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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
An asset-based approach to vulnerability, as presented in Voices of the Poor: Can Anyone Hear Us? and World Development Report 2000/2001: Attacking Poverty, provides a possible theoretical framework for understanding vulnerability to human trafficking. Case studies, field studies and narratives of human trafficking provide evidence that the assets of victims of trafficking play a significant role in human trafficking. This appears to be true both with regard to how traffickers exploit victim assets and with regard to how successful human trafficking prevention efforts are implemented. By exploring and further establishing this connection, I hope to provide evidence that a model of human trafficking acquisition incorporating elements of victim assets and the assets of communities deserves field-testing. Such field-testing will hopefully confirm the deep connection between assets and human trafficking activity and establish the necessary connections anti-trafficking activists will need to create a predictive version of the model with regard to individual vulnerability to human trafficking. Lastly, I argue that, provided the connection between human trafficking vulnerability and victim asset levels holds, an asset-based approach provides a rhetorical framework to resist policies that compromise asset levels of particularly vulnerable populations.
ContributorsFees, Kyle Elliot (Author) / Stancliff, Michael (Thesis advisor) / Behl, Natasha (Committee member) / Murphy Erfani, Julie (Committee member) / Arizona State University (Publisher)
Created2015
Description
Africa is misrepresented and mis-imaged in the western media. Because of this, notions and beliefs about atrocities that take place on the continent lack context, leaving people to think that Africa is a place of misery, darkness and despair; a monolithic land where evil resides. The image of Africa as the "heart of darkness" was conjured following the Joseph Conrad novel and the idea of Africa as the "Dark Continent" still pervades Western thought. This is an inadequate understanding of Africa, and lacks the context to comprehend why many of the atrocities in Africa occur. I will explore two atrocities in Africa, the 1994 Rwanda Genocide and child slavery on Lake Volta in Ghana. I believe that both these examples reflect how the label of evil is insufficient to describe the circumstances around each atrocity. In order to understand such events we must understand the part that colonialism and poverty play in the disruption of pan-African culture. The "evils" of these two phenomenon, are in many cases the result of the Western world's past involvement in Africa and are remnants and extensions of the disruption caused.
ContributorsBork, Paul (Author) / Simmons, William P (Thesis advisor) / Erfani, Julie (Committee member) / Anokye, Duku A (Committee member) / Arizona State University (Publisher)
Created2011
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
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
This thesis looks at the 1842 Supreme Court ruling of Prigg v. Pennsylvania, the events leading up to this case, and the subsequent legislative fallout from the decision. The Supreme Court rendered this ruling in an effort to clear up confusion regarding the conflict between state and federal law with regard to fugitive slave recovery. Instead, the ambiguities contained within the ruling further complicated the issue of fugitive slave recovery. This complication commenced when certain state legislatures exploited an inadvertent loophole contained in the ruling. Thus, instead of mollifying sectional tension by generating a clear and concise process of fugitive slave recovery, the Supreme Court exacerbated sectional tension. Through an analysis of newspapers, journals, laws and other contemporary sources, this thesis demonstrates that Prigg v. Pennsylvania and the subsequent legislative reactions garnered much attention. Through a review of secondary literature covering this period, a lack of demonstrable coverage of this court case emerges, which shows that scant coverage has been paid to this important episode in antebellum America. Additionally, the lack of attention paid to this court case ignores a critical episode of rising sectional tension during the 1840s.
ContributorsCoughlin, John (Author) / Schermerhorn, Calvin (Thesis advisor) / O'Donnell, Catherine (Thesis advisor) / Whitaker, Matthew (Committee member) / Arizona State University (Publisher)
Created2010
Description
Magic, divination, and obeah appear in some form in almost all of Jamaica’s near-continuous revolts from the time the British took the island in 1655 to the decades following the abolition of slavery in 1834. Although discussions of African diasporic spiritual systems were very much alive in the early modern centuries, the forms that emerged in early colonial Jamaica have received little scholarly treatment. This study is an attempt to inject culture into the story of African resistance to slavery and colonialism in Jamaica by reconceptualizing three major rebellions as cultural rather than military histories and by highlighting the role of magic and divination in the genesis of these freedom struggles. The First Maroon War, Tacky’s Revolt, and the 1823 Boxing Day Conspiracy illuminate a clear system of supernatural understanding that came to include a definite link to political resistance and rebellion. These understandings were recognized by enslaved or formerly enslaved Africans as well as the British in Jamaica and abroad. Some work must be done to delineate what European settlers were responding to as the idea of obeah—and how it was related to European ideas about witchcraft and illicit magic—from the ideas held among African peoples. This is especially significant following Tacky’s Revolt, when the first anti-obeah laws in the Caribbean made obeah an explicitly political action. Europeans were clearly wrapped up in the politics of obeah to a degree that did not concern Africans. However, Africans also used obeah as a crucial form of political resistance. Thus, these three cases allow both British and African ideas about obeah to be traced over a century to reinject a cultural history of African-derived spirituality into an otherwise political narrative.
