University, Diss., 2005--Bonn.

Thesis (M. Eng.)(Electrical)--University of Pretoria, 2005. / Summaries in English and Afrikaans. Includes bibliographical references. Available on the Internet via the World Wide Web.

No description available.

Several different classes of trans-Neptunian objects (TNOs) have been identified based on their optical and near-infrared colors. As part of the Colours of the Outer Solar System Origins Survey (Col-OSSOS), we have obtained g-, r-, and z-band photometry of 26 TNOs using Subaru and Gemini Observatories. Previous color surveys have not utilized z-band reflectance, and the inclusion of this band reveals significant surface reflectance variations between sub-populations. The colors of TNOs in g - r and r - z show obvious structure, and appear consistent with the previously measured bi-modality in g - r. The distribution of colors of the two dynamically excited surface types can be modeled using the two-component mixing models from Fraser & Brown. With the combination of g - r and r - z, the dynamically excited classes can be separated cleanly into red and neutral surface classes. In g - r and r - z, the two dynamically excited surface groups are also clearly distinct from the cold classical TNO surfaces, which are red, with g - r greater than or similar to 0.85 and r - z less than or similar to 0.6, while all dynamically excited objects with similar g - r colors exhibit redder r - z colors. The z-band photometry makes it possible for the first time to differentiate the red excited TNO surfaces from the red cold classical TNO surfaces. The discovery of different r - z colors for these cold classical TNOs makes it possible to search for cold classical surfaces in other regions of the Kuiper Belt and to completely separate cold classical TNOs from the dynamically excited population, which overlaps in orbital parameter space.

The accumulating but small set of large semimajor axis trans-Neptunian objects (TNOs) shows an apparent clustering in the orientations of their orbits. This clustering must either be representative of the intrinsic distribution of these TNOs, or else have arisen as a result of observation biases and/or statistically expected variations for such a small set of detected objects. The clustered TNOs were detected across different and independent surveys, which has led to claims that the detections are therefore free of observational bias. This apparent clustering has led to the so-called "Planet 9" hypothesis that a super-Earth currently resides in the distant solar system and causes this clustering. The Outer Solar System Origins Survey (OSSOS) is a large program that ran on theCanada-France-Hawaii Telescope from 2013 to 2017, discovering more than 800 new TNOs. One of the primary design goals of OSSOS was the careful determination of observational biases that would manifest within the detected sample. We demonstrate the striking and non-intuitive biases that exist for the detection of TNOs with large semimajor axes. The eight large semimajor axis OSSOS detections are an independent data set, of comparable size to the conglomerate samples used in previous studies. We conclude that the orbital distribution of the OSSOS sample is consistent with being detected from a uniform underlying angular distribution.

Aux environs de Paris, entre le cœur d’agglomération et la couronne rurale, entre ville et campagne, s’étend un espace hybride où la part des espaces végétalisés – boisements, espaces agricoles, délaissés – est prépondérante mais fragmentée par les espaces bâtis. Le Conseil régional d’Île-de-France a cherché à mettre en valeur cet entre-deux au début des années 1980 au travers d’un projet de ceinture verte, outil d’aménagement conçu au cours du XXe siècle pour lutter contre l’étalement urbain. Faute de moyens, ne tranchant pas sur des limites précises, se chargeant de fonctions fluctuantes, la Ceinture verte est restée à l’état de projet flou. Dans le même temps, l’espace de la Ceinture verte n’a eu de cesse d’être investi par des attentes environnementales des citadins : quête d’un cadre de vie et de loisirs proches de la « nature », préoccupations en faveur de la biodiversité, recherche de services écosystémiques. Cette thèse montre le poids de ces attentes socio-environnementales sur la végétation, la territorialisation à laquelle elle participe ou la déterritorialisation dont elle est le symptôme, selon qu’elle est désirée ou délaissée. En observant les caractéristiques très anthropiques de la flore, cette thèse donne donc à voir la dimension sociale de la végétation en Ceinture verte, par-delà les velléités environnementales. Pour y parvenir, elle recourt à des méthodes géomatiques, d’analyse paysagère et de biogéographie (via des analyses statistiques multivariées de données botaniques originales), dans le cadre renouvelé d’une géographie environnementale qui participe indissociablement de la géographie physique et de la géographie humaine. En Ceinture verte, la question environnementale est d’abord un instrument de l’aménagement urbain contribuant à la qualité du cadre de vie au sein des espaces les plus favorisés (la vallée de Chevreuse est ici prise en exemple), et à la mise en ordre urbaine des espaces les moins bien intégrés à la métropole (la Plaine de Pierrelaye en est une illustration). Se construit ainsi à la périphérie de Paris une nature domestiquée, jardinée, urbanisée. / In the surroundings of Paris, between the urban heart and the rural outer ring, between the city and the countryside, lies an hybrid area mainly composed of vegetation spaces – woodland, cropland, spontaneous vegetation – which are fragmented by the urban sprawl. In the early 1980’s, the Île-de-France regional Council sought to protect those in-between spaces by promoting a Green belt. In the case of Paris, due to a lack of law support, confusions in the boundaries and evolving functions, the implementation of this planning tool, developed to contain urban sprawl along the 20th century, failed. Meanwhile, the area of the Green belt has never stopped gaining environmental attention from city dwellers. There, they especially seek a quality of life and leasures in « natural » landscapes, they are concerned about biodiversity preservation, they wish to benefit from ecosytem services. This thesis shows the impact of socio-environmental expectations on vegetation spaces by shaping or dismantling territories, depending on the attractiveness of the vegetation or its neglect. Hence, by highlighting the anthropogenic characteristics of plants, our work shows the social dimension of vegetation, despite the environmental intentions. Geomatic methods, landscape analysis and biogeography methods (statistical analysis of botanical data) are conveyed in the spirit of a renewed environmental geography which mingles physical and human geography. In the Île-de-France Green belt, environmental issues serve urban planning objectives, i.e. contribute to the quality of life in the wealthier parts (Vallée de Chevreuse is used as an example here) and put into urban order the less integrated areas (Plaine de Pierrelaye illustrates this aspect). As a result, a domesticated, gardened, even urbanised type of nature is being created in the surroudings of Paris.

