Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999. / Includes bibliographical references (p. 161-172). / by Barbara G.H. Ressler. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000. / Includes bibliographical references (leaves 70-71). / by Jason R. Fortier. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 103-105). / Due to improvements in electronics manufacturing, electronic implants keep decreasing in size and are moving towards integrated-circuit (IC) based designs. As implant electronics become significantly smaller with the use of ICs, traditional implant packaging become a limiting factor on implant miniaturization. Additionally, current packaging techniques can be expensive, and time and labor intensive. Building electronic packages can require many materials, multiple machines, and several manufacturing steps. This thesis explores cold spray as an alternative packaging method that would address the issues associated with traditional packaging. Cold spray could be used to create conformal packaging around electronic implants. Two biocompatible packaging materials, ultra high molecular weight polyethylene (UHMWPE) and titanium, were cold sprayed on two different electronic material substrates, silicon and polyimide. The results from these experiments are presented in this work. / by Molly A. Berringer. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995. / Includes bibliographical references (leaves 187-190). / by Neal A. Mitra. / M.S.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1994. / Includes bibliographical references (leaf 52). / by Hans-Georg Liemke. / B.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1994. / Includes bibliographical references. / by David Ridgway Otis, Jr. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003. / Includes bibliographical references (p. 335-340). / This thesis presents methods of characterizing the convergence, error, stability, and robustness properties of Adaptive Feedforward Cancellation (AFC) for use on fast tool servos in high-precision turning applications. Previous work has shown that classical control techniques can be used to analyze the stability and robustness of an AFC loop. However, determination of the convergence and error properties of the closed-loop system to changes in the reference or disturbance signal is not an obvious output of these analyses. We have developed a method of viewing AFC from an oscillator amplitude control (OAC) perspective, which provides additional use of classical control techniques to determine the convergence and error properties of the closed-loop system. AFC is a form of repetitive control that can be used to significantly improve periodic trajectory following/disturbance rejection. Fast tool servos used in high-precision turning applications commonly follow periodic trajectories and develop large errors, which usually occur at integer harmonics of the fundamental spindle rotation frequency. We have developed a loop-shaping approach to designing multiple resonator AFC controllers and have implemented this design on a commercially available piezoelectric (PZ) driven FTS using a PC-based digital control system. Our view of Adaptive Feedforward Cancellation from an oscillator amplitude control perspective builds upon previous work in the literature. We use an averaging analysis to simplify the single resonator AFC system into two coupled single-input single-output (SISO) oscillator amplitude control loops and show that by using the correct rotation matrix, these loops are effectively decoupled. This simplification provides the use of classical control techniques to approximate the dynamics of the closedloop output to changes in the amplitude or frequency of the reference/disturbance signal. The simulated and experimental results conform well to our analytical predictions for sufficiently low gain values. / by Joseph Harry Cattell. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1987. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Bibliography: p. 263-279. / by Steven Jeffrey Gordon. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 49-50). / The purpose of this study was to determine whether students with strong spatial-visual skills tend to design more complex mechanisms for the undergraduate course Design and Manufacturing I. The Purdue Spatial Visualization Test was administered to 137 students enrolled in the course. Test scores were compared to student self-evaluations of experience with tasks associated with spatial reasoning such as building origami models and sketching. The complexity of 34 student robots was analyzed using metrics such as the percentage of moving components in the mechanism. Gender differences in scores on the spatial visualization test were significant, consistent with results of prior studies. A significant correlation between spatial reasoning and origami experience was found for male students tested. Most mechanism complexity criteria were not found to be significantly correlated with spatial-visual ability, although the correlation between the percentage of moving components and spatial test scores approached significance with a negative correlation. These results suggest that strong spatial-visual abilities may be used to simplify engineering design rather than increase its complexity. / by Tiffany Tseng. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student submitted PDF version of thesis. / Includes bibliographical references (p. 130-139). / This thesis presents an integrated study of high efficiency photoanodes for water splitting using silicon and iron-oxide. The fundamental limitations of silicon to water splitting applications were overcome by an ultrathin iron-oxide film stack and a pH-adjusted electrochemical environment. It was experimentally demonstrated that this functional photoanode has very strong photoactivity exceeding the performance of previously reported systems. A complete theoretical explanation is provided with experimental substantiations. Two major obstacles of the application of silicon to water splitting are its high valence band edge and the lack of catalytic functionality. The solution for band edge mismatch is to facilitate the unique pH response of silicon with respect to electrolyte pH. As opposed to the low pH, a high pH electrolyte allows the silicon valence band edge to be located below the oxygen evolution potential, providing physical platform for the water oxidation reaction. In this platform, the introduction of a thin iron-oxide layer was proved to effectively catalyze the anode reaction which is otherwise impossible. The very thin film enables the separation of the two key functions of the photoelectrode: photocarrier generation and catalysis. Since the iron-oxide film has a very low absorption of incident light, phorocarriers are generated in the silicon layer, while the surface still maintains catalytic functionality. By this functional separation, it was possible to overcome the loss incurred by poor electronic and photovoltaic properties of iron-oxide. The thin semiconducting film also allows a space charge region to span beyond the catalyst layer to silicon, inducing a large built-in potential to lower the required overpotential. Additional improvement was made by adopting silicon microfabrication techniques to maximize light harvesting and minimize potential losses in silicon layer. By vertical wires and ohmic contact formation, the onset potentials were decreased and the current-potential slopes were steepened, resulting in current density as high as 17 mA/cm² at zero overpotential. These results were obtained with two of the most abundant materials, and as such shows the prospect of an efficient solar-driven water splitting pathway. In addition, the comprehensive theoretical explanations will contribute to searching for further system improvements. / by Kimin Jun. / Ph.D.