Cette thèse est constituée de quatre chapitres. Le premier contient les notions de base qui permettent d'aborder les divers thèmes qui y sont étudiés. Le second est consacré à l'étude des sous-variétés lagrangiennes d'une variété presque kählérienne. J'y présente les résultats obtenus en collaboration avec Burcu Bektas, Joeri Van der Veken et Luc Vrancken. Dans le troisième, je m'intéresse à un problème de géométrie différentielle affine et je donne une classification des hypersphères affines qui sont isotropiques. Ce résultat a été obtenu en collaboration avec Luc Vrancken. Et enfin dans le dernier chapitre, je présente quelques résultats sur les surfaces de translation et les surfaces homothétiques, objet d'un travail en commun avec Rafael López. / Abstract in English not available

The objective of this research is to evaluate and introduce a new methodology regarding rural highway safety. Current practices rely on crash prediction models that utilize specific explanatory variables, whereas the depository of knowledge for past research is the Highway Safety Manual (HSM). Most of the prediction models in the HSM identify the effect of individual geometric elements on crash occurrence and consider their combination in a multiplicative manner, where each effect is multiplied with others to determine their combined influence. The concepts of 3-dimesnional (3-D) representation of the roadway surface have also been explored in the past aiming to model the highway structure and optimize the roadway alignment. The use of differential geometry on utilizing the 3-D roadway surface in order to understand how new metrics can be used to identify and express roadway geometric elements has been recently utilized and indicated that this may be a new approach in representing the combined effects of all geometry features into single variables. This research will further explore this potential and examine the possibility to utilize 3-D differential geometry in representing the roadway surface and utilize its associated metrics to consider the combined effect of roadway features on crashes. It is anticipated that a series of single metrics could be used that would combine horizontal and vertical alignment features and eventually predict roadway crashes in a more robust manner. It should be also noted that that the main purpose of this research is not to simply suggest predictive crash models, but to prove in a statistically concrete manner that 3-D metrics of differential geometry, e.g. Gaussian Curvature and Mean Curvature can assist in analyzing highway design and safety. Therefore, the value of this research is oriented towards the proof of concept of the link between 3-D geometry in highway design and safety. This thesis presents the steps and rationale of the procedure that is followed in order to complete the proposed research. Finally, the results of the suggested methodology are compared with the ones that would be derived from the, state-of-the-art, Interactive Highway Safety Design Model (IHSDM), which is essentially the software that is currently used and based on the findings of the HSM.

Three dimensional (3D) surface feature extractions based on mean (H) and Gaussian (K) curvature analysis of range maps, also known as depth maps, is an important tool for machine vision applications such as object detection, registration and recognition. Mean and Gaussian curvature calculation algorithms have already been implemented and examined as software. In this thesis, hardware based digital curvature processors are designed. Two types of real time surface feature extraction and classification hardware are developed which perform mean and Gaussian curvature analysis at different scale levels. The techniques use different gradient approximations. A fast square root algorithm using both LUT (look up table) and linear fitting technique is developed to calculate H and K values of the surface described by the 3D Range Map formed by fixed point numbers. The proposed methods are simulated in MatLab software and implemented on different FPGAs using VHDL hardware language. Calculation times, outputs and power analysis of these techniques are compared to CPU based 64 bit float data type calculations.

A model is presented to use normalized multi-linear tension and compression material characteristics of strain-hardening textile reinforced concrete and derive closed form expressions for predicting moment-curvature capacity. A set of design equations are derived and simplified for use in spreadsheet based applications. The model is applicable for both strain-softening and strainhardening materials. The predictability of the simplified model is checked by model calibration and development of design charts for moment capacity and stress developed throughout the cross section of a flexural member. Model is calibrated by predicting the results of Alkali Resistant Glass and Polyethylene fabrics. A case for the flexural design of Glass Fiber Reinforced Concrete (GFRC) specimen as a simply supported beam subjected to distributed load is used to demonstrate the design procedure.

