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  • 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.
1

Propensity Score for Causal Inference of Multiple and Multivalued Treatments

Gu, Zirui 01 January 2016 (has links)
Propensity score methods (PSM) that have been widely used to reduce selection bias in observational studies are restricted to a binary treatment. Imai and van Dyk extended PSM to estimate non-binary treatment effect using stratification with P-Function, and generalized inverse treatment probability weighting (GIPTW). However, propensity score (PS) matching methods on multiple treatments received little attention, and existing generalized PSMs merely focused on estimates of main treatment effects but omitted potential interaction effects that are of essential interest in many studies. In this dissertation, I extend Rubin’s PS matching theory to general treatment regimens under the P-Function framework. From theory to practice, I propose an innovative distance measure that can summarize similarities among subjects in multiple treatment groups. Based on this distance measure I propose four generalized propensity score matching methodologies. The first two methods are extensions of nearest neighbor matching. I implemented Monte Carlo simulation studies to compare them with GIPTW and stratification on P-Function methods. The next two methods are extensions of the nearest neighbor caliper width matching and variable matching. I define the caliper width as the product of a weighted standard deviation of all possible pairwise distances between two treatment groups. I conduct a series of simulation studies to determine an optimal caliper width by searching the lowest mean square error of average causal interaction effect. I further compare the ones with optimal caliper width with other methods using simulations. Finally, I apply these methods to the National Medical Expenditure Survey data to examine the average causal main effect of duration and frequency of smoking as well as their interaction effect on annual medical expenditures. Using proposed methods, researchers can apply regression models with specified interaction terms to the matched data and simultaneously obtain both main and interaction effects estimate with improved statistical properties.
2

Perturbation Auxiliary Problem Methods to Solve Generalized Variational Inequalities

Salmon, Geneviève 21 April 2001 (has links)
The first chapter provides some basic definitions and results from the theory of convex analysis and nonlinear mappings related to our work. Some sufficient conditions for the existence of a solution of problem (GVIP) are also recalled. In the second chapter, we first illustrate the scope of the auxiliary problem procedure designed to solve problems like (GVIP) by examining some well-known methods included in that framework. Then, we review the most representative convergence results for that class of methods that can be found in the literature in the case where F is singlevalued as well as in the multivalued case. Finally, we somewhat discuss the particular case of projection methods to solve affine variational inequalities. The third chapter introduces the variational convergence notion of Mosco and combines it with the auxiliary problem principle. Then, we recall the convergence conditions existing for the resulting perturbed scheme before our own contribution and we comment them. Finally, we introduce and illustrate the rate of convergence condition that we impose on the perturbations to obtain better convergence results. Chapter 4 presents global and local convergence results for the family of perturbed methods in the case where F is singlevalued. We also discuss how our results extend or improve the previous ones. Chapter 5 studies the multivalued case. First, we present convergence results generalizing those obtained when there is no perturbations. Then, we relax the scheme by means of a notion of enlargement of an operator and we provide convergence conditions for this inexact scheme. In Chapter 6, we build a bundle algorithm to solve problem (GVIP) and we study its convergence.
3

Topological Degree and Variational Inequality Theories for Pseudomonotone Perturbations of Maximal Monotone Operators

Asfaw, Teffera Mekonnen 01 January 2013 (has links)
Let X be a real reflexive locally uniformly convex Banach space with locally uniformly convex dual space X* . Let G be a bounded open subset of X. Let T:X⊃ D(T)⇒ 2X* be maximal monotone and S: X ⇒ 2X* be bounded pseudomonotone and such that 0 notin cl((T+S)(D(T)∩partG)). Chapter 1 gives general introduction and mathematical prerequisites. In Chapter 2 we develop a homotopy invariance and uniqueness results for the degree theory constructed by Zhang and Chen for multivalued (S+) perturbations of maximal monotone operators. Chapter 3 is devoted to the construction of a new topological degree theory for the sum T+S with the degree mapping d(T+S,G,0) defined by d(T+S,G,0)=limepsilondarr 0+ dS+(T+S+ J,G,0), where dS+ is the degree for bounded (S+)-perturbations of maximal monotone operators. The uniqueness and homotopy invariance result of this degree mapping are also included herein. As applications of the theory, we give associated mapping theorems as well as degree theoretic proofs of known results by Figueiredo, Kenmochi and Le. In chapter 4, we consider T:X D(T)⇒ 2X* to be maximal monotone and S:D(S)=K⇒ 2X* at least pseudomonotone, where K is a nonempty, closed and convex subset of X with 0isinKordm. Let Phi:X⇒ ( infin, infin] be a proper, convex and lower-semicontinuous function. Let f* isin X* be fixed. New results are given concerning the solvability of perturbed variational inequalities for operators of the type T+S associated with the function f. The associated range results for nonlinear operators are also given, as well as extensions and/or improvements of known results by Kenmochi, Le, Browder, Browder and Hess, Figueiredo, Zhou, and others.
4

