abstract: Nighttime visibility of pavement markings is provided by glass beads embedded into the striping surface. The glass beads take light from the vehicle headlamps and reflect it back to the driver. This phenomenon is known as retroreflection. Literature suggests that the amount of the bead embedded into the striping surface has a profound impact on the intensity of the retroreflected light. In order to gain insight into how the glass beads provide retroreflection, an experiment was carried out to produce paint stripes with glass beads and measure the retroreflection. Samples were created at various application rates and embedment depths, in an attempt to verify the optimal embedment and observe the effect of application rate on retroreflection. The experiment was conducted using large, airport quality beads and small, road quality beads. Image analysis was used to calculate the degree to which beads were embedded and in an attempt to quantify bead distribution on the stripe surface. The results from the large beads showed that retroreflection was maximized when the beads were embedded approximately seventy percent by bead volume. The results also showed that as the application rate increased, the retroreflection increased, up to a point and then decreased. A model was developed to estimate the retroreflectivity given the amount of beads, bead spacing, and distribution of bead embedment. Results from the small beads were less conclusive, but did demonstrate that the larger beads are better at providing retroreflection. Avenues for future work in this area were identified as the experiment was conducted. / Dissertation/Thesis / M.S. Civil Engineering 2014

Neste trabalho foram estudadas duas composições vítreas, a saber: 30PbF2 - 15InF3 - 20GaF3 - 15ZnF2 - 20CaF2, chamada fluoroindogalato e 41,5Al2O3 - 47,4CaO - 7SiO2 - 4,1MgO, chamada LSCA ( do inglês Low Silica content Calcium Aluminate). A matriz de fluoroindogalato foi dopada com dois conjuntos de íons terras-raras: Tm3+ + Ho3+ e Er3++Yb3+, enquanto que a matriz LSCA foi dopada apenas com os íons Er3+:Yb3+. O objetivo do trabalho foi a caracterização destas matrizes como possíveis meios ativos para laser de estado sólido nas regiões de 2,0 µm (Ho3+) e 2,8µm (Er3+). Neste sentido, foram realizados os experimentos de absorção óptica, fotoluminescência e tempo de vida. A partir dos dados obtidos, foram calculados os parâmetros de intensidade de Judd-Ofelt, os microparâmetros de transferência de energia e o coeficiente de ganho óptico das transições eletrônicas 5I7→ 5I8 (Ho3+) e 4I11/2→ 4I13/2 (Er3+). A contribuição deste trabalho a espectroscopia de terras-raras em vidros está na caracterização destes íons em termos dos parâmetros de transferência de energia via os modelos de Dexter e Yokota e Tanimoto. Haja vista que tais dados não se encontram disponíveis na literatura especializada. Os resultados mostraram que ocorrem processos de transferência de energia de ordem mais alta que dipolo-dipolo nas interações Tm3+→ Tm3+ e Tm3+→ Ho3+. A transição 5I7 → 5I8 do Ho3+ apresenta coeficiente de ganho óptico positivo a partir da densidade de excitação de 1,2 kW/cm2. Os processos de transferência de energia Er3+→ Er3+ e Er3+→ Yb3+ ocorrem via mecanismo de dipolo-dipolo e a transição 4I11/2→ 4I13/2 do Er3+ não é auto-terminada na matriz de fluoroindogalato. O coeficiente de ganho óptico para esta transição é sempre positivo para qualquer densidade de excitação. . A matriz LSCA apresenta auto-terminação da transição 4I11/2→ 4I13/2 do Er3+, sendo portanto, necessária a inserção dos mecanismos de upconversion para a observação de ganho óptico nesta transição eletrônica / In this work two vitreous compositions were studied, that are: fluoroindogalate (30PbF2 - 15InF3 - 20GaF3 - 15ZnF2 - 20CaF22) and LSCA (41,5Al2O3 - 47,4CaO - 7SiO2 - 4,1MgO) - Low Silica Content Calcium Aluminates. The fluoroindogalate host was doped with two sets of rare earth ions: Tm3+ + Ho3+ and Er3++Yb3+, whereas the LSCA host was only doped with Er3+ and Yb3+ ions. The aim of the work was the characterization of these hosts as possible active media for solid state lasers in the spectral regions of 2,0 µm (Ho3+) and 2,8µm (Er3+). In this sense, optical absorption, photoluminescence and lifetime experiments were performed. From the resulting data, Judd-Ofelt intensity parameters, energy transfer microparameters and the electronic transitions 5I7→ 5I8 (Ho3+) and 4I11/2→ 4I13/2 (Er3+) optical gain coefficients were calculated. This work\'s contribution to the rare earth spectroscopy lies in the characterization of such