1,720,955 research outputs found
Relation entre l’état métallurgique d’aciers inoxydables martensitiques et les émissions de particules en situation de freinage
No full textBraking by friction is a source of particulate emissions critical to air quality, particularly in urban environments. Most of these particles are metal oxides, nanometric in size and potentially carcinogenic. They can bypass natural barriers and accumulate in the human body and biota, constituting a major public health and environmental issue. Iron oxides are the most common particles, originating from the wear of friction materials, notably the lamellar graphite cast iron that makes up the great majority of automotive brake discs. The aim of this thesis is to examine the potential for reducing these emissions at their source, through the use of alternative stainless steels to cast iron. Different grades of martensitic stainless steels are developed and compared with a lamellar graphite cast iron used as a reference. Two brake linings are considered to discriminate wear processes and their link with particulate emissions. To gain a better understanding of particle production and emission factors, the research focused on linking the dynamics of emissions with the tribological circuit and the thermomechanical loading of the disc-pad contact. To this end, we have developed an experiment capable of reproducing braking scenarios representative of urban and suburban traffic on a laboratory tribometer. The instrumentation set up includes a system for sampling and analyzing particle emissions, coupled with tribological, thermal and thermomechanical loading monitoring. The multiphysics and multiscale approach adopted is based on "operando" and "post mortem analyses of rubbed surfaces, wear and particle emissions. It questions the involvement of materials within the tribological triplet, and considers environmental, first-bodies (disc and pad) and usage factors. Links are established with the tribological circuit, the contact loading and the localization of energy dissipation in the contact. Wear processes are studied in relation to microstructures, deformation mechanisms and metallurgical transformations in the vicinity of the disc's worn surface, as well as surface oxidation mechanisms, for a better understanding of source flow formation and third-body circulation within the tribological circuit. The work, co-financed by the Hauts-de-France region and the Initiative d'Excellence Université de Lille, was carried out in partnership with APERAM Stainless SteelLe freinage par friction est une source d'émission de particules critiques pour la qualité de l’air, particulièrement en milieu urbain. La plupart de ces particules sont constituées d’oxydes métalliques, de taille nanométrique et potentiellement cancérogènes. Elles peuvent franchir les barrières naturelles et s'accumuler dans le corps humain et le vivant, constituant ainsi un problème majeur de santé publique et environnemental. Les oxydes de fer sont les particules les plus courantes, provenant de l'usure des matériaux de friction, notamment la fonte à graphite lamellaire qui constitue la grande majorité des disques de frein automobile. L'objectif de la thèse porte sur le potentiel de réduction à la source de ces émissions par l’usage d’aciers inoxydables alternatifs à la fonte. Différentes nuances d'aciers inoxydables martensitiques sont développés et comparés à une fonte à graphite lamellaire utilisée comme référence. Deux garnitures de frein sont considérées afin de discriminer les processus d’usure et leur lien avec les émissions de particules. Pour mieux comprendre les facteurs déterminant de la production et de l'émission de particules, les travaux se sont attachés à lier la dynamique des émissions avec le circuit tribologique et la sollicitation thermomécanique du contact disque - garniture. Pour cela, une expérimentation est développée, capable de reproduire des scénarios de freinage représentatifs de la circulation automobile urbaine et périurbaine sur un tribomètre de laboratoire. L'instrumentation mise en place comprend un système de prélèvement et d’analyse des émissions de particules couplé à un monitoring tribologique, thermique et thermomécanique de la sollicitation. La démarche multiphysique et multiéchelle adoptée s’appuie ainsi sur des analyses "operando" et "post mortem", qu’il s’agisse des surfaces frottées, de l’usure et des particules émises. Elle questionne l’implication des matériaux au sein du triplet tribologique, et considère des facteurs environnementaux, premiers corps (disque et garniture) et d’usage. Des liens sont établis avec le circuit tribologique, la sollicitation et la localisation de la dissipation de l'énergie dans le contact. Les processus d'usure sont étudiés en relation avec les microstructures, les mécanismes de déformation et les transformations métallurgiques à proximité de la surface frottée du disque, ainsi que les mécanismes d’oxydation en surface, pour une meilleure compréhension de la formation des débits source et de la circulation du troisième corps au sein du circuit tribologique. Les travaux, co-financés par la région Hauts-de-France et l'Initiative d'Excellence Université de Lille, ont fait l'objet d'un partenariat avec la société APERAM Stainless Stee
