1,721,107 research outputs found
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
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
Combinatorial and algorithmic aspects of identifying codes in graphs
No full textUn code identifiant est un ensemble de sommets d'un graphe tel que, d'une part, chaque sommet hors du code a un voisin dans le code (propriété de domination) et, d'autre part, tous les sommets ont un voisinage distinct à l'intérieur du code (propriété de séparation). Dans cette thèse, nous nous intéressons à des aspects combinatoires et algorithmiques relatifs aux codes identifiants.Pour la partie combinatoire, nous étudions tout d'abord des questions extrémales en donnant une caractérisation complète des graphes non-orientés finis ayant comme taille minimum de code identifiant leur ordre moins un. Nous caractérisons également les graphes dirigés finis, les graphes non-orientés infinis et les graphes orientés infinis ayant pour seul code identifiant leur ensemble de sommets. Ces résultats répondent à des questions ouvertes précédemment étudiées dans la littérature.Puis, nous étudions la relation entre la taille minimum d'un code identifiant et le degré maximum d'un graphe, en particulier en donnant divers majorants pour ce paramètre en fonction de l'ordre et du degré maximum. Ces majorants sont obtenus via deux techniques. L'une est basée sur la construction d'ensembles indépendants satisfaisant certaines propriétés, et l'autre utilise la combinaison de deux outils de la méthode probabiliste : le lemme local de Lovasz et une borne de Chernoff. Nous donnons également des constructions de familles de graphes en relation avec ce type de majorants, et nous conjecturons que ces constructions sont optimales à une constante additive près.Nous présentons également de nouveaux minorants et majorants pour la cardinalité minimum d'un code identifiant dans des classes de graphes particulières. Nous étudions les graphes de maille au moins 5 et de degré minimum donné en montrant que la combinaison de ces deux paramètres influe fortement sur la taille minimum d'un code identifiant. Nous appliquons ensuite ces résultats aux graphes réguliers aléatoires. Puis, nous donnons des minorants pour la taille d'un code identifiant des graphes d'intervalles et des graphes d'intervalles unitaires. Enfin, nous donnons divers minorants et majorants pour cette quantité lorsque l'on se restreint aux graphes adjoints. Cette dernière question est abordée via la notion nouvelle de codes arête-identifiants.Pour la partie algorithmique, il est connu que le problème de décision associés à la notion de code identifiant est NP-complet même pour des classes de graphes restreintes. Nous étendons ces résultats à d'autres classes de graphes telles que celles des graphes split, des co-bipartis, des adjoints ou d'intervalles. Pour cela nous proposons des réductions polynomiales depuis divers problèmes algorithmiques classiques. Ces résultats montrent que dans beaucoup de classes de graphes, le problème des codes identifiants est algorithmiquement plus difficile que des problèms liés (tel que le problème des ensembles dominants).Par ailleurs, nous complétons les connaissances relatives à l'approximabilité du problème d'optimisation associé aux codes identifiants. Nous étendons le résultat connu de NP-difficulté pour l'approximation de ce problème avec un facteur sous-logarithmique (en fonction de la taille du graphe instance) aux graphes bipartis, split et co-bipartis, respectivement. Nous étendons également le résultat connu d'APX-complétude pour les graphes de degré maximum donné à une sous-classe des graphes split, aux graphes bipartis de degré maximum 4 et aux graphes adjoints. Enfin, nous montrons l'existence d'un algorithme de type PTAS pour les graphes d'intervalles unitaires.An identifying code is a set of vertices of a graph such that, on the one hand, each vertex out of the code has a neighbour in the code (domination property), and, on the other hand, all vertices have a distinct neighbourhood within the code (separation property). In this thesis, we investigate combinatorial and algorithmic aspects of identifying codes.For the combinatorial part, we first study extremal questions by giving a complete characterization of all finite undirected graphs having their order minus one as minimum size of an identifying code. We also characterize finite directed graphs, infinite undirected graphs and infinite oriented graphs having their whole vertex set as unique identifying code. These results answer open questions that were previously studied in the literature.We then study the relationship between the minimum size of an identifying code and the maximum degree of a graph. In particular, we give several upper bounds for this parameter as a function of the order and the maximum degree. These bounds are obtained using two techniques. The first one consists in the construction of independent sets satisfying certain properties, and the second one is the combination of two tools from the probabilistic method: the Lovasz local lemma and a Chernoff bound. We also provide constructions of graph families related to this type of upper bounds, and we conjecture that they are optimal up to an additive constant.We also present new lower and upper bounds for the minimum cardinality of an