Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999. / Includes bibliographical references (leaf 72). / by Marcelo Augusto Quintella. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 151-155). / Intermittently-operated water systems struggle to equitably and effectively distribute clean water to customers. One common customer response to intermittency is to supplement the water system's pressure by using a household, or residential, booster pump. When such booster pumps are directly connected to the water utility's supply pipe, without an underground isolation tank (sump), they often induce negative pressure in the supply pipe which increases the flow rate. Unfortunately, where leakage rates are high, this negative pressure also increases the risk of contaminant intrusion. This thesis presents the iterative design and field testing of a patent-pending, full-bore, back-pressure regulating valve. The valve's simple mechanism relies on a stabilized collapsing tube, or 'Starling Resistor,'which when installed at a customer's connection, controls the flow rate and prevents booster pumps from creating negative pressure in the supply pipe. In collaboration with the Delhi Jal Board and several private partners, the valve's performance was verified in two rounds of field trials in neighborhoods of New Delhi, India including Pitampura, Azad Market, Vivek Vihar, Malvia Nagar, and Vasant Vihar. Using a crossover study, the valve was found to reduce the total contamination risk across all 19 tested houses during supply times by a median of 80%. The valve prevented 96% of pressure below -1 meter and an average of 53 minutes per day, per connection of total negative pressure. In an estimated worst-case scenario for contaminant intrusion, the presence of the valve reduced the contamination risk by two orders of magnitude at six customer connections - enough to correspond to significant reductions in health risks. / by David Donald James Taylor. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997. / Includes bibliographical references (p. 171-172). / by Donald R. Nohavec. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995. / Includes bibliographical references (p. 121). / by Crispin Mount Miller. / Ph.D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / "September 2007." / Includes bibliographical references (p. 94-95). / The purpose of this thesis is to identify a solution for one of the several mechanical concerns that Varian Semiconductor Equipment is facing to achieve its goal. Managers and engineers are trying to lead Varian Semiconductor Equipment to a flow line shipment program, the intent being to eliminate the clean room area and ship all of the components of the ion implanter directly from the flow line to the customer, without the currently necessary step of a final assembly. In particular this work examines the correct alignment of the source chamber inside the terminal module prior to the final assembly of ion implantation equipment. In the flow line shipment context, the correct alignment of subassembly components becomes a critical aspect and needs to be checked before a shipment, since assembly errors or out of specification components from suppliers may lead to long delays and reworks. This last aspect cannot be ignored, since if adjustments and modifications can easily be accomplished in the flow line without conspicuous waste of time, the same cannot be said in the field, thousands miles away from the factory. Specifically, the contribution of the project is to achieve the right orientation of the source chamber in relation to the position of the feet of the terminal module, by designing a mechanical fixture. The tool has been conceived to be used directly in the terminal module flow line, in order to allow technicians to quickly perform a correct alignment and easily point out any possible misalignment due to bad components or assembly errors. The main components of the fixture are the jig that checks the position of the insulators and a vertical target where two lasers shoot to align the source chamber. / by Matteo Liscaio. / M.Eng.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008. / Includes bibliographical references (leaf 46). / At MD Company (Singapore), the syringe value stream faces escalating labor cost and high labor turnover. Two labor allocations were proposed previously to optimize current labor resources, with the aim of controlling the labor cost effectively without affecting the production. Proposal Two, which had demonstrated significant increase in productivity and reduced labor cost through computer simulations, entailed an addition of two workers each in the new dedicated inspector and material handler job designations. The associated new job scopes combine tasks which are currently assigned broadly to production technicians working on the syringe production floor. A work study approach was undertaken with the broad aim of reducing waste from the new job scopes, as well as to verify headcount used in the simulation of Proposal 2. Dedicating tasks to individuals presented opportunities to reduce repetition and to achieve collective savings via changes in methods. Within the work study, a method study provided a theoretical basis of how best to carry out the new job scopes, while a time study established time needed to perform a given set of tasks. Results found were consistent with that from simulation of Proposal 2. Further improvements were made in reducing inspection cycle time through streamlining of inspections. Identification and separation of tasks which are not performed constantly paved the way for one of the two material handlers to be hired on an overtime basis. Future iterative identification of waste and its removal could help current work converge to an optimal work standard. / by Gar Yan Ng. / M.Eng.