Search Results (4,910)

Silica-based optical fibers suffer radiation-induced attenuation (RIA) in radiation-intensive environments, severely reducing their lifespan. We propose a kinetic model based on the evolution of multiple color centers to accurately simulate defect density and quantitatively characterize RIA. The irradiation experiments were conducted using a Co-60 gamma-ray source at a dose rate of 1.25 Gy/s and a controlled temperature of 10 ± 2 °C, with measurements performed at 1310 nm and 1550 nm wavelengths. The model was experimentally validated using fluorine–germanium co-doped fibers. Fitting results demonstrate high accuracy, with a coefficient of determination (R²) > 0.999, normalized root mean square error (NRMSE) < 0.57%, and mean absolute error (MAE) < 0.74 dB/km. Furthermore, it successfully decouples complex macroscopic RIA signals into distinct transient and steady-state defect pools. This phenomenological decoupling enables band-dependent damage analysis and serves as a baseline for evaluating steady-state degradation of F-Ge co-doped fibers under constant irradiation. Full article

To address the major safety hazard that heat released from mining polyurethane (PU) reinforcement materials may induce spontaneous combustion of residual coal in goaf, this study selected No. 3 coal from Wangzhuang Coal Mine, Shanxi Lu’an, as the research object. A self-developed large-capacity, large-scale experimental system was used to conduct programmed heating experiments on 2.0 kg multi-particle-size coal-PU mixed samples. The effects of PU content on characteristic gas release, crossing point temperature (CPT), residue morphology, and TGA-DSC characteristic temperatures were systematically investigated, and the reaction-kinetic evolution was further analyzed using the distributed activation energy model (DAEM). The results show that coal and PU exhibit a significant synergistic enhancement effect during co-heating. As the PU content increased, the release concentrations of CO, C₂H₄, and C₂H₆ increased markedly, and their initial release temperatures decreased, whereas CH₄ generation was inhibited by hydrogen-radical competition; no C₂H₂ was produced below 400 °C. The CPT decreased linearly with an increasing PU content, with an average decrease of approximately 8.5 °C for every 10% increase in PU content. Residue morphology showed clear critical features: glassy agglomerates appeared when the PU content exceeded 16.67%, and dense bulk coking occurred when the PU/coal mass ratio was greater than 1:10. TGA-DSC analysis showed that when the PU/coal ratio was lower than 1:10, the ignition temperature of the mixed sample was higher than that of pure coal, indicating an inhibitory synergistic effect. When the ratio exceeded 1:10, the ignition temperature decreased significantly, and the synergy shifted to promotion; increasing the heating rate shifted the characteristic temperatures to higher values and increased the reaction intensity. DAEM analysis further confirmed that when the PU ratio exceeded 1:10, the apparent activation energy of the mixed samples was lower than that of pure coal. Coal powder also acted as a physical skeleton that effectively dispersed molten PU, eliminated the activation-energy peaks of pure PU in the conversion ranges of 30–50% and 70–90%, and substantially improved combustion stability. Mechanistically, low-temperature PU melting and coating optimized heat and mass transfer, medium-temperature pyrolysis released active radicals and combustible gases that altered coal pyrolysis pathways and the radical reaction environment, and high-temperature hydrogen-radical competition reshaped the gas-product distribution. Together, these processes form a complete chain of synergistic spontaneous combustion. This study identifies key safety threshold parameters for PU reinforcement materials, recommends a PU content of ≤9.10%, and identifies CO and C₂H₄ as priority early-warning gases, providing direct experimental evidence for characteristic-gas-based early warning and mine fire prevention. Full article

