Dissertations / Theses on the topic 'Stabilité des equilibres'
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Zaccaria, Federico. "Contributions à l'analyse de la performance des robots parallèles continus." Electronic Thesis or Diss., Ecole centrale de Nantes, 2023. http://www.theses.fr/2023ECDN0045.
Continuum parallel robots (CPRs) are manipulators employing multiple flexible beams arranged in parallel and connected to a rigid endeffector. CPRs promise higher payload and accuracy than serial CRs while keeping great flexibility. As the risk of injury during accidental contact between a human and a CPR should be reduced, CPRs may be used in large-scalecollaborative tasks or assisted robotic surgery. There exist various CPR designs, but the prototype conception is rarely based on performance considerations, and the CPRs realization in mainly based on intuitions or rigid-link parallel manipulators architectures. This thesis focuses on the performance analysis of CPRs, and the tools needed for such evaluation, such as workspace computation algorithms. In particular, workspace computation strategies for CPRs are essential for the performance assessment, since the CPRs workspace may be used as a performance index or it can serve for optimal-design tools. Two new workspace computation algorithms are proposed in this manuscript, the former focusing on the workspace volume computation and the certification of its numerical results, while the latter aims at computing the workspace boundary only. Due to the elastic nature of CPRs, a key performance indicator for these robots is the stability of their equilibrium configurations. This thesis proposes the experimental validation of the equilibrium stability assessment on a real prototype, demonstrating limitations of some commonly used assumptions. Additionally, a performance index measuring the distance to instability is originally proposed in this manuscript. Differently from themajority of the existing approaches, the clear advantage of the proposed index is a sound physical meaning; accordingly, the index can be used for a more straightforward performance quantification, and to derive robot specifications
Boulogne, Thomas. "Jeux stratégiques non-atomiques et applications aux réseaux." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2004. http://tel.archives-ouvertes.fr/tel-00008759.
Culverwell, Ian Dennis. "Resistive Z-pinch equilibria and stability." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/47833.
Li, Weiye. "Stability of equilibria in dynamic oligopolies." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/290535.
Longbottom, Aaron W. "The stability of magnetohydrostatic equilibria in the solar corona." Thesis, Edinburgh Napier University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385908.
Cloke, Martin. "Vortical equilibria of the Euler equations : construction and stability." Thesis, Imperial College London, 2007. http://hdl.handle.net/10044/1/1276.
Ianni, Antonella. "Interaction patterns, learning processes and equilibria in population games." Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244508.
Samà, Camí Anna. "Equilibria in Three Body Problems: stability, invariant tori and connections." Doctoral thesis, Universitat Autònoma de Barcelona, 2004. http://hdl.handle.net/10803/3087.
Nava, Gaxiola Citlalitl. "Point vortices on the hyperboloid." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/point-vortices-on-the-hyperboloid(7d806d94-b989-442e-a685-838fed01c0d4).html.
Akhtar, Mahmood. "Microemulsions formation, stability and their characterisations." Thesis, Brunel University, 1996. http://bura.brunel.ac.uk/handle/2438/5004.
Appella, Andrea. "Stabilità dei punti di equilibrio per sistemi di equazioni differenziali ordinarie." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Huynh, Vaiyee. "Stabilité Posturale d’un Exosquelette Actif de Jambes." Thesis, Ecole centrale de Nantes, 2017. http://www.theses.fr/2017ECDN0035/document.
The postural stability of leg exoskeletons, no matter their purposes (medical, military or civil), is a real issue since the user is fastened to them. Indeed, in order to respect the will of the user and his movements to the maximum, we have to study the system balance. Therefore, the purpose of this thesis is to develop balance strategies for a leg exoskeleton designed for industrial applications such as static work. It is about assisting the balance of the coupled system (user +exoskeleton) by dealing with the exoskeleton’s balance subjected to the user’s action. We present a balance control which is inspired by control methods developed by CEA-LIST for the Hercule exoskeleton, as well as by human balance strategies. It is mainly based on the instantaneous capture point concept. The first contribution of this thesis is the application of a classical instantaneous capture point control to a leg exoskeleton that assists a user. The user’s intention is first detected through the position of the instantaneous capture point and the assistance provided by the exoskeleton differs. The second contribution focuses on how we candistribute the effort to the legs. The experience of the «Master-Slave » control of CEA-LIST showed that the main difficulty, for a user, is to handle the weight transfer in order to take the swing leg off and make a step. We suggest a newleg distribution, that is able to anticipate a step. The last contribution is related to the underactuation of the exoskeleton in the double support phase. We propose an optimization algorithm that aims at following the leg distribution, and at managing the interaction forces between the user and the exoskeleton
LEE, HAN YEANG. "GARNET-ORTHOPYROXENE EQUILIBRIA IN THE FMAS SYSTEM: EXPERIMENTAL AND THEORETICAL STUDIES, AND GEOLOGICAL APPLICATIONS (GEOTHERMOMETRY, GEOBAROMETRY)." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183775.
