Search Results (1,663)

Dispersive soils are widely distributed in the seasonally frozen regions of northeastern China, where hydrothermal dynamics driven by seasonal freeze–thaw (FT) cycles dominate the hydrological evolution and mechanical deterioration of soil masses, posing a serious threat to the long-term stability of hydraulic engineering in cold regions. However, the hydro–thermo–mechanical (HTM) coupled degradation mechanisms of dispersive clay from the South Nenjiang Main Canal remain poorly understood, particularly the linkage between FT-induced microstructural evolution and macroscopic mechanical behavior. In this study, low-plasticity dispersive clay specimens were subjected to 0–12 FT cycles. Unconsolidated undrained (UU) triaxial tests were conducted to evaluate mechanical behavior, while scanning electron microscopy (SEM) combined with the Pore and Crack Analysis System (PCAS) was used to quantify microstructural evolution. Results indicated that increasing FT cycles transformed the stress–strain response from mild strain-softening to strain-hardening, with the failure mode evolving toward bulging-type ductile failure. Cohesion exhibited a pronounced exponential decay, with the most significant degradation occurring within the first three FT cycles and stabilizing after approximately six FT cycles, whereas the internal friction angle showed only minor variation. At the microscale, porosity and total pore area increased continuously through micropore coalescence and macropore development, with a slight decrease in fractal dimension indicating reduced pore boundary complexity and smoothed pore interfaces due to frost heave-induced pore merging. The FT-induced hydrothermal disturbance promoted pore-water phase transition and redistribution, resulting in progressive pore enlargement and loss of structural integrity. Because the specimens were tested in sealed, closed-system conditions with a nearly constant total water content, this degradation chain is attributable specifically to in situ ice–water phase transitions and internal pore-water redistribution, i.e., water-phase-change-driven processes, rather than to external water supply. It is demonstrated that interparticle bond breakage and pore expansion–coalescence driven by ice–water phase transitions dominate strength degradation, promoting a transition from structure-dominated to friction-dominated strength behavior. A normalized cohesion reduction factor and a cohesion degradation index are further proposed to quantify the progressive loss of structural integrity and to provide a design-oriented tool for cold-region geotechnical practice. These findings provide a basis for stability assessment and hazard mitigation of dispersive soils in cold-region engineering. Full article

To reveal the evolution of overburden movement, slope deformation, and fracture damage during highwall mining, a physical similarity model was established based on the geological conditions of the Heishan Open-Pit Mine, Xinjiang. The excavation extended through the model thickness and was idealized as a continuous slot. Different chamber heights were considered to simulate the extraction of Coal Seam 13-2 and the subsequent mining of the overlying Coal Seam 9. Overburden and slope displacements, fracture-area ratio, and fractal dimension were analyzed using the MatchID-2D digital image correlation method, displacement monitoring, and fracture image processing. The results show that deformation initially concentrates in the chamber roof and lower overburden and subsequently propagates toward the slope toe and surface, exhibiting distinct stage-dependent and spatially differentiated characteristics. As the chamber height increases, overburden subsidence, slope-toe displacement, fracture-area ratio, and fractal dimension all increase. During the extraction of Coal Seam 9, displacement continues to accumulate within the previously formed deformation zones, accompanied by further propagation and coalescence of existing fractures. The results characterize progressive local damage and spatially coordinated deformation within the model. These findings improve understanding of overburden-slope deformation and fracture evolution under the investigated conditions. Full article

Exceptional points are parameter values at which two eigenvalues and their corresponding eigenfunctions coalesce, rendering the wave operator defective. They arise widely in non-Hermitian wave physics and disrupt the modal expansions on which semi-analytic scattering methods rely. For lined acoustic waveguides, an augmented mode-matching ansatz that restores completeness at such a degeneracy—by adjoining the generalised eigenfunction obtained from the derivative of the parametrised duct mode with respect to its transverse spectral parameter—has been established for junctions between duct sections with discrete modal sets. This article extends that ansatz to an open, radiating configuration: a rigid feed duct communicates through an impedance-lined throat, tuned to an order-two exceptional point, with a half-space bounded by a rigid flange. The radiating mouth replaces the discrete modal closure by a continuous spectrum, so the augmented basis must be matched against an improper spectral integral. The half-space field is generated by the aperture velocity, which builds the rigid-flange condition into the representation exactly, and the resulting improper integrals are rendered analytic by branch-aware substitutions whose cutoff is tied to the retained modal content. The formulation is validated on the matching and boundary conditions themselves: pointwise continuity of pressure and of normal velocity at the internal junction, pointwise pressure continuity at the radiating mouth, the vanishing of the normal velocity on the rigid flange, and the recovery of the classical flanged-duct radiation problem in the rigid limit, cross-checked against an independent implementation. The full lined problem, including the defective case, has been further verified against an independent finite-volume solution of the same boundary-value problem, whose grid-converged fractions agree with the mode-matching values to within $8\times {10}^{-5}$. A conserved-power identity is monitored as a necessary but not sufficient check. Numerical experiments confirm the known breakdown of the standard expansion at the exceptional point and the well-conditioned convergence of the augmented one in this radiating setting, and a scan of the complex admittance plane, refined by local optimisation and repeated across throat lengths and frequencies, shows that flange radiation detunes the absorption optimum away from the exceptional point, by an amount that grows with the radiated share of the power budget and vanishes as the throat lengthens. Full article

