No / To mitigate potential interferences with coexisting wireless systems operating over 3.3-3.6 GHz, 5.15-5.35 GHz, or 5.725-5.825 GHz bands, four novel band-notched antennas suitable for ultra-wideband (UWB) applications are proposed. These include UWB antennas with a single wide notched band, a single narrow notched band, dual notched bands, and triple notched bands. Each antenna comprises a half-circle shaped patch with an open rectangular slot and a half-circle shaped ground plane. Good band-notched performance is achieved by using high permittivity and low dielectric loss substrate, and inserting quarter-wavelength horizontal/vertical stubs or alternatively embedding quarter-wavelength open-ended slots within the feed line. The results of both simulation and measurement confirm that the gain suppression of the single and multiple band-notched antennas in each desired notched band are over 15 dB and 10 dB, respectively. The radiation pattern of the proposed triple band-notched design is relatively stable across the operating frequency band.

Le travail de cette thèse est en rapport avec les métamatériaux et ses applications. Tout d’abord, un état de l’art est dressé en présentant leur évolution depuis leur apparition en 19ème siècle jusqu’au nos jours. Les notions sur les milieux chirale, bi-anisotrope, cristaux photoniques et quelques applications dans ces milieux sont données. Ensuite, nous présentons les équations classiques de Maxwell dans les milieux complexes. L’effet bi-anisotrope dans les métamatériaux est ensuite validé par l’extraction des paramètres caractéristiques du matériau main gauche (LHM). La validation a été faite en utilisant deux types différents du résonateur avec inclusion (SRR). Les métamatériaux sont également étudiés comme des cristaux photoniques quand les dimensions utilisées sont de l’ordre de la longueur d’onde correspondant.De plus, les résonateurs SRR et multi-SRR sont analysés du point de vue analytique et électromagnétique afin d’extraire leur fréquence de résonance. Par conséquent, ces composants peuvent être introduits dans différents types de conception; La surface conductrice magnétique artificielle (AMC) illustre un cas explicite et efficace de ces derniers. Une antenne dipôle, placée sur cette surface à la place d’un plan de masse conventionnel, a été étudiée comme une application des métamatériaux. Les résultats relatifs sur la directivité, le gain et le coefficient de réflexion montrent une nette amélioration. Une antenne multi-bandes, comme une autre application des métamatériaux, a également été conçue et simulée. Le résonateur SRR est inséré dans l’antenne de départ afin de créer une autre résonance, et par conséquent une autre bande est ainsi créée. / The work in this thesis deals with metamaterials, its components and applications. A historical overview about these materials, features and researches in the domain are presented. Chiral media, binaisotropic materials and photonic crystals are also studied in order to visualize physics behind metamaterials.Electromagnetic properties in complex media are widely investigated. Starting from Maxwell’s equations, bi-anisotropic materials and their effect are deeply analyzed whereas two types of Split Ring Resonator (SRR) are treated to determine constitutive parameters of Left Handed Materials (LHM). The metamaterials are also studied as photonic crystals since the effective medium approach is not applicable when the dimensions of the inclusions tend to the operating wavelength.Moreover, SRRs and Multi SRRs are synthesized analytically and electromagnetically in order to extract their resonant frequencies. Consequently, these components could be introduced in any design; Artificial Magnetic Conductor (AMC) surface is an efficient case. Thus, a low profile antenna positioned over such surface is examined as an application of metamaterials. The results of directivity, gain and reflection coefficient are of great importance and affirm the employing of metamaterials in such applications. A dual band PCB antenna, as another application of metamaterials, is designed and simulated. The SRR element studied in the previous chapters is used as the trap which inserted in the arm of the antenna in order to create another resonance, and consequently another band is created.

