Thesis (doctoral)--Universität Göttingen.

Ce travail porte principalement sur un composant issu des concepts d'ingénierie de dispersion des métamatériaux et des cristaux photoniques qu'est la "superlentille". Un bref rappel des fondamentaux sur les cristaux photoniques bidimensionnels pour l’étude des structures de bandes est fait, avant de présenter les différents régimes de réfraction extraordinaires que l’on peut mettre en évidence en exploitant l’isotropie et/ou l’anisotropie des courbes de dispersion. Une lentille plate à cristaux photoniques ainsi que les solutions envisagées pour en optimiser la résolution et l’adaptation à son milieu environnant sont présentées (collaboration Institut Fresnel/Marseille). Les méthodes de fabrication de cette lentille, issues des technologies de la nanoélectronique, sont également présentées. L'originalité de notre procédé réside en sa simplicité car il ne nécessite qu'un seul niveau de masque pour la lithographie électronique et la gravure profonde pour transférer la totalité de notre dispositif sur l'échantillon. Les caractérisations sont effectuées grâce à un microscope optique en champ proche (ICB / Université de Dijon) et les images interprétées, en recourant notamment aux résultats de simulations tridimensionnelles. Nous explorons ensuite une application dans le domaine de la détection de cibles et de l’imagerie, basée sur les techniques de tomographie en réflexion. Enfin, des dispositifs exploitant une ingénierie localisée de l'indice issus des techniques de l’optique de transformation de type lentilles à gradient d’indice et tapis magiques sont abordés afin d'élargir notre champ d’applications. / This work is devoted to the « superlens », a photonic device issued from dispersion engineering concepts. A brief review of the basic concepts of two dimensional photonic crystals for band structure formation is given, followed by a presentation of the different regimes of ultra-refraction which can be evidences by exploiting the isotropy and/or anisotropy of the dispersion branches. The negative refraction properties of a fully dielectric heterostructure aimed to operate at 1.55 µm are detailed, as well as a full study of a photonic crystal based flat lens. In that case, efforts are devoted to the optimization of the resolution and to the device matching to its environment (collaboration : Fresnel Institute in Marseille). The fabrication process for such a lens, which makes use of advanced tools of nanoelectronics, is then presented. The originality of our process stands in its simplicity since only one mask level is used, for the lithography and the deep etching, to transfer the full design on the sample. Characterization is done using a SNOM (ICB / Dijon University) ant the images are interpreted using three-dimensional simulation results. Then, we explore a specific application in the domain of target detection and imaging, using tools of reflecting tomography, for which the flat lens could bring an added value compared to classical approaches. Finally, devices exploiting a local dispersion index engineering (concepts of transformation optics) like “gradient index lenses” or “magical carpets” are envisaged to enlarge the field of applications.

Orientador: Vera Lucia da Silveira Nantes Button / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-03T18:01:19Z (GMT). No. of bitstreams: 1 Nascimento_ValeriaMonteirodo_M.pdf: 13720053 bytes, checksum: 762bfe926811a50d1ae9423a52388630 (MD5) Previous issue date: 2003 / Mestrado

Localization is one of the most interesting research areas in wireless networks. It is mostly used for tracking and monitoring applications such as traffic monitoring, search and rescue, navigation and so on. A good quality system can be defined from its accuracy when operating in severe interference environments that contaminate the signals and therefore reduce the system performance. The main issue for localization is channel propagation, e.g., line of sight or non-line of sight channel which should be studied in order to improve the system efficiency.    In order to perform a localization, most algorithms use two steps: ranging and positioning. For ranging, the two popular techniques that are widely used for distance measurement are received signal strength (RSS) and time of arrival (TOA). RSS ranging technique uses the power of the received signals to identify the distance between a transmitter and a receiver. TOA ranging technique uses time of the signal traveling between a transmitter and a receiver to identify the distance, thus it requires synchronization. The measurements are processed by using a localization algorithm afterwards. However, these techniques suffer from multipath fading and other errors, so there always exists error in the estimated position.    In this thesis, TOA ranging technique is used for different estimation methods. Simulation results are performed using MATLAB, while the real results are obtained from Pozyx indoor positioning platform. Several estimation algorithms comprising of maximum likelihood (ML), linearized least square (LLS), weighted centroid (WC), and fingerprinting (FP) are studied in detail. The testing area is indoor environment which is suitable for LOS, NLOS and combined situations. The measured data is then used for ranging and localization. We concentrate on comparing and discussing these results in this thesis.

