LOUIS University of Alabama in Huntsville
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Understanding the Physiological Mechanisms of Thermal Tolerance in Three Reef-Bulding Species of Coral
No full textCorrelated unsteady interactions between a normal shock wave, lambda foot, and other flow events
Get PDFThis dissertation considers interactive relationships between a normal shock wave and the downstream shock wave leg of the associated lambda foot, as well as between a normal shock wave, time-varying static pressure, surface temperature fluctuations, and surface heat flux variations as measured along the bottom surface of the test section. Such relationships are investigated as they vary with two different magnitudes of inlet unsteady Mach wave intensity and are characterized using shadowgraph flow visualization data, as well as power spectral density, magnitude squared coherence, and time lag data. Employed for the investigation is a specialty test section with an inlet Mach number of 1.54, as utilized within a transonic/supersonic wind tunnel. Considered are both high and low inlet Mach wave intensity distributions at the test section entrance, denoted HMWI and LMWI. The most significant sources of flow unsteadiness within the present investigation are mostly associated with the normal and oblique shock waves (with LMWI), and mostly with inlet flow disturbances from unsteady Mach waves (with HMWI). The present experimental results additionally evidence important connections between the normal shock wave and unsteady flow events within lower portions of the lambda foot, especially near the adjacent boundary layer separation region. Additionally, this study considers the interactions of the time-varying length of the separation zone below the normal shock wave boundary layer interaction relative to other parts of the flow and the surface static pressure variation. Overall data trends indicate that separation length flow events at different frequencies are generally more strongly correlated with unsteady surface static pressure and with the instantaneous tracked normal shock wave location with HMWI, relative to the LMWI arrangement. In addition, with HMWI, results for the lowest frequencies considered indicate that unsteady flow events propagate from the separation zone to the normal shock wave and then to the Kulite sensor below the normal shock wave. In contrast, with LMWI, results for the lowest frequencies indicate that unsteady flow events propagate from the normal shock wave to the Kulite sensor below the normal shock wave and then to the separation zone
In situ diagnosis of internal short circuit caused thermal runaway
No full textInternal short circuit (ISC) caused thermal runaway is a critical challenge for Li-ion batteries. Our group reported a method for simultaneous triggering and in situ measurement of critical ISC parameters including temperature, current, and resistance to quantify ISC behaviors. However, cells in the previous study were unable to experience thermal runaway due to insufficient capacity. In this Thesis, the method was implemented in 4-Ah cells. Cells with Al-anode and Al-Cu ISC experienced thermal runaway while cells with cathode-anode and cathode-Cu ISC did not, highlighting the effects of cell capacity and ISC resistance. Additionally, we investigated the effects of state-of-charge (SOC) and thermal boundary conditions. Low SOC and strong cooling mitigated thermal runaway in cells with Al-anode ISC because high ISC current and heat generation rate could not be maintained. These findings demonstrated the effectiveness of the method in quantifying ISC behaviors and enhanced the understanding of ISC caused thermal runaway
Changing Stations: The Multidisciplinary Nature of Work in a Small Museum
No full texthttps://louis.uah.edu/rceu-hcr/1501/thumbnail.jp
Pulsed Laser Ablation of Metals in Organic Solvents for Coordination and Cross-coupling Reactions
No full texthttps://louis.uah.edu/rceu-hcr/1527/thumbnail.jp
Synthesis of poly (L-glutamine) of controlled chain length : a novel synthetic approach for developing models to study polyQ diseases
Get PDFThe abnormal expansion of poly (L-glutamine) repeats beyond a normal threshold (with disease onset at \u3e35 repeat units) has been linked with several neurodegenerative diseases classified as poly (Q) diseases. To investigate the role of this uncontrolled polyQ expansion in disease onset, it is important to understand the changes that occur when the length of poly (L-glutamine) sequences surpasses the normal threshold. To comprehend the role and behavior of these expanded segments, it is essential to develop synthetic techniques that allow polymer production with controlled length. This ensures the accurate representation of healthy and abnormal poly (L-glutamine) segments. However, a direct synthesis route of this polymer has proven challenging and there is no reported method for synthesizing poly (L-glutamine) with controlled chain lengths. Therefore, the