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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
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
Today in the U.S. the narrative of the “bad drug” has become quite a familiar account. There is an ever-growing collection of pharmaceutical products whose safety and efficacy has been debunked through the scandalous exposure of violations of integrity on the part of researchers, lapses in procedure and judgment on the part of the FDA, and reckless profiteering on the part of big pharma. However, a closer look reveals that the oversights and loopholes depicted in the bad drug narrative are not incidental failures of an otherwise intact, effective system. Rather, bad drugs, like good drugs, are a product of normal operations of the system; the same processes, actors, and influences manifest in both. The aim of this project is to shed light on these processes, actors, and influences at work in drug normalization by interrogating the peculiar case of the drug Lupron. Lupron exhibits all of the controversial features of the “bad drug” narrative but has remained an endorsed and embraced staple of the infertility industry. This contradiction situates Lupron to expose a number of the contingencies on which drug normalization rests more generally. In order to put forth an explanatory model for drug normalization, three such contingencies are described in detail for the case at hand: the nature of drug regulation, the structures and value that underpin the medical categorization of diseases, and the inextricability of post-medicine from the forces of industry. These contingencies provide some explanatory power for understanding not only the retention of Lupron but the ways in which all drugs are produced, validated, and perpetuated in a society.
ContributorsStevenson, Christine, M.S (Author) / Brian, Jennifer (Thesis advisor) / Hurlbut, Benjamin (Thesis advisor) / Maienschein, Jane (Committee member) / Arizona State University (Publisher)
Created2015
Description
Glucose sensors have had many paradigm shifts, beginning with using urine, to point of care blood, now being approved for implant. This review covers various aspects of the sensors, ranging from the types of surface chemistry, and electron transduction. All the way to the algorithms, and filters used to alter and understand the signal being transduced. Focus is given to Dr. Hellerâ’s work using redox mediators, as well as Dr. Sode in his advances for direct electron transfer. Simple process of designing sensors are described, as well as the possible errors that may come with glucose sensor use. Finally, a small window into the future trends of glucose sensors is described both from a device view point, as well as organic viewpoint. Using this history the initial point of care sensor for insulin published through LaBelle’s lab is reevaluated critically. In addition, the modeling of the possibility of continuously measuring insulin is researched. To better understand the design for a continuous glucose sensor, the basic kinetic model is set up, and ran through a design of experiments to then optimized what the binding kinetics for an ideal insulin molecular recognition element would be. In addition, the phenomena of two electrochemical impedance spectroscopy peaks is analyzed, and two theories are suggests, and demonstrated to a modest level.
ContributorsProbst, David L (Author) / LaBelle, Jeffery (Thesis advisor) / Caplan, Micheal (Committee member) / Cook, Curtiss (Committee member) / Arizona State University (Publisher)
Created2018
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
This is a project about medicine and the history of a condition called premenstrual syndrome (PMS), its “discovery” and conceptual development at both scientific and socio-cultural levels. Since it was first mentioned in medical literature, PMS has been explored empirically as a medical condition and conceptually as non-somatic cultural phenomenon. Many attempts have been made to produce scientific, empirical evidence to bolster the theory of PMS as a biological disease. Some non-medical perspectives argue that invoking biology as the cause of PMS medicalizes a natural function of the female reproductive system and shallowly interrogates what is actually a complex bio-psycho-social phenomenon. This thesis questions both sides of this debate in order to reveal how criteria for PMS were categorized despite disagreement surrounding its etiology.
This thesis illustrates how the concept of PMS developed and was informed by the discovery of hormones and the resulting field of endocrinology that provided a framework for conceptualizing PMS. It displays how the development of the medical diagnostic category of PMS developed in tandem with the emergence of the field of endocrinology and was legitimized and effectively medicalized through this connection. The diagnosis of PMS became established though the diagnostic techniques like questionnaires in spite of persistent disagreement over its definition. The thesis shows how these medical concepts and practices legitimated the category of PMS, and how it has become ubiquitous in contemporary culture.
This thesis illustrates how the concept of PMS developed and was informed by the discovery of hormones and the resulting field of endocrinology that provided a framework for conceptualizing PMS. It displays how the development of the medical diagnostic category of PMS developed in tandem with the emergence of the field of endocrinology and was legitimized and effectively medicalized through this connection. The diagnosis of PMS became established though the diagnostic techniques like questionnaires in spite of persistent disagreement over its definition. The thesis shows how these medical concepts and practices legitimated the category of PMS, and how it has become ubiquitous in contemporary culture.
