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- Genre: Masters Thesis
- Creators: Arizona State University
- Creators: Bakkaloglu, Bertan
- 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
Blind and visually impaired individuals have historically demonstrated a low participation in the fields of science, engineering, mathematics, and technology (STEM). This low participation is reflected in both their education and career choices. Despite the establishment of the Americans with Disabilities Act (ADA) and the Individuals with Disabilities Education Act (IDEA), blind and visually impaired (BVI) students continue to academically fall below the level of their sighted peers in the areas of science and math. Although this deficit is created by many factors, this study focuses on the lack of adequate accessible image based materials. Traditional methods for creating accessible image materials for the vision impaired have included detailed verbal descriptions accompanying an image or conversion into a simplified tactile graphic. It is very common that no substitute materials will be provided to students within STEM courses because they are image rich disciplines and often include a large number images, diagrams and charts. Additionally, images that are translated into text or simplified into basic line drawings are frequently inadequate because they rely on the interpretations of resource personnel who do not have expertise in STEM. Within this study, a method to create a new type of tactile 3D image was developed using High Density Polyethylene (HDPE) and Computer Numeric Control (CNC) milling. These tactile image boards preserve high levels of detail when compared to the original print image. To determine the discernibility and effectiveness of tactile images, these customizable boards were tested in various
university classrooms as well as in participation studies which included BVI and sighted students. Results from these studies indicate that tactile images are discernable and were found to improve performance in lab exercises as much as 60% for those with visual impairment. Incorporating tactile HDPE 3D images into a classroom setting was shown to increase the interest, participation and performance of BVI students suggesting that this type of 3D tactile image should be incorporated into STEM classes to increase the participation of these students and improve the level of training they receive in science and math.
university classrooms as well as in participation studies which included BVI and sighted students. Results from these studies indicate that tactile images are discernable and were found to improve performance in lab exercises as much as 60% for those with visual impairment. Incorporating tactile HDPE 3D images into a classroom setting was shown to increase the interest, participation and performance of BVI students suggesting that this type of 3D tactile image should be incorporated into STEM classes to increase the participation of these students and improve the level of training they receive in science and math.
ContributorsGonzales, Ashleigh (Author) / Baluch, Debra P (Thesis advisor) / Maienschein, Jane (Committee member) / Ellison, Karin (Committee member) / Arizona State University (Publisher)
Created2015
Description
Conceptual change has been a large part of science education research for several decades due to the fact that it allows teachers to think about what students' preconceptions are and how to change these to the correct scientific conceptions. To have students change their preconceptions teachers need to allow students to confront what they think they know in the presence of the phenomena. Students then collect and analyze evidence pertaining to the phenomena. The goal in the end is for students to reorganize their concepts and change or correct their preconceptions, so that they hold more accurate scientific conceptions. The purpose of this study was to investigate how students' conceptions of the Earth's surface, specifically weathering and erosion, change using the conceptual change framework to guide the instructional decisions. The subjects of the study were a class of 25 seventh grade students. This class received a three-week unit on weathering and erosion that was structured using the conceptual change framework set by Posner, Strike, Hewson, and Gertzog (1982). This framework starts by looking at students' misconceptions, then uses scientific data that students collect to confront their misconceptions. The changes in students' conceptions were measured by a pre concept sketch and post concept sketch. The results of this study showed that the conceptual change framework can modify students' preconceptions of weathering and erosion to correct scientific conceptions. There was statistical significant difference between students' pre concept sketches and post concept sketches scores. After examining the concept sketches, differences were found in how students' concepts had changed from pre to post concept sketch. Further research needs to be done with conceptual change and the geosciences to see if conceptual change is an effective method to use to teach students about the geosciences.
ContributorsTillman, Ashley (Author) / Luft, Julie (Thesis advisor) / Middleton, James (Committee member) / Semken, Steven (Committee member) / Arizona State University (Publisher)
Created2011
Description
The nature of science (NOS) is included in the National Science Education Standards and is described as a critical component in the development of scientifically literate students. Despite the significance of NOS in science education reform, research shows that many students continue to possess naïve views of NOS. Explicit and reflective discussion as an instructional approach is relatively new in the field of research in NOS. When compared to other approaches, explicit instruction has been identified as more effective in promoting informed views of NOS, but gaps in student understanding still exist. The purpose of this study was to deepen the understanding of student learning of NOS through the investigation of two variations of explicit instruction. The subjects of the study were two seventh grade classes taught by the same classroom teacher. One class received explicit instruction of NOS within a plate tectonics unit and the second class received explicit instruction of NOS within a plate tectonics unit plus supporting activities focused on specific aspects of NOS. The instruction time for both classes was equalized and took place over a three week time period. The intention of this study was to see if the additional NOS activities helped students build a deeper understanding of NOS, or if a deep understanding could be formed solely through explicit and reflective discussion within content instruction. The results of the study showed that both classes progressed in their understanding of NOS. When the results of the two groups were compared, the group with the additional activities showed statistically significant gains on two of the four aspects of NOS assessed. These results suggest that the activities may have been valuable in promoting informed views, but more research is needed in this area.
