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- Genre: Masters Thesis
- Creators: Arizona State University
- Creators: Chakraborty, Bijeta
- Member of: ASU Electronic Theses and Dissertations
Description
Efficiency of components is an ever increasing area of importance to portable applications, where a finite battery means finite operating time. Higher efficiency devices need to be designed that don't compromise on the performance that the consumer has come to expect. Class D amplifiers deliver on the goal of increased efficiency, but at the cost of distortion. Class AB amplifiers have low efficiency, but high linearity. By modulating the supply voltage of a Class AB amplifier to make a Class H amplifier, the efficiency can increase while still maintaining the Class AB level of linearity. A 92dB Power Supply Rejection Ratio (PSRR) Class AB amplifier and a Class H amplifier were designed in a 0.24um process for portable audio applications. Using a multiphase buck converter increased the efficiency of the Class H amplifier while still maintaining a fast response time to respond to audio frequencies. The Class H amplifier had an efficiency above the Class AB amplifier by 5-7% from 5-30mW of output power without affecting the total harmonic distortion (THD) at the design specifications. The Class H amplifier design met all design specifications and showed performance comparable to the designed Class AB amplifier across 1kHz-20kHz and 0.01mW-30mW. The Class H design was able to output 30mW into 16Ohms without any increase in THD. This design shows that Class H amplifiers merit more research into their potential for increasing efficiency of audio amplifiers and that even simple designs can give significant increases in efficiency without compromising linearity.
ContributorsPeterson, Cory (Author) / Bakkaloglu, Bertan (Thesis advisor) / Barnaby, Hugh (Committee member) / Kiaei, Sayfe (Committee member) / Arizona State University (Publisher)
Created2013
Description
This research examined the perceptions of refugees towards social entrepreneurship in Arizona through focus group discussions with 77 members of the refugee communities that have been organized under nine groups. Business experience, problem solving experience, conception of social entrepreneurship, examples, opportunities, support, and needs emerged as the themes of the study. Available opportunities as well as barriers for refugee social entrepreneurship based on the views of refugees in Arizona were explained. The difference between commercial entrepreneurship and social entrepreneurship was highlighted and some examples of refugee social entrepreneurship described. Qualitative data analysis revealed that refugees in Arizona have entrepreneurial characteristics such as risk taking, hardworking, problem solving, and determination. They also have a good understanding of commercial entrepreneurship but very little understanding of social entrepreneurship. The findings underlined that social entrepreneurship can be used as a helpful strategy for self-sufficiency of refugees residing in Arizona. Given their life trajectories, refugees in Arizona have high potential to be social entrepreneurs with the right exposure and training. If supported adequately and planned appropriately, the refugee social entrepreneurship project can lead to self-sufficiency and faster integration of participating individuals to the mainstream society. The findings may spark interest among practitioners, policy makers, and scholars. It may redefine refugee social work practices as the passion of enterprising empowers refugees and helps them to discover self-confidence and rebrand their image. Policy makers may consider incorporating refugee social entrepreneurship in to the current self-sufficiency plan for refugee resettlement. Future research needs to investigate how refugee social entrepreneurs can be successful and focus on the measurement of their success.
ContributorsMerie, Kassaw (Author) / Androff, David (Thesis advisor) / Klimek, Barbara (Committee member) / Krysik, Judy (Committee member) / Arizona State University (Publisher)
Created2015
Description
Class D Amplifiers are widely used in portable systems such as mobile phones to achieve high efficiency. The demands of portable electronics for low power consumption to extend battery life and reduce heat dissipation mandate efficient, high-performance audio amplifiers. The high efficiency of Class D amplifiers (CDAs) makes them particularly attractive for portable applications. The Digital class D amplifier is an interesting solution to increase the efficiency of embedded systems. However, this solution is not good enough in terms of PWM stage linearity and power supply rejection. An efficient control is needed to correct the error sources in order to get a high fidelity sound quality in the whole audio range of frequencies. A fundamental analysis on various error sources due to non idealities in the power stage have been discussed here with key focus on Power supply perturbations driving the Power stage of a Class D Audio Amplifier. Two types of closed loop Digital Class D architecture for PSRR improvement have been proposed and modeled. Double sided uniform sampling modulation has been used. One of the architecture uses feedback around the power stage and the second architecture uses feedback into digital domain. Simulation & experimental results confirm that the closed loop PSRR & PS-IMD improve by around 30-40 dB and 25 dB respectively.
