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Development of data assimilation for analysis of ion drifts during geomagnetic storms
No full textThe primary objective of this dissertation is to gain insight into geomagnetic storm effects at mid-latitudes induced by solar activity. Geomagnetic storms affect our everyday lives because they give rise to transient signal loss, data transmission errors, negatively impacting users of satellite navigation systems. The Nighttime Localized Ionospheric Enhancement (NILE) is a localized plasma enhancement that because it is not well understood, drives the design of satellite-based augmentationsystems.
To better secure operation of technological infrastructure, it is essential to build a comprehensive understanding of the atmospheric drivers, especially during solar active periods. Instrument measurements and climate models serve as valuable tools in obtaining information regarding the occurrence of space weather events; nonetheless, both sources exhibit quantitative and qualitative limitations. Data assimilation, an evolving technique, integrates measurements and model information to optimize the state estimations.
This dissertation presents developments in a data assimilation algorithm known as Estimating Model Parameters from Ionospheric Reverse Engineering (EMPIRE), and its applications in investigating the atmospheric behaviors under varying solar conditions. EMPIRE is a data assimilation algorithm specifically designed for upper atmospheric driver estimation of neutral wind and ion drifts at user-defined spatial and temporal scales. The EMPIRE application in this work aims to contribute to a more comprehensive understanding of the effects of the NILE.
EMPIRE utilizes the Kalman filter to optimize state calculations primarily based on electron density rates, provided by other data assimilation algorithms. Earlier runs of the algorithm used pre-defined values for the background state covariance cross time. To address model limitations under changing geomagnetic conditions, the algorithm is enhanced by concurrently updating the background state covariance during assimilation processes. Additionally, representation error is incor-
porated as a component of the observation error, and error analysis is performed through a synthetic-data study. Previously, EMPIRE fused Fabry-Perot Interferometer (FPI) neutral wind measurements, demonstrating increased agreement with validation neutral wind data. In this work, this approach is extended to augment Coherent Scatter Radar (CSR) ion drift measurements from Super Dual Auroral Radar Network (SuperDARN), providing additional insights into EMPIRE’s estimated field-perpendicular ion motion. For an in-depth exploration of storm-related NILE, both EMPIRE and another data assimilation method, the Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension coupled with Data Assimilation Research Testbed (WACCM-X + DART), is implemented for a storm event to test the proposed NILE driving mechanism. Furthermore, this dissertation introduces a Kalman smoother technique into the EMPIRE to enhance its ability to assess past storm events, and to explore the potential for algorithm improvements
Exploring the role of perceived trustworthiness on leader humility's effectiveness
No full textOver the last decade, several studies have uncovered the value of leader humility; however, these findings fail to consider the contextual factors that may alter when and how humility plays a role. The current study looks to bridge this gap, by exploring how the effectiveness of perceived leader humility on follower outcomes (i.e., state learning goal orientation, feedback seeking behaviors, and employee engagement) is contingent upon follower perceptions of the leader’s trustworthiness. Data was collected from 160 leader-follower dyads across a variety of industries, using a cross-sectional design. Results from the study reinforced earlier findings that leader humility is often associated with positive follower outcomes such as seeking more feedback and reporting a higher learning goal orientation; however, these results were contingent upon how trustworthy they perceived the leader to be. Additionally, the study found evidence that perceptions of leader trustworthiness were related to group-based differences (e.g., age, gender). Together, these findings serve as a reminder that studying leader behaviors in isolation often risks simplifying the complex reality most leader’s face when trying to implement leader behaviors and skills
In situ EXAFS studies of novel Palladium-based anode catalysts for direct ethanol and formic acid fuel cells
No full textIn this work we made nanoscale uniform deposition of Pd based anode catalyst on the transition metal Au (with atomic ratio Pd:Au=1:10) support of direct liquid ethanol
fuel cells (DLEFCs) and direct liquid formic acid fuel cells (DLFAFCs). Synthesizing
with uniform dispersion and catalyst nanoparticle dimensions understand the role of Pd
reaction on its support in the direct EOR (ethanol oxidation reaction) and FOR (formic
acid reaction) pathways, we performed in situ Pd K-edge X-ray absorption spectroscopy
measurements as a function of potential using a custom-designed flow cell with the
catalyst deposited on the glassy carbon window. We did in-situ EXAFS to better
understand the reaction mechanism of Pd1@Au10 anode catalyst with EOR and AOR in
