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Rosset, Nicolas. "Simulation rapide d'interactions vent-obstacle. Application à la modélisation de paysages désertiques et à la conception de voiture." Electronic Thesis or Diss., Université Côte d'Azur, 2024. http://www.theses.fr/2024COAZ4054.
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L'omniprésence de l'air autour de nous en fait un élément indispensable à prendre en compte pour simuler des phénomènes naturels et concevoir des objets immergés dans ce fluide. En fonction de leur taille et de leur nature, les objets sont des obstacles qui peuvent être transportés, déformés ou ralentis au contact de l'air. Ainsi, le vent érode et modèle les paysages naturels, et les véhicules sont conçus pour lui offrir une moindre résistance. Étudier ces phénomènes implique de comprendre et de modéliser les interactions vent-obstacle. Cette modélisation représente un défi de par la nature non linéaire des équations qui gouvernent l'écoulement des fluides. Représenter précisément le comportement d'un fluide requiert souvent de faire appel à des solveurs très couteux en temps, ce qui limite grandement leur utilisation dans certains contextes. Nous explorons dans cette thèse des méthodes permettant de décrire efficacement ces influences vent-obstacle afin de les simuler et d'anticiper leurs impacts dans deux cas d'usage où le besoin de résultats rapides est crucial :Dans un premier temps, nous nous intéressons à la conception de voiture en proposant un outil fournissant des retours aérodynamiques aux designers automobiles sur les formes qu'ils proposent. Afin de permettre de rapides itérations sur le design, ces retours sur le comportement de l'écoulement autour des formes proposées doivent être interactifs. Dans un second temps, nous étudions différentes approches permettant de modéliser des paysages désertiques, permettant à la fois de simuler des dunes et de décrire les motifs créés par érosion/déposition du sable autour de bâtiments. Ici, l'obstacle, à savoir le terrain, évolue constamment à mesure que le sable est érodé puis déposé par le vent. Le vent doit être à son tour mis à jour lors de chacune de ces étapes. Ces itérations nécessitent une méthode appropriée afin de ne pas produire des temps de calcul trop importants. Nous surmontons ces problèmes en proposant des méthodes cherchant les meilleurs compromis temps de calcul/précision des phénomènes à l'œuvre dans chacun des cas. Nous identifions pour cela les caractéristiques nécessaires de l'écoulement afin de limiter la complexité de nos algorithmes et présentons notamment des méthodes à base d'apprentissage qui nous permettent d'accélérer nos algorithmes. Dans le cas du design de voiture, nous montrons comment entraîner notre système d'aide sur des observations instantanées et synchronisées, plus riches en informations que des données moyennées. Le modèle neuronal que nous obtenons, associé à une paramétrisation apprise des formes, nous permet en outre d'inverser la formulation du problème et de proposer au designer des formes optimisées. Nous assemblons ces outils et démontrons leur efficacité dans le cas de profils 2D. Dans le cas de la modélisation de paysages désertiques, nous notons que la saltation est le mode de transport de sable prédominant, ce qui nous permet de simplifier notre algorithme. Couplé à une simulation rapide de vent, nous obtenons une méthode efficace inspirée des sciences naturelles et de l'informatique graphique. Nous validons nos approximations en comparant nos résultats à des mesures effectuées dans le monde réel. Enfin, dans la perspective d'inverser l'algorithme de dépôt de sable pour le design inverse d'infrastructure, nous décrivons des résultats préliminaires d'accélération de la simulation de d'air en développant une formulation auto-apprenante prédisant un vent moyenné au-dessus d'un terrain. Cette méthode étant basée sur des réseaux de neurones, elle est prometteuse pour le design inverseThe air being ubiquitous around us, it is a vital element to take into account to simulate natural phenomena, and design object immersed in this fluid. Depending on their size and nature, objects can be transported, deformed or slowed down by contact with air. In this way, wind erodes and shapes natural landscapes, and vehicles are designed to offer them less resistance. Studying these phenomena involves understanding and modeling wind-obstacle interactions. This is a challenging task, given the non-linear nature of the equations governing fluid flow. Accurately representing fluid behavior often requires the use of time-consuming solvers, which severely limits their use in certain contexts. In this thesis, we explore methods for efficiently describing these wind-obstacle influences in order to simulate them and anticipate their impacts in two use cases where the need for rapid results is crucial: Firstly, we focus on car design, proposing a tool to provide aerodynamic feedback to car designers on the shapes they propose. To enable rapid iterations on the design, this feedback on the flow behavior around the proposed shapes must be interactive. In a second step, we study different approaches to modeling desert landscapes, both simulating dunes and describing the patterns created by sand erosion/deposition around buildings. Here, the obstacle - the terrain - is constantly changing as sand is eroded and deposited by the wind. The wind must in turn be updated at each of these stages. These iterations require an appropriate method to avoid excessive computation times. We overcome these problems by proposing methods that seek the best compromise between computation time and accuracy of the phenomena at work in each case. We identify the necessary flow characteristics to limit the complexity of our algorithms, and present learning-based methods to speed up our algorithms. In the case of car design, we show how to train our aid system on instantaneous, synchronized observations, which are richer in information than averaged data. The neural model we obtain, combined with a learned parameterization of shapes, enables us to invert the problem formulation and propose optimized shapes to the designer. We assemble these tools and demonstrate their effectiveness in the case of 2D profiles.In the case of modeling desert landscapes, we note that saltation is the predominant mode of sand transport, which enables us to simplify our algorithm. Coupled with a fast wind simulation, we obtain an efficient method inspired by both natural sciences and computer graphics. We validate our approximations by comparing our results with real-world measurements.Finally, with a view to inverting the sand deposition algorithm for reverse infrastructure design, we describe preliminary results for accelerating air simulation by developing a self-learning formulation predicting averaged wind over a terrain. As this method is based on neural networks, it shows promise for inverse design
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Tarnoff, David. "Episode 7.05 – Flipping Bits using the Bitwise Inverse and Bitwise-XOR." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/computer-organization-design-oer/55.
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Inverting or flipping the bits of an integer is the third and last method of “bit bashing” we will discuss. There are two ways to invert bits: either flip all of them at once or use a mask to identify which bits to flip and which to leave alone.
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Mas, Baixeras Albert. "Optimization of inverse reflector design." Doctoral thesis, Universitat de Girona, 2011. http://hdl.handle.net/10803/22705.
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Aquesta tesi presenta un nou mètode pel disseny invers de reflectors. Ens hem centrat en tres temes principals: l’ús de fonts de llum reals i complexes, la definició d’un algoritme ràpid pel càlcul de la il•luminació del reflector, i la definició d’un algoritme d’optimització per trobar més eficientment el reflector desitjat.
