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DSpace at MIT (83,207 recursos)
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Mechanical Engineering - Master's degree

Mostrando recursos 1 - 20 de 3,218

1. Boundary condition effects on vibrating cantilever beams - Monti, Jonathan David
Compliant mechanisms continue to see increased used in many areas of modem engineering. Their low cost, ease of production and manufacturing, and precision of motion have made them attractive solutions to many controlled motion systems such as nanopositioners or linear platforms. However, in some applications the stiffness requirements for the devices to function properly and the stiffness requirements for devices to survive outside effects such at vibration or impulse create a conflict which cannot be rectified with traditional engineering approaches. By utilizing boundary controls which acted only when a flexure reached a certain deflection, the original purpose of the device...

2. Research maturity levels : implementation and refinement of an online tool for characterizing the progression of research - Liggett, Melinda L. (Melinda Lois)
Technology Readiness Levels are used in industry to help allocate resources, plan research and development, and clarify communication. Research Maturity Levels, proposed by Ming Leong in 2011, are designed to bring these same benefits to the academic research community. At its inception, the RML framework was accessible by a paper survey, and administrators of the survey could provide a visualization of research progress to respondents of the survey. In order to develop the survey as a helpful tool, the RML Framework was developed into an online tool. This enabled automatic visualizations and greater access to the framework. Discussed in this...

3. Decentralized mixing function control strategy for multi-robot informative persistent sensing applications - Hall, Gavin Chase
In this thesis, we present a robust adaptive control law that enables a team of robots to generate locally optimal closed path persistent sensing trajectories through information rich areas of a dynamic, unknown environment. This controller is novel in that it allows the robots to combine their global sensor estimates of the environment using a mixing function to opt for either: (1) minimum variance (probabilistic), (2) Voronoi approximation, or (3) Voronoi (geometric) sensing interpretations and resulting coverage strategies. As the robots travel along their paths, they continuously sample the environment and reshape their paths according to one of these three...

4. Phase stabilization of laser beams in a cold atom accelerometer - Byrne, Nicole (Nicole Malenie)
A cold atom accelerometer measures the displacement of a proof mass of laser cooled atoms with respect to an instrument reference frame. The cold atom interferometer's reference frame is defined by a pair of specially prepared, counter-propagating laser beams, that measure inertially induced atom displacements with nm scale resolution. This corresponds to acceleration sensitivities comparable to state of the art electro-mechanical accelerometers. In dynamic environments, sensitivity is limited by the stability of the relative laser phase of the two interrogation laser beams, which is adversely affected by vibrations and temperature fluctuations of the interrogation beam optics. Without an independent measurement,...

5. Magnetically suspended reaction sphere with one-axis hysteresis drive - Zhou, Lei., S.M. Massachusetts Institute of Technology
This thesis presents the design, modeling, implementation, and control of a magnetically suspended reaction sphere with one-axis hysteresis drive (1D-MSRS). The goal of this project is two fold: (a) exploring the design for a reaction sphere in 3D for spacecraft's attitude control, and (b) studying the performance of the hysteresis motor in reaction wheel applications. The 1D-MSRS is a motor with a spherical rotor with its rotor magnetically suspended in all translational directions, and is driven about the vertical axis by hysteresis drive. The magnetic suspension of the sphere is realized by arranging one electromagnet on top of the sphere,...

6. Ion implantation for figure correction of high-resolution x-ray telescope mirrors - Chalifoux, Brandon D
Fabricating mirrors for future high-resolution, large-aperture x-ray telescopes continues to challenge the x-ray astronomy instrumentation community. Building a large-aperture telescope requires thin, lightweight mirrors; due to the very low stiffness of thin mirrors, these are difficult to fabricate, coat, and mount, while achieving and maintaining the required surface figure accuracy. Ion implantation offers a potential solution for fabricating high-accuracy mirrors, by providing capability for fine figure correction of mirror substrates. Ion implantation causes local sub-surface stress that is a function of ion fluence, which results in changes in curvature. In principle, implanting to cause the right amount of stress in...