JADANZA, RICCARDO DANILO. "Morse index and linear stability of relative equilibria in singular mechanical systems." Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2599754.
Cerfon, Antoine Julien. "Analytic calculations of MHD equilibria and of MHD stability boundaries in fusion plasmas." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/76494.
Cataloged from PDF version of thesis.
Includes bibliographical references.
In this work, two separate aspects of ideal MHD theory are considered. In the first part, analytic solutions to the Grad-Shafranov equation (GSE) are presented, for two families of source functions: functions which are linear in the flux function T , and functions which are quadratic in T. The solutions are both simple and very versatile, since they describe equilibria in standard tokamaks, spherical tokamaks, spheromaks, and field reversed configurations. They allow arbitrary aspect ratio, elongation, and triangularity as well as a plasma surface that can be smooth or possess a double or single null divertor X-point. The solutions can also be used to evaluate the equilibrium beta limit in a tokamak and spherical tokamak in which a separatrix moves onto the inner surface of the plasma. In the second part, the reliability of the ideal MHD energy principle in fusion grade plasmas is assessed. Six models are introduced, which are constructed to better describe plasma collisonality regimes for which the approximations of ideal MHD are not justified. General 3-D quadratic energy relations are derived for each of these six models, and compared with the ideal MHD energy principle. Stability comparison theorems are presented. The main conclusion can be summarized in two points. (1) In systems with ergodic magnetic field lines, ideal MHD accurately predicts marginal stability, even in fusion grade plasmas. (2) In closed field line geometries, however, the ideal MHD predictions must be modified. Indeed, it is found that in collisionless plasmas, the marginal stability condition for MHD modes is inherently incompressible for ion distribution functions that depend only on total energy. The absence of compressibility stabilization is then due to wave particle resonances. An illustration of the vanishing of plasma compressibility stabilization in closed line systems is given by studying the particular case of the hard-core Z-pinch.
by Antoine Julien Cerfon.
Ph.D.
D'Izzia, Salvatore. "stabilita' delle soluzioni di equazioni differenziali e dinamica delle popolazioni." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Saramito, Bernard. "Analyse mathematique et numerique de la stabilite d'un plasma." Paris 6, 1987. http://www.theses.fr/1987PA066615.
Marin, Thibault. "Conception et validation d'un nouvel outil d'évaluation de la stabilité posturale en position érigée." Thesis, Reims, 2018. http://www.theses.fr/2018REIMS035.
Design and validation of a new tool for assessing postural stability in quiet standing(SAP3D: 3D Postural Analysis System)Postural stability in quiet standing is a subject’s ability to maintain its balance or to regain it after a perturbation. Multiple organs contribute to ensure postural stability, under a regulation ensured by the central nervous system. The alteration of one or several of these organs (following a trauma, a pathology or simply due to ageing) modifies the subject’s behavior and its ability to maintain stability. Current systems for postural evaluation rely mostly on center of pressure and/or center of mass assessment, disregarding the intersegmental postural behavior: such measurements are possible, but most tools are complex and expensive. The SAP3D system was developed as a new tool for postural stability assessment, allowing for center of mass and multi-segmental three dimensional modeling based on a single inexpensive camera. Validation of the SAP3D system compared to a standard optoelectronic system shows excellent agreement and a satisfyingly low average residue between the two systems. In a clinical setup, the SAP3D system confirms that postural steadiness mechanisms are i) less efficient with eyes closed than eyes opened; ii) negatively affected by ageing; iii) positively affected by regular practice of an activity such as dancing, at least for young women; iv) altered in pathological or injured patients. Although many technical improvements are being considered, the SAP3D system is a reliable, quick, accessible and low-cost clinical alternative to the existing systems for postural evaluation.Keywords: balance; steadiness; motor control; kinematics; center of mass; elderly; ageing; dance; low-cost
Wilson, Fiona. "Equilibrium and stability properties of collisionless current sheet models." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/3548.
Serban, Ionel. "Analyse multifactorielle de l'influence de l'environnement sur la stabilité et la locomotion humaine." Thesis, Artois, 2011. http://www.theses.fr/2011ARTO0205/document.
