Matching Items (7)
Filtering by
- 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
Using an integrated perspective of the Grief Work Hypothesis and Posttraumatic Growth Theory, this study was designed to contribute to the sparse existing cross-cultural research by examining and comparing individuals' emotional adjustment and posttraumatic growth in the United States (US) and China. Another main goal was to unfold the predictive effects of different dimensions of locus of control, coping strategies and social support on the outcomes and further, to explore cultural differences in the underlying mechanisms. Web-based survey was disseminated and administered in the US and China. One thousand and seventy-eight participants completed the survey and met the criteria such that they were eighteen years old or older and experienced death of a loved one six to thirty-six months ago. As expected, US participants experienced higher levels of subjective well-being, lower levels of complicated grief and posttraumatic growth than Chinese participants. They also reported higher external yet lower internal locus of control, less frequent use of active and avoidance coping, and less informational support and negative social interactions than their Chinese counterparts. No difference in emotional support was evidenced between the two cultures. After controlling for demographic, loss-related information and the impact of post-bereavement life events, hierarchical regression analyses revealed that culture, external locus of control, avoidance coping and negative social interactions were unique predictors of complicated grief. Furthermore, the relation between external locus of control and complicated grief was weaker for US participants compared to that for Chinese participants. Culture, external and internal locus of control, active and avoidance coping, and negative social interactions significantly predicted individuals' subjective well-being after the loss. Additionally, culture, internal locus of control, active and avoidance coping, informational support, and negative social interactions were identified as unique predictors of posttraumatic growth. Specifically, an interaction effect of avoidance coping x culture emerged such that avoidance coping significantly predicted posttraumatic growth only for US participants. This study extracted the underlying mechanisms of predicting individuals' emotional adjustment and personal growth following bereavement. The influence of culture was also highlighted. Application of existing theories to the Chinese culture and clinical implications of the current study were discussed.
ContributorsTao, Chun, M.S (Author) / Miller, Paul A. (Thesis advisor) / Vargas, Perla A (Committee member) / Hall, Deborah L. (Committee member) / Arizona State University (Publisher)
Created2014
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
The bereaved and those who have experienced trauma have received support through music therapy. However, there has been no research on the effectiveness of music therapy as a therapeutic intervention for those who have experienced the loss of a loved one by suicide. While every loss presents its own challenges, those who experience a suicide loss may need extra support to process the traumatic nature of the death. This study aims to explore the current research on grief and trauma to determine what information can be applied to the care of those who have experienced a suicide loss. The present study is a group case study of survivors of suicide who have experienced a loss within the last 3 years. Participants received weekly music therapy sessions for four weeks. All participants completed the Inventory of Traumatic Grief, prior to and at the conclusion of the music therapy sessions, and the pre and post test scores were compared. Additionally qualitative data was collected throughout the sessions, indicating any common themes that emerged throughout the sessions and the participants’ reactions to the interventions, as well as in a short questionnaire following the four sessions.
ContributorsEdmonds, Alexis Elaine (Author) / Rio, Robin (Thesis advisor) / Crowe, Barbara (Committee member) / Humphreys, Jere (Committee member) / Arizona State University (Publisher)
Created2016
Description
The American Psychiatric Association's Diagnostic and Statistical Manual, the official guidebook to psychiatric diagnosis in America, currently exempts the recently bereaved from being diagnosed with depression unless their experiences are marked by feelings of extreme worthlessness, significant functional impairment, psychotic symptoms, psychomotor retardation, or suicidal ideation. Ordinary symptoms of depression, such as sleeplessness or loss of appetite, are considered healthy, functional emotional responses to the loss of a loved one. The bereavement exemption is slated for removal in the upcoming fifth edition of the Diagnostic and Statistical Manual, functionally redefining the emotional distress of bereavement as a psychiatric disorder. This study employs genealogical analysis to expose the multiplicity of forces that shape modern psychiatry and the ways that the redefinition of depression functions strategically in the social negotiation of truth and power. Under the guise of etiological and prescriptive neutrality, the redefinition of depression promotes a deeply biological model of psychiatric disorder, a medicalized understanding of human emotion, and a pharmacological approach to the treatment of emotional distress. Through genealogical analysis, this project seeks to enable informed, meaningful ethico-political responses to these developments.
ContributorsMeeth, John (Author) / Edson, Belle (Thesis advisor) / Palazzolo, Kellie (Thesis advisor) / Quinlivan, Raena (Committee member) / Arizona State University (Publisher)
Created2011
Description
Relations between two aspects of the parent-child relationship, parent warmth and modeling of emotion expression, and youth internalizing and externalizing problems and maladaptive grief were examined in a longitudinal sample of parentally bereaved youth. Youth expressive suppression was tested as a mediator of these relations and youth age was examined as a moderator. Parentally bereaved youth (N=244) aged 8 to 16 and their parents were assessed at three timepoints. Across 14 months, parent modeling of maladaptive emotion expression was significantly associated with increased parent report of both internalizing and externalizing problems, and youth report of parental warmth was significantly associated with decreased youth report of externalizing problems. There was no support for youth expressive suppression mediating these relations and the pattern of relations did not differ significantly by youth age. Implications for intervention programs targeting parents and youth are discussed.
ContributorsUhlman, Rana Natasha Goble (Author) / Wolchik, Sharlene A (Thesis advisor) / Anderson, Samantha F (Committee member) / Meier, Madeline H (Committee member) / Arizona State University (Publisher)
Created2021