Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995. / Includes bibliographical references (p. 177-187). / by Fredrik Turville Thwaites. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996. / Includes bibliographical references (p. 115-117). / by Ammar Adnan Al-Nahwi. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references (leaves 115-132). / Surfactants, or surface active agents, are chemicals exhibiting amphiphilic behavior toward a solvent. This amphiphilic character leads to increased activity at interfaces and to self-assembly into micellar aggregates beyond a threshold surfactant concentration, referred to as the critical micelle concentration (CMC), in bulk solutions. As a result of these unique attributes, surfactants are used in many pharmaceutical, industrial, and environmental applications, including biological separations, fat metabolism during digestion, drug delivery, and water purification. Selection of the appropriate surfactant for a given application is often motivated by the need to control bulk solution micellization properties, such as the CMC and the micelle shape and size. The ability to make molecular-level predictions of these surfactant properties would allow formulators in industry to speed up the design and optimization of new surfactant formulations. In this thesis, a combined computer simulation/molecular-thermodynamic (CS-MT) modeling approach was developed and utilized to study the micellization behavior of ionic branched surfactants, which are a class of surfactants of great industrial relevance in applications such as detergency, emulsification, and enhanced-oil recovery. In the CSMT modeling approach, molecular dynamics (MD) simulations are used to obtain input parameters for molecular-thermodynamic (MT) modeling of surfactant micellization.This approach is motivated by the limitations inherent in computer simulations (the high computational expense associated with modeling self-assembly) and in MT modeling approaches (their restriction to structurally and chemically simple surfactants). One key input required for traditional MT modeling is the identification of the hydrated ("head") and the dehydrated ("tail") portions of surfactants in a self-assembled micellar aggregate. Using the results of MD simulations of surfactants in a micellar environment, a novel head and tail identification method was developed based on the determination of a conceptual micelle core-water interface. The introduction of an interfacial region consisting of partially hydrated, neutral atomic groups required formulating an improved surfactant tail packing approach. / (cont.) Another key input required in the CS-MT modeling approach is the fractional degree of hydration of each atomic group in the ionic branched surfactants considered in this thesis, which can be used to accurately quantify the hydrophobic driving force for micelle formation in aqueous media. Fractional hydration profiles were obtained by conducting two MD simulations, one in a bulk water environment and the other in a micellar environment. By investigating the radial distribution function (RDF) between each surfactant group and hydrating atoms which are capable of forming hydrogen-bonds and coordinate-bonds, an updated cutoff distance for counting hydrating contacts was selected. These simulated fractional hydration profiles were then utilized as inputs in the MT model, which enables calculation of the minimum free energy associated with micelle formation, from which the CMC and the optimal micelle shape and size can be predicted at the molecular level. The MD simulations were shown to extend the applicability of the traditional MT modeling approach to more complex surfactant systems than had been possible to date. A rich variety of ionic branched surfactants were modeled using the new CS-MT modeling approach, including two homologous series of simple secondary alkyl sulfonates and three classes of more complex ionic branched surfactants possessing aromatic moieties. For each of the ionic branched surfactants modeled, the predictions of the CS-MT modeling approach were found to be in reasonable agreement with the experimental data, including accounting for the chemical and structural complexities of the branched surfactants more accurately. The CS-MT modeling approach developed in this thesis not only extends our ability to make accurate molecular-level predictions of the micellization behavior of complex surfactants, but it also contributes to our overall fundamental understanding of the solution behavior of surfactants. / by Shangchao Lin. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 105-108). / In problems of dispersive wave propagation governed by two distinct restoring-force mechanisms, the phase speed of linear sinusoidal wavetrains may feature a minimum, cmin, at non-zero wavenumber, kmin. Examples include waves on the surface of a liquid in the presence of both gravity and surface tension, flexural waves on a floating ice sheet, in which case capillarity is replaced by the flexural rigidity of the ice, and internal gravity waves in layered flows in the presence of interfacial tension. The focus here is on deep-water gravity-capillary waves, where cmin = 23 cm/s with corresponding wavelength Amin = 27r/kmin = 1.71 cm. In this instance, ignoring viscous dissipation, cmin is known to be the bifurcation point of two-dimensional (plane) and three-dimensional (fully localized) solitary waves, often referred to as "lumps"; these are nonlinear disturbances that propagate at speeds below cmin without change of shape owing to a perfect balance between the opposing effects of wave dispersion and nonlinear steepening. Moreover, Cmin is a critical forcing speed, as the linear inviscid response to external forcing moving at Cmin grows unbounded in time, and nonlinear effects as well as viscous dissipation are expected to play important parts near this resonance. In the present thesis, various aspects of the dynamics of gravity-capillary lumps are investigated theoretically. Specifically, it is shown that steep gravity-capillary lumps of depression can propagate stably and they are prominent nonlinear features of the forced response near resonant conditions, in agreement with companion experiment for the generation of gravity-capillary lumps on deep water. These findings are relevant to the generation of ripples by wind and to the wave drag associated with the motion of small bodies on a free surface. / by Yeunwoo Cho. / Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references. / The Clearpath Robotics Kingfisher M200 robot is an unmanned water surface vehicle with payload autonomy capability. This allows users to develop autonomy control on an offboard computer until it is ready for use on the autonomous vehicle. The Massachusetts Institute of Technology's Battelle Autonomy Laboratory plans to utilize this feature in both teaching and research applications so that users can develop autonomous missions on off-board single-board computers and then easily integrate their missions with the vehicles when ready. Although the M200's payload bay includes a waterproof data connection port, there is no provided environmental protection for the payload computer itself. This paper documents the design and production of a waterproof payload computer module that allows for the operation of the single-board computer, data interface with the M200's on-board computer and for the attachment of additional USB components. The Raspberry Pi was selected as the most appropriate single-board computer and the Otterbox Drybox 3000 was selected as the most appropriate enclosure. Electrical circuitry was designed to allow for power to the computer, data communication with the M200 and USB connections for additional components, and combination of cable glands and panel-mounted connectors were used to allow these connections to be accessible from the outside of the enclosure while retaining a NEMA 4 waterproof enclosure rating. In order to create a robust and user-friendly module, a system of strain relief and component orientation was designed. Continuous testing and adapting of prototypes resulted in a compact, operational payload module that can easily be interfaced with the Kingfisher M200 to provide payload autonomy as well as offer two additional USB ports for the connection of additional components. This design aims to be easily reproducible by other Kingfisher M200 users, as well as adaptable to other payload autonomy applications. / by Emily L. Dunne. / S.B.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1955. / Vita. / Includes bibliographical references (leaf 30en Edits Sent). / by Paul R. Paslay. / Sc.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (page 28). / A key step in genetic engineering is the delivery of genetic material into the cell. Increasing bacterial cell transformation efficiency can help advance an area of scientific research with a wide range of applications. Previous work has demonstrated conjugated oligoelectrolytes (COEs) neutralize the surface charge of bacterial cells and increase membrane permeability, which can potenitally increase their competence in accepting exogenous DNA. This study tested the effect of the COE DSSN+ combined with electroporation on the transformation of Escherichia coli cells. Multiple experiments with varying concentrations of DSSN+ and varying voltages provided bacterial colony growth and transformation efficiency data for each of the testing conditions. A repeatable experimental procedure is outlined with comments on potential future work that can help better understand and improve cell transformation. While this study cannot make any statistically significant claim from the data, the results of the experiments still provide necessary insight into the effect of DSSN+ on cell transformation. / by Nicholas Fernandez. / S.B.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995. / Includes bibliographical references (p. 92-94). / by Sophie Debost. / M.S.

Massachusetts Institute of Technology. Dept. of Mechanical Engineering. Thesis. 1966. Mech.E. / Bibliography: leaves 65-72. / Mech.E.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997. / Includes bibliographical references (leaf 51). / by Arthur Russell von Waldburg. / B.S.