ions in terms of the energy transfer parameters using the Dexter, and Yokota and Tanimoto models considering that these data are not available in the specialized literature. The results have shown that higher than dipole-dipole order processes occur in the interactions Tm3+→ Tm3+ and Tm3+→ Ho3+. The Ho3+ 5I7→ 5I8 transition presents positive optical gain coefficient starting from the excitation density of 1.2 kW/cm2. The energy transfer processes Er3+→ Er3+ and Er3+→ Yb3+ occur via dipole-dipole mechanism and the Er3+ 4I11/2→ 4I13/2 transition is not auto terminated in the fluoroindogalate host. The optical gain coefficient for this transition is always positive for any excitation density. The LSCA host presents auto termination of the Er3+ 4I11/2→ 4I13/2 making it necessary the insertion of upconversion mechanisms for the observation of the optical gain in this electronic transition

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A busca de melhores características elétricas, acompanhada de crescentes evoluções tecnológicas e novos materiais passivantes para junções semicondutoras vem sendo bastante pesquisados nas últimas décadas. Existem dois tipos de passivação: por filmes finos ou por filmes espessos. No primeiro caso são realizadas deposições de óxido de silício, carbeto de silício, nitreto de silício, enquanto que no segundo caso faz-se uso de materiais como borrachas de silicone ou vidros. A escolha entre filme fino e filme espesso está relacionada diretamente ao custo/benefício e as características do dispositivo final. Na indústria de semicondutores de potência opta-se pelos filmes espessos devido às grandes dimensões dos dipositivos e ao custo do processo empregado nas linhas de produção. Os passivantes mais utilizados em semicondutores de potência são borrachas de silicone e vidros. Os vidros inorgânicos são mais estáveis a temperaturas elevadas do que as borrachas de silicone. Neste trabalho procuramos desenvolver e controlar um processo de passivação a vidro em junções semicondutoras de dispositivos de potência para que seja usado numa linha de produção de diodos retificadores de alta estabilidade. Existem diferentes tipos de vidros para esta aplicação como os vidros de Al-Pb-B-Si e os vidros de Zn-B-Si. No presente trabalho foi realizada uma comparação entre a influência da composição química dos vidros, a granulometria do pó (frita) deste vidro, com a tensão de ruptura e corrente de fuga dos diodos levando em conta o rendimento do processo. Observou-se que fritas de vidro de Al-Pb-B-Si com granulometrias mais finas resultam em tensões de ruptura maiores com um rendimento de produção de até 33% superior aos demais casos. As correntes de fuga , à temperatura ambiente, para fritas de vidro de Zn-B-Si e Al-Pb-B-Si com diferentes granulometrias, se mostrou pràticamente a mesma. / The search for better electrical properties, new passivating materials for semiconductors junctions and the process of obtaining those ones have being studied intensively in the latest decades. There are two types of passivation layers: thick film and thin film. The first one is obtained by the deposition of silicon oxides, silicon nitride or silicon carbide, while in the second one is obtained through the application of silicon rubber or glass over the exposed juntion. The decision of using one or another depends on cost/benefit and desired electrical properties of the devices. In the semiconductor power industry the thick films are frequently used because the devices dimensions are large and the cost of these processes are cheaper than those of thin films. Silicon rubber and glass are widely used by this industry. The silicon rubbers are materials that show temperature resistance up to 2000C. The inorganic glasses are more stables at high temperatures. In this work we developed a process of glass passivation for power semiconductors devices, controlled this process and it is in use in a production line of a semiconductor power device industry. There are a few glasses for this application where the two more widely used are Al-B-Pb-Si glass and Zn-B-Si glass. In this work it was compared the influence of the glass chemical composition as well as frit grain size of the glass, over the breakdown voltage and leakage current of the devices. It was observed that glasses of Al-B-Pb-Si with smaller grain size gave better values of breakdown voltage with a production yield bigger up to 33%. It was obtained leakage current values of the same magnitude, at ambient temperature, for both kinds of glasses with different grain sizes and composition.