Fibrilação de logicas na hierarquia de Leibniz

Fernández, Victor Leandro 30 June 2005 (has links)
Orientador: Marcelo Esteban Coniglio / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Filosofia e Ciencias Humanas / Made available in DSpace on 2018-08-04T20:57:48Z (GMT). No. of bitstreams: 1 Fernandez_VictorLeandro_D.pdf: 6531217 bytes, checksum: 2a972c9e9fa860af8f9cc57b3e1bb73d (MD5) Previous issue date: 2005 / Resumo: Neste trabalho investigamos com um enfoque abstrato um processo de combinações de lógicas conhecido como Fibrilação de lógicas. Em particular estudamos a transferência, mediante fibrilação, de certas propriedades intrínsecas às lógicas proposicionais. As noções mencionadas são as de protoalgebrizabilidade, equivalencialidade e algebrizabilidade. Ditas noções fazem parte da "Hierarquia de Leibniz" , conceito fundamental da chamada Lógica Algébrica Abstrata. Tal hierarquia classifica as diferentes lógicas segundo o seu grau de algebrizabilidade. Assim, nesta tese estudaremos se, quando duas lógicas possuem alguma dessas propriedades, a fibrilação delas possui também tal característica. Com o objetivo de diferençar os diferentes modos de fibrilação existentes na literatura, analisamos duas maneiras de fibrilar lógicas: Fibrilação categorial (ou C-fibrilação) e Fibrilação no sentido de D. Gabbay (G-fibrilação). Também estudamos uma variante da Gfibrilação de lógicas conhecida como Fusão de lógicas. Assim, damos diferentes condições que devem valer para que a C-fibrilação de uma lógica protoalgébrica seja também protoalgébrica, e procedemos de forma similar com as outras propriedades que constituem a Hierarquia de Leibniz. No caso da G-fibrilação e da fusão de lógicas chegamos a diversos resultados análogos aos anteriores, os quais permitem ter uma visão geral da relação entre Lógica Algébrica Abstrata e as Combinações de lógicas / Abstract: ln this thesis we investigate, with an abstract approach, a process of combinations of logics known as fibring of logics. ln particular we study the transference by fibring of certain properties, intrinsic to propositionallogics: protoalgebricity, equivalenciality and algebraizability. The notions above belong to the "Leibniz Hierarchy", a fundamental concept of the so-called Abstract Algebraic Logic. Such hierarchy classifies the logics according to its algebraizability degree. So, in this thesis we will study whether, given two logics having some of these properties, the fibring of them still has that property. With the aim of distinguishing the different techniques of fibring existing in the literature, we analyze two methods of fibring logics: Categorial Fibring (or C-fibring) and Fibring in D. Gabbay's sense (G-fibring). We also study a variant of G-fibring known as fusion of logics. So, we give different conditions that must hold in order to obtain a protoalgebraic logic by means of C-fibring of protoalgebric logics. We proceed in a similar way with the other properties that constitutes the Leibniz Hierarchy. With respect to G-fibring and fusion, we arrive to similar results which allow us to get an overview of the relation between Abstract AIgebraic Logic and the subject of combinations of logics / Doutorado / Doutor em Filosofia
5

Circuitos quaternarios : somador e multiplicador / Quaternary circuits : adder and multiplier

