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1
Загородня, Тетяна Миколаївна. "Моделі та інформаційна технологія забезпечення компетентності випускників вищого навчального закладу з урахуванням вимог роботодавця". Thesis, Сумський державний університет, 2015. http://repository.kpi.kharkov.ua/handle/KhPI-Press/18188.
Повний текст джерелаАнотація:
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.13.06 – інформаційні технології. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2015. У дисертаційній роботі вирішена актуальна науково-практична задача обґрунтування та розробки інформаційної технології забезпечення компетентності випускників ВНЗ з урахуванням вимог роботодавця до компетентності фахівців. Проаналізовано наукові досягнення в області підвищення ефективності навчання з урахуванням модульної системи і компетентісного підходу, сформульовано основні вимоги до інформаційної системи підтримки прийняття рішень для викладацького складу з метою вдосконалення процесу навчання студентів технічних спеціальностей, зокрема, майбутніх інженерів. Створено математичну модель представлення компетентності студентів як складної агрегованої характеристики. Розроблено модель багатокритеріальної оптимізації параметрів навчального процесу, яка дозволяє максимізувати функцію компетентності. Розроблено і впроваджено відповідну інформаційну технологію підтримки прийняття рішень, яка дозволяє проводити оптимізацію процесу навчання студентів технічних спеціальностей задля підвищення їхньої компетентності, що відповідає вимогам роботодавців. Здійснено оптимізацію параметрів навчального процесу для студентів заочної форми навчання, які вивчають дисципліну "Теоретичні основи електротехніки", що дозволяє підвищити сформований рівень компетентності на 20-35 %. Результати впроваджено та використано під час організації навчального процесу у провідних закладах вищої освіти України.
2
Загородня, Тетяна Миколаївна. "Моделі та інформаційна технологія забезпечення компетентності випускників вищого навчального закладу з урахуванням вимог роботодавця". Thesis, НТУ "ХПІ", 2015. http://repository.kpi.kharkov.ua/handle/KhPI-Press/18178.
Повний текст джерелаАнотація:
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.13.06 – інформаційні технології. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2015.
У дисертаційній роботі вирішена актуальна науково-практична задача обґрунтування та розробки інформаційної технології забезпечення компетентності випускників ВНЗ з урахуванням вимог роботодавця до компетентності фахівців. Проаналізовано наукові досягнення в області підвищення ефективності навчання з урахуванням модульної системи і компетентісного підходу, сформульовано основні вимоги до інформаційної системи підтримки прийняття рішень для викладацького складу з метою вдосконалення процесу навчання студентів технічних спеціальностей, зокрема, майбутніх інженерів. Створено математичну модель представлення компетентності студентів як складної агрегованої характеристики. Розроблено модель багатокритеріальної оптимізації параметрів навчального процесу, яка дозволяє максимізувати функцію компетентності. Розроблено і впроваджено відповідну інформаційну технологію підтримки прийняття рішень, яка дозволяє проводити оптимізацію процесу навчання студентів технічних спеціальностей задля підвищення їхньої компетентності, що відповідає вимогам роботодавців. Здійснено оптимізацію параметрів навчального процесу для студентів заочної форми навчання, які вивчають дисципліну "Теоретичні основи електротехніки", що дозволяє підвищити сформований рівень компетентності на 20-35 %. Результати впроваджено та використано під час організації навчального процесу у провідних закладах вищої освіти України.Thesis for a Candidate Degree in Technical Sciences, Specialty 05.13.06 – Information technologies. – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2015. In the dissertation the relevant scientific and practical problem is solved, which is related to study and development of information technology for ensuring competencies of graduates to meet the requirements of the employer for the competence of professionals. Scientific achievements in the field of improving of learning efficiency based on a modular system and the competence approach were analyzed. The basic requirements to decision support information system for teaching staff were formulated in order to improve the learning process of students of technical specialties, including future engineers. A mathematical model of competence representation as a complex aggregated characteristic was created. The model of multicriteria optimization of the parameters of learning process was developed, which allows to maximize the competence function. The decision support information technology was developed and deployed. It allows to optimize the learning process of students of technical specialties for improvement of their competence and satisfaction of employers requirements. The optimization of parameters of learning process for students of low residence education was performed. It was done for discipline «Theoretical Foundations of Electrical Engineering» and allowed to increase the level of competence by 20–35 %. The results were used for organization of learning process in leading universities of Ukraine.
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Yang, Baofen. "Geometric deformable models using the level set method." Mémoire, Université de Sherbrooke, 2005. http://savoirs.usherbrooke.ca/handle/11143/4664.
Повний текст джерелаАнотація:
Geometric deformable models for active contours have brought tremendous impact to classical problems in image processing such as providing ways to devise efficient computational algorithms for automatic segmentation. This is achieved by using the level set method, which allows handling automatic changes in topology while providing a framework for very fast numerical schemes. However, topological flexibility is not desired when an object with known topology is sought. It is natural to capture the target in a way that gives the correct topology. A geometric deformable model with topology preserving is developed that can guarantee the topology will be preserved while all the computational advantages of the level set approach are maintained. A key issue in object detection using the shape of the object’s boundary and surface reconstruction using slice contours is the ability to identify the complete boundaries of the segmented objects in the scene. The segmentation results provided by geometric deformable models are usually dependent on the contour initialization, and in most cases, the results of the segmentation will only provide partial objects boundaries. A new method based on digital topology is proposed to detect the complete boundary information of the segmented objects. By carrying out a topological analysis of the objects, this method can provide the right initialization that can capture all the boundaries of the objects in certain cases.
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MUKHERJEE, NANDINI. "3D DEFORMABLE CONTOUR SURFACE RECONSTRUCTION: AN OPTIMIZED ESTMATION METHOD." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1078255615.
Повний текст джерела
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Hazarika, Neep. "An inverse method for blended wing-body configurations." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/12498.
Повний текст джерела
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Zhang, Kejun. "3D image applications of a 2D constrained deformable contour method." Cincinnati, Ohio : University of Cincinnati, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1092408492.
Повний текст джерела
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Li, Ziyun. "Haptic Dissection of Deformable Objects using Extended Finite Element Method." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31445.
Повний текст джерелаАнотація:
Interactive dissection simulation is an important research topic in the virtual reality (VR) community.
There are many efforts on this topic; however, most of them focus on building a realistic simulation system regardless of the cost, and they often require expensive workstations and specialized haptic devices which prevent broader adoption.
We show how to build a realistic dissection simulation at an affordable cost, which opens up applications in elementary education for virtual dissections which are currently not feasible.
In this thesis, we present a fast and robust haptic system for interactive dissection simulations of finite elements based deformable objects which supports two type of haptic interactions: point contacts and cuts.
We design a semi-progressive virtual dissection scheme of deformable objects in a real-time application.
The quality and performance of visual/haptic feedback is demonstrated on a low-end commercial desktop PC with a haptic device.
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ZHANG, KEJUN. "3D MEDICAL IMAGE APPLICATIONS OF A 2D CONSTRAINED DEFORMABLE CONTOUR METHOD." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1092408492.
Повний текст джерела
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Arrou-Vignod, Pierre. "Simultaneous modal adjustment of multiple aircraft configurations using an optimization method." Thesis, KTH, Lättkonstruktioner, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-234839.
Повний текст джерелаАнотація:
When designing an airplane, it is necessary to know precisely the vibration modes of the structure. To do so, the Finite Element model of the airplane is adjusted to ground vibration tests results using optimization. Particularly, for airplanes able to carry several external payloads, this adjustment process must be performed for all payloads configurations. In this Master Thesis, the possibility of adjusting simultaneously different airplane configurations to their respective tests results is explored. Such a method ensures that the final Finite Element model is the same in all configurations. After implementation in the company’s software, this method is subsequently tested over two configurations. The results obtained are compared to those from separate adjustment of the models with the same variable parameters. Comparison shows that simultaneous model adjustment is promising. A better choice of variable parameters is required to improve results.Vid konstruktion av flygplan är det nödvändigt att kunna beräkna egensvängningsformer och egenfrekvenser för strukturen. För att göra detta anpassas ett flygplans finita element-modell till vibrationstestresultat med hjälp av optimering. Speciellt för flygplan som kan bära flera uppsättningar extern nyttolast måste denna justeringsprocess göras för alla nyttolastkonfigurationer. I detta examensarbete utforskas möjligheten att justera olika flygplanskonfigurationer samtidigt mot deras respektive testresultat. Den här metoden säkerställer att den slutliga finita element-modellen är identisk för alla konfigurationer. Efter genomförandet i företagets program testas metoden på två konfigurationer. Resultaten jämförs med de från separat anpassning av modellerna med samma designparametrar. Jämförelsen visar att samtidigt modelljustering är lovande. Ett bättre val av designparametrar krävs för att förbättra resultaten.
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Le, Moigne Alan. "A discrete Navier-Stokes adjoint method for aerodynamic optimisation of BlendedWing-Body configurations." Thesis, Cranfield University, 2002. http://hdl.handle.net/1826/826.
Повний текст джерелаАнотація:
An aerodynamic shape optimisation capability based on a discrete adjoint solver for Navier-
Stokes flows is developed and applied to a Blended Wing-Body future transport aircraft.
The optimisation is gradient-based and employs either directly a Sequential Quadratic Programming
optimiser or a variable-fidelity optimisation method that combines low- and
high-fidelity models. The shape deformations are parameterised using a B´ezier-Bernstein
formulation and the structured grid is automatically deformed to represent the design changes.
The flow solver at the heart of this optimisation chain is a Reynolds averaged Navier-
Stokes code for multiblock structured grids. It uses Osher’s approximate Riemann solver
for accurate shock and boundary layer capturing, an implicit temporal discretisation and
the algebraic turbulence model of Baldwin-Lomax. The discrete Navier-Stokes adjoint
solver based on this CFD code shares the same implicit formulation but has to calculate
accurately the flow Jacobian. This implies a linearisation of the Baldwin-Lomax model.
The accuracy of the resulting adjoint solver is verified through comparison with finitedifference.
The aerodynamic shape optimisation chain is applied to an aerofoil drag minimisation problem.
This serves as a test case to try and reduce computing time by simplifying the fidelity
of the model. The simplifications investigated include changing the convergence level of
the adjoint solver, reducing the grid size and modifying the physical model of the adjoint
solver independently or in the entire optimisation process. A feasible optimiser and the use
of a penalty function are also tested. The variable-fidelity method proves to be the most ef-
ficient formulation so it is employed for the three-dimensional optimisations in addition to
parallelisation of the flow and adjoint solvers with OpenMP. A three-dimensional Navier-
Stokes optimisation of the ONERA M6 wing is presented. After describing the concept
of Blended Wing-Body and the studies carried out on this aircraft, several aerodynamic
optimisations are performed on this geometry with the capability developed in this thesis.
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Merugu, Satyanarayana. "Analysis of geared shaft configurations and thin-rimmed gears using finite element method." Connect to resource, 2001. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1137611592.
