Orientador: João Carlos Silos Moraes / Coorientador: Sandro Márcio Lima / Banca: Eudes Borges de Araújo / Banca: Antonio Carlos Ferreira Seridonio / Banca: Noelio Oliveira Dantas / Banca: Luiz Antonio de Oliveira Nunes / Resumo: No presente trabalho foram sintetizados vidros Te-Li-Ti (TLT) dopados com Er3+ e também codopados com Er3+/Yb3+ para o estudo das propriedades da emissão em 1,5m do íon. Inicialmente foi estudado um conjunto com diferentes concentrações de Er3+ para ver a dependência com a concentração de dopante da eficiência quântica de emissão (). Foi empregado como método experimental de análise a técnica de lente térmica (LT) e os resultados foram confrontados com os determinados usando dados espectroscópicos combinados com a teoria de Judd-Ofelt. Embora sejam fortemente dependentes com a concentração, os valores de  para as concentrações mais baixas de dopante (~76% para o vidro TLT: 0,05% molar de Er2O3) são maiores que os valores reportados na literatura para o mesmo íon em outras matrizes teluritos. Adicionalmente, o sistema codopado com Er3+/Yb3+ foi estudo a fim de avaliar se a adição do Yb3+ na matriz promove o aumento da emissão do érbio em 1,5 m, excitando o nível emissor via Yb3+. Os resultados mostraram que há um eficiente mecanismo de transferência de energia do Yb3+ para o Er3+ de maneira que a intensidade de emissão no infravermelho foi aumentada. Ademais, avaliou-se a existência ou não da emissão "downconversion" em 980 nm do itérbio mediante excitação do Er3+ no visível. Do ponto de vista do "downconversion", que é interessante para aplicação do material em placas solares à base de silício, os resultados mostraram, pela primeira vez em um vidro telurito, que o efeito ocorre com uma eficiência na transferência de energia do Er3+ para o Yb3+ de 56%, indicando que o material tem boa perspectiva para utilização comercial / Abstract: In this paper Er3+ doped and Yb3+/ Er3+codoped Te-Li-Ti (TLT) glasses were synthesized to study the properties of the emission at 1.5 m. One set was initially studied with different Er3+ concentrations to see the dependence of emission quantum efficiency () with the dopant concentration. The thermal lens spectrometry (TL) was employed as the method of experimental analysis and the results were compared with those determined using spectroscopic data combined with the Judd-Ofelt theory. Although they are highly dependent on the concentration, the  values for the lower dopant concentrations (~ 76% for the TLT glass doped with 0.05 mol% Er2O3) are higher than those reported in literature for the same ion at tellurite other matrices. Additionally, the Er3+ / Yb3+ codopado system was studied to evaluate the increased emission of erbium at 1.5 m as a function of Yb3+ increment by excitation in the metastable state in Yb3+. The results show that there is an efficient transfer of energy from Yb3+ to Er3+, so that the infrared emission of Er3+ was increased, as was desired. Furthermore, we assessed whether or not the issue ytterbium downconversion emission at 980 nm upon excitation visible in the Er3+. From the viewpoint of the downconversion mechanism, which is interesting for application of the material in solar cells based on silicon, the results showed for the first time in a glass tellurite, which effect occurs with efficiency in energy transfer from Er3+ Yb3+ to 56%, indicating that the material has good prospects for commercial use / Doutor

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Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第16403号 / 工博第3484号 / 新制||工||1526(附属図書館) / 29034 / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 三浦 清貴, 教授 平尾 一之, 教授 田中 勝久 / 学位規則第4条第1項該当

Master of Science / Department of Architectural Engineering and Construction Science / Sutton F. Stephens / Glass can be beautiful and strong, so why is it not used more often as a structural material? Most often the reasoning is because people fear its perceived fragile and dangerous nature. Although this is the perception, it is far from the reality. Structurally designed glass can even withstand higher loads than steel. The following report will present several advantages of using glass as a structural material. Because understanding the history of glass can foster a greater understanding of where the future of glass is headed, it is discussed early on. After this, the focus is on how to make a mixture of molten liquid into a structural member. The manufacturing process is at the root of the strength of glass, as are the material properties. The composition and properties of glass are addressed before discussing various uses of glass as a structural material. As architects begin to ask for more structural glass in their projects, structural engineers must be prepared to design the systems or to specify performance criteria to a specialty engineer. To aid in design, published guidelines and testing must be utilized and are therefore discussed. In a glass structural system, the glass is not the only aspect that needs an engineer's attention. Connections present a special challenge when designing with structural glass, but several different forms of connections have been successfully demonstrated in construction. To tie all the previous topics together, three examples of structural glass systems are presented. Europe has been using glass as a structural material for years, but the United States has been slow to follow the trend. Glass has been proven to work as a structural material that can create impressive visual impact. With the support of the glass manufacturing industry and the courage of design engineers, the United States could easily start a movement towards building with structural glass.

Please read the abstract in the section 00front of this document / Dissertation (Master of Architecture)--University of Pretoria, 2005. / Architecture / unrestricted

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A glass electrode is described which is capable of detecting photosynthetic CO₂ uptake by monitoring the concentration of CO₂ dissolved in a small drop of algal suspension. Consideration of current theory suggests that transients should occur in the rate of CO₂ uptake which are similar to but distinct from those observed in O₂ evolution rate. These transients should be most readily observed when cells are illuminated alternately with wavelengths of 650 nm and 705 mn. The preliminary results show that C0₂ uptake by photosynthesis can be monitored by this apparatus. Although transients were not observed, this may be due to the rather low sensitivity. There is a discussion of shortcomings of the apparatus, and of improvements necessary before transients can be observed. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Certain surface-active media can considerably influence the flow and fracture properties of the .solids they wet. The effects of various lubricating media on the sliding friction behaviour of diamond on soda-lime glass were studied in the present research. An experimental apparatus was constructed to slide a hemispherical diamond linearly and at constant speed across the surface of a Corning type 2947 soda-lime glass microslide and to measure the resultant friction force. Tests were conducted in a variety of liquid and gaseous media at sliding speeds ranging from 0.001 cm/sec to 0.4 cm/sec. As a base for comparison initial tests were conducted in a high vacuum — 8 at 4 x 10 ⁻⁸. The results showed that all the media enhanced material displacement from that observed in high vacuum. In addition, the friction force was observed to rise with displaced material. A simple theory was used to predict with reasonable agreement the results obtained in in vacuum and air only. The greatest increase in displaced material was observed in heptyl alcohol. Scanning electron micrographs of the friction tracks suggest that heptyl; alcohol softened the surface of the glass. This is in agreement with previous work. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

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The problem with which this investigation is concerned is the discovery of suitable uses for the enameling kiln in the arts and crafts program at the junior college level in the production of kiln-formed glass and the testing of methods and materials that will permit work of aesthetic merit at a nominal cost to the students and the school.