Дисертації з теми "Stability analysi"
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Besse, Apollos. "Modélisation mathématique de la leucémie myéloide chronique." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1105/document.
Повний текст джерелаThis thesis deals with the dynamics of models of chronic myeloid leukemia (CML). Models of interest describe leukemic cell populations in the bone marrow or in the blood, in competition with healthy cell populations or with the immune system. In a first chapter, we propose a mathematically tractable version of an ordinary differential equation model that describes the interaction of the immune system with leukemic cells. We characterize the existence of steady states and their stability and then we provide a complete bifurcation analysis in co-dimension 1. In a second chapter, we confront this model with clinical data. In a third chapter we propose and analyze a simplified version of a model of partial differential equations that describes the proliferation and differentiation of leukemic stem cells in the bone marrow and the effect of an TKI treatment on these cells. We are interested in the long-term behavior of the solutions, and its dependence on treatment. In a fourth and final chapter, we are interested in the stability of scalar and autonomous differential equations with two delays, which appear naturally in the modeling of many biological or physical phenomena, such as CML
Jin, Chi. "Analyse de stabilité de systèmes à coefficients dépendant du retard." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS411/document.
Повний текст джерелаSystems with delay-dependent coefficients have been encountered in various applications of science and engineering. However, general and systematic stability analysis is rarely reported in the rich literature on time-delay systems. This thesis is committed to the stability analysis of such class of systems.Stability analysis methods are developed based on the corresponding characteristic equation following a generalized tau-decomposition approach. Given a delay interval of interest, we are able to identify all the critical delay values contained in this interval for which the characteristic equation admits roots on the imaginary axis of the complex plane. Various root crossing direction criteria are proposed to determine whether these characteristic roots move toward the left or the right half complex plane as the delay parameter sweeps through these critical delay values. The number of unstable characteristic roots for any given delay can thus be determined. Our analysis covers systems with a single delay or commensurate delays under certain assumptions. The root crossing direction criteria developed in this thesis can be applied to characteristic roots with multiplicity, or characteristic roots whose locus parametrized by the delay is tangent to the imaginary axis. As an application, it is demonstrated that systems with delay-dependent coefficients can arise from control schemes that use delayed output to approximate its derivatives for stabilization. The stability analysis methods developed in this thesis are tailored and applied to find the delay intervals that achieve a demanded convergence rate of the closed-loop system
Maatar, Dhouha. "Analyse des signaux stabilométriques et de la stabilité chez l’Homme : application à la biométrie." Thesis, Paris Est, 2013. http://www.theses.fr/2013PEST1161/document.
Повний текст джерелаBiometrics refers to automatic recognition of individuals. It is based on their physiological and / or behavioral. The postural control, despite that is a human behavioral characteristic, has not been well developed in the field of biometrics. The work performed in this thesis is based on the stabilometric signals analysis ant biometric application. Firstly, a study of the postural information especially the stabilometric signal is carried out through traditional analysis namely temporal, frequency and stochastic analysis and two decomposition methods named principle components analysis (ACP) decomposition and wavelet decomposition. The ACP method, based on the additive model, allows decomposing the signal into three components: a trend signal, a rambling signal and a trembling signal. The wavelet decomposition method allows decomposing the signal into three levels of detail signals and three signal levels of approximation. Through the study of postural stability, spectral analysis and phase analysis of the different components from the ACP and the wavelet decomposition, the comparison of these two methods concludes that the ACP method is more appropriate than the wavelet decomposition to analyze the stabilogram. From the decomposition methods and classical methods of analysis, several parameters are extracted to study the effect of different factors on postural stability and the center of mass displacement. These factors are named vision, direction, proprioception, age, gender, height and weight. A second aspect of this work is devoted to the application of biometrics, from the extracted parameters and through ANOVA statistic analysis, those that are most discriminative are used to identify subjects and classify them according to age, gender, weight and size. This biometric application is performed by three classification methods namely, K-NN, LDA and SVM. Biometric applications result in respectable recognition rate exceeding 80%. Therefore, it is inferred that the analysis of postural control is promising in the field of biometrics
Cherifi, Abdelmadjid. "Contribution à la commande des modèles Takagi-Sugeno : approche non-quadratique et synthèse D -stable." Thesis, Reims, 2017. http://www.theses.fr/2017REIMS016/document.
Повний текст джерелаThis work deals with the stability analysis and the stabilisation of nonlinear systems represented by T-S models.The goal is to reduce the conservatism of the stability conditions, obtained through the direct Lyapunov methodand written, when it is possible, as LMIs. In this framework, two main contributions has been proposed. First ofall, we have proposed some new conditions based on FLICs, strictly LMIs and without any order restrictions, forthe non-quadratic design of control laws devoted to stabilize T-S models. Indeed, in this non-quadratic context,the existing works are only available for 2nd order T-S models. In order to unlock this restriction, the proposed conditions have been obtained based on the proof of a dual property. Then, starting from the fact that few worksdeals with the closed-loop performances specification, some new LMI conditions (quadratic and non-quadratic)have been proposed via the D-stability concept. As a first step, D-stabilizing PDC and non-PDC controller designhas been considered for nominal T-S models. Then, these results have been extended to uncertain T-S models.Moreover, it has been highlighted, from an example of the attitude D-stabilization of a quadrotor model, that wecan make use of uncertain T-S models to cope with nonlinear models involving nonlinearities depending on bothstate and input variables
Cosson, Marjorie. "Stabilité du réseau électrique de distribution. Analyse du point de vue automatique d'un système complexe." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLC065/document.