Повний текст джерелаАнотація:
Thesis (M.S.)--Ohio State University, 2001.Advisor: Donald R. Houser, Dept. of Mechanical Engineering. Includes bibliographical references (leaves 109-110). Available online via OhioLINK's ETD Center
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Johansson, John. "Efficient implementation of the Particle Level Set method." Thesis, Linköping University, Media and Information Technology, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-59579.
Повний текст джерелаАнотація:
The Particle Level set method is a successful extension to Level set methods to improve thevolume preservation in fluid simulations. This thesis will analyze how sparse volume data structures can be used to store both the signed distance function and the particles in order to improve access speed and memory efficiency. This Particle Level set implementation will be evaluated against Digital Domains current Particle Level set implementation. Different degrees of quantization will be used to implement particle representations with varying accuracy. These particles will be tested and both visual results and error measurments will be presented. The sparse volume data structures DB-Grid and Field3D will be evaluated in terms of speed and memory efficiency.
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Mosahebi, Mohamadi Ali. "An implicit adaptive non-linear frequency domain method for periodic viscous flows on deformable grids." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114474.
Повний текст джерелаАнотація:
An implicit adaptive Nonlinear Frequency Domain method (NLFD) has been developed and validated for the Navier-Stokes equations on deformable grids. Although the computational time for periodic flows is reduced by using the NLFD approach in comparison with classical time marching schemes, the adaptive NLFD approach leads to additional reductions in the overall computational effort. A novel adaptation strategy that allows both mode augmentation and reduction enables the adaptive approach to gain a factor of two reduction in memory and computational cost at anequivalent solution accuracy to the non-adaptive approach. In order to further accelerate the convergence, the non-linear LU-SGS technique, which is an implicit time marching approach, is implemented. In the non-linear LU-SGS method, the computational cells are treated locally; hence, its implementation is quite suitable for the adaptive NLFD method, where different cells have dierent number of modes and therefore has to be treated individually. Through an innovative approach, each mode is updated separately within each cell, while the coupling eects of the other modes,which are included in the Fourier expression of the solution are transferred to the right-hand side and are iteratively updated. As a result, the computational efficiency of the implicit solver is not decreased as the number of modes increases. Through the developed implicit solver, more than one order of magnitude speed up is obtainedcompared to the modied ve-stage Runge-Kutta explicit approach. Finally, the concept of dynamic or moving/deformable grid is extended to the present approach for numerical simulation of physical periodic problems, where the flow periodicity is induced from a moving/deforming object. The approach is validated for 2D laminar vortex shedding behind stationary, plunging, and pitching cylinder and airfoil cases.Cette thèse prèsente la formulation et la validation d'une méthode adaptative, implicite et non-linéaire dans le domaine fréquentiel (NLFD) conçue pour la solution des équations de Navier-Stokes sur maillages déformables. Comparé à un schéma d'intégration temporel classique, cette méthode réduit le temps de calcul d'écoulements périodiques en résolvant les équations dans le domaine des fréquences et en implémentant une stratégie adaptative. Cette stratégie consiste à augmenter ou retrancher localement le nombre d'harmonique utilisées lors du calcul, et permet de diminuer par deux le temps et l'espace mémoire requis par le calcul. A fin de résoudre efficacement le systeme d'équations obtenu, une méthode LU-SGS implicite est utilisée. Le schéma non-linéaire LU-SGS traite chaque cellule du maillage de façon locale, et donc est particulièrement adapté à notre méthode fréquentielle adaptative où le nombre d'harmoniques utilisées varie d'une cellule à l'autre. Les flux échangés entre deux cellules voisines sont transférés par le biais d'un terme source qui est mis à jour de façon itérative. De cette manière, le taux de convergence du schéma demeure indépendant du nombre d'harmoniques utilisées. Nous démontrons que la méthode LU-SGS permet un facteur d'accélération de plus d'un ordre de grandeur comparée au schéma Runge-Kutta explicite. Finalement, le concept de maillage déformable est aussi inclus à notre méthode de calcul pour écoulements périodiques. L'approche est validé en simulant l'écoulement laminaire autour d'un cylindre et d'un profil aérodynamique en mouvement oscillatoire.
14
Ding, Wei. "Free vibration studies of shear deformable plates by the traditional superposition and Superposition-Galerkin method." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/9522.
Повний текст джерелаАнотація:
In the first part of the present study, it is demonstrated that the traditional superposition method lends itself successfully to obtaining of eigenvalues and mode shapes for completely free shear deformable plates, namely, the thick isotropic plates and symmetric cross-ply laminated plates. The effect of transverse shear deformation is taken into account by means of the first order shear deformation relationship as developed by Mindlin. The governing differential equations are satisfied exactly throughout the plate domain and free edge boundary conditions are satisfied to any desired degree of accuracy. These appear to be the first accurate solutions to these important completely free plate vibration problems. Subsequently, a new modified Superposition-Galerkin method is developed for analyzing the free vibration problem of symmetric cross-ply plates with any combination of clamped and simply supported boundary conditions. It is shown that this new approach leads to vast simplification of computational procedures in comparison to the traditional superposition method. Nevertheless it is seen that excellent agreement is achieved when results obtained by the Galerkin-Superposition method are compared with those generated by previous researchers. It is expected that this new modified method will have application to various families of laminated plate vibration problems.
15
Uosukainen, Seppo. "JMC method applied to active control of sound : theoretical extensions and new source configurations /." Espoo [Finland] : Technical Research Centre of Finland, 1999. http://www.vtt.fi/inf/pdf/publications/1999/P386.pdf.
Повний текст джерела
16
Le, Moigne Alan. "A discrete Navier-Stokes adjoint method for aerodynamic optimisation of Blended Wing-Body configurations." Thesis, Cranfield University, 2002. http://dspace.lib.cranfield.ac.uk/handle/1826/826.
Повний текст джерелаАнотація:
An aerodynamic shape optimisation capability based on a discrete adjoint solver for Navier-Stokes flows is developed and applied to a Blended Wing-Body future transport aircraft. The optimisation is gradient-based and employs either directly a Sequential Quadratic Programming optimiser or a variable-fidelity optimisation method that combines low- and high-fidelity models. The shape deformations are parameterised using a B´ezier-Bernstein formulation and the structured grid is automatically deformed to represent the design changes. The flow solver at the heart of this optimisation chain is a Reynolds averaged Navier- Stokes code for multiblock structured grids. It uses Osher’s approximate Riemann solver for accurate shock and boundary layer capturing, an implicit temporal discretisation and the algebraic turbulence model of Baldwin-Lomax. The discrete Navier-Stokes adjoint solver based on this CFD code shares the same implicit formulation but has to calculate accurately the flow Jacobian. This implies a linearisation of the Baldwin-Lomax model. The accuracy of the resulting adjoint solver is verified through comparison with finitedifference. The aerodynamic shape optimisation chain is applied to an aerofoil drag minimisation problem. This serves as a test case to try and reduce computing time by simplifying the fidelity of the model. The simplifications investigated include changing the convergence level of the adjoint solver, reducing the grid size and modifying the physical model of the adjoint solver independently or in the entire optimisation process. A feasible optimiser and the use of a penalty function are also tested. The variable-fidelity method proves to be the most efficient formulation so it is employed for the three-dimensional optimisations in addition to parallelisation of the flow and adjoint solvers with OpenMP. A three-dimensional Navier-Stokes optimisation of the ONERA M6 wing is presented. After describing the concept of Blended Wing-Body and the studies carried out on this aircraft, several aerodynamic optimisations are performed on this geometry with the capability developed in this thesis.
17
Khan, Irfan. "Direct numerical simulation and analysis of saturated deformable porous media." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34664.
Повний текст джерелаАнотація:
Existing numerical techniques for modeling saturated deformable porous media are based on
homogenization techniques and thus are incapable of performing micro-mechanical investigations, such as the effect of micro-structure on the deformational characteristics of the media. In this research work, a numerical scheme is developed based on the parallelized hybrid lattice-Boltzmann finite-element method, that is capable of performing micro-mechanical investigations through direct numerical
simulations.
The method has been used to simulate compression of model saturated porous media made of
spheres and cylinders in regular arrangements. Through these simulations it is found that in the limit of small Reynolds number, Capillary number and strain, the deformational behaviour of a real porous media can be recovered through model porous media when the parameters porosity, permeability and bulk compressive modulus are matched between the two media.
This finding motivated research in using model porous geometries to represent more complex
real porous geometries in order to perform investigations of deformation on the latter. An attempt has been made to apply this technique to the complex geometries of ªfeltº, (a fibrous mat used in paper industries). These investigations lead to new understanding on the effect of fiber diameter on the bulk properties of a fibrous media and subsequently on the deformational behaviour of the media. Further the method has been used to investigate the constitutive relationships in deformable porous media.
Particularly the relationship between permeability and porosity during the deformation of the media is investigated. Results show the need of geometry specific investigations.
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Sengupta, Agniva. "Visual tracking of deformable objects with RGB-D camera." Thesis, Rennes 1, 2020. http://www.theses.fr/2020REN1S069.
Повний текст джерелаАнотація:
Le suivi d'objets déformable à partir d’informations visuelles à de nombreuses applications dans le domaine de la robotique, de l'animation ou de la simulation. Dans cette thèse, nous proposons de nouvelles approches pour le suivi d'objets rigides et non rigides à l'aide d'une caméra RGB-D. Cette thèse comporte quatre contributions principales. La première contribution est une nouvelle approche de suivi d'objets dans des images RGB-D qui utilise des erreurs basées sur la profondeur et la photométrie pour suivre et localiser des formes complexes en utilisant leur modèle 3D grossier. La seconde contribution porte sur une méthode de suivi d'objets non rigides reposant sur une approche par éléments finis (FEM) pour suivre et caractériser les déformations. La troisième contribution est une approche de suivi de la déformation qui minimise une combinaison d'erreurs géométriques et photométriques tout en utilisant la FEM comme modèle de déformation. Finalement, la quatrième contribution consiste à estimer les propriétés d'élasticité d'un objet analysant ses déformations toujours à l'aide d'une caméra RGB-D. Une fois les paramètres d'élasticité estimés, la même méthodologie peut être réutilisée pour caractériser les forces de contactTracking soft objects using visual information has immense applications in the field of robotics, computer graphics and automation. In this thesis, we propose multiple new approaches for tracking both rigid and non-rigid objects using a RGB-D camera. There are four main contributions of this thesis. The first contribution is a rigid object tracking method which utilizes depth and photometry based errors for tracking complex shapes using their coarse, 3D template. The second contribution is a non-rigid object tracking method which uses co-rotational FEM to track deforming objects by regulating the virtual forces acting on the surface of a physics based model of the object. The third contribution is a deformation tracking approach which minimizes a combination of geometric and photometric error while utilizing co-rotation FEM as the deformation model. The fourth contribution involves estimating the elasticity properties of a deforming object while tracking their deformation using RGB-D camera. Once the elasticity parameters have been estimated, the same methodology can be re-utilized for tracking contact forces on the surface of deforming objects
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Asdal, Bent. "Static and free vibration analysis of advanced composites using shear-deformable rectangular plate finite elements." Thesis, Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/80092.