The thesis Contributions to research concerning the influences of the environment on human stability and locomotion proposes theoretical and experimental researches in the very complex domain of the influences of environment, described through its specific parameters, on locomotion and stable equilibrium of human body’s performances, characterized by pressure center and by the forces generated in the plantar area. The thesis is structured in eight chapters and, among them: four are concerned on introduction, thesis objectives, conclusions, original contribution and thesis valorization (published papers and research grants)/future research directions. The next four develop, consistently, the thesis subject, beginning with critical analyze of the specialized literature that is followed by the analyze of specific parameters of the environment, the analyze of the human locomotion and stability and of influences of environment on human locomotion and stable equilibrium. It contains 195 pages, 147 figures and 22 tables and is accompanied by 5 annexes on 50 pages concerning the experimental research. During the research program, the author elaborated and published 13 papers in the proceedings of different scientific events in Romania and abroad and was a part of two research teams for scientific grants
Spiegler, Adam. "Stability of Generic Equilibria of the 2n Dimensional Free Rigid Body Using the Energy-Casimir Method." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/194821.
Jost, Pierre. "Apport de technique informatiques a l'etude des complexes polynucleaires du nolybdene vi : equilibres de formation et cinetique de condensation en milieu nacl 0,1 m." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13112.
MOIROT, FRANCK. "Etude de la stabilite d'un equilibre en presence de frottement de coulomb. Application au crissement des freins a disque." Palaiseau, Ecole polytechnique, 1998. http://www.theses.fr/1998EPXX0074.
Bellon, Pascal. "Contribution a l'etude des equilibres contraints en science des materiaux : couches heteroepitaxiees, couches implantees dans le gaas : critere de stabilite de composes sollicites." Paris 6, 1989. http://www.theses.fr/1989PA066039.
Abate, Domenico. "Modelling and control of RFX-mod tokamak equilibria." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3421955.
La presente tesi tratta la modellazione e il controllo di plasmi in equilibrio, a sezione non circolare e relativi all’esperimento RFX-mod operante come tokamak. L’obiettivo è di sviluppare un modello complessivo di RFX-mod (includendo plasmaconduttori- controllore) con finalità di controllo elettromagnetico del plasma. L’esperimento RFX-mod è stato descritto con modelli caratterizzati da un crescente livello di complessità, coinvolgendo sia dati teorici che sperimentali. Il codice CREATE-L è stato usato per lo sviluppo di modelli linearizzati di risposta di plasma, con ipotesi semplificative sulla rappresentazione delle strutture conduttrici (approssimazione assialsimmetrica). Questi modelli, grazie alla loro semplicità, sono stati utilizzati per la progettazione del sistema di controllo. Il codice CarMa0 è stato usato per sviluppare modelli analoghi ma con una rappresentazione tridimensionale delle strutture conduttrici; questi permettono di verificare l’accuratezza dei modelli semplificati e indagare l’importanza delle strutture tridimensionali sulla dinamica del sistema. Il codice CarMa0NL ha permesso la trattazione di fenomeni evolutivi nel tempo e nonlineari (e.g. disruzioni, transizioni limiter-divertor, transizioni L-H etc.). L’attività può essere suddivisa in due parti: la prima riguarda la modellizzazione di plasmi a basso β teorici, non ottenuti sperimentalmente, usati come riferimento per la progettazione e l’implementazione del sistema di controllo della forma e della posizione verticale del plasma; la seconda parte, è legata ai risultati delle campagne sperimentali sui plasmi a sezione non circolari in diversi regimi, dal basso β al modo H, con particolare attenzione allo sviluppo di un nuovo modello linearizzato di risposta di plasma per i nuovi regimi di equilibrio raggiunti. L’attività di ricerca è caratterizzata da molteplici problematiche e peculiarità sia in termini di modellazione che di controllo. La pronunciata non circolarità della forma di plasma e i diversi regimi coinvolti hanno influenzato fortemente l’attività di modellazione che ha richiesto, infatti, lo sviluppo di molteplici strumenti computazionali e di analisi dati. Per quanto concerne il controllo, la non completa osservabilità della dinamica del sistema e la necessità di ridurre l’ordine del modello sono solo alcuni degli aspetti che hanno determinato la progettazione del sistema di controllo di forma e di posizione verticale. La prima