Les micro-résonateurs optiques comptent parmi les dispositifs les plus importants en photonique. Les résonateurs WGM sont assez particuliers. Il s'agit de composant présentant une symétrie circulaire comme c'est le cas des sphères, des anneaux, des disques et des tores. Les résonateurs WGM présentent un facteur de qualité exceptionnel et un volume modal très faible. Ces appareils peuvent être utilisés dans plusieurs domaines, notamment la télédétection, le filtrage optique et l'optique non linéaire. D'autres applications sont possibles en biologie, médecine, spectroscopie moléculaire, surveillance environnementale, astronomie et astrophysique grâce à l'exploitation du rayonnement moyen infrarouge. Les micro-résonateurs optiques comportent un grand nombre de transitions vibrationnelles qui agissent comme des «empreintes» pour de nombreuses molécules organiques permettant le développement d'applications spectroscopiques innovantes et de nouveaux capteurs. Il convient de noter que l'atmosphère de la terre est transparente au niveau des deux fenêtres de transmission atmosphérique. La première est comprise entre 3 et 5 μm et la seconde entre 8 et 13 μm, ce qui rend possible des applications telles que la détection d'explosifs à distance ainsi que le brouillage de communication confidentielles. La large fenêtre de transparence en verres de chalcogénures dans le domaine spectral infrarouge rend envisageable le développement de nombreuses applications. Les verres de chalcogénure sont caractérisés par une bonne résistance mécanique et une durabilité chimique suffisante dans l'eau et l'atmosphère. Par ailleurs, l'indice de réfraction élevé, le rendement quantique élevé, l'énergie de phonon faible et la solubilité importante des terres rares permettent des émissions dans le domaine spectral du moyen IR. Dans cette thèse, la conception de dispositifs innovants en chalcogénure pour des applications utilisant le moyen infrarouge est étudiée en utilisant un code d'ordinateur personnel formé de façon aléatoire. Les appareils reposent sur des trois types de micro-résonateurs : les microsphères, les micro-disques et les microbulles. Les résonateurs WGM sont efficacement excités à l'aide de fibres nervurées et de guides d'ondes optiques de forme conique. Le nouveau procédé de conception est développé en utilisant la méthode d'optimisation par essaims particulaires (PSO). Elle permet de maximiser le gain d'un amplificateur reposant sur une microsphère d'émission laser dopée à l'erbium à 4,5 μm. Une technique innovante permettant de caractériser les propriétés spectroscopiques de la terre rare intégrant la recherche électromagnétique en mode WGM grâce à l'algorithme PSO a été développée. Les valeurs récupérées sont entachées d’une erreur inférieure à celle prévue par les instruments de mesure ayant un coût élevé. Des applications intéressantes peuvent être obtenues en excitant le micro-résonateur avec une fibre conique présentant deux LPG identiques sur les côtés. En effet, les FLP peuvent sélectionner le couplage de modes de fibre avec le résonateur WGM. En utilisant différentes paires de FLP identiques, opérant dans différentes bandes de longueurs d'onde, il est possible de coupler de façon sélective différents résonateurs à l'aide de la même fibre optique. Un code informatique aléatoire a été développé et validé. Il a démontré la faisabilité d'un capteur de microbulles de glucose. Un microdisque en terre rare dopé est étudié pour obtenir une source de lumière compacte et économique dans l'infrarouge moyen. Un code informatique est développé afin de simuler un micro-disque de terre rare dopé et associé à deux guides d'ondes nervurés, un pour le signal et l'autre pour la pompe. Le modèle est validé à l'aide d'un micro-disque dopée à l'erbium émettant à 4,5 μm. Ce dispositif très prometteur pour des applications dans le moyen infrarouge est obtenu en utilisant un micro-disque de praséodyme dopé émettant à 4,7 μm. / Optical micro-resonators represent one of the most important devices in photonics. A special kind is constituted by the WGM resonators, i.e. devices with circular symmetry such as spheres, rings, disks and toroids. They are characterized by very small dimensions, exceptionally quality factor and very low modal volume becoming a valuable alternative to the traditional optical micro-resonators, such as Fabry-Pérot cavities. These devices allow applications in several fields, such as sensing, optical filtering and nonlinear optics. In particular, different applications in biology and medicine, molecular spectroscopy, environmental monitoring, astronomy and astrophysics are feasible in Mid-Infrared wavelength range. For example, it includes a lot of strong vibrational transitions that act as “fingerprints” of many bio-molecules and organic species allowing the develop of innovative