Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1967. / Bibliography: leaves 163-164. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1998. / Includes bibliographical references (leaves 206-214). / by Srihari Balasubramanian. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005. / Includes bibliographical references (p. 177-184). / Snowboarding, since its creation, has become one of the most widely practiced winter sports. Unfortunately, most snowboarding enthusiasts are unable to snowboard year round due to geographic and financial limitations. One possible solution to this dilemma is the development of a device that simulates snowboarding. Using a Deterministic Design process developed in MIT's Precision Engineering Research Group, a Snowboarding Exercise Machine is created. This design features a carriage constrained to move back and forth along a curved track. Rotational sensations are created using an angular motion module mounted onto the carriage. The end result of this effort is a proof of concept prototype, which indicates that the output kinematics are desirable. Additional work and sponsorship is required to bring the proof of concept prototype to a commercially available product. / by Timothy A. Vanderpoel. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004. / Includes bibliographical references (p. 89-91). / This research 1) explores the feasibility of developing a non-invasive probe to precisely quantify microcirculatory blood flow (tissue perfusion), in real time and in absolute units, and 2) presents designs and models of such a probe, along with an evaluation of various design-model combinations. Bowman et al. have developed an invasive thermodiffusion probe that measures tissue perfusion accurately, continuously, and in real time. This method employs a self-heated thermistor placed in perfused tissue. From a knowledge of the power required to heat the thermistor probe to a given temperature, perfusion can be calculated using an analytical or numerical model. Using Bowman's thermodiffusion probe (designed for invasive use) in a non-invasive manner, a perfusion study was performed. The data clearly show the promise of a non-invasive thermodiffusion perfusion probe (designed for non-invasive use), and the design of such a probe was pursued by adapting the invasive technology for a non-invasive probe. Because perfusion is not actually measured but calculated from measured quantities by a model of the probe and perfused tissue, the design of the non-invasive probe occurred hand-in-hand with the development of analytical models. / (cont.) The results of the clinical study are presented, as well as two designs together with possible one-dimensional analytical models. Using a finite-difference model of the two probe designs and the underlying perfused tissue, the errors that result from approximating these designs as one-dimensional models have been determined. It is shown that modeling a thin, disk-shaped thermistor probe as a hemisphere of appropriate radius can result in an error in calculated perfusion which is small enough for clinical use. / by Steven Knight Charles. / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / Includes bibliographical references (leaf 36). / The process of assistive reproduction is often a headache and heartache for those who choose to go through it. The field currently relies heavily on morphological characteristics to determine embryo health and development success, a highly unreliable method. While they appear healthy at implantation, many embryos, in reality, have poor development potential and fail to survive within the womb. Therefore, to offset the high chances of miscarriage, multiple eggs are implanted in the uterus. This has occasionally lead to multi-fetal pregnancies, which have a higher maternal mortality risk, and, in general, is more physically demanding. This thesis researches a microfluidic device that aids in the crucial stages of in vitro- fertilization. The device allows for a fertilized egg to be cultured within, and provides the ability to carefully monitor its health through a series of metabolic assays, a better indication of embryo health. This microfluidic embryo health monitoring device is comprised of two layers of channel networks. It works through passing fluids along flow channels that are driven by control channels. The control layer, when pressurized with gas, operates as valves and peristaltic pumps along the flow layer to pump and transport fluids through the flow channels. As embryonic fluids are passed through the channels, the status of the fertilized egg can be monitored with metabolic assays taken of the embryo at various detection sites. / by Jin Xu. / S.B.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1968. / Bibliography: leaves 43-44. / B.S.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010. / 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. 51-52). / Atomic Layer Deposition (ALD) is a process used to deposit nanometer scale films for use in nano electronics. A typical experimental reactor consist of a warm wall horizontal flow tube, a single disc mounted halfway down the tube, and an alternating cycle flow between a reactant gas and a wash in a carrier gas. The process is governed by the desire to achieve a uniform coating on the substrate layer. Optimization is currently accomplished by monitoring the precursor delivery and the growth of the film and adjusting flow rates accordingly. Maslar et al (2008) showed that it is possible to use in situ monitoring of the gas phase for optimization. With the data provided from that work, it is now possible to verify a numerical model of the flow process. The process can be thought of in 5 parts: unsteady undeveloped pipe flow, mixing, flow around a disc, flow impinging on a disc, boundary layer reactions on a wall. In this thesis, I numerically simulated the unsteady undeveloped pipe flow, mixing and boundary layer reactions on the wall. I also describe but do not solve a model for the complete process and propose criteria for optimization. / by A. Andrew D. Jones, III. / S.B.

