Les avancées dans le domaine des NUIs (interfaces utilisateur naturelles) permettent aux concepteurs de développer de nouvelles techniques efficaces et faciles à utiliser pour l'interaction 3D. Dans ce contexte, les interfaces mobiles attirent beaucoup d'attention sur la conception de techniques d'interaction 3D pour une utilisation ubiquitaire. Nos travaux de recherche se focalisent sur la proposition de nouvelles techniques d’interaction pour faciliter la sélection et la manipulation d'objets dans des environnements virtuels s’exécutant sur des interfaces mobiles. En effet, l'efficacité et la précision de la sélection des l'objets sont fortement affectés par la taille de la cible et la densité de l’environnement virtuel. Pour surmonter le problème d'occlusion du bout des doigts sur les Smartphones, nous avons conçu deux techniques de sélection reposant sur le toucher. Nous avons également conçu deux techniques hybrides à main levée pour la sélection à distance de petits objets. Pour effectuer une manipulation d’objets contraints sur les Tablet-PC, nous avons proposé une technique bimanuelle basée sur un modèle asymétrique. Les deux mains peuvent être utilisés en collaboration, afin de spécifier la contrainte, déterminer le mode de manipulation et de contrôler la transformation. Nous avons également proposé deux autres techniques de manipulation à une seule main en utilisant les points de contacts identifiés. Les évaluations de nos techniques démontrent qu'ils peuvent améliorer l'expérience des interactions utilisateurs sur des interfaces mobiles. Nos résultats permettent aussi de donner quelques lignes directrices pour améliorer la conception de techniques d'interactions 3D sur des interfaces mobiles. / The advances in the field of NUIs (Natural User Interfaces) can provide more and more guidelines for designers to develop efficient and easy-to-use techniques for 3D interaction. In this context, mobile devices attract much attention to design 3D interaction techniques for ubiquitous usage. Our research work focuses on proposing new techniques to facilitate object selection and manipulation in virtual environments on mobile devices. Indeed, the efficiency and accuracy of object selection are highly affected by the target size and the cluster density. To overcome the fingertip occlusion issue on Smartphones, we have designed two touch-based selection techniques. We have also designed two freehand hybrid techniques for selection of small objects displayed at a distance. To perform constrained manipulation on Tablet-PCs, we have proposed a bimanual technique based on the asymmetrical model. Both hands can be used in collaboration, in order to specify the constraint, determine the manipulation mode, and control the transformation. We have also proposed two other single-hand manipulation techniques using identified touch inputs. The evaluations of our techniques demonstrate that they can improve the users’ interaction experience on mobile devices. Our results permit also to give some guidelines to improve the design of 3D interactions techniques on mobile devices.

2D-3D registration is one of the underpinning technologies that enables image-guided intervention in computer-assisted orthopaedic surgery (CAOS). Preoperative 3D images and surgical plans need to be mapped to the patient in the operating room before they can be used to augment the surgical intervention, and this task is generally fulfilled by using 2D-3D registration which spatially aligns a preoperative 3D image to a set of intraoperative fluoroscopic images. The key problem in 2D-3D registration is to define an accurate similarity metric between the 2D and 3D data, and choose an appropriate optimization algorithm. Various similarity metrics and optimization algorithms have been proposed for 2D-3D registration; however, current techniques have several critical limitations. First, a good initial guess - usually within a few millimetres from the true solution - is required, and such capture range is often not wide enough for clinical use. Second, for currently used optimization algorithms, it is difficult to achieve a good balance between the computation efficiency and registration accuracy. Third, most current techniques register a 3D image of a single bone to a set of fluoroscopic images, but in many CAOS procedures, such as a multi-fragment fracture treatment, multiple bone pieces are involved. In this thesis, research has been conducted to investigate the above problems: 1) two new registration techniques are proposed that use recently developed optimization techniques, i.e. Unscented Kalman Filter (UKF) and Covariance Matrix Adaptation Evolution Strategy (CMA-ES), to improve the capture range for the 2D-3D registration problem; 2) a multiple-object 2D-3D registration technique is proposed that simultaneously aligns multiple 3D images of fracture fragments to a set of fluoroscopic images of fracture ensemble; 3) a new method is developed for fast and efficient construction of anatomical atlases; and 4) a new atlas-based multiple-object 2D-3D registration technique is proposed to aid fracture reduction in the absence of preoperative 3D images. Experimental results showed that: 1) by using the new optimization algorithms, the robustness against noise and outliers was improved, and the registrations could be performed more efficiently; 2) the simultaneous registration of multiple bone fragments could achieve a clinically acceptable global alignment among all objects with reasonable computation cost; and 3) the new atlas construction method could construct and update intensity atlases accurately and efficiently; and 4) the use of atlas in multiple-object 2D-3D registration is feasible. / Thesis (Ph.D, Computing) -- Queen's University, 2011-09-28 10:58:04.406

