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Thesis (DTech (Science))--Peninsula Technikon, Cape Town, 2003. / The impetus for the refinement and renewal of daily-used products has spurred international interest in investigating the small in homogeneities that might exist in these products. This interest has become an important part in the design philosophy, which is based on structural information gained by the analysis of these products. It is this drive that initiated the study to investigate the simultaneous use of novel nuclear analytical techniques such as micro proton induced X-ray emission( u-PlXE), micro proton induced gamma-ray emission (u-PlGE) and micro proton backscattering (u-RBS) to achieved a broader and yet deeper insight into the fine structure of products. The fundamental underlying physical principles of these techniques are discussed to gain in-depth knowledge on how to them to obtain the desired information. Also determined was the degree of accuracy that could be attained in the application of this knowledge. These principles were evaluated in conjunction with the instrumentation with which the applicability of these techniques could then be further extended. More so is the use of sophisticated software that facilitated the use of both physical and instrumental parameters. After describing the necessary implements to achieve this further know-how, products of industrial origin were investigated to determine in homogeneities that existed in those products and compared those theoretical values. The first application was made to ceramic-based sorption electrodes to be used in the purification of wastewater.

This thesis relates a technique for increasing the optical strength of NaCl and KCl single-crystal samples. The 1.06-μm pulsed laser damage thresholds were increased by factors as large as 4.6 for a bulk NaCl single-crystal sample. The bulk laser damage breakdown threshold (LDBT) of the crystal was measured prior to and after heat treatment at 800*C using a Nd:YAG laser operating at 1.06 μm. Bulk and surface LDBTs were also studied on samples annealed at 400° C. These samples showed differences in damage morphology on both cleaved and polished surfaces, and the cleaved surfaces had improved damage thresholds. However, neither the polished surfaces nor the bulk showed improved threshold at the lower annealing temperature.

The effects of radiation on an operational amplifier were investigated through simulation. The μA 741 was simulated using Spice. Under normal conditions the 741 had the following properties: offset Voltage (Vos) of 0.8 mV, bias current (IB) of 27 nA, offset current (Ios) of 1 nA, and an open loop gain (A0.1.) of 112 dB. When exposed to neutron fluence of 5 x 10¹³ n/cm², these parameters changed to offset voltage of 45 mV, bias current of 1500 nA, offset current of 500 nA, and an open loop gain of 66 dB. A new circuit is proposed that provides improvements in the above parameters. The modified circuit gives a Vos of 3 mV, IB of 200 nA, Ios of 34 nA and A0.1. of 93 dB following exposure to a neutron fluence of 5 x 10¹³n/cm².

The ion implantation process is a very precise, controllable, and reproducible method used to enhance material properties of finished components such as ball bearings. Essentially, the target material is bombarded by accelerated ions to form a thin alloyed layer in the substrate. As the ions deposit their kinetic energy in the target it begins to heat up. To prevent thermal distortion in the finished pieces the ion implantation is performed at dose levels (dependent on the ion fluence and time duration of implantation) to insure that the target pieces stay at relatively low temperatures. Consequently, the low temperature requirement for many applications limits the economic, and probably, the physical success of ion implantation. The purpose of this study was to show the applicability of using a two-dimensional computer code developed to model plasma disruptions and subsequent energy deposition on a fusion reactor first wall to calculate surface and bulk temperature information during ion implantation. In turn the code may assist researchers pursuing development of adequate cooling for target materials in an attempt to overcome the low temperature constraint. All data supported the hypotheses that the two-dimensional code previously developed for fusion reactor applications was adequate to model the ion implantation process. / Graduation date: 1992

