1,720,980 research outputs found
Transfert couplé de chaleur et de masse par convection mixte avec changement de phase dans un canal
Get PDFThis thesis deals with a numerical study of laminar, mixed convection flow associated with mass transfer and phase change in a parallel plate channel. The plates are maintained at a constant uniform temperature and the lower plate is covered by thin liquid water film. The liquid film is assumed to be extremely thin and its temperature is equal to the wall temperature. A 2D fully elliptical model, associated with the Boussinesq assumption, is used to take into account axial diffusion. The solution of this mathematical model is based on the finite volume method and the velocity-pressure coupling is handled by the SIMPLER algorithm. Combined buoyancy forces effects on laminar mixed in symmetrical isothermal channel were investigated. Results show that buoyancy forces have an important effect on the hydrodynamic field as well as on the heat and mass transfer characteristics. Thus, for cold plates and an upward hot air flow, these forces induce a flow reversal near the plates for high air temperatures and mass fractions. Additionally, heat transfer associated with phase change (i.e. latent heat transfer) is more important compared with sensible heat transfer. Flow reversal was investigated in symmetrical isothermal vertical channel and asymmetrical isothermal inclined channel. For the inclined channel, only the lower plate is wetted by a thin liquid water film while the other one is impermeable. We discuss the effect of the buoyancy forces on the hydrodynamic, heat and mass fields. Thus, these forces induce a flow reversal when there intensities are important. It is established that heat transfer associated with phase change is, sometimes, more significant than sensible heat transfer. Furthermore, this importance depends on the mass fraction gradient. The conditions for the existence of flow reversal are presented in charts and analytical expressions. These charts specify the critical thermal Grashof number as a function of the Reynolds number for different values of the solutal Grashof number and different channel inclinations
Transfert couplé de chaleur et de masse par convection mixte avec changement de phase dans un canal
No full textThis thesis deals with a numerical study of laminar, mixed convection flow associated with mass transfer and phase change in a parallel plate channel. The plates are maintained at a constant uniform temperature and the lower plate is covered by thin liquid water film. The liquid film is assumed to be extremely thin and its temperature is equal to the wall temperature. A 2D fully elliptical model, associated with the Boussinesq assumption, is used to take into account axial diffusion. The solution of this mathematical model is based on the finite volume method and the velocity-pressure coupling is handled by the SIMPLER algorithm. Combined buoyancy forces effects on laminar mixed in symmetrical isothermal channel were investigated. Results show that buoyancy forces have an important effect on the hydrodynamic field as well as on the heat and mass transfer characteristics. Thus, for cold plates and an upward hot air flow, these forces induce a flow reversal near the plates for high air temperatures and mass fractions. Additionally, heat transfer associated with phase change (i.e. latent heat transfer) is more important compared with sensible heat transfer. Flow reversal was investigated in symmetrical isothermal vertical channel and asymmetrical isothermal inclined channel. For the inclined channel, only the lower plate is wetted by a thin liquid water film while the other one is impermeable. We discuss the effect of the buoyancy forces on the hydrodynamic, heat and mass fields. Thus, these forces induce a flow reversal when there intensities are important. It is established that heat transfer associated with phase change is, sometimes, more significant than sensible heat transfer. Furthermore, this importance depends on the mass fraction gradient. The conditions for the existence of flow reversal are presented in charts and analytical expressions. These charts specify the critical thermal Grashof number as a function of the Reynolds number for different values of the solutal Grashof number and different channel inclinations
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
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
Écoulement dans un tube en oscillation radiale étude numérique et visualisation expérimentale
No full textLe travail présenté dans ce mémoire concerne l'étude numérique et expérimentale de l'écoulement en développement dans un tube soumis à des oscillations radiales et sinusoïdales dans un plan horizontal. Au mieux de la connaissance de l'auteur, ce problème n'a fait l'objet d'aucune étude publiée à ce jour. L'étude envisagée a pour objet de comprendre, d'un point de vue fondamental, l'effet des oscillations du tube sur les caractéristiques de l'écoulement ainsi que sur sa structure. L'étude numérique est basée sur un modèle mathématique parabolique dans la direction de l'axe du tube. L'adimensionalisation du modèle mathématique montre que le problème considéré est régi par trois paramètres indépendants: le nombre de Reynolds de l'écoulement (Re), le nombre de Reynolds d'oscillation (Re&omega;) et l'amplitude des oscillations du tube (A). Ce modèle est résolu par une méthode numérique de volumes finis. Les résultats numériques montrent une dynamique d'écoulement complexe et intéressante. Ainsi, les oscillations du tube induisent un écoulement transversal. Cet écoulement est particulièrement intéressant pour les systèmes de transferts de chaleur et/ou de masse, d'autant plus que le profil de vitesse axiale est tel que son maximum reste confiné près de l'axe du tube. Par ailleurs, les oscillations du tube peuvent induire un renversement de l'écoulement axial dépendamment des valeurs des paramètres Re, Re&omega; et A. L'étude expérimentale consiste en une visualisation de la structure de l'écoulement considéré. Cette visualisation révèle que les oscillations du tube induisent une transition précoce de l'écoulement vers la turbulence à des nombres de Reynolds relativement faibles (Re < 2000). La valeur de Re pour laquelle l'écoulement n'est plus laminaire dépend de la fréquence des oscillations du tube (soit Re&omega;). Cette valeur est d'autant plus basse que Re&omega; est élevé. Une cartographie de la structure l'écoulement a été établie couvrant une large gamme de débit (Re) et de fréquence d'oscillation (Re&omega;)
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