Effective gages to measure skin friction and heat transfer have been established over decades. One of the most important criteria in designing such a gage is the physical size of the gage to minimise the interference of the flow, as well as the mass of these devices. The combined measurement of skin friction and heat flux using one single gage on the other hand, present unique opportunities and with it, unique technical problems. The objective of this study is therefore to develop a cost-effective single gage that can be used to measure both skin friction and heat flux. The method proposed in this study is to install a coaxial thermocouple into an existing skin friction gage to measure the unsteady temperature on the surface of the gage. By using the temperature history and a computer program the heat flux through the surface can be obtained through an iterative guessing method. To ensure that the heat flux through the gage is similar to the heat flux through the rest of the surface, the gage is manufactured of a material very similar to the rest of the surface. Walker developed a computer program capable of predicting the heat flux through a surface from the measured surface temperature history. The program is based on an inverse approach to calculate the heat flux through the surface. The biggest advantages of this method are its stability and the small amount of noise induced into the system. The drawback of the method is that it is limited to semi-infinite objects. For surfaces with a finite thickness, a second thermocouple was installed into the system some distance below the first thermocouple. By modifying the computer program these two unsteady temperatures can be used to predict the heat flux through a surface of finite thickness. As part of this study, the effect of noise induced by the Cook-Felderman technique, found in the literature were investigated in detail and it was concluded that the method proposed in this study is superior to this Cook-Felderman method. Heat flux measurements compared well with measurements recorded with heat flux gages. In all cases evaluated the difference was less than 20%. It can therefore be concluded that heat flux gages on their own can measure surface heat flux very accurately. These gages are however too large to install in a skin-friction gage. The method introduced in this study is noisier than the heat flux gages on their own, but the size which is very important, is magnitudes smaller when using a coaxial thermocouple, to measure the surface temperature history. / Master of Science

No / BACKGROUND: A Full Thickness Macular Hole (FTMH) is often associated with vitreomacular traction, and this can be asymmetric with vitreomacular traction on one side of the hole but not the other. In cross-section, the elevated retinal rim around a developed FTMH is seen as a drawbridge elevation, and this drawbridge elevation may be used as a measure of morphological change. Examination of the drawbridge elevation of the retinal rim in FTMH with asymmetric vitreomacular traction may help to clarify the role of vitreomacular traction in the development of FTMH. METHOD: Cases of FTMH were identified with an initial OCT scan showing vitreomacular traction on one side of the hole only and that had a follow-up OCT scan showing progression of the hole. A tangent to the retinal surface at a distance of 700 microns from the axis of the hole was used as a marker of the drawbridge elevation of the retinal rim around the macular hole. Comparisons of the drawbridge elevation and change in drawbridge elevation between the sides with and without initial vitreomacular traction were made. RESULTS: There was no significant difference between the drawbridge elevation, or change in drawbridge elevation, on the side of the hole with initial vitreomacular traction compared to the side without initial traction. CONCLUSION: There is some intrinsic mechanism within the retina to link the morphological changes on the two sides of a FTMH. A bistable hypothesis of FTMH formation and closure is postulated to explain this linkage.