parte è basata su dati teorici generati dal codice di equilibrio MAXFEA e poi utilizzati per derivare il modello linearizzato attraverso il codice CREATE-L. In questo contesto, sono stati prodotti due modelli di riferimento per le configurazioni magnetiche relative a plasmi non circolari: il singolo nullo inferiore (LSN) e il singolo nullo superiore (USN). I modelli CREATE-L sono i più semplici in termini di complessità di modellazione, in quanto le strutture conduttive della macchina sono descritte nell’approssimazione assialsimmetrica. D’altro canto, le proprietà semplici ma affidabili del modello CREATE-L hanno portato alla progettazione del sistema di controllo di forma e posizione verticale del plasma di RFX-mod, che è stato in seguito testato e utilizzato con successo per aumentare le prestazioni del plasma. Successivamente, è stata condotta un’analisi sui possibili effetti 3D delle strutture conduttrici sulle due configurazioni di plasma di riferimento, producendo dunque modelli linearizzati caratterizzati da un sempre maggiore livello di complessità. Una dettagliata descrizione volumetrica (3D) delle strutture conduttrici di RFX-mod è stata eseguita e inclusa nei modelli linearizzati di plasma attraverso il codice CarMa0. Successivamente, è stato eseguito un confronto tra l’accuratezza di questo modello e quello precedente 2D. Le diverse ipotesi e approssimazioni dei vari modelli consentono una chiara identificazione dei fenomeni chiave che governano l’evoluzione dell’instabilità verticale n = 0 in scariche RFX-mod tokamak e quindi forniscono informazioni fondamentali nella pianificazione ed esecuzione di esperimenti correlati oltre che nella raffinazione del progetto del sistema di controllo. Infine, il modello di equilibrio evolutivo non lineare CarMa0NL, che comprende le strutture volumetriche 3D, è stato utilizzato per modellare gli effetti non lineari simulando una variazione di corrente lineare "fittizia". La seconda parte è costituita da un’attività di modellazione strettamente correlata ai risultati delle campagne sperimentali. In particolare, sono stati eseguiti nuovi modelli linearizzati per i plasmi sperimentali nella configurazione USN per tutti i regimi di plasma coinvolti, cioè dal basso β fino al modo H. È stata ideata e sviluppata una procedura iterativa per la produzione di modelli linearizzati di risposta di plasma estremamente accurati, al fine di riprodurre al meglio i dati sperimentali. I nuovi modelli hanno consentito ulteriori studi sulla stabilità verticale, inclusi gli effetti della parete 3D, nei tre diversi regimi studiati (basso β, β intermedio, modo H). I modelli linearizzati assialsimmetrici (CREATE-L) sono stati analizzati dal punto di vista della teoria dei controlli, rilevando caratteristiche peculiari in termini di funzione di trasferimento SISO associata al controllo della stabilità verticale e in termini di modello completo MIMO relativo al controllo di forma. Il modello MIMO è stato utilizzato per indagare le oscillazioni nella forma del plasma osservate sperimentalmente in alcune scariche a β intermedio. L’evoluzione temporale non lineare della scarica di plasma, per plasmi sperimentali a regimi a basso β, è stata effettuata usando il codice di equilibrio evolutivo CarMa0NL. Infine, è stata studiata l’instabilità verticale per i plasmi sperimentali in termini di un possibile rapporto tra i parametri del plasma e il suo verificarsi; a tal fine è stata eseguita la soluzione del problema inverso per la produzione di equilibri di plasma teorici di riferimento, prodotti come variazioni sui parametri dei plasmi osservati sperimentalmente, il che comporta una vasta gamma di metodi numerici descritti in dettaglio. Successivamente, è stato adottato un test di ipotesi statistica per confrontare i valori medi dei parametri di plasma, sia sperimentali che teorici, associati a due diversi comportamenti in termini di stabilità verticale.
Zehetbauer, Josef [Verfasser], and Christoph [Akademischer Betreuer] Walker. "Stability of equilibria for a nonlinear population model with age- and spatial-structure / Josef Zehetbauer ; Betreuer: Christoph Walker." Hannover : Gottfried Wilhelm Leibniz Universität Hannover, 2019. http://d-nb.info/1204459304/34.
TORNESE, CALOGERO. "Discrete approximations of the Perona-Malik equation: convergence and classification of the equilibria." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2009. http://hdl.handle.net/2108/731.
Cozzolino, Emilia. "Modelli Matematici per l’Epidemiologia." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/22182/.
Moya, Horacio Dorigan. "Estudo potenciométrico dos equilíbrios no sistema manganês (II) / azoteto." Universidade de São Paulo, 1993. http://www.teses.usp.br/teses/disponiveis/46/46133/tde-30072008-072805/.