Повний текст джерелаTo maintain the voltage within specified limits, local control laws of distributed generators (DGs) reactive power (Q) with respect to their voltage (U) have been considered. This work studies the impact of Q(U) control laws on distribution feeders’voltage stability. An empirical study confirms the risk of voltage instability and highlights its dependence on control law parameters. To help distribution grid operators to choose these parameters, three methods assessing stability are formulated.First, a formal method based on discrete abstraction and bisimulation calculation is developed. The proposed approach yields precise results but with a high computational load. Then, to overcome this issue, an analytical criterion adapting Q(U) control laws response time with respect to grid parameters is formulated. Finally, a general criterion, valid in any cases, is established in order to be included in the grid codes. To conclude this work, extension to more complex cases is discussed
Heng, Yaguang. "Décrochage tournant dans un diffuseur lisse radial : Étude de stabilité et effet sur la performance." Thesis, Paris, ENSAM, 2017. http://www.theses.fr/2017ENAM0049/document.
Повний текст джерелаAbstract:The behavior of work-absorbing turbomachines (pumps, compressors) operating at off design conditions, and especially at partial flow rates, is subject to instability phenomena that could affect their performance and can be dramatic for the machines or their environment. This study is focused on the rotating stall in the vaneless diffuser, the objective is to propose a theoretical model to fast predict the characteristics of such an instability. An experimental study is performed first to obtain those characteristics of rotating stall in a transparent vaneless diffuser of a radial impeller. The effect of rotating stall on the diffuser performance is discussed based on the static pressure measurements. The result shows rotating stall improved the diffuser pressure recovery, and the reasons are proposed. Based on the experimental setup, a linear stability analysis which is constructed by the continuity equation, momentum equation and vorticity equations, is proposed. The experimental characteristics of rotating stall: number and propagation velocity of stall cells, are theoretical calculated. The growth rate in the linear model, is proposed to determine the critical stall condition, and the dominant stall mode when different stall modes exist intermittently. The theoretical velocity and pressure fluctuations are also plotted to show the diffuser flow at stall condition. The abilities and limits of the linear stability analysis are concluded through the comparisons between theoretical and experimental results. Based on the linear model, a nonlinear stability analysis is extended to consider the nonlinear combinations which are neglected in the linear model, the aim is to give corrections (from nonlinear terms) to the linear results of rotating stall, the conclusions and discussions are made at the end
Špíšková, Marcela. "Návrh na zajištění finanční stability podniku." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2007. http://www.nusl.cz/ntk/nusl-221541.
Повний текст джерелаSmejkalová, Helena. "Návrh na zajištění finanční stability podniku." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2007. http://www.nusl.cz/ntk/nusl-221565.
Повний текст джерелаDal, Ferro Nicola. "Investigating the effects of SOC on soil structure: three-dimensional visualisation and modelling." Doctoral thesis, Università degli studi di Padova, 2012. http://hdl.handle.net/11577/3423348.
Повний текст джерелаLa quantificazione della struttura del suolo è di primaria importanza per determinare gli effetti di diverse pratiche colturali sul terreno. La struttura è influenzata dal contenuto di carbonio organico (SOC), il quale è ampiamente identificato come il principale indicatore della fertilità del suolo, anche grazie alle sua attitudine di migliorarne la struttura fisica. Le interazioni che legano la struttura al SOC sono complesse e principalmente legate alla capacità di agire come agente aggregante tra le particelle che compongono la matrice del suolo. Molti studi si sono concentrati sulle dinamiche che legano il SOC e la microporosità degli aggregati (che è riconosciuta come un surrogato della complessa struttura del suolo) trascurando, in questo modo, la macroporosità, la quale non è individuabile in campioni di piccole dimensioni. Le misure fatte a scala di aggregato, perciò, ricoprono solo una parte delle importanti e complesse proprietà di un suolo. Di conseguenza è importante valutare l’effetto che esercita il SOC sia in piccoli aggregati che in campioni indisturbati. L’obiettivo generale di questo lavoro è valutare gli effetti di diversi regimi di fertilizzazione (organica, minerale e mista) in una prova di lungo periodo, iniziata nel 1962, gestita secondo una monosuccessione di mais. Sono stati analizzati sia aggregati di piccole dimensioni (pochi mm), che campioni indisturbati (5 cm di diametro, 6 cm di altezza), con innovative tecniche tridimensionali. La tesi è strutturata in cinque capitoli: il primo è una review sulle interazioni struttura del suolo-SOC e sulle tecniche tridimensionali utilizzate per la quantificazione della struttura. Il secondo capitolo analizza gli effetti del SOC e delle frazioni umiche sulla stabilità di struttura degli aggregati, individuando inoltre un nuovo meccanismo, legato alla diversa distribuzione della porosità, finora non considerato. Il terzo capitolo confronta e combina la porosimetria a intrusione di mercurio e la microtomografia a raggi X per la caratterizzazione della struttura. Il quarto capitolo analizza tridimensionalmente la struttura di campioni indisturbati e gli effetti del SOC sulla struttura stessa. Infine, l’ultimo capitolo riporta le conclusioni generali del lavoro.
Xavier, Mathieu. "Étude analytique et numérique du développement de la striction multiple pour des cylindres métalliques en expansion dynamique." Thesis, Université de Lorraine, 2019. http://www.theses.fr/2019LORR0064/document.
