Thesis (Ph.D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (April 25, 2007) Vita. Includes bibliographical references.

Thesis (M.S.) University of Missouri-Columbia, 2004. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (June 30, 2006). Vita. Includes bibliographical references.

Made available in DSpace on 2014-06-11T19:25:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-02Bitstream added on 2014-06-13T19:12:14Z : No. of bitstreams: 1 fernandes_flf_me_guara.pdf: 1433508 bytes, checksum: b98071dd0cdb48e4a99b7eb1d07efb66 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Universidade Estadual Paulista (UNESP) / Este trabalho trata da simulação da ótica do olho humano, em especial a determinação do perfil de índices de refração do cristalino. Mostramos que a hipótese de índice de refração constante, para os meios óticos, não é adequada quando o objetivo é minimizar aberrações e se fazer um estudo da imagem formada na retina. Desenvolvemos um código computacional que utiliza a técnica do Traçado de Raio (ray tracing) acoplada a um processo de busca e otimização (recozimento simulado), visando determinar o perfil de variação dos índices de refração do cristalino, com a condição de minimização das aberrações. A parametrização do modelo foi baseada em resultados da Literatura e utilizamos faces asféricas (parabólicas). Para validar nosso modelo, comparamos nossos resultados com outros modelos existentes, e verificamos a qualidade da imagem formada na retina / This work deals with the human eye optics simulation, focusing in the lens refraction index profile. We show that the hypothesis of constant refraction index, for the lens, is not adequate when the objective is minimize aberrations and to study the image formed in the retina. We developed a computational code that uses the ray tracing technique coupled to a search and optimization algorithm (simulated annealing), seeking to determine the profile of the refraction index for the crystalline lens that minimize the aberrations. The model's parametrization was based on Literature results and we implemented aspherical faces for the lenses. In order to validate our results, we compare with those in the Literature, and verify the image quality formed on the retina

No description available.

Orientador: Carlos Renato Zacharias / Banca: Ernesto Vieira Neto / Banca: Alvaro Jose Damião / Resumo: Este trabalho trata da simulação da ótica do olho humano, em especial a determinação do perfil de índices de refração do cristalino. Mostramos que a hipótese de índice de refração constante, para os meios óticos, não é adequada quando o objetivo é minimizar aberrações e se fazer um estudo da imagem formada na retina. Desenvolvemos um código computacional que utiliza a técnica do Traçado de Raio (ray tracing) acoplada a um processo de busca e otimização (recozimento simulado), visando determinar o perfil de variação dos índices de refração do cristalino, com a condição de minimização das aberrações. A parametrização do modelo foi baseada em resultados da Literatura e utilizamos faces asféricas (parabólicas). Para validar nosso modelo, comparamos nossos resultados com outros modelos existentes, e verificamos a qualidade da imagem formada na retina / Abstract: This work deals with the human eye optics simulation, focusing in the lens refraction index profile. We show that the hypothesis of constant refraction index, for the lens, is not adequate when the objective is minimize aberrations and to study the image formed in the retina. We developed a computational code that uses the ray tracing technique coupled to a search and optimization algorithm (simulated annealing), seeking to determine the profile of the refraction index for the crystalline lens that minimize the aberrations. The model's parametrization was based on Literature results and we implemented aspherical faces for the lenses. In order to validate our results, we compare with those in the Literature, and verify the image quality formed on the retina / Mestre

Polymer samples of polytetrafluoroethylene (PTFE) and a PTFE-glass weave (RF- 35P) are exposed to low pressure, non-equilibrium glow discharge plasmas for enhanced wettability as measured by static contact angles. Plasma treatments are performed in two parallel plate RF plasma systems, a downstream microwave plasma and a barrel etcher using feed gases composed of H₂, N₂, Ar, He, and 0₂. Surface analysis of the topography and chemical composition of treated samples is performed by atomic force microscopy (AFM), attenuated total reflection infrared (ATR-IR) spectroscopy, x-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (ToF SIMS). Optical emission spectroscopy is used to correlate wettability to reactive species in the plasma, and plasma parameters to species emission. In the parallel plate plasma systems, the contact angle can change from approximately 95° to 5° with treatment while treatments in the downstream and barrel etcher systems do not result in a contact angle change. The difference in plasma performance is attributed to ion bombardment. Plasmas composed of 20 to 80% H₂O in (H₂ + N₂) give the best wettability improvement. Plasma exposure significantly reduces the surface fluorine content followed by incorporation of nitrogen, oxygen and hydrogen, apparently as amino, hydroxyl and carbonyl functional groups with evidence of an amide. The incorporation of oxygen likely originates through peroxy radicals subsequent to plasma exposure. It is proposed that using a higher applied power creates a more reactive surface. A larger percentage of H₂ in the plasma tends to passivate the surface, leading to a smaller wettability improvement which is correlated to the atomic hydrogen concentration in the plasma. The addition of He or Ar into the H₂/N₂ plasma tends to dilute or weaken the plasma effect on wettability. To a much greater extent, the addition of oxygen also decreases the wettability. This latter effect is attributed to etching reactions which result in a more hydrophobic surface. An etch rate of approximately 0.2 μ/min is observed, and this is the first report of PTFE etching with 0₂/H₂/N₂. The distance between the parallel plate electrodes (gap) is a significant factor for the wettability of treated polymers, while power, pressure and flow rate are not. The optimal storage conditions to retain the wettability of H₂/N₂ plasma-treated RF-35P are low pressure and low temperature. The following model of PTFE surface modification is proposed. Ion bombardment creates reactive sites that initiate surface reactions. Reactive species from the H₂/N₂ plasma modify the surface through incorporation of amino, hydroxyl and carbonyl surface groups. These new groups increase the polymer wettability. Atomic hydrogen in the mixture is required to improve the wettability, but too high of a concentration will passivate the surface and lessen the wettability improvement. If oxygen is present, the modified surface is etched away leaving a refreshed, more hydrophobic surface. / Graduation date:2006

