<div>Powder Bed Fusion Additive Manufacturing enables the fabrication of metal parts with complex geometry and elaborates internal features, the simplication of the assembly process, and the reduction of development time. However, the lack of consis-tent quality hinders its tremendous potential for widespread application in industry. This limits its ability as a viable manufacturing process particularly in the aerospace and medical industries where high quality and repeatability are critical. A variety of defects, which may be initiated during the powder-bed fusion additive manufacturing process, compromise the repeatability, precision, and resulting mechanical properties of the final part. The literature review shows that a non-uniform temperature distribution throughout fabricated layers is a signicant source of the majority of thermal defects. Therefore, the work introduces an online thermography methodology to study temperature distribution, thermal evolution, and thermal specications of the fabricated layers in powder-bed fusion process or any other thermal inherent AM process. This methodology utilizes infrared technique and segmentation image processing to extract the required data about temperature distribution and HAZs of the layer under fabrication. We conducted some primary experiments in the FDM process to leverage the thermography technique and achieve a certain insight to be able to propose a technique to generate a more uniform temperature distribution. These experiments lead to proposing an innovative chessboard scanning strategy called tessellation algorithm, which can generate more uniform temperature distribution and diminish the layer warpage consequently especially throughout the layers with either geometry that is more complex or poses relatively longer dimensions. In the next step, this work develops a new technique in ABAQUS to verify the proposed scanning strategy. This technique simulates temperature distribution throughout a layer printed by chessboard printing patterns in powder-bed fusion process in a fraction of the time taken by current methods in the literature. This technique compares the temperature distribution throughout a designed layer printed by three presented chessboard-scanning patterns, namely, rastering pattern, helical pattern, and tessellation pattern. The results conrm that the tessellation pattern generates more uniform temperature distribution compared with the other two patterns. Further research is in progress to leverage the thermography methodology to verify the simulation technique. It is also pursuing a hybrid closed-loop online monitoring (OM) and control methodology, which bases on the introduced tessellation algorithm and online thermography in this work and Articial Neural Networking (ANN) to generate the most possible uniform temperature distribution within a safe temperature range layer-by-layer.</div>

La fonction d'une protéine est souvent subordonnée à l'interaction avec un certain nombre de partenaires. L'étude de la structure tridimensionnelle de ces complexes, qui ne peut souvent se faire expérimentalement, permettrait la compréhension de nombreux processus cellulaires. Le travail présenté ici se compose de deux parties. La première traite de la mise en place d'une fonction de score pour l'amarrage protéine-protéine et la deuxième de l'étude cristallographique d'une protéine tétramérique qui est une cible antibiotique potentielle : la thymidylate synthase X de Paramecium bursaria Chlorella virus. La modélisation des complexes protéine-protéine ou docking comporte deux étapes successives : d'abord, un grand nombre de conformations sont générées, puis une fonction de score est utilisée pour les classer. Cette fonction de score doit prendre en compte à la fois la complémentarité géométrique des deux molécules et les propriétés physico-chimiques des surfaces en interaction. Nous nous sommes intéressés à la seconde étape à travers le développement d'une fonction de score rapide et fiable. Ceci est possible grâce à la tessellation de Voronoï de la structure tridimensionnelle des protéines. En effet, les tessellations de Voronoï ou de Laguerre se sont avérées être de bons modèles mathématiques de la structure des protéines. En particulier, cette formalisation permet de faire une bonne description de l'empilement et des propriétés structurales des résidus. Cette modélisation rend compte l'empilement des résidus à l'interface entre deux protéines. Ainsi, il est possible de mesurer un ensemble de paramètres sur des complexes protéine-protéine dont la structure est connue expérimentalement et sur des complexes leurres générés artificiel- lement. Ces paramètres, sont la fréquence d'apparition des résidus ou des paires de résidus, les volumes des cellules de Voronoï, les distances entre les résidus en contact à l'interface, la surface de l'interface et le nombre de résidus à l'interface. Ils ont été utilisés en entrée de procédures d'apprentissage statistique. Grâce à ces procédures (apprentissage logistique, séparateurs à vaste marge (SVM) et algorithmes génétiques), on peut obtenir des fonctions de score efficaces, ca- pables de séparer les leurres des structures réelles. Dans un deuxième temps, j'ai déterminé expérimentalement la structure de la thymidylate synthase X, cible antibiotique de choix. La thymidylate synthase X est une flavoprotéine qui a été découverte récemment. Elle intervient dans la synthèse du dTMP chez la plupart des procaryotes mais n'existe pas chez les eucaryotes supérieurs. Cette protéine catalyse le transfert de methyle du tétrahydrofolate vers le dUMP grâce à son cofacteur le FAD et au NADPH qui intervient comme substrat. La structure tridimensionnelle de l'homotétramère de la thymidylate synthase X en présence de son cofacteur, le FAD, a été résolue à 2.4 Å par remplacement moléculaire. Comme pour les structures de thymidylate synthase X de Thermotoga maritima et de Mycobacterium tuberculosis précédemment résolues, le monomère se compose d'un coeur de feuillets β et de deux hélices α à son extrémité. Le site actif se trouve à l'interface de trois monomères, la partie isoalloxazine du FAD étant accessible au solvant et proche d'une longue boucle flexible. La fixation du FAD dans cette structure est légèrement différente de celles déjà observées par la conformation de la partie adénine. Cette structure, associée aux études de mutagénèse dirigée de nos collaborateurs, a permis de mettre évidence des résidus jouant un rôle majeur lors de la catalyse.