Les fonts de llum estan representades per models near-field, que es comprimeixen amb un error molt petit, fins i tot per fonts de llum amb milions de raigs i objectes a il•luminar molt propers. Llavors proposem un mètode ràpid per obtenir la distribució de la il•luminació d’un reflector i la seva comparació amb la il•luminació desitjada, i que treballa completament en la GPU. Finalment, proposem un nou mètode d’optimització global que permet trobar la solució en menys passos que molts altres mètodes d’optimització clàssics, i alhora evitant mínims locals.This thesis presents new methods for the inverse reflector design problem. We have focused on three main topics: the use of real and complex light sources, the definition of a fast lighting simulation algorithm to compute the reflector lighting, and the definition of an optimization algorithm to more efficiently find the desired reflector. The light sources are represented by near-field datasets, that are compressed with a low error, even with millions of rays and for very close objects. Then, we propose a fast method to obtain the outgoing light distribution of a reflector and the comparison with the desired one, working completely in the GPU. Finally, a new global optimization method is proposed to search the solution in less steps than most other classic optimization methods, also avoiding local minima.
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Medd, Adam Jon. "Inverse design of turbomachinery blades." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0010/MQ34391.pdf.
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Okamoto, Kei. "Optimal numerical methods for inverse heat conduction and inverse design solidification problems." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Dissertations/Fall2005/k%5Fokamoto%5F120905.pdf.
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Djedidi, Mouad. "Design of a Fast Antenna Characterization Method Exploiting Echoes." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS348/document.
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Les techniques de mesure de diagramme de rayonnement d’antenne actuelles partagent un paradigme commun qui stipule que l’information utile est exclusivement portée par le signal de test généré. Cela implique un effort mécanique fastidieux en faisant tourner l'antenne sous test ou en déplaçant le système de sondes afin de couvrir des angles de mesure différents jusqu'à ce qu'une caractérisation complète soit effectuée ; une limitation qui est généralement surmontée en utilisant des systèmes multisondes coûteux. En outre, toute réflexion provenant du site de mesure et des équipements de test est considérée comme parasite perturbant le signal de test et est ainsi minimisée.Dans cette thèse, un concept de mesure du diagramme de rayonnement d'antenne remettant en cause ce paradigme commun est présenté comme un moyen d'accélérer le processus de caractérisation en utilisant des systèmes économiques. Le paradigme proposé consiste en la génération d'un ensemble d'échos contrôlées, en utilisant des configurations impliquant des plaques réfléchissantes, qui contribueraient directement à la mesure en couvrant différents angles, et récupérer les informations portées par l'ensemble des signaux générés simultanément. Une diversité fréquentielle est introduite afin de générer un système d'équations équilibré où le vecteur inconnu contenant les valeurs du diagramme de rayonnement est récupéré en inversant un problème matriciel. Par conséquent, une attention considérable est accordée au conditionnement du modèle mathématique afin d'assurer la stabilité et la robustesse du systèmeTrois configurations de différents niveaux de complexité en termes d'échos contrôlés sont étudiées, en mettant l'accent sur la configuration la plus simple impliquant un seul écho contrôlé. Des modèles ont été mis au point, avec des contraintes de conception des configurations proposées en termes de dimensionnement et de bandes passante de fonctionnement, mettant en évidence la viabilité mathématique du concept. Les aspects pratiques ont également été évalués en étudiant la tolérance des modèles développés vis-à-vis des erreurs systématiques, ainsi qu’à l'impact de l’application d'un ensemble d’hypothèses simplificatrices. La faisabilité du concept ainsi que son utilité pour accélérer le processus de caractérisation par rapport aux techniques classiques ont été mises en évidence par des simulations numériques. Ce travail ouvre la porte à l'exploitation des échos, généralement considérés comme perturbateurs, dans un contexte de mesure d’antennesCurrent antenna radiation pattern measurement techniques share a common paradigm which states that useful information is exclusively carried by the generated test signal. This implies an excessive, time consuming, mechanical effort by rotating the antenna under test or displacing the probe system in order to cover different measurement angles until a complete scan is performed; a limitation that is typically overcome using costly multi-probe systems. Moreover, any reflection from the measurement site and test equipment is considered spurious as it perturbs the test signal and thus is minimized.In this thesis, an antenna radiation pattern measurement concept challenging this common paradigm is introduced as a mean of accelerating the characterization process using cost-efficient systems. The proposed paradigm consists in the generation of a set of controlled echoes, using set-ups involving highly-reflective plates, which would directly contribute to the measurement alongside the line-of-sight signal by covering different measurement angles, and retrieving the ARP information carried by the set of all generated signals concurrently. Frequency diversity is used in order to generate a balanced system of equations where the unknown ARP vector is retrieved by inverting a matrix problem. Consequently, a considerable attention is paid into the conditioning of the mathematical model in order to ensure the system stability and accuracy.Three configurations of different complexity levels in terms of controlled echoes are studied, with focus on the simplest configuration involving a single controlled echo. Models have been developed with design guidelines for the proposed configurations in terms of set-up dimensions and operating frequency bandwidth highlighting the mathematical viability of the concept. Practical issues were also assessed by studying the tolerance of developed models to systematic practical errors, as well as to the impact of an applied set of simplifying assumptions. The feasibility of the concept as well as its usefulness in accelerating the measurement process with respect to classical techniques were highlighted via numerical simulations. This thesis opens the door for exploiting echoes, generally regarded as a nuisance, in an antenna measurements context
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Garcia, Martin Juan Antonio. "RNA inverse folding and synthetic design." Thesis, Boston College, 2016. http://hdl.handle.net/2345/bc-ir:106989.
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Thesis advisor: Welkin E. JohnsonThesis advisor: Peter G. Clote
Synthetic biology currently is a rapidly emerging discipline, where innovative and interdisciplinary work has led to promising results. Synthetic design of RNA requires novel methods to study and analyze known functional molecules, as well as to generate design candidates that have a high likelihood of being functional. This thesis is primarily focused on the development of novel algorithms for the design of synthetic RNAs. Previous strategies, such as RNAinverse, NUPACK-DESIGN, etc. use heuristic methods, such as adaptive walk, ensemble defect optimization (a form of simulated annealing), genetic algorithms, etc. to generate sequences that minimize specific measures (probability of the target structure, ensemble defect). In contrast, our approach is to generate a large number of sequences whose minimum free energy structure is identical to the target design structure, and subsequently filter with respect to different criteria in order to select the most promising candidates for biochemical validation. In addition, our software must be made accessible and user-friendly, thus allowing researchers from different backgrounds to use our software in their work. Therefore, the work presented in this thesis concerns three areas: Create a potent, versatile and user friendly RNA inverse folding algorithm suitable for the specific requirements of each project, implement tools to analyze the properties that differentiate known functional RNA structures, and use these methods for synthetic design of de-novo functional RNA molecules
Thesis (PhD) — Boston College, 2016
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Biology
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Sakamoto, Julia. "Inverse Optical Design and Its Applications." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/216969.
