Search Results (5,663)

Tooth crack, as a typical fault, directly affects the meshing characteristics of gears, which causes abnormal vibration and noise during the gear meshing process, with some even threatening the operational safety of the mechanical device. Meanwhile, the mapping relation between the tooth crack and the actual meshing characteristics is still unclear under the tooth surface morphology and lubrication properties. Aiming at this issue, an integrated time-varying meshing stiffness (I-TVMS) model with cracks is proposed under the complex and variable working conditions. Based on the potential energy method, the analytical expressions with cracks are derived and calculated, and, then, the variation laws of I-TVMS under different crack parameters, tooth surface morphology, and structural and excitation parameters are investigated. Combined with the healthy tooth, the crack increases the contact load on the tooth surface, and reduces the oil film thickness, which decreases the I-TVMS of the cracked tooth. The greater the crack depth and torque is, the smaller the oil film thickness, and the weaker the I-TVMS fluctuation will be. The influence of the crack angle depends on the crack type and meshing region. The tooth-root crack is more sensitive in the single-tooth region, whereas the tooth surface crack shows a larger change only in the double-tooth mean value. When the crack location transitions from the tooth root to the tooth top, the stiffness attenuation gradually weakens. Full article

Octopus maya is a fast-growing species from the Yucatán Peninsula with high economic relevance, accounting for a major share of regional fishery production. However, a significant fraction of the organism, rich in type I collagen, is discarded as by-products, representing a promising and underutilized source for sustainable biomaterials. This study evaluated, through a 3² factorial design, the effect of two factors on the rheological and dynamic mechanical properties of film-forming solutions (FFS). The first factor was the type of food-grade polysaccharide: chitosan (Ch), hydroxypropyl methylcellulose (HPMC), or starch (S). The second factor was the proportion of each polysaccharide blended with ultrasound-extracted Octopus maya insoluble collagen (CIPM), using polysaccharide ratios of 30:70, 50:50, and 70:30 (w/w). This approach aims to valorize octopus by-products through the recovery and functional utilization of collagen. Rheological properties were determined by rotational and oscillatory rheometry at 25 °C, with flow curves fitted to the Carreau-Yasuda model. All formulations exhibited pseudoplastic behavior (n < 1), with viscosity decreasing as shear rate increased. Pure CIPM showed high viscosity (190.36 Pa·s at 1 s⁻¹), which decreased (0.3–10.44 Pa·s) in HPMC and chitosan systems, suggesting their potential suitability for applications requiring fluidity, such as spray coatings or film-forming solutions, based on their rheological properties. In contrast, starch-based systems exhibited higher viscosities (33.54–197.53 Pa·s) and a more structured viscoelastic profile (G′ > G″), suggesting potential suitability for thick coatings or gels requiring structural stability, although these applications were not experimentally validated. These results demonstrate that CIPM-polysaccharide systems enable tunable rheological properties, supporting the use of Octopus maya collagen as a sustainable functional material for advanced food and biomaterial design. Full article

We demonstrate the molecular beam epitaxy growth of two-dimensional van der Waals ferromagnet Fe₃GaTe₂ films with precisely controlled thicknesses down to a single unit cell. Magneto-optical Kerr effect microscopy measurements reveal robust room-temperature ferromagnetism with perpendicular magnetic anisotropy persisting across all thicknesses, including finite coercivity in monolayer films. The magnetic domain structures show strong thickness dependence: ultrathin films exhibit near-single-domain states without resolved domain nucleation or domain wall propagation, while thicker films develop complex multi-domain configurations featuring bubble-like domains. These findings underscore the pivotal role of dimensional confinement in modulating the magnetic properties of Fe₃GaTe₂ and provide critical insights into thickness-dependent phenomena in two-dimensional magnets, advancing their prospects for room-temperature spintronic applications. Full article

