LOUIS University of Alabama in Huntsville
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UAH Undergraduate Research
Get PDFThe UAH Undergraduate Research course offers a valuable opportunity to explore the world of undergraduate research and discover how it can enhance your college journey through practical hands-on activities. Participating in research is not a requirement for graduation, but could offer learning experiences beyond the classroom.https://louis.uah.edu/oer/1004/thumbnail.jp
Roots of Imperial Botany: The Utilization of Wardian Cases and Botanic Gardens in Establishing British Economic Hegemony in the Victorian Era
Get PDFhttps://louis.uah.edu/honors-399/1000/thumbnail.jp
Generation of true random numbers with a first order chaotic circuit
Get PDFTrue randomness backed by first principles theory is surprisingly rare in physically implemented circuit for cybersecurity applications. This thesis provides an illustrative case of a chaotic one-dimensional map circuit with a design driven by a need for rudimentary theory concerned with the limits of its entropy production. Analysis, simulation, and hardware measurements are evaluated against statistical randomness tests issued by the National Institute of Standards and Technology. Interestingly, the results provided here highlight strong relationships between first principles theory of design and measured results when varying parameters. We observe matching characteristics between analytic, simulated and measured hardware results for NIST performance indicators of entropy and randomness. Altogether, this work enables theoretical guidance for entropy assurance in a class of chaotic oscillators used as hardware security primitives
Solar Orbiter and SDO Observations of an On-Disk Active Region Coronal Jet
Get PDFhttps://louis.uah.edu/rceu-hcr/1485/thumbnail.jp
Understanding battery degradation and failure with impedance and imaging techniques
Get PDFWith the increasing desire for fast charging capabilities in lithium-ion batteries due to the popularity of electric vehicles, research has recently been focused on increasing energy and power density while simultaneously revealing the need for improved understanding of degradation mechanisms to achieve the desired safety and fast charge performance. The work presented seeks to further understanding of mechanical, temperature, and electrochemical degradation mechanisms within varying battery chemistries and geometries through evaluation of impedance response and multiscale imaging techniques. First, in order to understand the limitations of mechanical and electrical integrity of battery systems, a combined application of impedance characterization and X-ray imaging yields a viable approach to establishing an understanding of interactions between mechanics and impedance changes within multiple battery geometries. Second, a connection between morphological and chemical changes within electrode microstructure due to charge cut-off voltage and operating temperature was considered. Results elucidated the need for further modification of the electrode to prevent undesired degradation, while maintaining overall cell capacity. Lastly, to advance the knowledge of the multifaceted relationship between microstructure, macrostructure, and observed electrochemical behavior, a deeper understanding of transport mechanisms within thick electrodes is developed. Results show a clear correlation between lithium transport behavior and anode microstructure, bridging the gap between microstructural observation and electrochemical behavior. Through the above mentioned experimental results, a clear relationship between degradation mechanisms, changing battery impedance, and electrode microstructure is illustrated. Novel multiscale techniques combining electrochemical response, X-ray imaging, and neutron imaging are used to complement commonly used techniques and to develop a deeper understanding of observed degradation mechanisms
Hierarchical multi-label text classification in Earth science datasets
Get PDFThis thesis addresses the challenging problem of hierarchical multi-label text classification and introduces a novel zero-shot approach that recommends the label up to the depth of hierarchy in which it is confident. In order to validate the efficacy of the proposed method, we experimented using various potential embedding models such as text-embedding-ada-002, mpnet-all, instructor embeddings, and nasa-smd-ibm-st on Earth science datasets. The experimental results reveal that all considered embedding models surpass the baseline model supervised learning classifier, demonstrating the superiority of the proposed zero-shot approach. This proposed solution can minimize the label imbalance problem typically observed in the supervised learning approach. The findings from this research can help scholars, researchers, policymakers and environmental scientists better understand and tackle urgent global issues. Experimenting with the proposed framework on datasets belonging to other domains such as biology, physics, medicine, etc. can be a next step to better understand the rigidity of the model
Query augmentation for information retrieval (IR) using large language model (LLM)
No full textIn the context of exponential data growth, the efficient retrieval of information remains a known challenge. One key problem lies in bridging the gap between the search query and the information available. This thesis introduces a framework for information retrieval with the help of large language models (LLMs) along with query augmentation. Given a query, its sub-queries are created, using a fine tuned Seq2Seq (sequence to sequence) model through a technique called knowledge distillation. Different prompting methods are applied to produce an efficient query graph. The graph generated is then fed through a retrieval augmented generation (RAG) pipeline to respond to the original question. Experimental results on open source question answering dataset HotpotQA achieved over 51% exact match with ground truth
Characterization of size effects in additively manufactured GRCop-42 and their influence on mechanical response
Get PDFThis study investigates size effects on microstructure, mechanical behavior, and fatigue performance of additively manufactured GRCop-42. Systematic analyses, encompassing changes on powder composition, wall thickness, and heat treatment, was conducted on specimens produced through laser powder bed fusion (L-PBF) and laser powder direct energy deposition (DED) techniques. L-PBF specimens exhibited a reduction in strength and elongation with decreasing thickness, attributed to increasing porosity as specimen’s thickness decreases. Conversely, in DED specimens, decreasing mechanical properties with thickness were associated to surface topography. Emphasizing the non-generalizability of size effects across AM methods. Size effects were also investigated on high cycle fatigue, as tensile properties cannot be readily translated into fatigue properties. Fatigue testing of L-PBF specimens revealed internal defects as operative features responsible for an early fatigue failure, which were remediated by hot isostatic pressing. Fractography unveiled size-dependent fatigue characteristics, particularly an increased presence of brittle features on thinner specimens. This investigation highlights the significance of size effect considerations for GRCop-42 in AM applications
Thermal processing of Al-Zn-Cu-Mg-Zr laser powder bed fusion material for increased ductility
Get PDFAlthough the use of wrought high strength aluminum alloys is prevalent throughout aerospace systems, they often have long lead times and become difficult to source throughout the long lifecycle of aviation systems. Laser Powder Bed Fusion (LPBF) Additive Manufacturing (AM) provides opportunity to directly manufacture wrought equivalent aluminum products without forging supply chain challenges. If these LBPF components are made with the same aluminum material system with similar strength and ductility, they can be a direct replacement for traditionally manufactured components. However, existing 7xxx aluminum alloys are prone to cracking during fusion welding and therefore are not readily produced through LPBF. Therefore, a 7xxx aluminum alloy capable of LPBF with similar strength and elongation to heritage AA7075 and AA7050 for aerospace industry utility is desired. The objective of this work is to evaluate the material performance of LPBF 7A77 aluminum alloy as a substitute material for traditionally wrought 7XXX series aluminum alloy aerospace parts. This work demonstrated the 7A77 alloy can produce crack-free structures with resulting mechanical properties that exceed the wrought alloy with optimized aging heat treatments