Glacial isostatic adjustment (GIA) is the process by which the solid Earth responds to past and present-day changes in glaciers, ice caps, and ice sheets. This thesis focuses on vertical crustal motion of the Earth caused by GIA, which is influenced by several factors including lithosphere thickness, mantle viscosity profile, and changes to the thickness and extent of surface ice. The viscosity of the mantle beneath Antarctica is a poorly constrained quantity due to the rarity of relative sea-level and heat flow observations. Other methods for obtaining a better-constrained mantle viscosity model must be investigated to obtain more accurate GIA model predictions. The first section of this study uses seismic wave tomography to determine mantle viscosity. By calculating the deviation of the P- and S-wave velocities relative to a reference Earth model (PREM), the viscosity can be determined. For Antarctica mantle viscosities obtained from S20A (Ekstrom and Dziewonski, 1998) seismic tomography in the asthenosphere range from 1016 Pa∙s to 1023 Pa∙s, with smaller viscosities beneath West Antarctica and higher viscosities beneath East Antarctica. This agrees with viscosity expectations based on findings from the Basin and Range area of North America, which is an analogue to the West Antarctic Rift System. Section two compares bedrock elevations in Antarctica to crustal thicknesses, to infer mantle temperatures and draw conclusions about mantle viscosity. Data from CRUST 2.0 (Bassin et al., 2000), BEDMAP (Lythe and Vaughan, 2001) and specific studies of crustal thickness in Antarctica were examined. It was found that the regions of Antarctica that are expected to have low viscosities agree with the hot mantle trend found by Hyndman (2010) while the regions expected to have high viscosity are in better agreement with the trend for cold mantle. Bevis et al. (2009) described new GPS observations of crustal uplift in Antarctica and compared the results to GIA model predictions, including IJ05 (Ivins and James, 2005). Here, we have generated IJ05 predictions for a three layered mantle (viscosities ranging over more than four orders of magnitude) and compared them to the GPS observations using a χ2 measure of goodness-of-fit. The IJ05 predictions that agree best with the Bevis et al. observations have a χ2 of 16, less than the null hypothesis value of 42. These large values for the best-fit model indicate the need for model revisions and/or that uncertainties are too optimistic. Equally important, the mantle viscosities of the best-fit models are much higher than expected for West Antarctica. The smallest χ2 values are found for an asthenosphere viscosity of 1021 Pa•s, transition zone viscosity of 1023 Pa∙s and lower mantle viscosity of 2 x 1023 Pa∙s, whereas the expected viscosity of the asthenosphere beneath West Antarctica is probably less than 1020 Pa∙s. This suggests that revisions to the IJ05 ice sheet history are required. Simulated annealing was performed on the ice sheet history and it was found that changes to the recent ice load history have the strongest effect on GIA predictions. / Graduate

Objetivos: Avaliar a composição corporal através da medida das dobras cutâneas (DC) intra e inter observador em mulheres na fase reprodutiva. Estimar a confiabilidade de dois protocolos de medidas de dobras cutâneas com o método Absorciometria Radiológica de Dupla Energia (DEXA). Métodos: A amostra foi composta por 90 mulheres com faixa etária de 18 a 37 anos, com Índice de Massa Corporal entre 18 e <= 39,9 Kg/m². A reprodutibilidade dos métodos foram avaliados pelos coeficientes de correlação de concordância (CCC) e coeficiente de Saint Laurent e pelos limites de concordância e gráficos de Bland-Altman. Resultados: A comparação intra observador foi excelente (CCC = 0,99) para os valores das medidas de DC tricipital, supraíliaca, coxa, soma das dobras e percentual de gordura. O mesmo ocorreu na comparação inter observador (CCC = 0,99). As medidas das DC tricipital foram as que apresentaram maior CCC (0,98), seguido da medida da coxa (0,90), e a medida da DC da suprailíaca foi a menor (0,89). A soma das DC e o percentual de gordura tiveram valores de 0,95. Já os protocolos de medidas de DC comparados entre si e com o padrão ouro DEXA, obtiveram valores de concordância baixa (0,35). Conclusões: Nossos achados mostraram que a comparação intra e inter observador foi satisfatória, contribuindo para a reprodutibilidade das medidas de DC. Os protocolos de avaliação das DC não tiveram concordância quando comparados com a DEXA / Objectives: Assessing body composition by measuring the intra and inter observer skin folds in women in the reproductive phase and estimate the reliability of two protocols skinfold measures with radiographic absorptiometry method of dual energy absorptiometry (DEXA). Methods: The sample consisted of 170 women aged 18-37 years with body mass index between 18 and <= 39.9 kg / m². The reproducibility of methods and skinfold thickness were evaluated by the coefficient of concordance correlation (CCC) and coefficient of Saint Laurent and the limits of agreement and Bland-Altman. Results: Comparison intra observer was excellent with the same values of the CCC (0.99) for the measurements of skinfold thickness of the triceps, suprailiac, thigh and fat percentage. The same occurred in the comparison inter observer (CCC = 0.99). The measures of skinfold thickness of the triceps showed the greatest CCC (0.98), followed by thigh (0.90), and the suprailiac was the lowest (0.89). The sum of the measurements of skinfold thickness and the percentage of fat had CCC values of 0.95. Already the reliability of two protocols skinfold thickness measures compared with the gold standard DEXA method was low (CCC = 0.35). Conclusions: Our findings showed that compared intra and inter observer was satisfactory, contributing to the reproducibility of skin folds. Assessment protocols skinfold did not have agreement when compared with DEXA

