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1
Wang, Zhibo. « Estimations non-asymptotiques et robustes basées sur des fonctions modulatrices pour les systèmes d'ordre fractionnaire ». Electronic Thesis or Diss., Bourges, INSA Centre Val de Loire, 2023. http://www.theses.fr/2023ISAB0003.
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Cette thèse développe la méthode des fonctions modulatrices pour des estimations non-asymptotiques et robustes pour des pseudo-états des systèmes nonlinéaires d'ordre fractionnaire, des systèmes linéaires d'ordre fractionnaire avec des accélérations en sortie, et des systèmes à retards d'ordre fractionnaire. Les estimateurs conçus sont fournis en termes de formules intégrales algébriques, ce qui assure une convergence non-asymptotique. Comme une caractéristique essentielle des algorithmes d'estimation conçus, les mesures de sorties bruitées ne sont impliquées que dans les termes intégraux, ce qui confère aux estimateurs une robustesse contre les bruits. Premièrement, pour les systèmes nonlinéaires d'ordre fractionnaire et partiellement inconnu, l'estimation de la dérivée fractionnaire du pseudo-état est abordée via la méthode des fonctions modulatrices. Grâce à la loi de l'indice additif des dérivées fractionnaires, l'estimation est décomposée en une estimation des dérivées fractionnaires de la sortie et une estimation des valeurs initiales fractionnaires. Pendant ce temps, la partie inconnue est estimée via une stratégie innovante de fenêtre glissante. Deuxièmement, pour les systèmes linéaires d'ordre fractionnaire avec des accélérations comme sortie, l'estimation de l'intégrale fractionnaire de l'accélération est d'abord considérée pour les systèmes mécaniques de vibration d'ordre fractionnaire, où seules des mesures d'accélération bruitées sont disponibles. Basée sur des approches numériques existantes qui traitent des intégrales fractionnaires, notre attention se limite principalement à l'estimation des valeurs initiales inconnues en utilisant la méthode des fonctions modulatrices. Sur cette base, le résultat est ensuite généralisé aux systèmes linéaires plus généraux d'ordre fractionnaire. En particulier, le comportement des dérivées fractionnaires à zéro est étudié pour des fonctions absolument continues, ce qui est assez différent de celui de l'ordre entier. Troisièment, pour les systèmes à retards d'ordre fractionnaire, l'estimation du pseudo-état est étudiée en concevant un système dynamique auxiliaire d'ordre fractionnaire, qui fournit un cadre plus général pour générer les fonctions modulatrices requises. Avec l'introduction de l'opérateur de retard et du changement de coordonnées généralisé bicausal, l'estimation du pseudo-état du système considéré peut être réduite à celle de la forme normale correspondante. Contrairement aux travaux précédents le schéma présenté permet une estimation directe du pseudo-état plutôt que d'estimer les dérivées fractionnaires de la sortie et un ensemble de valeurs initiales fractionnaires. De plus, l'efficacité et la robustesse des estimateurs proposés sont vérifiées par des simulations numériques dans cette thèse. Enfin, un résumé de ce travail et un aperçu des travaux futurs sont tirésThis thesis develops the modulating functions method for non-asymptotic and robust estimations for fractional-order nonlinear systems, fractional-order linear systems with accelerations as output, and fractional-order time-delay systems. The designed estimators are provided in terms of algebraic integral formulas, which ensure non-asymptotic convergence. As an essential feature of the designed estimation algorithms, noisy output measurements are only involved in integral terms, which endows the estimators with robustness against corrupting noises. First, for fractional-order nonlinear systems which are partially unknown, fractional derivative estimation of the pseudo-state is addressed via the modulating functions method. Thanks to the additive index law of fractional derivatives, the estimation is decomposed into the fractional derivatives estimation of the output and the fractional initial values estimation. Meanwhile, the unknown part is fitted via an innovative sliding window strategy. Second, for fractional-order linear systems with accelerations as output, fractional integral estimation of the acceleration is firstly considered for fractional-order mechanical vibration systems, where only noisy acceleration measurements are available. Based on the existing numerical approaches addressing the proper fractional integrals of accelerations, our attention is primarily restricted to estimating the unknown initial values using the modulating functions method. On this basis, the result is further generalized to more general fractional-order linear systems. In particular, the behaviour of fractional derivatives at zero is studied for absolutely continuous functions, which is quite different from that of integer order. Third, for fractional-order time-delay systems, pseudo-state estimation is studied by designing a fractional-order auxiliary modulating dynamical system, which provides a more general framework for generating the required modulating functions. With the introduction of the delay operator and the bicausal generalized change of coordinates, the pseudo-state estimation of the considered system can be reduced to that of the corresponding observer normal form. In contrast to the previous work, the presented scheme enables direct estimation for the pseudo-state rather than estimating the fractional derivatives of the output and a bunch of fractional initial values. In addition, the efficiency and robustness of the proposed estimators are verified by numerical simulations in this thesis. Finally, a summary of this work and an insight into future work were drawn
2
Katugampola, Don Udita Nalin. « ON GENERALIZED FRACTIONAL INTEGRALS AND DERIVATIVES ». OpenSIUC, 2011. https://opensiuc.lib.siu.edu/dissertations/387.
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In this paper we present a generalization to two existing fractional integrals and derivatives, namely, the Riemann-Liouville and Hadamard fractional operators. The existence and uniqueness results for single term fractional differential equations (FDE) have also been established. We also obtain the Mellin transforms of such generalized fractional operators which are important in solving fractional differential equations.
3
Schiavone, S. E. « Distributional theories for multidimensional fractional integrals and derivatives ». Thesis, University of Strathclyde, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382492.
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Traytak, Sergey D., et Tatyana V. Traytak. « Method of fractional derivatives in time-dependent diffusion ». Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-193646.
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Traytak, Sergey D., et Tatyana V. Traytak. « Method of fractional derivatives in time-dependent diffusion ». Diffusion fundamentals 6 (2007) 38, S. 1-2, 2007. https://ul.qucosa.de/id/qucosa%3A14215.
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Munkhammar, Joakim. « Riemann-Liouville Fractional Derivatives and the Taylor-Riemann Series ». Thesis, Uppsala University, Department of Mathematics, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-121418.
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Haveroth, Thais Clara da Costa. « On the use of fractional derivatives for modeling nonlinear viscoelasticity ». Universidade do Estado de Santa Catarina, 2015. http://tede.udesc.br/handle/handle/2069.
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Previous issue date: 2015-10-26Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Dentre a vasta gama de polímeros estruturais atualmente disponíveis no mercado, este trabalho está particularmente voltado ao estudo do polietileno de alta densidade. Embora este material já tenha sido investigado por diversos autores, seu típico comportamento viscoelástico não-linear apresenta dificuldades na modelagem. Visando uma nova contribuição, este trabalho propõe a descrição de tal comportamento utilizando uma abordagem baseada em derivadas fracionários. Esta formulação produz equações constitutivas fracionais que resultam em boas propriedades de ajuste de curvas com menos parâmetros a serem identificados que nos métodos tradicionais. Neste sentido, os resultados experimentais de fluência para o polietileno de alta densidade, avaliados em diferentes níveis de tensão, são ajustados por este esquema. Para estimar a deformação à níveis de tensão que não tenham sido medidos experimentalmente, o princípio da equivalência tensão-tempo é utilizado e os resultados são comparados com aqueles apresentados por uma interpolação linear dos parâmetros. Além disso, o princípio da superposição modificado é aplicado para predizer a comportamento de materiais sujeitos a níveis de tensão que mudam abruptamente ao longo do tempo. Embora a abordagem fracionária simplifique o problema de otimização inversa subjacente, é observado um grande aumento no esforço computacional. Assim, alguns algoritmos que objetivam economia computacional, são estudados. Conclui-se que, quando acurária é necessária ou quando um modelo de séries Prony requer um número muito grande de parâmetros, a abordagem fracionária pode ser uma opção interessante.
