Three-dimensional UAV path planning in complex environments poses substantial challenges owing to high-dimensional search spaces, nonlinear operational constraints, and multimodal solution landscapes. Although particle swarm optimization (PSO) has demonstrated considerable promise for this task, conventional PSO variants exploit only a limited subset of the historical positional data generated during the search process, thereby constraining their overall optimization capability. To overcome this limitation, this paper proposes a neural-guided multi-strategy particle swarm optimization algorithm (NGMS-PSO), which systematically mines evolutionary process data to enhance algorithmic search performance. Specifically, a neural network is trained on collected evolutionary data to construct a neural-fusion evolutionary operator that provides knowledge-driven directional guidance throughout the search. An evolutionary state indicator is further introduced to stratify the swarm into elite, normal, and exploratory subpopulations, each governed by tailored evolutionary strategies that collectively maintain a dynamic balance between exploitation and exploration. To mitigate premature convergence, an adaptive escape mechanism is additionally incorporated, which applies targeted perturbations to particles exhibiting evolutionary stagnation. Extensive comparative experiments conducted across test scenarios of varying complexity against 11 competitive algorithms demonstrate that NGMS-PSO consistently generates safe, smooth, and cost-efficient UAV trajectories, achieving statistically significant performance improvements in the majority of cases.
Full-annulus unsteady RANS simulations are performed for a turbofan nacelle with its fan and booster stages under a 45-knot crosswind at 115% design speed. The inlet distortion develops naturally from the nacelle-crosswind interaction. The time-averaged flow field agrees with the preceding steady RANS result to within 0.1% in mean total pressure ratio and total temperature ratio at the fan outlet, confirming that the incidence-driven circumferential work redistribution is adequately captured by the steady approach. The time-resolved AIP distortion index, however, exhibits strong intermittent peaks in the outer-span region that exceed the RANS level by a factor of four. Spectral analysis confirms that the unsteady pressure field is governed by deterministic rotor-distortion interaction, with no indication of self-excited rotating instability. In the distorted sector at 95% span, the upstream relative Mach number rises from 1.35 to 1.66, the passage shock shifts approximately 50 mm downstream, and the tip leakage flow extends to the adjacent leading-edge plane, indicating the onset of spillage. The tip leakage vortex breaks down within the distorted arc, while the undistorted sector retains a compact and coherent vortex structure. The blade loading increase is concentrated near the tip, with the peak chordwise pressure difference at 95% span approximately doubling, whereas the loading at 50% span remains nearly unchanged. At the present operating condition, the crosswind distortion moves the fan tip locally closer to the stability boundary within a limited circumferential arc, but the overall fan response remains quasi-steady.
To resolve that the lightweight, ablation resistance and thermal insulation of thermal insulation materials for solid rocket motors (SRMs) are difficult to synergistically improve, an innovative strategy of "high-temperature responsive controllable expansion" is proposed. Expandable microspheres (EMs) were introduced into the EPDM rubbers to prepare a new type of controllable expansion insulation material. These materials maintain a dense and continuous structure during manufacturing stages. And they can form uniform cell structure through in-situ expansion of EMs when exposed to high temperatures, realizing the dynamic synergistic improvement of thermal insulation and ablation resistance. It is shown that the EPDM-165 formula has the optimal comprehensive performance. The linear ablation rate decreases by 43.8%, the charring rate decreases by 13.4%, and the maximum backside temperature decreases by 29.5% compared with the basic formula. In the ablation motor test, the charring rate in the high-speed section is reduced by 40.7% compared with the basic formula. By controlling the formation time of the cell structure, this study effectively circumvents the problems of loose char layer and reduced ablation resistance of traditional foaming materials. It provides a new technical path for the performance breakthrough of thermal insulation materials for SRMs. It should be noted that the controllable expansion insulation materials have the limitation of performance degradation under long-term ablation conditions. And further optimization is required by improving the heat resistance of EMs and regulating the stability of the cell structure.
