Thesis (M. Sc.)--University of Hong Kong, 1998. / Includes bibliographical references (leaf.

Thesis (M. Sc.(Urb. Plan.))--University of Hong Kong, 1994. / Includes bibliographical references (leaves [79]-82).

Thesis (M. Sc.)--University of Hong Kong, 1993. / "Workshop report." Includes bibliographical references (leaves 51-52).

Biodiversity offsetting mechanisms are increasingly applied worldwide as a new solution to the current biodiversity crisis. The offsetting approach is idealised as a means to achieve no net loss of biodiversity. Offsetting mechanisms aim to quantify residual biodiversity losses and enable developers to account for residual impacts off-site. Despite rising global application, the effectiveness of offsetting is by no means assured. The question of whether and how offsetting can be operationalised to achieve no net loss has become a key focal point in debates surrounding their effectiveness. Environmental Impact Assessment, or EIA, has been portrayed as an obvious 'vehicle' for integrating offsetting into existing corporate management systems and planning systems, and therefore a key factor over how offsetting mechanisms operate. This research critically investigated the nature of integration and interactions between EIA and offsetting using a three phase qualitative research design, which brought together analysis of emerging policy, expert interviews and in-depth case studies.

Engineering composites and especially long fibre carbon composites have been in high demand not only in aerospace and automotive applications, but also in high end everyday applications. In aerospace, carbon composites are used predominantly for secondary structures attached by joints or fasteners to various alloys or even different composites, and are exposed to service loads and repetitive impacting. Impact fatigue (IF) is not studied adequately for long cycles and relevant literature is investigating mainly drop weight tests and high speed projectile experiments. The main aim of this research was to investigate the behaviour long fibre CFRP'S exposed to repeated low-velocity, low energy impacts, and to observe the damage effects of this regime on the structural integrity of these materials. Two types of specimen configurations using CFRPS's were used and exposed to loading conditions relevant to the Izod impact fatigue test (IIFT), and the tensile impact fatigue test (TIFT), in order to determine the fatigue behaviour of the specimens for each of these load conditions. For the IIFT, the fatigue life was investigated using IM7/8552 unidirectional specimens and T700/LTM45 cross-ply specimens were utilised for the TIFT. The specimen thicknesses were altered in both cases and parametric studies were carried out, where it was seen that IF results in high level of scatter and the apparent decrease in life was seen at relatively modest levels of maximum force after relatively few cycles. In the case of the IIFT, a durability limit was not apparent which increases the complications when designing against IF. In the case of the TIFT the stiffness deterioration was reflected as an increase of the loading time, in the force vs time graph, over the total fatigue life span. Fatigue crack growth was investigated using fractography and X-ray micro-CT at the micro and macro level. It was seen, that IF had the potential to initiate cracks and to cause their propagation at low levels of loading. For the IIFT, a single crack was growing substantially in the fibre direction and across the sample width causing matrix cracking and probably breaking of some fibres, which acted as impact wave guides since matrix cracks were propagating initially along the length of the fibres. In the case of the TIFT multiple damage modes were presented (matrix cracks, axial splits and delaminations). Their sequence and progression was successfully v captured and contrasted against the number of impacts. Axial splits governed the damage scenario, with delaminations extending between them and the free edges. For the TIFT, IF was studied using the force-life (F-Nf) and energy-life (E-Nf) curves. The tests undertaken showed that when halving the thickness of the laminates the fatigue life presented a 10-fold decrease as well as higher scatter. Finite element modelling was undertaken to validate the experimental data of the TIFT test. Successful simulation of a single impact was carried out using a fully transient 3-D model of the actual experiment configuration which involved geometric non-linearities in addition to the multiple contact conditions. The analysis was undertaken using the Abaqus 6.11 explicit solver. Since the numerical single impact results (force vs time response) was in agreement with the experimental results, the crack modes, experimentally observed, were also incorporated in the model utilising the use of the cohesive zone elements (CZE).

