Dissertations / Theses on the topic 'Discrete metric'

The notion of a partial translation algebra was introduced by Brodzki, Niblo and Wright in [11] to provide an analogue of the reduced group C*-algebra for metric spaces. Such an algebra is constructed from a partial translation structure, a structure which any bounded geometry uniformly discrete metric space admits; we prove that these structures restrict to subspaces and are preserved by uniform bijections, leading to a new proof of an existing theorem. We examine a number of examples of partial translation structures and the algebras they give rise to in detail, in particular studying cases where two different algebras may be associated with the same metric space. We introduce the notion of a map between partial translation structures and use this to describe when a map of metric spaces gives rise to a homomorphism of related partial translation algebras. Using this homomorphism, we construct a C*-algebra extension for subspaces of groups, which we employ to compute K-theory for the algebra arising from a particular subspace of the integers. We also examine a way to form a groupoid from a partial translation structure, and prove that in the case of a discrete group the associated C*-algebra is the same as the reduced group C*-algebra. In addition to this we present several subsidiary results relating to partial translations and cotranslations and the operators these give rise to.

Orientador: Sueli Irene Rodrigues Costa
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática, Estatística e Computação Científica.
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Resumo: Reticulados no 'R^n' são conjuntos discretos de pontos gerados como combinações inteiras de vetores linearmente independentes. A estrutura e as propriedades de reticulados vêm sendo exploradas em diversas áreas, dentre elas a Teoria da Informação. Neste trabalho fizemos um estudo de reticulados q-ários na métrica da soma, os quais estão relacionados aos códigos q-ários. Iniciamos com o estudo de reticulados gerais abordando questões como, densidade de empacotamento, determinação da região de Voronoi, equivalência de reticulados e processos de decodificação, fazendo um paralelo destas questões na métrica euclidiana e na métrica da soma. Em seguida, no Capitulo 2, tratamos brevemente os conceitos de códigos corretores de erros, onde os códigos q-ários estão inseridos e códigos lineares definidos sobre corpos finitos. No estudo dos códigos q-ários consideramos a distancia de Lee que e uma alternativa a usual métrica de Hamming. Por fim, no Capitulo 3, abordamos os reticulados q-ários que são obtidos a partir de códigos q-ários pelo processo conhecido como Construção A. Estudamos uma forma de se decodificar um reticulado q-ário via a Construção A, usando a decodificação do código e vice-versa e discutimos um algoritmo de decodificação (Lee Sphere Decoding) para reticulados q-ários que possuem matriz geradora de formato especial
Abstract: Lattices in 'R^n' are discrete sets of points generated as integer combinations of linearly independent vectors. The structure and properties of lattices have been explored in several areas, including Information Theory. In this work, we study q-ary lattices which are obtained from q-ary codes in the sum metric. We begin the study of general lattices, approaching topics as packing density, Voronoi regions, lattice equivalence and decoding processes, considering both the Euclidean and sum metric. In Chapter 2, we introduce some error correcting codes concepts focusing on q-ary codes and the more general class of linear codes defined over finite fields. In the study of q-ary codes, we consider the Lee distance, as an extension and alternative to the usual Hamming metric. Finally, in Chapter 3, we approach the q-ary latt ices, which are obtained from q-ary codes via the so called Construction A. We study a q-ary lattice decoding process, relate it to the associate code decoding and discuss a decoding algorithm for lattices which have special generator matrices
Mestrado
Matematica
Mestre em Matemática

Spherical, Euclidean, and hyperbolic simplices can be characterized by the dihedral angles on their codimension-two faces. These characterizations analyze the Gram matrix, a matrix with entries given by cosines of dihedral angles. Hyperideal hyperbolic simplices are non-compact generalizations of hyperbolic simplices wherein the vertices lie outside hyperbolic space. We extend recent characterization results to include fully general hyperideal simplices. Our analysis utilizes the Gram matrix, however we use inversive distances instead of dihedral angles to accommodate fully general hyperideal simplices.For two-dimensional triangulations, an angle structure is an assignment of three face angles to each triangle. An angle structure permits a globally consistent scaling provided the faces can be simultaneously scaled so that any two contiguous faces assign the same length to their common edge. We show that a class of symmetric Euclidean angle structures permits globally consistent scalings. We develop a notion of virtual scaling to accommodate spherical and hyperbolic triangles of differing curvatures and show that a class of symmetric spherical and hyperbolic angle structures permit globally consistent virtual scalings.The double tetrahedron is a triangulation of the three-sphere obtained by gluing two congruent tetrahedra along their boundaries. The pentachoron is a triangulation of the three-sphere obtained from the boundary of the 4-simplex. As piecewise flat manifolds, the geometries of the double tetrahedron and pentachoron are determined by edge lengths that gives rise to a notion of a metric. We study notions of Einstein metrics on the double tetrahedron and pentachoron. Our analysis utilizes Regge's Einstein-Hilbert functional, a piecewise flat analogue of the Einstein-Hilbert (or total scalar curvature) functional on Riemannian manifolds.A notion of conformal structure on a two dimensional piecewise flat manifold is given by a set of edge constants wherein edge lengths are calculated from the edge constants and vertex based parameters. A conformal variation is a smooth one parameter family of the vertex parameters. The analysis of conformal variations often involves the study of degenerating triangles, where a face angle approaches zero. We show for a conformal variation that remains weighted Delaunay, if the conformal parameters are bounded then no triangle degenerations can occur.

