1,720,984 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Local tournaments and in-tournaments
No full textA digraph without loops, multiple arcs and cycles of length two is called a local tournament if the set of in-neighbors as well as the set of out-neighbors of every vertex induces a tournament. In claiming adjacency only for vertices that have a common out-neighbor, this class can be further generalized to the class of in-tournaments. Hence local tournaments and in-tournaments are generalizations of tournaments in such a way that the general adjacency of vertices is transferred to only those pairs of vertices that share a local property. In this thesis we study the path and cycle structure of local tournaments and in-tournaments and the related topic of vertex deletion. The required terminology and notation as well as the basic structural properties of local tournaments and in-tournaments are established in Chapter 1. The remaining part of this thesis is subdivided in three parts. In the first part consisting of Chapters 2 to 4 we investigate the path structure of local tournaments and in-tournaments. The first problem we deal with in Chapter 2 is to develop the structure necessary for a local tournament to be not arc-traceable, i.e. to contain an arc that does not belong to a Hamiltonian path. Using this structure we give various sufficient criteria for a local tournament to be arc-traceable. Our results extend those of Busch, and Busch, Jacobson and Reid for tournaments. In the next two chapters - Chapters 3 and 4 - we focus on shorter paths in local tournaments and in-tournaments. We study and confirm a conjecture of Volkmann and, subsequently, consider variations of Volkmann's problem. The second part of this thesis consists of two chapters in which we investigate the following problem: How many non-separating vertices has a strongly connected local tournament or in-tournament in terms of minimum vertex degree? In Chapter 5 we generalize results of Kotani for tournaments and of Meierling and Volkmann for local tournaments. The topic of Chapter 6 is the problem of vertex deletion, where we ask for the existence of two distinct vertices in a strongly connected local tournament whose removal preserves the strong connectivity of the digraph. We characterize all local tournaments with exactly two such vertices thereby generalizing a result of Las Vergnas for tournaments. The third part of this thesis is devoted to the cycle structure of local tournaments and in-tournaments. A reformulation of the results of Chapter 6 shows that we characterized all local tournaments with exactly two cycles of length order minus one. Using a special parameter, the quasi-girth of a local tournament, we investigate in Chapter 7 how many cycles of a given length, a strongly connected local tournament has at the least. This problem has already been studied and solved completely by Moon, and Las Vergnas for tournaments and our results generalize those of Las Vergnas. The interesting problem of complementary cycles in strongly connected local tournaments is investigated in Chapter 8. In 1996 Guo and Volkmann solved the question whether a 2-connected local tournament has complementary cycles in characterizing the exceptional digraphs. This result was generalized and extended in various forms. For example, Meierling and Volkmann characterized all 2-connected in-tournaments that are not cycle complementary. In this chapter we investigate the structure of strongly connected, but not 2-connected, local tournaments that are not cycle complementary. As applications we present sufficient criteria for a strongly connected local tournament to have k vertex disjoint cycles that span its vertex set. Our results extend and generalize those of Li and Shu for tournaments. In the last chapter we consider extendable cycles in strongly connected in-tournaments. In 1989 this property was introduced by Hendry in the context of general digraphs and subsequently studied by Tewes and Volkmann for in-tournaments. We solve a conjecture of Tewes and Volkmann in the affirmative
Local tournaments with the minimum number of Hamiltonian cycles or cycles of length three
No full textAbstractA digraph without loops, multiple arcs and directed cycles of length two is called a local tournament if the set of in-neighbors as well as the set of out-neighbors of every vertex induces a tournament.In this paper we consider the following problem: Given a strongly connected local tournament D of order n and an integer 3≤r≤n, how many directed cycles of length r exist in D?Bang-Jensen [1] showed in 1990 that every strongly connected local tournament has a directed Hamiltonian cycle, thus solving the case r=n. In 2009, Meierling and Volkmann [8] showed that a strongly connected local tournament D has at least n−r+1 directed cycles of length r for 4≤r≤n−1 unless it has a special structure.In this paper, we investigate the case r=3 and present a lower bound for the number of directed cycles of length three. Furthermore, we characterize the classes of local tournaments achieving equality in the bounds for r=3 and r=n, respectively
Local tournaments and in-tournaments
No full textA digraph without loops, multiple arcs and cycles of length two is called a local tournament if the set of in-neighbors as well as the set of out-neighbors of every vertex induces a tournament. In claiming adjacency only for vertices that have a common out-neighbor, this class can be further generalized to the class of in-tournaments. Hence local tournaments and in-tournaments are generalizations of tournaments in such a way that the general adjacency of vertices is transferred to only those pairs of vertices that share a local property. In this thesis we study the path and cycle structure of local tournaments and in-tournaments and the related topic of vertex deletion. The required terminology and notation as well as the basic structural properties of local tournaments and in-tournaments are established in Chapter 1. The remaining part of this thesis is subdivided in three parts. In the first part consisting of Chapters 2 to 4 we investigate the path structure of local tournaments and in-tournaments. The first problem we deal with in Chapter 2 is to develop the structure necessary for a local tournament to be not arc-traceable, i.e. to contain an arc that does not belong to a Hamiltonian path. Using this structure we give various sufficient criteria for a local tournament to be arc-traceable. Our results extend those of Busch, and Busch, Jacobson and Reid for tournaments. In the next two chapters - Chapters 3 and 4 - we focus on shorter paths in local tournaments and in-tournaments. We study and confirm a conjecture of Volkmann and, subsequently, consider variations of Volkmann's problem. The second part of this thesis consists of two chapters in which we investigate the following problem: How many non-separating vertices has a strongly connected local tournament or in-tournament in terms of minimum vertex degree? In Chapter 5 we generalize results of Kotani for tournaments and of Meierling and Volkmann for local tournaments. The topic of Chapter 6 is the problem of vertex deletion, where we ask for the existence of two distinct vertices in a strongly connected local tournament whose removal preserves the strong connectivity of the digraph. We characterize all local tournaments with exactly two such vertices thereby generalizing a result of Las Vergnas for tournaments. The third part of this thesis is devoted to the cycle structure of local tournaments and in-tournaments. A reformulation of the results of Chapter 6 shows that we characterized all local tournaments with exactly two cycles of length order minus one. Using a special parameter, the quasi-girth of a local tournament, we investigate in Chapter 7 how many cycles of a given length, a strongly connected local tournament has at the least. This problem has already been studied and solved completely by Moon, and Las Vergnas for tournaments and our results generalize those of Las Vergnas. The interesting problem of complementary cycles in strongly connected local tournaments is investigated in Chapter 8. In 1996 Guo and Volkmann solved the question whether a 2-connected local tournament has complementary cycles in characterizing the exceptional digraphs. This result was generalized and extended in various forms. For example, Meierling and Volkmann characterized all 2-connected in-tournaments that are not cycle complementary. In this chapter we investigate the structure of strongly connected, but not 2-connected, local tournaments that are not cycle complementary. As applications we present sufficient criteria for a strongly connected local tournament to have k vertex disjoint cycles that span its vertex set. Our results extend and generalize those of Li and Shu for tournaments. In the last chapter we consider extendable cycles in strongly connected in-tournaments. In 1989 this property was introduced by Hendry in the context of general digraphs and subsequently studied by Tewes and Volkmann for in-tournaments. We solve a conjecture of Tewes and Volkmann in the affirmative
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