De plus en plus d'applications ont pour objectif d'automatiser l'analyse des comportements humains afin d'aider ou de remplacer les experts qui réalisent actuellement ces analyses. Cette thèse traite de l'analyse des expressions faciales qui fournissent des informations clefs sur ces comportements. Les travaux réalisés portent sur une solution innovante permettant de définir efficacement une expression d'un visage, indépendamment de la morphologie du sujet. Pour s'affranchir des différences de morphologies entre les personnes, nous utilisons des modèles d'apparence spécifiques à la personne. Nous proposons une solution qui permet à la fois de tenir compte de l'aspect continu de l'espace des expressions et de la cohérence des différentes parties du visage entre elles. Pour ce faire, nous proposons une approche originale basée sur l'organisation des expressions. Nous montrons que l'organisation des expressions, telle que définie, est universelle et qu'elle peut être efficacement utilisée pour définir de façon unique une expression : une expression est caractérisée par son intensité et sa position relative par rapport aux autres expressions. La solution est comparée aux méthodes classiques basées sur l'apparence et montre une augmentation significative des résultats de reconnaissance sur 14 expressions non basiques. La méthode a été étendue à des sujets inconnus. L'idée principale est de créer un espace d'apparence plausible spécifique à la personne inconnue en synthétisant ses expressions basiques à partir de déformations apprises sur d'autres sujets et appliquées sur le neutre du sujet inconnu. La solution est aussi mise à l'épreuve dans un environnement multimodal plus complet dont l'objectif est la reconnaissance d'émotions lors de conversations spontanées. Les résultats montrent que la solution est efficace sur des données réelles et qu'elle permet l'extraction d'informations essentielles à l'analyse des émotions. Notre méthode a été mise en œuvre dans le cadre du challenge international AVEC 2012 (Audio/Visual Emotion Challenge) où nous avons fini 2nd, avec des taux de reconnaissance très proches de ceux obtenus par les vainqueurs. La comparaison des deux méthodes (la nôtre et celles des vainqueurs) semble montrer que l'extraction des caractéristiques pertinentes est la clef de tels systèmes.

<p>Metamaterials are artificially structured materials which attain their unconventional macroscopic properties from their cellular configuration rather than their constituent chemical composition. The judicious design of this cellular structure opens the possibility to program and control the optical, mechanical, acoustic, or thermal responses of metamaterials. This Ph.D. dissertation focuses on scalable design and manufacturing strategies for optical and mechanical metamaterials.<br> <br> </p> <p>The fabrication of optical metamaterials still relies heavily on low-throughput process such as electron beam lithography, which is a serial technique. Thus, there is a growing need for the development of high-throughput, parallel processes to make the fabrication of optical metamaterials more accessible and cost-effective. The first part of this dissertation presents a scalable manufacturing method, termed “roll-to-roll laser induced superplasticity” (R2RLIS), for the production of flexible optical metamaterials, specifically metallic near-perfect absorbers. R2RLIS enables the rapid and inexpensive fabrication of ultra-smooth metallic nanostructures over large areas using conventional CO₂ engravers or inexpensive diode lasers. Using low-cost metal/epoxy nanomolds, the minimum feature size obtained by R2RLIS was <40 nm, facilitating the rapid fabrication of flexible near-perfect absorbers at visible frequencies with the capability to wrap around non-planar surfaces.</p> <p> </p> <p>The existing approaches for designing mechanical metamaterials are mostly <i>ad hoc</i>, and rely heavily on intuition and trial-and-error. A rational and systematic approach to create functional and programmable mechanical metamaterials is therefore desirable to unlock the vast design space of mechanical properties. The second part of this dissertation introduces a systematic, algorithmic design strategy based on Voronoi tessellation to create architected soft machines (ASMs) and twisting mechanical metamaterials (TMMs) with programmable motion and properties. ASMs are a new class of soft machines that benefit from their 3D-architected structure to expand the range of mechanical properties and behaviors achievable by 3D printed soft robots. On tendon-based actuation, ASMs deform according to the topologically encoded buckling of their structure to produce a wide range of motions such as contraction, twisting, bending, and cyclic motion. TMMs are a new class of chiral mechanical metamaterials which exhibit compression-twist coupling, a property absent in isotropic materials. This property manifests macroscopically and is independent of the flexible material chosen to fabricate the TMM. The nature of this compression-twist coupling can be programmed by simply tuning two design parameters, giving access to distinct twisting regimes and tunable onset of auxetic (negative Poisson’s ratio) behavior. Taking a metamaterial approach toward the design of soft machines substantially increases their number of degrees of freedom in deformation, thus blurring the boundary between materials and machines.</p>

