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Articles 1531 - 1560 of 29652
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Isotopic Analysis Of Lithium Hydroxide Monohydrate Using Laser-Induced Breakdown Self-Reversal Isotopic Spectrometry (Libris) And Machine Learning, Madison R. Moran
Isotopic Analysis Of Lithium Hydroxide Monohydrate Using Laser-Induced Breakdown Self-Reversal Isotopic Spectrometry (Libris) And Machine Learning, Madison R. Moran
Theses and Dissertations
High-resolution Laser-Induced Breakdown Self-Reversal Isotopic Spectrometry (LIBRIS) is implemented to record the 15.8 pm Li I 670.8 nm isotopic shift in LiOH · H2O samples of varying 6, 7Li abundance. A simple univariate linear regression demonstrates an acquired isotopic shift of 13.813 ± 1.21 pm in samples varying from 3 to 95 6Li at%. Supervised machine learning regressions are trained on self-reversal wavelength locations in order to quantify 6Li abundance. A stacked ensemble using two base learners yields the superlative characterization of 6Li abundance with RMSE of 5.66 at% and detection limit of 18.8 at%. Using …
Transfer Efficiencies Of Surface-To-Surface Transport Of Micron-Sized Actinide Surrogate Particles, Austin R. Powell
Transfer Efficiencies Of Surface-To-Surface Transport Of Micron-Sized Actinide Surrogate Particles, Austin R. Powell
Theses and Dissertations
Particle effluent of varying sizes is released during routine activities within laboratory environments and these particles can come in contact with a wide range of surfaces. Particles of micron size or smaller can be especially pervasive and can transfer between multiple subsequent surfaces, leading to the progressive contamination of a laboratory. Understanding the transport dynamics of micron sized particles will help inform facility personnel of the possibility of contamination by these potentially hazardous materials of interest. In this research, the transfer efficiency of micron sized surrogate actinide particles (Europium-doped Gadolinium Oxysulfide (EGOS)) is measured for multiple materials, between two particle …
Quantum Ghost Imaging Through An Atmospheric Turbulence Simulator, Mikaela R. Morris
Quantum Ghost Imaging Through An Atmospheric Turbulence Simulator, Mikaela R. Morris
Theses and Dissertations
The use of single photons and photon pairs has become a cornerstone for new developments in the sensing and imaging community for their ability to improve image resolution and signal to noise readings in low light environments and large standoff distances. Quantum imaging techniques have an ability to overcome the fundamental limits of classical imaging, like diffraction. Quantum ghost imaging, a specific type of quantum imaging, uses a bi-photon pair produced during the process of spontaneous parametric down conversion to produce an image. The pair is split using a beam splitter, the signal photon is transmitted through an aperture and …
Measurements Of The Radioisotope Production Cross Section Of 193Ir(N,N')193mIr Between 0.5–9 Mev, Ronnie P. Rera
Measurements Of The Radioisotope Production Cross Section Of 193Ir(N,N')193mIr Between 0.5–9 Mev, Ronnie P. Rera
Theses and Dissertations
This thesis covers a measurements of the radioisotope production cross section of 193Ir(n,n′) 193mIr between 0.5–9 MeV is discussed. The experiment was performed at the University of Notre Dame St.ANA 5U accelerator laboratory. Experimental planning, data collection, analysis, results, and impacts are discussed.