Повний текст джерелаThis work deals with the fragmentation of dynamically expanding metal shells and covers a problem of interest for both civil and military industries. For both fields of application, it is crucial to predict the size and the speed of fragments, resulting from the destruction of shells in order to measure the consequences that it could have on structures. Current models study the growth of a defect within the material and are able to determine a characteristic size of fragments. Nevertheless, these models require a hypothesis whose validity is questionable when the rate of deformation is important. In this work, we propose a new analytical model for cylinders (equivalent to the dynamic extension of a plate) to overcome this hypothesis and study the influence of the initial defect by following its time evolution. The model is compared successfully with results performed with a finite element method. Our work notably expands the framework of classical linear stability analyses. As a major outcome, the proposed approach is able to track the evolution of a perturbation even for small plastic strain, when the flow may be stable. In addition it is shown that the present approach can predict accurately the time where the elastic unloading is observed in finite element simulations
Del, Guercio Gerardo. "Optimal streaks amplification in wakes and vortex shedding control." Phd thesis, Toulouse, INPT, 2014. http://oatao.univ-toulouse.fr/12244/1/Del_Guercio.pdf.
Повний текст джерелаCaldeira, André. "Techniques d'analyse de stabilité et synthèse de contrôle pour des systèmes hyperboliques." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT041/document.
Повний текст джерелаThis work studies boundary control strategies for stability analysis and stabilization of first-order hyperbolic system coupled with nonlinear dynamic boundary conditions. The modeling of a flow inside a pipe (fluid transport phenomenon) with boundary control strategy applied in a physical experimental setup is considered as a case study to evaluate the proposed strategies. Firstly, in the context of finite dimension systems, classical control tools are applied to deal with first-order hyperbolic systems having boundary conditions given by the coupling of a heating column dynamical model and a ventilator static model. The tracking problem of this complex dynamics is addressed in a simple manner considering linear approximations, finite difference schemes and an integral action leading to an augmented discrete-time linear system with dimension depending on the step size of discretization in space. Hence, for the infinite dimensional counterpart, two strategies are proposed to address the boundary control problem of first-order hyperbolic systems coupled with nonlinear dynamic boundary conditions. The first one approximates the first-order hyperbolic system dynamics by a pure delay. Then, convex stability and stabilization conditions of uncertain input delayed nonlinear quadratic systems are proposed based on the Lyapunov-Krasovskii (L-K) stability theory which are formulated in terms of Linear Matrix Inequality (LMI) constraints with additional slack variables (introduced by the Finsler's lemma). Thus, strictly Lyapunov functions are used to derive an LMI based approach for the robust regional boundary stability and stabilization of first-order hyperbolic systems with a boundary condition defined by means of a nonlinear quadratic dynamic system. The proposed stability and stabilization LMI conditions are evaluated considering several academic examples and also the flow inside a pipe as case study
Cochoy, Jérémy. "Decomposability and stability of multidimensional persistence." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS566/document.
Повний текст джерелаIn a context where huge amounts of data are available, extracting meaningful and non trivial information is getting harder. In order to improve the tasks of classification, regression, or exploratory analysis, the approach provided by topological data analysisis to look for the presence of shapes in data set.In this thesis, we investigate the properties of multidimensional persistence modules in order to obtain a better understanding of the summands and decompositions of such modules. We introduce a functor that embeds the representations category of any quiver whose graph is a rooted tree into the category of ℝ²-indexed persistence modules. We also enrich the structure of persistence module arising from the cohomology of a filtration to a structure of persistence algebra.Finally, we generalize the approach of Crawley Beovey to multipersistence and identify a class of persistencemodules indexed on ℝ² which have simple descriptor and an analog of the decomposition theorem available in one dimensional persistence
Battiston, Geoffray. "Amélioration des performances du régulateur des masques à oxygène." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC039.
Повний текст джерелаThe vibratory behavior of a regulated oxygen mask is studied here. The oxygen mask integrates a regulator which sends oxygen in response to a demand flow. The vibrations take the form of pressure variations in the mask volume, at the entry of the nasal ways, and their origin is unknown. Among the goals of this thesis work, we will try first to understand the origin and to characterize this phenomenon after a detailed modeling of the regulator, taking accurately into account its geometry. Second, the stabilization of the system’s dynamical trajectory will be studied by applying the Routh criterion to a linearized model around an equilibrium point. Third, some additional dynamical and physical phenomena will be investigated in order to push forward the understanding of the mask functionning. Fourth, and as an opening, time will be taken to mention supplementary tracks for the study of this system
Kaiser, Thomas. "Impact of Flow Rotation on Flame Dynamics and Hydrodynamic Stability." Thesis, Toulouse, INPT, 2019. http://oatao.univ-toulouse.fr/24115/1/Kaiser_Thomas.pdf.
Повний текст джерелаLerisson, Gaétan. "Stabilité d'une onde de gravité interne, analyse locale, globale et croissance transitoire." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX017/document.