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We present a new method for determining the complete set of patient-specific ocular parameters, including surface curvatures, asphericities, refractive indices, tilts, decentrations, thicknesses, and index gradients. The data consist of the raw detector outputs of one or more Shack-Hartmann wavefront sensors (WFSs); unlike conventional wavefront sensing, we do not perform centroid estimation, wavefront reconstruction, or wavefront correction. Parameters in the eye model are estimated by maximizing the likelihood. Since a purely Gaussian noise model is used to emulate electronic noise, maximum-likelihood (ML) estimation reduces to nonlinear least-squares fitting between the data and the output of our optical design program. Bounds on the estimate variances are computed with the Fisher information matrix (FIM) for different configurations of the data-acquisition system, thus enabling system optimization. A global search algorithm called simulated annealing (SA) is used for the estimation step, due to multiple local extrema in the likelihood surface. The ML approach to parameter estimation is very time-consuming, so rapid processing techniques are implemented with the graphics processing unit (GPU).We are leveraging our general method of reverse-engineering optical systems in optical shop testing for various applications. For surface profilometry of aspheres, which involves the estimation of high-order aspheric coefficients, we generated a rapid ray-tracing algorithm that is well-suited to the GPU architecture. Additionally, reconstruction of the index distribution of GRIN lenses is performed using analytic solutions to the eikonal equation. Another application is parameterized wavefront estimation, in which the pupil phase distribution of an optical system is estimated from multiple irradiance patterns near focus. The speed and accuracy of the forward computations are emphasized, and our approach has been refined to handle large wavefront aberrations and nuisance parameters in the imaging system.
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Ahmadi, Majid. "Aerodynamic inverse design of transonic turbomachinery cascades." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0003/NQ40321.pdf.
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Skare, Steven Edward. "An Inverse Design Method for Supersonic Airfoils." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/731.
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Airfoil design is one of the most important aspects of aircraft design. Slight changes in airfoil geometry can lead to significant changes in a wide variety of aircraft performance metrics. Inverse design methods offer an efficient alternative to standard direct methods. The key to this design problem is to derive a direct relationship between changes in airfoil geometry and changes in pressure or velocity distributions. This relationship is then used to modify an initial airfoil and its pressure distribution to match a target pressure distribution, which is specified by design parameters. At this point, the engineer now has a final airfoil based off of the design requirements.
This paper attempts to provide a quick and easy inverse design method for a wide variety of supersonic scenarios. This is accomplished by using the class-shape transformation technique to parameterize airfoils during an iterative process. The robustness of the method is demonstrated through several distinct design cases including supersonic airfoils, unique geometries, and a Sears-Haack body.
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Lane, Kevin A. "Novel Inverse Airfoil Design Utilizing Parametric Equations." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/346.
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The engineering problem of airfoil design has been of great theoretical interest for almost a century and has led to hundreds of papers written and dozens of methods developed over the years. This interest stems from the practical implications of airfoil design. Airfoil selection significantly influences the application's aerodynamic performance. Tailoring an airfoil profile to its specific application can have great performance advantages. This includes considerations of the lift and drag characteristics, pitching moment, volume for fuel and structure, maximum lift coefficient, stall characteristics, as well as off-design performance.
A common way to think about airfoil design is optimization, the process of taking an airfoil and modifying it to improve its performance. The classic design goal is to minimize drag subject to required lift and thickness values to meet aerodynamic and structural constraints. This is typically an expensive operation depending on the selected optimization technique because several flow solutions are often required in order to obtain an updated airfoil profile. The optimizer requires gradients of the design space for a gradient-based optimizer, fitness values of the members of the population for a genetic algorithm, etc.
An alternative approach is to specify some desired performance and find the airfoil profile that achieves this performance. This is known as inverse airfoil design. Inverse design is more computationally efficient than direct optimization because changes in the geometry can be related to the required change in performance, thus requiring fewer flow solutions to obtain an updated profile. The desired performance for an inverse design method is specified as a pressure or velocity distribution over the airfoil at given flight conditions. The improved efficiency of inverse design comes at a cost. Designing a target pressure distribution is no trivial matter and has severe implications on the end performance. There is also no guarantee a specified pressure or velocity distribution can be achieved. However, if an obtainable pressure or velocity distribution can be created that reflects design goals and meets design constraints, inverse design becomes an attractive option over direct optimization.
Many of the available inverse design methods are only valid for incompressible flow. Of those that are valid for compressible flow, many require modifications to the method if shocks are present in the flow. The convergence of the methods are also greatly slowed by the presence of shocks. This paper discusses a series of novel inverse design methods that do not depend on the freestream Mach number. They can be applied to design cases with and without shocks while not requiring modifications to the methods. Shocks also do not have a significant impact on the convergence of the methods. Airfoils are represented with parametric equations from the CST method to control shape changes and relate them to the required changes in the pressure or velocity distribution. To display the power of the methods, design cases are presented in the subsonic and transonic regimes. A circulation control design case is also presented using one of the methods to further show the robustness of the method.
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Papay, Michael L. "A general inverse design procedure for aerodynamic bodies." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/38556.
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Tiow, Wee Teck. "Inverse design of turbomachinery blades in rotational flow." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325463.
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Poletti, Francesco. "Direct and inverse design of microstructured optical fibres." Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/47759/.
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Microstructured optical fibres, where an arrangement of air holes running longitudinally along the fibre guides light in either a solid or a hollow core, have created new opportunities in diverse areas of science and technology. Applications range from the generation of supercontinuum light to optical sensing, nonlinear telecom devices and the generation and delivery of extremely high optical powers. Photonic bandgap fibres, allowing light guidance in a hollow core, are also extensively studied. The main issues preventing accurate simulations of the properties of fabricated fibres are identified and addressed. An ideal, accurate representation of a realistic fibre is then proposed and employed to obtain fundamental scaling rules and to study the interactions between air guided and surface guided modes. Anticrossings between these modes in slightly asymmetric structures are identified as the cause for the unusual polarisation effects experimentally observed in these fibres. And finally, guidelines for fabricating fibres with the widest possible operational bandwidth possible are developed and presented.
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França, Francis Ramos. "Inverse thermal design combining radiation, convection and conduction /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Nguyen, Thai Dung. "Application of robust and inverse optimization in transportation." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62482.
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Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 79-82).
We study the use of inverse and robust optimization to address two problems in transportation: finding the travel times and designing a transportation network. We assume that users choose the route selfishly and the flow will eventually reach an equilibrium state (User Equilibrium). The first part of the thesis demonstrates how inverse and robust optimization can be used to find the actual travel times given a stable flow on the network and some noisy information on travel times from different users. We model the users' perception of travel times using three different sets and solve the robust inverse problem for all of them. We also extend the idea to find parametric functional forms for travel times given historical data. Our numerical results illustrate the significant improvement obtained by our models over a simple fitting model. The second part of the thesis considers the network design problem under demand uncertainty. We show that for affine travel time functions, the deterministic problem can be formulated as a mixed integer programming problem with quadratic objective and linear constraints. For the robust network design problem, we propose a decomposition scheme: breaking a tri-level programming problem into two smaller problems and re-iterating until a good solution is obtained. To deal with the expensive computation required by large networks, we also propose a heuristic robust simulated annealing approach. The heuristic algorithm is computationally tractable and provides some encouragingly results in our simulations.
by Thai Dung Nguyen.
S.M.
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Roddis, Mark Edward. "On the inverse design of marine ducted propulsor blading." Thesis, University College London (University of London), 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265865.
