Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1990. / Includes bibliographical references (leaves 77-78). / by Jens Olof Mattias Karlsson. / M.S.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 79-89). / Perfusion in peripheral tissues is fundamental to the characterization of both local and global cardiovascular health. However, despite the inherent accessibility of tissues such as skin to microvascular measurements, there is still a need for routine, noninvasive methods for obtaining relevant assessments of the human microcirculation. Human microvasculature includes the arterioles, capillaries, and venules that supply tissues with nutrients, circulate humoral products, and remove waste. The process of circulatory distribution is an efficient and highly structured process that distributes output through a regulation of local and global mechanisms that match blood flow to tissue need. These mechanisms are still not fully understood, but they do indicate a practical and potentially valuable connection between coronary and peripheral vascular function. Current methods of measuring perfusion in a reliable way are invasive, involve complicated procedures, do not permit continuous data collection, and are relatively expensive. The design of a noninvasive perfusion monitoring system that can routinely and continuously monitor perfusion in accessible tissues such as skin would have significant potential in applications requiring an understanding of the microvasculature as well as its diagnostic potential in a variety of circulatory disease states including (but not limited to) atherosclerosis, ischemic events, and wound healing ability. / by Vivian V. Li. / S.B.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008. / Includes bibliographical references (p. 215-219). / A ship moving on the free surface produces energetic breaking bow waves which generate spray and air entrainment. Present experimental, analytic, and numerical studies of this problem are costly, inaccurate and not robust. This thesis presents new cost-effective and accurate computational tools for the design and analysis of such ocean systems through a combination of physics-based and learning-based models. Methods which immerse physical boundaries on Cartesian background grids can model complex topologies and are well suited to study breaking bow waves. However, current methods such as Volume of Fluid and Immersed Boundary methods have numerical and modeling limitations. This thesis advances the state of the art in Cartesian-grid methods through development of a new conservative Volume-of-fluid algorithm and the Boundary Data Immersion Method, a new approach to the formulation and implementation of immersed bodies. The new methods are simple, robust and shown to out perform existing approaches for a wide range of canonical test problems relevant to ship wave flows. The new approach is used to study breaking bow waves through 2D+T and 3D simulations. The 2D+T computations compare well with experiments and breaking bow wave metrics are shown to be highly sensitive to the ship geometry. 2D+T breaking bow wave predictions are compared quantitatively to 3D computations and shown to be accurate only for certain flow features and very slender high speed vessels. Finally the thesis formalizes the study and development of physics-based learning models (PBLM) for complex engineering systems. A new generalized PBLM architecture is developed based on combining fast simple physics-based models with available high-fidelity data. / (cont.) Models are developed and trained to accurately predict the wave field and breaking bow waves of a ship orders of magnitude faster than standard methods. Built on the new boundary immersion approaches, these computational tools are sufficiently cost-effective and robust for use in practical design and analysis. / by Gabriel David Weymouth. / Sc.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1986. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Vita. / Bibliography: leaves 30-31. / by Shoichi Hashimoto. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 50-51). / Vibrotactile displays are based on mechanical stimulation delivered using an array of motors to communicate with the user. The way in which the display's motors are spaced and positioned on the body can have a significant impact on the effectiveness of communication, especially for tactile displays used to convey spatial information. The objective of the present research was to determine how the surface waves induced by vibrotactile stimulation of the skin varied as a function of the site on the body where the motors were mounted, and how these waves influenced the ability to localize vibrotactile stimulation. Three locations on the body were selected for study: the palm, the forearm, and the thigh. A flexible printed circuit board containing 3-axis micro-accelerometers was fabricated to measure the amplitude and frequency of surface waves produced by a vibrating motor at each body site. Results of these experiments showed significant differences in the frequency and amplitude of vibration on the glabrous skin on the palm as compared to the hairy skin on the arm and thigh. The palm had the highest frequency and lowest amplitude surface waves, and the forearm and thigh were very similar with lower frequency higher amplitude surface waves. No anisotropies were found from surface wave measurements. Most wave attenuation occurred within the first 8 mm