Повний текст джерелаInternal gravity waves that exist in a continuously stratified fluid are particularly important in the ocean. They transport energy and are thought to generate turbulent mixing, which contribute to the deep ocean circulation.We generate an internal wave beam that propagates in a continuously stratified fluid with direct numerical simulations. This situation is equivalent to a tidal wave, where the tidal flow oscillates over a topography and generates a wave. Experimental results obtained by cite{Bourget13} are recovered, ie. the beam destabilizes into a small scale mode. We consider the effect of an horizontal mean flow on the instability and lower the forcing frequency in order to compensate for the doppler effect and to keep locally the same wave. A limit case appears when the forcing becomes stationary. This case is equivalent to a lee wave appearing when a stratified fluid flows over a topography.For small mean flow, small scale instabilities develop as in the tidal case. The beam then stabilizes at intermediate mean flows and destabilizes again for increasing flow speed. At this second threshold, down to the lee wave case, the instability is of much larger scale than for the tidal case. Varying the Reynolds number, the Froude number, the wave angle or the beam size doesn't affect the instability scale selection : a small scale instability in the tidal regime, and large scale instability in the lee regime.We show that the instability mechanism may be interpreted using the triadic instability. Scale selection corresponds to different branches of triadic resonance. We confirm the presence of a stability region for intermediate value of the mean advection velocity by computing the linear eigenmode as Floquet mode with an Arnoldi-Krylov technique and show that the leading eigenmode has a negative growth rate.In the lee wave, case the flow is unstable and a selective frequency damping method cite{Akervik06} is used to compute a steady base flow. We then implement a linear direct-adjoint method to compute the optimal perturbations that maximizes the total energy at different time horizons. At short time horizon, the optimal perturbation is small scale while at large time the perturbation switches to a large scale solution and converges to the large scale mode observed through the nonlinear simulations. Short time transients correspond to the small scale triadic instability advected by the flow whereas the long time large scale instability corresponds to large scale branch of the triadic instability that is able to sustain the flow.We propose an interpretation of the selection of these different instabilities in term of absolute and convective instability. In the case of the lee wave, the large scale instability is absolute whereas the small scale instability is convective (and dominates the short time transient growth because it has a larger local growth rate). When the mean flow is varied, the properties of small scale and large scale instabilities exchange: in the tidal case the short scale instability is absolute and the large scale convective. This conjecture is confirmed by computing the impulse response around a plane monochromatic internal gravity wave in an extended two dimensional periodic domain. The spatio temporal evolution of a perturbation localized in space and time points out the formation of three different wave packets corresponding to different branches of triadic instability. Using the triadic theory with finite detuning cite{McEwan77},we derive the group velocity at the maximum growth rate of the three different branches of triadic instability and find a good agreement with the velocity of the three wave paquet maxima in the impulse response. Analyzing the impulse response along rays, i.e. at x/t and z/tconstant, we compute the absolute growth rate along all possible rays and validate our conjecture
Chekila, Abdelfateh. "Analyse non linéaire de la stabilité de l'écoulement de Poiseuille plan d'un fluide rhéofluidifiant." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0022/document.
Повний текст джерелаThe aim of this study is to understand the influence of the nonlinear rheological behaviour of the shear-thinning fluids on the flow stability and transition to turbulence. First, a linear stability analysis using modal approach was carried out. Results clearly highlight the stabilizing effect of shear-thinning. Then, as a first approach to take into account nonlinear effects of viscosity perturbation on the flow stability, a weakly nonlinear stability analysis is performed in the neighbourhood of the critical conditions. Results indicate that shear-thinning reduces the viscous dissipation and, in contrast to inertial terms, the nonlinear viscous terms tend to accelerate the flow and act in favour of supercritical bifurcation. Finally, a nonlinear stability analysis is done by following solution branches in the parameter space using continuation techniques. To deal with highly nonlinear viscous terms, a pseudo-spectral code is developed. Nonlinear equilibrium solutions was found and characterized for various values of the rheological parameters
Bassam, Maya. "Étude de la stabilité de quelques systèmes d'équations des ondes couplées sur des domaines bornés et non bornés." Thesis, Valenciennes, 2014. http://www.theses.fr/2014VALE0034/document.
Повний текст джерелаThe thesis is driven mainly on indirect stabilization system of two coupled wave equations and the boundary stabilization of Rayleigh beam equation. In the case of stabilization of a coupled wave equations, the Control is introduced into the system directly on the edge of the field of a single equation in the case of a bounded domain or inside a single equation but in the case of an unbounded domain. The nature of thus coupled system depends on the coupling equations and arithmetic Nature of speeds of propagation, and this gives different results for the polynomial stability and the instability. In the case of stabilization of Rayleigh beam equation, we consider an equation with one control force acting on the edge of the area. First, using the asymptotic expansion of the eigenvalues and vectors of the uncontrolled system an observability result and a result of boundedness of the transfer function are obtained. Then a polynomial decay rate of the energy of the system is established. Then through a spectral study combined with a frequency method, optimality of the rate obtained is assured
Ko, Tung Yeung. "Stability of networks /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202007%20KO.
Повний текст джерелаMcLean, M. R. "Analysis of wellbore stability." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/7178.
Повний текст джерелаGazi, Veysel. "Stability Analysis of Swarms." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1029812963.
Повний текст джерелаLukášová, Klára. "Návrh na zajištění finanční stability podniku." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2007. http://www.nusl.cz/ntk/nusl-221404.
Повний текст джерелаHadravová, Hana. "Finanční analýza obchodní společnosti." Master's thesis, Vysoká škola ekonomická v Praze, 2008. http://www.nusl.cz/ntk/nusl-4681.
Повний текст джерелаHrúz, Dušan. "Priebeh hospodárskeho cyklu v rokoch 2000-2015 u Švédska, Švajčiarska a Poľska a riešenie fázy recesie." Master's thesis, Vysoká škola ekonomická v Praze, 2017. http://www.nusl.cz/ntk/nusl-360692.
Повний текст джерелаNováčková, Kristýna. "Stabilita komplexů huminových kyselin s těžkými kovy." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2011. http://www.nusl.cz/ntk/nusl-216721.
Повний текст джерелаZemková, Klára. "Hodnocení finanční situace podniku a návrhy na její zlepšení." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2008. http://www.nusl.cz/ntk/nusl-221715.
Повний текст джерелаRigaud, Alexandre. "Analyse des notions de stabilité pour les modèles 2D de Roesser et de Fornasini-Marchesini." Thesis, Poitiers, 2022. http://www.theses.fr/2022POIT2307.
