Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
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Description
The Magnetoplasmadynamic (MPD) thruster is an electromagnetic thruster that produces a higher specific impulse than conventional chemical rockets and greater thrust densities than electrostatic thrusters, but the well-known operational limit---referred to as ``onset"---imposes a severe limitation efficiency and lifetime. This phenomenon is associated with large fluctuations in operating voltage, high rates of electrode erosion, and three-dimensional instabilities in the plasma flow-field which cannot be adequately represented by two-dimensional, axisymmetric models. Simulations of the Princeton Benchmark Thruster (PBT) were conducted using the three-dimensional version of the magnetohydrodynamic (MHD) code, MACH. Validation of the numerical model is partially achieved by comparison to equivalent simulations conducted using the well-established two-dimensional, axisymmetric version of MACH. Comparisons with available experimental data was subsequently performed to further validate the model and gain insights into the physical processes of MPD acceleration. Thrust, plasma voltage, and plasma flow-field predictions were calculated for the PBT operating with applied currents in the range $6.5kA < J < 23.25kA$ and mass-flow rates of $1g/s$, $3g/s$, and $6g/s$. Comparisons of performance characteristics between the two versions of the code show excellent agreement, indicating that MACH3 can be expected to be as predictive as MACH2 has demonstrated over multiple applications to MPD thrusters. Predicted thrust for operating conditions within the range which exhibited no symptoms of the onset phenomenon experimentally also showed agreement between MACH3 and experiment well within the experimental uncertainty. At operating conditions beyond such values , however, there is a discrepancy---up to $\sim20\%$---which implies that certain significant physical processes associated with onset are not currently being modeled. Such processes are also evident in the experimental total voltage data, as is evident by the characteristic ``voltage hash", but not present in predicted plasma voltage. Additionally, analysis of the predicted plasma flow-field shows no breakdown in azimuthal symmetry, which is expected to be associated with onset. This implies that perhaps certain physical processes are modeled by neither MACH2 nor MACH3; the latter indicating that such phenomenon may not be inherently three dimensional and related to the plasma---as suggested by other efforts---but rather a consequence of electrode material processes which have not been incorporated into the current models.
ContributorsParma, Brian (Author) / Mikellides, Pavlos G (Thesis advisor) / Squires, Kyle (Committee member) / Herrmann, Marcus (Committee member) / Arizona State University (Publisher)
Created2011
Description
ABSTRACT There is a body of literature--albeit largely from the UK and Australia--that examines the ways in which class and gender influence life course, including educational attainment; however, much of this literature offers explanations and analyses for why individuals choose the life course they do. By assuming a cause-effect relationship between class and gender and life course, these studies perpetuate the idea that life can be predicted and controlled. Such an approach implies there is but one way of viewing--or an "official reading" of--the experience of class and gender. This silences other readings. This study goes beneath these "interpretations" and explores the phenomenon of identity and identity making in women who grew up working-class. Included is an investigation into how these women recognize and participate in their own identity making, identifying the interpretations they created and apply to their experience and the ways in which they juxtapose their educative experience. Using semi-structured interview I interviewed 21 women with working-class habitués. The strategy of inquiry that corresponded best to the goal of this project was heuristics, a variant of empathetic phenomenology. Heuristics distinguishes itself by including the life experience of the researcher while still showing how different people may participate in an event in their lives and how these individuals may give it radically different meanings. This has two effects: (1) the researcher recognizes that their own life experience affects their interpretations of these stories and (2) it elucidates the researcher's own life as it relates to identity formation and educational experience. Two, heuristics encourages different ways of presenting findings through a variety of art forms meant to enhance the immediacy and impact of an experience rather than offer any explanation of it. As a result of the research, four themes essential to locating the experience of women who grew up working class were discovered: making, paying attention, taking care, and up. These themes have pedagogic significance as women with working-class habitués navigate from this social space: the downstream effect of which is how and what these women take up as education.
