The impact of the self-sealing band on interior ballistics is investigated during the gun launching, and a high-precision interior ballistics coupling algorithm that takes leakage into account is proposed. This study focuses on a 65 mm short-barrel, equal-caliber balanced cannon, integrating Abaqus finite element software with an interior ballistics calculation programme. It uses a User-defined AMPlication Load (VUAMP) subroutine to achieve real-time coupling calculations of the chamber pressure and self-sealing band deformation, correcting variations in the chamber pressure. Experimental results show that the coupling algorithm offers the higher precision compared to traditional interior ballistics models and can effectively capture the impact of leakage on the interior ballistics performance. Further research reveals that changes in the charge amount and assembly gap significantly affect the sealing performance of the self-sealing band and the leakage of propellant gases, which in turn influence the chamber pressure and projectile velocity. The high-precision coupling algorithm proposed in this paper provides the effective theoretical support for the design of the self-sealing band and the analysis of cannon performance.

An all-silica-fiber thulium-doped fiber laser emitting at 0.82 μm on the transition from 3H4 to the ground state 3H6 outputs 105 W continuous-wave power and 555 W quasi-continuous-wave instantaneous power with 0.96% duty cycle in 240 μs rectangular pulses. The system comprises a double-clad thulium-doped fiber designed and fabricated in-house, incorporated into an all-fiber cavity and cladding-pumped by diode lasers at 0.79 μm. Co-lasing at 1.9 μm counteracts population trapping in 3F4. The slope efficiency reaches 64% and 77.5% under quasi-continuous-wave and continuous-wave operations, respectively. Under quasi-continuous-wave conditions, the beam quality M2 becomes 2.2 (beam parameter product: 0.57 mm mrad) and 2.45 (0.64 mm mrad) in orthogonal directions at approximately 250 W of instantaneous output power. In addition, a modified quasi-continuous-wave setup is continuously wavelength-tunable from 812 to 835 nm. We believe this is the first reported demonstration of high-power laser operation of the 3H4 → 3H6 transition in a thulium-doped fiber.

A type of signal-interference fourth-order dual-band bandpass filter (BPF) with multiple out-of-band transmission zeros (TZs) is reported. A second-order dual-band BPF block is firstly discussed, which is composed of two microstrip-to-slotline vertical transitions that are back-to-back connected by means of an in-parallel asymmetrical microstrip-line-based closed loop. It exhibits spectrally symmetrical passbands regarding the design frequency fD and three TZs at the inter-band region. Subsequently, by using stepped-impedance-line segments at the longest path of the transversal signal-interference closed loop, its dual-band BPF counterpart with second-order spectrally asymmetrical dual passbands is presented. Next, in order to increase the filter order as well as the number of out-of-band TZs for augmented stopband attenuation, a fourth-order dual-band BPF circuit is conceived. To this aim, two Y-shaped stepped-impedance microstrip stubs are loaded at the input and output ports of the previously devised second-order frequency-symmetrical dual-band BPF block. The RF operational principles of all these dual-band BPFs are detailed through their associated transmission-line-based equivalent circuits. Moreover, for experimental-demonstration purposes, a 1.154-/2.818-GHz two-layer microstrip proof-of-concept prototype of a fourth-order sharp-rejection dual-band BPF is designed, simulated, and characterized. It features inter-band power-rejection levels higher than 28.68 dB and lower-/upper-stopband attenuation levels above 40.92 dB from DC to 4.64 GHz.

This article aims at facilitating the widespread application of Energy Management Systems (EMSs), especially in buildings and cities, in order to support the realization of future carbon-neutral energy systems. We claim that economic viability is a severe issue for the utilization of EMSs at scale and that the provisioning of forecasting and optimization algorithms as a service can make a major contribution to achieving it. To this end, we present the Energy Service Generics software framework that allows the derivation of fully functional services from existing forecasting or optimization code with ease. This work documents the strictly systematic development of the framework, beginning with requirement analysis, from which a sophisticated design concept is derived, followed by a description of the implementation of the framework. Furthermore, we present the concept of the Open Energy Services community, our effort to continuously maintain the service framework but also provide ready-to-use forecasting and optimization services. Finally, an evaluation of our framework and community concept, as well as a demarcation between our work and the current state of the art, is presented.

