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- Genre: Masters Thesis
- Creators: Arizona State University
- Creators: Chakraborty, Bijeta
- Creators: Peterson, Cory
- 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
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
Zoos are a unique collection-based institution with deep roots in the social structure of modern society. From their beginnings as elite menageries to display power or wealth, they have evolved into public institutions committed to providing exemplary animal care, and recreational and educational opportunities for visitors. More recently, zoos have developed a series of significant conservation programs and partnerships around the globe, efforts that have proved vital to saving endangered species such as the Arabian oryx (Oryx leucoryx) and California condor (Gymnogyps californianus), among other species.
Intrinsic to the development of modern zoo designs are the interwoven concerns of naturalism and animal welfare. Animal welfare, in particular, has become the paramount responsibility for professionally run zoological institutions as they seek to become centers of conservation and education without compromising animal wellbeing. Animal welfare and naturalism (understood as a design feature in zoo exhibits) are typically harmonious objectives, but these goals have occasionally clashed in implementation. While animal welfare and naturalism are defined in various (and not always consistent) ways in the literature, in-depth interviews of leading professionals and scholars in the zoo community and multi-dimensional case studies of exemplary, accredited institutions (including the Phoenix Zoo, the San Diego Zoo, Woodland Park Zoo and Arizona-Sonora Desert Museum) provide unique insight into the shifting meaning of these terms and how welfare and naturalism have and continue to shape the
development of modern zoo enclosures. This study concludes by suggesting a possible
future trajectory for innovative and alternative zoo designs that incorporate both animal welfare and naturalism without sacrificing either goal.
Intrinsic to the development of modern zoo designs are the interwoven concerns of naturalism and animal welfare. Animal welfare, in particular, has become the paramount responsibility for professionally run zoological institutions as they seek to become centers of conservation and education without compromising animal wellbeing. Animal welfare and naturalism (understood as a design feature in zoo exhibits) are typically harmonious objectives, but these goals have occasionally clashed in implementation. While animal welfare and naturalism are defined in various (and not always consistent) ways in the literature, in-depth interviews of leading professionals and scholars in the zoo community and multi-dimensional case studies of exemplary, accredited institutions (including the Phoenix Zoo, the San Diego Zoo, Woodland Park Zoo and Arizona-Sonora Desert Museum) provide unique insight into the shifting meaning of these terms and how welfare and naturalism have and continue to shape the
development of modern zoo enclosures. This study concludes by suggesting a possible
future trajectory for innovative and alternative zoo designs that incorporate both animal welfare and naturalism without sacrificing either goal.
ContributorsBoyle, Kristen E (Author) / Minteer, Ben A (Thesis advisor) / Ellison, Karin (Committee member) / Cunningham, Stan (Committee member) / Arizona State University (Publisher)
Created2017
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
Two recent tourism trends are the growing wildlife tourism subsector of nature-based tourism and the increased use of social media in both marketing and for tourists to share their experiences. Until recently, the connection between social media and wildlife tourism remained understudied, and tourist behavior on Instagram after visiting wildlife tourism attractions (WTAs) remains unstudied. Some researchers call for more tourism research using social media data created by tourists, called user-generated content (UGC), to understand them. This netnographic study examines tourists who visited a range of WTAs by analyzing their post-visit photos and captions on Instagram through the lens of involvement theory to evaluate the strength of their connection to wildlife and conservation. Previous research has indicated that wildlife tourism can have extraordinary benefits to conservation and communities, but some WTAs, some of which are photo-prop tourism attractions where animals are handed over to tourists for selfies, have negative impacts on individual animals and species due to illegal sourcing, improper care, human interaction, and habituation. Findings from this study suggest that WTAs with good or excellent conservation and welfare practices lead to more highly involved tourists, ultimately benefitting community investment, animal welfare, and conservation efforts via the flow of tourist dollars and spread of information on social media, the tourist changing their behavior, or all of the aforementioned. Conversely, WTAs with negative conservation and welfare practices do not foster the same level of tourist involvement as their counterparts, often leading to more anthropocentric Instagram posts that do not spread conservation messaging or imply environmental behavior change. The implications from this research suggest that wildlife tourism attraction management practices should focus on conservation and welfare for the improvement of conservation efforts via policies, enforcement, larger governing bodies or organizations advocating or taking action, and future research on the potential impact COVID-19 had on the wildlife tourism industry.
ContributorsKredens, Claire Victoria (Author) / Vogt, Christine (Thesis advisor) / Budruk, Megha (Thesis advisor) / van Riper, Carena (Committee member) / Arizona State University (Publisher)
Created2021
Description
This project analyzes the efforts of Seoul Grand Park Zoo (the largest and most important zoo on the Korean peninsula) to develop and achieve the highest standards in conservation, education, animal welfare, and research over the last three decades. Founded primarily as an entertainment venue in 1984, the zoo has struggled to become a scientific center that adequately provides for the animals under its care and promotes the advancement and dissemination of knowledge. Drawing on interviews from zoo officials, academics, conservationists, and animal-rights activists, I explore the animal welfare management and conservation priorities of a prominent Asian institution. Although the zoo has made significant improvements in animal welfare, it remains constrained by limited resources and government indifference. These constraints have also restricted the zoo’s ambition to become a major center for conservation; it currently concentrates on a handful of projects with broad popular appeal. Based on my interviews, greater collaboration, better communication with other researchers, and more systematic sharing of data would be especially beneficial for expanding the zoo’s conservation agenda. As research and conservation become a more prominent part of the zoo’s portfolio, potential conflicts may arise with zoo’s current emphasis on the welfare of the individual animals under its care.
ContributorsClay, Anne Safiya (Author) / Minteer, Ben (Thesis advisor) / Collins, James (Committee member) / Broglio, Ronald (Committee member) / Arizona State University (Publisher)
Created2015