This PhD thesis, consisting of an introduction, four papers, and some supplementary results, studies the problem of finding an optimal realization of a given finite metric space: a weighted graph which preserves the metric's distances and has minimal total edge weight. This problem is known to be NP-hard, and solutions are not necessarily unique.

It has been conjectured that extremally weighted optimal realizations may be found as subgraphs of the hereditarily optimal realization Γ_d, a graph which in general has a higher total edge weight than the optimal realization but has the advantages of being unique, and possible to construct explicitly via the tight span of the metric.

In Paper I, we prove that the graph Γ_d is equivalent to the 1-skeleton of the tight span precisely when the metric considered is totally split-decomposable. For the subset of totally split-decomposable metrics known as consistent metrics this implies that Γ_d is isomorphic to the easily constructed Buneman graph.

In Paper II, we show that for any metric on at most five points, any optimal realization can be found as a subgraph of Γ_d.

In Paper III we provide a series of counterexamples; metrics for which there exist extremally weighted optimal realizations which are not subgraphs of Γ_d. However, for these examples there also exists at least one optimal realization which is a subgraph.

Finally, Paper IV examines a weakened conjecture suggested by the above counterexamples: can we always find some optimal realization as a subgraph in Γ_d? Defining extremal optimal realizations as those having the maximum possible number of shortest paths, we prove that any embedding of the vertices of an extremal optimal realization into Γ_d is injective. Moreover, we prove that this weakened conjecture holds for the subset of consistent metrics which have a 2-dimensional tight span

Cette thèse est construite autour de deux types d'estimation de l'état d'un système, traités séparément. Le premier problème abordé concerne la construction d'observateurs positifs basés sur la métrique de Hilbert. Le second traite de la synthèse d'observateurs par intervalles pour différentes familles de systèmes dynamiques et la construction de lois de commande robustes qui stabilisent ces systèmes.Un système positif est un système dont les variables d'état sont toujours positives ou nulles lorsque celles-ci ont des conditions initiales qui le sont. Les systèmes positifs apparaissent souvent de façon naturelle dans des applications pratiques où les variables d'état représentent des quantités qui n'ont pas de signification si elles ont des valeurs négatives. Dans ce contexte, il parait naturel de rechercher des observateurs fournissant des estimées elles aussi positives ou nulles. Dans un premier temps, notre contribution réside dans la mise au point d'une nouvelle méthode de construction d'observateurs positifs sur l'orthant positif. L'analyse de convergence est basée sur la métrique de Hilbert. L'avantage concurrentiel de notre méthode est que la vitesse de convergence peut être contrôlée.Notre étude concernant la synthèse d'observateurs par intervalles est basée sur la théorie des systèmes dynamiques positifs. Les observateurs par intervalles constituent un type d'observateurs très particuliers. Ce sont des outils développés depuis moins de 15 ans seulement : ils trouvent leur origine dans les travaux de Gouzé et al. en 2000 et se développent très rapidement dans de nombreuses directions. Un observateur par intervalles consiste en un système dynamique auxiliaire fournissant un intervalle dans lequel se trouve l'état, en considérant que l'on connait des bornes pour la condition initiale et pour les quantités incertaines. Les observateurs par intervalles donnent la possibilité de considérer le cas où des perturbations importantes sont présentes et fournissent certaines informations à tout instant
This thesis presents new results in the field of state estimation based on the theory of positive systems. It is composed of two separate parts. The first one studies the problem of positive observer design for positive systems. The second one which deals with robust state estimation through the design of interval observers, is at the core of our work.We begin our thesis by proposing the design of a nonlinear positive observer for discrete-time positive time-varying linear systems based on the use of generalized polar coordinates in the positive orthant. For positive systems, a natural requirement is that the observers should provide state estimates that are also non-negative so they can be given a physical meaning at all times. The idea underlying the method is that first, the direction of the true state is correctly estimated in the projective space thanks to the Hilbert metric and then very mild assumptions on the output map allow to reconstruct the norm of the state. The convergence rate can be controlled.Later, the thesis is continued by studying the so-called interval observers for different families of dynamic systems in continuous-time, in discrete-time and also in a context "continuous-discrete" (i.e. a class of continuous-time systems with discrete-time measurements). Interval observers are dynamic extensions giving estimates of the solution of a system in the presence of various type of disturbances through two outputs giving an upper and a lower bound for the solution. Thanks to interval observers, one can construct control laws which stabilize the considered systems

