1,720,962 research outputs found
Application des méthodes de suivi d'interface à la simulation numérique des écoulements diphasiques gaz-liquide
Get PDF166 p. : ill. ; 30 cmDans cette thèse, nous décrivons une méthode numérique utilisée dans la simulation de l'écoulement d'une bulle en ascension ainsi que la coalescence de bulles dans un liquide visqueux. Le schéma numérique du modèle est basé sur la méthode volume de fluide (VOF) des code libre SURFER et OpenFOAM. ces code utilisent un algorithme de suivi d'interface pour la simulation des écoulements à deux phases. une tentative de génération d'un solveur couplé sur la base des modèles VOF et magnétohdrodynamique a également été effectuée afin de simuler le mouvement d'une bulle dans un liquide métallique sous l'influence d'un champ magnétique longitudinal. toutes les simulations ont été effectuées en calcul parallèle sous MPI sur des ordinateur personnels hétérogéne
Simulation numérique de l'écoulement Gaz-liquide ascendant à poches dans une conduite verticale
Get PDF78 p. : ill. ; 30 cmCe mémoire est consacré à l'étude et à la résolution numérique de l'écoulement Gaz-liquide ascendant à poches dans une conduite verticale. Une premiere partie est consacrée à la présentation des principes généraux de la modélisation en écoulements diphasiques. Une attention particuliere est accordée aux techniques de suivi et de capture d'interface et plus précisement la méthode VOF( volume of fluid). la modélisation est ensuite formalisée dans le cas de l'écoulement vertical à poches. nous nous interssons plus particulierement au couplage entre la méthode VOF du code SURFER et la modélisation déterminist
Application des méthodes de suivi d'interface à la simulation numérique des écoulements diphasiques gaz-liquide
No full text166 p. : ill. ; 30 cmDans cette thèse, nous décrivons une méthode numérique utilisée dans la simulation de l'écoulement d'une bulle en ascension ainsi que la coalescence de bulles dans un liquide visqueux. Le schéma numérique du modèle est basé sur la méthode volume de fluide (VOF) des code libre SURFER et OpenFOAM. ces code utilisent un algorithme de suivi d'interface pour la simulation des écoulements à deux phases. une tentative de génération d'un solveur couplé sur la base des modèles VOF et magnétohdrodynamique a également été effectuée afin de simuler le mouvement d'une bulle dans un liquide métallique sous l'influence d'un champ magnétique longitudinal. toutes les simulations ont été effectuées en calcul parallèle sous MPI sur des ordinateur personnels hétérogéne
Simulation numérique de l'écoulement Gaz-liquide ascendant à poches dans une conduite verticale
No full text78 p. : ill. ; 30 cmCe mémoire est consacré à l'étude et à la résolution numérique de l'écoulement Gaz-liquide ascendant à poches dans une conduite verticale. Une premiere partie est consacrée à la présentation des principes généraux de la modélisation en écoulements diphasiques. Une attention particuliere est accordée aux techniques de suivi et de capture d'interface et plus précisement la méthode VOF( volume of fluid). la modélisation est ensuite formalisée dans le cas de l'écoulement vertical à poches. nous nous interssons plus particulierement au couplage entre la méthode VOF du code SURFER et la modélisation déterminist
Enhanced approach for CDF quantification in Seismic Probabilistic Safety Assessment of a Research Reactor
Get PDFIn Probabilistic Safety Analysis (PSA) applications, it is common practice to employ approximations with the expectation or assumption of a small overestimation in the quantification of the Core Damage Frequency (CDF). The overestimation of the CDF depends on the Minimal Cut Sets (MCS) structures and event probabilities but the amount of conservatism is generally unknown. Hence, when dealing with large and non-coherent fault trees, conventional approaches to model dependencies in event trees analysis using coherent approximations are shown to be inaccurate. The limitation of the techniques in terms of accuracy of the solutions becomes apparent. For instance, the quantification methods using Rare Event (REA) and Min Cut Upper Bound (MCUB) approximations valid in internal event PSA may result in excessively conservative results in Seismic PSA. Therefore, in order to calculate the accurate top event probability from a fault tree rather than improving the direct probability calculation from cut sets, the Binary Decision Diagram (BDD) is introduced for more exact quantification. BDD development highlights the effort to reduce the conservatism caused by RAE and MCUB computations. The analysis carried out in this work, within the Seismic Probabilistic Safety Assessment (SPSA) of a nuclear Research Reactor (RR) case study using BDD framework shows that the approach is feasible and effective in evaluating the seismic risk of core damage and provide reasonable assurance that related decisions on real-time risk status can be taken robustly and with confidence
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
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