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Computation of the position and orientation of an object with respect to a camera from its images is called pose estimation problem. Pose estimation is one of the major problems in computer vision, robotics and photogrammetry. Object tracking, object recognition, self-localization of robots are typical examples for the use of pose estimation. Determining the pose of an object from its projections requires 3D model of an object in its own reference system, the camera parameters and 2D image of the object. Most of the pose estimation algorithms require the correspondences between the 3D model points of the object and 2D image points. In this study, four well-known pose estimation algorithms requiring the 2D-3D correspondences to be known a priori / namely, Orthogonal Iterations, POSIT, DLT and Efficient PnP are compared. Moreover, two other well-known algorithms that solve the correspondence and pose problems simultaneously / Soft POSIT and Blind- PnP are also compared in the scope of this thesis study. In the first step of the simulations, synthetic data is formed using a realistic motion scenario and the algorithms are compared using this data. In the next step, real images captured by a calibrated camera for an object with known 3D model are exploited. The simulation results indicate that POSIT algorithm performs the best among the algorithms requiring point correspondences. Another result obtained from the experiments is that Soft-POSIT algorithm can be considered to perform better than Blind-PnP algorithm.

Les contraintes environnementales imposent de trouver des solutions pour limiter les émissions gazeuses (gaz à effet de serre) ainsi que d’éliminer les matériaux nocifs dans les produits de consommation. L’étude de solutions alternatives devient donc un point clé au développement des produits futurs. Dans ce contexte, les véhicules électriques et hybrides sont en forte progression sur le marché mais leur développement commercial reste fortement lié à leur fiabilité, plus particulièrement à celle des organes contrôlés par l’électronique de puissance. Notre étude s’inscrit dans ce cadre et se focalise sur la pâte d’argent micrométrique, matériau candidat au remplacement des solutions à base de plomb pour le report des puces. Si la pâte d’argent est assez bien caractérisée pour ses propriétés électriques, peu de données sont reportées dans littérature quant à ses propriétés mécaniques, pourtant indispensables pour appréhender la durée de vie des assemblages complets. Dans la thèse, une méthode originale d’élaboration des échantillons a été développée. Basée sur les recommandations d’utilisation donnée par le fournisseur, elle a été adaptée afin de d’obtenir des échantillons massifs dont la microstructure brute et après vieillissement en température est identique à celle des brasures réelles. Après élaboration, le taux porosité, compris entre 15 % et 20 %, n’évolue pas au cours de vieillissements représentatifs des conditions d’utilisation réelles. Seule la morphologie des pores évolue, pour laquelle un grossissement, respectant les cinétiques du mûrissement d’Ostwald, et une évolution de la distribution spatiale est observée. Les propriétés mécaniques sont une fonction de la densité à l’état brut. Après vieillissement des échantillons massifs, si les propriétés élastiques ne varient pas (à densité constante), la dispersion des propriétés plastiques sont reliées à la modification de la distribution spatiale des pores. L’évolution des propriétés élastiques sur les échantillons représentatifs des brasures est attribuée aux mécanismes de relaxation des contraintes d’élaboration. Une fois celles-ci relaxées, les propriétés sont identiques pour les deux états (massif et couche mince) et sont donc intrinsèques au matériau. / The requirement for reducing the use of harmful materials in convenience goods hasprompted investigation into alternative solutions. Along with the need to drastically limit theemission of greenhouse gases, the increase of electric or hybrid vehicles in the market reliesmostly on their dependability with a specific focus on reliability of the embedded powerelectronics. The study of alternative materials to lead (Pb) or Pb-based alloys for die bondingis a critical step towards realising an environmentally friendly solution. Micrometric silverpaste was chosen as a candidate because of its excellent electrical properties. However, fewdata are available in the literature concerning its mechanical properties, mandatory to modelthe entire electronic system for service life assessment. The processing route, based on thesintering of micrometric powder, provides a material with significant porosity that is knownto alter the mechanical properties when compared to the dense material. In this thesis, anoriginal processing route was developed in order to obtain bulk samples with the samemicrostructure of real solder joints either before or after ageing. The mechanical properties vsdensity was established prior to or after aging. After aging, the elastic properties do not varywhile the dispersion observed for the plastic properties is connected with the microstructureevolution. The evolution of the elastic properties on the representative samples of solder jointsafter aging is attributed to the mechanisms of stress relaxation. Once these relaxed, theproperties are identical for both states (bulk and thin layer) and are thus intrinsic in thematerial.