Purdue School of Engineering and Technology, Indianapolis / Powder Bed Fusion Additive Manufacturing enables the fabrication of metal parts with complex geometry and elaborates internal features, the simplification of the assembly process, and the reduction of development time. However, the lack of consistent quality hinders its tremendous potential for widespread application in industry. This limits its ability as a viable manufacturing process particularly in the aerospace and medical industries where high quality and repeatability are critical. A variety of defects, which may be initiated during the powder-bed fusion additive manufacturing process, compromise the repeatability, precision, and resulting mechanical properties of the final part. The literature review shows that a non-uniform temperature distribution throughout fabricated layers is a significant source of the majority of thermal defects. Therefore, the work introduces an online thermography methodology to study temperature distribution, thermal evolution, and thermal specifications of the fabricated layers in powder-bed fusion process or any other thermal inherent AM process. This methodology utilizes infrared technique and segmentation image processing to extract the required data about temperature distribution and HAZs of the layer under fabrication. We conducted some primary experiments in the FDM process to leverage the thermography technique and achieve a certain insight to be able to propose a technique to generate a more uniform temperature distribution. These experiments lead to proposing an innovative chessboard scanning strategy called tessellation algorithm, which can generate more uniform temperature distribution and diminish the layer warpage consequently especially throughout the layers with either geometry that is more complex or poses relatively longer dimensions. In the next step, this work develops a new technique in ABAQUS to verify the proposed scanning strategy. This technique simulates temperature distribution throughout a layer printed by chessboard printing patterns in powder-bed fusion process in a fraction of the time taken by current methods in the literature. This technique compares the temperature distribution throughout a designed layer printed by three presented chessboard-scanning patterns, namely, rastering pattern, helical pattern, and tessellation pattern. The results confirm that the tessellation pattern generates more uniform temperature distribution compared with the other two patterns. Further research is in progress to leverage the thermography methodology to verify the simulation technique. It is also pursuing a hybrid closed-loop online monitoring and control methodology, which bases on the introduced tessellation algorithm and online thermography in this work and Artificial Neural Networking (ANN) to generate the most possible uniform temperature distribution within a safe temperature range layer-by-layer.

Treemaps are a popular space-filling visualization of hierarchical data that maps an attribute of a datum, or a data aggregate, to a proportional amount of area. Assuming a rectangular treemap consisting of nested rectangles (also called tiles), there are multiple possible valid tiling arrangements. A common criterion for optimization is aspect ratio. Nevertheless, treemaps usually consist of multiple rectangles, so the aspect ratios need be aggregated. The basic definition of aspect ratio (width divided by height) cannot be meaningfully aggregated. Given this, a definition of aspect ratio that does not differentiate height from width was suggested. This definition allows for meaningful aggregation, but only as long as there are no large differences in the data distribution, and the target aspect ratio is 1:1. Originally, a target aspect ratio of 1:1 was deemed to be axiomatically ideal. Currently, perceptual studies have found an aspect ratio of 1:1 to lead to the largest area estimation error. However, with any other target this definition of aspect ratio cannot be meaningfully aggregated. This thesis suggests a correction that can be applied to the current metric and would allow it to be meaningfully aggregated even when there are large value differences in the data. Furthermore, both the uncorrected and corrected metrics can be generalized for any target (i.e. targets other than 1:1). Another issue with current evaluation techniques is that algorithm fitness is evaluated through Monte Carlo trials. In this method, synthetic data is generated and then aggregated to generate a single final result. However, tiling algorithm performance is dependant on data distribution, so a single aggregateresult cannot generalize overall performance. The alternative suggested in this thesis is visual cluster analysis, which should hold more general predictive power.All of the above is put into practice with an experiment. In the experiment, a new family of tiling algorithms, based on criteria derived from the results of the perceptual tests in literature,is compared to the most popular tiling algorithm, Squarify. The results confirm that there are indeed vast but consistent value fluctuations for different normal distributions. At least for a target aspect ratio of 1.5, the new proposed algorithms are shown to perform better than Squarify for most use cases in terms of aspect ratio.