Reflected Laser Light As A Diagnostic Insight For Femtosecond Laser-Plasma Coupling, David S. Stiles
Reflected Laser Light As A Diagnostic Insight For Femtosecond Laser-Plasma Coupling, David S. Stiles
Theses and Dissertations
High-energy laser technology is critical for military, scientific, and industrial applications, but traditional mixed-radiation facilities are hindered by cost, scheduling constraints, and lack of portability. A high-repetition-rate, cost-effective alternative is needed to meet evolving application needs and timelines. This study investigates changes in reflected laser intensity to diagnose coupling efficiency and optimize energetic particle generation in ultraintense laser-target interactions. Using an ultraintense 35 femtosecond, 9 - 12 mJ laser and a deuterated water target, reflected laser light was captured via high-resolution imaging, while energetic electron and X-ray data were collected using a custom spectrometer and ion chamber, respectively. Statistical analysis …
Grassmannian Codes From Stratified Frames, William J. Brinkley
Grassmannian Codes From Stratified Frames, William J. Brinkley
Theses and Dissertations
An equichordal tight fusion frame (ECTFF) is a finite sequence of equi-dimensional subspaces of a Euclidean space that achieves equality in Conway, Hardin and Sloane's simplex bound. Every ECTFF is an optimal Grassmannian code with respect to the chordal distance. We introduce a method for constructing an ECTFF from any finite sequence of unit norm tight frames that happen to be stratified in a certain sense. We moreover show how to construct stratified unit norm tight frames from a difference family for a finite abelian group, as well as from a suitable combination of a resolvable balanced incomplete block design …
Implications Of Magnetic Evolution On Coronal Loop Thermal Variation Prior To Solar Flares, Kara L. Kniezewski
Implications Of Magnetic Evolution On Coronal Loop Thermal Variation Prior To Solar Flares, Kara L. Kniezewski
Theses and Dissertations
Solar flares are intense bursts of electromagnetic radiation, which occur due to a rapid destabilization and reconnection of the magnetic field. While flares are a magnetic phenomena, very little attention has been paid to thermal conditions in the corona prior to flare onset. This study serves as a follow-on to Kniezewski et al., 2024, where the EUV emission from coronal loops was observed to vary substantially and without any coherence between channels before 53 off-limb flares. These variations suggest multiple mechanisms within the coronal magnetic field are responsible for heating fluctuations. Here, the 3D magnetic field is modeled using a …
Best Estimate Reconstruction Of The Control Profile For A Maneuvering Reentry Vehicle, Justin R. Evans
Best Estimate Reconstruction Of The Control Profile For A Maneuvering Reentry Vehicle, Justin R. Evans
Theses and Dissertations
Astrodynamic reentry is an increasingly important flight regime as countries around the world develop new spacecraft and weapons. A design of interest is that of hypersonic glide vehicles with the ability to maneuver in the atmosphere. As these vehicles become more common across the world, it has become advantageous to track foreign reentry tests in order to determine capabilities. While current observation techniques may allow position and velocity to be tracked across the trajectory, orientation of the vehicle is not always observable. The ability to find vehicle orientation across time gives insight into the performance characteristics of the vehicle. This …
Fatigue Behavior Of Two Advanced C/Sic Composites At 1200°C In Air, Conner A. Adams
Fatigue Behavior Of Two Advanced C/Sic Composites At 1200°C In Air, Conner A. Adams
Theses and Dissertations
High-temperature tension-tension fatigue behavior of two advanced carbon/silicon carbide (C/SiC) ceramic matrix composites (CMCs) was investigated. Both composites were reinforced with T300 carbon fibers. Laminated carbon fiber preforms consisted of 24 plies of plain weave fabric in a 0/90 layup. The first composite, C/CVI-SiC, was processed by chemical vapor infiltration (CVI) of SiC into the fiber preform. Prior to the CVI process, the fiber preforms were coated with a duplex pyrolytic carbon and boron carbide fiber coating to create a weak fiber- matrix interphase. The second composite, C/HYPR-SiC, was also processed via CVI, but had an oxidation inhibited matrix comprising …
Investigation Of Neutron Inelastic Scatter Cross Sections On 16O, Molly A. Wakeling
Investigation Of Neutron Inelastic Scatter Cross Sections On 16O, Molly A. Wakeling
Theses and Dissertations