identifying code in specific graph classes. We study graphs of girth at least 5 and of given minimum degree by showing that the combination of these two parameters has a strong influence on the minimum size of an identifying code. We apply these results to random regular graphs. Then, we give lower bounds on the size of a minimum identifying code of interval and unit interval graphs. Finally, we prove several lower and upper bounds for this parameter when considering line graphs. The latter question is tackled using the new notion of an edge-identifying code.For the algorithmic part, it is known that the decision problem associated to the notion of an identifying code is NP-complete, even for restricted graph classes. We extend the known results to other classes such as split graphs, co-bipartite graphs, line graphs or interval graphs. To this end, we propose polynomial-time reductions from several classical hard algorithmic problems. These results show that in many graph classes, the identifying code problem is computationally more difficult than related problems (such as the dominating set problem).Furthermore, we extend the knowledge of the approximability of the optimization problem associated to identifying codes. We extend the known result of NP-hardness of approximating this problem within a sub-logarithmic factor (as a function of the instance graph) to bipartite, split and co-bipartite graphs, respectively. We also extendthe known result of its APX-hardness for graphs of given maximum degree to a subclass of split graphs, bipartite graphs of maximum degree 4 and line graphs. Finally, we show the existence of a PTAS algorithm for unit interval graphs
Aspects combinatoires et algorithmiques des codes identifiants dans les graphes
No full textWe study combinatorial and algorithmic aspects of identifying codes in graphs. An identifying code is a set of vertices of a graph such that, on the one hand, each vertex out of the code has a neighbour in the code, and, on the other hand, all vertices have a distinct neighbourhood within the code. We characterize those graphs and digraphs that reach the known upper bounds on the minimum size of an identifying code. We also give new lower and upper bounds on this parameter for graphs of given maximum degree, graphs of girth at least 5, interval graphs and line graphs. Further, we study the computational complexity of the decision and optimization problems associated with the notion of an identifying code. We show that these problems remain computationally difficult, even when restricted to bipartite, co-bipartite, split, interval or line graphs. Finally, we give a \textsf{PTAS} algorithm for unit interval graphs.Nous étudions des aspects combinatoires et algorithmiques relatifs aux codes identifiants dans les graphes. Un code identifiant est un ensemble de sommets d'un graphe tel que, d'une part, chaque sommet hors du code a un voisin dans le code et, d'autre part, tous les sommets ont un voisinage distinct à l'intérieur du code. Nous caractérisons tout d'abord les graphes orientés et non-orientés atteignant les bornes supérieures connues pour la taille minimum d'un code identifiant. Nous donnons également de nouveaux majorants et minorants sur ce paramètre pour les graphes de degré maximum donné, les graphes de maille au moins 5, les graphes d'intervalles et les graphes adjoints. Nous étudions ensuite la complexité algorithmique des problèmes de décision et d'optimisation associés à la notion de code identifiant. Nous montrons que ces problèmes restent algorithmiquement difficiles, même quand on les restreint aux graphes bipartis, co-bipartis, split, d'intervalles ou adjoints. Enfin, nous donnons un algorithme PTAS pour les graphes d'intervalles unitaires
Combinatorial and algorithmic aspects of identifying codes in graphs
No full textUn code identifiant est un ensemble de sommets d'un graphe tel que, d'une part, chaque sommet hors du code a un voisin dans le code (propriété de domination) et, d'autre part, tous les sommets ont un voisinage distinct à l'intérieur du code (propriété de séparation). Dans cette thèse, nous nous intéressons à des aspects combinatoires et algorithmiques relatifs aux codes identifiants.Pour la partie combinatoire, nous étudions tout d'abord des questions extrémales en donnant une caractérisation complète des graphes non-orientés finis ayant comme taille minimum de code identifiant leur ordre moins un. Nous caractérisons également les graphes dirigés finis, les graphes non-orientés infinis et les graphes orientés infinis ayant pour seul code identifiant leur ensemble de sommets. Ces résultats répondent à des questions ouvertes précédemment étudiées dans la littérature.Puis, nous étudions la relation entre la taille minimum d'un code identifiant et le degré maximum d'un graphe, en particulier en donnant divers majorants pour ce paramètre en fonction de l'ordre et du degré maximum. Ces majorants sont obtenus via deux techniques. L'une est basée sur la construction d'ensembles indépendants satisfaisant certaines propriétés, et l'autre utilise la combinaison de deux outils de la méthode probabiliste : le lemme local de Lovasz et une borne de Chernoff. Nous donnons également des constructions de familles de graphes en relation avec ce type de majorants, et nous conjecturons que ces constructions