Diploma thesis deals with elastohydrodynamic lubrication of point contacts, which surfaces are influenced by topography and velocity vector of one rubbing surface is misaligned. Author summarizes knowledge of previously published research articles, which fundamentally enrich current state of knowledge. Diploma thesis contains experimental measurement results of the film thickness and the way of lubrication film formation in elliptical contact for different ellipticity parameters, kinds of rubbing surfaces and angles of the velocity vector. New findings have helped to better understand the behaviour of highly loaded lubricated contacts taking place in machine components and completed the current state of knowledge with results that can be used in next thorough study of this issue.

This diploma thesis deals with experimental study of the effect of surface grooves on distribution of lubricant film in elastohydrodynamic lubricated point contact. Lubricant film thickness was measured by ball-on-disc apparatus using an optical interferometry technique - thin film colorimetric interferometry. The effects of groove geometry, lubricant and operating conditions were studied in this diploma thesis. The effects of these variables are evaluated based on newly suggested parameter Rgi (groove influence ratio). Groove influence ratio is defined as an influenced film thickness influenced by groove divided by film thickness for smooth surfaces.

This thesis deals with the experimental study of the formation of the lubricating film used for sintered metal parts impregnated with oil. The thickness of the lubricating film in a line contact is measured by the method of optical interferometry of thin lubricating films. In this thesis, the effects of various operating parameters on the formation of the lubricating film are described. The usage of impregnated lubricant leads to insufficient supply of lubricant to the contact. Individual results are significantly influenced by the degree of flooding of the contact area.

Positive identification can be problematic if fingerprinting, DNA, dental history, etc. are no longer available. This may be possible through techniques such as facial approximation, but any form of craniofacial identification requires intimate knowledge of human craniofacial anatomy. Where children are involved, craniofacial changes due to facial growth further complicate matters and require knowledge of tissue thickness and variation in facial shapes. These have hardly been studied in children of African descent. The aims of this study were to provide data on tissue thickness and craniofacial proportions of South African Black and Coloured children and to document the lateral profile shape changes between the ages of 6 and 13 years. Tissue thickness was measured using cephalograms of South African children (n = 388). After digitizing the images, tissue thickness measurements were taken at 11 mid-facial landmarks from each image using the iTEM measuring program. Craniofacial proportions were assessed through assessing standardized anterior and lateral facial photographs of 1749 children. Measurements of facial features were taken using iTEM, from which 28 standard facial indices were calculated. For both tissue thickness and craniofacial indices comparisons between groups per age, sex and ancestry were statistically analyzed. In addition, geometric morphometrics were used to describe lateral facial shape changes and differences age, sex and ancestry (n = 800). The results showed that tissue thickness differences at lower face landmarks are more pronounced in age groups per ancestry as opposed to differences per age and sex. Facial profile per facial shape, class and ancestry showed differences at all landmarks. Craniofacial indices indicated that Coloured children have wider heads, foreheads and faces compared to Black children. The height of the nose and lower lip is longer in Coloured children compared to Black children. In Coloured children, mandibular height and lower face height is shorter in relation to total face height. Males have wider heads, foreheads, mandibles and faces compared to females. The degree of prognathism is dictated by ancestry and to a lesser extent by age and sex as findings showed that maxillary prognathism was more prominent in Black children, while mandibular prognathism were more pronounced in male children. South Africans have a relative concave lateral facial profile due to the maxilla and mandible being more prognathic than in North American children. Differences in lateral face shape between children of various ages, sexes and ancestral groups were visualized through the relative displacement of landmarks related to the forehead and lower face. The resultant differences in lateral facial profile can assist in more accurate estimation of age and ancestry of unknown children. This research created reference datasets for tissue thickness and craniofacial indices of South African children of Black and Coloured ancestry per age and sex that will be useful in the diagnosis of facial dysmorphology and for facial reconstruction / approximation of juvenile remains. It also shed more light on facial growth patterns in the various groups. / Thesis (PhD)--University of Pretoria, 2015. / tm2015 / Anatomy / PhD / Unrestricted

