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Synthesis and Electrochemical Characterization of Alkali Metal Borides as Redox Active Anion Frameworks
Get PDFRedox activity in intercalation cathodes is commonly attributed to changes in oxidation states of transition metal ions. Recently, a growing body of evidence revealed that the redox activity of oxygen contributes to the capacity of some known cathodes. We focused on designing an oxygen free intercalation cathode with redox-active anions. In order to overcome the entropic driving force for the decomposition of a charged redox active anion cathode, we looked for chemistries with solid (no gases) possible decomposition products. Additionally, the involvement of anions in a network of covalent bonds with shared electrons was considered as a possible way for the structure stabilization on anion oxidation. Rather than forming a localized hole on an anion, the whole network would be oxidized. Secondly, the involvement of an anion in multiple strong covalent bonds can hinder the decomposition kinetically. The ternary hexaboride type sodium pentaborocarbide both, chalcogenide and transition metal free, was cycled reversibly electrochemically and systematic changes of unit cell parameters were observed on the framework oxidation. For the first time, a hexaboride type carboboride anion framework was reversibly electrochemically cycled almost at elevated room temperatures. In the search for chemistries beyond lithium ion batteries the synthesis of magnesium pentaborocarbide was carried out by aliovalent ion exchange of the parent sodium pentaborocarbide structure from which density functional theory predicts excellent magnesium ion conductivities. Trilithium nonaboride was synthesized and electrochemically characterized as a weak anode material which supports a small amount of intercalation and deintercalation of lithium at room temperature demonstrated by charge discharge and cyclic voltammetry
Experimental Tests and Numerical Study of Trajectories of Different Types of Dropped Objects
Get PDFIn marine and offshore engineering, dropped objects, such as drill pipes, anchor chains, containers and some small parts, can accidentally fall into the water from ships or offshore platforms, causing casualties on deck or damage to underwater equipment. Damaged equipment can further harm the environment, such as oil spills from damaged wellheads. Therefore, for safe engineering and environmental protection reasons, we need to develop methods and tools that can predict the trajectory of dropped objects.
In this dissertation, we first study containers dropped from ships. More and more containers are falling into the sea due to bad weather. Containers lost at sea can negatively impact shipping companies, traders and consumers, and the environment. The problem of locating and recycling discarded containers is a challenging engineering problem. We design and implement a series of model tests of small-scale container models to study their falling trajectories for retrieving. We first build a standard 20-foot container model in SOLIDWORKS. Then, export the three-dimensional (3D) geometric model in STL (Standard Tessellation Language) format to the Stratasys F170 Fused Deposition Modeling (FDM) printer. A total of six models, which are made of Acrylonitrile Styrene Acrylate (ASA), are printed for testing purposes. They represent three different loading conditions, different densities, and centers of gravity (COGs). The physical models were dropped into the towing tank of the University of New Orleans (UNO). It was found from the experimental tests that the effect of the initial position after sinking would lead to a certain initial rotational speed, which had a great influence on the lateral displacement, which in turn affected the final landing position. And it can be further observed that these models typically flip for approximately 0-5 cycles during a drop in a water depth of 1.8 meters. This series of model tests not only provided experimental data for the study of the trajectory of box-shaped objects, but also provided valuable references for offshore salvage operations and pipeline layout design.