ContributorsChakraborty, Bijeta (Author) / Bakkaloglu, Bertan (Thesis advisor) / Garrity, Douglas (Committee member) / Ozev, Sule (Committee member) / Arizona State University (Publisher)
Created2012
Description
The United States resettles more refugees each year than any country, yet little is known about the influence that the Refugee Resettlement Program has on our communities. Program evaluation in the United States is primarily concerned with outcomes and efficiency; while there has been an absence of collecting data to measure the impact that social programs have on communities. This study explores the impact of refugee resettlement on a metropolitan area by surveying professionals with experience working or volunteering with refugee populations. These professionals rate the extent to which they believe refugee resettlement influences social, economic, and environmental variables in the community, and explain the nature of the influence they believe the program has on the community. The data collected from these surveys will introduce the perceived impact of refugee resettlement from the perspective of those with professional experience in the area. By exploring the effects that the Refugee Resettlement Program has on Phoenix, this data can assist in the creation of community assessments for refugee resettlement and comparable social programs.
ContributorsMody, Elizabeth Hatch (Author) / Klimek, Barbara (Thesis advisor) / Morales, Joanne (Committee member) / Brown, Mary-Ellen (Committee member) / Arizona State University (Publisher)
Created2018
Description
This project seeks to explore how organizations work toward refugee and immigrant integration through forming different types of coalitions and strategic networks. Semi-structured interviews were conducted to identify when coalitions emerge between refugee organizations and immigrant rights groups in order to examine their development, from how the coalitions broadly conceive of refugee and immigrant rights, to how they organize resources and information sharing, service provision, policy advocacy, and policy implementation. The project is guided by the question: What explains the formation of coalitions that advocate for both immigrant rights and refugee rights? Through examining the formation and development of these coalitions, this thesis engages at the intersections of immigration federalism, refugee studies and human rights scholarship to reveal deeper complexities in the politics of immigrant integration. The project sharpens these three scholarly intersections by three multi-level jurisdictions – California and Arizona in the United States and Athens in Greece – and by employing comparative analysis to unpack how national governments and federalism dynamics shape coalition building around immigrant integration.
ContributorsAmoroso-Pohl, Melanie Hope (Author) / Colbern, Allan (Thesis advisor) / Keahey, Jennifer (Committee member) / Walker, Shawn (Committee member) / Arizona State University (Publisher)
Created2019
Description
The current immigration flow to the United States from Mexico has been polarized by politicians and anti-immigration groups, with a rhetoric that immigrants are a danger to the sovereignty of the country and an economic burden. These accusations ignore the role played by trade agreements in causing such migration patterns by displacing Mexican migrants and how U.S. immigration policies subsequently condemn these economically displaced migrants into illegality. This thesis examines the role national governments and laws of both the United States and Mexico play in formalizing the undocumented flow and the contestation of these economic migrants. I challenge the contemporary view of trade agreements as pull factors by showing how they also function as problematic push factors of migration through displacing Mexicans from their land and any meaningful form of economic security. Once displaced, these communities seek opportunities by migrating to the U.S., where they cross into illegality. Together, examining displacement and subsequent illegality, this thesis reveals the problematic, yet hidden role played by trade agreements in Mexican migration to the U.S. and gaps in current U.S. immigration laws that has preserved the injustices created when neoliberal economic policies and immigration politics provide no protection to impacted indigenous communities.
ContributorsValenzuela, Cinthia (Author) / Colbern, Allan (Thesis advisor) / Comstock, Audrey (Committee member) / Elenes, C Alejandra (Committee member) / Arizona State University (Publisher)
Created2019
Description
Resettled refugees face numerous challenges including unsafe living conditions, loss of permanent shelter, adjustment to a new culture, loneliness, and separation from family, friends, and community. Of particular importance is the lack of a feeling of sense of community (SOC) within their new surroundings. SOC is not only worthwhile as an outcome of its own, but may also predict additional positive outcomes such as resilience and cultural adjustment. Literature has shown participation in sport can develop youth positively and build social skills, while studies in other regions of the world have also found a sport team setting to be a place for immigrants to experience SOC. In this study, I use a congruent mixed methods approach to both explore the experience of SOC for youth refugees in a soccer club, and examine the relation of SOC to resilience and cultural adjustment. Using photo-elicitation and semi-structured interviews with 11 youth participants, the qualitative portion of the study explored SOC among youth participants. Findings note the presence of SOC as matched to theoretical frameworks both specific to sport, and to a more general theory of SOC. Further data were collected through questionnaires distributed to club members. Results from the quantitative analysis indicate a significant positive relation between SOC and resilience, and SOC and perceived acculturation. This study’s contribution is to illustrate how refugee youth in a sport club in the United States experience SOC, and the impact of that SOC. Results suggest practical implications for sport managers who wish to provide positive sport experiences for youth refugees.
