1,721,122 research outputs found
Praktische Algorithmen für das "Deletion Into Small Components" Problem
No full textThis thesis considers the Deletion Into Small Components problem, which given an undirected graph G and an integer c, asks for a set D of vertices of G having minimum size such that every component of G\D has size at most c. The problem has long been known to have applications for measuring the vulnerability of computer networks and has recently found applications in AI Planning and Integer Linear Programming. Since the problem is NP-complete it is a challenging problem to design algorithms that are efficient on real-world instances. In this thesis the development and implementation of efficient algorithms, such as exact and heuristic algorithms, for this problem are presented. Our main contributions are the development and implementation of three exact algorithms and four heuristic algorithms for the problem. In particular, w.r.t. exact algorithms, we implement and improve upon a known fixed-parameter algorithm and develop and implement a SAT-encoding and an ILP-encoding for the problem. Concerning heuristic algorithms, we introduce two novel heuristics for the computation of lower bounds and one greedy algorithm for the computation of upper bounds. Finally, we implement a novel heuristic algorithm that allows the computation of lower bounds and upper bounds and is based on splitting the instance, using so-called balanced separators, into smaller sub-instances that are admissible for an exact method. Our experiments show that our exact algorithms are able to solve graphs with medium size (up to 200 vertices), the proposed separator based algorithm can solve the graphs with large size(up to 2000 vertices) and other heuristics performs well on very large graphs (up to 10000 vertices). Finally, it can be clearly observed that the relative performance of the various algorithms depends strongly on the respective structural properties of instances, which means that for almost every algorithm there are instances on which the algorithm performs best.Diese These behandelt das "Deletion Into Small Components"Problem, welches für einen gegebenen ungerichteten Graphen G und einer natürlichen Zahl c, nach einer kleinstmöglichen Knotenmenge D fragt, so dass jede Komponente des Graphen G-D höchstens c Konten beinhaltet. Neben lange bekannten Anwendungen für das Problem für das Messen der Verwundbarkeit von Computer Netzwerken, sind vor kurzem auch wichtige Anwendungen des Problems für AI Planning sowie Integer Linear Programming hinzugekommen. Da das Problem NP-vollständig ist, ist das Design von effizienten Algorithmen für das Problem eine interessante Herausforderung. In dieser These entwickeln und implementieren wir effiziente Algorithmen, wie z.B. exakten aber auch heuristischen Algorithmen, für dieses Problem. Die Hauptbestandteile dieser These sind die Entwicklung und Implementierung von drei exakten sowie vier heuristischen Algorithmen für dieses Problem. Bei den drei exakten Algorithmen handelt es sich um eine stark verbesserte Version eines existierenden exakten Algorithmus sowie jeweils eine neu entwickelte Codierung des Problems nach SAT (propositional satisfiability) und ILP (Integer Linear Programming). Die heuristischen Algorithmen beinhalten zwei neue Ansätze zur Bestimmung von unteren Schranken sowie einen Greedy-Ansatz zur Bestimmung von oberen Schranken für das Problem. Der wohl interessanteste heuristische Ansatz erlaubt die gleichzeitige Bestimmung von unteren und oberen Schranken und basiert auf einer rekursiven Methode welche die Instanz mit Hilfe von sogenannten balancierten Separatoren in immer kleinere Teile aufspaltet, welche dann exakt gelöst werden können. Unsere Experimente zeigen, dass unsere exakten Methoden für Graphen bis zu einer Grösse von ca. 200 Knoten anwendbar sind, unsere auf balancierten Separatoren basierende Heuristik auf Graphen bis zu einer Grösse von ca. 2000 Knoten anwendbar ist, und alle weiteren heuristischen Ansätze sehr gut für Graphen bis zu einer Grösse von ca. 10000 Knoten funktionieren. Weiterhin ist deutlich erkennbar, dass die relative Performance der verschiedenen Algorithmen sehr stark von den jeweiligen strukturellen Eigenschaften der Instanzen abhängt und es somit beinahe für jeden Algorithmus Instanzen gibt für die der Algorithmus am besten geeignet ist
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
- …