Among the wide range of structural polymers currently available in the market, this work is concerned particularly with high density polyethylene. The typical nonlinear viscoelastic behavior presented by this material is not trivial to model, and has already been investigated by many authors in the past. Aiming at a further contribution, this work proposes modeling this material behavior using an approach based on fractional derivatives. This formulation produces fractional constitutive equations that result in good curve-fitting properties with less parameters to be identified when compared to traditional methods. In this regard, experimental creep results of high density polyethylene evaluated at different stress levels are fitted by this scheme. To estimate creep at stress levels that have not been measured experimentally, the time-stress equivalence principle is used and the results are compared with those presented by a linear interpolation of the parameters. Furthermore, the modified superposition principle is applied to predict the strain for materials subject to stress levels which change abruptly from time to time. Some comparative results are presented showing that the fractional approach proposed in this work leads to better results in relation to traditional formulations described in the literature. Although the fractional approach simplifies the underlying inverse optimization problem, a major increase in computational effort is observed. Hence, some algorithms that show computational cost reduction, are studied. It is concluded that when high accuracy is mandatory or when a Prony series model requires a very large number of parameters, the fractional approach may be an interesting option.
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Shi, Chen Yang. « High order compact schemes for fractional differential equations with mixed derivatives ». Thesis, University of Macau, 2017. http://umaclib3.umac.mo/record=b3691348.
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Atkins, Zoe. « Almost sharp fronts : limit equations for a two-dimensional model with fractional derivatives ». Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/55759/.
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We consider the evolution of sharp fronts and almost-sharp fronts for the ↵-equation, where for an active scalar q the corresponding velocity is defined by u = r?(−#)−(2 − ↵)/2q for 0 < ↵ < 1. This system is introduced as a model interpolating between the two-dimensional Euler equation (↵ = 0) and the surface quasi-geostrophic (SQG) equation (↵ = 1). The study of such fronts for the SQG equation was introduced as a natural extension when searching for potential singularities for the three-dimensional Euler equation due to similarities between these two systems, with sharp-fronts corresponding to vortex-lines in the Euler case (Constantin et al., 1994b). Almost-sharp fronts were introduced in C´ordoba et al. (2004) as a regularisation of a sharp front with thickness $, with interest in the study of such solutions as $ ! 0, in particular those that maintain their structure up to a time independent of $. The construction of almost-sharp front solutions to the SQG equation is the subject of current work (Fe↵erman and Rodrigo, 2012). The existence of exact solutions remains an open problem. For the ↵-equation we prove analogues of several known theorems for the SQG equations and extend these to investigate the construction of almost-sharp front solutions. Using a version of the Abstract Cauchy Kovalevskaya theorem (Safonov, 1995) we show for fixed 0 < ↵ < 1, under analytic assumptions, the existence and uniqueness of approximate solutions and exact solutions for short-time independent of $; such solutions take a form asymptotic to almost-sharp fronts. Finally, we obtain the existence and uniqueness of analytic almost-sharp front solutions.
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Jarrah, Bilal. « Fractional Order and Inverse Problem Solutions for Plate Temperature Control ». Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40551.
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Surface temperature control of a thin plate is investigated. Temperature is controlled on one side of the plate using the other side temperature measurements. This is a decades-old problem, reactivated more recently by the awareness that this is a fractional-order problem that justifies the investigation of the use of fractional order calculus. The approach is based on a transfer function obtained from the one-dimensional heat conduction equation solution that results in a fractional-order s-domain representation.
Both the inverse problem approach and the fractional controller approach are studied here to control the surface temperature, the first one using inverse problem plus a Proportional only controller, and the second one using only the fractional controller.
The direct problem defined as the ratio of the output to the input, while the inverse problem defined as the ratio of the input to the output. Both transfer functions are obtained, and the resulting fractional-order transfer functions were approximated using Taylor expansion and Zero-Pole expansion. The finite number of terms transfer functions were used to form an open-loop control scheme and a closed-loop control scheme. Simulation studies were done for both control schemes and experiments were carried out for closed-loop control schemes.
For the fractional controller approach, the fractional controller was designed and used in a closed-loop scheme. Simulations were done for fractional-order-integral, fractional-order-derivative and fractional-integral-derivative controller designs. The experimental study focussed on the fractional-order-integral-derivative controller design.
The Fractional-order controller results are compared to integer-order controller’s results. The advantages of using fractional order controllers were evaluated. Both Zero-Pole and Taylor expansions are used to approximate the plant transfer functions and both expansions results are compared.
The results show that the use of fractional order controller performs better, in particular concerning the overshoot.
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Blanc, Emilie. « Time-domain numerical modeling of poroelastic waves : the Biot-JKD model with fractional derivatives ». Phd thesis, Aix-Marseille Université, 2013. http://tel.archives-ouvertes.fr/tel-00954506.
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Une modélisation numérique des ondes poroélastiques, décrites par le modèle de Biot, est proposée dans le domaine temporel. La dissipation visqueuse à l'intérieur des pores est décrite par le modèle de perméabilité dynamique, développé par Johnson-Koplik-Dashen (JKD). Certains coefficients du modèle de Biot-JKD sont proportionnels à la racine carrée de la fréquence : dans le domaine temporel, ces coefficients introduisent des dérivées fractionnaires décalées d'ordre 1/2, qui reviennent à un produit de convolution. Basé sur une représentation diffusive, le produit de convolution est remplacé par un nombre fini de variables de mémoire, dont la relaxation est gouvernée par une équation différentielle ordinaire locale en temps, ce qui mène au modèle de Biot-DA (approximation diffusive). Les propriétés du modèle de Biot-JKD et du modèle de Biot-DA sont analysées : hyperbolicité, décroissance de l'énergie, dispersion. Pour déterminer les coefficients de l'approximation diffusive, différentes méthodes de quadrature sont proposées : quadratures de Gauss, procédures d'optimisation linéaire ou non-linéaire sur la plage de fréquence d'intérêt. On montre que l'optimisation non-linéaire est la meilleure méthode de détermination. Le système est modélisé numériquement en utilisant une méthode de splitting : la partie propagative est discrétisée par un schéma aux différences finies ADER, d'ordre 4 en espace et en temps, et la partie diffusive est intégrée exactement. Une méthode d'interface immergée est implémentée pour discrétiser la géometrie sur une grille cartésienne et pour discrétiser les conditions de saut aux interfaces. Des simulations numériques sont présentées, pour des milieux isotropes et isotropes transverses. Des comparaisons avec des solutions analytiques montrent l'efficacité et la précision de cette approche. Des simulations numériques en milieux complexes sont réalisées : influence de la porosité d'os spongieux, diffusion multiple en milieu aléatoire.
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Shabankhah, Mahmood. « Integral means of the derivatives of Blaschke products and zero sequences for the Dirichlet space ». Thesis, Université Laval, 2008. http://www.theses.ulaval.ca/2008/25900/25900.pdf.
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Fernandez, Arran. « Analysis in fractional calculus and asymptotics related to zeta functions ». Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/284390.
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This thesis presents results in two apparently disparate mathematical fields which can both be examined -- and even united -- by means of pure analysis. Fractional calculus is the study of differentiation and integration to non-integer orders. Dating back to Leibniz, this idea was considered by many great mathematical figures, and in recent decades it has been used to model many real-world systems and processes, but a full development of the mathematical theory remains incomplete. Many techniques for partial differential equations (PDEs) can be extended to fractional PDEs too. Three chapters below cover my results in this area: establishing the elliptic regularity theorem, Malgrange-Ehrenpreis theorem, and unified transform method for fractional PDEs. Each one is analogous to a known result for classical PDEs, but the proof in the general fractional scenario requires new ideas and modifications. Fractional derivatives and integrals are not uniquely defined: there are many different formulae, each of which has its own advantages and disadvantages. The most commonly used is the classical Riemann-Liouville model, but others may be preferred in different situations, and now new fractional models are being proposed and developed each year. This creates many opportunities for new research, since each time a model is proposed, its mathematical fundamentals need to be examined and developed. Two chapters below investigate some of these new models. My results on the Atangana-Baleanu model proposed in 2016 have already had a noticeable impact on research in this area. Furthermore, this model and the results concerning it can be extended to more general fractional models which also have certain desirable properties of their own. Fractional calculus and zeta functions have rarely been united in research, but one chapter below covers a new formula expressing the Lerch zeta function as a fractional derivative of an elementary function. This result could have many ramifications in both fields, which are yet to be explored fully. Zeta functions are very important in analytic number theory: the Riemann zeta function relates to the distribution of the primes, and this field contains some of the most persistent open problems in mathematics. Since 2012, novel asymptotic techniques have been applied to derive new results on the growth of the Riemann zeta function. One chapter below modifies some of these techniques to prove asymptotics to all orders for the Hurwitz zeta function. Many new ideas are required, but the end result is more elegant than the original one for Riemann zeta, because some of the new methodologies enable different parts of the argument to be presented in a more unified way. Several related problems involve asymptotics arbitrarily near a stationary point. Ideally it should be possible to find uniform asymptotics which provide a smooth transition between the integration by parts and stationary phase methods. One chapter below solves this problem for a particular integral which arises in the analysis of zeta functions.
