Search Results (486)

Repeated mining of shallow-buried close-distance coal seams can disturb the fractured strata remaining in the goaf of the upper coal seam. Under gully terrain, mining disturbance is coupled with surface-relief effects, which may reactivate the overburden structure and induce dynamic strata-pressure behavior. In particular, when the working face advances across gullies, the change in surface slope alters the spatial distribution of roof load, while lower-seam extraction further disturbs the fractured rock mass formed by upper-seam mining, increasing the risk of severe strata-pressure behavior and support-crushing accidents. Taking the cross-ditch mining of the 2⁻² and 3⁻¹ coal seams in Anshan Coal Mine as the research object, this study integrates field geological investigation, theoretical calculation, physical similarity simulation, and field engineering verification to analyze overburden structural evolution, key-stratum breaking characteristics, and support-load variation under gully terrain. The results show that gully landforms generate obvious nonuniform loading above the working face. During upslope advance, the roof load gradually increases from the goaf side to the solid-coal side, causing tensile stress concentration at the fixed end of the key stratum and accelerating rock-stratum failure. A cantilever rock-beam mechanical model subjected to parabolic nonuniform loading was established, and the maximum breaking interval of the key stratum was calculated as 24.09 m. With increasing gully slope angle, the load gradient intensifies, the rock-beam breaking interval decreases, and the risk of overburden instability increases. Physical similarity simulation indicates that, when the 2⁻² coal seam working face passes through the 45° steep-slope section, the fractured overburden is more likely to form a stepped rock-beam structure, accompanied by slope rotation, stepped surface subsidence, and a sharp increase in support pressure. Under the 30° gentle-slope condition, The lateral confinement effect is stronger, roof movement is more gradual, and support-pressure fluctuation is reduced. During subsequent extraction of the lower 3⁻¹ coal seam, repeated mining disturbance reactivates the overlying goaf structure, and the upper stepped rock beam and lower hinged rock beam couple to form a double composite structure. When the fracture lines of the upper and lower key strata are staggered, the instability load of the upper structure is mainly buffered by caved gangue and interburden strata. The calculated support resistance in the asynchronous breaking stage is 8248.04 kN, which agrees well with the field-measured value of 8273 kN. When the fracture lines tend to coincide and synchronous breaking occurs, the unstable load of the upper key block is transferred downward and superimposed on the structural load of the lower key block, increasing the required support resistance to 15,165.55 kN, far exceeding the rated working resistance of the ZY9200/15/29 hydraulic support. Sensitivity analysis indicates that gully slope angle is the dominant factor affecting support resistance. As the slope angle increases from 30° to 60°, the support resistance increases from 13,228.65 kN to 18,278.43 kN, and the normalized support-resistance index increases from 0.872 to 1.205. Therefore, synchronous breaking of double key strata is the main mechanical cause of sudden support-load increase and support-crushing risk during cross-ditch mining of shallow-buried close-distance coal seams. The results can provide a basis for hydraulic support selection, roof weakening, weighting-interval control, and dynamic strata-pressure prevention under similar conditions. Full article

This study investigates the hotspot stress concentration characteristics of rectangular concrete-filled steel tube (CFST) truss joints under bridge deck composite action. Two truss specimens, with and without a reinforced concrete deck, were tested under midspan vertical loading. Nominal stresses and hotspot stresses were measured at typical welded joint details, and finite element models were developed to examine the effect of deck thickness on hotspot stress distribution and potential fatigue-vulnerable regions. The results show that the chord-to-brace intersection corners exhibit much higher hotspot stresses than other locations, indicating that these regions are potential fatigue-vulnerable details requiring attention in fatigue evaluation. Bridge deck composite action significantly changes the load-transfer path and local stress distribution. Compared with the specimen without a deck, the hotspot stresses in the upper joint are markedly reduced, with the maximum reduction at key measurement points reaching approximately 85%. Meanwhile, the controlling hotspot stress location shifts from the chord corner of the upper joint to the brace corner of the lower joint. Increasing deck thickness further reduces the hotspot stresses in the upper joint, whereas the lower joint shows weaker and nonuniform variations. These findings indicate that deck composite action and deck thickness should be considered in the fatigue assessment of rectangular CFST composite truss bridges. Full article