Nuclear data underpin a number of applications across nuclear reactor design, medicine, astrophysics, nonproliferation, national security, and other related fields. However, data are conflicting or missing across the spectrum of isotopes and reactions, and theoretical calculations can only go so far to predict nuclear properties. A key reaction with incomplete data is neutron inelastic scatter on 16O, which reduces neutron energies and produces high-energy gamma rays that are often not taken into account in simulations of nuclear reactors, nuclear weapon detonations, nuclear fusion, and other areas. To fill these gaps, the Gamma-Energy Neutron-Energy Spectrometer for Inelastic Scattering, or GENESIS, …
Extension Of The Circular Restricted N-Body Problem (Crnbp) To Varying Multi-Body Gravitational Systems, Annika J. Gilliam
Extension Of The Circular Restricted N-Body Problem (Crnbp) To Varying Multi-Body Gravitational Systems, Annika J. Gilliam
Theses and Dissertations
Multi-body dynamical models are a valuable tool used to examine certain aspects of spacecraft orbital mechanics by applying assumptions to restrict the problem. The Circular Restricted Three-Body Problem (CR3BP), one of these dynamical models, has been examined extensively in the last few decades; however, this model is not sufficient in the case of more than two massive celestial bodies gravitationally affecting a spacecraft. A novel model called the Circular Restricted N-Body Problem (CRNBP) is studied in this research as an alternative to the traditional CR3BP where necessary. A variety of systems are examined in this thesis, including the Jovian, Saturnian, …
Universal Model Based Systems Engineering Rendezvous And Proximity Operations Mission Planner, Thomas J. Kelly
Universal Model Based Systems Engineering Rendezvous And Proximity Operations Mission Planner, Thomas J. Kelly
Theses and Dissertations
This thesis addresses the fragmentation and inefficiencies in current Rendezvous and Proximity Operations (RPO) mission planning by developing an integrated Model-Based Systems Engineering (MBSE) framework. The research explores the design and implementation of RPO missions using System Modeling Language (SysML) and Matlab-based physics simulation to improve mission planning processes. Key objectives include the standardization of mission requirement characterization, the development of evaluation criteria for mission plans, and the implementation of iterative design methods to refine RPO strategies. The study leverages the Hill-Clohessy-Wiltshire (HCW) equations for initial mission planning, incorporating rigid-body attitude control with properties generated from the physical description, and …
Approximating Three-Body Trajectories With A Knot Theory Inspired Model For Orbit Generation And Determination, Mason R. Mill
Approximating Three-Body Trajectories With A Knot Theory Inspired Model For Orbit Generation And Determination, Mason R. Mill
Theses and Dissertations
This thesis explores a novel approach to approximating three-body trajectories using a knot theory-inspired model for orbit generation and determination. Traditional methods for solving the Circular Restricted Three-Body Problem (CR3BP) rely on numerical integration and correction schemes to generate trajectories, often requiring iterative refinements. This research investigates the application of knot theory principles—such as torus knots, Alexander polynomials, and Reidemeister moves—to categorize and model complex orbital trajectories in the CR3BP. By leveraging these mathematical tools, the study aims to enhance trajectory prediction, orbit determination, and mission planning for spacecraft operating in the cislunar environment. The results demonstrate that knot theory …
Analyzing And Mapping Hypersonic Cruise Vehicle Maneuvers, Kyle T. Monsma
Analyzing And Mapping Hypersonic Cruise Vehicle Maneuvers, Kyle T. Monsma
Theses and Dissertations
This thesis develops a computational framework for analyzing the stability, control, and maneuverability of hypersonic cruise vehicles using surrogate modeling and trajectory propagation techniques. A polynomial ridge regression approach is implemented to create a continuous aerodynamic model from discrete force-moment data, enabling rapid stability and control assessments across Mach and altitude ranges. Vinh’s equations of motion are utilized to account for Earth’s curvature and gravitational effects, refining trajectory analysis for maneuver feasibility studies. Energy maneuverability diagrams, turn rate charts, and short-period stability metrics are generated to visualize flight performance constraints and dynamic stability characteristics. The results highlight the impact of …
Assessing The Feasibility Of Managed Aquifer Recharge For The United States Air Force, Daniel Hendrix
Assessing The Feasibility Of Managed Aquifer Recharge For The United States Air Force, Daniel Hendrix
Theses and Dissertations