Повний текст джерелаАнотація:
A comparison of rectangular finite elements based on a first order shear deformation plate theory and a refined higher order plate theory is presented. Special attention is given to the representation of transverse shear strain, the phenomenon of "shear locking", and the selection of the interpolating polynomial. Both C⁰ and C¹ continuity elements are represented; the elements range from: 3 or 5 DOF per node, and 12 - 27 DOF per element. Static and free vibration analysis of isotropic and laminated plates with thicknesses ranging from extremely thin to very thick are presented, along with a convergence study. The finite element results are compared with the exact plate theory solutions. Of the elements investigated, the modified refined higher order theory element exhibits the best overall behavior.Master of Science
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Ilmane, Amine. "Développements autour de la méthode d'interactions de configurations en champ moyen." Thesis, Nice, 2015. http://www.theses.fr/2015NICE4115/document.
Повний текст джерелаАнотація:
Dans cette thèse ont été développés de nouveaux outils de calcul théorique de spectres moléculaires rovibrationnels qui permettent de mieux traiter les états vibrationnels très excités ainsi que les mouvements de grandes amplitudes avec la méthode d’interactions de configurations en champ moyen. Dans un premier temps, nous avons discuté la question du choix des bases modales et les différents compromis à trouver afin de pallier aux défauts possibles des surfaces d'énergie potentielle. Dans ce cadre nous avons également développé un critère de sélection visant à améliorer la qualité des fonctions d'ondes rovibrationnelles de base. Ces approches ont été appliquées avec succès à la molécule de méthane CH4.Dans un second temps, nous avons implémenté un algorithme de calcul formel des opérateurs d'énergie cinétique en coordonnées quelconques qui permet d'avoir des expressions exactes ainsi que leurs développements en série de Taylor ou Fourier, qui exploite au mieux les potentialités du logiciel MATHEMATICA et a permis d'obtenir des hamiltoniens rovibrationnels en coordonnées de valence de façon particulièrement efficace. Enfin, nous avons généralisé la méthode d’interactions de configurations en champ moyen en ajoutant de façon perturbative un champ effectif d'ordre deux. Nous avons appliqué cette généralisation à la molécule de péroxyde d'hydrogène HOOH, ce qui a permis de montrer son intérêt tant pour l'amélioration des niveaux d'énergie que des fonctions d'onde associées, lorsqu'on a affaire à des groupes de degrés de liberté bien séparés énergétiquementIn this thesis we developed new theoretical tools for molecular rovibrational spectra for a better description of the excited vibrational states and movements with large amplitudes using mean field configuration interaction method. First, we discussed the choice of modal basis and different trade-off to overcome the possible shortcomings of potential energy surfaces. In this context we have also developed selection criteria to improve the quality of rovibrational wave functions. These approaches have been successfully applied to the methane molecule (CH4). Secondly, we have implemented a formal algorithm for calculating the kinetic energy operators in arbitrary coordinates that allows the derivation of exact expressions and their Taylor and Fourier series, using, in a very efficient way, the capabilities of the software MATHEMATICA which yield to the derivation of rovibrational Hamiltonians in valence coordinated. Finally, we have generalized the mean-field configuration interaction method by adding perturbatively a second order effective field. We applied this generalization to the hydrogen peroxide molecule (HOOH), which has shown an improvement for both energy levels and the associated wave functions, when dealing with groups of degrees of freedom that are energetically well separated
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HE, LEI. "A COMPARISON OF DEFORMABLE CONTOUR METHODS AND MODEL BASED APPROACH USING SKELETON FOR SHAPE RECOVERY FROM IMAGES." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1059746287.
Повний текст джерела
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Lebrun, Takorabet Maryse. "Étude de configurations de bobines supraconductrices destinées au stockage d'énergie." Vandoeuvre-les-Nancy, INPL, 1998. http://www.theses.fr/1998INPL052N.
Повний текст джерелаАнотація:
La configuration de bobines pour le stockage d'énergie magnétique à base de matériaux supraconducteurs est définie au travers de trois critères. Ces trois critères caractérisent la capacité de stocker de l'énergie, la quantité de fils supraconducteurs nécessaire et la pollution électromagnétique engendrés par une forme de bobine. Deux nouvelles formes de bobines sont présentées. La première est basée sur 2 distributions sphériques de courants surfaciques. La deuxième est basée sur la structure polygonale et est une conjugaison d'un courant surfacique et d'un courant volumique. Ces deux structures ont pour principales caractéristiques théoriques un champ localement constant et une pollution électromagnétique nulle. En utilisant les trois critères, ces deux formes s'avèrent très compétitives au regard des autres formes existantes. Deux prototypes ont confirmé la faisabilité technologique et les caractéristiques théoriques précitées. Plusieurs méthodes de discrétisation (méthode de Fourier, développement en série du potentiel vecteur et annulation des moments multipolaires) sont envisagées pour le système sphérique étudié théoriquement et continument par résolution laplacienne. D’autres méthodes de discrétisation sont établies à l'aide de calcul de champ en 3D (loi de Biot et Savart) ou bien les éléments finis, pour tout système basé sur la réunion de plusieurs solénoïdes (tore, fagot).
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Rhayem, Taoufik. "Etude du confort vertical et longitudinal d'un vehicule ferroviaire : systeme deformable." Paris 6, 1986. http://www.theses.fr/1986PA066518.
Повний текст джерелаАнотація:
Presentation d'un modele mathematique permettant d'etudier le confort vertical et longitudinal d'un vehicule ferroviaire. L'etude du comportement de la voie a ete faite en la considerant comme une poutre deformable reposant sur des traverses longitudinales, de raideur et d'amortissement uniformement repartis
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Di, Stasio Jean. "The CD-Lagrange scheme, a robust explicit time-integrator for impact dynamics : A new singular mass formulation, and an extension to deformable-deformable contact." Thesis, Lyon, 2021. http://www.theses.fr/2021LYSEI029.
Повний текст джерелаАнотація:
Les pneumatiques sont complexes à simuler car les matériaux y sont hétérogènes, incompressibles et non-linéaires. De plus la géométrie descend jusqu’à l’échelle millimétrique pour les sculptures de la bande de roulement, ce qui requiert un maillage fin. Le modèle éléments finis présente donc un grand nombre de degrés de liberté, reliés par des équations non-linéaires. En dynamique, la simulation est d’autant plus compliquée avec des chocs. Néanmoins elle est cruciale dans le processus de conception pneumatique, où elle apporte une meilleur compréhension de la physique ceci sans tests réels. Les schémas explicites rendent possible les simulations de chocs, car ils résolvent facilement les non-linéarités avec un coup calcul bas. Associés à une formulation de contact précise , ils forment des schémas robustes, précis et efficaces pour la dynamique non-linéaire avec impacts. Ce travail vise à choisir et un tel schéma, et l’améliorer pour la simulation de chocs sur pneumatiques.La première partie est un benchmark identifiant le schéma CD-Lagrange. L’intégration temporelle est réalisée par le schéma de la différence centrée, et le contact imposé par multiplicateurs de Lagrange sur la vitesse. Deux possibilités d’amélioration sont identifiées. La première est d’atteindre un impact conservatif, seul instant où le schéma n’est pas symplectique. La seconde amélioration est d’étendre la formulation au contact déformable-déformable.La deuxième partie vise à atteindre la conservation de l’énergie à l’impact en adaptant la méthode de la masse singulière au CD-Lagrange. Une première formulation 1D est construite. Elle démontre une amélioration majeure du bilan d’énergie. Deux formulations 3D sont ensuite explorées.La troisième partie introduit les méthodes mortier dans le CD-Lagrange. Elles permettent de traiter un contact déformable-déformable de manière robuste, même en présence de friction et de grands glissements. Une technique d’accélération est proposée pour résoudre le problème de contact, ceci sans perte de précisionTyres are complex structures to simulate. The materials are heterogeneous and incompressible with non-linear responses. The geometry goes to the millimetre scales for tread patterns. For a finite elements simulation a precise mesh is then required. The model has then a large number of degrees of freedom and non-linear material laws. In dynamics, the simulation becomes even more challenging especially with impacts. Nevertheless it is crucial in the tire design process because it brings a deeper comprehension of the tire and avoids test on real structures. The explicit time-integration make feasible the impact simulations. They handle easily the non-linearities with a very low computational cost for a time-step. Merged with a precise contact formulation, they form robust, accurate and efficient schemes for addressing impact simulations. This work aims to choose and improve an explicit scheme for non-linear dynamics with impacts. The first part is a benchmark for selecting a scheme and enhance its possibilities of improvement. The selected one is the CD-Lagrange: an explicit scheme based on central difference method, a contact enforcement by Lagrange multipliers, and a contact condition on velocity. Two mains improvements are identified and explored. Firstly, the energy conservation at impact would make the scheme symplectic for deformable bodies. Secondly the formulation must be enlarged to deformable–deformable contact. The second part aims then to achieve the conservation of energy by adapting the singular mass matrix to the CD-Lagrange. The formulation is firstly built in 1D, and shows a major improvement for the energy balance. Then two possible extensions are explored for the 3D cases. The third part presents the CD-Lagrange scheme with a mortar formulation for deformable-deformable contact. It handles with stability and accuracy large sliding and friction. An acceleration technique is proposed for solving the contact problem, without any loss of accuracy
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Mukkananchery, Abey. "Iterative Methods for the Reconstruction of Tomographic Images with Unconventional Source-detector Configurations." VCU Scholars Compass, 2005. http://scholarscompass.vcu.edu/etd/1244.
Повний текст джерелаАнотація:
X-ray computed tomography (CT) holds a critical role in current medical practice for the evaluation of patients, particularly in the emergency department and intensive care units. Expensive high resolution stationary scanners are available in radiology departments of most hospitals. In many situations however, a small, inexpensive, portable CT unit would be of significant value. Several mobile or miniature CT scanners are available, but none of these systems have the range, flexibility or overall physical characteristics of a truly portable device. The main challenge is the design of a geometry that optimally trades image quality for system size. The goal of this work has been to develop analysis tools to help simulate and evaluate novel system geometries. To test the tools we have developed, three geometries have been considered in the thesis, namely, parallel projections, clam-shell and parallel plate geometries. The parallel projections geometry is commonly used in reconstruction of images by filtered back projection technique. A clam-shell structure consists of two semi-cylindrical braces that fold together over the patient's body and connect at the top. A parallel plate structure uses two fixed flat or curved plates on either side of the patient's body and image from fixed sources/detectors that are gated on and off so as to step the X-ray field through the body. The parallel plate geometry has been found to be the least reliable of the three geometries investigated, with the parallel projections geometry being the most reliable. For the targeted application, the clam-shell geometry seems to be the solution with more chances to succeed in the short term. We implemented the Van Cittert iterative technique for the reconstruction of images from projections. The thesis discusses a number of variations on the algorithm, such as the use of the Conjugate Gradient Method, several choices for the initial guess, and the incorporation of a priori information to handle the reconstruction of images with metal inserts.