Under low-temperature and high-humidity conditions, stable ice layers readily form on asphalt pavements in cold regions, and the enhanced ice–asphalt interfacial adhesion significantly increases deicing difficulty and traffic safety risks. To clarify the factors governing ice–asphalt interfacial adhesion strength, this study combines macroscopic pull-off tests and molecular dynamics simulations to systematically investigate the effects of interfacial contact area, temperature, pull-off rate, and molecular characteristics of representative asphalt components. The pull-off results show that adhesion strength increases markedly with decreasing temperature, rising from approximately 163 kPa at −2 °C to 242 kPa at −10 °C. In contrast, the nominal adhesion strength decreases with increasing ice specimen size, suggesting that size-related interfacial heterogeneity and nonuniform stress transfer may contribute to the pull-off response. The adhesion strength also generally decreases as the pull-off rate increases. Molecular dynamics simulations show that smaller asphalt–ice interfacial models exhibit higher molecular-scale nominal adhesion responses, while temperature-dependent simulations provide short-range asphalt–ice interaction descriptors for interpreting the experimental temperature trend. The calculated short-range asphalt–ice interaction energy becomes less negative from −531.4 to −352.5 kJ mol⁻¹ with increasing temperature, supporting the experimentally observed strengthening of adhesion at lower temperatures. Single-molecule pull-off simulations of 12 representative asphalt molecules reveal pronounced molecular differences, with molecular-scale nominal adhesion strengths ranging from 303.7 to 734.6 MPa. Asphaltene and polar aromatic molecules generally show stronger adhesion, which is associated with larger projected contact area, flatter molecular configurations, and heteroatom-induced polar sites. The molecular polarity index shows a moderate positive association with molecular-scale nominal adhesion strength. These results establish a scale-aware mechanistic correspondence between macroscopic pull-off behavior and molecular interaction descriptors at the ice–asphalt interface, providing insights for interfacial adhesion regulation and anti-icing design of asphalt pavement materials in cold regions. Full article

While global climate change is fundamentally reshaping thermal regimes, capturing these shifts in topographically diverse regions remains a significant hurdle for standard gridded datasets. This study provides a comprehensive spatiotemporal analysis of 16 extreme temperature indices across Northern Carpathian from 1980 to 2024 using the E-OBS dataset. The QDM framework proved highly effective in neutralizing elevation-induced temperature biases, which reached up to 5.1 °C in raw E-OBS data. Beyond simple bias removal, the correction significantly improved the daily accuracy of the dataset, with RMSE values at high-altitude stations, such as the Chopok summit (1995 m), decreasing from 5.1 °C to 2.3 °C. Both Warm Days (TX90p) and Summer Days (SU) show near-perfect Field Coherence (C_f = 100% and 98%, respectively). A prominent feature of this temporal national average trend is its inherent asymmetry; the Annual Minimum (TNn) is climbing nearly twice as fast (+1.1 °C/decade) as the Annual Maximum (TXx) (+0.6 °C/decade), though the warming of these coldest nights is more localized (74.5% coherence). We also identified a clear signal of Elevation-Dependent Warming (EDW), with absolute maximums surging most aggressively in the Northern Carpathians at +1.6 °C/decade. Conversely, cold-tail indices like Ice Days are in a concurrent nationwide retreat (C_f = 97%), a shift that significantly reduces the physical window for winter tourism and alters the climatic envelope for fragile mountain ecosystems. Ultimately, these results position Slovakia as a high-sensitivity climate region where observed trends often outpace broader Central European averages, highlighting the urgent need for localized, nature-based adaptation strategies. Full article

Defect engineering of anatase TiO₂ nanosheets by hydrogen reduction is a compelling strategy to boost visible light photocatalytic Cr(VI) reduction, a process of vital importance for detoxifying highly toxic and carcinogenic Cr(VI) pollutants. However, the necessary high-temperature hydrogen treatment invariably induces morphological collapse, negating the structural merits of the two-dimensional nanosheets. Herein, we propose an ethylenediamine reflux protection strategy combined with hydrogen reduction to fabricate defect-rich TiO₂ nanosheets (EN-TiO_2−x-NS) that preserve the original morphology. The resulting EN-TiO_2−x-NS retained the square nanosheet structure and (001) facets, while Ti³⁺ and oxygen vacancies were successfully introduced. The bandgap narrowed from 2.95 to 2.55 eV, leading to enhanced visible light absorption and charge separation efficiency. For photocatalytic Cr(VI) reduction under visible light, EN-TiO_2−x-NS achieved a removal rate of 97.3% within 20 min, with a rate constant 1.93 times higher than that of pristine TiO₂ nanosheets and 3.17 times higher than that of the directly hydrogenated sample. The catalyst also exhibited excellent cycling stability. This work demonstrates a synergistic strategy combining morphology preservation and defect engineering, providing a new approach for designing high-performance TiO₂-based photocatalysts. Full article

