The primary focus of this work is to explore the effect of interface on thermal, mechanical, and chemical properties of carbon nanotubes (CNTs) and the methods to modify the interface between CNTs and CNTs based composites. CNTs are potentially promising fibers for ultra-high-strength composites. The load transfer between the inner and outer tubes in multiwall nanotubes (MWNTs) has to be clearly understood to realize the potential of MWNTs in composites and other applications such as nano-springs, and nano-bearings. This dissertation studies the load transfer between the walls of MWNTs in both tension and compression using molecular dynamics simulations. It is found that only the minimal load is transferred to the inner nanotube in tension. The load transfer of capped nanotubes in compression is much higher than in tension. The presence of a few interstitial atoms between the walls of MWNTs can significantly improve the stiffness and enhance the load transfer to the inner nanotubes in both tension and compression. The modification of the interface of CNTs is a key factor for effectively using CNTs in many applications. The use of molecular statics and dynamics helps exploring ion irradiation as a method for functionalization of CNTs. It is found that ion bombardment of single and Multiwall carbon nanotubes creates vacancies and defects, which can act as high-energy sites for further chemical reactions; furthermore, ion irradiation of CNTs embedded in polymer matrix creates chemical attachments between CNTs and polymer matrix, enhancing the compositing process. Mechanical property simulations based on tension and pullout tests indicate that the chemical links between constituents in CNT–polymer systems result in higher load transfer, and hence, better composite properties. The effect of the interface turns out to be very crucial for printing in nanolithography processes. Molecular dynamics simulation is applied to extract interface properties, such as friction and adhesion, in nanoscale; later, the properties are input into a large-scale FEM model. As found, the protrusion problem is caused by many factors, such as strength of polymer at high temperature, thermal expansion properties, and depth of metal. / A Dissertation submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Fall Semester, 2006. / Date of Defense: October 9, 2006. / Nanolithography, Multiscale simulation, composites, load transfer, carbon nanotubes, molecular dynamics simulation, interface / Includes bibliographical references. / Namas Chandra, Professor Directing Dissertation; Petru Andrei, Outside Committee Member; Leon van Dommelen, Committee Member; Anter El-Azab, Committee Member; Chiang Shih, Committee Member.

In recent years, NASA has become interested in densified fuels such as solid hydrogen. A change from liquid to solid-state fuel storage would result in an approximately 15% smaller onboard fuel tank, and thus a lower gross vehicle lift off weight. A lower lift off weight would allow for heavier payloads, more crewmembers, or longer space flight missions. The ability to store and use solid-state fuels would also lend to the possibility of more powerful atomic based propellants, such as boron or carbon, in the future. However, currently used techniques for liquid based mass gauging, required for quantifying the remaining mass in onboard fuel tanks, are not applicable to solid mass gauging. A new mass gauging technique is required to implement the use of solid-state fuel. It is required that this new mass gauging technique be capable of continuous measurement despite variations in fuel distribution, changes in gravitational forces, and other effects associated with mass in motion experienced during space flight. Furthermore, this technique and its related equipment must be minimally invasive to the fuel system, both mechanically and thermally. Advanced Technologies Group (ATG), has recently developed an optical mass gauging system with promising results in ground based tests on liquid hydrogen. The optical mass gauging system developed by ATG is coupled to a fuel tank via fiber-optic cables and utilizes the unique absorption spectra of molecular hydrogen, a tunable laser light source, a pseudo-integration optical sphere, and a spectrometer to gauge mass. A nearly monochromatic light, including an absorption wavelength for molecular hydrogen at a given intensity, is reflected uniformly within the pseudo integration sphere containing hydrogen. The intensity of the absorption wavelength is attenuated by hydrogen mass absorption, and the remainder is uniformly reflected about the internal surface of the pseudo-integration sphere. A ratiometric calculation is then used to approximate the attenuation due to mass, and ultimately the mass present, based on intensity measurements taken for an absorption wavelength and a non-absorption wavelength from the spheres internal surface. This system is minimally invasive and can be used to gauge quantities of solid mass by adjusting the emitted spectra to overlap the primary absorption wavelength of solid hydrogen at approximately 797.4 [nm]. In the present work, a solid hydrogen particle generator was designed and fabricated to test the response of the solid hydrogen optical mass gauging system (SHOMGS) prototype developed by ATG. The solid hydrogen particle generator consists of several components. Pre-cooled hydrogen gas (~80 K) was introduced from a cold trap into an encapsulated temperature controlled reservoir that was partially submerged in a bath of liquid helium at 4.2 K. This