Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item DATA-DRIVEN ANALYSIS OF INDIVIDUAL THERMAL COMFORT WITH PERSONALIZED COOLING(2018) Dalgo, Daniel Alejandro; Srebric, Jelena; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation presents numerical and experimental results on the effects of Personal Cooling Devices (PCDs) on the energy consumption of buildings and the thermal comfort of occupants. The objective of this analysis was to quantify the tradeoffs of thermal comfort and energy savings associated with PCD technology. Furthermore, this investigation included an electrical cost analysis associated with PCDs at the building level for different cities across the United States. The results of energy and cost analyses, at the building level, indicated the potential for cooling energy and cost savings associated with shifting the electricity consumption during the peak hours to the off-peak hours of the day. The numerical analysis of human thermal comfort demonstrated the potential for PCDs to regulate human thermal comfort at warm environmental conditions. The thermal comfort level achieved in the numerical simulations were within the limits recommended by ASHRAE Standard 55. In addition, the numerical simulations permitted the evaluation of PCD performance based on thermal comfort, and the amount of sensible heat remove from the human body. The experimental work evaluated the performance of PCDs using both subjective and objective measurements of thermal comfort for 14 human subjects. The results demonstrated the ability of a PCD to change and maintain acceptable thermal comfort micro-environments for human subjects under warm conditions. Furthermore, the results showed that a PCD had measurable effects on physiological variables that control the thermoregulatory process of the human body. Specifically, variables such as skin temperature and heart rate variability in the time and frequency domain responded to the micro-environment created by the PCD. This research established a relationship between skin temperature, heart rate variability, and thermal comfort. Overall, this investigation performed a comprehensive analysis of the interaction of PCDs with: building energy consumption, human subjects, and human physiological processes; and demonstrated the potential to recognize human subjects’ thermal comfort based on physiological signals.Item AN INITIAL EVALUATION OF IBI VIZEDIT: AN RSHINY APPLICATION FOR OBTAINING ACCURATE ESTIMATES OF AUTONOMIC REGULATION OF CARDIAC ACTIVITY(2018) Barstead, Matthew; Rubin, Kenneth H; Human Development; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Photoplethysmogram (PPG) sensors are increasingly used to collect individual heart rate data during laboratory assessments and psychological experiments. PPG sensors are relatively cheap, easy to use, and non-invasive alternatives to the more common electrodes used to produce electrocardiogram recordings. The downside is that these sensors are more susceptible to signal distortion. Often, the most relevant measures for understanding psychological processes that underlie emotions and behaviors are measures of heart rate variability. As with all measures of variability, outliers (i.e., signal artifacts) can have outsized effects on the final estimates; and, given that these scores represent a primary variable of interest in many research contexts, the successful elimination of artefactual points is critical to the ability to make valid inferences with the data. Prior to the development of IBI VizEdit, there was no single, integrated processing and editing pipeline for PPG data. The present pair of studies offers and initial evaluation of the program’s performance. Study 1 is focused on the efficacy of a novel approach to imputing sections of particularly corrupted PPG signal. Study 2 tests the ability of trained editors to reliably use IBI VizEdit as well as the validity of estimates of cardiac activity during a prescribed set of laboratory tasks. Study 1 suggests that the novel imputation approach, under certain conditions and using certain parameterizations may hold promise as a means of accurately imputing missing sections of data. However, Study 1 also clearly demonstrates the need for further refinement and the consideration of alternative implementations. The results from Study 2 indicate that IBI VizEdit can be reliably used by trained editors and that estimates of cardiac activity derived from its output are likely valid.