spectroscopic applications and novel sensors. In addition, the earth's atmosphere is transparent in two atmospheric transmission windows at 3–5 μm and 8–13 μm and then applications such as remote explosive detection, e.g. in airports and for border control, and covert communication systems are feasible. The wide transparency window of chalcogenide glasses in Mid-Infrared makes possible the development of several devices. Chalcogenide glasses are characterized by good mechanical strength and chemically durability in water and atmosphere. Furthermore, the high refractive index, high quantum efficiency, the low phonon energy and high rare-earth solubility enables the emissions at long wavelengths.In this thesis, the design of innovative chalcogenide devices for applications in Mid-Infrared is investigated using an ad-hoc home-made computer code. The devices are based on three kinds of micro-resonators: microspheres, micro-disks and microbubbles. The WGM resonators are efficiently excited by using tapered fiber and ridge waveguides. A novel design procedure is developed using the particle swarm optimization approach (PSO). It allows to maximize the gain of an amplifier based on an erbium-doped microsphere lasing at 2.7 μm.An innovative technique in order to characterize the spectroscopic properties of rare-earth is developed integrating the WGM electromagnetic investigation with PSO algorithm. The method is based on two subsequent steps: in the first one, the geometrical parameters are recovered, in the second one, the spectroscopic parameters. The recovered values are affected by an error less than that provided by high-cost measurement instruments. Furthermore, the procedure is very versatile and could be applied to develop innovative sensing systems.Interesting applications could be obtained exciting the micro-resonator by a tapered fiber with two identical LPGs on the sides. Indeed the LPGs can select the fiber modes coupling with the WGM resonator. Using different pairs of identical LPGs operating in different wavelength bands, it is possible to selective couple different micro-resonators by using the same optical fiber. An ad-hoc computer code is developed and validated and it demonstrated the feasibility of a microbubble glucose sensor.In order to obtain a compact and cost-saving light source in Mid-Infrared, rare-earth doped micro-disk are investigated. A computer code is developed in order to simulate a rare-earth doped micro-disk coupled to two ridge waveguide, one at signal wavelength and the other one at pump wavelength. The model is validated using an erbium-doped micro-disk emitting at 4.5 μm. A very promising device for application in Mid-Infrared is obtained using a praseodymium-doped micro-disk emitting at 4.7 μm.

Thesis (PhD (Electical and Electronic Engineering))--University of Stellenbosch, 2006. / Resonant frequencies and Q-factors of microwave ring resonators are predicted using interpolation- based modelling. A robust and efficient multivariate adaptive rational-multinomial combination interpolant is presented. The algorithm models multiple resonance frequencies of a microwave ring resonator simultaneously by solving an eigenmode problem. To ensure a feasible solution when using the Method of Moments, a frequency dependent scaling constant is applied to the output model. This, however, also induces a discontinuous solution space across the specific geometry and requires that the frequency dependence be addressed separately from other physical parameters. One-dimensional adaptive rational Vector Fitting is used to identify and classify resonance frequencies into modes. The geometrical parameter space then models the different mode frequencies using multivariate adaptive multinomial interpolation. The technique is illustrated and evaluated on both two- and three-dimensional input models. Statistical analysis results suggest that models are of a high accuracy even when some resonance frequencies are lost during the frequency identification procedure. A three-point rational interpolant function in the region of resonance is presented for the calculation of loaded quality factors. The technique utilises the already known interpolant coefficients of a Thiele-type continued fraction interpolant, modelling the S-parameter response of a resonator. By using only three of the interpolant coefficients at a time, the technique provides a direct fit and solution to the Q-factors without any additional computational electromagnetic effort. The modelling algorithm is tested and verified for both high- and low-Q resonators. The model is experimentally verified and comparative results to measurement predictions are shown. A disadvantage of the method is that the technique cannot be applied to noisy measurement data and that results become unreliable under low coupling conditions.