Passive daytime radiative cooling (PDRC) materials require high solar reflectance and high atmospheric window emissivity. However, high solar reflectance achieved by scattering strategies often relies on porous structures, which can compromise the material’s mechanical reliability. To address this trade-off, we develop a layered alumina nanofiber membrane (LANM) by dual-nozzle electrospinning with programmed alternating deposition, in which alternating deposition and subsequent removal of alumina precursor layers and sacrificial polyvinyl alcohol (PVA) interlayers generate a continuously layered architecture with periodic interfaces and interlayer air gaps. This interfacial geometric design enables simultaneous regulation of solar-band scattering and bending load transfer within a single alumina system. Because photon flux attenuates with depth, shallow interfaces contribute more strongly than deeper ones; therefore, the micro-layered architecture enhances scattering while maintaining high emissivity in the atmospheric window. In outdoor testing, LANM achieved a maximum sub-ambient temperature reduction of ~5.8 °C, representing a further improvement of about 2.4 °C compared to Monolithic alumina nanofiber (ANM). Moreover, interlayer interfaces induce a multiple-neutral-axis mechanism and segmented stress transfer, thereby improving bending deformability rather than load-bearing strength. Full article

Ti-Al intermetallic compounds (Ti-Al IMCs) are emerging as lightweight, high-temperature structural materials with considerable application potential. Owing to their low density and high-temperature capability, these materials can improve the thrust-to-weight ratio of aeroengines, enhance the high-temperature service performance of aircraft, increase fuel efficiency, and improve adaptability to harsh environments. However, their intrinsic room-temperature brittleness leads to high cutting forces, elevated cutting temperatures, and severe tool wear during machining, making it difficult to ensure machining quality and limiting their large-scale applications in the aerospace industry. Ultrasonic vibration-assisted machining (UVAM) introduces a high-frequency, low-amplitude intermittent cutting mechanism that actively regulates material removal and offers a feasible route for overcoming the machining bottleneck of Ti-Al IMCs. This review summarizes the recent progress in UVAM for machining Ti-Al IMCs. First, the typical applications and machining characteristics of Ti-Al IMCs are discussed. Existing studies are then reviewed in terms of cutting performance, including cutting force, cutting temperature, chip morphology, tool wear, and post-machining surface integrity, including surface roughness, surface defects, residual stress, and work hardening. The reviewed evidence indicates that UVAM can reduce cutting forces and temperatures, improve chip morphology, and extend the tool life. It can also improve machined surface integrity by decreasing surface roughness, suppressing surface defects, inducing beneficial residual compressive stress layers, and regulating work-hardening behavior. This review provides systematic theoretical guidance and technical references for improving the machinability of Ti-Al IMCs via UVAM, thereby enabling the controllable, high-performance, and high-reliability fabrication of these difficult-to-machine materials in aerospace precision manufacturing. Full article

