1,721,379 research outputs found
Blocking Sets in
No full textIn this paper we provide a generalisation the MPS construction of a blocking set of PG(r, qn) using subspaces of dimension s≤n-2, determining some minimal blocking sets in PG(r, q2n)
Kikkawa left loops and Symmetric 2-structures
No full textWe approach the existence of class 1 symmetric 2-structures by studying a class of left loops related to them. Such left loops turn out to satisfy a relation very similar to the left Bol property, and they are of exponent 2. Then we give a characterization of these left loops by means of invariant involution sets, and classify them according to the cardinality of the point stabilizers, comparing then our results with the classification of symmetric 2-structures given in [3]
Existence of λ-fold non-zero sum Heffter arrays through local considerations
No full textThe paper [Costa et al., Discrete Math. 345 (2022), 112952] introduced, for cyclic groups, the class of partially filled arrays of the non-zero sum Heffter array that are, as the Heffter arrays, related to difference families, graph decompositions, and biembeddings. Here we generalize this definition to any finite group. Given a subgroup J of order t of a finite group (G, +), a λ-fold non-zero sum Heffter array over G relative to J,λNHG,J (m, n; h, k), is an m×n partially filled array with entries in G such that: each row contains h filled cells and each column contains k filled cells; for every x ∈ G \ J, the sum of the occurrences of x and −x is λ; the sum of the elements in every row and column is, following the natural orderings from left to right for the rows and from top to bottom for the columns, different from 0. The 2022 paper by Costa et al. also presented a complete, probabilistic solution for the existence problem in case λ = 1 and G = Zv which is the starting point of this investigation. In this paper we will consider the existence problem for a generic value of λ and a generic finite group G, and we present an almost complete solution to this problem. In particular, we will prove, through local considerations (inspired by the Lovász Local Lemma), that there exists a λ-fold non-zero sum Heffter array over G relative to J whenever the trivial necessary conditions are satisfied and |G| ≥ 41. This value can be reduced to 29 in case the array does not contain empty cells. Finally, we will show that these arrays give rise to biembeddings of multigraphs into orientable surfaces and we provide new infinite families of such embeddings
Alternating parity weak sequencing
No full textA subset Sof a group G(,+)ist-weakly sequenceable if there is an ordering (y(1),..., y(k)) of its elements such that the partial sums s(0), s(1),.., s(k), given by s(0)=0 and s(i) =Sigma(i)(j=1)y(j) for 1 3 is prime, e 3 is prime and t <= 8. A subset of G is balanced if it contains the same number of even elements and odd elements and an alternating parity ordering alternates even and odd elements. Then using a hybrid approach that combines both Ramsey theory and the probabilistic method we also prove, for groups G that are semidirect products of a generic(nonnecessarily abelian) group N and Z(2), that all sufficiently large balanced subsets of the non identity elements admit an alternating parity t-weak sequencing. The same procedure works also for studying the weak sequenceability for generic sufficiently large (not necessarily balanced) sets. Here we have been able to prove that, if the size of a subset S of a group G is large enough and if S does not contain 0, then S is t-weakly sequenceable
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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