• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 26
  • 12
  • 4
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 70
  • 70
  • 24
  • 21
  • 15
  • 14
  • 14
  • 13
  • 12
  • 9
  • 9
  • 8
  • 8
  • 7
  • 7
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Transformadas integrais, modelagem fracionária e o sistema de Lotka-Volterra

Gomes, Arianne Vellasco [UNESP] 21 February 2014 (has links) (PDF)
Made available in DSpace on 2014-08-13T14:50:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-02-21Bitstream added on 2014-08-13T17:59:56Z : No. of bitstreams: 1 000768672.pdf: 713902 bytes, checksum: bffc0a4e01880e1ffdb1dcb96c2a05b6 (MD5) / Este trabalho trata do Cálculo Fracionário e suas aplicações em problemas biológicos. Nas aplicações nos concentramos no sistema de Lotka-Volterra clássico e fracionário, para depois analisar o controle biológico da praga da cana-de-açúcar. Como trabalho futuro, propomos analisar as aplicações do sistema de Lotka-Volterra fracionário em problemas reais do câncer, com saturação de crescimento tumoral enfocando tratamento quimioterápico / This work is about Fractional Calculus and its applications in biological problems. In the applications we focus on the classical Lotka-Volterra system and into the corresponding fractional order version to examine the biological control of sugar cane’s pest. As future work, we analyze the fractional system in real problems of cancer, with saturation of tumor growth with a focus on chemotherapy
22

Transformadas integrais, modelagem fracionária e o sistema de Lotka-Volterra /

Gomes, Arianne Vellasco. January 2014 (has links)
Orientador: Rubens de Figueiredo Camargo / Coorientador: Paulo Fernando de Arruda Mancera / Banca: Edmundo de Oliveira Capela / Banca: Alexys Bruno Alfonso / Resumo: Este trabalho trata do Cálculo Fracionário e suas aplicações em problemas biológicos. Nas aplicações nos concentramos no sistema de Lotka-Volterra clássico e fracionário, para depois analisar o controle biológico da praga da cana-de-açúcar. Como trabalho futuro, propomos analisar as aplicações do sistema de Lotka-Volterra fracionário em problemas reais do câncer, com saturação de crescimento tumoral enfocando tratamento quimioterápico / Abstract: This work is about Fractional Calculus and its applications in biological problems. In the applications we focus on the classical Lotka-Volterra system and into the corresponding fractional order version to examine the biological control of sugar cane's pest. As future work, we analyze the fractional system in real problems of cancer, with saturation of tumor growth with a focus on chemotherapy / Mestre
23

A study of three variable analogues of certain fractional integral operators

Khan, Mumtaz Ahmad, Sharma, Bhagwat Swaroop 25 September 2017 (has links)
The paper deals with a three variable analogues of certain fractional integral operators introduced by M. Saigo. Resides giving three variable analogues of earlier known fractional integral operators of one variable as a special cases of newly defined operators, the paper establishes certain results in the form of theorems including integration by parts.
24

Matrizes operacionais e formalismo coadjunto em equações diferenciais fracionais. / Operational matrices and coadjoint formalism in fractional differential equations.

William Alexandre Labecca de Castro 29 September 2015 (has links)
O método das matrizes operacionais é expandido para o corpo complexo a ordens arbitrárias pela abordagem de Riemann-Liouville e Caputo com ênfase nas séries de Fourier complexas. Elabora-se uma adaptação do formalismo bra-ket de Dirac à linguagem tensorial no espaço de Hilbert de funções com expansões finitas para uso específico na teoria de equações diferenciais e matrizes operacionais, denominado \\Formalismo Coadjunto\". Estende-se o tratamento aos operadores fracionais de Weyl para períodos genéricos a fim de determinar as matrizes operacionais de derivação e integração de ordem arbitrária na base complexa de Fourier. Introduz-se um novo método de resolução de equações diferenciais ordinárias lineares e fracionais não-homogêneas, denominado \\Modelagem Operacional\", que permite a obtenção de soluções de equações de alta ordem com grande precisão sem a necessidade de imposição de condições iniciais ou de contorno. O método apresentado é aperfeiçoado por meio de um novo tipo de expansão, que denominamos \"Séries Associadas de Fourier\", a qual apresenta convergência mais rápida que a série de Fourier original numa restrição de domínio, possibilitando soluções de EDOs e EDFs de alta ordem com maior precis~ao e ampliando a esfera de casos passíveis de resolução. / Operational matrices method is expanded to complex field and arbitrary orders by using the Riemann-Liouville and Caputo approach with emphasis on complex Fourier series. Dirac\'s bra-ket notation is associated to tensor procedures in Hilbert spaces for finite function expansions to be applied specifically to dfferential equations and operational matrices, being called \\Coadjoint Formalism\". This treatment is extended to Weyl fractional operators for generic periods in order to establish the integral and derivative operational matrices of fractional order to complex Fourier basis. A new method to solve linear non-homogeneous ODEs and FDEs, called \\Operational Modelling\"is introduced. It yields high precision solutions on high order dfferential equations without assumption of boundary or initial conditions. The presented method is improved by a new kind of function expansion, called \\Fourier Associated Series\", which yields a faster convergence than original Fourier in a restrict domain, enabling to obtain solutions of high order ODEs and FDEs with excellent precision and broadening the set of solvable equations.
25