To achieve the optimal balance between structural safety and stripping economy for the rock slopes of a specific open-pit iron mine, a rigorous mathematical modeling and computational framework was established. In contrast to traditional simplified pseudo-static evaluations, authentic monitored seismic and blasting waveforms were integrated within an explicit dynamic strength reduction model to ensure that transient stress wave propagation and progressive failure paths of rock slopes were accurately captured. Furthermore, a constrained multi-objective optimization model was established so that the nonlinear trade-off between dynamic safety margins and stripping volumes could be quantitatively resolved. Based on the application to the studied open-pit slopes, it was revealed that severe deep plastic yielding and topological shear band coalescence were caused by transient dynamic stress waves when the slope angle was steepened to 45°. Consequently, the factor of safety (FS) was abruptly reduced to an unsafe range of 1.01 to 1.20. Through the effective exclusion of this high-risk 45° configuration, a global optimal mining slope angle of 42° was rigorously established. At this optimal angle, a robust factor of safety ranging from 1.45 to 1.98 was consistently maintained across all extreme multi-field coupled conditions. Ultimately, from an engineering perspective, dynamic shear failure paths were successfully interrupted, and the need for expensive structural reinforcement was eliminated. Economically, waste rock stripping volumes were significantly minimized, whereby the overall stripping ratio was optimized, and life-cycle excavation efficiency was maximized. Full article

Understanding the failure behavior of cylindrical-hole hard rocks is essential for rockburst prevention in deep underground engineering. In this study, fractal–statistical analysis was combined with true triaxial testing and discrete element modeling to quantify the rate-dependent failure and crack-network evolution of holed granodiorite. The results showed that, with an increasing loading rate, the peak axial stress increased from 143 to 190 MPa, the peak axial strain decreased from 1.24% to 0.86%, and the post-peak brittleness index increased from 0.83 to 1.19. The final failure pattern evolved from multi-crack tension–shear coupled failure to localized dominant fracture and intense hole-wall exfoliation. The mass fractal dimension of rockburst fragments increased with loading rate, reflecting a transition toward finer and more dispersed fragmentation. To extend the experimentally observed hole-wall failure mechanism to adjacent openings, a calibrated PFC3D double-hole model was further established. The numerical results revealed that crack interaction was governed by stress-concentration superposition and progressive rock-bridge damage, and the hole-spacing ratio controlled the connectivity and complexity of the crack network. As S/2R increased from 1.25 to 2.00, the dominant fracture-band inclination increased from 27° to 54°, reflecting a transition from steep inter-hole coalescence to more inclined and spatially dispersed fracture development. Full article

Q355 carbon steel was exposed for 0.5 and 1 year in Pingtan Strait to examine how surface-wetness changes affect early rust-layer evolution and localized corrosion. Environmental monitoring, corrosion-rate measurements, rust-phase analysis, and electrochemical characterization were combined to characterize corrosion in this humid, salt-laden marine atmosphere. The exposure regime shifted from sustained wetness during the first half-year to frequent wet–dry cycling during the second. Although the average corrosion rate remained nearly unchanged, localized corrosion intensified and adjacent pits became interconnected. This change was closely associated with the evolution of the rust-phase assemblage and its spatial distribution. After 0.5 years, β-FeOOH was dominant, consistent with a long time of wetness (TOW) and Cl⁻ enrichment in surface electrolyte films, and pits remained largely isolated. After 1 year, Fe₃O₄ increased substantially and became the dominant phase, possibly because frequent wet–dry cycling altered oxygen transport within the rust and repeatedly produced locally oxygen-deficient conditions. Fe₃O₄ enrichment promoted continued pit deepening, followed by pit expansion and coalescence. Meanwhile, local α-FeOOH enrichment developed in relatively oxygen-rich regions near the rust surface and inhibited lateral pit propagation. Thus, shifts in the wetting regime of the humid, salt-rich Pingtan atmosphere markedly regulate localized corrosion of Q355 steel by controlling rust-phase evolution and spatial distribution. Full article