Повний текст джерелаThis thesis presents the results of research work on different notions of stability used in the literature of multidimensional dynamical systems. More precisely, within the framework of the 2D Roesser and Fornasini-Marchesini models, we analyze the notions of stability in the sense of Lyapunov, asymptotic stability, exponential stability(ies) and structural stability, as well as the relations between these different properties. The first chapter of this thesis carries out a certain number of reminders concerning the definitions of stability and the links which exist between them, with the aim of establishing a solid framework in order to extend these notions from the 1D case to the 2D case. Once these reminders have been established, we present the 2D models that we are studying. The second chapter lists the stability definitions used for the 2D Roesser and Fornasini-Marchesini models and establishes the links between these different definitions. In the third chapter, we propose a necessary and sufficient condition of asymptotic stability for a certain class of linear discrete 2D Fornasini-Marchesini models. The fourth and last chapter proposes a detailed study of a non-linear 1D model which has the rare characteristic of being both attractive and unstable, and we generalize this particular model to the 2D case in order to establish which properties are conserved. or not when passing from the 1D case to the 2D case
Ansaldi, Tobias. "Compressible single and dual stream jet stability and adjoint-based sensitivity analysis in relationship with aeroacoustics." Phd thesis, Toulouse, INPT, 2016. http://oatao.univ-toulouse.fr/17505/13/Ansaldi_Tobias.pdf.
Повний текст джерелаSůra, Jan. "Míry stability optimálního řešení úlohy LP vzhledem k účelové funkce." Master's thesis, Vysoká škola ekonomická v Praze, 2015. http://www.nusl.cz/ntk/nusl-264470.
Повний текст джерелаHarb, Ammar. "Discrete Stability of DPG Methods." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/2916.
Повний текст джерелаMaisonneuve, Vivien. "Analyse statique des systèmes de contrôle-commande : invariants entiers et flottants." Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0007/document.
Повний текст джерелаA critical software is a software whose malfunction may result in death or serious injury to people, loss or severe damage to equipment or environmental harm.Software engineering for critical systems is particularly difficult, and combines different methods to ensure the quality of produced software.Among them, formal methods can be used to prove that a software obeys its specifications.This thesis falls within the context of the validation of safety properties for critical software, and more specifically, of numerical properties for embedded software in control-command systems.The first part of this thesis deals with Lyapunov stability proofs.These proofs rely on computations with real numbers, and do not accurately describe the behavior of a program run on a platform with machine arithmetic.We introduce a generic, theoretical framework to adapt the arguments of Lyapunov stability proofs to machine arithmetic.A tool automatically translates the proof on real numbers to a proof with floating-point numbers.The second part of the thesis focuses on linear relation analysis, using an abstract interpretation based on the approximation by convex polyhedrons of valuations associated with each control point in a program.We present ALICe, a framework to compare different invariant generation techniques.It comes with a collection of test cases taken from the program analysis literature, and interfaces with three tools, that rely on different algorithms to compute invariants: Aspic, iscc and PIPS.To refine PIPS results, two code restructuring techniques are introduced, and several improvements are made to the invariant generation algorithms and evaluated using ALICe
Bridel-Bertomeu, Thibault. "Investigation of unsteady phenomena in rotor/stator cavities using Large Eddy Simulation." Thesis, Toulouse, INPT, 2016. http://oatao.univ-toulouse.fr/17867/1/BRIDEL_BERTOMEU.pdf.
Повний текст джерелаGuo, Xiangfeng. "Probabilistic stability analysis of an earth dam using field data." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALI017.
Повний текст джерелаUncertainties of soil properties are widely encountered in the field of geotechnical engineering especially for earth dams which are constructed with earthen materials. In recent years, there is an increasing need, motivated by the deficiencies of the traditional deterministic approach or guided by the national regulations such as in France, of accounting for these uncertainties for a safe assessment of large dams particularly in the framework of risk analysis studies. However, probabilistic analyses are still complex and not so easy to implement in practice due to the limited number of in-situ measurements, expensive computation efforts and lack of implementation of reliability methods in commercial simulation tools. Moreover, most of the previous studies are based on academic cases and hypothetic data.This work attempts to deal with the aforementioned issues by providing a probabilistic analysis study for the stability of a real earth dam using available field data. This study includes the following main elements: (1) definition of the soil variability by using the available measurements; (2) development of the deterministic models; (3-4) dam probabilistic analyses using the random-variables and random-fields approaches; (5) three-dimensional reliability analysis of the considered dam. Advanced reliability methods, such as the adaptive surrogate modelling, are introduced for the studied earth dam problem. This allows accurately estimating the dam failure probability and the safety factor statistics with a significantly reduced calculation time. In addition, some issues, that remain unknown or unclear in the field of the dam probabilistic analysis, are discussed (e.g. global sensitivity analysis of the soil hydraulic and shear strength parameters; performance survey of five reliability methods; simulation/comparison of three different kinds of random fields: generic (unconditional-stationary), conditional and nonstationary). The presented work, based on real measurements, could be a good supplement to the existing probabilistic studies of geo-structures. Readers will find useful information from the obtained results in order to better solve the practical geotechnical problems in a probabilistic framework
Issa, Ibtissam. "Some results on the stabilization of elastic/viscoelastic transmission problems with Kelvin-Voigt or fractional Kelvin-Voigt damping." Thesis, Aix-Marseille, 2021. http://theses.univ-amu.fr.lama.univ-amu.fr/211207_ISSA_690cu840ucxbzr880kpmyt859oe_TH.pdf.