Another focus of this dissertation is the numerical study of the trajectory of cylindrical objects. We first propose a state-space model of a dropped cylinder based on Aanesland\u27s (1987) 2D equations of motion and Xiang at al. (2016)\u27s 3D equations of motion. Then we further investigate the heave-pitch coupling term in 3D theory, which was ignored in 2D theory, and find that this term significantly affects the trajectory of dropped cylindrical objects. Then in the state-space model, the original deterministic trajectory is described as a stochastic process by adding small perturbations that satisfy Gaussian distribution to the initial state of the dropped cylinder. Second, three probabilistic methods of state estimation, namely Monte Carlo (MC) method, unscented method, and Cubature method, are used to predict the trajectory envelope of dropped objects and provide reliable results. The MC method is a classical method for solving stochastic problems and has been applied to study the motion of dropped objects. However, it always requires a sufficiently large sample, resulting in a large amount of computation, which is not suitable for practical applications, especially real-time monitoring. The simulation results show that two other advanced statistical methods, unscented method, and Cubature method, give similar results compared to the MC method, but they consume much less computation time. Therefore, the first two methods significantly increase their application possibilities, providing an effective way for envelope prediction of dropped cylindrical objects in marine transportation or marine operations. Furthermore, the Cubature method requires no additional tuning compared to the unscented method, reducing the computation time, making it easier and more suitable for dynamic and real-time risk assessment of dropped objects for maritime transport and installation
Thermo-Mechanical Process Modeling of Friction Stir Deposition of Ti6Al4V Alloy
Get PDFAdditive friction stir deposition (AFSD) is a novel metal additive manufacturing (AM) process that enables fast, scalable manufacturing of metal and alloys by utilizing friction stirring and metal feeding processes together. Thermo-mechanical process optimization during the AFSD process is very critical for ensuring better quality control, improved microstructure, and desired thermo-mechanical properties. In this study, the numerical models based on computational fluid dynamics are developed to investigate spatial thermal and flow behaviors such as temperature evolution, wall heat flux, material velocity, pressure distribution, etc. in the metal printing of Ti6Al4V alloy via the AFSD process. The material conversation law with a steady state flow is applied where the heat generation is measured in considering stacking/ slipping conditions. To measure the temperature evolution, the steady state conservation of energy equation is formulated where viscous dissipation is implemented due to plasticity. The numerical results show the material deposition as a highly viscous flow where the temperature evolution is optimized around 20% below the melting temperature. Similarly, wall heat flux, material velocity, pressure distribution, etc. are exhibited with varying process conditions. Finally, the numerical model is validated with the published literature and the convergence study is performed for reducing the numerical cost
Machine Learning Based Design Methodology for Electric Machines
Get PDFReplacing a portion of high-energy Permanent Magnets (PMs) with low-energy PMs, generally known as hybrid PM machines, is an effective solution to lower the manufacturing cost in PM machines. However, partial removal of high-energy PMs without proper design adjustments could lower the overall torque capacity and introduces operational expenses. In addition, the hybrid structure requires a coordinated distribution between the two types of PMs to ensure a smooth operation. Such sophisticated design considerations could impose a high computational burden and may not be easily achievable with classical design methods. This dissertation presents a semi-analytical and deep-learning-based design methodology to facilitate design, development and optimization of PM machines. The ultimate goal is to lower the manufacturing cost of PM based electric machine systems, while keeping the operational quality intact. This includes basic performance measures of the machine such as Back electromagnetic force (EMF), power factor, cogging torque and electromagnetic torque. Cogging torque causes major operational setbacks for PM machine operation, particularly in applications where a quiet performance is desired. For this reason, this dissertation presents a heuristic optimization framework to optimize the cogging torque in Surface-mounted PM (SPM) machines consisting of a hybrid magnetic structure (i.e., rare-earth and ferrite magnets). To avoid excessive computational time and volume associated with Finite Element (FE)-based optimization solutions, the analytical approach is paired up with the optimization algorithm to determine the optimal design while FE is utilized for verification and validation purposes. Next, a novel topology of a hybrid PM machine is designed and proposed by coupling FE with deep neural network (DNN) algorithm. Finally, the DNN (prediction model) successfully predicts the machine\u27s performance for any random set of parameters, as confirmed via FE. Then the prediction model is used to optimize the machine performance using a heuristic optimization algorithm
2+2: Academic Success Predictors of Two-Year Transfer Student Athletes
Get PDFThis study addresses the academic success of upper division, NCAA Division I, student athletes who begin their post-secondary academic career at a two-year institution. It is motivated by two research questions: 1) Are predictors of academic success similar for transfer and non-transfer student athletes? 2) Are predictors of academic success similar for transfer student athletes and transfer non-athlete students? Schlossberg’s (1981) theory of transition aided in conceptually framing these research questions.
Data for this study was gathered from three regionally accredited four-year universities located in southern Louisiana, all housing an NCAA Division I athletic program. Multilevel binomial logistic regression was used to identify variables promoting, or inhibiting, academic success. Academic success, defined as graduation, was the dependent variable. Independent variables were selected based upon the “4’s” of Schlossberg’s theory: Situation, Self, Social Support, and Strategies for Coping.
Results of this research indicate transfer student athletes do not perform academically like their non-transfer, or native, peer athletes. Specifically, transfer students are slightly less likely to graduate than their native student athlete peers. The results further provide that participant sport and gender are the strongest predictors of academic success for transfer student athletes. Further, the number of full-time support staff and coaches also played a strong role in predicting academic success for transfer students. In particular, the more full-time staff members the athlete had access to the more likely the student was to graduate. However, the more coaches the athlete had access to, the less likely the student was to graduate. The results showed no statistically significant difference in completion rates between the student athlete and non-athlete student transfer populations.