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Jiang, Xin. « A Systematic Approach for Digital Hardware Realization of Fractional-Order Operators and Systems ». University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1386649994.
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Mucha, Ján. « Pokročilé metody parametrizace online písma osob s grafomotorickými obtížemi ». Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-438731.
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Grafomotorické obtíže (GD) výrazně ovlivňují kvalitu života školním věkem počínajíc, kde se vyvíjejí grafomotorické schopnosti, až do důchodového věku. Včasná diagnóza těchto obtíží a terapeutický zásah mají velký význam k jejich zlepšení. Vzhledem k tomu, že GD souvisí z vícerými symptomy v oblasti kinematiky, základní kinematické parametry jako rychlost, zrychlení a švih prokázaly efektivní kvantizaci těchto symptomů. Objektivní výpočetní systém podpory rozhodování pro identifikaci a vyšetření GD však není dostupný. A proto je hlavním cílem mé disertační práce výzkum pokročilé metody parametrizace online písma pro analýzu GD se speciálním zaměřením na využití metod zlomkového kalkulu. Tato práce je první, která experimentuje s využitím derivací neceločíselného řádu (FD) pro analýzu GD pomocí online písma získaného od pacientů s Parkinsonovou nemocí a u dětí školního věku. Byla navržena a evaluována nová metoda parametrizace online písma založena na FD využitím Grünwald-Letnikova přístupu. Bylo dokázáno, že navržená metoda významně zlepšuje diskriminační sílu a deskriptivní schopnosti v oblasti Parkinsonické dysgrafie. Stejně tak metoda pozitivně ovlivnila i nejmodernější techniky v oblasti analýzy GD u dětí školního věku. Vyvinutá parametrizace byla optimalizována s ohledem na výpočetní náročnost (až o 80 %) a také na vyladění řádu FD. Ke konci práce byly porovnány víceré přístupy výpočtu FD, jmenovitě Riemann-Liouvillův, Caputův společně z Grünwald-Letnikovým přístupem za účelem identifikace těch nejvhodnějších pro jednotlivé oblasti analýzy GD.
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Teodoro, Graziane Sales 1990. « Cálculo fracionário e as funções de Mittag-Leffler ». [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/306995.
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Orientador: Edmundo Capelas de OliveiraDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica
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Resumo: O cálculo fracionário, nomenclatura utilizada para cálculo de ordem não inteira, tem se mostrado importante e, em muitos casos, imprescindível na discussão de problemas advindos de diversas áreas da ciência, como na matemática, física, engenharia, economia e em muitos outros campos. Neste contexto, abordamos a integral fracionária e as derivadas fracionárias, segundo Caputo e segundo Riemann-Liouville. Dentre as funções relacionadas ao cálculo fracionário, uma das mais importantes é a função de Mittag-Leffler, surgindo naturalmente na solução de várias equações diferenciais fracionárias com coeficientes constantes. Tendo em vista a importância dessa função, a clássica função de Mittag-Leffler e algumas de suas várias generalizações são apresentadas neste trabalho. Na aplicação resolvemos a equação diferencial associada ao problema do oscilador harmônico fracionário, utilizando a transformada de Laplace e a derivada fracionária segundo Caputo
Abstract: The fractional calculus, which is the nomenclature used to the non-integer order calculus, has important applications due to its direct involvement in problem resolution and discussion in many fields, such as mathematics, physics, engineering, economy, applied sciences and many others. In this sense, we studied the fractional integral and fractional derivates: one proposed by Caputo and the other by Riemann-Liouville. Among the fractional calculus's functions, one of most important is the Mittag-Leffler function. This function naturally occurs as the solution for fractional order differential equations with constant coeficients. Due to the importance of the Mittag-Leffler functions, various properties and generalizations are presented in this dissertation. We also presented an application in fractional calculus, in which we solved the differential equation associated the with fractional harmonic oscillator. To solve this fractional oscillator equation, we used the Laplace transform and Caputo fractional derivate
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Matematica Aplicada
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Pedjeu, Jean-Claude. « Multi-time Scales Stochastic Dynamic Processes : Modeling, Methods, Algorithms, Analysis, and Applications ». Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4383.
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By introducing a concept of dynamic process operating under multi-time scales in sciences and engineering, a mathematical model is formulated and it leads to a system of multi-time scale stochastic differential equations. The classical Picard-Lindel\"{o}f successive approximations scheme is expended to the model validation problem, namely, existence and uniqueness of solution process. Naturally, this generates to a problem of finding closed form solutions of both linear and nonlinear multi-time scale stochastic differential equations. To illustrate the scope of ideas and presented results, multi-time scale stochastic models for ecological and epidemiological processes in population dynamic are exhibited. Without loss in generality, the modeling and analysis of three time-scale fractional stochastic differential equations is followed by the development of the numerical algorithm for multi-time scale dynamic equations. The development of numerical algorithm is based on the idea if numerical integration in the context of the notion of multi-time scale integration. The multi-time scale approach is applied to explore the study of higher order stochastic differential equations (HOSDE) is presented. This study utilizes the variation of constant parameter technique to develop a method for finding closed form solution processes of classes of HOSDE. Then then probability distribution of the solution processes in the context of the second order equations is investigated.
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Oliveira, Daniela dos Santos de 1990. « Derivada fracionária e as funções de Mittag-Leffler ». [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/306994.
Texte intégralRésumé :
Orientador: Edmundo Capelas de OliveiraDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica
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Resumo: Neste trabalho apresentamos um estudo sobre as funções de Mittag-Leffler de um, dois e três parâmetros. Apresentamos a função de Mittag-Leffler como uma generalização da função exponencial bem como a relação que esta possui com outras funções especiais, tais como as funções beta, gama, gama incompleta e erro. Abordamos, também, a integração fracionária que se faz necessária para introduzir o conceito de derivação fracionária. Duas formulações para a derivada fracionária são estudadas, as formulações proposta por Riemann-Liouville e por Caputo. Investigamos quais regras clássicas de derivação são estendidas para estas formulações. Por fim, como uma aplicação, utilizamos a metodologia da transformada de Laplace para resolver a equação diferencial fracionária associada ao problema do oscilador harmônico fracionário
Abstract: This work presents a study about the one- two- and three-parameters Mittag-Leffler functions. We show that the Mittag-Leffler function is a generalization of the exponential function and present its relations to other special functions beta, gamma, incomplete gamma and error functions. We also approach fractional integration, which is necessary to introduce the concept of fractional derivatives. Two formulations for the fractional derivative are studied, the formulations proposed by Riemann-Liouville and by Caputo. We investigate which classical derivatives rules can be extended to these formulations. Finally, as an application, using the Laplace transform methodology, we discuss the fractional differential equation associated with the harmonic oscillator problem
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Matematica Aplicada
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Miloš, Japundžić. « Uopštena rešenja nekih klasa frakcionih parcijalnih diferencijalnih jednačina ». Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2016. https://www.cris.uns.ac.rs/record.jsf?recordId=102114&source=NDLTD&language=en.
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Doktorska disertacija je posvećena rešavanju Košijevog problema odabranih klasa frakcionih diferencijalnih jednačina u okviru Kolomboovih prostora uopštenih funkcija. U prvom delu disertacije razmatrane su nehomogene evolucione jednačine sa prostorno frakcionim diferencijalnim operatorima reda 0 < α < 2 i koeficijentima koji zavise od x i t. Ova klasa jednačina je aproksimativno rešavana, tako što je umesto početne jednačine razmatrana aproksimativna jednačina data preko regularizovanih frakcionih izvoda, odnosno, njihovih regularizovanih množitelja. Za rešavanje smo koristili dobro poznate uopštene uniformno neprekidne polugrupe operatora. U drugom delu disertacije aproksimativno su rešavane nehomogene frakcione evolucione jednačine sa Kaputovimfrakcionim izvodom reda 0 < α < 2, linearnim, zatvorenim i gusto definisanimoperatorom na prostoru Soboljeva celobrojnog reda i koeficijentima koji zaviseod x. Odgovarajuća aproksimativna jednačina sadrži uopšteni operator asociran sa polaznim operatorom, dok su rešenja dobijena primenom, za tu svrhu u disertaciji konstruisanih, uopštenih uniformno neprekidnih operatora rešenja.U oba slučaja ispitivani su uslovi koji obezbeduju egzistenciju i jedinstvenostrešenja Košijevog problema na odgovarajućem Kolomboovom prostoru.Colombeau spaces of generalized functions. In the firs part, we studied inhomogeneous evolution equations with space fractional differential operators of order 0 < α < 2 and variable coefficients depending on x and t. This class of equations is solved approximately, in such a way that instead of the originate equation we considered the corresponding approximate equation given by regularized fractional derivatives, i.e. their regularized multipliers. In the solving procedure we used a well-known generalized uniformly continuous semigroups of operators. In the second part, we solved approximately inhomogeneous fractional evolution equations with Caputo fractional derivative of order 0 < α < 2, linear, closed and densely defined operator in Sobolev space of integer order and variable coefficients depending on x. The corresponding approximate equation is a given by the generalized operator associated to the originate operator, while the solutions are obtained by using generalized uniformly continuous solution operators, introduced and developed for that purpose. In both cases, we provided the conditions that ensure the existence and uniqueness solutions of the Cauchy problem in some Colombeau spaces.
