Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2005. / Includes bibliographical references (p. 116-119). / Advanced aircraft noise abatement approach procedures -- characterized by decelerating, continuous descent approaches using idle thrust, and enabled by flight guidance technologies such as GPS and FMS -- have been shown to reduce operational aircraft noise on communities surrounding airports. However, implementation in the near future presents two challenges. The first is to mitigate the adverse effects on aircraft performance of uncertainties in pilot response, weather, and other system components. The second is to enhance the ability of air traffic controllers to separate aircraft that are decelerating at different rates. The work in this thesis primarily addresses the first challenge by developing, first, a methodology to determine the optimum design parameters for a continuous descent approach, and, second, a new pilot cueing system. The methodology involved: 1) conducting a simulator-based, human factors experiment to obtain models of pilot delay in extending flaps/gear in conditions with and without turbulence; 2) formulating the procedure's parameters as strategic and tactical control variables; 3) using the pilot delay models and the parameter formulation to perform a Monte Carlo Simulation to resolve the conflicting objectives of reducing noise and increasing probability of target achievement. Simulation results showed that the flap schedule has to be designed for a 50-ft- higher-than the target altitude without turbulence, and a 200-ft for turbulence; 4) determining the feasibility space of the parameters in different wind conditions. Results showed that when the wind uncertainty is large, accounting for the uncertainty in the procedure design significantly reduces the effectiveness of the procedure. / (cont.) A new pilot cueing system that does not require additional aircraft automation was developed to help pilots manage the deceleration of aircraft and achieve target conditions in a changing environment. The cueing system, consisting of gates (i.e., altitude/speed checkpoints) and a recommended flap schedule, was designed and evaluated in a second experiment using a desktop simulator which showed that gates reduce target error to within five knots and provide comparable performance to that of more automated systems without increasing pilot workload. Because the gates have the potential of enabling aircraft to fly consistent speed profiles, it is hypothesized that their implementation would address the second challenge by enhancing the controller's ability to predict aircraft trajectories and their future separation. / by Nhut Tan Ho. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999. / Includes bibliographical references (leaf 116). / by Shereen Eletribi. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / "June 2007." / Includes bibliographical references (leaves 238-272). / Structural catastrophic failure of naval vessels due to extreme loads such as underwater or air explosion, high velocity impact (torpedoes), or hydrodynamic loads (high speed vessels) is primarily caused by fracture. Traditionally, naval structures have been designed to resist yielding, buckling and fatigue, but not fracture. Consequently, adequate methods and procedures to design ships against fracture have not been developed. The rapidly increasing application of lightweight materials, such as aluminum alloys, in the shipbuilding industry requires fundamental understanding of mechanisms and mechanics of fracture that govern naval stiffened panels. Therefore, a comprehensive tool consisting of application of advanced fracture models, material calibration, and validation through component testing is provided that will increase the survivability envelope and speed up the development process of new vessels. Cracking is a major cause of structural degradation, which is a primary source of costly repair work on metal structures. This thesis studies the structural response of various stiffened plates and compares them with unstiffened plates represented by compact tension (CT) specimens. / (cont.) An extensive experimental program is presented that includes coupon testing and small and intermediate scale tests on naval aluminum structures including a variety of monolithic T-type extruded and flatbar welded specimens. Representative naval designs are selected and subjected to quasi-static loading and a number of key parameters, such as geometry, loading rate and structural configuration are evaluated with respect to fracture. Numerical modeling and analyses of ductile fracture initiation and propagation on a pre-cracked geometry using a commercial finite element code (ABAQUS), taking into account the behavior of simple uncracked material, has been performed showing a very good agreement with small and intermediate scale tests. Two major contributions of this thesis are the mapping of crack patterns in stiffened plates and the development of a methodology which enables ship designers to evaluate critical areas within a structure with respect to crack initiation, propagation, optimum material usage, and computational cost. / by Konstantinos P. Galanis. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 205-213). / The substantial growth in industrial production, demand for materials, and population has led to an increasing need for sustainable manufacturing processes to mitigate the negative impacts on the environment and meet the needs of future generations. One proposed direction is remanufacturing, which is a process whereby used products having reached their end-of-life, are restored back to useful service-life. Remanufacturing utilizes the energy and embedded value retained in a product upon reaching end-of-life. Remanufacturing can close the loop between disposal and supply chains, extend the service lifetime of products, conserve resources, and help mitigate environmental consequences attributed to landfilling. Moreover, by preserving the geometrical architecture of cores, remanufacturing can reduce the needs for raw material processing and many manufacturing processes, hence, saving energy. A critical issue to consider when evaluating energy savings in remanufacturing is the product use phase: how well does the remanufactured device perform in the use phase compared to a similar new product from an energy standpoint? To answer this question, we utilize Life Cycle Assessments framework. Using this methodology, we quantify cumulative energy demands of a remanufactured product during its lifecycle and compare it to an equivalent new product. We conduct an analysis of lifecycle energy savings of remanufacturing for 19 different products in 8 distinct product case studies (4 product case studies discussed in detail in this thesis). / (cont.) By performing lifecycle evaluations we conclude that remanufacturing can be a net energy-saving option for products that have energy requirements dominated by the production phase. Moreover, our energy analysis sheds light on the importance of considering use phase while evaluating the energy savings potential of remanufacturing. We conclude that from a total life cycle perspective, remanufacturing may be a net energy saving as well as a net energy expending end-of-life option. We argue that in investigating energy savings of remanufacturing as an end-of-life option, one should also evaluate large-scale critical factors in order to effectively address the systems challenges associated with remanufacturing. Our retrospective approach signifies the importance of studying critical factors such as technological improvements, policy interventions, economic incentives, and business models in order to draw inferences about energy and economic savings potential of remanufacturing. In addition, we argue that the generalized claims about remanufacturing as the ultimate end-of-life option are not only subject to dynamic global changes, but also restricted by the limitations in the lifecycle environmental methodologies. Lastly, we conclude that the evaluations for product remanufacturing and energy savings are more valuable and justified if conducted on a case-by-case basis. / by Avid Boustani. / S.M.