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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
One in six children in the developing world is engaged in Child labor. Child labor is considered an issue that violates children's rights in many countries and Iraq is no exception. In 2004, Iraq had 1,300,000 children between the ages of eight and sixteen years engaged in work (UNICEF.com, 2004). This study identifies the major causes of child labor in Iraq and investigates the consequences of this issue. In this thesis I draw on the comparison of former regimes in Iraq and Egypt and how those regimes were mistreating their citizens by making them live under poverty and oppression while they were receiving support from the U.S. Poverty is the major cause behind Iraqi children engaging in work. I used the data I collected in Iraq, in the city of Nasiriyah, of 28 working children to explain the relationship between poverty, students drop out of school, family attitude towards education and the child engagement in work. At the end of the thesis I offer a list of recommendations to try to address the problem of child labor in Iraq. The recommendations and regulations are for Iraqi government and the NGOs to take into consideration in trying to resolve and regulate the issue of child labor to rescue the children in Iraq from more exploitation in the future.
ContributorsAl-Taee, Hawraa F (Author) / Elenes, C (Thesis advisor) / Erfani, Julie M (Committee member) / Ali, Souad (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
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
ABSTRACT
The purpose of involvement of Non-Governmental organizations (NGOs) in armed conflict resolution is to help to keep peace, protect innocent people, contribute to relief operations, to advocate, assist in the reconstruction and development programs. This action is always carried out through the NGOs grassroots mediation processes. This study investigates the prospective of implementing humanitarian programs to help and care for the young war child survivors of the 1991 to 2001 civil wars in Sierra Leone.
To explore the intervention of the NGOs activities in the civil wars in Sierra Leone, I examined three NGOs and one governmental institution as case study organizations. The NGOs include 1) UNICEF, 2) World Vision, 3) Plan International and 4) the Ministry of Social Welfare, Gender, and Childrens’ Affair (MSWGCA) as government agency. The research investigates the NGOs and MSWGC’s specific services provided to children during and after the war in Sierra Leone. The specific services include: 1) the NGOs’ implementing policies, 2) who got served and under what conditions, 3) what models of services do they use, 4) what kind of government policies were put in place, 5) what were the challenges they faced, and 6) what were their strategies during and after the civil war in Sierra Leone. There were also ten Adult Survivors of Childhood Exposure to War (ASCEW) members interviewed to balance the NGOs’ claims. Based on my literature review and findings on ASCEW, I make my recommendations to allow the organizations to move forward with their humanitarian operations.
The purpose of involvement of Non-Governmental organizations (NGOs) in armed conflict resolution is to help to keep peace, protect innocent people, contribute to relief operations, to advocate, assist in the reconstruction and development programs. This action is always carried out through the NGOs grassroots mediation processes. This study investigates the prospective of implementing humanitarian programs to help and care for the young war child survivors of the 1991 to 2001 civil wars in Sierra Leone.
To explore the intervention of the NGOs activities in the civil wars in Sierra Leone, I examined three NGOs and one governmental institution as case study organizations. The NGOs include 1) UNICEF, 2) World Vision, 3) Plan International and 4) the Ministry of Social Welfare, Gender, and Childrens’ Affair (MSWGCA) as government agency. The research investigates the NGOs and MSWGC’s specific services provided to children during and after the war in Sierra Leone. The specific services include: 1) the NGOs’ implementing policies, 2) who got served and under what conditions, 3) what models of services do they use, 4) what kind of government policies were put in place, 5) what were the challenges they faced, and 6) what were their strategies during and after the civil war in Sierra Leone. There were also ten Adult Survivors of Childhood Exposure to War (ASCEW) members interviewed to balance the NGOs’ claims. Based on my literature review and findings on ASCEW, I make my recommendations to allow the organizations to move forward with their humanitarian operations.
ContributorsBockarie, Michael Idriss (Author) / Anokye, Akua D (Thesis advisor) / Erfani, Julie M (Committee member) / Vaughan, Suzanne (Committee member) / Arizona State University (Publisher)
Created2016
Description
The nature and correlates of emerging internalizing symptoms in young children are largely unknown. Maternal factors such as psychological symptoms and detached parenting style have been found to be present in children with anxiety and depression. Further, child attentional control in task completion has been associated with difficulty related to internalizing problems. This study tested hypotheses that child anxiety and depression at age five could be predicted by a combination of maternal distress and maternal detached behavior recorded at age three. An additional hypothesis was tested to determine if child attentional control at age four may be a partial mediator of the relation between maternal symptoms and parenting to child internalizing symptoms. Using structural equation modeling, no hypotheses were supported; child internalizing problems were not significantly predicted by maternal distress nor detached parenting. Further, child attentional control was not predicted by maternal distress or detached behavior, nor did attentional control predict internalizing problems. Findings indicate that over a two-year interval, childhood internalizing problems at age five are likely best predicted by early internalizing problems at age three. There was no support that the mother or child factors tested were predictive of child outcomes.
ContributorsSkelley, Shayna (Author) / Crnic, Keith A (Thesis advisor) / Eisenberg, Nancy (Committee member) / MacKinnon, David (Committee member) / Arizona State University (Publisher)
Created2010
Description
Much of the current literature regarding the well being of children of incarcerated
parents has focused largely on the trauma that results from losing a parent to incarceration. Little research has been dedicated to examining the pre-existing trauma and negative life experiences these children are exposed to prior to parental incarceration. Using cross-sectional data on children (N = 1,221) from a representative study of Arizona Department of Corrections inmates, the present study examines the relationships among children who have contact with Child Protective Services (CPS) prior to parental incarceration and: (1) parental substance abuse, (2) exposure to violence and (3) parental mental illness. Nearly a quarter of all children whose inmate parents were interviewed were contacted by CPS before experiencing parental incarceration. Children whose inmate parents reported being unemployed or less involved in the lives of their children and children who were reportedly exposed to violence were significantly more likely to have been contacted by CPS prior to experiencing parental incarceration as were younger children. The children of incarcerated mothers were more likely to have been contacted by CPS than were the children of incarcerated fathers. This effect remained even after controlling for additional parent, child and family risk factors for CPS contact such as prior history of incarceration and race.
parents has focused largely on the trauma that results from losing a parent to incarceration. Little research has been dedicated to examining the pre-existing trauma and negative life experiences these children are exposed to prior to parental incarceration. Using cross-sectional data on children (N = 1,221) from a representative study of Arizona Department of Corrections inmates, the present study examines the relationships among children who have contact with Child Protective Services (CPS) prior to parental incarceration and: (1) parental substance abuse, (2) exposure to violence and (3) parental mental illness. Nearly a quarter of all children whose inmate parents were interviewed were contacted by CPS before experiencing parental incarceration. Children whose inmate parents reported being unemployed or less involved in the lives of their children and children who were reportedly exposed to violence were significantly more likely to have been contacted by CPS prior to experiencing parental incarceration as were younger children. The children of incarcerated mothers were more likely to have been contacted by CPS than were the children of incarcerated fathers. This effect remained even after controlling for additional parent, child and family risk factors for CPS contact such as prior history of incarceration and race.
ContributorsMcCaskill, Whitney (Author) / Rodriguez, Nancy (Thesis advisor) / Wright, Kevin (Committee member) / Tasca, Melinda (Committee member) / Krysik, Judy (Committee member) / Arizona State University (Publisher)
Created2014