The equilibria of complex formation between manganese(II) cations and azide anions were studied in aqueous medium by an indirect potentiometric method, at 25°C and ionic strengh 2.0 M (NaClO4). The equilibrium data were based on pH measurements of Mn(II) in N3¯/HN3 buffers. Metal ion concentration changing from 20 to 100 mM have defined one single formation curve of n_ (Bjerrum function) vs. [N 3 ¯ ] which is an evidence that only mononuclear species ara present in the working solutions. Integration of the formation curve from the best n¯vs. [N3¯] data leads to Fronaeus function data. They were properly treated to obtain the formation by a variety of methods (graphic and mathematical). The best set formed is: β1 = 4,15 ± 0,02 M-1 , β2 = 6,61 ± 0,04 M-2 , β3 = 3,33 ± 0,02 M-3 , β4 = 0,63 ± 0,01 M-4 . The complex are weaks and are is agreement with the Irving and Williams rule, i. e., less stable than the corresponding complexes of Ni(II) and Co(II). At ligand concentration higher t than 1,0 M there were conditions for a slow spontaneous oxidation of manganese(II) complexes to manganese to manganese(III), with remarkable spectral changes.
Cabanas, Valdés Rosa Mª. "Evaluación del efecto de los ejercicios de Core Stability para mejorar el equilibrio en sedestación y control de tronco en los pacientes que han sufrido un ictus." Doctoral thesis, Universitat Internacional de Catalunya, 2015. http://hdl.handle.net/10803/314582.
Neumann, Berenice Anne Verfasser], and Sören [Akademischer Betreuer] [Christensen. "Stationary Equilibria of Mean Field Games with Finite State and Action Space : Existence, Computation, Stability, and a Myopic Adjustment Process / Berenice Anne Neumann ; Betreuer: Sören Christensen." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2020. http://nbn-resolving.de/urn:nbn:de:gbv:18-103134.
Neumann, Berenice Anne [Verfasser], and Sören [Akademischer Betreuer] Christensen. "Stationary Equilibria of Mean Field Games with Finite State and Action Space : Existence, Computation, Stability, and a Myopic Adjustment Process / Berenice Anne Neumann ; Betreuer: Sören Christensen." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2020. http://d-nb.info/1205880992/34.
BARBIERI, GIOVANNI. "IL NEOREALISMO RIVISITATO. IL RUOLO DELLA CONCENTRAZIONE, DELLA GEOGRAFIA E DELLA SOCIALIZZAZIONE IN UN MODELLO AMPLIATO DELLA TEORIA DELL'EQUILIBRIO DI POTENZA." Doctoral thesis, Università Cattolica del Sacro Cuore, 2017. http://hdl.handle.net/10280/17947.
What does effectively determine systemic stability? Does international anarchy always determine a threat to survival? The structural model introduced in this work focuses on two main variables, power concentration and geography, to demonstrate how structural constraints shape States’ base motivations to action, and how the resulting behaviors condition the observable systemic outcomes. Furthermore, I introduce the socialization process as an intervening variable, enabled by specific structural conditions. Socialization could inhibit the systemic balancing tendency by narrowing States’ foreign policy options. From the theoretical point of view, the model modifies the realist assumption towards constant structural incentives to action. By focusing on the role played by power concentration and geography in shaping States’ motivations, it is possible to link together the shifts in international power distribution with shifts in structural incentives. Nonetheless, the model loses the rather mechanistic character of structural realism, making balancing one among many viable options. From the empirical point of view, I apply the model against three case studies, trying to demonstrate how the existence of concentrated or diffused power structures determines systemic stability or instability.
BARBIERI, GIOVANNI. "IL NEOREALISMO RIVISITATO. IL RUOLO DELLA CONCENTRAZIONE, DELLA GEOGRAFIA E DELLA SOCIALIZZAZIONE IN UN MODELLO AMPLIATO DELLA TEORIA DELL'EQUILIBRIO DI POTENZA." Doctoral thesis, Università Cattolica del Sacro Cuore, 2017. http://hdl.handle.net/10280/17947.
What does effectively determine systemic stability? Does international anarchy always determine a threat to survival? The structural model introduced in this work focuses on two main variables, power concentration and geography, to demonstrate how structural constraints shape States’ base motivations to action, and how the resulting behaviors condition the observable systemic outcomes. Furthermore, I introduce the socialization process as an intervening variable, enabled by specific structural conditions. Socialization could inhibit the systemic balancing tendency by narrowing States’ foreign policy options. From the theoretical point of view, the model modifies the realist assumption towards constant structural incentives to action. By focusing on the role played by power concentration and geography in shaping States’ motivations, it is possible to link together the shifts in international power distribution with shifts in structural incentives. Nonetheless, the model loses the rather mechanistic character of structural realism, making balancing one among many viable options. From the empirical point of view, I apply the model against three case studies, trying to demonstrate how the existence of concentrated or diffused power structures determines systemic stability or instability.