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1989. / by David Andrew Costello. / B.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001. / "June 2001." / Includes bibliographical references (leaves 66-71). / Exploratory space missions of the future will require robotic systems to lead the way by negotiating and mapping very rough terrain, collecting samples, performing science tasks, and constructing facilities. These robots will need to be adaptable and reconfigurable in order to achieve a wide variety of objectives. Conventional designs using gears, motors, bearings, encoders, and many discrete components will be too complex, heavy, and failure-prone to allow highly-reconfigurable systems to be feasible. This thesis develops new concepts that may potentially enable the design of self-transforming space explorers. The vision of this research is to integrate compliant bistable mechanisms with large numbers of binary-actuated embedded smart materials. Compliant mechanisms are lightweight and robust. Binary actuation is the idea of using an actuator in a discrete on/off manner rather than in a continuous manner. A binary actuator is easy to control and robust, and by using tens or hundreds of binary actuators, one can approximate a continuous system, much like a digital computer can approximate an analog system. The first part of this thesis examines the fundamental planning issues involved with systems having large numbers of binary actuators. The notion of a workspace is described and applied to the optimization of a manipulator design. Methods for solving the forward and inverse kinematics are discussed in the context of this application. These methods are extended to the trajectory and locomotion planning problems. Methods for planning systems of substantial complexity are developed in the context of exploratory space robotics. The second part of this thesis presents experimental demonstrations that examine elements of the concept. The results of several design prototypes are discussed. / by Matthew D. Lichter. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002. / Includes bibliographical references (p. 89-92). / by Prabhat K. Sinha. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004. / Includes bibliographical references (leaves 59-60). / We have developed a system for studying chemotaxis in a microfabricated system. The goal was to develop a system capable of generating spatially and temporally stable concentration gradients of a chemotactic molecule while providing a viable environment for the cell. Numerical models were generated to investigate fluid flow in microchannels for given geometries. Through computational modeling and experimentally-driven iteration of the design, features of the chamber were determined and geometry was established. Prototypes of the system were fabricated using soft lithography and multi-layer soft lithography techniques. Three fluid delivery methods for establishing gradients in the system have been studied: gravity feed system, dual-syringe pump feed system, and integrated individually-controlled peristaltic pump feed system. We were able to create spatially and temporally stable gradients using the dual-syringe feed setup. Two syringes were used to pump a chemokine and a buffer in parallel channels that are connected by a cross-channel and terminated to a single output. Microbeads in the flow were used to confirm the lack of movement in the cross-channel. Human neutrophil viability over the course of several hours and directed cell movement was demonstrated in microchannels. / by Maiya Shur. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 95-98). / Describing transport in fluid flows has been a long-standing challenge in dynamical systems theory, with applications to industrial and natural flows. The detection of Lagrangian structures that stay coherent over time helps gain insight into the evolution of a system's dynamics and the fate of transport. Whereas most techniques to detect coherent structures rely on a dense velocity field, techniques based on sparse datasets are increasingly being developed. The braid theory approach to detect Lagrangian coherent structures from sparse sets of trajectories is tested through a periodic, two-dimensional Stokes flow, the rotor-oscillator flow. Combined theoretical and numerical studies have shown that this flow can offer chaotic regimes with islands of coherence. The flow was recreated experimentally in a laboratory based on the findings of these theoretical studies. The braid theory approach was found to successfully detect coherent groups from sparse trajectories, although it is very sensitive to the quality of that data available. / by Margaux Filippi. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 35-36). / Cellular heterogeneity plays a critical role in processes like embryonic development, drug-resistance, and immune response. The ability to select and manipulate individual cells greatly increases the ability to study heterogeneity within cultures. As such, a number of different single cell sorting techniques have been developed. While filling their respective niches, there does not currently exist a system capable of sorting individual cells based upon an arbitrary set of morphological or otherwise observable features while providing good enough throughput to deal with working within biologically relevant timescales. To address this need, an integrated system for the selection and manipulation of single cells in 2D culture was developed by automating both the selection of cells using computer vision and manipulation of cells using micro-capillaries. This system was then applied to study intestinal organoid formation. Specifically, current protocols for the production of intestinal organoids suffer from low yield, with only ~12% of the highly heterogeneous nascent spheroids successfully maturing into intestinal organoids. It was found that by sorting for nascent spheroids that had an effective diameter greater than 75[mu]m and had an inner mass, the maturation percentage was increased to ~40%. Separately, the system was fitted with a microfluidic device capable of producing a local trypsin zone within 2D culture and single adherent cells were lifted. This shows promise for expanding the set of applications that single cell sorting can be applied. / by Jacob Guggenheim. / S.M.