Ph.D.

Made available in DSpace on 2014-10-09T12:46:31Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:22Z (GMT). No. of bitstreams: 1 07977.pdf: 2200288 bytes, checksum: 75fcd64975e2719bf0f41d38ec387c77 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Cooling channels are designed in blades to protect the blades from damage at high temperature in a gas turbine. ELE Advanced Technology Ltd. is a UK company specialised in machining cooling channels in turbine blades using electro-chemical techniques. The wall thicknesses between these cooling channels and the surface of the turbine blade influences the performance of cooling channels and are required to be accurately machined and then inspected. At present, the company measures the wall thicknesses using a hand-held contact ultrasonic probe, which is time-consuming and not very accurate. In this project, an inspection machine has been designed and built for the purpose of automating the procedure of measuring wall thicknesses in turbine blades. The inspection machine measures wall thicknesses based on immersion ultrasonic testing technique and the actuator is a six-axis industrial robot controlled by a computer. Control algorithms have been developed to automate the entire measuring process. Acquired ultrasonic data is also automatically processed using Matlab scripts for wall thickness evaluation. However, prior to the ultrasonic measurement, the probe path has to be calculated. Matlab script has been developed to automatically calculate a probe path using a point cloud of the blade digitized on a CMM as an input. The calculation of the probe path, in general, involves triangulation, parameterisation and B-spline surface approximation. Normal 3D triangulation methods were tested; nevertheless, the results were unsatisfactory. Therefore, a triangulation algorithm is developed based on B-spline curve and 2D Delaunay triangulation. After the probe path is calculated, a localisation method, based on iterative closest point algorithm, is implemented to transform the probe path from CMM to the inspection machine. Several experiments were designed and conducted to study the capability of the ultrasonic probe. Experimental results confirmed the feasibility of using an immersion ultrasonic probe for measuring the wall thicknesses; however, the experiments revealed several limitations of immersion ultrasonic testing, such as the angle of incidence of ultrasonic waves must be maintained within an angular deviation of ±1° from the surface normal to achieve accurate test results. Wall thicknesses of three turbine blades from one batch were measured on the inspection machine. A CT scan image was used as reference to compare the measured wall thicknesses with results obtained using contact probes. The comparison showed the wall thicknesses measured on the inspection machine were much more accurate than using contact probes.

Made available in DSpace on 2014-10-09T12:46:31Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:22Z (GMT). No. of bitstreams: 1 07977.pdf: 2200288 bytes, checksum: 75fcd64975e2719bf0f41d38ec387c77 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

We present global and regional correlations between whole-rock values of Sr/Y and La/Yb and crustal thickness for intermediate rocks from modern subduction-related magmatic arcs formed around the Pacific. These correlations bolster earlier ideas that various geochemical parameters can be used to track changes of crustal thickness through time in ancient subduction systems. Inferred crustal thicknesses using our proposed empirical fits are consistent with independent geologic constraints for the Cenozoic evolution of the central Andes, as well as various Mesozoic magmatic arc segments currently exposed in the Coast Mountains, British Columbia, and the Sierra Nevada and Mojave- Transverse Range regions of California. We propose that these geochemical parameters can be used, when averaged over the typical lifetimes and spatial footprints of composite volcanoes and their intrusive equivalents to infer crustal thickness changes over time in ancient orogens.