Malservisi, Alessandro. "Caratterizzazione meccanica e modellazione agli Elementi Finiti della parete rocciosa di Vardzia." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/12890/.
Leubner, S., R. Schneider, A. Dubavik, S. Hatami, N. Gaponik, U. Resch-Genger, and A. Eychmüller. "Influence of the stabilizing ligand on the quality, signal-relevant optical properties, and stability of near-infrared emitting Cd1₁₋ₓHgₓTe nanocrystals." Royal Society of Chemistry, 2014. https://tud.qucosa.de/id/qucosa%3A36257.
Mezerdi, Mohamed Amine. "Equations différentielles stochastiques de type McKean-Vlasov et leur contrôle optimal." Electronic Thesis or Diss., Toulon, 2020. http://www.theses.fr/2020TOUL0014.
We consider Mc Kean-Vlasov stochastic differential equations (SDEs), which are SDEs where the drift and diffusion coefficients depend not only on the state of the unknown process but also on its probability distribution. These SDEs called also mean- field SDEs were first studied in statistical physics and represent in some sense the average behavior of an infinite number of particles. Recently there has been a renewed interest for this kind of equations in the context of mean-field game theory. Since the pioneering papers by P.L. Lions and J.M. Lasry, mean-field games and mean-field control theory has raised a lot of interest, motivated by applications to various fields such as game theory, mathematical finance, communications networks and management of oil resources. In this thesis, we studied questions of stability with respect to initial data, coefficients and driving processes of Mc Kean-Vlasov equations. Generic properties for this type of SDEs, such as existence and uniqueness, stability with respect to parameters, have been investigated. In control theory, our attention were focused on existence, approximation of relaxed controls for controlled Mc Kean-Vlasov SDEs
Lusuardi, Alice. "Modelli matematici per lo studio di popolazioni interagenti in un ecosistema." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13547/.
Rêgo, Marroni de Sá. "Formulação teórica dos fundamentos da otimização global topográfica com análise de desempenho e aplicações à estabilidade de fases de misturas termodinâmicas." Universidade do Estado do Rio de Janeiro, 2015. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=8404.
Métodos de otimização que utilizam condições de otimalidade de primeira e/ou segunda ordem são conhecidos por serem eficientes. Comumente, esses métodos iterativos são desenvolvidos e analisados à luz da análise matemática do espaço euclidiano n-dimensional, cuja natureza é de caráter local. Consequentemente, esses métodos levam a algoritmos iterativos que executam apenas as buscas locais. Assim, a aplicação de tais algoritmos para o cálculo de minimizadores globais de uma função não linear,especialmente não-convexas e multimodais, depende fortemente da localização dos pontos de partida. O método de Otimização Global Topográfico é um algoritmo de agrupamento, que utiliza uma abordagem baseada em conceitos elementares da teoria dos grafos, a fim de gerar bons pontos de partida para os métodos de busca local, a partir de pontos distribuídos de modo uniforme no interior da região viável. Este trabalho tem dois objetivos. O primeiro é realizar uma nova abordagem sobre método de Otimização Global Topográfica, onde, pela primeira vez, seus fundamentos são formalmente descritos e suas propriedades básicas são matematicamente comprovadas. Neste contexto, propõe-se uma fórmula semi-empírica para calcular o parâmetro chave deste algoritmo de agrupamento, e, usando um método robusto e eficiente de direções viáveis por pontos-interiores, estendemos o uso do método de Otimização Global Topográfica a problemas com restrições de desigualdade. O segundo objetivo é a aplicação deste método para a análise de estabilidade de fase em misturas termodinâmicas,o qual consiste em determinar se uma dada mistura se apresenta em uma ou mais fases. A solução deste problema de otimização global é necessária para o cálculo do equilíbrio de fases, que é um problema de grande importância em processos da engenharia, como, por exemplo, na separação por destilação, em processos de extração e simulação da recuperação terciária de petróleo, entre outros. Além disso, afim de ter uma avaliação inicial do potencial dessa técnica, primeiro vamos resolver 70 problemas testes, e então comparar o desempenho do método proposto aqui com o solver MIDACO, um poderoso software recentemente introduzido no campo da otimização global.