Water stress is becoming an increasing global issue, with 4 billion people (50% of the world’s population) experiencing water stress at least one month per year. By 2050, 60% of the world’s population and $70 trillion USD in global gross domestic product will be affected. This research analyzes 78 CONUS USAF installations to determine location-specific water stress and feasible Managed Aquifer Recharge (MAR) solutions. Although thousands of MAR projects have been implemented globally, active-duty USAF installations have yet to contribute to solving this growing issue. Important factors such as required subsurface conditions, physical limitations, design, cost, and regulatory constraints are …
Investigation Of The Convective Heat Transfer Driving Potential For Hypersonic Flows, Roderick A. Mills
Investigation Of The Convective Heat Transfer Driving Potential For Hypersonic Flows, Roderick A. Mills
Theses and Dissertations
Accurately determining adiabatic wall temperature is critical for characterizing surface heating in hypersonic flows. The differences between adiabatic wall temperature and stagnation temperature for Mach 6 flow are examined. A two-dimensional explicit finite difference scheme was developed to analyze heat transfer within an angled wedge and to assess the applicability of the classical semi-infinite solid solution to the Fourier Heat Equation for estimating adiabatic wall temperature and convective heat transfer coefficients. Experimental surface temperature data were extracted from infrared thermography obtained during Mach 6 wind tunnel tests, and the semi-infinite solid solution was applied to estimate the adiabatic wall temperature. …
Fatigue Behavior Of An Advanced Sic/Sic Composite With An Array Of Small Cooling Holes At 1200°C, Tess K. Panchyshyn
Fatigue Behavior Of An Advanced Sic/Sic Composite With An Array Of Small Cooling Holes At 1200°C, Tess K. Panchyshyn
Theses and Dissertations
Tension-tension fatigue behavior of an advanced melt-infiltrated (MI) silicon carbide/silicon carbide (SiC/SiC) composite was evaluated, and basic tensile properties measured, at 1200°C in laboratory air. The composite consists of a melt-infiltrated SiC matrix reinforced with laminated Hi-Nicalon Type-S fibers woven in a 5-harness satin weave. The Hi-Nicalon-S fiber preforms were coated with a boron nitride (BN) fiber coating by chemical vapor infiltration (CVI). The melt-infiltrated matrix was consolidated by combining CVI-SiC with SiC particulate slurry and molten silicon infiltration. The finished ceramic matrix composite (CMC) had a fiber volume fraction of 33%. Additionally, the effect of multiple small holes on …
Adiabatic And Overall Effectiveness Superposition Theory For Upstream Phantom Cooling On A Film Cooled Leading Edge, Nathaniel J. Stout
Adiabatic And Overall Effectiveness Superposition Theory For Upstream Phantom Cooling On A Film Cooled Leading Edge, Nathaniel J. Stout
Theses and Dissertations
Film cooling experimentation aims to improve the cooling performance while minimizing the amount of coolant flow redirected from the compressor. The coolant flow that is used for film cooling reduces the maximum thrust any gas turbine engine can produce. Finding creative ways to improve cooling performance without increasing the amount of coolant used, like phantom cooling, is essential for the gas turbine industry to improve engine performance while increasing turbine components’ lifespan. Phantom cooling refers to any secondary cooling effect that propagates downstream from its original cooling application to cool subsequent turbine components. Phantom cooling is actively gaining more attention …
Reentry Vehicle Trajectory Analysis & Performance (Re-Tap) Development And Application To Spacex Starship, Emma L. Webb
Reentry Vehicle Trajectory Analysis & Performance (Re-Tap) Development And Application To Spacex Starship, Emma L. Webb
Theses and Dissertations
A modeling simulation tool for exo-to-endo atmospheric flight is developed to characterize errors associated with varying simulation fidelities from 3 to 6 degrees-of-freedom (DOF). Engineering approximation errors are quantified and compared with flight data from Apollo 10 and the first Space Shuttle Orbiter reentry (STS-1). The reentry reachability optimal control problem (OCP) is formulated in 6DOF and compared with point-mass solutions, revealing that point-mass solutions oversimplify the problem. A cylindrical reentry vehicle (CRV-1), similar to the SpaceX Starship, is introduced with necessary details for 6DOF analysis. The performance and reentry control capabilities of CRV-1 are captured through 6DOF solutions of …
Event-Based Camera Simulation And Neural Network Processing For Autonomous Aerial Refueling, Stephanie C. Hanson
Event-Based Camera Simulation And Neural Network Processing For Autonomous Aerial Refueling, Stephanie C. Hanson
Theses and Dissertations