Historically 3D game environments have almost always been immutable. Mutable environments are a technical challenge that will affect performance. For games of the future to continue approaching realism, mutable environments are an essential step. Popularized by the game title Minecraft (2009), the use of voxel engines in games has become increasingly common. However, by the nature of the discrete position of voxels, the method is limited in representing arbitrary polyhedral shapes like angled slopes. It also prohibits smooth mutations including proper movement and rotation of objects within the voxelization. This is generally mitigable with more voxels. However, this paper proposes a more precise solution to the problem. A tetrahedral mesh engine (tetra engine). By altering tetrahedral topology, vertex positions, and material of individual tetrahedrons, tetras are intended to solve the issue of arbitrary polyhedral shapes for voxels. Additionally, the tetrahedral mesh shows other promises such as providing a robust collision detection method and as an acceleration structure for e.g. raycasting. The research question can be summarized as investigating the feasibility of a tetra engine as a mutable game environment. 3 sub-research questions are given: The first regarding performance, the second regarding robustness, and the third different types mutations. The research questions are addressed along with a proof of concept (POC). The POC intends to investigate a proposal for the most efficient robust solution possible for the most basic mutation type known as edits. Because of time constraints, it does not cover all parts of the research questions but works as a bottom-up approach to understand what is required to realize a full-fledged tetra engine. Thus, a large part of the research question is answered theoretically both hypothetically with grounds from the POC and through previous work. The result shows a much more critical robustness consideration than expected and suggests relying on slower but more robust algorithms that are known to work. In conclusion, nothing suggests that a scalable future-proof tetra engine is impossible, but the algorithms required are much less efficient than those for voxels and robustness is an issue to overcome. However, numerous hypothetical advantages particularly regarding deformation and fluid simulation are still recognized and it is not obvious that future mutable environments would not benefit from a tetra engine rather than voxels. / Historiskt sätt har 3D-datorspelmiljöer nästan uteslutande varit oföränderliga. Det finns goda anledningar till detta. Föränderliga miljöer är en teknisk utmaning som påverkar speleffektiviteten. Om man däremot vill fortsätta utveckla mer realistiska datorspel är föränderliga spelmiljöer ett naturligt steg. Spelet Minecraft (2009) populariserade användandet av voxlar i datorspel vars material kan ändras för att förändra miljön. Sedan dess har voxlar i datorspel blivit mer och mer populära. Dock, på grund av voxlars diskreta positioner har de begränsningar i dess förmåga att representera godtyckliga polyedriska former så som arbiträrt vinklade plan. Detta omöjliggör även mjuka rörelser inklusive rörelse och rotering inom voxeliseringen. Det här problemet kan generellt dämpas med hjälp av mindre och fler voxlar. Men, för att lösa problemet ordentligt föreslår den här rapporten en annan lösning, nämligen en tetrahedrisk-mesh-motor (tetramotor). Genom att ändra tetraedrisk topologi, hörn positioner, samt material av individuella tetraedrar ska tetrorna kunna forma arbiträra polyedriska former och lösa problemet med voxlar. Utöver detta visar en tetraedrisk mesh andra intressanta möjligheter likt en metod för robust kollisions hantering och som en accelereringsstruktur för till exempel ray-casting. Forskningsfrågan kan sammanfattas som att utforska tillämpbarheten av en tetramotor för föränderliga datorspelsmiljöer. Tre underfrågor ges: Den första handlar om beräkningseffektivitet, den andra angående robusthet och den tredje oliky typer av mutationer. Forskningsfrågorna angrips med hjälp av en proof of concept lösning (POC). POC:en är menad att utforska ett förslag på en effektiv och robust metod för direkta förändringar. På grund av tidsbegränsningar så täcker inte POC:en alla delar av frågeställningarna men är menad som en botten upp lösning för att inse och förstå kraven för en komplett tetramotor. På grund av detta är en stor del av forskningsfrågorna svarade teoretiskt, både hypotetiskt baserat på insikterna från POC:en och med grund från tidigare forskning. Resultatet visar en mycket mer kritisk hänsyn till robusthet än förväntat och föreslår att man använder sig av långsammare men fungerande existerande lösningar. Slutsatsen är att inget tyder på att en skalbar framtidssäker tetramotor är en omöjlighet, men att algoritmerna är mycket långsammare än de som krävs för voxlar. Däremot finns potentieally fördelar med en tetra motor, främst med hänsyn till deformering och flödessimulering. Det är därför inte självklart att framtida muterbara spelmijöer inte skulle ha fördelar av en tetramotor istället för voxlar.

