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Electro-Chemo-Mechanics of Several Pure Metal Anodes for Rechargeable Batteries
No full textBy enabling constant access to electronic devices and seamless communication capabilities, energy storage devices have greatly improved our lives. With advances in technology over time, the demand for larger capacity and longer lifetime energy storage devices continues to increase. Still, technological hurdles, such as safety issues, kinetic limitations, and material degradation over time, remain that must be addressed to enable the next generation of high-capacity batteries. While battery research primarily has focused on improvements in electrochemistry, higher capacity technologies have necessitated a shift to the focus towards more multidisciplinary approaches in research.
This dissertation explores battery materials from a mechanical and coupled electro-chemo-mechanical perspective by evaluating various materials��� intrinsic mechanical properties and analyzing their mechanical behaviors during electrochemical cycling. Fracture behavior of sodium was investigated, highlighting its extreme ductility and flaw-insensitivity at room temperature. Furthermore, calcium was mechanically assessed at various length scales, which unveiled calcium���s relatively limited ���indentation size effects��� as compared to counterparts of Li and Na metal, likely due to its relatively high melting point and relatively low dislocation spacing. Additionally, various lithiated compositions and phases of Li���Mg alloy anode were mechanically evaluated via nanoindentation. XRD patterns on post-mortem lithiated Mg samples revealed that Li���Mg alloy anodes undergo a single-phase transformation electrochemically, from the Mg-rich �� phase (HCP) to Li-rich �� phase (BCC). Furthermore, the nanoindentation hardness and elastic modulus of Li���Mg was found to significantly decrease with increasing lithium concentration. This dissertation also investigates the mechanical behavior of pure lithium metal anodes under various electrochemical conditions. These tests uncovered a marked current-dependent mechanical stress response of lithium. Keeping in mind that the processes of electrodeposition of lithium and the growth of Li dendrites, while distinct, share similar underlying mechanisms, these measurements provide important insight into understanding the growth of Li dendrites.
Overall, this dissertation investigates the mechanics of various battery anode materials that exhibit an intimate interplay between mechanics and electrochemistry; their overall performance in practice is thus highly dependent on their mechanical behavior. As such, this dissertation provides general insight into understanding energy storage systems in terms of the intricate interactions between mechanics and electrochemistry
University Faculty Perceptions About Disability, Accommodations, and Access
No full textOpportunities and expectations for students with disabilities to earn a postsecondary degree have grown over recent decades. Despite positive improvements, disabled students lag behind non-disabled peers in degree attainment. Simultaneously, growing numbers of disabled students are enrolling with increasingly complex experiences, including a significant growth in mental health conditions among college students, and institutions of higher education are struggling to respond.
Faculty and staff in higher education have noticed these trends, but have done little more than keep up with increasing demands. Though prior researchers have long focused on the experiences of students, considerably less effort has been put into understanding the experience of faculty or staff involved in creating disability access. Faculty experiences are essential to understand because of their critical role in disability access.
Prior research on faculty experiences teaching disabled college students has largely featured survey-based, quantitative designs that have provided valuable aggregated insights, but offer little context of their faculty participants or the factors behind their responses. The purpose of this study was to qualitatively assess faculty experiences and perceptions of teaching students with disabilities. Faculty participants with at least five years of experience were recruited from a single, culturally bound university.
This study yielded data that add new insights to the literature, and implications for practice. The findings identified faculty hold strong, paradoxical views about bureaucratic systems that shape how disability access occurs in a university setting. Specifically, they have a dynamic and interactive relationship with the systems at hand, which are modified through relationships and trust of those involved. Faculty were generally supportive and positive of disabled students and disability resource staff, while simultaneously questioning and fearing the bureaucratic system deployed to ensure disability access. This study situated participant perspectives relative to their experiences navigating institutional systems, and therefore adds factors related to bureaucracy and trust to the literature, while also confirming a variety of prior researcher���s findings. While this study contributes new insights to the literature and best practices, further research is needed to ensure faculty are adequately prepared and supported when teaching disabled students
Experimental Studies on Measurements in Oil-Gas-Water Flow and Turbulent Flow Field in Wind Generated Water Waves
No full textThis thesis presents experimental studies in multiphase flows with two main topics: (1) measurements in oil-gas-water flow using the fiber optic reflectometer (FOR) technique; (2) turbulent flow field in wind generated water waves.
The application of the single-probe fiber optic reflectometer (FOR) technique has been investigated to determine the velocities and size of oil droplets rising in a static water column. The droplet velocity, residence time, and chord length measurements were validated by comparing with the results from high-speed images using the bubble image velocimetry (BIV) technique and the image gradient method. Subsequently, the application of the FOR technique has been extended to oil-gas-water three-phase flows by investigating the accuracy of phase discrimination and measuring the velocity and size of bubbles and droplets. The technique was expanded to identify water, air bubbles, and oil droplets and to quantify the velocity and size of bubbles and droplets in an oil-gas-water three-phase flow through the processing of acquired signals.