Event-based cameras excel in dynamic environments, and do not face challenges like washout and motion blur, like a frame-based camera. This work describes the process used to collect the first EBS data collect for use in AAR, and develops an event simulator to generate synthetic training data for evaluating CNN architectures on asynchronous data. The three models compared are a traditional CNN, a YOLO-based CNN, and an asynchronous sparse CNN. The YOLO-based model achieved the best accuracy, while the sparse CNN, despite being less optimized, maintained an average IoU of 0.9. These results highlight the potential of asynchronous approaches for …
Heterogeneous Boid Swarm Performance Under Environmental And Neighbor Communication Link Variability, Jonathan C. Oxborrow
Heterogeneous Boid Swarm Performance Under Environmental And Neighbor Communication Link Variability, Jonathan C. Oxborrow
Theses and Dissertations
Artificial swarms are of growing interest in numerous fields and use cases. As their utilization increases drones and robots with different capabilities will be required to coordinate for task completion thus creating heterogeneous swarms. Swarm individuals generally communicate with all neighbors inside their sensor range generating a significant amount of message traffic. Previous research of a heterogeneous group in a non-physical environment has shown that restricting communication to only one neighbor of each different capability maintained performance. This work applies that finding to a heterogeneous boid swarm with the addition of varied environmental conditions. The swarm is comprised of three …
Misalignment Uncertainty In Near-Field Thz Scattering Experiments, Philip Patterson
Misalignment Uncertainty In Near-Field Thz Scattering Experiments, Philip Patterson
Theses and Dissertations
This research investigates the effect of misalignment on the near-field scattering of cylinders in the 550-700 GHz frequency band. A Type-1 calibration is performed on previously collected data, using a near-field physical optics solution to simulate scattering at various positions and orientations. The alignment of the cylinders at the time of measurement is predicted by comparing the range profiles of the theoretical and calibrated responses. The data with the most similar range profiles had a mean calibration difference metric of -2.78 dB and a standard deviation of -0.57 dB, demonstrating the presence of sources of error that are dominant over …
Palindrome: A Bi-Directional Multi-Object Detection Framework For Relative Navigation And Autonomous Docking, Liam A. Weinfurtner
Palindrome: A Bi-Directional Multi-Object Detection Framework For Relative Navigation And Autonomous Docking, Liam A. Weinfurtner
Theses and Dissertations
This work introduces a bi-directional, multi-object detection framework that integrates pose estimates from both receiver- and tanker-mounted cameras to improve accuracy and redundancy. A modular YOLO-based detection pipeline is trained using synthetic and real imagery, leveraging a bootstrap transfer learning approach to enhance sim-to-real performance. System evaluation in both virtual and real-world environments demonstrates improved detection robustness, pose estimation accuracy, and scalability. These advancements contribute to the development of AI-driven vision systems for AAR and other autonomous docking applications.
Thin-Filament Pyrometry In A Rotating Detonation Engine, Theodore B. Guetig
Thin-Filament Pyrometry In A Rotating Detonation Engine, Theodore B. Guetig
Theses and Dissertations
Rotating Detonation Engine (RDE) proves beneficial by creating a pressure rise across the combustor rather than a pressure drop seen in traditional aircraft combustors. Coupled with this high pressure is a high temperature in the detonation engine that is difficult to measure as it varies spatially and temporally. Thin-Filament Pyrometry (TFP) was performed on a 6-in RDE to measure these high temperatures. Temperature profiles were obtained over a variety of mass flows, equivalence ratios, and different axial locations within the RDE providing insight into the mixing process and where the heat release occurs. Successful determination of these temperature profiles within …
Improvement Of Microcracking And Mechanical Properties Of Tungsten Fabricated Via Laser Powder Bed Fusion Through Alloying With Reactive Secondary Constituents, William S. Mockel
Improvement Of Microcracking And Mechanical Properties Of Tungsten Fabricated Via Laser Powder Bed Fusion Through Alloying With Reactive Secondary Constituents, William S. Mockel
Theses and Dissertations
Tungsten (W), a Group VI transition metal, possesses a number of advantageous properties, most notably its impressive mechanical performance at extreme temperatures. While tungsten's nature render traditional manufacturing methods difficult, additive manufacturing through laser powder bed fusion (LPBF) presents a promising avenue for fabricating tungsten components. However, the material’s high ductile-to-brittle transition temperature combined with the embrittling effect of impurities mean that the residual stresses imparted by LPBF result in microcracking in tungsten, degrading its usefulness. This study sought to improve the characteristics of LPBF-W through the removal of embrittling oxygen content via alloying with low concentrations of reactive elements, …