ContributorsMelville, Melissa (Author) / Luft, Julie (Thesis advisor) / Baker, Dale (Committee member) / Brem, Sarah (Committee member) / Arizona State University (Publisher)
Created2011
Description
Writing scientific explanations is increasingly important, and today's students must have the ability to navigate the writing process to create a persuasive scientific explanation. One aspect of the writing process is receiving feedback before submitting a final draft. This study examined whether middle school students benefit more in the writing process from receiving peer feedback or teacher feedback on rough drafts of scientific explanations. The study also looked at whether males and females reacted differently to the treatment groups. And it examined if content knowledge and the written scientific explanations were correlated. The study looked at 38 sixth and seventh-grade students throughout a 7-week earth science unit on earth systems. The unit had six lessons. One lesson introduced the students to writing scientific explanations, and the other five were inquiry-based content lessons. They wrote four scientific explanations throughout the unit of study and received feedback on all four rough drafts. The sixth-graders received teacher feedback on each explanation and the seventh-graders received peer-feedback after learning how to give constructive feedback. The students also took a multiple-choice pretest/posttest to evaluate content knowledge. The analyses showed that there was no significant difference between the group receiving peer feedback and the group receiving teacher feedback on the final drafts of the scientific explanations. There was, however, a significant effect of practice on the scores of the scientific explanations. Students wrote significantly better with each subsequent scientific explanation. There was no significant difference between males and females based on the treatment they received. There was a significant correlation between the gain in pretest to posttest scores and the scientific explanations and a significant correlation between the posttest scores and the scientific explanations. Content knowledge and written scientific explanations are related. Students who wrote scientific explanations had significant gains in content knowledge.
ContributorsLange, Katie (Author) / Baker, Dale (Thesis advisor) / Megowan, Colleen (Committee member) / Middleton, James (Committee member) / Arizona State University (Publisher)
Created2011
Description
The under-representation of women in science, technology, engineering and mathematics (STEM) fields indicates the presence of gender related barriers that impacted the persistence of women in science and engineering doctoral studies. The purpose of this study was to investigate the barriers of women doctoral students in STEM fields which identified supporting factors for them as well. This study also tried to determine if there was any difference in perceiving barriers among three disciplines - engineering, life sciences and natural sciences. An online questionnaire (19 Likert-type questions and one open-ended question) was sent to women STEM doctoral students studying at the Arizona State University (ASU). Questions were based on some factors which might act as obstacles or supports during their doctoral studies. Both quantitative and qualitative analyses were conducted. Factors such as work-life balance, time-management, low self-confidence, lack of female role model, fewer numbers of women in science and engineering classes, and male dominated environment revealed as significant barriers according to both the analyses but factors such as difficulty with the curriculum, gender discrimination, and two-career problem were chosen as barriers only in the free response question. Positive treatment from advisor, family support, availability of funding, and absence of sexual harassment assisted these women continuing their PhD programs at ASU. However, no significant difference was observed with respect to perceiving barriers among the three groups mentioned above. Recommendations for change in science and engineering curricula and active recruitment of female faculty are discussed to reduce or at best to remove the barriers and how to facilitate participation and retention of more women in STEM fields especially at the doctoral level.
ContributorsChaudhuri, Dola (Author) / Baker, Dale (Thesis advisor) / Sandlin, Jennifer (Committee member) / Edwards, Vicki (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
Assemblers and compilers provide feedback to a programmer in the form of error messages. These error messages become input to the debugging model of the programmer. For the programmer to fix an error, they should first locate the error in the program, understand what is causing that error, and finally resolve that error. Error messages play an important role in all three stages of fixing of errors. This thesis studies the effects of error messages in the context of teaching programming. Given an error message, this work investigates how it effects student’s way of 1) understanding the error, and 2) fixing the error. As part of the study, three error message types were developed – Default, Link and Example, to better understand the effects of error messages. The Default type provides an assembler-centric single line error message, the Link type provides a program-centric detailed error description with a hyperlink for more information, and the Example type provides a program centric detailed error description with a relevant example. All these error message types were developed for assembly language programming. A think aloud programming exercise was conducted as part of the study to capture the student programmer’s knowledge model. Different codes were developed to analyze the data collected as part of think aloud exercise. After transcribing, coding, and analyzing the data, it was found that the Link type of error message helped to fix the error in less time and with fewer steps. Among the three types, the Link type of error message also resulted in a significantly higher ratio of correct to incorrect steps taken by the programmer to fix the error.
ContributorsBeejady Murthy Kadekar, Harsha Kadekar (Author) / Sohoni, Sohum (Thesis advisor) / Craig, Scotty D. (Committee member) / Jordan, Shawn S (Committee member) / Gary, Kevin A (Committee member) / Arizona State University (Publisher)
Created2017
Description
Background: The Academy of Nutrition and Dietetics states that it is possible for a vegetarian to obtain the recommended amount of nutrients with a properly planned diet but nutrient deficiencies, such as vitamin B12 deficiency, may occur if diet planning is not optimal. An early indicator of B12 deficiency is raised homocysteine concentrations in blood which can cause health issues.