In the second part of this thesis, the turbulent flow field in wind generated waves has been studied. The experiments were performed in a wind-wave-current flume with three freestream wind speeds using a particle image velocimetry (PIV) technique. The Bond number and the shear velocity-fetch based Reynolds number were found to correlate the wind wave regimes well. The turbulent dissipation rates were determined based on spatial gradient of instantaneous velocities and one-dimensional velocity spectrum in temporal space. In addition, the turbulent kinetic energy (TKE) budget including its production, dissipation, advection, and turbulent transport was presented. The production-dissipation ratio increased significantly as the wind speed increased, likely attributed to the increased roughness over the substantial coverage of micro-breaking waves. Subsequently, the turbulent flow filed beneath the water surface has also been investigated under the same experimental conditions used for airflow measurements. The friction velocities were estimated from both air- and water- side measurements with the mean velocity profile and the eddy-correlation methods. The result from the comparison of different methods is useful in determining the scaling of water side turbulence such as dissipation rate of turbulence kinetic energy with the air side velocity measurements, or vice versa
Sustainable Plastic Waste Recycling: Economics and Circularity Metrics
No full textOver the past few decades, the surge in plastic waste has created an urgent need for sustainable recycling methods to align with the Circular Economy (CE) goals. Process systems engineering (PSE) models have emerged as invaluable tools in plastic waste recycling, facilitating sustainability-driven problem-solving, optimizing process frameworks, and guiding the journey toward environmentally conscious circular solutions. This work proposes a robust mathematical model to optimize different recycling technologies, including pyrolysis, gasification, mechanical recycling, and incineration, striking a balance between economic feasibility and contribution to circular economy objectives. The model recognizes the potential of chemical recycling derivatives as versatile raw materials for various applications, including methanol synthesis, ammonia synthesis, hydrogen production, and more. It reveals the possibility of plastic waste yielding energy and valuable products through open- and closed-loop recycling pathways. A novel degree of circularity metric (DOCI) is enlisted to assess these pathways' contributions to the CE critically. It integrates various vital metrics, ensuring a holistic evaluation of each recycling route, encompassing material utilization, energy demand, water usage, waste generation, carbon footprint, economic viability, co-product utilization, recyclability, quality of the product, and technology maturity. An illustrative case study involving 20 scenarios for recycling plastic waste was evaluated and analyzed against incineration as a base case. The optimization results reveal that pyrolysis refinery technology offers promising avenues for producing sustainable fuels and olefins by tripling the base case profitability and more than 25% improvement in the total degree of circularity. Moreover, seeking the maximum possible circularity can be achieved by combining methanol synthesis and the pyrolysis refinery. This will provide an overall net profit of $29 M USD/y and a 44% enhancement of the DOCI of the base case. The flexible weight allocation for DOCI individual indicators in the optimization process emphasizes the significance of tailored solutions aligned with system-specific needs. Comparisons between plastic waste and conventional feedstocks are carried out, unveiling a product-dependent cost-effectiveness landscape. Capacity-level sensitivity analysis reveals that the optimal solutions consistently outperform the base case regarding circularity and profitability
Probabilistic Clustering Methods for Complex Data and Related Topics
No full textProbabilistic clustering involves identifying mutually exclusive subsets of data in a probabilistic manner by characterizing the probability distribution on the space of partitions, enabling uncertainty quantification. Random partition models serve as prior probability models for probabilistic clustering, which are closely connected to Bayesian nonparametric models involving discrete random structures. This dissertation aims to contribute to the existing literature on probabilistic clustering and related topics by introducing new key concepts and novel methodologies.
First, we offer new perspectives on exchangeable random partition models based on the concept of balancedness and risk equilibrium/penalization priors with respect to a loss function. The balancedness property provides a better understanding of what probabilistic clustering model works better and what does not for different applications. The notion of risk equilibrium and penalization priors, which are not limited to clustering problems, provide the development of objective and regularized prior model probabilities in light of the effect of loss functions.
Next, we suggest Bayesian hierarchical models with non-exchangeable random partition models associated with a graph that represents complex dependence structures. We start by introducing the low-rank horseshoe prior based on random spanning trees, which simultaneously detects structured sparsity and smoothness of high-dimensional parameters associated with the graph. Also, we introduce the graph product partition model where a probability of partition is defined as a product of cohesion functions capturing internal and external connectivity. This formulation does not rely on graph generative assumptions and can be used as a robust alternative for the probabilistic clustering of graphs with node attributes.
