1,720,957 research outputs found
On combinatorial search problems which involve graphs
No full textCombinatorial search problems are represented as follows: An finite set M is searched for an object x by selecting a subset of a finite set of tests F such that they identify x uniquely. In this thesis 3 types of search problems are treated by solving some special problems involving graphs as structural element:1. The decision problem for graph properties.2. Group tests on graphs/hypergraphs in the sequential case.3. Group tests on graphs in the predetermined case.These problems require a specification of the set M according to the related problem. But more important is the influence on the set of admitted test functions F by the use of graphs by which one intends to find interesting restrictions on F. (I.e.: they should need some interesting mathematics, but also yield some results by not being to complex and unmanageable.) We always restrict to a binary answer (0/1 or yes/no ...). We look for a method to construct a subset of F that identifies x. Any algorithm is only allowed to compute the subset due to the known facts of the model. x, of cause, is unknown. A main question is, for example, whether the the algorithm is sequential or predetermined: in the first case, the answers of the former questions can be used to compute the next in a sequence. In the latter case, all questions have to be chosen before getting the answers.1. A graph property is a subset of graphs on a fixed vertex set of n vertices, the set being invariant under permutation of the vertices. An unknown graph G is to be tested for having property P. The admissible questions are "Is e an an edge of G?" for all possible edges, i.e. sets of vertices with two elements. If for every sequential algorithm there is a graph G (called the worst case )such that we have to test all edges to decide whether G is in P, then P is called evasive. It is a long standing conjecture that all monotone nontrivial graph properties are evasive. This conjecture is settled in the case n=p^k, p prime (Kahn et al.). Also an asymptotic bound for the necessary number of questions is known, but it is a relatively weak bound. In this thesis an improvement of this bound is shown. The topological methods of the prime case and asymptotic case are used in a neat proof. Moreover, I illustrate the use of computers in attacking evasiveness. 2. A group test is a search for a subset D of a set X. Depending on the model, there are some sets Y, subsets of X, that represent questions of the form "Is the intersection of D and Y empty?" When using the edges of a graph/hypergraph as the set X, each possible set Y is defined by some vertices such that Y is the set of edges only incident with these vertices. There is a conjecture of Du and Hwang (generalized to hypergraphs) describing a bound of the number of questions in the worst case and containing a constant c which is conjectured to exist. There is an algorithm in the case of graphs proving the conjecture for a constant c. I give a simpler algorithm and a better bound. Moreover, the hope is to generalize this algorithm to hypergraphs and prove the conjecture. I intended to give concrete hints where the obstacles to the generalization lie.3. The model is this of section 2, but |D|=1 and with the strong restriction to predetermined algorithms. This changes the situation entirely: only a weak bound for the number of questions needed in the worst case, and only for some special graphs G good bounds are known. Although the case "G is bipartite and complete" is almost trivial and can be shown to be (quasi) optimal, there is no bound for bipartite graphs, even in the seemingly simple case of G being a tree. Yet I found a good bound in this case as I think. The proof is in no way trivial. I think it is an interesting application of combinatorial and graph theoretic methods. Furthermore, it suggests that it is hard to find a much simpler algorithm for that bound. Finally, I show that the conjectured optimality (i.e., the minimum number of questions is that information theory gives us) cannot be shown with the idea of the proof
On combinatorial search problems which involve graphs
No full textCombinatorial search problems are represented as follows: An finite set M is searched for an object x by selecting a subset of a finite set of tests F such that they identify x uniquely. In this thesis 3 types of search problems are treated by solving some special problems involving graphs as structural element:1. The decision problem for graph properties.2. Group tests on graphs/hypergraphs in the sequential case.3. Group tests on graphs in the predetermined case.These problems require a specification of the set M according to the related problem. But more important is the influence on the set of admitted test functions F by the use of graphs by which one intends to find interesting restrictions on F. (I.e.: they should need some interesting mathematics, but also yield some results by not being to complex and unmanageable.) We always restrict to a binary answer (0/1 or yes/no ...). We look for a method to construct a subset of F that identifies x. Any algorithm is only allowed to compute the subset due to the known facts of the model. x, of cause, is unknown. A main question is, for example, whether the the algorithm is sequential or predetermined: in the first case, the answers of the former questions can be used to compute the next in a sequence. In the latter case, all questions have to be chosen before getting the answers.1. A graph property is a subset of graphs on a fixed vertex set of n vertices, the set being invariant under permutation of the vertices. An unknown graph G is to be tested for having property P. The admissible questions are "Is e an an edge of G?" for all possible edges, i.e. sets of vertices with two elements. If for every sequential algorithm there is a graph G (called the worst case )such that we have to test all edges to decide whether G is in P, then P is called evasive. It is a long standing conjecture that all monotone nontrivial graph properties are evasive. This conjecture is settled in the case n=p^k, p prime (Kahn et al.). Also an asymptotic bound for the necessary number of questions is known, but it is a relatively weak bound. In this thesis an improvement of this bound is shown. The topological methods of the prime case and asymptotic case are used in a neat proof. Moreover, I illustrate the use of computers in attacking evasiveness. 2. A group test is a search for a subset D of a set X. Depending on the model, there are some sets Y, subsets of X, that represent questions of the form "Is the intersection of D and Y empty?" When using the edges of a graph/hypergraph as the set X, each possible set Y is defined by some vertices such that Y is the set of edges only incident with these vertices. There is a conjecture of Du and Hwang (generalized to hypergraphs) describing a bound of the number of questions in the worst case and containing a constant c which is conjectured to exist. There is an algorithm in the case of graphs proving the conjecture for a constant c. I give a simpler algorithm and a better bound. Moreover, the hope is to generalize this algorithm to hypergraphs and prove the conjecture. I intended to give concrete hints where the obstacles to the generalization lie.3. The model is this of section 2, but |D|=1 and with the strong restriction to predetermined algorithms. This changes the situation entirely: only a weak bound for the number of questions needed in the worst case, and only for some special graphs G good bounds are known. Although the case "G is bipartite and complete" is almost trivial and can be shown to be (quasi) optimal, there is no bound for bipartite graphs, even in the seemingly simple case of G being a tree. Yet I found a good bound in this case as I think. The proof is in no way trivial. I think it is an interesting application of combinatorial and graph theoretic methods. Furthermore, it suggests that it is hard to find a much simpler algorithm for that bound. Finally, I show that the conjectured optimality (i.e., the minimum number of questions is that information theory gives us) cannot be shown with the idea of the proof
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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