Student Number : 0400188H - MSc(Eng) Dissertation - School of Mining - Faculty of Engineering and the Built Environment / The occurrence of fracturing due to high stress levels is a major factor with regard to hangingwall stability in deep level gold mine stopes. However, rock falls cannot be the result of these fractures alone. Blocks in the hangingwall strata must be defined by a combination of the stress induced fractures and naturally occurring geological planes of weakness. These planes include bedding planes and joint planes. The importance of the natural joints and bedding planes in defining the instability has not been given the attention that it deserves, to the extent that there are apparently no documented, published data available on joint set characteristics. This is perhaps an indication that such data do not exist on the mines. To remedy this situation, detailed scan-line joint mapping exercises have been carried out in several geological environments in two gold mines. The joint data collected on joint geometry included orientation, spacing and length. The results presented in this dissertation are believed to be the first such data available on jointing in gold mines. The main conclusions from the interpretation of these data are that there are two dominant joint sets in stope hangingwalls and at least one of these sets is shallow dipping. In development tunnels there is one predominant set of shallow dipping bedding planes. Both in stope hangingwalls and in development tunnels, steeply dipping random joints constitute half of the mapped joints. The statistical joint data obtained was used to investigate and analyse the potential for rock falls in stopes. This involved the prediction of characteristic block parameters such as expected block sizes and rock fall thicknesses. These predictions show good agreement with measurements made of actual rockfalls (generic results). Most unstable blocks in stope hangingwalls are less than a cubic meter in size. These blocks are more likely to fall between support elements than fail the supports, whilst failure of the fewer large blocks (20%) usually involves failure of support elements. It is concluded that failure probabilities are largely related to joint geometry. Common failure modes for small blocks are single plane sliding and ‘dropping out’ whilst larger blocks usually fail by rotation. The study increases understanding of rock fall mechanisms and the support-block interaction. The results of the analyses of block stability that have been reported in this dissertation show disturbingly high probabilities of failure in the stope face area (or working area), particularly for blocks that are smaller than about 1.5 cubic metres in size. The study has demonstrated the important influence that natural joints have on hangingwall block stability, and the importance of joint mapping to produce statistical joint data that can be used in the assessment of stability against rock falls. Although joint mapping may be a tedious exercise in mines, it has been shown to give similar results regarding heights of rock falls to that interpreted from collection of empirical incident and accident record data over a ten-year period. It is considered that this could provide good input data for the design of stope support.

AIM: To compare the stability of a non-cylindrical implant using piezoelectric drilling (Piezoimplant) with a cylindrical implant with conventional drilling (Nobel Biocare™). MATERIALS AND METHODS: Three adult female Gottingen miniature pigs were used for the surgical implantation. Three implants on each quadrant, randomized split-mouth design using cylindrical or non-cylindrical implants (n=36). Osteotomies were prepared using either conventional drilling technique as per manufacturer’s instruction (Nobel Biocare™) or using piezoelectric drilling (Piezotome® (P2) (Satelec Acteon, Merignac, France) with new implant prototype tips (Fraunhofer Center for Manufacturing Innovation). The minipigs were sacrificed at 4, 8 and 12-weeks. Stability tests (three per implant) using wireless Periotest® “M” were done at the start point and after euthanization. RESULTS: R-square (ANOVA) test was plotted comparing implant design, weeks 4, 8 and 12, and location (mandible and maxilla) for stability analysis. In this model, the R-square is only 0.51, which indicates only 51% of the response variability can be explained by the fitted model. Among all the 3 factors, group (experiment vs control) is the most significant one, followed by week. Location significance is the least among the three factors. CONCLUSION: In mandibular and maxillary sites in minipigs where non-cylindrical prototype implants (piezoimplant) were inserted by piezoelectric site preparation, statistically significant differences were found between control and test group stability measurements, but no differences in week (4, 8 or 12) and location among the two groups (mandible and maxilla). Stability was like the cylindrical implants. Meaning that Piezoimplants could be an alternative for narrow residual ridges. / 2020-03-14T00:00:00Z

