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This work is the first 3-D continuum study of the free vibration of skewed and simultaneously skewed and twisted, cantilever parallelepipeds. The purpose of this study is to make available in the literature an enlarged data base of natural frequencies of these practical problems for researchers and design engineers to draw upon. The Ritz method is used to determine approximate natural frequency data. The total potential energy of the parallelepipeds is formulated using the three-dimensional theory of elasticity. The three orthogonal displacement components (u,v,w) are each approximated by finite triple series of simple algebraic polynomials with arbitrary coefficients (which are determined by applying the Ritz method). All terms of the series are constructed to satisfy the geometric boundary conditions at the fixed end of the parallelepiped. No other kinematic constraints are imposed in this analysis. Hence, the finite series of algebraic polynomials are both admissible and "mathematically complete" (75). Several convergence studies of natural frequencies are conducted on cantilever parallelepipeds. Effects of geometrical parameters such as side ratio, thickness ratio, skew angle, and twisted angle are presented in the form of nondimensional tables and graphs. Accuracy of solution method is substantiated through comparison with existing rectangular, skewed, and twisted plate results. The central focus of these comparisons are to verify the correctness and accuracy of free vibration data obtained by investigators using classical plate theories and two- and three-dimensional finite element methods.

Otoacoustic emissions (OAEs) have been under investigation since their discovery 30 years ago (Kemp, 1978). Otoacoustic emissions are quiet sounds generated within the cochlea that can be detected with a sensitive microphone placed within the ear canal. They are used clinically as a hearing screening tool but have the potential for diagnostic and monitoring purposes. For this dissertation, high-resolution instrumentation was developed for improving the acquisition of OAEs. It was shown that a high bit-depth device is required in order to simultaneously characterize the ear canal and the cochlear responses. This led to a reduction in the stimulus artifact that revealed early latency, high-frequency otoacoustic emissions. Next, a swept-tone technique originally developed for use in acoustical systems was formally developed for use in the human ear. The swept-tone technique allows for the simultaneous acquisition of a system's impulse response and its distortion components. The swept-tone was first used in this study to characterize the ear canal transfer properties. From that transfer function, a compensation routine was developed which equalized the magnitude and phase distortions of the ear canal. As a result, an improved acoustical click could be presented to the ear, which allowed for further reduction of the stimulus artifact, revealing early latency emissions. Spectral flatness and effective duration measurements of the compensated click showed an improvement over traditional click stimuli. Furthermore, wavelet analysis and time-frequency latency computations showed that higher frequency otoacoustic emissions were recoverable when using a compensated click stimulus. The swept-tone technique was then utilized for the direct acquisition of otoacoustic emissions. The swept-tone response was compressed to an impulse response and compared to a standard click response. It was found that several similarities exist between the two response types. The divergences, primarily in the low-frequencies, have implications in the generation mechanisms involved in a click-evoked otoacoustic emission. The swept-tone response provided some clinical benefits, namely in an improved signal-to-noise ratio, and in the removal of obstructive synchronized spontaneous OAEs when compared to a standard click response. Current methods are restricted by noise contamination, and the use of a swept-tone technique can reduce the acquisition time by up to a factor of four, compared to standard click methods. These implications and future potential studies are discussed.

Transition of the attachment fine boundary layer was investigated using a large swept cylinder. Results for natural transition and transition tripping with two-dimensional trip wires were simila to those obtained by Poll using a similar, but smaller, model. ]Lower displacement thickness Reynolds numbers but larger trip sizes, than for the flat-plate boundary layer, were required for transition. The investigation of transition tripping was then extended to involve three-dimensional trips. The attachment line boundary layer was less susceptible to three-dimensional trips than to two-dimensional trips but upper and lower bounds of attachment line Reynolds number for transition were identical. It was also found that the roughness Reynolds numbers for fully effective three-dimensional trips were similar for the attachment line and flat-plate boundary layers. Another common feature was the more abrupt upstream movement of the transition front with increasing Reynolds number for three-dimensional trips than for two-dimensional trips. Turbulence spreading downstream of a three-dimensional trip was also examined and, as in the flat-plate boundary layer, was found to be heavily dependent on Reynolds number (varying from 3° at low Reynolds number to a value approaching 10° as Reynolds number exceeded the value for natural transition), but was also dependent on either the trip size or the initial conditions at which the trip first introduced turbulent spots. The effects of higher levels of freestrearn turbulence were then investigated for both two-dimensional and three-dimensional trips. With a small increase in freestrea turbulence the conditions for transition with twodimensional trips were affected far more than those for three-dimensional trips, for which only the transition completion conditions were affected signfficantly, resulting in a reduced extent ofthe transition region. Larger levels of turbulence appeared to have similar effects on the two trip types. Restrictions in model length and windspeed for the higher turbulence tests prevented an accurate investigation of the effects of turbulence,on the upper and lower bounds for transition tripping and on the influence of spanwise distance at higher levels of turbulence. Finally, the interaction between two trips positioned on the attachment line was examined. The effect of the second trip on the transition Reynolds number was found to a function of the streamwise separation distance between the two trips.