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Orientador: Rosana Maria Caram / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-19T03:21:43Z (GMT). No. of bitstreams: 1 Roriz_VictorFigueiredo_D.pdf: 10020580 bytes, checksum: b85781c508b837b2a89be30231390421 (MD5) Previous issue date: 2011 / Resumo: Saliências e reentrâncias existentes nas superfícies típicas das edificações, tanto na escala da rugosidade quanto das ondulações (de uma telha, por exemplo), constituem obstáculos que podem diferenciar o comportamento das mesmas em relação aos fluxos por radiação, se comparadas a superfícies perfeitamente lisas e planas. Absortividades e emissividades são propriedades dos materiais, enquanto absortâncias e emitâncias são características das superfícies, sendo influenciadas não apenas pelo material de que são constituídas, mas também por sua geometria. Esta pesquisa objetivou verificar tais influências, por meio de desenvolvimentos teóricos, e por procedimentos experimentais. Foi desenvolvido um modelo teórico de cálculo para o chamado "efeito cavidade", que permite estimar as absortâncias e emitâncias efetivas de uma superfície. As estimativas resultantes foram comparadas às obtidas em procedimentos clássicos para cálculo deste mesmo efeito. Foram realizados ensaios de campo, a céu aberto e sob condições climáticas reais, possibilitando uma análise do fenômeno na presença de outros fluxos de calor e sob a influência das diversas variáveis do clima. Para complementar os dados, experimentos foram realizados sob condições controladas, possibilitando aferir o modelo teórico. A fim de quantificar as implicações dos efeitos acima mencionados, simulações foram feitas no software EnergyPlus, considerando uma edificação de geometria simples, submetida ao clima da cidade de Brasília, com diferentes propriedades radiantes para as telhas. Adotando-se absortâncias e emitâncias efetivas, as simulações revelaram diferenças acima de 2.5oC nas temperaturas internas do ar, em relação às obtidas supondo-se que a cobertura fosse lisa e plana. No caso de uso de condicionadores de ar, esta diferença pode provocar uma variação de até 30% nas estimativas de consumo de energia elétrica. A pesquisa demonstrou que, para as superfícies normalmente encontradas nas edificações, o modelo proposto é adequado e pode contribuir para o aperfeiçoamento dos estudos de comportamento térmico e energético dos edifícios / Abstract: On surfaces perfectly flat and smooth, there are no obstacles to the radiant flow. However, typical surfaces of buildings have bumps and hollows that can significantly change the behaviour of them. The absorptivity and emissivity are properties of materials, while the emittance and absorptance are surface characteristics, being influenced not only by the material they are made, but also by its geometry and surface feature. This research aimed to verify such influences by means of theoretical and experimental procedures. A theoretical model for calculating the so-called "cavity effect" was developed, which allows to estimate the effective absorptance and Emittance of a surface. The resulting estimates were compared with those obtained in classical procedures for calculating the same effect. Field tests were conducted under actual weather conditions, allowing an analysis of the phenomenon in the presence of other heat fluxes and under the influence of different climate variables. To complement the data, experiments were performed under controlled conditions, allowing to test the theoretical model. In order to quantify the implications of the effects mentioned above, simulations were made with the software EnergyPlus considering a simple geometry building, submitted to the climate of the city of Brasilia, with different radiant properties of the roofs Adopting effective absorptances and emittance, simulation results show differences of up to 2.5 ° C in the internal air temperature, compared to those obtained ignoring the influences that the ripples of the tiles have on radiant flows. Considering the use of air conditioners, this could represent up to 30% variation in the energy consumption estimative. Research has shown that for surfaces typically found in buildings, the proposed model is adequate and may contribute to the improvement of thermal and behavioral studies of buildings / Doutorado / Arquitetura e Construção / Doutor em Engenharia Civil

The contributions of nonlinear absorption processes to laser-induced damage of three selected groups of transparent dielectrics were investigated. The studied materials were irradiated and non-irradiated fused silica, doped and undoped fluorozirconate glass and cubic zirconia stabilized with yttria. The laser-induced damage thresholds, prebreakdown transmission, and nonlinear absorption processes were studied for several specimens of each group. Experimental measurements were performed at wavelengths of 1064 nm and 532 nm using nanosecond and picosecond Nd:YAG laser pulses. In the irradiated fused silica and fluorozirconate glasses, we found that there is a correlation between the damage thresholds at wavelength λ and the linear absorption of the studied specimens at λ/2. In other words, the laser-induced breakdown is related to the probability of all possible two-photon transitions. The results are found to be in excellent agreement with a proposed two-photon-initiated electron avalanche breakdown model. In this model, the initial "seed" electrons for the formation of an avalanche are produced by two-photon excitations of E' centers and metallic impurity levels which are located within the bandgaps of irradiated Si02 and fluorozirconate glasses, respectively. Once the initial electrons are liberated in the conduction band, a highly absorbing plasma is formed by avalanche impact ionization. The resultant heating causes optical damage. In cubic zirconia, we present direct experimental evidence that significant energy is deposited in the samples at wavelength 532 nm prior to electron avalanche formation. The mechanism is found to be due to formation of color centers (F+ or F° centers) by the two-photon absorption process. The presence of these centers was directly shown by transmission measurements. The two-photon absorption (2PA) process was independently investigated and 2PA coefficients obtained. The accumulated effects of the induced centers on the nonlinear absorption measurements were also considered and the 2PA coefficients were measured using short pulses where this effect is negligible. At room temperature, the color centers slowly diffuse out of the irradiated region. The density of these centers was monitored as a function of time. The initial distribution of the centers was assumed to have a Gaussian profile. For this model the diffusion equation was solved exactly and the diffusion constant obtained.

This work investigates the challenges associated with designing silicon-germanium (SiGe) analog and mixed-signal circuits capable of operating reliably in extreme environment conditions. Three extreme environment operational conditions, namely, operation over an extremely wide temperature range, operation at extremely low temperatures, and operation under radiation exposure, are considered. As a representative for critical analog building blocks, bandgap voltage reference (BGR) circuit is chosen. Several architectures of the BGRs are implemented in two SiGe BiCMOS technology platforms. The effects of wide-temperature operation, deep cryogenic operation, and proton and x-ray irradiation on the performance of BGRs are investigated. The impact of Ge profile shape on BGR's wide-temperature performance is also addressed. Single-event transient response of the BGR circuit is studied through microbeam experiments. In addition, proton radiation response of high-voltage transistors, implemented in a low-voltage SiGe platform, is investigated. A platform consisting of a high-speed comparator, digital-to-analog (DAC) converter, and a high-speed flash analog-to-digital (ADC) converter is designed to facilitate the evaluation of the extreme environment capabilities of SiGe data converters. Room temperature measurement results are presented and predictions on how temperature and radiation will impact their key electrical properties are provided.