primary focus of this research is to design and develop a robust synthetic protocol for the synthesis of poly (L-glutamine) oligomers with 10 to 50 repeat units. The synthesis of poly(L-glutamine) was achieved through the controlled ring-opening polymerization of γ-benzyl-L-glutamate N-carboxyanhydride initiated by a well-defined initiator. The resulting polymer was deprotected with Trimethylsilyl iodide (TMSI) to generate a free acid that is crucial for the next final amidation step to achieve poly(L-glutamine). The reaction conditions, including monomer-to-initiator ratio, solvent choice, and reaction temperature, were carefully optimized to achieve controlled polymerization. These polymer samples with different lengths will be further characterized to study the biophysical behavior and their relation to polyQ diseases. This research will offer valuable insights into the synthesis and subsequent characterization of well-defined poly(L-glutamine)
Estimating surface sulfur dioxide concentrations over eastern China using OMI satellite data
Get PDFSulfur dioxide (SO2) is a key air pollutant as it contributes to negative health effects, acid rain, and aerosol formation. Using satellite data to monitor surface SO2 concentrations can fill in the gaps of ground-based air quality networks in less populated areas. In this study, SO2 retrievals from the Ozone Monitoring Instrument (OMI) were employed to estimate annual and seasonal average surface SO2 concentrations over eastern China, a major anthropogenic source region, from 2015 to 2018. The OMI-derived surface SO2 concentrations had a similar spatial distribution and temporal trends as ground-based measurements from an air quality monitoring network, but they were underestimated by 75-80%. As the SO2 concentrations decreased over the study period, the consistency between the OMI-derived concentrations and in-situ measurements also worsened. As global SO2 emissions decrease, higher resolution satellites and models, or new methods such as machine learning, may be more useful for this application
Neural acceleration of graph partitioning
Get PDFGraph Partitioning is a critical problem in numerous scientific and engineering domains including social network analysis, VLSI design, and many more. Spectral methods are known to produce quality partitions while minimizing edge cuts for a wide range of problems. However, the computational cost associated with the calculation of the Fiedler vector, an eigenvector associated with the second smallest eigenvalue of the graph Laplacian, remains a significant bottleneck. In this paper, we present an neural acceleration approach to spectral bisection partitioning by replacing the traditional eigenvalue calculation with a simple artificial neural network model to approximate the fiedler vector. We demonstrate that our approach achieves partitioning quality comparable to spectral bisection while significantly reducing the computational overhead, making it more scalable and efficient for large-scale problems
Sensor fusion for enhancing motion capture : integrating optical and inertial motion capture systems
Get PDFThis study aimed to create and evaluate a custom sensor fusion algorithm based on Gauss-Newton optimization that combines Optical Motion Capture (OMC) and Inertial Motion Capture (IMC) measurements to combat the limitations of solely using each system. The goal was to demonstrate how inertial measurement unit (IMU) data can be seamlessly integrated into motion capture data to provide a more efficient and reliable gap filling process for future research. The algorithm takes the first and last frame of OMC data, as quaternions, and fills the rest with IMU gyroscope orientation data to simulate gaps of up to ten minutes. The algorithm presented average total errors of \u3c 2.0° across a 5-minute duration for all three sensor placements. The results demonstrated that the fusion of these two sensing modalities is feasible and shines light on the possibility of more field-based studies for human motion analysis
Experimental and numerical investigation of combined mechanical, electrical, and thermal response of LR61 alkaline batteries at various loading rates
Get PDFLithium batteries are present in most electronic devices and machines but pose a serious threat to users if they are over heated, over charged, or otherwise physically damaged. In order to better understand the underlying causes of lithium battery fires, testing procedures at various rates of low, intermediate, and dynamic are established with less volatile 1.5 V LR61 alkaline batteries. The various rates are to cover representative loading rates from scenarios ranging from dropping a cell phone a short distance to a high-rate drone collision with an aircraft. Material characterization is also done on the metal casing to better understand the material behavior. These test results are used for preliminary investigations of numerical modeling methods that combine the mechanical, electrical, and thermal effects