Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2017-02-10T11:07:35Z No. of bitstreams: 1 Jair Carlos Muller_.pdf: 2333529 bytes, checksum: 36c56be5b98f22351456fbe4e419d28f (MD5) / Made available in DSpace on 2017-02-10T11:07:35Z (GMT). No. of bitstreams: 1 Jair Carlos Muller_.pdf: 2333529 bytes, checksum: 36c56be5b98f22351456fbe4e419d28f (MD5) Previous issue date: 2016-10-04 / CNPQ – Conselho Nacional de Desenvolvimento Científico e Tecnológico / Este trabalho apresenta um estudo geométrico de um refletor Fresnel linear para a produção de energia térmica com uso de um rastreador solar para orientação dos espelhos. A realização deste trabalho teve como base o estudo do sistema de coordenadas empregado para o cálculo da inclinação dos espelhos em função da posição do Sol em um determinado instante. O método utilizado considera que a radiação direta proveniente do Sol atinja o centro do espelho, cuja inclinação a cada instante permite a reflexão dessa radiação para o centro do absorvedor, situado a uma dada altura em relação ao plano contendo o eixo dos espelhos. Através do estudo da inclinação dos espelhos, foram analisadas as influencias causadas pela distância entre espelhos, altura do receptor, largura dos espelhos e o número de espelhos. Com estes parâmetros analisados, implementou-se uma simulação em MATLAB que forneceu valores de potência refletida no plano de entrada do concentrador secundário, valores de perdas por sombreamento, bloqueio, desfocagem e posição angular de cada fileira de espelho. Tendo estes dados como base foi construído um rastreador solar controlado por um micro controlador Arduino, que permite orientar as fileiras de espelhos com um único motor e eixo de acoplamento. O programa no micro controlador verifica data e hora como dados iniciais, depois as coordenadas geográficas de latitude 29º 45’ 17,979” S e longitude 51º 9’ 1,019” W do local. Assim, foi possível comprovar, através de imagens refletidas pelos espelhos no receptor secundário, que os parâmetros de posição angular estão corretos e que a concentração dos raios solares no absorvedor do concentrador secundário tem precisão adequada, fornecendo ao sistema confiabilidade para sua utilização. / This paper presents a geometric study of a linear Fresnel reflector for the production of thermal energy with use of a solar tracker for orientation of mirrors. This work was based on the study of the coordinate system used for the calculation of the slope of the mirrors as function of the sun’s position at a given time. The method considers that the solar direct radiation reaches the center of the mirror, whose slope at each instant allows the reflection of this radiation to the center of the absorber located at a given height from the plane containing the axis of the mirrors. Through the study of slope of mirrors, were analyzed the influences caused by the distance between mirrors, the height of receiver, width of the mirrors and the number of mirrors. With these parameters, it was implemented a simulation in MATLAB which provided power values reflected in the secondary concentrator inlet plane, values of losses by shading, blocking, by defocus and the angular position of each row of mirror. Having these data as base was built a controlled solar tracker by an Arduino micro controller, which allows directing the rows of mirrors with a single engine and coupling shaft. The program in micro controller checks the date and time as initial data, then the geographical coordinates of latitude 29° 45 ' 17.979 "S and longitude 51° 9 ' 1.019" W the local. Thus, it was possible to prove, through images reflected by mirrors on the secondary receiver, that the angular position parameters are correct and that the concentration of sunrays in the absorber secondary hub has adequate accuracy, providing the system reliability for its use.

QC 20100901

Realising Si-based electrically driven light emitters in a process technology compatible with mainstream microelectronics CMOS technology is key requirement for the implementation of low-cost Si-based optoelectronics and thus one of the big challenges of semiconductor technology. This work has focused on the development of microcavity enhanced silicon LEDs (MCLEDs), including their design, fabrication, and experimental as well as theoretical analysis. As a light emitting layer the abrupt pn-junction of a Si-diode was used, which was fabricated by ion implantation of boron into n-type silicon. Such forward biased pn-junctions exhibit room-temperature EL at a wavelength of 1138 nm with a reasonably high power efficiency of 0.1% [1]. Two MCLEDs emitting light at the resonant wavelength about 1150 nm were demonstrated: a) 1 MCLED with the resonator formed by 90 nm thin metallic CoSi2 mirror at the bottom and semitranparent distributed Bragg reflector (DBR) on the top; b) 5:5 MCLED with the resonator formed by high reflecting DBR at the bottom and semitransparent top DBR. Using the appoach of the 5:5 MCLED with two DBRs the extraction efficiency is enhanced by about 65% compared to the silicon bulk pn-junction diode.

