PREVALENCE OF TEMPOROMANDIBULAR DISORDERS AMONG ORTHODONTIC PATIENTS (CROSS-SECTIONAL CLINICAL SURVEY)

Orthodontic treatment as a risk factor for the development of temporomandibular disorders (TMD) has been a controversy in literature. The aim of this study was to evaluate the prevalence of TMD, as defined in the Diagnostic Criteria (DC)/TMD Axis II, among orthodontic patients. A cross-sectional study (N=180) consisted of 3 groups: 60 control patients seeking orthodontic consultation, 60 patients undergoing orthodontic treatment for 3-5 months, 60 patients undergoing orthodontic treatment for 10-14 months. Patients answered a structured questionnaire that rated their oral parafunctions according to the Oral Behavior Checklist (OBC), pain intensity levels according to the Graded Chronic Pain Scale (GCPS), jaw functional limitations according to the Jaw Functional Limitation Scale 20 (JFLS-20), psychosocial factors (PHQ-9) and somatization levels (PHQ-15). The Chi Square test showed a statistically significant difference p-value=0.001 among both active orthodontic groups (3-5 months/10-14 months) regarding masticatory limitation (53.3%), vertical mobility limitation (41.7% for 3-5 months and 55.0% 10-14 months) and verbal & emotional expression limitation (53.3% 3-5 months and 66.7% 10-14 months). The findings revealed that as orthodontic treatment progresses, the limitation increases. Moreover, no statistical significance was observed between the three groups regarding oral parafunctional habits, chronic pain levels, psychosocial status and somatization. Orthodontic treatment is not a major factor associated with the symptoms of the TMD. Further prospective studies are needed to evaluate the true role of orthodontic treatment in the development of TMD

Microstructural characterization of a Canadian oil sand

The microstructure of oil sand samples extracted at a depth of 75 m from the estuarine Middle McMurray formation (Alberta, Canada) has been investigated by using high resolution 3D X-Ray microtomography ($\mu$CT) and Cryo Scanning Electron Microscopy (CryoSEM). $\mu$CT images evidenced some dense areas composed of highly angular grains surrounded by fluids that are separated by larger pores full of gas. 3D Image analysis provided in dense areas porosity values compatible with in-situ log data and macroscopic laboratory determinations, showing that they are representative of intact states. $\mu$CT hence provided some information on the morphology of the cracks and disturbance created by gas expansion. The CryoSEM technique, in which the sample is freeze fractured within the SEM chamber prior to observation, provided pictures in which the (frozen) bitumen clearly appears between the sand grains. No evidence of the existence of a thin connate water layer between grains and the bitumen, frequently mentioned in the literature, has been obtained. Bitumen appears to strongly adhere to the grains, with some grains completely being coated. The curved shape of some bitumen menisci suggests a bitumen wet behaviour

DTW-Global Constraint Learning Using Tabu Search Algorithm

AbstractMany methods have been proposed to measure the similarity between time series data sets, each with advantages and weaknesses. It is to choose the most appropriate similarity measure depending on the intended application domain and data considered. The performance of machine learning algorithms depends on the metric used to compare two objects. For time series, Dynamic Time Warping (DTW) is the most appropriate distance measure used. Many variants of DTW intended to accelerate the calculation of this distance are proposed. The distance learning is a subject already well studied. Indeed Data Mining tools, such as the algorithm of k-Means clustering, and K-Nearest Neighbor classification, require the use of a similarity/distance measure. This measure must be adapted to the application domain. For this reason, it is important to have and develop effective methods of computation and algorithms that can be applied to a large data set integrating the constraints of the specific field of study. In this paper a new hybrid approach to learn a global constraint of DTW distance is proposed. This approach is based on Large Margin Nearest Neighbors classification and Tabu Search algorithm. Experiments show the effectiveness of this approach to improve time series classification results

Etude par tomographie X et modélisation par éléments finis du comportement mécanique des mousses solides

