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Scaling Laws for the Noise-equivalent Angle and C-tilt, G-tilt Anisoplanatism Due to Scintillation
No full textIn this paper, we derive single-integral solutions, applicable in the weak-to-moderate scintillation regime, for both the noise equivalent angle (NEA) due to scintillation and the scintillation-induced root mean squared error (RMSE) between gradient tilt (G-tilt) and centroid tilt (C-tilt). In practice, the NEA due to scintillation gives a measure of the scintillation-induced track error, whereas the scintillation-induced RMSE between C-tilt and G-tilt gives a measure of the C-tilt, G-tilt anisoplanatism due to scintillation. Assuming spherical-wave propagation, we fit closed-form expressions to the numerically integrated solutions. These closed-form expressions serve as “scaling laws,” and we validate their use with wave-optics simulations. At large, we determine that the one-axis NEA due to scintillation scales as a function of aperture size, propagation distance, wavelength, and Rytov number, whereas the one-axis scintillation-induced RMSE between C-tilt and G-tilt scales proportionally to the Rytov number when normalized by the diffraction angle. These findings will aid in the design of active electro-optical systems, which inevitably experience the effects of scintillation when imaging through distributed-volume turbulence
Preliminary investigation of debris propagation dynamics in the Jovian system using the circular restricted 3- and N-body problems
No full textIncreasing A-type CO\u3csub\u3e3\u3c/sub\u3e\u3csup\u3e2−\u3c/sup\u3e Substitution Decreases the Modulus of Apatite Nanocrystals
Get PDFBiological apatite mineral is highly substituted with carbonate (CO32−). CO32− can exchange for either phosphate, known as B-type, or hydroxyl groups, known as A-type. Although the former has been extensively studied, A-type CO32− substituted apatites are poorly understood. Therefore, A-type CO32− apatites with biologically relevant levels of CO32− (1.7–5.8 wt%) were prepared and characterized. The addition of A-type CO32− into the apatite structure caused the predicted expansion of the a-axis and contraction of the c-axis in the unit cell. This was accompanied by a significant modification in the atomic order, especially along the a-axis plane, and crystallite size. A combination of in situ loading with synchrotron X-ray Diffraction and Density Functional Theory showed that increasing A-type CO32− substitutions also reduced the bulk and elastic moduli of the crystals. These results show that although A-type CO32− may inhibit lattice changes caused by B-type CO32−, A-type CO32− enhances the reduction in crystal order and mineral stiffness. These results help us to identify the possible contributions of A-type CO32− substitutions in biological apatites that contain both A- and B-type CO32−. In addition, this implies that the stiffness of bioapatite may change with increasing A-type CO32− substitutions, potentially altering the fracture mechanics of calcified tissues and biomaterials
The Impact of Solar Angle and Cloud Shadows on 3D Reconstruction of Rolling Stock Cargo
Get PDFMeeting the relentless demand for more efficient air cargo transportation is of paramount importance for commercial needs and military missions. This study describes an experiment to test an innovative approach that harnesses cutting-edge stereoscopic vision technology to create 3D point clouds of rolling stock cargo across varying solar angles and cloud shadow conditions. Virtual cargo point clouds are generated by calibrating and systematically organizing the depth and location points from an RGB-D camera and then reprojecting them in a virtual environment. Measurement accuracy was rigorously tested across six camera positions in various combinations of weather conditions against physical ground truth measurements. The high accuracy of such systems offers detailed, real-time insights into optimized cargo loading under unpredictable outdoor conditions. The findings, informed by both quantitative and qualitative analyses, reveal the impact of solar position, cloud coverage, and camera placement on the completeness of the point clouds, quality of the depth points, and accuracy of the measurements. This study provides insights to push the boundaries of cargo logistics possibilities in challenging outdoor environments
An Engineering Approach to Asymptotics and Approximations: With Applications in Optical Wave Propagation and Imaging in Turbulence
No full textEnhanced Nuclear Binding near the Proton Drip Line Opens Possible Bypass of the\u3csup\u3e64\u3c/sup\u3e Ge Rapid Proton Capture Process Waiting Point
Get PDFWe performed astrophysics model calculations with updated nuclear data to identify a possible bypass of the 64Ge waiting point, a defining feature of the rapid proton capture (rp) process that powers type I X-ray bursts on accreting neutron stars. We find that the rp-process flow through the 64Ge bypass could be up to 36% for astrophysically relevant conditions. Our results call for new studies of 65Se, including the nuclear mass, β-delayed proton emission branching, and nuclear structure as it pertains to the 64As(p, γ) reaction rate at X-ray burst temperatures
AFIT Librarian Newsletter : Check It Out (January 2025)
Get PDFWelcome to the first edition of our quarterly newsletter! We are excited to share with you the latest updates from our library
Spectral analysis of light interstitial segregation energies in Ni: The role of local Cr coordination for boron and carbon
No full textUnderstanding interstitial segregation in chemically complex alloys requires accounting for chemical and structural heterogeneity of interfaces, motivating approaches that move beyond scalar descriptors to capture the full spatial and compositional spectra of segregation behavior. Here, we introduce a spectral segregation framework that maps distributions of segregation energies for light interstitials in Ni as a function of local Cr coordination. Boron exhibits a broad, rugged energy spectrum with significant positional flexibility whereas carbon remains confined to a narrow spectrum with minimal displacement. At the free surface, Cr-rich coordination destabilizes both interstitials (e.g., positive segregation energies), in sharp contrast to the stabilizing role of Cr at the GB. This inversion establishes a natural segregation gradient that drives interstitials away from undercoordinated internal surfaces and toward GBs. These results underscore the limitations of single-valued segregation descriptors and demonstrate how a distributional approach reveals the mechanistic origins of interstitial–interface interactions in chemically heterogeneous alloys