Objetivos: Avaliar a composição corporal através da medida das dobras cutâneas (DC) intra e inter observador em mulheres na fase reprodutiva. Estimar a confiabilidade de dois protocolos de medidas de dobras cutâneas com o método Absorciometria Radiológica de Dupla Energia (DEXA). Métodos: A amostra foi composta por 90 mulheres com faixa etária de 18 a 37 anos, com Índice de Massa Corporal entre 18 e <= 39,9 Kg/m². A reprodutibilidade dos métodos foram avaliados pelos coeficientes de correlação de concordância (CCC) e coeficiente de Saint Laurent e pelos limites de concordância e gráficos de Bland-Altman. Resultados: A comparação intra observador foi excelente (CCC = 0,99) para os valores das medidas de DC tricipital, supraíliaca, coxa, soma das dobras e percentual de gordura. O mesmo ocorreu na comparação inter observador (CCC = 0,99). As medidas das DC tricipital foram as que apresentaram maior CCC (0,98), seguido da medida da coxa (0,90), e a medida da DC da suprailíaca foi a menor (0,89). A soma das DC e o percentual de gordura tiveram valores de 0,95. Já os protocolos de medidas de DC comparados entre si e com o padrão ouro DEXA, obtiveram valores de concordância baixa (0,35). Conclusões: Nossos achados mostraram que a comparação intra e inter observador foi satisfatória, contribuindo para a reprodutibilidade das medidas de DC. Os protocolos de avaliação das DC não tiveram concordância quando comparados com a DEXA / Objectives: Assessing body composition by measuring the intra and inter observer skin folds in women in the reproductive phase and estimate the reliability of two protocols skinfold measures with radiographic absorptiometry method of dual energy absorptiometry (DEXA). Methods: The sample consisted of 170 women aged 18-37 years with body mass index between 18 and <= 39.9 kg / m². The reproducibility of methods and skinfold thickness were evaluated by the coefficient of concordance correlation (CCC) and coefficient of Saint Laurent and the limits of agreement and Bland-Altman. Results: Comparison intra observer was excellent with the same values of the CCC (0.99) for the measurements of skinfold thickness of the triceps, suprailiac, thigh and fat percentage. The same occurred in the comparison inter observer (CCC = 0.99). The measures of skinfold thickness of the triceps showed the greatest CCC (0.98), followed by thigh (0.90), and the suprailiac was the lowest (0.89). The sum of the measurements of skinfold thickness and the percentage of fat had CCC values of 0.95. Already the reliability of two protocols skinfold thickness measures compared with the gold standard DEXA method was low (CCC = 0.35). Conclusions: Our findings showed that compared intra and inter observer was satisfactory, contributing to the reproducibility of skin folds. Assessment protocols skinfold did not have agreement when compared with DEXA