Equações diferenciais fracionárias e as funções de Mittag-Leffler / Fractional differential equations and the Mittag-Leffler functions

Contharteze, Eliana, 1984- 11 June 2014 (has links)
Orientador: Edmundo Capelas de Oliveira / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica / Made available in DSpace on 2018-08-26T02:22:44Z (GMT). No. of bitstreams: 1 Contharteze_Eliana_D.pdf: 2292843 bytes, checksum: c606ccefade98acff6e3f2b74c2ac021 (MD5) Previous issue date: 2014 / Resumo: Apresentamos operadores de integração e derivação fracionárias, que em particular, podem ser utilizados para descrever um processo difusivo anômalo através de uma equação diferencial fracionária. Como aplicação, discutimos uma equação diferencial fracionária associada ao processo de desaceleração de nêutrons, utilizando as transformadas integrais de Laplace e Fourier e através de uma conveniente implementação computacional, obtemos gráficos associados à solução dessa equação. Algumas propriedades dos operadores de integração e derivação fracionárias são mencionadas e utilizadas para escrever o teorema fundamental do cálculo fracionário. A clássica função de Mittag-Leffler, envolvendo um parâmetro e a função de Mittag-Leffler com dois parâmetros desempenham um papel importante no estudo das equações diferenciais fracionárias. A chamada função de Mittag-Leffler com três parâmetros, que generaliza as duas anteriores, emerge naturalmente no estudo da equação diferencial fracionária associada ao problema do telégrafo. Novas representações para as funções de Mittag-Leffler foram obtidas em termos de integrais impróprias de funções trigonométricas, a partir do cálculo da transformada de Laplace inversa sem usar um contorno de integração e como aplicação, encontramos algumas integrais impróprias interessantes que, geralmente, são demonstradas por aproximação com o uso de análise de Fourier ou teoria dos resíduos / Abstract: We present the operators of fractional integration and differentiation, which can be used to describe an anomalous diffusion process by means of a fractional differential equation. As an application we discuss a fractional differential equation associated with the slowing-down of neutrons using Laplace and Fourier transforms. With the help of a convenient computational implementation we obtain graphs of the solutions of this equation. Some properties of the operators of fractional integration and differentiation are mentioned and used to demonstrate the fundamental theorem of fractional calculus. The classical Mittag-Leffler function with one parameter and the Mittag-Leffler function with two parameters play an important role in the study of fractional differential equations. The so-called Mittag-Leffler function with three parameters, which generalizes the previous two functions, naturally arises in the study of the fractional differential equation associated with the telegraph problem. By calculating the inverse Laplace transform without using contour integration we obtain new representations for the Mittag-Leffler functions in terms of improper integrals of trigonometric functions; as an application we obtain some interesting improper integrals which are usually proved by approximation using Fourier analysis or residue theory / Doutorado / Matematica Aplicada / Doutora em Matemática Aplicada
26

Sobre cálculo fracionário e soluções da equação de Bessel / About fractional calculus and solutions of the Bessel's equation