>Magister Scientiae - MSc / Introduction: Nanoparticles (NPs) are gaining increased popularity for cancer treatment, especially the multifunctional nanoparticles like Quantum dots (QDs) which have a wide range of applications in nanotheranostics, cell imaging and targeted drug delivery to cancerous tissue. QDs comprise of very tiny crystals of a semiconductor material (diameter: 2-10 nm) capable of producing bright, intensive and size-tuneable near-infrared fluorescence emissions. In particular, 3-mercaptopropionic acid -capped Cadmium Telluride Quantum Dots with a zinc sulphide shell (MPA-capped CdTe/ZnS QDs), are known to be very stable, highly photoluminescent, less toxic with long-lasting “fluorophore” effects, thus making them the preferred QDs for this study. Aims: To synthesize and characterize biocompatible MPA-capped CdTe/ZnS QDs to determine size range, polydispersity index (PdI), zeta (ζ) potential, photoluminescence (PL) spectra, stability in various milieus as well as to evaluate the effects of the synthesized QDs on the viability and morphology of neuroblastoma (NB) and glioblastoma (GB) cell lines using the WST-1 cell viability assay, imaging and cell cycle analysis. Materials and methods: MPA-capped CdTe/ZnS QDs were synthesized and analysed with the Zetasizer to determine ζ-potential, hydrodynamic (hd) size and PdI, while high resolutiontransmission electron microscopy (HR-TEM) was used to validate the hd size and elemental composition using energy dispersive X-ray (EDX) spectra. Pl absorption and emission spectra were obtained with a fluorometer and stability studies were done using UV-Vis spectroscopy, permitting further biological evaluation. A concentration range of 5-20μg/ml QDs was exposed to U87 and SH-SY5Y cancer cell lines to determine biological effects at different time points, using the WST-1 assay. Confocal fluorescence microscopy was used to establish uptake and cellular localization of the QDs, cell morphology was visualized with an inverted microscope while cell cycle distribution analysis was done using the C6 flow cytometer.

Bi-layered materials are a reduced weight derivative of the sandwich structure and are comprised of one thin skin face reinforced by a thick layer of low density material. Bi-layered materials are characterized by high flexural stiffness and are a viable alternative to conventional sandwich materials in applications where the functional requirements can be met without the second face sheet of the sandwich. For structural applications bi-layered materials are required to have oil canning and buckling resistance. This work addresses the buckling of shallow bi-layered arches using numerical and analytical approaches. A numerical, finite element model is developed to simulate the buckling phenomenon and the results were compared with known experimental data. An analytical model was developed using the energy method analysis and the buckling load was predicted from the minimum energy criterion. Comparison of the numerical and analytical results yielded fairly good agreement. An imperfection analysis conducted by means of the numerical model indicated that the load carrying capacity of bi-layered structures is reduced by up to 40% due to the presence of material and geometric imperfections. A parametric study conducted using the analytical model has been described to setup design guidelines for shallow bi-layered arches. It was found that the use of bi-layered structures can result in weight reduction of around 70% when compared with equivalent single layered structure.

