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Tooley, Scott. "The effects of surface tension on free surface flows intersecting rigid walls." Thesis, University of East Anglia, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251709.
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Zhao, Xujun. "Surface loading and rigid indentation of an elastic layer with surface energy effects." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/12598.
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With the growing interest in nanotechnology, it is becoming important to understand the nanoscale mechanics to achieve successful design and fabrication of nanoscale devices. However, the classical continuum theory is not directly applicable to the analysis of nanoscale domains due to size-dependent behavior of nanostructures. Since the surface-to-volume ratio of a nanoscale domain is relatively high compared to that of a macro-scale domain, the energy associated with atoms at or near a free surface is different from that of atoms in the bulk. The effect of surface free energy therefore needs to be considered. Ultra-thin film/substrate systems, which are encountered in applications involving nanocoatings, nanotribology and material characterization based on nano-indentation, may be analyzed using modified continuum elasticity theory incorporating surface energy effects.
This thesis presents a set of analytical solutions for elastic field of a layer of nanoscale thickness bonded to a rigid base under surface loading and indentation by a rigid body. Surface energy effects are accounted for by using Gurtin-Murdoch elasticity theory. Fourier and Hankel integral transforms are used to solve the two- and three- dimensional boundary-value problems involving non-classical boundary conditions associated with the generalized Young-Laplace equation. In the case of a two-dimensional semi-infinite medium, the solutions can be expressed in closed form. The elastic field is found to depend on the layer thickness and surface elastic constants, and the influence of surface energy is shown to be more significant under a horizontal load than under a vertical load. A characteristic length scale related to the surface material properties can be identified for the present class of problems. The solution for the indentation problem is considered for flat, conical and spherical rigid indenters. The mixed boundary-value problem corresponding to a rigid indenter is formulated in terms of a dual integral equation system that is solved by using numerical quadrature. Selected numerical results are presented to show the influence of the indenter shape, surface properties and size-dependency of response.
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Bauer, Sebastian [Verfasser], and Joachim [Akademischer Betreuer] Hornegger. "Rigid and Non-Rigid Surface Registration for Range Imaging Applications in Medicine / Sebastian Bauer. Gutachter: Joachim Hornegger." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2014. http://d-nb.info/107583452X/34.
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Chhatkuli, Ajad. "Local analytic and global convex methods for the 3D reconstruction of isometric deformable surfaces." Thesis, Clermont-Ferrand 1, 2016. http://www.theses.fr/2016CLF1MM27/document.
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Cette thèse contribue au problème de la reconstruction 3D pour les surfaces déformables avec une seule caméra. Afin de modéliser la déformation de la surface, nous considérons l’isométrie puisque de nombreuses déformations d’objets réels sont quasi-isométriques. L’isométrie implique que, lors de sa déformation, la surface ne peut pas être étirée ou compressée. Nous étudions deux problèmes. Le premier est le problème basé sur une modèle 3D de référence et une seule image. L’état de l’art propose une méthode locale et analytique de calcul direct de profondeur sous l’hypothèse d’isométrie. Dans cette méthode, la solution pour le gradient de la profondeur n’est pas utilisée. Nous prouvons que cette méthode s’avère instable lorsque la géométrie de la caméra tend à être affine. Nous fournissons des méthodes alternatives basées sur les solutions analytiques locales des quantités de premier ordre, telles que les gradients de profondeur ou les normales de la surface. Nos méthodes sont stables dans toutes les géométries de projection. Dans le deuxième type de problème de reconstruction sans modèle 3D de référence, on obtient les formes de l’objet à partir d’un ensemble d’images où il apparaît déformé. Nous fournissons des solutions locales et globales basées sur le modéle de la caméra perspective. Dans la méthode locale ou par point, nous résolvons pour la normale de la surface en chaque point en supposant que la surface est infinitésimalement plane. Nous calculons ensuite la surface par intégration. Dans la méthode globale, nous trouvons une relaxation convexe du problème. Celle-ci est basée sur la relaxation de l’isométrie en contrainte d’inextensibilité et sur la maximisation de la profondeur en chaque point de la surface. Cette solution combine toutes les contraintes en un seul programme d’optimisation convexe qui calcule la profondeur et utilise une représentation éparse de la surface. Nous détaillons les expériences approfondies qui ont été réalisées pour démontrer l’efficacité de chacune des méthodes. Les expériences montrent que notre solution libre de modèle de référence local fonctionne mieux que la plupart des méthodes précédentes. Notre méthode local avec un modèle 3D de référence et notre méthode globale sans modèle 3D apportent de meilleurs résultats que les méthodes de l’état de l’art en étant robuste au bruit de la correspondance. En particulier, nous sommes en mesure de reconstruire des déformations complexes, non-lisses et d’articulations avec la seconde méthode; alors qu’avec la première, nous pouvons reconstruire avec précision de déformations larges à partir d’images prises avec des très longues focalesThis thesis contributes to the problem of 3D reconstruction for deformable surfaces using a single camera. In order to model surface deformation, we use the isometric prior because many real object deformations are near-isometric. Isometry implies that the surface cannot stretch or compress. We tackle two different problems. The first is called Shape-from-Template where the object’s deformed shape is computed from a single image and a texture-mapped 3D template of the object surface. Previous methods propose a differential model of the problem and compute the local analytic solutions. In the methods the solution related to the depth-gradient is discarded and only the depth solution is used. We demonstrate that the depth solution lacks stability as the projection geometry tends to affine. We provide alternative methods based on the local analytic solutions of first-order quantities, such as the depth-gradient or surface normals. Our methods are stable in all projection geometries. The second type of problem, called Non-Rigid Shape-from-Motion is the more general templatefree reconstruction scenario. In this case one obtains the object’s shapes from a set of images where it appears deformed. We contribute to this problem for both local and global solutions using the perspective camera. In the local or point-wise method, we solve for the surface normal at each point assuming infinitesimal planarity of the surface. We then compute the surface by integration. In the global method we find a convex relaxation of the problem. This is based on relaxing isometry to inextensibility and maximizing the surface’s average depth. This solution combines all constraints into a single convex optimization program to compute depth and works for a sparse point representation of the surface. We detail the extensive experiments that were used to demonstrate the effectiveness of each of the proposed methods. The experiments show that our local template-free solution performs better than most of the previous methods. Our local template-based method and our global template-free method performs better than the state-of-the-art methods with robustness to correspondence noise. In particular, we are able to reconstruct difficult, non-smooth and articulating deformations with the latter; while with the former we can accurately reconstruct large deformations with images taken at very long focal lengths
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Darbandi, Hossein B. "New surface descriptors for matching and recognition of three-dimensional rigid objects." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/17456.
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In this work we propose new surface descriptors for matching and recognition of three-dimensional rigid objects by encoding the fluctuation of the surface and the variation of its normal around an oriented surface point. The surface of the object is encoded into three features vectors as the surface signatures on each point of the surface, and then the collection of signatures is used to match and recognize the object. The signatures encode the curvature, symmetry, and convexity of the surface around an oriented point. The new descriptors are robust to noise, sampling density, scale, rotation, clutter, and occlusion. In this work we use Computer Aided Design (CAD) to create models and test objects represented by triangular meshes.
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Innmann, Matthias [Verfasser]. "Practical 3D Reconstruction of Non-Rigid Objects and Surface Reflectance / Matthias Innmann." München : Verlag Dr. Hut, 2021. http://d-nb.info/1232847690/34.
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Lund, Hugh Michael. "The impact and rupture of a water-filled balloon on a rigid surface." Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/245343.
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The dropping of a water-filled latex balloon onto a flat, rigid surface is an experiment that is known and has been performed by many, but on which there is no existing published work. High-speed images taken of the process revealed a range of phenomena, many of which had not been previously observed. After release, a water-filled balloon accelerates down and impacts with the tank floor. Upon impact, the balloon deforms through the propagation of waves up the balloon from the impact point. If the balloon does not rupture during this deformation, it then bounces up off the surface, the whole process similar to that when a water droplet bounces on a hydrophobic surface. Often, however, the balloon ruptures. This occurs through the propagation of one or more cracks through the balloon, leading to the rapid retraction of the membrane over the water’s surface, and consequent ejection of a fine spray of water droplets behind it. If there are any waves on the balloon at the moment of rupture, a larger-scale growth of the interfacial amplitude occurs, of the same wavelength as the preburst waves. Eventually, gravity dominates, as the water slumps down and spreads over the flat surface. In this thesis, the process described above is examined in detail, both experimentally and theoretically. To gain some insight into the behaviour of the latex balloons, their static and quasi-static behaviour is examined. A experimental method better than simply dropping the balloons was derived, permitting the accurate quantitative measurement of the process. In this new method, the balloons were held stationary, forced at a set frequency, then ruptured with a pin. The pre-burst waves are then shown to be accurately modelled by linear theory, with tension in the membrane acting much like a fluid surface tension. The behaviour of the rubber in retraction from large initial stretches is shown to be disperse, in contrast with that observed for retractions from small initial stretches, due to both non-linearity in the rubber and drag from the water on the strip. The spray ejected behind the rubber is explained as consequence of the inherent instability of the Gaussian velocity field in the wake. Finally, the late-time growth of the interfacial amplitude is examined, and argued to be closely-related to the Richtmyer-Meshkov instability. A model is then derived for the case of a balloon oscillated and burst with water both inside and outside, and is shown to be in approximate agreement with experiments.
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Dalrymple, Amy Janel. "The Effect of Adhesion on the Contact of an Elastica with a Rigid Surface." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/36111.
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The understanding of topics such as friction, wear, lubrication, and adhesive bonds is dependent on the ability to measure surface and interfacial energies. The surface energies of liquids may be measured accurately using a variety of techniques; however, surface energies of solids are much more difficult to accurately measure. In an attempt to develop a method that can be used to measure surface and interfacial energies of solids, this thesis proposes the use of a elastica. The elastica acts as an extremely flexible beam and provides a structure that will permit measurable deformation of the solid by relatively small surface attractions. The ends of the elastica are lifted, bent, and clamped vertically at an equal height and specified distance apart. They are then moved downward, allowing the strip to make contact with a flat, rigid, horizontal surface.
Two adhesion models are investigated. First, a JKR-type analysis, which examines the effect of adhesion forces that exist within the area of contact between the elastica and the rigid surface, is considered. Various values for the work of adhesion are examined. A DMT-type analysis, which assumes that the adhesion forces act in the region just outside of the contact area, is also considered. Results are obtained for linear and constant forces. Various values for the maximum DMT force and the vertical separation between the elastica and the rigid substrate at which the adhesion forces terminate are examined. Results from the two types of analyses are compared.Master of Science
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Wannasingha, Usa. "Nested rigid-lid and free-surface numerical primitive equation ocean models for the Faroese Channels." Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324026.
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Maji, S., P. R. Hanmaiahgari, R. Balachandar, Jaan H. Pu, A. M. Ricardo, and R. M. L. Ferreira. "A review on hydrodynamics of free surface flows in emergent vegetated channels." MDPI, 2020. http://hdl.handle.net/10454/17820.