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009. / Includes bibliographical references (p. 109-110). / A new apparatus was constructed to fit the Impact and Crashworthiness Lab's dual actuator custom-made loading frame that has force or position control. The strip is pre-bent into an elbow configuration and fastened by the vertical and horizontal grips. One end of the metal strip is subjected to a predefined constant restraining force, while the other is pulled with a constant velocity to cause a rolling deformation over a prescribed die radius. A series of 40 tests, using TRIP 690 steel, was performed for various combinations of die radius, magnitude of pretension, and die/strip friction. Based on the experimental results, a deformation and failure map was generated, showing ranges of safe forming. Depending on the interplay of different parameters, fracture occurs either on the sidewall or on the die radius, in which case, a close examination of the surface reveals it is slant. Combined theoretical, experimental, and numerical analyses are presented. The present study confirmed previous results published in the literature [1,5] that the pretension needed to fracture a metal strip increases with die radius and tends asymptotically to a constant value. What is new in the present investigation, however, is that this relationship has been quantified for a particular steel of interest for automotive applications. In addition, a method was outlined to predict fracture through finite element simulations, which was lacking in the earlier treatment of a similar problem. / by Danielle Léa Issa. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 113-120). / This thesis describes the development of an independent, on-board visual servoing system which allows a computationally impoverished aerial vehicle to autonomously identify and track a dynamic surface target. Image segmentation and target tracking algorithms are developed for the specific task of monitoring whales at sea. The computer vision algorithms' estimates prove to be accurate enough for quadrotor stabilization while being computationally fast enough to be processed on-board the platform. This differs from current techniques which require off-board processing of images for vehicle localization and control. The vision algorithm is evaluated on video footage to validate its performance and robustness. The quadrotor is then modeled to motivate and guide the development of Linear Quadratic Regulator (LQR) controllers for maneuvering the quadrotor. The controllers are tuned using a motion capture system which provides ground truth state measurements. The vision system is integrated into the control scheme to allow the quadrotor to track an iCreate. Additionally, an Extended Kalman Filter (EKF) fuses the vision system position estimates with attitude and acceleration measurements from an on-board Inertial Measurement Unit (IMU) to allow the quadrotor to track a moving target without external localization. / by William Clayton Selby. / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 22). / Granular medias such as sands, beads and even coffee exhibit the phenomenon of jamming when exposed to compressive stresses. Jamming refers to the process by which a normally smooth flowing material comprised of discrete individual grains forms a pseudo-solid when subjected to stress. Under normal loading, the interactions between individual particles of the material are not great enough to severely inhibit relative motion but when the macroscopic material is subjected to a large compressive force, the interlocking of and friction between the individual granular particles takes over and forms an interlocked, solid like structure. The extent to which a media jams is dependent upon many properties of the media including the size, shape, homogeneity, surface texture and chemical makeup of the particles. It is also dependent upon the magnitude of the force applied to the media and the distribution of the force applied. Using vacuum to apply stress, jammed media can be used to create easily reconfigurable structural elements. The analysis of such a structural element is very similar to analyses done in soil mechanics where the "strength" of the soil depends on the stress applied, the rate of stress application and the physical properties of the soil particles themselves. Most applications of soil mechanics (such as with buildings or vehicles) are concerned with the interaction of the force at what could relatively be considered the surface of the soil due to the much greater diameter of Earth. A jammed media structure is of finite thickness and thus loads can easily permeate through the entire structure. Thus to properly understand the mechanics under which jamming can occur a simple model was created. This model looks into the behavior of jammed structures subjected to three point bending. It does so by examining the forces between the individual particles and using simple beam bending mechanics. A downward trend was observed in the strength of a jammed structure relative to the grain size of the granular media. This trend was corroborated by a physical test of beams on an Instron machine. / by Sammy Mohsen Khalifa. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002. / Includes bibliographical references (p. 165-170). / Piezoelectric Micro-Hydraulic Transducers are compact high power density transducers, which can function bi-directionally as actuators/micropumps and/or power generators. They are designed to generate 0.5-1W power at frequencies of ~10-20kHz, resulting in high power densities approaching 500W/kg. These devices are comprised of a main chamber, two actively controlled valves, a low-pressure reservoir and a high-pressure reservoir. This thesis reports on modeling and design considerations for Micro-Hydraulic Piezoelectric Power Generators. Since these devices are complex fluid and structural systems, comprehensive simulation tools are needed for effective design. Operation of each subcomponent of the device is highly coupled and every design decision should be made with remaining components in mind. A system level simulation tool has been developed using Matlab/Simulink, by integrating models for different energy domains, namely fluids, structures, piezoelectrics and circuitry. The simulation architecture allows for integration of the elastic equations of structural members into the dynamic simulations as well as monitoring of important parameters such as chamber pressure, flowrate, and various structural component deflections and stresses. Using the simulation, the operation of the system is analyzed and important design considerations are evaluated. Fluidic oscillations within the system are analyzed and an optimization procedure for the membrane structure within the main chamber is presented. Parameter studies are performed for different piezoelectric materials, system compliances, and circuit topologies. Tradeoffs between operation conditions and their effect on the performance are discussed. A design procedure is developed. Results indicate that system efficiency is highly dependent on compliances within the device structure, the type of piezoelectric material used and rectifier circuit topology. / by Onnik Yaglioglu. / S.M.