1,720,966 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
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
Sparse preconditioners for dense complex linear systems arising in some radar cross section computations
Full text linkWe present a sparse preconditioner for efficient iterative solution of large dense linear systems that arise in radar cross section computations for a perfectly conducting scatterer using a high-order surface integral equation algorithm. The algorithm allows the linear systems to be assembled efficiently but overall efficiency of the method can only be achieved using iterative solvers with an appropriate preconditioner. We demonstrate the effectiveness and efficiency of our preconditioner for electromagnetic scattering linear systems with tens of thousands of unknowns arising in radar cross section computations for small to medium electromagnetic-sized scatterers
A coupled FEM-BEM algorithm for the inverse acoustic medium problem
Full text linkWe present a numerical scheme for reconstructing the refractive index of an inhomogeneous two dimensional medium using acoustic far field data. The numerical scheme is based only on the mild assumption that the inhomogeneous medium is contained in the unit disk, and does not require axis-symmetry or other similar restrictions. Reconstruction of the refractive index, without the assumption of axis-symmetry, is achieved using an expansion in the high order Logan--Shepp polynomials. The Logan--Shepp expansion coefficients of the refractive index are formulated as the solution of a nonlinear equation, which is solved using a regularised Newton-type solver. Nonlinear function evaluations, which involve solving a forward scattering problem, are performed using an efficient coupled finite-element/\penalty \exhyphenpenalty boundary element method, which ensures that the radiation condition is incorporated exactly. The scheme is demonstrated by reconstructing challenging continuous and discontinous media from noisy far field data.
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Sparse approximate inverse preconditioners for electromagnetic surface scattering simulations
Full text linkSimulation of electromagnetic waves scattered by a connected three dimensional non-convex obstacle at medium frequencies (where the size of the obstacle is 10 to 100 times the incident wavelength) requires a non-asymptotic approach. Standard boundary element schemes at such frequencies require millions of unknowns. However, recently developed high-order algorithms require only tens of thousands of unknowns at medium frequencies for a class of three dimensional obstacles. At such frequencies we use a sparse approximation to the scattering matrix and so iterative solvers are required. We describe an efficient scheme to solve the associated linear systems using sparse approximate inverse preconditioners. The sparse preconditioners developed in this work facilitate efficient solutions of complex dense linear systems arising in electromagnetic scattering simulations.
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Scattering by stochastic boundaries: hybrid low- and high-order quantification algorithms
Full text linkWe present an efficient framework for simulating the average wave scattering properties of two dimensional randomly shaped particles with statistical properties similar to model aerosols particles that are important in atmospheric science applications. Our framework is based on an efficient high order discretisation of the spatial dimensions and parallel implementations for the large number of stochastic dimensions. We demonstrate our framework by simulating the mean (and higher order moments) of the far field of the model particles. We use tens of thousands of Monte Carlo, quasi-Monte Carlo and sparse grid generalised polynomial chaos realisations of the random particle model.
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