Royal Military Academy

This study focuses on the Ion Cyclotron Range of frequency (ICRF) Travelling Wave Array (TWA) launcher proposed for the WEST tokamak. This launcher aims to mitigate the detrimental effects associated with resonant ICRF launchers, currently used in most magnetic plasma confinement experiments. The WEST TWA launcher, characterized by reduced near fields and an optimized spatial spectrum, is compared to current WEST ICRF launchers. The parallel component of the electric field on the limiters is particularly investigated, which is a proxy for sheath rectification and impurity production. Full-wave modelling using ANSYS HFSS software, paired with an in-house Python library, was employed to simulate the near fields generated by the TWA and WEST ICRF launchers. The models use experimental equilibrium and plasma profiles from a WEST discharge, with perfect electric conductor boundaries and artificial loss added to the plasma dielectric tensor to damp wavefield amplitude away from the launcher. Results indicate that the TWA launcher present design significantly reduces the amplitude of the toroidal components of the electric field on the limiter surfaces by a factor of more than four compared to the WEST ICRF launchers, which is expected to reduce the impurity production.

Railguns have the potential to revolutionize parts of naval warfare. They can be mounted on ships to replace conventional naval artillery guns, with much higher obtainable muzzle velocities reaching up to well over 2000 m/s. This allows striking targets at much larger distances going up to 500 km (Hundertmark and Lancelle, 2014). If a railgun is introduced as a next-generation naval artillery gun, a number of requirements need to be fulfilled and additional components would need to be installed for powering the railgun so it can function properly as an artillery piece. A lot of these requirements would also need to be fulfilled to introduce a railgun-based close-in weapon system (CIWS). A CIWS is a last hard-kill solution for defending against inbound anti-ship missiles, but also inbound unmanned aerial systems (UASs) and even fast inbound attack vessels (FAIVs). The use of a railgun as a potential next-generation CIWS using rapid fire (Schneider et al., 2009) allows firing multiple projectiles to an inbound threat to obtain an acceptable success rate given uncertainties on the future position of the threat and the true trajectory of the projectile. In general, the artillery system and CIWS will not be operated at the same time, so having co-use of required components where possible allows for a better integration during the electrical weaponization of naval vessels. During the operation of the CIWS, the ship is expected to be in a mode of emergency, reducing all nonessential electrical consumption to a minimum. The Zumwalt-class destroyer is taken as a model for an all-electric-powered ship, where most of the produced energy (78 MW) (Kasper, 2015) could be allocated to the weapon system in case of a requested naval artillery fire or a CIWS firing in a last resort self-defense or fleet-defense situation. In this article, the requirements for naval artillery are compared with those for a CIWS identifying the potential level of co-use which could be imaged when both these railguns are implemented on a destroyer or other naval vessel. In particular, the consequences for the generation of the required pulsed power will be discussed. This comprises the design of the high power components, the energy storage, and its connection to the power grid of the naval vessel. The task is to design an SWaP-optimized solution being able to drive both weapon systems.

Purpose:Although many studies have demonstrated that prolonged cognitive load can impair subsequent cognitive and physical performance, commonly described as mental fatigue, more recent findings suggest that the relationship is more nuanced. Moreover, significant heterogeneity between different smaller studies makes it difficult to summarize definitive conclusions. The aim of the present study was to provide a more robust examination of the detrimental effects of sustained cognitive demands on cognitive and physical performance fatigability using a large sample within a controlled environment.Methods:One hundred seventeen participants (57 female; 32 ± 9 yr) were included in this randomized counterbalanced crossover experiment (NCT05576935) consisting of familiarization, intervention (45-min individualized Stroop task), and control (45-min self-chosen documentary) sessions. Performance was evaluated using a 6-min GoNoGo task and a 20-min cycling time trial. Multiple secondary outcomes, such as rate of perceived exertion (RPE), feelings of fatigue, and motivation, were incorporated to explore their relationship to possible behavioral effects.Results:There was a significant worsening of GoNoGo reaction time between conditions (P < 0.001; ηp2 = 0.07). A trend toward significance was found regarding the negative influence of the Stroop task on time trial distance (P = 0.059; d = 0.20), which was linked to a significant decrease in cadence (P = 0.042; d = 0.22) in the intervention condition. Moreover, the feelings of physical fatigue (P < 0.001; ηp2 = 0.01), mental fatigue (P < 0.001; r = 0.37–0.47), and RPE (P = 0.002; ηp2 = 0.01) remained higher during the time trial in the intervention condition compared with the control condition.Conclusions:In the present study, prolonged cognitive effort impaired specific cognitive and physical performance outcomes, consistent with the characteristics of mental fatigue. Secondary outcomes show an important role for the feeling of fatigue in the determination of physical performance.