3D printing applications have achieved increased success as an additive manufacturing (AM) process. Micro-structure of mechanical/biological materials present design challenges owing to the resolution of 3D printers and material properties/composition. Biological materials are complex in structure and composition. Efforts have been made by 3D printer manufacturers to provide materials with varying physical, mechanical and chemical properties, to handle simple to complex applications. As 3D printing is finding more medical applications, we expect future uses in areas such as hip replacement - where smoothness of the femoral head is important to reduce friction that can cause a lot of pain to a patient. The issue of print resolution plays a vital role due to staircase effect. In some practical applications where 3D printing is intended to produce replacement parts with joints with movable parts, low resolution printing results in fused joints when the joint clearance is intended to be very small. Various 3D printers are capable of print resolutions of up to 600dpi (dots per inch) as quoted in their datasheets. Although the above quoted level of detail can satisfy the micro-structure needs of a large set of biological/mechanical models under investigation, it is important to include the ability of a 3D slicing application to check that the printer can properly produce the feature with the smallest detail in a model. A way to perform this check would be the physical measurement of printed parts and comparison to expected results. Our work includes a method for using ray casting to detect features in the 3D CAD models whose sizes are below the minimum allowed by the printer resolution. The resolution validation method is tested using a few simple and complex 3D models. Our proposed method serves two purposes: (a) to assist CAD model designers in developing models whose printability is assured. This is achieved by warning or preventing the designer when they are about to perform shape operations that will lead to regions/features with sizes lower than that of the printer resolution; (b) to validate slicing outputs before generation of G-Codes to identify regions/features with sizes lower than the printer resolution.

Die vorliegende Dissertation beschäftigt sich mit der thermo-mechanischen Beschreibung und Bewertung von keramischen Filtern für die Metallschmelze-Filtration mithilfe der Finiten-Elemente-Methode. Infolge des zellularen Aufbaus des Werkstoffs handelt es sich um ein Mehrskalenproblem. Grundlegende Aufgaben der Arbeit waren deshalb die geometrische und mechanische Modellbildung sowie die Untersuchung verschiedener effizienzsteigernder Methoden zur Gewinnung einer akkuraten numerischen Lösung. Dabei wurden sowohl verschiedene Verfahren aus der Fachliteratur implementiert und kritisch bewertet, als auch neue Ansätze verfolgt. Die Untersuchungen konzentrierten sich auf das effektive elastische und elastisch-plastische Verhalten von Kelvin-, Weaire-Phelan- und Voronoi-Strukturen. Insbesondere die entwickelten Methoden und Werkzeuge zur automatisierten Modellbildung gestatten in einfacher Weise die Umsetzung von Parameterstudien und Optimierungsaufgaben. Aus darauf aufbauenden Sensitivitätsstudien wurden Empfehlungen hinsichtlich der geometrischen und mechanischen Modellbildung für zellulare Werkstoffe abgeleitet. Diese betreffen auch vielfach eingesetzte Methoden zur Modellreduktion für diese Werkstoffe und tragen somit zukünftig zu einer effizienteren Bewertung von Filterstrukturen bei.

In computer graphics we can handle unstructured triangular 3D meshes which are not too usable for processing through their irregularity. In these situations it occurs need of conversion that 3D mesh to more suitable representation. Some kind of 3D spline surface can be proper alternative because it institutes regularity in the form of control points grid and that's why it is more suitable for next processing. During conversion, which is described in this thesis, quadrilateral 3D mesh is constructed at first. This mesh has regular structure but mainly the structure corresponds to structure of control points grid of resulting 3D spline surface. Created quadrilateral 3D mesh can be saved and consequently used in specific modeling applications for T-spline surface creation.