nanoscale. Compared EOR with FOR electrochemical performance showed Pd@Au&C
played better in ethanol than HCOOH and more stable which the the current density can
reach up to 1216.25 mA·mg-1 Pd of EOR with Pd1@Au10&C in 1M KOH+1M EtOH
(CH3CH2OH) on the ethanol fuel cells (DLEFCs), and 3.56 times higher of the EOR
current compared with commercial Pd@
Characterization of Novel Concrete Formulations: High-Volume Fly Ash for Precast Industry Use and Non-Proprietary UHPC
No full textThe use of high-volume fly ash concretes can be challenging for high-early strength applications, such as in precast construction, largely due to potential delays in strength gain resulting from relatively lower heats of hydration of the underlying binder formulations. Considering that the use of higher levels of available fresh or landfilled fly ash as a replacement for traditional ordinary Portland cement (OPC) could result in more sustainable mix designs, a framework to develop novel, high-volume fly ash mixes with optimized dosages of commercial grade gypsum and accelerating admixtures to enhance early-age strength performance. Early-age mechanical properties such as compressive strength, modulus of rupture, and modulus of elasticity were evaluated starting within 24 hours of specimen preparation. Experimental test results were then characterized and subsequently analyzed relative to current design provisions to highlight the best performing trial mixes (with respect to the early-age strength target) and cases where current design provisions are either unconservative or overly-conservative with respect to the test data. Additionally, thermal properties of concrete produced with fly ash were tested with two different curing environments, along with using code equations to determine if high volume fly ash provides a higher thermal resistance compared to OPC concrete. Wrapping up cementitious replacement with non-proprietary ultra high-performance concrete (UHPC) for transportation structures. Then reproducing mixtures to ensure target compressive strength values could be reached. Followed by increasing batch size to a larger quantity using a large mixer to create full-size specimens
In situ EXAFS studies of novel Palladium-based anode catalysts for direct ethanol and formic acid fuel cells
No full textIn this work we made nanoscale uniform deposition of Pd based anode catalyst on the transition metal Au (with atomic ratio Pd:Au=1:10) support of direct liquid ethanol
fuel cells (DLEFCs) and direct liquid formic acid fuel cells (DLFAFCs). Synthesizing
with uniform dispersion and catalyst nanoparticle dimensions understand the role of Pd
reaction on its support in the direct EOR (ethanol oxidation reaction) and FOR (formic
acid reaction) pathways, we performed in situ Pd K-edge X-ray absorption spectroscopy
measurements as a function of potential using a custom-designed flow cell with the
catalyst deposited on the glassy carbon window. We did in-situ EXAFS to better
understand the reaction mechanism of Pd1@Au10 anode catalyst with EOR and AOR in
nanoscale. Compared EOR with FOR electrochemical performance showed Pd@Au&C
played better in ethanol than HCOOH and more stable which the the current density can
reach up to 1216.25 mA·mg-1 Pd of EOR with Pd1@Au10&C in 1M KOH+1M EtOH
(CH3CH2OH) on the ethanol fuel cells (DLEFCs), and 3.56 times higher of the EOR
current compared with commercial Pd@
Effect of Temperature on Salmonella Growth During Sprouting and Post-Harvest Storage of Broccoli Sprouts
No full textSprouts, such as broccoli, are a popular and nutritious food source. The microbial contamination of sprouts is often associated with seeds. The optimal conditions for germination and growth of seeds are similar to those needed for the proliferation of microorganisms such as Salmonella and Escherichia coli. These conditions, along with the fact that sprouts are usually consumed raw or lightly cooked contribute significantly to the risk of sprouts in causing foodborne illness outbreaks. This study evaluated the effect of temperature on the growth of Salmonella in broccoli sprouts during sprouting and post-harvest storage. The impact of pathogen load and seed treatment were also examined. Five hundred grams of broccoli seeds inoculated with 1 or 5 log CFU/g of Salmonella were treated either with water or 20,000 ppm Ca(OCl)2 for 15 min. Treated seeds were sprouted in glass jars at 4°C for 21 days or 20°C for 7 days. Harvested sprouts were stored at 4, 7, 10 for 21 days or at 25°C for 7 days. Samples were taken for analysis of Salmonella levels by plate count and culture enrichment. For seeds inoculated with a high or low level of Salmonella and treated with water, the pathogen grew and reached ~8 logs during sprouting at 20°C, while it decreased by 3 or 2 logs, respectively, during 21 days of sprouting at 4°C. For sprouts grown at 20°C, Salmonella population did not change during postharvest storage regardless of storage temperature. For sprouts grown at 4°C, no Salmonella proliferation was observed when the harvested sprouts were stored at 4, 7, or 10°C. But during storage at 25°C, the pathogen increased by 4 or 2 logs in sprouts grown from seeds inoculated at the high or low level, respectively. Seed treatment with 20,000 ppm Ca(OCl)2 reduced Salmonella on seeds by less than 1 log CFU/g. Salmonella growth during sprouting and storage of sprouts grown from Ca(OCl)2 treated seeds followed the same trend as that observed in sprouts grown from seeds treated with water. Sprouting at low temperatures inhibited pathogen proliferation. It was concluded that maintaining the cold chain (at below 10°C) during storage of sprouts is critical to prevent pathogen regrowth