To address the issues of low mechanical rock-breaking efficiency and severe tool wear in hard rock, this study investigates the mechanical deterioration and abrasivity response of granite subjected to rapid flame-jet heating followed by liquid nitrogen cooling, with rock pre-treatment in thermal-assisted rock breaking as the background. Fine-grained granite specimens were heated by flame jet to temperatures ranging between 200 and 600 °C and then subjected to natural cooling or sudden liquid nitrogen cooling. Physical parameter measurements, uniaxial compression tests, Brazilian splitting tests, and CERCHAR abrasivity tests were conducted using national standards to investigate the evolution of thermal damage and the effect of cooling path. The results show that the damage degree of granite continuously increases with increasing heating temperature, and the damage induced by liquid nitrogen cooling is greater than that induced by natural cooling. Visible cracks begin to appear on the specimen surface after 300 °C, while crack propagation and structural deterioration become more pronounced at 500–600 °C. Among the measured physical parameters, P-wave velocity is the most sensitive to damage, with a maximum attenuation rate of 60.6%. The deterioration of the physical structure further reduces the load-bearing capacity and deformation performance of granite. After liquid nitrogen cooling at 600 °C, the uniaxial compressive strength, tensile strength, and elastic modulus decrease to 92.6 MPa, 1.42 MPa, and 17.4 GPa, respectively, corresponding to reductions of 56.0%, 87.7%, and 69.3% compared with the untreated specimens. The tensile strength is the most sensitive mechanical parameter to liquid nitrogen cooling. The CERCHAR abrasivity index decreases from 3.81 to 2.12. Liquid nitrogen cooling advances the transition of granite abrasivity from high to medium from 400–500 °C to 300–400 °C. The integrated analysis indicates that the non-uniform temperature field generated by rapid flame-jet heating and the differences in thermal deformation among minerals promote the initiation of initial cracks. The additional shrinkage stress induced by liquid nitrogen cooling further drives crack propagation and coalescence, eventually leading to the coupled reduction in the strength, stiffness, and abrasivity of granite. The results provide laboratory-scale evidence for evaluating granite pre-treatment under rapid flame-jet heating and liquid nitrogen cooling and offer a reference for thermal-assisted mechanical rock breaking and standardized abrasivity reduction. However, the relationship between CAI and actual tool wear still requires further verification. Full article

Climate change is altering soil organic carbon stocks and the associated carbon fluxes of cropland ecosystems—including organic matter mineralization, microbial respiration rates, and CO₂ emissions—through shifts in temperature and moisture regimes. Ecosystem respiration, the main pathway linking terrestrial carbon pools to atmospheric CO₂, directly governs the carbon source–sink balance of croplands. As integral components of the agroecosystem, soil microorganisms directly participate in ecosystem respiration and organic carbon transformation: they contribute to heterotrophic respiration through the decomposition of organic matter, while also synthesizing new organic compounds, forming microbial biomass, and promoting organic carbon stabilization, with their community composition and metabolic activity adjusting to changing environmental conditions. To synthesize research progress and clarify how the field has evolved over the past three decades, we analyzed 290 publications (1991–2025) from the Web of Science Core Collection, combining bibliometric tools (CiteSpace 7.0, VOSviewer 1.6.20) with a structured evidence synthesis to map the research landscape, knowledge structure, hotspot evolution, and mechanistic understanding of the microbial processes underlying cropland ecosystem respiration. Publication output has grown steadily, led by China (161 publications; 55.5%) and the United States (47; 16.2%), which together account for 71.7% of the sample. The knowledge structure has coalesced around five core themes (ecosystem respiration, soil microbial communities, soil organic carbon, carbon cycling, and agricultural management), corresponding to 14 major thematic clusters (Q = 0.668, S = 0.778). Rather than strictly sequential stages, these thematic areas developed largely in parallel, with a gradual shift in research emphasis over time: early work centered on fundamental carbon-cycle processes, including soil respiration flux, organic matter decomposition, and CO₂ release, whereas later research increasingly emphasized microbial community structure, functional mechanisms, carbon use efficiency, soil organic carbon stabilization, carbon sequestration, fungal communities, and ecological stoichiometry. The responses of cropland respiration to climate change are context-dependent: under specific conditions their direction and magnitude may be dominated by a single limiting factor, whereas overall they emerge from the coordinated interplay of temperature, moisture, substrate supply, and agricultural management, within which microbial processes play a central but still incompletely resolved role. Future research should prioritize long-term in situ observations, multi-factor coupling experiments, and functional validation of microbial processes, and integrate microbial mechanisms into ecosystem models to strengthen predictions of cropland carbon cycling and support agricultural emission reduction, carbon sequestration, and sustainable management. Full article