Mingoto Junior, Carlos Roberto 12 December 2005 (has links)
Orientador: Alberto Martins Jorge / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-09T08:44:01Z (GMT). No. of bitstreams: 1 MingotoJunior_CarlosRoberto_M.pdf: 657421 bytes, checksum: dc6ef4bc58fb70a90293781871a969c6 (MD5) Previous issue date: 2005 / Resumo: Os circuitos quaternários são uma alternativa para o processamento das informações, que, atualmente, acontece de forma binária. Ainda em fase de definições, a lógica multivalores mostra-se como um campo de pesquisas que pode auxiliar a busca pelo incremento de desempenho e redução de área de ocupação dos transistores de um circuito integrado. A lógica multi-valores utilizando-se de quatro dígitos na representação das informações é a lógica quaternária. Neste trabalho são propostos alguns blocos básicos de circuitos eletrônicos quaternários que, progressivamente, são aglutinados formando blocos mais complexos para finalmente construir-se um circuito meio-somador, um somador completo e um multiplicador quaternários. As montagens são feitas e testadas em simulador de circuitos eletrônicos e operam em modo corrente com transistores bipolares NPN e PNP / Abstract: The quaternary circuits are an alternative to data processing that, nowadays, occurs in a binary way. Still in a definition stage, the multiple-valued logic seems to be a research area to aid the increase of performance and reduction of area of the transistors inside an integrated circuit. The multiple-valued logic using four digits to represent the data is called quaternary logic. In this work are proposed some basic blocks of electronic quaternary circuit which are progressively joined to become more complex blocks and finally a half-adder, a full adder and a multiplier. The configurations are done and evaluated in a circuit simulator operating in a current-mode with bipolar NPN and PNP transistors / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica
6

Nolinear Evolution Equations and Optimization Problems in Banach Spaces

Lee, Haewon January 2005 (has links)
No description available.
7

Vícehodnotové logické systémy pro technické aplikace / Multivalued logic systems for technical applications

Turek, Vojtěch January 2008 (has links)
Velmi často je vyžadováno, aby automatizovaná zařízení byla jistým způsobem "inteligentní", tedy aby jejich řídicí systémy uměly emulovat rozhodovací proces. Tato diplomová práce poskytuje obecný formální popis vícehodnotových logických systémů schopných zmíněné emulace a jejich souvislost s teorií fuzzy množin. Jsou uvedeny způsoby vytváření matematických modelů založených na lingvistických datech. Dále se práce zabývá znalostními bázemi a jejich vlastnostmi. Součástí této práce je také počítačový program sloužící k tvorbě slovních modelů.
8

Théorèmes de point fixe et principe variationnel d'Ekeland

Dazé, Caroline 02 1900 (has links)
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.
9

Fixed point results for multivalued contractions on graphs and their applications