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Tregde, Vidar. "Aspects of ship design: optimization of aft hull with inverse geometry design." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-134.
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The main contribution of this thesis is on the study of optimization methods in aft hull design. The optimization methods are inverse geometry design methods to find an aft hull with the flow velocities we specify. The analytic foundation for the flow is given by Stratford in [31], and gives a prescribed velocity distribution on the aft body. With the parameter β we have adjusted this flow to have a certain margin to separation along the pressure recovery region.
This principle and optimization method are successfully applied to design of ships with pram-type aft hull. The 2D optimized profiles corresponds to centerline buttock, and 3D hull sections are extended from this centerline buttock with a bilge radius.
Stratfords original pressure distribution for pressure recovery region were meant for Reynolds numbers up to 107. We have extended Stratfords formula to yield for ship full scale Reynolds numbers to 109.
Different optimization methods were programmed and tested. The best routine for our optimization of aft hull with Stratford flow, was when the offset y-value were the optimization parameter to be changed. When we tried to optimize a complete 2D profile with a given pressure distribution, it worked best to use the variables in a B-spline as the optimization parameter.
Extensive windtunnel tests and towing tank tests are carried out. The tests verified the hydrodynamic properties of the hulls.
Towing tests indicates that the optimized hull lines have lower total resistance than conventional ships with the same main dimensions. Both the frictional, viscous pressure resistance and wave making resistance are significantly lower. Further we can increase cargo capacity with the same power consumption, and achieve a more favourable distribution of the displacement in the aft hull.
This study has shown us that the slant angle for the bottom of the aft hull should not excess 15º with horizontal plane due to danger of separation over the bilge, and longitudinal vortices forming.
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Tixier, Eliott. "Variability modeling and numerical biomarkers design in cardiac electrophysiology." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066325/document.
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Cette thèse de doctorat est consacrée à l'étude de la variabilité observée dans les mesures d'électrophysiologie (i.e. l'activité électrique des tissus biologiques) cardiaque et à la conception de biomarqueurs numériques extraits de ces mesures. Les applications potentielles sont nombreuses, pouvant aller d'une meilleure compréhension des modèles électrophysiologiques existants à l'évaluations des effets nocifs de médicaments en passant par le diagnostic de pathologies cardiaques. Les modèles d'électrophysiologie cardiaque présentés dans ce travail sont, soit des équations différentielles ordinaires (EDOs), soit des équations aux dérivées partielles (EDPs), selon qu'ils concernent l'échelle cellulaire ou l'échelle du tissu. Dans les deux cas, ces modèles sont hautement non linéaires et nécessitent d'intenses ressources computationnelles. Nous adoptons l'approche suivante : de prime abord, nous développons des outils numériques afin de répondre à des problèmes généraux, au-delà de l'électrophysiologie. Puis, nous appliquons ces outils à des mesures synthétiques d'électrophysiologie dans différents scénarios réalistes et, lorsque cela est possible, à des mesures expérimentales. Dans la première partie de cette thèse, nous présentons une méthode générale pour estimer la densité de probabilité de paramètres incertains de modèles basés sur des EDOs ou des EDPs. La méthode est non intrusive et repose sur des évaluations "hors-ligne" du modèle direct, ce qui la rend en pratique computationellement moins dispendieuse que d'autres approches plus sophistiquées. La méthode est illustrée avec des mesures synthétiques et expérimentales d'électrophysiologie. Dans la seconde partie de cette thèse, nous présentons une méthode de sélectionde biomarqueurs à partir des sorties de modèles en vue d'effectuer des tâches de classification ou de résoudre des problèmes d'estimation de paramètres. La méthode repose sur la résolution d'un problème d'optimisation creux. La méthode est illustrée avec des modèles simples et ensuite appliquée à des mesures synthétiques, incluant des enregistrements d'électrocardiogramme, et à des données expérimentales obtenues à partir de mesures de matrices de microélectrodesThis PhD thesis is dedicated to the study of the variability observed in cardiac electrophysiology (i.e. the electrical activity of biological tissues) measurements and to the design of numerical biomarkers extracted from these measurements. The potential applications are numerous, ranging from a better understanding of existing electrophysiology models to the assessment of adverse effects of drugs or the diagnosis of cardiac pathologies. The cardiac electrophysiology models considered in the present work are either ODEs or PDEs depending on whether we focus on the cell scale or the tissue scale. In both cases, these models are highly non-linear and computationally intensive. We proceed as follows: first we develop numerical tools that address general issues and that are applicable beyond the scope of cardiac electrophysiology. Then, we apply those tools to synthetic electrophysiology measurements in various realistic scenarios and, when available, to real experimental data. In the first part of this thesis, we present a general method for estimating the probability density function (PDF) of uncertain parameters of models based on ordinary differential equations (ODEs) or partial differential equations (PDEs). The method is non-instrusive and relies on offline evaluations of the forward model, making it computationally cheap in practice compared to more sophisticated approaches. The method is illustrated with generic PDE and ODE models. It is then applied to synthetic and experimental electrophysiology measurements. In the second part of this thesis, we present a method to extract and select biomarkers from models outputs in view of performing classication tasks or solving parameter identification problems. The method relies on the resolution of a sparse optimization problem. The method is illustrated with simple models and then applied to synthetic measurements, including electrocardiogram recordings, and to experimental data obtained from micro-electrode array measurements
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Srinivasa, Gopala Raghavan Venugopalan. "Banded matrices with banded inverses." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61896.
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Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 99).
We discuss the conditions that are necessary for a given banded matrix to have a banded inverse. Although a generic requirement is known from previous studies, we tend to focus on the ranks of the block matrices that are present in the banded matrix. We consider mainly the two factor 2-by- 2 block matrix and the three factor 2-by-2 block matrix cases. We prove that the ranks of the blocks in the larger banded matrix need to necessarily conform to a particular order. We show that for other orders, the banded matrix in question may not even be invertible. We are then concerned with the factorization of the banded matrix into simpler factors. Simpler factors that we consider are those that are purely block diagonal. We show how we can obtain the different factors and develop algorithms and codes to solve for them. We do this for the two factor 2-by-2 and the three factor 2-by-2 matrices. We perform this factorization on both the Toeplitz and non-Toeplitz case for the two factor case, while we do it only for the Toeplitz case in the three factor case. We then look at extending our results when the banded matrix has elements at its corners. We show that this case is not very different from the ones analyzed before. We end our discussion with the solution for the factors of the circulant case. Appendix A deals with a conjecture about the minimum possible rank of a permutation matrix. Appendices B & C deal with some of the miscellaneous properties that we obtain for larger block matrices and from extending some of the previous work done by Strang in this field.
by Venugopalan Srinivasa Gopala Raghavan.
S.M.
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Neppalli, Srinivas. "Design, construction, inverse kinematics, and visualization of continuum robots." Master's thesis, Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-10312008-144310.
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Portas, Lance Owen. "Inverse design of airfoil thickness distributions in incompressible flow." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0010/MQ59866.pdf.