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Wang, Zhicun. "Time-Domain Simulations of Aerodynamic Forces on Three-Dimensional Configurations, Unstable Aeroelastic Responses, and Control by Neural Network Systems." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11181.
Повний текст джерелаАнотація:
The nonlinear interactions between aerodynamic forces and wing structures are numerically investigated as integrated dynamic systems, including structural models, aerodynamics, and control systems, in the time domain. An elastic beam model coupled with rigid-body rotation is developed for the wing structure, and the natural frequencies and mode shapes are found by the finite-element method. A general unsteady vortex-lattice method is used to provide aerodynamic forces. This method is verified by comparing the numerical solutions with the experimental results for several cases; and thereafter applied to several applications such as the inboard-wing/twin-fuselage configuration, and formation flights. The original thought that the twin fuselage could achieve two-dimensional flow on the wing by eliminating free wing tips appears to be incorrect. The numerical results show that there can be a lift increase when two or more wings fly together, compared to when they fly alone. Flutter analysis is carried out for a High-Altitude-Long-Endurance aircraft wing cantilevered from the wall of the wind tunnel, a full-span wing mounted on a free-to-roll sting at its mid-span without and with a center mass (fuselage). Numerical solutions show that the rigidity added by the wall results in a higher flutter speed for the wall-mounted semi-model than that for the full-span model.
In addition, a predictive control technique based on neural networks is investigated to suppress flutter oscillations. The controller uses a neural network model to predict future plant responses to potential control signals. A search algorithm is used to select the best control input that optimizes future plant performance. The control force is assumed to be given by an actuator that can apply a distributed torque along the spanwise direction of the wing. The solutions with the wing-tip twist or the wing-tip deflection as the plant output show that the flutter oscillations are successfully suppressed with the neural network predictive control scheme.Ph. D.
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Sigüenza, Julien. "Fluid-structure interaction problems involving deformable membranes : application to blood flows at macroscopic and microscopic scales." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT301/document.
Повний текст джерелаАнотація:
Cette thèse traite plusieurs aspects scientifiques inhérents à la simulation numérique de problèmes d'interaction fluide-structure impliquant de fines membranes déformables. Deux cas spécifiques relatifs à la biomécanique cardiovasculaire sont considérés : l'interaction de l'écoulement sanguin avec la valve aortique (qui se produit à l'échelle macroscopique), et l'interaction de la membrane des globules rouges avec ses fluides interne et externe (qui se produit à l'échelle microscopique). Dans les deux cas, le couplage fluide-structure est géré par l'intermédiaire d'un formalisme de frontières immergées, en représentant la membrane par un maillage Lagrangien se mouvant au travers d'un maillage fluide Eulérien. Lorsque l'on traite la dynamique des globules rouges, la membrane est considérée comme étant une structure sans masse et infiniment fine. La première question à laquelle on s'intéresse dans cette thèse est la manière de modéliser la microstructure complexe de la membrane des globules rouges. Un moyen possible pour caractériser un modèle de membrane adapté est de simuler l'expérience des pinces optiques, qui consiste en une configuration expérimentale bien contrôlée qui permet d'étudier la mécanique individuelle d'un globule rouge isolé dans une large gamme de déformations. Plusieurs modèles pertinents sont identifiés, mais les caractéristiques de déformation mesurées durant l'expérience des pinces optiques se révèlent n'être pas assez sélectives pour être utilisées dans un contexte de validation. Des mesures de déformation additionnelles sont proposées, qui pourraient permettre une meilleure caractérisation de la mécanique de la membrane des globules rouges. En ce qui concerne les configurations macroscopiques, une méthode numérique innovante est proposée afin de gérer des simulations numériques de membranes 3D continues, en conservant le formalisme de frontières immergées. Dans cette méthode, appelée méthode des frontières immergées épaisses, la membrane a une épaisseur finie. La précision et la robustesse de la méthode sont démontrées par l'intermédiaire d'une variété de cas tests bien choisis. La méthode proposée est ensuite appliquée à un problème d'interaction fluide-structure réaliste, à savoir l'interaction d'un écoulement (sanguin) pulsé avec une valve aortique biomimétique. Une étude combinée expérimentale et numérique est menée, montrant que la méthode est capable de capturer la dynamique globale de la valve, ainsi que les principales caractéristiques de l'écoulement en aval de la valve. Tous les développements ont été effectués dans le solveur YALES2BIO (http://www.math.univ-montp2.fr/~yales2bio/) développé à l'IMAG, qui est donc disponible pour toutes autres améliorations, validations et études applicativesThis thesis deals with several scientific aspects inherent to the numerical simulation of fluid-structure interaction problems involving thin deformable membranes. Two specific cases relevant to cardiovascular biomechanics are considered: the interaction of the blood flow with the aortic valve (which occurs at the macroscopic scale), and the interaction of the red blood cells membrane with its inner and outer fluids (which occurs at the microscopic scale). In both cases, the fluid-structure interaction coupling is handled using an immersed boundary formalism, representing the membrane by a Lagrangian mesh moving through an Eulerian fluid mesh.When dealing with red blood cells dynamics, the membrane is considered to be an infinitely thin and massless structure. The first question which is addressed in the present thesis work is how to model the complex microstructure of the red blood cells membrane. A possible way to characterize a suitable membrane model is to simulate the optical tweezers experiment, which is a well-controlled experimental configuration enabling to study the individual mechanics of an isolated red blood cell in a large range of deformation. Some relevant membrane models are identified, but the deformation characteristics measured during the optical tweezers experiment reveal to be not selective enough to be used in a validation context. Additional deformation measurements are proposed, which could allow a better characterization of the red blood cell membrane mechanics.Regarding the macroscopic configurations, an innovative numerical method is proposed to handle numerical simulations of 3D continuum membranes, still within the immersed boundary formalism. In this method, called immersed thick boundary method, the membrane has a finite thickness. The accuracy and robustness of the method are demonstrated through a variety of well-chosen test cases. Then, the proposed method is applied to a realistic fluid-structure interaction problem, namely the interaction of a pulsatile (blood) flow with a biomimetic aortic valve. A combined experimental and numerical study is led, showing that the method is able to capture the global dynamics of the valve, as well as the main features of the flow downstream of the valve.All the developments were performed within the YALES2BIO solver (http://www.math.univ-montp2.fr/~yales2bio/) developed at IMAG, which is thus available for further improvements, validations and applicative studies
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Nakhaei, Mohsen. "Layer-specific multiscale mechanical modeling of arterial structures with evolving fiber configurations." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEM014.
Повний текст джерелаАнотація:
Les tissus artériels sont constitués de réseaux de collagène et d'élastine diversement organisés et présentent un comportement anisotrope hautement non linéaire ainsi que la capacité de supporter de grandes déformations réversibles. Ces dernières s'accompagnent d'un réarrangement progressif des réseaux de fibres induit parle chargement. Dans cette thèse, l'important couplage entre la morphologie de la microstructure artérielle et sa réponse mécanique nous a motivé à développer un modèle multi-échelle détaillé de la paroi artérielle. Le cadre de la micromécanique des milieux continus a été utilisé dans une approche incrémentale pour calculer la contrainte, la déformation et les réorientations de fibres. Les extensions du problème d'inclusion de la matrice d'Eshelby permettent d'obtenir des expressions analytiques pour les tenseurs de concentration, qui relient le tenseur de vitesse de déformation macroscopique à la vitesse de déformation et à la vorticité moyennés sur les phases. Nous avons modélisé séparément le comportement de l'adventice et de la média, avant de proposer un modèle complet pour l'artère. De plus, le modèle de comportement multi-échelle a été implémenté dans une formulation éléments finis non linéaire, afin de réaliser des calculs de structure sur l'artère. Le modèle a été validé par différents ensembles de données expérimentales sur des échantillons artériels de différentes espèces. Les résultats montrent que le modèle est capable d'estimer la contribution de chaque tunique dans la réponse macroscopique du tissu pour différents chargements et peut prédire avec précision à la fois la réponse macroscopique et la cinématique microscopique des fibresArterial tissues are made of variously organized collagen and elastin networks and exhibit a highly nonlinear anisotropic behavior with the ability to sustain large reversible strains and to undergo a load-induced progressive morphological rearrangement of the microstructure. In the present study motivated by these specificities of arterial mechanics, we developed a detailed multi-scale model of the arterial wall. The framework of finite strain continuum micromechanics was employed in an incremental approach to compute stress, strain, and fiber reorientations. The extensions of Eshelby’s matrix-inclusion problem allowed for deriving analytical expressions for the concentration tensors, which relate the macroscopic strain rate tensor to phase-averaged strain rate and vorticity. The model accounts for the universal patterns across different scales in the two mechanically significant layers of arteries, namely the adventitia and the media. Furthermore, the multi-scale constitutive model was implemented in a non-linear finite element formulation to solve the structural model of the artery. The model was validated against different experimental data sets on arterial samples from different species. The results show that the model is able to estimate the contribution of each component into the macroscopic response of the tissue for different loading and can predict both the macroscopic response and microscopic fiber kinematics accurately. We submit that such model would help in predicting the evolution of the mechanical tissue response overtime during, for instance, remodeling and growth or damage
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Adedoyin, Adetokunbo Adelana. "Determination of best practice guidelines for performing large eddy simulation of flows in configurations of engineering interest." Master's thesis, Mississippi State : Mississippi State University, 2007. http://library.msstate.edu/etd/show.asp?etd=etd-06222007-140721.
Повний текст джерела
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Wang, Hao. "Analysis of the quasicontinuum method and its application." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:8bef60f0-74f1-44f5-bcbe-d64d4afad15f.
Повний текст джерелаАнотація:
The present thesis is on the error estimates of different energy based quasicontinuum (QC) methods, which are a class of computational methods for the coupling of atomistic and continuum models for micro- or nano-scale materials. The thesis consists of two parts. The first part considers the a priori error estimates of three energy based QC methods. The second part deals with the a posteriori error estimates of a specific energy based QC method which was recently developed. In the first part, we develop a unified framework for the a priori error estimates and present a new and simpler proof based on negative-norm estimates, which essentially extends previous results. In the second part, we establish the a posteriori error estimates for the newly developed energy based QC method for an energy norm and for the total energy. The analysis is based on a posteriori residual and stability estimates. Adaptive mesh refinement algorithms based on these error estimators are formulated. In both parts, numerical experiments are presented to illustrate the results of our analysis and indicate the optimal convergence rates. The thesis is accompanied by a thorough introduction to the development of the QC methods and its numerical analysis, as well as an outlook of the future work in the conclusion.
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Manohar, Vasant. "Facial skin motion properties from video : modeling and applications." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0003288.
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Voznyuk, Ivan. "Méthodes de décomposition de domaines pour la modélisaton électromagnétique et l'imagerie micro-onde quantitative dans des configurations tridimensionnelles de grande taille." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4732/document.
