Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 46-47). / Micro and nanostructured surfaces have broad applications including heat transfer enhancement in phase-change systems and liquid manipulation in microfluidic devices. While significant efforts have focused on fabricating static micro/nanostructured arrays, uniform arrays that can be dynamically tuned have not yet been demonstrated. In this work, we present a novel fabrication process for magnetically tunable microstructured surfaces, where the tilt angle can be controlled upon application of an external magnetic field. We also demonstrated this platform for droplet manipulation in heat transfer applications. The tunable surfaces consist of ferromagnetic nickel (Ni) pillars on a soft PDMS substrate. The pillars have diameters of 23-35 [mu]m, pitches of 60-70 [mu]m, and heights of 70-80 [mi]m. We used vibrating sample magnetometry to obtain hysteresis loops of the Ni pillar arrays which match well the properties of bulk Ni. With a field strength of 0.5 tesla and a field angle of 600, a uniform 10.5± 1 tilt angle of the pillar arrays was observed. Furthermore, we developed a model to capture the tilt angle as a function of the magnetic field, and showed that by replacing nickel to cobalt, the tilt angle could be increased to 30' with the same field. Meanwhile, simulations show good agreement with the experiments. Future work will focus on using these surfaces to actively transport water droplets and spread the liquid film via pillar movement. This work promises tunable surface designs for important device platforms in microfluidics, biological and optical applications. / by Yangying Zhu. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 97-104). / This research proposes and examines noninvasive, quantitative techniques to characterize tissue. The primary metrics investigated include estimation of longitudinal speed of sound and shearwave elastography. Additional metrics investigated include bioimpedance and functional tests specifically for muscle health quantification. Diagnosing and monitoring of health of muscle and liver tissue is the motivating clinical need. These proposed metrics and techniques are noninvasive, quantitative, and do not require calibration. Current standards of care for liver and muscle health include biopsy for liver and muscle or electromyography for muscle. Functional tests, also a gold standard for functional muscle health, are not as quantitative or robust as the metrics proposed here due to changes from patient type and mobility level. The metrics proposed here do not have the limitations as the current gold standards and can be applied robustly to patients for screening, diagnosis, and monitoring of disease - making medicine more precise and personalized. / by Rebecca Elizabeth Zubajlo. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 175-185. / by Bruce Graham Johnson. / M.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001. / Includes bibliographical references. / Combustion chamber deposits are found in virtually all internal combustion engines after a few hundred hours of operation. Deposits form on cylinder, piston, and head surfaces that are in contact with fuel-air mixture during the engine cycle. The effects of deposits include increased engine-out NOx emissions, octane requirement increase, and changes in flame speed and thermal efficiency. A framework is developed for examining the physical and chemical processes that contribute to the formation of combustion chamber deposits. First, a hypothesis for the general mechanism of deposit formation is developed from a review of previous work on this issue. The key features of this mechanism are formation of deposit precursor species from fuel and air as the flame quenches at the engine wall, diffusive and convective transport of these species to the wall, and condensation or adsorption at the wall surface. The experimental system and methodology developed in this work are meant to provide insight into the interactions between these processes, and in particular to study the chemical mechanisms that contribute to the formation of deposit precursor species. A cooled low pressure flat flame burner is used to produce steady-state propane-air flames doped with toluene, a known deposit forming species. / (cont.) Profiles of concentrations and temperature are measured using infrared spectroscopy and gas chromatography techniques. In conjunction with the experiments, a one-dimensional numerical model is developed, capable of simulating flame quenching with deposition over a range of conditions extending from the low pressure, steady state burner experiments to high pressure, rapid transient engine conditions, using chemical mechanisms of precursor formation that may be determined experimentally. Modeling of deposition with simplified chemical mechanisms reveals that deposition by condensation can reproduce trends observed in experiments by other researchers; however, adsorption could still be a contributing factor. Experimental observations of toluene-doped flames show the formation of oxygenated compounds such as benzaldehyde and benzofuran, which are likely deposit precursor candidates. The methodology developed in this thesis shows promise for determining deposit precursor identities and formation mechanisms for important fuel components, and for clarifying the role of gas-phase processes in the formation of combustion chamber deposits. / by Christopher O'Brien. