1,720,969 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
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
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Belief Refinement Approaches to Communication and Inference Problems
Full text linkThis dissertation considers a problem where a single agent or a group of agents aim to estimate/learn unknown (possibly time-varying) parameters of interest despite making noisy observations. The agents take a Bayesian-like approach by maintaining a posterior probability distribution or “belief" over a parameter space conditioned on past observations. The agents aim to iteratively refine their belief over the parameter space as new information is acquired from their private observations or through collaboration with other agents. In particular, the agents aim to ensure that sufficient belief is assigned in neighborhoods centered around the true parameter with high probability or “reliability". In the context of communication problems considered in this dissertation, the agents may be active, i.e., agents may additionally take actions which provide new observations. Furthermore, agents may employ an adaptive strategy, i.e., using their past actions and the resulting observations, agents can adaptively choose actions to control the concentration of the belief. When the agents are active, we propose and analyze adaptive belief refinement approaches to obtain belief concentration on the unknown parameter with high reliability. In a different context, namely that of decentralized inference, we consider passive agents. Here, agents face an additional challenge due to the statistical insufficiency of their private observations to learn the unknown parameter. While individual agents’ observations are not informative enough, we assume that the agents’ observations are collectively informative to learn the unknown parameter. Here, we propose and analyze decentralized belief refining strategies to collaboratively obtain belief concentration on the unknown parameter. In the first part of this dissertation, we consider active strategies that are extensions of the posterior matching strategy (PM) introduced by Horstein, which is a generalization of the well-known binary search algorithm. We propose and analyze PM based strategies in the context of modern communication systems, namely the problem of establishing initial access in mm-Wave communication and spectrum sensing for Cognitive Radio. We propose and analyze channel coding strategies for real-time streaming and control applications. The second part of the dissertation investigates the belief refinement approaches for decentralized learning. In particular, it focusing on developing and analyzing a decentralized learning rule for statistical hypothesis testing and its application to decentralized machine learning
Modélisation des composites MOFs/Oxyde de graphène et leurs performances pour le captage de CO2
No full textLa problématique du réchauffement de la planète causé par l’émission de gaz à effet de serre est actuellement un enjeu sociétal majeur. La capture de CO2 par l’utilisation de matériaux poreux apparait comme une solution viable. Des composites construits à partir de l’assemblage d’oxyde de graphène (GO) et de matériaux hybrides poreux de type MOFs ont récemment été proposés comme des candidats prometteurs pour l’adsorption sélective du CO2 vis-à-vis d’autres gaz, comme N2 et CH4. Dans cette thèse, une attention particulière a été portée à la construction de modèles structuraux pour le GO incorporant différentes fonctionnalités chimiques. Une méthodologie computationnelle innovante intégrant des approches quantiques et classiques (Dynamique Moléculaire) a été ensuite mise en œuvre pour construire des modèles microscopiques des composites MOF/GO et caractériser leurs interfaces en termes de taux de recouvrement, nature des sites d’interaction et déformation du GO, des paramètres qui jouent un rôle majeur dans la compatibilité du composite. Cette étude a été menée de façon systématique en faisant varier la nature à la fois du MOF et de la fonctionnalisation du GO. Par la suite, les performances de séparation de ces systèmes ont été modélisées à l'aide de simulations Monte Carlo. Cet effort computationnel a été mené en lien étroit avec des données expérimentales issues de différentes collaborations au sein du projet H2020 EU GRAMOFON. Les conclusions de cette thèse ouvrent la voie à un développement plus rationnel des membranes à matrice mixte MOF/GO.Recently, most of the research attention has been focused on controlling global warming resulting from the emission of greenhouse gases. The advantage of developing adsorbents for physisorption-based CO2 capture resides in the reduction of energy penalty and easier recyclability. Composite systems (MOF/GO) made from the assembly of graphene oxide (GO) with Metal organic frameworks (MOFs) together with tailored functionalities have been recently revealed as promising candidates to selectively adsorb CO2 over diverse gases including N2 and CH4. In this PhD, an innovative computational methodology