The high-voltage spinel ${\mathrm{LiNi}}_{0.5}{\mathrm{Mn}}_{1.5}{\mathrm{O}}_4$ (LNMO) is a promising cobalt-free cathode material for lithium-ion batteries, yet its integration as a binder-free thin film on metallic current collectors via simple solution routes remains underexplored. Here, LNMO films were synthesized on 304 stainless steel (SS304) by metal–organic decomposition (MOD) from metal–acetate precursors in ethanol, followed by spin-coating and annealing at 500, 600, and 700 °C under flowing ${\mathrm{O}}_2$. The films were characterized by XRD, FESEM–FIB cross-sectioning, EDS, and XPS, and tested as binder-free cathodes by cyclic voltammetry and galvanostatic charge/discharge. All samples are dense, approximately 1.9 μm thick, and crystallize in the disordered spinel phase. The LNMO crystallite size increases from 21.9 to 43.8 nm between 500 and 700 °C, while the grain size also shows a temperature dependence, increasing the average size from 25 up to 56 nm in diameter. XPS confirms ${\mathrm{Mn}}^{4+}$ as the dominant manganese surface species (45–49%) across all samples. The films deliver reversible discharge capacities of 92, 92, and 70 mAh ${\mathrm{g}}^{-1}$ at 0.1 C for LNMO500, LNMO600, and LNMO700, respectively, with well-defined ${\mathrm{Ni}}^{2+}{\mathrm{/Ni}}^{3+}$ and ${\mathrm{Ni}}^{3+}{\mathrm{/Ni}}^{4+}$ redox peaks at 4.7 and 4.8 V. DFT calculations independently predict a voltage plateau at ∼4.7 V for $0.2\le x\le 1$, in agreement with the experimental profiles. These findings establish MOD as a viable, vacuum-free route to the synthesis of nanostructured LNMO cathodes. Full article

This study investigated the rheological, structural, barrier, mechanical, optical, and thermal properties of composite edible films based on citrus pectin and vegetable purées derived from broccoli, cauliflower, pumpkin, carrot, and their blends. Film-forming formulations were characterized in terms of rheological behavior, thickness, microstructure, gas and water vapor permeability, optical and mechanical properties, water contact angle, and thermal stability. The incorporation of vegetable purées significantly modified the properties of the pectin-based matrices. All film-forming solutions exhibited non-Newtonian shear-thinning behavior, with flow behavior index values below unity. The addition of vegetable purées markedly increased viscosity and flow resistance, indicating the formation of more structured systems with stronger intermolecular interactions. Apparent viscosity increased from 0.19 Pa·s in the control sample to 1.41 Pa·s and 1.19 Pa·s in the broccoli (B) and broccoli–cauliflower (B-CF) formulations, respectively, while the consistency coefficient increased from 0.29 to 51.38 Pa·sⁿ. Composite films exhibited lower water contents (0.090–0.114 gH₂O·g_d.m.⁻¹) than the control film (0.179 gH₂O·g_d.m.⁻¹) and were thicker (170–282 μm) than the pure pectin film (125 μm). Barrier analysis revealed a reduction in water vapor permeability from 18.99·10⁻¹⁰ to 10.74–14.69·10⁻¹⁰ g·m⁻¹·s⁻¹·Pa⁻¹ and a decrease in carbon dioxide permeability from 21.95 to 10.47–17.91 GRT. The carrot-containing film exhibited the highest tensile strength (62.17 MPa), whereas the pumpkin–carrot film demonstrated the most favorable combination of barrier and mechanical properties, including the lowest oxygen permeability (6.95 GRT), low water vapor permeability (10.74·10⁻¹⁰ g·m⁻¹·s⁻¹·Pa⁻¹), and high tensile strength (51.02 MPa). Thermogravimetric analysis revealed similar three-stage degradation profiles for all samples, while vegetable incorporation modified moisture release and increased residual mass. The obtained results confirmed the research hypothesis that vegetable-processing by-products can serve as valuable structure-forming components of pectin-based composite films and that interactions between vegetable-derived biopolymers and citrus pectin improve the mechanical, barrier, and functional properties of the resulting materials. Among the tested formulations, the pumpkin–carrot film demonstrated the greatest potential for further development as a biodegradable packaging material. The utilization of vegetable by-products in pectin-based films represents a sustainable approach supporting circular economy principles and the development of environmentally friendly packaging systems. Full article