7. A digital computer solution for laminar flow : heat transfer in circular tubes - Goldberg, Perry
by Perry Goldberg.

8. Where solar thermal meets photovoltaic for high-efficiency power conversion - Bierman, David M. (David Matthew)
To develop disruptive techniques which generate power from the Sun, one must understand the aspects of existing technologies that limit performance. Solar thermal and solar photovoltaic schemes dominate today's solar market but both bring intrinsic and practical constraints. What will tomorrow's solar market look like? Third generation solar power generation techniques to utilize a larger portion of the solar spectrum are a promising path for high efficiency power generation, but experimental demonstrations remain limited. In this work, the components of a solar thermophotovoltaic power converter are introduced and discussed. While solar thermophotovoltaic devices have the potential to convert sunlight into...

9. Optimizing interventions for the treatment of vascular flow disruptions - Boval, Brett Lawrence
All tissues rely on perfusion and therefore intact blood flow. When flow is disrupted the coupled interaction between the functional and fluid domains of a tissue is impeded and viability is lost. Aortic stenosis is a paradigmatic example of vascular flow disruption. In health there is no gradient across the aortic valve and pressure generated in the left ventricle is transmitted without loss to the aorta. Pressure gradients across the valve force the left ventricle pressure to rise accordingly, straining this proximal pumping chamber, and when it can no longer compensate, affecting distal blood flow and organ perfusion. Aortic stenosis...

10. Tumor cell extravasation in an in vitro microvascular network platform - Chen, Michelle B. (Michelle Berkeley)
A deeper understanding of the mechanisms of tumor cell extravasation is essential in creating therapies that target this crucial step in cancer metastasis. Extravasation assays exist, but with limitations; data from in vivo models are frequently inferred from low-resolution end-point assays while most in vitro platforms are limited in their physiological relevance of the tumor microenvironment. To address this need, we developed a microfluidic platform to study tumor cell extravasation from in vitro microvascular networks formed via vasculogenesis. Various techniques to yield optimal networks were assessed in order to achieve an appropriate balance between vascular growth, remodeling and stabilization. These...

11. Design and implementation of safety control for a class of stochastic order preserving systems with application to collision avoidance near intersections - Mojtaba, Forghani (Forghani Oozroody)
In this thesis, we have designed and implemented a safety control system for collision avoidance near intersections. We have solved the corresponding control problems for a general class of systems that also includes the scenario of the two consecutive vehicles approaching an intersection, which leads to the design of the collision avoidance system. We have gathered the data of behavior of drivers as they approach intersections and have built a stochastic model for that through an optimization problem. The model generates a non-deterministic profile for acceleration of a vehicle which is not equipped with the collision avoidance system and it...

12. Computer assisted design reflection : a web application to improve early stage product in startup companies - Gimenez, Clayton C. (Clayton Christopher)
This thesis investigates the concept of computer-assisted design reflection. The work details the development of a prototype framework and reflection engine. Reflection is a critical process in design. It allows a designer to learn from experience to improve future results. When applied throughout the design process, it can also improve the quality of design decisions as they are made. We have observed that, unfortunately, design teams in startup environments often do not reflect sufficiently, leading to poor results that can cause a company to fail. A computer-assisted system could prompt reflection regularly and also compile responses from designers and users...

13. A grid-level alkali liquid metal battery recycling process : design, implementation, and characterization - Thomas, Dale Arlington, III
The application of liquid metal batteries for large scale grid-level energy storage is being enabled through the development of research conducted at the Massachusetts Institute of Technology (MIT) in 2006. A recycling process to facilitate the end-of-life cycle for alkali or alkaline earth liquid metal batteries was designed, implemented, and characterized through a collaboration between MIT and a battery company. The process developed utilizes recycling methodologies developed and successfully implemented for the recycling of lead-acid and lithium ion batteries. The two methodologies selected for implementation were physical separation and hydrometallurgical material separation. The combination of these two methods results in...