Finally, we propose the logistic-beta process, whose logistic transformation yields a stochastic process with common beta marginals that have significant computational benefits. It has great potential in applications to dependent Bayesian nonparametric models involving beta distributions, related to probabilistic clustering of non-exchangeable data. We illustrate with a Bayesian density regression problem based on the newly proposed logistic-beta dependent Dirichlet process
Cryo-Em Structures of Single-Strand RNA Pepeviruses and the Interaction with Their Host Receptor, Type IV Pilus
No full textPositive-sense single-stranded RNA bacteriophages (ssRNA phages) have recently been reclassified because of the increase in the number of genomes discovered in metagenomes and metatranscriptomes. ssRNA phages infect gram-negative bacteria and are known to be structurally and genetically simple RNA viruses. Their infectivity is dependent on host retractile pili. Despite the discovery of ssRNA phages since 1960, only the structures of mature virions for F-pilus-specific E. coli phage (coliphage) MS2 and Q�� were solved by cryo-electron microscopy (cryo-EM). Mature virions of coliphages are composed of a single copy of maturation protein (Mat) and a capsid containing a single strand of genomic RNA (gRNA). Mat is an essential protein required for phage adsorption onto pili. However, ssRNA phages are diverse, as they infect several gram-negative bacteria and target different types of pili. Pseudomonas aeruginosa pepeviruses, PP7 and LeviOr01, infect their hosts through type IV pili (T4P). Here, we present the cryo-EM structures of pepevirus PP7 and LeviOr01, which are distinct from those of coliphages. These T4P targeting phages unexpectedly contain two Mat proteins in mature virions. One of the Mat proteins is internalized (MatIN) inside the virion, whereas the other is exposed (MatEX) for T4P binding. LeviOr01 exhibits plasticity in its assembly through Mat, in which particles with defined gRNA containing only a single MatIN and no Mat proteins are observed. Although mature PP7 virions always consist of two Mat proteins, a region of PP7-gRNA surprisingly displays high plasticity by adopting several conformations. This discovery underlines the importance of structural studies in mature virions and suggests that the structural simplicity of ssRNA phages might require reconsideration. We also solved the complex structure of PP7 bound to purified T4P from PAO1 to better understand host recognition and the entry mechanism. These findings provide insights into the exploitation of pepeviruses for phage therapy and biotechnological applications
Immediate and Lifelong Consequences of In Utero Exposure to Alcohol: A Systemic and Multi-organ Approach
No full textPrenatal alcohol exposure (PAE) has an estimated prevalence of ~8 to15% in North America, making it the largest single cause of neurodevelopment disabilities and growth deficits. There is increasing recognition that Fetal Alcohol Spectrum Disorders (FASDs) is a ���whole-body��� disease, impacting the health of the individual immediately in utero and persistently throughout the lifespan, likely due to epigenetic alterations and stem cell reprogramming. To gain a better understanding of the more immediate consequences of PAE, I first characterize the consequences of PAE on the placental transcriptome, correlating these changes to observed differences in fetal growth and placental blood flow in a murine model. Secondly, I utilize a murine neural stem cell (NSC) culture model equivalent to mid-1st to 2nd trimester in humans to study the adaptive role of ethanol sensitive Gag-Like Proteins (GLPs) in NSCs. In addition, I also focus on the lifelong impact of PAE, characterizing baseline health differences in young adult (5 mo) PAE rats and identifying an association of a pro-inflammatory state of mesenteric adipose tissue and liver with changes in behavior. Subsequently, I examine transcriptomic differences in the enteric organs (mesenteric adipose tissue and liver) that occur as a response to a health stressor (cerebrovascular ischemic stroke), correlating differences in response to observed impaired recovery post-stroke. Overall, this dissertation focuses on examining PAEinduced (mal)adaptations at different critical time points in development and in life
Effect of Overnight Storage Conditions on Dimensional Stability of Conventional Injection Molded, 3D Printed and Milled Complete Dentures
No full textStatement of problem: In modern prosthodontics the fabrication method of complete dentures has become more diverse than ever with the introduction of 3D printing and milling manufacturing. Despite the variety of manufacturing methods developed, the storage recommendations have remained virtually unchanged and untested for new manufacturing methods. Water storage has traditionally been advised at nighttime to prevent denture base distortion through the loss of moisture in the acrylic resin matrix. With the advent of CAD/CAM 3D printed denture bases and Milled denture bases from solid pucks of preprocessed acrylic the necessity to store dentures in liquid when not in use to the authors knowledge has remained untested.
Purpose: The aim of this study was to evaluate whether there is any typical deformation pattern of Injection molded, 3D printed and milled complete dentures stored in different overnight storage conditions for 14 days.
