Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 126-132). / This Masters thesis, conducted in support of the All Electric Ship (AES) early design effort, presents two computational programs for analysis and simulation: a full-scale, end-to-end AES simulator and an analytical performance and stability assessment tool for the ship's propulsion drive; the integrated power system (IPS). The AES simulator incorporates high order techniques for the hull modeling with low order, low effort models for the propellers, IPS, and prime movers, culminating in a fully-coupled, end-to-end, simulation environment, which is still practical for high effort studies like uncertainty quantification or optimization. The most appealing characteristic of this program is the time domain hull model with combines nonlinear maneuvering equations, seakeeping equations, and second order wave force equations. This allows for the prediction of propeller elevation and inflow velocity in random seas, and effectively the high fidelity modeling of propeller load schedules. This capability is vital for AES design where propeller load fluctuations can lead to large electrical power transients onboard. To demonstrate the capability of the AES simulator, ship trails are run in calm and random seas. IPS state evolutions are given to show the propagation of load disturbances. Monte Carlo methods are applied to assess transients in the inherently random sea environment. The IPS assessment tool attempts analytical quantification of the performance and stability of the Purdue MVDC Testbed, a scaled IPS composed of analagous elements: electric machinery, power converters, MVDC distribution, and bus voltage/induction motor torque control schemes. The thesis details the applicable nonlinear equations and the tools for identifying system equilibrium points. Then, small displacement theory is used to attain linear state space matrices valid near the operating points, from which traditional stability and performance techniques can be applied. Methods for closed loop analysis are suggested including ways to assess the hysteretic control elements used for induction motor torque control. Results from experiments with the high fidelity, high effort, Purude MVDC Testbed model are used for validation. / by Kyle Schmitt. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005. / Includes bibliographical references (p. 77-82). / The tongue is a structurally complex muscular organ, composed of a continuum of variably aligned intrinsic and extrinsic fibers. An understanding tongue structure and function, both under normal and pathological conditions, requires a complete three dimensional representation of fiber orientations present in the whole tissue. In order to investigate lingual myoarchitecture in the mammalian tongue, we employed several magnetic resonance imaging techniques generally based on direction specific differences in water diffusion. Muscle tissue in particular exhibits significant diffusion anisotropy in the direction of fibers, from which diffusion imaging is able to infer fiber direction. In this thesis research, several diffusion weighted MRI signal acquisition and post processing methods were tested, namely diffusion spectrum imaging (DSI), DSI with tractography, q-ball imaging, diffusion tensor imaging (DTI), and ADC and FA mapping. Each imaging method was evaluated in three ways: 1) finite element simulation using 2D structures to model the diffusion environment in an idealized situation, 2) MRI of microfluidic phantoms to quantify the effects of experimental conditions with a known diffusion environment, and 3) MRI of biological tissue, namely ex vivo cow and in vivo human tongues. The results demonstrated the capacity of DSI alone and in association with tractography to depict complex intravoxel and intervoxel fiber populations, in which a voxel is a 1-5 mm cubic imaged volume. In particular, our findings have identified and characterized on a structural basis a novel set of interwoven fiber populations. / (cont.) Future work will be directed to defining the mechanical significance of these interwoven fiber populations in carrying physiological tissue deformations. / by Lee Magnusson. / S.M.

Thesis (S.M. in Ocean Systems Management)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 190-193). / Seakeeping analysis is a fundamental part of the design process of a ship. Due to its complexity, seakeeping analysis is usually completed in a late stage of the design process. Although this approach can be successfully used for monohull vessels, it is not optimal in designing more innovative hull forms, due to the high degree of uncertainty of the seakeeping performances of these vessels. The recent interest in multihull vessels poses a problem to the naval architecture world as little is known about such hull forms and a limited number of design tools is available to analyze them. These concerns led to the development of the I-Marine Seakeeping Analysis Toolbox that aims to help students and naval architects alike understand the importance of seakeeping analysis and the seakeeping capabilities of multihull vessels. The Toolbox includes five different seakeeping programs suitable for the analysis of multihull vessels and is accessible through a web interface. The integrated nature of I-Marine strongly facilitates the usage of the programs, making it a great educational tool to learn seakeeping analysis without any previous programming knowledge. / (cont.) This thesis shows that a tool such as I-Marine could be effectively used in calculating the seakeeping capabilities of multihulls and successfully integrated in the preliminary design of a vessel, leading to numerous advantages such as a higher efficiency in the design process, a reduction in the risk of designing multihulls, and an expansion of the design envelope. / by Cosimo Malesci. / S.M.in Ocean Systems Management

