1,721,019 research outputs found
Scanning integer matrices by means of two rectangular windows
No full textThis paper deals with the reconstruction of integer matrices from rectangular scans. In particular, since the case of one rectangular scan has already been treated in a previous paper, we consider two rectangular scans, given as two integer matrices, and we investigate the existence and the possibility of reconstruction of a third binary matrix which is compatible with them. Furthermore, our inspection implies interesting side results about the number of these reconstructed matrices for different choices of the dimensions of two windows used in the input scans
Reconstruction of Discrete Sets from Three or More X-Rays
No full textThe problem of reconstructing a discrete set from its X-rays in a finite number of prescribed directions is NP-complete when the number of prescribed directions is greater than two. In this paper, we consider an interesting subclass of discrete sets having some connectivity and convexity properties and we provide a polynomial-time algorithm for reconstructing a discrete set of this class from its X-rays in directions (1, 0), (0, 1) and (1, 1). This algorithm can be easily extended to contexts having more than three X-rays
A bijection for the total area of parallelogram polyominoes
No full textThe sum of the areas of the parallelogram polyominoes having semi-perimeter n+2 is equal to 4^n. In this paper we give a simple proof of this property by means of a mapping from the cells of parallelogram polyominoes having semi-perimeter n+2 to the 4^n words of length n of the free monoid {a; b; c; d}^∗. This mapping works in linear time. Then, we introduce a tiling game arising from this enumerative property
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
Reconstruction of 4- and 8-connected convex discrete sets from row and column projections
No full textIn this paper we examine the problem of reconstructing a discrete two-dimensional set from its two orthogonal projection (H,V) when the set satisfies some convexity conditions. We show that the algorithm of the paper [Int. J. Imaging Systems and Technol. 9 (1998) 69] is a good heuristic algorithm but it does not solve the problem for all (H,V) instances. We propose a modification of this algorithm solving the problem for all (H,V) instances, by starting to build the "spine". The complexity of our reconstruction algorithm is O(mn·log(mn)·min{m2,n2}) in the worst case. However, according to our experimental results, in 99% of the studied cases the algorithm is able to reconstruct a solution without using the newly introduced operation. In such cases the upper bound of the complexity of the algorithm is O(mn·log(mn)). A systematic comparison of this algorithm was done and the results show that this algorithm has the better average complexity than other published algorithms. The way of comparison and the results are given in a separate paper [Linear Algebra Appl. (submitted)]. Finally we prove that the problem can be solved in polynomial time also in a class of discrete sets which is larger than the class of convex polyominoes, namely, in the class of 8-connected convex set
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
Reconstruction of lattice sets from their horizontal, vertical and diagonal X-rays
No full textIn this paper, we study the problem of reconstructing a lattice set from its X-rays in a finite number of prescribed directions. The problem is NP-complete when the number of prescribed directions is greater than two. We provide a polynomial-time algorithm for reconstructing an interesting subclass of lattice sets (having some connectivity properties) from its X-rays in directions (1,0), (0,1) and (1,1). This algorithm can be easily extended to contexts having more than three X-rays
CPO Models for Infinite Term Rewriting
No full textInfinite terms in universal algebras are a well-known topic since the seminal work of the ADJ group. The recent interest in the field of term rewriting (TR) for infinite terms is due to the use of term graph rewriting to implement TR, where terms are represented by graphs: so, a cyclic graph is a finitary description of a possibly infinite term. In this paper we introduce infinite rewriting logic, working on the framework of rewriting logic proposed by Jose Meseguer. We provide a simple algebraic presentation of infinite computations, recovering the infinite parallel term rewriting, originally presented by one of the authors to extend the classical, set-theoretical approach to TR with infinite terms. Moreover, we put all the formalism on firm theoretical bases, providing (for the first time, to the best of our knowledge, for infinitary rewriting systems) a clean algebraic semantics by means of (internal) 2-categories
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