ContributorsBussey, Max (Author) / Barnes, Andrew (Thesis advisor) / Alexander, Leslie (Committee member) / Usman, Aribidesi (Committee member) / Arizona State University (Publisher)
Created2021
Description
The Enlightenment era in the West is traditionally referred to as the “Age of Reason” and the cradle of liberalism, which has been perhaps the dominant political ideology in the West since the eighteenth century. Philosophers such as John Locke and John Stuart Mill are credited with developing liberalism and their theories continue to be studied in terms of liberty, the social contract theory, and empiricism. While liberalism is heralded as a societal advancement in the field of philosophy, some thinkers’ actions were not consistent with their written principles. This essay investigates how John Locke was involved in the creation and perpetuation of slavery in North America, but later crafted and endorsed more liberal ideologies in his writings. This dual nature of Locke has a prominent place in academia and scholarly research. Many try to address the contradictory nature of Locke by looking to the location he had in mind when crafting his philosophies, specifically those concerning the state of nature, slavery, property rights, and empiricism. While some concepts, like slavery, seem to find him contemplating only English citizens, Locke’s reference to Indigenous Americans in his philosophical works supports the argument that the philosopher’s ideology was not necessarily written exclusively for English application. By analyzing Locke’s philosophy and his economic involvement in the Carolina colony through a postcolonial theoretical framework, this essay aims to understand the Eurocentrism of Locke and how his philosophy was applied differently across borders. Using postcolonial theory, this thesis concludes Locke was a colonialist and Western author who portrayed non-European cultures, practices, and experiences for European consumption and application.
ContributorsCundiff, Caroline Rose (Author) / O'Donnell, Catherine (Thesis advisor) / Wright, Johnson (Committee member) / Barth, Jonathan (Committee member) / Arizona State University (Publisher)
Created2021
Description
Slavery is a significant factor to consider when studying Mexica society and its economy, including societal roles and gendered labor. Many scholars who explore slavery within this culture and state look at the topic from specific angles and focus on the post-conquest and colonial periods. Pre-Columbian slavery is mentioned only briefly in the histories of the Mexica despite it being a key facet of their way of life. Questions of gender and class in relation to slavery are often missing from examinations of the topic. This project will, therefore, examine the process of enslavement, slave status and labor, and the written and visual evidence of enslaved individuals within Mexica society during the fifteenth and early sixteenth century. By specifically examining slavery within the city-states of Tenochtitlan, Texcoco, and the Mexica region, this thesis will argue that enslaved women played a much more significant role than enslaved men, and that slaves constituted a social class in pre-Columbian Mexica society.
ContributorsRodriguez, Jennifer N. (Author) / Baker, Hannah (Thesis advisor) / Smith, Michael E. (Committee member) / Avina, Alexander (Committee member) / Arizona State University (Publisher)
Created2021
Description
This thesis explores the historical development of the criminal justice system across four eras. The system has been utilized to control and exploit Black people for economic gain. After the American Revolution, and the rise of the penitentiary, many argued that imprisoning individuals for labor was reminiscent of the institution of slavery itself, which highlights the criminal justice system's potential to target and control Black people. During the pre-Civil War era, white slave owners established slave patrols to prevent enslaved Black people from leaving their plantation, and to control the movement of Blacks more broadly. These early slave patrols provided an institutional foundation for the later development of the modern police force. During Reconstruction, the Ku Klux Klan adopted the methods of slave patrols to maintain white supremacy and control over Blacks with lynching becoming everyday occurrences. During the Jim Crow era, Black communities faced widespread discrimination, and the system was used to enforce racial segregation and maintain white dominance. The Civil Rights Movement marked a turning point against Jim Crow. However, the post-Civil Rights era was met with the War on Drugs and the rise of mass incarceration, which disproportionately affected Black communities. To gain equality, Black people have consistently been met with backlash, often supported by the criminal justice system. While reforming the system is necessary, it is unlikely to eliminate racism and white supremacy. A more comprehensive approach is needed to address the root causes of these issues and ensure equality and justice for all.Keywords: white supremacy, racism, color-blind, police violence, slave patrol, slavery, convict leasing system
ContributorsMoore, Antonio Lamont (Author) / Keahey, Jennifer (Thesis advisor) / Kim, Linda (Committee member) / Hepner, Tricia R (Committee member) / Arizona State University (Publisher)
Created2023