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Analysis of the Circular Restricted N-Body Problem (CRNBP) in the Sun-Venus System
No full textThird-body dynamical approximations such as the Circular Restricted 3-Body Problem (CR3BP) have become ubiquitous in orbital mechanics in determining useful trajectories in systems with two massive bodies and a spacecraft. These models provide a better estimation of real-world trajectories than the simple 2-Body Problem (2BP), but the addition of a greater number of massive celestial bodies to gain insights into the effect of additional gravitational perturbations would enable the design of more accurate trajectories without reliance on a higher-fidelity ephemerides N-body model. As this extension to the CR3BP, the Circular Restricted N-body Problem (CRNBP) was first presented in 2022 by Negri and Prado [1]. Using that CRNBP model, initial conditions from the Sun-Venus CR3BP are propagated numerically in CRNBP for multiple orbit types to include the gravitational effects of Mercury and Earth. The resulting trajectories are compared between the two models, demonstrating that significant perturbing effects and a reliance on the initial phase angles of the tertiary and quaternary bodies exist. Some trajectories and initial phase angle cases are identified to be less perturbed over the time period of propagation, which may aid in the selection of more stable trajectories or the selection of an initial epoch at which to enter certain orbits. This analysis demonstrates the main benefit of the CRNBP model. Additionally, the application of Poincaré mapping to this problem and the challenges with this approach are examined
Lensless Shadow Imaging via Fusion of Phase Retrieval and Image Reconstruction from Correlations Algorithms
No full textThe recent global pandemic has served to intensify interest in analyzing microdroplets suspended in the air that can possibly carry pathogens thus demonstrating an airborne transmission mechanism with potentially devastating consequences. Although COVID-19 turned out to be not as virulent as some other diseases encountered in the past, the possibility of airborne transmission of diseases remains a substantial concern. In this paper the potential for an optical sensor to image airborne particles is investigated. The proposed sensor would use optical radiation to probe the atmosphere through a pinhole aperture. Simulations conducted as part of this research reveal that droplets of the diameter in the range of micrometers can be imaged using the proposed technique, thus potentially allowing for the content of the air to be characterized with regard to its droplet size distribution and density
An Optimal Strategy for Off-Board Proximal Sensing of a Target: Part 2
No full textIn an era of preparation for potential future conflict, it is of utter importance to uncover methods of amplifying crewed aircraft capability with novel un-crewed systems. To further that goal, this work considers a two-agent scenario of a faster, unmanned turn-constrained pursuer with an engagement zone (EZ) and a non-maneuvering mobile evader. The pursuer aims to capture an evader with its circular EZ. The pursuer\u27s EZ is dynamic and shifts as a function of the evader\u27s velocity vector in both magnitude and direction. Using nonlinear optimal control techniques, the optimal trajectory and minimum time to engage the evader are determined for various pursuer initial headings and positions through MATLAB simulation. The results build a control strategy given the scenario, with analytic solution validation. Results lay a foundation to model pursuer-evader capture scenarios with a dynamic EZ, leading to general guidelines for real-time control strategies. This work culminates in an attempt to find an algorithm that would yield a dispersal surface in any pursuer/evader scenario and establish a comparative angle for the pursuer to guarantee optimal turn direction to engage the evader in minimum time
PyO3: Building Python Extension Modules in Native Rust with Performance and Safety in Mind
No full textPython and Rust are both powerful programming languages, each offering unique benefits depending on individual use cases. Rust is a lower-level programming language built with speed and safety as integral features. Python, known for being more user-friendly, has an extensive library with over 350,000 publicly available packages [1]. Writing Rust software can be a daunting and meticulous task, as its syntax and strict compiler demand careful attention to detail. This meticulousness often pays off in the form of highly performant and safe code. Conversely, Python has a straightforward syntax that allows programmers a wide range of flexibility in writing code. However, Python’s performance can be limiting, often requiring the use of native C or C++ libraries for computationally heavy tasks. This paper introduces the PyO3 crate, which enables programmers to seamlessly integrate native Python modules and Rust code within the same project, allowing for the development of high-performance Python extension modules using Rust. Additionally, it provides insights into interfacing between the two code bases using various PyO3 tools. This approach enables programmers to benefit from combining both languages while maintaining good coding standards by keeping them separate and interfacing between them. PyO3 opens the door for Rust to replace C and C++ in Python modules, offering a safer alternative while not compromising efficiency
Hidden-phase Compensation in Extended-beacon Adaptive Optics