Optimization methods that use optimality conditions of first and/or second order are known to be efficient. Commonly, such iterative methods are developed and analyzed in the light of knowledge concerning the mathematical analysis in n-dimensional Euclidean spaces, whose nature is of local character. Consequently, these methods lead to iterative algorithms that perform only local searches. Thus, the application of such algorithms to the calculation of global minimizers of a non-linear function, especially non-convex and multimodal, depends strongly on the location of the starting points. The Topographical Global Optimization method is a clustering algorithm, which uses an ingenious approach based on elementary concepts of graph theory, in order to generate good starting points for local search methods, from points distributed uniformly in the interior of the feasible set. The purpose of this work is two-fold. The first is a revisit to the Topographical Global Optimization method, where, for the first time, its foundations are formally described and its basic properties are mathematically proven. In this context, we propose a semi-empirical formula for computing the key parameter of this clustering algorithm, and, using a robustand efficient direction interior-point method, we extend the use of the Topographical Global Optimization method to problems with inequality constraints. The second objective is the application of this method to the phase stability analysis of mixtures, a difficult and important global optimization problem of the chemical engineering thermodynamics. Furthermore, in order to have an initial assessment of the power of this technique,first we solve 70 test problems, and then compare the performance of the method considered here with the MIDACO solver, a powerful software recently introduced in the field of global optimization.
Gillet, Frédéric. "Dynamique non linéaire de surfaces vicinales hors de l'équilibre." Université Joseph Fourier (Grenoble), 2000. http://www.theses.fr/2000GRE10204.
Lebel, Guilhem. "Prévision des charges aéromécaniques des rotors d'hélicoptère : Application aux pales à double flèche." Thesis, Lyon, INSA, 2012. http://www.theses.fr/2012ISAL0025.
New generation blades have led to new load computation problems due to the evolution of the general shape, with forward and backward sweep. The BlueEdgeTM blade pattented by Eurocopter imposes to reconsider the development methodology and thus it is no longer possible to speak of straight blades and the models used for load computation have to be evaluated. The objective of this thesis is to determine what has to be modified and improved in current load computation methodology in order to reach an acceptable predictive level. This work considers both aerodynamic and dynamic models implemented in the HOST multi-body computer code. The aerodynamics models are based on the hypothesis of a two dimensional flow. The use of the CFD software \emph{elsA} is evaluated. Attention is given to rotor dynamics models that have an impact on loads, such as lead-lag damper models, blade element models and hub models. This thesis presents the different models and gives orientations relating to efficient load computation methodology. The aerodynamics models are compared to windtunnels experiments from the literature. This study leads also to perform flight tests and to investigate the dampers behavior on test benches in order to confront the computed loads to the reality of the helicopter operation. The proposed methodology is able to compute with a good accuracy rotor loads for stabilized flight cases
Machado, Martínez Juan Eduardo. "Some Problems on the Analysis and Control of Electrical Networks with Constant Power Loads On Existence of Equilibria of Multi-Port Linear AC Networks With Constant-Power Loads An Adaptive Passivity-Based Controller of a Buck-Boost Converter with a Constant Power Load Power-Controlled Hamiltonian Systems: Application Electrical Systems with Constant Power Loads On the Existence and Long-Term Stability of Voltage Equilibria in Power Systems with Constant Power Loads Active Damping of a DC Network with a Constant Power Load: An Adaptive Observer-based Design." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS445.
The continuously increasing demand of electrical energy has led to the conception of power systems of great complexity that may extend even through entire countries. In the vast majority of large-scale power systems the main primary source of energy are fossil fuels. Nonetheless, environmental concerns are pushing a major change in electric energy production practices, with a marked shift from fossil fuels to renewables and from centralized architectures to more distributed ones. One of the main challenges that distributed power systems face are the stability problems arising from the presence of the so-called Constant Power Loads (CPLs). These loads, which are commonly found in information and communication technology facilities, are known to reduce the effective damping of the circuits that energize them, which can cause voltage oscillations or even voltage collapse. In this thesis, the main contributions are focused in understanding and solving diverse problems found in the analysis and control of electrical power systems containing CPLs. The contributions are listed as follows. (i) Simply verifiable conditions are proposed to certify the non existence of steady states in general, multi-port, alternating current (AC) networks with a distributed array of CPLs. These conditions, which are based on Linear Matrix Inequalities, allow to discard the values of the loads' powers that would certainly produce a voltage collapse in the whole network. (ii) For general models of some modern power systems, including High-Voltage Direct Current transmission networks and microgrids, it is shown that if equilibria exist, then there is a characteristic high-voltage equilibrium that dominates, entry-wise, all the other ones. Furthermore, for the case of AC power systems under the standard decoupling assumption, this characteristic equilibrium is shown to be long-term stable. (iii) A class of port-Hamiltonian systems, in which the control variables act directly on the power balance equation, is explored. These systems are shown to be shifted passive when their trajectories are constrained to easily definable sets. The latter properties are exploited to analyze the stability of their---intrinsically non zero---equilibria. It is also shown that the stability of multi-port DC electrical networks and synchronous generators, both with CPLs, can be naturally studied with the proposed framework. (iv) The problem of regulating the output voltage of the versatile DC buck-boost converter feeding an {em unknown} CPL is addressed. One of the main obstacles for conventional linear control design stems from the fact that the system's model is non-minimum phase with respect to each of its state variables. As a possible solution to this problem, this thesis reports a nonlinear, adaptive controller that is able to render a desired equilibrium asymptotically stable; furthermore an estimate of the region of attraction can be computed. (v) The last contribution concerns the active damping of a DC small-scale power system with a CPL. Instead of connecting impractical, energetically inefficient passive elements to the existing network, the addition of a controlled DC-DC power converter is explored. The main contribution reported here is the design of a nonlinear, observer-based control law for the converter. The novelty of the proposal lies in the non necessity of measuring the network's electrical current nor the value of the CPL, highlighting its practical applicability. The effectiveness of the control scheme is further validated through experiments on a real DC network
Rai, Nacer-Eddine. "Analyse et prévision de certains glissements de terrains naturels." Phd thesis, Grenoble 1, 1992. http://tel.archives-ouvertes.fr/tel-00682856.