Tires are the most influential component of the vehicle as they constitute the only contact between the vehicle and the road and have to generate and transmit forces necessary for the driver to control the vehicle. The demand for the tire models are increasing due to the need to study the variations of force generation mechanisms due to various variables such as load, pressure, speed, and road surface irregularities. Another need from the vehicle manufactures is the study of potential incompatibilities associated with safety systems such as Anti-lock Braking System (ABS) and Electronic Stability Control (ESC) and tires. For vehicle dynamic simulations pertaining to the design of safety systems such as ABS, ESC and ride controllers, an accurate and computationally efficient tire model is required. As these control algorithms become more advanced, they require accurate and extended validity in the range of frequencies required to cover dynamic response due to short wavelength road disturbances, braking and steering torque variations. Major thrust has been provided by the tire industry to develop simulation models that accurately predict the dynamic response of tires without the use of computationally intensive tools such as FEA. The objectives of this research are • To develop, implement and validate a rigid ring tire model and a simulation tool to assist both tire designers and the automotive industry in analyzing the effects of tire belt vibrations, road disturbances, and high frequency brake and steering torque variations on the handling, braking, and ride performances of the vehicle. • To further enhance the tire model by considering dynamic stiffness changes and temperature dependent friction properties. • To develop, and implement novel control algorithms for braking, stability, and ride performance improvements of the vehicle
Ph. D.

Dans cette thèse, nous développons un modèle du second ordre pour la représentation des formes (courbes et surfaces) grâce à la théorie des cycles normaux. Le cycle normal d'une forme est le courant associé à son fibré normal. En introduisant des métriques à noyaux sur les cycles normaux, nous obtenons une mesure de dissimilarité entre formes qui prend en compte leurs courbures. Cette mesure est ensuite utilisée comme terme d'attache aux données dans une optique d'appariement et d'analyse de formes par les déformations. Le chapitre 1 est une revue du domaine de l'analyse de formes par les déformations. Nous insistons plus particulièrement sur la mise en place théorique et numérique du modèle de Large Deformation Diffeomorphic Metric Mapping (LDDMM). Le chapitre 2 se concentre sur la représentation des formes par les cycles normaux dans un cadre unifié qui englobe à la fois les formes continues et discrètes. Nous précisons dans quelle mesure cette représentation contient des informations de courbure. Enfin nous montrons le lien entre le cycle normal d'une forme et son varifold. Dans le chapitre 3, nous introduisons les métriques à noyaux. Ainsi, nous pouvons considérer les cycles normaux dans un espace de Hilbert avec un produit scalaire explicite. Nous détaillons ce produit scalaire dans le cas des courbes et surfaces discrètes avec certains noyaux, ainsi que le gradient associé. Nous montrons enfin que malgré le choix de noyaux simples, nous ne perdons pas toutes les informations de courbures. Le chapitre 4 utilise cette nouvelle métrique comme terme d'attache aux données dans le cadre LDDMM. Nous présentons de nombreux appariements et estimations de formes moyennes avec des courbes ou des surfaces. L'objectif de ce chapitre est d'illustrer les différentes propriétés des cycles normaux pour l'analyse des déformations sur des exemples synthétiques et réels
In this thesis, we develop a second order model for the representation of shapes (curves or surfaces) using the theory of normal cycles. The normal cycle of a shape is the current associated with its normal bundle. Introducing kernel metrics on normal cycles, we obtain a dissimilarity measure between shapes which takes into account curvature. This measure is used as a data attachment term for a purpose of registration and shape analysis by deformations. Chapter 1 is a review of the field of shape analysis. We focus on the setting of the theoretical and numerical model of the Large Deformation Diffeomorphic Metric Mapping(LDDMM).Chapter 2 focuses on the representation of shapes with normal cycles in a unified framework that encompasses both the continuous and the discrete shapes. We specify to what extend this representation encodes curvature information. Finally, we show the link between the normal cycle of a shape and its varifold. In chapter 3, we introduce the kernel metrics, so that we can consider normal cycles in a Hilbert space with an explicit scalar product. We detail this scalar product for discrete curves and surfaces with some kernels, as well as the associated gradient. We show that even with simple kernels, we do not get rid of all the curvature informations. The chapter 4 introduces this new metric as a data attachment term in the framework of LDDMM. We present numerous registrations and mean shape estimation for curves and surfaces. The aim of this chapter is to illustrate the different properties of normal cycles for the deformations analysis on synthetic and real examples