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YesThis review paper addresses the structure of the mean flow and key turbulence quantities in free-surface flows with emergent vegetation. Emergent vegetation in open channel flow affects turbulence, flow patterns, flow resistance, sediment transport, and morphological changes. The last 15 years have witnessed significant advances in field, laboratory, and numerical investigations of turbulent flows within reaches of different types of emergent vegetation, such as rigid stems, flexible stems, with foliage or without foliage, and combinations of these. The influence of stem diameter, volume fraction, frontal area of stems, staggered and non-staggered arrangements of stems, and arrangement of stems in patches on mean flow and turbulence has been quantified in different research contexts using different instrumentation and numerical strategies. In this paper, a summary of key findings on emergent vegetation flows is offered, with particular emphasis on: (1) vertical structure of flow field, (2) velocity distribution, 2nd order moments, and distribution of turbulent kinetic energy (TKE) in horizontal plane, (3) horizontal structures which includes wake and shear flows and, (4) drag effect of emergent vegetation on the flow. It can be concluded that the drag coefficient of an emergent vegetation patch is proportional to the solid volume fraction and average drag of an individual vegetation stem is a linear function of the stem Reynolds number. The distribution of TKE in a horizontal plane demonstrates that the production of TKE is mostly associated with vortex shedding from individual stems. Production and dissipation of TKE are not in equilibrium, resulting in strong fluxes of TKE directed outward the near wake of each stem. In addition to Kelvin–Helmholtz and von Kármán vortices, the ejections and sweeps have profound influence on sediment dynamics in the emergent vegetated flows.
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Bhatta, Ram S. "Dynamics of Coupled Large Amplitude Motions from Small Non-Rigid Molecules to Conjugated Polymers." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1353339449.
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Wu, Min. "Adhesion and Surface Energy Profiles of Large-area Atomic Layers of Two-dimensional MoS2 on Rigid Substrates by Facile Methods." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849762/.
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Two-dimensional (2D) transition metal dichalcogenides (TMDs) show great potential for the future electronics, optoelectronics and energy applications. But, the studies unveiling their interactions with the host substrates are sparse and limits their practical use for real device applications. We report the facile nano-scratch method to determine the adhesion energy of the wafer scale MoS2 atomic layers attached to the SiO2/Si and sapphire substrates. The practical adhesion energy of monolayer MoS2 on the SiO2/Si substrate is 7.78 J/m2. The practical adhesion energy was found to be an increasing function of the MoS2 thickness. Unlike SiO2/Si substrates, MoS2 films grown on the sapphire possess higher bonding energy, which is attributed to the defect-free growth and less number of grain boundaries, as well as less stress and strain stored at the interface owing to the similarity of Thermal Expansion Coefficient (TEC) between MoS2 films and sapphire substrate. Furthermore, we calculated the surface free energy of 2D MoS2 by the facile contact angle measurements and Neumann model fitting. A surface free energy ~85.3 mJ/m2 in few layers thick MoS2 manifests the hydrophilic nature of 2D MoS2. The high surface energy of MoS2 helps explain the good bonding strength at MoS2/substrate interface. This simple adhesion energy and surface energy measurement methodology could further apply to other TMDs for their widespread use.
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Lacis, Ugis. "Models of porous, elastic and rigid materials in moving fluids." Doctoral thesis, KTH, Stabilitet, Transition, Kontroll, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-195679.
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Tails, fins, scales, and surface coatings are used by organisms for various tasks, including locomotion. Since millions of years of evolution have passed, we expect that the design of surface structures is optimal for the tasks of the organism. These structures serve as an inspiration in this thesis to identify new mechanisms for flow control. There are two general categories of fluid-structure-interaction mechanisms. The first is active interaction, where an organism actively moves parts of the body or its entire body in order to modify the surrounding flow field (e.g., birds flapping their wings). The second is passive interaction, where appendages or surface textures are not actively controlled by the organism and hence no energy is spent (e.g., feathers passively moving in the surrounding flow). Our aim is to find new passive mechanisms that interact with surrounding fluids in favourable ways; for example, to increase lift and to decrease drag. In the first part of this work, we investigate a simple model of an appendage (splitter plate) behind a bluff body (circular cylinder or sphere). If the plate is sufficiently short and there is a recirculation region behind the body, the straight position of the appendage becomes unstable, similar to how a straight vertical position of an inverted pendulum is unstable under gravity. We explain and characterize this instability using computations, experiments and a reduced-order model. The consequences of this instability are reorientation (turn) of the body and passive dispersion (drift with respect to the directionof the gravity). The observed mechanism could serve as a means to enhance locomotion and dispersion for various motile animals and non-motile seeds. In the second part of this thesis, we look into effective models of porous and poroelastic materials. We use the method of homogenization via multi-scale expansion to model a poroelastic medium with a continuum field. In particular, we derive boundary conditions for the velocity and the pressure at the interface between the free fluid and the porous or poroelastic material. The results obtained using the derived boundary conditions are then validated with respect to direct numerical simulations (DNS) in both two-dimensional and three-dimensional settings. The continuum model – coupled with the necessary boundary conditions – gives accurate predictions for both the flow field and the displacement field when compared to DNS.Många djur använder sig av fjäll, päls, hår eller fjädrar för att öka sin förmåga att förflytta sig i luft eller vatten. Eftersom djuren har genomgått miljontals år av evolution, kan man förvänta sig att ytstrukturernas form är optimala för organismens uppgifter. Dessa strukturer tjänar som inspiration i denna avhandling för att identifiera nya mekanismer för manipulering av strömning. Samverkan mellan fluider och strukturer (så kallad fluid-struktur-interaktion) kan delas upp i två kategorier. Den första typen av samverkan är aktiv, vilket innebär att en organism aktivt rör hela eller delar av sin kropp för att manipulera det omgivande strömningsfältet (till exempel fåglar som flaxar sina vingar). Den andra typen är passiv samverkan, där organismer har utväxter (svansar, fjärdar, etc.) eller ytbeläggningar som de inte aktivt har kontroll över och som således inte förbrukar någon energi. Ett exempel är fjädrar som passivt rör sig i det omgivande flödet. Vårt mål är att hitta nya passiva mekanismer som växelverkar med den omgivande fluiden på ett fördelaktigt sätt, exempelvis genom att öka lyftkraften eller minska luftmotståndet. I den första delen av detta arbete undersöker vi en enkel modell för en utväxt (i form av en platta) bakom en cirkulär cylinder eller sfär. Om plattan är tillräckligt kort och om det finns ett vak bakom kroppen kommer det upprätta läget av plattan att vara instabilt. Denna instabilitet är i princip samma som uppstår då man försöker balansera en penna på fingret. Vi förklarar den bakomliggande mekanismen av denna instabilitet genom numeriska beräkningar, experiment och en enkel modell med tre frihetsgrader. Konsekvenserna av denna instabilitet är en omorientering (rotation) av kroppen och en sidledsförflyttning av kroppen i förhållande till tyngdkraftens riktning. Denna mekanism kan användas djur och frön för att öka deras förmåga att förflytta eller sprida sig i vatten eller luft. I den andra delen av avhandlingen studerar vi modeller av porösa och elastiska material. Vi använder en mångskalig metod för att modellera det poroelastiska materialet som ett kontinuum. Vi härleder randvillkor för både hastighetsfältet och trycket på gränssnittet mellan den fria fluiden och det poroelastiska materialet. Resultaten som erhållits med de härledda randvillkoren valideras sedan genom direkta numeriska simuleringar (DNS) för både två- och tredimensionella fall. Kontinuumsmodellen av materialet kopplad genom randvillkoren till den fria strömmande fluiden predikterar strömnings- och förskjutningsfält noggrant i jämförelse med DNS.
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Zhou, Xu. "Synthesis and characterization of rigid nanoporous hypercrosslinked copolymers for high surface area materials with potential hydrogen storage capabilities." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/78048.
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Hydrogen storage remains a major technological barrier to the widespread adoption of hydrogen as an energy source. Organic polymers offer one potential route to useful hydrogen storage materials. Recently, Frechet and his coworkers described a series of hypercrosslinked polymers with high surface area and studied their surface properties and hydrogen storage capacities. McKeown and his coworkers studied a class of materials termed Polymers of Intrinsic Microporosity (PIMs) which are also based on a "hypercrosslinked" concept. We enchained N-substituted maleimide and functionalized stilbene alternating copolymers into a "hypercrosslinked system" to achieve high rigidity, high surface areas, high aromatic content and good thermal stability.
Hypercrosslinked copolymers of N-(3-methylphenyl)maleimide (3MPMI), 4-methyl stilbene (4MSTBB), vinylbenzyl chloride (VBC) and divinyl benzene (DVB) were synthesized. Scanning electron micrographs (SEM) show the copolymers are porous and some examples have shown surface areas over 1200 m²/g. We have also found the incorporation of 3MPMI and 4MSTBB improves the thermal stability and raises the glass transition temperature of the copolymer. However, the incorporation of 3MPMI and 4MSTBB decreases the hypercrosslinking density and therefore causes a decrease in the copolymer surface area. The systematic study of styrene (STR) – vinylbenzyl chloride (VBC) – divinyl benzene (DVB) networks indicates that a low density of chloromethyl groups leads to a decrease in surface area. Therefore, we are continuing to investigate other monomers, such as N-substituted maleimide and functionalized stilbene containing chloromethyl groups, in order to enhance thermal stability while maintaining surface area.
In order to increase the enthalpy of hydrogen adsorption and thus raise the temperature of hydrogen storage, the monomer N,N-dimethyl-N',N'-diethyl-4,4'-diaminostilbene (4,4'DASTB-3MPMI) which contains electron donating groups was incorporated into hypercrosslinked polymer particles. Hypercrosslinked polymer (4,4'DASTB-3MPMI)1.0(VBC)98.5(DVB).50 exhibits a surface area of 3257 m²/g.Master of Science
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Allain, Benjamin. "Suivi volumétrique de formes 3D non rigides." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAM017/document.