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Ma, Xu. "Generalized inverse lithography methods for phase-shifting mask design." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 38 p, 2007. http://proquest.umi.com/pqdweb?did=1338919391&sid=3&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Tapia, Fidencio. "Inverse methodology for multi-point aerodynamic rotor blade design." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/13335.
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Raharjo, R. Firson Joko. "Two-dimensional inverse design and optimization of turbomachinery blades." Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406622.
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Grayson, James M. (James Morris). "Economic Statistical Design of Inverse Gaussian Distribution Control Charts." Thesis, University of North Texas, 1990. https://digital.library.unt.edu/ark:/67531/metadc332397/.
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Statistical quality control (SQC) is one technique companies are using in the development of a Total Quality Management (TQM) culture. Shewhart control charts, a widely used SQC tool, rely on an underlying normal distribution of the data. Often data are skewed. The inverse Gaussian distribution is a probability distribution that is wellsuited to handling skewed data. This analysis develops models and a set of tools usable by practitioners for the constrained economic statistical design of control charts for inverse Gaussian distribution process centrality and process dispersion. The use of this methodology is illustrated by the design of an x-bar chart and a V chart for an inverse Gaussian distributed process.
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Alhejji, Ayman Khalid. "Dynamic Neural Network-based Adaptive Inverse Optimal Control Design." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/dissertations/891.
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This dissertation introduces a Dynamical Neural Network (DNN) model based adaptive inverse optimal control design for a class of nonlinear systems. A DNN structure is developed and stabilized based on a control Lyapunov function (CLF). The CLF must satisfy the partial Hamilton Jacobi-Bellman (HJB) equation to solve the cost function in order to prove the optimality. In other words, the control design is derived from the CLF and inversely achieves optimality when the given cost function variables are determined posterior. All the stability of the closed loop system is ensured using the Lyapunov-based analysis. In addition to structure stability, uncertainty/ disturbance presents a problem to a DNN in that it could degrade the system performance. Therefore, the DNN needs a robust control against uncertainty. Sliding mode control (SMC) is added to nominal control design based CLF in order to stabilize and counteract the effects of disturbance from uncertain DNN, also to achieve global asymptotic stability. In the next section, a DNN observer is considered for estimating states of a class of controllable and observable nonlinear systems. A DNN observer-based adaptive inverse optimal control (AIOC) is needed. With weight adaptations, an adaptive technique is introduced in the observer design and its stabilizing control. The AIOC is designed to control a DNN observer and nonlinear system simultaneously while the weight parameters are updated online. This control scheme guarantees the quality of a DNN's state and minimizes the cost function. In addition, a tracking problem is investigated. An inverse optimal adaptive tracking control based on a DNN observer for unknown nonlinear systems is proposed. Within this framework, a time-varying desired trajectory is investigated, which generates a desired trajectory based on the external inputs. The tracking control design forces system states to follow the desired trajectory, while the DNN observer estimates the states and identifies unknown system dynamics. The stability method based on Lyapunov-based analysis is guaranteed a global asymptotic stability. Numerical examples and simulation studies are presented and shown for each section to validate the effectiveness of the proposed methods.
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Lieberman, Chad Eric. "Parameter and state model reduction for Bayesian statistical inverse problems." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54213.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 113-118).
Decisions based on single-point estimates of uncertain parameters neglect regions of significant probability. We consider a paradigm based on decision-making under uncertainty including three steps: identification of parametric probability by solution of the statistical inverse problem, propagation of that uncertainty through complex models, and solution of the resulting stochastic or robust mathematical programs. In this thesis we consider the first of these steps, solution of the statistical inverse problem, for partial differential equations (PDEs) parameterized by field quantities. When these field variables and forward models are discretized, the resulting system is high-dimensional in both parameter and state space. The system is therefore expensive to solve. The statistical inverse problem is one of Bayesian inference. With assumption on prior belief about the form of the parameter and an assignment of normal error in sensor measurements, we derive the solution to the statistical inverse problem analytically, up to a constant of proportionality. The parametric probability density, or posterior, depends implicitly on the parameter through the forward model. In order to understand the distribution in parameter space, we must sample. Markov chain Monte Carlo (MCMC) sampling provides a method by which a random walk is constructed through parameter space. By following a few simple rules, the random walk converges to the posterior distribution and the resulting samples represent draws from that distribution. This set of samples from the posterior can be used to approximate its moments.
(cont.) In the multi-query setting, it is computationally intractable to utilize the full-order forward model to perform the posterior evaluations required in the MCMC sampling process. Instead, we implement a novel reduced-order model which reduces in parameter and state. The reduced bases are generated by greedy sampling. We iteratively sample the field in parameter space which maximizes the error in full-order and current reduced-order model outputs. The parameter is added to its basis and then a high-fidelity forward model is solved for the state, which is then added to the state basis. The reduction in state accelerates posterior evaluation while the reduction in parameter allows the MCMC sampling to be conducted with a simpler, non-adaptive 3 Metropolis-Hastings algorithm. In contrast, the full-order parameter space is high-dimensional and requires more expensive adaptive methods. We demonstrate for the groundwater inverse problem in 1-D and 2-D that the reduced-order implementation produces accurate results with a factor of three speed up even for the model problems of dimension N ~~500. Our complexity analysis demonstrates that the same approach applied to the large-scale models of interest (e.g. N > 10⁴) results in a speed up of three orders of magnitude.
by Chad Eric Lieberman.
S.M.
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Medd, Adam Jon. "Enhanced inverse design code and development of design strategies for transonic compressor blading." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2002. http://wwwlib.umi.com/cr/syr/main.
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May, Alexander. "Inverse scattering designs of optical waveguides and fibres." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/399923/.
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Optical fibres and waveguides have become vital components in communication systems ranging from on-chip interconnects in datacentres, to trans-oceanic submarine communication cables. Typically, they are designed in a trial-and-error manner and the objective of this thesis was to investigate their inverse design using a method known as inverse-scattering. In contrast to methods of design optimisation where an initial refractive form of index profile of some kind must be chosen, inverse-scattering makes no such assumptions other than that of which modes are carried by the structure and what their respective propagation constants are. Initially, the control over group-velocity dispersion in a single-mode planar waveguide with fixed propagation constant was investigated by considering the form of the transverse reflection response by which the modal properties of the waveguide may be specified, as discussed in the literature. It was demonstrated that common features of dispersion-engineered waveguides were obtained corroborating their use in the existing literature and further understanding of these features was developed. Extending the study to multimode planar waveguides through the application of an inverse-scattering method rooted in the quantum mechanical community, the properties of multiple guided modes, such as their group-velocities and modal gain were controlled. The realisation that both gain and loss are required in a refractive index profile to have exact equalisation of modal gain across multiple modes was novel and differed from existing approaches using genetic algorithms. In addition to this, the design of waveguide couplers by which power can be transferred from one waveguide to another was considered by an approach differing from that of the increasingly popular supersymmetric (SUSY) approach in the literature. Attention turned to the design of few-mode optical fibres which are at the forefront of technology. Since the planar waveguide designs above were found to contain ‘depressions’ and ‘rings’, similar such features were investigated in an optical fibre based upon the knowledge that there were similarities in the modal intensity profiles of the first few linearly polarised (LP) modes in a fibre, and that of the TE modes in planar waveguides. Core depressions and ‘rod-like’ refractive index perturbations were implemented and found to increase the spacing between mode groups. Following on from the above successes, inverse-scattering techniques were applied directly to the cylindrical symmetry of optical fibres and their associated LP modes. A particular feature of this work was the realisation that the propagation constants of such modes can only be specified at the start of the design process for a fixed value of the azimuthal symmetry of the fibre mode. A finding by other researchers using the SUSY technique had been that the modes in coupled fibres (trunk-partner pairs) could only be ‘matched’ when the azimuthal symmetry of the trunk and partner modes differed. The inverse-scattering method in this thesis, on the other hand, does not have this limitation.
