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Description
Ingestion of high temperature mainstream gas into the rotor-stator cavities of a gas turbine is one of the major problems faced by the turbine designers. The ingested gas heats up rotor disks and induces higher thermal stresses on them, giving rise to durability concern. Ingestion is usually reduced by installing seals on the rotor and stator rims and by purging the disk cavity by secondary air bled from the compressor discharge. The geometry of the rim seals and the secondary air flow rate, together, influence the amount of gas that gets ingested into the cavities. Since the amount of secondary air bled off has a negative effect on the gas turbine thermal efficiency, one goal is to use the least possible amount of secondary air. This requires a good understanding of the flow and ingestion fields within a disk cavity. In the present study, the mainstream gas ingestion phenomenon has been experimentally studied in a model single-stage axial flow gas turbine. The turbine stage featured vanes and blades, and rim seals on both the rotor and stator. Additionally, the disk cavity contained a labyrinth seal radially inboard which effectively divided the cavity into a rim cavity and an inner cavity. Time-average static pressure measurements were obtained at various radial positions within the disk cavity, and in the mainstream gas path at three axial locations at the outer shroud spread circumferentially over two vane pitches. The time-average static pressure in the main gas path exhibited a periodic asymmetry following the vane pitch whose amplitude diminished with increasing distance from the vane trailing edge. The static pressure distribution increased with the secondary air flow rate within the inner cavity but was found to be almost independent of it in the rim cavity. Tracer gas (CO2) concentration measurements were conducted to determine the sealing effectiveness of the rim seals against main gas ingestion. For the rim cavity, the sealing effectiveness increased with the secondary air flow rate. Within the inner cavity however, this trend reversed -this may have been due to the presence of rotating low-pressure flow structures inboard of the labyrinth seal.
ContributorsThiagarajan, Jayanth kumar (Author) / Roy, Ramendra P (Thesis advisor) / Lee, Taewoo (Committee member) / Mignolet, Marc (Committee member) / Arizona State University (Publisher)
Created2013
Description
This study investigates the effectiveness of the use of Concept-Based Instruction (CBI) to facilitate the acquisition of Spanish mood distinctions by second semester second language learners of Spanish. The study focuses on the development of Spanish mood choice and the types of explanations (Rule-of-Thumb vs. Concept-based) used by five students before and after being exposed to Concept-Based Instruction regarding the choice of Spanish mood following various modalities .The students in this study were presented with a pedagogical treatment on Spanish mood choice that included general theoretical concepts based on Gal'perin's (1969, 1992) didactic models and acts of verbalization, which form part of a Concept-Based pedagogical approach. In order to ascertain the effectiveness of the use of concept-based tools to promote the ability to use Spanish mood appropriately over time, a pre and post-test was administered to the group in which students were asked to respond to prompts containing modalities that elicit the indicative and subjunctive moods, indicate their level of confidence in their response, and verbalize in writing a reason for their choice. The development of these abilities in learners exposed to CBI was assessed by comparing pre and post-test scores examining both forms and explanations for the indicative and subjunctive modality prompts given. Results showed that students continued to rely on Rule-of-Thumb explanations of mood choice but they did expand their use of conceptually-based reasoning. Although the quantitative and qualitative analyses of the results indicate that most students did improve their ability to make appropriate mood choices (forms and explanations) after the CBI treatment, the increased use of conceptually-based explanations for their mood choices led to both correct and incorrect responses.
ContributorsBeus, Eric (Author) / Lafford, Barbara (Thesis advisor) / Beas, Omar (Committee member) / Cerron-Palomino, Alvaro (Committee member) / Arizona State University (Publisher)
Created2013
Description
Time adolescents spend in organized or informal skill based activities after school is associated with a variety of positive developmental outcomes. Little is known about how siblings might shape adolescents' motivation to participate in after-school activities. The current study applied the expectancy value model and ecological theory to understand if sibling behaviors were related to adolescents' after-school activities for 34 Mexican origin families. Qualitative and quantitative results suggested siblings engaged in five promoting behaviors (i.e., support, provider of information, role modeling, comparison, co-participation) and three inhibiting behaviors (i.e., babysitting, transportation, and negativity) towards adolescent activity participation. Furthermore, sibling behaviors differed by adolescent characteristics (i.e., cultural orientation, familism, and neighborhood) and sibling characteristics (i.e., gender, age). The results provide evidence of the various promoting and inhibiting socialization behaviors sibling might use to influence adolescents' activity motivation.
