Rod fastened rotor is widely used in gas turbine, aero engine, and other occasions. The bending stiffness of the contact interface directly affects the stable operation of the rotor. Dynamic model of the rod fastened rotor-bearing system has been established considering nonuniform stiffness of interface. The motion equation of this system has been deduced from Lagrange's equations. The linear dynamic characteristics of this rotor has been investigated, such as Campbell diagram, critical speed, and formation, and the nonlinear characteristics of this system, such as chaos and bifurcation, has been investigated too. The result shows that "bistable state" characteristic appeared on the rod fastened rotor system; that is, there are two critical speeds for each order, and they are all positive precession critical speed, and the amplitude response to the lower critical speed is much larger than that its counterparts to the higher critical speed. In terms of nonlinear characteristics, the rod fastened bearing system has experienced periodic 1 motion, multiple periodic motion, quasi-periodic motion, periodic 1 motion, and chaotic motion successively.

To address the drag reduction requirements of superhydrophobic surface coatings for underwater vehicle hulls, this study designed a synthesis method based on resin substrate modification and filler modification according to superhydrophobic coating synthesis techniques. Three types of superhydrophobic microstructured surface coatings were prepared: polyurethane resin, silicone resin, and fluororesin. The coatings were fabricated by incorporating fluorine-modified SiO₂ nanoparticles into the modified resin matrices to construct hierarchical micro/nanostructures. The main components and synthesis processes for each coating were determined. Performance tests were conducted to evaluate mechanical properties (thickness, hardness, adhesion, wear resistance), functional characteristics (surface morphology, static/dynamic hydrophobic angles), and environmental resistance (seawater immersion, salt spray stability, thermal stability). Five surface coating test plans for underwater vehicle hull models were proposed, and drag reduction experiments were carried out to compare total drag, drag coefficient, and drag reduction rate across coating plans. Experimental results indicated that the silicone resin superhydrophobic coating with F660 + 8% SiO₂ exhibited the best comprehensive performance, while the PU + 6% SiO₂ superhydrophobic coating achieved optimal drag reduction at speeds below 9 m/s, meeting the performance criteria for underwater vehicle hull applications.

Marine deck coatings suffer from premature failures such as wear thinning, flaking, and brittle cracking under repeated rolling, abrupt stopping/steering, and high shear loads of heavy equipment due to the imbalance of hardness, strength, toughness, and wear resistance. To address this issue, a rolling load-resistant coating system with an epoxy–amine/epoxy–thiol dual-crosslinked network was constructed using liquid polysulfide rubber (Lp-3) as the key crosslinking modifier, and the effect of Lp-3 content (0–2 wt%) on the comprehensive performance of the coating was systematically investigated. The results showed that the coating achieved the optimal synergy of properties at 1 wt% Lp-3 loading: Shore hardness reached 88.7 HD with the pencil hardness maintained at 8H, adhesion strength increased to 7.2 MPa, Taber abrasion loss significantly decreased to 14.8 mg, tensile strength rose from 5.5 MPa to 12.4 MPa, elongation at break nearly doubled, shear strength reached 10.2 MPa, and the failure mode transformed from brittle cleavage to ductile shear. Mechanistic analysis revealed that the terminal thiol groups of Lp-3 underwent a click reaction with epoxy groups, covalently embedding flexible polysulfide segments into the rigid epoxy network and forming Fe–S interfacial chemical bonds to enhance adhesion. The microphase separation, chain relaxation, and energy dissipation mechanisms effectively blunted crack propagation and alleviated stress concentration, while maintaining sufficient surface hardness and the continuity of the load-bearing skeleton. This work realizes the synergistic optimization of high strength, high toughness, strong adhesion, and excellent wear resistance for marine deck coatings and provides a new strategy and critical technical parameters for the design of functional coatings under heavy-duty dynamic service environments.

To address the issues of color cast, insufficient contrast, and detail loss in underwater optical images, this paper proposes an underwater image enhancement method based on multi-scale fusion and detail sharpening. The algorithm first applies an improved Gray World White Balance method with color compensation to perform color correction on the original underwater image. Subsequently, two processed images are generated for fusion: the first image is obtained by applying a Particle Swarm Optimization-enhanced Contrast Limited Adaptive Histogram Equalization (CLAHE) algorithm to the color-corrected image to enhance contrast; the second image is produced by applying an adaptive gamma correction algorithm to improve uneven illumination regions. These two images are then fused using a multi-scale fusion strategy. Finally, a weighted multi-scale detail sharpening technique is employed to further enhance the texture details of the fused image, yielding the final enhanced result. The performance of the proposed method is evaluated using no-reference underwater image quality metrics: the Underwater Image Quality Measure (UIQM) and the Patch-based Contrast Quality Index (PCQI), and tested on the open-source dataset from Nanyang Technological University. Experimental results demonstrate that the proposed method leads to an improvement in underwater image quality in both qualitative and quantitative assessments.

Combustion oscillations can cause severe damage to combustion systems and compromise the reliability of energy conversion devices. To achieve early identification of the transition toward combustion instability, this study proposes an adaptive kurtosis‐based detection method using dynamic pressure signals. The feasibility of temporal kurtosis ( T K ^∗ ) as a precursor indicator of combustion oscillations is investigated using experimental pressure data obtained from both a Rijke tube combustor and a swirl combustor. The statistical characteristics of kurtosis under stable combustion, intermittent oscillation, and limit‐cycle oscillation conditions are first analyzed, revealing the relationship between pressure signal distribution evolution and combustion stability variation. Furthermore, the temporal evolution of T K ^∗ during the formation of combustion oscillations is investigated, demonstrating that the increase of T K ^∗ is associated with the gradual excitation of thermoacoustic modes and the transition from stable combustion to instability. An adaptive sliding‐window algorithm based on the fluctuation characteristics of dynamic pressure signals is developed to improve the robustness and efficiency of online monitoring. The results demonstrate that temporal kurtosis can serve as a quantitative statistical indicator for tracking stability degradation and provide an effective criterion for real‐time assessment and early warning of combustion oscillations.