1,721,071 research outputs found
Domination numbers and noncover complexes of hypergraphs
No full textLet H be a hypergraph on a finite set V. A cover of H is a set of vertices that meets all edges of H. If W is not a cover of H, then W is said to be a noncover of H. The noncover complex of H is the abstract simplicial complex whose faces are the noncovers of H. In this paper, we study homological properties of noncover complexes of hypergraphs. In particular, we obtain an upper bound on their Leray numbers. The bound is in terms of hypergraph domination numbers. Also, our proof idea is applied to compute the homotopy type of the noncover complexes of certain uniform hypergraphs, called tight paths and tight cycles. This extends to hypergraphs known results on graphs. (C) 2021 Elsevier Inc. All rights reserved.11Nsciescopu
Rainbow independent sets on dense graph classes
No full text© 2021 Elsevier B.V.Given a family I of independent sets in a graph, a rainbow independent set is an independent set I such that there is an injection ϕ:I→I where for each v∈I, v is contained in ϕ(v). Aharoni et al. (2019) determined for various graph classes C whether C satisfies a property that for every n, there exists N=N(C,n) such that every family of N independent sets of size n in a graph in C contains a rainbow independent set of size n. In this paper, we add two dense graph classes satisfying this property, namely, the class of graphs of bounded neighborhood diversity and the class of r-powers of graphs in a bounded expansion class.11Nsciescopu
A system of disjoint representatives of line segments with given k directions
No full text© 2021 Elsevier B.V.We prove that for all positive integers n and k, there exists an integer N=N(n,k) satisfying the following. If U is a set of k nonzero vectors in the plane and JU is the set of all line segments in direction u for some u∈U, then for every N families F1,…,FN, each consisting of n mutually disjoint segments in JU, there is a set {A1,…,An} of n disjoint segments in ⋃1≤i≤NFi and distinct integers p1,…,pn∈{1,…,N} satisfying that Aj∈Fpj for all j∈{1,…,n}. We generalize this property for underlying lines on fixed k directions to k families of simple curves with certain conditions.11Nsciescopu
sj-pdf-1-mrj-10.1177_00222437211050351 - Supplemental material for Home-Tutoring Services Assisted with Technology: Investigating the Role of Artificial Intelligence Using a Randomized Field Experiment
No full textSupplemental material, sj-pdf-1-mrj-10.1177_00222437211050351 for Home-Tutoring Services Assisted
with Technology: Investigating
the Role of Artificial Intelligence
Using a Randomized Field Experiment by Jun Hyung Kim, Minki Kim, Do Won Kwak and Sol Lee in Journal of Marketing Research</p
Badges and rainbow matchings
No full text© 2021 Elsevier B.V. All rights reserved.
Drisko proved that 2n - 1 matchings of size n in a bipartite graph have a rainbow matching of size n. For general graphs it is conjectured that 2n matchings suffice for this purpose (and that 2n- 1 matchings suffice when n is even). The known graphs showing sharpness of this conjecture for n even are called badges. We improve the previously best known bound from 3n- 2 to 3n- 3, using a new line of proof that involves analysis of the appearance of badges. We also prove a ``cooperative'' generalization: for t > 0 and n >= 3, any 3n - 4 + t sets of edges, the union of every t of which contains a matching of size n, have a rainbow matching of size n.11Nsciescopu
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
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