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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
Diet quality is closely intertwined with overall health status and deserves close examination. Healthcare providers are stretched thin in the current stressed system and would benefit from a validated tool for rapid assessment of diet quality. The Rapid Eating and Activity Assessment for Participants Short Version (REAP-S) represents one such

Diet quality is closely intertwined with overall health status and deserves close examination. Healthcare providers are stretched thin in the current stressed system and would benefit from a validated tool for rapid assessment of diet quality. The Rapid Eating and Activity Assessment for Participants Short Version (REAP-S) represents one such option. The objective of the current study was to evaluate the effectiveness of the REAP-S and Healthy Eating Index 2010 (HEI-2010) for scoring the diet quality of omnivorous, vegetarian and vegan diets. Eighty-one healthy male and female subjects with an average age of 30.9 years completed the REAP-S as well as a 24-hour dietary recall. REAP-S and HEI-2010 scores were calculated for each subject and evaluated against each other using Spearman correlations and Chi Square. Further analysis was completed to compare diet quality scores of the HEI-2010 and REAP-S by tertiles to examine how closely these two tools score diet quality. The mean HEI-2010 score was 47.4/100 and the mean REAP-S score was 33.5/39. The correlation coefficient comparing the REAP-S to the HEI-2010 was 0.309 (p=0.005), and the REAP-S exhibited a precision of 44.4% to the HEI-2010 for diet quality. The REAP-S significantly correlated with the HEI-2010 for whole fruit (r=0.247, p=0.026), greens and beans (r=0.276, p=0.013), seafood proteins (r=0.298, p=0.007), and fatty acids (r=0.400, p<0.001). When evaluated by diet type, the REAP-S proved to have increased precision in plant-based diets, 50% for vegetarian and 52% for vegan, over omnivorous diets (32%). The REAP-S is a desirable tool to rapidly assess diet quality in the community setting as it is significantly correlated to the HEI-2010 and requires less time, labor and money to score and assess than the HEI-2010. More studies are needed to evaluate the precision and validity of REAP-S in a broader, more diverse population.
ContributorsBliss, Courtney (Author) / Johnston, Carol (Thesis advisor) / Tasevska, Natasha (Committee member) / Levinson, Simin (Committee member) / Arizona State University (Publisher)
Created2015
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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
Objective: Parents play a critical role in their child's diets, yet there is lack of research in

the US comparing parental perception of their child’s diet with quantitatively assessed diet quality. We examined the association between parent perception of their child’s overall diet and the child’s diet quality, as measured by

Objective: Parents play a critical role in their child's diets, yet there is lack of research in

the US comparing parental perception of their child’s diet with quantitatively assessed diet quality. We examined the association between parent perception of their child’s overall diet and the child’s diet quality, as measured by frequency of consumption of key food categories.

Methods: Secondary analysis was conducted using data from two independent cross- sectional panels of surveys with parents of a 3-18 year old child. Data collection took place in 2009-2010 and 2014, the random sample was drawn from low-income cities. Well-established survey questions assessed parental perception of their child’s diet and frequency of consumption of fruits, vegetables, sugar-sweetened beverages (SSB), fast food and unhealthy snacks. Diet quality scores were calculated for each child, with higher scores reflective of healthier diets (max score= 40). Ordered logistic regressions examined associations between parental perception and consumption of food categories. Multinomial logistic regressions examined associations between levels of concordance in parent perception and diet scores by demographic sub-groups.

Results: Almost half of children were non-Hispanic black (46%) and 40% were Hispanic. Overall 52% of parents strongly agreed, 33% somewhat agreed, 10% somewhat disagreed, and 4% strongly disagreed that their child eats a healthy diet. The mean diet quality score for the sample was 20.58 ± 6.7. Children from our sample with the unhealthiest diet had a mean frequency of fruit intake = 0.8 times/day and SSBs = 2.2 times/day. Children with the healthiest diet had a mean consumption of fruit=1.7/day and

SSBs= 0.4/day. Parental perception of their child’s diet was significantly higher when their child consumed more fruit (p<0.001) and vegetables (p<0.001) and lower when their child consumed more fast food (p<0.001), SSBs (p=0.01) and unhealthy snacks (p=0.02). Over half of parents overestimated the healthfulness of their child’s diet (61%). Parent, child and household demographics did not moderate this association.