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Dans cette thèse nous proposons des algorithmes pour le suivi 3D du mouvement des objects déformables à partir de plusieurs caméras vidéo. Bien qu’une suite de reconstructions tridimensionnelles peut être obtenue par des méthodes de reconstruction statique, celle-ci ne représente pas le mouvement. Nous voulons produire une représentation temporellement cohérente de la suite de formes prises par l’object. Précisément, nous souhaitons représenter l’objet par une surface maillée 3D dont les sommets se déplacent au cours du temps mais dont la topologie reste identique.Contrairement à beaucoup d’approches existantes, nous proposons de représenter le mouvement du volume intérieur des formes, dans le but de mieux représenter la nature volumétrique des objets. Nous traitons de manière volumétrique les problèmes fondamentaux du suivi déformable que sont l’association d’éléments semblables entre deux formes et la modélisation de la déformation. En particulier, nous adaptons au formes volumétriques les modèles d’association EM-ICP non-rigide ansi que l’association par détection par apprentissage automatique.D’autre part, nous abordons la question de la modélisation de l’évolution temporelle de la déformation au cours d’une séquence dans le but de mieux contraindre le problème du suivi temporel. Pour cela, nous modélisons un espace de forme construit autour de propriétés de déformations locales que nous apprenons automatiqument lors du suivi.Nous validons nos algorithmes de suivi sur des séquences vidéo multi-caméras avec vérité terrain (silhouettes et suivi par marqueurs). Nos résultats se révèlent meilleurs ou équivalents à ceux obtenus avec les méthodes de l’état de l’art.Enfin, nous démontrons que le suivi volumétrique et la représentation que nous avons choisie permettent de produire des animations 3D qui combinent l’acquisition et la simulation de mouvementIn this thesis we propose algorithms for tracking 3D deformable shapes in motion from multiview video. Although series of reconstructed 3D shapes can be obtained by applying a static reconstruction algorithm to each temporal frame independently, such series do not represent motion. Instead, we want to provide a temporally coherent representation of the sequence of shapes resulting from temporal evolutions of a shape. Precisely, we want to represent the observed shape sequence as a 3D surface mesh whose vertices move in time but whose topology is constant.In contrast with most existing approaches, we propose to represent the motion of inner shape volumes, with the aim of better accounting for the volumetric nature of the observed object. We provide a fully volumetric approach to the fundamental problems of deformable shape tracking, which are the association between corresponding shape elements and the deformation model. In particular, we extend to a volumetric shape representation the EM-ICP tracking framework and the association-by-detection strategy.Furthermore, in order to better constrain the shape tracking problem, we propose a model for the temporal evolution of deformation. Our deformation model defines a shape space parametrized by variables that capture local deformation properties of the shape and whose values are automatically learned during the tracking process.We validate our tracking algorithms on several multiview video sequences with ground truth (silhouette and marker-based tracking). Our results are better or comparable to state of the art approaches.Finally, we show that volumetric tracking and the shape representation we choose can be leveraged for producing shape animations which combine captured and simulatated motion
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Robertson, Francis. "An experimental investigation of the drag on idealised rigid, emergent vegetation and other obstacles in turbulent free-surface flows." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/an-experimental-investigation-of-the-drag-on-idealised-rigid-emergent-vegetation-and-other-obstacles-in-turbulent-freesurface-flows(07165357-67da-461d-a6a2-ed4970e2cb0c).html.
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Vegetation is commonly modelled as emergent arrays of rigid, circular cylinders. However, the drag coefficient (CD) of real stems or trunks is closer to that of cylinders with a square cross-section. In this thesis, vegetation has been idealised as square cylinders in laboratory experiments with a turbulence intensity of the order of 10% which is similar to that of typical river flows. These cylinders may also represent other obstacles such as architectural structures. This research has determined CD of an isolated cylinder and cylinder pairs as a function of position as well as the average drag coefficient (CDv) of larger arrays. A strain gauge was used to measure CD whilst CDv was computed with a momentum balance which was validated by strain gauge measurements for a regularly spaced array. The velocity and turbulence intensity surrounding a pair of cylinders arranged one behind the other with respect to mean flow (in tandem) were also measured with an Acoustic Doppler Velocimeter. The isolated cylinder CD was found to be 2.11 in close agreement with other researchers. Under fixed flow conditions CD for a cylinder in a pair was found to be as low as -0.40 and as high as 3.46 depending on their relative positioning. For arrays, CDv was influenced more by the distribution of cylinders than the flow conditions over the range of conditions tested. Mean values of CDv for each array were found to be between 1.52 and 3.06. This new insight therefore suggests that CDv for vegetation in bulk may actually be much higher than the typical value of 1 which is often assumed to apply in practice. If little other information is available, a crude estimate of CDv = 2 would be reasonable for many practical applications. The validity of a 2D realizable k-epsilon turbulence model for predicting the flow around square cylinders was evaluated. The model was successful in predicting CD for an isolated cylinder. In this regard the model performed as well as Large Eddy Simulations by other authors with a significant increase in computational efficiency. However, the numerical model underestimates CD of downstream cylinders in tandem pairs and overestimates velocities in their wake. This suggests it may be necessary to expand the model to three-dimensions when attempting to simulate the flow around two or more bluff obstacles with sharp edges.
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Josi, Johannes. "Nodal rational sextics in the real projective plane." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS076.
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Cette thèse est consacrée à l’étude des courbes sextiques nodales, et en particulier des sextiques rationnelles, dans le plan projectif réel. Deux sextiques nodales réelles ayant k points doubles sont dites rigidement isotopes si elles peuvent être reliées par un chemin dans l’espace des sextiques nodales réelles ayant k points doubles. Le résultat principal de la première partie de la thèse donne une classification à isotopie rigide près des sextiques nodales irréductibles sans points doubles réels, généralisant la classification des sextiques non-singulières obtenue par Nikulin. La seconde partie porte sur les sextiques ayant des points doubles réels : une classification est obtenue pour les sextiques nodales séparantes, c’est-à-dire celles dont la partie réelle sépare leur complexification (l’ensemble des points complexes) en deux composantes connexes. Ce résultat est appliqué au cas des sextiques rationnelles réelles pouvant être perturbées en des sextiques maximales ou presque maximales (dans le sens de l’inégalité de Harnack). L’approche retenue repose sur l’étude des périodes des surfaces K3, se basant notamment sur le Théorème de Torelli Global de Piatetski-Shapiro et Shafarevich et le Théorème de Surjectivité de Kulikov, ainsi que sur les résultats de Nikulin portant sur les formes bilinéaires symétriques intégralesThis thesis studies nodal sextics (algebraic curves of degree six), and in particular rational sextics, in the real projective plane. Two such sextics with k nodes are called rigidly isotopic if they can be joined by a path in the space of real nodal sextics with k nodes. The main result of the first part of the thesis is a rigid isotopy classification of real nodal sextics without real nodes, generalizing Nikulin’s classification of non-singular sextics. In the second part we study sextics with real nodes and we describe the rigid isotopy classes of such sextics in the case where the sextics are dividing, i.e., their real part separates the complexification (the set of complex points) into two halves. As a main application, we give a rigid isotopy classification for those nodal real rational sextics which can be perturbed to maximal or next-to-maximal sextics in the sense of Harnack’s inequality. Our approach is based on the study of periods of K3 surfaces, drawing on the Global Torelli Theorem by Piatetski-Shapiro and Shafarevich and Kulikov’s surjectivity theorem, as well as Nikulin’s results on symmetric integral bilinear forms
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Chen, Zengshi. "Dynamics and control of collision of multi-link humanoid robots with a rigid or elastic object." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1158442034.
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Shaheed, Rawaa. "3D Numerical Modelling of Secondary Current in Shallow River Bends and Confluences." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34922.
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Secondary currents are one of the important features that characterize flow in river bends and confluences. Fluid particles follow a helical path instead of moving nearly parallel to the axis of the channel. The local imbalance between the vertically varying centrifugal force and the cross-stream pressure gradient results in generating the secondary flow and raising a typical motion of the helical flow. A number of studies, including experimental or mathematical, have been conducted to examine flow characteristics in curved open channels, river meanders, or confluences. In this research, the influence of secondary currents is studied on the elevation of water surface and the hydraulic structures in channel bends and confluences by employing a 3D OpenFOAM numerical model.
The research implements the 3D OpenFOAM numerical model to simulate the horizontal distribution of the flow in curved rivers. In addition, the progress in unraveling and understanding the bend dynamics is considered. The finite volume method in (OpenFOAM) software is used to simulate and examine the behavior of secondary current in channel bends and confluences. Thereafter, a comparison between the experimental data and a numerical model is conducted. Two sets of experimental data are used; the data provided by Rozovskii (1961) for sharply curved channel, and the dataset provided by Shumate (1998) for confluent channel.
Two solvers in (OpenFOAM) software were selected to solve the problem regarding the experiment; InterFoam and PisoFoam. The InterFoam is a transient solver for incompressible flow that is used with open channel flow and Free Surface Model. The PisoFoam is a transient solver for incompressible flow that is used with closed channel flow and Rigid-Lid Model. Various turbulence models (i.e. Standard k-ε, Realizable k-ε, LRR, and LES) are applied in the numerical model to assess the accuracy of turbulence models in predicting the behaviour of the flow in channel bends and confluences. The accuracies of various turbulence models are examined and discussed.
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Utkutug, Deniz. "A Parametric Study Investigating The Inertial Soil-structure Interaction Effects On Global And Local Deformation Demands Of Multistory Steel Mrf Structures Resting On Surface Rigid Mat Foundations." Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610490/index.pdf.
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In reality, dynamic response of a structure supported on a compliant soil may vary significantly from the response of same structure when supported on a rigid base. A parametric study is conducted for the analysis of the variation in the global and the local deformation demands caused by the inertial soil-structure interaction effects. For the purposes of the study, nonlinear dynamic analyses are performed on 7 steel moment-resisting frame models, which are prepared by the virtue of fixed-base and flexible-base (interacting) conditions. Foundation is modeled with the Truncated Cone Model (Wolf, 1994) with the frequency independent coefficients. Free-field earthquake acceleration records are selected to conform to NEHRP equivalent Site Classes C and D. The study is limited to the structures founded on surface rigid mat foundations subjected to vertically propagating horizontally polarized coherent shear waves. Statistical analysis based on multiple linear regression procedure is performed to represent the variation in the response. Within the scope of the study, the wave parameter and the aspect ratio are observed to be directly proportional to the variation in the response, as a general trend. Maximum beneficial contribution of the SSI is found to be 6% in both global and local deformation demands. In addition, the contribution of inertial interaction effects is found to be in a decreasing trend for the increasing levels of ductility demands. Finally, upper limits of wave parameter for H/R=0.5, 1, 2 and 3 are calculated where the variation in the demands are capped at 1.0.
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Geraldi, N. R. "Wetting of non rigid surfaces." Thesis, Nottingham Trent University, 2015. http://irep.ntu.ac.uk/id/eprint/203/.
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In the world of anti-wetting surfaces, many superhydrophobic substrates comprise rigid structures on rigid substrates. The development of a thin flexible substrate would allow new avenues to be explored to fully take advantage of the non-wetting properties of superhydrophobicity. This thesis presents a novel production method and subsequent analysis of thin, conformable, superhydrophobic films based on the embedding of carbon nano-particles (CNPs) into the surface of polydimethylsiloxane (PDMS) substrates. Firstly experiments were performed to determine the effects of surface roughness on the capillary origami process. It was found that the droplet wrapping process could be controlled with the appropriate choice of liquid. Using a wetting liquid would see an enhanced wrapping state whereas use of a dewetting liquid would see a complete suppression of the wrapping process. The second set of experiments concentrated on determining whether or not it is possible to reduce the drag force experienced on cylinders in a laminar flow situation. By comparing an uncoated cylinder to a CNP PDMS coated cylinder of equivalent diameter, it was determined that it is possible to reduce the drag by a maximum of 28%. The last tests were to determine the potential of the surface as a snail-repellent material. A set of experiments, designed to compare the repellent and adhesive properties of the surface were performed. It was seen that these surfaces show promise as a snail repellent surface. This surface is in keeping with the hypothesis of Shirtcliffe et al. [1] which states an effective snail repellent surface shows anti-adhesive properties and maintains a high receding contact angle in the presence of an anionic surfactant.
