Search 50,000+ articles, datasets, theses and working papers across all
SHAREOK communities — full text, open access, and freely citable.
- 50,796Publications
- 30,468Authors
- 99%Open Access
- 28.9MDownloads
Browse the repository
42 Communities·178 Collections
Recent Submissions
Item type:Item, Access status: Open Access , DEVELOPMENT OF A CORRELATION-BASED INVERSION METHOD FOR AEROSOL REMOTE SENSING(University of Oklahoma – Graduate College, 2026) Huang, Taozhong; Xu, Feng; Gao, Lan; Redemann, Jens; Wang, Chenghao; Weng, BinbinAccurate characterization of aerosol microphysical properties from diverse remote sensing platforms is essential for quantifying aerosol-radiation and aerosol-cloud interactions. However, aerosol retrieval remains a highly ill-posed inversion problem, particularly when operating under limited information content. To address this challenge, this dissertation introduces two distinct applications that improve state-of-the-art retrieval techniques by incorporating well-characterized a priori constraints. The first application develops a surface model parameter conversion algorithm that bridges a priori information from semi-empirical, Ross–Li-based surface model parameters to physical, Rahman–Pinty–Verstraete (RPV)-based surface parameters. Validated through Directional Hemispherical Reflectance (DHR) and Bidirectional Reflectance Factor (BRF) comparisons, the algorithm demonstrates a highly successful conversion capability. Further retrieval tests indicate that the conversion algorithm introduces minimal impact to the aerosol inversion, providing a robust mechanism for surface a priori initialization. The second application presents the Correlation based Inversion Method for Aerosol Properties (CIMAP) framework, an aerosol inversion strategy that utilizes Principal Component Analysis (PCA) to implement intrinsic correlation constraints among aerosol properties. By retaining a targeted number of Principal Components (PCs), CIMAP substantially reduces the state vector dimensionality, enhancing both numerical stability and computational efficiency. The framework is evaluated under two configurations: CIMAP-A: Utilizes ground-based AERONET observations across three distinct regions (southeast coast of the US, northern China, and southern Africa). Using only 7–8 PCs out of 30, CIMAP-A achieves a processing speed acceleration of over 80% while maintaining high accuracy relative to official AERONET inversion products, yielding Mean Absolute Difference (MAD) of 0.005, 0.019, 0.039, 0.003, 0.013 μm, 0.02 μm and for Aerosol Optical Depth (AOD), Single Scattering Albedo (SSA), Real and Imaginary parts of Refractive Index (RIR and RII), effective radius of fine and coarse modes of particle size distribution (PSD), respectively. CIMAP-P: Applies the framework to multi-angle, multi-spectral, space-borne polarimetric observations using POLDER data, integrating the surface conversion algorithm. Validation against collocated AERONET references shows strong agreement, with AOD MAD ranging from 0.015 to 0.042 and SSA MAD from 0.048 to 0.070 across reference wavelengths and 0.032 μm and 0.402 μm for the effective radius of fine- and coarse-mode PSD, exhibiting performance competitive with multiple Generalized Retrieval of Aerosol and Surface Properties (GRASP) algorithm configurations. Limitations of the CIMAP configurations are discussed, alongside potential expansions toward globally covering observations and possible improvements to constraint construction. Ultimately, the flexible and computationally efficient architecture of CIMAP, with its surface initialization capability, positions it as a highly promising inversion framework for maximizing the rich information content offered by next-generation polarimetric missions.Item type:Item, Access status: Open Access , DEVELOPMENT AND EVALUATION OF NOVEL AIR HANDLING UNIT CONTROL STRATEGIES FOR IMPROVED BUILDING DEMAND FLEXIBILITY AND THERMAL COMFORT(University of Oklahoma – Graduate College, 2026) Tiamiyu, Nurayn; SONG, LI; TANG, CHOON YIK; CAI, JIE; SHABGARD, HAMIDREZA; ZHANG, DONGBuildings account for a significant share of electrical power demand, up to 80% in some regions in the United States. With many flexible loads, buildings have the potential to reduce power demand during peak times and provide demand flexibility. Building enables demand flexibility through measures such as shifting energy use to another time and shedding of load. Applying advanced control strategies to heating, ventilation, and air conditioning (HVAC) loads allows buildings to reduce the electricity consumed during peak hours. While various demand control (DC) strategies have been employed in commercial buildings, they often fail to accurately shift and shed loads while maintaining occupant thermal