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Kárský, Vilém. « Modelování LTI SISO systémů zlomkového řádu s využitím zobecněných Laguerrových funkcí ». Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-316278.
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This paper concentrates on the description of fractional order LTI SISO systems using generalized Laguerre functions. There are properties of generalized Laguerre functions described in the paper, and an orthogonal base of these functions is shown. Next the concept of fractional derivatives is explained. The last part of this paper deals with the representation of fractional order LTI SISO systems using generalized Laguerre functions. Several examples were solved to demonstrate the benefits of using these functions for the representation of LTI SISO systems.
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Ahmad, Khan Mumtaz, et K. S. Nisar. « On a Generalizations of Lauricella’s Functions of Several Variables ». Pontificia Universidad Católica del Perú, 2014. http://repositorio.pucp.edu.pe/index/handle/123456789/97061.
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The present paper introduces 10 Appell’s type generalized functions Ni, i = 1, 2, ...... 10 by considering the product of n − 3F2 functions. The paper contains Fractional derivative representations, Integral representations and symbolic forms similar to those obtained by J. L. Burchnall and T. W.Chaundy for the four Appell’s functions, have been obtained for these newly defined functions N1, N2.......N10. The results obtained are believed to be new.El presente artículo introduce 10 tipo de funciones generalizadas tipo Appell Ni, 1 ≤ i ≤ 10, considerando el producto de n funciones 3F2. El artículo contiene representaciones por derivadas fraccionales, representaciones integrales y formas simbólicas similares a aquellas obtenidas por J. L. Burchnall y T. W. Chaundy para las cuatro funciones de Appell, han sido obtenidas para estas nuevas funciones N1, N2.......N10. Los resultados parecen ser nuevos.
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Oti, Vincent Bediako. « Numerické metody pro řešení počátečních úloh zlomkových diferenciálních rovnic ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-445462.
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Tato diplomová práce se zabývá numerickými metodami pro řešení počátečních problémů zlomkových diferenciálních rovnic s Caputovou derivací. Jsou uvedeny dva numerické přístupy spolu s přehledem základních aproximačních formulí. Dvě verze Eulerovy metody jsou realizovány v Matlabu a porovnány na základě numerických experimentů.
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Ouloin, Martyrs. « Méthode d’inversion d’un Modèle de diffusion Mobile Immobile fractionnaire ». Thesis, Avignon, 2012. http://www.theses.fr/2012AVIG0504/document.
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L’étude expérimentale du transport de soluté dans les milieux poreux montre des écarts à la loi de Fick. D’autre part, des progrès importants ont été accomplis sur le transport en milieu poreux, en supposant que les fluides (et les traceurs) en mouvement dans ces milieux sont arrêtés pendant des durées aléatoires. La matrice solide rend cette idée plausible. Nous étudions un modèle utilisant cette idée en l’associant à des durées d’immobilisation sans moyenne finie, en fait distribuées par des lois de Lévy. On arrive ainsi au modèle MIM fractionnaire, ou fractal.Ce modèle est une équation aux dérivées partielles pour la densité de traceur. Il équivaut à supposer que les particules de fluide et de traceur font des déplacements régis par un processus stochastique. Ce dernier est la limite hydrodynamique de marches au hasard fondées sur des déplacements convectifs, des sauts gaussiens, et des arrêts distribués suivant une loi de Lévy. Ces deux versions du même modèle donnent deux méthodes de simulation numérique.Nous montrons comment mettre en œuvre ces méthodes. Ceci a pour but la maîtrise d’outils de simulation, afin de comparer avec des données expérimentales pour savoir si ce modèle convient pour décrire le transport dans un milieu donné. Cette simulation, pour être efficace, nécessite la connaissance des paramètres du transport de soluté au sein du milieu donné. Ils sont difficilement mesurables et/ou identifiables en pratique. Donc, il faut pouvoir les estimer à partir de grandeurs qu’on sait mesurer directement, comme la densité d’un traceur. Pour cela, nous avons mis en place une méthode d’inversion qui permet d’extraire les paramètres du modèle MIM fractionnaire, à partir de données expérimentales. Cette méthode d’inversion est basée sur la transformation de Laplace. Elle utilise le lien entre les paramètres de transport du modèle MIM fractionnaire, et les dérivées de la transformée de Laplace des solutions de ce modèle. Ce lien est exact dans un milieu semi-infini, et seulement approché dans un milieu fini.Après avoir testé cette méthode en l’appliquant à des données numériques en essayant de retrouver leurs paramètres à "l’aveugle", nous l’appliquons à des données issues d’une expérience de traçage en milieu poreux insaturéAppealing models for mass transport in porous media assume that fluid and tracer particles can be trapped during random periods. Among them, the fractional version of the Mobile Immobile Model (f-MIM) was found to agree with several tracer test data recorded in environmental media.This model is equivalent to a stochastic process whose density probability function satisfies an advection-diffusion equation equipped with a supplementary time derivative, of non-integer order. The stochastic process is the hydrodynamic limit of random walks accumulating convective displacements, diffusive displacements, and stagnation steps of random duration distributed by a stable Lévy law having no finite average. Random walk and fractional differential equation provide complementary simulation methods.We describe that methods, in view of having tools for comparing the model with tracer test data consisting of time concentration curves. An other essential step in this direction is finding the four parameters of the fractional equation which make its solutions fit at best given sets of such data. Hence, we also present an inversion method adapted to the f-MIM. This method is based on Laplace transform. It exploits the link between model's parameters and Laplace transformed solutions to f-MIM equation. The link is exact in semi-infinite domains. After having checked inverse method's efficiency for numerical artificial data, we apply it to real tracer test data recorded in non-saturated porous sand
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Punurai, Somrat. « Determinants of Outbound Cross-border Mergers and Acquisitions by Emerging Asian Acquirers ». Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc700107/.
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This dissertation identifies key determinants of outbound cross-border mergers and acquisitions (M&As) by emerging Asian acquirers during 2001-2012. Using a zero-inflated model that takes into account different mechanisms governing country pairs that never engage in cross-border M&As and country pairs that actively participate in cross-border M&As, I uncover unique patterns for emerging Asian acquirers. Emerging Asian acquirers originate from countries with lower corporate tax rates than those countries where their targets are located. Furthermore, the negative impact of an international double tax burden is significantly larger than that found in previous studies. While country governance differences and geographical and cultural differences are important determinants of international M&As, relative valuation effects are muted. Coefficients of these determinants vary substantially, depending on whether targets are located in developing or advanced nations. Also, determinants differ considerably between active and non-active players in cross-border M&As. Moreover, comparisons of empirical models illustrate that estimating a non-linear model and taking into account both the bounded nature and non-normal distributions of fractional response variables lead to different inferences from those drawn from a linear model estimated by the ordinary least squares method. Overall, emerging Asian acquirers approach the deals differently from patterns documented in developed markets. So, when evaluating foreign business combinations or devising policies, managers or policymakers should consider these differences.
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Coja, Michael. « Effective vibro-acoustical modelling of rubber isolators ». Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-266.
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Nenad, Grahovac. « Анализа дисипације енергије у проблемима судара два или више тела ». Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2011. http://dx.doi.org/10.2298/NS20111208GRAHOVAC.
