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The coaxial aperture structure has been under intensive study in recent years, particularly since it exhibits electromagnetic transmission resonances that are stronger than its circular aperture counterpart. In our work, we study the resonance properties of a coaxial aperture in a perfect electric conductor (PEC) and in a real metal. For PEC, The dielectric constant is in finite and for real metal the dielectric constant is fi nite. We develop theory for reflection phase and amplitude in coaxial aperture at the end of a metal plate. While most of the past works of coaxial aperture focused on the propagation of light within the aperture structure and ignore the reflection at end-face,we fi nd that the reflection properties at the end-face are critical to determine both the wavelength and quality of Fabry-Perot resonant transmission of coaxial structure. Finite-di fference time-domain calculations agree well with our theory. We fi rst consider the PEC case, and later to develop the theory to account for real metal case. In real metal, the phase and amplitude of reflection are quantitatively diff erent from PEC because of plasmonic e ffects. Such di fference arises from the new physics associated with surface plasmons. This work is of interest to ongoing studies of coaxial structures in metal fi lms, which could impact many fields including filter e ffect,optical sensing, optical trapping, near- field spectroscopy and metamaterials. / Graduate

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Made available in DSpace on 2018-08-01T22:35:19Z (GMT). No. of bitstreams: 1 tese_10120_Resumo Final de Dissertação - Yanne Boaventura Nobre. pdf20170919-103059.pdf: 11621 bytes, checksum: 30ce3b21acd5a0ae49544b182b88db08 (MD5) Previous issue date: 2017-07-27 / A indústria de alimentos é responsável por 68% do volume das embalagens plásticas consumidas no mundo, sendo os polímeros sintéticos a principal fonte desta produção. Porém, estes materiais geram impactos negativos ao meio ambiente uma vez que apresentam pequena degradabilidade quando expostos a fatores naturais. Como alternativa, o uso de biopolímeros vem sendo explorado para o desenvolvimento de embalagens biodegradáveis. Polissacarídeos de grande interesse da indústria de fármacos e alimentos, quitosana e pectina, foram utilizados na elaboração de blendas poliméricas para a produção de filmes biodegradáveis e ativos. Os filmes compostos por quitosana:poli(álcool vinílico) (70:30 e 60:40) e pectina:poli(álcool vinílico) (30:70 e 20:80), adicionados de sorbato de potássio, foram elaborados e caracterizados por técnicas de MEV, FTIR e DSC, aspectos visuais, afinidade com a água, biodegradabilidade e quanto as suas propriedades mecânicas. Posteriormente foram aplicados sobre as massas de pastel e estas foram caracterizadas quanto aos aspectos físico-químicos e microbiológicos. Os filmes de QUI70, QUI60 apresentaram caráter hidrofóbico. Já os filmes de pectina, destacaram-se quanto aos bons aspectos de elasticidade e rasgabilidade dos filmes. Ambos os filmes apresentarm bons aspectos de cor e transparência, e boa biodegradabilidade, cerca de 35%. Quanto ao controle microbiano, os filmes ativos de QUI70 e QUI60 apresentaram alta efetividade no controle de mesófilos, reduzindo até 2,5 ciclos log. Os aspectos físico-químicos das massas intercaladas por filmes ativos de QUI70, QUI60, PEC30 e PEC20 foram capazes de manter a estabilidade físico química e qualidade do produto. Os aspectos de textura equipararam-se a massa comercial. Concluíu-se portanto, que o desenvolvimento de filmes a partir de blendas de quitosana:PVA e pectina:PVA por método de casting é viável e possui potencias aplicações para a indústria de massas frescas tipo pastel.

Hydrogen has been identified as a potential energy carrier due to its high energy capacity and environmental harmlessness. Compared with hydrogen production from hydrocarbons such as methane and naphtha in a conventional hydrogen energy system, photocatalytic hydrogen evolution from water splitting offers a more economic approach since it utilizes the abundant solar irradiation as energy source and water as initial reactant. Powder photocatalyst, which generates electrons and holes under illumination, is the origin where the overall reaction happens. High solar energy conversion efficiency especially from visible range is commonly the target. Besides, cocatalyst for hydrogen and oxygen evolution is also playing an essential role in facilitating the charge separation and enhancing the kinetics. In this thesis, the objective is to achieve high energy conversion efficiency towards water splitting from diverse aspects. The third chapter focuses on a controllable method to fabricate metal pattern, which is candidate for hydrogen evolution cocatalyst while chapter 4 is on the combination of strontium titanium oxide (SrTiO3) with graphene oxide (GO) for a better photocatalytic performance. In the last chapter, photoelectrochemical water splitting by Ta3N5 photoanode and FeOOH as a novel oxygen evolution cocatalyst has been investigated.

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