L’objectif de cette étude est de caractériser le bruit de graillonnement des boîtes de vitesses automobiles, qui résulte des chocs entre les pignons au niveau des rapports non engagés, sous l’effet des fluctuations de vitesses imposées par le moteur. Outre les paramètres de conception de la boîte de vitesses et les conditions de fonctionnement, les paramètres qui gouvernent la réponse dynamique des pignons fous sont les couples de traînée et les caractéristiques des contacts qui gouvernent les chocs entre dents. Un modèle numérique non linéaire a été élaboré pour caractériser la réponse dynamique d’un pignon fou. Il permet d’identifier le seuil d’excitation au-delà duquel le phénomène de graillonnement apparaît et de qualifier la très grande diversité de comportements dynamiques susceptibles d’être observés, en fonction du niveau d’excitation adimensionnée, du jeu de denture et du coefficient de restitution des chocs entre dents. Les paramètres inconnus ont été identifiés expérimentalement, grâce à l’exploitation d’un banc d’acyclisme et l’implémentation de codeurs optiques sur les pignons menant et fou. Des essais en réponse libre amortie ont permis de discriminer les différentes sources de dissipation(roulements, palier du pignon fou, barbotage, etc.) et de valider les modèles permettant d’identifier le couple de traînée s’exerçant sur chaque pignon fou. D’autres essais en régime de fonctionnement stationnaire ont permis de décrire le coefficient de restitution des chocs entre les pignons, sa dispersion et sa variation avec la vitesse d’impact. Les mesures effectuées sous une excitation maîtrisée ont permis de caractériser le comportement dynamique du pignon fou et de valider les hypothèses retenues et les résultats numériques obtenus par le modèle non linéaire, recalé à partir des paramètres préalablement identifiés. Enfin, l’analyse du transfert entre les impulsions générées au niveau des pignons et la réponse vibratoire du carter a permis d’évaluer expérimentalement et numériquement le critère qui qualifie le bruit de graillonnement rayonné par la boîte de vitesses. La mise en oeuvre du modèle numérique permet d’analyser l’influence des paramètres de conception de la boîte de vitesses et de proposer des solutions qui minimisent le graillonnement, pour l’ensemble des rapports de la boîte et des conditions de fonctionnement. / The aim of this work is to characterize the rattle noise of automotive gearboxes, resulting from impacts between toothed wheels of unselected gear ratios. Dynamic response of idle gears firstly depends on design parameters and engine operating conditions. The unknown parameters are the drag torque acting on the idle gear and characteristics of impacts between teeth.A non linear dynamic model has been developed in order to identify dynamic response of idle gears. It allows identification of excitation threshold beyond which rattle noise rises, and describes the wide variety of dynamic behaviors that are likely to appear, depending on the dimensionless excitation amplitude, the clearance between gears and the restitution coefficient of impacts between teeth. The unknown parameters have been identified experimentally through implementation of optical encoders in the gearbox and the operation of a specific acyclism test bench. Analysis of the free damped response of the gearbox allowed discrimination of the different dissipation sources (bearings, connection between idle gear and shaft, churning, etc.). Models proposed to identify the drag torque have been validated. Further tests under stationary operating conditions allowed measurement of the restitution coefficient of impacts and its velocity dependent probability density function. Experiments under controlled excitation were used to characterize the dynamic behavior of the idle gear and validate the assumptions and the numerical results obtained from the non linear dynamic model, fitted with the parameters previously identified. Finally, the transfer between the impulses generated at the gears and the housing vibration has been investigated to evaluate experimentally and numerically the criterion used to describe the rattle noise radiated from the gearbox. The implementation of the model allows analysis of the influence of the gearbox design parameters and solutions that minimize rattle noise can be proposed for all gear ratios and operating conditions of the gearbox.

The objective of this research was to better understand how impact angle influences headform dynamic response and brain tissue deformation. A bare headform was impacted using a pneumatic linear impactor at 5.5 m/s. The impacts were directed on the front and side location at angles of 0, 5, 10 and 15° rightward rotations as well as -5, -10 and -15° (leftward) rotations at the side to examine the characteristics of the head and neckform on the results. Peak resultant linear and rotational accelerations from the headform as well as peak maximum principal strain (MPS) and von Mises stress (VMS) estimated from a brain finite element model were used to measure the effect of impact angle. Significant results were dependent upon the impact angle and location as well as the dependent variable used for comparison (p <0.05). Impact angle produced significant differences in rotational acceleration and MPS at both the front and side; however angle only had an effect on VMS and linear acceleration at the front and side locations, respectively. These findings show that the effect of impact angle is asymmetrical and is specific to the dependent variable. This study suggests that varying impact angle alone may not be as influential on headform dynamic response and brain tissue deformation and that the severity of an impact may be more of a function of how both location and angle create high risk conditions.

