Devido à sua alta taxa de mortalidade as doenças cardiovasculares vem sendo foco de pesquisas nos últimos anos. Estima-se que neste grupo, 42% das mortes foram consequência de doença coronariana (CHD) em 2012. Para auxiliar o acompanhamento de pacientes com CHD, este estudo teve como objetivo investigar um método simples e robusto que segmenta de maneira semi-automática a área da neoíntima em Tomografias Intravasculares por Coerência Óptica no Domínio da Frequência (FD-IOCT), a mais recente técnica de imagear vasos internamente. O método foi dividido em duas etapas. A primeira segmenta a área contida pelo lúmen através de operações morfológicas com valores de intensidade e aplicação da limiarização Otsu. Na segunda, o foco foi segmentar a área contida por partes de stent onde duas estratégias foram desenvolvidas e comparadas. Ambas as etapas (segmentação de área de lúmen e de stent) obtiveram resultados acurados com aproximadamente 98% de Verdadeiro Positivo, enquanto o Falso Positivo foi próximo de 3% para o lúmen e 5% para stent, onde uma das estratégias (para delimitar a área contida por stent) apresentou um tempo de execução 50 vezes maior que a outra. O método foi utilizado em 443 imagens com diferentes características e os resultados são encorajadores. / Due to its high mortality rate cardiovascular diseases have been the focus of research in recent years. It is estimated that among these, 42% of deaths were due to coronary heart disease (CHD) in 2012. To monitor patients with CHD, the goal of this study was to investigate a simple and robust method that segments semi-automatically the neointimal area on Frequency Domain Intravascular Optical Coherence Tomography (FD-IOCT), the latest technology to view vessels internally. The method was divided into two steps. The first one segments the area contained by the lumen through morphological operations on intensity values and the Otsu threshold. In the second one, the focus was to segment the area contained by stent struts where two strategies were developed and compared. Both steps (lumen and stent strut area segmentation) obtained accurate results with true positives approximately 98%, while the false positives were close to 3% for the lumen and 5% for the stent, where one strategy (to delimit the area contained by stent struts) showed run time of 50 times the other. The method was executed on 443 images with different characteristics and the results are encouraging.

Cette thèse porte sur la dynamique des différentes mésophases liquides cristallines et des transitions de phase d'un modèle colloïdal de particules en forme de bâtonnent: les virus fd. L'étude de l'auto-organisation des cristaux liquides colloïdaux traite des phénomènes les plus simples de formation de systèmes structurés. Dans un système où les particules anisotropes ont des interactions de noyau rigide, l'auto-organisation est purement entropique en raison de la maximisation du volume libre du système. Ainsi, il y a une modification de la dynamique qui peut être mesurée, et fournisse des informations sur le volume libre disponible et la structure de la mésophase.La dynamique des bâtonnets fd peut être mesurée avec précision à l'aide de techniques de microscopie à fluorescence. Nous quantifions la dynamique autour des transitions de phase et l'effet de la flexibilité et de la longueur en tant que mécanisme pour relâcher la contrainte de leurs voisins. En outre, dans une structure lamellaire guest-host, nous avons prouvé la pérmeation favorisée des bâtonnets longs guest à travers les couches de la matrice Smectique hast formée de plus petites particules. Dans ces conditions, la super-diffusion de la particule invitée est également observée lorsqu'elle se diffuse dans une limite de grain. Il s'agit d'un pas en avant pour comprendre la dynamique des systèmes structurés colloïdaux et aussi dans le développement des nouveaux matériaux basés sur des diffuseurs rapides avec des applications potentielles dans la biologie médicale. Les résultats expérimentaux sont très prometteurs et stimulantes. / This thesis treats the dynamics of the different liquid crystalline mesophases and phase transitions of a model colloïdal of rod-like particles: the fd viruses. The study of the self-organization of colloïdal liquid crystals treats the simplest phenomena of forming structured systems. In a system where anisotropie particles have hard core interactions, the self-organization is purely entropy driven due to the maximization of the free volume of the system. Thus, there is a change on the dynamics at single particle level that can be measured, providing information on the available free volume and the structure of the mesophase.The fd rods are a versatile colloïdal system and their self-dynamics can be accurately measured using fluorescence microscopy techniques. We quantify the relaxation of the dynamics around the phase transitions and the effect of flexibility and length as a mechanism to release the constraint of their neighbors. Moreover, in a guest-host lamellar structure we demonstrate that a big guest particle is faster than the small host, if the guest particle is not commensurate in the host energy landscape. In these conditions, also the super-diffusion of the guest particle is observed when it diffuses into a grain boundary. This is a step forward to understand the dynamics of colloïdal structured systems and also in the development the new materials based on fast diffusers with potential applications in drug delivery. The extensive experimental results are completed by a whole analysis and interpretation, being very promising and challenging.

