1,720,969 research outputs found
Book Embeddability of Series-Parallel Digraphs
No full textIn this paper we deal with the problem of computing upward two-page book embeddings of
Two Terminal Series–Parallel (TTSP) digraphs, which are a subclass of series–parallel digraphs. An optimal
O(n) time and space algorithm to compute an upward two-page book embedding of a TTSP-digraph with n
vertices is presented. A previous algorithm of Alzohairi and Rival [1] runs in O(n3) time and assumes that the
input series–parallel digraph does not have transitive edges. An application of this result to a computational
geometry problem is also discussed. More precisely, upward two-page book embeddings are used to deal with
the upward point-set embeddability problem, i.e., the problem of mapping planar digraphs onto a given set
of points in the plane so that all edges are monotonically increasing in a common direction. The equivalence
between upward two-page book embeddability and upward point-set embeddability with at most one bend per
edge on any given set of points is proved. An O(n log n)-time algorithm for computing an upward point-set
embedding with at most one bend per edge for TTSP-digraphs is presented
Curve-Constrained Drawings of Planar Graphs
No full textLet be the family of 2D curves described by concave
functions, let be a planar graph, and let be a linear
ordering of the vertices of . is a {\em curve embedding} of
if for any given curve there exists a
planar drawing of such that: (i) the vertices are constrained
to be on with the same ordering as in , and (ii)
the edges are polylines with at most one bend. Informally
speaking, a curve embedding can be regarded as a two-page book
embedding in which the spine is bent. Although deciding whether a
graph has a two-page book embedding is an NP-hard problem, in this
paper it is proven that every planar graph has a curve embedding
which can be computed in linear time. Applications of the concept
of curve embedding to upward drawability and point-set
embeddability problems are also presented
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
Point-set embeddings of trees with given partial drawings
No full textAbstractGiven a graph G with n vertices and a set S of n points in the plane, a point-set embedding of G on S is a planar drawing such that each vertex of G is mapped to a distinct point of S. A geometric point-set embedding is a point-set embedding with no edge bends. This paper studies the following problem: The input is a set S of n points, a planar graph G with n vertices, and a geometric point-set embedding of a subgraph G′⊂G on a subset of S. The desired output is a point-set embedding of G on S that includes the given partial drawing of G′. We concentrate on trees and show how to compute the output in O(n2logn) time in a real-RAM model and with at most n−k edges with at most 1+2⌈k/2⌉ bends, where k is the number of vertices of the given subdrawing. We also prove that there are instances of the problem which require at least k−3 bends on n−k edges
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
Introducing fairness in network visualization
No full textMotivated by the need for decision-making systems that avoid bias and discrimination, the concept of fairness recently gained traction in the broad field of artificial intelligence, stimulating new research also within the information visualization community. In this paper, we introduce a notion of fairness in network visualization, specifically for orthogonal and for straight-line drawings of graphs, two foundational paradigms in the field. We investigate the following research questions: (i) What is the price, in terms of global readability, of incorporating fairness constraints in graph drawings? (ii) How unfair is a graph drawing that does not optimize fairness as a primary objective? We present both theoretical and empirical results. In particular, we design and implement two optimization algorithms for multi-objective functions, one based on an ILP model for orthogonal drawings, and one based on gradient descent for straight-line drawings. In a nutshell, we experimentally show that it is possible to significantly increase the fairness of a drawing by paying a relatively small amount in terms of reduced global readability. Also, we present a use case in which we qualitatively evaluate our approach on a practical scenario
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
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