Investigating Variables Influencing Diagnostic Discrepancies Between the ADOS-2 and SRS-2
No full textThis study aims to investigate variables that may influence the alignment between the ADOS 2 and SRS-2 assessment scores in children with autism spectrum disorder (ASD). Specific variables include gender, age, race, ethnicity, comorbid diagnoses, family history of ASD, intellectual functioning, and language skills. A sample of 165 children aged 2 to 17 was analyzed using Pearson’s r correlation coefficients to assess the alignment of total and domain scores. Additionally, univariate moderation analyses were conducted to explore the impact of demographic and clinical factors on the relationship between the SRS-2 total T-score and ADOS-2 total CS. Findings reveal no significant linear correlations between the ADOS-2 total CS and SRS-2 total T-score, nor between their specific domain scores, contrary to our initial hypotheses. However, moderation analyses indicate that gender identity significantly impacts the relationship, with stronger associations observed in girls compared to boys. This suggests that clinicians should be aware of discrepancies between clinician observations and parent reports, advocating for a multi-method assessment approach. The study emphasizes the need for tailored diagnostic strategies that consider individual differences, enhancing diagnostic accuracy and intervention efficacy for diverse ASD presentations. Ultimately, this research highlights the complexities of ASD assessment and underscores the importance of integrating multiple informants and assessment modalities for a comprehensive understanding of each child's unique profile. Future direction for research and clinical work are discussed
Optimal Power Allocation Over Gaussian Broadcast Channels
No full textFor Gaussian broadcast channel, the maximal capacity region can be achieved. A power assignment over Gaussian broadcast channels splits the power budget at the access point among all user channel pairs subject to per-channel upper bounds on the sum power, and is optimal if it maximizes the weighted sum-rate (WSR). The capacity region reaches its maximum when the weighted sum rate over Gaussian broadcast channels is maximum, making this a classic and significant problem within the wireless communication community.This thesis begins by addressing the problem of maximizing the WSR. In the single Gaussian broadcast channel, the traditional methods for computing optimal power assignment have utilized Lagrange multipliers for convex optimizations, with computational complexities ranging from to . A more recent approach has reduced this to . We propose a new geometric algorithm for optimal power assignment over a single Gaussian broadcast channel. This algorithm operates with linear complexity, provided all users are pre-sorted by weight or noise. Our method offers an intuitive water-filling interpretation, which subsequently allows us to develop a water-filling algorithm for optimal power assignment over parallel Gaussian broadcast channels. The complexity of this algorithm remains linear in terms of the number of user-channel pairs, assuming pre-sorted users by weight. For computing an optimal power assignment over parallel Gaussian broadcast channels, no explicit time complexity is known in the literature. Due to power constraints imposed by the base station, energy efficiency is an essential metric to evaluate the performance of these transmissions. Following the WSR optimization, we then tackle the problem of maximizing the weighted energy efficiency (WEE). In this context, a power assignment over parallel Gaussian broadcast channels involves splitting a power budget at the access point among all channel-user pairs, subject to per-channel upper bounds on the sum power. This allocation yields specific rate allocations to each channel-user pair. The WEE is defined as the ratio of the weighted sum rate to the sum-power plus a fixed positive overhead. The Max-WEE problem seeks a power assignment that maximizes the WEE. Although special variants of Max-WEE, such as those with unit weights or two users per channel, have been extensively studied, existing algorithms for these variants lack known bounds on running time. This is primarily because they rely on general-purpose methods for fractional programming.In this thesis, we derive fundamental properties and closed-form expressions for the maximum WEE. Building on these theoretical foundations, we devise a simple yet effective water-filling algorithm for solving the Max-WEE problem. Our algorithm, under the assumption that all users are pre-sorted by weight, has the linear complexity in terms of the number of channel-user pairs. Furthermore, under a mild pre-sorting condition, we develop an additional linear-complexity algorithm for the Max-WEE problem, subject to rate demand constraints.Overall, our research presents novel and efficient algorithms for power assignment over Gaussian broadcast channels, including the algorithms for maximizing the WSR, and the algorithms for maximizing the WEE. These algorithms demonstrates significant potential for practical applications in wireless communication systems. Our work offers a comprehensive solution to fundamental problems in the field and paves the way for further advancements in wireless communications