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Rahmati, M. T. "Incompressible Navier-Stokes inverse design method based on unstructured meshes." Thesis, University College London (University of London), 2006. http://discovery.ucl.ac.uk/1445805/.
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Two inverse methods for turbomachinery blade design are developed. In these inverse design approaches blade shapes are computed for a specified design parameter such as mass-averaged tangential velocity or pressure loading distribution. These inverse methods directly define a geometry needed to obtain these prescribed target design parameters which are related to the performance of turbomachinery blades. The first method is based on the prescription of pressure loading on the blade while the second method is based on the prescription of mass-averaged tangential velocity on the blade. In both methods the blade thickness is also prescribed. These choices of target design prescription allow the designer to control the blade work distribution and the overall flow field effectively. It also prevents the generation of unrealistic blades as the designer directly control the blade thickness. Mesh movement algorithm is an integral part of the current inverse design method as once the blade surface is modified during the design iterations the corresponding unstructured mesh also has to be altered. The mesh movement algorithm is based on a linear tension spring analogy which is a very fast and robust mesh movement method. The capabilities of these design methodologies have been verified for inverse design of two dimensional turbomachinery blades. The flow analysis algorithm is an integral part of the current methodologies. It is based on the incompressible Navier-Stokes flow equations on unstructured meshes. The capability of the flow analysis algorithm is verified for three-dimensional external and internal incompressible flow solutions. Indeed the current method is applied for simulation of flow over marine propeller blades in open water. Also it is applied for the flow analysis of the stator and rotor blades of a low-speed axial turbine.
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Li, Hong. "An inverse reliability method and its applications in engineering design." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0026/NQ38929.pdf.
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Lee, Jae-Moon. "Probabilistic inverse aerodynamic design optimization for natural laminar flow wings." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/11984.
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Iliffe, Christopher. "An inverse predictive model for the design of functional textiles." Thesis, University of Newcastle upon Tyne, 2016. http://hdl.handle.net/10443/3351.
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Coated woven fabrics are used for large scale structures including airports and sports stadia. Manufacturers produce a range of fabrics from which a single fabric is selected by the structural engineer based on design criteria such as stiffness, weight, strength and formability. Designs must therefore utilise a fabric with properties which may not be optimal for that particular application. This thesis develops and tests a model that allows a bespoke coated woven fabric to be designed with specified mechanical properties such as tensile stiffness, Poison’s ratio and shear stiffness. A method is developed to ‘invert’ an existing predictive mechanistic ‘unit cell’ model using the derivatives of the equations defining the unit cell. The existing model is altered to enable the prediction of shear characteristics in addition to tensile properties by the inclusion of the coating using a finite element representation. The ‘inverse’ model is shown to accurately design a fabric for specific and attainable targets of Young’s modulus, Poisson’s ratio, and shear stiffness which have been derived using the predictive model for various fabric stress states. The effect of variability in fabric parameters on the tensile response of a fabric is considered using both Monte Carlo and FORM analysis. The sensitivity of the fabric response to biaxial loading is calculated using the direction cosines defined in the FORM methodology. The calculation of fabric sensitivity also enables a detailed investigation of the sensitivity of fabric stress-strain behaviour to variation in individual fabric parameters. A method is developed to design fabrics with mechanical properties which are robust to changes in manufacturing parameters by altering the geometry of the fabric. The model is validated by comparing the inverse model output to unit cell model input and also to biaxial test results. The inverse model shows excellent fidelity with results calculated using the unit cell model, but fails to adequately reproduce the actual fabric geometry when target stiffness values are based on biaxial test data. A method for the removal of yarns from fabrics and tensile testing of coated fabric yarn specimens is also developed. iii It is common practice to use a plane stress formulation to approximate the stress-strain response of a coated woven fabric. Comparison of the model output with biaxial test results necessitated the creation of a method for the calculation of fabric tensile stiffness at multiple stress states instead of a single set of elastic constants. This approach takes into account the complex nonlinear behaviour of architectural fabrics by considering the variation in stress-strain behaviour at different biaxial stress states. The final inverse model provides a novel tool for the design of coated woven fabric with prescribed mechanical responses at multiple stress states that is robust to variations in its constituent parameters, with scope for future application in textile architecture, medical textiles and industrial textiles.
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Poon, Joseph Kin-Shing. "Multiprocessor-compatible inverse kinematics and path planning for robots." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29165.
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Novel algorithms in robot inverse kinematics and path planning are proposed. Emphasis
is placed on real-time execution speed with multiprocessors and adaptability to unpredictable environments. The inverse kinematics algorithm is an iterative solution
which is applicable to many classes of industrial robots, and is stable at and around singularities. The method is based on a simple functional analysis of each link of a manipulator and projecting vectors on the coordinate frame of each joint. Heuristic rules are used to control a mobile manipulator base and to guide the manipulator
in the case of non-convergence caused by joint limits. The path planning algorithm uses a potential surface in a quantized configuration space. Paths are guaranteed to be collision-free for all parts of the robot. Local minimum regions on the potential surface are filled on demand by extending the obstacles. Arbitrarily shaped obstacles in 3-dimensions can be handled. Using a hierarchical collision detection
technique, high execution speed can be maintained even with many complex shaped obstacles in the workspace. The path planning method can theoretically be applied to any manipulator with any degrees of freedom. The implementation of the inverse kinematics and path planning algorithms in a parallel hierarchical multiprocessor computer structure designed for the control of robots is proposed and investigated. Communication among the processors is by point-to-point message passing via asynchronous serial links with message buffers. Computer simulations are used to demonstrate the appropriateness and feasibility of this computer structure
for robot control.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Gallegos, Carlos Mario 1973. "Motion based design : solution algorithms to the inverse problem with applications to seismic design." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/46143.
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Wogrin, Sonja. "Model reduction for dynamic sensor steering : a Bayesian approach to inverse problems." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/43739.
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Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 97-101).