In this thesis, a cavity-backed slot antenna array is designed for relatively wide instantaneous bandwidth, high gain and low sidelobes. The array consists of four, rectangular, slot elements, arranged side-by-side in a linear array and developed around 5GHz. Two feed points, at opposing sides of the printed array, each excite two of the slot elements through a series feed. This bidirectional feed presents symmetry to the design and prevents the tendency of beam-drift versus frequency as is common with many series-fed arrays. While being fed in-phase, the array will maintain boresight at broadside over the entire operating bandwidth. Also, the additional port allows for the potential introduction of a phase offset and, therefore, beam tilt. Finally, the printed array is designed to function within a quarter-wave, metallic cavity to achieve unidirectional radiation and improve gain.

The presence of gas hydrates offshore of eastern Canada has long been inferred from estimated stability zone calculations, but the physical evidence is yet to be discovered. While geophysical evidence derived from seismic and borehole logging data provides indications of hydrate occurrence in a number of areas, the results are not regionally comprehensive and, in some cases, are inconsistent. In this study, the results of systematic seismic mapping along the Scotian and Newfoundland margins are documented. An extensive set of 2-D and 3-D, single and multi-channel, seismic reflection data comprising ~45,000 line-km was analyzed for possible evidence of hydrate. Bottom simulating reflectors (including one double BSR) were identified at five different sites, ranging between 300 and 600 m below the seafloor and in water depths of 1000 to 2900 m. The combined area of the five BSRs is 1720 km2, which comprises a small proportion of the theoretical stability zone area along the Scotian and Newfoundland margins (~635,000 km2). The apparent paucity of BSRs may relate to the rarity of gas hydrates on the margin or may be simply due to geophysical limitations in detecting hydrate.

Dans cette thèse, nous étudions le problème du réflecteur. Etant données une source lumineuse et une cible à éclairer avec une certaine distribution d'intensité, il s'agit de construire une surface réfléchissant la lumière issue de la source vers la cible avec la distribution d'intensité prescrite. Ce problème se pose dans de nombreux domaines tels que l'art ou l'architecture. Le domaine qui nous intéresse ici est le domaine automobile. En effet, cette thèse Cifre est réalisée en partenariat avec l'entreprise Optis qui développe des logiciels de simulation de lumière et de conception optique utilisés dans les processus de fabrication des phares de voiture. Les surfaces formant les réflecteurs des phares de voiture doivent répondre à un certain nombre de critères imposés par les fabricants ainsi que les autorités de contrôle nationales et internationales. Ces critères peuvent être objectifs comme par exemple l'encombrement du véhicule ou encore le respect des normes d'éclairage mais peuvent également être subjectifs comme l'aspect esthétique des surfaces. Notre objectif est de proposer des outils industrialisables permettant de résoudre le problème du réflecteur tout en prenant en compte ces critères. Dans un premier temps, nous nous intéresserons au cas de sources lumineuses ponctuelles. Nous reprenons les travaux d'Oliker, Glim, Cafarrelli et Wang qui montrent que le problème du réflecteur peut être formulé comme un problème de transport optimal. Cette formulation du problème est présentée et mise en œuvre dans un cas discret. Dans un second temps, nous cherchons à prendre en compte les critères imposés par les fabricants de phares de voitures. Nous nous sommes intéressés ici aux contraintes d'encombrement et d'esthétique. La solution choisie consiste à utiliser des surfaces de Bézier définies comme le graphe d'une certaine fonction paramétrée par un domaine du plan. Les surfaces de Bézier permettent d'obtenir des surfaces lisses et la paramétrisation par un domaine du plan permet de gérer l'encombrement et le style d'un réflecteur. Nous avons proposé une méthode heuristique itérative par point fixe pour obtenir ce type surface. Enfin, dans un dernier temps, nous prenons en compte des sources lumineuses non ponctuelles. L'approche proposée consiste à adapter itérativement les paramètres du réflecteur de façon à minimiser une distance entre intensité souhaitée et intensité réfléchie. Ceci nous a conduits à proposer une méthode d'évaluation rapide de l'intensité réfléchie par une surface. Les méthodes développées durant cette thèse ont fait l'objet d'une implémentation dans un cadre industriel en partenariat avec l'entreprise Optis. / The far-field reflector problem consists in building a surface that reflects light from a given source back into a target at infinity with a prescribed intensity distribution. This problem arises in many fields such as art or architecture. In this thesis, we are interested in applications to the car industry. Indeed, this thesis is conducted in partnership with the company Optis that develops lighting and optical simulation software used in the design of car headlights. Surfaces in car headlight reflectors must satisfy several constraints imposed by manufacturers as well as national and international regulatory authorities. These constraints can be objective such as space requirements or compliance with lighting legal standards but can also can be subjective such as the aesthetic aspects of surfaces. Our goal is to provide industrializable tools to solve the reflector problem while taking into account these constraints. First, we focus on the case of point light sources. We rely on the work of Oliker, Glim, Cafarrelli and Wang who show that the reflector problem can be formulated as an optimal transport problem. This formulation of the problem is presented and implemented in a discrete case. In a second step, we take into account some of the constraints imposed by car headlight manufacturers, such as the size and the style of the reflector. The chosen solution consists in using Bezier surfaces defined as the graph of a function parameterized over a planar domain. Bezier surfaces allow to obtain smooth surfaces and the parameterization over a planar domain allows to control the size and style of the reflector. To build the surface, we propose a heuristic based on a fixed-point algorithm. Finally, we take into account extended light sources. We present an approach that iteratively adapts the parameters of the reflector by minimizing the distance between the desired intensity and the reflected intensity. This led us to propose a method that efficiently evaluates the reflection of light on the surface. Methods developed in this thesis were implemented in an industrial setting at our partner company Optis.

