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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
Problemy gier stochastycznych i ich złożoność
No full textWe study a class of games introduced by Mio to capture the probabilistic μ-calculi called branching games. They are a subclass of stochastic two-player zero-sum turn-based infinite-time games of imperfect information. Branching games extend Gale-Stewart games by allowing players to split the execution of a play into new concurrent sub-games that continue their execution independently. In consequence, the play of a branching game has a tree-like structure, as opposed to linearly structured plays of Gale-Stewart games.
In this thesis, we focus our attention on regular branching games. Those are the branching games whose pay-off functions are the indicator functions of regular sets of infinite trees, i.e. the sets recognisable by finite tree automata. We study the problems of determinacy, game value computability, and the related problem of computing a measure of a regular set of infinite trees.
Determinacy is a property of a game that guarantees that none of the players gains or loses an advantage by revealing their strategy at the start of the game. In general, branching games are not determined: not even under mixed strategies nor when the winning sets are topologically simple. On the positive side, we show that regular branching games with open winning sets are determined under mixed strategies. Moreover, we show that game automata definable winning sets guarantee a stronger version of determinacy – the determinacy under pure strategies. Both results are accompanied by examples showing the limits of used techniques.
We give an answer to the problem of computing a value of a regular branching game. We show that a mixed value of a non-stochastic branching game is uncomputable and that a pure value of a stochastic branching game is also uncomputable. On the other hand, we provide an algorithm that computes all pure values of a given non-stochastic regular branching game.
We partially solve the problem of computing measures of regular sets of trees. We provide an algorithm that computes the uniform measure of a regular winning set in two cases. Either when it is defined by a first-order formula with no descendant relation or when it is defined by a Boolean combination of conjunctive queries.
Finally, we use real-life data to show how to incorporate game-theoretic techniques in practice. We propose a general procedure that given a time series of data extracts a reactive model that can be used to predict the evolution of the system and advise on the strategies to achieve predefined goals. We use the procedure to create a game based on Markov decision processes that is used to predict and control level of pest in a tropical fruit farm.W pracy badamy klasę gier zwanych grami rozgałęziającymi. Gry rozgałęziające zostały wprowadzone przez Mio w celu uchwycenia semantyki probabilistycznego rachunku mu. Stanowią one podklasę stochastycznych dwuosobowych gier turowych o sumie zerowej i nieskończonym czasie rozgrywki. Gry rozgałęziające rozszerzają gry Gale'a-Stewarta poprzez to, że pozwalają podzielić rozgrywkę, tworząc nowe podgry, które są rozgrywane równolegle i niezależnie. Z tego powodu rozgrywka gry rozgałęziającej ma strukturę drzewiastą, w przeciwieństwie do liniowej struktury rozgrywek w grach Gale'a-Stewarta.
W niniejszej rozprawie doktorskiej skupiamy się na regularnych grach rozgałęziających. Są to te gry rozgałęziające, w których funkcja wypłaty jest funkcją charakterystyczną regularnego zbioru nieskończonych drzew, to jest zbioru nieskończonych drzew, który jest rozpoznawany przez skończony automat na drzewach. W pracy skupiamy się głównie na problemie determinacji, na obliczalności wartości gier oraz na powiązanym z grami problemie obliczania miary regularnych zbiorów drzew.
Determinacja jest to własność gry, która gwarantuje, że żaden z graczy nie zyska ani nie straci przewagi poprzez ujawnienie swojej strategii na początku gry. Pokazujemy, że gry rozgałęziające nie muszą być zdeterminowane: ani gdy zbiory wygrywające są topologicznie proste, ani w przypadku, gdy dopuścimy strategie mieszane. Z drugiej strony, pokazujemy, że regularne gry rozgałęziające z otwartymi zbiorami wygrywającymi są zdeterminowane w strategiach mieszanych. Co więcej, pokazujemy, że te gry są zdeterminowane w strategiach czystych, jeśli zbiory wygrywające są rozpoznawalne przez automaty growe. Dla obu rezultatów konstruujemy przykłady pokazujące granice użytych technik.
Rozwiązujemy także problem obliczalności wartości gier pokazując, że mieszane wartości niestochastycznych gier rozgałęziających nie są obliczalne oraz, że czyste wartości gier stochastycznych także nie są obliczalne. Z drugiej strony, opisujemy algorytm, który wylicza czyste wartości niestochastycznych gier rozgałęziających.
Częściowo rozwiązujemy problem obliczania miar regularnych zbiorów drzew. Przedstawiamy algorytm, który oblicza miarę zbioru drzew, względem jednorodnej miary na drzewach, w dwu przypadkach: kiedy zbiór jest zdefiniowany poprzez formułę pierwszego rzędu nie używającą relacji potomka oraz gdy zbiór jest zdefiniowany poprzez boolowską kombinację zapytań koniunkcyjnych.
Wreszcie, pokazujemy w jaki sposób możemy zastosować bogate techniki teorii gier w praktyce. Proponujemy procedurę, która na podstawie szeregu czasowego tworzy reaktywny model pozwalający przewidzieć ewolucję modelowanego systemu i tworzyć strategie pozwalające zrealizować uprzednio zdefiniowane cele, jeśli takie strategie istnieją. Używamy wyżej wymienionej procedury, by stworzyć grę bazującą na procesach decyzyjnych Markowa, która pozwala przewidzieć i kontrolować poziomy obecności szkodników w tropikalnym sadzie owocowym
Lindenmayer graph languages, first-order theories and expanders
No full textCombinatorial generation of expander families and Lindenmayer-style development models are both parallel in nature. Both can be handled within proposed parallel graph grammar formalism. Their first-order properties can then be checked by encompassing the generated graph language into an appropriate automatic structure
Signal automata and hidden Markov models
No full textA generic method for inferring a dynamical hidden Markov model from a time series is proposed. Under reasonable hypothesis, the model is updated in constant time whenever a new measurement arrives
Lindenmayer graph languages, first-order theories and expanders
Full text linkCombinatorial generation of expander families and Lindenmayer-style
development models are both parallel in nature. Both can be handled within
proposed parallel graph grammar formalism. Their first-order properties can
then be checked by encompassing the generated graph language into an
appropriate automatic structure
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
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