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The effect of particle size, velocity, and angle of attack was investigated on the roughness and erosion rate of unmasked channels machined in borosilicate glass using abrasive jet micro-machining (AJM). Single impact experiments were conducted to quantify the damage due to the individual alumina particles. Based on these observations, an analytical model from the literature was modified and used to predict the roughness and erosion rate. A numerical model was then developed to simulate the brittle erosion process leading to the creation of unmasked channels as a function of particle size, velocity, dose, impact angle and target material properties. For the first time, erosion was simulated using models of two damage mechanisms: crater removal due to the formation and growth of lateral cracks, and edge chipping. Accuracy was further enhanced by simulating the actual relationship between particle size, velocity and radial location within the jet using distributions measured with high-speed laser shadowgraphy. The process of post-blasting AJM channels with abrasive particles at a relatively low kinetic energy was also investigated in the present work by measuring the roughness reduction of a reference unmasked channel in borosilicate glass as a function of post-blasting particle size, velocity, dose, and impact angle. The numerical model was modified and used to simulate the post-blasting process leading to the creation of smooth channels as a function of particle size, velocity, dose, impact angle, and target material properties. Finally, the effect of alumina particle kinetic energy and jet impact angle on the roughness and erosion rate of channels machined in borosilicate glass using abrasive slurry jet micro-machining (ASJM) was investigated. The analytical and numerical models derived for AJM, were found to predict reasonably well the roughness and the erosion rate of ASJM channels, despite the large differences in the fluid media, flow patterns, and particle trajectories in AJM and ASJM.

The effect of particle size, velocity, and angle of attack was investigated on the roughness and erosion rate of unmasked channels machined in borosilicate glass using abrasive jet micro-machining (AJM). Single impact experiments were conducted to quantify the damage due to the individual alumina particles. Based on these observations, an analytical model from the literature was modified and used to predict the roughness and erosion rate. A numerical model was then developed to simulate the brittle erosion process leading to the creation of unmasked channels as a function of particle size, velocity, dose, impact angle and target material properties. For the first time, erosion was simulated using models of two damage mechanisms: crater removal due to the formation and growth of lateral cracks, and edge chipping. Accuracy was further enhanced by simulating the actual relationship between particle size, velocity and radial location within the jet using distributions measured with high-speed laser shadowgraphy. The process of post-blasting AJM channels with abrasive particles at a relatively low kinetic energy was also investigated in the present work by measuring the roughness reduction of a reference unmasked channel in borosilicate glass as a function of post-blasting particle size, velocity, dose, and impact angle. The numerical model was modified and used to simulate the post-blasting process leading to the creation of smooth channels as a function of particle size, velocity, dose, impact angle, and target material properties. Finally, the effect of alumina particle kinetic energy and jet impact angle on the roughness and erosion rate of channels machined in borosilicate glass using abrasive slurry jet micro-machining (ASJM) was investigated. The analytical and numerical models derived for AJM, were found to predict reasonably well the roughness and the erosion rate of ASJM channels, despite the large differences in the fluid media, flow patterns, and particle trajectories in AJM and ASJM.

To make a camera more user friendly or let it operate without an user the camera objective needs to be able to put thecamera lens in focus. This functionality requires a motor of some sort, due to its many benefits the ultrasonic motor is apreferred choice. The motor requires a driving circuit to produce the appropriate signals and this is what this thesis is about.Themain difficulty that needs to be considered is the fact that the ultrasonic motor is highly non-linear.This paper will give a brief walk through of how the ultrasonic motor works,its pros and cons and how to control it. How thedriving circuit is designed and what role the various components fills. The regulator is implemented in C-code and runs on amicro processor while the actual signal generation is done on a CPLD. The report ends with a few suggestions of how toimprove the system should the presented solution not perform at a satisfactory level.

Over 13 million people live in Guatemala, and among this population more than 50% live below the poverty line. One proposed solution to mitigate the large percentage of poverty in the country is micro-entrepreneurship. A compost micro-enterprise is a small business, which collects organic raw material and processes it into stable humus material for the purpose of applying to soils to increase crop yields. Developing such micro-enterprises could not only indirectly improve current soil nutrient deficiencies specific to the region, but also provide alternative incomes for the already agriculturally involved community. The success or failure of enterprises practicing composting may be measured by a plethora of figures or outcomes. Employee characteristics are one variable that should be taken into consideration when estimating the efficiency of an agricultural enterprise's operations and productivity. While a variable, such as an employee characteristic, may not be able to be quantified exactly it should be argued that this variable can have a structural impact on productivity. Another crucial variable considered when developing such a micro-enterprise is accounting for its input and output. It is explained the issue of costs within micro-enterprises is complex and should be considered not only in terms of fees but also in terms of payments in any kind, such as entry and exit presence, and the duration of the apprenticeship. When an enterprise has failed to account for its various inputs and consequent output, it has become unsustainable because it has not satisfied basic economic, social and security needs presently and for its future. This study identified and described employee characteristics and documented the inputs and outputs of compost micro-enterprises in Chimaltenango, Guatemala. The study found that employee characteristics, particularly gender, age, and occupation affected a micro-enterprise's access to markets as well as row materials, and how efficiently tasks were completed. Costs of labor, raw material, transport, packaging, energy and the location the micro-enterprise itself heavily influenced profitability. The production of any product on a large scale must anticipate how positive financial outcomes will occur because profitability may not arrive as planned. If the revenue cannot be determined and/or made, compost micro-enterprise may fail to be a sustainable, much less a viable option for alternative income streams.