sont optimales à une constante additive près.Nous présentons également de nouveaux minorants et majorants pour la cardinalité minimum d'un code identifiant dans des classes de graphes particulières. Nous étudions les graphes de maille au moins 5 et de degré minimum donné en montrant que la combinaison de ces deux paramètres influe fortement sur la taille minimum d'un code identifiant. Nous appliquons ensuite ces résultats aux graphes réguliers aléatoires. Puis, nous donnons des minorants pour la taille d'un code identifiant des graphes d'intervalles et des graphes d'intervalles unitaires. Enfin, nous donnons divers minorants et majorants pour cette quantité lorsque l'on se restreint aux graphes adjoints. Cette dernière question est abordée via la notion nouvelle de codes arête-identifiants.Pour la partie algorithmique, il est connu que le problème de décision associés à la notion de code identifiant est NP-complet même pour des classes de graphes restreintes. Nous étendons ces résultats à d'autres classes de graphes telles que celles des graphes split, des co-bipartis, des adjoints ou d'intervalles. Pour cela nous proposons des réductions polynomiales depuis divers problèmes algorithmiques classiques. Ces résultats montrent que dans beaucoup de classes de graphes, le problème des codes identifiants est algorithmiquement plus difficile que des problèms liés (tel que le problème des ensembles dominants).Par ailleurs, nous complétons les connaissances relatives à l'approximabilité du problème d'optimisation associé aux codes identifiants. Nous étendons le résultat connu de NP-difficulté pour l'approximation de ce problème avec un facteur sous-logarithmique (en fonction de la taille du graphe instance) aux graphes bipartis, split et co-bipartis, respectivement. Nous étendons également le résultat connu d'APX-complétude pour les graphes de degré maximum donné à une sous-classe des graphes split, aux graphes bipartis de degré maximum 4 et aux graphes adjoints. Enfin, nous montrons l'existence d'un algorithme de type PTAS pour les graphes d'intervalles unitaires.An identifying code is a set of vertices of a graph such that, on the one hand, each vertex out of the code has a neighbour in the code (domination property), and, on the other hand, all vertices have a distinct neighbourhood within the code (separation property). In this thesis, we investigate combinatorial and algorithmic aspects of identifying codes.For the combinatorial part, we first study extremal questions by giving a complete characterization of all finite undirected graphs having their order minus one as minimum size of an identifying code. We also characterize finite directed graphs, infinite undirected graphs and infinite oriented graphs having their whole vertex set as unique identifying code. These results answer open questions that were previously studied in the literature.We then study the relationship between the minimum size of an identifying code and the maximum degree of a graph. In particular, we give several upper bounds for this parameter as a function of the order and the maximum degree. These bounds are obtained using two techniques. The first one consists in the construction of independent sets satisfying certain properties, and the second one is the combination of two tools from the probabilistic method: the Lovasz local lemma and a Chernoff bound. We also provide constructions of graph families related to this type of upper bounds, and we conjecture that they are optimal up to an additive constant.We also present new lower and upper bounds for the minimum cardinality of an identifying code in specific graph classes. We study graphs of girth at least 5 and of given minimum degree by showing that the combination of these two parameters has a strong influence on the minimum size of an identifying code. We apply these results to random regular graphs. Then, we give lower bounds on the size of a minimum identifying code of interval and unit interval graphs. Finally, we prove several lower and upper bounds for this parameter when considering line graphs. The latter question is tackled using the new notion of an edge-identifying code.For the algorithmic part, it is known that the decision problem associated to the notion of an identifying code is NP-complete, even for restricted graph classes. We extend the known results to other classes such as split graphs, co-bipartite graphs, line graphs or interval graphs. To this end, we propose polynomial-time reductions from several classical hard algorithmic problems. These results show that in many graph classes, the identifying code problem is computationally more difficult than related problems (such as the dominating set problem).Furthermore, we extend the knowledge of the approximability of the optimization problem associated to identifying codes. We extend the known result of NP-hardness of approximating this problem within a sub-logarithmic factor (as a function of the instance graph) to bipartite, split and co-bipartite graphs, respectively. We also extendthe known result of its APX-hardness for graphs of given maximum degree to a subclass of split graphs, bipartite graphs of maximum degree 4 and line graphs. Finally, we show the existence of a PTAS algorithm for unit interval graphs
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