Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The shape of the knee’s trochlear groove is a very important factor in the overall stability of the knee. However, a quantitative description of the normal three-dimensional geometry of the trochlea is not available in the literature. This is also reflected in the poor outcomes of patellofemoral arthroplasty (PFA). In this study, a standardised method for femoral parameter measurements on three-dimensional femur models was established. Using software tools, virtual femur models were aligned with the mechanical and the posterior condylar planes and this framework was used to measure the femoral parameters in a repeatable way. An artificial neural network (ANN), incorporating the femoral parameter measurements and classifications done by experienced surgeons, was used to classify knees into normal and abnormal categories. As a result, 15 knees in the database were classified by the ANN as being normal. Furthermore, the geometry of the normal knees was analysed by fitting B-spline curves and circular arcs on their sagittal surface curves to prove and reconfirm that the groove has a circular shape on a sagittal plane. Self-organising maps (SOM), which is a type of ANN, was trained with the acquired data of the normal knees and in this way the normal trochlear geometry could be predicted. The prediction of the anterior-posterior (AP) distance and the trochlear heights showed an average agreement of 97 % between the actual and the predicted normal geometries. A case study was conducted on four types of trochlear dysplasia to determine a normal geometry for these knees, and a virtual surface reconstruction was performed on them. The study showed that the trochlea was deepened after the surface reconstruction, having an average trochlea depth of 5.5 mm compared to the original average value of 2.9 mm. In summary, this research proposed a quantitative method for describing and predicting the normal geometry of a knee by making use of ANN and the femoral parameters that are unaffected by trochlear dysplasia. / AFRIKAANSE OPSOMMING: Die vorm van die trogleêre keep is ’n belangrike faktor in patella-stabiliteit. Tog is ’n kwantitatiewe beskrywing van die normale driedimensionele geometrie van die troglea nog nie beskikbaar nie, wat duidelik blyk uit die swak uitkomste van patellofemorale artroplastie (PFA). In hierdie studie is ’n gestandaardiseerde metode vir die meting van femorale parameters op grond van driedimensionele femurmodelle ontwikkel. Die femurmodel is in lyn gebring met die meganiese en posterior kondilêre vlak, welke raamwerk gebruik is om die femorale parameters op ’n herhaalbare wyse te meet. Die normale knieë is geklassifiseer met ’n kunsmatige neurale netwerk (ANN), wat die femorale parameter-mate sowel as die chirurgiese klassifikasie ingesluit het, en 15 knieë is gevolglik as normaal aangewys. Die normaleknie-geometrie is ontleed deur B-latkrommes en sirkelboë op die sagittale oppervlak-kurwes aan te bring om te bewys en te herbevestig dat die keep uit ’n sirkelvorm op ’n sagittale vlak bestaan. Die ingesamelde data van die normale knieë is ingevoer by selfreëlende kaarte (SOM), synde ’n soort ANN, wat die navorser in staat gestel het om die normale trogleêre geometrie te voorspel. Die voorspelling van die anterior-posterior (AP) afstand en die trogleêre hoogtes toon ’n gemiddelde ooreenkoms van meer as 97 % tussen die werklike en voorspelde normale geometrie. ’n Gevallestudie is op vier soorte trogleêre displasie uitgevoer om die normale geometrie te voorspel en ’n oppervlakrekonstruksie daarop uit te voer. Hierdie studie het getoon dat die troglea ná oppervlakrekonstruksie verdiep was, met ’n gemiddelde trogleadiepte van 5.5 mm in vergelyking met die aanvanklike gemiddelde waarde van 2.9 mm. Hierdie navorsing het dus ’n metode aan die hand gedoen vir die kwantitatiewe beskrywing en voorspelling van normale geometrie met behulp van ANN sowel as met die femorale parameters wat nie deur die trogleêre displasie geraak word nie.

This thesis details the development of a model of driver behaviour at railway level crossings that allows the probability of an accident under different conditions and interventions to be calculated. A method for classifying different crossings according to their individual risk levels is also described.