Background: Pharmacy-related performance measures have gained significant attention in the transition to value-based healthcare. Pharmacy-level quality measures, including those developed by the Pharmacy Quality Alliance, are not yet publicly accessible. However, the publication of report cards for individual pharmacies has been discussed as a way to help direct patients towards high-quality pharmacies. This study aimed to measure the relative strength of patient preferences for community pharmacy attributes, including pharmacy quality. Additionally, this study aimed to identify and describe community pharmacy market segments based on patient preferences for pharmacy attributes. Methods: This study elicited patient preferences for community pharmacy attributes using a discrete choice experiment (DCE) among a sample of 773 adults aged 18 years and older. Six attributes were selected based on published literature, expert opinion, and pilot testing feedback. The attributes included hours of operation, staff friendliness/courtesy, pharmacist communication, pharmacist willingness to establish a personal relationship, overall quality, and a drug-drug interaction specific quality metric. Participants responded to a block of ten random choice tasks assigned by Sawtooth v9.2 and two fixed tasks, including a dominant and a hold-out scenario. The data were analyzed using conditional logit and latent class regression models, and Hierarchical Bayes estimates of individual-level utilities were used to compare preferences across demographic subgroups. Results: Among the 773 respondents who began the survey, 741 (95.9%) completed the DCE and demographic questionnaire. Overall, study participants expressed the strongest preferences for quality-related pharmacy attributes. The attribute importance values (AIVs) were highest for the specific, drug-drug interaction (DDI) quality measure, presented as, “The pharmacy ensured there were no patients who were dispensed two medications that can cause harm when taken together,” (40.3%) and the overall pharmacy quality measure (31.3%). The utility values for 5-star DDI and overall quality ratings were higher among women (83.0 and 103.8, respectively) than men (76.2 and 94.5, respectively), and patients with inadequate health literacy ascribed higher utility to pharmacist efforts to get to know their patients (26.0) than their higher literacy counterparts (16.3). The best model from the latent class analysis contained three classes, coined the Quality Class (67.6% of participants), the Relationship Class (28.3%), and the Convenience Class (4.2%). Conclusions: The participants in this discrete choice experiment exhibited strong preferences for pharmacies with higher quality ratings. This finding may reflect patient expectations of community pharmacists, namely that pharmacists ensure that patients are not harmed by the medications filled at their pharmacies. Latent class analysis revealed underlying heterogeneity in patient preferences for community pharmacy attributes.

Les systèmes automatisés de production (SAP) représentent une classe importante des systèmes industriels qui sont de plus en plus complexes vue le grand nombre d’interaction et d’interconnexion entre leurs différents composants. En conséquence, ils sont plus sensibles aux dysfonctionnements dont les conséquences peuvent être importantes en termes de productivité, de sécurité et de qualité de production. Un défi majeur est alors de développer une approche intelligente qui peut être utilisée pour le diagnostic de ces systèmes afin de garantir leurs suretés de fonctionnement. Dans le cadre de cette thèse, nous nous intéressons seulement au diagnostic des SAP ayant une dynamique discrète. Nous présentons dans le premier chapitre ces systèmes, les dysfonctionnements possibles et la terminologie du diagnostic utilisée. Ensuite, nous présentons un état de l’art de différentes méthodes et approches existantes et aussi une synthèse de ces méthodes. Cette synthèse nous a motivé de choisir une approche à base de donnée qui s’appuie sur une technique d’apprentissage automatique, qui est le raisonnement à partir de cas (RàPC). Pour cela, nous avons présenté dans le deuxième chapitre un état de l’art sur l’apprentissage automatique et ses différentes méthodes en mettant l’accent essentiellement sur le RàPC et ses utilisations pour le diagnostic des systèmes industriels. Cette étude nous a permis de proposer dans le chapitre 3 une approche d’aide au diagnostic qui se base sur le RàPC. Cette approche s’appuie sur une phase hors ligne et une phase en ligne. La phase hors ligne permet de définir un format de représentation de cas et de construire une base de cas normaux (BCN) et une base de cas défaillants (BCD) à partir d’une base de données d’historique. La phase en ligne permet d’aider les opérateurs humains de surveillance à la prise de la décision du diagnostic la plus adéquate. Les résultats des expérimentations sur un système de tri de caisses ont présentés les piliers de cette approche qui résident au niveau du format de représentation de cas proposé et au niveau de la base de cas utilisé. Pour résoudre ces problèmes et améliorer les résultats, un nouveau format de représentation de cas est proposé dans le chapitre 4. Selon ce format et à partir des données issues du système simulé après son émulation en mode normal et fautif, les cas de la base de cas initiale sont construits. Ensuite, une phase de raisonnement et d’apprentissage incrémental est présentée. Cette phase permet non seulement le diagnostic du système surveillé mais aussi d’enrichir la base de cas suite à l’apparition des nouveaux comportements inconnus. Les expérimentations présentées dans le chapitre 5 sur « le plateau tournant » qui est un sous système du système « tri de caisses » ont permis de montrer l’amélioration des résultats et aussi d’évaluer et de comparer les performances de l’approche proposée vis-à-vis certaines approches d’apprentissage automatique et vis-à-vis une approche à base de modèle pour le diagnostic du plateau tournant
Automated production systems (APS) represents an important class of industrial systems that are increasingly complex given the large number of interactions and interconnections between their different components. As a result, they are more susceptible to malfunctions, whose consequences can be significant in terms of productivity, safety and quality of production. A major challenge is to develop an intelligent approach that can be used to diagnose these systems to ensure their operational safety. In this thesis, we are only interested in the diagnosis of APS with discrete dynamics. We present in the first chapter these systems, the possible malfunctions and the used terminology for the diagnosis. Then, we present a state of the art of the existing methods for the diagnosis of this class of systems and also a synthesis of these methods. This synthesis motivated us to choose a data-based approach that relies on a machine learning technique, which is Case-Based Reasoning (CBR). For this reason, we presented in the second chapter a state of the art on machine learning and its different methods with a focus mainly on the CBR and its uses for the diagnosis of industrial systems. This study allowed us to propose in Chapter 3 a Case Based Decision Support System for the diagnosis of APS. This system is based on an online block and an offline block. The Offline block is used to define a case representation format and to build a Normal Case Base (NCB) and a Faulty Case Base (FCB) from a historical database. The online block helps human operators of monitoring to make the most appropriate diagnosis decision. The experiments results perform on a sorting system presented the pillars of this approach, which reside in the proposed case representation format and in the used case base. To solve these problems and improve the results, a new case representation format is proposed in chapter 4. According to this format and from the data acquired from the simulated system after its emulation in normal and faulty mode, cases of the initial case base are build. Then, a reasoning and incremental learning phase is presented. This phase allows the system diagnosis and the enrichment of the case base following the appearance of new unknown behaviors. The experiments presented in Chapter 5 and perform on the 'turntable' which is a subsystem of the 'sorting system” allowed to show the improvement of the results and also to evaluate and compare the performances of the proposed approach with some automatic learning approaches and with a model-based approach to turntable diagnosis