Standard crystalline silicon photovoltaic (PV) modules are designed to continuously convert solar energy into electricity for 25 years. However, the continual generation of electricity by the PV modules throughout their designed service life has been a concern. The key challenge has been the untimely fatigue failure of solder interconnections of solar cells in the modules due to accelerated thermo-mechanical degradation. The goal of this research is to provide adequate information for proper design of solar cell solder joint against fatigue failure through the study of cyclic thermo-mechanical stresses and strains in the joint. This is carried-out through finite element analysis (FEA) using ANSYS software to develop the solar cell assembly geometric models followed by simulations. Appropriate material constitutive model for solder alloy is employed to predict number of cycles to failure of solder joint, hence predicting its fatigue life. The results obtained from this study indicate that intermetallic compound thickness (TIMC); solder joint thickness (TSJ) and width (WSJ) have significant impacts on fatigue life of solder joint. The impacts of TIMC and TSJ are such that as the thicknesses increases solder joint fatigue life decreases. Conversely, as solder joint width (WSJ) increases, fatigue life increases. Furthermore, optimization of the joint is carried-out towards thermo-mechanical reliability improvement. Analysis of results shows the design with optimal parameter setting to be: TIMC -2.5μm, TSJ -20μm and WSJ -1000μm. In addition, the optimized model has 16,264 cycles to failure which is 18.82% more than the expected 13,688 cycles to failure of a PV module designed to last for 25 years.

M. Tech. (Mechanical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / The purpose of this study was to design a composite overwrapped pressure vessel by combining the best optimal structural options. This study investigated the effects of constituents such as fibre and shell thickness, on the bursting strength. Thereafter, these constituents were combined in order to achieve optimization of strength for an improved sustainable composite pressure vessel. The analytical method was carried out using the Tsai-wu failure theorem. The developed analytical equations were solved with Matlab 2016 software to determine composite fibre and shell thickness. With variation of the vessel’s liner, a total of 56 parts were created on two different profiles with purpose of generating of vessels resistant to bursting failure. Henceforth, the structural integrity of fibre imparted into the design was optimally analyzed at an angle of 55⁰, through the negative and positive directions. The shell thickness overwrapping the liner, being as well an influential factor to this optimization, was, therefore, analyzed on symmetrical and asymmetrical lamination patterns. The optimal fibre and shell thickness range were thereafter determined on a first ply failure and hoop stress threshold approach. Additionally, the identified optimal range of pressure vessel constituents were numerically validated, on Abaqus/CAE software, to have a degree of reassurance on the result generated, using Hashin failure criteria. Optimal design with improved strength and weight factor was therefore achieved by combining the generated optimal vessel constituents yielded from Minitab software version 2016. The generated results of the study revealed no change on the fibre thickness determined with respect to direction. For shell thickness on the other hand, asymmetrical pattern was identified as the desired sequence of lamination. In addition, with two profiles considered in the research, the composite constituents were found for a p value of 0.066, to be optimal on profile 1 at 0.0048 mm of liner, 0.0005 mm of fibre and 0.0027 mm of shell. The profile 2 on the other hand, revealed optimization of liner at 0.0095 mm, fibre at 0.0021 mm and shell at 0.0055 mm. Through combination of these ultimate constituents the response optimizer on Minitab software generated optimal bursting strength with factor of 4% improvement with a weight reduction of 33% compared to the stainless steel vessel. It was, therefore, concluded that profile 1 was the most optimal with hoop strength of 123.43 MPa, Von Mises of 178.56 MPa and Tresca of 179.48 MPa.

No description available.

No / Ultrasonic technology provides a powerful and noninvasive method of in-process measurement during injection molding and extrusion. Changes in the velocity, attenuation and reflection coefficients of high frequency sound waves can be related to the state and conditions of the materials through which they propagate. The velocity of an ultrasonic wave changes with density and elastic moduli; this allows information on solidification and material properties to be collected during the molding cycle. The time of flight of the wave is a function of velocity and path length. This paper shows that it can be correlated with the residual wall thickness of polymer in the mold during gas assisted injection molding.