The introduction of broadband systems to communication and radar technologies has demanded the design of broadband antennas. In this thesis, broadband log-periodic dipole antennas and reflector antennas are investigated. A dual polarized log-periodic dipole antenna and a reflector antenna are designed and analyzed within the frequency band of 0.4-18 GHz. Basic theory and calculations about mutual coupling between the linear antenna elements are given. The currents at the bases of dipoles of the log-periodic antenna are found and these currents are used as inputs for the design of the reflector antenna. After the simulations made with MATLAB&Ograve / and FORTRAN, a prototype single polarized log-periodic antenna is produced. Developments on the prototype antenna are performed, both to improve the electrical characteristics of the antenna and to make the final design realizable. After the performance of the single polarized log-periodic antenna is found satisfactory, dual polarized antenna is produced. Performances of both single and dual polarized log-periodic antennas are measured in the anechoic chamber at ASELSAN&reg / Inc. After the measurements of the antenna, using the currents at the bases of the dipoles, a reflector antenna is designed using &ldquo / MIR&rdquo / program written in FORTRAN, which is based on physical optics method. A method to calculate the aperture blockage of the reflector is developed. Simulation results of reflector antenna are given.

Thesis (MScEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: This thesis presents a thorough study of the printed sinuous antenna and its characterisation as a feed for re ector antenna applications. Two di erent techniques are used in this study, namely a parametric study and an e cient surrogate based optimisation strategy. A planar sinuous antenna over a re ecting ground plane, with no absorber lining, is designed following a parameter study from which e ective design guidelines are derived. The designed prototype displays a bandwidth ratio of more than 3 : 1 from 1:9􀀀6:2 GHz, at a measured return loss of 10 dB, representing a signi cant improvement over the octave band previously achieved with a similar antenna. An optimisation based approach is followed in formally investigating a conical sinuous antenna over a re ecting ground plane. An e cient surrogate based optimisation strategy, in which the antenna's response is approximated by a Kriging model, is used. The search for optimal design parameters as well as improvements in the accuracy of the Kriging model is accomplished by using expected improvement as the in ll sampling criterion. The antenna is optimised for return loss, aperture e ciency for a prime-focus paraboloid re ector as well as cross-polarisation and results from the optimisation are used to derive e ective design guidelines and performance limitations. The investigations are conducted for the 2 􀀀 6 GHz band and the obtained results can be easily applied for designs with wider bandwidths. Simulation results reveal improved return loss, aperture e ciency and cross-polarisation performances compared to what has previously been reported for this antenna. / AFRIKAANSE OPSOMMING: Hierdie tesis bied 'n deeglike studie van die gedrukte stroombaanbord sinuous antenna, sowel as die karakterisering daarvan as voer vir re ektor antenna toepassings. Twee verskillende tegnieke word gebruik, naamlik 'n parametriese studie en 'n surrogaat-gebaseerde optimering strategie. E ektiewe doeleindes vir die ontwerp is van 'n parameter studie afgelei, waarvolgends 'n planêre sinuous antenna met 'n weerkaatsingsgrondvlak ontwerp is sonder enige absorberende materiale. Die prototipe vertoon beter as 'n 3 : 1 bandwydte van 1:9 GHz tot 6:2 GHz teen 'n gemete weerkaatsingskoë siënt van beter as 􀀀10 dB, wat dui op 'n aansienlike verbetering teenoor die oktaaf bandwydte wat voorheen met 'n soorgelyke antenna bereik is. 'n Optimering-gebaseerde benadering is gebruik om ondersoek in te stel in die gebruik van 'n koniese sinuous antenna met 'n weerkaatsingsgrondvlak. 'n Doeltre ende surrogaat-gebaseerde optimeering strategie is gebruik, waar die antenna se weergawe deur 'n Kriging model benader word. Die verwagte verbetering is gebruik as maatstaf in die soektog vir optimale ontwerpsparameters, sowel as om die akkuraatheid van die Kriging model te verbeter. Die antenna is geoptimeer vir sy weerkaatsingskoë siënt, stralingsvlak e ektiwiteit for 'n paraboloïed antenna sowel as kruispolarisasie. Resultate van die optimering is gebruik om e ektiewe riglyne vir die ontwerp en grense vir die werkverrigting op te stel. Die antenna is ondersoek vir die 2 tot 6 GHz frekwensieband en die resultate wat verkry is kan maklik op ontwerpe met selfs wyer bandwydtes toegepas word. Simulasie resultate dui op 'n verbetering in weerkaatsingskoë siënt, stralingsvlak e ektiwiteit en kruispolarisasie in vergelyking met wat berig is vir hierdie antenna.