Orientadores: Wagner dos Santos Oliveira, Leila Peres / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-12T08:56:57Z (GMT). No. of bitstreams: 1 Paiva_VanessaGiusti_M.pdf: 3847622 bytes, checksum: 3b220ff7426435a8efb069e376425300 (MD5) Previous issue date: 2008 / Resumo: O objetivo deste trabalho foi avaliar a resistência mecânica e a morfologia de fratura de resinas acrílicas sem e com reforço, processadas por microondas. Foram confeccionados 20 cp, sendo eles, Sem Reforço (SR), P246 5%, P246 8%, FSR 5%, FSR 8%, 688 5%, 688 8%, M14P 5% e M14P 8%, medindo 65 x 10 x 2,5mm, sendo os cp SR o grupo controle e os outros com os reforços de filamentos de fibra de vidro e microfibra de vidro. Utilizou-se para confecção das formulações estudadas a resina Vipi Wave, preparadas numa potência de 20 minutos/180W e 5 minutos/450W. Para as análises mecânicas foram feitas análises de variância e teste de Tukey, p<0,05. Constatou-se um aumento significativo para todos os cp reforçados submetidos aos ensaios de resistência à flexão e ao módulo de elasticidade, destacando-se os reforços (P246 5%, P246 8%, 688 5% e 688 8%). Para a análise da dureza (Esquerda, Central e Direita) e para resistência ao impacto não foi observada diferença estatística significante entre o grupo controle e os demais cp reforçados. Para a análise morfológica microestrutural da fratura foram utilizados fragmentos resultantes dos testes de impacto. Verificou-se uma melhor adesão entre a matriz polimérica e os reforços (P246 5%, P246 8%, 688 5% e 688 8%). Comparando-se os resultados dos ensaios mecânicos e a análise morfológica, concluiu-se que os reforços (P246 5%, P246 8%, 688 5% e 688 8%) apresentaram os melhores resultados, p<0,05. Mesmo não sendo observada uma melhora na adesão entre os reforços (FSR 5% e FSR 8%) e a matriz polimérica, estes apresentaram resultados estatisticamente significantes, p<0,05, em relação aos ensaios de resistência à flexão e ao módulo de elasticidade. / Abstract: The purpose of the present study is to evaluate the mechanical resistance and the fracture morphology of acrylic resins reinforced with glass fiber filaments and glass microfiber. 20 proof bodies (PB) were produced from each group, namely, no reinforcement (NR - control), P246 5%, P246 8%, FSR 5%, FSR 8%, 688 5%, 688 8%, M14P 5% and M14P 8%, measuring 65 x 10 x 2,5mm. These were made of a Vipi Wave microwave polymerized resin. Potencies employed were 20 minutes/180W and 5 minutes/450W. In order to perform the mechanical analysis, variation analysis and Tukey test p<0,05 were used. It was evidenced a significant improvement for all cp reinforcements submitted for flexion resistance analysis and the elasticity module analysis, evidencing the reinforcements (P246 5%, P246 8%, 688 5% e 688 8%). For the hardness tests (Left, Right and Center) and for impact. it was not observed significant differences between the control group and the reinforced PBs. For microstructure morphology characterization were used fragments origned from impact tests. Through this technique, it was evidenced some positive interaction between the polymeric matrix and the reinforced PBs. Comparing the results of the mechanic analysis and morphologic analysis, is was concluded that that reinforcements (P246 5%,P246 8%, 688 5% e 688 8%) presented the best results, p<0,05. Even that a better adhesion was not observed between reinforcement (FSR 5% e FSR 8%) and polymeric matrix, these presented significant improvements results, p<0,05, in relation to flexion resistance analysis and elasticity module analysis. / Mestrado / Ciencia e Tecnologia de Materiais / Mestre em Engenharia Química

The use of knitting technology with advanced fibres such as glass, carbon and aramid, to produce near-net-shape fabrics has in recent years received increasing interest from the composite materials community. Knitted fabrics have the potential of being used in engineering structures with complex shapes in conjunction with a suitable liquid moulding technique, such as Resin Transfer Moulding (RTM), due to their excellent drapeability and manufacturability. During previous studies in textile reinforced composites, an intimate relationship between the fabric architecture and the damage development has been demonstrated. In this work, the quasi-static tensile loading deformation behaviour and the relation between the fabric architecture and damage development have been studied for a weft knitted glass fabric. Tensile properties have been examined and the failure mechanisms have been identified experimentally by analysing the damage process in-situ with a camera and by studying fracture surfaces using scanning electron microscopy (SEM). The acoustic emission technique was used to support the microscopic analysis. The work has investigated the tensile properties and failure mechanisms of three knitted fabric reinforced composite laminates reinforced with a Milano weft knitted glass fabric. The three composites were (i) a single layer of fabric reinforcing epoxy resin, (ii) a single knitted fabric layer sandwiched between 0&deg; glass