Liquid Argon Time Projection Chambers (LArTPCs) represent one of the most widely utilized neutrino detection techniques in neutrino experiments, for instance, in the Short Baseline Neutrino (SBN) program and the future large-scale LArTPC: Deep Underground Neutrino Experiment (DUNE). The high-end technique, facilitating excellent spatial and calorimetric reconstruction resolution, also enables testing exotic Beyond Standard Model (BSM) theories, such as baryon number violation (BNV) processes (e.g., proton-decay, neutron-antineutron oscillation). At the same time, Machine Learning (ML) techniques have demonstrated their ubiquitous use in recent decades; ML techniques have also become some of the most powerful tools in high-energy physics (HEP) analyses. Furthermore, the development of algorithms to cater to the needs of problems in HEP (i.e., triggering, reconstruction, improving sensitivity, etc.) has also become an active area of research. By developing a combined approach using Convolutional Neural Network (CNN) and Boosted Decision Tree (BDT) techniques, the sensitivity of neutron-antineutron oscillation in DUNE is evaluated for a projected exposure of 400kton⋅ years. Additionally, to meet the triggering requirement to select such rare events in DUNE, such a search is only supported with highly efficient self-triggering algorithms. An ML-based self-triggering scheme for large-scale LArTPCs, such as DUNE, is also developed with the intention of implementation on field-programmable gate arrays (FPGAs). The ML-based approach for searching for neutron-antineutron oscillation can be demonstrated and validated on the current LArTPC MicroBooNE. The analysis in MicroBooNE represents the first-ever search for neutron-antineutron oscillation in a LArTPC. DUNE's projected 90％ C.L. sensitivity to the neutron antineutron oscillation lifetime is 6.45✕10³² years, assuming 1.327✕10³⁵ neutron⋅ years, equivalent to 10 years of DUNE far detector exposure (400kton⋅ years). For MicroBooNE, assuming 372 seconds of exposure (equivalent to 3.13✕10³⁶ neutron⋅ years), the 90% C.L. lifetime sensitivity is found at 3.07✕10²⁵ yrs, after accounting for Monte-Carlo statistical uncertainty and systematic uncertainty from detector effects.

MicroBooNE is a liquid argon time projection chamber that collected neutrino data at Fermilab's Booster Neutrino Beam from 2015 to 2020. One of its primary goals is to investigate the “Low Energy Excess” of neutrino events observed by the MiniBooNE experiment, for which candidate photon-like interpretations include an underestimation of neutrino neutral current (NC) resonant Δ production with subsequent radiative decay or another anomalous source of single photon production in neutrino interactions. In particular, NC Δ radiative decay is poorly constrained background process to electron neutrino measurements and could be a sizable contribution to the “Low Energy Excess.” This thesis will present the analysis developed to search for NC Δ → N𝛾 events in MicroBooNE, consisting of a boosted decision tree based event selection with an NC neutral pion background constraint, using data from the first three years of operations corresponding to 6.9 × 10²⁰ POT.

A test-bench is created that injects digital pulses that emulate ATLAS LAr Front End Board electronic signal pulses in order to test prototypes. The prototypes are for new electronics for an upgrade to the CERN Large Hadron Collider that increases the rate of proton-proton collisions by an order of magnitude. This High-Luminosity Large Hadron Collider requires a completely new Trigger and Data Acquisition system to deal with information from detectors. One such system that is currently being developed is the Liquid Argon Signal Processor (LASP) whose architecture is based on Field Programmable Gate Arrays (FPGA). Validation of individual modules of the LASP are of key importance in the development cycle. Additionally, verification of module behaviour with real ATLAS pulses will not be available until much later in the project timeline. The injector project is implemented on an Intel Stratix 10 FPGA, using a soft-core NIOS II processor for TCP/IP communication with a workstation in order to transfer Monte Carlo simulation pulses to the FPGA, where it is then stored in a 2 GB DDR3 external memory. The pulses are then retrieved into internal memory buffers and are transmitted to the LASP at 40 MHz. The user is in complete control of the data pulses injected which is a vital property that would test LASP behaviour for different cases and possible failure modes. / Graduate

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Internal combustion engines (ICEs) are essential for the welfare of today’s human civilization yet they contribute to almost 10% of the global CO2 emissions. Reducing the carbon footprint of the ICEs can be achieved by either increasing the engine efficiency to reduce fuel consumption or the utilization of carbon-neutral fuels. This dissertation aims to investigate the effect of the oxidizer composition on the efficiency and performance of the homogenous charge compression ignition (HCCI) engine. It also aims to study the behavior of hydrogen in HCCI engines. The experiments are conducted using a Cooperative Fuel Research (CFR) engine. The study also involves using chemical kinetics simulations to estimate the ignition delay time of hydrogen which is relevant to the HCCI mode of combustion. The results suggest that the specific heat ratio of the oxidizer does not significantly affect the HCCI engine efficiency. On the fuel side, hydrogen showed high sensitivity to engine running conditions due to the lack of negative temperature coefficient (NTC).