Motivation - Brain-derived neurotrophic factor (BDNF) is a protein complex, synthesised and secreted mainly by the central nervous system and is involved in neuronal maintenance. Research suggests that BDNF is implicated in various neurological and psychiatric diseases, while recent evidence suggests a role for the neurotrophin on the periphery as well. Indeed, the specific functional role of BDNF and its action mechanism in the cardiovascular system, especially in that of Africans, is yet to be determined. The cardiovascular health profile of black South Africans is a major concern as research has shown that this group suffers from an array of cardiovascular risk factors that may result in organ damage. Sub-clinical atherosclerosis or structural endothelial dysfunction contributes to ever-increasing morbidity and mortality in the world. However, no studies regarding the associations between BDNF and structural vascular disease have been undertaken relating to black African participants. Objectives - The objective of this study was to determine whether BDNF is associated with changes in ambulatory blood pressure (BP) and whether a relationship between BDNF and structural endothelial dysfunction exists in black African male and female participants, determined by cross sectional wall area (CSWA) and albumin:creatinine ratio (ACR). Methodology - The study included 172 black African teachers (82 males and 90 females) who were employed by the Kenneth Kaunda Education district of the North-West Province, South Africa. Ambulatory blood pressure recordings were obtained with the use of a Meditech CE120 CardioTens ® apparatus. Blood pressure readings were measured at 30 min intervals during the day and 60 min intervals during the night. Anthropometric measurements were performed in triplicate by registered level II anthropometrists according to standardised procedures. A high-resolution ultrasound scan with carotid intima-media thickness (CIMT) images from at least two optimal angles of the left and right common carotid artery were obtained using a SonoSite Micromaxx ultrasound system. The lumen diameter between the near and far wall of the lumen-intima interface and the averages of both the left and right common carotid arteries were calculated. Subsequently, the carotid cross-sectional wall area (CSWA) was calculated. Participants, who fasted overnight, provided eight-hour blood and urine samples to determine serum BDNF and metabolic markers, for example, hyperglycaemia (HbA1c) and gamma glutamyl transferase (GGT). Urinary albumin and creatinine levels were determined by means of a turbidimetric method with the use of a Unicel DXC 800 analyser from Beckman and Coulter (Germany) and expressed as a ratio between albumin and creatinine (ACR). BDNF median split x Gender interaction effects for structural ED justified stratification of BDNF into low and high (≤ / > 1.37 ng/ml) gender groups. Results and Conclusion - On average, male participants were overweight (BMI 25-30kg/m2) and abused more alcohol.21 African men revealed a vulnerable cardiometabolic profile with values exceeding cut–points (European Society of Hypertension). These men demonstrated increased acute and chronic glucose (HbA1c) levels indicating a pre-diabetic state; as well as a disturbed lipid profile with lower HdL and increased triglycerides. Overall BDNF levels were lower than reference ranges (6.97 – 42.6 ng/ml). The men revealed mean lower BDNF levels, ambulatory BP values exceeding guideline cut-points (ambulatory SBP > 130mmHg; DBP > 80mmHg) as well as a hypertensive state compared to their female counterparts. Pertaining to structural endothelial dysfunction, the mean ACR value in men exceeded normal laboratory values (< 3.5mg/mmol). The African women displayed an obese state with low grade inflammation (CRP, 12.27 ± 11.67mg/l). A single two-way ANCOVA interaction on main effects (BDNF median split x Gender) demonstrated significant interaction for CIMTf [F (1,164); 3.99, p=0.05] and cholesterol [F (1,164); 4.12, p=0.05]. Therefore, a median split approach was followed which stratified gender groups into lower (≤ 1.37 ng/ml) and higher BDNF levels (>1.37 ng/ml). The low BDNF men revealed higher cholesterol than the high BDNF group, independent of BMI and age. Only the low BDNF women indicated significantly higher values for structural vascular markers (p< 0.05) than the high BDNF female group. In conclusion, we accept our hypothesis, as hypertrophic remodelling of the carotid artery was associated with lower BDNF levels. This may imply attenuated or possibly down-regulated BDNF levels acting as a compensatory mechanism for the mean higher BP levels. In women, metabolic risk and hypertrophic remodelling were evident within higher circulating levels of BDNF, underpinning different underlying mechanisms for impaired neurotrophin health in men and women. Novel findings of BDNF revealed the impact of central neural regulation on the circulatory system, which may contribute to cardiometabolic risk in Africans. / MSc (Physiology), North-West University, Potchefstroom Campus, 2014