This research will investigate various swept wing models, designing the mechanism for their pitching motion and control, designing wind tunnel implementation, and performing data measurements and analysis using particle image velocimetry. A NACA0012 section with an aspect ratio of AR = 4, free stream velocity of U∞=34 m/s, and Reynolds Number is Rec=2x105. Swept airfoils of Λ=0°, 15°, and 30° will be pitched sinusoidally between an AoA of 4°and 22°, at a reduced frequency of k=πfc/U∞=0.2. Higher sweep angles developing arch-type vortices interact with wing tip flow and abrupt tip stall is observed. Lower sweep angles possessed defined leading edge vortices persist near the tip after lift has collapsed at mid span. Stall angle was delayed during dynamic motion of the wing as well as the presence of arch and ring type vortices increased with sweep angle and contributed to flow reattachment along the top surface of the wing.

An inverted airfoil mounted above a flat plate was used to create laminar separation bubbles on a flat plate in water tunnel experiments at low Reynolds numbers. Boundary layer suction ensured that the flow remained attached to the wing. Two-dimensional PIV measurements were used to qualitatively and quantitatively characterize the spanwise bubble variation on an unswept wing and on the same wing featuring a 22 degree sweep. The separation bubbles were recorded at varied span-wise locations in a 31.5 cm wide region of the flow. The limitations of this measurement region were dictated by the focal length of the laser optic used for PIV measurements. The straight wing exhibited approximately uniform time averaged separation positions across the span of the wing. The reattachment locations varied only slightly which was expected due to the transition to turbulent flow before reattachment. A form of bubble "breathing" was observed in the laminar separation bubbles on the straight wing and is believed to have affected the mean reattachment locations for two data points recorded. The shedding frequencies on the straight wing were slightly higher than those obtained from CFD simulations. The swept wing planform showed significantly more variation in the mean separation and reattachment locations with respect to the leading edge of the wing. There is a general trend of the separation locations moving upstream in the direction of the aft leading edge. The reattachment points are shown to move downstream as the separation points move upstream relative to the leading edge and visa versa, displaying an inverse relationship between the two. The bubble lengths were found to be slightly longer on the swept wing compared to the straight wing usually by about 10%. The shedding frequencies on the swept wing were found to be lower than the straight wing. The quality of flow in the water tunnel may have degraded over time, showing signs of increased free stream turbulence. After data collection, it was also discovered that the boundary layer suction on the wing was not constant at all span-wise locations. It is believed that the introduction of wing sweep intensified the effect of insufficient suction on the structure of the bubbles observed. The present results were in agreement with previous research for bubble structure but the dynamic instabilities were found to differ slightly.

This thesis presents an algorithm for collision detection for an autonomous articulated vehicle following pregenerated paths in a mining environment. Two types of vehicles are studied. The tricycle vehicle and the articulated vehicle. The characteristics of the mine is presented. A way of using these characteristics is studied. An algorithm for collision detection using the swept area of the vehicle following a pregenerated path is given. As proof of concept a small implementation is also given along, with a few examples. / Validerat; 20101217 (root)

Otoacoustic Emissions (OAE) are minute acoustic responses originating from the cochlea as a result of an external acoustic stimulus and are recorded using a sensitive microphone placed in the ear canal. OAEs are acquired by synchronous stimulation with an acoustic click or tone burst and recording of the post-stimulus responses. This method of acquiring OAEs is known as transient evoked otoacoustic emissions (TEAOE) and is commonly used in clinics as a screening method for hearing and cochlear functionality in infants. Recently, a novel method of acquiring OAEs utilizing a swept-tone, or chirp, as a stimulus was developed. This method used a deconvolution process to compress the swept tone response into an impulse or click-like response. Because the human ear does not hear all frequencies (pitches) at equal loudness the swept-tone stimulus was equalized in amplitude with respect to frequency. This equalized stimulus will be perceived by the ear as equally loud in all frequencies. In this study a new hearing level equalized stimulus was designed and the OAE responses were analyzed and compared to conventional click evoked OAEs. The equalized swept-tone stimulus evoked greater magnitude OAE responses when compared to the conventional methods. It was also able to evoke responses in subjects that had little TEOAEs which might fail conventional hearing screening.