Повний текст джерелаАнотація:
Cette thèse porte sur la modélisation des ondes électromagnétiques en milieu complexe et à haute fréquence. Ceci reste un défi, de part les besoins en temps de calcul et en place mémoire que cela suscite. L'idée de la méthode Finite Element Tearing and Interconnect (FETI) est de diviser le domaine en sous-domaines distincts dans lesquels des problèmes électromagnétiques peuvent être résolus de manière indépendante. Une modification de la méthode classique, appelée FETI-DPEM2-full, est ici proposée afin d'améliorer le processus numérique. Les champs diffractés par différents objets ont ainsi été simulés et comparés avec succès à des champs expérimentaux. A partir de ces champs, les techniques d'imagerie micro-onde permettent de déterminer les paramètres électromagnétiques des objets illuminés. Ce problème inverse peut être réécrit sous la forme d'un problème d'optimisation faisant appel à la résolution de deux problèmes directs à chaque itération. Une méthode de type quasi-Newton a donc été couplée efficacement avec la méthode FETI-DPEM2-full. Des reconstructions obtenues à partir de champs mesurés sont présentées et valident la chaîne méthodologique proposéeThis PhD work is devoted to the electromagnetic modeling of threedimensional large-scale wave propagation problems, which is very challenging in terms of memory and computation time. The main idea of the Finite Element Tearing and Interconnect (FETI) method is to divide the domain into non-overlapping subdomains where each electromagnetic problem can be independently solved. A modification of the classical FETI method, called the FETI-DPEM2-full method, is proposed herein to improve the numerical process. The fields scattered by various structures have thus been computed and successfully compared with measured fields. From these experiments, quantitative microwave imaging algorithms attempt to estimate the physical parameters of the illuminated target. This inverse problem is recasted into a minimization problem where two forward problems are required at each iteration step. A quasi-Newton algorithm has thus been efficiently coupled with the FETI-DPEM2-full method. Reconstructions of various targets from measured scattered fields have been successfully performed, which validates the effectiveness of the proposed methodology
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Matsumoto, Nobuyuki. "Geometry of configuration space in Markov chain Monte Carlo methods and the worldvolume approach to the tempered Lefschetz thimble method." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263464.
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Koussa, Badreddin. "Optimisation des performances d'un système de transmission multimédia sans fil basé sur la réduction du PAPR dans des configurations réalistes." Thesis, Poitiers, 2014. http://www.theses.fr/2014POIT2260/document.
Повний текст джерелаАнотація:
Ce travail de thèse s'intéresse à l'optimisation des performances de transmissions multimédias par une approche originale combinant des circuits radiofréquences, tel que l'am-plificateur de puissance et les distorsions du canal de transmission. Les signaux OFDM sont très sensibles aux non-linéarités de l'amplificateur à cause des fortes fluctuations du niveau du signal, caractérisées par le PAPR. Afin de réduire le PAPR, on propose tout d'abord d'améliorer la méthode TR en termes de rapidité de convergence et de réduction du PAPR, en comparant plusieurs algorithmes d'optimisation. On montre que l'algorithme du gradient con-jugué offre les meilleures performances tout en respectant les spécifications fréquentielles du standard IEEE 802.11a. Par la suite, la méthode TR est évaluée expérimentalement en pré-sence d'un amplificateur de puissance (SZP-2026Z) en utilisant un banc de mesures. On montre ainsi que la méthode TR permet une amélioration de la qualité de transmission. Cette amélioration peut être utilisée pour modifier le point de fonctionnement de l'amplificateur et per-mettre ainsi une réduction de 18 % de la puissance consommée. Les résultats expérimentaux ont conduit au choix d'un modèle réaliste d'amplificateur en considérant les effets mémoires. Ce dernier a été intégré dans une chaîne de simulation SISO comprenant également un modèle réaliste de canal de transmission. La chaîne décrite a permis d'évaluer les performances de la méthode TR dans des conditions de transmission réalistes. Enfin, on propose d'appliquer la méthode TR dans une chaîne MIMO-OFDM en boucle fermée dédiée à la transmission de contenus multimédias scalables dans un environnement réaliste, en utilisant le standard IEEE 802.11n. Cette étude présente une évaluation originale de l'impact de la méthode TR sur la qualité visuelle des images transmises, en prenant en compte le contenu multimédia, la non-linéarité de l'amplificateur et les distorsions apportées par le canalIn this thesis, we are interested on the performances optimization of multimedia transmissions systems with an original contribution combining RF circuits' imperfections presented by the power amplifier (PA) nonlinearities and the transmission channel distortions. The studied system uses the OFDM technique which is the most widespread multicarrier modulation in recent radio communications systems. However, its major drawback is the high PAPR value, which degrades the transmission quality due to the PA nonlinearities. To reduce the PAPR, we first propose to improve the TR method in terms of convergence speed and PAPR reduction, by studying several optimization algorithms. We show that the conjugate gradient algorithm provides the best performance while respecting the frequency specifica-tions of the IEEE 802.11a standard. Thereafter, TR method has been evaluated experimentally in the presence of a commercial PA (SZP-2026Z) and using a measurement bench. It is shown that the TR method improves the quality of service (QoS), with 18% reduction in PA power consumption. The experimental study has resulted to choosing a realistic PA model consider-ing memory effects. This PA model has been integrated into a SISO simulation chain includ-ing also a realistic channel model. This chain is used to evaluate the TR method performances under realistic transmission conditions. Finally, we propose to apply the TR method in a closed-loop MIMO-OFDM chain dedicated to the transmission of scalable multimedia con-tent in a realistic context with the IEEE 802.1n standard. This study presents a new contribu-tion of the TR method evaluation to improve the visual quality of the JPWL transmitted imag-es, considering in the same time the multimedia content, the PA nonlinearity and the channel transmission distortions
35
Galdames, Francisco José. "Segmentation d'images IRM du cerveau pour la construction d'un modèle anatomique destiné à la simulation bio-mécanique." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENS007/document.
Повний текст джерелаАнотація:
Comment obtenir des données anatomiques pendant une neurochirurgie ? a été ce qui a guidé le travail développé dans le cadre de cette thèse. Les IRM sont actuellement utilisées en amont de l'opération pour fournir cette information, que ce soit pour le diagnostique ou pour définir le plan de traitement. De même, ces images pre-opératoires peuvent aussi être utilisées pendant l'opération, pour pallier la difficulté et le coût des images per-opératoires. Pour les rendre utilisables en salle d'opération, un recalage doit être effectué avec la position du patient. Cependant, le cerveau subit des déformations pendant la chirurgie, phénomène appelé Brain Shift, ce qui altère la qualité du recalage. Pour corriger cela, d'autres données pré-opératoires peuvent être acquises, comme la localisation de la surface corticale, ou encore des images US localisées en 3D. Ce nouveau recalage permet de compenser ce problème, mais en partie seulement. Ainsi, des modèles mécaniques ont été développés, entre autres pour apporter des solutions à l'amélioration de ce recalage. Ils permettent ainsi d'estimer les déformations du cerveau. De nombreuses méthodes existent pour implémenter ces modèles, selon différentes lois de comportement et différents paramètres physiologiques. Dans tous les cas, cela requiert un modèle anatomique patient-spécifique. Actuellement, ce modèle est obtenu par contourage manuel, ou quelquefois semi-manuel. Le but de ce travail de thèse est donc de proposer une méthode automatique pour obtenir un modèle du cerveau adapté sur l'anatomie du patient, et utilisable pour une simulation mécanique. La méthode implémentée se base sur les modèles déformables pour segmenter les structures anatomiques les plus pertinentes dans une modélisation bio-mécanique. En effet, les membranes internes du cerveau sont intégrées: falx cerebri and tentorium cerebelli. Et bien qu'il ait été démontré que ces structures jouent un rôle primordial, peu d'études les prennent en compte. Par ailleurs, la segmentation résultante de notre travail est validée par comparaison avec des données disponibles en ligne. De plus, nous construisons un modèle 3D, dont les déformations seront simulées en utilisant une méthode de résolution par Éléments Finis. Ainsi, nous vérifions par des expériences l'importance des membranes, ainsi que celle des paramètres physiologiquesThe general problem that motivates the work developed in this thesis is: how to obtain anatomical information during a neurosurgery?. Magnetic Resonance (MR) images are usually acquired before the surgery to provide anatomical information for diagnosis and planning. Also, the same images are commonly used during the surgery, because to acquire MRI images in the operating room is complex and expensive. To make these images useful inside the operating room, a registration between them and the patient's position has to be processed. The problem is that the brain suffers deformations during the surgery, in a process called brain shift, degrading the quality of registration. To correct this, intra-operative information may be used, for example, the position of the brain surface or US images localized in 3D. The new registration will compensate this problem, but only to a certain extent. Mechanical models of the brain have been developed as a solution to improve this registration. They allow to estimate brain deformation under certain boundary conditions. In the literature, there are a variety of methods for implementing these models, different equation laws used for continuum mechanic, and different reported mechanical properties of the tissues. However, a patient specific anatomical model is always required. Currently, most mechanical models obtain the associated anatomical model by manual or semi-manual segmentation. The aim of this thesis is to propose and implement an automatic method to obtain a model of the brain fitted to the patient's anatomy and suitable for mechanical modeling. The implemented method uses deformable model techniques to segment the most relevant anatomical structures for mechanical modeling. Indeed, the internal membranes of the brain are included: falx cerebri and tentorium cerebelli. Even though the importance of these structures is stated in the literature, only a few of publications include them in the model. The segmentation obtained by our method is assessed using the most used online databases. In addition, a 3D model is constructed to validate the usability of the anatomical model in a Finite Element Method (FEM). And the importance of the internal membranes and the variation of the mechanical parameters is studied
36
Krah, Tim. "Development and application of a selected configuration interaction method : from dispersive interactions to photo-induced magnetism in Prussian blue analogues." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAF035/document.
Повний текст джерелаАнотація:
Dans une première partie, la structure électronique de deux membres de la famille des Analogues de Bleu de Prusse (ABP) a été inspectée à l'aide de méthodes basées sur la fonction d'onde. Dans l'ABP NiFe, un changement du couplage magnétique a été mis en évidence lors d'une déformation structurale locale. Basé sur les résultats obtenus pour l'ABP CoFe, un rôle clé dans le processus photomagnétique observé dans ce matériau est attribué aux lacunes cristallines. Dans une deuxième partie, un développement méthodologique a été mené jusqu'à l'implémentation de la méthode FRACCIS (FRAgmented Contracted Configuration Interaction of Single excitations). Elle permet de concentrer l'effort numérique sur un petit nombre de déterminants physiquement importants. De plus, elle constitue un outil d'analyse pour mesurer l'importance de certaines excitations dans le système inspecté. L'application à (H2)2 et C4H6 montre qu'une réduction majeure de l'espace d'IC est possible en gardant une bonne précision par rapport aux valeurs de référence. Ce travail contribue aux efforts vers l'analyse rationnelle de la corrélation électroniqueIn the first part, the electronic structure of two members of the family of Prussian Blue Analogues (PBA) has been inspected using wave function-based methods. The NiFe PBA exhibits a change of the magnetic coupling under a local structural deformation. Based on the results obtained for the CoFe PBA, a key role in the photomagnetic process observed in this material is attributed to the crystal vacancies. In a second part, a methodological development has been carried out and has lead to the implementation of the FRACCIS method (FRAgmented Contracted Configuration Interaction of Single excitations). It allows to concentrate the numerical effort on a small number of physically relevant determinants. Furthermore, it constitutes an analysis tool to measure the importance of certain excitations in the inspected system. The application to (H2)2 et C4H6 shows that a major reduction of the CI space is possible while keeping good accuracy with respect to reference values. This work contributes to the efforts towards a rational analysis of electronic correlation
37
Wåhlin, Pernilla. "Theoretical Actinide Chemistry – Methods and Models." Doctoral thesis, Stockholms universitet, Fysikum, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-54848.