Today, Sport Utility Vehicles are marketed as both on-road and off-road vehicles. This results in a compromise when designing the suspension of the vehicle. If the suspension characteristics are fixed, the vehicle cannot have good handling capabilities on highways and good ride comfort over rough terrain. The rollover propensity of this type of vehicle compared to normal cars is high because it has a combination of a high centre of gravity and a softer suspension. The 4 State Semi-active Suspension System (4S4) that can switch between two discrete spring characteristics as well as two discrete damper characteristics, has been proven to overcome this compromise. The soft suspension setting (soft spring and low damping) is used for ride comfort, while the hard suspension setting (stiff spring and high damping) is used for handling. The following question arises: when is which setting most appropriate? The two main contributing factors are the terrain profile and the driver’s actions. Ride comfort is primarily dependant on the terrain that the vehicle is travelling over. If the terrain can be identified, certain driving styles can be expected for that specific environment. The terrains range from rough and uncomfortable to smooth with high speed manoeuvring. Terrain classification methods are proposed and tested with measured data from the test vehicle on known terrain types. Good results were obtained from the terrain classification methods. Five terrain types were accurately identified from over an hour’s worth of vehicle testing. Handling manoeuvres happen unexpectedly, often to avoid an accident. To improve the handling and therefore safety of the vehicle, the 4S4 can be switched to the hard suspension setting, which results in a reduced body roll angle. This decision should be made quickly with the occupants’ safety as the priority. Methods were investigated that will determine when to switch the suspension to the handling mode based on the kinematics of the vehicle. The switching strategies proposed in this study have the potential, with a little refinement, to make the ride versus handling decision correctly. Copyright 2007, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Bester, R 2007, The ride comfort versus handling decision for off-road vehicles, MEng dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-10252007-111611 / > / Dissertation (MEng (Mechanical Engineering))--University of Pretoria, 2007. / Mechanical and Aeronautical Engineering / unrestricted

Die Nutzung von terrestrischen Ökosystemen zur Befriedigung der Grundbedürfnisse der Menschheit hat tiefgreifende Auswirkungen auf das Erdsystem und führte zur Ausprägung von anthropogen dominierten Landsystemen. Diese sind von hoher Komplexität, da sie aus einer Vielzahl von unterschiedlichsten Einflussfaktoren angetriebenen Landnutzungsveränderungen hervorgegangen sind. Aktuelle Forderungen nach einer nachhaltigen zukünftigen Landnutzung erfordern ein fundiertes und integratives Verständnis dieser Komplexität. Das Hauptziel dieser Arbeit ist es, ein besseres Verständnis der raum-zeitlichen Muster und Determinanten des Landsystemwandels, insbesondere der Landnutzungsintensität, in Europa zwischen 1990 und 2010 zu erlangen. Europa ist ein interessantes Studiengebiet, da es jüngst starke Landnutzungsveränderungen erlebte und seine Heterogenität zu einer Vielfalt von Landsystemen und Landsystemveränderungen führte. Das Ziel der Arbeit wurde durch (i) die Kartierung von Intensitätsmustern und deren Veränderungen in Forst- und Agrarsystemen sowie der Ermittlung der dafür einflussreichsten räumlichen Determinanten und (ii) die Kartierung und Charakterisierung archetypischer Muster und Entwicklungsverläufe von Landsystemen untersucht. Die Ergebnisse dieser Arbeit zeigten einen deutlichen Ost-West-Unterschied in Landsystemmustern und -veränderungen in Europa, mit intensiv genutzten und intensivierenden Regionen vor allem in Westeuropa. Dennoch wurde Europa vor allem durch relativ stabile Landsystemmuster gekennzeichnet und (De-)Intensivierungstrends waren nur von untergeordneter Bedeutung. Intensitätsmuster und -veränderungen waren stark an Standortbedingungen gebunden, vor allem an edaphische, klimatische, und länderspezifische Besonderheiten. Diese Arbeit erweitert das Verständnis des Landsystemwandels in Europa und kann zur Entwicklung wissenschaftlicher und politikbezogener Maßnahmen sowie zur Erreichung einer nachhaltigeren Landnutzung in Europa beitragen. / The utilisation of terrestrial ecosystems to satisfy the basic needs of humankind has profound impacts on the Earth System and led to the development of human-dominated land systems. These are substantially complex as they evolved from a multitude of land-change pathways driven by a variety of influential factors. Current calls for a more sustainable future land-use require a sound and integrative understanding of this complexity. The main goal of this thesis is to better understand the spatio-temporal patterns and the determinants of land-system change in Europe between 1990 and 2010, especially with regard to land-use intensity. Europe serves as an interesting study region as it recently experienced a period of marked land-use change, and since its large environmental, political, and socio-economic heterogeneity resulted in a diversity of land systems and land-change pathways. Land-system changes in Europe were examined by (i) mapping patterns and changes in forestry and agricultural intensity and identifying the most influential spatial determinants related to these changes, and (ii) mapping and characterising archetypical patterns and trajectories of land systems considering both land-use extent and intensity indicators. Results revealed a distinct east-west divide in Europe’s land-system patterns and change trajectories, with intensively used and intensifying regions particularly located in Western Europe. However, Europe was mainly characterised by relatively stable land-systems patterns with (de-) intensification trends being only of minor importance. Land-use intensity levels and changes were strongly related to site conditions, especially with regard to soil and climate, as well as to country-specific characteristics. By fostering the understanding of land-system change, this thesis has the potential to contribute to scientific and policy-related actions that address current efforts to guide future land systems in Europe to a more sustainable use.