United States Air Force Academy

The main part of the precession/nutation of the Earth is due to its gravitational interaction with the Moon and the Sun. Such interaction can be characterized by the Earth geopotential that depends on the orbital ephemerides of the Moon and the Sun. In turn, the ephemerides can be expressed in terms of the so-called fundamental arguments that comprise: the mean anomaly of the Moon (l); the mean anomaly of the Sun (l’); the mean argument of latitude of the Moon (F); the mean elongation of the Moon from the Sun (D); and the mean longitude of the Moon’s mean ascending node (Ω) —to shorten, Delaunay arguments.Common theoretical developments, for example, those based on the Hamiltonian formalism (e.g., Kinoshita 1977 or Escapa et al. 2017), or practical evaluation of the nutation series (e.g., IERS Conventions 2010, sec 5.7.1) assume that Delaunay arguments can be approximated as linear in time. However, strictly speaking this is not the case (e.g., Simon et al. 1994), the arguments being polynomials in time of fourth degree.In view of the current demands on Earth rotation determination (about 1mm on the Earth surface); the guidelines of IAG 2019 and IAU 2021 resolutions; and the terms of reference of the IAU / IAG Joint Working Group on Consistent Improvement of the Earth rotation Theory (CIERT), it is necessary to assess the accuracy of such approximation both because the mandatory consistent development of the models, and also because its potential numerical relevance.In this communication, within the Hamiltonian framework, we will derive the contributions to the nutations due to the non-linear time evolution of Delaunay arguments, comparing them with the common linear case. We will also discuss the practical implications from the point of view of the standards and the operational use of the nutation series.Acknowledgments.- This work has been partially supported by the Spanish projects PID2020-119383GB-I00 funded by Ministerio de Ciencia e Innovación and SEJIGENT/2021/001 funded by Generalitat Valenciana.

Abstract We present results from Space Test Program Satellite‐6 (STP Sat‐6) in geosynchronous orbit. The electron detector, named SEED (Solid‐state Energetic Electron Detector) is built entirely from commercial‐off‐the‐shelf (COTS) parts. The instrument data show the electron environment over the entire energy range of detection and over angular resolution. We compare the instrument data to the Magnetospheric Particle Sensor—High Energy (MPS‐HI) data onboard GOES‐17 located nearby to STP Sat‐6 which were briefly available for 19 days. We conclude that instruments made from COTS components are an inexpensive and viable way to build particle detectors for geosynchronous orbit.

Abstract The development of conductive polymer composites is critical for advancing low-cost, flexible electrochemical sensors. In this study, carbon black-polyvinylidene fluoride (CB-PVDF) composites were fabricated using various processing methods, extrusion, injection molding, spin coating, and solution casting, to investigate the relationship between morphology, crystallinity, and electrochemical performance in sensor applications. Structural integrity of the PVDF matrix was confirmed via NMR spectroscopy, with FTIR and Raman analyses revealing the presence of multiple crystalline phases and minor spectral shifts due to carbon black addition. Thermal analysis via TGA and DSC showed high thermal stability across all composites, with degradation temperatures remaining above 430 °C and crystallinity varying by processing method. Scanning electron microscopy (SEM) revealed significant differences in carbon black dispersion, with solution-processed films demonstrating more uniform distribution compared to thermally processed samples. Electrochemical sensor analysis using cyclic voltammetry (CV) indicated that sanded extruded CB-PVDF fibers exhibited the highest electroactive surface area (23.8 m 2 /g) and the most consistent redox activity across a range of solvents, outperforming injection molded and solution cast films. These results highlight the critical role of processing in tailoring composite properties and identify sanded extruded CB-PVDF fibers as a promising platform for high-performance electrochemical sensor applications.

The purpose of the study is to assess the self-assessment of future specialists in physical culture regarding their attitudes toward the values of Russian civilization. Research methods and organization. Methods of research such as analysis, synthesis, generalization, and a questionnaire survey were used. The analysis of the research results was carried out based on a questionnaire survey of 1st-3rd year full-time students of the Lesgaft National State University of Physical Education, Sport and Health, St. Petersburg, conducted in October-November 2025. Research results and conclusions. The study revealed a mixed stance among students concerning the values of Russian civilization (RC). On the one hand, the vast majority of respondents recognize their belonging to RC; correctly and comprehensively identify the characteristics of Russian physical culture; perceive the differences between Russian and foreign sports; highly appreciate Russia's contribution to global physical culture; and associate their professional future with Russia. However, less than half of them feel connected to Russia's sporting achievements; many students note their insufficient attention to issues of domestic history, traditions, and customs in the field of physical education for the younger generation; and they are either unable or find it difficult to interpret universal human values and the achievements of world civilization and culture through the lens of RC values in the field of physical culture, among other aspects. The study proposed a conditional grouping of the symbols of RC in sports: "an outstanding figure in national sports"; "a sport traditionally dominated by Russian athletes," "national sports mascots," "a symbolic image".

