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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
Postwar suburban sprawl resulted in environmental consequences that engendered backlash from those concerned about the quality life in the places they lived, played, and worked. Few cities grew as rapidly as Phoenix and therefore the city offers an important case study to evaluate the success and limits of environmentalism in shaping urban growth in the postwar period.
Using three episodes looking at sanitation and public health, open space preservation, and urban transportation, I argue three factors played a critical role in determining the extent to which environmental values were incorporated into Phoenix's urban growth policy. First, the degree to which environmental values influenced urban policy depends on the degree to which they fit into the Southwestern suburban lifestyle. A desire for low-density development and quality of life amenities like outdoor recreation resulted in decisions to extend municipal sewers further into the desert, the creation of a mountain preserve system, and freeways as the primary mode of travel in the city. Second, federal policy and the availability of funds guided policies pursued by Phoenix officials to deal with the unintended environmental impacts of growth. For example, federal dollars provided one-third of the funds for the construction of a centralized sewage treatment plant, half the funds to save Camelback Mountain and ninety percent of the construction costs for the West Papago-Inner Loop. Lastly, policy alternatives needed broad and diverse public support, as the public played a critical role, through bond approvals and votes, as well as grassroots campaigning, in integrating environmental values into urban growth policy. Public advocacy campaigns played an important role in setting the policy agenda and framing the policy issues that shaped policy alternatives and the public's receptivity to those choices.
Urban policy decisions are part of a dynamic and ongoing process, where previous decisions result in new challenges that provide an opportunity for debate, and the incorporation of new social values into the decision-making process. While twenty-first century challenges require responses that reflect contemporary macroeconomic factors and social values, the postwar period demonstrates the need for inclusive, collaborative, and anticipatory decision-making.
Using three episodes looking at sanitation and public health, open space preservation, and urban transportation, I argue three factors played a critical role in determining the extent to which environmental values were incorporated into Phoenix's urban growth policy. First, the degree to which environmental values influenced urban policy depends on the degree to which they fit into the Southwestern suburban lifestyle. A desire for low-density development and quality of life amenities like outdoor recreation resulted in decisions to extend municipal sewers further into the desert, the creation of a mountain preserve system, and freeways as the primary mode of travel in the city. Second, federal policy and the availability of funds guided policies pursued by Phoenix officials to deal with the unintended environmental impacts of growth. For example, federal dollars provided one-third of the funds for the construction of a centralized sewage treatment plant, half the funds to save Camelback Mountain and ninety percent of the construction costs for the West Papago-Inner Loop. Lastly, policy alternatives needed broad and diverse public support, as the public played a critical role, through bond approvals and votes, as well as grassroots campaigning, in integrating environmental values into urban growth policy. Public advocacy campaigns played an important role in setting the policy agenda and framing the policy issues that shaped policy alternatives and the public's receptivity to those choices.
Urban policy decisions are part of a dynamic and ongoing process, where previous decisions result in new challenges that provide an opportunity for debate, and the incorporation of new social values into the decision-making process. While twenty-first century challenges require responses that reflect contemporary macroeconomic factors and social values, the postwar period demonstrates the need for inclusive, collaborative, and anticipatory decision-making.
ContributorsDi Taranto, Nicholas (Author) / Hirt, Paul (Thesis advisor) / Vandermeer, Philip (Committee member) / Smith, Karen (Committee member) / Arizona State University (Publisher)
Created2015
Description
Targeted growth is necessary for sustainable urbanization. There is a pattern in China of rapid development due to inflated projections. This creates "ghost towns" and underutilized urban services that don't support the population.
In the case of Taiyuan, this industrial third-tier city of 4.2 million people. A majority of the newer residential services and high-end commercial areas are on the older, eastern side of the city. Since 2007, major urban investments have been made in developing the corridor that leads to the airport, including building a massive hospital, a new sports stadium, and "University City". The intention of the city officials is to encourage a new image of Taiyuan- one that is a tourist destination, one that has a high standard of living for residents. However, the consequences of these major developments might be immense, because of the required shift of community, residents and capital that would be required to sustain these new areas. Much of the new development lacks the reliable and frequent public transit of the more established downtown areas.