fibre unidirectional plies (again with the glass reinforcing epoxy resin), and (iii) the same knitted glass fabric but this time used as the reinforcement in commercially produced high fibre volume fraction composites (using the RTM technique). The variation of mechanical properties with angle (from wale to course) has been measured for the single layer of the fabric reinforcing epoxy resin by orientating the wale direction of the fabric at different angles. Mechanical properties have been measured for each angular orientation and comparisons were made between them, especially with regard to the planes of final failure. The single layer composites failed as soon as the first damage was initiated. Hence, to investigate damage accumulation, a novel technique was employed to manufacture a sandwich laminate, which consisted in placing a single knitted fabric layer between 0&deg; glass fibre unidirectional plies. The success of this method is that the accumulation of damage in the knitted architecture was allowed to be studied and some characteristics of crack initiation and crack propagation could be related to the fabric geometry and structure. Experiments on these model transparent materials have been complemented by tests on two types of commercial knitted fabric composite manufactured by the RTM process. Characterization of these materials under tensile loading has been carried out for monotonic and cyclic loading and the results have been compared with those found for the single layer and the sandwich model material. Various failure mechanisms such as cracking at loop cross-over points, resin matrix cracking, fibre bundle debonding and tensile fracture of fibre bundles in failed specimens were observed. The behaviour of the commercial RTM specimens has been discussed in the light of the results obtained from the model single layer and sandwich specimens.

Chemical strengthening via ion exchange is commonly used in the industry to produce ultra-thin and resistant glasses used for high-tech applications. This process results in the formation of an ion-exchanged region near the glass surface that is under significant compressive stress, which tremendously improves the mechanical strength and the scratch resistance of the glass. The aim of this thesis is to deepen our fundamental understanding of the ion-exchange mechanisms. Since the mechanical strength against brittle fracture of ion-exchanged glasses depends on the compressive stress at the surface and the depth of interdiffusion, special attention was paid to the two main parameters affecting those properties: the parent glass composition and stress relaxation processes.First, the effect of the parent glass composition on interdiffusion properties was analyzed. We focused our study on the effect of the alkali oxide:alumina ratio and the ionic potential (charge:radius) of divalent cations on the interdiffusional properties. An increase of the Al2O3 content in Na+/K+ ion-exchanged silicate glasses leads to a reduction of the depth of interdiffusion layer and an enhancement of the surface compressive stress. These trends are shown to be consistent with the compositional variation of the glass connectivity and hence, the stress relaxation occurring during the ion-exchange. It is also found that the depth of interdiffusion is higher for glasses containing divalent cations with a higher ionic potential such as Mg and Zn. This is attributed to the larger free volume available and the weaker Na-O bonds in those glasses. Second, the structural origin of stress relaxation is investigated. In the Na+/K+ ion exchanged glasses, the K+-foreign cations are introduced in the cages of the Na+-host cations. Due to stress relaxation, the size of the K-O coordination shell in ion-exchanged glasses increases. This increase is achieved by two structural adaptation mechanisms: a contraction of the Na-O, Ca-O and Mg-O coordination shell and both a shortening of the Si-NBO distances and an opening of the Q4 Si-O-Si angles. The greater knowledge developed in this thesis on the effect of parent glass composition on interdiffusion mechanisms and stress relaxation processes provides further insight into practical ways to optimize the mechanical strength of ion-exchanged glasses. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

lass fibre reinforced plastic (GRP) structural profiles, in standard shapes and sizes are now being commercially manufactured by the process of pultrusion. GRP profiles are light weight, posses higher specific strengths and are more durable than the conventional metal or concrete counterparts. GRP pultruded profiles have open or closed cross-sections comprising thin composite walls of low elastic moduli. Stability failure has been identified as the main cause of failure for these profiles when subjected to compressive stresses, as it may occurs at stresses much lower than the ultimate strengths. Therefore, the load carrying capacities of composite compression members mainly depends upon stability criteria. The conventional stability analyses for the prediction of buckling loads