Coaxial magnetic gears (CMGs) have emerged as a promising alternative to conventional mechanical gear systems due to their contactless torque transmission, low maintenance requirements, and high reliability. However, under high-speed operation, conductivity-induced eddy current losses become dominant and significantly limit thermal performance. This study comparatively investigates the coupled electromagnetic and thermal behavior of two compact CMGs with identical torque capacity using M400-50A electrical steel and cobalt-based Hiperco 50A. Coupled electromagnetic–thermal finite element analyses are performed from 1000 to 12,000 rpm under worst-case natural convection conditions. The results demonstrate that the use of Hiperco 50A reduces core losses by up to 71% at high speeds and enables approximately 7.3% greater volumetric compactness owing to its higher saturation capability. Eddy-current-related losses remain the dominant loss mechanism at elevated speeds, causing inner-rotor permanent-magnet temperatures to exceed the allowable limits of NdFeB materials. Under natural convection, the outer permanent-magnet temperature remains below the critical threshold of 200 °C up to approximately 5800 rpm for the M400-50A design. With Hiperco 50A, this limit increases to approximately 6000 rpm under identical operating conditions, corresponding to an improvement of about 3%. These findings demonstrate the thermal benefits of high-saturation magnetic alloys; however, additional cooling strategies are required for operation at higher speeds. Full article

As MicroLED technology scales below 10 μm, Cu is increasingly utilized for interconnects due to its high thermal and electrical conductivity. However, Cu-induced degradation in GaN remains a critical reliability concern. This study investigates 10 nm Ni, Ti, and Pt barriers in Cu/Al stacks on green GaN-on-Si devices with a mesa diameter of 350 μm after isothermal annealing at 100 °C, 200 °C, and 300 °C for 2 h, aiming to provide a reference for future barrier design in scaled MicroLED devices. Electrical and electroluminescence measurements show that while 100–200 °C annealing optimizes contact resistance, higher temperatures cause Cu interdiffusion with metal-dependent severity. Ti emerges as the optimal general-purpose barrier, achieving the highest EL intensity among annealed samples at 300 °C, demonstrating that higher-temperature annealing enhances rather than degrades performance, thanks to effective Cu blocking and improved contact formation. Pt offers comparable barrier effectiveness with superior thermal stability, maintaining stable electrical characteristics and retaining 42% of peak EL intensity even at 300 °C. In contrast, Ni exhibits insufficient blocking, suffering 83% EL quenching and severe electrical degradation at 300 °C. Notably, as-deposited PtCuAl devices show an unexpected carrier localization effect yielding the highest recorded EL intensity (2750 a.u.), suggesting contact engineering opportunities. These findings establish a barrier effectiveness hierarchy (Ti ≈ Pt >> Ni) for thermal stability. Full article

The disposal of high-water-content bentonite slurry generated from underground construction presents prominent environmental and technical challenges, calling for low-carbon and efficient consolidation technologies. This study proposes an integrated flocculation–preloading–electro-osmosis (FPE) method using anionic polyacrylamide (APAM) combined with ground granulated blast furnace slag to strengthen dewatering and stabilization of bentonite slurry. Settlement column experiments were conducted to determine the optimal APAM dosages. A series of FPE consolidation experiments were performed to monitor drainage, settlement, electrical current, temperature and post-treatment soil properties, combined with microstructural analysis to reveal the synergistic mechanism. The results show that APAM creates abundant seepage channels via adsorption bridging and flocculation, significantly accelerating early-stage drainage and settlement rates without obviously increasing total drainage and final settlement. The polymer hydrogel homogenizes soil structure, leading to a gradual increase in moisture content and decrease in shear strength from anode to cathode, and effectively eliminates cracking during electro-osmosis. The temporary seepage channels induce a faster initial current rise, while the polymer coating increases apparent resistivity after free water discharge, thereby reducing current and temperature during the electro-osmotic consolidation stage. Appropriate APAM dosage thickens the electric double layer to raise the free swell ratio, whereas excessive dosage restricts swelling by particle coating. Microscopic observations confirm that chain-structured APAM and flocculent C-(A)-S-H hydration products cement soil particles and fill pores, improving soil integrity and shear strength. Overall, APAM improves early-stage efficiency and soil uniformity/integrity. In addtion, its combined effect with slag on bentonite shear strength increase is relatively higher than that of 0% slag condition. The integrated FPE technique realizes synchronous high-efficiency dewatering and low-carbon stabilization of high-water-content bentonite slurry, providing a novel and practical solution for engineering slurry disposal. Full article

