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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
Sometimes difficult life events challenge our existing resources in such a way that routinized responses are inadequate to handle the challenge. Some individuals will persist in habitual, automatic behavior, regardless of environmental cues that indicate a mismatch between coping strategy and the demands of the stressor. Other individuals will marshal adaptive resources to construct new courses of action and reconceptualize the problem, associated goals and/or values. A mixed methods approach was used to describe and operationalize cognitive shift, a relatively unexplored construct in existing literature. The study was conducted using secondary data from a parent multi-year cross-sectional study of resilience with eight hundred mid-aged adults from the Phoenix metro area. Semi-structured telephone interviews were analyzed using a purposive sample (n=136) chosen by type of life event. Participants' beliefs, assumptions, and experiences were examined to understand how they shaped adaptation to adversity. An adaptive mechanism, "cognitive shift," was theorized as the transition from automatic coping to effortful cognitive processes aimed at novel resolution of issues. Aims included understanding when and how cognitive shift emerges and manifests. Cognitive shift was scored as a binary variable and triangulated through correlational and logistic regression analyses. Interaction effects revealed that positive personality attributes influence cognitive shift most when people suffered early adversity. This finding indicates that a certain complexity, self-awareness and flexibility of mind may lead to a greater capacity to find meaning in adversity. This work bridges an acknowledged gap in literature and provides new insights into resilience.
ContributorsRivers, Crystal T (Author) / Zautra, Alex (Thesis advisor) / Davis, Mary (Committee member) / Kurpius, Sharon (Committee member) / Arizona State University (Publisher)
Created2014
Description
Daily life stressors and negative emotional experiences predict poor physical and psychological health. The stress response of the hypothalamic-pituitary-adrenal axis is a primary biological system through which stressful experiences impact health and well-being across development. Individuals differ in their capacity for self-regulation and utilize various coping strategies in response to stress. Everyday experiences and emotions are highly variable during adolescence, a time during which self-regulatory abilities may become particularly important for adapting to shifting social contexts. Many adolescents in the U.S. enter college after high school, a context characterized by new opportunities and challenges for self-regulation. Guided by biopsychosocial and daily process approaches, the current study explored everyday stress and negative affect (NA), cortisol reactivity, and self-regulation assessed at the momentary, daily, and trait level among a racially/ethnically and socioeconomically diverse sample of first-year college students (N = 71; Mage = 18.85; 23% male; 52% non-Hispanic White) who completed a modified ecological momentary assessment. It was expected that within-person increases in momentary stress level or NA would be associated with cortisol reactivity assessed in college students' naturalistic settings. It was predicted that these within-person associations would differ based on engagement coping responses assessed via momentary diary reports, by the range of engagement coping responses assessed via diary reports at the end of the day, and by higher trait levels of self-regulation assessed via standard self-report questionnaire. Within-person increases in momentary stress level were significantly associated with momentary elevations in cortisol only during moments characterized by greater than usual engagement coping efforts (i.e., within-person
increases). At a different level of analysis, within-person increases in momentary stress level were significantly associated with increases in cortisol only for those with low trait levels of coping efficacy and engagement coping. On average, within-person increases in momentary NA were significantly associated with cortisol reactivity. Tests of moderation revealed this momentary association was only significant for those with low trait levels of support-seeking coping.
increases). At a different level of analysis, within-person increases in momentary stress level were significantly associated with increases in cortisol only for those with low trait levels of coping efficacy and engagement coping. On average, within-person increases in momentary NA were significantly associated with cortisol reactivity. Tests of moderation revealed this momentary association was only significant for those with low trait levels of support-seeking coping.
ContributorsSladek, Michael Ronald (Author) / Doane, Leah D (Thesis advisor) / Eisenberg, Nancy (Committee member) / Luecken, Linda J. (Committee member) / Arizona State University (Publisher)
Created2015
Description
Playing tennis professionally is a stressful profession. However, it has the potential to be even more stressful for players who must move from their home country in order to train. If not dealt with, these stresses have the potential of causing many negative outcomes, including increasing levels of distress, in these professional tennis players. It is known that resources play a role in reducing or buffering levels of stress and distress among individuals, but there are competing theories as to how this occurs. Using Ensel and Lin's models of stress processes, this is an exploratory study that identifies the stresses and distresses professional Taiwanese tennis players face and the resources they use to cope. Participants included in this study are professional Taiwanese tennis players (2 males and 2 females) who continuously attend national and international tennis competitions and have both domestic and world ranks. Results from the semi-structured interviews revealed that challenges, frustration, resources, and toughness were four general themes to describe stresses and distresses professional Taiwanese tennis players face and the resources they use to cope. Future research for professional tennis players is also discussed.
