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Complete Solution of the Lady in the Lake Scenario
Get PDFIn the Lady in the Lake scenario, a mobile agent, L, is pitted against an agent, M, who is constrained to move along the perimeter of a circle. L is assumed to begin inside the circle and wishes to escape to the perimeter with some finite angular separation from M at the perimeter. This scenario has, in the past, been formulated as a zero-sum differential game wherein L seeks to maximize terminal separation and M seeks to minimize it. Its solution is well-known. However, there is a large portion of the state space for which the canonical solution does not yield a unique equilibrium strategy. This paper provides such a unique strategy by solving an auxiliary zero-sum differential game. In the auxiliary differential game, L seeks to reach a point opposite of M at a radius for which their maximum angular speeds are equal (i.e., the antipodal point). L wishes to minimize the time to reach this point while M wishes to maximize it. The solution of the auxiliary differential game is comprised of a Focal Line, a Universal Line, and their tributaries. The Focal Line tributaries\u27 equilibrium strategy for L is semi-analytic, while the Universal Line tributaries\u27 equilibrium strategy is obtained in closed form
Accelerated Multiobjective Calibration of Fused Deposition Modeling 3D Printers Using Multitask Bayesian Optimization and Computer Vision
Get PDFProper process parameter calibration is critical to the success of fused deposition modeling (FDM) three-dimensional (3D) printing, but is time-consuming and requires expertise. While existing systems for autonomous calibration have demonstrated success in calibrating for a single objective, users may need to balance multiple conflicting objectives. Herein, an easily deployable, camera-based system for autonomous calibration of FDM printers that optimizes for both part quality and completion time is presented. Autonomous calibration is achieved through a novel, multifaceted computer vision characterization and a multitask learning extension to Bayesian optimization. The system is demonstrated on four popular filament types using two distinct 3D printers. The results show that the system significantly outperforms manufacturer calibration across the machine and material configurations, achieving an average improvement of 32.2% in quality and a 31.2% decrease in completion time with respect to a popular benchmark
Celebrating 25 Years of Collaboration: A Bibliography of AFIT-AFRL’s Top 50 Most-cited Works
Get PDFThis bibliography compiles the 50 most-cited collaborative publications between the Air Force Institute of Technology (AFIT) and the Air Force Research Laboratory (AFRL) from 2000 to early 2025, showcasing their interdisciplinary impact across advanced science and engineering. Spanning materials science, remote sensing, terahertz spectroscopy, nanomaterials, aerospace, fatigue mechanics, biomedical applications, communication systems, optics, machine learning, and hypersonic engineering, the works highlight innovative methodologies and transformative applications. This collection underscores AFIT-AFRL’s contributions to cutting-edge research, offering valuable insights for researchers, engineers, and stakeholders in defense and technology development
Analysis of Magnetic Anomaly Maps and Navigation Performance Using Flight Test Data
No full textExcerpt: This work examines six magnetic maps produced by NGA which differ in leveling method (unleveled, leveled, and microleveled) and survey line spacing to determine what makes a good magnetic anomaly map for navigation
Experimental Investigation of Ranque–Hilsch Vortex Tube Performance Characteristics With High-Temperature Air
No full textRanque–Hilsch vortex tubes split an incoming fluid stream into two outgoing streams—one cooler and one warmer than the inlet stream, all without any supplied external power or moving parts. These impressive devices have been the subject of a great deal of research over the years, but little progress has been made in characterizing their behavior at elevated inlet temperatures. With promising potential as a thermal management device in high-temperature applications, characterization of vortex tube behavior at elevated temperatures is necessary. In the present work, a commercial Ranque–Hilsch vortex tube was modified, replacing a polymer vortex generator with a brass version to allow for higher temperature operation. Inlet total temperatures were varied between 350 K and 500 K, the highest applied to vortex tubes of which the authors are aware in the open literature, and the resulting temperature separation characteristics were examined. The high-temperature vortex tube experiments necessitated a wider range of higher Mach number inlet conditions than studied previously, and the results suggest a strong dependence of the temperature separation on the inlet Mach number. A dependence on the inlet Reynolds number was also observed, with greater sensitivity at lower Reynolds numbers. Abstract © ASME
Formulation of Explicit Nonlinear Thermoelastic Terms Using Additive Thermal Strains
No full textA new method of including geometrically nonlinear thermoelastic effects in a total Lagrangian finite element formulation is developed and demonstrated. This method provides explicit formulas for the thermoelastic terms, allows greater insight into the relationship between linear and nonlinear thermoelasticity and provides alternative nonlinear solution methods. The explicit formulation is accomplished through defining a new thermal strain term, called the additive thermal strain. The relative difference between the exact thermoelastic load and commonly used approximations is investigated. It is shown that the geometrically nonlinear thermoelastic formulation reduces to the standard linear thermoelastic formulation with appropriate assumptions
Superposition of Overall Cooling Effectiveness on a Turbine Blade Leading Edge
No full textIncreasingly harsh turbine environments necessitate the design of more advanced cooling techniques as well as the prediction of those cooling schemes\u27 performance at engine conditions. For several decades, film cooling design has been accelerated through a low-order superposition of adiabatic effectiveness in order to quickly approximate the combined effect of multiple rows of cooling holes, the individual rows of which have already been characterized. While that legacy technique can approximately superpose the benefits of multiple rows of external film cooling holes, it is unable to superpose the added benefits of additional internal cooling features. This limitation of traditional film cooling superposition has been overcome with a new technique that allows superposition of overall effectiveness, which is influenced by both external film cooling and internal cooling. In this article, the new overall effectiveness superposition technique is evaluated in a turbine airfoil leading edge showerhead region. The superposition technique is effective at predicting the added benefit of an additional row of cooling holes in the leading-edge region along with the associated internal cooling that accompanies the additional row of cooling holes. Special care must be taken, however, due to pressure gradients associated with the leading-edge curvature
Analyzing LF/VLF Lightning Waveforms to Estimate D-region Electron Density Profiles
Get PDFLightning waveforms in the low frequency (LF; 30–300 kHz) and the very low frequency (VLF; 3–30 kHz) bands can be exploited to produce data-driven ionospheric D-region 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 are reflected by the ionosphere. Here, we expand upon previous methods to include filtering and spectral analysis, and account for oblique propagation to produce higher-order estimates for reflection altitudes and corresponding electron densities. Once estimated, reflection altitudes and corresponding electron densities can be used to derive parameters β and h′, which define an EDP for the D-region. In this study, the lightning waveform (LW) analysis is demonstrated using a single representative 24-h dataset over the Southeast United States, and then extended to a total of 10 separate datasets with varying locations and ionospheric conditions. The LW-derived D-region EDPs are in agreement with predictions made by the Faraday International Reference Ionosphere model, and the LW EDPs β and h′ values are consistent with previous LF/VLF-derived estimates
