Titre de l'écran-titre (visionné le 12 janvier 2024) / La curiethérapie est une modalité de traitement du cancer utilisant le rayonnement ionisant d'une source radioactive. En curiethérapie à haut débit de dose (HDR), un appareil motorisé blindé est utilisé pour guider la source radioactive à proximité ou à l'intérieur de la tumeur par l'intermédiaire d'applicateurs intracavitaires (IC) et/ou de cathéters interstitiels (IS). En s'arrêtant un certain temps (temps d'arrêt) à des positions spécifiques (positions d'arrêt), une dose de rayonnement conforme peut être adminisitrée à la tumeur tout en épargnant les organes à risque (OARs) avoisinants. Cependant, en raison de la nature du rayonnement ionisant, il est impossible d'administrer une dose de radiation curative à la tumeur sans exposer les OARs. Ces objectifs contradictoires doivent donc être optimisés simultanément. Par conséquent, le problème de planification de traitement en curiethérapie est intrinsèquement un problème d'optimisation multicritère (MCO), où de nombreuses solutions optimales (solutions Pareto-optimales) caractérisent les compromis cliniquement importants. Actuellement, les algorithmes commerciaux de planification en curiethérapie sont limités à l'ajustement manuel d'un objectif et/ou des temps d'arrêt. À cet égard, les algorithmes de planification inverse ne peuvent générer qu'un seul plan de traitement par cycle d'optimisation (en quelques secondes de temps de calcul) sans garantie de rencontrer les critères cliniques lors du premier cycle. Cette approche peut rendre la tâche de planification itérative et fastidieuse pour les planificateurs/planificatrices. Par conséquent, la qualité du plan peut dépendre des compétences de l'utilisateur/utilisatrice. En outre, la génération itérative d'un plan de traitement par cycle d'optimisation, comme c'est le cas en clinique, ne permet pas au planificateur/ planificatrice d'explorer facilement les compromis entre le tumeur cible et les OARs. La littérature présente également une lacune importante en ce qui concerne les méthodes d'optimisation permettant d'intégrer efficacement les applicateurs IC/IS complexes récents (par exemple, l'applicateur Venezia fabriqué par Elekta, Veenendaal, Pays-Bas) pour la curiethérapie du cancer du col de l'utérus. Le principal défi pour ces applicateurs complexes est de déterminer automatiquement le nombre optimal de cathéters, leur position et leur profondeur compte tenu du grand nombre de degrés de liberté dans le problème d'optimisation et des grandes variations dans la forme des tumeurs. Pour résoudre ces problèmes, cette thèse propose une nouvelle génération d'algorithmes d'optimisation et de planification interactive pour la curiethérapie. Pour atteindre cet objectif, un algorithme MCO (gMCO) basé sur une unité de processeur graphique (GPU) est d'abord mis en œuvre et comparé à un algorithme de planification inverse standard utilisé en clinique. gMCO met en œuvre un nouveau schéma d'optimisation des plans en parallèle sur l'architecture GPU permettant d'optimiser des milliers de plans Pareto-optimaux en quelques secondes. Ensuite, pour tirer pleinement profit de MCO en clinique, une interface graphique interactive appelée gMCO-GUI est développée. Cette interface permet au planificateur/planificatrice de naviguer et d'explorer les compromis en temps réel à partir des plans Pareto-optimaux générés par gMCO. gMCO-GUI permet entre autre d'afficher les indices dose-volume histogram (DVH), les courbes DVH et les lignes d'isodose pendant la navigation. Pour intégrer le flux de travail MCO dans la clinique, la mise en service de gMCO et de gMCO-GUI est effectuée en comparaison avec Oncentra Prostate et Oncentra Brachy, deux systèmes de planification de traitement largement utilisés. Suite à la mise en service, afin de caractériser l'utilisation de la planification interactive MCO en clinique, une étude inter-observateurs est menée. Deux physiciens/physiciennes expérimentés sont invités à replanifier 20 cas de cancer de la prostate chacun à l'aide de la planification interactive MCO. La qualité des plans préférés (obtenus par navigation) est comparée entre les deux physiciens/ phyciennes et le temps de planification MCO est enregistré. De plus, trois radio-oncologues sont invités à comparer l'aveugle les plans MCO (générés par les physiciens/physiciennes) et les plans cliniques afin d'établir le meilleur plan pour chaque patient. Finalement, motivé par le manque d'algorithmes d'optimisation des cathéters et de la dose dans le traitement du cancer du col de l'utérus dans les logiciels commerciaux et dans la littérature, un nouvel algorithme d'optimisation multicritère des cathéters pour les applicateurs IC/IS complexes tels que l'applicateur Venezia est conçu. Le problème d'optimisation avec l'applicateur Venezia est difficile car les composants de l'applicateur ne sont pas coplanaires. Le gain dosimétrique de l'optimisation simultanée des cathéters et MCO est comparé à MCO seul (cathéters cliniques) et aux