Dans cette thèse, nous étudions le problème du réflecteur. Etant données une source lumineuse et une cible à éclairer avec une certaine distribution d'intensité, il s'agit de construire une surface réfléchissant la lumière issue de la source vers la cible avec la distribution d'intensité prescrite. Ce problème se pose dans de nombreux domaines tels que l'art ou l'architecture. Le domaine qui nous intéresse ici est le domaine automobile. En effet, cette thèse Cifre est réalisée en partenariat avec l'entreprise Optis qui développe des logiciels de simulation de lumière et de conception optique utilisés dans les processus de fabrication des phares de voiture. Les surfaces formant les réflecteurs des phares de voiture doivent répondre à un certain nombre de critères imposés par les fabricants ainsi que les autorités de contrôle nationales et internationales. Ces critères peuvent être objectifs comme par exemple l'encombrement du véhicule ou encore le respect des normes d'éclairage mais peuvent également être subjectifs comme l'aspect esthétique des surfaces. Notre objectif est de proposer des outils industrialisables permettant de résoudre le problème du réflecteur tout en prenant en compte ces critères. Dans un premier temps, nous nous intéresserons au cas de sources lumineuses ponctuelles. Nous reprenons les travaux d'Oliker, Glim, Cafarrelli et Wang qui montrent que le problème du réflecteur peut être formulé comme un problème de transport optimal. Cette formulation du problème est présentée et mise en œuvre dans un cas discret. Dans un second temps, nous cherchons à prendre en compte les critères imposés par les fabricants de phares de voitures. Nous nous sommes intéressés ici aux contraintes d'encombrement et d'esthétique. La solution choisie consiste à utiliser des surfaces de Bézier définies comme le graphe d'une certaine fonction paramétrée par un domaine du plan. Les surfaces de Bézier permettent d'obtenir des surfaces lisses et la paramétrisation par un domaine du plan permet de gérer l'encombrement et le style d'un réflecteur. Nous avons proposé une méthode heuristique itérative par point fixe pour obtenir ce type surface. Enfin, dans un dernier temps, nous prenons en compte des sources lumineuses non ponctuelles. L'approche proposée consiste à adapter itérativement les paramètres du réflecteur de façon à minimiser une distance entre intensité souhaitée et intensité réfléchie. Ceci nous a conduits à proposer une méthode d'évaluation rapide de l'intensité réfléchie par une surface. Les méthodes développées durant cette thèse ont fait l'objet d'une implémentation dans un cadre industriel en partenariat avec l'entreprise Optis. / The far-field reflector problem consists in building a surface that reflects light from a given source back into a target at infinity with a prescribed intensity distribution. This problem arises in many fields such as art or architecture. In this thesis, we are interested in applications to the car industry. Indeed, this thesis is conducted in partnership with the company Optis that develops lighting and optical simulation software used in the design of car headlights. Surfaces in car headlight reflectors must satisfy several constraints imposed by manufacturers as well as national and international regulatory authorities. These constraints can be objective such as space requirements or compliance with lighting legal standards but can also can be subjective such as the aesthetic aspects of surfaces. Our goal is to provide industrializable tools to solve the