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Анализиран је судар два тела као и дисипација енергије укључена кроз механизам сувог трења моделираног неглатком вишевредносном функцијом и кроз деформацију вискоеластичног штапа чији модел укључује фракционе изводе. Проблем судара два тела је приказан у форми Кошијевог проблема који припада класи неглатких вишевредносних диференцијалних једначина произвољног реалногреда. Кошијев проблем је решен нумеричким поступком заснованим на Тарнеровом алгоритму. Испитано је кретање система и дисипација енергије за разне вредности улазних параметара. Показано је да се уведене методе могу применити и на проблем судара три тела.Analiziran je sudar dva tela kao i disipacija energije uključena kroz mehanizam suvog trenja modeliranog neglatkom viševrednosnom funkcijom i kroz deformaciju viskoelastičnog štapa čiji model uključuje frakcione izvode. Problem sudara dva tela je prikazan u formi Košijevog problema koji pripada klasi neglatkih viševrednosnih diferencijalnih jednačina proizvoljnog realnogreda. Košijev problem je rešen numeričkim postupkom zasnovanim na Tarnerovom algoritmu. Ispitano je kretanje sistema i disipacija energije za razne vrednosti ulaznih parametara. Pokazano je da se uvedene metode mogu primeniti i na problem sudara tri tela.
Impact of two bodies was analyzed as well as energy dissipation, which was included through dry friction phenomena modelled by a set-valued function, and through deformation of a viscoelastic rod modelled by fractional derivatives. The impact problem was presented in the form of the Cauchy problem that belongs to a class of set-valued fractional differential equations. The Cauchy problem was solved by the numerical procedure based on Turner’s algorithm. Behaviour and energy dissipation of the system was investigated for different values of input parameters. It was shown that suggested procedure can be applied on the problem of impact of three bodies.
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Fino, Ahmad. « Contributions aux problèmes d'évolution ». Phd thesis, Université de La Rochelle, 2010. http://tel.archives-ouvertes.fr/tel-00437141.
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Dans cette thèse, nous nous intéressons à l'étude de trois équations aux dérivées partielles et d'évolution non-locales en espace et en temps. Les solutions de ces trois solutions peuvent exploser en temps fini. Dans une première partie de cette thèse, nous considérons l'équation de la chaleur nonlinéaire avec une puissance fractionnaire du laplacien, et obtenons notamment que, dans le cas d'exposant sur-critique, le comportement asymptotique de la solution lorsque $t\rightarrow+\infty$ est déterminé par le terme de diffusion anormale. D'autre part, dans le cas d'exposant sous-critique, l'effet du terme non-linéaire domine. Dans une deuxième partie, nous étudions une équation parabolique avec le laplacien fractionnaire et un terme non-linéaire et non-local en temps. On montre que la solution est globale dans le cas sur-critique pour toute donnée initiale ayant une mesure assez petite, tandis que dans le cas sous-critique, on montre que la solution explose en temps fini $T_{\max}>0$ pour toute condition initiale positive et non-triviale. Dans ce dernier cas, on cherche le comportement de la norme $L^1$ de la solution en précisant le taux d'explosion lorsque $t$ s'approche du temps d'explosion $T_{\max}.$ Nous cherchons encore les conditions nécessaires à l'existence locale et globale de la solution. Une toisième partie est consacré à une généralisation de la deuxième partie au cas de systèmes $2\times 2$ avec le laplacien ordinaire. On étudie l'existence locale de la solution ainsi qu'un résultat sur l'explosion de la solution avec les mêmes propriétés étudiées dans le troisième chapitre. Dans la dernière partie, nous étudions une équation hyperbolique dans $\mathbb{R}^N,$ pour tout $N\geq2,$ avec un terme non-linéaire non-local en temps. Nous obtenons un résultat d'existence locale de la solution sous des conditions restrictives sur les données initiales, la dimension de l'espace et les exposants du terme non-linéaire. De plus on obtient, sous certaines conditions sur les exposants, que la solution explose en temps fini, pour toute condition initiale ayant de moyenne strictement positive.
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Wiedmann, Steffen. « Nouvelles propriétés de transport dans les systèmes d'électrons multicouches ». Thesis, Toulouse, INSA, 2010. http://www.theses.fr/2010ISAT0018/document.
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Ce travail de cette thèse présente les études sur l'influence du nouveau dégrée de liberté quantique, causé par le couplage tunnel entre les couches, sur les propriétés de transport des multi-puits quantiques dans un champ magnétique, à basse température, et sous irradiation micro-ondes. De nouvelles oscillations de résistance sont observées dans les systèmes d’électrons bi- et multicouches. Elles résultent d'une interférence entre les oscillations entre les sous-bandes et les oscillations induites par les micro-ondes. Des états à résistance nulle apparaissent lorsque les systèmes bicouches de haute qualité sous irradiation micro-ondes même en présence d’une diffusion additionnelle. Le mécanisme inélastique de la photorésistance est la contribution dominante à basses températures et sous un champ électronique modéré. Ce modèle confirme l'intégrité des estimations théoriques pour le temps de relaxation inélastique et mène à une explication satisfaisante de la photorésistance dans les systèmes d’électrons bi-et multicouches. Dans un champ magnétique intense, la suppression de l’effet tunnel entre les couches provoque des nouveaux états corrélés à cause d’une interaction électron-électron entre les différentes couches. Dans cette thèse, les systèmes électroniques tricouches, formés par de triples puits quantiques révèlent de nouveaux états de l’effet Hall Quantique fractionnaire si l’effet tunnel est supprimé par une composante parallèle du champ magnétique aux très basses températures (mK)This work is devoted to the investigation of the influence of the additional quantum degree of freedom caused by tunnel coupling on transport properties of multilayer electron systems in magnetic fields, at low temperatures and under microwave excitation. Microwave-induced resistance oscillations in bi- and multilayer electron systems are the consequence of an interference of magneto-intersubband and microwave-induced resistance oscillations which leads to peculiar oscillations in magnetoresistance. High-quality bilayer systems exposed to microwave irradiation exhibit zero-resistance states even in the presence of intersubband scattering. The inelastic mechanism of microwave photoresistance is found to be the dominant contribution at low temperatures and moderate microwave electric field. This model confirms the reliability of theoretical estimates for the inelastic relaxation time and leads to a satisfactory explanation of photoresistance in bi- and multilayer electron systems. In high magnetic fields, the suppression of tunnelling between layers causes new correlated states owing to electron-electron interaction in neighboured layers. In this thesis, trilayer electron systems formed by triple quantum wells reveal new fractional quantum Hall states if tunnelling is suppressed by a parallel component of the magnetic field at mK temperatures
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Malik, Salman Amin. « Contributions aux équations aux dérivées fractionnaires et au traitement d'images ». Phd thesis, Université de La Rochelle, 2012. http://tel.archives-ouvertes.fr/tel-00825874.
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Dans cette thèse, nous nous intéressons aux équations aux dérivées fractionnaires et leurs applications au traitement d'images. Une attention particulière a été apportée à un système non linéaire d'équations différentielles fractionnaires. En particulier, nous avons étudié les propriétés qualitatives des solutions d'un système non linéaire d'équations différentielles fractionnaires qui explosent en temps fini. L'existence des solutions locales pour le système, le profil des solutions qui explosent en temps fini sont présentés. Nous étudierons le problème inverse pour l'équation de diffusion linéaire en une dimension et en deux dimensions. Nous sommes intéressés par trouver un terme source inconnu d'une équation de diffusion non locale. Les conditions aux limites considérées sont non locales et le problème spectral est non auto-adjoint. L'existence et l'unicité de la solution du problème inverse sont présentées.D'autre part, nous proposons un modèle basé sur l'équation de la chaleur linéaire avec une dérivée fractionnaire en temps pour le débruitage d'images numériques. L'approche utilise une technique de pixel par pixel, ce qui détermine la nature du filtre. En contraste avec certain modèles basés sur les équations aux dérivées partielles pour le débruitage de l'image, le modèle proposé est bien posé et le schéma numérique est convergent. Une amélioration de notre modèle proposé est suggéré.
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Dannawi, Ihab. « Contributions aux équations d'évolutions non locales en espace-temps ». Thesis, La Rochelle, 2015. http://www.theses.fr/2015LAROS007/document.
