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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
This study examines the relations among three aspects of temperament (shyness, impulsivity, and effortful control), resting respiratory sinus arrhythmia (RSA) recorded during a calming film and RSA suppression during three behavioral measures of effortful control, and adjustment (anxiety and externalizing behavior) in a sample of 101 preschool-age children. Principal components analysis was used to create composites for effortful control, shyness, impulsivity, anxiety, and externalizing behavior, and hierarchical regression analysis was used to test the study hypotheses. As expected, baseline RSA was negatively related to effortful control in shy children, but was unrelated to effortful control in children who were not shy. It was hypothesized that high baseline RSA would reduce the relation between shyness and anxiety, and between impulsivity and externalizing behavior; this hypothesis was supported for externalizing behavior, but not for anxiety. The interaction between impulsivity and RSA as a predictor of externalizing was statistically independent of effortful control, indicating that these are unique effects. Finally, it was hypothesized that RSA suppression would be positively related to effortful control for children low, but not high, in shyness. There was a marginal interaction between shyness and RSA suppression, with RSA suppression marginally negatively related to EC for children low in shyness, but unrelated to effortful control for children high in shyness; the direction of this association was opposite predictions. These findings indicate that RSA is more strongly related to effortful control for children high in shyness, and that it consequently may not be appropriate to use RSA as an index of EC for all children. This study also draws attention to the need to consider the context in which baseline RSA is measured because a true baseline may not be obtained for shy children if RSA is measured in an unfamiliar laboratory context. The finding that high RSA moderated (but did not eliminate) the relation between impulsivity and externalizing behavior is consistent with the conceptualization of RSA as a measure of self-regulation, but further research is needed to clarify the mechanism underlying this effect.
ContributorsSulik, Michael John (Author) / Eisenberg, Nancy (Thesis advisor) / Spinrad, Tracy L. (Committee member) / Lemery-Chalfant, Kathryn (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
Poor executive cognitive functioning (ECF) is associated with a variety of alcohol-related problems, however, it is not known whether poor ECF precedes the onset of heavy drinking. Establishing the temporal precedence of poor ECF may have implications for our understanding of the development of Alcohol Use Disorder (AUD). The present study tests associations between early-adolescent ECF and young-adult risky drinking and alcohol-related problems in a prospective study of youth followed to young adulthood. Participants completed three ECF tasks at ages 11-14 and reported on their risky drinking and alcohol-related problems at ages 18-24. A latent ECF factor was created to determine whether early-adolescent ECF was associated with drinking outcomes after controlling for relevant covariates (e.g., age, sex, family history of AUD). Early-adolescent ECF, as measured by a latent factor, was unrelated to young-adult alcohol misuse and alcohol-related problems. However, sensitivity analyses revealed that an individual ECF task tapping response inhibition predicted young-adult peak drinks in a day. Present findings suggest that ECF is not a robust predictor of risky drinking or alcohol-related problems, and that this relation may be specific to the ECF component of response inhibition.
ContributorsJones, Connor Brian (Author) / Meier, Madeline (Thesis advisor) / Chassin, Laurie (Committee member) / McClure, Samuel (Committee member) / Arizona State University (Publisher)
Created2017
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
Alexithymia is a personality trait characterized by a diminished ability to identify and describe feelings, as well as an inability to distinguish physical symptoms associated with emotional arousal. Alexithymia is elevated in both patients with epilepsy (a neurologically-based seizure disorder) and psychogenic nonepileptic seizures (PNES; a psychological condition mimicking epilepsy); however, different neuropsychological processes may underlie this deficit in the two groups. To expand on previous research considering factors contributing to alexithymia in these populations, we examined the extent to which scores on the Toronto Alexithymia Scale (TAS-20) were predicted by performance on measures of executive and language functioning. We studied 138 PNES and 150 epilepsy patients with video-EEG confirmed diagnoses. Neuropsychological tests were administered to assess executive functioning (interference scores of the Stroop Color-Word Test and Part B of the Trail Making Test) and language functioning (Animals, Controlled Oral Word Association Test, and Boston Naming Test). Hierarchical linear regressions revealed that the relationships between disparate neuropsychological domains and alexithymia were not moderated by diagnosis of PNES or epilepsy. Multiple regression analyses within each group demonstrated that phonemic verbal fluency and response inhibition were significant predictors of alexithymia in epilepsy. Thus, alexithymia may reflect impairments in language and aspects of executive functioning in both PNES and epilepsy.