In many settings, distributed sensors provide dynamic measurements over a specified time horizon that can be used to reconstruct information such as parameters, states or initial conditions. This estimation task can be posed formally as an inverse problem: given a model and a set of measurements, estimate the parameters of interest. We consider the specific problem of computing in real-time the prediction of a contamination event, based on measurements obtained by mobile sensors. The spread of the contamination is modeled by the convection diffusion equation. A Bayesian approach to the inverse problem yields an estimate of the probability density function of the initial contaminant concentration, which can then be propagated through the forward model to determine the predicted contaminant field at some future time and its associated uncertainty distribution. Sensor steering is effected by formulating and solving an optimization problem that seeks the sensor locations that minimize the uncertainty in this prediction. An important aspect of this Dynamic Sensor Steering Algorithm is the ability to execute in real-time. We achieve this through reduced-order modeling, which (for our two-dimensional examples) yields models that can be solved two orders of magnitude faster than the original system, but only incur average relative errors of magnitude O(10-3). The methodology is demonstrated on the contaminant transport problem, but is applicable to a broad class of problems where we wish to observe certain phenomena whose location or features are not known a priori.
by Sonja Wogrin.
S.M.
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Kurtulus, Berkin. "Development of a Tool for Inverse Aerodynamic Design and Optimisation of Turbomachinery Aerofoils." Thesis, KTH, Flygdynamik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-293353.
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The automation of airfoil design process is an ongoing effort within the field of turbo-machinery design, with significant focus on developing new reliable and consistent methods that can meet the needs of the engineers. A wide variety of approaches has been in use for inverse airfoil design process which benefit from theoretical inverse design, statistical methods, empirical discoveries and many other ways to solve the design problem. This thesis work also develops a tool in Python to be used in airfoil aerodynamic design process that is simple, fast and accurate enough for initial design of turbo-machinery blades with focus on turbine airfoils used for operation in aircraft engines. To convey the decision-making process during development a simplified case is presented. The underlying considerations are discussed. Other available methods in the literature used for similar problems, are also evaluated and compared to demonstrate the advantages and limitations of the methods used within the tool. The inverse design problem is formulated as a multi-objective optimization problem to handle various different objectives that are relevant for aerodynamic design of turbo-machinery airfoils. Test runs are made and the results are discussed to assess how robust the tool is and how the current capabilities can be modified or extended. After the development process, the tool is verified to be a suitable option for real-life design optimization tasks and can be used as a building block for a much more comprehensive tool that may be developed in the future.Automatisering av processen för design av vingprofiler kräver fortlöpande insatser inom området turbomaskindesign, med stort fokus på att utveckla nya tillförlitliga och konsekventa metoder som kan tillgodose ingenjörernas behov. Ett stort antal olika tillvägagångssätt har provats för omvänd design av vingprofiler såsom teoretisk invers design, statistiska metoder, empiriska upptäckter och många andra sätt att lösa designproblemet. Detta avhandlingsarbete är också ett lyckat försök att utveckla ett verktyg i Python som ska användas i den aerodynamiska designprocessen; det är enkelt, snabbt och noggrant för den initiala designen av turbomaskinblad med fokus på turbinblad som för användning i flygmotorer. För att förmedla beslutsprocessen under utvecklingen presenteras ett förenklat fall. De underliggande övervägandena diskuteras. Andra tillgängliga metoder i litteraturen som används för liknande problem utvärderas och jämförs för att visa fördelarna och begränsningarna med de metoder som används i verktyget. Det omvända designproblemet formuleras som ett multi-objektivt optimeringsproblem för att hantera olika mål som är relevanta för aerodynamisk design av turbomaskiner. Testkörningar görs och resultaten diskuteras för att bedöma hur robust verktyget är och hur de nuvarande funktionerna kan modifieras eller utökas. Efter utvecklingsprocessen verifieras verktyget som ett lämpligt alternativ för verkliga designoptimeringsuppgifter och kan användas som en byggsten för ett mycket mer omfattande verktyg som kan utvecklas i framtiden.
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Hill, Ian Gregory. "Design of an inverse photoemission spectrometer for studies of quantum wires." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/nq22465.pdf.
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Call, Mikael. "Inverse Shortest Path Routing Problems in the Design of IP Networks." Licentiate thesis, Linköpings universitet, Optimeringslära, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-66378.
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This thesis is concerned with problems related to shortest pathrouting (SPR) in Internet protocol (IP) networks. In IP routing, alldata traffic is routed in accordance with an SPR protocol, e.g. OSPF.That is, the routing paths are shortest paths w.r.t. some artificialmetric. This implies that the majority of the Internet traffic isdirected by SPR. Since the Internet is steadily growing, efficientutilization of its resources is of major importance. In theoperational planning phase the objective is to utilize the availableresources as efficiently as possible without changing the actualdesign. That is, only by re-configuration of the routing. This isreferred to as traffic engineering (TE). In this thesis, TE in IPnetworks and related problems are approached by integer linearprogramming. Most TE problems are closely related to multicommodity routingproblems and they are regularly solved by integer programmingtechniques. However, TE in IP networks has not been studied as much,and is in fact a lot harder than ordinary TE problems without IProuting since the complicating shortest path aspect has to be takeninto account. In a TE problem in an IP network the routing isperformed in accordance with an SPR protocol that depends on a metric,the so called set of administrative weights. The major differencebetween ordinary TE problems and TE in IP networks is that all routingpaths must be simultaneously realizable as shortest paths w.r.t. thismetric. This restriction implies that the set of feasible routingpatterns is significantly reduced and that the only means available toadjust and control the routing is indirectly, via the administrativeweights. A constraint generation method for solving TE problems in IP networksis outlined in this thesis. Given an "original" TE problem, the ideais to iteratively generate and augment valid inequalities that handlethe SPR aspect of IP networks. These valid inequalities are derived byanalyzing the inverse SPR problem. The inverse SPR problem is todecide if a set of tentative routing patterns is simultaneouslyrealizable as shortest paths w.r.t. some metric. When this is not thecase, an SPR conflict exists which must be prohibited by a validinequality that is then augmented to the original TE problem. Toderive strong valid inequalities that prohibit SPR conflicts, athorough analysis of the inverse SPR problem is first performed. Inthe end, this allows us to draw conclusions for the design problem,which was the initial primary concern.
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Santos, Luis Carlos de Castro. "A hybrid inverse optimization method for aerodynamic design of lifting surfaces." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/12105.
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Brock, Jerry S. "A consistent direct-iterative inverse design method for the Euler equations." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/40033.
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A new, consistent direct-iterative method is proposed for the solution of the aerodynamic inverse design problem. Direct-iterative methods couple analysis and shape modification methods to iteratively determine the geometry required to support a target surface pressure. The proposed method includes a consistent shape modification method wherein the identical governing equations are used in both portions of the design procedure. The new shape modification method is simple, having been developed from a truncated, quasi-analytical Taylor's series expansion of the global governing equations. This method includes a unique solution algorithm and a design tangency boundary condition which directly relates the target pressure to shape modification. The new design method was evaluated with an upwind, cell-centered finite-volume formulation of the two-dimensional Euler equations. Controlled inverse design tests were conducted with a symmetric channel where the initial and target geometries were known. The geometric design variable was a channel-wall ramp angle, 0, which is nominally five degrees. Target geometries were defined with ramp angle perturbations of J10 = 2 %, 10%, and 20 %. The new design method was demonstrated to accurately predict the target geometries for subsonic, transonic, and supersonic test cases; M=0.30, 0.85, and 2.00. The supersonic
test case efficiently solved the design tests and required very few iterations. A stable and convergent solution process was also demonstrated for the lower speed test cases using an under-relaxed geometry update procedure. The development and demonstration of the consistent direct-iterative method herein represent the important first steps required for a new research area for the advancement of aerodynamic inverse design methods.Ph. D.