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Tonin, Mateus Guimarães. "Análise isogeométrica aplicada a problemas de interação fluido-estrtura e superfície livre." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/163325.
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O presente trabalho tem por objetivo desenvolver uma formulação numérica baseada em Análise Isogeométrica para o estudo de problemas de interação fluido-estrutura (IFE) em aplicações envolvendo corpos rígidos submersos, onde escoamentos incompressíveis de fluidos Newtonianos com superfície livre são considerados. Propõe-se o emprego da Análise Isogeométrica por permitir a unificação entre os procedimentos de pré-processamento e análise, melhorando assim as condições de continuidade das funções de base empregadas tanto na discretização espacial do problema como na aproximação das variáveis do sistema de equações. O sistema de equações fundamentais do escoamento é formado pelas equações de Navier-Stokes e pela equação da conservação de massa, descrita segundo a hipótese de pseudo-compressibilidade, em uma formulação cinemática ALE (Arbitrary Lagrangean- Eulerian). A consideração da superfície livre no escoamento se dá tratando o fluido como um meio bifásico, através do método Level Set. O corpo rígido apresenta não linearidade na rotação e restrições representadas por vínculos elásticos e amortecedores viscosos, sendo a equação de equilíbrio dinâmico resolvida através do método de Newmark. O esquema de acoplamento sólido-fluido adotado é o particionado convencional, que impõe condições de compatibilidade cinemáticas e de equilíbrio sobre a interface sólido-fluido, analisando ambos os meios de maneira sequencial. A discretização das equações governantes é realizada através do esquema explícito de dois passos de Taylor-Galerkin, aplicado no contexto da Análise Isogeométrica. Por fim, são analisados alguns problemas da Dinâmica de Fluidos Computacional, de onde se concluiu que os resultados obtidos são bastante consistentes com os fenômenos envolvidos, com as ferramentas exclusivas da Análise Isogeométrica, como o refinamento k, melhorando a convergência dos resultados. Para escoamentos bifásicos, verificou-se que o método Level Set obteve resultados bastante promissores apresentando, entretanto, uma dissipação numérica excessiva. Propõe-se, para estudos futuros, a elaboração de esquemas numéricos que conservem melhor o volume da fase líquida do escoamento.The present work aims to development of a numerical formulation based on Isogeometric Analysis for the study of Fluid-Structure Interaction problems in applications involving rigid bodies submerged, considering incompressible Newtonian flows with free surface. The use of the Isogeometric Analysis allows unification between the preprocessing and analysis steps, improving then the continuity of the base functions employed, both in the spatial discretization and approximation of the variables in the system of equations. The fundamental flow equations are formed by the Navier-Stokes and the mass conservation, described by de pseudo-compressibility hypothesis, in an ALE (Arbitrary Lagrangean-Eulerian) kinematic formulation. The free surface consideration of the flow is handled treating the fluid like a two- phase medium, using the Level Set method. The rigid body considers nonlinearity in rotation, and restrictions represented by elastic springs and viscous dampers, with the dynamic equilibrium equation being resolved using the Newmark’s method. The solid-fluid coupling scheme is the conventional partitioned, which imposes kinematics and equilibrium compatibility conditions on the solid-fluid interface, analyzing both mediums in a sequential manner. The governing equations are discretized using the explicit two step Taylor-Galerkin method, applied in an Isogeometric Analisys context. Finally, some Computational Fluid Dinamics problems are analysed, from which it was concluded that the results obtained are quite consistent with phenomena involved, with the unique tools of Isogeometric Analysis, such as k-refinement, improving the convergence of the results. For biphasic flows, it was verified that the Level Set method obtained very promising results, presenting, however, an excessive numerical dissipation. For future studies, it is proposed the elaboration of numerical schemes that better preserve the volume of the liquid phase of the flow.
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Mitsui, Kentaro. "Bimeromorphic geometry of rigid analytic surfaces." 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142438.
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Braux-Zin, Jim. "Contributions aux problèmes de l'étalonnage extrinsèque d'affichages semi-transparents pour la réalité augmentée et de la mise en correspondance dense d'images." Thesis, Clermont-Ferrand 1, 2014. http://www.theses.fr/2014CLF1MM13/document.
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La réalité augmentée consiste en l'insertion d'éléments virtuels dans une scène réelle, observée à travers un écran. Les systèmes de réalité augmentée peuvent prendre des formes différentes pour obtenir l'équilibre désiré entre trois critères : précision, latence et robustesse. On identifie trois composants principaux : localisation, reconstruction et affichage. Nous nous concentrons sur l'affichage et la reconstruction. Pour certaines applications, l'utilisateur ne peut être isolé de la réalité. Nous proposons un système sous forme de "tablette augmentée" avec un écran semi transparent, au prix d'un étalonnage adapté. Pour assurer l'alignement entre augmentations et réalité, il faut connaître les poses relatives de l'utilisateur et de la scène observée par rapport à l'écran. Deux dispositifs de localisation sont nécessaires et l'étalonnage consiste à calculer la pose de ces dispositifs par rapport à l'écran. Le protocole d'étalonnage est le suivant : l'utilisateur renseigne les projections apparentes dans l'écran de points de référence d'un objet 3D connu ; les poses recherchées minimisent la distance 2D entre ces projections et celles calculées par le système. Ce problème est non convexe et difficile à optimiser. Pour obtenir une estimation initiale, nous développons une méthode directe par l'étalonnage intrinsèque et extrinsèque de caméras virtuelles. Ces dernières sont définies par leurs centres optiques, confondus avec les positions de l'utilisateur, ainsi que leur plan focal, constitué par l'écran. Les projections saisies par l'utilisateur constituent alors les observations 2D des points de référence dans ces caméras virtuelles. Un raisonnement symétrique permet de considérer des caméras virtuelles centrées sur les points de référence de l'objet, "observant" les positions de l'utilisateur. Ces estimations initiales sont ensuite raffinées par ajustement de faisceaux. La reconstruction 3D est basée sur la triangulation de correspondances entre images. Ces correspondances peuvent être éparses lorsqu'elles sont établies par détection, description et association de primitives géométriques ou denses lorsqu'elles sont établies par minimisation d'une fonction de coût sur toute l'image. Un champ dense de correspondance est préférable car il permet une reconstruction de surface, utile notamment pour une gestion réaliste des occultations en réalité augmentée. Les méthodes d'estimation d'un tel champ sont basées sur une optimisation variationnelle, précise mais sensible aux minimums locaux et limitée à des images peu différentes. A l'opposé, l'emploi de descripteurs discriminants peut rendre les correspondances éparses très robustes. Nous proposons de combiner les avantages des deux approches par l'intégration d'un coût basé sur des correspondances éparses de primitives à une méthode d'estimation variationnelle dense. Cela permet d'empêcher l'optimisation de tomber dans un minimum local sans dégrader la précision. Notre terme basé correspondances éparses est adapté aux primitives à coordonnées non entières, et peut exploiter des correspondances de points ou de segments tout en filtrant implicitement les correspondances erronées. Nous proposons aussi une détection et gestion complète des occultations pour pouvoir mettre en correspondance des images éloignées. Nous avons adapté et généralisé une méthode locale de détection des auto-occultations. Notre méthode produit des résultats compétitifs avec l'état de l'art, tout en étant plus simple et plus rapide, pour les applications de flot optique 2D et de stéréo à large parallaxe. Nos contributions permettent d'appliquer les méthodes variationnelles à de nouvelles applications sans dégrader leur performance. Le faible couplage des modules permet une grande flexibilité et généricité. Cela nous permet de transposer notre méthode pour le recalage de surfaces déformables avec des résultats surpassant l'état de l'art, ouvrant de nouvelles perspectivesAugmented reality is the process of inserting virtual elements into a real scene, observed through a screen. Augmented Reality systems can take different forms to get the desired balance between three criteria: accuracy, latency and robustness. Three main components can be identified: localization, reconstruction and display. The contributions of this thesis are focused on display and reconstruction. Most augmented reality systems use non-transparent screens as they are widely available. However, for critical applications such as surgery or driving assistance, the user cannot be ever isolated from reality. We answer this problem by proposing a new “augmented tablet” system with a semi-transparent screen. Such a system needs a suitable calibration scheme:to correctly align the displayed augmentations and reality, one need to know at every moment the poses of the user and the observed scene with regard to the screen. Two tracking devices (user and scene) are thus necessary, and the system calibration aims to compute the pose of those devices with regard to the screen. The calibration process set up in this thesis is as follows: the user indicates the apparent projections in the screen of reference points from a known 3D object ; then the poses to estimate should minimize the 2D on-screen distance between those projections and the ones computed by the system. This is a non-convex problem difficult to solve without a sane initialization. We develop a direct estimation method by computing the extrinsic parameters of virtual cameras. Those are defined by their optical centers which coincide with user positions, and their common focal plane consisting of the screen plane. The user-entered projections are then the 2D observations of the reference points in those virtual cameras. A symmetrical thinking allows one to define virtual cameras centered on the reference points, and “looking at” the user positions. Those initial estimations can then be refined with a bundle adjustment. Meanwhile, 3D reconstruction is based on the triangulation of matches between images. Those matches can be sparse when computed by detection and description of image features or dense when computed through the minimization of a cost function of the whole image. A dense correspondence field is better because it makes it possible to reconstruct a 3D surface, useful especially for realistic handling of occlusions for augmented reality. However, such a field is usually estimated thanks to variational methods, minimizing a convex cost function using local information. Those methods are accurate but subject to local minima, thus limited to small deformations. In contrast, sparse matches can be made very robust by using adequately discriminative descriptors. We propose to combine the advantages of those two approaches by adding a feature-based term into a dense variational method. It helps prevent the optimization from falling into local minima without degrading the end accuracy. Our feature-based term is suited to feature with non-integer coordinates and can handle point or line segment matches while implicitly filtering false matches. We also introduce comprehensive handling of occlusions so as to support large deformations. In particular, we have adapted and generalized a local method for detecting selfocclusions. Results on 2D optical flow and wide-baseline stereo disparity estimation are competitive with the state of the art, with a simpler and most of the time faster method. This proves that our contributions enables new applications of variational methods without degrading their accuracy. Moreover, the weak coupling between the components allows great flexibility and genericness. This is the reason we were able to also transpose the proposed method to the problem of non-rigid surface registration and outperforms the state of the art methods
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Nogneng, Dorian. "Non-rigid correspondences between surfaces embedded in 3D." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX109/document.