SANTOS, A. S. L. Problema de Yamabe modificado em variedades compactas de dimensão quatro e métricas críticas do funcional curvatura escalar. 2017. 58 f. Tese (Doutorado em Matemática) – Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2017. / Submitted by Andrea Dantas (pgmat@mat.ufc.br) on 2017-05-25T19:34:47Z No. of bitstreams: 1 2017_tese_aslsantos.pdf: 535461 bytes, checksum: 8c3ddbdd33d74c4eb7b265354b3bafb3 (MD5) / Rejected by Rocilda Sales (rocilda@ufc.br), reason: Boa tarde, Eu revisei a Tese de ALEX SANDRO LOPES SANTOS, e encontrei um pequeno erro na capa, ele colocou os seguintes elementos: UNIVERSIDADE FEDERAL DO CEARÁ CENTRO DE CIÊNCIAS PROGRAMA DE PÓS-GRADUAÇÃO EM MATEMÁTICA DOUTORADO EM MATEMÁTICA Mas deve ser alterado para: UNIVERSIDADE FEDERAL DO CEARÁ CENTRO DE CIÊNCIAS DEPARTAMENTO DE MATEMÁTICA PROGRAMA DE PÓS-GRADUAÇÃO EM MATEMÁTICA Com os demais elementos da Tese, não há nenhum problema de formatação. Atenciosamente, on 2017-05-26T15:06:03Z (GMT) / Submitted by Andrea Dantas (pgmat@mat.ufc.br) on 2017-05-29T13:47:44Z No. of bitstreams: 1 2017_tese_aslsantos.pdf: 536279 bytes, checksum: f37ece7d8035a2d9c788c45d2e7807ae (MD5) / Approved for entry into archive by Rocilda Sales (rocilda@ufc.br) on 2017-05-29T14:08:17Z (GMT) No. of bitstreams: 1 2017_tese_aslsantos.pdf: 536279 bytes, checksum: f37ece7d8035a2d9c788c45d2e7807ae (MD5) / Made available in DSpace on 2017-05-29T14:08:17Z (GMT). No. of bitstreams: 1 2017_tese_aslsantos.pdf: 536279 bytes, checksum: f37ece7d8035a2d9c788c45d2e7807ae (MD5) Previous issue date: 2017-05-19 / In the fisrt part of this work we investigate the modified Yamabe problem on four-dimensional manifolds whose the modifiers invariants depending on the eigenvalues of the Weyl curvature tensor and they are described in terms of maximum and minimum of the biorthogonal (sectional) curvature. We provide some geometrical and topological properties on four-dimensional manifolds in terms of these invariants. In the second part we investigate the critical points of the total scalar curvature functional restricted to space of metrics with constant scalar curvature of unitary volume, for simplicity CPE metrics. It was conjectured in the 1980’s that every CPE metric must be Einstein. We prove that such a conjecture is true under a second-order vanishing condition on the Weyl tensor. / Na primeira parte deste trabalho investigamos o problema de Yamabe modificado em variedades de dimensão quatro cujos invariantes modificadores dependem dos autovalores do tensor de Weyl e são descritos em termos do máximo e mínimo da curvatura biortogonal (seccional). Fornecemos algumas propriedades geométricas e topológicas para tais variedades em termos destes invariantes. Na segunda parte investigamos os pontos críticos do funcional curvatura escalar total restrito ao espaço de métricas com curvatura escalar constante e volume unitário, abreviadamente chamamos de métricas CPE. Conjecturou-se na década de 1980 que toda métrica CPE deve ser Einstein. Provamos que tal conjectura é verdadeira sob uma condição de nulidade sobre o divergente de segunda ordem do tensor de Weyl.

Made available in DSpace on 2015-03-26T13:45:36Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2162893 bytes, checksum: 4b666208fbc222c17155380c6989fbf1 (MD5) Previous issue date: 2013-07-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this work we study of the curvature projective plane at a point of a 3-manifold immersed in Rn n ≥ 4, based one the thesis of R. R. Binotto [1]. We analyzed the different types of surfaces that describe the projective. We show that it can to be described as an isomorphism of the Veronese s surface of order 2 followed by a linear transformation and a translation. We also relate the types of a point on a 3-manifold with the degenericity of projective in the normal space. We conclude this study by analyzing the curvature locus of points in a n-manifold immersed in codimension 2, according to [14]. We present some examples, analyzing a few geometric properties of the curvature locus and comment on some results related to the geometry of a 3-manifold in codimension 2. / Neste trabalho fazemos um estudo do projetivo de curvatura em um ponto de uma 3-variedade imersa em Rn , n ≥ 4, tendo como base a tese de de R. R. Binotto [1]. Analisamos os diferentes tipos de superfícies que descrevem o projetivo, mostramos que este pode ser descrito como um isomorfismo da superfície de Veronese de ordem 2 seguido de uma transformação linear e de uma translação. Também relacionamos os tipos de pontos da 3-variedade com a degenericidade do projetivo no espaço normal. Finalizamos o estudo analisando o locus de curvatura em pontos de uma n-variedade imersa em codimenso 2, de acordo com [14], apresentamos alguns exemplos, analisando algumas propriedades geométricas do locus de curvatura e comentamos alguns resultados relacionados à geometria de uma 3-variedade em codimensão 2.

