Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / Includes bibliographical references (p. 29). / This research assesses the effects of planar flexural elements on the repeatability of a high-precision kinematic coupling. Few devices exist that are capable of passive, repeatable nanoscale fixturing; this research facilitates the design of such devices by providing a more complete understanding of how flexural elements affect their performance. Improvements in coupling technology are expected to decrease production and assembly costs in a variety of industries where repeatable fixturing is required (e.g. the semiconductor, automotive, and tooling and machinery industries), and have the potential to improve the quality of research in a wide range of fields by increasing the speed and accuracy of manufacturing processes and metrology systems. Flexures serve to improve the performance of ball-and-flat contacts by preventing motion of the flats in the direction perpendicular to the contacts while allowing motion in tangential directions, thus reducing the effects of friction and wear at the interface. Flexural elements have been used to reduce hysteresis and prevent overconstraint in kinematic couplings but the use of planar flexures as friction and wear reducing devices has not been previously studied. / (cont.) A kinematic coupling that uses planar flexures was designed, constructed and tested. This coupling showed similar repeatability to a rigid coupling used as a control when the ball-and-flat contacts of both were free of wear; however, the flexure-based coupling performed much better than the control coupling after the contacts had been roughened by material failures resulting from repeated loading. / by Martin Alan Segado. / S.B.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997. / Includes bibliographical references (leaf 123). / by Jacob Einhorn. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009. / Includes bibliographical references (leaves 185-192). / Handling and assembling individual nanostructures to bigger scale systems such as MEMS have been the biggest challenge. A deterministic assembly of individual carbon nanotubes by transplanting them to MEMS structures is demonstrated with a new assembly method, "transplanting assembly." This thesis describes development of a novel assembly technique by transforming individual CNTs assemblable, which enables manual, parallel or automated assembly of individual CNTs in a deterministic way. The key idea of transplanting assembly is to grow individual CNT strands on a substrate at optimal growth conditions, to encapsulate individual CNTs into micro-scale carrier blocks and to transplant them to the target locations. This new assembly method enables products such as CNT-tipped AFM probes in a predictable and repeatable manner. The major research topics discussed in this thesis are: (1) the methods to grow vertically aligned single strand CNTs at predefined locations, (2) the encapsulation method to preserve/control the orientation/exposed length of an individual CNT during transplanting, and (3) the assembly scheme to locate/release an individual CNT at the target location. An array of CNTs was grown from the nickel nano-dots, which were defined on Si substrates using electron-beam lithography followed by metal deposition and lift-off processes. Each CNT strand was embedded into a MEMS scale polymer block which serves as a CNT carrier. A double polymeric layer encapsulation was designed and implemented: the top SU-8 forms the body of the carrier while the bottom PMGI layer holds the body until the release of the carrier from the substrate and then is going to be removed to expose the CNT tip with a predefined length. A model was developed to predict mechanical behavior of individual CNTs under the flow of liquid polymers. Manual assembly of a polymer block to the end of a tipless AFM cantilever forms a CNT-tipped AFM probe, which can be accomplished in minutes without laborious weeding, trimming and welding process. The AFM scanning results confirmed the CNTtipped AFM probe's much improved imaging performance and potential for scanning soft biological samples at nanometer resolutions. / by Soohyimg Kim. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 221-225). / As energy becomes an increasingly important issue for generations to come, it is crucial to develop tools for valuing and understanding energy projects from an economic perspective since ultimately only economically viable solutions will be pushed forward. A model is developed for valuing a generic offshore floating wind farm from a corporate finance perspective. The model is used to value the project based on multiple valuation metrics and to generate sensitivity analyses on multiple important technical, cost and financial parameters. It is found that offshore wind projects can be economically viable under current conditions contingent on high annual mean wind speed and government support. In addition, it is also found that financial parameters prove to be equally or even more important than technical parameters in affecting the overall project value. Furthermore, the wind speed and power output are modeled using a mean reverting Ornstein - Uhlenbeck process whereby it is found that while wind speed is positively autocorrelated, the averaging period plays an important role in determining the nature and extent of the autocorrelation. Finally, the valuation is extended and generalized to a Black-Scholes option based valuation of any project whose underlying asset follows a mean reverting process, whereby a model is developed to find the debt and equity values under the assumption of time independence. The tools developed for this purpose can prove to be useful in other applications besides energy, such as shipping and commodities, as the underlying characteristics of energy projects are often similar across other markets. / by Andrew Nanopoulos. