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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
ABSTRACT In an attempt to advocate body-conscious design and healing work environments, this research study of holistic health in the workplace explores cognitive, social and physical well-being in four small US offices that are between 1000 and 4000 square feet and employ three to twelve employees. Holistic health, as pursued in this research, includes social health, emotional health and physical health. These three factors of holistic health have been identified and investigated in this study: biophilia: peoples' love and affiliation with other species and the natural environment; ergonomics: the relationship between the human body, movement, the immediate environment and productivity; and exercise: exertion of the body to obtain physical fitness. This research study proposes that employees and employers of these four participating workplaces desire mobility and resources in the workplace that support holistic health practices involving biophilia, ergonomics, and exercise. Literature review of holistic health and the holistic health factors of this research topic support the idea that interaction with other species can be healing, ergonomic body-conscious furniture and equipment increase productivity, limit body aches, pains and health costs; and exercise stimulates the mind and body, increasing productivity. This study has been conducted primarily with qualitative and flexible research approaches using observation, survey, interview and pedometer readings as methods for data collection. Two small corporate franchise financial institutions and two small private healthcare providers from both Arizona and Georgia participated in this study. Each office volunteered one employer and two employee participants. Of the holistic health factors considered in these four case studies, this study found that a majority of participants equally valued emotional health, social health and physical health. A majority of participants declared a preference for workplace environments with serene natural environments with outdoor spaces and interaction with other species, work environments with body-conscious furniture, equipment and workstations, as well as exercise space and equipment. As these particular workplace environments affirmed value for elements of the factors biophilia, ergonomics and exercise, all three factors are considered valueable within the workplaces of these case studies. Furthermore, factors that were said to contribute to personal productivity in participating workplaces were found as well as sacrifices that participants stated they would be willing to make in order to implement their preferred work environment(s). In addition, this study recorded and calculated average miles walked by participants in each workplace as well as existing incentives and descriptions of ideal work environments. Implications of this research study involve interior design, industrial design and fashion design that can accommodate the desires of the four participating workplaces. Major design implications involve accommodating these particular workplaces to provide personnel with opportunities for holistic health in working environments. More specific implications of office related design involve providing access to natural environments, body-conscious equipment and spaces, as well as opportunities for exercise and social interaction. These elements of the factors biophilia, ergonomics and exercise were found to be said to contribute to cognitive, social and physical health.
ContributorsMcEwan, April (Author) / White, Philip (Thesis advisor) / Shraiky, James (Committee member) / Barry, Rebecca (Committee member) / Arizona State University (Publisher)
Created2011
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
Excessive gestational weight gain (GWG) during pregnancy is a major public health concern. Studies have reported more than 70% of pregnant women gain excessive weight which may pose increased maternal and fetal risks. Little is known about the relationships of GWG to behavioral factors (i.e., physical activity, sleep, social support) and maternal mental health (i.e., stress, anxiety, depression) during pregnancy. This descriptive, cross-sectional study explored the relationships of GWG to behavioral factors and maternal mental health during pregnancy. Secondarily, this study described the preferences, uses of, and interests in alternative approaches as well as the mental health differences between users and non-users of alternative approaches during pregnancy. A national survey was administered to women ≥8 weeks pregnant, ≥18 years old, and residing in the United States (N=968). Bivariate correlations were used to determine relationships between GWG and variables of interest. Independent t-tests were used to observe mental health differences between users and non-users of alternative approaches. Data were analyzed throughout pregnancy and by trimester. Throughout pregnancy, significant relationships were found in GWG to stressful events (r=-.112, p<.01), depression (r=.066, p<.05), mindfulness (r=-.067, p<.05), and sleep (r=.089, p<.01). When GWG was assessed by trimester, stressful events were significant in the second (r=-.216, p<.01) and third trimesters (r=-.085, p<.05). Depression remained positively related to GWG in the first (r=.409, p<.01) and second trimesters (r=.162, p<.01). A positive relationship emerged between GWG and anxiety in the first trimester (r=.340, p<.01) and physical activity became significant in the second (r=-.136; p<.05) and third trimesters (r=-.100; p<.05). Mindfulness was the only variable significantly related to GWG throughout all time points. Mean anxiety (d=.236; p=.001) and depression (d=.265; p<.001) scores were significantly lower in users compared to non-users of alternative approaches throughout pregnancy and when assessed by trimester anxiety (d=.424; p=.001) and depression (d=.526; p<.001) were significant in the second trimester. This study provides a framework for future analyses in GWG and maternal mental health. The information presented here may inform future interventions to test the effectiveness of alternative approaches to simultaneously manage maternal mental health and GWG due to the integrative nature of alternative approaches.
ContributorsMatthews, Jennifer L. (Author) / Huberty, Jennifer L (Thesis advisor) / Leiferman, Jenn (Committee member) / Larkey, Linda (Committee member) / McClain, Darya (Committee member) / Arizona State University (Publisher)
Created2015
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
Healthy lifestyle behaviors including quality nutrition have been shown to successfully prevent chronic disease or minimize symptoms. However, many physicians lack the knowledge and skills to provide adequate nutrition counseling and education for their patients. A major component of this problem is that medical schools are not required to teach nutrition education. The purpose of this feasibility study was to compare the changes in the perceived importance of nutrition in the medical field in medical students before and after participating in a week-long interactive nutrition course in order to determine if a week-long course can positively influence students’ perceptions of nutrition. Ultimately by changing these perceptions, medical students may be able to better help patients prevent chronic disease. The participants were first year medical students at the Mayo Clinic School of Medicine (Scottsdale, AZ) who chose to participate in this medical school “Selective”. The study included a five-day curriculum of case-studies, lectures from specialized health professionals, and a cooking class led by a chef who trained in France. An anonymous pre- and post-study questionnaire with five-point Likert scale questions was used to measure changes in attitudes. The data suggest that students’ perceptions regarding the importance and relevance of nutrition in the medical shifted slightly more positive after attending this Selective, although these shifts in attitude were not statistically significant. Limitations of this study include a small sample size and selection bias, which may have decreased the potential of having significant results. Both of these factors also make the results of this study less generalizable to all medical students. This study supports the need for a larger experimental study of a similar design to verify that an interactive, evidence-based nutrition class and culinary experience increases medical students’ positive perceptions of nutrition in the medical field.
ContributorsBaum, Makenna (Author) / Johnston, Carol (Thesis advisor) / Levinson, Simin (Committee member) / Sears, Dorothy (Committee member) / Arizona State University (Publisher)
Created2020