Rodrigues, Fabio Grangeiro, 1980- 02 December 2015 (has links)
Orientador: Edmundo Capelas de Oliveira / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica / Made available in DSpace on 2018-08-26T23:00:41Z (GMT). No. of bitstreams: 1 Rodrigues_FabioGrangeiro_D.pdf: 1185818 bytes, checksum: 96f82c6ff4622e4ecdd3ccae79803dae (MD5) Previous issue date: 2015 / Resumo: Neste trabalho é apresentado um modo de se obter soluções de um caso particular da equação hipergeométrica confluente, a equação de Bessel de ordem p, utilizando-se da teoria do cálculo de ordem arbitrária, também conhecido popularmente por cálculo fracionário. Em particular, discutimos alguns equívocos identificados na literatura e levantamos questionamentos sobre algumas interpretações a respeito dos operadores formulados segundo Riemann-Liouville quando aplicados a certos tipos de funções. Para tanto, apresentamos inicialmente os operadores de integração e diferenciação fracionárias segundo as formulações mais clássicas (Riemann-Liouville, Caputo e Grünwald-Letnikov) e, em seguida, apresentamos o operador de integrodiferenciação fracionária que é a tentativa de unificar as operações de integração e diferenciação sob um único operador. Ao longo do texto indicamos as principais propriedades destes operadores e citamos algumas das suas aplicações comumente encontrados na Matemática, Física e Engenharias / Abstract: In this thesis we discuss the solvability of the Bessel's differential equation of order p, which is a particular case of the confluent hypergeometric equation, from the perspective of the theory of calculus of arbitrary order, also commonly known as fractional calculus. In particular, we expose some misconceptions encountered in the literature and we raise some questions about interpretations of the Riemann-Liouville operators when acting on certain types of functions. In order to do so, we present the main fractional operators (Riemann-Liouville, Caputo and Grünwald-Letnikov) as well as the fractional integrodifferential operator, which is an unified view of both integration and differentiation under a single operator. We also show the main properties of these operators and mention some of its applications in Mathematics, Physics and Engeneering / Doutorado / Matematica Aplicada / Doutor em Matemática Aplicada
27

Decentralized Coordination of Multiple Autonomous Vehicles

Cao, Yongcan 01 May 2010 (has links)
This dissertation focuses on the study of decentralized coordination algorithms of multiple autonomous vehicles. Here, the term decentralized coordination is used to refer to the behavior that a group of vehicles reaches the desired group behavior via local interaction. Research is conducted towards designing and analyzing distributed coordination algorithms to achieve desired group behavior in the presence of none, one, and multiple group reference states. Decentralized coordination in the absence of any group reference state is a very active research topic in the systems and controls society. We first focus on studying decentralized coordination problems for both single-integrator kinematics and double-integrator dynamics in a sampled-data setting because real systems are more appropriate to be modeled in a sampled-data setting rather than a continuous setting. Two sampled-data consensus algorithms are proposed and the conditions to guarantee consensus are presented for both fixed and switching network topologies. Because a number of coordination algorithms can be employed to guarantee coordination, it is important to study the optimal coordination problems. We further study the optimal consensus problems in both continuous-time and discrete-time settings via an linear-quadratic regulator (LQR)-based approach. Noting that fractional-order dynamics can better represent the dynamics of certain systems, especially when the systems evolve under complicated environment, the existing integer-order coordination algorithms are extended to the fractional-order case. Decentralized coordination in the presence of one group reference state is also called coordinated tracking, including both consensus tracking and swarm tracking. Consensus tracking refers to the behavior that the followers track the group reference state. Swarm tracking refers to the behavior that the followers move cohesively with the external leader while avoiding inter-vehicle collisions. In this part, consensus tracking is studied in both discrete-time setting and continuous-time settings while swarm tracking is studied in a continuous-time setting. Decentralized coordination in the presence of multiple group reference states is also called containment control, where the followers will converge to the convex hull, i.e., the minimal geometric space, formed by the group references states via local interaction. In this part, the containment control problem is studied for both single-integrator kinematics and double-integrator dynamics. In addition, experimental results are provided to validate some theoretical results.
28

Dynamic Analysis of Fractionally-Damped Elastomeric and Hydraulic Vibration Isolators