Materials & Methods: One edentulous maxillary typodont model was used as reference for fabrication of n=60 samples of identical digitally designed denture bases. Each denture base was approximately 2 mm thick and n= 20 samples were fabricated from each respective material; Ivobase injection molded pink hybrid denture base resin, Sprintray denture base EU 3D printed resin and Avadent Milled denture bases PMMA Puck LIGHT ��� Universal Shoulder. n=10 samples from each material group were randomly assigned to either a wet or dry storage group. All denture bases were submerged in 37 ��C Water bath for 12 hrs. and alternated for 14 days between their respective storage conditions and heated water bath simulating the oral cavity. Samples were scanned at 3-time intervals time ���0��� (T0), on the 7th day (T1), on the 14th day (T2). Scans were measured for deviations from the reference scan. Statistical analysis performed using Kruskal-Wallis with Bonferroni corrections (����=0.05) for between group differences and Related Samples Friedmans Two-way analysis of variance by ranks for within group differences.
Results: The Group 2 denture bases fabricated from the Ivobase and placed in the dry storage conditions demonstrated greater dimensional change with statistically significant differences in RMS value compared to the Group 1 Ivobase wet storage conditions (p< 0.003). In addition, the Group 3 & 4 Sprintray (wet/dry) demonstrated lower RMS values (p<0.007 & p<0.015) and better stability over time compared to the Group 2 Ivobase dry storage at time points T0-T2. The Avadent milled dentures demonstrated greater RMS value and distortion than the Group 1 Ivobase wet (p<.001), Group 3 Sprint ray wet (p<.001) and Group 4 Sprintray dry (p<.001). There was no significant difference in RMS value between the dry storage and wet storage of the Avadent denture bases.
Conclusions: Statistically greater dimensional changes were found in the dry storage group of Ivobase denture bases compared to the wet denture bases. Sprintray 3D printed denture bases exhibited no statistically significant dimensional changes in 14 days when stored in wet or dry conditions. Avadent milled denture bases exhibited no statistically significant dimensional changes in 14 days when stored in wet or dry conditions, but experienced greater dimensional change compared to Ivobase wet and Sprintray wet/dry storage conditions. All groups regardless of timepoint or storage conditions experience dimensional changes less than <1mm
"Trust to Us, the Union Men of the South": The 1866 Southern Loyalist Convention and the Fight for Reconstruction
No full textIn 1866, unconditional Unionists of the South, who had remained loyal to the United States during its civil war, convened in Philadelphia to express their displeasure with President Andrew Johnson. In their view, Johnson���s willful inaction enabled traitors rather than Unionists to continue dominating Southern politics in the aftermath of the war. If the Union defeated the Confederacy but its supporters remained in power, Unionists��� staunch devotion to the Union was rendered pointless. The 1866 Southern Loyalist Convention was the culmination of years of political struggles. Scholarly literature on Southern Unionists is extensive, yet historians have overlooked the significance of this convention. This thesis argues that the convention utilized a narrative of suffering that Southern Unionists employed consistently throughout the Civil War and Reconstruction. In various pamphlets published early in the crisis, Southern Unionists voiced their disapproval of secession and had articulated their perspectives on national affairs. By concentrating those disparate voices in a single location, the Southern Loyalist Convention amplified long standing whispers of Unionist dissatisfaction. Collectively, these broadsheets pointed to deep divisions among Unionists, generally involving disagreements about African American enfranchisement. Despite the internal divisions that ultimately prevented them from forming a powerful Unionist coalition, Southern Unionists were consistent in a few key ways. They insisted upon their undying support for the Union, demanded the implementation of their agenda, and constructed a powerful narrative of their own suffering. Their mutual misery, in fact, became the foundation upon which Unionists built relationships with each other at this convention. This thesis considers how the 1866 Convention contributed to a post-war narrative that historians have labeled the ���Won Cause��� memory of the war
A Test for Stationarity Using a Local Average of the Autocovariance of the Discrete Fourier Transform
No full textThe discrete Fourier transform of a second-order stationary process has been found to be asymptotically uncorrelated, a property which can be leveraged to create a test statistic for stationary. Building off this, we propose a version of the test where the test statistic is created by taking the local average over several partitions of the canonical frequencies, standardized using the heteroskedicity-consistent standard errors. Under the null hypothesis of stationarity this test statistic will be distributed as the sum-of-F distributions, while under the alternative hypothesis of local stationarity it will be distributed as the sum of non-central F distributions. Simulation studies show that locally averaging the DFT can result in a significant increase of power compared to globally averaging the DFT, and performs similarly to the Wavelet Packet Test, another contemporary test for stationarity