The notion of umbilic points and principal curvature lines are traditionally studied in surfaces of R3. Our goal is to extend these notions to surfaces immersed in R4. For this, we will analyze the image of the second fundamental form, restricted to the unit circle in the normal plane of the surface. We show that this image is an ellipse, called ellipse of curvature. The points where the ellipse of curvature becomes a circle are called axiumbilics points and lines corresponding to large and small axes of the ellipse are called, respectively, of principal and mean axial lines. In this work we describe the structure of the principal axial lines on surfaces immersed in R4 in the neighborhood of generic axiumbilics points. / As noções de pontos umbílicos e linhas de curvatura principal são tradicionalmente estudadas em superfícies do R3. Nosso objetivo é estender essas noções para superfícies imersas em R4. Para isto, analisaremos a imagem da segunda forma fundamental, restrita ao círculo unitário, no plano normal da superfície. Mostraremos que tal imagem é uma elipse, chamada elipse de curvatura. Os pontos onde a elipse de curvatura se torna um círculo são chamados pontos axiumbílicos e as linhas correspondentes ao eixo maior e menor da elipse são chamadas, respectivamente, de linhas axiais principais e médias. Neste trabalho descreveremos a estrutura das linhas axiais principais de imersões de superfícies em R4 na vizinhança de pontos axiumbílicos genéricos.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2015-05-14T14:51:34Z No. of bitstreams: 2 Dissertação - Carlos Antônio Freitas da Silva - 2015.pdf: 659907 bytes, checksum: c43cf65b3e27833fcd6b4ab11eb79239 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-05-14T14:53:28Z (GMT) No. of bitstreams: 2 Dissertação - Carlos Antônio Freitas da Silva - 2015.pdf: 659907 bytes, checksum: c43cf65b3e27833fcd6b4ab11eb79239 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-05-14T14:53:28Z (GMT). No. of bitstreams: 2 Dissertação - Carlos Antônio Freitas da Silva - 2015.pdf: 659907 bytes, checksum: c43cf65b3e27833fcd6b4ab11eb79239 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-02-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this dissertation we will study Finsler Geometry. In particular, we will study Randers Geometry that which can be viewed as Riemannian Geometry with a pertubation. Furthermore Randers metrics are also obtained as solution to Zermelo’s Navigation Problem. We will also use classification theorems of Randers metrics of constant flag curvature and Einstein Randers metrics in terms of Zermelo’s Navigation Problem. Using Randers metrics we are going to construct a 3-parameter family of Einstein-Finsler metrics with non-constant flag curvature and to get such family we use a Killing vector field and a Riemannian metric which is the Hawking Taub-NUT metric. / Neste trabalho estudaremos a Geometria de Finsler. Em particular, estudaremos a Geometria de Randers que pode ser visto como a mais simples perturbação da Geometria Riemanniana. Além disso, veremos também que métricas de Randers podem ser obtidas como soluções do Problema Navegacional de Zermelo. Utilizaremos também resultados que caracterizam métricas de Randers com curvatura flag constante e métricas de Randers do tipo Einstein em termos do Problema Navegacional de Zermelo. Usando métricas de Randers vamos construir uma família a 3 parâmetros de métricas de Einstein-Finsler com curvatura flag não constante e para obter tal família utilizaremos um campo de Killing e uma métrica Riemanniana que é a métrica de Hawking Taub-NUT.

Submitted by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-06-19T17:00:58Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) dissertação-Thiago Lucas-FINAL.pdf: 424556 bytes, checksum: 504bc5cad61e90dcf5cfc403f099b634 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-06-19T17:01:10Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) dissertação-Thiago Lucas-FINAL.pdf: 424556 bytes, checksum: 504bc5cad61e90dcf5cfc403f099b634 (MD5) / Made available in DSpace on 2018-06-19T17:01:10Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) dissertação-Thiago Lucas-FINAL.pdf: 424556 bytes, checksum: 504bc5cad61e90dcf5cfc403f099b634 (MD5) Previous issue date: 2016-12-14 / In this dissertation we will present a demonstration that a linear Weingarten translation surface in Euclidean space and Lorentz-Minkowski space should have constant mean curvature or constant Gaussian curvature. The work is based on the article "Translation surfaces of linear Weingarten type" Antonio Bueno and Rafael López. / Nesta dissertação apresentaremos uma demonstração de que uma superfície de translação Weingarten linear no espaço euclidiano e no espaço Lorentz- Minkowski deve ter curvatura média constante ou curvatura de Gauss constante. O trabalho é baseado no artigo "Translation surfaces of linear Weingarten type"de Antonio Bueno e Rafael López.

The curvature of a contraction T in the Cowen-Douglas class is bounded above by the curvature of the backward shift operator. However, in general, an operator satisfying the curvature inequality need not be contractive. In this thesis, we characterize a slightly smaller class of contractions using a stronger form of the curvature inequality. Along the way, we find conditions on the metric of the holomorphic Hermitian vector bundle E corresponding to the operator T in the Cowen-Douglas class which ensures negative definiteness of the curvature function. We obtain a generalization for commuting tuples of operators in the Cowen-Douglas class. Secondly, we obtain an explicit formula for the curvature of the jet bundle of the Hermitian holomorphic bundle E f on a planar domain Ω. Here Ef is assumed to be a pull-back of the tautological bundle on gr(n, H ) by a nondegenerate holomorphic map f :Ω →Gr (n, H ). Clearly, finding relationships amongs the complex geometric invariants inherent in the short exact sequence 0 → Jk(Ef ) → Jk+1(Ef ) →J k+1(Ef )/ Jk(Ef ) → 0 is an important problem, whereJk(Ef ) represents the k-th order jet bundle. It is known that the Chern classes of these bundles must satisfy c(Jk+1(Ef )) = c(Jk(Ef )) c(Jk+1(Ef )/ Jk(Ef )). We obtain a refinement of this formula: trace Idnxn ( KJk(Ef )) - trace Idnxn ( KJk-1(Ef ))= KJk(Ef )/ Jk-1(Ef )(z).