Introduction: Heavy metal contamination in water represents a major environmental and public health challenge because toxic ions frequently occur as complex multi-species mixtures rather than isolated pollutants. This study presents a numerical design and optimization of a surface plasmon resonance (SPR) sensor based on a LaF/Au/BaTiO₃/WS₂ heterostructure for monitoring refractive-index changes associated with mixed heavy metal ions in aqueous media. Methodology: The optical response of the multilayer sensor was evaluated using the transfer matrix method under TM-polarized illumination at 633 nm. Systematic optimization was performed for the prism substrate, Au thickness, dielectric oxide layer, and 2D nanomaterial interface. The final configuration consisted of a LaF prism, 50 nm Au film, 2.0 nm BaTiO₃ spacer, and 0.80 nm WS₂ monolayer. Sensor performance was assessed using resonance-angle shift, sensitivity, detection accuracy, quality factor, figure of merit, FWHM, attenuation, and estimated limit of detection. Results and Discussion: The optimized LaF/Au/BaTiO₃/WS₂ configuration produced stable simulated SPR responses across single, binary, quaternary, and five-ion heavy metal matrices. The WS₂ monolayer provided the highest angular displacement among the evaluated 2D materials, while BaTiO₃ improved field confinement and limited optical damping in the numerical model. The configuration maintained attenuation near 1.6%, FWHM values around 7.9°, detection accuracy between 0.030 and 0.032 deg⁻¹, and model-based refractometric LoD values down to 3.49 × 10⁻⁵ RIU under the assumed angular-resolution criterion. Conclusions: The proposed LaF/Au/BaTiO₃/WS₂ SPR configuration provides a numerical framework for label-free monitoring of refractive-index changes associated with complex heavy-metal-ion mixtures in contaminated water. Experimental fabrication and testing are required to validate the simulated performance. Full article

Accurate quantitative diagnosis of spall sizes in rolling bearings is often hindered by the limitations of conventional dynamic models in characterizing temperature-dependent contact behavior. To address this issue, this paper presents a quantitative diagnosis method that incorporates point-contact thermo-elastohydrodynamic lubrication (TEHL) characteristics into a classical bearing dynamic framework. Specifically, rather than using prescribed or constant contact parameters, an improved equivalent stiffness–damping representation of the bearing contact interface is formulated based on TEHL-derived oil-film pressure, thickness, and temperature, while taking into account the inner–outer raceway thermal asymmetry. This localized lubricated contact representation is subsequently integrated into a classical five-degree-of-freedom (5-DOF) dynamic model to evaluate the double-impact response caused by outer-ring spalls. Comparative simulations using conventional 5-DOF, 4-DOF, and 2-DOF models, alongside experiments on a 6205-2-RS bearing with a 0.6 mm outer-ring defect, validate the proposed method. The results demonstrate that utilizing the TEHL-derived stiffness–damping representation significantly reduces spall-size estimation errors, improving both the accuracy and the physical interpretability of bearing fault quantification under thermally coupled conditions. Full article