reservoir utilized the latent heat of the liquid helium bath as well as the heat capacity of the helium vapor to condense the hydrogen gas into liquid at approximately 19 K. Following condensation of a desired quantity of liquid hydrogen, the ullage in the reservoir was pressurized with helium gas to create a favorable pressure gradient for injection. A valve at the base of the reservoir was then opened to inject a fine spray of liquid hydrogen through an injection nozzle into a SHOMGS equipped pseudo-integration sphere containing a bath of liquid helium at approximately 4.2 K. The liquid helium bath of the sphere is used to solidify the droplets of liquid hydrogen into solid particles. A coaxial capacitor liquid level sensor was used in the liquid hydrogen reservoir to quantify the amount of mass injected from the particle generation system during each injection. Seven experiments were conducted. In each experiment, 10 to 20 mass injections were made to determine the response of the SHOMGS and the reproducibility of the results from the particle generation system. Raw data was recorded of the liquid hydrogen conditions before and after each injection, as well as associated changes in capacitance. These values were then used to calculate the injected mass. In addition, raw data was recorded from the SHOMGS regarding changes in reflected light intensity corresponding to each injection. Ratiometric analysis was performed on the light intensity data and this response was plotted against the quantities of mass injected to correlate the SHOMGS response. Following this battery of tests, several conclusions were determined. The solid hydrogen particle generator is capable of repeatable results and can provide known quantities of solid hydrogen with a calculated mass error of 10-20% dependant largely on the amount injected. The SHOMGS developed by ATG exhibits responses correlated to changes in mass injected. Following further development, this prototype could be modified for use on future space flight platforms. / A Thesis submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Degree Awarded: Summer Semester, 2004. / Date of Defense: July 1, 2004. / Solid hydrogen, mass gauging, hydrogen, space cryogenics, optical mass gauging / Includes bibliographical references. / Steven W. Van Sciver, Professor Directing Thesis; Cesar A. Luongo, Committee Member; Peter N. Kalu, Committee Member.

Localized magnetic particle hyperthermia heating treatment using ferromagnetic and superparamagnetic nanoparticles continue to be an active area of cancer research. Magnetic hyperthermia is a promising therapeutic method for treatment of cancer. It's based on the intratumoral deposition of biocompatible magnetic nanoparticles followed by exposure to a high-frequency electromagnetic field. The dissipation of energy connected especially with magnetic hysteresis losses, Neel and Brown relaxations results in a local heating of the active particles and consequently leads to the destruction of the cancer cells. Magnetic nanoparticle materials used has to have high specific power loss and a suitable temperature dependence of power loss allowed by an adjustment of the Curie temperature to about 315 K (43 °C). Overheating is ruled out due to a decrease of the magnetic hysteresis losses in the vicinity of the Curie temperature. One way to solve this task is the use of magnetic nanoparticles with the magnetic properties suitably modified by compositional variations. This dissertation, reports on localized magnetic hyperthermia studies using newly fabricated, as-synthesized, self-heating magnetic nanoparticles. Exposed to an alternating magnetic field, these nanoparticles act as localized heat sources at certain target regions inside the human body. Superparamagnetic nanoparticles provide attractive biotechnical and physiological advantages such as: direct injection through blood vessel due to ease of control of particle size, remote controlling of transport to tumor cells by externally applied magnetic field gradients, and resonant response to a time varying magnetic field resulting in heating up nanoparticles. In this dissertation, a report of the very promising and successful self-heating temperature rising characteristics of MnZn-ferrite, ZnGd-ferrite, GdZnCe-ferrite and ZnNd-ferrite nanoparticles obtained by chemical methods, mainly, co-precipitation process and under different applied magnetic fields and frequencies to confirm the effectiveness as hyperthermia agents. Magnetic and structural properties of these nanoparticles were analyzed in order to study the physical nature of self-heating characteristics and to investigate the effectiveness as hyperthermia agents in biomedicine. All four types of nanoparticle systems showed both superparamagnetic and ferromagnetic behaviors depending on particle sizes. Dominant magnetic heating mechanisms were studied and qualitatively identified, and a newly developed mathematical model to calculate the magnetic heating power was derived. The derived model proved to be in good agreement with the experimental results. / A Dissertation submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Summer Semester, 2007. / Date of Defense: June 29, 2007. / Blocking Temperature, Magnetic Heating, Debye Relaxation, Neel Relaxation, Curie Point, Calorimetric, Dominant Mechanism, AC Susceptibility, Nanoparticle Synthesis / Includes bibliographical references. / Ching-Jen Chen, Professor Directing Dissertation; Jim P. Zheng, Outside Committee Member; Peter N. Kalu, Committee Member; Chifu Wu, Committee Member.