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abstract: Multiple-input multiple-output systems have gained focus in the last decade due to the benefits they provide in enhancing the quality of communications. On the other hand, full-duplex communication has attracted remarkable attention due to its ability to improve the spectral efficiency compared to the existing half-duplex systems. Using full-duplex communications on MIMO co-operative networks can provide us solutions that can completely outperform existing systems with simultaneous transmission and reception at high data rates. This thesis considers a full-duplex MIMO relay which amplifies and forwards the received signals, between a source and a destination that do not a have line of sight. Full-duplex mode raises the problem of self-interference. Though all the links in the system undergo frequency flat fading, the end-to-end effective channel is frequency selective. This is due to the imperfect cancellation of the self-interference at the relay and this residual self-interference acts as intersymbol interference at the destination which is treated by equalization. This also leads to complications in form of recursive equations to determine the input-output relationship of the system. This also leads to complications in the form of recursive equations to determine the input-output relationship of the system. To overcome this, a signal flow graph approach using Mason's gain formula is proposed, where the effective channel is analyzed with keen notice to every loop and path the signal traverses. This gives a clear understanding and awareness about the orders of the polynomials involved in the transfer function, from which desired conclusions can be drawn. But the complexity of Mason's gain formula increases with the number of antennas at relay which can be overcome by the proposed linear algebraic method. Input-output relationship derived using simple concepts of linear algebra can be generalized to any number of antennas and the computation complexity is comparatively very low. For a full-duplex amplify-and-forward MIMO relay system, assuming equalization at the destination, new mechanisms have been implemented at the relay that can compensate the effect of residual self-interference namely equal-gain transmission and antenna selection. Though equal-gain transmission does not perform better than the maximal ratio transmission, a trade-off can be made between performance and implementation complexity. Using the proposed antenna selection strategy, one pair of transmit-receive antennas at the relay is selected based on four selection criteria discussed. Outage probability analysis is performed for all the strategies presented and detailed comparison has been established. Considering minimum mean-squared error decision feedback equalizer at the destination, a bound on the outage probability has been obtained for the antenna selection case and is used for comparisons. A cross-over point is observed while comparing the outage probabilities of equal-gain transmission and antenna selection techniques, as the signal-to-noise ratio increases and from that point antenna selection outperforms equal-gain transmission and this is explained by the fact of reduced residual self-interference in antenna selection method. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2018

Nematic liquid crystals are mesogenic materials that are popular working materials for optical displays. There has been an increased interest in bistable liquid crystal devices which support two optically distinct stable equilibria. These devices typically exploit a complex geometry or anchoring conditions, which often induces defects in the equilibria. There remains a great deal to be understood about the structure of the defects and how they stabilize multiple equilibria in modern devices. This thesis focuses on four problems: the first three explore the effect of confinement and defects on nematic equilibria in simple geometries, with the aim of exploring multistability in these geometries; the fourth problem concerns the fine structure of point defects, essential for future modelling of nematic equilibria in more complex geometries. Firstly, we study nematic liquid crystals confined to two-dimensional rectangular wells using the Oseen-Frank theory. Secondly, we study equilibria within a semi-infinite rectangular domain with weak tangential anchoring on the surfaces. Thirdly, we study nematic equilibria within two-dimensional annuli. We derive explicit expressions for the director fields and free energies of equilibria within these geometries and discuss the stability of the predicted states. These three problems are motivated by the experimental work on colloidal nematic liquid crystals, which we interpret in the context of our results. Finally, we study the fine structure and stability of the radial hedgehog defect in the Landau-de Gennes theory with a sixth order bulk potential, relevant to the observability of global biaxial phases in a model with higher order potential terms.

The topic of this thesis is the transfer of information in vehicles using bus systems. The theoretical part is devoted to the description of communication as a means of passing information and to the mode of communication between individual technical systems via communication networks. Furthermore, it summarizes the specifics of selected communication systems. The practical part of the thesis includes an experiment for which the building of a CAN FD bus model was required. For communication purposes, the programming of SPI protocol on the Field Programmable Gate Array (FPGA) was crucial to provide access to the CAN FD controller. The result is a bus receiving and transmitting test and a timing test for reading and writing data.