No description available.

The complex interrelations among the different physical processes involved in acid fracturing make it difficult to design, and later, to predict the outcome of stimulation jobs. Actual tendencies require the use of computational models to deal with the dynamic interaction of variables. This thesis presents a new study of acidized surface textures by means of a laser profilometer to improve our understanding of the remaining etched surface topography and its hydraulic response. Visualization plots generated by the profilometer identified hydrodynamic channels that could not be identified by the naked eye in acidized surfaces. The plots clarified the existence of rock heterogeneities and revealed how the processes of dissolution function in chalk rock. Experimental data showed clearly that the effect of dissolution depends on the type of rock and the fluid system; dolomite, for example, dissolves more rapidly but more roughly than limestone. Fluid leakoff rate and temperature also affect the dissolution. Further research is necessary to clarify the effects of conductivity.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references (leaves 129-132).

The principal excitation to a vehicle's chassis system is the road profile. Simulating a vehicle traversing long roads is impractical and a method to produce short roads with given characteristics must be developed. By understanding the characteristics of the road, a reduced set of models can be created from which appropriate representations of the terrain can be synthesized. Understanding the characteristics of the terrain requires the ability to accurately measure the terrain topology. It is only by increasing the fidelity and resolution of terrain topology data that application of these data can be advanced. The first part of this work presents the development of a high fidelity 3-D laser terrain measurement system. The system is developed for both on-highway and off-road measurement. It is capable of measuring terrain in three dimensions, whereas current systems measure separate 2-D profiles in each wheel path of the vehicle. The equipment setup and signal processing techniques are discussed, as well as future improvements and applications of this enabling technology. The second part of this work develops a method of characterizing non-stationary road profile data using ARIMA (Autoregressive Integrated Moving Average) modeling techniques. The first step is to consider the road to be a realization of an underlying stochastic process. The model identification techniques are demonstrated. Statistical techniques are developed and used to examine the distribution of the residual process and the results are demonstrated. The use of the ARIMA model parameters and residual distributions in classifying road profiles is also discussed. By classifying various road profiles according to given model parameters, any synthetic road realized from a given class of model parameters will represent all roads in that set, resulting in a timely and efficient simulation of a vehicle traversing any given type of road. / Master of Science

Metrological data from sample surfaces can be obtained by using a variety of profilometry methods. Atomic Force Microscopy (AFM), which relies on contact inter-atomic forces to extract topographical images of a sample, is one such method that can be used on a wide range of surface types, with possible nanometer range resolution. However, AFM images are commonly distorted by convolution, which reduces metrological accuracy. This type of distortion is more significant when the sample surface contains high aspect ratio features such as lines, steps or sharp edges - structures commonly found in semiconductor devices and applications. Aiming at mitigating these distortions and recovering metrology soundness, we introduce a novel image deconvolution scheme based on the principle of stereo imaging. Multiple images of a sample, taken at different angles, allow for separation of convolution artifacts from true topographic data. As a result, perfect sample reconstruction and probe shape estimation can be achieved in certain cases. Additionally, shadow zones, which are areas of the sample that cannot be probed by the AFM, are greatly reduced. Most importantly, this technique does not require a priori probe characterization. It also reduces the need for slender or sharper probes, which, on one hand, induce less convolution distortion but, on the other hand, are more prone to wear and damage, thus decreasing overall system reliability. / Singapore-MIT Alliance (SMA)

PURPOSE: To determine the potential discoloration of provisional materials by exposure to beverages and evaluate the efficacy of simulated tooth-brushing on stain removal and the effect on surface roughness. METHODS: Materials included: Jet Set-4 (Lang), Protemp Plus (3M ESPE), Luxatemp (DMG), Artbloc (Merz), Telio-CAD (Ivoclar), and Vita-CAD (Vita). Specimens (n=10/group) were immersed in: distilled water, coffee, red wine, tea, coke and cranberry juice. Color measurements were taken (Xritei5 spectrophotometer) at: baseline, 24 hours, 4 and 8 weeks. Specimens in coffee and red wine for 8 weeks were exposed to tooth-brushing for three minutes and color measurements were taken subsequently. Color differences (ΔE) after treatments were calculated using one-way ANOVA, MANOVA and post hoc Tukey test. Another group of specimens (n=10/group) were exposed to tooth-brushing under a 1.91N load using toothpaste slurry (Crest® Cavity Protection) for 20,000 cycles in two modes: soft and medium bristles (both Oral B Indicator®). Surface roughness was measured using a Mitutoyo SJ201 profilometer before and after brushing. Surface roughness Ra values were compared using one-way ANOVA and post hoc Tukey test. RESULTS: Coke and water had no significant discoloration effect (p>0.05). Red wine and coffee exhibited the highest discoloration effect. CAD-CAM blocks showed significantly lower color change, at all durations, and after brushing (p<0.001). Tooth-brushing had a significant effect (Ra) on Telio-CAD, Artbloc, Jet Set-4 and Vita-CAD. Protemp-Plus and Luxatemp groups showed no significant difference. CONCLUSIONS: Traditional materials showed less color stability when compared to CAD/CAM blocks. Tooth-brushing effect varies depending on bristle and material type.

No description available.

In the automotive industry one of the methods used in accelerating the design, testing and development of a system or a vehicle is the use of virtual vehicle simulations. The simulations cut costs in the form of fewer prototypes required for actual testing and accelerated fault finding in the design of a system. The simulation results are very dependent on the model used for the simulation and the inputs to the system. Feasible results can often be obtained with a simplified model if the correct input data is supplied to the simulation. In South Africa, the commercial, military and off-road vehicle industries mainly use the test tracks at the Gerotek Test Facilities for ride comfort and durability tests over repeatable terrains. Terrain profiles of these tracks are not available and cannot be measured using commercially available inertial profilometers due to the severe roughness of the terrain. This study concentrates on obtaining the input data in the form of the terrain profile used for vehicle simulations and field tests in which a vehicle is driving on rough terrains. The input data is referred to as the profile of the terrain and the profiled terrains are the actual terrains used for testing. Three different methods are used in measuring the profile of the terrain namely a mechanical profilometer, photogrammetry and a 3-D scanner using a laser displacement sensor. These methods are evaluated by profiling the same section of the Belgian paving and calculating the Displacement Spectral Densities. The most efficient method is used to profile additional terrains. The terrain profiles thus obtained is used as input to an existing off-road vehicle simulation model built in MSC Adams View. This model has previously been verified over discrete obstacles where excellent correlation with experimental results was obtained. Comparison between simulated and measured results over the terrains profiled in this study also gives good correlation, establishing further confidence in the measured terrain profiles. / Dissertation (MEng)--University of Pretoria, 2009. / Mechanical and Aeronautical Engineering / unrestricted

No description available.

Thesis (M.Eng.(Mechanical and Aeronautical Engineering))--University of Pretoria, 2008. / Includes bibliographical references.