ContributorsDecker, Shannon Irene (Author) / Blumenfeld-Jones, Donald (Thesis advisor) / Richards-Young, Gillian (Committee member) / Sandlin, Jennifer (Committee member) / Arizona State University (Publisher)
Created2011
Description
Current economic conditions necessitate the extension of service lives for a variety of aerospace systems. As a result, there is an increased need for structural health management (SHM) systems to increase safety, extend life, reduce maintenance costs, and minimize downtime, lowering life cycle costs for these aging systems. The implementation of such a system requires a collaborative research effort in a variety of areas such as novel sensing techniques, robust algorithms for damage interrogation, high fidelity probabilistic progressive damage models, and hybrid residual life estimation models. This dissertation focuses on the sensing and damage estimation aspects of this multidisciplinary topic for application in metallic and composite material systems. The primary means of interrogating a structure in this work is through the use of Lamb wave propagation which works well for the thin structures used in aerospace applications. Piezoelectric transducers (PZTs) were selected for this application since they can be used as both sensors and actuators of guided waves. Placement of these transducers is an important issue in wave based approaches as Lamb waves are sensitive to changes in material properties, geometry, and boundary conditions which may obscure the presence of damage if they are not taken into account during sensor placement. The placement scheme proposed in this dissertation arranges piezoelectric transducers in a pitch-catch mode so the entire structure can be covered using a minimum number of sensors. The stress distribution of the structure is also considered so PZTs are placed in regions where they do not fail before the host structure. In order to process the data from these transducers, advanced signal processing techniques are employed to detect the presence of damage in complex structures. To provide a better estimate of the damage for accurate life estimation, machine learning techniques are used to classify the type of damage in the structure. A data structure analysis approach is used to reduce the amount of data collected and increase computational efficiency. In the case of low velocity impact damage, fiber Bragg grating (FBG) sensors were used with a nonlinear regression tool to reconstruct the loading at the impact site.
ContributorsCoelho, Clyde (Author) / Chattopadhyay, Aditi (Thesis advisor) / Dai, Lenore (Committee member) / Wu, Tong (Committee member) / Das, Santanu (Committee member) / Rajadas, John (Committee member) / Papandreou-Suppappola, Antonia (Committee member) / Arizona State University (Publisher)
Created2011
Description
The high strength to weight ratio of woven fabric offers a cost effective solution to be used in a containment system for aircraft propulsion engines. Currently, Kevlar is the only Federal Aviation Administration (FAA) approved fabric for usage in systems intended to mitigate fan blade-out events. This research builds on an earlier constitutive model of Kevlar 49 fabric developed at Arizona State University (ASU) with the addition of new and improved modeling details. Latest stress strain experiments provided new and valuable data used to modify the material model post peak behavior. These changes reveal an overall improvement of the Finite Element (FE) model's ability to predict experimental results. First, the steel projectile is modeled using Johnson-Cook material model and provides a more realistic behavior in the FE ballistic models. This is particularly noticeable when comparing FE models with laboratory tests where large deformations in projectiles are observed. Second, follow-up analysis of the results obtained through the new picture frame tests conducted at ASU provides new values for the shear moduli and corresponding strains. The new approach for analysis of data from picture frame tests combines digital image analysis and a two-level factorial optimization formulation. Finally, an additional improvement in the material model for Kevlar involves checking the convergence at variation of mesh density of fabrics. The study performed and described herein shows the converging trend, therefore validating the FE model.
ContributorsMorea, Mihai I (Author) / Rajan, Subramaniam D. (Thesis advisor) / Arizona State University (Publisher)
Created2011
Deviant bodies resisting online: examining the intersecting realities of women of color in Xbox Live
Description
Employing qualitative methods and drawing from an intersectional framework which focuses on the multiple identities we all embody, this dissertation focuses on oppressions and resistance strategies employed by women of color in Xbox live, an online gaming community. Ethnographic observations and narrative interviewing reveal that women of color, as deviants within the space, face intersecting oppressions in gaming as in life outside the gaming world. They are linguistically profiled within the space based off of how they sound. They have responded with various strategies to combat the discrimination they experience. Some segregate themselves from the larger gaming population and many refuse to purchase games that depict women in a hyper-sexualized manner or that present people of color stereotypically. For others, the solution is to "sit-in" on games and disrupt game flow by 'player-killing' or engage in other 'griefing' activities. I analyze this behavior in the context of Black feminist consciousness and resistance and uncover that these methods are similar to women who employ resistance strategies for survival within the real world.