Surface icing poses a significant risk to unmanned aerial vehicles (UAVs) and compact aerospace platforms, where limited onboard power and space require efficient anti-/de-icing surfaces. In this study, micro/nanostructures were fabricated on TC4 titanium alloy (Ti–6Al–4V) surfaces by femtosecond laser processing at different scanning speeds. The effects of scanning speed on surface morphology, wettability, static freezing, dynamic droplet behavior, and electrothermal de-icing performance were systematically investigated. Increasing the scanning speed induced nonlinear changes in microstructure height and surface roughness, while variations in ablation intensity caused nonuniform material redistribution. The surface processed at 250 mm/s showed the best anti-icing performance, with a water contact angle of 157.5 ± 0.5° and a maximum freezing delay 21.5 times longer than untreated TC4. During electrothermal de-icing, melting initiated at discrete ice–substrate contact points, forming coalesced meltwater films, while interfacial stress concentration promoted crack propagation and rapid ice detachment. Compared with untreated surfaces, ice detachment time (250 mm/s) achieved complete ice detachment at approximately 152 s, whereas ice on the untreated surface remained adhered after 270 s of continuous heating, representing a de-icing time reduction of at least 44%. These results demonstrate that combining laser-fabricated microstructures with electrothermal heating effectively reduces real ice–substrate contact, providing an enhanced anti-/de-icing strategy for lightweight, long-endurance UAV applications under identical electrical input. Full article

Black alder (Alnus glutinosa (L.) Gaertn.) wood is characterized by rapid and frequently non-uniform color changes after felling and during hydrothermal processing. These changes are largely associated with extractive compounds, among which oregonin, a phenolic diarylheptanoid glycoside, has been identified as a precursor of the characteristic orange-red coloration. However, information on the thermal stability of oregonin remains limited. This study investigated the effect of temperature and exposure time on oregonin content in black alder bark extract. Aliquots of the extract were exposed to isothermal conditions of 30, 40, 50, and 60 °C for up to 24 h. In a separate trial, a treatment at 98 °C was conducted to simulate the temperature conditions associated with wood saturated water steaming at atmospheric pressure. Oregonin concentration was determined using reversed-phase high-performance liquid chromatography with diode-array detection. Oregonin content remained comparatively stable during 24 h exposure at 30, 40, 50 and 60 °C, with reductions of 6.00%, 3.00%, 2.78%, and 1.64%, respectively, without clear increase in oregonin loss with increasing temperature. Exposure to 98 °C resulted in the most pronounced decrease in oregonin content, with a reduction of 43.93%. The results indicate comparatively high stability of oregonin during 24 h exposure at 30–60 °C, whereas a pronounced decrease was observed in the separate aqueous treatment at 98 °C. These findings are relevant for understanding chemical changes in alder extractives during wood drying and steaming and demonstrate the importance of minimizing unnecessary heat exposure during sample preparation, extraction, and storage. Full article

Multiferroic composite semiconductor fibers enable non-contact magnetic control but may also operate under spatially nonuniform thermal conditions. This study develops a one-dimensional analytical model for a symmetric CoFe₂O₄/ZnO/CoFe₂O₄ fiber subjected to local magnetic and temperature fields with independently prescribed widths. The model combines piezomagnetic, piezoelectric, pyroelectric, thermoelastic, and semiconductor effects and provides closed-form solutions for the electric potential, electric field, polarization, and electron concentration perturbation. Local magnetic and thermal inputs generate localized potential barriers and wells through distinct pathways. Where the excitation regions overlap, their contributions may reinforce, compete with, or partially cancel each other. The initial electron concentration affects the carrier-screening strength and spatial localization of the electrical response, whereas the layer-thickness ratio influences the competition between piezomagnetic actuation and piezoelectric conversion. An independent finite-element calculation closely reproduces the analytical potential distribution for the baseline case. This study clarifies the interaction between the magnetic and thermal contributions to open-circuit carrier redistribution and provides a field-distribution baseline for future biased, contact-resolved transport analyses of multiferroic micro- and nanostructures. Full article