Background: Fat distribution, rather than total body fat, has been identified as a significant risk factor for chronic disease. Patterning of subcutaneous fat, in particular, may play a pervasive role in shaping the metabolic milieu that is critical for disease development. Several studies have shown that early-life nutrition may influence later body composition. The effect of breastfeeding and formula feeding on early patterns of subcutaneous fat deposition, however, are uncertain. Objective: At a time when early infant growth is emerging as a predictor for later chronic disease, it is the aim of the present analysis to investigate whether feeding style (breastfeeding versus formula feeding) modifies subcutaneous fat growth rates and trajectories in the first year of life with a focus on the historical iterations of WHO infant feeding recommendations (0 to 4 months, 4 to 6 months, and 6 to 12 months of age). Methods: This is an ex post-facto design that utilizes data collected as part of a longitudinal growth study in the first year of life. Subcutaneous fat mass was anthropometrically assessed weekly by skinfold thickness (triceps, quadriceps, calf, subscapular, suprailiac, midaxillary, and abdominal) in 21 infants. Feeding data were collected through daily parental records and are entered here as a categorical variable (predominantly breast fed and predominantly formula fed). Multi-level mixed effects models for repeated measures were used (STATA 14) adjusting for age, sex, weight, birthweight, and number of feeding episodes per day. Statistical significance was accepted at p Results:Infants experienced fat accretion only during the first four months, and this was limited to peripheral skinfolds. Thereafter, subcutaneous skinfolds followed a trend of declining rates. Breastfed and formula fed infants, however, demonstrated different patterns of subcutaneous fat deposition in both the sum of skinfolds and in each skinfold site. During the first four months, formula fed infants experienced greater rates for the subscapular, abdominal, suprailiac, trunk, quadriceps, sum of skinfolds (p Conclusion: Weekly skinfold assessments of seven subcutaneous sites have identified that feeding style predicts differences in deposition patterns in the first year of life. Breastfed infants demonstrated both slower rates of accretion and decline by comparison with their formula fed peers. This analysis further suggests that the first four months may be a critical period for subcutaneous fat deposition. Feeding specific effects were identified for truncal deposition and utilization, which suggests that future studies may benefit from depot-specific inquiries.

The uniform thickness of knots has been used to investigate knotted polymers and DNA strands. Even though these structures carry great length, it is unusual for them to contain knots. However, when they do, it can cause gene malfunctions. In fact, scientist have demonstrated that knotting may cause a loss of genetic material by blocking DNA replication and also blocking transcription of a gene into its active protein. Since it is possible for biological structures, such as polymers and DNA strands, to exhibit forces or charges of different strengths the idea of a non uniform thickness of a knot is explored. In his work, O. Durumeric provides a definition for the non uniform thickness. This thesis will provide an alternative characterization for the non uniform thickness of a knot, which is more conducive to computer calculations.

<p> Background: Vitamin D activity is important for the functioning of a broad range of body systems. Some of these, including the skeletal, immune, and cardiovascular systems, are particularly relevant in the management of HIV-infection; thus, and in consideration of evidence that factors associated with the scenario of HIV-infection can disrupt vitamin D metabolism, the assessment of vitamin D status in people living with HIV-infection may be particularly important. In this thesis, I address cardiovascular implications of vitamin D status in HIV-infection. More specifically, and based on a growing body of evidence implicating low vitamin D status in the development of cardiovascular disease (CVD), I hypothesized that in HIV-positive adults low 25-hydroxyvitamin D (25(0H)D) concentration would be associated with increased subclinical vascular disease as measured by carotid intima-medial thickness (IMT).</p> <p> Methods: Using regression analyses I cross-sectionally studied the relationship between 25(0H)D and carotid IMT in 283 participants of the Canadian HIV Vascular Study, a prospective study of CVD risk among HIV-positive Canadians.</p> <p> Results: The prevalence of vitamin D deficiency in the Canadian HIV Vascular study was surprisingly low. Plasma 25(0H)D by quartile was not associated with carotid IMT. However, in restricted cubic spline regression analyses designed to accommodate non-linearity there was evidence of an inverted U-shaped 25(0H)D-carotid IMT relationship. In exploratory regression models restricted to participants comprising the suboptimal range of vitamin D status, lower 25(0H)D concentration was statistically significantly associated with lower carotid IMT after adjustment for known CVD risk factors and other variables hypothesized to potentially confound a 25(0H)D-carotid IMT association.</p> <p> Main implication: While inference from these exploratory findings requires cautious interpretation, future investigations into the relationship between vitamin D status and vascular disease should consider the problem of non-linearity as a feature of primary analyses; otherwise, such studies might fail to detect a true association.</p> / Thesis / Master of Science (MSc)

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