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Dans cette thèse, nous nous intéressons à l'étude de quatre équations d'évolution non-locales. Les solutions de ces quatre équations peuvent exploser en temps fini. Dans la théorie des équations d'évolution non-linéaires, une solution est qualifiée de globale si elle est définie pour tout temps positif. Au contraire, si une solution existe seulement sur un intervalle de temps [0; T) borné, elle est dite locale. Dans ce dernier cas et quand le temps maximal d'existence est relié à une alternative d'explosion, on dit aussi que la solution explose en temps fini. Dans un premier travail, nous considérons l'équation de Schrödinger non-linéaire avec une puissance fractionnaire du laplacien, et nous obtenons l'explosion de la solution en temps fini Tmax > 0 pour toute condition initiale positive et non-triviale dans le cas d'exposant sous-critique. Ensuite, nous étudions une équation des ondes amorties avec un potentiel d'espace-temps et un terme non-linéaire et non-local en temps. Nous obtenons un résultat d'existence locale d'une solution dans l'espace d'énergie sous des conditions restrictives sur les données initiales, la dimension de l'espace et la croissance du terme non-linéaire. De plus, nous obtenons l'explosion de la solution en temps fini pour toute condition initiale de moyenne strictement positive. De plus, nous étudions un problème de Cauchy pour l'équation d'évolution avec un p- Laplacien avec une non linéarité non-locale en temps. Dans ce cadre, nous nous intéressons à l'étude de l'existence locale d'une solution de cette équation ainsi qu'un résultat de non-existence de solution globale. Finalement, nous étudions l'intervalle maximal d'existence des solutions de l'équation des milieux poreux avec un terme non-linéaire non-local en tempsIn this thesis, we study four non-local evolution equations. The solutions of these four equations can blow up in finite time. In the theory of nonlinear evolution equations, a solution is qualified as global if it isdefined for any time. Otherwise, if a solution exists only on a bounded interval [0; T), it is called local solution. In this case and when the maximum time of existence is related to a blow up alternative, we say that the solution blows up in finite time. First, we consider the nonlinear Schröodinger equation with a fractional power of the Laplacien operator, and we get a blow up result in finite time Tmax > 0 for any non-trivial non-negative initial condition in the case of sub-critical exponent. Next, we study a damped wave equation with a space-time potential and a non-local in time non-linear term. We obtain a result of local existence of a solution in the energy space under some restrictions on the initial data, the dimension of the space and the growth of nonlinear term. Additionally, we get a blow up result of the solution in finite time for any initial condition positive on average. In addition, we study a Cauchy problem for the evolution p-Laplacien equation with nonlinear memory. We study the local existence of a solution of this equation as well as a result of non-existence of global solution. Finally, we study the maximum interval of existence of solutions of the porous medium equation with a nonlinear non-local in time term
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Imamovic, Arnela. « Cash is [no longer] king : is an e-krona the answer ? : - a de lege ferenda investigation of the Swedish Riksbank's issuing mandate and other legal callenges in relation to economic effects on the payment market ». Thesis, Linköpings universitet, Filosofiska fakulteten, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-156410.
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For the past decades, the Swedish public’s payment habits have changed, where the majority of the public has abandoned the old way of making payments, using cash, and instead opted for more modern payment solutions, digital money. The difference between cash and digital money is that cash is physical and only issued by the Riksbank, whereas digital money is created by and stored on accounts at commercial banks. The question of what role the state should have on the payment market is an important point of discussion. But it is not categorically a new question; the Swedish government is tackling essentially the same problem today as it has been doing many times before. Today’s problem is to some extent however manifested in a different way. During the 20th century, discussions were held whether or not the Riksbank should have the exclusive right to issue banknotes. It was considered unnecessary, inappropriate and dangerous. The idea that the Riksbank could cover the entire economy’s need for banknotes was, according to the commercial banks, unreasonable. Nonetheless, in 1904 the exclusive right became fait accompli; the government intervened and gave the Riksbank the banknote monopoly. We are now finding ourselves facing a similar situation, where there is a difference of opinion regarding the Riksbank’s role on the payment market. It is therefore nothing new, but rather an expected task for the government, and thus the central bank, to analyze major changes and draw conclusions from them. The problem is essentially about cash being phased out by digital means of payment. In order to therefore solve the problem, the Riksbank has started a project to investigate whether or not the Riksbank should issue digital cash to the Swedish public, what the Riksbank calls an e-krona. To introduce an e-krona would be a major step, but for the public to not have access to a government alternative, seeing as cash usage is declining, is also a major step. No decision has been made yet regarding whether the e-krona will be introduced on the market or not. A decision that however has been made, is that the Riksbank is now working on building an e-krona to develop and assess the technique. Nonetheless, an introduction would undoubtedly have consequences for both the Riksbank and the commercial banks, which ultimately means it would have effects on the economy as a whole. What about regulatory aspects; is the Riksbank even allowed to issue an e-krona under current legislation? The answer is affirmative, to a certain extent. There are furthermore many other uncertainties regarding how an e-krona would affect the economy; the Riksbank does not fully answer many of the system issues in its project reports. The question of whether or not it even is up to the Riksbank to make a decision on the matter of an introduction is also questioned by the author in the thesis.
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Rakotonasy, Solonjaka Hiarintsoa. « Modèle fractionnaire pour la sous-diffusion : version stochastique et edp ». Phd thesis, Université d'Avignon, 2012. http://tel.archives-ouvertes.fr/tel-00839892.
Texte intégralRésumé :
Ce travail a pour but de proposer des outils visant 'a comparer des résultats exp'erimentaux avec des modèles pour la dispersion de traceur en milieu poreux, dans le cadre de la dispersion anormale.Le "Mobile Immobile Model" (MIM) a été à l'origine d'importants progrès dans la description du transport en milieu poreux, surtout dans les milieux naturels. Ce modèle généralise l'quation d'advection-dispersion (ADE) e nsupposant que les particules de fluide, comme de solut'e, peuvent ˆetre immo-bilis'ees (en relation avec la matrice solide) puis relˆachées, le piégeage et le relargage suivant de plus une cin'etique d'ordre un. Récemment, une version stochastique de ce modèle a 'eté proposée. Malgré de nombreux succès pendant plus de trois décades, le MIM reste incapable de repr'esenter l''evolutionde la concentration d'un traceur dans certains milieux poreux insaturés. Eneffet, on observe souvent que la concentration peut d'ecroˆıtre comme unepuissance du temps, en particulier aux grands temps. Ceci est incompatible avec la version originale du MIM. En supposant une cinétique de piégeage-relargage diff'erente, certains auteurs ont propos'e une version fractionnaire,le "fractal MIM" (fMIM). C'est une classe d''equations aux d'eriv'ees par-tielles (e.d.p.) qui ont la particularit'e de contenir un op'erateur int'egral li'e'a la variable temps. Les solutions de cette classe d'e.d.p. se comportentasymptotiquement comme des puissances du temps, comme d'ailleurs cellesde l''equation de Fokker-Planck fractionnaire (FFPE). Notre travail fait partie d'un projet incluant des exp'eriences de tra¸cageet de vélocimétrie par R'esistance Magn'etique Nucl'eaire (RMN) en milieuporeux insatur'e. Comme le MIM, le fMIM fait partie des mod'eles ser-vant 'a interpréter de telles exp'eriences. Sa version "e.d.p." est adapt'eeaux grandeurs mesur'ees lors d'exp'eriences de tra¸cage, mais est peu utile pour la vélocimétrie RMN. En effet, cette technique mesure la statistiquedes d'eplacements des mol'ecules excit'ees, entre deux instants fixés. Plus précisément, elle mesure la fonction caractéristique (transform'ee de Fourier) de ces d'eplacements. Notre travail propose un outil d'analyse pour ces expériences: il s'agit d'une expression exacte de la fonction caract'eristiquedes d'eplacements de la version stochastique du mod'ele fMIM, sans oublier les MIM et FFPE. Ces processus sont obtenus 'a partir du mouvement Brown-ien (plus un terme convectif) par des changement de temps aléatoires. Ondit aussi que ces processus sont des mouvement Browniens, subordonnéspar des changements de temps qui sont eux-mˆeme les inverses de processusde L'evy non d'ecroissants (les subordinateurs). Les subordinateurs associés aux modèles fMIM et FFPE sont des processus stables, les subordinateursassoci'es au MIM sont des processus de Poisson composites. Des résultatsexp'erimenatux tr'es r'ecents on sugg'er'e d''elargir ceci 'a des vols de L'evy (plusg'en'eraux que le mouvement Brownien) subordonnés aussi.Le lien entre les e.d.p. fractionnaires et les mod'eles stochastiques pourla sous-diffusion a fait l'objet de nombreux travaux. Nous contribuons 'ad'etailler ce lien en faisant apparaˆıtre les flux de solut'e, en insistant sur une situation peu 'etudiée: nous examinons le cas o'u la cinétique de piégeage-relargage n'est pas la mˆeme dans tout le milieu. En supposant deux cinétiques diff'erentes dans deux sous-domaines, nous obtenons une version du fMIMavec un opérateur intégro-diff'erentiel li'e au temps, mais dépendant de la position.Ces r'esultats sont obtenus au moyen de raisonnements, et sont illustrés par des simulations utilisant la discrétisation d'intégrales fractionnaires etd'e.d.p. ainsi que la méthode de Monte Carlo. Ces simulations sont en quelque sorte des preuves numériques. Les outils sur lesquels elles s'appuient sont présentés aussi.