Повний текст джерелаThis thesis is devoted to study the stabilization of some locally coupled systems. First, we study the stability of a one-dimensional coupled wave equations with two interior non smooth viscous dampings where we establish exponential stability. Second, we study the stabilization of a locally coupled wave equations with only one internal viscoelastic damping of Kelvin-Voigt type. Both the damping and the coupling coefficients are non smooth. Using a spectrum approach, we prove the non-uniform stability of the system. Next, using a frequency domain approach, combined with a piecewise multiplier technique and the construction of a new multiplier satisfying some ordinary differential equations, we show that the energy of the smooth solution of the system decays polynomially. Third, we investigate the energy decay of hyperbolic systems of wave-wave, wave-Euler Bernoulli beam and beam-beam types. Indeed, the two equations are coupled through boundary connection with only one localized non smooth fractional Kelvin Voigt damping. We establish a polynomial energy decay rate. Finally, we study the stability of a multidimensional system of two wave equations coupled by velocities with only one localized non-smooth Kelvin-Voigt damping. By using a spectral analysis, we prove the non uniform stability of the system. Further, using a frequency domain approach combined with a multiplier technique, we establish some polynomial stability results by considering different geometric conditions on the coupling and the damping domains. In addition, in the absence of any geometric condition, we establish two polynomial energy decay rates of the system on a square domain
Fahlberg-Stojanovska, Linda Dianne. "Stochastic stability of Lozi mappings." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184748.
Повний текст джерелаZhang, Liang. "Stability analysis of atomic structures." Diss., University of Iowa, 2006. http://ir.uiowa.edu/etd/70.
Повний текст джерелаRoderick, Christopher. "Stability analysis of polymer brushes." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85644.
Повний текст джерелаEverding, Vanessa Quigley. "Stability Analysis of Human Walking." Case Western Reserve University School of Graduate Studies / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1232680311.
Повний текст джерелаDjaneye-Boundjou, Ouboti Seydou Eyanaa. "Particle Swarm Optimization Stability Analysis." University of Dayton / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1386413941.
Повний текст джерелаPeterson, Jennifer Lynn. "Probability analysis of slope stability." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=1070.
Повний текст джерелаTitle from document title page. Document formatted into pages; contains viii, 91 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 63-64).
Della, rossa Matteo. "Non smooth Lyapunov functions for stability analysis of hybrid systems." Thesis, Toulouse, INSA, 2020. http://www.theses.fr/2020ISAT0004.
Повний текст джерелаModeling of many phenomena in nature escape the rather common frameworks of continuous-time and discrete-time models. In fact, for many systems encountered in practice, these two paradigms need to be intrinsically related and connected, in order to reach a satisfactory level of description in modeling the considered physical/engineering process.These systems are often referred to as hybrid systems, and various possible formalisms have appeared in the literature over the past years.The aim of this thesis is to analyze the stability of particular classes of hybrid systems, by providing Lyapunov-based sufficient conditions for (asymptotic) stability. In particular, we will focus on non-differentiable locally Lipschitz candidate Lyapunov functions. The first chapters of this manuscript can be considered as a general introduction of this topic and the related concepts from non-smooth analysis.This will allow us to study a class of piecewise smooth maps as candidate Lyapunov functions, with particular attention to the continuity properties of the constrained differential inclusion comprising the studied hybrid systems. We propose ``relaxed'' Lyapunov conditions which require to be checked only on a dense set and discuss connections to other classes of locally Lipschitz or piecewise regular functions.Relaxing the continuity assumptions, we then investigate the notion of generalized derivatives when considering functions obtained as emph{max-min} combinations of smooth functions. This structure turns out to be particularly fruitful when considering the stability problem for differential inclusions arising from regularization of emph{state-dependent switched systems}.When the studied switched systems are composed of emph{linear} sub-dynamics, we refine our results, in order to propose algorithmically verifiable conditions.We further explore the utility of set-valued derivatives in establishing input-to-state stability results, in the context of perturbed differential inclusions/switched systems, using locally Lipschitz candidate Lyapunov functions. These developments are then used in analyzing the stability problem for interconnections of differential inclusion, with an application in designing an observer-based controller for state-dependent switched systems
Ferraresso, Francesco. "On the spectral stability of polyharmonic operators on singularly perturbed domains." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3426790.