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

A novel dual-plasma process for the synthesis of organic layer-coated metal nanoparticles is presented. Metal nanoparticles are synthesized by the low-pressure pulsed arc evaporation of a metal cathode surface, followed by the in-flight deposition of a thin organic layer by capacitively-coupled radio-frequency (CCRF) plasma polymerization from a gaseous hydrocarbon monomer. The system is simple to operate and can be designed for high throughput. The combination of the synthesis and surface treatment of metal nanoparticles in the whole system avoids newly produced metal nanoparticles from being contaminated by surrounding environment. / A home-made self-oscillatory pulsed power supply has been designed and built for the arc evaporation of metal sources. The stability of the pulsed arc system and the cathode erosion rate are discussed. The inductor present in the discharge loop is shown to have a stabilizing effect on the train of pulsed arcs. It was shown that the erosion rate was strongly dependent on peak arc currents due to the increased emission of macroparticles with peak arc currents, and the yield of metal nanoparticles was found to be slightly influenced by the peak arc current. / The produced coated copper nanoparticles were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). It was revealed that the coated copper nanoparticles have a metal core of size ranging from a few to 50 nm, and that the thickness of the organic layer ranges from 3 to 10 nm. The smallest copper nanoparticles are crystalline, while the organic coating has a macromolecular structure and shows a hydrophobic behavior. The XPS results showed that the plasma polymer film is chemically adsorbed onto the surface of the copper nanoparticle. / The effects of operating conditions such as reactor pressure and inert gas flow rate on the average size of the produced bare copper nanoparticles were studied. It was demonstrated that the metal nanoparticle size tends to decrease with decreasing reactor pressure, while inert gas flow rate has little influence on the mean nanoparticle size. / The morphology of the plasma polymer coating was revealed to be strongly dependent on the RF plasma power, reactor pressure, and inert gas flow rate. Two kinds of organic films were produced: a smooth, uniform and dense polymer film and a liquid polymer film. Based on a series of experiments, a "characteristic map" for the in-flight plasma polymerization from the C2H 6 monomer generating an organic layer onto the Cu nanoparticles was developed. A simplified free-radical mechanism was proposed for the plasma polymerization from ethane. / Other metal sources such as iron and aluminum were used as cathodes in the arc evaporation reactor. Transmission electron microscopy confirmed the production of coated nanoparticles similar in morphology to the ones obtained with the copper cathode. Lastly, ethylene glycol vapor were introduced as an alternative monomer into the plasma polymerization region. A non-uniform coating was observed on the metal nanoparticle surface.

Plasma polymerisation (PP) is an emerging processing technology with immense potential for future industrial applications, which is increasingly being used for the fabrication of functional coatings on polymeric substrates. In this technique, the solid polymeric film is directly deposited onto the substrate surface to create a new surface of very interesting and unique properties. PP utilizes gas phase chemistries in low-pressure environment to produce well-defined high quality films in controllable and tunable fashion. A major advantage of this process is that it is an environmental safety technique and strategically superior compared to other thin film deposition techniques such as spin coating and spray coating. In general, the quality of the plasma polymer film can be controlled, precisely and reproducible. However, mechanism of the coating under plasma polymerisation is complex and has not yet been completely understood. / The ethylene propylene diene terpolymers (EPDMs) are increasingly being used in numerous technological applications, such as automotive sealing sections (~25kg of elastomer is used in an average car) due to their elasticity. ozone resistance, low weight, ease of fabrication in desired shape/form; favorable mechanical properties and low cost. However, the deficiency of EPDM in the surface specific secondary engineering characteristics that may play a critical role in many applications is encountered. The performance of this elastomeric materials may be further enhanced by deposition of organic surface coatings, which can satisfy one or more surface specific functions including, hydrophobicity, low friction, high abrasion resistance, decorative and protective coatings against harsh terrestrial and/or space environments, etc. / In this PhD thesis the objectives of the research were focused on: (i) creation of low friction and high abrasion resistance ultra thin functional PP coating onto EPDM substrate surface using fluorocarbons and organosilicones as precursors, (ii) investigation of the structure-property-processing relationship of the deposited film in detail, (iii) development of new plasma thin film characterisation and performance evaluation techniques. / Thesis (PhDAppliedScience)--University of South Australia, 2004.

Plasma polymerisation (PP) is an emerging processing technology with immense potential for future industrial applications, which is increasingly being used for the fabrication of functional coatings on polymeric substrates. In this technique, the solid polymeric film is directly deposited onto the substrate surface to create a new surface of very interesting and unique properties. PP utilizes gas phase chemistries in low pressure environment to produce well-defined high quality films in controllable and tunable fashion. A major advantage of this process is that it is an environmental safety technique and strategically superior compared to other thin film deposition techniques such as spin coating and spray coating. In eneral, the quality of the plasma polymer film can be controlled, precisely and reproducible. However, mechanism of the coating under plasma polymerisation is complex and has not yet been completely understood. / PhDAppliedScience