comfort. Additionally, existing DC strategies face challenges in quantifying load reduction, achieving precise DC and ensuring even distribution of the reduced cooling load across thermal zones. These limitations highlight a critical research gap in effectively integrating demand flexibility with occupant comfort in building energy management systems. This dissertation develops and evaluates advanced control strategies for building demand control and thermal comfort using both simulation and experimental test beds. An innovative Energy Feedback (EF) control strategy and a novel Duct Static Pressure (DSP) cascade control strategy were first proposed, and their individual control performances were assessed using an experimental test bed. Subsequently, the integrated dynamic performance of the proposed EF and DSP cascade control strategies was evaluated against a baseline control strategy using a calibrated Modelica-based virtual test bed. Performance metrics such as settling time, relative error (RE), and the range of average zone temperature (RZT) are used as measures of quick response, control accuracy, and even cooling load sharing, respectively. The most effective strategy for minimizing the negative impact on occupant comfort during demand control is identified. The proposed control strategy demonstrated the fastest response and achieved precise load shedding, with a settling time of 0.03 hours, an RE of 0.01%, and an RZT of 0.00448°C. In contrast, the baseline strategy had a long settling time of 5.05 hours, an RE of 12.52%, and an RZT of 0.05°C. An optimization-based control strategy was incorporated into the EF Controller to provide effective setpoint control for achieving load shifting through precooling and load shedding during peak demand periods while minimizing electricity cost. The optimization-based control strategy enabled the modulation of the cooling load setpoint based on weather conditions and the building's daily load profile. This involved developing a reduced-order thermal model, estimating its parameters for control purposes, and developing and implementing the Optimization-Based EF Controller on the calibrated virtual test bed. The performance of the proposed Optimization-Based EF–DSP Cascade Control strategy was evaluated and compared with the baseline demand control strategy and a non-optimized EF–DSP Control strategy that utilized constant cooling load setpoints. The Optimization-Based EF Controller yielded a total electricity cost saving of 12.8% compared with the non-optimized controller, including an 8.7% reduction during the on-peak period and a 15.4% reduction during the off-peak period. The proposed Optimization-Based EF Control provides an effective approach for achieving demand-flexible HVAC operation by simultaneously reducing cooling energy consumption, minimizing electricity cost, maintaining occupant thermal comfort, and mitigating rebound effects. Finally, the performance of the Optimization-Based EF Controller was experimentally validated, and two practical implementation approaches for applying the optimization-derived EF setpoints on an HVAC system, namely the Schedule-Based EF Control and the Adaptive EF Control, were evaluated. Among the key contributions of this dissertation are the following: (i) the development and experimental evaluation of novel EF and DSP cascade control strategies to achieve accurate demand control and evenly distribute the reduced cooling load among thermal zones; (ii) the development and calibration of a Modelica-based virtual test bed that comprises of an AHU system and building envelope, and its application to the integrated performance assessment of the proposed control strategies; and (iii) the development and implementation of an optimization-based control framework that generates and communicates optimized control signals to the EF controller.Item type:Item, Access status: Open Access , Where Do Amateurs Go to Become Pros? A Comparison of the Current Competition Systems in Collegiate Esports to Traditional Collegiate Sport Environments(2024-04-04) Fisackerly, Wil; Hwang, YongjinResearchers are interested in how the collegiate esports model can follow that of the traditional sports talent pipelines. This piece seeks to conceptualize the manifestations of collegiate esports unique from traditional sports, as it integrates into the higher education model. In the current esports ecosystem, game developers own all intellectual property associated with the games and thus run the operations of leagues and/or tournaments themselves. Because of this, the pipeline seen in traditional sports is not transferrable or mimicked in the collegiate esports realm. The result is unique considerations for higher education administrators and coordinators regarding the retention of