A study of the importance, elements and techniques of architectural contextualism. Contextual architecture is here defined as architecture that creates relationships with its specific site or its broader physical or visual environment. This study posits the comprehensive definition of architectural contextualism on multiple levels: denotatively, connotatively, historically, philosophically, and in its aspects of critical regionalism. American architects adept at the practice of architectural contextualism during the mid-twentieth century offer principles and techniques. These architects are John Carl Warnecke, E. Fay Jones, and George White and others. This research has yielded the systematic, comprehensive definition of contextualism, a set of metrics which can be used as a basis of design and aid in the evaluation of the degree to which a building or set of buildings and their landscape are contextually congruent.

Orientador: Regina Célia Galvão Frem
Co-orientador: Marco Aurélio Cebim
Banca: José Clayston Melo Pereira
Banca: Rogéria Rocha Gonçalves
Banca: José Maurício Almeida Caiut
Banca: Sérgio Antonio Marques de Lima
Resumo: Materiais luminescentes despertam grande interesse nas pesquisas devido à variedade de aplicações, podendo ser empregados em displays eletrônicos, lâmpadas fluorescentes e diodos emissores de luz, por exemplo. Neste contexto, os íons lantanídeos trivalentes são destaque pois apresentam propriedades luminescentes únicas como alta pureza de cor, tempo de vida de nano a milissegundos e linhas de emissão definidas e estreitas provenientes de transições intraconfiguracionais 4f-4f. No entanto, devida à natureza proibida dessas transições, os íons lantanídeos apresentam baixa absortividade molar. Para suprir essa deficiência, pode ser realizada a coordenação destes íons co m bons grupos cromóforos capazes de transferir energia para os níveis 4f dos lantanídeos. Outra estratégia para melhorar as propriedades luminescentes de materiais é através da combinação e/ou dopagem utilizando diferentes lantanídeos, o que pode resultar na emissão de ambos os íons ou na emissão preferencial de um deles por meio de processos de transferência de energia. Espécies bimetálicas heteronucleares e polímeros de coordenação porosos ( Metal Organic Frameworks, MOFs ) se destacam neste cenário. Neste trabalho foram estudadas quatro séries de compostos bimetálicos heteronucleares utilizando succinato de sódio e ácido 3,5-dicarbóxipir azolico como ligantes e variando a razão entre dois íons lantanídeos distintos, Gd 3+ :Eu 3+, Gd 3+ :Tb 3+, Dy 3+ :Eu 3+ e Eu 3+ :Tb 3+ . Os compostos obtidos foram caracterizados po r difração de raios X de monocristal e de pó, espectroscopia na região do IV, análise térmica, espectroscopia de reflectância difusa, espectroscopia de fotoluminescênc ia com excitação UV, luminescência com excitação por raios X e microscopia eletrônica de varredura associada à espectroscopia por energia dispersiva. Os complexos apresentaram interessantes propriedad...
Abstract: 12 ABSTRACT Luminescent materials attract interest in rese arch due to the diversity of applications. These materials can be used at electronic displays, fluorescent lamps and light emitting diodes, for example. In this contex t, trivalent lanthanide ions are interesting because of their unique luminescent properties like high color purity, nano to milliseconds lifetime and narrow emission lines from 4f-4f transitions. However, because of the nature of forbidden 4f-4f transitions, lanthanide ions have low molar absorptivity. To supply this deficiency, th e lanthanide ions can be coordinated to chromophore groups, capable of transfer ener gy to the 4f levels of lanthanides. It is also possible to improve the luminescent prop erties of materials by combining different lanthanides, which can result in the emission of both ions or in the preferential emission of one of them by energy transfer processes. Bimetallic heteronuclear complexes and metal organic frameworks (MOFs) are interesting in this context. In this work, four bimetallic heteronuclear compounds series with sodium succinate and 3,5- dicarboxypyrazolate ligands were prepared with different lanthanides ratio, Gd 3+ :Eu 3+, Gd 3+ :Tb 3+, Dy 3+ :Eu 3+ e Eu 3+ :Tb 3+ . The compounds were characterized by single crystal and powder X-ray diffraction, Fourier transform infrared spectroscopy, thermal analysis, UV-Vis spectroscopy, photoluminescence spectroscopy, X-ray excited optical luminescence and field emission gun-scanning electron microscopy, with energy dispersive X-ray spectroscopy. The complexes present interesting luminescent properties. In Gd 3+ compounds series, by increasing the amount of Gd 3+ ions in the sample, the intensity of the relative charge tr ansfer band also increases, indicating that the Gd 3+ ions play an important role in the energy transfer mechanism from ligands to the lanthanides. The intensity parameters, the radiat...
Doutor

