1,721,005 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
Randomized algorithms: theory and implementation
Full text linkTato práce pojednává o vybraných příkladech náhodných algoritmů a ukazuje tak jejich užitečnost a jednoduchost. První kapitola se zabývá algoritmy na hledání minimálního řezu grafu. Čtenáři je důkladně představena teorie dané problematiky a podrobně vysvětlen princip algoritmu. Spočtena je úspěšnost s délkou běhu a přiložena je také implementace kódu. Dále je navrženo vylepšení a řádně porovnáno s původním algoritmem. Zjistíme, že drobnou úpravou lze vytvořit velmi efektivní algoritmus, avšak za cenu mírného nárůstu délky běhu. V druhé kapitole pak zkoumáme pojem disperze. Čtenáře zasvětíme do problematiky a představíme vybrané odhady, které lze konstruovat pomocí pravděpodobnostních metod. Hlavním výsledkem práce je pak spojení disperze s jiným kombinatorickým problémem – restriction setem. To nám umožní provést nové spodní odhady na disperzi. Kromě toho ukážeme také nové, alternativní důkazy již známých odhadů. Nakonec provedeme srovnání s aktuálně nejlepšími odhady.This paper discusses selected examples of random algorithms and thus shows their usefulness and simplicity. The first chapter deals with algorithms for finding a minimal graph cut. The reader is thoroughly introduced to the problem theory and the principle of the algorithm is explained in detail. The success rate and running time are calculated and the implementation of the code is also included. Further improvements are proposed and properly compared with the original algorithm. We find that a small modification can create a very efficient algorithm, but at the cost of slightly extending the running time. In the second chapter, we deal with the concept of dispersion. We introduce the reader into the problem and present selected estimates that can be constructed using probabilistic methods. The main result of the work is then to connect the dispersion with another combinatorial problem – the restriction set. This allows us to make new lower estimates on the dispersion. In addition, we also show new, alternative evidence of already known estimates. Finally, we make a comparison with the currently best estimates
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
Laplacian matrix and its applications
Full text linkGrafy a Markovské řetězce je možné reprezentovat pomocí matic. Jednou z nejběžnějších forem reprezentace pro grafy je Laplaceova matice. Tato práce o ní dává ucelený přehled a nachází Laplaceova spektra několika základních typů grafů. Dále shrnuje základní obecné spektrální vlastnosti Laplaceovy matice a normalizované Laplaceovy matice pro neorientované grafy, jejich vzájemný vztah i vztah s maticí přechodu z teorie Markovských řetězců. Dále se práce věnuje aplikaci daných matic, primárně ve spectral clusteringu. Vedle toho definujeme novou Laplaceovu matici pro orientované grafy a ověřujeme její vlastnosti. Vše je na konci ukázáno formou numerické simulace na třech grafech.Graphs and Markov chains can be represented by matrixes. One of the most common representations is the Laplacian matrix. This thesis summaries knowledge about the Laplacian matrix and prove Laplacians of some particular graphs. Then it summarises the basic generic properties of the Laplacian matrix and the Normalized Laplacian matrix of unoriented graphs, their relations and their relation with the Transition matrix from Markov chain theory. Then we consider the application of these matrixes, especially in spectral clustering. In the thesis, we also analyze the new Laplacian matrix for oriented graphs and proves its properties. Everything concludes in the form of numerical simulation on three particular graphs
Parallel graph algorithms for GPU
Full text linkTato bakalářská práce je zaměřená na několik běžných grafových problémů a na jejich řešení s pomocí paralelních grafových algoritmů. Jedná se o problémy nalezení maximální nezávislé množiny, minimální kostry grafu, souvislých a silně souvislých komponent. Tato práce poskytuje teoretický kontext potřebný pro popsání zmíněných problémů a navrhuje jejich řešení za pomoci běžných sekvenčních algoritmů. Hlavní snaha práce však směřuje k algoritmům paralelním a jejich implementaci využívající CUDA, C++ a knihovnu TNL. Tyto implementace jsou schopny běhu jak na GPU paralelně, tak na CPU sekvenčně (či paralelně s pomocí OpenMP). Práce obsahuje detailní popis těchto algoritmů a jejich implementace. Také informuje o procesu testování správné funkčnosti, měření výkonu na různých zařízeních (GPU, CPU) a uprávách vedoucích k lepšímu výkonu. Výstupem práce jsou plně funkční a otestované implementace pro 3 ze 4 problémů. Pro problém minimální kostry grafu je výstup rozpracovaná částečně fungující implementace.This bachelor thesis targets several common graph problems and their solutions using parallel graph algorithms. These are the problems of finding the maximal independent set, minimal spanning tree, connected and strongly connected components. This paper provides the theoretical context needed to describe the aforementioned problems and proposes their solutions using common sequential algorithms. However, the main effort of the thesis is directed towards parallel algorithms and their implementation using CUDA, C++, and the TNL library. These implementations are capable of running both on the GPU in parallel and on the CPU sequentially (or in parallel using OpenMP). This thesis contains a detailed description of these algorithms and their respective implementations. It also reports on the process of correctness testing, performance measurements on different devices (GPU, CPU), and further improving performance. The output of this work is fully functional and tested implementations for 3 of the 4 problems. For the minimal spanning tree problem, a semi-functional work-in-progress implementation is offered
Analytic and Probabilistic Techniques in Combinatorics
Full text linkV této práci představujeme a uvádíme na příkladech pravděpodobnostní metodu a Lovászovo lokální lemma. Definujeme nerepetitivní barevnost grafu a dokazujeme třemi různými způsoby, že každou cestu lze nerepetitivně obarvit z libovolných seznamů čtyř barev. Jmenovitě to jsou důkazy pomocí levoruké varianty Lovászova lokálního lemma, metodou komprese entropie a Rosenfeldovým počítáním.In this thesis, we introduce and illustrate on examples the probabilistic method and Lovász local lemma. We define the nonrepetitive colouring of a graph and prove in three different ways that any path can be nonrepetitively coloured from abitrary lists of four colours. Specifically, these are proofs using the lefthanded version of the Lovász local lemma, the entropy compression method, and the Rosenfeld counting
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
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