Depuis quelques décennies, la technologie de contrôle de la fréquence a été au coeur de l'électronique des tempsmodernes grâce à son vaste domaine d'applications dans les systèmes de communication, les ordinateurs, les systèmesde navigation ou de défense militaire. Les dispositifs temps-fréquence fournissent des stabilités de fréquence et despuretés spectrales élevées dans le domaine de la stabilité court-terme. L'amélioration de la performance de cesdispositifs reste un grand défi pour les chercheurs. La réduction du bruit afin d'augmenter cette stabilité court-terme etd'éviter les commutations non souhaitées entre les canaux est donc très souhaitable. Il est communément admis que lalimitation fondamentale à cette stabilité court-terme est due au bruit flicker de fréquence des résonateurs. Dans cemanuscrit, un premier chapitre rappelle quelques faits de base sur l’acoustique, la cristallographie et les définitions dudomaine temps-fréquence nécessaires à l’étude des résonateurs et oscillateurs ultra-stables. Le deuxième chapitre estconsacré à un résumé de la littérature sur le bruit de fréquence en 1/f. Ensuite, le troisième chapitre concerne nos étudessur le modèle quantique de bruit en 1/f du Pr. Handel, qui, bien que critiqué par beaucoup, est encore le seul qui fournitune estimation de l'amplitude de plancher de bruit en 1/f et qui n'est pas infirmé par les données expérimentales. Dans lequatrième chapitre, une autre approche, basée sur le théorème de fluctuation-dissipation, est utilisée afin de mettre descontraintes numériques sur un modèle de bruit en 1/f causé par une dissipation interne (ou de structure) proportionnelleà l'amplitude, et non à la vitesse. Le dernier chapitre est consacré aux résultats expérimentaux. Le design et lesparamètres du résonateur ultra-stable utilisé lors de cette étude sont décrits. Les mesures de bruit de phase sur plusieurslots de résonateurs sont données. Les mesures des paramètres de résonateur ont été effectuées à basse température afinde les corréler avec les résultats de bruit. Afin d'évaluer rapidement la qualité des différents résonateurs, une autreapproche dans le domaine temporel a été testée. Elle utilise des oscillations pseudo-périodiques transitoires mettant lesoscilloscopes numériques actuellement disponibles à leurs limites de capacité. Enfin, les conclusions et perspectivessont présentées. / Since a few decades, frequency control technology has been at the heart of modern day electronics due to its huge areaof applications in communication systems, computers, navigation systems or military defense. Frequency controldevices provide high frequency stabilities and spectral purities in the short term domain. However, improvement of theperformance of these devices, in terms of frequency stability, remains a big challenge for researchers. Reducing noise inorder to increase the short term stability and avoid unwanted switching between channels is thus very desirable. It iscommonly admitted that the fundamental limitation to this short-term stability is due to flicker frequency noise in theresonators. In this manuscript, a first chapter recalls some basic facts about acoustic, crystallography and definitions oftime and frequency domain needed to explore ultra-stable resonators and oscillators. The second chapter is devoted to asummary of the literature on flicker frequency noise. Then, the third chapter concerns our studies on Handel’s quantum1/f noise model, which although criticized by many, is still the only one that provides an estimation of the flooramplitude of 1/f noise that is not invalidated by experimental data. In the fourth chapter, another approach, based on thefluctuation-dissipation theorem, is used in order to put numerical constraints on a model of 1/f noise caused by aninternal (or structural) dissipation proportional to the amplitude and not to the speed. The last chapter is devoted toexperimental results. An ultra-stable resonator used during this study is described. Phase noise measurements on severalbatches of resonators are given. Measurements of resonator parameters have been done at low temperature in order tocorrelate them with noise results. Another approach with a procedure that use transient pseudo periodic oscillations andput to their limits the capacities of presently available digital oscilloscopes, is presented, in order to assess rapidly thequality of various resonators. Finally, conclusions and perspectives are given.

Para a espectroscopia de alta resolução e metrologia óptica em geral, é desejável um laser com linha espectral estável e de alta potência de saída para bombear diferentes tipos de ressonadores, como osciladores paramétricos óticos (OPO Optical Parametric Oscillator). Os lasers de frequência única disponíveis estão no alcance de potência de saída de 10 Watts, enquanto que, dependendo da aplicação e do tipo de OPO, é desejável uma maior potência (> 20 W). Neste trabalho foi desenvolvido um laser de frequência única e alta potência com base em módulos de bombeio por diodos e tendo como meio ativo o granada de alumínio de ítrio dopado com neodímio (Nd:YAG). Dois bastões de Nd:YAG bombeados transversalmente por diodo, foram utilizadas em uma configuração de ressonador em anel com saída polarizada de onda continua (CW continuous-wave), qualidade de feixe modo transversal eletromagnético (TEM00) e potência de saída de 105,2 W. A potência de saída alcançada é, a nosso entender, a mais alta para lasers em anel no modo fundamental transversal polarizado contínuo usando módulos Nd:YAG comuns com bombeamento lateral. O ressonador permitiu a sintonização de potência em uma grande faixa dinâmica e obteve excelente qualidade de feixe, usando uma placa de meia onda entre os dois bastões para compensação de birrefringência. A operação de frequência única foi alcançada usando cristal de granada de térbio-gálio (TGG-Terbium Gallium Garnet), dois imãs e um etalon, com uma potência de saída de 51,60 W e uma largura a meia altura da curva (FWHM) espectral de aproximadamente 17 MHz. / For high resolution spectroscopy, a high power, stable line output laser is desirable for pumping different types of optical parametric oscillator resonators (OPO). Single-frequency lasers are in the range of 10 watts of output power, while, depending on the application and the OPO type, higher power (> 20 W) is desirable. In this work a single frequency high power laser based on diode pumping modules with Nd:YAG as the active medium was developed. Two Nd:YAG bars transversally pumped by diodes were used in a configuration of a CW polarized ring resonator with beam quality TEM00 and output power of 105,2 W. The output power achieved is, to our knowledge, the highest for continuous polarized fundamental mode ring lasers using standard Nd:YAG modules with side pumping. The resonator allowed the tuning power in a large dynamic range and obtained excellent beam quality using a half-wave plate between the two rods for birefringence compensation. The single frequency operation was achieved using a TGG (Terbium Gallium Garnet) crystal, two magnets and an etalon, with an output power of 51.60 W and a 17 MHz full width at half maximum (FWHM) spectral width.

