1,720,985 research outputs found
Reconstruction of the deformation of a tubular scene for the use of a pack of miniaturized capsules in the small intestine
No full textL'intestin grêle est un organe complexe à observer de l'intérieur du fait de sa longueur et sa tortuosité. Pourtant cela reste nécessaire dans le cadre du diagnostic et du suivi de certaines maladies telles que la maladie de Crohn ou les polyposes. Si les capsules endoscopiques permettent depuis plus de vingt ans de parcourir l'intégralité de l'intestin grêle, son déplacement passif soumis au péristaltisme et sa faible fréquence d'acquisition d'image rendent l'analyse chronophage et fastidieuse. La reconstruction 3D de l'intestin grêle à partir des vidéos est une piste envisagée pour faciliter l'analyse et localiser les lésions. Cette reconstruction n'est pas aisée du fait des facteurs environnementaux : la déformation de l'intestin, sa forme tubulaire et sa texture uniforme, mais aussi techniques avec des images de faible résolution et un mouvement et une vitesse de la capsule non contrôlés.Après l'analyse du besoin clinique, nous introduisons le concept de meute de capsules endoscopiques miniatures. L'utilisation d'une telle meute pourra rendre possible l'observation de l'intestin chez les patients atteints de sténoses, c'est-à-dire un rétrécissement de la lumière intestinale suite à l'inflammation des tissus. Elle évitera aussi certains examens préliminaires à l'utilisation des capsules actuelles pour ces patients et pourra être utilisée plus largement chez les enfants. Dans ce contexte, nous proposons une modification des procédures de diagnostic et de suivi de la maladie de Crohn. Cependant, la réduction de la qualité de l'image de ces mini-capsules, par la diminution de la résolution et le manque de lumière, impactera non seulement la visibilité des lésions, mais aussi les algorithmes de reconstruction. De ce fait, nous réfléchissons aux différentes stratégies de reconstruction déformable et multivue de l'intestin grêle. Nous posons ainsi les bases d'un algorithme de reconstruction et localisation simultanés pour l'intestin, le GutSLAM. Pour cela, nous réfléchissons aux modifications des dernières méthodes de SLAM déformable dans l'état de l'art, afin de tenir compte de la topologie tubulaire de l'intestin. Nous nous concentrons principalement sur le module de suivi des déformations. Pour cela, nous choisissons d'utiliser une méthode de reconstruction par le mouvement de scènes déformables (NRSfM : Non-Rigid Structure-from-Motion) de l'état de l'art capable de reconstruire les déformations fronto-parallèles à partir de deux images. Nous l'adaptons à l'utilisation d'un gabarit tubulaire pour reconstruire les déformations radiales observées dans l'intestin grêle. Deux approches sont proposées. La première consiste à passer par l'intermédiaire d'une image virtuelle, obtenue à partir des coordonnées polaires, pour calculer la relation entre les points dans les deux images nécessaire à la déformation du gabarit. Dans la seconde approche, nous calculons les déformations directement à partir de ces images virtuelles. Nous ne les avons pas intégré dans un algorithme complet de SLAM déformables, toutefois ces méthodes présentent des résultats encourageants pour la reconstruction de la déformée à partir de deux vues.The small intestine is a complex organ to observe from the inside, due to its length and tortuosity. However, it is essential for diagnosing and monitoring certain diseases such as Crohn's disease and polyposis. Although endoscopic capsules have been used for over twenty years to scan the entire small intestine, its passive movement, subject to peristalsis, and low image acquisition frequency make analysis time-consuming and tedious. 3D reconstruction of the small intestine from video is one way of facilitating analysis and locating lesions. Such reconstruction is not easy, however, due to environmental factors such as the deformation of the intestine, its tubular shape and uniform texture, as well as technical factors such as low-resolution images and uncontrolled capsule movement and speed.After analyzing the clinical need, we introduce the concept of a pack of miniature endoscopic capsules. The use of such a pack will make it possible to observe the intestine in patients with stenosis, i.e. narrowing of the intestinal lumen as due to tissue inflammation. It will also obviate the need for certain examinations preliminary to the use of current capsules for these patients, and could be used more widely in children. In this context, we propose a modification of the procedures for diagnosing and monitoring Crohn's disease. However, the reduced image quality of these mini-capsules, through lower resolution and lack of light, will impact not only lesion visibility, but also reconstruction algorithms. As a result, we are considering different strategies for deformable and multiview reconstruction of the small intestine. We are thus laying the foundations for a simultaneous reconstruction and localization algorithm for the intestine, the GutSLAM. To this end, we are considering modifications to the last methods from state-of-the-art of deformable SLAM, to take account of the tubular topology of the intestine. Our main focus is on the deformation tracking module. For this, we choose to use a Non-Rigid Structure-from-Motion (NRSfM) method from state-of-the-art, which is capable of reconstructing fronto-parallel deformations from two images. We adapt it to the use of a tubular template to reconstruct radial deformations observed in the small intestine. Two approaches are proposed. The first involves using a virtual image, obtained from polar coordinates, to calculate the relationship between points in the two images required to deform the template. In the second approach, we calculate the deformations directly from these virtual images. We have not integrated them into a complete deformable SLAM algorithm, however these methods show encouraging results for deformation reconstruction from two views
Reconstruction 3D déformable basée sur l'image utilisant la géométrie différentielle et les connexions de Cartan.
