible applications. We approximate the centrality indexes of a complex network. These are indexes that measure the importance of a node in terms of communicability in a graph.
In the second part we propose some sequence transformations. Using sequence transformations we can use the elements of a sequence to obtain another sequence which converges faster to the same limit of the original one. Indeed, in numerical analysis and applied mathematics we often consider sequences arising, for example, from iterative methods that converge so slowly that they become useless. It has been proved that there cannot exist a transformation able to accelerate every sequence. Moreover, usually better results are given by transformations which are built to accelerate little classes of sequences. For this reason in the second chapter of this part we define three new transformations able to accelerate a class of sequences which extends the class of the well-known Aitken's process. We then consider the best of the three transformations and give some necessary conditions under which it accelerates the convergence of a given sequence. Finally, this transformation is compared with some of the most used transformations (Aitken's process, ε-algorithm, θ-algorithm, Levin type transformation) obtaining competitive results
Generalizations of Aitken's process for a certain class of sequences
No full textIn this paper, we construct several sequence transformations whose kernels contain sequences of the form S-n = S+a(n)lambda(n), n = 0, 1,, where S and lambda are unknown parameters, and (an) is a known sequence. These transformations generalize Aitken's Delta(2) process. We provide certain sufficient conditions under which one of our transformations accelerates the convergence of certain types of sequences. Finally, we illustrate these theoretical results through several numerical experiments using diverging and converging sequences
The Short-term Rational Lanczos Method and Applications
Full text linkRational Krylov subspaces have become a reference tool in dimension reduction procedures for several application problems. When data matrices are symmetric, a short-term recurrence can be used to generate an associated orthonormal basis. In the past this procedure was abandoned because it requires twice the number of linear system solves per iteration compared with the classical long-term method. We propose an implementation that allows one to obtain the rational subspace reduced matrices at lower overall computational costs than proposed in the literature by also conveniently combining the two system solves. Several applications are discussed where the short-term recurrence feature can be exploited to avoid storing the whole orthonormal basis. We illustrate the advantages of the proposed procedure with several examples
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
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
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