CC BY 4.0 Correspondence Address: M. Pyasik; Laboratory of Cognitive Neuroscience, Department of Languages and Literatures, Communication, Education and Society, University of Udine, Udine, Italy; email: maria.pyasik@uniud.it The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Cryogenic Temperature Sensitive Paint (cryo-TSP) has been employed to investigate the flow topology over the DU89-134 airfoil at chord-based Reynolds numbers Rec = 2.5 × 10⁵ and Rec = 5 × 10⁵, and flow temperature of T = 233.15 K. Spanwise-averaged surface temperature distributions and their gradients were analyzed to determine the locations of flow separation, transition, and reattachment. Results indicate that in most observed cases, the flow is characterized by a separation-induced transition, which is concomitant with the formation of a Laminar Separation Bubble (LSB). In one case, the flow transitions directly to turbulence without prior separation, followed by a turbulent separation. This behavior is attributed to the formation of ice crystals on the leading edge of the airfoil.

This paper introduces a compact spider-shaped monopole antenna tailored for tactical HF radio communication using Near Vertical Incidence Skywave (NVIS) propagation. The antenna structure is designed to maximize high-angle radiation, enabling communication across obstructed or mountainous terrain. Featuring a top-loaded radial configuration and choke balun for impedance matching, the prototype antenna achieved a significantly improved VSWR of 1.19. Field deployment confirmed reliable HF communication at a distance of 346 kilometers, highlighting the design’s practical relevance for mobile military operations.

Mental fatigue (MF) is a psychobiological state induced by prolonged exertion that has the potential to reduce performance. In military operations, MF coincides with inadequate sleep, circadian disruption and other stressors, further increasing the risk of fatigue-related errors of judgement and reduction in physical and psychological performance. Experienced leaders can detect MF, but multimodal monitoring and assessment technologies still cannot duplicate this capability. Experiments to define signals that cue this human percept could inform future technologies. Countermeasures include engagement strategies, brain endurance training to extend physical endurance, and caffeine and modafinil to temporarily sustain performance. An infrastructure for physiological monitoring and integrated analyses will advance team performance enhancement, along with the use of explainable and interpretable artificial intelligence modelling, refined through iterative experimentation. More precise definitions that distinguish MF from other types of fatigue will help advance the development of monitoring technologies and countermeasures by targeting the right physiological and behavioural metrics.

Contemporary engineering systems, such as electrical circuits, mechanical systems with shocks, and chemical reactions with rapid kinetics, are often characterized by dynamics that can be modeled using stiff differential equations with events.Stiffness typically arises in these systems due to the presence of both rapidly changing and slowly changing components.This stiffness requires extremely small time steps to maintain stability when using traditional numerical integration techniques.Recently, quantization-based techniques have emerged as an effective alternative for handling such complex models.Methods like the Quantized State System (QSS) and the Linearly Implicit Quantized State System (LIQSS) offer promising results, particularly for large sparse stiff models.Unlike classic numerical integration methods, which update all system variables at each time step, the quantized approach updates individual system variables independently.Specifically, in quantized methods, each variable is updated only when its value changes by a predefined quantization level.Moreover, these methods are advantageous when dealing with discontinuous events.An event is a discontinuity where the state of the system abruptly changes at a specific point.Classic methods may struggle with events: They either undergo expensive iterations to pinpoint the exact discontinuity instance or resort to interpolating its location, resulting in unreliable outcomes.Therefore, this QSS strategy can significantly reduce computational effort and improve efficiency in large sparse stiff models with frequent discontinuities (Pietro et al., 2019).

Outdoor noise measurement is highly uncertain due to its strong dependence on environmental conditions. In firearm noise studies, these uncertainties are amplified by the impulsive nature of the noise and the lack of large datasets, making long-term meteorological averaging and stochastic techniques impractical. Numerical models also face limitations, with most commercial software relying on coefficient-based environmental predictions. This study investigates uncertainties and environmental effects in outdoor firearm noise propagation, combining experimental and numerical approaches to understand their impacts. The expanded uncertainty of systematic (Type B) uncertainties contribute up to ±4.1 [dB], while random (Type A) uncertainties, influenced by environmental variability, range from ±0.5 to ±10 [dB], predominantly affecting mid- to high-frequency bands at extended distances. A refined 2D Nonlinear Progressive Equation (NPE) model is used to simulate varying terrains and atmospheric conditions. Results reveal that sound-dampening terrains, such as grass, cause significant amplitude and spectral shifts compared to asphalt, with attenuations up to 10 [dB] at specific frequencies and distances. Downwind conditions enhance high-frequency propagation, while upwind scenarios reduce signal strength, with notable effects indicatively happening beyond 65 [m]. The findings highlight the importance of environmental characterization and advanced modeling as complementary tools for understanding and contextualizing uncertainties in firearm noise studies, supporting the development of improved methodologies for military and civilian acoustic applications.