Design And Evaluation Of A Deployment Mechanism For A Space-Based Origami Mirror In Cubesat Missions, Arturo Luna
Design And Evaluation Of A Deployment Mechanism For A Space-Based Origami Mirror In Cubesat Missions, Arturo Luna
Theses and Dissertations
The space environment’s suboptimal lighting conditions and eclipse periods impede inspection and on-orbit servicing missions. To abate this problem, the Air Force Institute of Technology (AFIT) launched the Mirror Illumination for Reconnaissance and Rendezvous of Orbital Resident Systems (MIRRORS) initiative. This initiative provides augmented illumination to resident space objects (RSOs) by reflecting the sun’s rays from a mirror satellite. Leveraging origami-inspired designs for compact packaging, AFIT developed a cube origami flasher mirror constructed from aluminum panels that unfolds passively via Nitinol hinges. This research investigates the necessary deployment and panning mechanisms for a dynamic, space-based origami mirror to advance the …
Mechanical Response Of Triply Periodic Minimal Surface Gyroid Structures Under Combined Loading, Jay B. Patel
Mechanical Response Of Triply Periodic Minimal Surface Gyroid Structures Under Combined Loading, Jay B. Patel
Theses and Dissertations
This work explored combined tensile and torsional loads applied to additively manufactured Inconel 718 specimens employing Triply Periodic Minimal Surface (TPMS) structures. The gyroid TPMS unit cell was selected with two variations of cylindrical cell maps, a rectangular cell map, and a spherical cell map. All four variants were tested in an axial-torsion test frame at room temperature using equal parts of vertical and angular displacement control until failure. The combined loading in these tests utilized tension and torsion. The data from the tests were compared to finite element analysis (FEA) models to visualize when yielding was predicted. Finally, the …
Deep Reinforcement Learning For Leo Satellite Grouping, James E. Minteer
Deep Reinforcement Learning For Leo Satellite Grouping, James E. Minteer
Theses and Dissertations
This research investigates jamming evasion using DRL to provide an autonomous solution that repositions a geostationary satellite experiencing directed, terrestrial based jamming. Second, this thesis applies DRL to an area of research for LEO satellite constellations, user grouping, using a portion of an Air Force Research Lab reinforcement learning framework. As LEO satellites orbit the earth, they must constantly re-evaluate not only which users they are able to connect to, but on which of its multiple beams. This model succeeds in finding a balance between maximizing signal strength and minimizing overhead from switching user assignments, all while requiring fewer costly …
An Analytical Approach In Solving A Two-On-One Pursuit Evasion Differential Game With Fast Evader And No-Point Capture, Nathan T. Morrow
An Analytical Approach In Solving A Two-On-One Pursuit Evasion Differential Game With Fast Evader And No-Point Capture, Nathan T. Morrow
Theses and Dissertations
This paper is concerned with a co-planar pursuit-evasion scenario where two Pursuers (P) are after an Evader (E). The players are holonomic/can turn on a dime and their speeds, VP and VE, are constant, but the evader is faster than the pursuers, that is, the speed ratio parameter μ = VE/VP > 1. The Pursuers are endowed with a circular capture disc whose radius l > 0. A differential game (DG) with three states and one parameter is addressed through geometric and analytical methods where a partial solution is outlined and visualized. The game is split …
Analyzing Lf/Vlf Lightning Waveforms To Estimate D-Region Electron Density Profiles: Process, Application, And Comparison, William R. Smith
Analyzing Lf/Vlf Lightning Waveforms To Estimate D-Region Electron Density Profiles: Process, Application, And Comparison, William R. Smith
Theses and Dissertations
Lightning waveforms in the low frequency (LF; 30-300 kHz) and the very low frequency (VLF; 3-30 kHz) can be exploited to produce data-driven ionospheric Dregion electron density profile (EDP) estimates with significantly higher spatial and temporal coverage than previously available. The lightning waveforms used in this paper are signals detected in the LF/VLF of negative cloud-to-ground lightning by the Earth Networks Total Lightning Detection Network. Each waveform contains a ground wave and a time-delayed ionospheric reflection. The time delay between the ground wave and ionospheric reflection has previously been used to estimate a single specular reflection altitude, where LF/VLF emissions …