Objective: The amino acid methionine is consumed via dietary protein. Methionine is used in the biosynthesis of other proteins. After a removal of a methyl group, it makes homocysteine. Slightly raised homocysteine may promote greater synthesis of glutathione, an important endogenous antioxidant protectant. It can then be recycled back into methionine or converted into cysteine with the addition of various B-vitamins such as vitamin B12, folic acid, and vitamin B6. Cysteine then uses outside sources of glutamate and glycine to create glutathione (GSH). With the catalyst glutathione peroxidase it donates an electron and becomes the oxidized form, glutathione disulfide (GSSG). It can then convert back to GSH with the aid of glutathione reductase by using the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) as an electron donor. This study will examine glutathione levels in omnivores and vegetarians and see if it is related to vitamin B12 and homocysteine levels.
Design: This cross-sectional study encompassed 16 omnivores and 17 vegetarians from Phoenix, Arizona. A vegetarian diet was defined as one that excludes red meat, poultry, pork and seafood but allows dairy products and/or eggs; the diet had to be followed for at least one year. An omnivore diet is defined as eats meat daily. Participants completed a diet questionnaire and a vitamin B12, B6 and folate food questionnaire and provided a fasting blood sample.
Results: The mean plasma B12 and homocysteine did not differ between diet groups. Glutathione was significantly lower among vegetarians in comparison to omnivores, 1.9±0.5 and 2.3±0.7 mmol respectively (p=0.046).
Conclusions: The hypothesis was shown to be incorrect that vegetarians would have a higher glutathione level than omnivores as a result of their modest consumption of vitamin B12. The implications of a reduced glutathione status are discussed.
Objective: The amino acid methionine is consumed via dietary protein. Methionine is used in the biosynthesis of other proteins. After a removal of a methyl group, it makes homocysteine. Slightly raised homocysteine may promote greater synthesis of glutathione, an important endogenous antioxidant protectant. It can then be recycled back into methionine or converted into cysteine with the addition of various B-vitamins such as vitamin B12, folic acid, and vitamin B6. Cysteine then uses outside sources of glutamate and glycine to create glutathione (GSH). With the catalyst glutathione peroxidase it donates an electron and becomes the oxidized form, glutathione disulfide (GSSG). It can then convert back to GSH with the aid of glutathione reductase by using the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) as an electron donor. This study will examine glutathione levels in omnivores and vegetarians and see if it is related to vitamin B12 and homocysteine levels.
Design: This cross-sectional study encompassed 16 omnivores and 17 vegetarians from Phoenix, Arizona. A vegetarian diet was defined as one that excludes red meat, poultry, pork and seafood but allows dairy products and/or eggs; the diet had to be followed for at least one year. An omnivore diet is defined as eats meat daily. Participants completed a diet questionnaire and a vitamin B12, B6 and folate food questionnaire and provided a fasting blood sample.
Results: The mean plasma B12 and homocysteine did not differ between diet groups. Glutathione was significantly lower among vegetarians in comparison to omnivores, 1.9±0.5 and 2.3±0.7 mmol respectively (p=0.046).
Conclusions: The hypothesis was shown to be incorrect that vegetarians would have a higher glutathione level than omnivores as a result of their modest consumption of vitamin B12. The implications of a reduced glutathione status are discussed.
ContributorsManley, Rachel Christine (Author) / Johnston, Carol (Thesis advisor) / Levinson, Simin (Committee member) / Barth, Christina (Committee member) / Arizona State University (Publisher)
Created2019
Description
This teacher research study examined the effects of utilizing an intervention of Science Writing Heuristics (SWH) as a tool to increase learning during laboratory activities. Five of my eighth grade general science classes participated in this study. Two classes utilized SWH during their laboratory activities (the treatment group) and three classes performed and wrote up their labs in the more traditional, teacher-directed approach (the control group). The assessment scores of the students in the treatment group were compared to the assessment scores of the students in the control group. The post-assessments were analyzed utilizing a t-test. I was teacher in this study and the teacher of all five classes. Data from 41 students were analyzed in this study. A pre-assessment, six laboratory activities, instruction, and a post-assessment occurred within three weeks. The assessments were generated by myself and I performed a t-test using a two-sample analysis, assuming unequal variances (n=16 for treatment group, n=25 for control group) to compare the post-assessments from each group. Results indicated that there was no significant difference between the post-assessment scores of the treatment group with the post-assessment scores of control group (p=0.25). However, the t-test results revealed that when the pre- and post-assessments were compared, there was a significant difference (p=<0.05 for treatment group, p=<0.05 for control group). Each group showed considerable cognitive improvement between pre-assessment (mean scores: 52%-treatment group and 53%-control group) and the post-assessment (mean scores: 72%-treatment group and 80%-control group). This suggests that the presentation of the curriculum lacked a clear distinction between the treatment group and the control group yet benefited most students. Due to circumstances described in the limitations, further research is warranted.
ContributorsDrobitsky, Tamara (Author) / Luft, Julie (Thesis advisor) / Marsh, Josephine (Committee member) / Baker, Dale (Committee member) / Lyon, Edward (Committee member) / Arizona State University (Publisher)
Created2015