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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
Co-teaching is one of the most popular models for supporting students with disabilities in general education classrooms. In spite of this, there is a paucity of research on student perceptions of co-teaching. The purpose of this qualitative study was to investigate student perceptions of co-teaching in a high school biology classroom. Over nine weeks, data was collected from students in a co-taught and traditional classroom through observations and focus groups. Qualitative content analysis identified three themes and eight categories which highlight student perceptions of co-teaching. Themes and categories that emerged were: 1) Environment which included the categories of availability of help, students feeling supported and normalcy of the classroom, 2) Instruction which included student engagement, lesson activity and teacher(s) role(s) and, 3) Relationships which included relationships between teacher(s) and student(s) and parity between teachers. Information from the study deepens researchers' and practitioners' understanding of how students perceive co-teaching and provide new avenues for future research and best practices.
ContributorsLersch, Matthew (Author) / Lersch, Matthew S (Thesis advisor) / Kozleski, Elizabeth B. (Committee member) / Malian, Ida (Committee member) / Swadener, Elizabeth (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
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
In today's data-driven world, every datum is connected to a large amount of data. Relational databases have been proving itself a pioneer in the field of data storage and manipulation since 1970s. But more recently they have been challenged by NoSQL graph databases in handling data models which have an inherent graphical representation. Graph databases with the ability to store physical relationships between two nodes and native graph processing technique have been doing exceptionally well in graph data storage and management for applications like recommendation engines, biological modeling, network modeling, social media applications, etc.
Instructional Module Development System (IMODS) is a web-based software system that guides STEM instructors through the complex task of curriculum design, ensures tight alignment between various components of a course (i.e., learning objectives, content, assessments), and provides relevant information about research-based pedagogical and assessment strategies. The data model of IMODS is highly connected and has an inherent graphical representation between all its entities with numerous relationships between them. This thesis focuses on developing an algorithm to determine completeness of course design developed using IMODS. As part of this research objective, the study also analyzes the data model for best fit database to run these algorithms. As part of this thesis, two separate applications abstracting the data model of IMODS have been developed - one with Neo4j (graph database) and another with PostgreSQL (relational database). The research objectives of the thesis are as follows: (i) evaluate the performance of Neo4j and PostgreSQL in handling complex queries that will be fired throughout the life cycle of the course design process; (ii) devise an algorithm to determine the completeness of a course design developed using IMODS. This thesis presents the process of creating data model for PostgreSQL and converting it into a graph data model to be abstracted by Neo4j, creating SQL and CYPHER scripts for undertaking experiments on both platforms, testing and elaborate analysis of the results and evaluation of the databases in the context of IMODS.
Instructional Module Development System (IMODS) is a web-based software system that guides STEM instructors through the complex task of curriculum design, ensures tight alignment between various components of a course (i.e., learning objectives, content, assessments), and provides relevant information about research-based pedagogical and assessment strategies. The data model of IMODS is highly connected and has an inherent graphical representation between all its entities with numerous relationships between them. This thesis focuses on developing an algorithm to determine completeness of course design developed using IMODS. As part of this research objective, the study also analyzes the data model for best fit database to run these algorithms. As part of this thesis, two separate applications abstracting the data model of IMODS have been developed - one with Neo4j (graph database) and another with PostgreSQL (relational database). The research objectives of the thesis are as follows: (i) evaluate the performance of Neo4j and PostgreSQL in handling complex queries that will be fired throughout the life cycle of the course design process; (ii) devise an algorithm to determine the completeness of a course design developed using IMODS. This thesis presents the process of creating data model for PostgreSQL and converting it into a graph data model to be abstracted by Neo4j, creating SQL and CYPHER scripts for undertaking experiments on both platforms, testing and elaborate analysis of the results and evaluation of the databases in the context of IMODS.
ContributorsSaha, Abir Lal (Author) / Bansal, Srividya (Thesis advisor) / Bansal, Ajay (Committee member) / Gonzalez-Sanchez, Javier (Committee member) / Arizona State University (Publisher)
Created2017
Description
Clickers are a common part of many classrooms across universities. Despite the widespread use, education researchers disagree about how to best use these tools and about how they impact students. Prior work has shown possible differential impacts of clickers based on demographic indicators, such as age, gender, and ethnicity. To explore these topics a two-part project was designed. First, a literature review was completed focusing on past and current clicker practices and the research surrounding them. Second, original data, stratified by demographic characteristics, was collected on student perceptions of clickers. The literature review revealed that not all uses of clickers are created equal. Instructors in higher education first introduced clickers to enhance traditional pedagogies by simplifying common classroom tasks (e.g. grading, attendance, feedback collection). More recently, instructors pair clickers and novel pedagogies. A review of the identified benefits and drawbacks for students and instructors is provided for both approaches. Instructors can use different combinations of technological competency and pedagogical content knowledge that lead to four main outcomes. When instructors have both technological competency and pedagogical content knowledge, all the involved parties, students and instructors, benefit. When instructors have technological competency but lack pedagogical content knowledge, instructors are the main benefactors. When instructors have pedagogical content knowledge alone, students can benefit, but usefulness to the instructor decreases. When instructors have neither technological competency nor pedagogical content knowledge, no party benefits. Beyond these findings, recommendations are provided for future clicker research. Second, the review highlighted that clickers may have a differential impact on students of different demographic groups. To explore this dynamic, an original study on student views of clickers, which included demographic data, was conducted. The original study does not find significantly different enthusiasm for clickers by demographic group, unlike prior studies that explored some of these relationships. However, white students and male students are overrepresented in the group that does not enjoy clickers. This conclusion is supported by visual observations from the means of the demographic groups. Overall, based on the review of the literature and original research, if instructors pair clickers with validated pedagogies, and if researchers continue to study clicker classrooms, including which students like and benefit from clickers, clickers may continue to be a valuable educational technology.
ContributorsChambers, Elijah Lorenzo (Author) / Henderson, Joesph (Thesis advisor) / Ellison, Karin (Thesis advisor) / Chew, Matthew (Committee member) / Arizona State University (Publisher)
Created2020