from the motor, but there were still detectable amplitudes at a distance of 24 mm from the motor, which suggests that motor spacing should be at least 24 mm for this type of motor when used for precise spatial localization. A series of psychophysical experiments was conducted using a three-by-three array of motors in which the ability of subjects to localize the point of stimulation in an array was determined at each of the three body locations. The results from these experiments indicated that the palm had the highest localization accuracy (81% correct) as compared to the forearm and thigh which had similar localization accuracies (49% correct on forearm, 45% correct on thigh). Accuracy on the palm and forearm improved when the motor spacing increased from 8 mm to 16 mm, but increased spacing did not improve accuracy on the thigh. The results also showed that subjects were more able to identify the column of activation as opposed to the row of activation, which suggests a higher spatial acuity along the mediallateral as opposed to proximal-distal axis. The localization experiments indicate that glabrous skin is better suited for precise spatial localization than hairy skin, and that precise spatial localization requires an inter-motor spacing of more than 16 mm at these sites. / by Katherine O. Sofia. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999. / Includes bibliographical references (leaf 112). / by Michael D. Webb. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 40-41). / This work is about the development of a physiologically relevant model of the human airway. Various factors such as the cell model, physiochemical factors such as the cell substrate properties including its stiffness, shear stress, stretch, the air-liquid interface and the biochemical factors in the medium influence the biology of the cells. The aim of this work is to closely approximate conditions in an in vivo situation by engineering the above conditions in to the in vitro platform. An assay to introduce the cell substrate properties was developed in a glass bottomed petri dish type culture as well as a microfluidic device culture. The influence of the cell substrate on airway epithelial cell monolayer formation was investigated in detail by changing the stiffness of the substrate independently by changing the gel concentration, the gel formation pH and the height of the gel from a hard substrate. Further, we found that biochemical growth factors have a huge role in cell monolayer formation. A real-time measurement of monolayer integrity using electrical resistance measurements was developed. A shear stress application platform was developed and a stretch application platform was designed. The applications of such a platform with the inclusion of various physiologically relevant factors include the study of physiologic evolution of microbes such as the influenza virus. / by Vivek Sivathanu. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003. / Includes bibliographical references (p. 111-113). / by Dhanushkodi D. Mariappan. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1992. / Includes bibliographical references (leaves 210-216). / by Michael J. Massimino. / Ph.D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 91-93). / Ships sailing on the ocean have many inherent dangers. One of the most compelling is when they interact with severe stochastic waves, resulting in a loss of stability and adversely affecting their operation. This can result in extreme motions, at the very least making life difficult for crew, to potentially the most catastrophic events capsize, and loss of cargo and life. This compels the need to reliably predict vessel responses to wave interactions in order to aid the decision-making process for operating the ship safely. Despite the advances in computational methods and stochastic hydrodynamic theories to this date, a general framework, capable of handling nonlinear three-dimensional effects, arbitrary wave headings and unconventional hull geometries, is still missing from the engineer's toolbox. This thesis presents a new methodology for modeling the nonlinear responses and stability of a ship in stochastic waves. Invoking the weak-scatterer hypothesis, the radiation and diffraction effects are linearized, computed via a panel method, and cast into a state-space form, aided by applying the ESPRIT algorithm. Strong free surface nonlinearities present in the Froude-Krylov exciting and hydrostatic restoring forces are modeled by Fluid Impulse Theory. In parallel, the ambient seastate is represented by a multidimensional stochastic differential equation (SDE) conforming to a prescribed spectrum. Combining the state-space and seastate models capacitates the study of the nonlinear seakeeping and stability of a ship in a broad range of stationary seastates via stochastic calculus methods. Chief among them is the use of the Fokker-Planck equation (FPE), a deterministic partial differential equation governing the joint probability density function of the states of the SDE. The formulation for a rectangular barge rolling in beam waves is presented, with the approach readily extendable to six-degree-of-freedom responses. By deriving a state-space stochastic differential equation for the states governing the vessel response motions, the joint probability density can be found either by numerical Monte-Carlo simulation of the SDE, or by numerically solving the associated FPE. / by David F.H. Larson. / S.M.