plans cliniques basé sur les critères EMBRACE-II. En résumé, une nouvelle génération d'algorithmes d'optimisation et de planification interactive est développée pour la curiethérapie. Les cinq chapitres principaux de cette thèse rapportent les résultats et les contributions scientifiques de ces algorithmes comparés à la planification clinique standard. La thèse guide également les utilisateurs/utilisatrices dans l'intégration du flux de travail MCO interactif dans la clinique. / Brachytherapy is a treatment modality for cancer using ionizing radiation of a radioactive source. In high-dose-rate (HDR) brachytherapy, an afterloading unit is used to guide the radioactive source near or inside the tumor via intracavity (IC) applicators and/or interstitial (IS) catheters. By stopping a specific amount of time (dwell time) at specific positions (dwell positions), a conformal radiation dose can be delivered to the tumor while spearing nearby organs at risk (OARs). However, because of the nature of ionizing radiation, it is in fact impossible to deliver the curative dose to the tumor without exposing OARs. Instead, those conflicting objectives need to be simultaneously optimized. Therefore, the planning problem in HBR is inherently a multi-criteria optimization (MCO) problem, where many optimal solutions (Pareto-optimal solutions) can effectively characterize the clinically relevant trade-offs. Current commercial planning algorithms in HDR brachytherapy are limited to the manual fine-tuning of an objective and/or dwell times. In that regard, inverse planning algorithms can generate only one treatment plan per optimization run (few seconds of optimization time) without guarantee of meeting clinical goals in the first run, which makes the planning task iterative and cumbersome for the planners. Therefore, the plan quality may be dependent on the user skills. Furthermore, iterative generation of one treatment plan per optimization run as done in the clinic does not easily allow the planner to explore the trade-offs between targets and OARs. There is also an important gap in optimization methods in the literature to efficiently incorporate recent complex IC/IS applicators (e.g., the Venezia applicator manufactured by Elekta, Veenendaal, The Netherlands) for cervical cancer brachytherapy. The main challenge for these complex applicators is to automatically determine the optimal IS catheter number, position, and depth given large number of degrees of freedom in the optimization problem and large variations in tumor shapes. To address these problems, this thesis proposes next generation of optimization and interactive planning algorithms for brachytherapy. A graphics processing unit (GPU)-based MCO algorithm (gMCO) is first implemented and compared with a standard inverse planning algorithm used in the clinic. gMCO implements a novel parallel plan optimization scheme on GPU architecture that can optimize thousands of Pareto-optimal plans within seconds. Next, to fully benefit of MCO in the clinic, an interactive graphical user interface called gMCO-GUI is developed to allow the planner to navigate and explore the trade-offs in real-time through gMCO-generated plans. gMCO-GUI enables the display of dose-volume histogram (DVH) indices, DVH curves, and isodose lines during the plan navigation. To incorporate the proposed MCO workflow the clinic, the commissioning of gMCO and gMCO-GUI is conducted against Oncentra Prostate and Oncentra Brachy, two widely used treatment planning systems. Following the commissioning, and to further characterize the utilization of MCO interactive planning in the clinic, an inter-observer study is conducted. Two experienced physicists are asked to re-plan 20 prostate cases each using MCO interactive planning. The quality of the preferred plans (obtained by plan navigation) is compared between the two physicists and the MCO planning time is recorded. In addition, three radiation oncologists are invited to blindly compare MCO plans (generated by physicists) and clinical plans to assess the best plan for each patient. Finally, motivated by the lack of catheter and dose optimization algorithms in the treatment of cervical cancer in commercial software and in the literature, a novel simultaneous catheter optimization and MCO algorithm for complex IC/IS applicators such as the Venezia applicator is designed. The optimization problem with the Venezia applicator is challenging because the applicator components are non coplanar. The dosimetric gain of simultaneous catheter optimization and MCO is compared with MCO alone (clinical catheters), and clinical plans following EMBRACE-II criteria. In summary, next generation of optimization and interactive planning algorithms are developed for brachytherapy. The five main chapters of this thesis report the findings and scientific contributions of these algorithms compared with standard clinical planning. The thesis also guide users in the integration of the proposed interactive MCO workflow in the clinic.