Fredette, Luke January 2016 (has links)
No description available.
29

Fractional-Order Structural Mechanics: Theory and Applications

Sansit Patnaik (13133553) 21 July 2022 (has links)
<p>The rapid growth of fields such as metamaterials, composites, architected materials, porous solids, and micro/nano materials, along with the continuing advancements in design and fabrication procedures have led to the synthesis of complex structures having intricate material distributions and non-trivial geometries. These materials find important applications including biomedical implants and devices, aerospace and naval structures, and micro/nano-electromechanical devices. Theoretical and experimental evidences have shown that these structures exhibit size-dependent (or, nonlocal) effects. This implies that the response of a point within the solid is affected by a collection of points; ultimately a manifestation of the multiscale deformation process. Broadly speaking, at a continuum level, the mathematical description of these multiscale phenomena leads to integral constitutive models, that account for the long-range interactions via nonlocal kernels. </p> <p><br></p> <p>Despite receiving considerable attention, the existing class of approaches to nonlocal elasticity are predominantly phenomenological in nature, following from their definition of the material parameters of the nonlocal kernel based on 'representative volume element' (RVE)-based statistical homogenization of the heterogeneous microstructure. The size of the RVE required for practical simulation, does not achieve a full-resolution of the intricate heterogeneous microstructure, and also implicitly enforces the use of symmetric nonlocal kernels to achieve thermodynamic consistency and mathematically well-posedness. The latter restriction directly limits the application of existing approaches only to the linear deformation analysis of either periodic or isotropic nonlocal structures. Additionally, the lack of a consistent characterization of the nonlocal effects, often results in inconsistent (also labeled as 'paradoxical') predictions depending on the nature of the external loading. In order to address these fundamental theoretical gaps, this dissertation develops a fractional-order kinematic approach to nonlocal elasticity by leveraging cutting-edge mathematical operators derived from the field of fractional calculus.</p> <p><br></p> <p>In contrast to the class of existing class of approaches that adopt an integral stress-strain constitutive relation derived from the equilibrium of the RVE, the fractional-order approach is predicated on a differ-integral (fractional-order) strain-displacement relation. The latter relation is derived from a fractional-order deformation-gradient mapping between deformed and undeformed configurations, and this approach naturally localizes and captures the effect of nonlocality at the root of the deformation phenomena. The most remarkable consequence of this reformulation consists in its ability to achieve thermodynamic and mathematical consistency, irrespective of the nature of the nonlocal kernel. The convex and positive-definite nature of the formulation enabled the use of variational principles to formulate well-posed governing equations, the incorporation of nonlinear effects, and enabled the development of accurate finite element simulation methods. The aforementioned features, when combined with a variable-order extension of the fractional-order continuum theory, enabled the physically consistent application of the nonlocal formulation to general continua exhibiting asymmetric interactions; ultimately a manifestation of material heterogeneity. Indeed, a rigorous theoretical analysis was conducted to demonstrate the natural ability of the variable-order in capturing the role of microstructure in the deformation of heterogeneous porous solids. These advantages allowed the application of the fractional-order kinematic approach to accurately and efficiently model the response of porous beams and plates, with random microstructural descriptions. Results derived from multiphysical loading conditions, as well as nonlinear deformation regimes, are used to demonstrate the causal relation between the kinematics-based fractional-order characterization of nonlocal effects and the natural role of microstructure in determining the macroscopic response of heterogeneous solids. The potential implications of the developed formalism on scientific discovery of material laws are examined in-depth, and different areas for further research are identified.</p>
30

Mathematical analysis of generalized linear evolution equations with the non-singular kernel derivative

Toudjeu, Ignace Tchangou 02 1900 (has links)
Linear Evolution Equations (LEE) have been studied extensively over many years. Their extension in the field of fractional calculus have been defined by Dαu(x, t) = Au(x, t), where α is the fractional order and Dα is a generalized differential operator. Two types of generalized differential operators were applied to the LEE in the state-of-the-art, producing the Riemann-Liouville and the Caputo time fractional evolution equations. However the extension of the new Caputo-Fabrizio derivative (CFFD) to these equations has not been developed. This work investigates existing fractional derivative evolution equations and analyze the generalized linear evolution equations with non-singular ker- nel derivative. The well-posedness of the extended CFFD linear evolution equation is demonstrated by proving the existence of a solution, the uniqueness of the existing solu- tion, and finally the continuous dependence of the behavior of the solution on the data and parameters. Extended evolution equations with CFFD are applied to kinetics, heat diffusion and dispersion of shallow water waves using MATLAB simulation software for validation purpose. / Mathematical Science / M Sc. (Applied Mathematics)

Page generated in 0.1369 seconds