Hydroplaning is a major concern on high speed roadways during heavy rainfall events. Hydroplaning tools are widely used by designers to reduce their roadway’s hydroplaning potential, therefore reducing the possibilities of severe crashes. This dissertation presents two methodologies for improving the prediction of hydroplaning potential. The first phase focused on improving an existing widely used software called PAVDRN. Using multiple datasets from the Florida Department of Transportation, the author filtered the data using specific criteria to leave only truly dynamic hydroplaning crashes. The author then evaluated PAVDRN’s prediction capabilities and assessed its reliability in predicting a hydroplaning crash. Using past accident statistics, the author accounted for extraneous factors that are difficult to capture, such as driver behavior, and obtained probability factors for a more realistic estimate of hydroplaning risk on roadways. The second phase focused on improving the modeling technique used in hydroplaning prediction tools. Currently when assessing a roadway’s hydroplaning potential, the roadside drainage is not considered in the analysis. The author modeled a combined pavement-drainage system using a 1D/2D method to better capture the effects of roadside drainage, especially in the events of flooding. The methodology used in modeling successfully captures the backwater effects that are caused under critical flooding conditions. Lastly the author created a new tool (MY-PAVDTCH) to provide design engineers with updated waterfilm thickness values under roadside drainage flooded conditions.

In the field of apparatus engineering and pipeline construction wall thicknesses of 100 mm are processed and joined with heated tool butt welding. The welding procedure is regarded as well-understood. However, there are no systematic experimental investigations into the wall thicknesses above 30 mm published. The welding parameters for high wall thicknesses of PE (polyethylene) and PP (polypropylene) are extrapolated as it is given in the guidelines of DVS (Deutscher Verband für Schweißen und verwandte Verfahren e.V.). However, cases of damage to welded pipelines show that not enough understanding of the process management and the weld properties is available for the welding of large pipe dimensions. The present study investigates the welding behaviour of semi- finished products (plates and pipes) with wall thicknesses up to 100 mm. The mechanical properties are tested in short-term tests and in long-term tensile creep tests. The results relating to the fusion behaviour basically show a curved melt profile which influences the mechanical behaviour of the welded components. The tensile creep tests establish a tendency towards the premature failure of the peripheral regions.

Magister Scientiae (Medical Bioscience) - MSc(MBS) / Cardiovascular diseases (CVD) are among the top 10 causes of death in all ages in South Africa. The prevalence of maternal smoking and alcohol consumption during pregnancy is alarmingly high in South Africa. In utero exposure to nicotine and alcohol may cause CVD later in life. There is a global need for early detection of CVD especially those vulnerable during early childhood, to prevent the development of CVD risk factors in adulthood. The aim of this study was to compare CVD risk in five-year-old children from a low socio-economic population with in utero dual exposure to nicotine and alcohol and in utero nicotine exposure by measuring carotid intima-media thickness (cIMT), anthropometric measurements and clinical measurements including blood pressure. A case-control study was conducted on 468 children at five years old through interviews to collect data on demographic characteristics and health statistics. The cIMT was measured using B-mode ultrasonography. Anthropometric measurements were taken such as skinfold thickness, waist circumference, height and weight to calculate Body Mass Index (BMI). Blood pressure measurements such as systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) and heart rate (HR) were taken. The data was analysed using SPSS version 26. Descriptive and inferential statistics (Spearman’s correlations, non-parametric partial correlations), Kruskal-Wallis H, Chi-square tests and logistic regression were used for statistical analysis. Results showed a significantly higher right cIMT (RcIMT) (0.36 ± 0.05 mm; P < 0.01) in children with in utero exposure to nicotine and alcohol during pregnancy and a higher RcIMT in males (0.37 ± 0.06 mm; P < 0.01) with in utero dual exposure to nicotine and alcohol when compared to females. A significant association was found between in utero dual exposure to nicotine and alcohol and a high RcIMT, specifically in females at five years old after the adjustment for confounders (B= -1.618, P = 0.002). Consequently, females in the dual exposed group were 7.6 times more likely to exhibit higher RcIMT with a relative risk of 2.6 times greater to children with no exposure. Females also had significantly higher SBP (U= 3829.50, p <0.01), DBP (U= 3527.50, p <0.05), MAP (U= 3561.00, p <0.05) and HR (U= 3887.50, p <0.01) in the dual exposed group. Cardiovascular risk factors were modestly prevalent at five years old in children with in utero teratogen exposures. However, increased adiposity indices were not observed in this population at five years old and were not associated with teratogen exposures. This may indicate that dual exposure to nicotine and alcohol has a significant effect on the intima-media thickness of the carotid arteries in children, but not necessarily on central and peripheral adiposity at five years old. Therefore, CVD risk factors need to be identified early in children in low socioeconomic regions with in utero exposure to nicotine and alcohol to prevent CVD later in life.