To address the complex and highly variable wheel–rail adhesion behavior on high-speed railway curves, this study establishes a numerical wheel–rail rolling contact model based on starved elastohydrodynamic lubrication (EHL) theory and Herschel–Bulkley rheological characteristics. The model validation yielded RMSE = 0.0228, MAE = 0.0217, MAPE = 11.80%, R² = 0.828, and a 95% confidence interval of the mean residual of −0.0298 to −0.0136. The study focuses on the initial operational phase after application, systematically quantifying the fluid-dynamic regulation mechanisms of water-based friction modifiers once a thin, starved lubricating film has been formed on the rail surface under curving conditions. By analyzing rail profiles (CHN60 and CHN60N), operating parameters, and track geometry, this study shows how adhesion behavior on curved track sections is governed by the coupled effects of contact mechanics and lubrication. As the outer rail superelevation increases from 0 to 70 mm, the adhesion coefficient decreases by approximately 15–25%, mainly because the reduced normal force shifts the wheel–rail interface toward the Stribeck transition regime. Increasing axle load from 14 t to 30 t reduces the dimensionless film thickness, but the enlarged contact area contributes to a more stable adhesion level, with an increase of about 12%. Compared with the CHN60 profile, the CHN60N profile exhibits better geometric conformity, producing a lubricating film that is 10–15% thicker and leading to a lower and more stable adhesion coefficient, decreasing from approximately 0.35 to 0.1. The results also identify a critical lateral displacement of around −4 mm, beyond which the contact radius becomes stable and the adhesion coefficient reaches a minimum plateau. These findings clarify the competing effects of fluid entrainment and metallic asperity contact, and provide quantitative guidance for friction management and friction modifier application on curved track sections. Full article

Citrus peel is examined here as a naturally evolved protective surface, with the goal of developing a transferable quantitative framework for extracting engineering-relevant descriptors from biological protective surfaces and using them as design templates for biomimetic counterparts. A single-specimen-per-species design is adopted to map intra-fruit geometric variation across regions and magnifications; absolute descriptor values are therefore reported as ordinal indicators of inter-species ranking rather than as population means. Five citrus species (lemon, orange, mandarin, grapefruit, and bitter orange) were characterised by mechanical testing (cutting, puncture, and compression; five replicates per fruit), gravimetric peel density and thickness, and scanning electron microscopy (SEM) at 100×–10,000×. The 135-image SEM dataset was processed with an automatic-calibration pipeline performing per-image scale-bar detection, multilevel-Otsu segmentation of albedo air space, cell-bounded surface segment (CBSS) and oil-gland segmentation on flavedo, and grey-level co-occurrence matrix (GLCM) texture analysis with a directional anisotropy index $A_F$. Calibration was consistent across all images (FoV × magnification $=\mathrm{403,273}\pm 410$ $\mathsf{\mu }$m$·\times$, $\pm 0.10\%$). Principal component analysis separated flavedo and albedo at every magnification (PC1 + PC2 = 84–92%). Within this dataset, grapefruit showed the densest CBSS cover (1072 ${\mathrm{mm}}^{-2}$) together with the highest oil-gland density (2.77 ${\mathrm{mm}}^{-2}$); bitter orange showed the largest CBSS area (23.7 $\mathsf{\mu }{\mathrm{m}}^2$) and the thickest peel (13.1 mm); mandarin showed the most directionally oriented flavedo film ($A_F=0.0885$); and lemon showed the most open albedo (${\phi }_{2D}=36.2\%$). Oil-gland equivalent diameter was essentially invariant (∼45 $\mathsf{\mu }$m) across the five fruits, while gland density varied 4.4-fold. The structural metrics define a layered descriptor space—a dense isotropic surface relief versus a thick cellular bulk—that supplies two distinct bioinspired-design priors: dense surface films as a structural prior for selective-permeability membranes and layered cellular cores as a prior for impact-absorbing panels. A modified-atmosphere packaging (MAP)-compatible biomimetic film is identified as one downstream design hypothesis requiring direct gas-permeability verification on synthetic membranes. Full article