Freeze–thaw cycling can strongly disturb the pore-water environment, soil fabric, and contaminant mobility of heavy-metal-contaminated loess, thereby threatening the long-term effectiveness of stabilization treatments in seasonally frozen regions. This study investigated the coupled hydro-environmental and geotechnical performance of Pb-contaminated loess (untreated control group, CK) treated with microbially induced calcium carbonate precipitation (MICP), graphene (GR)-assisted MICP, and graphene oxide (GO)-assisted MICP under controlled freeze–thaw cycles. One-dimensional consolidation tests, toxicity characteristic leaching procedure (TCLP) tests, zeta-potential measurements, X-ray fluorescence (XRF), and scanning electron microscopy (SEM) were conducted to evaluate compressibility evolution, Pb leaching behavior, interfacial electrochemical characteristics, mineralogical changes, and microstructural mechanisms. After 9 days of mineralization, MICP reduced the Pb leaching concentration from 38.05 to 23.00 mg L⁻¹, achieving a 39.55% reduction compared with untreated Pb-contaminated loess. Freeze–thaw cycling increased the susceptibility of treated loess to structural degradation and pore collapse, especially under medium to high vertical stresses. Nevertheless, the void ratio generally followed the order of CK > MICP > MICP + GR > MICP + GO under comparable loading and freeze–thaw conditions, indicating progressively enhanced resistance to compressive deformation. GR-assisted MICP showed an optimum dosage of approximately 1.0%, beyond which Pb leaching increased because of sheet restacking, agglomeration, and non-uniform biomineralization. In contrast, under up to 13 freeze–thaw cycles, GO-assisted MICP maintained the lowest void ratio and the most stable Pb immobilization performance among all treatments, demonstrating improved resistance against freeze–thaw-induced structural degradation. The results suggest that GO-assisted MICP can simultaneously improve Pb leaching control and soil-fabric stability, providing a promising low-carbon strategy for remediating heavy-metal-contaminated loess exposed to water-mediated freeze–thaw disturbance. Full article

The microstructures and torsional fracture morphologies of S2 alloy steel screwdriver bits were characterized by scanning electron microscopy (SEM). The bits were oil-quenched from 830 °C and 860 °C and subsequently tempered at 150 °C and 170 °C under three carbon potential levels (0.35, 0.40, and 0.45). In parallel, Deform-3D and Ansys Workbench were employed to simulate and compare the microstructure evolution during quenching, the residual stress field after quenching and tempering, and the stress distribution developed under torsional loading. The results reveal that the non-planar fracture and low qualification rate of the bits arise from two independent but synergistic mechanisms: (1) insufficient austenitizing at 830 °C fails to produce fully uniform austenite, resulting in non-uniform martensitic microstructure and inhomogeneous hardness distribution after quenching; (2) low furnace carbon potential (≤0.35) causes surface decarburization and the formation of massive ferrite at the near-surface region, which acts as preferential crack initiation sites. Furthermore, the transformation stress generated during quenching, the residual stress remaining after tempering, and the stress concentration at tooth edges under service loading jointly promote crack initiation and propagation. A uniform, high-hardness tempered martensite microstructure is obtained when the bits are austenitized at 860 °C with the carbon potential strictly maintained between 0.40 and 0.45, held for 60 min before oil quenching, and air-cooled after tempering at 170 °C. This optimized heat-treatment route eliminates surface decarburization, ensures microstructural homogeneity, reduces residual stress, and enables the bits to fail by planar fracture under torsional load with 100% qualification rate. Full article