Thesis: Ph. D., 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 225-228). / Flow through tip shroud cavity in a representative axial turbine vane-rotor stage environment is assessed for its role in loss generation and turbine durability. Steady and unsteady three-dimensional flow computations, complemented by control volume analyses, for varying shroud configurations provided results for establishing quantitative links between loss and ow processes as well as loss level scalings. Specifically tip shroud cavity flow is dominated by two counter-rotating vortices upstream, and a free expansion leakage jet downstream, of the tip seal, followed by a mixing shear layer at cavity exit. One of the vortices, the cavity inlet toroidal vortex, sets the loss level within the cavity inlet and the mass ow recirculated out of the cavity into the main flow path. It is found that tip shroud cavity flow incurs a 0:85% debit in stage eciency per 1% of main flow fluid through the cavity with approximately 50% generated in the free expansion of the tip seal leakage jet and 50% from cavity exit mixing. The proportion of total loss attributable to cavity exit mixing increases with tip seal gap. In addition, vane-rotor unsteady interaction induces an additional 0:25% debit in eciency per 1% of main flow fluid through the cavity. The additional efficiency penalty induced by vane-rotor unsteady interaction results from an enhancement of the cavity inlet toroidal vortex and associated recirculated mass flow. Overall cavity loss is set by cavity mass flow fraction, stagnation pressure ratio across tip seal, velocity disparity between cavity exit flow and rotor exit flow, and cavity inlet vortex strength. These findings were used to formulate a modified tip shroud configuration that nearly eliminates cavity exit mixing loss, but it incurs a penalty associated with cavity flow low Reynolds number effects and induced mismatching between vane and modified tip shroud. In the process of designing this modified tip shroud, it was found that the turbine main flow perceives the cavity as a line sink-source pair, permitting estimation of flow redistribution in the main flow path. Finally, any operational transients which eliminate tip seal clearance would lead to enhanced impingement heat transfer at blade tip due to recirculating ow from cavity inlet; this can increase the likelihood of blade failure. / by Timothy R. Palmer. / Ph. D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 145-149). / Car crashes cause a large number of fatalities and injuries, with about 33,000 people killed and 2.3 million injured in the United States every year. To prevent car crashes, the government and automotive companies have taken initiatives to develop and deploy communications among vehicles and between vehicles and infrastructure. By using such communications, we design centralized coordinators at road intersections, called supervisors, that monitor the dynamical state of vehicles and the current input of drivers and override them if necessary to prevent a collision. The primary technical problem in the design of such systems is to determine if the current drivers' input will cause an unavoidable future collision, in which case the supervisor must override the drivers at the current time to prevent the collision. This problem is called safety verification problem which is known to be computationally intractable for general dynamical systems. Our approach to solving the safety verification problem is to translate it to a computationally more tractable scheduling problem. When modeling an intersection as a single conflict area inside which the paths of vehicles intersect, we exactly solve the scheduling problem with algorithms that can handle a small number of vehicles in real-time. For a larger number of vehicles or with more complex intersection models, we approximately solve it within quantified approximation bounds by using mixed integer linear programming (MILP) formulations that, despite the combinatorial complexity, can be solved in real-time by available software such as CPLEX. Based on the solutions to the safety verification problem, we design a supervisor and prove that it ensures safety and is nonblocking, another major challenge of verification-based algorithms. We validate the supervisor using computer simulations and experiments. / by Heejin Ahn. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 128-133. / by Ruben David Cohen. / Ph.D.