Relationship between the metallurgical state of martensitic stainless steels and particulate emission in braking situation
No full textLe freinage par friction est une source d'émission de particules critiques pour la qualité de l’air, particulièrement en milieu urbain. La plupart de ces particules sont constituées d’oxydes métalliques, de taille nanométrique et potentiellement cancérogènes. Elles peuvent franchir les barrières naturelles et s'accumuler dans le corps humain et le vivant, constituant ainsi un problème majeur de santé publique et environnemental. Les oxydes de fer sont les particules les plus courantes, provenant de l'usure des matériaux de friction, notamment la fonte à graphite lamellaire qui constitue la grande majorité des disques de frein automobile. L'objectif de la thèse porte sur le potentiel de réduction à la source de ces émissions par l’usage d’aciers inoxydables alternatifs à la fonte. Différentes nuances d'aciers inoxydables martensitiques sont développés et comparés à une fonte à graphite lamellaire utilisée comme référence. Deux garnitures de frein sont considérées afin de discriminer les processus d’usure et leur lien avec les émissions de particules. Pour mieux comprendre les facteurs déterminant de la production et de l'émission de particules, les travaux se sont attachés à lier la dynamique des émissions avec le circuit tribologique et la sollicitation thermomécanique du contact disque - garniture. Pour cela, une expérimentation est développée, capable de reproduire des scénarios de freinage représentatifs de la circulation automobile urbaine et périurbaine sur un tribomètre de laboratoire. L'instrumentation mise en place comprend un système de prélèvement et d’analyse des émissions de particules couplé à un monitoring tribologique, thermique et thermomécanique de la sollicitation. La démarche multiphysique et multiéchelle adoptée s’appuie ainsi sur des analyses "operando" et "post mortem", qu’il s’agisse des surfaces frottées, de l’usure et des particules émises. Elle questionne l’implication des matériaux au sein du triplet tribologique, et considère des facteurs environnementaux, premiers corps (disque et garniture) et d’usage. Des liens sont établis avec le circuit tribologique, la sollicitation et la localisation de la dissipation de l'énergie dans le contact. Les processus d'usure sont étudiés en relation avec les microstructures, les mécanismes de déformation et les transformations métallurgiques à proximité de la surface frottée du disque, ainsi que les mécanismes d’oxydation en surface, pour une meilleure compréhension de la formation des débits source et de la circulation du troisième corps au sein du circuit tribologique. Les travaux, co-financés par la région Hauts-de-France et l'Initiative d'Excellence Université de Lille, ont fait l'objet d'un partenariat avec la société APERAM Stainless SteelBraking by friction is a source of particulate emissions critical to air quality, particularly in urban environments. Most of these particles are metal oxides, nanometric in size and potentially carcinogenic. They can bypass natural barriers and accumulate in the human body and biota, constituting a major public health and environmental issue. Iron oxides are the most common particles, originating from the wear of friction materials, notably the lamellar graphite cast iron that makes up the great majority of automotive brake discs. The aim of this thesis is to examine the potential for reducing these emissions at their source, through the use of alternative stainless steels to cast iron. Different grades of martensitic stainless steels are developed and compared with a lamellar graphite cast iron used as a reference. Two brake linings are considered to discriminate wear processes and their link with particulate emissions. To gain a better understanding of particle production and emission factors, the research focused on linking the dynamics of emissions with the tribological circuit and the thermomechanical loading of the disc-pad contact. To this end, we have developed an experiment capable of reproducing braking scenarios representative of urban and suburban traffic on a laboratory tribometer. The instrumentation set up includes a system for sampling and analyzing particle emissions, coupled with tribological, thermal and thermomechanical loading monitoring. The multiphysics and multiscale approach adopted is based on "operando" and "post mortem analyses of rubbed surfaces, wear and particle emissions. It questions the involvement of materials within the tribological triplet, and considers environmental, first-bodies (disc and pad) and usage factors. Links are established with the tribological circuit, the contact loading and the localization of energy dissipation in the contact. Wear processes are studied in relation to microstructures, deformation mechanisms and metallurgical transformations in the vicinity of the disc's worn surface, as well as surface oxidation mechanisms, for a better understanding of source flow formation and third-body circulation within the tribological circuit. The work, co-financed by the Hauts-de-France region and the Initiative d'Excellence Université de Lille, was carried out in partnership with APERAM Stainless Stee
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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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