Do these investments in medical complexes, sports stadiums and massive shopping centers create new jobs that impact the income disparity, or do these new areas take years to fill, creating vacuums of investment that remove funding from areas with established communities? Can Taiyuan move successfully to a post-industrial economy with these government interventions, or is it too much too soon?
By examining demographic data from 2000, 2007, 2009, 2011, and 2013, research on sustainability assessments in Chinese cities (Lu Jia), and translated government publications detailing the urbanization efforts in Taiyuan, I will assess the results of the urbanization changes instituted by the new mayor, Geng Yanbo. My thesis will evaluate the success and failures of these policies and the implications for Taiyuan.
In the case of Taiyuan, this industrial third-tier city of 4.2 million people. A majority of the newer residential services and high-end commercial areas are on the older, eastern side of the city. Since 2007, major urban investments have been made in developing the corridor that leads to the airport, including building a massive hospital, a new sports stadium, and "University City". The intention of the city officials is to encourage a new image of Taiyuan- one that is a tourist destination, one that has a high standard of living for residents. However, the consequences of these major developments might be immense, because of the required shift of community, residents and capital that would be required to sustain these new areas. Much of the new development lacks the reliable and frequent public transit of the more established downtown areas.
Do these investments in medical complexes, sports stadiums and massive shopping centers create new jobs that impact the income disparity, or do these new areas take years to fill, creating vacuums of investment that remove funding from areas with established communities? Can Taiyuan move successfully to a post-industrial economy with these government interventions, or is it too much too soon?
By examining demographic data from 2000, 2007, 2009, 2011, and 2013, research on sustainability assessments in Chinese cities (Lu Jia), and translated government publications detailing the urbanization efforts in Taiyuan, I will assess the results of the urbanization changes instituted by the new mayor, Geng Yanbo. My thesis will evaluate the success and failures of these policies and the implications for Taiyuan.
ContributorsDolins, Sarah-Laura (Author) / Webster, Douglas (Thesis advisor) / Golub, Aaron (Committee member) / Cai, Jianming (Committee member) / Arizona State University (Publisher)
Created2014
Description
Worldwide, riverine floodplains are among the most endangered landscapes. In response to anthropogenic impacts, riverine restoration projects are considerably increasing. However, there is a paucity of information on how riparian rehabilitation activities impact non-avian wildlife communities. I evaluated herpetofauna abundance, species richness, diversity (i.e., Shannon and Simpson indices), species-specific responses, and riparian microhabitat characteristics along three reaches (i.e., wildland, urban rehabilitated, and urban disturbed) of the Salt River, Arizona. The surrounding uplands of the two urbanized reaches were dominated by the built environment (i.e., Phoenix metropolitan area). I predicted that greater diversity of microhabitat and lower urbanization would promote herpetofauna abundance, richness, and diversity. In 2010, at each reach, I performed herpetofauna visual surveys five times along eight transects (n=24) spanning the riparian zone. I quantified twenty one microhabitat characteristics such as ground substrate, vegetative cover, woody debris, tree stem density, and plant species richness along each transect. Herpetofauna species richness was the greatest along the wildland reach, and the lowest along the urban disturbed reach. The wildland reach had the greatest diversity indices, and diversity indices of the two urban reaches were similar. Abundance of herpetofauna was approximately six times lower along the urban disturbed reach compared to the two other reaches, which had similar abundances. Principal Component Analysis (PCA) reduced microhabitat variables to five factors, and significant differences among reaches were detected. Vegetation structure complexity, vegetation species richness, as well as densities of Prosopis (mesquite), Salix (willow), Populus (cottonwood), and animal burrows had a positive correlation with at least one of the three herpetofauna community parameter quantified (i.e., herpetofauna abundance, species richness, and diversity indices), and had a positive correlation with at least one herpetofauna species. Overall, rehabilitation activities positively influenced herpetofauna abundance and species richness, whereas urbanization negatively influenced herpetofauna diversity indices. Based on herpetofauna/microhabitat correlations established, I developed recommendations regarding microhabitat features that should be created in order to promote herpetofauna when rehabilitating degraded riparian systems. Recommendations are to plant vegetation of different growth habit, provide woody debris, plant Populus, Salix, and Prosopis of various ages and sizes, and to promote small mammal abundance.