Повний текст джерелаIn questa tesi si studia la dipendenza degli autovalori di operatori differenziali ellittici di ordine superiore da perturbazioni singolari del dominio, con attenzione per gli operatori poliarmonici e per condizioni al bordo di tipo intermedio e Neumann. Si identificano opportune condizioni geometriche sul dominio iniziale, sui domini perturbati e sulla perturbazione al fine di assicurare la stabilità spettrale. Si caratterizzano i problemi differenziali limite, al variare dei parametri che regolano la deformazione del dominio iniziale. Si dimostra che, assumendo opportune ipotesi, gli autovalori e le proiezioni sugli autospazi associati al problema differenziale nel dominio perturbato convergono ai rispettivi autovalori e proiezioni associati al problema limite nel dominio iniziale. Inoltre si dimostra che i risolventi convergono compattamente al risolvente associato al problema limite. In particolare, si analizza dapprima la convergenza spettrale di una famiglia di operatori autoaggiunti, ellittici, di ordine superiore, con condizioni al bordo di tipo intermedio, su domini perturbati definiti localmente dal sottografico di date funzioni. Si dimostra un teorema di stabilità spettrale assumendo che la convergenza delle funzioni che rappresentano localmente la frontiera convergano in modo sufficientemente regolare. Si utilizza poi tale risultato per studiare il comportamento spettrale di operatori poliarmonici con condizioni al bordo di tipo intermedio quando la frontiera del dominio è soggetta ad una oscillazione periodica e singolare, adattando delle tecniche utilizzate da J.M. Arrieta e P.D. Lamberti nel caso dell'operatore biarmonico. Si dimostra che il problema limite dipende dal rapporto tra l'ampiezza dell'oscillazione e il periodo di oscillazione. Infatti esiste un valore limite per questo rapporto al di sopra del quale si ha stabilità spettrale, cioè gli autovalori e le proiezioni sugli autospazi associati alla famiglia di domini perturbati convergono ai corrispondenti autovalori e proiezioni associati allo stesso operatore differenziale nel dominio limite; al di sotto di tale valore critico invece l'operatore differenziale limite è differente, in quanto assume condizioni al bordo diverse sulla frontiera del dominio limite. Infine se il rapporto assume esattamente il valore critico, appare un `termine strano' in una delle condizioni al bordo associate al problema limite, che è stato caratterizzato in funzione della soluzione di un dato problema al bordo ausiliario. In questo caso limite si sfruttano tecniche dimostrative tipiche dell'omogeneizzazione periodica, come il metodo di `unfolding' e le decomposizioni micro-macroscopiche delle funzioni di Sobolev, presenti, ad esempio, in alcuni articoli di J. Casado-Diaz e collaboratori. Nel piano euclideo si considerano inoltre l'operatore biarmonico e l'operatore associato al sistema di Reissner-Mindlin, con condizioni al bordo di tipo Neumann, su un dominio `a bilanciere', che consiste di due domini regolari, limitati e disgiunti, collegati attraverso un canale sottile. Si analizza il comportamento limite dello spettro degli operatori e si caratterizza il limite degli autovalori e delle proiezioni sugli autospazi quando la larghezza del canale diminuisce fino ad annullarsi, adattando tecniche introdotte da J.M. Arrieta e collaboratori per l'operatore di Laplace con condizioni al bordo di tipo Neumann. Nelle applicazioni alla teoria dell'elasticità lineare, gli operatori in considerazione sono collegati alla deformazione di una piastra elastica, di materiale omogeneo e non vincolata, dovuta alla degenerazione di una delle sue dimensioni. In contrasto con il caso dell'operatore di Laplace, l'equazione limite risulta distorta da un coefficiente strano, che dipende dal coefficiente di Poisson della piastra modellizzata.
Jajoo, Vibhor. "Instabilités de Faraday dans les fluides binaires." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0929/document.
Повний текст джерелаWhile it is well known that the phenomenon of Faraday instability is a manifestation of vibrational acceleration, its behaviour when both the capillary and gravitational effects vanish, remains unexplored theoretically and experimentally. A detailed experimental and theoretical study is performed to understand the physics of this phenomenon in small rectangular geometry where the proximity of wall results in considerable sidewall stresses. A novel binary liquids system is utilized with low interfacial tension for a near flat interface. Thermal control of fluid system is utilized for achieving reduction in capillary force with study of miscible fluids where interfacial tension reduces to almost zero. In order to discriminate between gravity and capillarity effects, experiments were performed in parabolic flight campaigns. . For the theoretical approach a linear stability analysis is performed through Navier-Stokes equations in a Newtonian incompressible viscous fluid system. This is achieved through a Fourier Floquet method resulting into an eigenvalue problem. Equations are solved by including viscous damping effects for compensating sidewall stresses. Experimentally binary fluids provided a convenient option of changing the coefficient of interfacial tension by temperature control and going through immiscible to miscible system without change of liquid charge. Viscous damping rate is determined experimentally by measuring the linear damping rate. The correction in the theoretical calculations with the viscous damping rate helped in achieving a better understanding of the prediction of the experimental critical amplitude for sub-harmonic and harmonic modes
Pan, Qiujing. "Deterministic and Probabilistic Assessment of Tunnel Face Stability." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI044.
Повний текст джерелаIn the contemporary society, the utilization and exploitation of underground space has become an inevitable and necessary measure to solve the current urban congestion. One of the most important requirements for successful design and construction in tunnels and underground engineering is to maintain the stability of the surrounding soils of the engineering. But the stability analysis requires engineers to have a clear ideal of the earth pressure, the pore water pressure, the seismic effects and the soil variability. Therefore, the research aimed at employing an available theory to design tunnels and underground structures which would be a hot issue with high engineering significance. Among these approaches employed to address the above problem, limit analysis is a powerful tool to perform the stability analysis and has been widely used for real geotechnical works. This research subject will undertake further research on the application of upper bound theorem to the stability analysis of tunnels and underground engineering. Then this approach will be compared with three dimensional analysis and experimental available data. The final goal is to validate new simplified mechanisms using limit analysis to design the collapse and blow-out pressure at the tunnel face. These deterministic models will then be used in a probabilistic framework. The Collocation-based Stochastic Response Surface Methodology will be used, and generalized in order to make possible at a limited computational cost a complete parametric study on the probabilistic properties of the input variables. The uncertainty propagation through the models of stability and ground movements will be evaluated, and some methods of reliability-based design will be proposed. The spatial variability of the soil will be taken into account using the random field theory, and applied to the tunnel face collapse. This model will be developed in order to take into account this variability for much smaller computation times than numerical models, will be validated numerically and submitted to extensive random samplings. The effect of the spatial variability will be evaluated
Abdelmoula, Mohamed. "Phénomènes non linéaires et chaos dans les systèmes d’énergie renouvelable – Application à une installation photovoltaïque." Thesis, Reims, 2017. http://www.theses.fr/2017REIMS001/document.