No full textIn this paper, we use wave-optics simulations to explore the benefits of hidden-phase compensation for laser systems that employ extended-beacon adaptive optics. Specifically, we create a trade space, where we vary the strength of the scintillation as well as the size of the beacon, and score laser-system performance in terms of no phase compensation, perfect least-squares compensation, and perfect full-phase compensation. Here, “full phase” refers to the least-squares and hidden-phase components of the pupil-plane phase function. The results of this trade space lead to three main conclusions. (1) If the scintillation is weak and we have either a point-source beacon or a very small extended-source beacon, then we see similar performance with perfect least-squares and full-phase compensation; however, both significantly improve performance compared to the no compensation case. On the other hand, if the scintillation is strong and we have either a point-source beacon or a very small extended-source beacon, then we get a significant improvement in performance using perfect full-phase compensation compared to perfect least-squares compensation. (2) If the scintillation is strong, then there will be a large number of turbulence-induced branch points and branch cuts in the hidden-phase component of the pupil-plane phase function. These branch points and cuts will result in a major reduction in performance if left uncompensated. (3) If the extended-source beacon is large, then the associated rough-surface scattering and resultant speckle will corrupt the perfect least-squares and full-phase compensation to the point where performance is on par with or worse than the no compensation case. At large, (1)–(3) will inform the development of future laser systems that need to mitigate the effects of scintillation and speckle to perform extended-beacon adaptive optics
Segregation and ordering of light interstitials (B, C, H, and N) in Cr–Ni alloys: Implications for grain boundary stability in superalloy design
No full textExcerpt: Using Monte Carlo simulations, we identify the chemical and structural preferences of these interstitials in both bulk and GB environments, aligning with experimental segregation and precipitation trends. ... In support of ongoing hydrogen embrittlement mitigation strategies, we also examined hydrogen behavior
Surface Resistivity Correlation to Nano-Defects in Laser Powder Bed Fused Molybdenum (Mo)-Silicon Carbide (SiC) Alloys
Get PDFThe integration of Silicon Carbide (SiC) nanoparticles into Laser Powder Bed Fusion (LB-PBF) Molybdenum (Mo) printing represents a significant advancement in refractory metal additive manufacturing. Our investigation examined how varying SiC nanoparticle sizes affect the microstructural and electrical properties of LB-PBF-printed molybdenum components while maintaining a 0.01 mass fraction of Mo. At an Linear Energy Densities (LED) of 1.8 J/mm, the addition of 80 nm SiC particles achieved a 46% reduction in porosity, while sheet resistance decreased by 6% at LED of 2.0 J/mm with 80 nm SiC particles. These performance improvements stem from several mechanisms: SiC particles serve as oxygen scavengers, facilitate secondary phase formation, and enhance laser absorption efficiency. Their dual role as sacrificial oxidizing agents and Mo disilicide phase promoters represents a novel approach to addressing microcracking and porosity in LB-PBF-printed Mo components. Through systematic investigation of particle size effects on both microscale and nanoscale properties, our findings suggest that optimized nanoparticle addition could become a universal strategy for enhancing LB-PBF processing of refractory metals, particularly in applications requiring enhanced mechanical and electrical performance
A Note on Entire Large Solutions to Semilinear Elliptic Systems of Competitive Type
No full textWe consider the elliptic system Δu = p(|x|)uavb, Δv = q(|x|)ucvd on Rn (n ≥ 3) where a, b, c, d are positive constants with min {a,d} \u3e1, and the functions p and q are positive and continuous. We establish conditions on p and q, along with the exponents a, b, c, d, which ensure the existence of a positive entire solution satisfying lim|x|→∞ u(x) = lim|x|→∞ v(x) = ∞
Adiabatic Effectiveness Measurements of Film Cooling in Supersonic Flow
No full textHigh temperature, high supersonic Mach number flows can be encountered in different innovative propulsion systems configurations such as Rotating Detonation Combustors (RDCs) and scramjets, requiring the use of film cooling for the thermal management. For this reason, a clear understanding of the performance of film cooling in supersonic flow is paramount. This experimental study investigated the performance of film cooling in a supersonic flow at Mach 1.65 comparing it with subsonic flow operations at Mach 0.3. Adiabatic effectiveness measurements were performed using Pressure Sensitive Paint. This technique also provided pressure field maps, useful to enhance the understanding of the physical phenomena under investigation. Additionally, time-averaged schlieren images enabled the visualization of the flow field morphology and understanding of the underlying physics. Cylindrical holes both aligned with the flow and with a 30 degrees compound angle and 7-7-7 fan-shaped holes aligned with the flow were considered. The results indicated performance improvements in both centerline and laterally averaged adiabatic effectiveness induced by the action of the oblique shock forming upstream of the hole. The same shock is responsible for modifying the shape of the adiabatic effectiveness contour, determining a higher peak along the centerline which linearly decreases outward instead of showing the more typical bell shape. The fan-shaped holes outperform the other holes at any blowing ratio (BR) over 0.8 for supersonic main flow operations. Performance of cylindrical holes in supersonic flow follow the trend typically encountered in subsonic flows while also bringing the peak in adiabatic effectiveness upstream and closer to the hole exit