1,720,994 research outputs found
Framework pro experimentální studium modelů šíření názorů
No full textTitle: A Framework for Experimental Study of Opinion Diffusion Models Author: Dominik Jelínek institute: IUUK Supervisor: Martin Koutecký, IUUK Abstract: Our theoretical contribution centers on defining possible diffusion steps decreasing either Kendall-tau or Spearman's footrule distance between two bucket orders, which are orders with ties. These diffusion steps give us a new ability to work with, among others, election data where voters can specify any number of top preferences. From the practical contribution, we have developed an experimental framework specialized for working with bucket orders. The framework's easily extendable architecture provided by the usage of strategy design pattern allows for the generation and comparison of various models at a large scale. A part of a framework is an extensive list of important metrics and visualization techniques to observe and compare the behavior of different models. Keywords: bucket order, diffusion model, social network, framework, election iiiInformatický ústav Univerzity KarlovyComputer Science Institute of Charles UniversityMatematicko-fyzikální fakultaFaculty of Mathematics and Physic
A Framework For Experimental Evaluation of Opinion Diffusion Models
No full textTitle: A Framework for Experimental Study of Opinion Diffusion Models Author: Dominik Jelínek institute: IUUK Supervisor: Martin Koutecký, IUUK Abstract: Our theoretical contribution centers on defining possible diffusion steps decreasing either Kendall-tau or Spearman's footrule distance between two bucket orders, which are orders with ties. These diffusion steps give us a new ability to work with, among others, election data where voters can specify any number of top preferences. From the practical contribution, we have developed an experimental framework specialized for working with bucket orders. The framework's easily extendable architecture provided by the usage of strategy design pattern allows for the generation and comparison of various models at a large scale. A part of a framework is an extensive list of important metrics and visualization techniques to observe and compare the behavior of different models. Keywords: bucket order, diffusion model, social network, framework, election ii
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
Distributed Methods for Computing Approximate Equilibria
Full text linkWe present a new, distributed method to compute approximate Nash equilibria in bimatrix games. In contrast to previous approaches that analyze the two payoff matrices at the same time (for example, by solving a single LP that combines the two players’ payoffs), our algorithm first solves two independent LPs, each of which is derived from one of the two payoff matrices, and then computes an approximate Nash equilibrium using only limited communication between the players. Our method gives improved bounds on the complexity of computing approximate Nash equilibria in a number of different settings. Firstly, it gives a polynomial-time algorithm for computing approximate well supported Nash equilibria (WSNE) that always finds a 0.6528-WSNE, beating the previous best guarantee of 0.6608. Secondly, since our algorithm solves the two LPs separately, it can be applied to give an improved bound in the limited communication setting, giving a randomized expected-polynomial-time algorithm that uses poly-logarithmic communication and finds a 0.6528-WSNE, which beats the previous best known guarantee of 0.732. It can also be applied to the case of approximate Nash equilibria, where we obtain a randomized expected-polynomial-time algorithm that uses poly-logarithmic communication and always finds a 0.382-approximate Nash equilibrium, which improves the previous best guarantee of 0.438. Finally, the method can also be applied in the query complexity setting to give an algorithm that makes O(nlogn) payoff queries and always finds a 0.6528-WSNE, which improves the previous best known guarantee of 2/3
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
Inapproximability Results for Approximate Nash Equilibria.
Full text linkWe study the problem of finding approximate Nash equilibria that satisfy certain conditions, such as providing good social welfare. In particular, we study the problem ϵ-NE δ-SW: find an ϵ-approximate Nash equilibrium (ϵ-NE) that is within δ of the best social welfare achievable by an ϵ-NE. Our main result is that, if the randomized exponential-time hypothesis (RETH) is true, then solving 18-O(δ)-NE O(δ)-SW for an n×n bimatrix game requires nΩ~(δΛlogn) time, where Λ is a constant.Building on this result, we show similar conditional running time lower bounds on a number of decision problems for approximate Nash equilibria that do not involve social welfare, including maximizing or minimizing a certain player’s payoff, or finding approximate equilibria contained in a given pair of supports. We show quasi-polynomial lower bounds for these problems assuming that RETH holds, and these lower bounds apply to ϵ-Nash equilibria for all ϵ<18. The hardness of these other decision problems has so far only been studied in the context of exact equilibria
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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