Manganese is an essential alloying element in the 2nd and 3rd generation of Advanced High Strength steels (AHSS) containing 5 to 25% manganese. A combination of excellent strength and ductility makes these grades of steel attractive for the automotive industry. To produce these steels to meet metallurgical requirements the main concern for the steelmakers is to decrease the carbon concentration as low as 0.1% while suppressing the excessive manganese losses at high temperatures. Argon Oxygen Decarburization (AOD) is a promising candidate for the refining of high manganese steels. This work has studied the kinetics of decarburization and manganese losses during the argon oxygen bubbling into a wide range of iron-manganese-carbon alloys. It was shown that decreasing the initial carbon content increased the manganese loss. In the competition between manganese and carbon for oxygen, alloys with lower initial manganese concentrations consumed a higher portion of oxygen for decarburization. This behavior was not expected by thermodynamics and the results did not support the concept of the critical carbon content either. It was demonstrated that for lower range carbon (≤0.42%) alloys, the total manganese loss can be explained by considering multiple mechanisms in parallel; oxide formation (MnO) and vapor formation (Mn (g)), and formation of Manganese mist by evaporation-condensation (Mn (l)). The evaporation-condensation mechanism was proposed with the assumption that the heat generated from MnO and CO formation increases the temperature at the surface of the bubble which facilitates the evaporation of manganese at a high vapor pressure. Consequently, manganese vapor condenses as fine droplets at the lower temperature inside the bubble. Although dilution of oxygen with argon increased the efficiency of oxygen for decarburization as expected from the mechanism of the AOD process, manganese loss did not stop completely at higher argon concentrations in the gas mixture. Therefore, the bubble and melt do not fully equilibrate with respect to Mn and C. For high carbon alloys (1%), there was excess oxygen after accounting for CO and MnO formation. According to mass balance and thermodynamic calculations, and assuming manganese loss by evaporation was negligible it was shown that oxygen was distributed amongst MnO, FeO, CO, and CO2. It was demonstrated that increasing temperature resulted in the higher manganese loss as a mist and by simple evaporation due to the increased vapor pressure and less manganese loss by oxidation. Furthermore, it was found that the rate of decarburization increased with increasing temperature due to more partitioning of oxygen to carbon than manganese. In addition, it was found that the variations of depth of lance submergence did not affect the rate of decarburization or manganese loss. This means that the reactions occur within such a short time that prolonged time after the reaction is completed does not lead to a repartitioning of the species. / Thesis / Doctor of Philosophy (PhD)

<p>Continuous casting is a vital process in the production of semi-finished steel, converting molten metal into solid form. Primary cooling, a critical stage of this process, uses water to cool the solidifying shell as it descends through the mold. The quality of the final cast product is significantly influenced by the fluid flow characteristics during this phase. Given the inherent complexities and costs associated with experimental studies in this area, numerical modeling has emerged as a crucial tool for understanding, predicting, and optimizing fluid flow dynamics within the mold. This research focuses on the implications of argon injection within the mold during the primary cooling stage of the continuous casting process.</p><p>In this thesis, a comprehensive computational investigation of the transportation, entrapment, and fluid dynamic effects of argon injection is presented. Through an exploration of bubble sizes, SEN submergence depths, and slide gate openings, the study reveals how these parameters can significantly influence the casting process.</p><p>The research finds that argon bubble size plays a critical role in determining bubble trajectories and residence times, with smaller bubbles showing a longer residence time and increased boundary interaction due to the dominance of drag forces. The submergence depth of the submerged entry nozzle (SEN) also influences these factors, with deeper submergence resulting in longer bubble trajectories and greater residence times. The study highlights how bubble diameter impacts their entrapment probability, with bubbles ranging from 0.3mm to 0.6mm being most prone to entrapment.</p><p>The effects of argon injection on fluid flow within the SEN demonstrate an enhancement of turbulence, thus promoting a uniform outflow. However, excessively high argon flow rates risk a critical reduction in meniscus velocity, which could lead to overcooling. The research further elucidates the influence of argon on X-velocity near the mold's narrow faces, indicating a potential method for controlling dendritic growth and enhancing the final product quality.</p><p>This work underlines the complex and multifaceted impacts of argon injection on the continuous casting process. It suggests that through careful manipulation of argon bubble size, SEN submergence depth, and slide gate opening, it is possible to optimize the transportation and entrapment of argon bubbles, manage fluid flow dynamics, and ultimately, improve the quality of the cast product.</p>

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Converging cylindrical shock waves have been studied experimentally. Numericalcalculations based on the Euler equations and analytical comparisons basedon the approximate theory of geometrical shock dynamics have been made tocomplement the study.Shock waves with circular or polygonal shock front shapes have been createdand focused in a shock tube. With initial Mach numbers ranging from 2 to4, the shock fronts accelerate as they converge. The shocked gas at the centreof convergence attains temperatures high enough to emit radiation which isvisible to the human eye. The strength and duration of the light pulse due toshock implosion depends on the medium. In this study, shock waves convergingin air and argon have been studied. In the latter case, the implosion lightpulse has a duration of roughly 10 μs. This enables non-intrusive spectrometricmeasurements on the gas conditions.Circular shock waves are very sensitive to disturbances which deform theshock front, decreasing repeatability. Shocks consisting of plane sides makingup a symmetrical polygon have a more stable behaviour during focusing,which provides less run-to-run variance in light strength. The radiation fromthe gas at the implosion centre has been studied photometrically and spectrometrically.Polygonal shocks were used to provide better repeatability. Thefull visible spectrum of the light pulse created by a shock wave in argon hasbeen recorded, showing the gas behaving as a blackbody radiator with apparenttemperatures up to 6000 K. This value is interpreted as a modest estimation ofthe temperatures actually achieved at the centre as the light has been collectedfrom an area larger than the bright gas core.As apparent from experimental data real gas effects must be taken intoconsideration for calculations at the implosion focal point. Ideal gas numericaland analytical solutions show temperatures and pressures approaching infinity,which is clearly not physical. Real gas effects due to ionisation of theargon atoms have been considered in the numerical work and its effect on thetemperature has been calculated.The propagation of circular and polygonal have also been experimentallystudied and compared to the self-similar theory and geometrical shock dynamics,showing good agreement. / QC 20110502

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