Performance modelling and evaluation has long been considered of paramount importance to computer networks from design through development, tuning and upgrading. These networks, however, have evolved significantly since their first introduction a few decades ago. The Ubiquitous Web in particular with fast-emerging unprecedented services has become an integral part of everyday life. However, this all is coming at the cost of substantially increased security risks. Hence cybercrime is now a pervasive threat for today’s internet-dependent societies. Given the frequency and variety of attacks as well as the threat of new, more sophisticated and destructive future attacks, security has become more prevalent and mounting concern in the design and management of computer networks. Therefore equally important if not more so is security. Unfortunately, there is no one-size-fits-all solution to security challenges. One security defence system can only help to battle against a certain class of security threats. For overall security, a holistic approach including both reactive and proactive security measures is commonly suggested. As such, network security may have to combine multiple layers of defence at the edge and in the network and in its constituent individual nodes. Performance and security, however, are inextricably intertwined as security measures require considerable amounts of computational resources to execute. Moreover, in the absence of appropriate security measures, frequent security failures are likely to occur, which may catastrophically affect network performance, not to mention serious data breaches among many other security related risks. In this thesis, we study optimisation problems for the trade-offs between performance and security as they exist between performance and dependability. While performance metrics are widely studied and well-established, those of security are rarely defined in a strict mathematical sense. We therefore aim to conceptualise and formulate security by analogy with dependability so that, like performance, it can be modelled and quantified. Having employed a stochastic modelling formalism, we propose a new model for a single node of a generic computer network that is subject to various security threats. We believe this nodal model captures both performance and security aspects of a computer node more realistically, in particular the intertwinements between them. We adopt a simulation-based modelling approach in order to identify, on the basis of combined metrics, optimal trade-offs between performance and security and facilitate more sophisticated trade-off optimisation studies in the field. We realise that system parameters can be found that optimise these abstract combined metrics, while they are optimal neither for performance nor for security individually. Based on the proposed simulation modelling framework, credible numerical experiments are carried out, indicating the scope for further work extensions for a systematic performance vs security tuning of computer networks.

