Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Seawater desalination, the desalination of waters flowing back from hydraulic fracturing processes and brackish water desalination constitute important desalination applications. These have a combined market size in excess of $25 billion per annum and a combined water production rate equivalent to the domestic consumption of over 300 million people. Each application offers its own distinct challenge. Reductions in energy consumption are key to driving down seawater desalination costs. The optimisation of water treatment in tandem with the formulation of fracturing fluids is key to reducing water management costs and environmental impacts in hydraulic fracturing. The development of desalination technologies that allow for high water recovery and high product purity is key to meeting industrial and municipal needs from brackish water sources. This thesis develops and investigates three emerging technologies: forward osmosis, electrodialysis at high salinity and hybrid electrodialysis-reverse osmosis with a view to addressing the three above challenges. Forward osmosis has often been viewed as a technology with the potential to reduce energy consumption in seawater desalination. An analysis is therefore undertaken into the theoretical limits upon its energy requirements paying particular attention to the energy penalty involved in drawing water from the feed stream into a more concentrated solution. Although unaddressed in literature this energy penalty is an important and distinguishing factor between FO and other desalination technologies. In the case of seawater, it is shown to put FO at a disadvantage that makes it difficult to compete with reverse osmosis. Consequently, it is argued that forward osmosis research should be reoriented away from seawater desalination to focus on alternate applications where salinities are above those which reverse osmosis can handle or where draw solution regeneration is not required. For these alternate applications a new framework is provided that explains the influence of the membrane orientation upon water flux through the membrane, an insight that is of particular use in considering the trade-off between water flux and fouling. The conventional view of electrodialysis is that it is most cost effective for the desalination of low salinity waters, and less so for moderate and high salinities, such as those encountered in waters that flow back from hydraulic fracturing processes. A thermoeconomic analysis of the effect of salinity upon cost reveals a different picture whereby electrodialysis is most cost effective removing salt from streams with between 1,000 ppm and 20,000 ppm of total dissolved solids. At lower salinities performance is hampered by low solution conductivity and low salt removal rates. At higher salinities the process is thermodynamically inefficient as the chemical potential of salt is raised only by a small amount when transported into the concentrate stream. The conclusion is that applications requiring salt removal within this 'sweet spot' for electrodialysis, such as the treatment of waste waters from flue-gas desulphurisation and coal-bed methane production, merit accelerated investigation. Incumbent technologies for the recycling of water produced from shales are currently inefficient and expensive. A study of electrodialysis energy requirements and equipment costs indicates that they are similar to, or even lower than, those for distillation. By developing a numerical model of system performance, which was validated over the range of 250 ppm to 192,000 ppm NaCl, it was possible to optimise the electrodialysis stack voltage and bring about cost savings of up to 30% in certain cases. These results and this numerical model warrant and will guide further investigations of electrodialysis under field conditions. Finally, a hybrid electrodialysis-reverse osmosis system was designed and optimised such that the reverse osmosis unit shifts salt removal in the electrodialysis unit into its sweet spot. The combination of these two technologies results in a system that provides enhanced product purity and product recovery at reduced cost. A simple rule of thumb is provided to guide practitioners in their choice between hybrid and standalone systems. This rule allows a choice to be made based on the relative cost of water from electrodialysis and reverse osmosis. / by Ronan Killian McGovern. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (p. 111-114). / Advanced High Strength Steels (AHSS) are becoming increasingly popular in automotive design because of possible weight savings due to the high strength. However, traditional methods are not capable of predicting fracture in AHSS, leading to expensive redesign due to poor prediction of stamping and crash worthiness. Many scenarios in which fracture is a concern in automotive applications are in the range of quasi-static through intermediate strain rates (up to 850/s). Studies with high-speed hydraulic equipment and Hopkinson bars have shown that there is a dependence of fracture on strain rate, and that it may be a complex relationship. Recent work on quasi-static fracture has shown that the dependence of ductility on the stress triaxiality and Lode parameter must be accounted for, but this dependence has not been investigated in the dynamic range. The aim of the current thesis is to contribute a new methodology based on an instrumented drop tower that will allow for testing of ductility for low to intermediate strain rates over stress triaxialities ranging from one third to two thirds. The methodology begins with a very in-depth understanding of plasticity based on multi-axial experiments, continues with qusistatic punching experiments, and finishes with dynamic punching experiments. In the punching experiments, a thin sheet is clamped into a circular die and loaded in membrane tension through out-of-plane punching. The state of stress is changed from equi-biaxial to approximately uniaxial through the introduction of cutouts in the sides the membrane specimen. / (cont.) The quasistatic punching experiments are verified against a multi-axial fracture testing technique previously demonstrated by other researchers. From application of the aforementioned methodology to a steels used in sheet metal forming and crash worthiness, the current thesis has shed insight into the dependence of ductility on stress triaxiality, Lode parameter, and strain rate for quasi-static to intermediate strain rates. / by Carey Leroy Walters. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001. / Includes bibliographical references (leaves 85-88). / by Shivanshu Gupta. / S.M.