Computer graphics perspective is based on photography, the pin-hole camera model. This thesis examines the perspective as practiced by artists, who develop the picture geometry within the planar surface of the canvas. Their approach is flexible, depth is simulated with planar composition as the primary geometry. Renaissance artists discovered construction methods to draw the foreshortening of realistic pictures: the construction of a tiled floor in perspective was fundamental. This thesis presents the framework, a computer program, I developed to create the perspective of pictures based on the geometry practices of artists. Construction lines on the image plane simulate the 3D geometry of the pictorial space; cartoons of foreground elements are manipulated in 2D within the picture perspective; projected shadows, examples of double projection, are also included. A formalism, reformulating algebraically the straight-edge and compass evaluations, generalizes the planar geometry that solves the challenge of depicting 3D. A revised Painter’s algorithm produces the occlusions between the picture elements from sequencing them from their definitions on the canvas.

Computer graphics perspective is based on photography, the pin-hole camera model. This thesis examines the perspective as practiced by artists, who develop the picture geometry within the planar surface of the canvas. Their approach is flexible, depth is simulated with planar composition as the primary geometry. Renaissance artists discovered construction methods to draw the foreshortening of realistic pictures: the construction of a tiled floor in perspective was fundamental. This thesis presents the framework, a computer program, I developed to create the perspective of pictures based on the geometry practices of artists. Construction lines on the image plane simulate the 3D geometry of the pictorial space; cartoons of foreground elements are manipulated in 2D within the picture perspective; projected shadows, examples of double projection, are also included. A formalism, reformulating algebraically the straight-edge and compass evaluations, generalizes the planar geometry that solves the challenge of depicting 3D. A revised Painter’s algorithm produces the occlusions between the picture elements from sequencing them from their definitions on the canvas.

Cette thèse porte sur la catégorisation d'objets vidéo. L'objectif est d'associer des étiquettes sémantiques à des objets 2D présents dans les images/vidéos. L'approche proposée consiste à exploiter des bases d'objets 3D classifiés afin d'identifier des objets 2D inconnus. Nous proposons un schéma de reconnaissance d'objet, conçu pour fonctionner pour des applications en temps réel. La similitude entre des modèles 3D et des contenus 2D inconnu est évaluée à l'aide de la description 2D/3D. Une procédure de vote est ensuite utilisée afin de déterminer les catégories les plus probables de l'objet 2D. Nous proposons aussi une stratégie pour la sélection des vues les plus représentatives d'un objet 3D et un nouveau descripteur de contour (nommé AH). L'évaluation expérimentale a montré que, en employant la sélection intelligente de vues, le nombre de projections peut être diminué de manière significative (jusqu'à 5 fois) tout en obtenant des performances similaires. Les résultats ont également montré la supériorité de l'AH par rapport aux autres descripteurs adoptés. Une évaluation objective de la variabilité intra et inter classe des bases de données 3D impliqués dans ce travail est également proposé, ainsi qu'une étude comparative des approches d'indexations retenues. Une approche de segmentation interactive est également introduite. La méthode proposée est spécifiquement conçu pour surmonter les artefacts de compression tels que ceux mis en place par la compression JPEG. Enfin, nous présentons une plate-forme Web pour l'indexation/la recherche/la classification, qui intègre les différentes méthodologies utilisées dans cette thèse / This Ph.D. thesis tackles the issue of sill and video object categorization. The objective is to associate semantic labels to 2D objects present in natural images/videos. The principle of the proposed approach consists of exploiting categorized 3D model repositories in order to identify unknown 2D objects based on 2D/3D matching techniques. We propose here an object recognition framework, designed to work for real time applications. The similarity between classified 3D models and unknown 2D content is evaluated with the help of the 2D/3D description. A voting procedure is further employed in order to determine the most probable categories of the 2D object. A representative viewing angle selection strategy and a new contour based descriptor (so-called AH), are proposed. The experimental evaluation proved that, by employing the intelligent selection of views, the number of projections can be decreased significantly (up to 5 times) while obtaining similar performance. The results have also shown the superiority of AH with respect to other state of the art descriptors. An objective evaluation of the intra and inter class variability of the 3D model repositories involved in this work is also proposed, together with a comparative study of the retained indexing approaches . An interactive, scribble-based segmentation approach is also introduced. The proposed method is specifically designed to overcome compression artefacts such as those introduced by JPEG compression. We finally present an indexing/retrieval/classification Web platform, so-called Diana, which integrates the various methodologies employed in this thesis