Developing Practical Tools and Algorithms for Biomedical Image Compression and Analysis
No full textBiomedical imaging is fundamental to advancing medical research and clinical diagnostics, offering critical insights into complex biological structures and processes. However, the inherent complexity and variability of biomedical images demand the development of specialized tools and algorithms for accurate and efficient analysis. In this thesis, we present a suite of solutions aimed at addressing two central challenges in biomedical imaging: efficient data storage and advanced image analysis.First, we develop high-ratio compression techniques that drastically reduce the storage requirements of biomedical images while preserving their analytical fidelity. These methods enable us to archive and manage vast datasets more efficiently, without compromising the critical details necessary for research and diagnostics. By minimizing compression artifacts, we ensure the integrity of the images, allowing for fast data transmission and seamless long-term storage without loss of quality.For image analysis, we introduce advanced algorithms that significantly enhance the precision and performance of key imaging tasks. Our segmentation methods, leveraging multi-scale non-local correlations, allow us to accurately delineate complex tissues and cellular structures in challenging biological images. In the area of neuronal tracing, we create algorithms that improve the accuracy of mapping intricate connections in densely labeled multi-spectral datasets, providing deeper insights into biological networks. Furthermore, we propose a robust image registration algorithm that corrects alignment errors in multi-modal and longitudinal datasets, ensuring precise and reliable integration for downstream analyses.By combining these innovations, we offer a practical toolkit that streamlines both the storage and analysis of biomedical images. Our work has the potential to significantly enhance research and diagnostic processes, providing tools that improve efficiency, accuracy, and scalability in biomedical imaging
An Examination of the Bidirectional Associations between Sleep Quality and Binge Eating Using Ecological Momentary Assessment
No full textBinge eating (BE) is associated with impairments in psychosocial functioning and poor treatment response, and BE commonly occurs in at-risk populations including female adults. BE occurs transdiagnostically across the ED spectrum and maintains other ED behaviors (e.g., dietary restriction, purging). Thus, it is important to research factors that maintain BE over time. Research suggests that poor sleep quality (e.g., difficulty falling or staying asleep, restless sleep) could contribute to BE persistence due to potential bidirectional associations between sleep quality and BE and that negative affect (NA) and the time that BE occurs could explain the BE-sleep association. To extend this research, the current study used ecological momentary assessment (EMA) to examine 1) between- and within-person bidirectional associations between BE and sleep quality and 2) if momentary NA (assessed between sleep and BE) mediates and if the timing of BE moderates the within-person BE-sleep quality associations. For the current study, adults assigned female at birth (N=57) with recurrent BE (at least twice a week for the past three months) self-reported BE, sleep quality, and NA at baseline and over a 14-day EMA period. Hierarchical regression analyses found that higher BE severity at baseline significantly predicted lower sleep quality averaged over the EMA period (p=0.02) but was only approaching significance after controlling for baseline sleep quality and depression (p=0.06). Between-person aggregated BE severity over the EMA period was not significantly associated with aggregated sleep quality and sleep quality at baseline and aggregated was not significantly associated with aggregated BE severity or more frequent BE over the EMA period (p’s>0.05). Multilevel models found significant bidirectional associations within-person higher BE severity and poor sleep quality, such that higher BE severity predicted worse sleep quality later that night (p=0.03) and worse sleep quality predicted higher BE severity later that day (p=0.03). In contrast, poor sleep quality did not significantly predict an increased likelihood of BE and there were not significant differences in sleep quality between BE and non-BE days (p’s>0.05). Multilevel modeling also found that intermediate ratings of NA did not mediate the within-person associations between sleep quality and BE severity, sleep quality did not mediate the within-person association in which NA predicted BE severity, and BE timing did not significantly predict sleep quality or moderate within-person BE severity predicting poor sleep quality (p’s>0.05). This study was the first to use EMA to test the bidirectional associations between BE and sleep quality while also accounting for NA and BE timing. Results suggest that among AFAB adults BE severity may lead to worse sleep quality, independent of NA and BE timing, and worse sleep quality may lead to higher BE severity on days with BE, independent of NA. Findings from the current study support integrating interventions for sleep disturbances into treatments for BE-spectrum EDs