33
Chiao, Chien-Ying, et 喬建穎. « Random Vibration for Dynamical Systems with Fractional Derivatives ». Thesis, 2014. http://ndltd.ncl.edu.tw/handle/12505701870396658422.
Texte intégralRésumé :
碩士國立臺灣科技大學
營建工程系
102
This study presents an equivalent linear system approach for analying SDOF systems with fractional differential damping under nonstationary random excitations. The definition of the Riemann-Liouville fractional differential is adopted and the Newmark method is used as a tool for numerical analyses. The nonstationary excitations consider a Gaussian white noise process modulated by deterministic envelop functions. To approximate the displacement and velocity statistics, this paper uses deterministic steady-state responses for obtaining best equivalent stiffness and equivalent damping by which the original fractional differential system can then be replaced. In this framework,the traditional analytical methods such as the Liapunov Direct Method and the direct analytical method can then be directly executed. The study uses different values of damping ratio, fractional differential order and coefficient of strength to observe response differences between the approximated solutions and the Monte Carlo solutions. The results show that a reasonable precision level can be reached when the fractional coefficient is small.
34
Chen, Yu-Cheng, et 陳鈺承. « Numerical Analyses for Systems with Fractional Derivatives Dynamic ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/52352768531643616254.
Texte intégralRésumé :
碩士國立臺灣科技大學
營建工程系
101
This paper aims to study the fractional derivatives used in analysis of power system. This study is based on the definition of Riemann-Liouville fractional derivatives as the basis and introduced Newmark method to analyze the response of time history of dynamical systems. The study further use the dynamic system with a single degree of freedom to input different value of damping and fractional differential, and observe the response of free vibration;Finally, to analyze the response and differences of power system installed fractional damping system through 921 Taiwan Chi-Chi earthquake data. The results showed a rising value of fractional differential produce the trend transferred stiffness to damping of structure, with the increase in damping coefficient, and this trend will become more obvious. In addition, the use of response spectrum analysis found that the greater natural period, the more difference between the use of fractional and integer differential.
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Wang, Yao-Min, et 王堯民. « Random Vibration Analysis of Dynamical Systems with Fractional Derivatives ». Thesis, 2015. http://ndltd.ncl.edu.tw/handle/92216319302959500350.
Texte intégralRésumé :
碩士國立臺灣科技大學
營建工程系
103
This paper aim to study under white Gaussian noise of stationary random process excitations, by changing coefficient of fractional derivatives , fractional differential order and damping ratio parameter to observe the response of equivalent system and Monte Carlo Simulation with fractional differential system , then analyze the errors between both systems. The results showed that when the fractional differential order and coefficient of fractional derivatives increased, the response of system will decay and will be steady state sooner, which represents the energy dissipation capacity of system will become more obvious, and which conforms that a rising value of fractional differential order produce the trend transferred stiffness to damping of structure ; when coefficient of fractional derivatives increased, the accuracy of the equivalent system will reduce, and the errors also increased along with fractional differential order in the beginning, when fractional differential order closed to the range 0.7~0.75, the maximum value of relative errors will even up to about 18%.
36
Chou, Tse-An, et 周澤安. « Random Vibration Analysis of Dynamical Systems with Fractional Derivatives ». Thesis, 2017. http://ndltd.ncl.edu.tw/handle/sb4d4u.
Texte intégralRésumé :
碩士國立臺灣科技大學
營建工程系
105
This study investigates stochastic responses of single-degree-of-freedom systems with a fractional differential damping subjected to white noise excitations. Both the unit impulse response function method and the Monte Carlo method are used to analyze the response differences. The mean square of the response displacements are studied through the variation of parameters, including the damping ratio, the fractional differential order, and the fractional differential coefficient. The results show that an increase in the fractional order will result in a response decrease with a faster rate in reaching steady states. This implies an enhancement of the energy dissipation capacity of the system due to a substantial increase in the effective damping. Moreover, when the fractional coefficient and fractional order are increased simultaneously, the response of the system would even decrease more significantly. It was found that the results based on the impulse function method and Monte Carlo method agree with each other. It’s concluded that both methods can substitute each other when only a linear system is considered.
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Yu, Chun-Chieh, et 游竣傑. « Response of Free Vibration of Dynamical Systems with Fractional Derivatives ». Thesis, 2016. http://ndltd.ncl.edu.tw/handle/53443783416385973945.
Texte intégralRésumé :
碩士國立臺灣科技大學
營建工程系
104
This study presents a fundamental solution based on the Laplace transform method for a dynamical system with fractional derivatives. The system being investigated is a typical spring-mass system with an additional fractional order damping. This study also observes the response variations by changing the coefficient and the order of fractional derivatives, and the damping ratio parameter. The Caputo fractional derivative is assumed with an order α satisfying 0＜α＜1. The results show that the displacement responses exhibit ossillatory behavier with amplitude decaying over time. The displacement ultimately reaches zero in a smooth form. Addition to the displacement response, the associated velocity response is also presented. Where a similarly decayed ossillatory response type is observed.
38
Hung, Wei-Chi, et 洪偉齊. « An Analysis of Dynamical Systems with Fractional Derivatives Using Short Memory Principle ». Thesis, 2014. http://ndltd.ncl.edu.tw/handle/77306351083025056807.
Texte intégralRésumé :
碩士國立臺灣科技大學
營建工程系
102
This study presents an analysis of dynamical systems with fractional derivatives using the short memory principle. The study is based on the Remann-Liouville definition for the fractional derivative and the Newmark method is adopted to evaluate the responses. In this work, the response time history of a single-degree-of-freedom system is used as a comparison basis. The effects of different memory length and different fractional orders are identified by comparing the response differences between the short and full memory analyses. The feasibility of applying the short memory principle for response spectral analysis is also investigated where the 921 Taiwan Chi-Chi earthquake data are used as inputs. Study results show that under high fractional order, reasonable response accuracy can still be obtained when the short memory principle is applied.
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Alsandor, Yvonne Renee U. « Deterministic and random vibrations of systems with frequency-dependent parameters or fractional derivatives ». Thesis, 1998. http://hdl.handle.net/1911/17148.
Texte intégralRésumé :
Frequency and time domain analyses of system models containing frequency dependent parameters or fractional derivatives are considered. Both model types result in integro-differential equations in the time domain, and in algebraic equations in the frequency domain. The deterministic and random vibrations of these systems are considered. A deterministic solution technique is developed and its ability to accurately approximate a system response is shown. Techniques for the random vibration analysis are presented using the Monte Carlo simulation method. It is assumed that the power spectral density of the random excitations is known. An AR method is used to generate an ensemble of random excitations records compatible with the given spectral density. The deterministic solution technique is employed to obtain the corresponding ensemble of system responses. Numerical results are presented which show that the Monte Carlo Simulation method yields good estimates of statistical information for the system response.
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« Iterative determination of spar lines static equilibrium and improved dynamic modeling by fractional derivatives ». Thesis, 2009. http://hdl.handle.net/1911/61843.
Texte intégralRésumé :
Polyester mooring systems are used as permanent systems of floating production systems and offshore structures. Compared to other mooring systems, polyester has a highly non linear behavior, thus complicating the overall design. Three important parameters affect the polyester rope stiffness; the mean load, the load range, and the frequency of the loading. Ignoring the 'true' stiffness as influenced by these parameters, may lead to underestimate the load induced riser stresses and damage. Procedures for determining mooring line stiffness that is representative of the in service conditions are developed herein. Two stiffness values, the 'static' and 'dynamic', are iteratively calculated from real time data, and are correlated with laboratory tests. Furthermore, note that fractional derivative models have been extensively proposed in literature for accurately capturing frequency dependent behavior of materials. In this context, a modified Newmark algorithm that takes advantage of the Grunwald-Letnikov fractional derivative representation is developed to treat related structural dynamic problems. In addition, a statistical linearization approach is also developed for random vibration treatment of such systems. The modified Newmark Algorithm is used to conduct Monte Carlo studies demonstrating the reliability of the statistical linearization solution.
