1,721,057 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Physico-chemical mechanisms involved in the formation and evolution at abandonment of an innovative sedimentary material generated in a marine environment by cathodic polarisation
No full textCe travail de thèse porte sur un matériau (le Geocorail) formé par polarisation cathodique d’un treillis en acier disposé au sein d’un milieu sédimentaire marin. L’application de ce procédé est dédiée au renforcement des ouvrages côtiers dans la lutte contre le recul du trait de côte. L’objectif de cette étude est d’apporter des réponses relatives à l’influence des paramètres du procédé sur les propriétés physico-chimiques de ce matériau ainsi que l’évolution de celui-ci en condition d’abandon, c’est-à-dire lorsque la polarisation est arrêtée. Cette étude a été réalisée à travers une démarche expérimentale couplée avec des modèles numériques. Ces travaux ont été réalisés sur un matériau modèle formé en laboratoire et ont permis de mettre en évidence l’anisotropie de diffusion au sein de ce matériau dont l’épaisseur, la porosité et la masse volumique sont essentiellement contrôlées par la densité de courant et la durée de la polarisation. Ces deux derniers paramètres favorisent la formation de liant, constitué de brucite (Mg(OH)2) et d’aragonite (CaCO3), servant à l’agglomération du sédiment en place. La géométrie de ce sédiment est en outre un facteur primordial pour l’optimisation des propriétés du matériau. En ce qui concerne sa stabilité chimique en l’absence de polarisation, les analyses expérimentales et les modèles numériques ont révélé que l’aragonite se substitue à la brucite avec un rendement massique relativement faible, probablement lié à la forte diffusivité des matériaux analysés. La faible variation de la porosité et de la masse volumique (inférieur à 5% en 18 mois) rassure cependant de la stabilité du Geocorail dont les propriétés pourraient même s’améliorer avec le temps. Enfin, des modèles numériques de croissance et d’évolution de ce matériau à l’abandon ont été élaborés. Des voies d’amélioration ont également été proposées pour une meilleure prédiction de ces propriétés, voire la prédiction des propriétés mécaniques.This PhD work focused on the study of a material (Geocorail) formed by cathodic polarization applied in a marine sedimentary environment and used for the reinforcement of coastal structures in the fight against coastline recession. The objective of this study is to provide answers relative to the influence of the process parameters on the physico-chemical properties of this material as well as the evolution of the material under abandonment conditions, i.e. when the polarization is stopped. This was achieved through an experimental approach coupled with numerical models. This work was carried out on a laboratory material and its diffusion anisotropy within this material, the thickness, porosity and density of which are essentially controlled by the applied current density and the polarization time. These two parameters promote the formation of a binder, consisting of brucite (Mg(OH)2) and aragonite (CaCO3), which serves to agglomerate the sediments in place. The geometry of this sediment is also a key factor in optimizing the properties of this material. With regard to its chemical stability in the absence of polarization, experimental analyses and numerical models revealed that brucite substitutes for aragonite with a relatively low mass yield, probably linked to the high diffusivity of the studied materials. The small variation in porosity and density (less than 5% in 18 months) however ensures the stability of the Geocorail, whose properties could even improve with time. Finally, numerical models of the growth and evolution in abandon condition were developed. Some ways of improvement were also proposed for a better prediction of these properties, and even for the mechanical characterization using numerical method
Service life prediction of reinforced concrete structures using a performance-based approach in the case of carbonation or chloride ion induced corrosion
No full textLa corrosion des armatures en acier est la plus grande cause de défaillance des ouvrages en béton armé. Ce phénomène électrochimique est déclenché par la présence d’ions chlorure en quantité suffisante au niveau de l’armature ou la carbonatation du béton d’enrobage (action du CO2). L’objectif de cette thèse est de développer des modèles utilisables par l’ingénieur dans une démarche d’approche performantielle pour la prédiction de la durée d’utilisation des ouvrages en béton armé soumis à l’attaque par les ions chlorure ou la carbonatation, suite à l’amorçage et au développement de la corrosion en leur sein. Il s’agit du développement de trois modèles : un modèle de transfert des ions chlorure, un modèle de carbonatation et un modèle de corrosion