Belt drives are used in numerous applications to transmit power between various machine elements. One limitation of the use of belt drives is the poor convergence of complex models which did not make them applicable for manufacturing use in industry. A source of convergence failure is the sharp changes in the solution. It is believed that the inclusion of an Elastic/Perfectly-Plastic (EPP) friction law into the belt/pulley contact mechanics can yield mathematical models with enhanced accuracy. This new friction model more accurately captures the true behavior of an elastic belt that exhibits microslip prior to fully-developed slip than previous regularized friction models. The Elastic/Perfectly-Plastic friction model was applied to a two-pulley flat belt system, and the equations of motions were derived using Hamilton's Principle. The results from the analytical model were compared to results from a finite element model. It was found that, unlike Coulomb's Law, the solutions with the EPP model had no slope discontinuities in the normal force. The elimination of these slope discontinuities could potentially help alleviate convergence issues for more complex models. It was also found that if the EPP spring stiffness is too small, then the belt cannot undergo the prescribed tension change. If it is too large, then the EPP model approaches Coulomb's Law and sharp changes appear. The Elastic/Perfectly-Plastic friction model was also applied to a v-belt model. It was found that the solutions and convergence properties with the EPP friction model were similar to the solutions with the Coulomb friction model. When compared to Coulomb's Law, the range of possible high tensions for a given low tension was reduced slightly for the EPP friction. Convergence fails due to sharp changes of the inclination angle and the sliding angle. Because the sharp changes occur when the belt exits the pulley, the EPP friction model cannot smooth the slope discontinuities.

The ENE trending Brandberg West - Goantagab Sn-W belt is located in the Southern Kaoko Zone of the northern coastal branch of the Damara Orogen. The lithologies in this area are turbiditic and consist of three schist units separated by two marble horizons, all of which are correlated with the Swakop Group. The formations are intensely folded by at least three episodes of which the first two are coaxial and resulted in prominent, approximately N-S trending, structures. Sn and Sn-W mineralization predominantly occurs as vein and replacement type mineralization. Vein type mineralization occurs as Brandberg West, Frans Prospect, Gamigab Prospect and the Goantagab Mining Area. The vein type mineralization is accompanied by intense alteration, consisting of greisenization, sericitization, hematitization and carbonatization. Replacement-type, hematite-cassiterite mineralization, occurs in the Goantagab Mining area in the marble close to, or at the schist marble contact. Intense ferruginous alteration of the marbles in this area, is associated with veins, which terminate against, or cross cut the marble. A regional metal zonation, ranging from Sn-W mineralization with minor sulphides at Brandberg West to Sn-sulphide mineralization at Goantagab can be detected. This metal zonation is attributed to the distance of the mineral locality from the source area, with Goantagab representing a distal and Brandberg West a proximal position relative to the source area. Structural, mineralogical and geological features of the mineralization in this area suggest that processes of ore genesis may be related to anorogenic magmatism of Karoo age.