are not considered adequate as the GRP material is orthotropic and its behaviour is different from steel (non-yielding). The existing guidance for the design of composite members under compression ignores the presence of geometrical imperfections inherited in the pultruded profiles, whilst, experimental evidence suggests considerable loss of stiffness due to the imperfections particularly in the intermediate column heights. The design guidance provided by the manufacturers gives empirical equations based on data obtained from experiments on specified profiles. A universal design curve based on the experimental results of concentrically loaded GRP columns has been developed and presented. However, conducting a vast experimental study is not always feasible. The need to develop a procedure, predicting failure load numerically for the development of a design curve for GRP columns has been recognised. Two GRP box-sections (closed square cross-sections) have been investigated for failure/buckling loads using experimental and numerical methods. In the experimental phase, specimen columns of various heights have been concentrically loaded in compression to measure the failure loads. Experimental results have been compared with the theoretical predictions made using classical methods and the equations given by the design manuals. Based on the experimental and analytical failure loads, an experimental design curve has been derived. In the numerical study, 3-dimensional full scale finite element models representing experimental configuration of the composite columns, have been analysed using both linear and nonlinear solutions. Imperfections of known amplitudes have been included parametrically to establish the sensitivity of the failure loads towards imperfections. Imperfect model have been calibrated for the estimation of imperfection amplitude present in the profiles using experimental data. Using the numerical and analytical data, a design curve has been derived establishing interaction coefficients for each profile. The numerical design curve is compared with the experimental design curve for the validation of the numerical procedure adopted in this study. Effects of perforations (circular holes) on the buckling stiffness of GRP box-section columns have also been investigated. Holes are drilled in the walls of profiles and tested experimentally to measure the loss in the buckling loads. Finite element models of columns with holes have been developed and analysed for buckling loads. Comparisons of experimental and numerical results are plotted. For use in the numerical representation of the composite columns, mechanical properties of the orthotropic GRP material of the both sections have been established analytically and experimentally. In-plane shear properties have been measured by physically testing standard sized coupons, extracted along the length of profiles. However, short coupons were available in the transverse directions due to dimensional constraints. Short coupons, similar in geometry to the standard coupon, but smaller in size, have been validated for performance using finite element analyses and comparing the outcomes with the models of standard coupons. Both standard and short coupons have been used for the experimental measurement of the in-plane shear properties. Compression properties have also been measured experimentally. Ultimate failure/buckling loads of the composite columns depend upon their heights, material properties, and the cross-sectional dimensions. These factors have been combined into one characteristic parameter 'λ', the slenderness ratio. As the later two factors are constant for a particular box-section profile, the ultimate loads depend upon column heights. Four types of failure modes; global, local, modal interaction and material failure have been observed. The loss in the buckling stiffness is minimal for smaller circular holes, provided the interval between holes is not less than 20 times the diameter of the holes. For bigger holes and an inter hole spacing of 10time the diameter, a loss of 30% have been measured. Finite element representation of pultruded columns adequately predicted the numerical failure loads and failure modes for most of the column heights.

This paper examines the history of installation art and explains the concept and themes within my installation component of the studio art major. It details how readymades, site-specificity, and an emphasis on experiential work all contributed to the creation of installation art as a medium. Next, I turn to my own work, exploring the theme of representing time and altering the perceptions of the viewer. Through a web of fishing line and tempered glass, the installation visually imitates a single, frozen moment of an explosion that the viewer can walk into and explore. The paper continues with a discussion of relevant themes in the work by contemporary artists Ori Gerst, Heide Fasnacht, Cornelia Parker, E.V. Day, Lee Bontecou, and James Turrell, and concludes with ideas for the continuation of the project in the spring 2014 semester.