Este trabalho tem como foco principal apresentar os resultados e as contribuições da pesquisa experimental comparativa de subcoberturas em sistemas de cobertura. Para tal fim foram utilizados quatro protótipos localizados no canteiro experimental do CRHEA - EESC em São Carlos, São Paulo. Os protótipos foram construídos da mesma forma e com os mesmos materiais: tijolo comum, laje cerâmica recapeada com concreto; cobertos com telhas de fibrocimento e submetidos às mesmas excitações de clima ao ar livre. A análise foi feita aplicando um curto intervalo de clima, com respaldo teórico da climatologia dinâmica. Um dos protótipos serviu como testemunho e não recebeu a instalação de nenhuma subcobertura. Os outros três receberam cada um, respectivamente, subcobertura de foil (isolante por reflexão, ou barreira de radiação), lã de rocha (isolante convencional, condutividade térmica k) e de caixas cartonadas Tetra Pak, um resíduo, como isolante por reflexão e câmara de ar, já que foram utilizadas fechadas e uma ao lado da outra. Foram monitoradas as temperaturas superficiais da telha e da laje e, das temperaturas de bulbo seco no ático e na parte interna dos protótipos a 1,10 m de altura. As medidas de aquisições de dados foram feitas através de CR10X Campbell Scientific automático com medições em 30 segundos, armazenados e totalizados em 30 minutos, o que resultou em valores de clima ao livre e em recinto fechado muito precisos. / Thermal comfort achievement can be done by using thermal reflexive barriers, meaning energy savings and avoiding health problems of air conditioning. It can also be done by using building construction waste materials as Tetra Pak boxes, a low cost reflexive insulation, and applying an industrial \"foil\" which the same effect on reducing indoor air temperatures. In the same way traditional thermal insulation materials were used on this research as the mineral wool (conventional insulation material, thermal conductivity - k values). The analysis was made applying short intervals of climate such as recommended by the dynamic climatic approach. The use of foil insulation can be justified because of its behavior as a reflective barrier and because it has a lot of acceptation; mineral wool (mineral source with low k insulation values) for being a traditional kind of thermal insulation and the Tetra Pak box, because it is a reflective insulation and also because of its waste recycle usage characteristic. The research shows the insulation thermal efficiency applied on three kinds of fiber asbestos cover system, which makes the indoor air temperatures inside of comfort zones values, as intended to expose by graphics, made by real time and automatic experimental measurements. The measurements of data acquisitions were made by automatic CR10X Campbell Scientific Inc., 30 seconds scanner and totalized storage as 30 minutes average intervals. This means a very accurate result of values of outdoor and indoor climate translated by indoor and out door air temperatures.

Electrical insulating liquids, organic esters, conductivity, dielectric, permittivity

Charge transport, charging, and subsequent electrostatic discharge due to interactions with the space environment are primary concerns of spacecraft designers. Developing a physical understanding of the interactions of charge with the multitude of materials that spacecraft are composed of is a critical step in understanding and mitigating both short-term and long-term spacecraft degradation. In particular, the study of charge transport in highly insulating materials is critical as they store charge longer, with higher capacity, and with greater destructive capability than other materials.The Utah State University Materials Physics Group, with the funding of the NASA James Webb Space Telescope project and Rocky Mountain Space Consortium, have developed a complete and consistent theoretical model that predicts short-term and long-term storage capabilities based on physical material parameters. This model is applicable across a wide range of experimental systems designed to test specific behaviors that characterize charging phenomena.Modeling and understanding the complex relationships between the spacecraft and its surroundings are fundamentally based on detailed knowledge of how individual materials store and transport charge. The ability to better understand these effects will help make exploring the edges of the universe more stable, reliable, and economic.

Photoluminescence spectroscopy is one of the most efficient and sensitive non-contact techniques used to investigate defects in SiC. In this work, room temperature photoluminescence mapping is employed to identify different defects that influence material properties. The correlation of the distribution of these defects in n-type 4H-SiC substrates with electronic properties of SiC revealed connection between the deep levels acting as efficient recombination centers and doping in the substrate. Since deep levels are known to act as minority carrier lifetime killers, the obtained knowledge may contribute to our ability to control important characteristics such as minority carrier lifetime in SiC. In semi-insulating (SI) 6H-SiC, the correlation between room temperature infrared photoluminescence maps and the resistivity maps is used to identify deep defects responsible for semi-insulating behavior of the material. Different defects were found to be important in different families of SI SiC substrates, with often more than one type of defect playing a significant role. The obtained knowledge is expected to enhance the yield of SI SiC fabrication and the homogeneity of the resistivity distribution across the area of large SiC substrates.

