1,720,979 research outputs found
Some Numerical algorithms to evaluate Hadamard finite part integrals
No full textSome algorithms are described for the numerical evaluation of Hadamard finite part integrals of type Finite Part integral sign1 -1[f(x)/(x-t)2]υ α,β dx, |t| < 1, where υα,β is a Jacobi weight. Convergence results and some numerical examples are giv
Limite a posteriori del numero di condizione in norma spettrale per matrici tridiagonali
No full textIn this paper, we propose a new algorithm to bound the condition number in spectral norm of a tridiagonal matrix, with nonzero leading principal minors
Fast deconvolution with approximated PSF by RSTLS with antireflective boundary conditions
No full textThe problem of reconstructing signals and images from degraded ones is considered in this paper. The latter problem is formulated as a linear system whose coefficient matrix models the unknown point spread function and the right hand side represents the observed image. Moreover, the coefficient matrix is very ill-conditioned, requiring an additional regularization term. Different boundary conditions can be proposed. In this paper antireflective boundary conditions are considered. Since both sides of the linear system have uncertainties and the coefficient matrix is highly structured, the Regularized Structured Total Least Squares approach seems to be the more appropriate one to compute an approximation of the true signal/image. With the latter approach the original problem is formulated as an highly nonconvex one, and seldom can the global minimum be computed. It is shown that Regularized Structured Total Least Squares problems for antireflective boundary conditions can be decomposed into single variable subproblems by a discrete sine transform. Such subproblems are then transformed into one-dimensional unimodal real-valued minimization problems which can be solved globally. Some numerical examples show the effectiveness of the proposed approach
The numerical computation of some integrals on the real line
No full textWe discuss the approximation of integrals of type I(f;t)=∫Rf(x)K(x,t)e-x2|x|αdx,α>-1, K is the weakly singular algebraic kernel |x-t|λ,-1<λ<0, for "large" value of the parameter t. Moreover, we consider strongly oscillatory kernels of type K1(x,t)=sin(tx2),K2(x,t)=cos(tx2). Weighted error estimates in uniform and L1 norm are stated and numerical examples to confirm the efficiency of the proposed procedures are given
Computing integrals with an exponential weight on the real axis in floating point arithmetic
Full text linkThe aim of this work is to propose a fast and reliable algorithm for computing integrals of the type [Formula presented] where f(x) is a sufficiently smooth function, in floating point arithmetic. The algorithm is based on a product integration rule, whose rate of convergence depends only on the regularity of f, since the coefficients of the rule are “exactly” computed by means of suitable recurrence relations here derived. We prove stability and convergence in the space of locally continuous functions on R equipped with weighted uniform norm. By extensive numerical tests, the accuracy of the proposed product rule is compared with that of the Gauss–Hermite quadrature formula w.r.t. the function [Formula presented]. The numerical results confirm the effectiveness of the method, supporting the proven theoretical estimates
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
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