Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 51-52). / This thesis studies two different methods of harvesting electrical energy from everyday activities such as walking and running. It is a design study that aims to create a device which can be attached or incorporated into a shoe, ideally a military boot, so that soldiers can charge back-up batteries for their devices while out in the field. The goal was to create a device that could achieve a peak energy harvesting power output on the order of 0.1 Watts. The original concept for the device involved the use of macro piezoelectric fiber harvesters which harness strain energy from the sole of the shoe as it naturally bends and flexes throughout daily activity. Strain testing indicated the the maximum peak power output that could be expected from these actuators was on the order of 10- 4W to 10- 3 W, and testing of the harvesters themselves yielded peak power values on the order of 10 7W to 10-6W. These low power values turned the design study away from the use of piezoelectrics and a design incorporating a miniature air turbine coupled with an electromagnetic generator was introduced. Initial testing on this proof of concept device yielded peak power values on the order of 10- 4W to 10- 3W with much room for improvement. It was concluded that this sort of device would be more effective for harvesting energy from the shoes, and future iterations of the initial prototype were proposed. / by Kelsey C. Seto. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1992. / Includes bibliographical references (p. 137-143). / by Scott Arthur Banks. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1994. / Includes bibliographical references (leaves 135-136). / by Chen-An Chen. / M.S.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. / 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 (pages 39-41). / One of the most common treatments for men with localized prostate cancer is radiation therapy, which involves delivering small doses of radiation to the prostate for an extended period of time. Stereotactic-body radiation therapy (SBRT) is a form of radiotherapy that delivers increased dosage to the prostate with more precision. The results are shorter treatment times, increased effectiveness, and less toxicity to surrounding tissue. However, the prostate has been found to move around during treatment (intrafraction) and between treatments (interfraction). With greater precision, there is a greater risk of missing the target while the prostate is moving. This study assesses the impact of intrafractional prostate motion on the accuracy and efficiency of SBRT on CyberKnife. Prostate tracking log files were acquired from 6 patients with prostate cancer, which comprises18 SBRT fractions and 1,892 X-ray image registrations. Each image contains real-time prostate motion in 6D. The data were compared against clinically used margins to identify periods of large prostate motion during treatment. Results indicate significant periods of prostate motion, with the greatest movement occurring in anterior-posterior translation (6.2% outside margin) and pitch rotation (4.3% outside margin). The percentage of prostate motion beyond margins varied among patients, with an average of 12.8% outside clinical margins and 36.0% outside hypothetically reduced margins. The treatment time for each fraction was also recorded to quantify the efficiency of CyberKnife delivery. Because of motion-related delays, optimal setup of 5-15 minutes was seen in only 50% of the fractions, and optimal beam delivery times of 30-40 minutes in 44% of fractions. Thus, results suggest that treatment accuracy and efficiency were negatively affected by the occurrence of large prostate motion. Techniques that immobilize the prostate during treatment may be considered to reduce intrafractional prostate motion and ensure greater accuracy and efficiency of prostate cancer SBRT. / by Ricardo Eduardo De Armas. / S.B.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1991. / Includes bibliographical references (leaves 129-133). / by Tain-Yen Hsia. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995. / Includes bibliographical references. / by Kuo-Shen Chen. / M.S.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018. / 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 (pages 281-291). / The surfaces of many plants and animals are covered with a variety of micro-textures such as ribs or 3D tubules which can control surface-mediated properties such as skin friction. Inspired by the drag reducing ability of these natural structures, especially the ribbed features on shark denticles, passive drag reduction strategies such as micro-fabricated riblet surfaces have been developed and studied. Microgroove textures on the surface of objects such as hulls, wings or inner surface of pipes which are aligned in the stream-wise direction have been shown to reduce the wall friction by 4 - 8%. The mechanisms suggested for this form of drag reduction are viscous retardation of the flow in the grooves (both laminar and turbulent) and the displacement of vortical structures away from the wall in turbulent flows. Due to their effectiveness in altering the boundary layer structure and reducing the viscous drag force, use of riblets have been banned in various competitions such as the America's Cup. The current thesis work is partly focused on theoretical and numerical modelling (using the open source CFD package OpenFOAM) of the evolution of viscous boundary layers in the presence of various-shaped riblets (V-grooves as well as sinusoidal wrinkled surfaces) in high Reynolds laminar flow. We explore the effect of the dimensionless height to spacing of the grooves (aspect ratio) as well as the length of the wetted surface in the streamwise direction and how these change the total drag compared with a corresponding flat wall. We show that riblets retard the viscous flow inside the grooves and reduce the shear stress inside the grooves. But for this reduction to result in overall drag reduction, the riblet wall needs to be longer than a critical length. The total drag reduction achieved is a non-monotonic function of the aspect ratio of the riblets, with aspect ratios of order unity offering the largest reduction in the total drag. To eliminate the role of entrance effects, we additionally investigate the effect of stream-wise aligned riblet structures on fully-developed Taylor-Couette flow. We perform both experimental studies as well as time-dependent numerical simulations in both the laminar Couette and the Taylor vortex regime. We again explore the effect of the size of the riblets with respect to the geometry of the Taylor-Couette cell, as well as the aspect ratio of the riblet grooves and the shape of the grooves (V-groove, Rectangular, semi-circular, etc.). For the experiments, the cylindrical textured rotors are fabricated using 3D printing techniques and the rest of the Taylor-Couette cell is custom built using CNC machining. The test cell is then aligned and mounted on a stress-controlled rheometer to measure the velocity and the torque on the rotating inner cylinder. The numerical studies are performed using the open source CFD software package OpenFOAM to compare results and understand the physical mechanisms contributing to this drag reduction phenomenon. Again we observe a non-monotonic behavior for the reduction in torque as a function of the aspect ratio of the riblets tested, similar to the trend observed in the boundary layer analysis and we discuss the effect of changing the geometry of the flow as well as the riblet spacing on the changes in the total torque. When viewed holistically the results of these two studies show that, through careful design, a net reduction in viscous drag force can be robustly realized on micro-textured surfaces in high Reynolds number laminar flows through complex changes in near-wall stream-wise velocity profiles even in the absence of turbulent effects. The understanding of these changes can be effective in guiding the design of internal flows (pipes or ducts) and external flows (such as ship hulls, micro air vehicles or unmanned underwater vehicles) that are tailored and optimized to result in low frictional drag over the entire wetted surface in both laminar and turbulent regions. / by Shabnam Raayai Ardakani. / Ph. D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1988. / Includes bibliographical references. / by Mohamed Yahiaoui. / M.S.

Thesis. (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1987. / Bibliography: leaves 150-154. / by Ernest Dean Fasse. / M.S.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Bibliography: leaf 35. / by Linda Elizabeth Mar. / B.S.