The landscape of South African National Development Finance Institutions (DFIs) is comprised of twelve entities. Their institutional objectives range from supporting farmers, financing industrialisation, infrastructural development, and promoting financial inclusion. These DFI objectives fall under the umbrella of Private Sector Development (PSD) interventions. Literature established that the success of PSD is contingent on effective impact evaluation. Consequently, the main research question explored in this dissertation is: In what ways, and using what tools and systems, do South African DFIs measure the development impact of their investments? In support of the main question, two sub-questions were are also investigated. Firstly, whether impact evaluation systems provide credible, timely and relevant information. Secondly, whether impact evaluation systems support evidence-based decision making and learning. In response to these questions, a qualitative case study of six National DFIs was carried out. Semi-structured interviews were conducted with DFI staff members involved in impact evaluation. This was supported by secondary data from annual reports and organisational websites. It was established that, firstly, DFIs use non-uniform impact evaluation systems and tools to measure the impact of their investments. Secondly, the systems lack qualitative detail and focus on measuring outputs instead of outcomes. Thus, much emphasis is placed on monitoring instead of impact evaluation. This renders the impact evaluation systems and tools highly ineffective. Finally, whilst the avowed objective of DFIs is development, financial viability takes precedence when selecting projects. Therefore, an emerging conclusion was that systems in place do not support development impact evidence-based decision-making. These findings generated recommendations for changing the development impact evaluation tools and systems used by South African National DFIs. It is expected that recommended changes will maximise DFI socio-economic benefits.

A research report submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science, 2018 / South Africa has implemented regular amendments to the Environmental Impact Assessment (EIA) regulations in an attempt to improve the effectiveness of the process. One way of evaluating effectiveness is to assess the quality of EIA reports submitted for decision-making. This study aimed to assess whether the amendments to the National Environmental Management Act (NEMA), (Act no 107, 1998) EIA regulations in 2014 have contributed to better EIA report quality in South Africa in comparison to the previous EIA system. As such, a sample of 26 EIA reports, 16 under the 2010 EIA regulations and 10 under the 2014 EIA regulations, were reviewed using an adapted version of the Lee and Colley review package. The findings of this research revealed that overall report quality improved under the 2014 EIA regulatory system compared to the 2010 system. Furthermore, an improvement in the 2014 EIA report quality indicates that the decision-making process is more well informed and holistic, which further indicates an improvement in effectiveness of the EIA process. Key amendments to the 2014 EIA regulations that have an influence on EIA report quality include appendix 2 which outlines the objective, scope and content of a scoping report, appendix 3 which outlines the objective, scope and content of an EIA report, appendix 4 which outlines the content of an EMPr, and appendix 6 which outlines the content of a specialist report. It is thus concluded that amendments to the EIA regulations have in fact influenced report quality. These findings differed from those of other studies undertaken on EIA quality under the 2006 EIA system in comparison to the 1997 EIA system. Key words: Environmental Impact Assessment, Effectiveness, Environmental Impact Assessment Report, EIA Report Quality, EIA Regulations, National Environmental Management Act. / XL2019

The Chesapeake Bay impact structure is one of the largest and most well preserved impact structures on Earth. It has a unique morphology composed of an inner crater penetrating crystalline basement surrounded by a wider crater in the overlying sediments. In 2004, the U.S. Geological Survey conducted a seismic survey with the goals of constraining crater structure and in support of the drilling of a borehole into the deepest part of the crater. Travel-time and waveform inversion were applied to the data to produce a high-resolution velocity model of the crater. Low-fold reflection processing was also applied. Northeast of the crystalline crater, undeformed, eastward-sloping crystalline basement is ~1.5 km deep. The edge of the inner crater is at ~ 15 km radius and slopes gradually down to a depth of 1.5 - 1.8 km. A central peak of 4-5 km radius rises to a depth of ~0.8 km. Basement velocity in the crystalline crater is much lower than undeformed basement, which suggests ~10% fracturing of the crater floor, and up to 20% fracturing of the central uplift. A basement uplift and lateral change of velocity, interpreted as the edge of the transient crater, occurs at a radius of ~ 11 km. Assuming a 22 km diameter transient crater, scaling laws predict a ~30 km diameter crater and central peak diameter of 8-10 km. This indicates that post-impact collapse processes that created the ~ 30 km diameter crystalline crater were unaffected by the much weaker rheology of the overlying sediments. / Master of Science