The wheel-rail contact is at the core of all research related to vehicletrackinteraction. This tiny interface governs the dynamic performanceof rail vehicles through the forces it transmits and, like any high stressconcentration zone, it is subjected to serious damage phenomena. Thus,a clear understanding of the rolling contact between wheel and rail is keyto realistic vehicle dynamics simulation and damage analysis. In a multi-body dynamics simulation, the demanding contact problemshould be evaluated at about every millisecond for several wheel-rail pairs.Hence, a rigorous treatment of the contact is highly time-consuming.Simplifying assumptions are therefore made to accelerate the simulationprocess. This gives rise to a trade-o between the accuracy and computationaleciency of the contact model in use. Conventionally, Hertz+FASTSIM is used for calculation of the contactforces thanks to its low computational cost. However, the elliptic patchand pressure distribution obtained by Hertz' theory is often not realisticin wheel-rail contact. Moreover, the use of parabolic traction bound inFASTSIM causes considerable error in the tangential stress estimation.This combination leads to inaccurate damage predictions. Fast non-elliptic contact models are proposed by others to tacklethis issue while avoiding the tedious numerical procedures. The studiesconducted in the present work show that the accuracy of these models iscase-dependent. To improve the accuracy of non-elliptic patch and pressure estimation,a new method is proposed. The method is implemented in an algorithmnamed ANALYN. Comparisons show improvements in patch and, particularly,pressure estimations using ANALYN. In addition, an alternative to the widely-used FASTSIM is developed, named FaStrip. Unlike FASTSIM, it employs an elliptic traction boundand is able to estimate the non-linear characteristic of tangential stressdistribution. Comparisons show more accurate estimation of tangentialstress and slip velocity distribution as well as creep forces with FaStrip. Ultimately, an ecient non-elliptic wheel-rail contact model consistingof ANALYN and FaStrip is proposed. The reasonable computationalcost of the model enables it to be used on-line in dynamics simulationand its accuracy can improve the damage predictions. / <p>QC 20160202</p>

The tangential contact stiffness for ground Ti-6Al-4V surfaces is measured to linearly decrease with the application of tangential load. At the beginning of the application of tangential load, for ground surfaces, the ratio of the tangential contact stiffness to the normal contact stiffness is seen to be approximately half the Mindlin ratio. This is consistent with many other published experimental studies. Measurements of normal contact stiffness for ground surfaces conform to a model that posits a linear relationship between normal contact stiffness and normal load. An equivalent surface roughness parameter is defined for two surfaces in contact; and the normal contact stiffness for ground surfaces is observed to be inversely proportional to this parameter. Single asperity models were constructed to simulate the effect of different frictional laws and plasticity on the tangential displacement of an asperity contact. Further, multi-asperity modelling showed the effect of different normal load distributions on the tangential behaviour of interfaces. In addition, normal contact stiffness was modelled for a grid of asperities taking into account asperity interactions. A receding contact problem for which the required form of the distributed dislocations is bounded-bounded was solved. Then, a fundamental 2D frictional receding contact problem involving a homogeneous linear elastic infinite layer pressed by a line load onto a half-plane of the same material was analysed. This was done by the insertion of preformed distributed dislocations (or eigenstrains), which take into account the correct form of the separation of the interface at points away from the area of loading, along with corrective bounded-bounded distributions. The general method of solution was further refined and adapted to solve three other receding contact problems. The solutions demonstrated the robustness and applicability of this new procedure.

