1,720,953 research outputs found
Suppression d'aberrations optiques des capteurs à triangulation laser en substituant l'objectif à lentilles par une fente
Get PDFRÉSUMÉ : Ce mémoire présente les différents aspects du fonctionnement des capteurs de distance à triangulation laser: de l'émission du faisceau laser à la capture par caméra, en passant par l'objectif à lentilles, sans oublier le principe de triangulation et les algorithmes d'analyse d'images. Ce mémoire abordera aussi l'utilité, les avantages et désavantages de ces capteurs, ainsi que la recherche actuelle faite pour contourner leurs limitations. De plus, nous proposerons aussi une nouvelle méthode de capture de tache laser qui consiste à remplacer l'objectif à lentilles par une fente suffisamment petite pour exploiter la capture par sténopé et le principe de diffraction. Ainsi, mis à part l'astigmatisme, les aberrations optiques monochromatiques sphériques, de défocalisation, de coma, de courbure de champ et de distorsion sont évitées et la réflexion interne est diminuée au point de pratiquement disparaître. De plus, l'utilisation d'une fente réduit le nombre de pièces optiques dans le montage et simplifie la modélisation de la tache du laser pour en trouver le centre. Nous avons produit des jeux de données de capture d'image avec un objectif à lentilles puis avec une fente sur différents matériaux à l'aide d'un montage où la cible est posée sur une vis sans fin dont sa position est contrôlée par un moteur pas à pas à précision élevée. Avec ces données, nous avons extrait le centre de la tache laser avec différents algorithmes de traitement d'image. Ensuite, nous avons pu évaluer la qualité de l'ajustement de la courbe de triangulation sur les ensembles de points capturés par les deux méthodes. Nous concluons que la fente contourne bel et bien les aberrations optiques et la réflexion interne des objectifs à lentilles, ce qui rend la capture plus précise. De plus, comparée à un objectif à lentilles, la capture par fente demande beaucoup moins de pièces, ce qui diminuera les coûts et simplifierait l'entretien et la calibration. -- Mot(s) clé(s) en français : aberration optique, caméra à sténopé, capteur de distance, capteur de déplacement, capteur, diffraction, laser, lentille, mesure de distance, mesure sans contact, optique à sténopé, optique, triangulation laser, triangulation. --
ABSTRACT : This master's thesis presents the various aspects of the laser triangulation sensors: laser beam emission, camera capture, lenses, triangulation principle and image analysis algorithms. This thesis will also discuss the usefulness, advantages and disadvantages of these sensors, as well as current research being carried out to overcome their limitations. This thesis presents a new capture method for laser triangulation sensors that replaces the lens with a slit---effectively making it a pinhole camera---and exploiting diffraction effects. This new method circumvents optical aberrations such as spherical, defocusing, coma, field curvature, and lens distortion, and reduces lens flare to a point where it can be virtually ignored. Moreover, using a slit reduces the number of optical parts and simplifies the modeling of the laser spot to find its center. To test our proposed method, we generated data sets taking pictures with both a lens and a slit on different materials placed on a worm gear with its position controlled by a high precision step motor. With this data, we extracted the center of the laser spot with different image processing algorithms. It was then possible to assess the goodness of fit of the triangulation curve using the sets of points captured by both methods. We show that not only we circumvent the adverse effects of optical aberrations and lens flare, we obtain a more accurate estimation of the actual known distance of the target. Furthermore, compared to lens, slit capture requires fewer parts, which could cut costs and simplify maintenance and calibration. -- Mot(s) clé(s) en anglais : diffraction, displacement sensor, distance measurement, laser triangulation, laser, lens, non-contact measurement, optical aberration, optics, pinhole camera, pinhole optics, range sensor, sensor, triangulation
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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