Matching Items (6)
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
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
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
Vitamin D deficiency has been previously associated with a higher Alzheimer’s disease (AD) risk, a condition marked by dependent living and severe cognitive impairment. AD is histologically defined by the presence of brain amyloid beta (Aβ) plaques and neurofibrillary tangles. Ways to enhance Aβ clearance have been examined in order to sustain cognition and delay AD onset. In vitro and in vivo studies suggest that vitamin D might enhance brain Aβ transportation to the periphery by up-regulating P-glycoprotein production. The purpose of this study was to examine the effect of vitamin D supplementation on plasma Aβ in an older population.
This study was a parallel-arm, double-blinded, randomized control trial. Participants consumed either a vitamin D supplement or placebo once a week for eight weeks (n=23). Only vitamin D insufficient (serum total 25-OH, D < 30 ng/mL) people were included in the study, and all participants were considered to be cognitively normal (MMSE scores > 27). Serum total 25-OH, D and plasma Aβ1-40 measurements were recorded before and after the eight-week trial. The plasma Aβ1-40 change was compared between the vitamin D group and control group.
The vitamin D group experienced a 45% greater change in plasma Aβ1-40 than the control group. The effect size was 0.228 when controlling for baseline plasma Aβ1-40 (p=0.045), 0.197 when controlling for baseline plasma Aβ1-40 and baseline physical activity (p=0.085), and 0.179 when controlling for baseline plasma Aβ1-40, baseline physical activity, and age (p=0.116). In conclusion, vitamin D supplementation might increase brain Aβ clearance in humans, but physical activity and age also appear to modulate Aβ metabolism.
This study was a parallel-arm, double-blinded, randomized control trial. Participants consumed either a vitamin D supplement or placebo once a week for eight weeks (n=23). Only vitamin D insufficient (serum total 25-OH, D < 30 ng/mL) people were included in the study, and all participants were considered to be cognitively normal (MMSE scores > 27). Serum total 25-OH, D and plasma Aβ1-40 measurements were recorded before and after the eight-week trial. The plasma Aβ1-40 change was compared between the vitamin D group and control group.
The vitamin D group experienced a 45% greater change in plasma Aβ1-40 than the control group. The effect size was 0.228 when controlling for baseline plasma Aβ1-40 (p=0.045), 0.197 when controlling for baseline plasma Aβ1-40 and baseline physical activity (p=0.085), and 0.179 when controlling for baseline plasma Aβ1-40, baseline physical activity, and age (p=0.116). In conclusion, vitamin D supplementation might increase brain Aβ clearance in humans, but physical activity and age also appear to modulate Aβ metabolism.
ContributorsMiller, Brendan Joseph (Author) / Johnston, Carol (Thesis advisor) / Whisner, Corrie (Committee member) / Tasevska, Natasha (Committee member) / Arizona State University (Publisher)
Created2015
Description
ABSTRACT
Music therapy is a highly effective treatment when used in the care of persons with dementia (PWD) and singing in particular is found to be calming and pleasurable to PWD. Seniorsing.net is a music-based application for use in memory care that provides a fun and interactive sing along activity for PWD. Developed by a music therapist, the application is designed to engage the user in singing along with recorded song performances while lyrics are displayed on the device screen. Seniorsing.net is accessible on any mobile device and is intended to provide a positive musical experience for PWD, whether listening or singing along. This study was conducted to test the design aspects of the application for use with PWD and their caregivers. Eighteen dyads of participants/caregivers were recruited from the senior community. Participants were observed interacting with seniorsing.net by the music therapist to provide an understanding of the usability of seniorsing.net and to collect information on the responses of PWD to seniorsing.net. Caregivers were given the opportunity to evaluate seniorsing.net via survey. The parameters that were measured included visual clarity and appeal, audibility, clarity of directions and usability by PWD and their caregivers. Observations of participants showed positive interactions with the application. Over 64% of participants independently engaged in singing with the application and over 50% of participants were able to activate features of the application with minimal assistance. Caregiver feedback was also positive. Most caregivers strongly agreed or agreed to the effectiveness of the design and its ease of use with PWD. 100% of caregivers found the song performances to be appropriate and comfortable to follow and sing. Caregivers gave suggestions for improvement of seniorsing.net, such as including more song choices and having more written directions on some of the screens. In conclusion, seniorsing.net was found to be enjoyable and easy to use by PWD and their caregivers.
Keywords: Dementia, Music Therapy, Singing, Technology
Music therapy is a highly effective treatment when used in the care of persons with dementia (PWD) and singing in particular is found to be calming and pleasurable to PWD. Seniorsing.net is a music-based application for use in memory care that provides a fun and interactive sing along activity for PWD. Developed by a music therapist, the application is designed to engage the user in singing along with recorded song performances while lyrics are displayed on the device screen. Seniorsing.net is accessible on any mobile device and is intended to provide a positive musical experience for PWD, whether listening or singing along. This study was conducted to test the design aspects of the application for use with PWD and their caregivers. Eighteen dyads of participants/caregivers were recruited from the senior community. Participants were observed interacting with seniorsing.net by the music therapist to provide an understanding of the usability of seniorsing.net and to collect information on the responses of PWD to seniorsing.net. Caregivers were given the opportunity to evaluate seniorsing.net via survey. The parameters that were measured included visual clarity and appeal, audibility, clarity of directions and usability by PWD and their caregivers. Observations of participants showed positive interactions with the application. Over 64% of participants independently engaged in singing with the application and over 50% of participants were able to activate features of the application with minimal assistance. Caregiver feedback was also positive. Most caregivers strongly agreed or agreed to the effectiveness of the design and its ease of use with PWD. 100% of caregivers found the song performances to be appropriate and comfortable to follow and sing. Caregivers gave suggestions for improvement of seniorsing.net, such as including more song choices and having more written directions on some of the screens. In conclusion, seniorsing.net was found to be enjoyable and easy to use by PWD and their caregivers.
Keywords: Dementia, Music Therapy, Singing, Technology
ContributorsFranklin, Danielle (Author) / Rio, Robin (Thesis advisor) / Crowe, Barbara (Committee member) / Suzuki, Kotoka (Committee member) / Arizona State University (Publisher)
Created2015