Повний текст джерелаАнотація:
The chemistry of actinides in aqueous solution is important, and it is essential to build adequate conceptual models and develop methods applicable for actinide systems. The complex electronic structure makes benchmarking necessary. In the thesis a prototype reaction of the water exchange reaction for uranyl(VI), for both ground and luminescent states, described with a six-water model, was used to study the applicability of density functional methods on actinides and different solvation models. An excellent agreement between the wave function methods CCSD(T) and MP2 was obtained in the ground state, implying that near-minimal CASPT2 can be used with confidence for the reaction in the luminescent state of uranyl(VI), while density functionals are not suited to describe energetics for this type of reaction. There was an ambiguity concerning the position of the waters in the second hydration sphere. This issue was resolved by investigating a larger model, and prop- erly used the six-water model was found to adequately describe the water exchange reaction. The effect of solvation was investigated by comparing the results from conductor-like polarizable continuum models using two cavity models. Scattered numbers made it difficult to determine which solvation model to use. The final conclusion was that the water exchange reaction in the luminescent state of uranyl(VI) should be addressed with near-minimal CASPT2 and a solvation model without explicit cavities for hydrogens. Finally it was shown that no new chemistry appears in the luminescent state for this reaction. The thesis includes a methodological investigation of a multi-reference density functional method based on a range separation of the two-electron interaction. The method depends on a universal parameter, which has been determined for lighter elements. It is shown here that the same parameter could be used for actinides, a prerequisite for further development of the method. The results are in that sense promising.
38
Hureau, Jacques. "La transformation conforme et l'etude numerique d'ecoulements stationnaires ou instationnaires autour d'obstacles avec sillage." Orléans, 1988. http://www.theses.fr/1988ORLE2008.
Повний текст джерелаАнотація:
Description d'une methode numerique pour decrire l'ecoulement avec sillage autour d'un profil deformable. La methode utilise la transformation conforme du profil sur un cercle unite. Rappel de la theorie du profil deformable et de l'emission tourbillonnaire. Presentation d'un logiciel decrivant l'ecoulement
39
Itta, Francesca. "Biomechanical modeling of parotid glands morphing in head & neck radiation therapy treatments." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11221/.
Повний текст джерелаАнотація:
Durante i trattamenti radioterapici dei pazienti oncologici testa-collo, le ghiandole parotidee (PGs) possono essere indebitamente irradiate a seguito di modificazioni volumetriche-spaziali inter/intra-frazione causate da fattori quali il dimagrimento, l’esposizione a radiazioni ionizzanti ed il morphing anatomico degli organi coinvolti nelle aree d’irraggiamento. Il presente lavoro svolto presso la struttura di Fisica Medica e di Radioterapia Oncologica dell’A.O.U di Modena, quale parte del progetto di ricerca del Ministero della Salute (MoH2010, GR-2010-2318757) “ Dose warping methods for IGRT and Adaptive RT: dose accumulation based on organ motion and anatomical variations of the patients during radiation therapy treatments ”, sviluppa un modello biomeccanico in grado di rappresentare il processo di deformazione delle PGs, considerandone la geometria, le proprietà elastiche e l'evoluzione durante il ciclo terapeutico. Il modello di deformazione d’organo è stato realizzato attraverso l’utilizzo di un software agli elementi finiti (FEM). Molteplici superfici mesh, rappresentanti la geometria e l’evoluzione delle parotidi durante le sedute di trattamento, sono state create a partire dai contorni dell’organo definiti dal medico radioterapista sull’immagine tomografica di pianificazione e generati automaticamente sulle immagini di setup e re-positioning giornaliere mediante algoritmi di registrazione rigida/deformabile. I constraints anatomici e il campo di forze del modello sono stati definiti sulla base di ipotesi semplificative considerando l’alterazione strutturale (perdita di cellule acinari) e le barriere anatomiche dovute a strutture circostanti. L’analisi delle mesh ha consentito di studiare la dinamica della deformazione e di individuare le regioni maggiormente soggette a cambiamento. Le previsioni di morphing prodotte dal modello proposto potrebbero essere integrate in un treatment planning system per metodiche di Adaptive Radiation Therapy.
40
Costa, Jorge Carvalho. "Essential boundary and interface conditions in the meshless analysis of shells." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/3/3144/tde-24082016-080545/.
Повний текст джерелаАнотація:
Meshless methods provide a highly continuous approximation field, convenient for thin structures like shells. Nevertheless, the lack of Kronecker Delta property makes the formulation of essential boundary conditions not straightforward, as the trial and test fields cannot be tailored to boundary values. Similar problem arise when different approximation regions must be joined, in a multi-region problem, such as kinks, folds or joints. This work presents three approaches to impose both kinematic conditions: the well known Lagrange Multiplier method, used since the beginning of the Element Free Galerkin method; a pure penalty approach; and the recently rediscovered alternative of Nitsche\'s Method. We use the EFG discretization technique for thick Reissner-Mindlin shells and adapt the weak form as to separate displacement and rotational degrees of freedom and obtain suitable and separate stabilization parameters. This approach enables the modeling of discontinuous shells and local refinement on multi-region problems.Métodos sem malha geram campos de aproximação com alta continuidade, convenientes para estruturas finas como cascas. No entanto, a ausência da propriedade de Delta de Kronecker dificulta a formulação de condições essenciais de contorno, já que os campos de aproximação e teste não podem ser moldados aos valores de contorno. Um problema similar aparece quando diferentes regiões de aproximação precisam ser juntadas em um problema multi-regiões como dobras, vincos ou junções. Este trabalho apresenta três métodos de imposição ambas condições cinemáticas: o já conhecido método dos multiplicadores de Lagrange, usado desde o começo do método de Galekin sem elementos (EFG); uma abordagem de penalidade pura; e o recentemente redescoberto método de Nitsche. Nós usamos a técnica de discretização com EFG para cascas espessas de Reissner-Mindlin e adaptamos a forma fraca de forma a separar graus de liberdade de deslocamento e rotação e obter coeficientes de estabilização diferentes e apropriados. Essa abordagem permite a modelagem de cascas discontínuas e o refinamento local em problemas multi-regiões.
41
Hui, Fei. "Visual Tracking of Deformation and Classification of Object Elasticity with Robotic Hand Probing." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36477.
Повний текст джерелаАнотація:
Performing tasks with a robotic hand often requires a complete knowledge of the manipulated object, including its properties (shape, rigidity, surface texture) and its location in the environment, in order to ensure safe and efficient manipulation. While well-established procedures exist for the manipulation of rigid objects, as well as several approaches for the manipulation of linear or planar deformable objects such as ropes or fabric, research addressing the characterization of deformable objects occupying a volume remains relatively limited. The fundamental objectives of this research are to track the deformation of non-rigid objects under robotic hand manipulation using RGB-D data, and to automatically classify deformable objects as either rigid, elastic, plastic, or elasto-plastic, based on the material they are made of, and to support recognition of the category of such objects through a robotic probing process in order to enhance manipulation capabilities. The goal is not to attempt to formally model the material of the object, but rather employ a data-driven approach to make decisions based on the observed properties of the object, capture implicitly its deformation behavior, and support adaptive control of a robotic hand for other research in the future. The proposed approach advantageously combines color image and point cloud processing techniques, and proposes a novel combination of the fast level set method with a log-polar mapping of the visual data to robustly detect and track the contour of a deformable object in a RGB-D data stream. Dynamic time warping is employed to characterize the object properties independently from the varying length of the detected contour as the object deforms. The research results demonstrate that a recognition rate over all categories of material of up to 98.3% is achieved based on the detected contour. When integrated in the control loop of a robotic hand, it can contribute to ensure stable grasp, and safe manipulation capability that will preserve the physical integrity of the object.
42
Qasim, Lara. "System reconfiguration : A Model based approach; From an ontology to the methodology bridging engineering and operations Model-Based System Reconfiguration: A Descriptive Study of Current Industrial Challenges Towards a reconfiguration framework for systems engineering integrating use phase data An overall Ontology for System Reconfiguration using Model-Based System Engineering An Ontology for System Reconfiguration: Integrated Modular Avionics IMA Case Study A model-based method for System Reconfiguration." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPAST031.
Повний текст джерелаАнотація:
Les évolutions des systèmes doivent être gérées de manière à garantir l'efficacité et l'efficience du système tout au long de son cycle de vie, en particulier lorsqu'il s'agit de systèmes complexes qui nécessitent des années de développement et des dizaines d'années d'utilisation. La reconfiguration des systèmes est primordiale pour la gestion des systèmes complexes, car elle permet d'assurer la flexibilité et l'adaptabilité des systèmes en ce qui concerne leur évolution. La reconfiguration des systèmes assure l'efficacité opérationnelle et augmente les qualités des systèmes (par exemple, la fiabilité, la disponibilité, la sécurité, etc.).Cette thèse a été effectuée en partenariat avec une entreprise évoluant dans les domaines de l’aérospatial, de l’espace, du transport, de la défense et de la sécurité. Les entreprises portent un intérêt croissant sur la reconfiguration des systèmes afin de garantir leurs efficacités opérationnelles. L’objectif de cette thèse est de proposer une approche basée sur les modèles pour soutenir la reconfiguration de système.En effectuant une étude descriptive, basée sur une étude de terrain et l’analyse de l’état de l’art, le développement d’un support lié à la reconfiguration de système a été identifié comme enjeu industriel majeur. Le défi principal consiste à identifier les données relatives à la reconfiguration des systèmes et leurs mécanismes d’intégration afin d’atteindre cet objectif.Dans cette thèse, nous présentons une ontologie, que nous avons nommé OSysRec, qui intègre les données nécessaires pour la reconfiguration et gestion des systèmes. De plus, OSysRec agrège les trois aspects indispensables à la gestion des process de la reconfiguration de système: la structure, la dynamique, et la gestion.Nous présentons également une méthode basée sur les modèles (MBSysRec) qui intègre les données de reconfiguration et fait le lien entre les phases d’ingénierie et d’opération. Cette méthode est multidisciplinaire qui implique des générations combinatoires de configurations et des décisions multicritères pour leurs évaluations et sélections. Nous avons pu démontrer sur deux cas d’étude la validité de cette méthode pour trouver des solutions performantes et pertinentes.Cette thèse est un premier étape pour la mise en œuvre d’une approche basée sur les modèles pour la reconfiguration de système permettant leur flexibilité et leur adaptabilitéSystem evolutions have to be managed to ensure system effectiveness and efficiency through its whole lifecycle, particularly when it comes to complex systems that take years of development and dozens of years of usage. System Reconfiguration is key in complex systems management, as it is an enabler of system flexibility and adaptability regarding system evolutions. System reconfiguration ensures operational effectiveness and increases system qualities (e.g., reliability, availability, safety, and usability).This research has been conducted in the context of a large international aerospace, space, ground transportation, defense, and security company. This research aims at supporting system reconfiguration during operations.First, we conducted a descriptive study based on a field study and a literature review to identify the industrial challenges related to system reconfiguration. The main issue lies in the development of reconfiguration support. More specifically, challenges related to data identification and integration were identified.In this thesis, we present the OSysRec ontology, which captures and formalizes the reconfiguration data. The ontology synthesizes the structure, dynamics, and management aspects necessary to support the system reconfiguration process in an overall manner.Furthermore, we present a model-based method (MBSysRec) that integrates system reconfiguration data and bridges both the engineering and the operational phases. MBSysRec is a multidisciplinary method that involves combinatorial configuration generation and a multi-criteria decision-making method for configuration evaluation and selection.This thesis is a step towards a model-based approach for system reconfiguration of evolving systems, ensuring their flexibility and adaptability
43
Bousquet, Guillaume. "Déformation et découpe interactive de solides à géométrie complexe." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00877898.