Conclusions: Although parental perceptions that their child eats healthy are associated when their child eats more healthy foods and less unhealthy foods, parents’ perceptions still do not align with their child’s diet.
ContributorsEliason, Jessica (Author) / Ohri-Vachaspati, Punam (Thesis advisor) / DeWeese, Robin (Committee member) / Vega-Lopez, Sonia (Committee member) / Arizona State University (Publisher)
Created2019
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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
Food insecurity and childhood obesity are both major public health concerns in the United States of America. Research has not found a definite relationship between childhood obesity and food insecurity to date, with conflicting results being found due to differences in sample sizes and protocol for measuring key variables. Preschoolers

Food insecurity and childhood obesity are both major public health concerns in the United States of America. Research has not found a definite relationship between childhood obesity and food insecurity to date, with conflicting results being found due to differences in sample sizes and protocol for measuring key variables. Preschoolers (children aged 2-5 years) are a population of particular interest as there tends to be improved health behaviors and greater adaptability to change at this period of growth and development. This study aims to evaluate if there is a relationship between food insecurity and childhood obesity with diet quality as a mediator among preschoolers in the Phoenix area. A secondary data analysis from participants (n=154) from the SAGE (Sustainability via Active Garden Education) research project was used to evaluate food insecurity status, diet quality components (kcal, saturated fat, added sugars, and servings of juice, fruits, and vegetables), and anthropometrics (waist circumference and BMI percentile). No significant associations between food insecurity status, diet quality components, and anthropometric data were found. There was an increased rate of food insecurity and childhood overweight/obesity in this sample compared to state and national averages. Further research of high quality is necessary to determine whether a relationship exists between childhood obesity and food insecurity exists and in what context. Additionally, practice and policy will need to be implemented to decrease rates of food insecurity and childhood obesity among Phoenix preschoolers.
ContributorsGutierrez, Marisa (Author) / Bruening, Meg (Thesis advisor) / Whisner, Corrie (Committee member) / Lee, Rebecca E (Committee member) / Arizona State University (Publisher)
Created2020
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Description
The health of the planet and its people face considerable challenges; the climate faces threats of irreversible damage while chronic disease and obesity rates continue to rise. Both issues can be attributed in part to humanity’s poor treatment and attitude towards food. Humans throw away much of the nutritious food

The health of the planet and its people face considerable challenges; the climate faces threats of irreversible damage while chronic disease and obesity rates continue to rise. Both issues can be attributed in part to humanity’s poor treatment and attitude towards food. Humans throw away much of the nutritious food available, resulting in unhealthful diets and considerable amounts of food waste, leading to harmful greenhouse gas emissions. The current solutions for improving the separate matters of planetary and human health include tradeoffs between the two, despite their interrelatedness. Paradoxically, current research shows that increased fruit and vegetable intake is associated with increased food waste. Current literature has not emphasized a focus on interventions aimed to improve diet quality and food waste simultaneously.Recent research shows that mindfulness can have impacts on human health, such as in relation to chronic pain, mental wellbeing, and self-awareness. Mindful eating specifically has demonstrated improvements in disordered eating behaviors and relationship with food. Yet, no research has been conducted to explore mindful eating in relation to healthful and efficient relationships with food. Therefore, the present study explores mindfulness as a mechanism to improve diet quality and reduce food waste. The protocol presented in the study, titled Mindful Waste Watchers (MWW), was a 4-week novel virtual program incorporating nutrition education, household food waste reduction education, and mindfulness/mindful eating exercises into each lesson. Entry, exit, and 4-week follow-up surveys, each identical, were distributed to participants to assess diet quality, household food waste habits, mindful eating, mindfulness, and food appreciation, primarily by utilization of validated scales. The two primary outcomes evaluated in the present article were diet quality and household food waste behaviors. It was found that the intervention did not produce significant effects for either parameter, suggesting that the protocol was not feasible. However, a significant positive effect was found for food appreciation, a factor that may show promise in future research. While no significant effects were found for the primary outcomes, the findings of this study can be considered in future research targeted towards discovering effective interventions to improve diet quality and reduce household food waste.
ContributorsMoeller, Margaret Elizabeth (Author) / Wharton, Christopher (Thesis advisor) / DeWeese, Robin (Committee member) / Kniskern, Megan (Committee member) / Arizona State University (Publisher)
Created2024