Disc-cutter wear in abrasive strata is spatially non-uniform, yet mean wear depth cannot indicate where it concentrates. This retrospective feasibility study develops a machine-learning-based condition-monitoring framework that predicts the relative severity of eccentric wear from engineering data available before inspection, supervised by 3D-scan morphology labels. An Eccentric-Wear Morphology Index (EWI) is constructed from post-replacement 3D morphology and used solely as a relative-severity label; its tertile-based grades are cohort-relative rather than universal engineering thresholds. The analysis cohort comprised 244 quality-controlled 19-inch cutter rings, and an engineering-prioritized redundancy review condensed 58 candidate variables into a frozen 22-variable set. In five-fold out-of-fold evaluation, the Random Forest achieved 0.779 accuracy, 0.775 macro F₁, and 0.939 high-severity recall. With nested threshold selection, in which the operating threshold was chosen only within the training folds, the pooled held-out screening result reached 0.988 recall and 0.946 F₂ while including 41.0% of the samples in the review pool, and this operating point was insensitive to false-negative-to-false-positive cost ratios between 5:1 and 15:1. Grouping both rings of each twin cutter into the same fold left the screening operating points essentially unchanged. The framework shows potential to support within-project inspection prioritization; external validation and calibration remain necessary because the screening signal is strongly associated with service exposure and the project-specific cutter-change schedule. Full article

Hollow fiber loose nanofiltration (HF-LNF) has attracted increasing attention as a pressure-driven membrane platform that combines loose nanofiltration (LNF) selectivity with the high packing density and self-supporting geometry of hollow fibers. This review critically evaluates recent advances in HF-LNF membranes, including controllable fabrication strategies, surface functionalization techniques, and practical engineering applications, with a discussion of life cycle assessment (LCA) for evaluating the environmental and economic sustainability of HF membrane systems. Phase inversion, interfacial polymerization (IP), coating, and grafting are compared in terms of structural controllability, process complexity, selective-layer stability, modification uniformity, reproducibility, and scale-up feasibility. Phase inversion is relatively compatible with continuous hollow-fiber spinning, but independent regulation of the support and selective layer remains difficult. IP provides greater control over selective-layer chemistry and effective pore size, whereas coating and grafting offer flexible surface functionalization but may be limited by additional transport resistance, layer durability, and non-uniform modification of curved surfaces. Direct HF-LNF application remains concentrated on dye/salt separation. Based on the evidence from HF-NF or flat LNF systems, the potential of HF-LNF in water softening, heavy metal removal and emerging pollutant control is analyzed. Critical challenges restricting industrial translation are discussed, including poor long-term antifouling capacity and difficulties in large-scale, low-cost manufacturing. On this basis, LCA is further introduced as a decision-support framework for identifying potential environmental hotspots in membrane manufacturing and operation, while the limited availability and comparability of HF-LNF-specific life-cycle data are explicitly recognized. Ultimately, it is proposed to focus on novel functional materials, eco-friendly preparation processes, and scaled membrane engineering, aiming to offer theoretical support for the rational design and real-world industrial deployment of next-generation HF-LNF membranes. Full article

Deep longwall mining under large dip and advance inclinations can induce strongly asymmetric roof deformation and nonuniform load transfer, complicating the assessment of hydraulic support loading. Taking the 2902 working face of Chensilou Coal Mine as an engineering case, this study combines field monitoring, theoretical analysis, and FLAC3D simulation to investigate a recurrent M-shaped pressure distribution under a fixed geometry with dip and advance-direction inclinations of approximately 35°. Representative field profiles at cumulative advance distances of 40, 60, 80, and 100 m consistently exhibited an M-shaped hydraulic support pressure distribution. To interpret this spatial pattern, the main roof was represented as a bidirectionally inclined equivalent elastic plate with three clamped edges and one free edge, while the hydraulic support–immediate roof system was represented by a local Winkler foundation. The analytical solution identified two spatially separated roof-deflection concentration zones, and the FLAC3D results exhibited a broadly similar bimodal pressure tendency. The complete 28-day monitoring record was subsequently analyzed to examine whether the observed pattern persisted beyond the four representative advance stages, revealing two recurrent high-pressure sectors approximately within supports 45–75 and 105–135. The field, analytical, and numerical results showed approximate sector-level correspondence. This study therefore provides a case-specific mechanical framework relating recurrent zonal hydraulic support loading to spatially variable overburden loading, asymmetric equivalent boundary constraints, nonuniform main-roof flexure, and local roof–support load transfer. Full article