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La manipulation et le traitement d'énormes quantités de données en 3D est devenu un défi ayant d'innombrables applications, telles que la conception assistée par ordinateur, le calcul biomédical, les jeux interactifs, la perception des machines, la robotique, etc. Le traitement géométrique est un sujet de recherche à l'interface entre l'algorithmique, les mathématiques appliquées et l'informatique en lien avec les applications sus-mentionnées, qui existe depuis une cinquantaine d'années. C'est un domaine de recherche vaste qui inclut des sous-domaines. Le problème de correspondances de forme consiste à, étant donnée une paire de formes, trouver une "bonne" correspondance entre elles. Par exemple on peut vouloir que la correspondance préserve les distances géodésiques, ou des caractéristiques locales.Ce problème a attiré un intérêt croissant, en partie dû à ses nombreuses applications, par exemple en animation, interpolation de formes ou modélisation statistique de formes.Le cadre des correspondances fonctionnelles est un outil récent qui a dévoilé de nombreuses propriété utiles pour les correspondances de formes. Cette approche donne une représentation régulière et compacte du problème de correspondances entre formes, et la plupart des contraintes sur les correspondances fonctionnelles peuvent s'exprimer sous forme de contraintes linéaires ce qui permet une formulation du problème par moindres carrés. Dans cette thèse on se concentre sur le problème de correspondance de forme, spécifiquement en utilisant des correspondances fonctionnelles. Au Chapitre 1 on introduit les notions et notations de base qui seront utilisées le long de la thèse, liées aux surfaces continues ou discrètes, l'opérateur de Laplace-Beltrami, le problème de correspondance de forme non rigide, et le processus standard du calcul d'une correspondance fonctionnelle.Au Chapitre 2 on remarque que les correspondances fonctionnelles induites par des correspondances point à point doivent satisfaire des contraintes de préservation de produits point par point. On applique cette observation à des descripteurs de formes pour améliorer la formulation classique des contraintes sur les correspondances fonctionnelles. Cela mène à une approche qui permet d'extraire plus d'information des contraintes existantes et donne de meilleures correspondances, surtout lorsqu'il y a peu de descripteurs indépendants.Au Chapitre 3 on s'appuie sur la remarque précédente, mais cette fois dans le cas où on a déjà obtenu une correspondance fonctionnelle par une méthode existante. On remarque que la préservation du produit point par point peut aussi être utilisé pour étendre le domaine sur lequel la correspondance fonctionnelle peut transférer des fonctions. On montre que cela permet d'améliorer la précision du transfert de fonction.Au Chapitre 4 on étend l'approche proposée au Chapitre 3 en remarquant qu'au lieu d'utiliser le produit point par point de fonctions, la composition par n'importe quel opérateur fixé doit aussi être préservée. On utilise un réseau de neurones pour optimiser l'approximation d'une fonction donnée qu'on veut transférer, comme fonction point par point de fonctions d'une base précalculée, qu'on sait déjà transférer à l'aide de la correspondance fonctionnelle. Puis on décrit comment évaluer ce réseau de neurones entrainé sur l'image des fonctions de la base afin de construire l'image de la fonction que l'on souhaite transférer. On montre des résultats préliminaires qui suggèrent que cette méthode peut apporter des améliorations significatives au transfert de fonctions.Finalement, au Chapitre 5 on aborde les autres sujets étudiés lors de la thèse, qui n'ont aucun lien avec les correspondances non rigidesHandling and processing the massive amount of 3D data has become a challenge with countless applications, such as computer-aided design, biomedical computing, interactive games, machine perception, robotics, etc. Geometry Processing is an area of research at the interface between algorithmics, applied mathematics and computer science related to the above applications, that exists since approximately 50 years. It is a large topic of research that includes sub-areas. The problem of shape correspondence (also known as "shape matching") consists in, given a pair of shapes, finding a "good" correspondence between them. For example we may want the correspondence to preserve geodesic distances, or local geometric features.This problem has received a growing interest, in part due to its wide applicability, for example in animation, shape morphing or statistical shape modeling.The functional map framework is a recent tool that has shown many useful properties for shape matching. This approach provides a smooth compact representation of correspondences between shapes, and most constraints over functional maps can be expressed as linear constraints, which allows a least squares formulation of the problem.In this thesis we focus on the problem of shape correspondence, specifically using functional maps. In Chapter 1 we introduce basic notions and notations that will be used throughout the thesis, related to continuous and discrete surfaces, the Laplace-Beltrami operator, the problem of non-rigid shape matching, and the standard functional map computation pipeline.In Chapter 2 we notice that functional maps that are induced by point-to-point maps should satisfy point-wise product preservation constraints. We apply this observation to shape descriptors in order to improve the previous classical constraints on functional maps. This leads to an approach that allows to extract more information from existing constraints and results in better correspondences, particularly when the number of independent descriptors is small.In Chapter 3 we build on the previous remark, but this time in the situation where we already have a functional map that was computed by an existing method. We notice that the point-wise product preservation can also be used to extend the domain over which the given functional map can transfer functions. We show that this allows to improve the accuracy of function transfer.In Chapter 4 we extend the approach proposed in Chapter 3 by noticing that instead of using point-wise function products, the point-wise composition by any fixed operator should also be preserved. We use a neural network that optimizes the approximation of a given function that we want to transfer, as a point-wise function of some basis functions that we already know how to transfer using a given functional map. We then describe how to apply this trained network to the image of the basis functions to construct the image of the function that we want to transfer. We show preliminary results that suggest that this method can lead to significant improvement for function transfer.Finally, in Chapter 5 we mention other topics studied during the thesis, that are unrelated to non-rigid shape matching
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Shirafkan, Abbas. "Wettability and hydrophilicity of rigid and soft contact lens surfaces." Thesis, City University London, 1997. http://openaccess.city.ac.uk/8385/.
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In the last two decades an abundance of contact lens materials with unknown surface properties have been introduced as well as new contact lens design. Recent studies have identified the importance of physical and chemical interactions between materials and liquids. The purpose of this experimental research work was to investigate the relationship between a contact lens surface and a liquid. The wettability and hydrophilicity of both soft and rigid contact lens surfaces were determined using two novel techniques and an established method. The two novel techniques were the un-separated adherent quid/laser method and the adherent liquid/ maximum force method whereas the established technique involved monitoring the receding wetting angle and interface are a diameter of a sessile drop. Contact lens surface preparation and the method of removing a liquid from hydrated surfaces were found to be important variables when determining wettability or hydrophilicity. Experiments showed that the use of surface tension to remove liquid from hydrated surfaces significantly improved the reproducibility of subsequent measurements. Variation of the sessile drop wetting angle and interface area diameter with evaporation time demonstrated different values for different contact lenses. The clinical consequence of monitoring the receding values would be; if a material to spread tear break up time occurs the dry patches will be advanced on PMMA, rather than Paraperm contact lens. Surface hydrophilicity, if defined in terms of the maximum adherent force, describes the ability of a lens surface to attract a liquid, whereas wettability may be defined as the ability of a liquid to spread on a contact lens surface. The wettability and hydrophilicity, therefore, are two different issues. When a wetting angle is 01, or close to 0" the surface is described as wettable. Results demonstrated that Equalens had a greater surface wettability and hydrophilicity than the PMMA for pre-wear, but the post-wear hydrophilicity for PMMA was greater than Equalens. The use of each measurement method, therefore, resulted in a value that is intrinsically related to measurement method and definition. The clinical consequenceo f the valuesi s to help practitioners prescribea lens material either on wettability or hydrophilicity values. In contact lens practice, a lens surface is required to maintain a stable tear film and produce a long tear film break up time. A combination of hydrophilicty and wetting angle values can help to determine the requirement of wettability and hydrophilicity in the contact lens industry and also in practice. It can be concluded that no single test can fully describe the surface properties of contact lens surface materials, but it is proposed that information and results from a series of tests provides the most useful clinical description.
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Klamroth, Tillmann. "Quantum dynamics of atoms and electrons at non rigid solid surfaces." [S.l. : s.n.], 2000. http://www.diss.fu-berlin.de/2000/123/index.html.
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Shah, Said Khalid. "Non-rigid medical image registration using points, curves and parameterised surfaces." Thesis, University of East Anglia, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551208.
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This thesis describes different point based non-rigid registration methods in general and the "fast" radial basis functions (RBFs) non-rigid registration method in particular. We propose and implement three techniques for identifying features like points, curves and surfaces in medical images which represent displacement fields among such images and are later used in developing three corresponding fast and accurate non-rigid registration techniques. Each registration technique involves four main steps: feature extraction, correspondence between the features, RBF fitting to corresponding features, and evaluating the fitted method to the 3 D image data. The main goal of developing these three techniques is to see the effect of the increasing number of salient features in the form of anatomical point landmarks, curves and parameterised surfaces on the overall performance (speed and accuracy) of the tested registration algorithms. The point and curve based Fast RBF registration methods use manually placed anatomical point landmarks and principal curves, respectively. They ensure sub-second registration of standard-sized X-ray C'I' and MR datasets without loss of accuracy as compared to competing methods. However, both methods have limited performance in recovering large deformation due to small numbers of point landmarks. The surface based Fast RBF registration uses surface parameterisation and reparameterisation techniques as pre-processing steps to increase the number of point landmarks on a surface, establishing initial correspondences between points of a surface-pair using a minimum distortion based global surface parameterisation algorithm. Experimental results demonstrate target registration errors less than 2mm on intra-subject registration of various size 256/\3 MR real datasets. in conclusion, it is shown that the performance of the Fast RBF algorithm is less sensitive to the increasing number of point landmarks as compared to competing algorithms without substantial loss of accuracy.
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Ali, Reza. "Receptivity & transition in boundary layers over rigid and compliant surfaces." Thesis, University of Warwick, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397560.
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Bianchi, Carolina. "Extracting contact surfaces from point-cloud data for autonomous placing of rigid objects." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-280695.