<p><a>The quick, reliable, and sensitive detection of bacterial contamination is desired in areas such as counter bioterrorism, medicine, and food/water safety as pathogens such as<i> E. coli</i> can cause harmful effects with the presence of just a few cells. However, standard high sensitivity techniques require laboratories and trained technicians, requiring significant time and expense. More desirable would be a sensitive point-of-care device that could detect an array of pathogens without sample pre-treatment, or a continuous monitoring device operating without the need for frequent operator intervention.<br> <br> Optical microring resonators in silicon photonic platforms are particularly promising as scalable, multiplexed refractive index sensors for an integrated biosensing array. However, no systematic effort has been made to optimize the sensitivity of microrings for the detection of relatively large discrete analytes such as bacteria, which differs from the commonly considered cases of fluid or molecular sensitivity. This work demonstrates the feasibility of using high finesse microrings to detect whole bacterial cells with single cell resolution over a full range of potential analyte-to-sensor binding scenarios. Sensitivity parameters describing the case of discrete analyte detection are derived and used to guide computational optimization of microrings and their constituent waveguides, after considering a range of parameters such as waveguide dimension, material, modal polarization, and ring radius. The sensitivity of the optimized 2.5 µm radius silicon TM O-band ring is experimentally demonstrated with photoresist cellular simulants. A multiplexed optimized ring array is then shown to detect <i>E. Coli</i> cells in an experimental proof of concept.</a></p>

The objective of this work is to enhance and advance sensing technologies with the design and development of novel radio frequency (RF) sensors based on far-field and near-field principles of the electromagnetic (EM) resonances. In the first part of this thesis, original design and development of a passive RF temperature sensor, a passive RF strain sensor, and a passive RF pressure sensor are presented. The RF temperature sensor is presented in Chapter 3. It is based on split ring resonators loaded with bimorph cantilevers. Its operating principles and equivalent circuits are discussed in Chapter 4, where the design concept is illustrated to be robust and highly adaptable to different sensing ranges, environments, and applicable to other type of sensing beyond temperatures. The passive RF strain sensor, based on a patch antenna loaded with a cantilever-integrated open loop, is presented in Chapter 5, where it is demonstrated to have the highest strain sensitivity in the same remote and passive class of sensors in the state-of-the-art. Chapter 6 describes the passive RF pressure sensor, which is based on a dual-band stacked-patch antenna that allows both identification and sensing to be embedded in its unique dual resonant responses. In the second part of this thesis, an original and first-of-its-kind RF transducer is presented that enables non-touch sensing of human fingers within 3 cm of proximity (based on one unit sensor cell). The RF transducer is based on a slotted microstrip patch coupled to a half-wavelength parallel-coupled microstrip filter operating in the frequency range of 6 – 8 GHz. The sensing mechanism is based on the EM near-field coupling between the resonator and the human finger. Fundamentally different from the electric field capacitive sensing, this new method of sensing, the first of its kind, based on near-field interference that produces a myriad of nonlinearities in the sensing response, can introduce new capabilities for the interface of electronic displays (the detection is based on pattern recognition). What set this sensor and its platform apart from previous proximity sensors and microwave sensing platforms is the low profile planar structure of the system, and its compatibility with mobile applications. The thesis provides both breadth and depth in the proposed design and development and thus presenting a complete research in its contributions to RF sensing.