Les mousses constituent une classe de matériaux très importante de part leur champ dapplication (allégement de structure, protection contre les chocs, isolation thermique et sonore, etc) et leur poids économique qui se situe au niveau de laluminium ou du verre. Le besoin doptimiser les performances et daméliorer la sécurité nécessite que lon ait une bonne connaissance de la relation entre leurs propriétés et leur microstructure. Lapparition de techniques expérimentales permettant de caractériser en 3D la répartition de la matière (tomographie X) puis son comportement sous sollicitations mécaniques (essais in situ), et la nécessité de mieux comprendre pour pouvoir optimiser ces matériaux, motivent les nouveaux outils présentés dans ce travail de thèse. Dans ce cadre général, lobjectif particulier de cette thèse est la compréhension des mécanismes qui interviennent lors de la déformation des mousses et le développement dun outil de modélisation capable den rendre compte de manière prédictive. Le problème central auquel nous nous sommes attaqués est la décorrélation des rôles respectifs de la nature du matériau et de l\u27arrangement spatial de la phase solide. Notre démarche sest scindée en deux parties. Une partie expérimentale dont le but est de caractériser mécaniquement et morphologiquement une mousse modèle de polyuréthane. Une partie modélisation qui vise à mettre au point un outil numérique capable de rendre compte de la structure réelle de la mousse. Les deux parties se rejoignent enfin pour valider la technique de modélisation à partir des observations expérimentales. Une foi validée, la technique de modélisation est appliquée à dautres types de mousses et en particulier des mousses daluminium de faible densité à cellules ouvertes et fermées. La technique de modélisation est par la suite mise à profit pour étudier leffet des propriétés du matériau solide sur le comportement des mousses à travers la variation des paramètres dentrée des modèles étudiés ainsi que leur comportement sous dautres modes de sollicitation que la compression notamment en traction, en torsion et sous chargement multiaxial

New insights of foam flow dynamics in a high-complexity 2D micromodel

International audienceIn this work, we present direct observation of foam flow through a 2D porous microfluidic device. Through a specially designed image processing workflow, we perform individual bubble tracking and establish flow dynamics within the micromodel structure. In addition to our experimental data, we provide 2D and 3D numerical Newtonian flow simulations on equivalent digitized versions of the model, carried out using Lattice Boltzmann simulation codes for comparison. The results show that foam flow in our experimental conditions, low gas fraction and high injection velocity, demonstrate a high degree of similarity to the flow of a Newtonian fluid in both 2D and 3D simulations, in aspects of large-scale flow distribution homogeneity and specific flow passage activation. However, the foam data shows a larger spread of pore-scale flow velocities, spanning from blocked off areas of quasi-zero flow, to zones of high velocity, with velocities well above the Newtonian counterparts. For our model depth and characteristics, the 2D simulation demonstrates slightly more flow heterogeneity and is closer to the foam case. Detailed bubble tracking gives access to other characteristics of the foam flow inside the medium such as the dichotomy between the flow patterns of the smallest bubbles, typically dispersing and accessing most regions available, and the largest bubbles, which travel in long straight preferential paths exclusively. We show that intrinsically tied to these different flow patterns is the relationship between bubble velocity and bubble size, as we demonstrate distinct populations of trapped and flowing bubbles with distinct sizes. Finally, we explore the relationships between microstructural parameters and flow intensity and note a weak correlation to local structural parameters. Our study, which combines high spatial and time resolution, small network dimensions, high network complexity and efficient bubble tracking, therefore sheds new light on the study of foam flow in porous media

Estimations Of The Critical Percolation Threshold From The Zeros Of Connectivity Number

International audienc

Etude par tomographie X et modélisation par éléments finis du comportement mécanique des mousses solides

Les mousses constituent une classe de matériaux très importante de part leur champ d application (allégement de structure, protection contre les chocs, isolation thermique et sonore, etc ) et leur poids économique qui se situe au niveau de l'aluminium ou du verre. Le besoin d'optimiser les performances et d'améliorer la sécurité nécessite que l'on ait une bonne connaissance de la relation entre leurs propriétés et leur microstructure. L'apparition de techniques expérimentales permettant de caractériser en 3D la répartition de la matière (tomographie X) puis son comportement sous sollicitations mécaniques (essais in situ), et la nécessité de mieux comprendre pour pouvoir optimiser ces matériaux, motivent les nouveaux outils présentés dans ce travail de thèse. Dans ce cadre général, l'objectif particulier de cette thèse est la compréhension des mécanismes qui interviennent lors de la déformation des mousses et le développement d'un outil de modélisation capable d'en rendre compte de manière prédictive. Le problème central auquel nous nous sommes attaqués est la décorrélation des rôles respectifs de la nature du matériau et de l'arrangement spatial de la phase solide. Notre démarche s'est scindée en deux parties. Une partie expérimentale dont le but est de caractériser mécaniquement et morphologiquement une mousse modèle de polyuréthane. Une partie modélisation qui vise à mettre au point un outil numérique capable de rendre compte de la structure réelle de la mousse. Les deux parties se rejoignent enfin pour valider la technique de modélisation à partir des observations expérimentales. Une foi validée, la technique de modélisation est appliquée à d'autres types de mousses et en particulier des mousses d'aluminium de faible densité à cellules ouvertes et fermées. La technique de modélisation est par la suite mise à profit pour étudier l effet des propriétés du matériau solide sur le comportement des mousses à travers la variation des paramètres d'entrée des modèles étudiés ainsi que leur comportement sous d'autres modes de sollicitation que la compression notamment en traction, en torsion et sous chargement multiaxial.The mechanical properties of cellular materials are related to their micro-structure. In fact, macroscopic stresses are the consequence of stresses in the cell wall and struts and of stresses in the cell walls and struts and of the cell failure mechanisms. In the present work we perform tomography during in situ compression tests on different type of foams to inspect the 3D-microstructure and deformation mechanisms. We also present a method to transform large data images of actual microstructures into a tetrahedral mesh, which will be used to model the mechanical behaviour by the finite element method. We finally confront computation results and in situ observations to validate the model. X-ray Computed Micro Tomography (XRCMT) has been widely used recently as a non-destructive technique that gives picture of the interior of cellular solids. This allows studying architectural parameters and, when coupled with in situ loading tests, deformation mechanisms of foams. Local deformation mechanisms of closed cell foam have been studied during compression experimentally by X-Ray tomography and numerically by FEM. The presence of elastic buckling and plastic yielding of foam walls was observed. The combination of effective e modelling tools gives attractive opportunities to build sufficiently large data model to represent the foam structure. Once the modelling technique was validated, we use it to study the effect of various bulk material properties for a same microstructure of the foam on the mechanical behaviour. The mechanical response of these foams was also studied numerically under various uniaxial loads configuration and multiaxial loading.VILLEURBANNE-DOC'INSA LYON (692662301) / SudocSudocFranceF