Older adults often experience a decline in functional abilities, affecting their independence and mobility at home. Wearable lower-limb exoskeletons (LLEs) have the potential to serve as both assistive devices to support mobility and training tools to enhance physical capabilities. However, active end-user involvement is crucial to ensure LLEs align with users’ needs and preferences. This study employed a co-design methodology to explore home-based LLE requirements from the perspectives of older adults with mobility impairments and physiotherapists. Four older adults with self-reported mobility limitations participated by creating personas to represent different user needs and experiences (i.e., PERCEPT methodology), alongside four experienced physiotherapists who contributed their professional insights. As assistive devices, LLEs were seen as valuable for promoting independence, supporting mobility, and facilitating social participation, with essential activities including shopping, toileting, and outdoor walking. Physiotherapists expressed enthusiasm for integrating LLEs into remote rehabilitation programs, particularly to improve strength, balance, coordination, and walking speed. Key design considerations included a lightweight, discreet device that is easy to don and doff and comfortable for extended wear. Physiotherapists highlighted the potential of digital monitoring to assess physical parameters and personalize therapy. Fatigue emerged as a significant challenge for older adults, reinforcing the need for assistive LLEs to alleviate exhaustion and enhance functional independence. A shortlist of LLE features was drafted and scored, covering activity and design applications. These findings provide valuable insights into the design and usability of home-based LLEs, offering a foundation for developing devices that improve acceptance, usability, and long-term impact on healthy ageing.

The hypersonic vehicle surfaces are subjected to intense thermal loads during atmospheric re-entry. Such conditions induce material ablation and structural deformation, potentially causing changes to aerodynamic configuration that critically endanger mission integrity. In this paper, a mathematical model of thermochemical non-equilibrium magnetohydrodynamics (MHD) at low magnetic Reynolds number is introduced to investigate the effects of MHD on the flow field. Variation of the magnetic pole angle (θ), the flow field profiles are quantitatively analysed, including gas component distributions and aerodynamic heating characteristics. Results indicate that the heat flux at the stagnation point initially decreases and then increases with θ increasing, reaching a minimum at θ = 60°. A portion of the heat flux from the blunt position is transferred to the shoulder (α between 30° and 60°). Notably, the shock standoff distance also shows a non-monotonic trend with θ increasing, peaking at θ = 30°, mirroring the effect of θ on the stagnation point heat flux. As θ increases, the component of the Lorentz force along the X-direction gradually increases, with its peak position corresponding to the shock standoff distance. The electrons and nitrogen atoms are primarily concentrated at the blunt nose, while nitric oxide and oxygen atoms are predominantly distributed along the vehicle wall. The dissociation region of the gas is influenced by the shock standoff distance, which increases as the shock standoff distance increases. At θ = 30°, the concentration of oxygen atoms, nitrogen atoms, nitric oxide molecules and electrons on the stagnation point line reaches its maximum. The present study provides a theoretical foundation for the application of MHD thermal protection methods on hypersonic vehicles.

This paper introduces a high single-pulse energy, narrow-linewidth mid-infrared self-optical parametric oscillator (mid-IR SOPO) with a cavity length of 120 mm and a Nd:MgO:PPLN crystal. To achieve high single-pulse energy and high peak power in mid-IR light sources, a LiNbO3 electro-optic Q-switch (EOQ) is introduced for the first time in a mid-IR SOPO. A narrow-linewidth EOQ-SOPO rate equation is formulated, and experiments are conducted using a single Fabry–Pérot etalon. At a 500 μs pump pulse width, a 4.71 mJ single-pulse idler light at 3838.2 nm is achieved, with a linewidth of 0.412 nm, single-pulse width of 4.78 ns and peak power of 985 kW. At 200 μs, the idler light at 3845.2 nm exhibits a minimum linewidth of 0.212 nm.

There are multiple equilibrium points in the launching and unfolding process of the multi-body aircraft. Different equilibrium points exhibit different stability characteristics and change with parameters such as connection method. The changes in stability characteristics can also lead to the inability of multi-body aircraft to achieve stable deployment. To solve these problems, the dynamic stability of multi-body aircraft during falling is analysed based on bifurcation theory in this paper. In this paper, Lagrange multiplier method is used to establish the multi-body dynamics model of the multi-body aircraft, and the curly spring torque model is added. In order to consider the coupling effect between the wings and the influence of the relative motion between the flight units on the aerodynamic force, the reference angle-of-attack, the reference sideslip angle, the relative attitude angle and the relative attitude angular velocity between the flight units were introduced as new variables to establish the aerodynamic model of the multi-body aircraft. Based on the equilibrium equations, the equilibrium curve of the two-body aircraft is obtained by using the joint stiffness coefficient as the continuous variable parameter. The stability of the equilibrium point domain on each equilibrium curve was analysed by using linearised theory. The dynamic characteristics of the launching and unfolding process of the two-body aircraft were analysed using bifurcation theory, and the stable domain was obtained regarding the initial folding angle and connection stiffness coefficient. The influence of initial folding angle and connection stiffness coefficient on the dynamic characteristics of the launching and unfolding process and the meaning of the stability domain were analysed through numerical simulation calculations. Finally, the correctness of the analysis conclusion was verified through experiments on the two-body aircraft, accumulating the technical foundation for subsequent research on high-altitude deployment.