ContributorsBanville, Mélanie Josianne (Author) / Bateman, Heather L (Thesis advisor) / Brady, Ward (Committee member) / Stromberg, Juliet (Committee member) / Arizona State University (Publisher)
Created2011
Description
Urban sustainability is a critical component of sustainable human societies. Urban riparian parks are used here as a case study seeking to understand the social-ecological relationships between the subjective evaluation of ecosystem services and the vision and management of one kind of green infrastructure. This study explored attitudes towards ecosystem services, asking whether 1) the tripartite model is an effective framing to measure attitudes towards ecosystem services; 2) what the attitudes towards ecosystem services are and whether they differ between two types of park space; and 3) what the relationship is between management and the attitudinal assessment of ecosystem services by park users. A questionnaire was administered to 104 urban riparian park users in Phoenix, AZ evaluating their attitudes towards refugia, aesthetics, microclimate and stormwater regulation, and recreational and educational opportunities. The operationalization of the tripartite model was validated and found reliable, but may not be the whole story in determining attitudes towards ecosystem services. All components of attitude were positive, but attitudes were stronger in a habitat rehabilitation area with densely planted native species and low flows, than in a more classic park with mowed lawns and scattered vegetation, a mix of native and non-native species, and open water. Park users were more positive towards refugia, stormwater regulation, recreation, and educational opportunities in the habitat rehabilitation area. On the other hand, microclimate regulation and aesthetic qualities were valued similarly between the two parks. Most attitudes supported management goals, however park users valued stormwater regulation less than managers. Qualitative answers suggest that the quality of human interactions differ between the parks and park users consider both elements of society and the physical environment in their subjective evaluations. These findings reveal that park users highly value ecosystem services and that park design and management mediates social-ecological relationships, which should at least underlie the context of economic discussions of service value. This study supports the provision of ecosystem services through green infrastructure and suggests that an integration of park designs throughout urban areas could provide both necessary services as well as expand the platform for social-ecological interactions.
ContributorsWilson, Lea Ione (Author) / Childers, Daniel L. (Thesis advisor) / Larson, Kelli L. (Committee member) / Stromberg, Juliet (Committee member) / Arizona State University (Publisher)
Created2012
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
Although many studies have identified environmental factors as primary drivers of bird richness and abundance, there is still uncertainty about the extent to which climate, topography and vegetation influence richness and abundance patterns seen in local extents of the northern Sonoran Desert. I investigated how bird richness and abundance differed between years and seasons and which environmental variables most influenced the patterns of richness and abundance in the Greater Phoenix Metropolitan Area.
I compiled a geodatabase of climate, bioclimatic (interactions between precipitation and temperature), vegetation, soil, and topographical variables that are known to influence both richness and abundance and used 15 years of bird point count survey data from urban and non-urban sites established by Central Arizona–Phoenix Long-Term Ecological Research project to test that relationship. I built generalized linear models (GLM) to elucidate the influence of each environmental variable on richness and abundance values taken from 47 sites. I used principal component analysis (PCA) to reduce 43 environmental variables to 9 synthetic factors influenced by measures of vegetation, climate, topography, and energy. I also used the PCA to identify uncorrelated raw variables and modeled bird richness and abundance with these uncorrelated environmental variables (EV) with GLM.