reflector problem while taking into account these constraints. First, we focus on the case of point light sources. We rely on the work of Oliker, Glim, Cafarrelli and Wang who show that the reflector problem can be formulated as an optimal transport problem. This formulation of the problem is presented and implemented in a discrete case. In a second step, we take into account some of the constraints imposed by car headlight manufacturers, such as the size and the style of the reflector. The chosen solution consists in using Bezier surfaces defined as the graph of a function parameterized over a planar domain. Bezier surfaces allow to obtain smooth surfaces and the parameterization over a planar domain allows to control the size and style of the reflector. To build the surface, we propose a heuristic based on a fixed-point algorithm. Finally, we take into account extended light sources. We present an approach that iteratively adapts the parameters of the reflector by minimizing the distance between the desired intensity and the reflected intensity. This led us to propose a method that efficiently evaluates the reflection of light on the surface. Methods developed in this thesis were implemented in an industrial setting at our partner company Optis.

Les besoins croissants en moyens de télécommunication nécessitent le développement de grands réflecteurs spatiaux paraboliques. Un nouveau concept d'architecture d'antenne déployable est ainsi proposé en partenariat avec le CNES. La conception de son ossature repose sur une revue de solutions pour faire appel à des mécanismes de ciseau associés à des articulations flexibles. Des modélisations numériques par éléments finis sont d'abord développées pour simuler le déploiement par restitution de l'énergie emmagasinée dans ces articulations lors du pliage. Un démonstrateur expérimental avec un système de compensation gravitaire est ensuite réalisé. Des essais et mesures sont effectués pour caractériser son comportement en statique et dynamique puis sont comparés avec les résultats issus des simulations. La mise en forme de la surface réflectrice par un réseau de câbles est étudiée par la suite. Une méthode innovante de recherche de forme permettant d'obtenir un réseau parabolique en tension uniforme est alors proposée. Elle est appliquée à différentes typologies de réseaux et l'erreur de surface résultant de sa facettisation est évaluée. Le procédé d'accrochage de ce réseau sur l'ossature de l'antenne est également traité. / The growing needs in telecommunications require the development of large parabolic reflectors. A new conceptual design for the architecture of a deployable antenna is therefore proposed in partnership with the CNES. The design of its framework is based on a review of solutions which leads to scissor mechanisms associated with flexible joints. Numerical modelings with finite elements are first developed to simulate the deployment by the release of the energy stored in the joints after the folding. An experimental prototype with a gravity compensation device is then realized. Tests and measurements are performed to characterize the static and dynamic behavior and compared with the results of simulations. Shaping of the reflective surface by a net of cables is then studied. A new form-finding method for obtaining a net with a uniform tension is then proposed. It is applied to different parabolic typologies of nets and the error due to surface faceting is evaluated. The process of net attachment on the antenna rim structure is also treated.