Ingeniero Civil Electricista / Hoy en día es imposible imaginar no contar con la disponibilidad de acceso a exámenes médicos, que permitan la visualización de órganos y tejidos mediante sistemas no invasivos y de fácil aplicación, como son los ecógrafos. Sin embargo, en el presente se buscan más aplicaciones a este versátil método de examinación, como lo es la construcción de dispositivos ultra-portátiles, que permitan la ejecución de exámenes rutinarios de imagenología, pero en espacios reducidos y con un equipo energizado por baterías. Estadísticamente, es sabido que del total de las ecografías solicitadas; solo el 30% son realmente necesarias, por lo tanto, la inclusión de equipos de rápido acceso y de categoría portable, es un eslabón deseable en el proceso de diagnóstico médico. Es por ello que en esta memoria se plantea el diseño y fabricación de una plataforma electrónica que permita el manejo completo de un transductor ultrasónico, para realizar la construcción de este tipo de dispositivos. En este documento se describen los fundamentos, procedimientos y resultados obtenidos en la implementación de un sistema de accionamiento y recepción de señales, para la generación de imágenes de ultrasonido. En esta dirección, se presentan diseños, simulaciones, implementaciones y la construcción de diversas plataformas que otorgaron el aprendizaje necesario para la confección de un sistema de alta tecnología con condiciones de estado del arte en pulsación ultrasónica. Estas iteraciones, son directa consecuencia de una búsqueda estricta de optimizaciones para la plataforma definitiva. Adicionalmente, se presenta todo el desarrollo y análisis necesario para lograr la puesta en marcha de un transductor ultrasónico activo con multiplexión local. Esto, con el fin de poder utilizar un dispositivo de bajo costo after market , en contraposición a la expectativa de fabricar un transductor ultrasónico personalizado con altos costos de inversión y construcción, asociado a la baja cantidad de unidades a producir en relación al mercado mundial abastecido por China. Finalmente, se expone la generación de una completa plataforma digital basada, que permite capturar los datos salientes de un sistema de conversión análogo/digital con interfaz serializada, grabar temporalmente en una memoria de acceso aleatorio de alta velocidad, y finalmente volcar datos a un servidor donde se realizará la conformación. Tanto los desarrollos electrónicos como los de software, fueron íntegramente diseñados partiendo desde cero, contando únicamente con los conocimientos recabados durante una larga etapa de investigación. El diseño, cálculo y simulaciones de las plataformas, la confección de los circuitos impresos y el montaje de los componentes fue realizado en los laboratorios del Departamento de Ingeniería Eléctrica de la Universidad de Chile, en el contexto del proyecto Corfo Innova 09IEI-7183. Los resultados obtenidos permiten concluir que se completó de forma íntegra la cadena de diseño, partiendo desde el estudio de la tecnología actual, llegando a la construcción de un dispositivo que se puede considerar estado del arte en el ámbito de pulsación de piezoeléctricos para equipos de ultrasonografía. Se logró obtener una plataforma funcional, eficiente y con gran robustez a los ciclos de trabajo estrictos a los que fue sometido.

