Matching Items (7)
Filtering by
- Genre: Masters Thesis
- Creators: Arizona State University
- Creators: Chakraborty, Bijeta
- Member of: ASU Electronic Theses and Dissertations
Description
The purpose of this study was to examine whether a workplace environmental intervention would improve work-related outcomes including productivity, presenteeism and cognition. The secondary aim was to investigate whether work-related outcomes are correlated to observed changes in sitting time, physical activity, and sleep. The study was introduced as part of a naturalistic environmental change in which university staff and faculty were relocated into a new building (n=23). The comparison group consisted of university staff within the same college with no imminent plans to re-locate during the intervention period; there were no environmental changes to this workplace (n =10). Participants wore two behavioral monitoring devices, activPAL and GeneActiv, for 7 consecutive days at two time points (immediately prior and 16 weeks following the office relocation). Measures of productivity and presenteeism were obtained via four validated questionnaires and participants underwent cognitive performance testing. Baseline adjusted analysis of covariance statistical analyses were used to examine differences between groups in work-related outcomes. A residual analysis in regression was conducted to determine the differences between observed changes in sitting time, physical activity and sleep, and work-related outcomes. The results showed that a reduction in work hour sitting time was not detrimental to work related outcomes. Decreased sitting was observed to potentially improve presenteeism and absenteeism. Additionally, physical activity was shown to modestly improve productivity, presenteeism and absenteeism. Poor sleep patterns were associated with work impairment and increased absenteeism.
ContributorsPark, Anna (Author) / Buman, Matthew (Thesis advisor) / Crespo, Noe (Committee member) / Chisum, Jack (Committee member) / Arizona State University (Publisher)
Created2014
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
Scholarship on the rhetoric of place and space provides ample precedent for the study of structures as rhetorical texts; real and imagined places which convey meaning or memory, particularly monuments, memorials, and museums have been extensively studied, but loci of identity and history in institutions of higher education are under- examined. The following analysis of Arizona State University's Old Main building seeks to fill a gap in the study of place and space. As an entity which produces its own powerful discourses, Arizona State University expresses its historicity and institutional goals through varied and numerous media, but Old Main is one of the most critical, for the structure acts as an ethical proof in ASU's argument for its character, endurance, and worth. This examination addresses how ASU's ethos is articulated through the experiences of Old Main's past and current users, the instructional historical texts and artifacts displayed in the structure, the way that the building is mediated by ASU discourses, and the agency of the edifice itself. This work endeavors to answer Henri Lefebvre's call to improve widespread understanding of spaces as texts and their dialogue with users, and builds on the work of Carol Blair, Richard P. Dober, Diane Favro, and Bruno Latour, as well as that of Henri Lefebvre. To provide full context, this analysis integrates scholarship from the disciplines of campus planning, architecture, classical rhetoric, and the rhetoric of place and space.
ContributorsFulton, Holly Lynn (Author) / Lamp, Kathleen S. (Thesis advisor) / Goggin, Maureen (Committee member) / Rose, Shirley K. (Committee member) / Arizona State University (Publisher)
Created2014
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
Research indicates that adults are not acquiring enough physical activity. Increasing the use of stairs is an accessible way to weave high intensity physical activity into the daily routine. The purpose of this study is to test the effect of four environmental changes on ascending stair use in a mixed population of college students, faulty, and staff on a southwest college campus. The study design included a 10-week time series design with alternating baseline and intervention phases, including a directional cue represented by footprints on the ground, a positive prompt, a deterrent prompt and a combination phase. Data was collected with both an in-person tally and a video recording device. The study included 6,140 observations and coded variables included stair use, sex, number of bags carried, temperature, and volume. Rater reliability ranged from .81 to 1.0. Multivariate logistic regression was used to perform the statistic analysis. Stair use increased significantly from Washout 1 and the positive prompting phase with a 7% absolute increase and an odds ratio of 1.35 (95% CI 1.080-1.696). Stair use during the footprint phase, deterrent phase and combination phase did not increase significantly compared to the previous baseline or washout phases. Day of the week (Monday=reference, Tuesday CI=1.626, 95% CI 1.298-2.011, Wednesday OR=0.457, 95% CI 0.248-0.841, Thursday OR=1.434, 95% CI 1.164-1.766), sex (OR=1.376, 95% CI 1.173-1.613) and volume (OR=1.007, 95% CI 1.005-1.008) were significantly correlated to stair use. Women used the stairs more than men and higher volume situations were related to increased stair use. Temperature and baggage number were not related to stair use. The results of this study indicate that positive prompting with an environmental message theme is an effective method to increase stair use in a university setting.
ContributorsFord, Marley (Author) / Adams, Marc (Thesis advisor) / Der Ananian, Cheryl (Committee member) / Vaughan, Linda (Committee member) / Arizona State University (Publisher)
Created2015
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
Sparked by the Virginia Tech Shooting of 2007 and the resultant changes to the Family Educational Rights and Privacy Act, a review was conducted of FERPA's impact on university policies regarding student privacy and safety. A single, private university's policies were reviewed and a survey was distributed to 500 campus employees who had recently completed the university's FERPA training to determine if the university's current training was effective in training employees to understand FERPA's health and safety exceptions clause. The results showed that while the university's training was effective in training employees how to safeguard students' academic records, employees did not have a clear understanding of which information they could or should share in response to a threat to health and safety or to which university entity they should route safety concerns. The survey suggests that the university's FERPA training should be expanded to include training on FERPA's health and safety exceptions, including the communication of clear reporting lines for possible threats to campus safety and security.
ContributorsGilbert, Byron Jesse (Author) / Edwards, David A. (Thesis advisor) / Hild, Nicholas R. (Committee member) / Peterson, Danny M. (Committee member) / Arizona State University (Publisher)
Created2010