ContributorsPrice, Chara Dale (Author) / Simpkins, Sandra (Thesis advisor) / Updegraff, Kimberly (Committee member) / Menjivar, Cecilia (Committee member) / Arizona State University (Publisher)
Created2012
Description
This study was designed to influence consumer habits, specifically those relating to purchases of fruits, vegetables, and junk food. Previous studies have clearly shown the ineffectiveness of simply describing the health benefits of eating more fruits and vegetables (F/V). In contrast, this study aimed to change the result by changing the message: providing participants with insight into the hidden agendas of food companies and grocery stores, provide useful tips on how to include children when selecting F/V, and emphasizing the importance of parental modeling in regard to food purchases. Participants of this study were separated into two groups, the tour group and the education group. The tour group was guided through a grocery store where they learned about sales tactics and manipulations used by grocery stores and food companies to influence purchases. Education group participants were provided with an education session focusing on USDA and FDA handouts displaying current educational suggestions for increasing F/V consumption. Grocery store receipts were collected and analyzed to track the progress of both groups. The goal of the study was to identify a method of informing consumers that will produce a significant change in behavior. Increasing F/V consumption, even in relatively small amounts, would be an important step forward in improving the diet and overall health of Americans. This study was the first of its kind to measure purchasing patterns objectively (through analysis of purchase receipts, rather than personal opinion/evaluation surveys) and in a wide-scope retail environment that includes all grocery store purchases by participants. Significant increases or decreases in the amount of money spent on F/V, or the amount (pounds) of F/V purchased were not seen, however a small correlation (r = 0.133) exists when comparing the weight of F/V purchased pre/post intervention. Data from Food Frequency Questionnaires shows participants consuming significantly higher amounts of F/V post intervention (p=0.043). The tour group and education group experienced an average increase of 0.7 servings per day. Future interventions might benefit by extending their scope to include cooking demonstrations, in-home interventions, and education on healthy eating outside of the home.
ContributorsKinsfather, Diana (Author) / Johnston, Carol (Thesis advisor) / Hekler, Eric (Committee member) / Tetreault, Colin (Committee member) / Arizona State University (Publisher)
Created2013
Description
Modern day gas turbine designers face the problem of hot mainstream gas ingestion into rotor-stator disk cavities. To counter this ingestion, seals are installed on the rotor and stator disk rims and purge air, bled off from the compressor, is injected into the cavities. It is desirable to reduce the supply of purge air as this decreases the net power output as well as efficiency of the gas turbine. Since the purge air influences the disk cavity flow field and effectively the amount of ingestion, the aim of this work was to study the cavity velocity field experimentally using Particle Image Velocimetry (PIV). Experiments were carried out in a model single-stage axial flow turbine set-up that featured blades as well as vanes, with purge air supplied at the hub of the rotor-stator disk cavity. Along with the rotor and stator rim seals, an inner labyrinth seal was provided which split the disk cavity into a rim cavity and an inner cavity. First, static gage pressure distribution was measured to ensure that nominally steady flow conditions had been achieved. The PIV experiments were then performed to map the velocity field on the radial-tangential plane within the rim cavity at four axial locations. Instantaneous velocity maps obtained by PIV were analyzed sector-by-sector to understand the rim cavity flow field. It was observed that the tangential velocity dominated the cavity flow at low purge air flow rate, its dominance decreasing with increase in the purge air flow rate. Radially inboard of the rim cavity, negative radial velocity near the stator surface and positive radial velocity near the rotor surface indicated the presence of a recirculation region in the cavity whose radial extent increased with increase in the purge air flow rate. Qualitative flow streamline patterns are plotted within the rim cavity for different experimental conditions by combining the PIV map information with ingestion measurements within the cavity as reported in Thiagarajan (2013).
ContributorsPathak, Parag (Author) / Roy, Ramendra P (Thesis advisor) / Calhoun, Ronald (Committee member) / Lee, Taewoo (Committee member) / Arizona State University (Publisher)
Created2013
Description
Objective. Both the civic education literature and the political ambition literature leave a gap in addressing the impact of political science coursework on political ambition. I address this gap by specifying the relationships between civic education, political knowledge, and political ambition. Methods. I employ paired t tests, chi-square tests, and Fisher's exact probability tests on an original dataset of 174 paired pre- and post-test survey responses. My survey improves upon prior works in the ambition literature (Fox and Lawless 2013) by virtue of its field experiment design. Results. My findings indicate that political science coursework has a positive impact on political knowledge, but only among women, and that political science coursework has a negative impact (among women) on one of the most valid measures of political ambition—how likely one is to run for office in the future. Conclusions/Implications. The results have negative normative implications for those trying to use political education as an instrument to reduce the gender gap (see Lawless and Fox 2010, Fox and Lawless 2013) in political ambition. This suggests the need to explore further options for increasing political ambition, particularly among women.
ContributorsWiezel, Adi (Author) / Kittilson, Miki (Thesis advisor) / Fridkin, Kim (Committee member) / Woodall, Gina (Committee member) / Arizona State University (Publisher)
Created2014
Description
Mexican-origin adolescent females have the highest birthrate of all other ethnic groups in the U.S. Further, teen mothers are at significant risk for poor outcomes, including low educational attainment. Therefore, examining predictors of Mexican-origin teen mothers' educational attainment was the main goal of the current study. Future-oriented beliefs such as educational aspirations and expectations are suggested to have positive implications for adolescents' educational attainment in general. Therefore, guided by bioecological, social capital, status attainment, social learning, and collective socialization of neighborhood theories, the current study examined neighborhood, maternal, and cultural predictors of 190 Mexican-origin parenting adolescents' educational aspirations, expectations, and attainment. With respect to maternal predictors, the study examined mother figures' (i.e., grandmothers') educational attainment, and aspirations and expectations for the adolescent as predictors of adolescents' educational attainment. Using a multi-informant, longitudinal analytic model, results suggest that adolescents' educational expectations, rather than aspirations, significantly predicted adolescents' attainment one year later. Additionally, grandmothers' educational attainment was indirectly associated with adolescents' educational attainment via the educational expectations of both the grandmother and the adolescent. Further, the neighborhood context indirectly informed adolescents' educational attainment via both grandmothers and adolescents' educational expectations. Finally, adolescents' ethnic identity affirmation was significantly associated with adolescents' educational attainment two years later. Implications regarding the importance of educational expectations and ethnic identity affirmation for at-risk parenting adolescents' educational attainment will be discussed.