Повний текст джерелаIn order to satisfy future energy requirement and reduce environmental impact, application of clean renewable energy, have been reconsidered recently. In this context, a growing interest in isolated power system has been observed. The need of low power topologies fed by photovoltaic array avoiding the use oftransformer open the study of small-scale stand-alone power system. Hence, theneed to study the associated control design strategies ensuring stability, reliability and high efficiency.As systems become more complex, nonlinearities play an increasingly importantrole in stand-alone power system behaviour. Modeling must accurately reflect component and system dynamics. In addition, analysis tools should continue to workreliably, even under various system conditions, providing accurate predictions of systems behaviour.This work is devoted to the study of a stand-alone photovoltaic power system.The proposed structure consists on photovoltaic array, a dc-dc buck converter, anda load connected in cascade through a dc bus. The research efforts focus on themodeling process and stability analysis, which leads to an implementation with acomprehensive description validated through simulation results.After giving the state-of-the-art in second chapter, the manuscript is divided into four chapters. These parts are dedicated to photovoltaic plant modeling, the numeric simulation improvements and dynamic investigation of the photovoltaic system under digital controls.The thesis presents an overview of the photovoltaic generator models. Then, amodified photovoltaic array model is proposed. We also detailed the photovoltaic plant modeling process. An improved Differential-Algebraic Equations (DAEs)solver is then investigated. We also described the photovoltaic system by a simplified discrete model. Then, the dynamic stability analysis is detailled. In addition,we have studied the chaotic behaviour that appears in the photovoltaic plant basedon the two-cell dc-dc buck converter.The aim of the last part is to show, using control theory and numerical simulation,how to apply a method to stabilize the chaotic orbit. Finally, to accomplish this aim, a time-delayed feedback controller is used
Rondon, Andres. "Recherche d’un critère mécanique de stabilité dans le cadre du planning de l’arthroplastie totale de hanche. Analyse numérique du comportement vibratoire de l’implant et caractérisation de l’interface os-implant." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066059/document.
Повний текст джерелаThis thesis work is concerned with the enhancement of three-dimensional preoperative planning (P3D) tools for total hip reconstruction. When cementless implants are used, primary stability is vital for a good osseointegration. For this, a correct selection of the size and position of the implant is necessary. The surgeon may use P3D based on the computed tomography scanner of the patient’s hip to optimally select the implant’s size and anticipate the final implant’s position. Available planning methods lack a mechanical criterion reflecting the actual quality of the bone-implant contact. In this work we propose a method to improve P3D using a vibrational finite element analysis to calculate patient-specific mechanical parameters representative of primary stability. We found that the modal response of the stem is very sensitive to changes of the area and apparent stiffness of the bone-implant interface. A clear transition between loose and tight contact allowed the definition of thresholds that could potentially discriminate between a stable and an unstable stem. We also studied the effect of the broaching procedure and its relevance for P3D. The effect of broaching on bone microstructure at the bone-implant interface was analyzed using cadaveric samples and micro-computed tomography. A mapping of the stiffness of bone in contact with the implant was obtained with indentation on the same cadaveric samples
Tun, Yarzar. "Nonmodal Analysis of Temporal Transverse Shear Instabilities in Shallow Flows." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36886.
Повний текст джерелаBakhtiari, Siamak. "Stochastic finite element slope stability analysis." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/stochastic-finite-element-slope-stability-analysis(c1b451d9-8bf6-43ff-9c10-7b5209fb45c1).html.
Повний текст джерелаWang, Mengjie. "Stability analysis of three-dimensional boundary layers with parabolized stability equations /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487858106119026.
Повний текст джерелаHurel, Gabriel. "Simulation du comportement vibratoire non linéaire induit par frottement des freins aéronautiques." Thesis, Ecully, Ecole centrale de Lyon, 2014. http://www.theses.fr/2014ECDL0016.
Повний текст джерелаThis report deals with the non-linear transient simulation of the dynamic behaviour of aeronautic brake systems. The objective is to reproduce the occurrence and level of vibrations versus time in order to control and adjust design consequently. The braking tests highlight two eigenmodes, which are called whirl and squeal. If the level of these vibrations becomes too high, the structures of the wheel and the landing gear may be damaged. To avoid damage, the design has to be adjusted. To achieve this, Messier-Bugatti-Dowty requires a model that is able to predict the levels of vibrations of the brake when it is braking. This model must have an adequate accuracy, be linked to the digital mockup and not require tuning. First, the existing finite element model has to be improved because its initial accuracy is not acceptable. A study about gyroscopic effects allows to assess their impact on the frequency and the stability of whirl modes. A complete modelling of the test frame improves the squeal modes’ frequency accuracy. At last, the whirl modes are better simulated due to the development of a tyre model based on modal analysis data. Then, the finite element model is reduced in order to perform a temporal integration. A substructuring allows to separate the set of brake discs (heat sink), where friction and non-linearities are located, from the rest of the structure which is considered linear. Three heat sink reduction techniques are proposed. Their representativeness are estimated compared to the non-reduced model. The first technique is a nodal description of the heat sink. The equations of friction and non-linearity are analytical. For the second technique, the non-linearity is displaced to the extremity of the heat sink to uncouple it from friction. The third technique, more ambitious and complex, keeps the location and non-linearity in friction interfaces and discs geometry. A reduction technique enables to decrease the number of non-linear degrees of freedom. As a conclusion, transient simulations are computed from reduced models. Sensitivity studies are performed. Studied parameters are the type of integration solver, introduced damping, non-linearities, hydraulic pressure, and friction coefficient. Their impacts on level and duration of occurrence of vibrations is estimated