Neste trabalho, estudamos a existˆencia e multiplicidade de solu¸c˜oes de certos problemas p-sublineares envolvendo o operador p-laplaciano usando teoria de Morse. / The purpose of this text is to provide a didactic exposition of the paper “Solutions of p-sublinear p-Laplacian equation via Morse theory” by Yuxia Guo and Jiaquan Liu [8]. This paper addresses the existence and multiplicity of solutions for the problem where is a smooth, bounded domain of RN, p is the p-Laplacian operator and f satisfies certain conditions, in particular f is p-sublinear at 0. Morse theory is used to infer the existence of critical points of a functional associated to this problem. In Chapter 2, we introduce the necessary Morse theoretic concepts, assuming basic knowledge of singular homology theory. In Chapter 3, we introduce basic properties of the p-Laplacian operator, assuming knowledge of Sobolev spaces, including imbedding and compactness results. Finally, in Chapter 4, we follow Guo and Liu’s paper itself.

Este trabalho apresenta um estudo sobre segmentação de volumes médicos e uma solução para se obter malhas poligonais de pacientes específicos para uso em simulações de cirurgia. Malhas de pacientes específicos são importantes para planejamento de intervenções cirúrgicas e permitem uma melhor visualização de condições patológicas em um paciente, coisa não obtível em malhas geradas artisticamente. Nós analisamos quais são os fatores complicantes para se obter estas malhas de um paciente específico usando apenas imagens médicas obtidas em exames padrões. Para isso, nós revisamos diversos métodos existentes para segmentação de volumes médicos. Isso nos levou a definir os problemas com as técnicas existentes, e a desenvolver um método que não sofra destes problemas, utilizando pouca interação humana e não tendo dependências de mais dados que não o exame do paciente. Nosso alvo para obter malhas especificas foram órgãos de tecido mole, que são um caso especialmente complicado da área, graças a várias questões relacionadas às imagens médicas e à anatomia humana. Atacamos esse problema aplicando modificações geométricas em malhas especiais, que deformam até atingir a forma dos órgãos que se deseja segmentar. Os resultados mostram que nossa técnica conseguiu obter malhas específicas de pacientes a partir de volumes médicos com qualidade superior a de outros algoritmos de mesma classe. Graças a simplicidade do método desenvolvido, nossos resultados são facilmente implementáveis e reproduzidos. / This work presents a study about medical-volume segmentation and a solution to generate patient-specific meshes to use in patient-specific surgery simulations. Patientspecific meshes are useful assets for surgery planning and to allow better visualization of certain pathological conditions of a given patient, which are not obtainable by artistically designed meshes. We analyzed what are the complications to obtain a patient-specific mesh using only standard medical imagery exams. For that, we reviewed several medical volume segmentation techniques. It led us to define the problems within the existing techniques and to develop a method that does not suffer from these problems, with the least possible user interaction or relying on any other data other then the patient exam. Our target for obtaining specific meshes were soft tissue organs, which are a specially complicated case due to various issues related to the medical images and human anatomy. This is accomplished by geometrical operations over special meshes that deform until achieving the shape of the desired organ. Results show that our technique was able to obtain patient-specific meshes from medical images with superior quality than algorithms of the same class. Thanks to the simplicity of the developed approach, its also easy to implement and to reproduce our obtained results.

Consideraremos o problema elípitco $-\\Delta u + \\alpha\\chi_Du = \\lambda u$ em $\\Omega$, onde $\\Omega$ é um domínio de R^n com fronteira regular, e $D\\subset \\Omega$ é um subconjunto fechado de medida de Lebesgue fixada. A motivação para este problema vem da Mecânica, onde esta equação é encontrada no estudo de vibrações de uma membrana composta. Seja $\\lambda_1(D)$ o primeiro autovalor do problema, como função do conjunto D. Nesse trabalho mostraremos que $\\lambda_1$ é um autovalor simples, e estudaremos o problema de minimizar $\\lambda_1$ ao variarmos D no conjunto de todos os subconjuntos de medida fixada de $\\Omega$. Mais especificamente, determinaremos fórmulas para a variação primeira e segunda de $\\lambda_1$. / We will consider the elliptic problem $-\\Delta u + \\alpha\\chi_Du = \\lambda u in $\\Omega$, where $\\Omega$ is a domain in R^n with regular boundary, and $D \\subset\\Omega$ is a closed subset with prescribed Lebesgue measure. The motivation for this problem comes from Mechanics, where this equation models the vibrations of a composite membrane. Let $\\lambda_1(D)$ be the first eigenvalue of the problem, which is seen as a function of the set D. In this work, we will show that $\\lambda_1$ is a simple eigenvalue, and we will study the problem of minimizing $\\lambda_1(D)$ when D varies in the family of all closed subsets of $\\Omega$ with a given Lebesgue measure. More precisely, we will determine formulas for the first and the second variation of $\\lambda_1$.

Graphs provide interesting ways to generate families of lattice polytopes. In particular, one can use matrices encoding the information of a finite graph to define vertices of a polytope. This dissertation initiates the study of the Laplacian simplex, PG, obtained from a finite graph G by taking the convex hull of the columns of the Laplacian matrix for G. The Laplacian simplex is extended through the use of a parallel construction with a finite digraph D to obtain the Laplacian polytope, PD. Basic properties of both families of simplices, PG and PD, are established using techniques from Ehrhart theory. Motivated by a well-known conjecture in the field, our investigation focuses on reflexivity, the integer decomposition property, and unimodality of Ehrhart h*-vectors of these polytopes. A systematic investigation of PG for trees, cycles, and complete graphs is provided, which is enhanced by an investigation of PD for cyclic digraphs. We form intriguing connections with other families of simplices and produce G and D such that the h*-vectors of PG and PD exhibit extremal behavior.