Orientador: José Roberto Nunhez
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: As embalagens cartonadas assépticas para alimentos são comuns em nosso dia-a-dia. Tais embalagens são compostas por três materiais: papel, polietileno de baixa densidade e alumínio. Seu processo de reciclagem se dá em duas etapas sucessivas: a reciclagem do papel e a posterior reciclagem do composto de polietileno e alumínio. Durante a primeira etapa de reciclagem, um percentual das fibras de papel não é retirado do composto de polietileno e alumínio o que pode comprometer a qualidade de produtos feitos a partir da reciclagem deste composto. Para a extração do papel residual foi desenvolvido de maneira empírica um equipamento centrífugo em escala industrial. Visando o estudo do funcionamento deste equipamento fez-se a simulação deste usando o método dos elementos discretos (DEM). O primeiro passo foi a determinação de parâmetros físicos e de interação através de experimentos práticos e respectivas simulações computacionais para a calibração de um modelo, o qual foi conseguido de maneira satisfatória. Uma vez tendo o modelo calibrado, foram realizadas simulações com diferentes geometrias para o rotor e parte estática deste equipamento buscando levantar hipóteses para o entendimento do funcionamento do equipamento. Os resultados para diferentes especificações foram comparados e discutidos
Abstract: Milk and beverages carton packages are very common in our lives. These packages are made of three different materials: paper, low density polyethylene and aluminium. The recycling process of these packages takes place in two successive stages: the recycling of paper and the subsequent recycling of polyethylene and aluminium composite. During the first stage of recycling a percentage of the paper is not removed from the composite of polyethylene and aluminium which can compromise the quality of products made from recycling of this composite. An industrial-scale centrifuge equipment was developed empirically for extraction of residual paper. In order to study the operation of this equipment, it was made its simulation using the discrete element method (DEM). The first step was set-up of physical and interaction parameters through practical experiments and computer simulations to calibrate a model, which was achieved satisfactorily. Once the model was calibrated, simulations were performed with different geometries for rotor and static body of this equipment seeking hypotheses in order to understand equipment operation. The results for different specifications were compared and discussed
Mestrado
Processos em Tecnologia Química
Mestre em Engenharia Química

Building on the work of Conrad Plaut and Valera Berestovskii regarding uniform spaces and the covering spectrum of Christina Sormani and Guofang Wei developed for geodesic spaces, the author defines and develops discrete homotopy theory for metric spaces, which can be thought of as a discrete analog of classical path-homotopy and covering space theory. Given a metric space, X, this leads to the construction of a collection of covering spaces of X - and corresponding covering groups - parameterized by the positive real numbers, which we call the [epsilon]-covers and the [epsilon]-groups. These covers and groups evolve dynamically as the parameter decreases, changing topological type at specific parameter values which depend on the topology and local geometry of X. This leads to the definition of a critical spectrum for metric spaces, which is the set of all values at which the topological type of the covers change. Several results are proved regarding the critical spectrum and its connections to topology and local geometry, particularly in the context of geodesic spaces, refinable spaces, and Gromov-Hausdorff limits of compact metric spaces. We investigate the relationship between the critical spectrum and covering spectrum in the case when X is geodesic, connections between the geometry of the [epsilon]-groups and the metric and topological structure of the [epsilon]-covers, as well as the behavior of the [epsilon]-covers and critical values under Gromov-Hausdorff convergence.

Although it was invented by Mikhail Gromov, in 1987, to describe some family of groups[1], the notion of Gromov hyperbolicity has many applications and interpretations in different fields. It has applications in Biology, Networking, Graph Theory, and many other areas of research. The Gromov hyperbolicity constant of several families of graphs and geometric spaces has been determined. However, so far, the only known algorithm for calculating the Gromov hyperbolicity constant δ of a discrete metric space is the brute force algorithm with running time O (n4) using the four-point condition. In this thesis, we first introduce an approximation algorithm which calculates a O (log n)-approximation of the hyperbolicity constant δ, based on a layering approach, in time O(n2), where n is the number of points in the metric space. We also calculate the fixed base point hyperbolicity constant δr for a fixed point r using a (max, min)−matrix multiplication algorithm by Duan in time O(n2.688)[2]. We use this result to present a 2-approximation algorithm for calculating the hyper-bolicity constant in time O(n2.688). We also provide an exact algorithm to compute the hyperbolicity constant δ in time O(n3.688) for a discrete metric space. We then present some partial results we obtained for designing some approximation algorithms to compute the hyperbolicity constant δ.