ContributorsGray, Kishonna (Author) / Anderson, Lisa M. (Thesis advisor) / Cheong, Pauline (Committee member) / Lim, Merlyna (Committee member) / Arizona State University (Publisher)
Created2011
Description
Historians often characterize first ladies in the Progressive Era as representatives of the last vestiges of Victorian womanhood in an increasingly modern society. This dissertation argues that first ladies negotiated an image of themselves that fulfilled both traditional and modern notions of womanhood. In crafting these images, first ladies constructed images of their celebrity selves that were uniquely modern. Thus, images of first ladies in the Progressive Era show them as modest and feminine but also autonomous, intelligent, and capable. Using the historian Charles Ponce de Leon's research on modern human-interest journalism, I contend that first ladies in the Progressive Era worked with the modern press in a symbiotic relationship. This relationship allowed the press exclusive access to what was, ostensibly, the first lady's private, and therefore authentic, self. By purporting to reveal parts of their private lives in the press, first ladies showed themselves as down-to-earth despite their success and fulfilled by their domestic pursuits despite their compelling public lives. By offering the press exclusive access to their lives, first ladies secured the opportunity to shape specific images of themselves to appeal, as broadly as possible, to their husbands and parties' constituents and the American public. First ladies in the Progressive Era thus acted as political figures by using both public and private, or what historian Catherine Allgor terms, "unofficial spaces" to support and reflect their husbands and parties' political agendas. In examining representations of first ladies in popular magazines and newspapers from 1901 to 1921 in tandem with letters, memoirs, and other personal papers from these women, a clear pattern emerges. Despite personal differences, first ladies in the Progressive Era represented themselves according to a specific formula in the modern press. The images, constructed by first ladies in this time period, reflect shifts in economic, social, and political life in Progressive Era America, which called for women to be independent and intelligent yet still maintain their femininity and domesticity.
ContributorsHorohoe, Jill (Author) / Gullett, Gayle (Thesis advisor) / Longley, Rodney K (Committee member) / Warren-Findley, Jannelle (Committee member) / Arizona State University (Publisher)
Created2011
Description
Federal education policies call for school district leaders to promote classroom technology integration to prepare students with 21st century skills. However, schools are struggling to integrate technology effectively, with students often reporting that they feel like they need to power down and step back in time technologically when they enter classrooms. The lack of meaningful technology use in classrooms indicates a need for increased teacher preparation. The purpose of this study was to investigate the impact a coaching model of professional development had on school administrators` abilities to increase middle school teachers` technology integration in their classrooms. This study attempted to coach administrators to develop and articulate a vision, cultivate a culture, and model instruction relative to the meaningful use of instructional technology. The study occurred in a middle school. Data for this case study were collected via administrator interviews, the Principal`s Computer Technology Survey, structured observations using the Higher Order Thinking, Engaged Learning, Authentic Learning, Technology Use protocol, field notes, the Technology Integration Matrix, teacher interviews, and a research log. Findings concluded that cultivating change in an organization is a complex process that requires commitment over an extended period of time. The meaningful use of instructional technology remained minimal at the school during fall 2010. My actions as a change agent informed the school`s administrators about the role meaningful use of technology can play in instruction. Limited professional development, administrative vision, and expectations minimized the teachers` meaningful use of instructional technology; competing priorities and limited time minimized the administrators` efforts to improve the meaningful use of instructional technology. Realizing that technology proficient teachers contribute to student success with technology, it may be wise for administrators to incorporate technology-enriched professional development and exercise their leadership abilities to promote meaningful technology use in classrooms.
ContributorsRobertson, Kristen (Author) / Moore, David (Thesis advisor) / Cheatham, Greg (Committee member) / Catalano, Ruth (Committee member) / Arizona State University (Publisher)
Created2011
Description
A design methodology for a new breed of launch vehicle capable of lofting small satellites to orbit is discussed. The growing need for such a rocket is great: the United States has no capabilities in place to quickly launch and reconstitute satellite constellations. A loss of just one satellite, natural or induced, could significantly degrade or entirely eliminate critical space-based assets which would need to be quickly replaced. Furthermore a rocket capable of meeting the requirements for operationally responsive space missions would be an ideal launch platform for small commercial satellites. The proposed architecture to alleviate this lack of an affordable dedicated small-satellite launch vehicle relies upon a combination of expendable medium-range military surplus solid rocket motor assets. The dissertation discusses in detail the current operational capabilities of these military boosters and provides an outline for necessary refurbishments required to successfully place a small payload in orbit. A custom 3DOF trajectory script is used to evaluate the performance of these designs. Concurrently, a parametric cost-mass-performance response surface methodology is employed as an optimization tool to minimize life cycle costs of the proposed vehicles. This optimization scheme is centered on reducing life cycle costs per payload mass delivered rather than raw performance increases. Lastly, a novel upper-stage engine configuration using Hydroxlammonium Nitrate (HAN) is introduced and experimentally static test fired to illustrate the inherent simplicity and high performance of this high density, nontoxic propellant. The motor was operated in both pulse and small duration tests using a newly developed proprietary mixture that is hypergolic with HAN upon contact. This new propellant is demonstrated as a favorable replacement for current space vehicles relying on the heritage use of hydrazine. The end result is a preliminary design of a vehicle built from demilitarized booster assets that complements, rather than replaces, traditional space launch vehicles. This dissertation proves that such capabilities exist and more importantly that the resulting architecture can serve as a viable platform for immediate and affordable access to low Earth orbit.
