Matching Items (8)
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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
Efforts to privilege STEM (Science, Technology, Engineering, and Mathematics) disciplines, initiatives, and industries in American discourse are arguably the foremost expressions of scientific authority in contemporary educational policy. Citing a diverse body of STEM literature, I discuss the histories and rationales that sustain the promotion of STEM. In doing so, I appropriate two concepts -Michel Foucault's Regime of Truth and Hayden White's Emplotment- for the purpose of analyzing the complex interests embodied by STEM discourse. I argue that the Sputnik Narrative is the prevailing story in STEM advocacy discourse. I claim that STEM advocates typically emplot this history as a Romance. Furthermore, I classify two major bases of appeal (rationales) that appear within this literature to justify STEM projects and proposals, "competition" and "equity." Throughout my writing, I cite discursive strategies for challenging and reimagining STEM history. My goal in indicating these sites of narrative possibilities is broaden the discursive field to new, perhaps liberating possibilities.
ContributorsGeldis, Christopher (Author) / Harris, Lauren M (Thesis advisor) / Lyon, Edward (Committee member) / Greenes, Carole (Committee member) / Arizona State University (Publisher)
Created2014
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
Explaining Fukushima to children: a cross-cultural study of bodily functions as metaphor in Japanese
Description
This research proposes that a cross-cultural disconnect exists between Japanese and American English in the realm of bodily functions used as metaphor. Perhaps nowhere is this notion illustrated more clearly than by a cartoon that was inspired by recent tragic events in Japan. In the afternoon of Friday, March 11, 2011, the northeast coast of Japan was struck by a massive earthquake and tsunami that caused immeasurable loss of life and property and catastrophic damage to the nuclear power plant in Fukushima Prefecture. In the immediate wake of these events, Japanese artist Hachiya Kazuhiko, determined to make the situation comprehensible to children, created a cartoon in which he anthropomorphized the damaged Fukushima Daiichi reactor and likened the dangers associated with it to illness and bodily functions. This cartoon garnered considerable notoriety, both in Japan and abroad. The reactions of English speakers appeared to differ from those of Japanese speakers, suggesting the existence of a possible cross-cultural disconnect. This research into the reactions to the cartoon and other relevant literature (both in English and Japanese), viewed against federal regulations regarding the broadcast of "obscenity" in the United States, commentary on American society, and how the use of similar language in American cartoons is seen, clearly indicates that negative attitudes toward the use of bodily functions as metaphor exist in the United States, while the same usage is seen differently in Japan.
ContributorsHacker, Michael (Author) / Adams, Karen (Thesis advisor) / Gelderen, Elly van (Thesis advisor) / Prior, Matthew (Committee member) / Arizona State University (Publisher)
Created2012
Description
As urban populations rapidly increase in an era of climate change and multiple social and environmental uncertainties, scientists and governments are cultivating knowledge and solutions for the sustainable growth and maintenance of cities. Although substantial literature focuses on urban water resource management related to both human and ecological sustainability, few studies assess the unique role of waterway restorations to bridge anthropocentric and ecological concerns in urban environments. To address this gap, my study addressed if well-established sustainability principles are evoked during the nascent discourse of recently proposed urban waterway developments along over fifty miles of Arizona’s Salt River. In this study, a deductive content analysis is used to illuminate the emergence of sustainability principles, the framing of the redevelopment, and to illuminate macro-environmental discourses. Three sustainability principles dominated the discourse: civility and democratic governance; livelihood sufficiency and opportunity; and social-ecological system integrity. These three principles connected to three macro-discourses: economic rationalism; democratic pragmatism; and ecological modernity. These results hold implications for policy and theory and inform urban development processes for improvements to sustainability. As continued densification, in-fill and rapid urbanization continues in the 21st century, more cities are looking to reconstruct urban riverways. Therefore, the emergent sustainability discourse regarding potential revitalizations along Arizona’s Salt River is a manifestation of how waterways are perceived, valued, and essential to urban environments for anthropocentric and ecological needs.
ContributorsHorvath, Veronica (Author) / White, Dave D (Thesis advisor) / Mirumachi, Naho (Committee member) / Childers, Dan (Committee member) / Chester, Mikhail (Committee member) / Arizona State University (Publisher)
Created2019
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 project explores the nature of power dynamics in the dialogue of video gamers within designated online forums of discussion. Previous scholarly work has noted the lack of diverse representation and tolerance in the gaming community, despite statistics revealing that the video game community is not as homogeneous as it is often represented. Specifically, the prominent literature analyzing gaming culture focuses on poor representations of gender within video games and the gaming community itself, including sexualized and objectified depictions of women as well as prejudice toward women as members of the gaming community. More recent entries to the field of research draws attention to the experiences of other marginalized communities in gaming. This thesis, then, begs the question – what power dynamics emerge in the dialogue of people who consider themselves to be gamers? How are concepts of social identity expressed or constructed in communication, and what reinforces and legitimizes these relationships? This project will review a foundation of literature structuring the framework of this project, propose methodology for data collection and analysis, and explore themes discovered within the data analysis, which support or negate existing research and give insight to the proposed research questions.
ContributorsFitzgerald, Karina Marie (Author) / Nadesan, Majia (Thesis advisor) / Gray, Kishonna L. (Committee member) / Walker, Michael (Committee member) / Arizona State University (Publisher)
Created2020
Description
Academic recommendation letters are an essential component of institutional gatekeeping practices, yet few scholars have explored their use in the context of nationally competitive scholarships and fellowships. Using a mixed-methods framework, this study uses Hyland’s (2005a) taxonomy to analyze the frequency, form, and function of hedges and boosters across fifty-one recommendation letters submitted for a nationally competitive undergraduate STEM scholarship. Of the eighty-nine terms that occurred in the letters, there were thirty-seven boosting terms and fifty-one hedging terms (41% boosters and 59% hedges). Despite the higher rate of hedges, the majority of these terms were not used to express doubt. Results show that letter writers for prestigious programs use a combination of hedges and boosters alongside their status and expertise within the academy to sponsor promising undergraduate researchers. This study expands our understanding of recommendation letters outside of graduate-level selection processes and answers Hyland’s (2005b) call for more mixed method approaches and use of discourse analysis across academic genres.
ContributorsSalgado, Catherine (Author) / Prior, Matthew (Thesis advisor) / Van Gelderen, Elly (Committee member) / James, Mark A. (Committee member) / Arizona State University (Publisher)
Created2021