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Faraci, William Eric. "Design of a Resonant Snubber Inverter for Photovoltaic Inverter Systems." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/47800.
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With the rise in demand for renewable energy sources, photovoltaics have become increasingly popular as a means of reducing household dependence on the utility grid for power. But solar panels generate dc electricity, a dc to ac inverter is required to allow the energy to be used by the existing ac electrical distribution. Traditional full bridge inverters are able to accomplish this, but they suffer from many problems such as low efficiency, large size, high cost, and generation of electrical noise, especially common mode noise. Efforts to solve these issues have resulted in improved solutions, but they do not eliminate all of the problems and even exaggerate some of them.
Soft switching inverters are able to achieve high efficiency by eliminating the switching losses of the power stage switches. Since this action requires additional components that are large and have additional losses associated with them, these topologies have traditionally been limited to higher power levels. The resonant snubber inverter is a soft switching topology that eliminates many of these problems by taking advantage of the bipolar switching action of the power stage switches. This allows for a significant size reduction in the additional parts and elimination of common mode noise, making it an ideal candidate for lower power levels. Previous attempts to implement the resonant snubber inverter have been hampered by low efficiency due to parasitics of the silicon devices used, but, with recent developments in new semiconductor technologies such as silicon carbide and gallium nitride, these problems can be minimized and possibly eliminated.
The goal of this thesis is to design and experimentally verify a design of a resonant snubber inverter that takes advantage of new semiconductor materials to improve efficiency while maintaining minimal additional, parts, simple control, and elimination of common mode noise. A 600 W prototype is built. The performance improvements over previous designs are verified and compared to alternative high efficiency solutions along with a novel control technique for the auxiliary resonant snubber. A standalone and grid tie controller are developed to verify that the auxiliary resonant snubber and new auxiliary control technique does not complicate the closed loop control.Master of Science
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Bakri, Nizar. "Asservissement par camera d'un pendule inverse." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13222.
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Sager, Benay. "Stereolithography Characterization for Surface Finish Improvement: Inverse Design Methods for Process Planning." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-04092006-155545/.
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Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2006.Dr. David W. Rosen, Committee Chair ; Dr. Farrokh Mistree, Committee Member ; Dr. W. Jack Lackey, Committee Member ; Dr. Cliff Henderson, Committee Member ; Dr. Ali Adibi, Committee Member.
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Salah, Maher Jawad Younis. "Optimum plastic design of structures by generalized inverse theory and quadratic programming." Thesis, Queen Mary, University of London, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337445.
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Arnold, Sean. "Design of manufacturing systems with the aid of neural network inverse models." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12439.
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Young, Warren Frazer. "Pseudo inverse filter design for improving the axial resolution of ultrasound images." Thesis, University of Edinburgh, 1998. http://hdl.handle.net/1842/11658.
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This thesis is concerned with improving the quality of images from medical ultrasound examinations which often suffer from poor picture quality. In addition, the resolution of ultrasound images is poor compared to other medical imaging techniques. Ultrasound images have comparatively poor resolution (axial, lateral and contrast), and poor dynamic range. The axial resolution, and contrast resolution of medical ultrasound images can be improved by appropriate filtering of the RF ultrasound signal, prior to signal demodulation. In this thesis I present a pseudo inverse filter, suitable for improving the axial and contrast resolution of medical ultrasound images. This filter is based on a sigmoid function, and it approximates an inverse filter - but is less sensitive to noise than an inverse filter. I present results from applying the proposed filter, with a variety of parameter settings, to ultrasound images of three target objects: a near perfect plane reflector, a tissue mimicking phantom, and intravascular ultrasound (IVUS) images from the aorta of a rabbit. These three targets provide good test cases for the filter; the near perfect plane reflector is a good test of the filter under (near) ideal circumstances; the IVUS images are a realistic test of a medical situation in that they are virtually identical to human IVUS images; and the phantom provides a good midpoint between the first two cases. This midpoint is useful since it allows me to analyse a realistic image, while knowing exactly what the structure and shape of the target object is - this knowledge is not available for the IVUS images. Lastly, I present extensive comparisons with other filters that have been proposed for the filtering of ultrasound. These comparisons are both subjective and - more importantly - objective. In particular I make comparisons with the following filters: matched, inverse, phase correction, square root based, fourth root based, and Wiener filters.
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Cuvilliers, Pierre(Pierre Emmanuel). "The constrained geometry of structures : optimization methods for inverse form-finding design." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127853.
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Thesis: Ph. D. in Architecture: Building Technology, Massachusetts Institute of Technology, Department of Architecture, May, 2020Cataloged from PDF version of thesis.
Includes bibliographical references (pages [133]-145).
This dissertation aims to improve form-finding workflows by giving more control on the obtained shapes to the designer. Traditional direct form-finding allows the designer to generate shapes for structures that need to verify a mechanical equilibrium when built; however, it produces shapes that are difficult to control. This dissertation shows how the design of constrained structural systems is better solved by an inverse form-finding process, where the parameters and initial conditions of the direct form-finding process are automatically adjusted to match the design intent. By defining a general framework for the implementation of such workflows in a nested optimizer loop, the requirements on each component are articulated. The inner optimizer is a specially selected direct form-finding solver, the outer optimizer is a general-purpose optimization routine. This is demonstrated with case studies of two structural systems: bending-active structures and funicular structures.
These two systems that can lead to efficient covering structures of long spans. For bending-active structures, the performance (speed, accuracy, reliability) of direct form-finding solvers is measured. Because the outer optimization loop in an inverse form-finding setup needs to rely on a robust forward simulation with minimal configuration, we find that general-purpose optimizers like SLSQP and L-BFGS perform better than domain-specific algorithms like dynamic relaxation. Using this insight, an inverse form-finding workflow is built and applied with a closest-fit optimization objective. In funicular structures, this dissertation first focuses on a closest-fit to target surface optimization, giving closed-form formulations of gradients and hessian of the problem. Finding closed-form expressions of these derivatives is a major blocking point in creating more versatile inverse form-finding workflows.
This process optimizer is then reimplemented in an Automatic Differentiation framework, to produce an inverse form-finding tool for funicular surfaces with modular design objectives. This is a novel way of implement-ing such tools, exposing how the design intent can be represented by more complex objects than a target surface. Reproducing existing structures, and generating more efficient funicular shapes for them, the possibilities of the tool are demonstrated in exploring the design space and fine-tuned modifications, thanks to the fine control over the objectives representing the design intent.
by Pierre Cuvilliers.
Ph. D. in Architecture: Building Technology
Ph.D.inArchitecture:BuildingTechnology Massachusetts Institute of Technology, Department of Architecture
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Singh, Rahul. "Inclusion of Blockage Effects in Inverse Design of Centrifugal Pump Impeller Blades." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1427813446.
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