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Nowadays, thousands of humanworkers engage daily in non-creative and physically demanding tasks such as order-picking-and-placing. This task consists of collecting different goods from warehouse shelves and placing them in a container to fulfill an order. The robotics research community has put much effort into investigating the automation of the picking problem for robotic manipulators. The placing problem, however, has received comparably less attention. A robot tasked with placing a grasped object has to choose a suitable pose and motion to release the item inside a container, that may be partially filled with other goods. The aim of this thesis is to develop and evaluate a system that automates the placing of objects in a container, whose content is perceived through an RGB-D camera. To accomplish this goal, we developed a perception module that, taking as input the RGB-D data, estimates the volume of the objects inside the container and extracts horizontal surfaces as potential supporting regions for the object. We integrated this module with a state-of the- art placement planner to compute placement poses for the grasped object, that are stable and reachable by the robot among the perceived obstacles. We evaluated the system by manually reproducing the computed placements in different test scenarios. Our experiments confirm that with the developed pipeline it is possible to automatically compute feasible and stable placement poses for different objects in containers filled with various objects, perceived through an RGB-D camera.Nuförtiden deltar tusentals mänskliga arbetare dagligen i icke-kreativa och fysiskt krävande uppgifter som plockning och placering i lager. Dessa uppgifter består i att samla in olika varor från lagerhyllor och placera dem i en godsbehållare för att fullgöra en beställning. Robotforskningssamhället har lagt mycket möda på att undersöka automatiseringen av plockningsproblemet för robotmanipulatörer. Placeringproblemet har emellertid fått mindre uppmärksamhet. En robot som har till uppgift att placera ett greppat objekt måste välja en lämplig ställning och rörelse för att frigöra föremålet i en behållare, som kan fyllas delvis med andra varor. Syftet med detta examensarbete är att utveckla och utvärdera ett system som automatiserar placeringen av ett objekt i en behållare vars innehåll uppfattas genom en RGB-D-kamera. För att uppnå detta mål, utvecklade vi en datorseendemodul som tar emot RGB-D-data och beräknar volymen på objekten i behållaren. Denna modul extraherar också horisontella ytor från RGB-D-data, som används som potentiella stödregioner för objektet. Vi integrerade modulen med en placeringsplanerare av bästa möjliga slag för att beräkna placeringsställningar för det greppade objektet, som är stabila och kan nås av roboten bland de upplevda hindren. Vi utvärderade systemet genom att manuellt reproducera de beräknade placeringarna i olika testscenarier. Våra experiment bekräftar att med den utvecklade pipelinen är det möjligt att automatiskt beräkna och genomförbara stabila placeringar för olika objekt i behållare fyllda med olika varor, uppfattade genom en RGB-D-kamera.
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Yang, Fangkai. "Collision Detection between Dynamic Rigid Objects and Static Displacement Mapped Surfaces in Computer Games." Thesis, KTH, Numerisk analys, NA, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-170625.
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Collision detection often refers the detection of the intersection of two or more objects. Collision detection algorithms in Avalanche Studios’ game engine need not only to detect the collision, but to get the closest distance and handle penetration. Current algorithms perform well in most cases, but obtain poor accuracy or low efficiency in some cases. This paper will attempt to improve the performance in two ways. First, two new backward projection methods are derived and compared, achieving more accurate backwards projected points. The accurate backwards points are important in collision detection with the terrain surface. Second, multiresolution bounding volumes are constructed in the narrow phase collision detection. These bounding volumes improve the performance when performing collision detection between large complex objects and the terrain. These bounding volumes reduces the number of backward projections needed.Kollisionsdetektering avser oftast att detektera skärning mellan två eller fler objekt. Kollisionsdetekteringsalgoritmerna i Avalanche Studios spelmotor behöver inte bara upptäcka skärningar, utan även det närmsta avståndet och hantera penetration. Aktuella algoritmer presterar bra i de flesta fall, men erhåller i vissa fall låg noggrannhet eller effektivitet. Detta dokument kommer att förbättra prestandan på två sätt. Först härleds och jämförs två nya bakåtprojektionsmetoder, vilka resulterander i mer exakta bakåtprojicerade punkter. Korrekt bakåtprojektion är viktig för kollisionsdetektering mot terrängytan. Sedan konstrueras och nyttjas flerupplösta begränsnings volymer under den detaljerade kollisionsfasen. Dessa avgränsande volymer förbättrar prestanda när kollisionsdetektering sker mellan stora komplexa objekt och terrängen då de minskar antalet bakåt projiceringar som behöver utföras.
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Giacomoni, Catherine. "Analyse de quelques problèmes de fluides géophysiques." Corte, 2001. http://www.theses.fr/2001CORT3062.
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L'océan peut être considéré comme le poumon, le garde-manger et l'une des principales voies de communication de l'humanité. Il est donc capital de mieux le connaître et d'apprendre à simuler son comportement de façon à appréhender des phénomènes naturels tels que El Niño ou des phénomènes directement liés à l'activité humaine tels que le transport de pollution ou la modification des courants liée à l'aménagement du linéaire côtier. Tous les modèles d'océanographie physique dérivent des équations primitives compressibles de Navier-Stokes. Un certain nombre d'hypothèses sont généralement émises pour simplifier ces équations et obtenir des modèles de courantologie tel que celui de shallow water. A partir de ces modèles, d'autres hypothèses simplificatrices peuvent être introduites et nous testons en particulier la condition de rigid lid. Outre la modélisation de la courantologie, nous proposons un modèle couplant l'écorce terrestre et l'océan, de façon à simuler la formation d'un tsunami lors d'un tremblement de terre sous-marin. Notre objectif est d'analyser mathématiquement ces problèmes et de proposer des méthodes numériques dont l'utilisation est particulièrement adaptée à leur résolution. L'analyse des modèles étudiés respecte deux principes de base qui sont l'obtention d'estimations a priori et leur utilisation. Ces estimations nous fournissent le cadre fonctionnel qui guide la méthode de résolution. Nous construisons par la méthode de Galerkin des solutions approchées vérifiant les mêmes estimations a priori que celles obtenues puis nous utilisons la méthode de compacité pour passer à la limite dans les équations. Dans le cas des opérateurs non-linéaires des équations de Navier-Stokes, le passage à la limite est loin d'être trivial et nécessite des développements importants. Ces solutions approchées sont ensuite implémentées numériquement et fournissent pour les différents modèles étudiés une série de résultats que nous comparons à des résultats connus.
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Montalbano, Paul Joseph. "Multistable Shape-Shifting Surfaces (MSSSs)." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4169.
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This paper presents designs for Multistable Shape-Shifting Surfaces (MSSS) by introducing bistability into the Shape-Shifting Surface (SSS). SSSs are defined as surfaces that retain their effectiveness as a physical barrier while undergoing changes in shape. The addition of bistability to the SSS gives the surface multiple distinct positions in which it remains when shifted to, i.e. by designing bistability into a single SSS link, the SSS unit cell can change into multiple shapes, and stabilize within the resulting shape, while maintaining integrity against various forms of external assaults normal to its surface. Planar stable configurations of the unit cell include, expanded, compressed, sheared, half-compressed, and partially-compressed, resulting in the planar shapes of a large square, small square, rhombus, rectangle, and trapezoid respectively. Tiling methods were introduced which gave the ability to produce out-of-plane assemblies using planar MSSS unit cells. A five-walled rigid storage container prototype was produced that allowed for numerous stable positions and volumes. Applications for MSSSs can include size-changing vehicle beds, expandable laptop screens, deformable walls, and volume-changing rigid-storage containers. Analysis of the MSSS was done using pseudo-rigid-Body Models (PRBMs) and Finite Element Analysis (FEA) which ensured bistable characteristics before prototypes were fabricated.
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Jain, Sumit. "Exploiting contacts for interactive control of animated human characters." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44817.
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One of the common research goals in disciplines such as computer graphics and robotics is to understand the subtleties of human motion and develop tools for recreating natural and meaningful motion. Physical simulation of virtual human characters is a promising approach since it provides a testbed for developing and testing control strategies required to execute various human behaviors. Designing generic control algorithms for simulating a wide range of human activities, which can robustly adapt to varying physical environments, has remained a primary challenge.
This dissertation introduces methods for generic and robust control of virtual characters in an interactive physical environment. Our approach is to use the information of the physical contacts between the character and her environment in the control design. We leverage high-level knowledge of the kinematics goals and the interaction with the surroundings to develop active control strategies that robustly adapt to variations in the physical scene. For synthesizing intentional motion requiring long-term planning, we exploit properties of the physical model for creating efficient and robust controllers in an interactive framework. The control design leverages the reference motion capture data and the contact information with the environment for interactive long-term planning. Finally, we propose a compact soft contact model for handling contacts for rigid body virtual characters. This model aims at improving the robustness of existing control methods without adding any complexity to the control design and opens up possibilities for new control algorithms to synthesize agile human motion.
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Al-Qudsi, Ahmad Verfasser], Lorenzis Laura [Akademischer Betreuer] [De, and Michele [Akademischer Betreuer] Scaraggi. "Multiscale modeling of rubber hysteretic friction on rough rigid surfaces / Ahmad Al-Qudsi ; Laura De Lorenzis, Michele Scaraggi." Braunschweig : Technische Universität Braunschweig, 2020. http://d-nb.info/1207074284/34.
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Al-Qudsi, Ahmad [Verfasser], Lorenzis Laura [Akademischer Betreuer] De, and Michele [Akademischer Betreuer] Scaraggi. "Multiscale modeling of rubber hysteretic friction on rough rigid surfaces / Ahmad Al-Qudsi ; Laura De Lorenzis, Michele Scaraggi." Braunschweig : Technische Universität Braunschweig, 2020. http://d-nb.info/1207074284/34.
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Granger, Sébastien. "Une approche statistique multi-échelle au recalage rigide de surfaces : Application à l'implantologie dentaire." Phd thesis, École Nationale Supérieure des Mines de Paris, 2003. http://tel.archives-ouvertes.fr/tel-00633460.
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Le principal sujet de cette thèse est la mise au point d'algorithmes de recalage rigide de surfaces au sein de VirtualScope, un système de guidage per-opératoire dédié au percement des axes des implants dentaires. Elle est basée sur une approche purement statistique, qui, en essayant de maximiser la vraisemblance calculée à partir d'une modélisation explicite du bruit, permet de justifier l'utilisation de l'ICP pour le recalage d'amers géométriques, puis de proposer l'ICP/EM multi-échelles, un peu plus précis et surtout beaucoup plus robuste et rapide. De nouveaux modèles de bruits sont proposés pour adapter l'algorithme aux surfaces échantillonnées et bruitées. La prédiction théorique de l'incertitude est abordée, et permet en particulier de guider l'acquisition des données. L'étude expérimentale très poussée des performances de l'algorithme permet de régler efficacement ses paramètres, mettre au point des systèmes de sécurité, et garantir ainsi un fonctionnement parfaitement satisfaisant au sein de VirtualScope. La seconde partie de cette thèse aborde plus généralement le problème de la modélisation statistique des courbes et surfaces échantillonnées bruitées. En regroupant les travaux sur la saillance et le vote de tenseurs, elle présente la notion de champs de vote, qui permet d'exprimer la probabilité d'un élément de la courbe ou surface connaissant un autre élément. Elle donne des exemples rudimentaires mais facilement programmables de champs de votes, qui prennent en compte la forme de la surface et la façon dont les points ont été échantillonnés et bruités. Elle montre comment les appliquer avec succès au problème du recalage, puis indique comment ils pourraient servir pour dériver des algorithmes bayésiens pour de nombreuses autres applications concernant les courbes et surfaces. Ces travaux seraient alors susceptibles de déboucher sur la mise au point d'un canevas statistique et multi-échelles commun à toutes ces méthodes.
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Schulte, Walter B. III. "The frequency response, impulse response, and transfer function of an ocean waveguide." Thesis, Monterey, California. Naval Postgraduate School, 2004. http://hdl.handle.net/10945/1516.
