Thesis (Ph.D.)--Tufts University, 1999. / Adviser: Haris Doumanidis. Submitted to the Dept. of Mechanical Engineering. Includes bibliographical references (leaves 201-207). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Non-contact surface profilometry techniques, especially the phase-measuring profilometry, have been evolved dramatically over recent years. Besides the simple triangulation configuration with a fringe pattern projection system and digital imaging system, efficient computational surface profilometry techniques have also drawn tremendous attention from both academia and a wide range of applications. In the semiconductor industry, high-precision and high-speed, automated optical inspection systems are urgently needed to ensure high quality of semiconductor devices and yield improvement on the production and assembly line. However, by assuming the measured object to be stationary, conventional approaches are not suitable for surface profilometry of moving objects. Moreover, different sources of error such as the low contrast fringe patterns on the measured object, the unevenness in the illumination and the perspective projection effect from the optics will decrease the performance of surface profilometry. To meet these challenges, we have built fringe pattern projection prototypes with projector and camera arrays for surface profilometry of moving objects along the conveyor belt. This design helps to enlarge the field of view with parallel processing. In addition, we have presented an optimization framework to investigate the sources of the error for surface profilometry and generalize various computational surface profilometry approaches under different scenarios. Under this framework, first, we investigate two important factors determining the precision of surface profilometry, namely, the condition number of the phaseshift matrix and the fringe contrast within the images of the projected fringe patterns. Then, a regularized phase-shift algorithm has been proposed to improve the reconstruction results at the low contrast regions such as on the substrate of the semiconductor devices. Second, we study the intensity fluctuation caused by the uneven illumination for surface profilometry of moving objects. After that, an illumination-reflectivity-focus model has been suggested to describe the unevenness and an illumination-invariant phase-shift algorithm has been developed to handle this uneven illumination effect. Third, the perspective projection effect from the optics also affects the accurate phase-shift estimation for a moving object. Therefore, we propose a general polynomial phase-measuring profilometry model to establish the relationship between the phase-shift and height variation for each measured point. Accordingly, a polynomial phase-shift algorithm with error compensation technique has been put forward to improve the performance of the surface profilometry for moving objects. Both simulation and real experiments from the prototype have been conducted to verify the improvement on the performance of the proposed methodologies. Furthermore, these research results have demonstrated the effectiveness and efficiency of the presented optimization framework for investigating the sources of error for surface profilometry. Moreover, the proposed computational surface profilometry techniques and the corresponding fringe pattern projection systems have been used in automated optical inspection systems for yield improvement on the production line in the semiconductor industry. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

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published_or_final_version / Dentistry / Master / Master of Dental Surgery

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7 pp.

Approved for public release; distribution is unlimited. / The method of taking unsteady pressure measurements, on a research transonic compressor rig, was lost during the transition from the traditionally designed Vavra stage to the Sanger stage. The Sanger stage was designed using computational fluid dynamics (CFD) techniques. It required a new case wall in which the unsteady pressure sensors, due to outdated software and data acquisition system, were not initially installed. In the present study, unsteady pressure measurements were reestablished, with the installation of sensors and development of a new data acquisition and data reduction system. Data were taken at 60%, 70%, and 80% design speed. Data at 60% and 70% were compared to computational predictions and reasonable agreement was obtained. / Ensign, United States Navy

The definition of the shape of the geoid is a fundamental objective of geodesy, since it allows for the conversion between orthometric and ellipsoidal height systems. The geoid can be computed from gravity values measured over the surface of the earth, and considerable effort continues to achieve a global coverage of gravity values. One technique that has been very successful in recent years in providing gravity coverage in areas which previously have been too difficult to access is airborne gravimetry. This technique has proved very useful in covering near offshore regions, for example. The coastal regions of Australia are recognised as locations where airborne gravimetry has the potential to fill in missing gravity data. A pilot survey using an airborne gravity meter was undertaken off the north east coast of Australia. In areas that remain unsurveyed it is sometimes useful to fill in the missing gravity data values with predicted gravity values. Previous research has examined the possibility of predicting gravity values from other observed quantities. The best success has been achieved by using the gravity effect calculated from bathymetric information. Often the corresponding isostatic compensation is computed, and the combined bathymetric-isostatic gravity effect is used. However, the type and extent of compensation that exists in any particular region mostly remains unknown. Theoretical considerations indicate that the short wavelength part of the gravity field may be adequately modelled by the gravity effect of the bathymetry alone, without reference to an assumed compensation mechanism. With this in mind, a prediction scheme has been developed which utilises the short wavelength gravity field information implied by the bathymetry, combined with the long wavelength gravity field information from existing observed gravity. This scheme allows the prediction of ???fill-in??? gravity values in areas with limited observed gravity. The prediction technique was used on a test set of data off the east coast of Greenland. The prediction technique was seen to outperform a simple interpolation of gravity values by approximately ten percent. Geoid computations performed with the predicted gravity values indicate that the prediction technique can provide significant improvements in computed geoids.

Bibliography: l. 280-333. This study investigates the osteometry and variation of the human spine. 348 human skeletons dating from 28,000 B.C. to the mid-20th century A.D. from 24 sites mainly in Switzerland and Southern Germany, and without macroscopic pathology, were measured with a caliper. The samples showed a microevolutionary increase in most of the spinal variables. As both mean values and standard deviations increased, this higher intra-group variability could be explained to be a result of relaxed natural selection. Various environmental or genetic factors could explain the short-term alteration of the spinal osteometry. The relative smaller size and decrease with age of the bony outline of the neural pathways in males could explain their high vulnerability to modern lower back pathologies.

Aim: To determine the effect of removing or modifying smear layer from dentine on the Prepometer dentine thickness indicator device, which operates using electrical conductivity (Hager & Werken, Germany). Method: Twelve third molars were prepared by reducing the crowns to a flat dentine surface. Five reference points were marked and control Prepometer readings taken using its coloured LED display. Six teeth (Group E) were treated with 18% EDTA and six (Group T) with Tubulicid (Dental Therapeutics AB, Sweden). Readings were repeated. Dentine was removed in 0.5 mm increments, readings repeated and reductions continued for each tooth until the instrument gave a reading of 10 (red), indicating the pulp was close. Teeth were sectioned and the distance from the references to the pulp was measured. Readings at each level were compared using the t-test, Wilcoxon Signed Ranks test (WSR) and Ordinal Regression (OR). SEM was used to illustrate the effects of materials on the dentine. Results: For Group E (N = 160 pairs) t-test showed a significant (P = 0.026) difference between control and treatment scores. WSR also showed significance: E>control in 54 ranks, E< control in 33 and E = control in 73 (P =0.007). For group T (N = 155) t-test showed a highly significant (P = 0.005) difference. WSR showed T< control in 59 ranks, T> control in 37 and T = control in 59 (P =0.008). OR showed that a red light was obtained further from the pulp with EDTA treatment than with Tubulicid. SEM showed total smear layer removal in Group E and occlusion of tubule openings in Group T. Conclusion: Measurements of dentinal conductivity were significantly influenced by treatment with EDTA and Tubulicid. Conductivity increased after EDTA but decreased after treatment with Tubulicid, possibly owing to blocking of tubules.