ContributorsVillarreal, James Kendall (Author) / Squires, Kyle (Thesis advisor) / Lee, Taewoo (Committee member) / Shankar, Praveen (Committee member) / Sharp, Thomas (Committee member) / Wells, Valana (Committee member) / Arizona State University (Publisher)
Created2011
Description
ABSTRACT This dissertation focuses on Anne Moody's use of the autobiographical genre as an extension of her political activism. Noting consistent values and conventions that govern the writing of political activists, this study asserts that Moody's narrative is best situated in the genre of political autobiography--a term coined by Angela Davis. Using Margo V. Perkins' text as a base to define autobiography as activism, this dissertation illustrates the consistent values that characterize Moody's narrative as political autobiography, resistance literature, and ultimately Black Power literature. Building on the works of Joanne Braxton, Patricia Hill Collins, Angela Davis, Elizabeth Fox-Genovese, bell hooks, Margo V. Perkins, Assata Shakur, and Johnny Stover, this project demonstrates the use of Moody's autobiography as a collective form of resistance that is reflective of autobiography as activism. To frame its argument, this study theorizes how one comes into revolutionary consciousness, demonstrating the move toward activism as a process. Drawing on Sidonie Smith and Julia Watson's autobiographical theory that the "narrated I" is distinguished from the "narrating I," this study asserts, as Francoise Lionnet suggests, that the "narrating I" is the vehicle to deliver recollections relevant to the autobiographer's agenda. This study emphasizes that the early version of the self Moody creates is consciously linked to her role as a future activist, ultimately demonstrating her political evolution through the emphatic linking of the personal and political. Most importantly, this dissertation demonstrates that Moody's text represents a continuity--an autobiographical bridge--between representations of the Christian nonviolent civil rights movement and the Black Power movement of the late 1960's. This study argues that Moody's autobiography is ideologically poised at the intersection of civil rights and Black Power; therefore, it serves as both a civil rights autobiography and a Black Power autobiography. Coming of Age in Mississippi offers a unique contribution to the genre of Black Power autobiography for the way it facilitates unprecedented insight into the transition from non-violent civil rights ideology to revolutionary consciousness.
ContributorsFlanagan, Melissa A (Author) / Miller, Keith D. (Thesis advisor) / Stancliff, Michael (Committee member) / Anokye, Duku (Committee member) / Arizona State University (Publisher)
Created2011
Description
Most studies on refugee populations tend to focus on mental health issues and communicable diseases. Yet, reproductive health remains a major aspect of refugee women's health needs. African refugee women in the United States continue to experience some difficulties in accessing reproductive health services despite having health insurance coverage. The purpose of this study was to understand the reproductive health journey of African refugee women resettled in Phoenix, Arizona. This study also explored how African refugee women's pre-migration and post-migration experiences affect their relationships with health care providers. The study was qualitative consisting of field observations at the Refugee Women's Health Clinic (RWHC) in Phoenix, verbally administered demographic questionnaires, and semi-structured one-on-one interviews with twenty African refugee women (between the ages of 18 and 55) and ten health care providers. The findings were divided into three major categories: pre-migration and post migration experiences, reproductive health experiences, and perspectives of health care providers. The themes that emerged from these categories include social isolation, living between two cultures, racial and religious discrimination, language/interpretation issues and lack of continuity of care. Postcolonial feminism, intersectionality, and human rights provided the theoretical frameworks that helped me to analyze the data that emerged from the interviews, questionnaire and fieldnotes. The findings revealed some contrasts from the refugee women's accounts and the accounts of health care providers. While refugee women spoke from their own specific social location leading to more nuanced perspectives, health care providers were more uniform in their responses leading to a rethink of the concept of cultural competency. As I argue in the dissertation and contrary to conventional wisdom, culture per se does not necessarily translate to resistance to the American health care system for many African refugee women. Rather, their utilization (or lack thereof) of health services are better conceived within a broader and complex context that recognizes intersectional factors such as gender, racialization, language, displacement, and class which have a huge impact on the reproductive health seeking patterns of refugee women.
ContributorsJatau, Mary (Author) / Koblitz, Ann Hibner (Thesis advisor) / James, Stanlie (Committee member) / Robillard, Alyssa (Committee member) / Johnson, Crista (Committee member) / Arizona State University (Publisher)
Created2011