This study focuses on characterizing meso scaled pumps. These pumps match in design to micro mechanical pumps produced using surface micromachining technology. The objective of this study is to characterize the performance of the meso scaled pumps experimentally, analytically, and numerically in order to gain a better understanding of the functional behavior of micropumps. Both types of actuations, magnetically and mechanically driven pumps, are considered in this thesis. In the magnetic actuation, noninvasive coupling occurs between applied magnetic field and magnetically actuated material deposited on a movable actuator on the pump. Several advantages are reported when utilizing the magnetic actuation, including a reduction in the heat conduction from the motor to the bio fluids and a reduction on the hardware, particularly when using micro systems. A coupler was designed and manufactured to transmit the torque from the motor's shaft to the pump's shaft during mechanical coupling. The three micropumps to be characterized are the spiral pump, Von Karman pump, and crescent pump. These three micro pumps were fabricated at Sandia National Laboratory. In this study, three meso scaled pumps are characterized. The characterization for each mesopump was performed by pumping liquid water. A numerical simulation using CFDRC computer code was also performed for two viscous drag pumps (spiral, and Von Karman), and a comparison between the numerical, and experimental results was performed. Furthermore experimental data was compared to that predicted by analytical solution for spiral and crescent mesopumps. Characterization curves for each mesopump are then produced to provide a description of each pump's performance; moreover factors affecting the pump's performance are discussed. / A Thesis submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Degree Awarded: Spring Semester, 2006. / Date of Defense: November 30, 2005. / Positive Displacement Pump, Characterization, Viscous Drag Pumps, Numerical Computation / Includes bibliographical references. / Yousef S. Haik, Professor Directing Thesis; Ching-Jen Chen, Committee Member; Chi Fu Wu, Committee Member.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 167-171). / Supercritical water upgrading and desulfurization (SCWUDS) is a new concept in the oil refining industry wherein, crude oil is mixed with supercritical water in a reactor leading to chemical breakdown of the sulfur containing compounds (desulfurization) and cracking of long chain hydrocarbons to shorter chain compounds closer to commercial fuel components (upgrading). The focus of the present work is the development of a numerical tool to investigate the mixing of water and hydrocarbons under supercritical fully-miscible conditions (water and hydrocarbon forming a single phase) in a realistic 3-D cylindrical tee mixer geometry so as to develop an understanding of the effects of geometry, flow rates and fluid properties on the mixing dynamics which in turn will influence the rate of thermal cracking reactions of hydrocarbons and organosulfur compounds as well as the final product distributions. This work includes a consistent treatment of near-critical thermodynamics and transport property variations of real fluid mixtures. A Peng-Robinson EoS with simple van der Waals mixing rules is employed to model the near-critical thermodynamic behavior, with the mixture binary interaction parameter obtained from a Predictive Peng-Robinson approach using a group contribution method (PPR78). A 2nd order accurate finite-volume methodology is used for the numerical solution of the conservation equations. The developed numerical tool was used to investigate the mixing of supercritical water and a model hydrocarbon (n-decane) in a small-scale cylindrical tee mixer (pipe ID = 2.4mm) under fully miscible conditions. For a Reynolds number at the water inlet of 500 and a [delta]T between the two streams of l00K (Tw,in = 800K, Td,in= 700K), the flow downstream of the mixing joint remained laminar. Most of the mixing and heat transport occurs due to the circulating action of a counter-rotating vortex pair (CVP) in the hydrocarbon jet formed due to the reorientation of the vorticity preexisting in the hydrocarbon stream flowing through the vertical pipe. This CVP gets progressively weaker as it is advected downstream, due to vorticity diffusion and species and heat transport is dominated by molecular diffusion over small length scales in the far downstream region. Consequently, the mixing rate plateaus in the far downstream region of the tee mixer. Near-critical property variations were found to have a negligible impact on the flow field and mixing behavior under these conditions. However, for a 300K temperature difference between the two streams (Tw,in = 1000K, Td,in = 700K), the water-HC shear layer becomes unstable and rolls up downstream of 5 diameter lengths from the mixing joint. The onset of instability in the shear layer also triggers the stretching and breakdown of the hydrocarbon jet CVP leading to a significant enhancement in mixing manifested as a jump in the mixing rate and a thickening of the mean mixing layer. However, water n-decane mixing under identical inlet conditions but with constant physical properties, showed a stable shear layer with the flow reaching steady state. For a large [delta]T between the streams of 300K, the strong density increase (due to cooling of the water component) and the strong viscosity decrease (due to heating of the n-decane component) leads to a local increase in the Re within the mixing layer, resulting in the instability of the shear layer. SCW n-decane mixing with [delta]T = l00K was also simulated for increasingly higher Reynolds numbers up to the transition to turbulence. When the Reynolds number at the water inlet is increased to 700, the shear layer between the water and n-decane streams is found to become unstable near x = 6D downstream of the mixing joint followed by the subsequent roll up of the shear layer. The local increase of Re within the mixing layer due to mechanisms similar to the [delta]T = 300K case was found to be the cause of the shear layer instability. At Rew,in = 800 the unsteady small scale flow structures in the mixing layer and the consequent flow field fluctuations due to them are much stronger. The stretching and breakdown of the CVP in this case, is accompanied by stronger streamwise vorticity enhancement resulting in much faster mixing compared to the case of Rew,in = 700. / by Ashwin Raghavan. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1988. / Title as it appears in M.I.T. Graduate List, Feb. 1988: A modelling study of the influence of spark-ignition engine design parameters on engine thermal efficiency and performance. / Bibliography: leaves 63-65. / by Robert Todd Chang. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1987. / Bibliography: leaf 156. / by Arthur Hironari Ozaki. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (leaves 74-75). / At present, most fuel cells employ porous gas diffusion (PGD) electrodes. Although much effort has been spent on their development, the performance and cost of PGD electrodes are still major obstacles to the successful commercialization of fuel cells. As a means to bypass the drawbacks associated with PGD electrodes, several researchers have taken an alternative approach to electrode design by considering fluidized bed electrodes (FBEs), a type of flooded electrode that relies on convective rather than diffusive mass transport. Several reviews and past studies claim that FBEs have the potential for reaching high power density at a low cost due to several inherent advantages. However, the results so far of fluidized bed electrodes applied to fuel cells have been poor, and the past studies have not offered effective explanations for the discrepancy between expected and actual performance. A fluidized bed electrode model has been developed and applied to the data obtained by previous researchers in order to explain the poor performance of these past designs. As points of comparison, models have also been developed to predict the performance of packed bed electrodes and screen electrodes (two other flooded electrode designs). / (cont.) Separate models have been developed to consider both ionic and mass transport. Upper bounds on the performance of all three electrodes have been established, and then compared to the performance of PGD electrodes. The results of the models indicate that the PGD electrodes perform better than the packed bed or screen electrodes by at least a factor of two, unless the flooded electrodes are very short (on the order of millimeters). Both mass transfer and the saturation concentration of oxygen in the electrolyte serve as limitations in the flooded designs. The models also indicate that the two-phase and three-phase FBEs are inferior to the other flooded electrodes. The paper concludes with several recommendations for further work, including methods to boost performance. / by Justin Ruflin. / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / Includes bibliographical references (leaf 38). / With energy and environmental concerns becoming increasingly greater issues, electric vehicles are a promising alternative to internal combustion engine vehicles. More research and interest must be focused on battery technology and electric vehicles to make this a viable solution for the future of transportation. This project focuses on converting a 1974 Porsche 914, originally equipped with a 4-cylinder IC engine, into a full electric vehicle. The IC engine is replaced with a 50kW peak, 3-phase AC induction motor powered by twelve lithium-ion phosphate-metal cathode batteries. This paper goes through the conversion process as well as the necessary maintenance and driving techniques required to safely and efficiently operate an electric vehicle. Although the vehicle is complete it is currently in the debugging phase due to unforeseen electrical problems. The vehicle is planned to run by early June, 2007. Despite this setback, the project has been successful in starting a performance electric vehicle team, MIT EVT, and in increasing the appeal of electric vehicles in the MIT community. / by Emmanuel J. Sin. / S.B.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 87-88). / When decreasing of fossil fuel supplies and air pollution are two major society problems in the 21st century, rapid growth of internal combustion (IC) engines serves as a main producer of these two problems. In order to increase fuel efficiency, mechanical loss should be controlled in internal combustion engines. Interaction between piston ring pack and cylinder liner finish accounts for nearly 20 percent of the mechanical losses within an internal combustion engine, and is an important factor that affects the lubricant oil consumption. Among the total friction between piston ring pack and cylinder liner, boundary friction occurs when piston is at low speed and there is direct contact between rings and liners. This work focuses on prediction of contact between piston ring and liner finish based on 3D measured surface and different methods are compared. In previous twin-land oil control ring (TLOCR) deterministic model, Greenwood-Tripp correlation function was used to determine contact. The practical challenge for this single equation is that real plateau roughness makes it unreliable. As a result, micro geometry of liner surface needs to be obtained through white light interferometry device or confocal equipment to conduct contact model. Based on real geometry of liner finish and the assumption that ring surface is ideally smooth, contact can be predicted by three different models which were developed by using statistical Greenwood-Williamson model, Hertzian contact and revised deterministic dry contact model by Professor A.A. Lubrecht. The predicted contact between liner finish and piston ring is then combined with hydrodynamic pressure caused by lubricant which was examined using TLOCR deterministic model by Chen. et al to get total friction resulted on the surface of liner finish. Finally, contact model is used to examine friction of different liners in an actual engine running cycle. / by Qing Zhao. / S.M.