The curing quality of epoxy resin at wind turbine blade joint seams critically affects blade integrity and service reliability, yet conventional metallic heating systems often suffer from poor temperature uniformity, limited flexibility, and slow thermal response. In this study, a flexible and lightweight heating blanket based on carbon nanotube (CNT) electrothermal film was developed for blade reinforcement and in situ curing applications. The device employs a multilayer composite architecture consisting of a CNT heating layer, a nano-aerogel thermal insulation layer, a thermoplastic polyurethane electrical insulation layer, and a silicone-coated glass fiber protective layer, together with an intelligent temperature control system. The resulting blanket, with a total thickness of 3.85 mm, exhibited rapid and stable heating performance, increasing from 25 to 120 °C within 8 min. Under resin-curing conditions, it achieved an initial heating rate of 7.2 °C min⁻¹ and a temperature uniformity of ±2.6 °C, markedly outperforming a conventional Ni@Cr alloy heating blanket. Accelerated aging tests further demonstrated stable electrothermal performance under the tested condition. Those results indicate that the proposed CNT-based heating blanket provides an efficient and reliable thermal management strategy for large curved composite structures. Full article

The shock wave/boundary layer interaction (SWBLI) is a common flow phenomenon in high-speed aircraft flow fields. It is important to control the separation caused by SWBLI. This paper investigates the influence of spanwise periodic-motion micro-vortex generators (MVGs) on SWBLI. A combination of particle image velocimetry (PIV), high-frequency Schlieren and fluorescent oil-film visualization was employed to analyze the interaction region of a flat plate compression ramp model. The incoming flow Mach number was 6, and the MVGs oscillation frequencies were 10 Hz, 30 Hz and 50 Hz, respectively. The results reveal that neither the presence nor the spanwise oscillation in the MVGs fundamentally altered the separation–reattachment flow structure. Nonetheless, both factors contributed to an increase in boundary layer thickness and an expansion of the absolute size of the separation region. The trailing vortices generated by the MVGs exerted a stabilizing influence on near-wall turbulent structures, resulting in a reduction in surface friction drag. However, the drag reduction effect diminished as the oscillation frequency increased, corresponding to a weakening of the trailing vortex strength. Additionally, the MVGs and their spanwise oscillation modulated the low-frequency energy distribution of the flow, amplifying the low-frequency oscillation peak associated with the separation shock and raising the time-averaged oscillation position. Full article

Three-year atmospheric field-exposure tests were conducted on 304 austenitic stainless steel at the Great Wall and Zhongshan Stations in Antarctica to evaluate its corrosion behavior under severe polar conditions. The exposed specimens were dominated by localized corrosion with pronounced pitting characteristics at both sites. Corrosion was more severe at Zhongshan Station, and the mean corrosion rates at Great Wall and Zhongshan Stations were 1.428 and 1.643 μm y⁻¹, respectively. The mean/maximum pit depths were 4.16/5.51 μm at Great Wall Station and 5.85/8.24 μm at Zhongshan Station. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), grazing-incidence X-ray diffraction (GIXRD), and focused ion beam-transmission electron microscopy (FIB-TEM) showed that the corrosion products consisted mainly of β-FeOOH, α-FeOOH, and γ-Fe₂O₃, and the Antarctic exposure substantially altered the thickness, structure, and electrochemical response of the passive film. Compared with the unexposed specimen, the exposed specimens exhibited markedly lower charge-transfer resistance and higher donor density, indicating degradation of the protective passive film. Combined with the site-specific environmental features, the lower temperature, more intense freeze–thaw cycling, freezing-induced concentration of electrolytes, and stronger irradiation at Zhongshan Station are inferred to promote Cl⁻ enrichment in localized surface liquid films and destabilization of the passive film, thereby accelerating pit initiation and growth. These findings provide a mechanistic basis for material selection and corrosion-protection design for 304 stainless steel in polar engineering environments. Full article