Dinevari, Toktam 06 1900 (has links)
Nous présentons dans cette thèse des théorèmes de point fixe pour des contractions multivoques définies sur des espaces métriques, et, sur des espaces de jauges munis d’un graphe. Nous illustrons également les applications de ces résultats à des inclusions intégrales et à la théorie des fractales. Cette thèse est composée de quatre articles qui sont présentés dans quatre chapitres. Dans le chapitre 1, nous établissons des résultats de point fixe pour des fonctions multivoques, appelées G-contractions faibles. Celles-ci envoient des points connexes dans des points connexes et contractent la longueur des chemins. Les ensembles de points fixes sont étudiés. La propriété d’invariance homotopique d’existence d’un point fixe est également établie pour une famille de Gcontractions multivoques faibles. Dans le chapitre 2, nous établissons l’existence de solutions pour des systèmes d’inclusions intégrales de Hammerstein sous des conditions de type de monotonie mixte. L’existence de solutions pour des systèmes d’inclusions différentielles avec conditions initiales ou conditions aux limites périodiques est également obtenue. Nos résultats s’appuient sur nos théorèmes de point fixe pour des G-contractions multivoques faibles établis au chapitre 1. Dans le chapitre 3, nous appliquons ces mêmes résultats de point fixe aux systèmes de fonctions itérées assujettis à un graphe orienté. Plus précisément, nous construisons un espace métrique muni d’un graphe G et une G-contraction appropriés. En utilisant les points fixes de cette G-contraction, nous obtenons plus d’information sur les attracteurs de ces systèmes de fonctions itérées. Dans le chapitre 4, nous considérons des contractions multivoques définies sur un espace de jauges muni d’un graphe. Nous prouvons un résultat de point fixe pour des fonctions multivoques qui envoient des points connexes dans des points connexes et qui satisfont une condition de contraction généralisée. Ensuite, nous étudions des systèmes infinis de fonctions itérées assujettis à un graphe orienté (H-IIFS). Nous donnons des conditions assurant l’existence d’un attracteur unique à un H-IIFS. Enfin, nous appliquons notre résultat de point fixe pour des contractions multivoques définies sur un espace de jauges muni d’un graphe pour obtenir plus d’information sur l’attracteur d’un H-IIFS. Plus précisément, nous construisons un espace de jauges muni d’un graphe G et une G-contraction appropriés tels que ses points fixes sont des sous-attracteurs du H-IIFS. / In this thesis, we present fixed point theorems for multivalued contractions defined on metric spaces, and, on gauge spaces endowed with directed graphs. We also illustrate the applications of these results to integral inclusions and to the theory of fractals. chapters. In Chapter 1, we establish fixed point results for the maps, called multivalued weak G-contractions, which send connected points to connected points and contract the length of paths. The fixed point sets are studied. The homotopical invariance property of having a fixed point is also established for a family of weak G-contractions. In Chapter 2, we establish the existence of solutions of systems of Hammerstein integral inclusions under mixed monotonicity type conditions. Existence of solutions to systems of differential inclusions with initial value condition or periodic boundary value condition are also obtained. Our results rely on our fixed point theorems for multivalued weak G-contractions established in Chapter 1. In Chapter 3, those fixed point results for multivalued G-contractions are applied to graph-directed iterated function systems. More precisely, we construct a suitable metric space endowed with a graph G and an appropriate G-contraction. Using the fixed points of this G-contraction, we obtain more information on the attractors of graph-directed iterated function systems. In Chapter 4, we consider multivalued maps defined on a complete gauge space endowed with a directed graph. We establish a fixed point result for maps which send connected points into connected points and satisfy a generalized contraction condition. Then, we study infinite graph-directed iterated function systems (H-IIFS). We give conditions insuring the existence of a unique attractor to an H-IIFS. Finally, we apply our fixed point result for multivalued contractions on gauge spaces endowed with a graph to obtain more information on the attractor of an H-IIFS. More precisely, we construct a suitable gauge space endowed with a graph G and a suitable multivalued G-contraction such that its fixed points are sub-attractors of the H-IIFS.
10

Continuidade de atratores para sistemas dinâmicos: decomposição de Morse, equi-atração e domínios ilimitados / Continuity of attractors for dynamical systems: Morse decompositions, equiattraction and unbounded domains

Costa, Henrique Barbosa da 28 July 2016 (has links)
Neste trabalho estudamos a dinâmica assintótica de problemas parabólicos sob vista de diferentes teorias, particularmente interessados na estabilidade das propriedades dinâmicas dos sistemas. Estudamos a equi-atração no caso não autônomo pelos semifluxos skew-product, que transformam o sistema dinâmico não autônomo em um autônomo num espaço de fase conveniente. Para modelos multívocos, em que o semifluxo é uma função cujos valores são conjuntos, desenvolvemos a decomposição de Morse e mostramos sua equivalência com a existência de um funcional de Lyapunov, que é um resultado muito importante na teoria de semigrupos. Também estudamos a continuidade da dinâmica assintótica de um problema parabólico em um domínio ilimitado quando o aproximamos por domínios limitados específicos. / In this work we study assimptotic properties of parabolic problems under some different view of points, particularlly interested in the stability properties of the systems. We study equi-attraction in the non autonomous case using skew-product semiflows, which transform the non autonomous dynamical system into a autonomous one in a convenient phase space. For multivalued semiflows, in which the semiflow is a set valued function, we develop the Morse decomposition and show its equivalence with admiting a Lyapunov funcional, wich is a important result on the semigroup theory. We also study the continuity of the asymptotic dynamic for a parabolic problem in an unbouded domain when we approach it by bounded ones.

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