A number of movements produced in everyday life require not only coordination of joints within a limb, but also coordination between one or more limbs. The aim of this dissertation was to examine the influence of biomechanical constraints on intralimb coordination, interlimb coordination, and learning. Experiment 1 sought to determine if principles of the Leading Joint Hypothesis, when applied to a multijoint bimanual coordination task, could provide insight into the contribution of intralimb dynamics to interlimb coordination. Participants repetitively traced ellipse templates in an asymmetrical coordination pattern (i.e. both limbs moving counter-clockwise). Kinematic data of the upper limbs were recorded with a VICON camera system. Ellipse templates were oriented either tilted right or tilted left; yielding a total of four left arm-right arm leading joint combinations. The findings indicated that stability of interlimb coordination patterns were found to be influenced by whether arm movements were produced with similar or different leading joints. Bimanual asymmetric ellipse-tracing produced with similar leading joints were more stable than patterns produced with different leading joints. For example, asymmetric coordination patterns produced with similar leading joints exhibited less transient behavior than coordination patterns produced with different leading joints (p < .01). Experiment 2 expanded on these findings by employing a similar task and incorporating a learning component to assess how intralimb dynamics are tuned with practice of a novel coordination pattern. Participants were randomly assigned to one of three groups. One group practiced tracing a pair of ellipse templates that were oriented in such a way that required similar leading joints while the other two groups practiced tracing ellipse templates that required different leading joints. Early in practice, the group learning the coordination pattern with similar leading joints exhibited greater interlimb stability than the two groups learning with different leading joints. However, following two days of practice, performance of the groups learning with different leading joints improved to match that of the group learning with similar leading joints. The findings suggest that initial biomechanical constraints can be overcome with practice, resulting in similar performance regardless of whether being produced with similar or different leading joints.

The laminar-to-turbulent transition process in swept-wing boundary layers is often dominated by an inflectional instability arising from crossflow. It is now known that freestream turbulence and surface roughness are two of the key disturbance sources in the crossflow instability problem. Recent experimental findings have suggested that freestream turbulence of low intensity (less than 0.2%) may have a larger influence on crossflow instability than was previously thought. The present work involves experimental measurement of stationary and traveling crossflow mode amplitudes in freestream turbulence levels between 0.02% and 0.2%. A 1.83 m chord, 45-degree swept-wing model is used in the Klebanoff-Saric Wind Tunnel to perform these experiments. The turbulence intensity and length scales are documented. Although a significant amount of research on the role of turbulence has been completed at higher turbulence levels, comparatively little has been done at the low levels of the present experiments, which more closely reflect the flight environment. It is found that growth of the traveling crossflow mode is highly dependent on small changes to the freestream turbulence. Additionally, previously studied attenuation of saturated stationary disturbance amplitudes is observed at these low turbulence levels. The extent of laminar flow is also observed to decrease in moderate freestream turbulence.

University of Macau / Faculty of Science and Technology / Department of Mathematics

In this thesis we prove polynomial-in-time upper bounds for the orbital instability of solitons for subcritical generalized Korteweg-de Vries equations in $H^{s}_{x}(\mathbb{R})$ with $s < 1$. By combining coercivity estimates of Weinstein with the $I$-method as developed by Colliander, Keel, Staffilani, Takaoka, and Tao, we construct a modified energy functional which is shown to be almost conserved while providing us with an estimate of the deviation of the solution from the ground state curve. The iteration of the almost conservation law for the modified energy functional over time intervals of uniform length yields the polynomial upper bound.

In this thesis we prove polynomial-in-time upper bounds for the orbital instability of solitons for subcritical generalized Korteweg-de Vries equations in $H^{s}_{x}(\mathbb{R})$ with $s < 1$. By combining coercivity estimates of Weinstein with the $I$-method as developed by Colliander, Keel, Staffilani, Takaoka, and Tao, we construct a modified energy functional which is shown to be almost conserved while providing us with an estimate of the deviation of the solution from the ground state curve. The iteration of the almost conservation law for the modified energy functional over time intervals of uniform length yields the polynomial upper bound.

This thesis concerns delay-dependent robust stability analysis and stabilization for time-delay system with uncertainties. By choosing new Lyapunov-Krasovskii functional and using methods which can reduce conservativeness of stability condition in the literature, new delay-dependent sufficient stability conditions are obtained in terms of linear matrix inequality. It is shown that the new stability conditions can provide less conservative results than some existing ones. Furthermore, the new stability conditions are also used to design the state feedback controllers. Finally, numerical examples are given to show the derived results and compared with results in the literature.