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Étude de sensibilité de distribution du courant de Foucault et du profil de température des disques et d'engrenages droits en acier AISI-4340 traités par induction en utilisant des concentrateurs de flux
Get PDFRÉSUMÉ : Le traitement thermique superficiel par induction est un procédé de fabrication qui permet de produire la microstructure martensitique à haute compression à la surface de la pièce traitée afin d'augmenter la dureté superficielle, d'améliorer la résistance de tenue à l'usure et de fatigue et de maintenir le noyau ductile. Ce procédé est purement écologique, sans émission de gaz ou de fumées toxiques dans l'environnement. Néanmoins, le traitement d'une pièce mécanique par induction fait intervenir plusieurs facteurs et paramètres de contrôle du processus, notamment les propriétés du matériau, les paramètres et géométries de la machine et les conditions de chauffage. Afin d'exploiter correctement les ressources de ce procédé, il est nécessaire de développer des stratégies pour contrôler et ajuster les paramètres afin de produire avec précision les caractéristiques souhaitées de la surface durcie sans avoir recours au traditionnel processus d'essais et d'erreurs, long et coûteux. L'objectif du projet consiste à analyser les paramètres machines et géométries sur la distribution finale de températures afin de développer des modèles simples capables de prédire les températures et le profil de dureté avec une bonne précision pour des pièces mécaniques en acier AISI 4340 chauffées par induction en présence de concentrateurs de flux. Pour ce faire, une approche en trois phases a été adoptée. La première phase a consisté à la modélisation et la simulation par la méthode des éléments finis d'un modèle 2D axisymétrique avec le logiciel COMSOL afin d'analyser les effets de paramètres machines et géométries sur la profondeur de pénétration de courant induit pour un disque. Les paramètres impliqués comprennent la puissance machine, le temps de chauffe, l'écart entre la pièce et l'induction et l'écart entre les concentrateurs de flux et la pièce. Les résultats obtenus de cette étude ont permis d'établir les modèles de prédiction de profondeur de pénétration avec une précision de plus de 96%. La seconde phase a permis de mener une étude de sensibilité sur les profondeurs durcies pour développer les modèles fiables capables de prédire les profils de dureté en fonction de paramètres impliqués d'un disque en utilisant la même approche de la première phase. Les modèles proposés sont validés par des essais expérimentaux. Les résultats de simulation obtenus ont démontré un bon accord avec ceux obtenus par expérimentation. Enfin, la troisième phase a consisté à étudier les effets de variation de paramètres machines sur la distribution finale de température dans un engrenage droit chauffé par induction à doubles fréquences avec concentrateurs de flux. Un modèle 3D a été mis en œuvre par la méthode des éléments finis. Les paramètres machines impliqués sont, la densité de courant imposée dans l'inducteur et le temps de chauffage de deux fréquences (MF et HF). Les résultats obtenus ont conduit à des modèles capables de prédire les températures avec une haute précision dans un engrenage droit. -- Mot(s) clé(s) en français : Traitement thermique par induction, concentrateurs de flux, profil de dureté, acier AISI 4340, ANOVA, modèles de prédiction, méthode des éléments finis (FEM). --
ABSTRACT : Surface induction heat treatment is a manufacturing process that produces the high compression martensitic microstructure on the surface of the treated part to increase the surface hardness, improve the wear and fatigue resistance and maintain the ductile core. This process is purely environmentally friendly, with no emission of toxic gases or fumes into the environment. Nevertheless, the treatment of a mechanical part by induction involves several factors and process control parameters, including material properties, machine parameters and geometries and heating conditions. In order to properly exploit the resources of this process, it is necessary to develop strategies to control and adjust the parameters to accurately produce the desired characteristics of the cured surface without resorting to the traditional time-consuming and costly trial and error process. The objective of the project is to analyze the machine and geometry parameters on the final temperature distribution in order to develop simple models capable of predicting the temperatures and hardness profile with good accuracy for mechanical parts made of AISI 4340 steel heated by induction in the presence of flux concentrators. For this purpose, a three-phase approach was adopted. The first phase consisted in the modeling and simulation by the finite element method of a 2D axisymmetric model with COMSOL software in order to analyze the effects of machine parameters and geometries on the induced current penetration depth for a disk. The parameters involved include, machine power, heating time, part to induction gap and flux concentrator to part gap. The results obtained from this study allowed the establishment of penetration depth prediction models with an accuracy of more than 96%. The second phase conducted a sensitivity study on hardened depths to develop reliable models capable of predicting hardness profiles as a function of involved parameters of a disc using the same approach of the first phase. The proposed models are validated by experimental tests. The simulation results obtained showed a good agreement with those obtained by experimentation. Finally, the third phase consisted in studying the effects of machine parameters variation on the final temperature distribution in a spur gear heated by dual frequency induction with flux concentrators. A 3D model was implemented using the finite element method. The machine parameters involved are, the current density imposed in the inductor and the heating time of two frequencies (MF and HF). The results obtained have led to models capable of predicting temperatures with high accuracy in a spur gear. -- Mot(s) clé(s) en anglais : Induction heat treatment, Flux concentrators, Hardness profile, AISI 4340 steel, ANOVA, Prediction models, Finite element method (FEM)
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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