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Approved for public release, distribution is unlimitedIn this thesis, the ocean was modeled as a waveguide with an ideal pressure - release surface, and an ideal rigid bottom. The ocean waveguide was then treated as a linear, time - invariant, space - variant (TISV) filter or communication channel. The filter is time - invariant because no motion was modeled and because the properties of the ocean were assumed to be constant. The filter is space - variant because of the presence of the two boundaries, that is, the ocean surface and ocean bottom. This thesis investigates the ocean as a linear TISV filter by evaluating 1) the complex frequency response, 2) the impulse response, and 3) the transfer function of the ocean with respect to depth. It is shown that the TISV impulse response of the ocean contains information that can be used to help localize a target in range and whether the target is above or below the receiver. Computer simulation results were obtained by evaluating the three filter functions for several different test cases.
Ensign, United States Navy
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Ding, Yu. "Méthodes numériques sur l'équation intégrale aux bords pour le problème des ondes acoustiques diffractées par une surface rigide en 3D." Paris 11, 1989. http://www.theses.fr/1989PA112031.
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Cette thèse traite du problème de propagation des ondes acoustiques diffractées d'une surface rigide par équation intégrale aux bords. Equation intégrale peut s'écrire sous la forme: 1/2 u(t,x)=ui(t,x)+1/4π ∫r(x-y). N ⃗y)/∣x-y∣2. (u(τ,y))/∣x-y∣+1/c ∂u/∂t(τ,y))dσy où ui est l'onde incidente dans R3, Γ est la surface, n ⃗y est la normale unitaire à point y sur Γ, ∣x-y∣ la distance entre x et y, τ=t-∣x-y∣. Cette équation est une équation du potentiel retardé, et nous pouvons trouver un schéma explicite, successif en temps. Souvent, nous utilisons des méthodes de collocation, i. E. Une discrétisation par collocation en espace et par différences finies en temps. Dans cette thèse, nous donnons quelques méthodes de formulation variationnelle, en particulier, une méthode de formulation variationnelle du type Galerkin. Un théorème de convergence est démontré pour cette dernière dans le cas de deux plans parallèles. Les éléments constants par morceaux en espace et en temps sont utilisables pour la surface composée des facettes plans. Une comparaison des résultats numériques obtenus par la méthode de Galerkin et les méthodes de collocation est présentée. Quelques méthodes de couplage sont aussi proposées. Les comparaisons des résultats numériques sont données pour toutes les méthodes de couplage et non-couplageThis thesis deals with resolving the scattering problem of wave propagation via boundary integral equation (B. I. E. ) methods. It is well known that the problem for transient wave propagation scattering from a hard surface is usually described by means of a B. I. E. 1/2 u(t,x)=ui(t,x)+1/4π ∫r(x-y). N ⃗y)/∣x-y∣2. (u(τ,y))/∣x-y∣+1/c ∂u/∂t(τ,y))dσy where ui is the incident wave, the solution of wave equation in free field. Γ is the surface, n ⃗y the unitary normal at y on the surface Γ, ∣x-y∣ the distance between x and y, τ=t-∣x-y∣. This equation is a retarded potential equation, we can find an explicit marching in time scheme. Usually, we use collocation methods, that is, a discretisation by collocation in space and by finite difference in time. In this thesis, we give some variational formulation methods, in particular, a Galerkin type variational formulation method. A convergence theorem is proved for the Galerkin method in the case of two parallel planes. The constant elements by mesh in space and in time are usable for the surface composed by facet planes. A comparison of numerical results obtained by the Galerkin method and collocation methods is presented. Some coupling methods are also proposed. Comparisons of numerical results are given for all the coupling and non-coupling methods
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Gallardo, Mathias. "Contributions to Monocular Deformable 3D Reconstruction : Curvilinear Objects and Multiple Visual Cues." Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAC021/document.
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La reconstruction 3D monoculaire déformable est le problème général d'estimation de forme 3D d'un objet déformable à partir d'images 2D. Plusieurs scénarios ont émergé : le Shape-from-Template (SfT) et le Non-Rigid Structure-from-Motion (NRSfM) sont deux approches qui ont été grandement étudiées pour leur applicabilité. La première utilise une seule image qui montre un objet se déformant et un patron (une forme 3D texturée de l'objet dans une pose de référence). La seconde n'utilise pas de patron, mais utilise plusieurs images et estime la forme 3D dans chaque image. Les deux approches s'appuient sur le mouvement de points de correspondances entre les images et sur des a priori de déformations, restreignant ainsi leur utilisation à des surfaces texturées qui se déforment de manière lisse. Cette thèse fait avancer l'état de l'art du SfT et du NRSfM dans deux directions. La première est l'étude du SfT dans le cas de patrons 1D (c’est-à-dire des courbes comme des cordes et des câbles). La seconde direction est le développement d'algorithmes de SfT et de NRSfM qui exploitent plusieurs indices visuels et qui résolvent des cas réels et complexes non-résolus précédemment. Nous considérons des déformations isométriques et reconstruisons la partie extérieure de l'objet. Les contributions techniques et scientifiques de cette thèse sont divisées en quatre parties.La première partie de cette thèse étudie le SfT curvilinéaire, qui est le cas du patron curvilinéaire plongé dans un espace 2D ou 3D. Nous proposons une analyse théorique approfondie et des solutions pratiques pour le SfT curvilinéaire. Malgré son apparente simplicité, le SfT curvilinéaire s'est avéré être un problème complexe : il ne peut pas être résolu à l'aide de solutions locales non-holonomes d'une équation différentielle ordinaire et ne possède pas de solution unique, mais un nombre fini de solutions ambiguës. Une contribution technique majeure est un algorithme basé sur notre théorie, qui génère toutes les solutions ambiguës. La deuxième partie de cette thèse traite d'une limitation des méthodes de SfT : la reconstruction de plis. Cette limitation vient de la parcimonie de la contrainte de mouvement et de la régularisation. Nous proposons deux contributions qui s'appuient sur un cadre de minimisation d'énergie non-convexe. Tout d'abord, nous complétons la contrainte de mouvement avec une contrainte robuste de bord. Ensuite, nous modélisons implicitement les plis à l'aide d'une représentation dense de la surface basée maillage et d'une contrainte robuste de lissage qui désactive automatiquement le lissage de la courbure sans connaître a priori la position des plis.La troisième partie de cette thèse est dédiée à une autre limitation du SfT : la reconstruction de surfaces peu texturées. Cette limitation vient de la difficulté d'obtenir des correspondances (parcimonieuses ou denses) sur des surfaces peu texturées. Comme l'ombrage révèle les détails sur des surfaces peu texturées, nous proposons de combiner l'ombrage avec le SfT. Nous présentons deux contributions. La première est une initialisation en cascade qui estime séquentiellement la déformation de la surface, l'illumination de la scène, la réponse de la caméra et enfin les albédos de la surface à partir d'images monoculaires où la surface se déforme. La seconde est l'intégration de l'ombrage à notre précédent cadre de minimisation d'énergie afin de raffiner simultanément les paramètres photométriques et de déformation.La dernière partie de cette thèse relâche la connaissance du patron et aborde deux limitations du NRSfM : la reconstruction de surfaces peu texturées avec des plis. Une contribution majeure est l'extension du second cadre d'optimisation pour la reconstruction conjointe de la forme 3D de la surface sur toutes les images d'entrée et des albédos de la surface sans en connaître un patronMonocular deformable 3D reconstruction is the general problem of recovering the 3D shape of a deformable object from monocular 2D images. Several scenarios have emerged: the Shape-from-Template (SfT) and the Non-Rigid Structure-from-Motion (NRSfM) are two approaches intensively studied for their practicability. The former uses a single image depicting the deforming object and a template (a textured 3D shape of this object in a reference pose). The latter does not use a template, but uses several images and recovers the 3D shape in each image. Both approaches rely on the motion of correspondences between the images and deformation priors, which restrict their use to well-textured surfaces which deform smoothly. This thesis advances the state-of-the-art in SfT and NRSfM in two main directions. The first direction is to study SfT for the case of 1D templates (i.e. curved, thin structures such as ropes and cables). The second direction is to develop algorithms in SfT and NRSfM that exploit multiple visual cues and can solve complex, real-world cases which were previously unsolved. We focus on isometric deformations and reconstruct the outer part of the object. The technical and scientific contributions of this thesis are divided into four parts. The first part of this thesis studies the case of a curvilinear template embedded in 2D or 3D space, referred to Curve SfT. We propose a thorough theoretical analysis and practical solutions for Curve SfT. Despite its apparent simplicity, Curve SfT appears to be a complex problem: it cannot be solved locally using exact non-holonomic partial differential equation and is only solvable up to a finite number of ambiguous solutions. A major technical contribution is a computational solution based on our theory, which generates all the ambiguous solutions.The second part of this thesis deals with a limitation of SfT methods: reconstructing creases. This is due to the sparsity of the motion constraint and regularization. We propose two contributions which rely on a non-convex energy minimization framework. First, we complement the motion constraint with a robust boundary contour constraint. Second, we implicitly model creases with a dense mesh-based surface representation and an associated robust smoothing constraint, which deactivates curvature smoothing automatically where needed, without knowing a priori the crease location. The third part of this thesis is dedicated to another limitation of SfT: reconstructing poorly-textured surfaces. This is due to correspondences which cannot be obtained so easily on poorly-textured surfaces (either sparse or dense). As shading reveals details on poorly-textured surfaces, we propose to combine shading and SfT. We have two contributions. The first is a cascaded initialization which estimates sequentially the surface's deformation, the scene illumination, the camera response and then the surface albedos from deformed monocular images. The second is to integrate shading to our previous energy minimization framework for simultaneously refining deformation and photometric parameters.The last part of this thesis relaxes the knowledge of the template and addresses two limitations of NRSfM: reconstructing poorly-textured surfaces with creases. Our major contribution is an extension of the second framework to recover jointly the 3D shapes of all input images and the surface albedos without any template
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Woo, Sanghyuk. "Reconstruction de surface 3D et estimation du mouvement rigide 3D à partir d'un système de stéréovision active : application des algorithmes génétiques à l'analyse d'images." Dijon, 2003. http://www.theses.fr/2003DIJOS025.
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Joseph, Jerelle Aurelia. "Energy landscapes for protein folding." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/284923.