<p>This thesis investigates the possibility of improving black box fault diagnosis by a process called manifold learning, which simply stated is a way of finding patterns in recorded sensor data. The idea is that there is more information in the data than is exploited when using simple classification algorithms such as k-Nearest Neighbor and Support Vector Machines, and that this additional information can be found by using manifold learning methods. To test the idea of using manifold learning, data from two different fault diagnosis scenarios is used: A Scania truck engine and an electrical system called Adapt. Two linear and one non-linear manifold learning methods are used: Principal Component Analysis and Linear Discriminant Analysis (linear) and Laplacian Eigenmaps (non-linear).Some improvements are achieved given certain conditions on the diagnosis scenarios. The improvements for different methods correspond to the systems in which they are achieved in terms of linearity. The positive results for the relatively linear electrical system are achieved mainly by the linear methods Principal Component Analysis and Linear Discriminant Analysis and the positive results for the non-linear Scania system are achieved by the non-linear method Laplacian Eigenmaps.The results for scenarios without these special conditions are not improved however, and it is uncertain wether the improvements in special condition scenarios are due to gained information or to the nature of the cases themselves.</p>

Note de l'administrateur du service : le résumé de cette thèse est disponible dans le fichier déposé par l'auteur. Il ne peut techniquement pas être placé sous cette rubrique, dans la mesure où il contient des formules mathématiques avec des caractères grecs.

We investigate the structure of trees that have greatest maximum eigenvalue among all trees with a given degree sequence. We show that in such an extremal tree the degree sequence is non-increasing with respect to an ordering of the vertices that is obtained by breadth-first search. This structure is uniquely determined up to isomorphism. We also show that the maximum eigenvalue in such classes of trees is strictly monotone with respect to majorization. (author´s abstract) / Series: Research Report Series / Department of Statistics and Mathematics

In this thesis we use the method of Semantic Mirrors to create a graph of words that are semantically related to a seed word. Spectral graph partitioning methods are then used to partition the graph into subgraphs, and thus dividing the words into different word senses. These methods are applied to a bilingual lexicon of English and Swedish adjectives. A panel of human evaluators have looked at a few examples, and evaluated consistency within the derived senses and synonymy with the seed word.

In this thesis, we consider the following one dimensional p-Laplacian eigenvalue problem: -((y¡¦/s)^(p-1))¡¦+(p-1)(q-£fw)y^(p-1)=0 a.e. on (0,1) (0.1) and satisfy £\y(0)+ £\ ¡¦ (y¡¦(0)/s(0))=0 £]y(1)+£]¡¦ (y¡¦(1)/s(1))=0 (0.2) where f^(p-1)=|f|^p-2 f=|f|^p-1 sgnf; £\, £\¡¦, £], £]¡¦ ∈R such that £\^2+£\¡¦^2>0 and£]^2+£]¡¦^2>0; and the functions s,q,w are required to satisfy (1) s,q,w∈L^1(0,1); (2) for 0≤x≤1, we have s≥0,w≥0 a.e.; (3) for any x∈ (0,1), ¡ì_0^1 s(t)dt>0, ¡ì_0^x w(t)dt>0,and¡ì_x^1 w(t)dt>0; (4) if for some x_1<x_2,we have¡ì_ x1^x2 w(t)dt=0,then¡ì_ x1^x2 |q(t)|dt=0; (5) for all n∈N, there is a partition {£a_i^(n)}_i=1 ^2n of [0,1] such that for any 0<k≤n-1, ¡ì_£a_2k^(n)^ £a_2k+1^(n) w>0 and ¡ì_£a_2k+1^(n)^ £a_2k+2^(n) s>0. We call the above conditions Atkinson conditions, first introduce in [1].There conditions include the case when s,q,w∈L^1(0,1) and s,w>0 a.e. We use a generalized Prufer substitution and Caratheodory theorem to prove the existence and uniqueness for the solution of the initial value problem of (0.1) above. Then we generalize the Sturm oscillation theorem to one dimensional p-Laplacian and establish the Sturm-Liouville properties of the p-Laplacian operators with L^1 coefficient functions. Our results filled up some gaps in Binding-Drabek [3].

圖的譜半徑在數學方面以及其他領域有非常多的應用。在這篇論文裡，我們整理有關連通圖的拉普拉斯與無符號拉普拉斯譜半徑的論文。本文一開始探討一些圖的譜理論，並找出這些界限的關係。然後，我們將討論更精確的圖之拉普拉斯與無符號拉普拉斯譜半徑。最後，我們給一個例子，並使用前面所探討過的性質分析之。 / The spectral radius of a graph has been applied in mathenatics and in diverse disciplines.In this thesis, we survey some papers about the Laplacian spectral radius and the signless Laplacian spectral radius of a connected graph. Initially, we discuss some properties about the spectral graphs and find the relations between these bounds. Then, we discuss the upper bounds and lower bounds of the Laplacian and signless Laplacian spectral radius of a graph. In the end, we give an example and analyze it.