Micromix combustion technology emerges as a promising solution to address challenges in achieving clean combustion, particularly for hydrogen utilisation. This review provides a critical analysis for the potential of micromixing by delving into its core principles, diverse applications and the factors influencing its performance. The paper focuses on injector design, flame stabilisation and NOx mitigation strategies within the micromixing framework. Key findings include innovative burner designs, optimised air distribution techniques and the crucial role of fuel properties, especially for hydrogen combustion. The review highlights significant reductions in NOx emissions achieved through micromix combustion technology. For instance, NOx emissions were lowered to 2.2 ppm at φ = 0.4, representing a 45% improvement compared to conventional design configurations. Furthermore, a reduction of 40% in NOx emissions compared to standard configurations was observed at an equivalence ratio of 0.65. The study also compares NOx emissions between hydrogen and its blended fuels, showing lower emissions for methane. By highlighting the importance of optimising fuel mixture formation and flame stability for various operating conditions, this review underscores the significance of micromix combustion for advancing sustainable combustion technologies with low NOx emissions and reduced chance of flashback in hydrogen combustion.

Modeling detailed chemical kinetics is a primary challenge in combustion simulations. We present a novel framework to enforce physical constraints, specifically total mass and elemental conservation, during the reaction of ML models’ training for the reduced composition space chemical kinetics of large chemical mechanisms in combustion. In these models, the transport equations for a subset of representative species are solved with the ML approaches, while the remaining nonrepresentative species are “recovered” with a separate artificial neural network trained on data. Given the strong correlation between full and reduced solution vectors, our method utilizes a small neural network to establish an accurate and physically consistent mapping. By leveraging this mapping, we enforce physical constraints in the training process of the ML model for reduced composition space chemical kinetics. The framework is demonstrated here for methane, CH4, and oxidation. The resulting solution vectors from our deep operator networks (DeepONet)-based approach are accurate and align more consistently with physical laws.

Designing optimal assistive wearable devices is a complex task, often addressed using human-in-the-loop optimization and biomechanical modeling approaches. However, as the number of design parameters increases, the growing complexity and dimensionality of the design space make identifying optimal solutions more challenging. Predictive simulation, which models movement without relying on experimental data, provides a powerful tool for anticipating the effects of assistive devices on the human body and guiding the design process. This study aims to introduce a design optimization platform that leverages predictive simulation of movement to identify the optimal parameters for assistive wearable devices. The proposed approach is specifically capable of dealing with the challenges posed by high-dimensional design spaces. The proposed framework employs a two-layered optimization approach, with the inner loop solving the predictive simulation of movement and the outer loop identifying the optimal design parameters of the device. It is utilized for designing a knee exoskeleton with a damper to assist level-ground and downhill gait, achieving a significant reduction in normalized knee load peak value by $ 37\% $ for level-ground and by $ 53\% $ for downhill walking, along with a decrease in the cost of transport. The results indicate that the optimal device applies damping torques to the knee joint during the Stance phase of both movement scenarios, with different optimal damping coefficients. The optimization framework also demonstrates its capability to reliably and efficiently identify the optimal solution. It offers valuable insight for the initial design of assistive wearable devices and supports designers in efficiently determining the optimal parameter set.

The frequency responses of circulation control and separation control using mini-spoilers for loads attenuation on plunging swept and unswept wings were compared in a water tunnel study. At the pre-stall angle-of-attack, the effectiveness of the spoilers significantly diminishes with increasing reduced frequency of the plunging motion. For the leading-edge spoiler, this happens because the roll-up of the vorticity promotes flow reattachment and reduces the effectiveness of loads attenuation. For the trailing-edge spoiler, the effectiveness of lift attenuation also decreases with increasing reduced frequency, due to the shedding of leading-edge vortices and immersion of the trailing-edge spoiler in the separated flow. The decay of the frequency response for both types of spoilers is similar, implying that it is dictated by the flow separation near the leading edge of the wing in both cases. With increasing sweep angle of the wings, the spoilers’ effectiveness decreases significantly in comparison to the unswept wing. Strong spanwise flow develops for the leading-edge spoiler, which sheds a streamwise vortex, with the same direction of rotation as the wing-tip trailing vortex. This causes partial reattachment of the flow and reduction of the separation area behind the spoiler. With increasing reduced frequency, strong leading-edge vortices dominate the flow over the wing. The leading-edge vortices generate additional vortex lift and also cause the trailing-edge spoiler to be immersed in the massively separated flows. Both factors reduce the effectiveness of the spoilers.