Objectives: The critical role of nerve growth factor (NGF) in neuroprotection has been demonstrated in preclinical models of neuronal injury. Here, we investigated the neuroprotective effects of intranasal CHF6467, a recombinant mutant form of human NGF lacking algogenic activity, in transient (45 min) middle cerebral artery occlusion (tMCAo). Methods: Male Wistar rats (n = 20 per group) were treated intranasally with CHF6467 (20 µg/kg, 40 µL) or vehicle (0.9% saline, 40 μL). The first dose was administered 15 min after the onset of MCAo and the second dose 24 h later. Neurological behavioral tests were performed 24 and 48 h after tMCAo. Infarct volume was measured 48 h after tMCAo. Additionally, a separate cohort of rats underwent permanent MCAo (pMCAo) and received two intranasal doses of CHF6467 or vehicle, with long-term neurological outcome assessed 7 days later using the De Simoni neuroscore (n = 13–14 per group). CHF6467 levels were measured in intact brain samples from CHF6467-treated rats (n = 5) and vehicle-treated controls (n = 4). Samples were collected 2 h after the last administration. Results: CHF6467 significantly improved neurological and sensorimotor performance compared with the vehicle-treated rats. This functional effect was associated with a reduction in infarct volume that was positively correlated with neurological deficit improvement. In the pMCAo cohort, CHF6467-treated rats were more likely to achieve a favorable neurological outcome at seven days compared with the vehicle-treated animals. Intranasal CHF6467 reached the brain but showed variable and non-uniform distribution across regions. Levels were highest in the olfactory bulbs, while the cortex and striatum had lower concentrations. In vehicle-treated rats, the drug was undetectable. Conclusions: This study demonstrates the neuroprotective effects of CHF6467 against ischemic brain injury, evidenced by both functional improvement and reduction in infarct volume. Although it reaches the brain, its distribution is heterogeneous and assessed only at one time-point. Further studies should examine its longer-term distribution and underlying mechanisms. Full article

Hydrogel-based three-dimensional culture systems are widely used in tissue engineering; however, their maturation is often limited under static conditions. This study investigates the combined effects of dynamic perfusion and initial cell seeding density on remodeling behavior and mechanical properties of bioprinted collagen hydrogel constructs, with additional assessment of smooth muscle cell-like (SMC) differentiation. Rectangular constructs (30 × 15 × 1.5 mm) were fabricated using high-concentration collagen (30 mg/mL) with cell densities of 10 and 20 million cells/mL. MCDB- and DMEM-based media were first compared using growth curves, leading to the selection of MCDB differentiation medium for subsequent experiments. Constructs were then cultured statically or under dynamic perfusion (20 mL/min) for up to 7 days. Remodeling was evaluated by monitoring changes in construct dimensions over time. Static constructs exhibited non-uniform deformation and rolling, whereas dynamically perfused samples retained their geometry and underwent homogeneous contraction. Mechanical testing revealed a transition from stiff and brittle to more compliant and ductile behavior, with preserved load-bearing capacity at large strains. Remodeling and mechanical outcomes were strongly influenced by cell density and culture medium, with differentiation conditions promoting more stable constructs. These changes were accompanied by increased expression of smooth muscle–related markers under dynamic culture. Overall, dynamic perfusion and cell seeding density jointly govern remodeling and mechanical maturation of bioprinted collagen constructs, highlighting their importance for functional hydrogel-based tissue development. Full article