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Proteins are involved in numerous functions in the human body, including chemical transport, molecular recognition, and catalysis. To perform their function most proteins must adopt a specific structure (often referred to as the folded structure). A microscopic description of folding is an important prerequisite for elucidating the underlying basis of protein misfolding and rational drug design. However, protein folding occurs on heterogeneous length and time scales, presenting a grand challenge to both experiments and simulations. In computer simulations, challenges are generally mitigated by adopting coarse-grained descriptions of the physical environment, employing enhanced sampling strategies, and improving computing code and hardware. While significant advances have been made in these areas, for numerous systems a large spatiotemporal gap between experiment and simulations still exists, due to the limited time and length scales achieved by simulation, and the inability of many experimental techniques to probe fast motions and short distances. In this thesis, kinetic transition networks (KTNs) are constructed for various protein folding systems, via approaches based on the potential energy landscape (PEL) framework. By applying geometry optimisation techniques, the PEL is discretised into stationary points (i.e.~low-energy minima and the transition states that connect them). Essentially, minima characterise the low-lying regions of the PEL (thermodynamics) and transition states encode the motion between these regions (dynamics). Principles from statistical mechanics and unimolecular rate theory may then be employed to derive free energy surfaces and folding rates, respectively, from the KTN. Furthermore, the PEL framework can take advantage of parallel and distributed computing, since stationary points from separate simulations can be easily integrated into one KTN. Moreover, the use of geometry optimisation facilitates greater conformational sampling than conventional techniques based on molecular dynamics. Accordingly, this framework presents an appealing means of probing complex processes, such as protein folding. In this dissertation, we demonstrate the application of state-of-the-art theory, combining PEL analysis and KTNs to three diverse protein systems. First, to improve the efficiency of protein folding simulations, the intrinsic rigidity of proteins is exploited by implementing a local rigid body (LRB) approach. The LRB approach effectively integrates out irrelevant degrees of freedom from the geometry optimisation procedure and further accelerates conformational sampling. The effects of this approach on the underlying PEL are analysed in a systematic fashion for a model protein (tryptophan zipper\,1). We demonstrate that conservative local rigidification can reproduce the thermodynamic and dynamic properties for the model protein. Next, the PEL framework is employed to model large-scale conformational changes in proteins, which have conventionally been difficult to probe in silico. Methods based on geometry optimisation have proved useful in overcoming the broken ergodicity issue, which is associated with proteins that switch morphology. The latest PEL-based approaches are utilised to investigate the most extreme case of fold-switching found in the literature:~the α-helical hairpin to β-barrel transition of the C-terminal domain of RfaH, a bacterial transcription factor. PEL techniques are employed to construct the free energy landscape (FEL) for the refolding process and to discover mechanistic details of the transition at an atomistic level. The final part of the thesis focuses on modelling intrinsically disordered proteins (IDPs). Due to their inherent structural plasticity, IDPs are generally difficult to characterise, both experimentally and via simulations. An approach for studying IDPs within the PEL framework is implemented and tested with various contemporary potential energy functions. The cytoplasmic tail of the human cluster of differentiation 4 (CD4), implicated in HIV-1 infection, is characterised. Metastable states identified on the FEL help to unify, and are consistent with, several earlier predictions.
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Ruini, Mattia. "Modellazione di un sistema per la dissipazione delle vibrazioni generate dall'installazione delle fondazioni delle turbine eoliche." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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L’infissione nel fondale marino di pali in acciaio di grandi dimensioni costituenti la sottostruttura delle turbine eoliche provoca la nascita e la propagazione di un campo di vibrazioni inquinanti. Tali vibrazioni, le quali possono raggiungere elevate distanze, se al di sopra di particolari soglie di intensità, possono causare danni temporanei o permanenti, di natura fisiologica o comportamentale, alle forme di vita acquatiche circostanti il sito di collocamento dell’elemento strutturale. Tuttavia, diverse soluzioni sono state ideate per ridurne gli effetti nocivi: una di queste è il sistema air-bubble curtain. Tramite questo elaborato, si procede, in un primo momento, allo studio ed all’approfondimento delle equazioni governanti il problema vibro-acustico unitamente all’interazione con il sistema di dissipazione. Successivamente, si sfrutta il software di calcolo COMSOL Multiphysics per la creazione dei modelli necessari allo studio delle caratteristiche del sistema dissipativo. L’indagine ha interessato i parametri di distanza dal palo di fondazione, spessore della cortina di bolle, frazione di volume d’aria nella miscela, numero degli strati attorno al palo e forma di modellazione. Si è così riscontrato che il fattore che incide maggiormente sull’attenuazione del segnale è la frazione di volume d’aria nella miscela acqua-aria (poco influiscono spessore ed il numero di strati). Tuttavia, un’adeguata distanza tra dispositivo e sorgente sonora garantisce un’efficace azione smorzante unitamente ad uno spazio di lavoro modesto. L’assunzione di una forma più prossima a quella reale lascia comunque dei dubbi relativamente ad una maggiore efficacia.
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Lu, Jui-Ming, and 盧銳明. "Wave Transmission Characteristics of a rigid Surface." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/27321694821748994187.
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Walker, Kevin Casey. "Surface Geometry and the Haptic Rendering of Rigid Point Contacts." Thesis, 2013. http://hdl.handle.net/10012/7432.
Full textAbstract:
This thesis examines the haptic rendering of rigid point contacts in virtual simulations. The haptic renderers generate force feedback so that the operator can interact with the virtual scenes in a realistic way. They must be able to recreate the physical phenomena experienced in the real world without displaying any haptic artifacts. The existing renderers are decomposed into a projection function and a regulation scheme. It is shown that the pop-through artifact, whereby the virtual tool instantaneously jumps between two distant surface points, is caused whenever the operator encounters a singularity within the renderer's projection function. This was well known for the minimum distance based renderers, but it is shown here that such singularities arise with the constraint based renderers as well.
A new projection function is designed to minimize the existence of singularities within the model. When paired with an appropriate regulation scheme, this forms the proposed mapping renderer. The new projection is calculated by mapping the model onto a canonical shape where the haptic problem is trivial, e.g. a circle in the case of a 2D model of genus zero, which avoids pop-through on smooth models. The haptic problem is then recast as a virtual constraint problem, where the traditional regulation schemes, designed originally for planar surfaces, are shown to introduce a velocity dependent error on curved surfaces that can distort the model's rendering and to couple the regulation towards and dynamics along the constraint. Set stabilization control, based on feedback linearizing the haptic device with respect to a virtual output consisting of coordinates transversal and tangential to the model surface, is proposed as an alternative. It is shown to be able to decouple the system into transversal and tangential subsystems that can then be made asymptotically stable and assigned arbitrary dynamics, respectively.
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"Anticipatory Muscle Responses for Transitioning Between Rigid Surface and Surfaces of Different Compliance: Towards Smart Ankle-foot Prostheses." Master's thesis, 2019. http://hdl.handle.net/2286/R.I.53887.
Full textAbstract:
abstract: Locomotion is of prime importance in enabling human beings to effectively respond
in space and time to meet different needs. Approximately 2 million Americans live
with an amputation with most of those amputations being of the lower limbs. To
advance current state-of-the-art lower limb prosthetic devices, it is necessary to adapt
performance at a level of intelligence seen in human walking. As such, this thesis
focuses on the mechanisms involved during human walking, while transitioning from
rigid to compliant surfaces such as from pavement to sand, grass or granular media.
Utilizing a unique tool, the Variable Stiffness Treadmill (VST), as the platform for
human walking, rigid to compliant surface transitions are simulated. The analysis of
muscular activation during the transition from rigid to different compliant surfaces
reveals specific anticipatory muscle activation that precedes stepping on a compliant
surface. There is also an indication of varying responses for different surface stiffness
levels. This response is observed across subjects. Results obtained are novel and
useful in establishing a framework for implementing control algorithm parameters to
improve powered ankle prosthesis. With this, it is possible for the prosthesis to adapt
to a new surface and therefore resulting in a more robust smart powered lower limb
prosthesis.Dissertation/Thesis
Masters Thesis Biomedical Engineering 2019
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Shin-Fu, Lin, and 林順富. "The Vibratory Phenomena of a Machine Element Sliding on a Rigid Surface." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/75801645554516952486.
Full textAbstract:
碩士國立中興大學
機械工程學系
87
ABSTRACT In the present paper, the vibratory phenomena occurred in the pin-on-disk apparatus, which is simulated by a sliding element in contact with a rigid surface, are studied numerically. The topography of the rough surface is modeled respectively by a sinusoidal surface and a random surface described by a W-M function from the fractal theory. The numerical simulations on the vibratory system are carried out in different sliding speed and normal contact load. The time serious solutions and their frequency spectrum analysis of the vibratory amplitude are presented. The results show that the vibratory displacements are small for the sliding element in contact with a smooth surface under a light loading. However, the vibratory amplitude is moderately increased with the contact load. For the case of the sliding element in contact with a rough surface, the dynamic oscillation is significant as the sliding velocity and the contact load are increased
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Lai, Ming-Song, and 賴明松. "Reflection and Transmission of Incident Water Waves By Surface- Piercing Rigid Obstacles." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/36744264069816179059.
Full textAbstract:
碩士國立海洋大學
河海工程學系
85
Based on linear wave theory, the reflection of incident wave on surface-piercing obstacles are studied with constant depth. By calculating the reflection and transmission coefficients, the wave blocking effect can be discussed. In the constant water depth with a circular body, based on the Composite Boundary Element Method(CBEM), the changes in wave height for the circular body were calculated with different wave incident angles.As shown in the numerical results, for all the ocean structure, the wave blocking effect would increase as the d/h increases. This shows that the wave blocking effect is effective for deep water wave(or short crest wave). In the vertical plates, for static water level exists in between plates and similar to the d/h, the exist a Zero Reflection and Complete Transmission phenomena. Comparing the rectangular blocks with vertical plates, in deep water wave area, single vertical plate would provide effective wave blocking effect. As for shallow water, eight vertical plates would provide the most effective wave blocking effect. Calculation results for different plates show that, for plates with singularity relations would similar wave blocking effect.
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Badiu, Florin Vasile. "Study of multiple impacts of a rigid body with a flat surface." 2007. http://hdl.handle.net/10106/909.
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黃彥豪. "Contact based 3-D scanning system for non-rigid object surface measurement." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/w3n6y8.
Full textAbstract:
碩士國立暨南國際大學
資訊工程學系
106
Existing 3-D scanners can be classified into contact-based scanners and contactless scanners. Contactless scanners uses light sources and image sensors to measure the object surface and, therefore, it is fast and safe to measure most object surfaces. However, it is not suitable for object surfaces with specular reflection property or transparency. Conversely, contact-based 3-D scanners are generally accurate and suitable for objects with different kinds of optical properties. The drawbacks of the contact-based scanners include slow measurement speed and are not suitable for deformable and/or fragile surfaces because the probe may cause surface deformation or even damage the object surface. In this thesis, a contact-based 3-D scanner is developed to solve the problem of scanning deformable and/or fragile surfaces. Controller modules are designed to convert high-level command from computer to stepper motor driving pules. The driving pules are send to a stepper motor driver that controls the conducting timing of the stepper coils. We have also designed a probe sensing module which includes a band-pass amplifier and a comparator to process the signal from a piezo sensor. This module can detect tiny contact force which prevents any deformation or surface damage due to probe contact. Four experiments are contacted to test the accuracy of the developed 3-D scanner. The experimental results show that the measurement error is below 0.01 mm. We also show that the 3-D scanner can be used to scan the surface of a jelly without causing any damage to the jelly surface. Although the scanning speed is slow, the developed system can achieve much higher accuracy than general laser 3-D scanners.