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / Includes bibliographical references (p. 34-36). / This study examines glycosaminoglycan (GAG) density and aggregate compressive modulus HA of engineered cartilaginous implants. Culture parameters were developed to cause the goat articular chondrocyte seeded type II collagen scaffolds to generate 25 and 50% of the natural biochemical content of articular cartilage, with an overall goal of identifying construct compositions that might provide the most favorable response when implanted into defects in articular cartilage. Several scaffold cross-link densities were compared across constructs cultured in vitro to several time-points. The compressive modulus HA was measured through unconfined compression. One group of scaffolds averaged a compressive modulus one order of magnitude below that of natural tissue. Histological analysis verified that a chondrogenic phenotype was maintained and revealed a concentration of tissue development in the center of most scaffolds. This work includes a design for an original mechanical test apparatus for measuring the Poisson's ratio of the samples, enabling meaningful interpretation of indentation test results. / by Emily Pfeiffer. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002. / Includes bibliographical references (p. 68-71). / by Andreas R. Wingert. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 199-202). / Wind energy is one of the more viable sources of renewable energy and offshore wind turbines represent a promising technology for the cost effective harvesting of this abundant source of energy. To capture wind energy offshore, horizontal-axis wind turbines can be installed on offshore platforms and the study of hydrodynamic loads on these offshore platforms becomes a critical issue for the design of offshore wind turbine systems. A versatile and efficient hydrodynamics module was developed to evaluate the linear and nonlinear loads on floating wind turbines using a new fluid-impulse formulation - the Fluid Impulse Theory(FIT). The new formulation allows linear and nonlinear loads on floating bodies to be computed in the time domain, and avoids the computationally intensive evaluation of temporal and spatial gradients of the velocity potential in the Bernoulli equation and the discretization of the nonlinear free surface. The module computes linear and nonlinear loads - including hydrostatic, Froude-Krylov, radiation and diffraction, as well as nonlinear effects known to cause ringing, springing and slow-drift loads - directly in the time domain and a stochastic seastate. The accurate evaluation of nonlinear loads by FIT provides an excellent alternative to existing methods for the safe and cost-effective design of offshore floating wind turbines. The time-domain Green function is used to solve the linear and nonlinear free-surface problems and efficient methods are derived for its computation. The body instantaneous wetted surface is approximated by a panel mesh and the discretization of the free surface is circumvented by using the Green function. The evaluation of the nonlinear loads is based on explicit expressions derived by the fluid-impulse theory, which can be computed efficiently. / by Godine Kok Yan Chan. / Ph. D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1989. / Includes bibliographical references (leaves 133-138). / by Allen Corlies Ward. / Sc.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004. / Includes bibliographical references (leaves 77-82). / Autonomous mobility in rough terrain is becoming increasingly important for planetary exploration rovers. Increased knowledge of local terrain properties is critical to ensure a rover's safety, especially when driving on slopes or rough surfaces. This thesis presents two methods for using on-board sensors to identify local terrain conditions. The first method visually measures sinkage of a rover wheel into deformable terrain, based on a single color or grayscale image from a camera with a view of the wheel- terrain interface. Grayscale intensity is computed along the rim of the wheel, and the wheel-terrain interface is identified as the location with maximum change in intensity. The algorithm has been shown experimentally to give accurate results in identifying the terrain characteristics under a wide range of conditions. The second method classifies terrain based on vibrations induced in the rover structure by rover-terrain interaction during driving. Vibrations are measured using an accelerometer on the rover structure. The method uses a supervised learning approach to train a classifier to recognize terrain based on representative vibration signals during an off-line learning phase. Real-time terrain classification uses linear discriminant analysis in the frequency domain to identify gross terrain classes such as sand, gravel, or clay. The algorithm is experimentally validated on a laboratory testbed and on a rover in outdoor conditions. Results demonstrate the robustness of the algorithm on both systems. / by Christopher Allen Brooks. / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005. / Includes bibliographical references (p. 24). / Physical Intelligence refers to the ability of the human organism to smartly and precisely coordinate its internal components and interactions in its environment to solve physically complex tasks. While Physical Intelligence is a key part of physical movement, many pieces of physical fitness equipment fail to challenge or exercise the organism's internal intelligence. Therefore, the goal of this thesis is to design an apparatus that through performing a set of exercises, challenges and develops the body's physical intelligence. Several strategies for developing an apparatus to develop physical intelligence were considered, including an underwater treadmill and an elastic method of providing resistance while running. In the end, however, the strategy developed was the HandSkate, a handheld, low-friction device intended to train core and upper-body muscles by forcing the user to balance themselves and stabilize the HandSkates while performing simple, familiar exercises. Two concepts for the HandSkate were prototyped and tested. The first concept, the 'Boomerang' design, was prototyped from aluminum and consists of a flat, V-shaped base with a cantilevered handle. / (cont.) This design is small and comfortable to grip and performs well during exercises that benefit from independent hand movement. The second prototype, the 'T' design, is larger than the first but has several options for hand orientation and allows for a two-handed grip, which allows the user to perform exercises that work best with only one device. Both prototypes easily provide fine motion and provide instability, which challenges the user's physical intelligence while the user exercises. Future improvements include reducing the size of the 'T' design and manufacturing in lighter, less expensive materials. / by Benjamin D. Smith. / S.B.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997. / Includes bibliographical references (p. 69-73). / by Erica G. Atkeson. / M.S.