Bridge-arm reactors subjected to long-term AC–DC composite currents with multiple harmonics may develop non-uniform winding temperature rise and thermal-expansion mismatch, leading to localized thermal stress concentrations and potential insulation cracking. Unlike previous studies focused mainly on purely AC conditions, this study investigates a ±800 kV dry-type air-core bridge-arm reactor and develops a thermo-mechanical model incorporating AC–DC composite currents and harmonic losses. To mitigate thermal stress concentration, an axially segmented configuration is proposed to relieve the restraint associated with cumulative axial thermal expansion. The results show that a 65% axial segmentation ratio provides the best stress-regulation performance among the investigated cases. Under AC–DC composite conditions containing second- and fifth-order harmonics, the maximum Von Mises stress and maximum first-principal stress decrease by 33.42% and 38.11%, respectively, while the stress distribution becomes more uniform. The analysis is based on a two-dimensional axisymmetric model with one-way thermo-mechanical coupling and excludes long-term cyclic thermal aging and interfacial slip between winding and insulation layers. These findings provide theoretical support for the stress-oriented structural design and reliability assessment of high-capacity bridge-arm reactors. Full article

Cover cracking induced by steel corrosion is a critical issue governing the durability degradation of reinforced concrete structures in marine environments. The crack initiation and propagation processes dominated by non-uniform rust expansion stress fields urgently require high-resolution continuous monitoring techniques. In this study, based on the principle of Rayleigh backscattering, distributed optical fibers were embedded along the upper surface of specimens to conduct in situ monitoring of surface strain in concrete. The effects of specimen length, biochar content, cover thickness, and rebar diameter were systematically investigated. The results indicate that the surface strain evolution follows a two-stage pattern—a slow growth stage followed by a rapid rise stage—corresponding respectively to the early-stage filling of interfacial pores and stress accumulation, and the later-stage propagation of macroscopic cracks. Increasing specimen length significantly amplifies the spatiotemporal non-uniformity of strain, characterized by “locally high peak strains but low overall mean values,” with the onset time of strain surges differing by more than 50 h across different cross-sections. The incorporation of 0.5% biochar reduces the average strain by approximately 17% and delays crack initiation to 260 h. Increasing cover thickness from 25 mm to 40 mm exhibits the most pronounced inhibitory effect, achieving a 39% reduction in strain and delaying crack initiation to 320 h, primarily attributed to the extended chloride transport path and enhanced hoop confinement stiffness. Reducing rebar diameter from 20 mm to 12 mm decreases the peak strain to 79% of that of the standard specimen, owing to reduced rust product volume and increased relative cover thickness. The macro-cell effect driven by chloride concentration gradient transition zones is identified as a key factor governing crack initiation locations. Theoretical crack widths derived from strain integration of optical fiber data are slightly lower than measured values, yet the overall trends remain consistent. This study provides a quantitative basis for continuous monitoring and durability assessment of corrosion-induced cracking in marine environments. Full article

In suspended mussel farms, culture-layer food supply can be limited, whereas the 4–8 m subsurface layer is rich in particulate organic matter and seston. Using a representative aquaculture block off Gouqi Island, China, this study examined the hydrodynamic and transport effects of non-uniform hanging-depth layouts. The 0° uniform-depth layout was the reference. Five configurations were modeled: V-shaped, inverted V-shaped, uniform-depth (90° inflow), V-shaped (extended), and inverted V-shaped (extended). Flume PIV validated the model. Simulations used uniform and measured velocity-profile inflows, with and without density stratification; a passive tracer tracked seston-rich water from the 4–8 m layer. Uniform-depth hanging formed a low-velocity zone in the sleeve layer, limiting water exchange. Non-uniform layouts altered drag distribution and promoted tracer redistribution into overlying 3–5 m waters. In the V-shaped configuration, water was guided upward along sleeve bottoms in the downstream half of the aquaculture block (S2), where pronounced redistribution within the aquaculture block resulted in a tracer concentration of approximately 0.1362 in the 2–3 m layer. Stratification constrained upward spreading, whereas extended configurations may limit food replenishment through enhanced upper-layer blockage and filtering effects. Low-Richardson-number regions corresponded with tracer uplift and enhanced spreading, indicating local shear. Overall, the V-shaped configuration balanced in-farm replenishment, downstream transport, and flow maintenance without additional sleeve length. Full article