Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 34-35). / Human society and civilization rely on the constant availability of fresh water. In regions where a local source of potable water is not available, a transportation and distribution pipe system is employed. When these pipes feature cracks, holes, or leaks, the result is a substantial waste of energy and natural resources. As communities grow the loss due to these flaws becomes more costly, and the motivation to detect leaks increases. The purpose of this thesis project is to develop pressure difference-based sensing cells that can be used in an untethered leak-detection device. This device is to be deployed in water distribution networks to locate leaks so that water loss can be minimized. Design of these sensing cells and of the leak-detection device entails evaluating the size and shape of a leak's low pressure region. In this paper, leaks are investigated in this regard and a number of different pressure difference-sensing sensor technologies are explored and evaluated. A silicone-rubber deflecting membrane is selected for the application. The relationship between pressure-derived force acting on its surface and its maximum deflection is evaluated as a means of leak detection. Ultimately, testing reveals that these types of cells are simple and robust. While they deflect as anticipated, the formula used to predict their behavior does not fit the experimental results. It is concluded that this type of pressure difference-sensing membrane is well-suited for application within an untethered sensor, with the opportunity for deeper material selection and more accurate deflection analysis. / by Pall Magnus Kornmayer. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999. / Includes bibliographical references (p. 119-123). / by Dye-Zone A. Chen. / S.M.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996. / Includes bibliographical references (leaves 120-125). / by Vikas Sharma. / Sc.D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1964. / MICROFICHE COPY AVAILABLE IN ENGINEERING. MIT copy bound with: Commuter transportation: problems and solutions / Thomas J. Cerny, III. 1964. -- A study of methods of determining the softness of toilet tissue / William Bedford Harper, Jr. 1964. -- Comparison of burning rates, pressures, and temperatures for solid propellants under controlled and uncontrolled burning processes / Dennis Lee Hinrichs. 1964. -- Effect of vacuum on sliding friction coefficient / Clarence Walter Malick. 1964. -- Feasibility study of an active vibration damping system / William Andrew Nelson, Junior. 1964. -- A method of estimating electric power costs for underdeveloped countries / Walter Thomas Norwich. 1964. / Includes bibliographical references (leaves 11-12). / by David M. Anderson. / B.S.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 68-79). / Vapor condensation is routinely used as an effective means of transferring heat or separating fluids for applications ranging from personal electronic device thermal management to natural gas processing and electric power generation. Filmwise condensation, where the condensed fluid forms a liquid film, is prevalent in typical industrial-scale systems. Conversely, dropwise condensation, where the condensate forms discrete liquid droplets, results in an improvement in heat transfer performance of up to an order of magnitude compared to filmwise condensation. We explored rare earth oxides (REOs) as a potential coating to induce dropwise condensation of water; specifically, we experimentally demonstrated that the mechanism for REO hydrophobicity results from adsorption of contaminants from the atmosphere. We also used graphene, which is hydrophobic in nature, as a coating to achieve robust dropwise water condensation. With a graphene coating, we demonstrated a 4x improvement in water condensation heat transfer compared to filmwise condensation with robustness superior to state-of-the-art hydrophobic monolayer coatings. Meanwhile, low surface tension condensates pose a unique challenge since they often form a film, even on hydrophobic coatings. Lubricant infused surfaces (LIS) represent a potential solution, where a lubricant immiscible with the low surface tension condensate is infused into a rough structure on the condenser surface to repel the condensate. We developed a detailed surface-energy-based model to provide design guidelines for any arbitrary LIS system. We then characterized heat transfer coefficients during condensation of low surface tension fluids on LIS in a controlled environmental chamber for the first time, where a 5x improvement was demonstrated compared to filmwise condensation. The improved condensation heat transfer coefficients realized by LIS for low surface tension fluids and by REOs and graphene for water present opportunities for significant energy savings in device thermal management, heating and cooling, and power generation. / by Daniel John Preston. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1991. / Includes bibliographical references (leaves 169-174). / by Hang-sheng Hou. / Ph.D.

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

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000. / Includes bibliographical references (leaf 142). / The objective of this project is to design and fabricate a full-scale Chemical- Mechanical Polishing machine, whose performance is much higher than that of the existing technology. The machine consists of a lower structure, an upper structure, and a polishing head. This thesis covers the design of the upper structure in detail. The machine was recently built and tested. The upper machine frame, which is the moving component of this polishing tool, was designed for maximum rigidity using FEA analysis. Vibrational analysis was also performed to design a mechanically quiet system. All of the associated components were designed with extreme precision in mind. In addition to the upper structure, a loading mechanism was also designed for the polishing head. Two high-precision linear drive mechanisms, the z-axis and the x-axis, were designed as the two major axes of motion for this machine tool. The z-axis applies the normal polishing force of 1500 lbs. This axis has a travel of 8", maximum velocity of 4 in/sec, resolution of 50 nm, and a repeatability of 0.0005". The z-axis applies the load using a pneumatic piston, in parallel with a "rotary" ball screw. The x-axis moves the upper machine structure, which weighs over 2000 lbs. The x-axis has a travel of 82", a maximum velocity of 12 in/sec, a maximum acceleration of 0.2g's, a resolution of 10 microns, and a repeatability of 0.002". The x-axis is driven on both sides with two separate motors and ball screws. / by Amir Torkaman. / S.M.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1988. / Includes bibliographical references (leaf 22). / by George Alexander Holt III. / B.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. / Includes bibliographical references. / In order to utilize conducting polymer actuators as a viable engineering solution, it is necessary to produce usable levels of force with a reasonable bandwidth. Polypyrrole actuated at temperatures as high as 100 °C increases stress magnitudes by as much as 4x and stress rates by 5x. The effect is caused by a combination of decreased solution resistance and increased ion diffusion within the polymer. However, these temperatures cause accelerated degradation due to the time-temperature correlation common to viscoelastic polymers. Actuation at these temperatures can decrease cycle life by as much as 20x. Excessive heating without actuation can also result in poor actuator performance. Impedance spectroscopy coupled with electro-mechanical analysis highlighted previous results and also showed an improved frequency response from actuation at high temperatures. / by Michael R. Del Zio. / S.M.