China is rich in high-sulfur natural gas resources. During reservoir development, reservoir temperature and pressure reduction induces the precipitation of elemental sulfur. Subsurface sulfur deposition seriously affects the recovery and the stable production of high-sulfur gas reservoirs. This study utilized multiple experimental techniques, including CT scanning, scanning electron microscopy, energy spectrum analysis, and nuclear magnetic resonance. The experiments were conducted under different water saturation levels and pressure differences. The results showed that the permeability of the rock samples decreased after sulfur deposition. The permeability reduction varied from 0.004 mD to 8.852 mD, with a relative change of 10.2% to 29.8%. Meanwhile, sample porosity also declined, and the porosity damage ranged from 1.5% to 11.9%. Scanning electron microscopy showed that sulfur presented a membrane adsorption morphology on the surface of skeleton particles, with spherical particles protruding from the membrane. Rock samples with poorer physical properties showed lamellar superposition sulfur deposition. Sulfur deposition damage became more severe with increasing pressure difference and weakened as water saturation increased. Beyond a water saturation of 40.6%, further increases no longer reduce sulfur deposition damage. Full article

Maintaining effective fluid-loss control in water-based drilling fluids under coupled high-salinity, high-temperature, and high-density conditions remains a critical challenge in deep and ultra-deep drilling operations. In this study, a low-molecular-weight polymer fluid-loss additive (LM-ASQF) was synthesized via redox-initiated copolymerization of acrylamide, dimethyldiallylammonium chloride, and sodium allyl sulfonate. The synthesis route and proposed polymer structure were further illustrated to clarify the incorporation of amide, quaternary ammonium, and sulfonate functional units within the LM-ASQF molecular architecture. The polymer exhibited a controllable number-average molecular weight of 18.2–29.4 kDa with a unimodal distribution. Thermal analysis confirmed that no main-chain-dominated degradation occurred below 220 °C, indicating structural stability under high-temperature conditions. In drilling-fluid systems containing NaCl, CaCl₂, and mixed salts (0–20%), LM-ASQF maintained stable rheological properties, with apparent viscosity ranging from 26.1 to 41.6 mPa·s, while the API fluid loss was controlled within 5.8–11.2 mL. After thermal aging at 220 °C for 16 h, the API fluid loss remained below 13 mL in both freshwater and mixed-salt systems. In high-density systems (1.80–2.40 g/cm³), the drilling fluids preserved continuous rheological structures and showed no abrupt increase in filtration. Mechanistically, fluid-loss control was primarily attributed to synergistic interfacial adsorption of amide groups, hydration stabilization induced by sulfonate functionalities, and particle rearrangement-driven filter-cake densification, rather than viscosity enhancement through long-chain entanglement. This mechanism enables effective filtration control without excessive viscosity increase, thereby maintaining rheological compatibility under complex conditions. These results demonstrate that the low-molecular-weight design strategy provides a reliable approach for achieving stable fluid-loss control in water-based drilling fluids under high salinity, elevated temperature, and high-density conditions. Full article

This study aims to investigate the effects of heterogeneous microstructure and strain rate on the microstructural evolution and mechanical properties of ultrafine-grained (UFG) austenitic stainless steel during elevated-temperature tension. In this research, 17Cr-10Ni austenitic stainless steel was rolled to a 60% reduction in thickness at room temperature and 200 °C, followed by annealing at 1000 °C and 500 °C, respectively. The microstructural evolution of the annealed samples and high-temperature tensile specimens was characterized using optical microscopy, transmission electron microscopy, scanning electron microscopy equipped with electron backscatter diffraction, and X-ray diffraction. Results show that at room temperature, the heterogeneous twinned UFG (TW-UFG) sample, influenced by hetero-deformation-induced stress strengthening, maintains good ductility while exhibiting higher strength than the uniform UFG sample. During tensile deformation at 600 °C, grain refinement still contributes to strengthening, and the dominant deformation mechanism in the uniform UFG sample is dislocation dynamic recovery, whereas in the TW-UFG sample is detwinning combined with dynamic dislocation recovery. At low strain rates (10⁻⁴ s⁻¹), sufficient dynamic recovery and detwinning in the TW-UFG sample delay plastic instability and improve elongation. Full article