Повний текст джерелаАнотація:
Cette thèse consiste à explorer une nouvelle approche pour la simulation d'objets flexibles par la mécanique des milieux continus, dans le cadre d'applications graphiques interactives telles que le jeu vidéo ou l'entraînement aux gestes chirurgicaux. Elle s'inscrit en continuité d'un stage de M2-R sur ce même sujet. Il est important de pouvoir régler simplement un compromis entre précision et temps de calcul suivant la nature de l'application. Les approches actuelles de simulation utilisent principalement la méthode des éléments finis. Celle-ci repose sur un maillage volumique des objets qu'il est souvent difficile d'adapter dynamiquement aux besoins de l'application. La nouveauté introduite par cette thèse est d'utiliser des repères déformables comme primitives cinématiques, avec des champs de déplacements inspirés des méthodes de 'skinning' utilisées en informatique graphique. Le but est d'éviter ainsi les difficultés liées au maillage volumique, ainsi que de faciliter le raffinement et la simplification adaptatives par simple ajout ou suppression de repère déformable là où c'est souhaitable. Ce travail est financé par le projet européen 'Passport for Virtual Surgery', dont le but est de créer automatiquement des modèles physiques pour l'entraînement aux gestes de chirurgie hépatique, à partir de données médicales et anatomiques personnalisées. Dans ce contexte, Guillaume, en collaboration avec d'autres membres du projet, mettra en place les outils nécessaires pour construire la scène physique à partir d'images médicales segmentées et de connaissances anatomiques génériques. Le foie sera dans un premier temps représenté par des modèles physiques précédemment développés à EVASION et étendus aux opérations de découpe. Par la suite, il y appliquera son nouveau modèle mécanique basé sur des repères déformables. The aim of this thesis is to develop a new approach for the simulation of flexible objects based on the continous middle method, related with interactive graphics applications such as video games or training in surgery. It is a continuity of the M2 research internship on the same topic. It is important to simply settle a compromise between accuracy and time computing according to the application. Current simulation approaches mainly use the finite element method, which is based on a volumetric mesh of the simulated objects. It is often difficult to dynamically adapt the needs to the application. The novelty of this thesis is to use deformable reference frames as kinematic primitives, with displacement fields based on 'skinning' methods used in computer graphics. The aim is to avoid the difficulties associated with volumetric mesh, and make the refinement and the adaptive simplification easier by adding or deleting deformable reference frames if necessary. This work is funded by the European project 'Passport for Virtual Surgery', which aims to automatically create models for physical training in gestures of liver surgery, from medical and anatomical custom data. In this context, Guillaume, in collaboration with other members of the project, will develop the tools necessary to build the physical scene from segmented medical images and generic anatomical knowledge. The liver will initially be represented by physical models previously developed in the EVASION team and then extended to cutting operations. Thereafter, Guillaume will apply his new mechanical model based on deformable reference frames.
44
Akteke, Basak. "Derivative Free Optimization Methods: Application In Stirrer Configuration And Data Clustering." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/2/12606591/index.pdf.
Повний текст джерелаАнотація:
Recent developments show that derivative free methods are highly demanded by researches for solving optimization problems in various practical contexts.
Although well-known optimization methods that employ derivative information can be very effcient, a derivative free method will be more effcient in cases
where the objective function is nondifferentiable, the derivative information is
not available or is not reliable. Derivative Free Optimization (DFO) is developed
for solving small dimensional problems (less than 100 variables) in which
the computation of an objective function is relatively expensive and the derivatives
of the objective function are not available. Problems of this nature more
and more arise in modern physical, chemical and econometric measurements
and in engineering applications, where computer simulation is employed for the
evaluation of the objective functions.
In this thesis, we give an example of the implementation of DFO in an approach
for optimizing stirrer configurations, including a parametrized grid generator,
a flow solver, and DFO. A derivative free method, i.e., DFO is preferred because
the gradient of the objective function with respect to the stirrer&rsquos design variables is not directly available. This nonlinear objective function is obtained from the flow field by the flow solver. We present and interpret numerical results of this implementation. Moreover, a contribution is given to a survey and a distinction of DFO research directions, to an analysis and discussion of these. We also state a derivative free algorithm used within a clustering algorithm in combination with non-smooth optimization techniques to reveal the effectiveness of derivative free methods in computations. This algorithm is applied on some data sets from various sources of public life and medicine. We compare various methods, their practical backgrounds, and conclude with a summary and outlook. This work may serve as a preparation of possible future research.
45
Boussaid, Haithem. "Efficient inference and learning in graphical models for multi-organ shape segmentation." Thesis, Châtenay-Malabry, Ecole centrale de Paris, 2015. http://www.theses.fr/2015ECAP0002/document.
Повний текст джерелаАнотація:
Cette thèse explore l’utilisation des modèles de contours déformables pour la segmentation basée sur la forme des images médicales. Nous apportons des contributions sur deux fronts: dans le problème de l’apprentissage statistique, où le modèle est formé à partir d’un ensemble d’images annotées, et le problème de l’inférence, dont le but est de segmenter une image étant donnée un modèle. Nous démontrons le mérite de nos techniques sur une grande base d’images à rayons X, où nous obtenons des améliorations systématiques et des accélérations par rapport à la méthode de l’état de l’art. Concernant l’apprentissage, nous formulons la formation de la fonction de score des modèles de contours déformables en un problème de prédiction structurée à grande marge et construisons une fonction d’apprentissage qui vise à donner le plus haut score à la configuration vérité-terrain. Nous intégrons une fonction de perte adaptée à la prédiction structurée pour les modèles de contours déformables. En particulier, nous considérons l’apprentissage avec la mesure de performance consistant en la distance moyenne entre contours, comme une fonction de perte. L’utilisation de cette fonction de perte au cours de l’apprentissage revient à classer chaque contour candidat selon sa distance moyenne du contour vérité-terrain. Notre apprentissage des modèles de contours déformables en utilisant la prédiction structurée avec la fonction zéro-un de perte surpasse la méthode [Seghers et al. 2007] de référence sur la base d’images médicales considérée [Shiraishi et al. 2000, van Ginneken et al. 2006]. Nous démontrons que l’apprentissage avec la fonction de perte de distance moyenne entre contours améliore encore plus les résultats produits avec l’apprentissage utilisant la fonction zéro-un de perte et ce d’une quantité statistiquement significative.Concernant l’inférence, nous proposons des solveurs efficaces et adaptés aux problèmes combinatoires à variables spatiales discrétisées. Nos contributions sont triples: d’abord, nous considérons le problème d’inférence pour des modèles graphiques qui contiennent des boucles, ne faisant aucune hypothèse sur la topologie du graphe sous-jacent. Nous utilisons un algorithme de décomposition-coordination efficace pour résoudre le problème d’optimisation résultant: nous décomposons le graphe du modèle en un ensemble de sous-graphes en forme de chaines ouvertes. Nous employons la Méthode de direction alternée des multiplicateurs (ADMM) pour réparer les incohérences des solutions individuelles. Même si ADMM est une méthode d’inférence approximative, nous montrons empiriquement que notre implémentation fournit une solution exacte pour les exemples considérés. Deuxièmement, nous accélérons l’optimisation des modèles graphiques en forme de chaîne en utilisant l’algorithme de recherche hiérarchique A* [Felzenszwalb & Mcallester 2007] couplé avec les techniques d’élagage développés dans [Kokkinos 2011a]. Nous réalisons une accélération de 10 fois en moyenne par rapport à l’état de l’art qui est basé sur la programmation dynamique (DP) couplé avec les transformées de distances généralisées [Felzenszwalb & Huttenlocher 2004]. Troisièmement, nous intégrons A* dans le schéma d’ADMM pour garantir une optimisation efficace des sous-problèmes en forme de chaine. En outre, l’algorithme résultant est adapté pour résoudre les problèmes d’inférence augmentée par une fonction de perte qui se pose lors de l’apprentissage de prédiction des structure, et est donc utilisé lors de l’apprentissage et de l’inférence. [...]This thesis explores the use of discriminatively trained deformable contour models (DCMs) for shape-based segmentation in medical images. We make contributions in two fronts: in the learning problem, where the model is trained from a set of annotated images, and in the inference problem, whose aim is to segment an image given a model. We demonstrate the merit of our techniques in a large X-Ray image segmentation benchmark, where we obtain systematic improvements in accuracy and speedups over the current state-of-the-art. For learning, we formulate training the DCM scoring function as large-margin structured prediction and construct a training objective that aims at giving the highest score to the ground-truth contour configuration. We incorporate a loss function adapted to DCM-based structured prediction. In particular, we consider training with the Mean Contour Distance (MCD) performance measure. Using this loss function during training amounts to scoring each candidate contour according to its Mean Contour Distance to the ground truth configuration. Training DCMs using structured prediction with the standard zero-one loss already outperforms the current state-of-the-art method [Seghers et al. 2007] on the considered medical benchmark [Shiraishi et al. 2000, van Ginneken et al. 2006]. We demonstrate that training with the MCD structured loss further improves over the generic zero-one loss results by a statistically significant amount. For inference, we propose efficient solvers adapted to combinatorial problems with discretized spatial variables. Our contributions are three-fold:first, we consider inference for loopy graphical models, making no assumption about the underlying graph topology. We use an efficient decomposition-coordination algorithm to solve the resulting optimization problem: we decompose the model’s graph into a set of open, chain-structured graphs. We employ the Alternating Direction Method of Multipliers (ADMM) to fix the potential inconsistencies of the individual solutions. Even-though ADMMis an approximate inference scheme, we show empirically that our implementation delivers the exact solution for the considered examples. Second,we accelerate optimization of chain-structured graphical models by using the Hierarchical A∗ search algorithm of [Felzenszwalb & Mcallester 2007] couple dwith the pruning techniques developed in [Kokkinos 2011a]. We achieve a one order of magnitude speedup in average over the state-of-the-art technique based on Dynamic Programming (DP) coupled with Generalized DistanceTransforms (GDTs) [Felzenszwalb & Huttenlocher 2004]. Third, we incorporate the Hierarchical A∗ algorithm in the ADMM scheme to guarantee an efficient optimization of the underlying chain structured subproblems. The resulting algorithm is naturally adapted to solve the loss-augmented inference problem in structured prediction learning, and hence is used during training and inference. In Appendix A, we consider the case of 3D data and we develop an efficientmethod to find the mode of a 3D kernel density distribution. Our algorithm has guaranteed convergence to the global optimum, and scales logarithmically in the volume size by virtue of recursively subdividing the search space. We use this method to rapidly initialize 3D brain tumor segmentation where we demonstrate substantial acceleration with respect to a standard mean-shift implementation. In Appendix B, we describe in more details our extension of the Hierarchical A∗ search algorithm of [Felzenszwalb & Mcallester 2007] to inference on chain-structured graphs
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Pascon, João Paulo. "Modelos constitutivos para materiais hiperelásticos: estudo e implementação computacional." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-17042008-084851/.