M.S.

No description available.

M.S.

An experimental investigation was made to determine the role of gravitational and surface tension forces in the migration of liquid water through fiberglass insulation materials. Straightforward experimental procedures were devised to effectively isolate and quantify flow parameters considered important in describing the flow mechanisms involved. The study was conducted to supplement an earlier investigation into the thermal performance of wetted insulation materials. Darcy's Law was found to apply for the regime of flow encountered in which liquid water flows under the force of its own weight in horizontal rooftop insulation. Experimental determination of the constant of proportionality in Darcy's Law, the hydraulic conductivity, is all that is needed to describe the migration of liquid water in saturated fiberglass insulation. Capillary forces, originally thought to play a significant role in the movement of liquid water through fiberglass insulation, were found to be negligible. Capillary rise up a column of insulation measured no higher than 13 mm. / M.S.

Due to the fact that only comparative results were sought, the investigation was greatly simplified. On a comparative basis, the effects of external influences were largely eliminated from positions of vital importance and the use of an elaborate test, circuit was unnecessary. The equipment consisted of a high-voltage test transformer which supplied the test voltage; an induction regulator, auto transformer and generator field rheostats for voltage control; overload relay and aircore inductances for circuit protection; motor-generator set for a source of 60 cycle alternating voltage. The electrodes were circular, square edge brass discs. Specimens were immersed in lubricating oil for periods up to 40 hours and then tested for puncture strength. Following this, specimens were immersed for one hour and 24 hours and each of the two groups tested at intervals of time up to 720 hours. In each test the voltage was raised in steps of 200 volts, starting at 1000 volts. The puncture strength of the untreated paper was determined by testing a sufficient number of specimens over a period of days. The results obtained indicated no immediate deleterious effects of lubricating oil on paper. On the contrary, there was an improvement in puncture strength, accounted for by the fact that the relatively low voltages-used did not make ionization a serious factor. The results of tho long-time tests were unsatisfactory, as explained previously. However, they did permit the conclusion that deterioration of paper impregnated with lubricating oil would become apparent much sooner than if insulating oil were used. Oxidation, although probably existing, was apparently too slow to affect the results. / Master of Science

Dans ce rapport de thèse, nous présentons les résultats obtenus avec la croissance d'assemblages supramoléculaires hautement cristallins et stables à température ambiante sur des surfaces isolantes d'halogénures d'alcalins. L'objectif de cette étude est de caractériser structurellement ces réseaux auto-assemblés et de mettre en évidence l'ensemble des forces d'interaction mises en œuvre dans les processus de croissance et de diffusion, en combinant la microscopie à force atomique en mode non contact (nc-AFM) sous ultravide et des calculs théoriques basés sur la théorie de la fonctionnelle de la densité (DFT) et la dynamique moléculaire. Nous montrons comment des paramètres bien définis concernant le choix de la molécule d'une part tels que sa taille, sa forme, sa symétrie, sa flexibilité et sa fonctionnalité, et le choix du substrat d'autre part, influent sur la morphologie de croissance et permettent de contrôler les propriétés de diffusion des molécules en surface et donc la structure supramoléculaire résultante. / In this thesis, we report the results obtained with the growth of highly crystalline and stable supramolecular assemblies at room temperature on insulating surfaces of bulk alkali halides single crystals. The objective of this study is to structurally characterize these self-assembled networks and understand all the interaction forces involved in the growth and diffusion processes. This is performed by joint non-contact atomic force microscopy (nc-AFM) experiments in ultrahigh vacuum and theoretical calculations based on density functional theory (DFT) and molecular dynamics. We show how well-defined parameters for the choice of the molecule on the one hand such as size, shape, symmetry, flexibility and functionality, and the choice of the substrate on the other hand, influence the morphology growth and serve to steer the structure and diffusion properties of such systems.