The endothermic nature of methanol steam reforming (MSR) for hydrogen production induces varying thermal effects along the flow direction, resulting in a non-uniform temperature distribution within the catalytic bed. Optimizing temperature uniformity has been demonstrated to enhance hydrogen production efficiency. In this study, a novel Fresnel lens-driven non-evacuated tapered cavity solar reactor was proposed for methanol steam reforming, which can provide a reference for optimizing hydrogen production using Fresnel lens solar concentrators. The thermal flux distribution on the reactor’s inner walls was determined by Monte Carlo ray-tracing simulations. A three-dimensional CFD model integrating fluid flow, heat and mass transfer, and methanol steam reforming reaction kinetics was developed to investigate the effects of key operational parameters on this novel reactor performance. Multi-objective optimization using response surface methodology revealed that high reactant inlet temperature (T_in > 550 K) and low flow velocity (u_in < 0.2 m/s) conditions significantly improve reactor methanol conversion (99.99%) and hydrogen yield (91.48%), but at the cost of increased CO selectivity (S_CO > 28%). Conversely, low temperature (T_in < 500 K) and high flow velocity (u_in > 0.4 m/s) conditions suppress CO formation (S_CO < 0.03%), although with reduced hydrogen production efficiency. Full article

Purpose: This study aimed to develop and validate a comprehensive multi-sensor integrated platform for objective assessment of skeletal muscle recovery kinetics following exercise-induced muscle damage (EIMD), combining biomechanical, thermal, and biochemical monitoring modalities. Methods: Forty elite male athletes were randomized to microwave diathermy (MWD, n = 20, 2.45 GHz, 160 W, 45 min/session) or control (n = 20) groups. Time-synchronized multi-sensor assessments at baseline, 24 h, 48 h, and 72 h post-EIMD included: biomechanical sensors (knee flexion range of motion via goniometry and isokinetic peak torque), thermal sensor (skin surface temperature via infrared thermometry), and biochemical sensor array (serum CK, IL-6, and CRP via high-sensitivity ELISA). Two-way repeated-measures ANOVA with Bonferroni correction examined group × time interactions across all sensor channels. Results: Pre-study validation confirmed high reliability across all sensor modalities. Cross-modality concordance analysis revealed significant correlations between biomechanical and biochemical recovery trajectories (isokinetic torque vs. IL-6: r = −0.73, p < 0.001; pain vs. IL-6: r = 0.68, p < 0.001). MWD intervention demonstrated accelerated recovery across all sensor channels: complete ROM recovery by 48 h (MWDG post-2 vs. baseline, p > 0.05; CG post-3 43% below baseline, p < 0.001), complete isokinetic torque restoration by 72 h (MWDG post-3 vs. baseline, p > 0.05; CG 44% below baseline, p < 0.001), and near-complete pain resolution (VAS 1.70 ± 2.50 mm, p < 0.05). Biomarker sensors demonstrated differential recovery kinetics: IL-6 normalized by 48 h (1.52 ± 0.14 pg/mL, p > 0.05 vs. baseline), CRP approached baseline by 72 h (0.73 ± 0.24 mg/L, p > 0.05), while CK remained elevated at post-3 (169.70 ± 22.58 U/L, 30% above baseline, p < 0.001), indicating incomplete myofiber membrane integrity recovery despite resolution of systemic inflammatory markers. The control group exhibited persistent deficits across all sensor channels with no clinically meaningful recovery. Conclusions: This study validated an integrated multi-sensor platform for recovery assessment. Microwave diathermy demonstrated efficacy by 72 h with complete functional recovery and inflammatory normalization (though CK remained elevated). Cross-modality concordance (r = −0.73 to 0.68) confirmed superior assessment compared to single-modality approaches. This laboratory-based methodology provides a framework for future portable sensor systems in athletic surveillance. Full article