Scalzo, Vincenzo. "Social Nash Equilibria: variational stability and approximations." Tesi di dottorato, 2003. http://www.fedoa.unina.it/125/1/thesis_Scalzo.pdf.
Javame, Ali. "Mathematical assessment of the role of pap screening on HPV transmission dynamics." 2015. http://hdl.handle.net/1993/30166.
Kemp, Todd Murray. "Floating Bodies in the Absence of Gravity." Thesis, 2011. http://hdl.handle.net/10012/5848.
Bajaj, Saurabh. "Phase Stability and Thermodynamic Assessment of the Np-Zr system." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8773.
Ming-yuehTsai and 蔡明岳. "Interfacial stability and phase equilibria between the Au-Ge high-temperature Pb-free solder and Cu or Ni substrate." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/89m66f.
國立成功大學
材料科學及工程學系
102
High-temperature materials are demanding for high-power electronics, so the material of soldering need to support the high temperature. Currently, Pb is proven to be harmful to the environment and human health, so the searching for high temperature lead-free solders becoming to be a demanding need. In this study, we choose Au-Ge eutectic alloy to be the solder, reactions between Au-Ge solders and Ni or Cu substrates have to be investigated to evaluate the Au-Ge based high-temperature solders. In the results of the interfacial reaction between Au-12wt. % Ge (Au-12Ge) and Ni substrate, after a 8-hour reaction, the formation of F.C.C.-(Au, Ge, Ni)/NiGe alternating layers occurred in the interface. The stability diagrams and the 673 K isothermal section of the Au-Ge-Ni ternary system were calculated using the CALPHAD method to analyze the mechanism of alternating-layer formation. Ge was then determined to be the dominant diffusion specie. When Ge atoms accumulated at the NiGe/Ni2Ge interface, the interface became unstable and a new pair of F.C.C.-(Au, Ge, Ni)/NiGe would form, resulting in the previously-formed F.C.C.-(Au, Ge, Ni)/NiGe layers being separated from the original Ni2Ge/Ni substrate. The periodic thermodynamic instability caused subsequent nucleation of new alternating layers. The diffusion path across the interface is liquid/F.C.C.-(Au, Ge, Ni)/NiGe/⋯/F.C.C.-(Au, Ge, Ni)/NiGe/Ni2Ge/Ni. In the previous research, the alternating-layers structure was always found in the solid/solid interfacial reaction. Our research is the first diffusion couple that found this phenomenon only in the liquid/solid reaction, but not in the solid/solid reaction. In the past, the research of Au-12Ge/Cu interfacial reaction annealing at 400 oC and 300 oC, the unidentified “X” phase has been found and recognized as a ternary phase. The composition of X phase had a range from Au-74.72Cu-16.97Ge to Au-77.65Cu-15.58Ge. Therefore, we constructed the isothermal phase diagram of Au-Ge-Cu ternary system. We focus on the phase area near the ζ and ε1 phase. According to the new isothermal phase diagram, the “X” phase has been identified to be the ε1 phase.
Tuen, Li Huey. "Stability of a two-volume MRxMHD model in slab geometry." Master's thesis, 2017. http://hdl.handle.net/1885/131789.
NARDI, FRANCESCO. "L'incidenza del Patto di stabilità e crescita sull'equilibrio costituzionale dei poteri." Doctoral thesis, 2016. http://hdl.handle.net/11573/925126.