Background: Skinfold thickness (ST), waist circumference (WC) and hip circumference (HC) measurements are simple methods for assessing fat tissue at defined body parts. We examined these parameters in a cohort of healthy children and adolescents in Leipzig. Our study provides current percentile curves for biceps, triceps, subscapular and iliac crest ST, plus WC, HC, Waist-to-Hip Ratio and Waist-to-Height Ratio. Materials and methods: 6,344 visits were recorded involving 2,363 individuals from 3 to 16 years in age. Continuous age- and gender-related percentiles (3rd, 10th, median, 90th, 97th percentiles) were estimated using Cole's LMS method. Results: For biceps and triceps ST, boys show a peak at the beginning of adolescence with a subsequent decrease, while percentile values among girls rise across the age range. Subscapular and iliac crest percentiles also show increasing curves with disproportionately high values for P90 and P97. Boys show higher values of WC, girls have higher levels of HC. WC and HC median percentiles constantly increase in both sexes with a plateau at the age of 16 for girls. Conclusion: Trends for all parameters of body fat are in line with other national and international studies. Unlike the KiGGS study, our study provides circumference data across the whole of our age range, i.e. from 3-16 years.:I. Abkürzungsverzeichnis 1. Vorbemerkung 2. Wissenschaftlicher Hintergrund 2.1. Übergewicht und Adipositas im Kindes- und Jugendalter 2.2. Bestimmung des Körperfettanteils bei Kindern und Jugendlichen 2.3. Die Bedeutung kindlichen Übergewichts und dessen Folgeschäden 2.4. Assoziation von Körperfettparametern und kardiovaskulären Risikofaktoren im Fokus 2.5. Anthropometrische Referenzwerte für Kinder und Jugendliche in Deutschland 3. Fragestellung 4. Publikation 5. Zusammenfassung der Arbeit 6. Literaturverzeichnis II. Anlagen 1. Abbildungen 2. Tabellen 3. Formeln nach Slaughter zur Abschätzung des Körperfettanteils III. Darstellung des eigenen Beitrags IV. Erklärung über die eigenständige Abfassung der Arbeit VI. Danksagung