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Singh, Satwinder Jit. « New Solution Methods For Fractional Order Systems ». Thesis, 2007. https://etd.iisc.ac.in/handle/2005/885.
Texte intégralRésumé :
This thesis deals with developing Galerkin based solution strategies for several important classes of differential equations involving derivatives and integrals of various fractional orders. Fractional order calculus finds use in several areas of science and engineering. The use of fractional derivatives may arise purely from the mathematical viewpoint, as in controller design, or it may arise from the underlying physics of the material, as in the damping behavior of viscoelastic materials. The physical origins of the fractional damping motivated us to study viscoelastic behavior of disordered materials at three levels. At the first level, we review two first principles models of rubber viscoelasticity. This leads us to study, at the next two levels, two simple disordered systems. The study of these two simplified systems prompted us towards an infinite dimensional system which is mathematically equivalent to a fractional order derivative or integral. This infinite dimensional system forms the starting point for our Galerkin projection based approximation scheme.
In a simplified study of disordered viscoelastic materials, we show that the networks of springs and dash-pots can lead to fractional power law relaxation if the damping coefficients of the dash-pots follow a certain type of random distribution. Similar results are obtained when we consider a more simplified model, which involves a random system coefficient matrix.
Fractional order derivatives and integrals are infinite dimensional operators and non-local in time: the history of the state variable is needed to evaluate such operators.
This non-local nature leads to expensive long-time computations (O(t2) computations for solution up to time t). A finite dimensional approximation of the fractional order derivative can alleviate this problem. We present one such approximation using a Galerkin projection. The original infinite dimensional system is replaced with an equivalent infinite dimensional system involving a partial differential equation (PDE). The Galerkin projection reduces the PDE to a finite system of ODEs. These ODEs can be solved cheaply (O(t) computations). The shape functions used for the Galerkin projection are important, and given attention. Calculations with both global shape functions as well as finite elements are presented. The discretization strategy is improved in a few steps until, finally, very good performance is obtained over a user-specifiable frequency range (not including zero). In particular, numerical examples are presented showing good performance for frequencies varying over more than 7 orders of magnitude. For any discretization held fixed, however, errors will be significant at sufficiently low or high frequencies. We discuss why such asymptotics may not significantly impact the engineering utility of the method.
Following this, we identify eight important classes of fractional differential equations (FDEs) and fractional integrodifferential equations (FIEs), and develop separate Galerkin based solution strategies for each of them. Distinction between these classes arises from the fact that both Riemann-Liouville as well as Caputo type derivatives used in this work do not, in general, follow either the law of exponents or the commutative property. Criteria used to identify these classes include; the initial conditions used, order of the highest derivative, integer or fractional order highest derivative, single or multiterm fractional derivatives and integrals. A key feature of our approximation scheme is the development of differential algebraic equations (DAEs) when the highest order derivative is fractional or the equation involves fractional integrals only. To demonstrate the effectiveness of our approximation scheme, we compare the numerical results with analytical solutions, when available, or with suitably developed series solutions. Our approximation scheme matches analytical/series solutions very well for all classes considered.
42
Singh, Satwinder Jit. « New Solution Methods For Fractional Order Systems ». Thesis, 2007. http://hdl.handle.net/2005/885.
Texte intégralRésumé :
This thesis deals with developing Galerkin based solution strategies for several important classes of differential equations involving derivatives and integrals of various fractional orders. Fractional order calculus finds use in several areas of science and engineering. The use of fractional derivatives may arise purely from the mathematical viewpoint, as in controller design, or it may arise from the underlying physics of the material, as in the damping behavior of viscoelastic materials. The physical origins of the fractional damping motivated us to study viscoelastic behavior of disordered materials at three levels. At the first level, we review two first principles models of rubber viscoelasticity. This leads us to study, at the next two levels, two simple disordered systems. The study of these two simplified systems prompted us towards an infinite dimensional system which is mathematically equivalent to a fractional order derivative or integral. This infinite dimensional system forms the starting point for our Galerkin projection based approximation scheme.
In a simplified study of disordered viscoelastic materials, we show that the networks of springs and dash-pots can lead to fractional power law relaxation if the damping coefficients of the dash-pots follow a certain type of random distribution. Similar results are obtained when we consider a more simplified model, which involves a random system coefficient matrix.
Fractional order derivatives and integrals are infinite dimensional operators and non-local in time: the history of the state variable is needed to evaluate such operators.
This non-local nature leads to expensive long-time computations (O(t2) computations for solution up to time t). A finite dimensional approximation of the fractional order derivative can alleviate this problem. We present one such approximation using a Galerkin projection. The original infinite dimensional system is replaced with an equivalent infinite dimensional system involving a partial differential equation (PDE). The Galerkin projection reduces the PDE to a finite system of ODEs. These ODEs can be solved cheaply (O(t) computations). The shape functions used for the Galerkin projection are important, and given attention. Calculations with both global shape functions as well as finite elements are presented. The discretization strategy is improved in a few steps until, finally, very good performance is obtained over a user-specifiable frequency range (not including zero). In particular, numerical examples are presented showing good performance for frequencies varying over more than 7 orders of magnitude. For any discretization held fixed, however, errors will be significant at sufficiently low or high frequencies. We discuss why such asymptotics may not significantly impact the engineering utility of the method.
Following this, we identify eight important classes of fractional differential equations (FDEs) and fractional integrodifferential equations (FIEs), and develop separate Galerkin based solution strategies for each of them. Distinction between these classes arises from the fact that both Riemann-Liouville as well as Caputo type derivatives used in this work do not, in general, follow either the law of exponents or the commutative property. Criteria used to identify these classes include; the initial conditions used, order of the highest derivative, integer or fractional order highest derivative, single or multiterm fractional derivatives and integrals. A key feature of our approximation scheme is the development of differential algebraic equations (DAEs) when the highest order derivative is fractional or the equation involves fractional integrals only. To demonstrate the effectiveness of our approximation scheme, we compare the numerical results with analytical solutions, when available, or with suitably developed series solutions. Our approximation scheme matches analytical/series solutions very well for all classes considered.
43
Fonseca, Mafalda Seco da. « Soluções numéricas para um problema de difusão de Knudsen ». Master's thesis, 2018. http://hdl.handle.net/10316/86636.
Texte intégralRésumé :
Dissertação de Mestrado em Matemática apresentada à Faculdade de Ciências e TecnologiaUm processo de difusão é caracterizado pelo transporte de matéria devido ao movimento aleatório das moléculas. A difusão de Knudsen é um processo de difusão anómalo que ocorre em meios porosos, onde o transporte de matéria é efetuado maioritariamente pela colisão das moléculas com as paredes do meio. Nesta dissertação apresentamos um modelo que envolve difusão anómala. Este modelo é descrito por uma equação integro-diferencial que envolve um operador diferencial, que é uma derivada fracionária de Riemann-Liouville no tempo. A solução analítica de equações que utilizam derivadas fracionárias não é fácil de obter analiticamente e, por isso, é necessário recorrer a métodos numéricos com vista a encontrar soluções aproximadas. Vamos apresentar essencialmente dois métodos numéricos, um explícito e um implícito no tempo. A derivada fracionária é aproximada pela denominada fórmula de Grünwald-Letnikov. Estes métodos numéricos só terão interesse se forem estáveis e convergirem para a solução exata, pelo que a sua convergência é analisada através da análise de Fourier e do método da energia.
A diffusion process is characterized by the transport of matter as a result of random molecular motion. Knudsen diffusion is a anomalous diffusion process, which occurs in porous media, and where the transport of matter is mostly due to the collision of molecules with he inside walls. In this thesis, we present a model that involves anomalous diffusion. It is described by a integro-differential equation, which involves the Riemann-Liouville fractional derivative in time. The analytical solution of equations that involve fractional derivatives are difficult to obtain and therefore, we need to use numerical methods in order to find approximate solutions. We will present two numerical methods, an implicit and an explicit in time. The fractional derivative is approximated by Grünwald-Letnikov formula. These numerical methods need to be stable and converge to the exact solution. Hence the convergence and stability of the numerical methods are studied through the Fourier analysis and the energy method.