No full textReconstructing the 3D shape of objects from multiple images is an important goal in computer vision and has been extensively studied for both rigid and non-rigid (or deformable) objects. Structure-from-Motion (SfM) is an algorithm that performs the 3D reconstruction of rigid objects using the inter-image visual motion from multiple images obtained from a moving camera. SfM is a very accurate and stable solution. Deformable 3D reconstruction, however, has been widely studied for monocular images (obtained from a single camera) and still emains an open research problem. The current methods exploit visual cues such as the inter-image visual motion and shading in order to formalise a reconstruction algorithm. This thesis focuses on the use of the inter-image visual motion for solving this problem. Twotypes of scenarios exist in the literature: 1) Non-Rigid Structure-from-Motion (NRSfM) and 2) Shape-from-Template (SfT). The goal of NRSfM is to reconstruct multiple shapes of a deformable object as viewed in multiple images while SfT (also referred to as template-based reconstruction) uses a single image of a deformed object and its 3D template (a textured 3D shape of the object in one configuration) to recover the deformed shape of the object.We propose an NRSfM method to reconstruct the deformable surfaces undergoing isometric deformations (the objects do not stretch or shrink under an isometric deformation) using Riemannian geometry. This allows NRSfM to be expressed in terms of Partial Differential Equations (PDE) and to be solved algebraically. We show that the problem has linear complexity and the reconstruction algorithm has a very low computational cost compared to existing NRSfM methods. This work motivated us to use differential geometry and Cartan’s theory of connections to model NRSfM, which led to the possibility of extending the solution to deformations other than isometry. In fact, this led to a unified theoretical framework for modelling and solving both NRSfM and SfT for various types of deformations. In addition, italso makes it possible to have a solution to SfT which does not require an explicit modelling of deformation. An important point is that most of the NRSfM and SfT methods reconstruct the thin-shell surface of the object. The reconstruction of the entire volume (the thin-shell surface and the interior) has not been explored yet. We propose the first SfT method that reconstructs the entire volume of a deformable object.La reconstruction 3D d’objets à partir de plusieurs images est un objectif important de la vision par ordinateur. Elle a été largement étudiée pour les objets rigides et non rigides (ou déformables). Le Structure-from-Motion (SfM) est un algorithme qui effectue la reconstruction 3D d’objets rigides en utilisant le mouvement visuel entre plusieurs images obtenues à l’aide d’une caméra en mouvement. Le SfM est une solution très précise et stable. La reconstruction 3D déformable a été largement étudiée pour les images monoculaires (obtenues à partir d’une seule caméra) mais reste un problème ouvert. Les méthodes actuelles exploitent des indices visuels tels que le mouvement visuel inter-image et l’ombrage afin de construire un algorithme de reconstruction. Cette thèse se concentre sur l’utilisation du mouvement visuel inter-image pour résoudre ce problème. Deux types de scénarios existent dans la littérature: 1) le Non-Rigid Structure-from-Motion (NRSfM) et 2) le Shape-from-Template (SfT). L’objectif du NRSfM est de reconstruire plusieurs formes d’un objet déformable tel qu’il apparaı̂t dans plusieurs images, alors que le SfT (également appelé reconstruction à partir d’un modèle de référence) utilise une seule image d’un objet déformé et son modèle 3D de référence (une forme 3D texturée de l’objet dans une configuration) pour estimer la forme déformée de l’objet.Nous proposons une méthode de NRSfM pour reconstruire les surfaces déformables soumises à des déformations isométriques (les objets ne s’étirent pas ou ne se contractent pas sous une déformation isométrique) en utilisant la géométrie riemannienne. Cela permet d’exprimer le NRSfM en termes d’équations aux dérivées partielles et de le résoudre algébriquement. Nous montrons que le problème a une complexité linéaire et que l’algorithme de reconstruction proposé a un coût de calcul très bas comparé aux méthodes existantes de NRSfM. Ce travail nous a motivé à utiliser la géométrie différentielle et la théorie des connexions de Cartan pour modéliser le NRSfM, ce qui nous a permis d’étendre la solution à des déformations autres que l’isométrie. En fait, cela a conduit à un cadre théorique unifié pour modéliser et résoudre le NRSfM et le SfT pour différents types de déformations. Ce cadre permet également d’avoir une solution au SfT qui ne nécessite pas de modélisation explicite de la déformation. Un point important est que la plupart des méthodes de NRSfM et de SfT reconstruisent la surface de l’objet (hypothèse coque mince). La reconstruction de l’ensemble d’un volume (la surface et l’intérieur d’un objet) n’avait pas encore été explorée. Nous proposons la première méthode de SfT qui reconstruit le volume complet d’un objet déformable
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
3DVFX: 3D Video Editing using Non-Rigid Structure-from-Motion
No full textNumerous video post-processing techniques can add or remove objects to the observed scene in the video. Most of these techniques rely on 2D image points to perform the desired changes. Structure-from-Motion (SfM) has allowed the use of 3D points, however only for the objects that remain rigid in the scene. We propose to use both 2D image points and 3D points to modify the scene's deformable objects using Non-Rigid Structure-from-Motion (NRSfM). We rely on a recent effective NRSfM solution to develop a complete pipeline including manual 3D editing of an image and automatic 3D transfer of the edits. We perform object manipulation tasks such as retexturing a real deforming object.Eurographics 2019 - Short PapersImage and Vide
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
- …