Este trabalho teve como objetivos determinar propriedades mecânicas para ensaios não destrutivos em peças de madeira roliça por meio de ondas ultra-sônicas, por meio de correlação destes com ensaios estáticos e identificar a dependência da velocidade ultra-sônica em relação à geometria de peças roliças. A técnica de ultra-som é baseada na relação entre a propagação da onda ultra-sônica no material e as propriedades elásticas deste material. Na experimentação utilizou-se Eucalipto Citriodora e o procedimento desenvolveu-se em duas etapas: a primeira com peças roliças de tamanho estrutural e a segunda com corpos-de-prova retirados destas peças. As seguintes propriedades físicas e mecânicas foram avaliadas: densidade aparente a um teor de umidade de 12% (Dap,12%); teor de umidade (U); resistência à compressão paralela às fibras (fc0); módulo de elasticidade na compressão paralela às fibras (Ec0); resistência à flexão estática (MOR ou fM) e módulo de elasticidade na flexão estática (MOE ou EM0). Para determinação do módulo de elasticidade dinâmico (Ed) foram utilizados o aparelho de ultra-som Sylvatest, com transdutor exponencial de 22kHz, e o aparelho V-Meter Mark II, com transdutores de faces planas de 54 e 150 kHz. As transmissões foram realizadas nas direções longitudinal e radial, sendo que as peças ensaiadas se encontravam com teor médio de umidade de 12%. Os resultados indicam que a técnica de ultra-som é sensível à geometria das peças roliças. As análises estatísticas dos dados indicam que esta técnica de avaliação não destrutiva pode ser usada para avaliar as propriedades mecânicas de peças roliças de madeira com relativa confiabilidade. / The objective of this work is to evaluate the mechanical properties for nondestructive testing in round timber by ultrasonic waves, through the correlation of these with static tests, and to identify the dependence of the ultrasonic speed in relation to the geometry of roundwood. The ultrasound technique is based on the relation between the propagation of the ultrasonic wave in the material and the elastic properties of such a material. In the experimentation Eucalipto Citriodora was used and the procedure was developed in two stages: the first one with roundwood of structural size and second with specimens removed from these parts. The following physical and mechanical properties had been evaluated: apparent density at 12% (Dap,12%); moisture content (U); strength in compression parallel-to-grain (fc0); modulus of elasticity in compression parallel-to-grain (Ec0), modulus of rupture (MOR or fM) and modulus of elasticity (MOE or EM0). For determination of the dynamic modulus of elasticity (Ed) it was used the Sylvatest ultrasound device, with exponential transducer of 22kHz, as well as the V-Meter Mark II device, with plane transducers of 54 and 150 kHz. The results indicate that the ultrasound technique is sensible to the geometry of the roundwood. The statistical analyses of the data indicate that this technique of nondestructive evaluation can be used to evaluate the mechanical properties of round timber with relative reliability.

