ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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- All Subjects: chemical engineering
Underreporting of energy intake (EI) has been found to be an important consideration that interferes with accurate weight control assessment and the effective use of energy balance (EB) models in an intervention setting. To better understand underreporting, a variety of estimation approaches are developed; these include back-calculating energy intake from a closed-form of the EB model, a Kalman-filter based algorithm for recursive estimation from randomly intermittent measurements in real time, and two semi-physical identification approaches that can parameterize the extent of systematic underreporting with global/local modeling techniques. Each approach is analyzed with intervention participant data and demonstrates potential of promoting the success of weight control.
In addition, substantial efforts have been devoted to develop participant-validated models and incorporate into the Hybrid Model Predictive Control (HMPC) framework for closed-loop interventions. System identification analyses from Phase I led to modifications of the measurement protocols for Phase II, from which longer and more informative data sets were collected. Participant-validated models obtained from Phase II data significantly increase predictive ability for individual behaviors and provide reliable open-loop dynamic information for HMPC implementation. The HMPC algorithm that assigns optimized dosages in response to participant real time intervention outcomes relies on a Mixed Logical Dynamical framework which can address the categorical nature of dosage components, and translates sequential decision rules and other clinical considerations into mixed-integer linear constraints. The performance of the HMPC decision algorithm was tested with participant-validated models, with the results indicating that HMPC is superior to "IF-THEN" decision rules.
Idiographic Models of Walking Behavior for Personalized mHealth Interventions: Some Novel Approaches
Mohr's circles were constructed from experimentally-obtained shear stress values to quantitatively describe flowability of tested materials in terms of a flow function parameter. A high flow function value (>10) was indicative of a good flow.
By testing 120-180 µm, 120-350 µm, 180-250 µm, 250-350 µm, 430-600 µm, and 600-850 µm glass bead diameter ranges, an increase in size was seen to result in higher flow function values. The limitations of testing using the FT4 became apparent as inconsistent flow function values were obtained at 0% moisture with size ranges above 120-180 µm, or at flow function values of >21. Bead sizes larger than 430 µm showed significant standard deviation over all tested trials--when excluding size ranges above that value, the empirical model showed an average error of only 6.45%.
Wet material testing occurred at all tested glass bead size ranges using a deionized water content of 0%, 1%, 5%, 15%, and 20% by weight. The results of such testing showed a decrease in the resulting flow function parameter as more water content was added. However, this trend changed as 20% moisture content was achieved; the wet material became supersaturated, and an increase in flow function values was observed. The empirical model constructed, therefore, neglected the 20% moisture content regime.
Oxygen sorption/desorption properties of perovskite oxides with and without oxygen vacancy were investigated first by thermogravimetric analysis (TGA) and fixed-bed experiments. The oxide with unique disorder-order phase transition during desorption exhibited an enhanced oxygen desorption rate during the TGA measurement but not in fixed-bed demonstrations. The difference in oxygen desorption rate is due to much higher oxygen partial pressure surrounding the sorbent during the fixed-bed oxygen desorption process, as revealed by X-ray diffraction (XRD) patterns of rapidly quenched samples.
Research on using perovskite oxides as CO2-permeable dual-phase membranes was subsequently conducted. Two CO2-resistant MIEC perovskite ceramics, Pr0.6Sr0.4Co0.2Fe0.8 O3-δ (PSCF) and SrFe0.9Ta0.1O3-δ (SFT) were chosen as support materials for membrane synthesis. PSCF-molten carbonate (MC) and SFT-MC membranes were prepared for CO2-O2 counter-permeation. The geometric factors for the carbonate phase and ceramic phase were used to calculate the effective carbonate and oxygen ionic conductivity in the carbonate and ceramic phase. When tested in CO2-O2 counter-permeation set-up, CO2 flux showed negligible change, but O2 flux decreased by 10-32% compared with single-component permeation. With CO2 counter-permeation, the total oxygen permeation flux is higher than that without counter-permeation.
A new concept of CO2-permselective membrane reactor for hydrogen production via steam reforming of methane (SRM) was demonstrated. The results of SRM in the membrane reactor confirm that in-situ CO2 removal effectively promotes water-gas shift conversion and thus enhances hydrogen yield. A modeling study was also conducted to assess the performance of the membrane reactor in high-pressure feed/vacuum sweep conditions, which were not carried out due to limitations in current membrane testing set-up. When 5 atm feed pressure and 10-3 atm sweep pressure were applied, the membrane reactor can produce over 99% hydrogen stream in simulation.