Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 21). / The deliberate structuring of bimetallic nanoparticles has useful applications in both fuel cell applications and biomedical research. This thesis studies the replacement reaction between platinum ions and silver nanoparticles, with the goal of synthesizing platinum-shelled silver nanoparticles. Specifically, the molar feeding ratio and the temperature dependence on the reaction were investigated. At low levels of supplied platinum, the nanoshells were only partially formed, but at a 1:1 molar ratio, non-uniform thickness nanoshells were formed with large amounts of silver on the surface. The temperature dependence showed increasingly thick shell formation; however, cyclic voltammetry measurements indicated the surface of the nanoparticles contained excessive levels of silver, deeming the particles inadequate for use as fuel cell catalysts. Through high temperature reactions, the surface plasmon resonance excitations peaks of the silver nanoparticles were shifted 100nm higher, pushing the peaks closer to the visible spectrum from the deep ultraviolet region. / by Archimedes Stuk. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002. / Includes bibliographical references (leaves 36-38). / by Ana Gabriela Isasi. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 83-86). / This thesis addresses the problem of controlling a dynamical system subject to both parametric uncertainties and abrupt changes in the dynamic structure of the system, by proposing a shared control architecture predicated on a suitable division of responsibilities between supervisory human operators and adaptive control algorithms. Dynamical anomalies, such as the sudden introduction of unmodeled dynamics or time delays, present difficulties in control for both human operators and autonomous model-based control algorithms. Online adjustment to extenuate the effects of parametric uncertainty is possible through the proper use of adaptive control, and to a certain extent is paralleled by the learning of dynamics and adaptation of control policies by humans. Changes to the dynamic structure of the system, however, may lead to poor closed-loop performance and instability, regardless of whether the control input is determined by a human or adaptive control algorithm. The shared decision-making and control architecture introduced in this thesis tasks supervisory human operators with several high-level responsibilities in the mitigation of dynamical anomalies, and utilizes adaptive control algorithms for low-level control and command tracking duties. The shared controller is defined for dynamical systems where the full state is assumed to be measured as well as the case where only certain outputs are measured. The ability to respond to anomalies using this shared control architecture is demonstrated in several simulations of scenarios related to flight control, including the longitudinal control of an unmanned aerial vehicle whose actuator dynamics abruptly change from first-order to second-order, and the lateral-directional control of a fixed-wing aircraft subject to two anomalies concerning actuator dynamics and sensor dynamics. These simulations demonstrate how the division of responsibilities proposed in this thesis enables the recovery of closed-loop system stability and command tracking performance following the aforementioned anomalies. / by Benjamin T. Thomsen. / S.M.

Thesis (M.S.) Massachusetts Institute of Technology. Dept. of Mechanical Engineering, 1948. / Bibliography: leaf 41. / by James Patrick Hartnett. / M.S.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008. / "June 2008." / At the request of K2 Sports, in Seattle, Washington, a machine was constructed to measure the base profile of skis and snowboards. The measurements to be taken included overall length, running surface length, locations of the contact points, tip and tail height, and maximum camber height, each of these values having a strong effect on the performance of the ski or snowboard. Parts from two existing non-functioning machines, one acquired in K2 Sports' acquisition of Line Skis, and the other constructed by previous interns, were used to construct the new machine. The new machine was designed to function by placing the ski on two parallel flat surfaces on the Line machine's frame with a gap between for a laser sensor. The guide rail and cart system from the past interns' machine was retrofitted with the motor and controls of the Line machine and a new drive belt to carry the sensor along the length of the ski. A Micro Epsilon optoNCDT 1401-200 laser sensor having a resolution of 100 pm and a data acquisition rate of 1kHz was used to acquire the height data as the sensor moved at a controlled speed along the entire length of the ski. Data was recorded using Micro Epsilon's ild1401 Tool software, and processed automatically through a National Instruments LabVIEW Virtual Instrument. The machine was presented to K2 engineers on August 15, 2007. It accurately records the desired measurements which are helpful in predicting the performance effects of design changes to the ski or snowboard. The machine remains in daily use. / by Timothy F. Pier. / S.B.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1970. / Bibliography: leaf 15. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 73-75). / Recent works have discussed "chaotic" or "Type-II" riser motion and suggested that it is a general feature of VIV riser response. Chaotic riser response contains broad-banded harmonics and a combination of standing and traveling waves, unlike periodic or " Type-I" motion which contains only standing waves and exhibits very narrow harmonics. The extent to which regions of chaotic response increase the damage on the riser had not previously been explored in detail. To facilitate the exploration, a method for separating the effects of the fundamental frequency, higher harmonics, and the chaotic content was developed and applied to four cases from the NDP 38m data set. For test of a bare riser in uniform flow, the damage was increased by a factor of 2 when the higher harmonics of the signal were included and another factor of 2 when the broad-banded harmonics were included. Similar results were obtained for tests of the bare riser in sheared flow as well as a 50% straked riser in uniform and sheared flow. After the results have been supported by theoretical estimations from first principles, it is concluded that the increase in fatigue damage resulting from the chaotic behavior of the riser is as important as that of the higher harmonics of the signal. / by Rachel Elizabeth Price. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012. / Page 85 blank. Cataloged from PDF version of thesis. / Includes bibliographical references (p. 81-84). / Plug-in hybrid electric vehicles (PHEVs) are vehicles that utilize power from both an internal combustion engine and an electric battery that can be recharged from the grid. Simulations of series, parallel, and split-architecture PHEVs, as well as parallel and split PHEVs with ultracapacitors, were performed in Autonomie, the vehicle simulation package released by Argonne National Laboratory as the successor to the Powertrain System Analysis Toolkit (PSAT). The PHEV configurations were parameterized by battery capacity, motor peak power, engine peak power, and ultracapacitor capacity if applicable. Results were compared to EPA data for the Chevrolet Volt and Toyota Prius, showing close agreement on values for fuel consumption, charge-depleting range, and acceleration time. While most PHEVs today are of the series or split variety, analysis of the simulation results indicates that including features from a parallel architecture could improve performance without undue additional cost from components. In addition, ultracapacitors were found to have a significant positive effect on all-electric fuel consumption. Furthermore, pricing models were created to predict approximate MSRP and 5-year cost-to-own for future PHEVs. These models were incorporated into a graphical user interface built using MATLAB that allows access to the simulation results in a way that is accessible to the average consumer. / by Daniel Sotingco. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 277-284). / The performance of marine vehicles is largely influenced by interactions with the flow around their hull, both self-generated and environmentally driven. To improve performance through flow control, a detailed, real-time measurement of the near-field flow is necessary, yet such sensing capability is presently unavailable. Looking to nature for inspiration, fish employ the distributed pressure and velocity sensing capability of their lateral line sensory organ to mediate navigation and control behaviors that, if replicated, could benefit engineered systems. Through a series of towing tank and field experiments, it was found that while distributed pressure measurements on marine vehicles enabled the detection of near-body flow phenomena, the size, cost, and mounting requirements of commercial sensors lead to sparse arrays and substantial gaps in the characterization of the flow field. To address the challenges associated with obtaining spatially-dense pressure measurements on curved surfaces in marine environments, a new waterproof and conformal pressure sensor array was developed based on a closed-cell piezo resistive foam composed of carbon black-doped-silicone composite (CBPDMS foam). The response of the CBPDMS foam sensor arrays was characterized using periodic hydrodynamic pressure stimuli from vertical plunging and water waves, and a piecewise polynomial calibration was developed to describe the sensor response. The sensitivity and frequency response of the sensor arrays was also documented through a series of biologically-inspired hydrodynamic stimuli, including the flow from a dipole source, and the Karmin vortical wake flow behind a circular cylinder. The CBPDMS foam sensor arrays have significant advantages over existing commercial sensors for distributed flow reconstruction and control. They are found to have sensitivity on the order of 5 Pascal, frequency range of 0.5-35 Hertz, are contained in a waterproof and completely flexible package, and have material cost less than $10 per sensor. / by Jeff Ernest Dusek. / Ph. D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005. / Includes bibliographical references (leaves 43-46). / Thrombosis is an initiating response to a vascular injury, which aids in the repair and remodeling of the vessel wall. However, if this process remains unchecked, occlusion of the arterial lumen may quickly occur. The arterial vascular bed is a delicate and life-sustaining environment, in which a pathological thrombosis can bring about devastating conclusions such as acute vascular syndromes or post-interventional thrombosis. In order to explore these flow-dependent thrombotic reactions, it is essential to consider the physical environment present inside the vasculature. A novel in vitro, high-throughput method for creating one-pass blood flows has been developed to model the arterial environment. Flow is generated in a matrix of small glass tubes with varying inner diameters through the use of a constant pressure drop. Using this technique, a variety of flow rates are created in the numerous tubes, resulting in a variety of flow shear rates. In addition, this technique allows for the monitoring of sensitive, flow-dependent processes without the disturbances from pump action and circuit effects. A detailed discussion about the goals of the proposed systems is included, as well as the methodology employed to choose the optimal flow system, and the process by which the components of the system evolved in design. / (cont.) Finally, tests are formulated in order to explore the issues of biological feasibility, noise, precision, and accuracy related to the proposed system and make to make improvements on the design accordingly. / by Javier Jacobo Echenique. / S.B.