African countries have recently experienced an extraordinary and largely unanticipated boom in the uptake of mobile phones, and increasing rates of access to the internet. This thesis investigates how and why these information and communication technologies (ICT) are being adopted for use in Tanzanian micro and small enterprises (MSEs), and explores the changes they are bringing about to the existing business culture of marginalised economies. The study covers three sub-sectors of the Tanzanian economy: perishable foodstuffs trading, the informal construction industry and the export of African blackwood carvings. The analysis is based on fieldwork undertaken over a total of 15 months in 2002 and 2003, during which time business networks were revealed by physically following entrepreneurs and their contacts operating in different locations throughout the country. Entrepreneurs were asked to draw their own comparisons between the traditional pre-ICT situation and the improved ICT access of today. The discussion is informed by the findings of semi-structured interviews with these individuals, excerpts of which are presented in the text to give voice to the entrepreneurs. Various ingenious and at times unconventional methods of access to, and appropriation of, ICT is uncovered. Together these suggest that official indicators underestimate the thirst for digital consumption, especially for mobile phones, and help explain the flourishing informal economy of handset acquisition. Internet penetration and uptake for use in business, on the other hand, is revealed to be far slower. Nevertheless, the research does reveal that a sizeable amount of poorer entrepreneurs are using a triumvirate of hired or shared ICT – mobile phones, the Internet and the ‘old’ ICT of fax – to create what can appear to be a more formal enterprise than it may actually be. The ‘mobile office’ effectively allows poorer entrepreneurs to operate without premises, thereby saving costs on rent and allowing the enterprise to remain informal. This heralds a considerable change in the working practices of a significant branch of informal sector operators who have gone unnoticed, and calls for a reconstruction and redefinition of this crucial source of entrepreneurship in developing economies. Despite the huge uptake of mobile phones in particular, the work also cautions that some traditional pre-ICT aspects of the African business culture look set to remain for some time. It becomes clear that where entrepreneurs do decide to use ICT, reputation and recommendation are still very significant. This information is usually passed on when an entrepreneur meets in person with contacts from his very fluid informal networks of knowledge. Trust, and the need for direct, personal interaction through face-to-face contact – one of the most pervasive features of African MSE economies – emerge as a common theme across the case study industries and are likely to remain a crucial aspect of the way most MSE business is conducted. Mobile phones are seen to play a crucial role in improving the exchange of supply-anddemand information domestically, while a combination of applications (particularly e-mail) appear to act as tools with which to refresh relationships with sources of market information outside the country. It is suggested that ICT may be able to help entrepreneurs in moving from the personal to the impersonal exchange – a challenge that many other African businesses will also have to come to terms with as the Internet becomes an ever more important global trading tool.

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Cortical bone is a dynamic tissue which undergoes adaptive and pathological changes throughout life. An improved understanding of the spatio-temporal process of remodeling holds great promise for improving our understanding of bone development, maintenance and senescence. The use of micro-computed tomography (µCT) on living animals is relatively new and allows the three dimensional quantification of change in trabecular bone microarchitecture over time. The use of in vivo µCT is limited by the radiation dose created by the x-ray beam, with commercially available in vivo systems generally operating in the 10-20 um resolution range and delivering an absorbed dose between 0.5-1 Gy. Because dose scales to the power of four with resolution, in vivo imaging of the cortical canal network, which requires a higher resolution, has not been achieved. I hypothesized that using synchrotron propagation phase contrast µCT, cortical porosity could be imaged in vivo in rats at a dose on the same level as those used currently for trabecular bone analysis. Using the BMIT-BM beamline, I determined the optimal propagation distance and used ion chamber and lithium fluoride crystal thermoluminescent dosimetry to measure the absorbed dose of my in vivo protocol as well as several ex vivo protocols using synchrotron phase contrast µCT at 5 µm, 10 µm, and 11.8 µm and conventional desktop in vivo protocols using commercial µCT systems. Using synchrotron propagation phase contrast µCT, I scanned the forelimb of two adult Sprague-Dawley rats and measured an absorbed dose of 2.53 Gy. Using two commercial µCT system, I measured doses between 1.2-3.6 Gy for protocols at 18µm that are in common use. This thesis represents the first in vivo imaging of rat cortical porosity and demonstrates that an 11.8 µm resolution is enough to visualize cortical porosity in rats, with a dose within the scope of those used for imaging trabecular bone in vivo.

Pressboard, a high density cellulose-based material used for insulation in high voltage power transformers, exhibits stress relaxation during compressive loading. Investigating the micro-mechanical mechanisms responsible for the relaxation can lead to modifications of the production process to control the behaviour of the material. This investigation can be done using Synchrotron X-ray micro Computed Tomography which provides sufficient temporal and spatial resolutions to capture the stress relaxation process. In the present thesis, a compression rig for in-situ mechanical loading during X-ray micro Computed Tomography was designed and constructed. Local tomography scans with sub-micrometre resolution were obtained at the TOMCAT beamline at the Swiss Light Source, Paul Scherrer Institut, Switzerland. Several fibre segmentation techniques are analysed, together with Optical Flow and Digital Volume Correlation (DVC), methods used for estimating displacement, strain and velocity vector fields. Suitability of the tested methods is evaluated, and it is found that segmentation of individual fibres in a cellulose material of such a high density is probably not possible using currently available segmentation techniques. The movements during relaxation are measurable at the used resolution, and can be estimated using Optical Flow. Further work into correction of image shift due to rig movement between scans, as well as image artefact reduction should allow for measurement and comparisons of displacement during relaxation as well as DVC-computed strain measurements during compression, recreating earlier results.