1,721,004 research outputs found
Incorporation des appareils de voie dans les longs rails soudés
No full textIncorporation des appareils de voie dans les longs rails soudés : ce mémoire de fin de master en mécanique contient une modélisation des aiguillages dans les voies de chemin de fer. A l’initiative et à la demande d’Infrabel, gestionnaire du réseau ferré belge, ce travail vise à évaluer la possibilité de supprimer les joints de dilatation, ou tout autre dispositif permettant l’élongation et le déplacement des rails, à proximité des appareils de voie. Vu la difficulté d’évaluer dans un cadre théorique/analytique le comportement parfois contre-intuitif de la voie, une étude à l’aide d’éléments finis s’imposait. Le logiciel utilisé est « ABAQUS », produit de la marque Dassault Systèmes. Les éléments finis permettent de tenir réellement compte de chaque traverse et de chaque support dans l’évaluation de la résistance d’une voie soumise à une contrainte thermique. En effet, à partir d’une certaine température, la force de compression générée dans les longs rails soudés finit par vaincre la résistance de la voie et entraîne la destruction de la ligne par flambement. Les simulations réalisées illustrent le comportement de la voie soumise à la dilatation des rails qui la composent. Théorie et simulations convergent lorsqu’elles rendent compte de certaines caractéristiques comme la force de résistance au flambement et le déplacement des extrémités des voies. Une fois les résultats comparés aux expériences et aux observations réalisées par les ingénieurs des chemins de fer, la voie courante modélisée sert de base à la modélisation d’un appareil de voie. Ce modèle d’appareil est ensuite incorporé dans celui des longs rails. Les analyses montrent ensuite une augmentation de la contrainte axiale interne des rails au niveau des aiguilles. Cette augmentation correspond à une diminution de la force thermique maximale menant au flambement de l’ensemble, car il apparaît que l’appareil se comporte comme un lieu privilégié de concentration de contrainte. Finalement, on constate que la résistance de l’appareil dans les longs rails dépend principalement de sa géométrie propre et de la composition et de la résistance du ballast. La conclusion principale du mémoire est la suivante : la force critique de résistance au flambement diminue en raison de la présence de l’appareil mais cette diminution reste suffisamment faible pour qu’on puisse justifier la suppression des joints et appareils de dilatation à proximité des aiguillages tout en conservant une marge de sécurité confortable.Master [120] : ingénieur civil mécanicien, Université catholique de Louvain, 201
Fracture of 7xxx aluminium alloys with tailored friction stir processed microstructures
No full textThe present thesis investigates the influence of 7XXX aluminium alloys microstructure on damage mechanisms. 7XXX alloys are widely used as structural materials due to their high strength and low density. However, strength was obtained at the expense of ductility, which is a limiting factor for forming applications. Ductility can be related to the uniform elongation εu prior to material strain localization, or related to the fracture strain εf that is related to the ultimate strain level that the material reaches at failure. It was revealed in the literature that the microstructure of 7XXX alloys is affecting damage initiation, propagation and coalescence. This correlation between microstructural features and damage mechanisms opens the way for mechanical performances optimization by microstructural changes. Indeed, the 7XXX alloys microstructure is complex and its modification by thermomechanical and heat treatments is not obvious. This work focusses on manufacturing a variety of 7XXX microstructures prior to testing their mechanical properties. Friction Stir Processing (FSP) was selected for refining the 7XXX alloys microstructure. Obtaining FSPed material in full strength condition was a first achievement presented in this work. This specific FSPed material has a significantly higher ductility compared to the standard base alloy at equivalent tensile strength, which is a very interesting result of the present thesis. In situ X-ray tomography is used for revealing the changes in fracture mechanisms after FSP on 7XXX alloys. However, despite higher ductility, the FSPed 7XXX alloys do not show higher crack propagation resistance, which is an unexpected decoupling of the ductility versus toughness. Investigations were pursued for understanding better the damage mechanisms and the crack propagation behaviour of the manufactured 7XXX alloys microstructures. The understanding of damage sequence in 7XXX aluminium alloys is then transposed to a numerical model that simulates intrinsic components of the real microstructure in order to predict the material failure. This model offers an outlook for designing new 7XXX microstructures, reaching high strength, ductility and toughness simultaneously.(FSA - Sciences de l'ingénieur) -- UCL, 202
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
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