Thesis (M. Sc.)--University of Hong Kong, 1993. / "Workshop report." Includes bibliographical references (leaves 150-156).

Thesis (M.A.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 107-108).

Thesis (M.A.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 107-108). Also available in print.

A wing with a Wortmann FX-63-137-ESM airfoil section has been used to study some unique problems encountered in wing aerodynamics in the range of Reynolds numbers between 50,000 and 500,000. The wind-tunnel testing conducted in the 6'x 6' Stability tunnel included strain-gauge data, pressure data, and flow-visualization studies. The laminar separation bubble which frequently occurs on the upper surface of the wing is found to dominate its performance and gives rise to a hysteresis loop for lift and drag. Changes in airfoil performance due to positive flap or control surface deflections resemble changes witnessed at higher Reynolds numbers. Negative deflections are seen to considerably change the stall behavior and the flow over the airfoil. This is due to the considerably greater effect on the separation bubble for negative flap deflections. The structure and mechanism of the laminar separation bubble can also be altered by the introduction of selected acoustic disturbance and increased free-stream turbulence. The wind-tunnel test-section environment is, therefore, capable of considerably altering wing performance in this regime. / Ph. D. / incomplete_metadata

Master of Science

Call number: LD2668 .T4 1962 H37

published_or_final_version / abstract / Public Administration / Master / Master of Public Administration

At the Swedish Transport Administration two different maintenance strategies are practiced to keep cameras in road tunnels clean. The theory of Life Cycle Cost, LCC, is applied on maintenance depending on its Level of Automation, LoA, and is further developed. In the case of cameras, in Swedish road tunnels the processes demonstrate two different LoA. LCC is used to compare and analyze how the properties between semiautomatic and manual maintenance affect investment costs, operational costs and the cost of preventive and corrective maintenance. Semiautomatic cleaning maintenance of cameras in road tunnels indicate a larger LCC than manual maintenance. This is due to a larger investment cost for machinery, but a similar annual cost for preventive maintenance. The presented properties affecting LCC are placed in a general context. This emphasize the significance of examining costs at high level of detail and comprehend the properties causing the costs.

Thesis is submitted in partial fulfilment of the requirements for the degree of Master of Science in Engineering to the Faculty of Engineering and the Built Environment, School of Mining Engineering, University of the Witwatersrand, Johannesburg, 2017 / Boring of shafts and tunnels in hard rock mines is more prevalent in recent years in South Africa. This normally takes place under substantial stress conditions, where fracturing of rock occurs around the boundaries and ahead of advancing faces of excavations. Fracturing can have a significant impact on boring activities, in some instances causing sidewall spalling which can be extensive, with machine grippers unable to reach the sidewalls. In brittle rock, these fractures are commonly extensional in nature. This research has been undertaken to predict the initiation of extension fractures and their orientations ahead of machine driven tunnels. Furthermore, it will help to assess the stability of the excavations, by evaluating the potential for slab/plate failures. This was based on the typical in situ stress fields for underground deep level mines. The numerical analyses involved the generation of different plots:  Principal stress contour plots, depicting stress distributions around and ahead of tunnel excavation, using cutting planes;  Isosurfaces, showing zones of extension or potential extents of fracturing, applying the extension strain criterion; and  Trajectory ribbons, to demonstrate the orientations of fractures. Based on the results of the stress analyses, potential slab or plate formation was determined. It was noted that the fracture zone is a function of a tunnel size. For instance, a four-metre diameter tunnel is less likely to give boring problems than an eight-metre diameter tunnel. The failure of the tunnels was predicted by employing slab analysis methods. An eight-metre diameter tunnel had slenderness ratio as low as 22.3 as compared with a four-metre diameter tunnel with a slenderness ratio of 27. Looking at buckling stress versus slenderness ratio, this translates to buckling stress values of above 100 MPa for an eight-metre tunnel and to values just below 50 MPa for a four-metre tunnel. The outcome of the research gives a clear indication that boring activities could be undertaken under severe conditions. This could be detrimental to the cutter head, since large slabs and blocks could be encountered during boring. The results of this research can be beneficial in the evaluation of boring conditions prior to and during boring activities. / MT2018

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Civil Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographies. / M.S.