Embedded contact homology is an invariant of closed oriented contact 3-manifolds first defined by Hutchings, and is isomorphic to both Heegard Floer homology (by the work of Colin, Ghiggini and Honda) and Seiberg-Witten Floer cohomology (by the work of Taubes). The embedded contact chain complex is defined by counting closed orbits of the Reeb vector field and certain pseudoholomorphic curves in the symplectization of the manifold. As part of their proof that ECH=HF, Colin, Ghiggini and Honda showed that if the contact form is suitably adapted to an open book decomposition of the manifold, then embedded contact homology can be computed by considering only orbits and differentials in the complement of the binding of the open book; this fact was then in turn used to define a knot version of embedded contact homology, denoted ECK, where the (null-homologous) knot in question is given by the binding. In this thesis we start by generalizing these results to the case of rational open book decompositions, allowing us to define ECK for rationally null-homologous knots. In its most general form this is a bi-filtered chain complex whose homology yields ECH of the closed manifold. There is also a hat version of ECK in this situation which is equipped with an Alexander grading equivalent to that in the Heegaard Floer setting, categorifies the Alexander polynomial, and is conjecturally isomorphic to the hat version of knot Floer homology. The main result of this thesis is a large negative $n$-surgery formula for ECK. Namely, we start with an (integral) open book decomposition of a manifold with binding $K$ and compute, for all $n$ greater than or equal to twice the genus of $K$, ECK of the knot $K(-n)$ obtained by performing ($-n$)-surgery on $K$. This formula agrees with Hedden's large $n$-surgery formula for HFK, providing supporting evidence towards the conjectured equivalence between the two theories. Along we the way, we also prove that ECK is, in many cases, independent of the choices made to define it, namely the almost complex structure on the symplectization and the homotopy type of the contact form. We also prove that, in the case of integral open book decompositions, the hat version of ECK is supported in Alexander gradings less than or equal to twice the genus of the knot.

Kinshasa, la capitale de la République Démocratique du Congo est une ville plurilingue et pluriethnique du fait qu’elle fait l’objet d’un exode rural important. C’est dans cet environnement particulièrement plurilingue que le lingala est employé comme langue véhiculaire parfois en concurrence avec le français. C’est dans ce cadre que nous posons le problème des facteurs qui déterminent le choix du français, du lingala classique et du français dans cet espace. Au contact avec le français, langue officielle du pays, le discours kinois à base lingala présente aujourd’hui une hétérogénéité linguistique qui affecte plusieurs niveaux d’analyse que nous étudions sous l’étiquette d’alternance de langues : alternance interphrastique et alternance intraphrastique. Mais il existe aussi un fonds lexical d’origine européenne qui passe inaperçu aujourd’hui, grâce à leur intégration phonétique. Il a fallu recourir à ce qui reste de ressemblance formelle pour les déceler et proposer des hypothèses de leur évolution à partir de leurs étymons français, portugais ou anglais.Ce travail tente d’appréhender les questions formelles et sémantiques que présentent la langue lingala et le discours kinois, au contact avec les langues européennes, le français en particulier. Pour ce faire, nous avons eu recours à un corpus composé de discours effectivement prononcés mais qui ont tous la caractéristique d’être des discours publiés (publicités, chansons, édition du journal télévisé en lingala facile). / Kinshasa, capital of the Democratic Republic of the Congo, is a multilingual and multiethnic city due to its being the object of an important rural exodus. It is in this particular multilingual environment that Lingala is used as a vehicular language, sometimes in competition with French. This is the setting for which we discuss the factors determining the choice between using French only or using classical Lingala and French.The contact between French, the country’s official language, and the Lingala base has resulted in a linguistic heterogeneity which will be analysis on several levels using the theories of code-switching: intersentential code-switching and intrasentential code-switching. But there is also a substratum of European origin which goes unseen today because of its phonetic integration. We have had recourse to formal resemblances in order to discern elements of this substratum and its French, Portuguese, or English etymons and to propose hypotheses about their evolution.This study attempts to describe the formal and semantic questions posed by the Lingala language and by Kinois discourse when they come in contact with European languages and particularly with French. To do this, we have established a corpus of discourses which have been effectively pronounced but which are all published discourses (advertisements, songs, televised news shows in basic Lingala).