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996. / Includes bibliographical references (leaves 82-83). / by Sooyong Lee. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008. / Includes bibliographical references (leaves 59-60). / The goal of this study was to determine performance curves for a variety of positive displacement pumps in order to select an efficient and low cost option for use as a boiler feed pump in a 1-kWe organic Rankine cycle (ORC) system built by the Solar Turbine Group in Lesotho. The pumps tested included OEM plunger and piston pumps, and rotary vane-type power steering pumps purchased from a junk yard. Motor speed and torque were measured at different flow rates to determine the power consumed to move fluid in the prescribed pressure regime. The test station was designed to pump deionized water; it was intended that measurements and calculations would then be non-dimensionalized and used to predict the ORC working fluid's properties. Unfortunately, deionized water caused the power steering pump shafts to seize; the efficiencies were below anticipated and the pumps were unable to operate under the specified pressures. It was discovered, after WD-40 was added to the water, that power steering pumps performed best when moving fluids with more lubricity. The optimal pump was selected based on how the pump efficiency affected the overall ORC system efficiency, defined as the electrical work output divided by the heat input, and the net electric power output. Power steering pumps achieved efficiencies between 34%-54% under the desired ORC operating conditions with water-oil emulsion as the working fluid. For that pump efficiency range, the overall solar thermal electric ORC system efficiency would be 7.4%-8.5% and the overall system cost would be USD 4.59-5.27 per installed Watt. Made specifically for pumping hydroflurorcarbons, the working fluid used in STG's ORC, the OEM Dynex pump exhibited poorer performance than predicted. The pump efficiency of 31% gave a system efficiency of 7.1% and a cost of USD 6.40 per installed Watt. The OEM water piston and plunger pumps made by Hypro achieved efficiencies of 70% and 81%, respectively, under the same ORC operating conditions described above. / (cont) For those pump efficiencies, the overall system efficiencies would be 9.0% and 9.2% and the costs would be USD 4.58 and 4.63 per installed Watt, respectively. The most optimal pump is the HyproPiston pump; although it costs nearly six times that of a power steering pump, the overall system cost is lower when normalized over the power output. / by Cynthia Lin. / S.B.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, February 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (page 25). / The process of milling corn into flour in many rural communities of East Africa has remained a traditional mortar and pestle process for centuries. Milling machines have failed in these communities largely due to poor performance, as well as high cost, and as a result the incredibly labor intensive process continues. This study seeks to design and manufacture a prototype mill that will address the needs of the communities in question. Initial testing on existing milling equipment generated a quantitative understanding of the strengths and shortfalls of the available machines, and informed the design of a new mill. Once the design specifications were determined, a two stage, "twinmill" incorporating a stock low cost mill performing an initial coarse grind and a second identical mill that used modified grinding plates to produce finer flour was built. As expected, the two stage solution outperformed the existing machines by a significant margin: the acceptable flour yields rose from the 30-40 percent range, to consistently in the mid 60s. After subsequent modifications to the fine pass machine grinding plates, yields rose even higher, to an average of about 80 percent. / by Melvin Gustavo Salinas. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005. / Includes bibliographical references (leaf 51). / A process known as Constant Denaturant Capillary Electrophoresis is used to separate mutant from wild-type DNA at fractions down to 10-7. A device known as an Ultra-high Throughput Mutational Spectrometer is being created to run 10,000 parallel channels of CDCE in order to correlate multiple point mutations in DNA with the diseases that they can cause, such as cancer. By separating the DNA in large populations, the underlying causes of such diseases can be identified. To successfully run CDCE, a high viscosity polymer gel must be loaded into each of the 10,000 channels, each of which are composed of an individual glass capillary with a 75 m inner diameter. A mechanism was designed and tested which loaded gel into 8 channels simultaneously. The mechanism was used to test the relationship between gel loading time in relation to varied pressure and capillary length, through 45 total runs, with 8 channels per run. The relationships were characterized, resulting in two equations that enable an accurate prediction of the fill time necessary to load 10,000 parallel channels simultaneously under varied conditions. / by Nathan B. Ball. / S.B.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1994. / Includes bibliographical references (leaves 157-161). / by Yale Goldis. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999. / Includes bibliographical references (leaf 72). / by Andrew D. McCraith. / S.M.