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000. / Includes bibliographical references (p. 99-100). / by Benjamin T. Krupp. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003. / Includes bibliographical references (p. 119-120). / by Christian P. Grippo. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017. / Page 230 blank. Cataloged from PDF version of thesis. / Includes bibliographical references (pages 221-229). / Separating components of a gas from a mixture is a critical step in several important industrial processes including natural gas purification, hydrogen production, carbon dioxide sequestration, and oxy-combustion. For such applications, gas separation membranes are attractive because they offer relatively low energy costs but can be limited by low flow rates and low selectivities. Nanoporous graphene membranes have the potential to exceed the permeance and selectivity limits of existing gas separation membranes. This is made possible by the atomic thickness of the material, which can support sub-nanometer pores that enable molecular sieving while presenting low resistance to permeate flow. The feasibility of gas separation by graphene nanopores has been demonstrated experimentally on micron-scale areas of graphene. However, scaling up to macroscopic sizes presents significant challenges, including graphene imperfections and control of the selective nanopore size distribution across large areas. The overall objective of this thesis research is to develop macroscopic graphene membranes for gas separation. Investigation reveals that the inherent permeance of large areas of graphene results from the presence of micron-scale tears and nanometer-scale intrinsic defects. Stacking multiple graphene layers is shown to reduce leakage exponentially. A model is developed for the inherent permeance of multi-layer graphene and shown to accurately explain measured flow rates. Applying this model to membranes with created selective pores, it is predicted that by proper choice of the support membrane beneath graphene or adequate leakage sealing, it should be possible to construct a selectively permeable graphene membrane despite the presence of defects. Interfacial polymerization and atomic layer deposition steps during membrane fabrication are shown to effectively seal micron-scale tears and nanometer-scale defects in graphene. The support membrane is designed to isolate intrinsic defects and reduce leakage through tears. Methods of creating a high density of selectively permeable nanopores are explored. Knudsen selectivity is achieved using macroscopic three-layer graphene membranes on polymer supports by high density ion bombardment. Separation ratios exceeding the Knudsen effusion limit are achieved with single-layer graphene on optimized supports by low density ion bombardment followed by oxygen plasma etching, providing evidence of molecular sieving based gas separation through centimeter-scale graphene membranes. / by Michael S. H. Boutilier. / Ph. D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 107-110). / Ultrasound is a commonly used medical imaging modality for non-invasive examination of soft tissue. Clinical ultrasound scanning requires significant contact of the transducer face with the patient, and the contact force exerted by the sonographer can vary widely throughout a scan or from scan to scan. This thesis explores the design and development of an electromechanical system to measure the contact force during ultrasound scanning. The device is a handheld ultrasound probe with force sensors integrated into its housing such that the force distribution across the ultrasound transducer face can be measured. The device was used to perform shear wave elastography on tissue-mimicking phantoms and ex vivo tissue at varying force distributions. A gradient in applied pressure introduced a gradient in elasticity across the image for ex vivo tissue but not for phantoms. To consider how the device integrates into the overall system, a human factors study was done to compare feedback modalities provided to the human operator during ultrasound scanning. Visual feedback was more effective than haptic feedback for force tracking, but at expense of ultrasound path tracking. Lastly, two methods of data synchronization of the acquired force data and ultrasound images are considered. A three tap software synchronization method is a feasible alternative when hardware synchronization is unavailable. As a whole, this system will improve the repeatability and capabilities of ultrasound imaging. / by Athena Yeh Huang. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995. / Includes bibliographical references (p. 199-206). / by Denis Rancourt. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1994. / Includes bibliographical references (p. 183-193). / by Lian Fang. / Ph.D.