ContributorsFader, Nina (Author) / Legg, Eric (Thesis advisor) / Larsen, Dale (Committee member) / Klimek, Barbara (Committee member) / Arizona State University (Publisher)
Created2018
Description
In this thesis, a digital input class D audio amplifier system which has the ability
to reject the power supply noise and nonlinearly of the output stage is presented. The main digital class D feed-forward path is using the fully-digital sigma-delta PWM open loop topology. Feedback loop is used to suppress the power supply noise and harmonic distortions. The design is using global foundry 0.18um technology.
Based on simulation, the power supply rejection at 200Hz is about -49dB with
81dB dynamic range and -70dB THD+N. The full scale output power can reach as high as 27mW and still keep minimum -68dB THD+N. The system efficiency at full scale is about 82%.
to reject the power supply noise and nonlinearly of the output stage is presented. The main digital class D feed-forward path is using the fully-digital sigma-delta PWM open loop topology. Feedback loop is used to suppress the power supply noise and harmonic distortions. The design is using global foundry 0.18um technology.
Based on simulation, the power supply rejection at 200Hz is about -49dB with
81dB dynamic range and -70dB THD+N. The full scale output power can reach as high as 27mW and still keep minimum -68dB THD+N. The system efficiency at full scale is about 82%.
ContributorsBai, Jing (Author) / Bakkaloglu, Bertan (Thesis advisor) / Arizona State University (Publisher)
Created2015
Description
Through interviews and observations, this thesis provides an overview of refugee resettlement and explores the way one community is providing English language instruction to recently resettled refugees. It also describes the research process of this thesis so other researchers will be aware of the challenges such research contexts provide. In the southwestern state studied here, one of the refugee resettlement agencies holds the contract to provide English Language instruction to refugees. Other agencies provide supplemental English instruction and tutoring. The U.S. federal statute Immigration and Nationality Act, title 45 of the Code of Federal Regulations part 400--Refugee Resettlement Program, and the local contract between the state and the agency were examined to understand the laws, regulations, and contracted agreement governing the provision of English language instruction for refugees being resettled in the United States. English language faculty and staff, staff at refugee resettlement agencies, and a state official were interviewed to understand their goals and the challenges they face as they address the language needs of refugees. English language instruction classes were observed to note the consistencies as well as some discrepancies between interviews and what could actually be accomplished in the classroom. As the classes are unable to provide intensive language instruction, most students struggle with becoming proficient in English. A list of recommendations is included regarding ways the local community can better address linguistic needs of refugees. Yet as Fass (1985) argues, it is unknown whether changing refugee resettlement efforts will actually produce different results. Though there are problems, the way the linguistic needs are being addressed in this community is sufficient given the numerous other expectations put on the refugees and the refugee resettlement agencies.
ContributorsKielczewski, Sarah-Anne Laster (Author) / Adams, Karen L (Thesis advisor) / Gelderen, Elly van (Committee member) / Klimek, Barbara (Committee member) / Arizona State University (Publisher)
Created2010
Description
Immigrants and their U.S.-born children account for 26% of the American population as of 2020. Despite this large proportion, 14% of immigrants live below the federal poverty line compared to 12% of U.S.-born citizens. The immigrant population is vulnerable to food and housing insecurity and limited access to social services and medical care, on top of navigating the increasingly convoluted immigration system. Migrant women and children are especially at risk for systemic, poverty-related adversities. Periods of pregnancy and postpartum are particularly financially straining due to employment disruptions and additional expenses. Migrant mothers experience adverse health outcomes due to chronic stress, unstable living situations, integration barriers, and an unfavorable occupational environment during pregnancy. In addition to the postpartum needs of a new mother and her baby, these challenges may be barriers to maintaining breastfeeding. The unanticipated COVID-19 pandemic exasperated many existing systemic inequities and brought additional hardship. This study aims to investigate breastfeeding rates among immigrant mothers compared to U.S.-born mothers and other social disparities that affect health. While this study did not find a statistical difference between breastfeeding adherence and immigrant status during the COVID-19 pandemic, other risk factors relating to maternal-child health were identified. Immigrant families were more likely to experience job or income loss and a higher frequency of food insecurity compared to families with U.S.-born parents. The risks of being impoverished greatly reduce the incidence of breastfeeding, which can offer tremendous health benefits both to mother and baby. Most immigrants migrating to the U.S. are ethnic minorities who face additional societal disparities in culture, employment, economic stability, safety, and healthcare. The burden of social determinants of health that impact this population is not unique to adults. The moment a child is born into an immigrant family, particularly if they are also an ethnic minority, they inherit risk factors that can impact their entire lifespan. Ultimately, the risks associated with pregnancy and infant feeding are issues of social justice and health equity.
ContributorsFahmy, Gabriella (Author) / Whisner, Corrie (Thesis advisor) / Schuster, Roseanne (Thesis advisor) / Mayol-Kreiser, Sandra (Committee member) / Arizona State University (Publisher)
Created2023