ContributorsReynolds, Christopher Martin (Author) / Roberts, Nicole A. (Thesis advisor) / Burleson, Mary H (Committee member) / Nanez, Jose (Committee member) / Arizona State University (Publisher)
Created2017
Description
Individuals with autism spectrum disorder (ASD) are known to show impairments in various domains of executive function (EF) such as behavioral flexibility or inhibitory control. Research suggests that EF impairment in adults with ASD may relate to ASD core symptoms, restrictive behaviors and social communication deficits. Mindfulness-based stress reduction (MBSR) has shown promise for improving EF abilities in neurotypical adults, but research has not explored its efficacy or neural mechanisms in adults with ASD. This pilot study examines the effects of an 8-week MBSR intervention on self-report measures of EF and resting-state functional connectivity in a sample of adults with ASD. Fifty-four participants were assigned either to an MBSR group (n = 29) or a social support group (n = 25). Executive function was measured using the BRIEF-2 before and after the intervention for the twenty-seven participants in the second cohort. MBSR-specific improvements in EF were found for BRIEF measures of initiation, inhibition, and working-memory. Resting-state fMRI data was analyzed using independent component analysis (ICA), and group by time resting-state functional connectivity differences were observed between the cerebellar network and frontal regions including the right frontal pole (rFP), medial frontal cortex (MFC) and left and right superior frontal gyri (SFG). The MBSR group showed increases in functional connectivity between the cerebellum and EF regions which correlated with improvements in BRIEF-2 measures. These findings suggest that MBSR may improve EF domains in adults with ASD, and that increases in functional connectivity between the cerebellum and frontal regions while at rest may be a mechanism for such improvements.
ContributorsGuerithault, Nicolas (Author) / Braden, B. Blair (Thesis advisor) / Rogalsky, Corianne (Committee member) / Dixon, Maria (Committee member) / Arizona State University (Publisher)
Created2021
Description
The present study sought to understand traumatic brain injuries (TBI) impact on executive function (EF) in terms of anticipation amongst individuals with a background in soccer; along with other contributing factors of EF curtailments that inhibit athletes. Within this study 57 participants, with a background in soccer (high school, collegiate, and semi-professional), completed five EF tasks: working memory, cognitive flexibility, attentional control, and anticipation; pattern detection and athletic cues (temporal occlusion). The results of this study concluded that when TBI history, gender, and soccer athletic level are factors, athletes with a soccer level of collegiate and semi-professional had decrements related to pattern detection anticipation; meaning athletes at higher levels had lower average scores on the Brixton Spatial Anticipation Test (BSAT). Additionally, female athletes showed more anticipation decrements related to athletic cues, especially those that are reliant on the initiation of judgment. Overall undiagnosed TBIs and limited understanding on how to approach rehabilitation to mitigate EF decrements, continue to impede individual autonomy amongst athletes. Keywords: Traumatic brain injury, executive function, anticipation, soccer, temporal occlusion, Brixton Spatial Anticipation Test (BSAT), collegiate, semi-professional, pattern detection, rehabilitation
ContributorsEzenyilimba, Akuadasuo (Author) / Gray, Rob (Thesis advisor) / Chiou, Erin (Committee member) / Cooke, Nancy (Committee member) / Gutzwiller, Robert (Committee member) / Arizona State University (Publisher)
Created2021
Description
This study examines cognitive and motor function in typical older adults following acute exercise. Ten older adults (Mage = 65.1) completed a single session of assisted cycling (AC) (i.e., exercise accomplished through the use of a motor), voluntary cycling (VC) (self-selected cadence), and a no cycling (NC) control group. These sessions were randomized and separated by approximately one week. Both ACT and VC groups rode a stationary bicycle for 30-minutes each session. These sessions were separated by at least two days. Participants completed cognitive testing that assessed information processing and set shifting and motor testing including gross and fine motor performance at the beginning and at the end of each session. Consistent with our hypothesis concerning manual dexterity, the results showed that manual dexterity improved following the ACT session more than the VC or NC sessions. Improvements in set shifting were also found for the ACT session but not for the VC or NC sessions. The results are interpreted with respect to improvements in neurological function in older adults following acute cycling exercise. These improvements are balance, manual dexterity, and set shifting which have a positive effects on activities of daily living; such as, decrease risk of falls, improve movements like eating and handwriting, and increase ability to multitask.
ContributorsSemken, Keith (Author) / Ringenbach, Shannon (Thesis advisor) / Der Ananian, Cheryl (Committee member) / Buman, Matthew (Committee member) / Arizona State University (Publisher)
Created2015