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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 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
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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

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
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Description
The increasingly recurrent extraordinary flood events in the metropolitan area of Monterrey, Mexico have led to significant stakeholder interest in understanding the hydrologic response of the Santa Catarina watershed to extreme events. This study analyzes a flood mitigation strategy proposed by stakeholders through a participatory workshop and are assessed using

The increasingly recurrent extraordinary flood events in the metropolitan area of Monterrey, Mexico have led to significant stakeholder interest in understanding the hydrologic response of the Santa Catarina watershed to extreme events. This study analyzes a flood mitigation strategy proposed by stakeholders through a participatory workshop and are assessed using two hydrological models: The Hydrological Modeling System (HEC-HMS) and the Triangulated Irregular Network (TIN)-based Real-time Integrated Basin Simulator (tRIBS).

The stakeholder-derived flood mitigation strategy consists of placing new hydraulic infrastructure in addition to the current flood controls in the basin. This is done by simulating three scenarios: (1) evaluate the impact of the current structure, (2) implementing a large dam similar to the Rompepicos dam and (3) the inclusion of three small detention dams. These mitigation strategies are assessed in the context of a major flood event caused by the landfall of Hurricane Alex in July 2010 through a consistent application of the two modeling tools. To do so, spatial information on topography, soil, land cover and meteorological forcing were assembled, quality-controlled and input into each model. Calibration was performed for each model based on streamflow observations and maximum observed reservoir levels from the National Water Commission in Mexico.

Simulation analyses focuses on the differential capability of the two models in capturing the spatial variability in rainfall, topographic conditions, soil hydraulic properties and its effect on the flood response in the presence of the different flood mitigation structures. The implementation of new hydraulic infrastructure is shown to have a positive impact on mitigating the flood peak with a more favorable reduction in the peak at the outlet from the larger dam (16.5% in tRIBS and 23% in HEC-HMS) than the collective effect from the small structures (12% in tRIBS and 10% in HEC-HMS). Furthermore, flood peak mitigation depends strongly on the number and locations of the new dam sites in relation to the spatial distribution of rainfall and flood generation. Comparison of the two modeling approaches complements the analysis of available observations for the flood event and provides a framework within which to derive a multi-model approach for stakeholder-driven solutions.
ContributorsCázares Rodríguez, Jorge E (Author) / Vivoni, Enrique (Thesis advisor) / Wang, Zhihua (Committee member) / Mays, Larry W. (Committee member) / Arizona State University (Publisher)
Created2016
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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

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%.
ContributorsBai, Jing (Author) / Bakkaloglu, Bertan (Thesis advisor) / Arizona State University (Publisher)
Created2015
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Description
As global warming increases, sea levels continue to rise and world populations continue to grow; the Earth is nearing its tipping point. Human action, such as deforestation, mining, and industrialization, has had a profound effect on environments destroying wetlands, and the natural infrastructure needed to absorb rainfall and maintain vegetation.

As global warming increases, sea levels continue to rise and world populations continue to grow; the Earth is nearing its tipping point. Human action, such as deforestation, mining, and industrialization, has had a profound effect on environments destroying wetlands, and the natural infrastructure needed to absorb rainfall and maintain vegetation. Due to extreme changes in climate and temperature, people all over the world are increasingly affected by natural disaster. Unable to sustain their livelihoods, these individuals, become environmental refugees and are forced to flee their land and homes to obtain security in another region or country. Currently, there are approximately 25 million environmental refugees worldwide. Despite the soaring numbers, environmental refugees are not legally recognized or protected by the United Nations, and thus do not receive the same rights or assistance as a traditional refugee. This thesis analyzes definitions and interpretations of Environmental Refugees (ERs) through the frameworks of environmental justice and human rights law and identifies possible avenues of discourse available. Furthermore, this thesis examines the current United Nations definition of refugee and identifies the pros and cons to expanding the current definition to include those affected by natural disaster. Through the case study of New Orleans, Louisiana (NOLA), it is demonstrated how ERs are not only an issue facing developing countries, but also exist within developed nations. Hurricane Katrina in NOLA is an ethnographic example that demonstrates how during a time of natural disaster, a variety of past and present structural factors may contribute to the violation of human rights. This thesis then concludes with a discussion of possible categorizations of ERs and the concrete benefits of each category, and how lessons from NOLA can and should be applied to other ER situations in order to avoid human rights violations.
ContributorsDawes, Chelsey E (Author) / Casper, Monica (Thesis advisor) / Klimek, Barbara (Committee member) / Simmons, William (Committee member) / Arizona State University (Publisher)
Created2010
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Description
Small island developing states (SIDS) are on the very frontlines of climate change (UNDP, 2017). Increasing attention on the unique social, economic, and environmental vulnerabilities SIDS face has led to the discussion of the overall resilience of this population. Specifically, post-disaster studies of resilience carried out on SIDS have pointed

Small island developing states (SIDS) are on the very frontlines of climate change (UNDP, 2017). Increasing attention on the unique social, economic, and environmental vulnerabilities SIDS face has led to the discussion of the overall resilience of this population. Specifically, post-disaster studies of resilience carried out on SIDS have pointed to social resilience and education as two primary indicators of the overall resilience of these vulnerable communities (Aldrich, 2012; Muttarak & Lutz, 2014); yet social aspects of resilience related to SIDS have been underexplored, in comparison to ecological and economic themes (Berkes & Ross, 2013). Thus, the purpose of this qualitative study was to explore the personal and professional lived-natural disaster experiences of SIDS residents who are educators in order to understand their role in building social resilience within their community. In-depth interviews were conducted with educators employed at public and private schools in the United States Virgin Islands. The findings indicate that residents who are educators conceptualized resilience according to the following themes and sub-themes: (1) Social Process which involves Social Recovery and Community Alliances to ‘bounce back’ to an undefined level of normalcy and (2) Embodied Identity which was described in terms of Community Personifications of resilience as a trait in general citizens and educators. Participants identified internal and external resources as influential in how residents responded to natural disasters, by so doing, significantly contributing to positive post-disaster outcomes; these resources are referred to in the literature as protective factors (Rutter, 1985). The findings also demonstrate that educators had both a personal and professional responsibility to help their community contend with disasters, and this outcome is best explicated through the concept of protective factors. The research findings are significant because they: (1) contribute to the limited body of literature on social resilience in small island developing states, (2) demonstrate the importance of subjective perspectives in the development of disaster preparedness and management strategies for climate-vulnerable island populations, and (3) indicate a need for future research to use terminology which acknowledges the many ways in which disaster-prone communities have historically demonstrated and/or embodied resilience.
ContributorsEdmeade, Jendayi (Author) / Buzinde, Christine (Thesis advisor) / Nyaupane, Gyan (Committee member) / Gonzales, Angela (Committee member) / Manuel-Navarrete, David (Committee member) / Arizona State University (Publisher)
Created2020