integrating density functional theory calculations and force field-based molecular dynamics simulation has been applied to provide a first atomistic picture of the interactions at the MOF/GO interface with the main objective to characterize the nature of the interactions between the two components, the surface coverage, the GO conformation that all together are expected to play a key role in the compatibility of the composite. As a first step, a careful attention has been paid to develop a structural model for the GO containing –hydroxyl, -epoxy and –carboxylic groups consistent with the experimental observation on the C/O ratios. As a proof of concept, the zinc-based zeolite imidazole framework ZIF-8 has been considered and its MOF surface model has been taken from our previous work. The MOF/GO interface has been further built and detailed analysis of the MOF/GO interfaces has been generated. A systematic computational exploration of the impact of the nature of the MOFs as well as of the functionalization of GO has been further deployed. Subsequently, the adsorption and separation performances were modelled for these MOF/GO systems using Monte Carlo simulations. These computational findings were supported by experimental data collected within the frame of the H2020 EU GRAMOFON and paves way towards a more rationale development of mixed matrix membranes
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
Modélisation des composites MOFs/Oxyde de graphène et leurs performances pour le captage de CO2
No full textRecently, most of the research attention has been focused on controlling global warming resulting from the emission of greenhouse gases. The advantage of developing adsorbents for physisorption-based CO2 capture resides in the reduction of energy penalty and easier recyclability. Composite systems (MOF/GO) made from the assembly of graphene oxide (GO) with Metal organic frameworks (MOFs) together with tailored functionalities have been recently revealed as promising candidates to selectively adsorb CO2 over diverse gases including N2 and CH4. In this PhD, an innovative computational methodology integrating density functional theory calculations and force field-based molecular dynamics simulation has been applied to provide a first atomistic picture of the interactions at the MOF/GO interface with the main objective to characterize the nature of the interactions between the two components, the surface coverage, the GO conformation that all together are expected to play a key role in the compatibility of the composite. As a first step, a careful attention has been paid to develop a structural model for the GO containing –hydroxyl, -epoxy and –carboxylic groups consistent with the experimental observation on the C/O ratios. As a proof of concept, the zinc-based zeolite imidazole framework ZIF-8 has been considered and its MOF surface model has been taken from our previous work. The MOF/GO interface has been further built and detailed analysis of the MOF/GO interfaces has been generated. A systematic computational exploration of the impact of the nature of the MOFs as well as of the functionalization of GO has been further deployed. Subsequently, the adsorption and separation performances were modelled for these MOF/GO systems using Monte Carlo simulations. These computational findings were supported by experimental data collected within the frame of the H2020 EU GRAMOFON and paves way towards a more rationale development of mixed matrix membranes.La problématique du réchauffement de la planète causé par l’émission de gaz à effet de serre est actuellement un enjeu sociétal majeur. La capture de CO2 par l’utilisation de matériaux poreux apparait comme une solution viable. Des composites construits à partir de l’assemblage d’oxyde de graphène (GO) et de matériaux hybrides poreux de type MOFs ont récemment été proposés comme des candidats prometteurs pour l’adsorption sélective du CO2 vis-à-vis d’autres gaz, comme N2 et CH4. Dans cette thèse, une attention particulière a été portée à la construction de modèles structuraux pour le GO incorporant différentes fonctionnalités chimiques. Une méthodologie computationnelle innovante intégrant des approches quantiques et classiques (Dynamique Moléculaire) a été ensuite mise en œuvre pour construire des modèles microscopiques des composites MOF/GO et caractériser leurs interfaces en termes de taux de recouvrement, nature des sites d’interaction et déformation du GO, des paramètres qui jouent un rôle majeur dans la compatibilité du composite. Cette étude a été menée de façon systématique en faisant varier la nature à la fois du MOF et de la fonctionnalisation du GO. Par la suite, les performances de séparation de ces systèmes ont été modélisées à l'aide de simulations Monte Carlo. Cet effort computationnel a été mené en lien étroit avec des données expérimentales issues de différentes collaborations au sein du projet H2020 EU GRAMOFON. Les conclusions de cette thèse ouvrent la voie à un développement plus rationnel des membranes à matrice mixte MOF/GO
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