Thesis (M.S.) Massachusetts Institute of Technology. Dept. of Mechanical Engineering, 1951. / Bibliography: leaf 90. / by Helmut Ernst Weber. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1943. / MICROFICHE COPY AVAILABLE IN BARKER ENGINEERING LIBRARY. / by Lewis D. Lipschutz. / M.S.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017. / Page 150 blank. Cataloged from PDF version of thesis. / Includes bibliographical references (pages 133-145). / The information processing capability of the brain is realized by a complex network of neuron subtypes, whose identities, locations, and connections are precisely controlled by the expression of specific sets of genes. Disruptions in the delicate spatiotemporal patterns of gene expression underlie many neurological disorders. Zebrafish, a unique model organism for high-throughput applications, have become increasingly popular for neuroscience research because of its small size and optical transparency of its brain. However, current phenotypic analysis of zebrafish relies heavily on qualitative methods such as crude visual examination. Additionally, the speed of phenotyping zebrafish lines is currently significantly behind the rate of generation of new mutant lines. There is a pressing need for a high-throughput tool that can quantitatively characterize zebrafish phenotypes in detail. In this thesis, an optical projection tomography system has been developed to rapidly image brain-specific gene expression patterns in 3D at cellular resolution. Then registration algorithms and a collection of high-content analysis techniques-including correlation analysis, voxel-wise significance testing, and colocalization clustering-are applied to the reconstructed 3D dataset to automatically detect phenotypic changes. The system has been used to screen full brain phenotype at cellular resolution in a well-studied mutant line tofm808 with a point mutation at the fezf2 gene, a conserved master regulator that plays an important role in neurogenesis and neuronal subtype specification. The analysis successfully detects both monoaminergic diencephalic phenotypes, which have been extensively discussed in the literature, and novel telencephalic phenotypes that were previously overlooked. The telencephalic phenotypes, which include glutamatergic defects in the pallium (the closest counterpart of the neocortex in fish), reveal unexpected parallels between the fezf2 functions in zebrafish and mammals, opening up new opportunities for discovery. / by Yuelong Wu. / Ph. D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004. / Includes bibliographical references (p. 92-96). / Separation of biologically active molecules (BAM's) is a problem for the pharmaceutical and biotechnology industries. Current technologies addressing this problem require too many techniques, toxic additives, and time to filter desired materials. As a result, a new technology is needed. The objective of this thesis is to contribute towards the development of a new method for separating biologically active molecules in the size range of 0.5 nanometers to 500 nanometers. A normally open diaphragm valve is proposed that can control a gap formed by two flat surfaces. For accurate control of gap height, the valve was designed to ensure that the flat surfaces remain parallel during operation . Modularity was also part of design considerations to address issues of eventual biocompatibility breakdown specifically protein adsorption. Control of the gap has been achieved to increments of 1.8 nanometers. / by Mauricio R. Gutierrez. / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 37-38). / Directional solvent extraction has been demonstrated as a low temperature, membrane free desalination process. This method dissolves the water into an inexpensive, benign directional solvent, rejects the contaminants, then recovers pure water, and re-uses the solvent. In order to bring this technology closer to real world application, a continuous process prototype for a directional solvent extraction system was developed and tested. Octanoic acid was used as the solvent of choice, and a system capable of producing up to 7 gallons per day of fresh water was constructed. The system was tested to effectively desalinate the feed water, and the total system power was less than 7 kW. The system was constructed and first tested to run fresh water and solvent through it. Fresh water was dissolved in and separated, as expected, from the solvent at a rate of about 2 gpd. Saline water containing 3.5% sodium chloride was then used as feedwater and the desalinated water was recovered at a rate of about 1 gpd with an average salinity of 0.175%. Effective continuous operation of the directional solvent extraction prototype was demonstrated. Certain design improvements to increase efficiency, optimize component sizes, and decrease energy consumption are suggested. The demonstrated system has a wide range of applications, including production of fresh water from the sea, as well as, treatment of produced and flowback water from shale gas and oil extraction. / by Michael James Fowler. / S.B.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 55-58). / Design of efficient and cost-effective catalysts for the oxygen evolution reaction (OER) is crucial for the development of electrochemical conversion technologies. Recent experiments show that perovskite transition-metal oxides can exhibit high electro-catalytic activity for OER. Both binding strength of reaction intermediate and [sigma]*-antibonding (eg) orbital filling of transition-metal ions in the clean surface prove to be descriptors of perovksite activity. Plotting of activity vs. a descriptor gives a volcano curve. However, little is known about the thermodynamic stability and the catalytic activity of perovskite surface reconstructions. Reconstructions such as defect, adsorbate, and steps are widely detected in experiments. They are caused by realistic environment during fabrication, measurement, and eventual device operation. In this work, we apply first-principles density functional theory and ab initio electro-thermodynamics to investigate the environment-dependent surface reconstructions of perovskite, particularly those based on LaMnO 3. We develop a surface stability phase diagram as a function of pH and electrode potential, and compare those catalytic activities under realistic liquid environment of electrolysis device. Our results show that values of pH and electrode potential can greatly affect surface structure and its activity. The new approach developed in this work is applicable to other oxide catalysts. / by Xi Rong. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999. / Includes bibliographical references (p. 95-96). / by Burt David LaFountain. / S.M.