Accessing preferential foam flow paths in 2D micromodel using a graph- based 2-parameter model

International audienceThis study uses experimental data of pore-scale foam flow inside a high-complexity network to fit a graph-based model describing preferential flow paths based on characteristics of the porous medium. Two experiments, with equal gas fractions but varying injection rates, are modelled in parallel. Proposed paths are solution paths to the k-Shortest Paths with Limited Overlap (k-SPwLO) problem, applied to a graph representation of the porous medium with edge weights representing throat properties. A 1-parameter model, based on throat radius only is tested before integrating a second parameter, describing the alignment of the pores surrounding the throat with respect to injection pressure gradient. The preferential paths in both experiments vary in quantity and in the specific zones described. As such, fitted models characterizing preferential paths for either experiment show separate dependencies to structural parameters. Overall, the graph-based framework was able to capture many high-flow zones in various model parameter combinations, perhaps as consequence of the relatively spiked throat size distribution of the model. The optimized model for the high injection rate experiment markedly shows a non-zero dependence to the pore alignment to pressure gradient as well as throat size, whereas the lower injection rate experiment was best fitted to a model that made sole use of the throat radius

Finite element modelling of the actual structure of cellular materials determined by X-ray tomography

International audienceThe initial microstructure and local deformation mechanisms of a polyurethane foam during a compression test are investigated by means of X-ray microtomography. A methodology to mesh the actual solid volume is described. The polymer material behaviour is assumed to be elastoplastic. A predictive finite element modelling of the mechanical behaviour of cellular materials is then implemented. The validation of the modelling procedure is performed in relation to the macroscopic mechanical response as well as to the local deformation mechanisms observed during the experiments

New insights into tracer propagation in partially saturated porous media

This work deals with the influence of partial saturation on the transport process of a passive tracer. Transport experiments were done in a water-wet glass micromodel combined with specific optical techniques. Full water saturation was achieved by injecting initially the background solution and then the tracer, whereas for the partial saturation conditions, the micromodel was initially saturated with oil, and then sequential the background solution and the tracer were injected at the same flow rate. We have shown that in the investigated range of water saturations it exists a transition in the oil ganglia structure and size. For high water saturations oil ganglia have one or two pores in size, however for lower water saturations they comprise an important number of pores. Transport strongly depends on the size distribution of the oil ganglia as they create large percolating paths and stagnant zones. We also showed the existence of two different types of stagnant zones: zones accessible by diffusion into pores and zones only accessible by spatially limited diffusion in films. The major advantage of using glass micromodels lies in the fact that dispersion coefficients can be computed from concentrations averaged over the pore space or from concentrations at the outlet and simultaneously from spatial concentration profiles. Curves were fitted using the Advection–Dispersion Equation (ADE) with adequate boundary conditions. The fitting quality of the temporal evolution of the average and outlet concentration was very good. However, fitting of the concentration profiles could only be done for the higher water saturations. This is due to the fact that the Representative Elementary Volume (REV) of lower water saturations is larger than the micromodel. The results show that fitting the breakthrough curve in order to determine the dispersion coefficient in a partially saturated porous medium might be misleading. Indeed, when fitting the breakthrough curves we were able to compute a dispersion coefficient even in the case where the REV of the water saturation is larger than the micromodel. Consequently, the knowledge of the local concentration profiles as a function of time is necessary as it provides an additional information on the spatio-temporal behavior of the transport process and therefor a supplementary constraint of the fitting procedure. Finally, we observed a time dependent dispersion coefficient in the regime where oil ganglia comprise several pores. This fact might be attributed to the non-Gaussian nature of the transport