This paper reports the results of a study into V-ribbed belt noise generated as a result of tangential belt slip. The results of experimental studies to identify the belt operating conditions associated with belt noise are presented, together with the results of analytical studies to identify the mechanism of noise generation. It is concluded that tangential slip V-ribbed belt noise generation is controlled only by the amount of slip, and that the mechanism of noise generation is harmonic excitation of the fundamental vibration mode of the belt, with stick¿slip frictional behaviour providing the impetus for the vibration

While safety-belt use markedly reduces morbidity and mortality, many young adults in the U.S. do not buckle-up 100% of the time. Following a series of community-level interventions on a university campus, this dissertation project focused on promoting individual-level safety-belt use. More specifically, a targeted web-based assessment and brief motivational intervention for individuals with lower rates of safety-belt use was developed and tested. A Pilot Study conducted prior to the Main Study developed self-reported assessment measures for safety-belt use and motivation. Recruitment, baseline assessment, intervention, and follow-up assessment were conducted via the Internet. Student drivers who buckled-up less than 70% of the time and who met other eligibility requirements were enrolled in a within subjects, randomized, attention-controlled design. At baseline, each participant completed an assessment of: (1) demographics; (2) driving behaviors; and (3) social cognitive and motivational variables including knowledge, perceived importance, confidence (self-efficacy), and readiness to buckle-up. Participants were then randomly assigned to one of two groups: (1) an attention-control group receiving emailed general nutrition information or (2) a motivational interviewing-consistent feedback group receiving emailed personalized feedback. Dependent variables were re-assessed approximately ten days after feedback/general nutrition information were emailed via follow-up assessment. Outcomes analyses using non-parametric statistics were conducted twice. First, an analysis of “completers” was conducted using data from those who completed follow-up. Second, a more conservative intent-to-treat analysis was conducted after carrying the last observation forward for those who did not complete follow-up, assuming no change among those who did not complete follow-up. Overall, results suggest this web-based assessment and brief motivational intervention was feasible and acceptable to participants. Overall, results from both analyses found statistically significant increases in median driver and passenger belt use between baseline and follow-up among participants in both groups. Further, effect sizes suggest the magnitude of change was greater among those in the intervention group versus those in the attention-control group. Participants were then categorized according to whether or not they increased driver belt use by at least one instance between baseline and follow-up. Those who received the intervention were not significantly more likely than those who received general nutrition information (i.e., assessment only) to increase driver safety-belt use by at least one instance. No statistical differences were found in either the completer or intent-to-treat analyses. Yet, when participants were categorized according to whether or not they increased passenger belt use by at least one instance between baseline and follow-up, those who received the intervention were 1.75 times more likely than those who received general nutrition information (i.e., assessment only) to increase passenger safety-belt use by at least one instance. This difference was not found in the intent-to-treat analysis. In general, study participation was associated with increased ratings of motivation (i.e., importance, confidence, and readiness) at follow-up. Results were interpreted with caution given psychometric weaknesses including high intercorrelations found between constructs of motivation in the Pilot Study. However, median change in one construct, readiness, was investigated in post-hoc analyses. Using the intent-to-treat sample, it was found that participants who were categorized as having increased driver safety-belt use by at least one instance also reported statistically significant median changes in readiness to buckle-up as a driver. Those categorized as having increased passenger safety-belt use by at least one instance also reported statistically significant median changes in readiness to buckle-up as a passenger. Further, although there was a trend for participants in the intervention group to be more likely than those in the attention-control group to commit to buckling-up and asking others to do the same at follow-up, there were no significant differences in commitment between groups. However, regardless of group assignment, change in median readiness was associated with: (1) commitment to buckle-up as a driver; (2) commitment to buckle-up as a passenger; (3) commitment to ask others to buckle-up while acting as a driver; and (4) commitment to ask others to buckle-up while acting as a passenger. Overall, these studies found the Internet to be an acceptable and promising venue for assessment and brief motivational intervention to promote safety-belt use among university students. Further, safety-belt use and motivational constructs such as importance, confidence, and readiness may be measured via self-report methodology. Results suggest participation in the study was associated with improvement in safety-belt use and some levels of motivation. While there were trends for those in the intervention group to report greater increases, there were no statistically significant differences between the groups in the ITT analyses. In the completer analyses, it was found that those in the intervention group were significantly more likely to report increased passenger safety-belt use. Future research may elucidate more specific psychometric properties of new measures used. In particular, readiness may be a proxy motivational variable that appears to relate to change in safety-belt use among drivers and passengers as well as commitment to buckle-up and ask others to do the same. The simple process of assessment may be sufficient to produce changes in readiness related to behavior change. / Ph. D.