Повний текст джерелаАнотація:
O objetivo central deste trabalho é implementar modelos constitutivos hiperelásticos não lineares em um código computacional que faz análise não linear geométrica de cascas. São necessários, para este propósito, conceitos sobre álgebras linear e tensorial, cinemática, deformação, tensão, balanços, princípios variacionais, métodos numéricos e hiperelasticidade. Tal programa usa a formulação Lagrangiana posicional, o método dos elementos finitos, o princípio dos trabalhos virtuais e o método iterativo de Newton-Raphson para solução das equações não lineares. O elemento finito de casca possui dez nós, sete parâmetros por nó e variação linear da deformação ao longo da espessura. Para dedução dos novos modelos usou-se a decomposição multiplicativa do gradiente da função mudança de configuração, o tensor deformação de Green-Lagrange e o tensor da tensão de Piola-Kirchhoff de segunda espécie. O código desenvolvido foi usado em simulações de diversos exemplos e apresentou boa precisão na análise mecânica de polímeros naturais altamente deformáveis. A ocorrência do fenômeno travamento não se manifestou nas análises realizadas. A presente pesquisa confirmou outros trabalhos, reforçou a necessidade de se usar modelos hiperelásticos não lineares para simular o comportamento mecânico de polímeros naturais e apresentou resultados condizentes com dados experimentais existentes na literatura científica e às respectivas soluções analíticas.The main objective of this work is to implement nonlinear hyperelastic constitutive models in a computational code of geometrically nonlinear analysis of shells. For this purpose, concepts of linear and tensor algebras, kinematics, strain, stress, balances, variational principles, numerical methods and hyperelasticity are necessary. Such program uses the positional Lagrangian formulation, the finite element method, the principle of virtual work and the iterative method of Newton-Raphson for the solution of the nonlinear equations. The shell finite element has ten nodes, seven parameters per node and presents linear variation of the strain along the thickness. To achieve the new constitutive models the multiplicative decomposition of the deformation gradient, the Green-Lagrange strain tensor and the second Piola-Kirchhoff stress tensor are used. The developed code is tested for simulations of various examples and presents good accuracy in the mechanical analysis of highly deformable natural rubber. The locking phenomena didn\'t appear in the proposed analysis. The present research confirms other works, corroborates the need of using nonlinear hyperelastic models to simulate the mechanical behavior of natural rubber and presents suitable results when compared to existent experimental data of the scientific literature and to the respective analytical solutions.
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Bally, Benjamin. "Description des noyaux impairs à l'aide d'une méthode de fonctionnelle énergie de la densité à plusieurs états de référence." Phd thesis, Bordeaux, 2014. http://tel.archives-ouvertes.fr/tel-01023059.
Повний текст джерелаАнотація:
Dans ce manuscrit de thèse, nous nous intéressons à la description des noyaux atomiques composés d'un nombre impair de nucléons dans la méthode dite de la fonctionnelle énergie de la densité (EDF). Plus précisément, nous présentons et appliquons dans le cas de ces noyaux, des extensions à cette méthode : (i) la projection sur les bons nombres quantiques, (ii) le mélange de configurations à travers la méthode des coordonnées génératrices (GCM), qui permettent de prendre en compte dans nos calculs des corrélations de type " au-delà du champ moyen " entre les nucléons constituant le noyau. De telles extensions n'avaient jusqu'alors été employées, dans leurs versions les plus générales, qu'aux noyaux ayant à la fois un nombre pair de neutrons et de protons, et nous nous proposons donc de démontrer leurs applicabilités également dans le cas des noyaux impairs. Dans la première partie de ce travail, nous présentons le formalisme mathématique de la méthode EDF, en mettant tout particulièrement l'accent sur le traitement des symétries dans cette approche. Dans la seconde partie du manuscrit, nous appliquons notre modèle au cas du noyau de Mg25 et analysons les résultats sous différents angles (ex : précision numérique des résultats, convergence du mélange de configurations, comparaison avec les données expérimentales connues). Les premiers résultats obtenus dans ce travail de thèse sont encourageants et démontrent l'intérêt de notre approche pour les calculs théoriques de structure nucléaire.
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Ghaffari, Dehkharghani Seyed Amin. "Simulations numériques d’écoulements incompressibles interagissant avec un corps déformable : application à la nage des poissons." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4369/document.
Повний текст джерелаАнотація:
Une méthode numérique précise et efficace est proposée pour la simulation de corps déformables interagissant avec un écoulement incompressible. Les équations de Navier-Stokes, considérées dans leur formulation vorticité fonction de courant, sont discrétisées temporellement et spatialement à l'aide respectivement d'un schéma d'ordre 4 de Runge-Kutta et par des différences finies compactes. Grâce à l'utilisation d'un maillage uniforme, nous proposons un nouveau solveur direct au quatrième ordre pour l'équation de Poisson, permettant de garantir l'incompressibilité au zéro machine sur une grille optimale. L'introduction d'un corps déformable dans l'écoulement de fluide est réalisée au moyen d'une méthode de pénalisation de volume. La déformation du corps est imposée par l'utilisation d'un maillage lagrangien structuré mobile qui interagit avec le fluide environnant en raison des forces hydrodynamiques et du moment (calculés sur le maillage eulérien de référence). Une loi de contrôle efficace de la courbure d'un poisson anguilliforme nageant vers une cible prescrite est proposée. La méthode numérique développée prouve son efficacité et précision tant dans le cas de la nage du poisson mais aussi plus d'un grand nombre de problèmes d'interactions fluide-structureWe present an efficient algorithm for simulation of deformable bodies interacting with two-dimensional incompressible flows. The temporal and spatial discretizations of the Navier--Stokes equations in vorticity stream-function formulation are based on classical fourth-order Runge--Kutta and compact finite differences, respectively. Using a uniform Cartesian grid we benefit from the advantage of a new fourth-order direct solver for the Poisson equation to ensure the incompressibility constraint down to machine zero over an optimal grid. For introducing a deformable body in fluid flow, the volume penalization method is used. A Lagrangian structured grid with prescribed motion covers the deformable body which is interacting with the surrounding fluid due to the hydrodynamic forces and the torque calculated on the Eulerian reference grid. An efficient law for controlling the curvature of an anguilliform fish, swimming toward a prescribed goal, is proposed which is based on the geometrically exact theory of nonlinear beams and quaternions. Validation of the developed method shows the efficiency and expected accuracy of the algorithm for fish-like swimming and also for a variety of fluid/solid interaction problems
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Gomes, José Osmar. "Configurações identitárias de uma autarquia pública no contexto da defesa e inspeção agropecuária na ótica dos gestores." reponame:Repositório Institucional da UFES, 2015. http://repositorio.ufes.br/handle/10/1685.
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Esta dissertação tem por objetivo compreender como as transformações no contexto da defesa sanitária e inspeção agropecuária entre 1996 e 2014 se relacionam com as configurações identitárias do Idaf manifestadas por gestores nesse contexto. Trata-se de uma pesquisa qualitativa que descreve os processos identitários da organização por um olhar interpretativista, pelo entendimento das relações simbólicas que permeiam essa organização, observados em discursos dos sujeitos. Para coleta dos dados foram utilizadas pesquisa documental e entrevistas semiestruturadas individuais. As entrevistas foram realizadas com cinco sujeitos da organização nos meses de setembro e outubro de 2014. O método de análise foi a Análise de Conteúdo (KRIPPENDORFF, 1990) que busca investigar dados textuais através de técnicas que permitam compreendê-los com seus significados, referências, valorações e intenções. Pretendeu-se contribuir, com esse estudo, para a compreensão da identidade organizacional, em uma organização pública, no contexto da defesa sanitária e inspeção agropecuária. Os resultados permitiram identificar o Idaf como único e distinto de outras organizações e como essa identificação está relacionada às transformações do contexto agropecuário.
This research aims to understand how changes in the context of health protection and agriculture inspection between 1996 and 2014 relate to the Idaf identity configurations expressed by managers in this context. It is a qualitative research that seek to describe the identity processes of the organization by an interpretive look at understanding the symbolic relations that permeate this organization, observed in speeches of the subjects. For data collection were used desk research and semi-structured individual interviews. Interviews were conducted with five subjects of the organization in the months of September and October 2014. The analysis method was content analysis (KRIPPENDORFF, 1990) that investigates textual data through techniques to understand them with their meanings, references , valuations and intentions. It was intended to contribute to this study, for understanding the organizational identity in a public organization in the context of health protection and agricultural inspection. The results showed the Idaf as unique and distinct from other organizations and how this identification is related to change in agricultural context.
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Tsai, Gweo-cherng, and 蔡虢城. "Fabrication of micro deformable focusing mirror by bonding method." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/95456418406644345409.
Повний текст джерелаАнотація:
碩士逢甲大學
機械工程學所
95
Micro-optical-electromechanical system, aiming at optical applications in MEMS, uses deformable mirrors to conduct adaptive optics devices and to change the focal length of the mirror. This thesis designed and fabricated micro deformable focusing mirror by bonding method. The novel micro deformable focusing mirror was actuated with electrostatics to adjust the focal length. In analysis, plate and shell theories are used to obtain the relations among deformation and electrostatic force. In fabrication, use the bulk-micromachining to produce upper and lower electrode structures. Finally, upper electrode structure bonded lower electrode structure by wafer bonding technology. To avoid the damage of high temperature and high voltage from anodic bonding method, this thesis rendered an idea which is using photo resist as medium.