SILVA, André Leandro. Nanobiocompósitos superparamagnéticos para aplicação como antenas ressoadoras dielétricas. 2014. 126 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Departamento de Quimica Orgânica e Inorgânica, Programa de Pós-Graduação e Biotecnologia, Renorbio - Rede Nordeste de Biotecnologia, Fortaleza-CE, 2014. / Submitted by demia Maia (demiamlm@gmail.com) on 2016-05-20T13:09:52Z No. of bitstreams: 1 2014_tese_alsilva.pdf: 6480806 bytes, checksum: 946e32810e24c5137dfbba52bfd30bb8 (MD5) / Approved for entry into archive by demia Maia (demiamlm@gmail.com) on 2016-05-20T13:10:43Z (GMT) No. of bitstreams: 1 2014_tese_alsilva.pdf: 6480806 bytes, checksum: 946e32810e24c5137dfbba52bfd30bb8 (MD5) / Made available in DSpace on 2016-05-20T13:10:43Z (GMT). No. of bitstreams: 1 2014_tese_alsilva.pdf: 6480806 bytes, checksum: 946e32810e24c5137dfbba52bfd30bb8 (MD5) Previous issue date: 2014 / There is a growing global interest for the development of green technologies that allow the use of products with less damage to environment, as well as for maximum and sustainable use of natural resources. The main aim of this study was to develop superparamagnetic nanobiocomposites for application as dielectric resonator antennas. For this purpose, a biobased thermoset plastic was prepared by using cardanol as an alternative to petrochemical phenol. This thermoset plastic was used as a polymer matrix and biocomposites were prepared by using 15 wt% of untreated and modified sponge gourd fibers by chemical treatment (NaOH 5, 10, and 15 wt% and NaClO 1 wt%) as dispersed phase. For the nanobiocomposites preparation, besides the sponge gourd fibers insertion, the thermoset plastic were also impregnated with magnetite nanoparticles in different contents (1, 5, and 10 wt%). Techniques of Thermogravimetry (TG), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), Scanning Electron Microscopy (SEM), Optical Microscopy, Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Mössbauer Spectroscopy, Tensile testing, Dielectric measurements, Vibrating Sample Magnetometry (VSM) and Biodegradation in simulated soil were performed for characterization. The results showed that alkaline treatment improved the thermal stability and the crystallinity index of the sponge gourd fiber. The crosslinking agent used (Diethylenetriamine) was efficient and enabled complete cure for all materials. The biocomposites reinforced by treated fiber showed better thermal stability, superior performance in Tensile testing and greater biodegradation rates, when compared to the biocomposite reinforced by raw fiber. The magnetite particles exhibited nanometric size, high purity and crystallinity, and superparamagnetic character. All nanobiocomposites showed superparamagnetic behavior, excellent thermal stability, good biodegradation rates, and better mechanical strength for the material with magnetite 10 wt%. All dielectric resonators antennas exhibited satisfactory return loss and suitability for commercial and technological applications, especially for performance in broadband. / É crescente o interesse mundial pelo desenvolvimento de tecnologias chamadas “verdes” que possibilitem o uso de produtos com menor impacto ao meio ambiente, assim como também se fortalecem as políticas de incentivo ao aproveitamento máximo e sustentável dos recursos naturais. O principal objetivo desse estudo foi desenvolver nanobiocompósitos superparamagnéticos para aplicação como antenas ressoadoras dielétricas. Para tal, um plástico termorrígido biobaseado foi preparado utilizando o cardanol em alternativa aos fenóis petroquímicos. Esse plástico termorrígido foi utilizado como matriz para o preparo de biocompósitos, utilizando 15% em massa de fibra de bucha bruta e também modificada por tratamento químico (NaOH 5, 10 e 15% e NaClO 1%) como fase dispersa. Para o preparo dos nanobiocompósitos, além da fibra de bucha, nanopartículas de magnetita, sintetizadas pelo método da coprecipitação, foram impregnadas no plástico termorrígido em diferentes teores de 1, 5 e 10% em massa. Técnicas de Termogravimetria (TG), Calorimetria exploratória diferencial (DSC), Análise dinâmico-mecânica (DMA), Microscopia eletrônica de varredura (MEV), Microscopia óptica, Microscopia eletrônica de transmissão (MET), Difração de raios X (DRX), Espectroscopia no infravermelho com transformada de Fourier (FTIR), Espectroscopia Mössbauer, Ensaios de resistência à tração, Medidas dielétricas, Magnetometria de amostra vibrante (VSM) e Biodegradação em solo simulado foram utilizadas para caracterização. Os resultados mostraram que o tratamento alcalino melhorou a estabilidade térmica e o índice de cristalinidade da fibra de bucha. O agente reticulador utilizado (DETA) mostrou-se eficiente, possibilitando a cura completa dos materiais. Os biocompósitos com fibra tratada apresentaram maior estabilidade térmica, resistência à tração superior e melhor índice de biodegradação em relação ao biocompósito com fibra natural. A magnetita sintetizada exibiu tamanho nanométrico, além de alta pureza, alta cristalinidade e caráter superparamagnético. Todos os nanobiocompósitos exibiram superparamagnetismo e mostraram excelente estabilidade térmica, boas taxas de biodegradação e melhor resistência mecânica para o material com 10% de magnetita. Todas as antenas ressoadoras dielétricas preparadas apresentaram perda de retorno satisfatória e, portanto, adequação para fins comerciais e tecnológicos, com maior potencial para atuação em banda larga.

Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-22T17:35:38Z No. of bitstreams: 0 / Made available in DSpace on 2017-11-22T17:35:38Z (GMT). No. of bitstreams: 0 / O projeto de doutorado tem como objetivo estudo e montagem de um sistema laser que gere feixe laser de comprimento de onda sintonizável continuamente, com intervalo espectral na região infravermelho (IV) próximo e médio. O trabalho foi dividido em três partes: (i) laser de Nd:YAG @1064nm, (ii) aplicação deste sobre uma cavidade ressonante OPO e (iii) simulação de cavidades laser em anel. O laser de Nd:YAG foi montado e aprimorado a partir de outro laser desenvolvido anteriormente, o qual foi transformado em fonte polarizada pela inserção de um elemento óptico no seu interior. Em comparação com o laser não polarizado, ele apresentou potência de saída com valores relativamente altos, com um máximo de 30W, e melhora do fator de qualidade do feixe de M2<1,3 mais próximo do valor ideal igual a 1 e assim próximo do modo TEM00, adequado para aplicações de transferência de energia. A aplicação do laser Nd:YAG polarizado sobre uma cavidade OPO linear (meio ativo: cristal de Niobato de Lítio dopado 5%MgO:LiNbO3 com alternância de polarização, conhecido pela sigla PPLN) foi bem sucedida, por ter sido observado seu funcionamento pela geração em seu meio ativo dos feixes (&lambda;S, &lambda;C) sinal e complementar sintonizados continuamente, mostrando que valores de potência e fator de qualidade foram adequados e suficientes para ser testado em um OPO. Foi mensurada na saída potencia de 1W para o feixe complementar, onde a eficiência de inclinação da curva mostrou valores de 20,8% e 23,4% para bombeio pulsado (temperaturas do cristal TC=100°C/150°C), e o valor de 11,1% (TC=150°C) para bombeio contínuo. A aplicação da técnica knife-edge no feixe complementar (TC=150°C/rede periódica do cristal &Lambda;0=31,59m/ &lambda;C=2470nm) resultou em fator de qualidade do feixe de M2=5,75(165). Foi realizada simulação numérica, visando estudo e planejamento de duas cavidades em anel simétricas, com sintonização contínua dos feixes de interesse na saída. A primeira contém um cristal PPLN como meio ativo, onde ocorre Oscilação Paramétrica, gerando feixe na região espectral do IV médio. A segunda cavidade possui dois cristais, que são PPLN e Triborato de Lítio (LiB3O5 conhecido pela sigla LBO), onde ocorrem na ordem Oscilação Paramétrica e Geração de Segundo Harmônico, gerando feixe na região espectral entre visível e IV próximo. Foram obtidos dois conjuntos de valores de dimensões para as cavidades, usando base teórica e condições de contorno apropriadas ao realizar os cálculos necessários, fixadas as informações sobre os respectivos componentes ópticos, onde o feixe de bombeio @1064nm focalizado no centro do cristal PPLN possui valor de cintura de feixe pouco maior que 50 &mu;m. O laser de Nd:YAG @1064nm polarizado desenvolvido possui montagem simples e custo baixo de seus componentes, reduzindo o custo do sistema laser final onde foi aplicado, comparado com outros sistemas laser sintonizáveis. Deseja-se estudar o desenvolvimento destes para um modelo de frequência única, usando-o como fonte de bombeio para geração de feixes com largura de linha estreita, visando aplicação em espectroscopia. / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP