Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-07-25T17:20:25Z No. of bitstreams: 1 ANNAXSUEL ARAÚJO DE LIMA - DISSERTAÇÃO PPGMAT 2011..pdf: 581866 bytes, checksum: cc44cd422d4a48ddad0354f215805918 (MD5) / Made available in DSpace on 2018-07-25T17:20:25Z (GMT). No. of bitstreams: 1 ANNAXSUEL ARAÚJO DE LIMA - DISSERTAÇÃO PPGMAT 2011..pdf: 581866 bytes, checksum: cc44cd422d4a48ddad0354f215805918 (MD5) Previous issue date: 2011-04 / Neste trabalho, apresentamos métodos envolvendo sub e supersolução para estudar a existência de solução de certas equações elípticas. / In this work, we present methods involving sub and supersolution to study the existence of solution of certain elliptic equations.

Cette thèse est consacrée à l'analyse mathématique et numérique d'un problème d'interaction fluide-structure stationnaire, couplant un fluide newtonien, visqueux et incompressible, modélisé par les équations de Stokes 2D et une structure déformable, décrite par les équations d'une poutre 1D. Le fluide et la structure sont couplés via une condition aux limites de type frottement à l'interface.Dans l'étude théorique, nous montrons un résultat d'existence et unicité de solutions faibles, dans le cadre de petits déplacements, du problème de couplage fluide structure avec une condition de glissement de type Tresca en utilisant le théorème de point fixe de Schauder.Dans l'analyse numérique, nous étudions d'abord, l'approximation du problème de Stokes avec la condition de Tresca par une méthode d'éléments finis mixtes à quatre champs. Nous montrons ensuite une estimation d'erreur a priori optimale pour des données régulières et nous réalisons des tests numériques. Enfin, nous présentons un algorithme de point fixe pour la simulation numérique du problème couplé avec des conditions aux limites non linéaires. / This PHD thesis is devoted to the theoretical and numerical analysis of a stationary fluid-structure interaction problem between an incompressible viscous Newtonian fluid, modeled by the 2D Stokes equations, and a deformable structure modeled by the 1D beam equations.The fluid and structure are coupled via a friction boundary condition at the fluid-structure interface.In the theoretical study, we prove the existence of a unique weak solution, under small displacements, of the fluid-structure interaction problem under a slip boundary condition of friction type (SBCF) by using Schauder fixed point theorem.In the numerical analysis, we first study a mixed finite element approximation of the Stokes equations under SBCF.We also prove an optimal a priori error estimate for regular data and we provide numerical examples.Finally, we present a fixed point algorithm for numerical simulation of the coupled problem under nonlinear boundary conditions.

在本篇論文中，我們主要是探討有邊界值的二次微分一積分方程式的解的存在性及唯 一性的問題。在LAKSHRNIKANTHAN 和KHAVANIN的“二次微分一積分方程式及單調法“ （THE METHOD OF MIXED MONOTONY AND SECOND ORDER INTEGRO-DIFFERENTIAL SYSTE M, ANAL.２８（１９８８），１９９－２０６）中，他們利用到混合單調法的技巧： 將不具有任何單調性質的函數擴充到一混合單調函數（亦即此函數對某些變數是單調 非遞減，而對另外某些變數是單調非遞增），然後利用其上解及下解（UPPER, LOWER SOLUTION）來生成兩個單調數列，而此二單調數列具有同時均勻的收斂到原方程式的 解的性質，而完成其存在性，其唯一性則是利用最大原則法（MAXIMUM PRINCIPLE ） ，而完成了他們對二次微分一積分方程式的解的探討。 在上述中，我們認為作者給予擴充函數的性質太強了，故我們對條件放寬，允許它不 是混合單調函數，而另外給了較弱的限制條件，此時我們與證明方法有了改變，我們 用到了SCHAUDER的定點定理（FIXED POINT THEOREM ）：若Ｔ是一區間映到相同區間 的緊緻運算子（COMPACT OPERATOR），則存在一點Ｘ使得Ｔ（Ｘ）＝Ｘ。於是解便可 得到，其唯一性亦是利用最大原則法得到。 最後，我們必須確定我們所使用的擴充函數確實存在，所以我們給了一個關於擴充函 數存在的充分條件來保證它的確存在，而不只是一種理想函數而已。到此，再加上一 些數值結果，我們就完成了整篇的論文。

Le principe de contraction de Banach, qui garantit l'existence d'un point fixe d'une contraction d'un espace métrique complet à valeur dans lui-même, est certainement le plus connu des théorèmes de point fixe. Dans plusieurs situations concrètes, nous sommes cependant amenés à considérer une contraction qui n'est définie que sur un sous-ensemble de cet espace. Afin de garantir l'existence d'un point fixe, nous verrons que d'autres hypothèses sont évidemment nécessaires. Le théorème de Caristi, qui garantit l'existence d'un point fixe d'une fonction d'un espace métrique complet à valeur dans lui-même et respectant une condition particulière sur d(x,f(x)), a plus tard été généralisé aux fonctions multivoques. Nous énoncerons des théorèmes de point fixe pour des fonctions multivoques définies sur un sous-ensemble d'un espace métrique grâce, entre autres, à l'introduction de notions de fonctions entrantes. Cette piste de recherche s'inscrit dans les travaux très récents de mathématiciens français et polonais. Nous avons obtenu des généralisations aux espaces de Fréchet et aux espaces de jauge de quelques théorèmes, dont les théorèmes de Caristi et le principe variationnel d'Ekeland. Nous avons également généralisé des théorèmes de point fixe pour des fonctions qui sont définies sur un sous-ensemble d'un espace de Fréchet ou de jauge. Pour ce faire, nous avons eu recours à de nouveaux types de contractions; les contractions sur les espaces de Fréchet introduites par Cain et Nashed [CaNa] en 1971 et les contractions généralisées sur les espaces de jauge introduites par Frigon [Fr] en 2000. / The Banach contraction principle, which certifies that a contraction of a complete metric space into itself has a fixed point, is for sure the most famous of all fixed point theorems. However, in many case, the contraction we consider is only defined on a subset of a complete metric space. Of course, to certify that such a contraction has a fixed point, we need to add some restrictions. The Caristi theorem, which certifies the existence of a fixed point of a function of a complete metric space into itself satisfying a particular condition on d(x,f(x)), was later generalized to multivalued functions. By introducing different types of inwardness assumptions, we will be able to state some fixed point theorems for multivalued functions defined on a subset of a metric space. This is related to the recent work of French and Polish mathematicians. We were able to generalize some theorems to Fréchet spaces and gauge spaces such as the Caristi theorems and the Ekeland variational principle. We were also able to generalize some fixed point theorems for functions that are only defined on a subset of a Fréchet space or a gauge space. To do so, we used new types of contractions; contractions on Fréchet spaces introduced by Cain and Nashed [CaNa] in 1971 and generalized contractions on gauge spaces introduced by Frigon [Fr] in 2000.

Abstract The controversy about the monetary regime of the EC between the Britain and the other member countries made economists to study currency competition and currency substitution widely. This dissertation constructs a one-good, two-currency Brock model in discrete time. In the determinate model, we show the Gresham’s Law results as those in Weil’s. And we demonstrate the existence and uniqueness of a class of first-order Markov stationary sunspot equilibria. The existence of sunspot equilibria expresses another situation of currency competition that future situations may depend on the possibility of people’s expectations, not the growth rates of currencies and tries to provide another explain for the phenomena above.Britain and the other member countries made economists totudy currency competition and currency substitution widely .his dissertation constructs a one - good , two - currencyrock model in discrete time . In the determinate model , wehow the Gresham' s Law results as those in Weil's . And weemonstrate the existence and uniqueness of a class of firstorder Markov stationary sunpot equilibria . The existencef sunspot equilibria expresses another situation of currencyompetition that future situations may depend on the possibi-ity of people' s expectations , not the growth rates of cu -rencies and tries to provide another explain for the pheno -ena above .

Le principe de contraction de Banach, qui garantit l'existence d'un point fixe d'une contraction d'un espace métrique complet à valeur dans lui-même, est certainement le plus connu des théorèmes de point fixe. Dans plusieurs situations concrètes, nous sommes cependant amenés à considérer une contraction qui n'est définie que sur un sous-ensemble de cet espace. Afin de garantir l'existence d'un point fixe, nous verrons que d'autres hypothèses sont évidemment nécessaires. Le théorème de Caristi, qui garantit l'existence d'un point fixe d'une fonction d'un espace métrique complet à valeur dans lui-même et respectant une condition particulière sur d(x,f(x)), a plus tard été généralisé aux fonctions multivoques. Nous énoncerons des théorèmes de point fixe pour des fonctions multivoques définies sur un sous-ensemble d'un espace métrique grâce, entre autres, à l'introduction de notions de fonctions entrantes. Cette piste de recherche s'inscrit dans les travaux très récents de mathématiciens français et polonais. Nous avons obtenu des généralisations aux espaces de Fréchet et aux espaces de jauge de quelques théorèmes, dont les théorèmes de Caristi et le principe variationnel d'Ekeland. Nous avons également généralisé des théorèmes de point fixe pour des fonctions qui sont définies sur un sous-ensemble d'un espace de Fréchet ou de jauge. Pour ce faire, nous avons eu recours à de nouveaux types de contractions; les contractions sur les espaces de Fréchet introduites par Cain et Nashed [CaNa] en 1971 et les contractions généralisées sur les espaces de jauge introduites par Frigon [Fr] en 2000. / The Banach contraction principle, which certifies that a contraction of a complete metric space into itself has a fixed point, is for sure the most famous of all fixed point theorems. However, in many case, the contraction we consider is only defined on a subset of a complete metric space. Of course, to certify that such a contraction has a fixed point, we need to add some restrictions. The Caristi theorem, which certifies the existence of a fixed point of a function of a complete metric space into itself satisfying a particular condition on d(x,f(x)), was later generalized to multivalued functions. By introducing different types of inwardness assumptions, we will be able to state some fixed point theorems for multivalued functions defined on a subset of a metric space. This is related to the recent work of French and Polish mathematicians. We were able to generalize some theorems to Fréchet spaces and gauge spaces such as the Caristi theorems and the Ekeland variational principle. We were also able to generalize some fixed point theorems for functions that are only defined on a subset of a Fréchet space or a gauge space. To do so, we used new types of contractions; contractions on Fréchet spaces introduced by Cain and Nashed [CaNa] in 1971 and generalized contractions on gauge spaces introduced by Frigon [Fr] in 2000.

