Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Experimental investigations of the effects of surfactants on droplet production by bubbles rising to a free surface.(2013) Parmar, Karan Dharmesh; Duncan, James H; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Air bubbles traveling upwards from within a liquid, burst at the free surface and eject droplets into the air. The liquid droplets produced from the bursting of air bubbles at the free surface of the ocean have long been considered as constituting a significant fraction of the marine aerosol production. This process plays an important role in the transfer of mass and energy between the ocean and atmosphere. The droplets are generated by two distinct mechanisms which characterize the drops as either `jet droplets' or `film droplets.' The goal of this study is to obtain statistical data about the size of these droplets produced by air bubbles bursting on a non-quiescent free surface and study effects of surfactant on the droplet distribution. Two different surface conditions are created by using "clean" water and a 0.4% v/v aqueous solution of Triton X-100 surfactant. A bubble field is created with air injected through an array of hypodermic needles arranged in a grid pattern and five different bubble production rates are studied for each surface condition. Measurements of the bubble diameters as they approach the free surface are obtained with diffuse light shadowgraph images. A laser-light high-speed cinematic shadowgraph system is employed to record and measure the diameters and motions of the droplets. The movies are processed on a custom-built MATLAB code which measures droplets as small as 100 μm to within 7% error. Droplets with diameters between 50 and 100 μm are also measured, but with lower accuracy. The droplet size distributions as a function of the production rate and surfactant conditions are reported. The results show a clear distinction between the droplet distributions obtained in clean water and the surfactant solution. A bimodal droplet distribution is observed for clean water with at least two dominating diameter peaks. For the surfactant solution, a single distribution peak is seen.Item Reaction rates and textural development of hydrolysis reactions in the system MgO-SiO2-H2O(2011) Kerrigan, Ryan Jason; Candela, Philip A; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Experiments in the simplified systems MgO-SiO2-H2O (MSH) and MgO-SiO2-H2O-CO2 (MSHC) have been conducted by using hydrothermal diamond anvil cells to investigate reaction rates and the resulting textures at temperatures and pressures consistent with the temperatures and pressures of the Earth's crust. The conditions and simplified systems of the experiments serve as approximations for geologic environments wherein magnesium-rich rocks (i.e., mafic, ultramafic, and magnesium-rich carbonate rocks) are hydrothermally altered by silica-rich fluids. The hydrolysis reaction rates and textures that result from the irreversible interactions of olivine and magnesite with aqueous fluids in the presence of quartz have been characterized. Reaction rates have been determined by a new approach developed during this study, which uses in situ observation of reactant volume loss to determine the growth rate of the products of hydrolysis reactions. In addition, some experiments were analyzed by real-time synchrotron radiation analysis to identify the phases in the reactions and to provide semi-quantitative constraints on the kinetic data. Experiments performed in this study resulted in the development of several textural varieties. Talc grown during this study exhibited both fibrous and platy habits, textural variations that appeared to be controlled by: variations in the density of the aqueous phase, surface area of starting materials, rate of temperature increase, and the presence of strong chemical gradients. The primary growth of fibrous talc in these experiments demonstrates that the production of fibrous talc does not require the pseudomorphism of a fibrous precursor as previously suggested.Item Bit of nostalgia... for one or two percussionists and live electronics performer(2006-04-30) Boyd, Michael; DeLio, Thomas; Music; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bit of nostalgia is a work for one or two percussionists and a live electronics performer that explores performer creativity through a graphic score and investigates the ways that the objects performers interact with (instruments) shape their actions/performances. The percussionist(s) take an active role in designing the stage set-up for each performance by superimposing a grid on the performance space, and filling at least half of the sectors with combinations of instrument-types listed in the piece's instructions (including objects made of metal, wood, glass, paper, plastic, and stone). Each sector that contains groups of instruments also contains a music stand holding three of eighteen closely related score pages. The similarities inherent in the various score pages requires that performers frequently reinterpret quasi-redundant visual materials with greatly varying groups of instruments (and objects), emphasizing the differences between each instrument group. While the performance proceeds, another performer interprets the same score using Cycling 74's MAX/MSP (software that accomplishes real-time sound synthesis and processing) to process and playback sound segments from recordings of previous rehearsals and/or performances. To accomplish this, the computer performer utilizes some or all of nine MAX/MSP patches (single windows containing a user designed graphical interface) of my design that incorporate differently controlled ring modulation, filtering, and delay in isolation or various combinations. The percussionists directly respond to these sounds as well as each other while interpreting certain pages of the score that contain the letters I, O, and T (signifying imitate, oppose, and transform respectively). These letters direct the performers to address sounds/actions produced by the other performer, themselves, or the electronics through their interpretations. Through these interactions, I hope to bring a sense of self-history into the piece and create an interesting notion of depth which reflects a broader perspective of what constitutes a "work." Whereas one typically thinks of an artwork as a fixed entity such as a score, I am trying to overtly link and interconnect otherwise marginalized and disparate aspects that contribute to the totality of this piece such as rehearsals and performances.