players and their recruitment from other institutions and professional circles. This line of research will lay the foundation for future studies in collegiate esports and assist in building the literature on the esports ecosystem.Item type:Item, Access status: Open Access , Mapping Historical Land-Use and Land-Cover Change in Central Oklahoma: Integrating Historical Geospatial Data and Modern Aerial Imagery, 1871-2023(University of Oklahoma – Graduate College, 2026) Anwar, Adam; Filley, Timothy R; Hoagland, Bruce W; Yang, AnniReconstructing long-term land-cover change in heterogeneous landscapes is constrained by the fact that no single archive captures more than a century of fine-grained change, and that historical geospatial data are often inaccessible to the researchers who could use them. This thesis integrates nineteenth-century Public Land Survey System records, twentieth-century historical aerial photography, and modern orthophotography into a continuous, patch-scale reconstruction of land-cover change in the Upper Finn Creek Watershed (~1,300 ha), McClain County, Central Oklahoma, spanning 1871 to 2023, and applies that reconstruction at the site scale within University of Oklahoma’s Kessler Atmospheric and Ecological Field Station (KAEFS). Eleven land-cover maps were produced using a consistent six-class legend, manual photointerpretation of historical sources, and object-based classification of recent imagery, with overall accuracy ranging from 80.7% to 91.8%. The reconstruction reveals three phases of change: rapid post-settlement cultivation expansion to a maximum of 57.6% of the watershed by 1937, subsequent cultivation decline and grassland-pasture increase, and pronounced woody expansion after 1981, when forest rose from a low of 189.7 ha (14.6% of the watershed) to 459.0 ha (35.3%) by 2023. These transitions shifted from broad, contiguous cultivation blocks to diffuse grassland-to-forest infilling consistent with eastern redcedar (Juniperus virginiana) encroachment. To make these products usable, the reconstruction was organized into an interactive web platform (K-Viz) and applied at KAEFS, where roughly 78% of the station changed land cover class more than once since 1871. Historical imagery independently placed 15 sampled eastern redcedar trees at a mean detection-based age of 14.0 years, substantially younger than their mean allometric age of 28.1 years, indicating that field-based ages may overstate the duration of encroachment influence. This work demonstrates that integrating survey records, archival photography, and modern imagery yields a historically grounded, spatially explicit, and accessible basis for interpreting present-day landscapes shaped more by their past than their current appearance suggests.Item type:Item, Access status: Open Access , Toward a Comprehensive Detection Algorithm for Atmospheric Blocking Events(University of Oklahoma – Graduate College, 2026) Fields, Jacob Lee; Furtado, Jason; Cavallo, Steven; Sakaeda, Naoko; Ruppert, JamesAtmospheric blocking is a phenomenon in which upper-level atmospheric flow becomes quasi-stationary for an extended period (i.e., several days to weeks), leading to some of the most impactful large-scale extreme weather events in the mid-latitudes including droughts, heatwaves, flooding, and cold air outbreaks. Although blocking has long been recognized, the physical mechanisms responsible for blocking formation, maintenance, and decay remain poorly understood, posing a challenge for improving long-range weather forecasts. A key obstacle in this effort is the ambiguity in how blocked flow patterns should be defined, resulting in the absence of a unified objective blocking detection algorithm. Using ERA5 reanalysis data, this thesis develops a novel objective algorithm to comprehensively detect and characterize blocking events in the Northern Hemisphere. Building upon established blocking identification metrics, the algorithm incorporates three dimensional tracking to approximate the dynamic spatiotemporal evolution of blocked flow patterns. It also accounts for blocking diversity by classifying events into ridge and dipole flow patterns. Applying this algorithm, a data set of Northern Hemisphere blocking events from 1950–2024 is established. The resulting climatology and trends of blocking characteristics are broadly consistent with previous studies that use alternative detection methods. The relationships between blocking and latent heating, as well as the influence of the El Niño Southern Oscillation and the North Atlantic Oscillation, are examined. These relationships exhibit notable differences from previous findings. Overall, the results suggest that a comprehensive blocking detection approach offers meaningful improvement over more simplified algorithms.