[pt] Esse trabalho visa demonstrar os lemas de Sperner e aplicá-los nasdemonstrações do teorema de Monsky em Q2 e do teorema do ponto fixo deBrouwer em R2. Além disso, relatamos como esses lemas foram abordados com alunos da educação básica tendo como ferramenta educacional jogos de tabuleiro. / [en] This work aims to prove the Sperner s Lemmas and to apply them in proving the Monsky s Theorem in Q2 and the Brouwer fixed point Theorem in R2. Moreover, we report how these lemmas were addressed with students in basic education using board games as educational tools.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-07-10T17:20:01Z No. of bitstreams: 1 ORLANDO BATISTA DE ALMEIDA - DISSERTAÇÃO PPGMAT 2006..pdf: 835416 bytes, checksum: ebd7a7b886fc9fa8eddfddb98da9aa05 (MD5) / Made available in DSpace on 2018-07-10T17:20:01Z (GMT). No. of bitstreams: 1 ORLANDO BATISTA DE ALMEIDA - DISSERTAÇÃO PPGMAT 2006..pdf: 835416 bytes, checksum: ebd7a7b886fc9fa8eddfddb98da9aa05 (MD5) Previous issue date: 2006-05 / Nesta dissertação, seguindo o trabalho do Berestycki [7] e idéias desenvolvidas por Alves & de Figueiredo [3] e Alves, Corrêa & Gonçalves [4], estudamos a Teoria do Grau de Brouwer e Leray & Schauder, bem como o Método de Galerkin para obter solução de alguns problemas elípticos. / In this of dissertation, motivated by work of Berestycki [7] and ideas conceived byAlves & from Figueiredo [3] andAlves, Corrêa & Gonçalves [4], we styding the theory of Degree fromBrouwer and Leray & Schauder, well how theMethod from Galerkin to obtain solution of some ellíptic problems.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-07-22T14:08:51Z No. of bitstreams: 1 FRANCISCA LEIDMAR JOSUÉ VIEIRA - DISSERTAÇÃO PPGMAT 2009..pdf: 290173 bytes, checksum: 21a058b9a6d5dfdd80b44bb2f900d25f (MD5) / Made available in DSpace on 2018-07-22T14:08:51Z (GMT). No. of bitstreams: 1 FRANCISCA LEIDMAR JOSUÉ VIEIRA - DISSERTAÇÃO PPGMAT 2009..pdf: 290173 bytes, checksum: 21a058b9a6d5dfdd80b44bb2f900d25f (MD5) Previous issue date: 2009-03 / Capes / O resumo foi escrito utilizando formulas e equações matemáticas que não fora possíveis serem transcritas aqui. Para a visualizar o resumo recomendamos o downloado do arquivo. / The abstract was written using mathematical formulas and equations that could not be transcribed here. To view the summary we recommend downloading the file.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-05-26T17:30:30Z No. of bitstreams: 1 ceilimarcolinomoreira.pdf: 628590 bytes, checksum: 89404f2fdb6f6a266713327a91a21c05 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-29T19:02:09Z (GMT) No. of bitstreams: 1 ceilimarcolinomoreira.pdf: 628590 bytes, checksum: 89404f2fdb6f6a266713327a91a21c05 (MD5) / Made available in DSpace on 2017-05-29T19:02:09Z (GMT). No. of bitstreams: 1 ceilimarcolinomoreira.pdf: 628590 bytes, checksum: 89404f2fdb6f6a266713327a91a21c05 (MD5) Previous issue date: 2014-03-27 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho, apresentamos métodos envolvendo sub e supersolução para estudar a existência de solução, no sentido fraco, para três classes de problemas elípticos de segunda ordem com condição de fronteira de Dirichlet homogênea. Nos dois primeiros casos encontramos solução em W1,2 0 (Ω) e no terceiro caso encontramos solução em L1(Ω) com algumas restrições. / This paper presents methods involving sub and supersolution in order to learn the existence of weak solutions of three classes of second order elliptic problems with homogeneous Dirichlet boundary conditions. In the first two cases we find solution in W1,2 0 (Ω) and in the third case we find solution in L1(Ω) with some restrictions.