Este trabalho teve como objetivos determinar propriedades mecânicas para ensaios não destrutivos em peças de madeira roliça por meio de ondas ultra-sônicas, por meio de correlação destes com ensaios estáticos e identificar a dependência da velocidade ultra-sônica em relação à geometria de peças roliças. A técnica de ultra-som é baseada na relação entre a propagação da onda ultra-sônica no material e as propriedades elásticas deste material. Na experimentação utilizou-se Eucalipto Citriodora e o procedimento desenvolveu-se em duas etapas: a primeira com peças roliças de tamanho estrutural e a segunda com corpos-de-prova retirados destas peças. As seguintes propriedades físicas e mecânicas foram avaliadas: densidade aparente a um teor de umidade de 12% (Dap,12%); teor de umidade (U); resistência à compressão paralela às fibras (fc0); módulo de elasticidade na compressão paralela às fibras (Ec0); resistência à flexão estática (MOR ou fM) e módulo de elasticidade na flexão estática (MOE ou EM0). Para determinação do módulo de elasticidade dinâmico (Ed) foram utilizados o aparelho de ultra-som Sylvatest, com transdutor exponencial de 22kHz, e o aparelho V-Meter Mark II, com transdutores de faces planas de 54 e 150 kHz. As transmissões foram realizadas nas direções longitudinal e radial, sendo que as peças ensaiadas se encontravam com teor médio de umidade de 12%. Os resultados indicam que a técnica de ultra-som é sensível à geometria das peças roliças. As análises estatísticas dos dados indicam que esta técnica de avaliação não destrutiva pode ser usada para avaliar as propriedades mecânicas de peças roliças de madeira com relativa confiabilidade. / The objective of this work is to evaluate the mechanical properties for nondestructive testing in round timber by ultrasonic waves, through the correlation of these with static tests, and to identify the dependence of the ultrasonic speed in relation to the geometry of roundwood. The ultrasound technique is based on the relation between the propagation of the ultrasonic wave in the material and the elastic properties of such a material. In the experimentation Eucalipto Citriodora was used and the procedure was developed in two stages: the first one with roundwood of structural size and second with specimens removed from these parts. The following physical and mechanical properties had been evaluated: apparent density at 12% (Dap,12%); moisture content (U); strength in compression parallel-to-grain (fc0); modulus of elasticity in compression parallel-to-grain (Ec0), modulus of rupture (MOR or fM) and modulus of elasticity (MOE or EM0). For determination of the dynamic modulus of elasticity (Ed) it was used the Sylvatest ultrasound device, with exponential transducer of 22kHz, as well as the V-Meter Mark II device, with plane transducers of 54 and 150 kHz. The results indicate that the ultrasound technique is sensible to the geometry of the roundwood. The statistical analyses of the data indicate that this technique of nondestructive evaluation can be used to evaluate the mechanical properties of round timber with relative reliability.

Master of Science - Chemistry / Complexation of CrIII was studied using the ligand 2, 2’ Bipyridyl (Bpy). Potentiometric titration was used in the modelling of CrIII-Bpy complexes and establishment of complex stability constants by use of ESTA software package. Investigation of the mechanism involved in the voltammetric determination of chromium by adsorptive cathodic stripping voltammetry (AdCSV) showed different behavior of chromium in 0.1 M ammonium buffer when compared to a neutral electrolyte (0.1 M sodium nitrate). Alternating current voltammetry (ACV) showed evidence of Bpy adsorption on the electrode surface (HMDE) whereas CrIII did not show any adsorption evidence but complexes of CrIII-Bpy were also adsorbed onto the electrode. Cyclic voltammogram (CV) of Bpy exhibits a reversible process and CrIII was characterized by a quasireversible process. CrIII-Bpy is investigated here as a model metal-ligand system used in analytical procedure. A set of generalized requirements for the determination of CrIII by AdCSV is proposed and discussed. It is anticipated that the generalized requirements will be applicable to any metal-ligand system used by that analytical technique. It is assumed that it should lead to an “educated” choice of a suitable ligand in order to increase selectivity and improve the detection limit in ultra trace analysis (ppb-ppt levels) by AdCSV.

A obra não tem página de rosto / Tese de mestrado integrado. Engenharia Química. Faculdade de Engenharia. Universidade do Porto. 2009

This thesis discusses microstrip circuits and components with a slotted area on the ground plane. In recent years, various slot geometries have been placed on the ground plane with the purpose of reducing harmonics, producing frequency pass/stop-bands, and enhancing coupling effects. Among several ground slot geometries, a dumbbell shaped slot (DSS) is attractive because of its simple structure and easy analysis. The DSS and its applications to RF/microwave filters are studied and discussed. A lumped equivalent circuit model of the dumbbell shaped ground slot is introduced by utilizing resonator and filter theories. The accuracy of the equivalent circuit model is demonstrated through the comparison of circuit simulations and measurements. A lowpass filter (LPF) using slotted ground structure (SGS) with dumbbell shape is designed and measured to validate its theories. By using SGS techniques presented in this thesis, some other RF/microwave components such as a periodic structure, ultra-wideband bandpass filter (UWB-BPF), and rectenna with SGS-LPF are designed and tested.