14. Process reengineering for the product development process at an analytical instrument manufacturer - Tandon, Shubhang
In an analytical instrument manufacturing company, the new product development process was analyzed with the objective of reducing time to market, to full scale production of new products and to improve project management and communication in the organization. Several problem areas were identified in the study and the thesis focuses mainly on the systems level changes that the organization would have to make in order to address the identified issues. The problem areas in the organization were the lack of categorization of development efforts, lack of a clear project plan to guide the development effort, functional integration issues and the...

15. The addition of a calender machine to a pyrolytic graphite sheet production plant - Svenson, Ernest Knute
This thesis documents the process and challenges of adding a new calender machine to AvCarb Material Solutions' pyrolytic graphite production plant. Before the machine could be used for mass production, several experiments needed to be conducted to better understand the capabilities of the machine. A process control procedure was designed to set up the machine to produce parts within specification. By using a one-factor-at-a-time approach, the process capability (Cpk) ofthe calender machine can be significantly improved. Additionally, the calender machine was used to investigate the significance of common defects on the uncalendered material. Experiments show that spots that are 3...

16. Assembly lead time reduction in a semiconductor capital equipment plant through constraint based scheduling - Sedore, Blake William Clark
The assembly protocols for a semiconductor capital equipment machine were analyzed for potential lead time reduction. The objective of this study was to determine the minimum assembly lead time for the machine based on the constraints of design, space, and labor availability. An assembly requires the completion of a set of procedures that each contains assembly tasks. Precedence relationships between tasks indicate for each procedure what other tasks must be completed before it can start. Each procedure was assumed to have constant resource requirements throughout its duration. The Critical Path Method (CPM) was used to identify 13 procedures on the...

17. Process reengineering for new product introduction at an analytical instrument manufacturing firm - Ranjan, Aditya
The process of transforming Research and Development knowledge to successfully introducing new products in the market forms a key competency of an innovative company. This new product introduction process was studied at an analytical instrument manufacturing firm. The process of commercialization spanned a number of departments and the process flow lacked functional integration. The current introduction process also lacked a number of management processes, structured feedback loops for information transfer and data metrics for process assessment and evaluation. Due to this, the information related to product knowledge was lost in the process flow creating isolated compartments which was never shared...

18. Efficient scheduling to reduce setup times and increase utilization in a multiple-part manufacturing system - Puszko, Gregory D
Two scheduling procedures were developed to reduce the total setup time and increase utilization in a multiple-part-type manufacturing system with sequence-dependent setups. These scheduling systems focus on reducing setup time by taking advantage of part family setups. A part family is a set of parts that have similar geometries or use the same fixturing or tooling in a flexible machine, thus the labor involved in transitioning between two parts in a family is simpler, and therefore quicker, compared to the average machine setup. One of the scheduling procedures, the setup matrix methodology, was tested through implementation in an actual manufacturing...

19. The value of accurate automated data collection to manufacturing - Perez, Alfonso Alexander
The purpose of this thesis is to demonstrate the value of implementing a novel, accurate automated data collection system and to describe a practical method for doing so. This thesis addresses the value of accurate automated data collection to manufacturing, focusing on a combined passive power monitoring and auto RFID data collection system implemented within the CNC turning and CNC milling departments at the Waters Corporation Machining Center in Milford, Massachusetts. A detailed study of the machining center revealed that inaccurate data was being used to plan production. This thesis demonstrates a graphical approach and an analytical method which can...

20. Pyrolytic graphite production : automation of material placement - Olle, Chase R
This research examines the process and challenges associated with the addition of an autonomous transfer robot to a manufacturing line for AvCarb Material Solutions for use in production of pyrolytic graphite. Development of the system included the design and fabrication of an end-effector, selection of a SCA RA robotic arm, and incorporation of a vision system. The arm and the end-effector were tested to see if material would shift during transfer. The entire system was tested for repeatability and transfer time. The results of the test indicted that the transfer system would successfully meet specifications with high process capability given...

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