<p>The typical High Dose Rate (HDR) lung brachytherapy procedure involves inserting treatment catheters into the bronchi next to the tumour location using a bronchoscope. The anterior-posterior and lateral fluoroscopy images are acquired in order to localize the catheters prior to treatment. Although, these images enable accurate reconstruction of the catheter location, they do not allow for the visualization of the tumour or organs-at-risk due to poor soft tissue contrast. Although CT images offer an improved soft tissue contrast, moving the patient with catheters in place prior to each treatment is impractical.</p> <p>An alternative option is to use prior diagnostic or external beam radiation treatment planning CT images. These images cannot be used for treatment planning directly because of the variation in patient positioning between the CT and orthogonal images acquisition. In order to account for positioning differences, a 2D/3D registration algorithm that registers the orthogonal images with a previously acquired CT data was developed. The algorithm utilizes a rigid registration model based on a pixel/voxel intensity matching approach. A similarity measure combining normalized mutual information (NMI), image gradient, and intensity difference was developed. Evaluation of the algorithm was performed using tissue equivalent phantoms, and, in the clinical setting using data from six patients. The mean registration error was 2.1 mm and 3.2 mm for phantoms and patients respectively.</p> <p>External objects such as the treatment table and ECG leads are often in CT images, affecting the above mentioned 2D/3D registration. To address this, an algorithm for automatic removal of external objects from CT images was developed. This was applied to automatic contouring and removal of the fiducial markers in CT images used for external beam radiation therapy treatment planning for breast cancer. The algorithm was further modified to compute the girth of patients as part of a diagnostic radiology clinical trial.</p> / Doctor of Philosophy (PhD)

L’amélioration de la solidification de lingots d’acier industriels de plusieurs tonnes demeure un défi scientifique. Lors de cette étape cruciale, des hétérogénéités chimiques – à l’échelle du mètre – peuvent se développer. Le mouvement des grains solides qui se forment et se déplacent dans le bain liquide est un des leviers d’action sur la macroségrégation. L’inoculation permet d’agir sur le nombre, la taille et la morphologie de ces grains via des ajouts dans le métal liquide. Dans ce travail, les nuances 42CrMo4 et 34Cr4 ont été inoculées pour plusieurs formats de lingots. Des techniques de caractérisation (2D et 3D) ont été développées pour la comparaison des structures de solidification dendritiques avant et après inoculation. Une première série de lingotins (50 g) a montré l’effet affinant de poudres à bonne cohérence cristallographique avec la ferrite et l’effet grossissant d’un ferroalliage de cérium. Après une étude à plus grande échelle (8 kg) pour les meilleurs candidats (poudres de TiN, CeO2, Si3N4 et ferroalliage de cérium), un ajout de cérium a été fait dans un lingot industriel de 6,2 t. Le cérium, responsable de la croissance des grains équiaxes pour l’ensemble des lingots caractérisés. Il agit probablement sur les tensions interfaciales solide/liquide et moule/liquide tout en remplaçant les sites de germination nativement présents dans le métal liquide par des inclusions au cérium qui ne servent pas de sites de germination / Improving the solidification of large industrial steel ingots remains a scientific challenge. During casting chemical heterogeneities (macrosegregation), sometimes in the scale of meters, can arise. Solid grain motion is one phenomena responsible for macrosegregation. Inoculation allows the number, size and morphology of these grains to be modified through additions to the liquid metal. In this work 42CrMo4 and 34Cr4 grade steel ingots of several sizes were modified with potential inoculants. Characterization techniques (2D and 3D) were developed to compare dendritic solidification structures before and after inoculation. The first series of small ingots (50 g) showed grain refinement for powder additions with a low lattice misfit between the inoculant and solidifying melt, and a coarsening effect when ferrocerium was added. The best inoculant candidates (TiN, CeO2, Si3N4 powders and cerium ferroalloy) were tested in medium sized ingots, after which the cerium addition was tested with a 6,2 t industrial ingot. Cerium is responsible for coarsening the grain size in all sizes of cast ingots investigated. This is likely due to a modification of the solid/liquid and liquid/mold interfacial energy along with the replacement of existing sites with cerium inclusions which are not active during nucleation