To improve the wear resistance of 45 steel, nano-agglomerated Al₂O₃-TiO₂-CeO₂/carbon nanotubes (CNT) composite powders were prepared by spray drying and ball milling, followed by plasma spraying to fabricate coatings. The effect of CNT content on microstructure and wear resistance was investigated. The powders showed uniform size and high sphericity. Coatings mainly consisted of α-Al₂O₃, γ-Al₂O₃, and TiO₂. CNT addition refined grain size to 18.3 ± 1.1 nm. The high thermal conductivity of CNT reduced unmelted particles, improving coating density and element uniformity. Average coating thickness was 200 μm. When the CNT content reached 3 wt.%, the coating porosity decreased to 5.01 ± 0.72%. TEM analysis indicated that CeO₂ was mainly located at the grain boundaries. Moreover, the interfaces between CNT (002) and CeO₂ (220) appeared clean and well-bonded. As CNT content increased, microhardness and wear resistance first increased then decreased. At 3 wt.% CNT, the volumetric wear rate was 0.87 ± 0.15 × 10⁻⁵ mm³·N⁻¹·m⁻¹, representing an 8.46-times improvement in wear resistance compared to the substrate. The presence of CeO₂ enhanced the surface activity of CNT, facilitating the formation of lubricating films during friction and contributing to the superior wear resistance of the composite coating. Full article

Light-converting polymer coatings and films are emerging passive photonic materials for spectral engineering in sustainable and protected agriculture. By absorbing ultraviolet or weakly used spectral components and re-emitting in visible bands that overlap with photosynthetic pigments and plant photoreceptor action regions, these materials can modify the radiation environment without additional electrical energy input. This critical narrative review analyses light-converting polymer films and coatings from a materials and coatings perspective, with emphasis on photophysical mechanisms, polymer matrices, luminophore families, coating fabrication routes, optical transparency, photoluminescence, aggregation phenomena, photostability and scalability. The photobiological background is included as a concise framework that justifies the spectral targets of the conversion process. Rare-earth complexes, inorganic phosphors, quantum dots, aggregation-induced-emission systems and organic dyes are compared as candidate luminophores. Particular attention is devoted to the general challenges associated with organic luminescent coatings, including dispersion, aggregation, optical transparency, photostability, and scalability. A PMMA/PDI coating system is discussed only as an illustrative case study demonstrating these broader materials-design considerations. Extrusion, solution casting, spin-coating, dip-coating and sol–gel processing are evaluated as fabrication strategies for laboratory and large-area greenhouse applications. The work concludes by identifying the main gaps that must be addressed before practical deployment: quantitative UV–Vis and photoluminescence characterization, absolute quantum yield, haze and scattering, thickness and morphology mapping, accelerated UV aging, weathering resistance, toxicity assessment and crop-specific validation. Full article

Cutin, a natural polyester, has attracted attention as a precursor for bio-based materials mimicking plant cuticles, particularly in food packaging. Most studies focus on polycondensation of hydrolyzed cutin fractions or combining cutin hydrolysates with other components; however, cutin precipitation, conditions affecting it, and cutin isolate film properties, without addition of other filmogenic material, remain insufficiently understood. Owing to the pH-dependent solubility of cutin, which progressively decreases as pH is lowered from strongly alkaline to acidic conditions, this study investigates the influence of pH on cutin dispersion formation and characteristics, and evaluates the impact of these dispersion properties on the formation and performance of self-assembled cutin isolate films, with a view to developing films with improved water-barrier and moisture-resistance properties. The influence of three plasticizers, glycerol, propylene glycol, and polyethylene glycol 400, at two concentrations was also evaluated. Results demonstrated that pH is the primary factor influencing cutin isolate dispersion characteristics and film performance, with decreasing pH promoting cutin precipitation and particle aggregation, thereby inducing changes in film structure. The strongest effects were observed for swelling, solubility, and tensile strength, followed by water vapor permeability, elongation at break, and thickness. Plasticizer type mainly affected moisture content and significantly influenced permeability and thickness, while concentration of plasticizer primarily impacted permeability. Interactions between pH and plasticizer significantly influenced most properties. Films prepared from cutin dispersions at pH 6.5 and pH 5 with polyethylene glycol (10%) showed the best balance of mechanical and barrier properties. Additionally, films prepared from the cutin solutions at pH 12 with glycerol (20%) exhibited good mechanical performance and high solubility, suitable for specific applications. Full article