Renewable and clean energy is urgently needed to cope with the climate crisis. Photovoltaics (PV) has been the fastest growing technology in the clean energy market due to its low cost, and the abundance of solar energy. The capacity of silicon-based PV is rapidly expanding with evolving technologies. Passivating the solar cell’s electrical contacts is a widely accepted strategy for the PV industry to improve device power conversion efficiency (PCE). Polycrystalline silicon (Poly-Si) passivating contacts are one of the promising concepts in the emerging class of passivating contacts. In this dissertation, the passivation mechanism of Poly-Si passivating contacts is investigated. Moreover, the influence of dopant diffusion on the passivation quality is revealed. To address the side-effects of dopant diffusion, a thin buffer layer is inserted between the Poly-Si(p) layer and the $SiO_x$ layer. With such a buffer layer, the passivation of the Poly-Si passivating contact is improved, which in turn, enhances the device PCE. In addition to passivating contacts, this dissertation also explores carrier-selective contact of crystalline silicon (c-Si) and low work function metal – Li. Li is a very reactive metal which makes the fabrication process a challenge. To overcome such a challenge, the c-Si/ Li contact is fabricated by thermally decomposing stable $Li_3N$ powder instead of metal evaporation. The c-Si/Li contact shows an excellent electron-selective transport performance with a 0.39 eV energy barrier. Full-area Si/Li rear contact devices are fabricated, and >19% PCE and >80% fill factor are achieved. To accelerate the device optimization, a physical model embedded machine-learning approach is applied to transparent conductive oxide (TCO) materials optimization. In this work, empirical correlations between sputtering parameters and the deposited TCOs’ electrical properties are established. Then a Bayesian Parameter Estimation (BPE) algorithm is applied to learn the empirical model. With this BPE network, the TCOs’ electrical properties are successfully predicted with limited material characterizations. Thanks to the combination of BPE and a physical model network, the material optimization process is significantly accelerated. In summary, this dissertation explores different aspects to develop novel passivating and carrier-selective contacts for c-Si solar cells, and introduces an approach to accelerate the development processes.

No description available.

Yes / Objectives: To investigate the performance of a novel flat pack toric daily disposable contact lens compared with traditionally packaged toric lenses in a randomized, crossover study. Environmental attitudes to contact lens wear were also explored. Methods: Habitual contact lens wearers were recruited to wear a hioxifilcon A (Miru 1 day Flat Pack Toric, Menicon, Nagoya, Japan) test lens and a control lens: either nelfilcon A (Dailies AquaComfort Plus, Alcon, Geneva, Switzerland) or etafilcon A (1-Day Acuvue Moist, Johnson & Johnson, New Brunswick, NJ). Objective lens performance was assessed at fitting, and participants wore lenses in a randomized order for three consecutive days. Subjective measures of lens performance (comfort, vision, and handling) were then assessed by a questionnaire, with further questions on overall lens preference and environmental perceptions. Results: Objective measures of lens fit were similar for the test and control lenses, except for distance VA which was better with the control lenses (P<0.05; difference of two logMAR letters). End of day comfort was greater with the test lens, but this did not reach significance. Both lenses demonstrated similar scores for overall satisfaction. 87.5% of participants indicated the environmental impact of contact lenses to be important/extremely important to them, with 100% of participants identifying the flat pack packaging as having a smaller environmental impact. Conclusion: Overall, the lenses used in the study performed to similar levels. Environmental credentials are important to contact lens wearers, which may contribute to overall lens preference.

