Extracted features based multi-class classification of orthodontic images

The purpose of this study is to investigate computer vision and machine learning methods for classification of orthodontic images in order to provide orthodontists with a solution for multi-class classification of patients’ images to evaluate the evolution of their treatment. Of which, we proposed three algorithms based on extracted features, such as facial features and skin colour using YCbCrcolour space, assigned to nodes of a decision tree to classify orthodontic images: an algorithm for intra-oral images, an algorithm for mould images and an algorithm for extra-oral images. Then, we compared our method by implementing the Local Binary Pattern (LBP) algorithm to extract textural features from images. After that, we applied the principal component analysis (PCA) algorithm to optimize the redundant parameters in order to classify LBP features with six classifiers; Quadratic Support Vector Machine (SVM), Cubic SVM, Radial Basis Function SVM, Cosine K-Nearest Neighbours (KNN), Euclidian KNN, and Linear Discriminant Analysis (LDA). The presented algorithms have been evaluated on a dataset of images of 98 different patients, and experimental results demonstrate the good performances of our proposed method with a high accuracy compared with machine learning algorithms. Where LDA classifier achieves an accuracy of 84.5%

Quantification à partir d'images microtomographiques 3D de la structure des mousses solides

L'objectif de ce travail est de proposer une méthode de quantification des structures poreuses de mousses solides à partir d'images tomographiques à très haute résolution. Nous avons imagé des mousses polymères directement en 3D grâce à une technique de microtomographie par rayonnement synchrotron avec une résolution spatiale de 6.65 microns. Après la phase d'acquisition, des paramètres quantitatifs tels que l'épaisseur des parois de la matrices et le diamètre des bulles d'air doivent être mesurés. Nous comparons pour cela trois approches différentes : par ouverture, par épaisseur locale et par la méthode des sécantes (MIL). Ceci permet de valider les résultats des différentes méthodes. Cette quantification a été appliquée à la mesure sur image 3D des variations dues au changement de température dans le procédé de fabrication des mousses polymères

Contribution à l'étude de la résistance monotone et cyclique des soudures en aciers inoxydables austénitique 3 16L et duplex 2101

This thesis work aims to provide elements of understanding on the fatigue damage mechanisms of stainless steel tanks (manufactured by e.l.m. Leblanc). We are interested in identifying the factors influencing the fatigue behavior of tanks during cyclic pressure loading. ln order to distinguish the stages of crack initiation and propagation, we study the cyclic behavior of model welds. These results also made it possible to evaluate the influence of the process on the behavior of the welds. We complete this stud) with in-situ observations of crack initiation and propagation mechanisms in the presence of a notch.Ce travail de thèse vise à apporter des éléments de compréhensions sur les mécanismes endommagement par fatigue des réservoirs en aciers inoxydables (fabriqués par e.l.m. Leblanc). Nous nous sommes intéressés à identifier les facteurs influençant la tenue en fatigue de réservoirs lors du chargement cyclique de pression. Dans le but de distinguer les stades d'amorçage et de propagation de fissure, nous étudions le comportement en flexion cyclique des soudures modèles. Ces résultats ont permis également d'évaluer l'influence du procédé sur le comportemen des soudures. Nous complétons cette étude par des observations in-situ des mécanismes d'amorçage et de propagation d�� fissures en présence <l'entaille

Contribution to the study of the monotonie and cyclic behavior of welded austenitic 3 l 6L and duplex 2101 stainless steels

Ce travail de thèse vise à apporter des éléments de compréhensions sur les mécanismes endommagement par fatigue des réservoirs en aciers inoxydables (fabriqués par e.l.m. Leblanc). Nous nous sommes intéressés à identifier les facteurs influençant la tenue en fatigue de réservoirs lors du chargement cyclique de pression. Dans le but de distinguer les stades d'amorçage et de propagation de fissure, nous étudions le comportement en flexion cyclique des soudures modèles. Ces résultats ont permis également d'évaluer l'influence du procédé sur le comportemen des soudures. Nous complétons cette étude par des observations in-situ des mécanismes d'amorçage et de propagation d�� fissures en présence <l'entaille.This thesis work aims to provide elements of understanding on the fatigue damage mechanisms of stainless steel tanks (manufactured by e.l.m. Leblanc). We are interested in identifying the factors influencing the fatigue behavior of tanks during cyclic pressure loading. ln order to distinguish the stages of crack initiation and propagation, we study the cyclic behavior of model welds. These results also made it possible to evaluate the influence of the process on the behavior of the welds. We complete this stud) with in-situ observations of crack initiation and propagation mechanisms in the presence of a notch

2D and 3D Characterization of Metal Foams Using X-ray Tomography

International audienceno abstrac

In situ X-ray tomography measurements of deformation in cellular solids

International audienceno abstrac

DETECTION OF RING ARTIFACTS IN COMPUTED TOMOGRAPHIC IMAGES

International audienceIn X-ray Computed Tomography, ring artifacts can be caused by imperfect elements in a detector or also by defects or impurities in the scintillator's crystals. The artifacts appear on Computed Tomographic images as concentric rings superimposed on the images of the structures being scanned. The presence of such artifacts significantly complicates the post processing techniques such as noise reduction, binarization, or segmentation of image information. The efficacy of these techniques depends on the consistency of the method of classification and detection of ring artifacts. In this paper we present a simple, fast and efficient method to detect ring artifacts on Computed Tomographic images in the Polar domain

Segmentation of cancellous bone from high-resolution computed tomography images: influence on trabecular bone measurements

International audienceThe quantification of cancellous bone network from computed tomography (CT) images requires a segmentation step which is crucial and difficult because of the partial volume effect in CT images. In this paper, we present and evaluate a new approach for segmenting cancellous bone network from high-resolution CT (HRCT) slices. The idea is first to detect a skeleton from the crest lines of the structure and then to thicken it to extract the whole bone structure by satisfying local neighborhood constraints. The segmentation requires the adjustment of relative and not absolute parameters like most methods. We quantified the influence of these parameters on architectural measurements. Results were first validated by using a physical phantom and then examined on a series of 12 HRCT images of human lumbar vertebra of different ages. We demonstrated that the choice of segmentation parameters yielded important variability on architectural measurements (up to 20%), but less variability than a more commonly used approach. This stresses the importance of settle on the segmentation parameters for once, which is possible with the proposed method

Viewing the early stage of metal foam formation by computed tomography using synchrotron radiation

Foamed aluminium alloy containing 7wt.-% of Si is investigated by µm-resolved X-ray computed tomography (CT) using synchrotron radiation. The foam is fabricated employing a Powder metallurgical route. The evolution of foam microstructure is characterized by studying a series of samples representing different stages of foam expansion obtained by interrupting the foaming process for each sample at different foaming times. The computer tomographic reconstruction provides a 3D image of the pore structure as well as the spatial distribution of the blowing agent and of the pores at different foaming stages