Zhong Luo

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.

Bi-doped rare-earth iron garnet (Bi:RIG) single crystals are the core of optical isolators, and demand for them is surging due to the development of artificial intelligence (AI) technology. In this work, bismuth-doped terbium iron garnet (Bi:TbIG) single crystals with a composition of Bi_0.86Tb_2.14Fe₅O₁₂ and a size of 37 mm were successfully grown by the top-seeded solution growth (TSSG) method using a lead-containing flux system. These crystals exhibited a regular rhombic dodecahedron morphology enclosed by the {110} plane, and a growth rate of 0.018 mm/h perpendicular to the {110} planes. Systematic characterizations revealed that the crystals exhibited good compositional homogeneity, with no obvious Fe, Tb and Bi segregation from center to edge. Rocking curve tests presented a full width at half maximum of 172 arcsec. X-ray photoelectron spectroscopy (XPS) results demonstrated that Fe exists exclusively in the +3 valence state without detectable Fe²⁺, whereas Tb is present in the +4 valence state. In addition, O was lattice O²⁻, without obvious defects. Magneto-optical tests indicated that the uncoated TSSG-grown Bi:TbIG crystals had 71% transmittance in the 1200~1600 nm waveband, and a Faraday rotation coefficient of 0.132°/μm at 1310 nm. The 11 × 11 mm samples exhibited an extinction ratio stably above 40 dB. The 349 μm thick samples meet the application requirements of miniaturized optical isolators. This study verifies the feasibility of TSSG for growing Bi:TbIG single crystals, offering a new technical route for Bi:TbIG growth with potential value for practical application.

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.

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.

This paper studied the Moisture absorption behaviors, DMTA temperature spectrum, Infra-red spectrogram, Quasi-static characters of the dry and hygrothermal UHMWPE composites. The material was UHMWPE fiber reinforced polyurethane matrix composite manufactured by hot press method, which was firstly kept in a heating oven, and then put in a beaker of distilled 70°C water bath for 24 days and 60 days. The results show that there were two plateaus for the moisture absorption curve of the UHMWPE composites. The coupled effects of moisture and temperature reduce the composite glass transition temperature(Tg) by matrix plasticization and degrades the fiber/matrix interface. The storage modulus and loss modulus of dry and 24 days hygrothermal were gradually decreased in the initiatory calefaction, which drop sharply in Tg. The tensile strength was lossing in the beginning, and comeback to the initial at last in the hygrothermal environment. The quasi-static compressive strength is reduced by about 8% after 24 days treatment. Hygrothermal treatment has no effects on the quasi-static characters.

Dynamic properties of high strain rate and absorbing energy for laminate composites in the marine environment were studied in this paper. The high strain rate dynamic compressive tests were carried out on Split Hopkinson Pressure Bar(SHPB) experimental facility at strain rate 1800/s, 1530/s, 1230/s and 950/s. The front surface failure modes were Analyzed by optical micrographs. A fractured fibres mode was discussed in high rate compression. The stress-strain rate curves showed that, the specimen dynamic properties were better for the samples immersed in marine environment for 12 days. The energy absorption properties were test by ballistic trajectory experiment. Experimental results and penetration faces showed that, the ballistic trajectory properties with 60days of hygrothermal environment was better.