I found that bird richness and abundance were significantly different between seasons, but that richness and winter abundance were not significantly different across years. Bird richness was most influenced by soil characteristics and vegetation while abundance was most influenced by vegetation and climate. Models using EV as independent variables consistently outperformed those models using synthetically produced components from PCA. The results suggest that richness and abundance are both driven by climate and aspects of vegetation that may also be influenced by climate such as total annual precipitation and average temperature of the warmest quarter. Annual oscillations of bird richness and abundance throughout the urban Phoenix area seem to be strongly associated with climate and vegetation.
I compiled a geodatabase of climate, bioclimatic (interactions between precipitation and temperature), vegetation, soil, and topographical variables that are known to influence both richness and abundance and used 15 years of bird point count survey data from urban and non-urban sites established by Central Arizona–Phoenix Long-Term Ecological Research project to test that relationship. I built generalized linear models (GLM) to elucidate the influence of each environmental variable on richness and abundance values taken from 47 sites. I used principal component analysis (PCA) to reduce 43 environmental variables to 9 synthetic factors influenced by measures of vegetation, climate, topography, and energy. I also used the PCA to identify uncorrelated raw variables and modeled bird richness and abundance with these uncorrelated environmental variables (EV) with GLM.
I found that bird richness and abundance were significantly different between seasons, but that richness and winter abundance were not significantly different across years. Bird richness was most influenced by soil characteristics and vegetation while abundance was most influenced by vegetation and climate. Models using EV as independent variables consistently outperformed those models using synthetically produced components from PCA. The results suggest that richness and abundance are both driven by climate and aspects of vegetation that may also be influenced by climate such as total annual precipitation and average temperature of the warmest quarter. Annual oscillations of bird richness and abundance throughout the urban Phoenix area seem to be strongly associated with climate and vegetation.
ContributorsBoehme, Cameron (Author) / Albuquerque, Fabio Suzart (Thesis advisor) / Bateman, Heather L (Committee member) / Saul, Steven E (Committee member) / Arizona State University (Publisher)
Created2019
Description
Background: Adequate consumption of fruit and vegetables has been shown to prevent chronic diseases, such as cardiovascular disease, high blood pressure, and type two diabetes. The majority of Americans still consume inadequate daily servings of fruit and vegetables, which include women. Inadequate consumption of fruit and vegetables can be contributed to multiple barriers that hinder consumption in both urban and non-urban areas. The Special Supplemental Nutrition Program for Women, Infant, and Children (WIC) has been shown to positively influence fruit and vegetable consumption by providing healthy foods, such as fruit and vegetables. This study aims to compare the fruit and vegetable consumption of WIC and non-WIC participants between urban and non-urban Rural-Urban Commuting Area (RUCA) codes. Methods: This study was a cross-sectional, secondary analysis of a single time point from the Snuggle Bug/Acurrucadito Study, which had a sample size of (n=53) participants. The participants were separated into two groups, WIC participants, and non-WIC participants, and then further divided based on their respected RUCA code for comparison purposes. The assessment of fruit and vegetable consumption assessment derived from the participant’s 3-day food record. Results: The average consumption of fruit and vegetable consumption among participants was 3.8±2.5 servings There was an inverse relationship between WIC participation and fruit and vegetable consumption among all categories (fruit no juice -0.79, vegetables -0.32, vegetables no potato -0.32, fruit no juice and vegetables -1.1, and fruit no juice and vegetables no potato -1.1). However, none of the results were considered statistically significant. In addition, our study was unable to identify an association between fruit and vegetable consumption and locale due to the small sample size. Conclusions: There was no link observed between fruit and vegetable consumption and WIC participation. Further research of high quality is needed to confirm the relationship between fruit and vegetable consumption of WIC and non-WIC participants in urban and non-urban populations.
ContributorsOrtiz, Steven Michael (Author) / Bruening, Meg (Thesis advisor) / Whisner, Corrie (Committee member) / Shepard, Christina (Committee member) / Arizona State University (Publisher)
Created2022