ContributorsZietal, Bianca (Author) / Hurlbut, James (Thesis advisor) / Robert, Jason (Committee member) / Brian, Jennifer (Committee member) / Arizona State University (Publisher)
Created2016
Description
Writing speculative fiction is a valuable method for exploring the potential societal transformations elicited by advances in science and technology. The aim of this project is to use speculative fiction to explore the potential consequences of precision medicine for individuals’ daily lives. Precision medicine is a vision of the future in which medicine is about predicting, and ultimately preventing disease before symptoms arise. The idea is that identification of all the factors that influence health and contribute to disease development will translate to better and less expensive healthcare and empower individuals to take responsibility for maintaining their own health and wellness. That future, as envisioned by the leaders of the Human Genome Project, the Institute for Systems Biology, and the Obama administration’s Precision Medicine Initiative, is assumed to be a shared future, one that everyone desires and that is self-evidently “better” than the present. The aim of writing speculative fiction about a “precision medicine” future is to challenge that assumption, to make clear the values underpinning that vision of precision medicine, and to leave open the question of what other possible futures could be imagined instead.
ContributorsVenkatraman, Richa (Author) / Brian, Jennifer (Thesis advisor) / Maienschein, Jane (Thesis advisor) / Hurlbut, James (Committee member) / Arizona State University (Publisher)
Created2022
Description
In the last 200 years, advancements in science and technology have made understanding female sexual function and the female body more feasible; however, many women throughout the US still lack fundamental understanding of the reproductive system in the twenty-first century. Many factors contribute to the lack of knowledge and misconceptions that women still have. Discussing sexual health tends to make some people uncomfortable and this study aims to investigate what aspects of somewhat recent US history in women’s health care may have led to that discomfort. This thesis examines the question: what are some of the factors that shaped women’s reproductive medicine in the US from the mid 1800s and throughout the 1900s and what influence could the past have had on how women and their physicians understand female sexuality in medicine and how physicians diagnose their female patients in the twenty-first century. A literature review of primary source medical texts written at the end of the 1800s provides insight about patterns among physicians at the time and their medical practice with female patients. Factors like gendered expectations in medical practice, misconceptions about the female body and behaviors, and issues of morality in sex medicine all contributed to women lacking understanding of sex female reproductive functions. Other factors like a physician’s role throughout history and non-medical reproductive health providers and solutions likely also influenced the reproductive medicine women received. Examining the patterns of the past provides some insight into some of the outdated and gendered practices still exhibited in healthcare. Expanding sexual education programs, encouraging discussion about sex and reproductive health, and checking gendered implicit bias in reproductive healthcare could help eliminate echoes of hysteria ideology in the twenty-first century medicine.
ContributorsHorwitz, Rainey (Author) / Maienschein, Jane (Thesis advisor) / Hurlbut, Ben (Committee member) / Ellison, Karin (Committee member) / Arizona State University (Publisher)
Created2019
Description
Prior to the first successful allogeneic organ transplantation in 1954, virtually every attempt at transplanting organs in humans had resulted in death, and understanding the role of the immune mechanisms that induced graft rejection served as one of the biggest obstacles impeding its success. While the eventual achievement of organ transplantation is touted as one of the most important success stories in modern medicine, there still remains a physiological need for immunosuppression in order to make organ transplantation work. One such solution in the field of experimental regenerative medicine is interspecies blastocyst complementation, a means of growing patient-specific human organs within animals. To address the progression of immune-related constraints on organ transplantation, the first part of this thesis contains a historical analysis tracing early transplant motivations and the events that led to the discoveries broadly related to tolerance, rejection, and compatibility. Despite the advancement of those concepts over time, this early history shows that immunosuppression was one of the earliest limiting barriers to successful organ transplantation, and remains one of the most significant technical challenges. Then, the second part of this thesis determines the extent at which interspecies blastocyst complementation could satisfy modern technical limitations of organ transplantation. Demonstrated in 2010, this process involves using human progenitor cells derived from induced pluripotent stem cells (iPSCs) to manipulate an animal blastocyst genetically modified to lack one or more functional genes responsible for the development of the intended organ. Instead of directly modulating the immune response, the use of iPSCs with interspecies blastocyst complementation could theoretically eliminate the need for immunosuppression entirely based on the establishment of tolerance and elimination of rejection, while also satisfying the logistical demands imposed by the national organ shortage. Although the technology will require some further refinement, it remains a promising solution to eliminate the requirement of immunosuppression after an organ transplant.
ContributorsDarby, Alexis Renee (Author) / Maienschein, Jane (Thesis advisor) / Robert, Jason (Thesis advisor) / Ellison, Karin (Committee member) / Arizona State University (Publisher)
Created2020