As an advanced flexible dynamic sealing technology, the leakage characteristics of a finger seal (FS) is one of the key research areas in this technology field. Based on the fractal theory, this paper establishes a mathematical model of the FS main leakage rate considering the fractal wear effect by taking into account the influence of the wear height on the basis of the eccentric annular gap flow equation. Based on the Hagen-Poiseuille law and the fractal geometry theory of porous media, a mathematical model of the FS side leakage rate considering the fractal porous media seepage effect is developed. Then, a mathematical model of the FS total leakage rate is established. The results show that the mathematical model of the FS total leakage rate is verified with the test results, the maximum error rate is less than 5%, and the mathematical model of the FS total leakage rate is feasible. With the gradual increase in working conditions and eccentricity, the FS main leakage rate gradually increases. In addition, the effects of the fractal dimension, fractal roughness parameters and porosity after loading on the FS main leakage rate are negligible. As the fractal dimension of tortuosity after loading gradually decreases, the fractal dimension of porosity after loading gradually increases, and the FS side leakage rate gradually increases. As the porosity after loading gradually increases, the FS side leakage rate gradually increases. Under different working conditions, different fractal characteristic parameters and different porosities after loading, the weight of the FS main leakage rate is much greater than that of the FS side leakage rate by more than 95%.

Brush seals, as a fundamental dynamic sealing technology in the aerospace and energy propulsion industries, require performance enhancement through instantaneous adjustment of the friction coefficient and force analysis of brush filaments. This paper establishes an instantaneous friction coefficient correction method based on the open volume between bristles and the backing plate. The downstream section of the double-row brush wire (2.6 mm) was quantitatively identified as the maximum leakage point, and it was found that the vortex characteristic length in the downstream area is approximately 1–3 times the bristle gap, with an increasing pressure ratio enhancing downstream turbulence and reducing gas leakage. A cantilever beam structural model was developed to assess the motion, force, and hysteresis properties of a single filament. Additionally, a porous medium model was utilized to elucidate the flow field and temperature distribution within the seal. The results suggest that the lag angle increases linearly over the first one-third of the brush wire’s length from the free end to the fixed end and is directly proportional to the pressure difference ΔP, reaching a maximum of 10.18°. The viscous drag causes the radial force y-component F_xy to increase and then decrease near the free end. The rear baffle contact force, F_b, shows variable peaks at two-thirds of the filament length. The displacement at the brush filament’s free end, the deflection angle, and the bending moment are directly proportional to the pressure differential. As pressure increases, the deformed region propagates toward the fixed end, and the maximum displacement at the free end of the brush wire reaches 13.04 mm. The leakage rate increases nearly linearly with ΔP and its deformation, reaching a maximum of 0.00849 m²/s. The pressure gradient growth rates of 164%, 73%, and 29% at the front baffle corner demonstrate that adding pressure chambers on front and rear baffles is optimal for high-pressure scenarios (ΔP > 0.3 MPa), while the formation of vortices between bristles and rotor reduces tip friction force and front-row turbulent disturbance, providing design guidance for extending seal service life.

To investigate the synergistic regulatory mechanism of vein structure and temperature on crack propagation behavior in plant leaves, this study conducted systematic tensile tests to determine the fracture behavior of leaves with different numbers of veins (0, 1, and 2) at various pretreatment temperatures (35–55 °C). A fractal-corrected fracture energy model was subsequently developed. The results show that both the crack fractal dimension and fracture energy first increase and then decrease with rising temperature, peaking at 45 °C. Fracture energy decreases as the number of veins increases: by approximately 60% for a single vein, and nonlinearly for two veins (synergy factor ranging from 0.59 to 0.71), indicating diminishing toughening returns. When the angle between the crack propagation direction and the vein is less than 90°, veins do not provide a toughening effect but instead act as preferential failure pathways, although they prolong the overall crack propagation duration. Crack propagation velocity exhibits intermittent fluctuations. In the temperature range of 50–55 °C, toughness increases and velocity fluctuations diminish. For double-vein leaves, velocity fluctuations are mild in the early stage, but a pronounced peak occurs later upon interface breakthrough. This model provides a reference for the quantitative analysis of fracture behavior in plant leaves.

Fragmented thrombolytic actuators address the limited time window of thrombolysis agents and the risk of intimal injury from mechanical thrombectomy, emerging as a crucial method for rapid vascular recanalization. However, occluded vessels are often tortuous and narrow, imposing strict size constraints on the actuator. Moreover, the inability to assess thrombolysis efficacy in real-time during procedures impedes timely adjustments to control strategies for the actuator. To address these challenges, this study designs a conical piezoelectric actuator that employs high-frequency vibration in conjunction with a small dose of thrombolytics to fragment and accelerate thrombus dissolution. Firstly, structural parameters of the actuator are optimized using grey relational analysis combined with an improved entropy-weighting method, and the optimal design is prototyped and tested. Next, a real-time thrombolytic solution concentration detection algorithm based on an Improved Grey Wolf Optimizer–Support Vector Regression (IGWO-SVR) model is proposed. Finally, an experimental platform is constructed for validation and analysis. The results show that compared to the initial design, the optimized actuator has significantly improved kinematic and force performance, with the tip amplitude increasing by 42% and the output energy density reaching 3.3726 × 10⁻² W/mm³. The IGWO-SVR model yields highly accurate, stable concentration estimates, with a coefficient of determination (R²) of 0.9987 and a root-mean-square error (RMSE) of 0.8118. This work provides a pathway toward actuator miniaturization and real-time thrombolysis monitoring, with positive implications for future clinical applications.