1,721,005 research outputs found
Accurate MLPG Solution of 3D Potential Problems
No full textMeshless methods have been explored in many 2D problems and they
have been shown to be as accurate as Finite Element Methods (FEM). Compared
to the extensive literature on 2D applications, papers on solving 3D problems by
meshless methods are surprisingly few. Indeed, a main drawback of these methods
is the requirement for accurate cubature rules. This paper focuses on the so called
Meshless Local Petrov Galerkin (MLPG) methods. We show that accurate solutions
of 3D potential problems can be attained, provided suitable cubature rules
are identified, sparse data structures are efficiently stored, and strategies are devised
in order to speed up the computation flow, by avoiding unnecessary integral
evaluations. The ensuing MLPG linear systems result to be well conditioned, positive
definite ones. Their conditioning does not increase much when the mesh size
decreases. We show that cubature errors can lower MLPG convergence speed
An Orthogonal Accelerated Deflation Technique for Large Symmetric Eigenproblems
No full textAn improvement in accelerated conjugate gradient iterations is presented for the evaluation of several of the leftmost eigenpairs of large sparse symmetric positive definite matrices. The approach relies on an orthogonal deflation procedure and is based on the subsequent preconditioned conjugate gradient optimization of Rayleigh quotients over the restricted space orthogonal to the set of eigenvectors previously computed. Comparison with the accelerated simultaneous iterations performed over large finite element problems (with size up to 4500) shows that storage requirement is significantly less and CPU times may be reduced by a factor of two or more. © 1992
Meshless Solution of Potential Problems by Combining Radial Basis Functions and Tensor Product ones
Full text linkMeshless methods for the solution of Partial Differential Equations receive nowadays increasing attention. Many meshless strategies have been pro- posed. The majority of meshless variational methods one can find in the literature, use Radial Basis Functions (RBF) as generators of suitable trial and test spaces. One of the main problems encountered when exploiting RBF is performing numer- ical integrations over circles (when 2D problems are attacked, spheres for 3D ones). We exploit Tensor Product Functions (TPF) as the test function space. This strat- egy allows one to consider rectangular integration domains, which are much easier to manage. This paper numerically analyzes the effectiveness in solving potential problems of various settings for trial and test functions. Finally, the accuracy of our best choice method is analyzed, when using both uniform and pseudo–random meshes
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
Preconditioning of Sequential and Parallel Jacobi--Davidson Method
No full textWe exploit an optimization method, called DACG,
which sequentially computes the smallest eigenpairs
of a symmetric, positive definite, generalized eigenproblem,
by CG minimizations
of the Rayleigh quotient over subspaces of decreasing size.
In this paper we analyze the effectiveness of the
approximate inverse preconditioners,
AINV and FSAI as DACG preconditioners
for the solution of
Finite Element and Finite Difference eigenproblems.
Numerical tests on a Cray T3E Supercomputer were performed, showing the
high degree of parallelism
attainable by the code.
We found that AINV and FSAI are both effective preconditioners for our
DACG algorithm
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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