The results of this study add to the research by addressing how transfer student athletes move through post-secondary education on a path toward degree completion. The findings from this study are important because they can assist those working with transfer student athletes, especially academic advisors, to identify factors that promote academic success and degree completion
“They bloom vivid and repulsive as the truth”: The Feminist Gothic in Djuna Barnes’ Nightwood and Sylvia Plath’s The Bell Jar
Get PDFThe Female Gothic was coined by Ellen Moers in 1976, when literary scholars noticed that the discourse of Gothic literature skewed androcentric. The Female Gothic focused on a gynocentric lens giving breadth to notable Gothic women writer’s and stories. This paper delves within this lens and asserts a newer term, Feminist Gothic, in order to focus less on the gender binary in order to include women and queer individuals while adding Djuna Barnes and Sylvia Plath to the Gothic canon. There is no other academic sources that place Barnes’ Nightwood and Plath’s The Bell Jar in conversation with each other. In utilizing key Gothic elements such as the grotesque, the abject, and the uncanny, these authors’ characters demonstrate resistance to the constraints of normativity. Their grotesque odysseys illumine patriarchal structures of imprisonment as well as reimagine the possibilities of freedom
The Best Defense is a Good Offense: Teaching Phishing Defense Tactics Through a High Agency Playable Experience
Get PDFPhishing attacks are challenging to detect and can have severe consequences. For example, in 2020 alone, phishing attacks cost organizations more than $1.8 billion. Numerous phishing training programs such as reading materials, training videos, and games aim to mitigate the incurred losses. However, regardless of the medium, nearly all existing training places the learner in the role of the victim.
We hypothesize placing the players as an attacker tasked with strategically creating emails will naturally lead to players better recognizing phishing emails. Based on this hypothesis, we have developed an interactive game that trains the users against phishing attacks as an attacker. Our players actively craft simulated emails that employ various phishing techniques rather than passively receiving emails and being asked to classify them. We conducted user testing with 11 participants, and our results showed that participants recognized and understood phishing emails better after playing the game
At the Edge of Existence
Get PDFResponding to the current state of the world and the cataclysmic events that are shaping it, through photography and installation Rene Merino takes the viewer to Mardi Gras in the midst of a pandemic, on a world tour when travel was forbidden, and into the study of a searcher for the possibly extinct ivory-billed woodpecker. The body of work, which utilizes digital and analog photographic methods and installation practices, highlights the precarious state of life on earth, yet offers hope that humanity can maneuver away from the edge of calamity. Mardi Gras 2021 is comprised of black and white silver gelatin photographs, World Tour 2020 is a series of large, digital color photographs originally published as a book of postcards, and The Searcher’s Study (2022) is a room-sized installation that includes six black and white silver gelatin photographs, archival video, furniture, books, maps, and other items
Strain-based Design of Steel-Polymer-Steel Composite Pipes
Get PDFMany offshore single-wall pipelines and structural failures have occurred in the past. As a result, lives were lost, and billions of dollars were spent. In addition, natural disasters such as earthquake fault zones can cause a large volume of soil movement. This can easily damage single-wall pipelines or piles of fixed offshore platforms in the earthquake fault zone.
Currently, the single-wall pipelines are used for the offshore and onshore oil and gas industry. This research investigated the use of double-wall composite pipe steel-polymer-steel (SPS) in place of single-wall pipe to prevent such failures. The double-wall composite pipe has a larger displacement capacity, higher load capacity, the ability to take higher pressure, more heat resistance, and more ductility than the single-wall pipe. Hence, this research studied improvement using double-wall composite pipes and the test results were compared against the single-wall pipes. At the first step of the research, portal steel tubular beams verifications and validations were performed. Then, the laterally loaded steel pipe in clay verification exercises were conducted. Thereafter, the single-wall and double-wall composite pipes were analyzed in clay and the results were compared. Strain, von Mises stresses, and ovality of the pipes were observed and compared against the industry standard. Four-point beam bending tests were also performed for the single and double-wall composite pipes. Boned and unboned behavior of steel and polymer were studied for the composite pipe. The stiffnesses of the clay were changed and the behavior of the steel pipe was investigated. The stiffnesses of the polymer were varied and the behavior of the composite pipes was observed. The annulus size of composite pipes was also varied, and the analysis results were documented. Weld was introduced in the pipe connection and the welding effect was observed. This research work finds significant improvement in the SPS double-wall composite pipe