The separation of solids from biological wastewater treatment is an important step in the treatment process, as it has a significant impact on effluent water quality. The moving bed biofilm reactor (MBBR) technology is a proven upgrade or replacement wastewater treatment system for carbon and nitrogen removal. However, a challenge of this technology is the characteristics of the effluent solids that results in their poor settlement; with settling being the common method of solids removal. The main objective of this research is to understand and expand the current knowledge on the settling characteristics of MBBR produced solids and the parameters that influence them. In particular, in this dissertation, the impacts are studied of carrier types, biofilm thickness restraint design of carriers, and varying carbonaceous loading rates on MBBR performance, biofilm morphology, biofilm thickness, biofilm mass, biofilm density, biofilm detachment rate, solids production, particle size distribution (PSD) and particle settling velocity distribution (PSVD). With this aim, three MBBR reactors housing three different carrier types were operated with varying loading rates. In order to investigate the effect of carrier geometrical properties on the MBBR system, the conventional, cylindrically-shaped, flat AnoxK™ K5 carrier with protected voids was compared to two newly-designed, saddle-shaped Z-carriers with the fully exposed surface area. Moreover, the AnoxK™ Z-200 carrier was compared to the AnoxK™ Z-400 carrier to evaluate the biofilm thickness restraint design of these carriers, where the Z-200 carrier is designed for greater biofilm thickness-restraint. The Z-200 carrier is designed to limit the biofilm thickness to the level of 200 µm as opposed to 400 µm for the Z-400 carrier. Finally, to investigate the effects of varying carbonaceous loading rates on system removal performance, biofilm characteristics and solids characteristics, further analyses were performed at three different loading rates of 1.5 to 2.5 and 6.0 g-sBOD/m2·d in steady-state conditions. The PSD and the PSVD analyses were combined to relate these two properties. A settling velocity distribution analytical method, the ViCAs, was applied in combination with microscopy imaging and micro-flow imaging to investigate the relation of PSD and settling behaviour of MBBR produced particles. The obtained results have indicated that the carrier type significantly impacted the MBBR performance, biofilm, and particle characteristics. As such, the K5 carrier MBBR system demonstrated a statistically significantly higher carbonaceous removal rate and efficiency (3.8 ± 0.3 g-sBOD/m2·d and 59.9 ± 3.0% sBOD removal), higher biofilm thickness (281.1 ± 8.7 μm), higher biofilm mass per carrier (43.9 ± 1.0 mg), lower biofilm density (65.0 ± 1.5 kg/m3), lower biofilm detachment rate (1.7 ± 0.7 g-TSS/ m2·d) and hence lower solids production (0.7 ± 0.3 g-TSS/d) compared to the two Z-carriers. The Z-carriers' different shape exposes the biofilm to additional shear stress, which could explain why the Z-carriers have thinner and denser biofilm, resulting in higher solids production and lower system performance in comparison with K5. Moreover, the carrier type was also observed to impact the particle characteristics significantly. PSD analysis demonstrated a higher percentage of small particles in the Z-carrier system effluent and hence a significantly lower solids settling efficiency. Therefore, the solids produced in the K5 reactor have shown enhanced settling behaviour, consisting of larger particles with faster settling velocities compared to Z-carriers. This dissertation also investigated the effects of restraint biofilm thickness on MBBR performance by comparing the Z-200 biofilm thickness-restraint carrier to the Z-400 carrier. No significant difference was observed in removal efficiency, biofilm morphology, biofilm density, biofilm detachment rate, and solids production between the Z-200 to the Z-400 carriers. The PSD and the PSVD analyses did not illustrate any significant difference in the particles’ settling behaviour for these two biofilm thickness restraint carriers, indicating that the biofilm thickness-restraint carrier design was not a controlling factor in the settling potential of MBBR produced solids. Finally, this research studied the effect of varying loading rates and demonstrated a positive, strong linear correlation between the measured sBOD loading rate and the removal rate, indicating first-order BOD removal kinetics. The biofilm thickness, biofilm density and biofilm mass decreased when the surface area loading rate (SALR) was increased from 2.5 to 6.0 g-sBOD/m2·d. The solids retention time (SRT) was also shown to decrease by increasing the SALR, where the lowest SRT (1.7 ± 0.1 days) was observed at the highest SALR, with the highest cell viability (81.8 ± 1.7%). Significantly higher biofilm detachment rate and yield were observed at SALR 2.5, with the thickest biofilm and a higher percentage of dead cells. Consequently, a higher fraction of larger and rapidly settling particles was observed at SALR of 2.5 g-sBOD/m2·d, which leads to a significantly better settling behaviour of the MBBR effluent solids. This study expands the current knowledge of MBBR-produced particle characteristics and settling behaviour. A comprehensive understanding of the MBBR system performance and the potential influencing factors on the MBBR produced solids, particle characteristics, and their settleability will lead to optimized MBBR design for future pilot- and full-scale applications of the MBBR.

Asphalt mixture microstructure is formed by aggregates, bitumen binder and air voids. Aggregates make for up to 90% of the mixtures volume and the structure formed by them will depend mostly on their size distribution and shape. The study presented in this thesis has as main objective to develop a framework that allows the characterization of asphalt mixtures based on the aggregates gradation and its impact on pavement performance. Moreover, the study aims to identify the range of aggregate sizes which form the load carrying structure, called Primary Structure, and determine its quality. The method has been developed as a numerical procedure based on packing theory of spheres. Parameters like porosity, coordination number and disruption factor of the Primary Structure; and a binder distribution parameter for the different sub-structures have been used to evaluate the quality of the load carrying structure and predict the impact on several failure modes. The distribution of bitumen binder has been derived from a geometrical model which relates porosity of the mixture with film thickness of particles considering the overlapping reduction as the film grows. The model obtained is a closer approximation to a physical characteristic of the compacted mixture separated according to different elements of the structure. The framework has been evaluated on several field and laboratory mixtures and predictions have been made about their rutting performance and moisture resistance. The calculated parameters have compared favourably with the performances reported from the field and laboratory testing. The developed gradation analysis framework has proven to be a tool to identify those mixtures with a poor rutting performance based on the gradation of the aggregates. The Gradation - Based Framework has satisfactory distinguished between good and bad performance of asphalt mixtures when related to permanent deformation and moisture damage. The calculated parameters have allowed identifying and understanding the main mechanisms and variables involved in permanent deformation and moisture damage of asphalt mixtures. The developed model can be used as a tool to determine the optimal gradation to assure good performance for hot mix asphalt pavements. / QC 20120626