Dissertação de mestrado em Evolução e Biologia Humanas apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra
O estudo da dentição surge na Antiguidade Clássica, desenvolvendo-se para a análise da anatomia (formação e estudo histológico dentário) nos séculos XVIII e XIX (Alt et al., 1998). Os caracteres discretos começam a considerar-se na pesquisa de relações biológicas entre populações a partir do século XIX (Silva, 2002), surgindo a apreciação dos caracteres fenotípicos dentários a partir do trabalho de Lasker (1950, in Irish e Nelson, 2008). A consideração por graus da variação discreta dos caracteres identificados surge sistematicamente com o método ASUDAS (Turner et al., 1991). O presente trabalho teve como objectivos estudar os caracteres discretos de 163 mandíbulas e da dentição presente em 104 destas, caracterizando uma população de origem portuguesa, alojada no Museu de História Natural da FC-UP. Além disso, pretendeu-se caracterizar biologicamente essa amostra através do padrão estabelecido, quando comparado com o de outras populações mundiais e ibéricas. O sistema ASUDAS (Tuner et al., 1991), a que se acresceu um carácter sugerido por Weets (2009), foi usado para a caracterização morfológica dentária. Hauser e De Stefano (1989), Movsesjan et al. (1975 in Galera et al., 1995) e Albuquerque (1952) sugeriram metodologias de observação dos caracteres anatómicos mandibulares, aqui adoptadas. A diagnose sexual mandibular recorreu, ainda, a vários métodos complementares (Loth e Henneberg [1996], adaptado por Balci et al. [2005]; Buikstra et al., 1994; Ferenbach et al., 1980; Giles, 1964). As frequências de caracteres não-métricos dentários permitiram denotar a proximidade da população estudada com as populações europeias e, em menor grau, norte-africanas. A comparação com amostras ibéricas mostrou uma semelhança entre estas e o presente material, indiciando alguma proximidade com populações de território português. Os dados referentes a caracteres mandibulares corroboram a ligação biológica a populações europeias, o que era esperado. Este trabalho contribuiu assim para a caracterização de uma amostra que se presumia portuguesa , através da dentição inferior e da morfologia mandibular. O autor sugere investimento da investigação na caracterização da morfologia dentária das amostras portuguesas, recentes e de passados mais remotos, que contribuam para a interpretação da história ibérica, sublinhando a necessidade de garantir resultados completos e inequívocos.
The study of human dentition began in the Classical Era, developing towards the analysis of anatomy (dental formation and histology) in the 18th and 19th centuries (Alt et al., 1998). Discrete trais were used in the search for biological relationships between populations from the 19th century onwards (Silva, 2002), and the consideration of fenotypical dental traits was brought on by Lasker.s work (Lasker, 1950, in Irish e Nelson, 2008). The recording by degrees of expression was systematized by the ASUDAS method (Turner et al., 1991). The present work has the objective of studying the discrete traits of 163 mandibles and the dentition present in 104 of these, to characterize a population of portuguese origin, located at the Museu de Historia Natural da FC-UP. As well as this, there was the intention of biologically characterizing such sample, by comparing the established pattern with the ones found in world and iberian samples. The ASUDAS system, to which a trait suggested by Weets (2009) was added, was used to characterize the dental morphology. Hauser and De Stefano (1989), Movsesjan et al. (1975 in Galera et al., 1995) and Albuquerque (1952) suggested methods of recording mandibular non-metric traits, adopted herein. The mandibular sexual diagnosis was established through a multiplicity of complementary methodologies (Loth and Henneberg [1996], adapted by Balci et al. [2005]; Buikstra et al., 1994; Ferenbach et al., 1980; Giles, 1964). The frequencies of non-metric dental traits allowed the identification of the proximity of european samples and, to a lesser degree, of north African samples, to the present population. The comparison of iberian samples showed likeness between these and the present material, underlining some proximity with the populations in the current xv portuguese territory. The data referring to mandibular traits corroborate the biological link to european populations, which was expected. This work thus contributes to characterize a sample that was assumed to be Portuguese and natural of Oporto, through the inferior dentition and the mandibular traits. The author suggests that future researchers should invest in characterizing the portuguese samples, recent and otherwise, contributing to a greater knowledge of iberian history, also emphasizing the need to acquire complete and unequivocal results.

Tesis (Doctor en Matemática)--Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía, Física y Computación, 2017.
En esta tesis estudiamos las estructuras localmente conformes Kähler (LCK) y localmente conformes simplécticas (LCS) invariantes a izquierda en grupos de Lie, o equivalentemente tales estructuras en álgebras de Lie. Luego se buscan retículos (subgrupos discretos co-compactos) en dichos grupos. De esta manera obtenemos estructuras LCK o LCS en las solvariedades compactas (cociente de un grupo de Lie por un retículo). Específicamente estudiamos las estructuras LCK en solvariedades con estructuras complejas abelianas. Luego describimos explícitamente la estructura de las álgebras de Lie que admiten estructuras de Vaisman. También determinamos los grupos de Lie casi abelianos que admiten estructuras LCK o LCS y además analizamos la existencia de retículos en ellos. Finalmente desarrollamos un método para construir de manera sistemática ejemplos de álgebras de Lie equipadas con estructuras LCK o LCS a partir de un álgebra de Lie que ya admite tales estructuras y una representación compatible.
In this thesis we study left invariant locally conformal Kähler (LCK) structures and locally conformal symplectic structures (LCS) on Lie groups, or equivalently such structures on Lie algebras. Then we analize the existence of lattices (co-compact discrete subgroups) on these Lie groups. Therefore, we obtain LCK or LCS structures on compact solvmanifolds (quotients of a Lie group by a lattice). Specifically we study LCK structures on solvmanifold where the complex structure is abelian. Then we describe the structure of a Lie algebra admitting a Vaisman structure. On the other hand we determine the almost abelian Lie groups equipped with a LCK or LCS structures, and we also analize the existence of lattices on these groups. Finally we construct a method to produce examples of Lie algebras admitting LCK or LCS structures beginning with a Lie algebra with these structures and a compatible representation.