ContributorsHarvey-Mendoza, Elizabeth C (Author) / Umaña-Taylor, Adriana J. (Thesis advisor) / Updegraff, Kimberly A. (Committee member) / White, Rebecca (Committee member) / Arizona State University (Publisher)
Created2014
Description
Guided by Belsky's Determinants of Parenting Process Model, the goal of the present study was to examine how mothers' personality (i.e., Conscientiousness) and behaviors (i.e., sensitivity, structure, and negative control) relate to children's developmental outcomes, such as internalization (i.e., committed compliance and effortful control) and academic adaptation. A multi-method, longitudinal model included five waves of data to examine the processes of the relations among variables. Mothers' Conscientiousness was measured via self-reported data when children were 18 months of age (N = 256), mothers' parenting behaviors were measured through observational laboratory tasks when children were 30 months (N = 230), children's internalization was measured using mothers' and caregivers' reports as well as observational data at 42 months (N = 210), and children's school adaptation was measured when children were 72 and 84 months (Ns = 169 and 144) using mothers' and teachers' reports. Through a series of regression analyses, the results supported the mediated effect of effortful control in the relation between mothers' behaviors and children's school adaptation. As hypothesized, mothers' Conscientiousness marginally predicted children's internalization. Contrary to hypotheses, mothers' Conscientiousness was unrelated to parenting behaviors and children's academic adaptation. Mothers' sensitivity interacted with maternal structure to predict children's effortful control. Socioeconomic status and child sex interacted with mothers' behaviors in predicting the child's committed compliance. The discussion focuses on the unique role of parenting practices and personality on children's internalization and academic adaptation and on the existing literature. Implications of the study for clinicians and intervention researchers are offered.
ContributorsKopystynska, Olena (Author) / Spinrad, Tracy L. (Thesis advisor) / Eisenberg, Nancy (Committee member) / Valiente, Carlos (Committee member) / Arizona State University (Publisher)
Created2014
Description
This study intended to identify what children's perceptions and experiences are with contact improvisation and how these experiences relate to their education; their understanding of being an individual within a community; and their physical, social, and intellectual development. An interpretive phenomenological research model was used, because this study aimed to understand and interpret the children's experience with contact improvisation in order to find meaning relating to the form's possible benefits. The research was conducted over the course of ten weeks, which included classes, interviews, discussions, questionnaires, and journals. This study showed that contact improvisation empowered the children, opened the children's awareness, developed critical thinking, and created a deeper understanding and trust of the self and relationships formed within the class. The experiences found through teaching contact improvisation to these children showed that there are benefits to teaching children the form.
ContributorsCrissman, Angel (Author) / Schupp, Karen (Thesis advisor) / Dyer, Becky (Committee member) / O'Donnell, Timothy (Committee member) / Arizona State University (Publisher)
Created2014
Description
Teaching evolution has been shown to be a challenge for faculty, in both K-12 and postsecondary education. Many of these challenges stem from perceived conflicts not only between religion and evolution, but also faculty beliefs about religion, it's compatibility with evolutionary theory, and it's proper role in classroom curriculum. Studies suggest that if educators engage with students' religious beliefs and identity, this may help students have positive attitudes towards evolution. The aim of this study was to reveal attitudes and beliefs professors have about addressing religion and providing religious scientist role models to students when teaching evolution. 15 semi-structured interviews of tenured biology professors were conducted at a large Midwestern universiy regarding their beliefs, experiences, and strategies teaching evolution and particularly, their willingness to address religion in a class section on evolution. Following a qualitative analysis of transcripts, professors did not agree on whether or not it is their job to help students accept evolution (although the majority said it is not), nor did they agree on a definition of "acceptance of evolution". Professors are willing to engage in students' religious beliefs, if this would help their students accept evolution. Finally, professors perceived many challenges to engaging students' religious beliefs in a science classroom such as the appropriateness of the material for a science class, large class sizes, and time constraints. Given the results of this study, the author concludes that instructors must come to a consensus about their goals as biology educators as well as what "acceptance of evolution" means, before they can realistically apply the engagement of student's religious beliefs and identity as an educational strategy.
ContributorsBarnes, Maryann Elizabeth (Author) / Brownell, Sara E (Thesis advisor) / Brem, Sarah K. (Thesis advisor) / Lynch, John M. (Committee member) / Ellison, Karin (Committee member) / Arizona State University (Publisher)
Created2014