qui permettent d’estimer la durée d’initiation et la durée de propagation de corrosion. Ces modèles prennent en considération les facteurs liés au matériau (i.e. indicateurs de durabilité), à la mise en œuvre, à l’environnement et à la géométrie. La démarche adoptée pour le développement de ces modèles repose sur l’exploitation de plusieurs bases de données, sur des ouvrages vieillissants et des corps d’épreuve de bétons, issues de la littérature (BHP-2000, Perfdub, etc.). Ces exploitations ont permis d’améliorer la capacité prédictive de modèles existants (transfert des ions chlorure) et de développer de nouveaux modèles (carbonatation et corrosion).Steel reinforcement corrosion is the major cause of failure in reinforced concrete structures. This electrochemical process is induced by presence in sufficient quantity of chloride ions at the reinforcement or by concrete carbonation (CO2 action). This thesis aims to develop engineering performance-based models for the service life prediction of reinforced concrete structures subjected to chloride-induced or carbonation-induced corrosion initiation and propagation. It consists in developing three models : a chloride ions ingress model, a carbonation model and a corrosion model that allows to estimate the corrosion initiation time and propagation time. These models consider factors related to the material (i.e. durability indicators), processing, environment and geometry. The approach used to develop these models is based on using several literature databases of ageing structures and concrete testing specimens (BHP-2000, Perfdub, etc.). The use of these data allowed to improve the predictive capacity of existing models (chloride ingress model) and to develop new models (carbonation and corrosion models)
Carbonation of cementitious materials : study of CO2 diffusion
No full textLa carbonatation est une réaction chimique entre la matrice cimentaire et le dioxyde de carbone présent dans l’air qui va produire des carbonates de calcium et diminuer le pH de la solution interstitielle. Dans ce travail de thèse, nous nous sommes intéressés à ce phénomène par le biais de la diffusion du CO2 qui a été relativement peu investiguée jusqu’à présent. Cependant, la maîtrise de la diffusion du CO2 dans les matériaux cimentaires est à n’en pas douter une des clés dans la conception des modèles de carbonatation utilisés pour garantir la durabilité des ouvrages, mais aussi pour contrôler le « piégeage » du CO2 dans le but de réduire le bilan carbone du cycle de vie des constructions en béton. Pour investiguer la diffusion et la carbonatation, nous nous sommes focalisés sur des pâtes de ciment et des mortiers, à différents rapports « eau sur liant », formulés avec un ciment Portland et avec un liant composé de laitier de haut fourneau complété par le ciment Portland. Pour mener à bien ces travaux, nous avons développé un dispositif expérimental pour mesurer le coefficient de diffusion du CO2. Des essais de diffusion ont d’abord été menés sur des échantillons secs puis sur des échantillons partiellement saturés en eau. Pour interpréter ces derniers, nous avons conçu un modèle de carbonatation qui se voulait relativement simple, ce qui nous a permis d’observer la réponse du matériau vis-à-vis des paramètres du modèle. Nous avons ainsi pu mettre en évidence la compétition entre la diffusion du CO2 et les réactions chimiques au cours des essais.Carbonation is a chemical reaction between the cement matrix and the carbon dioxide in the air that will produce calcium carbonates and lower the pH of the interstitial solution. In this thesis, we are interested in this phenomenon through the diffusion of CO2 that has been relatively little investigated so far. However, mastering the diffusion of CO2 in cementitious materials is undoubtedly one of the keys in the design of carbonation models used to ensure the durability of structures, but also to control the "trapping" of CO2 in the aim to reduce the life cycle carbon footprint of concrete constructions. To investigate diffusion and carbonation, we focused on cement pastes and mortars, with different "water-to-binder" ratios, formulated with Portland cement and with a binder composed of blast furnace slag plus Portland cement. To carry out this work, we have developed an experimental device to measure the diffusion coefficient of CO2. Diffusion tests were first carried out on dry samples and then on partially saturated samples of water. To interpret these, we designed a model of carbonation that was meant to be relatively simple, which allowed us to observe the response of the material against the parameters of the model. We were able to highlight the competition between the diffusion of CO2 and the chemical reactions during the tests
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
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