ContributorsHung, Wei-Hsia (Author) / Rodriguez, Ariel (Thesis advisor) / Chuang, Shu-Tzu (Committee member) / Budruk, Megha (Committee member) / Hager, Mark A. (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
While the literature on caregivers of loved ones with Alzheimer's Disease and Related Disorders (ADRD) has continued to grow, the relationship of ethnicity and acculturation factors with regards to the coping strategies used by caregivers has not been extensively explored. The current study included participants from the Palo Alto site of the Resources for Enhancing Alzheimer's Caregiver Health (REACH) project. The study examined differences in coping strategies between 140 non-Hispanic White, 45 less acculturated Latina, and 61 more acculturated Latina caregivers. Univariate and Multivariate Analysis of Variance, as well as post hoc analyses, were conducted to determine the differences among the three groups. Results indicated less acculturated Latina caregivers employ more avoidant coping strategies compared to non-Hispanic White caregivers. However, no differences were found among the other groups in their use of avoidance coping. Moreover, there were no differences found in the use of social support seeking, count your blessings, problem focused, and blaming others coping among the three groups. These findings have important implications for the design of culturally relevant psychoeducational and therapeutic interventions aimed towards meeting the individual needs of these three populations. In addition, the findings expand on the understanding of maladaptive coping strategies that may be potentially exacerbating caregiver distress among Latina caregivers.
ContributorsFelix, Vitae (Author) / Arciniega, Guillermo M (Thesis advisor) / Robinson-Kurpius, Sharon (Committee member) / Coon, David W. (Committee member) / Arizona State University (Publisher)
Created2011
Description
Psychogenic non-epileptic seizures (PNES), is a conversion disorder thought to be linked to unresolved emotional distress. While some studies suggest that PNES patients do not attribute their somatic symptoms to severe psychological experiences (Stone, Binzer, & Sharpe, 2004; LaFrance & Barry, 2005), it is unclear what PNES patients do think causes their seizures, and the psychological consequences of those attributions. The aim of the present study was to investigate PNES patients' attributions for their seizures, and to determine how these attributions relate to stress and emotion regulation. It was hypothesized that participants who attribute their seizures to something (i.e., have an explanation for their seizures) will have lower perceived stress and less difficulty with emotion regulation than those who are unsure of the cause of their seizures. Twenty-four PNES participants completed a questionnaire assessing seizure diagnosis, characteristics of seizure impact, perceived stress, psychological symptoms, emotion regulation, attributions for seizures, and coping resources. Contrary to the hypothesis, having an explanation for seizures, rather than being “unsure” of seizure cause, was related to greater perceived stress. While it would seem that attributing unpredictable seizure events to a cause would lower perceived stress and emotion regulation difficulty, this study indicates that an attribution to an unknown cause may be more beneficial for the individual.
ContributorsBarker, Mallory (Author) / Roberts, Nicole A. (Thesis advisor) / Miller, Paul A. (Committee member) / Burleson, Mary H (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
This study examined whether the New Beginnings Program (NBP), a preventive parenting intervention, led to changes in coping strategies and coping efficacy in emerging adults whose families had participated in the program 15 years earlier. Gender and baseline risk were examined as moderators of these relations. Participants (M = 25.6 years; 50% female) were from 240 families that had participated in an experimental trial (NBP [mother-only, mother-child] vs. literature control). Data from the pretest and 15-year follow-up were used. Multiple regression analyses revealed that pretest risk interacted with program participation in the mother-only condition of the NBP such that offspring entering the program with higher pretest risk reported significantly less avoidant coping 15 years later. There was a marginal effect of participation in the NBP on problem-focused coping; emerging adults who had participated in the NBP had marginally higher levels of problem-focused coping. There were no significant main effects nor interactive program by risk or program by gender effects on support coping or coping efficacy. Results are discussed in terms of their implications for implementation of preventive interventions and research on pathways of coping.
ContributorsRhodes, Charla Aubrey (Author) / Wolchik, Sharlene A (Thesis advisor) / Tein, Jenn-Yun (Committee member) / Leucken, Linda (Committee member) / Arizona State University (Publisher)
Created2019
Description
This study was designed to examine the associations between food skills, resilience, and coping during the Covid-19 pandemic. Between April and June of 2020, a sample of 154 students, faculty, and staff from Arizona State University were surveyed. Each respondent was administered a survey containing demographic questions, a food skill questionnaire, and the 14-item Resilience Scale (RS). Results indicate that food skill was correlated with resilience (p<0.001) at an r=0.364 and r2=0.1243 and that resilience was correlated with coping during the Covid-19 pandemic (p<0.001) at an r=0.455. Correlations were also run between resilience score and the separate domains of food skill score: all domains remained significantly associated with resilience score (p<0.001) with a r=0.340 and r2=0.1173 for ‘Food Selection and Planning,’ r=0.312 and r2=0.0958 for ‘Food Preparation,’ and r=0.294 and r2=0.0767 for ‘Food Safety.’ Data seems to be consistent with contemporary research suggesting positive associations between diet quality and physiological resilience and positive associations between resilience and coping during the Covid-19 pandemic.
ContributorsPhares, Savanna Julene (Author) / Johnston, Carol (Thesis advisor) / McCoy, Maureen (Committee member) / Irving, Andrea (Committee member) / Arizona State University (Publisher)
Created2020