This review examines the integration of digital twin (DT) technology in livestock supply chain management, with particular attention to cattle and dairy systems, emphasizing stakeholder perspectives and its role in advancing sustainability and agricultural productivity. Positioned within the frameworks of Industry 4.0 and Agriculture 4.0, DT adoption offers opportunities for precision farming by enhancing decision-making, transparency, and efficiency. Stakeholders including farmers, distributors, government agencies, technology developers, and consumers acknowledge DTs’ potential benefits but also highlight concerns related to cost, technical expertise, data privacy, scalability, and infrastructure readiness. The review evaluates the effectiveness of DTs in improving livestock management through health monitoring, disease prevention, behavior and sentience analysis, environmental control, productivity optimization, waste reduction, and cyber-physical system integration. Additional applications include colostrum management, teat shape classification, virtual livestock farms, pasture monitoring, predictive modeling, and integrated farm data, demonstrating their transformative role in food production systems and sustainable agriculture. A conceptual framework has been developed to illustrate the essential contributions of DT technology across the livestock sector, aiming to guide researchers and practitioners in understanding applications and identifying future directions for effective implementation. Despite promising advances, barriers to large-scale adoption persist, particularly in developing regions where issues of data availability, high costs, and technological complexity hinder deployment. Future research should focus on strengthening model robustness and developing interdisciplinary frameworks to address diverse contexts, thereby improving the generalizability and practical utility of DT technology in livestock, dairy, and broader agricultural systems.

Cuboid helicopter sling loads (HSLs) impose severe operational constraints on rotary-wing aircraft due to high aerodynamic drag and flow-induced instabilities. These constraints limit maximum flight speed, operational range, fuel efficiency, and mission effectiveness while substantially increasing pilot workload and flight risk. This study investigates passive aerodynamic modifications to improve the stability and reduce the drag of cuboid underslung payloads through combined leading-edge and wake-based flow control strategies. Dynamic wind tunnel testing was conducted using a 1/16-scale model of an ISU-90 cargo container suspended from a ball joint to permit realistic six-degree-of-freedom motion. An onboard inertial measurement unit (IMU) measured angular kinematics while a force balance quantified aerodynamic loads across a velocity range scaled to operational helicopter speeds via Froude scaling. Building on prior work demonstrating that double-chamfer leading-edge modifications reduce drag but provide insufficient stability alone, whereas large trailing-edge fins achieve stabilization but induce excessive drag, this study systematically optimized fin geometry to minimize drag while maintaining stability. Systematic variation of fin geometry parameters—including planform area, sweep angle, taper ratio, aspect ratio, and deflection angle—revealed that deflection angle exerts the dominant influence on drag, followed by planform area. Sweep angle, taper ratio, and aspect ratio variations produced converging drag coefficients at higher velocities with no clear trends. The double chamfer corner profile on the forward faceplate was found to most effectively increase fin control authority, resulting in smaller area fins maintaining stability with zero deflection. A novel perturbation-based testing methodology was developed to assess dynamic stability, demonstrating that increased fin deflection improves damping of yaw disturbances. The results indicate that the minimum fin area capable of maintaining stability at zero deflection provides optimal performance, reducing drag coefficient by approximately 35% compared to large deflected fins while maintaining stability across the operational velocity range. These findings provide actionable design guidance for field-deployable passive stabilization systems that enhance HSL operational capabilities without active control complexity.

This study investigates the use of additively manufactured polyetherimide (PEI, Ultem 9085) as spacecraft shielding against micrometeoroids and orbital debris (MMOD), leveraging hypervelocity impact testing and computational simulation for both monolithic and multi-plate geometries. Because additive manufacturing enables mission-specific, potentially on-orbit shield fabrication, establishing the ballistic performance of AM Ultem across relevant velocity regimes is a critical first step. Shields were fabricated using fused filament fabrication (FFF) and subjected to hypervelocity impacts from 4-mm aluminum projectiles at 2.8–6.1 km/s. These experiments, performed at Texas A&M University’s Hypervelocity Impact Laboratory (HVIL) using a two-stage light-gas gun, were replicated with CTH shock-physics simulations matched to the test conditions. Agreement in penetration outcomes, debris-cloud morphology, and mass-loss trends across five validation shots indicates that the CTH model captures the dominant impact physics for engineering-level predictive use. Using this simulation framework, a ballistic-limit curve for monolithic Ultem 9085 was constructed for velocities from 2–8 km/s, establishing a baseline for assessing multi-plate architectures. Simulations show that two-, three-, and five-plate configurations reduce the required no-perforation thickness by approximately 13%, 17%, and 21%, respectively, relative to an equivalent-mass monolith. These improvements arise from enhanced projectile breakup and more distributed debris-cloud loading on downstream plates. Across all tested velocities, mass-savings percentages remained consistent, demonstrating that layering effects scale predictably with impact energy. Collectively, the results show that layered, additively manufactured PEI shielding provides a lightweight, tunable MMOD protection concept whose performance can be predicted with engineering-level fidelity using hydrocode tools such as CTH, supporting future mission-specific and potentially on-orbit AM fabrication.

The presented investigations look at the vortical flow physics and aerodynamic performance of a generic, multi-delta wing fighter aircraft configuration. The work is part of a DLR project looking at technologies and design requirements for next generation fighter aircraft. The present paper deals with the aerodynamic task of determining the aerodynamic performance and in particular the aerodynamic roll stability behavior. The investigations are carried out in cooperation with the Department of Aeronautics of the US Air Force Academy. The aim is to determine predictive capabilities for fighter aircraft configurations as part of a common approach between DLR and USAFA.