Increasingly, culturally and ethnically diverse environments provide an abundance of ordinary, everyday intergroup encounters, especially in public settings---often consisting of a conglomeration of positive and negative experiences. Yet few intergroup contact studies have focused on measuring and assessing contact in public settings. Reasons for this include both theoretical and methodological considerations. However, before the impact of mundane, everyday encounters on prejudice reduction can be assessed, it is necessary to examine the following questions: (1) Which situations are perceived as intergroup contact by participants? (2) How do individuals conceptualise where the boundaries for contact lie? (3) How are public and private forms of contact typically experienced? (4) Do they differ in the ways researchers have assumed in the past? and (5) Which methods are most appropriate for assessing public encounters? How can memory bias, temporality and locatedness be taken into account? Using qualitative, quantitative and near-time in-the-field methods, the following research examines these aspects in both public and private settings and provides first insights into how a novel method---the Contact Logger---can be used to assess the effects of public and private contact on attitudes. A three-day diary/interview study (N=17) explored how contact is experienced, understood and conceptualised in a variety of everyday intergroup contexts. This was followed by a survey study (N=525) that examined the boundaries of what is typically perceived as being contact. Insights from both studies fed into the development of a context-aware mobile application, which enabled the capturing of near-time intergroup encounters in situ. The usability of the resulting research tool---the Contact Logger---was tested, leading to further refinements. Following an initial feasibility study (N=104) that explored contact between young and older people, a field experiment (N=112) examined intergenerational contact in public and private contexts. Data collected with the Contact Logger were analysed on aggregate and day-to-day levels, and where possible compared to traditional retrospective survey data. Results from the first two studies indicated that while traditional intergroup encounters, such as contact with family and friends, are clearly conceptualised and viewed as contact, experiences and perceptions of contact in public settings are more disparate. Moreover, effects of such contact on attitudes are dependent on the idiosyncratic meaning attributed to the specific encounter as well as past experiences. Near-time data from a field-experiment (Study 5) provided evidence that intergroup encounters reported in situ compared to retrospective survey data differed in key variables (i.e., contact quality, duration, perceived status and group typicality). Correlational analyses between near-time and retrospective measures showed less correspondence than expected. Further, additional day-to-day analyses revealed that attitudes towards older people were less positive during weekends than weekdays, indicating that attitudes may be more dynamic than previously thought. Findings, as well as the different methodological and theoretical approaches, are critically discussed. Finally, a broad range of further applications for the Contact Logger are presented and important limitations are discussed.

Les travaux présentés à travers ce manuscrit s'inscrivent dans un contexte de recherches exploratoires sur l'optimisation des surfaces engrenantes. Après une étude approfondie de l'emploi des engrenages dans un environnement aéronautique, l'élaboration d'une nouvelle méthodologie de génération de profils de denture est proposée. Les travaux s'attachent à caractériser le comportement mécanique spécifique d'un montage d'engrenages dans les Boites de Transmission de Puissances (BTP) d'hélicoptère.Un outil informatique a été créé dans le module VBA (Visual Basic Application) d'Excel. Il permet de créer automatiquement des profils de denture conjugués et optimisés. Il a l'avantage de définir analytiquement plusieurs grandeurs physiques. L'outil a ainsi pour objectif de proposer des profils de denture optimisés selon plusieurs critères. Les « objectifs » retenus sont le rendement et la contrainte équivalente de Hertz au contact suivant le critère de Von Mises.Les travaux s'articulent autour de trois axes : - la reconstruction de profils conjugués de denture par une approche novatrice basée sur le « contact », - la construction de critères physiques (glissement, pression, contrainte, …), - la recherche de profils de denture optimaux en utilisant la simulation de Monte Carlo.Enfin, la perspective de rendre générique cette méthode afin qu'elle puisse générer n'importe quels types d'engrenage est envisagée en fin de manuscrit. / The work described in the present manuscript is part of exploratory researches dealing with gears meshing surfaces optimization. After a short study of gears used in an aeronautical environment, the development of an innovative tool for tooth profile design is defined. Then, the specific behavior of a gear mesh within a helicopter main gearbox (MGB) is evaluated.A VBA software has been coded under MS Excel to generate conjugated and optimized gear tooth profiles. It advantageously defines and uses several physical parameters with their analytical formulation. The software provides at the user optimized tooth profiles according to a couple of criteria. The two “objective” functions evaluated are the efficiency and the Hertz equivalent stress within the contact using the Von Mises criterion.The work has been focused on three aspects:- The design of conjugated tooth profiles by contact sharing,- The definition of the relevant physical parameters,- The optimization of tooth profiles using Monte Carlo SimulationEventually, a generic method to design gear profiles, taking into account any physical parameters related to a gear mesh, could be expected as a future of this thesis work.