Glass-fiber-reinforced polypropylene (GF/PP) composite foams combine reinforcement with weight reduction, but how GF content governs the competition between cell refinement and foam expansion under fixed-cavity molding remains unclear. GF/PP composite foams containing 0–15 wt.% GF and a fixed 5 wt.% PP-g-MAH were prepared by fixed-cavity MuCell injection molding. Gas-free melt rheology, crystallization, cellular morphology, density, and mechanical properties were evaluated. Increasing GF content raised the apparent viscosity and shifted crystallization toward higher temperatures. The cell density increased from 6.12 × 10⁴ to 1.56 × 10⁷ cells cm⁻³, whereas the average cell diameter decreased from 264.5 to 27.1 μm. However, the expansion ratio peaked at 1.27 for GF9 and then decreased to 1.12 for GF15, showing that continuous cell refinement did not produce a monotonic improvement in foam expansion. These trends suggest competing effects of GF on cellular development: at low-to-intermediate contents, GF interfaces may favor heterogeneous nucleation, while increased melt resistance may suppress excessive cell growth and coalescence; at higher contents, fiber crowding, reduced interfiber spacing, geometric confinement, and interfacial heterogeneity may increasingly restrict cell growth and foam expansion. Although the absolute tensile and flexural properties increased with GF content, the density-normalized properties and impact strength varied nonmonotonically. GF9 exhibited the highest measured mean specific tensile, flexural, and impact strengths, together with a mean impact strength of 24.4 kJ·m⁻², which was 32.6% higher than that of GF0. Thus, cell refinement alone does not ensure improved lightweight efficiency; an intermediate GF content provides the most favorable balance among cellular refinement, foam expansion, and fiber reinforcement. Full article

High-alumina fly ash and coal gangue were used as the main aluminosilicate precursors, and waste glass was introduced as a fluxing additive to prepare waste-derived ceramsites. Based on composition design assisted by the CaO-SiO₂-Al₂O₃-Na₂O phase diagram, the effects of sintering temperature and holding time on phase evolution, microstructure, bulk density, compressive strength, and environmental safety were systematically investigated. The results showed that waste glass promoted early liquid-phase formation and broadened the effective sintering window. As the sintering temperature increased from 1200 to 1300 °C, the bulk density continuously decreased from 1.77 to 1.19 g/cm³, whereas the compressive strength first increased from 4.9 MPa to a maximum of 10.0 MPa at 1240 °C and then decreased to 2.8 MPa because of the competition between skeletal consolidation and excessive pore coarsening. The main crystalline phases of the ceramsites were anorthite and mullite. Prolonged holding mainly accelerated pore coalescence and pore-wall thinning, resulting in a continuous decrease in compressive strength. TCLP and long-term leaching tests conducted in freshwater, saline, and acidic media showed that the release of hazardous elements remained very low. These results demonstrate that glass-assisted sintering is an effective route for converting coal-based solid wastes into environmentally safe ceramsites. Full article

Crystalline silicon cutting waste (SCW) is a promising secondary silicon resource for Al-Si alloy production, but high-melting Al₂O₃ generated during aluminothermic reduction hinders alloy droplet coalescence and slag–metal separation. In this study, a CaO-Al₂O₃-CaF₂ slag treatment strategy was developed to regulate in situ formed Al₂O₃ and improve Al-Si alloy recovery from SCW. The effects of slag composition, smelting temperature, and holding time on separation behavior, massive alloy yield, and Si recovery were investigated. Increasing CaF₂ content decreased the liquidus temperature and calculated the viscosity of the slag, thereby improving slag fluidity and promoting the migration and coalescence of Al-Si droplets. The optimal conditions were a smelting temperature of 1400 °C, a holding time of 10 min, and a slag composition of 20 wt.% Al₂O₃-20 wt.% CaO-60 wt.% CaF₂. Under these conditions, the massive alloy yield and Si recovery reached 89.32% and 83.43%, respectively. Mechanistic analysis indicated that the process involved alloying, slagging, and slag–metal separation. CaF₂ promoted the formation of a low-melting, low-viscosity liquid slag, which facilitated slag aggregation, droplet migration, and efficient slag–metal separation. This work provides a low-cost and efficient technical approach for the high-value recycling of SCW, showing potential for future industrial application. Full article

Intersecting fissures strongly affect stress transfer and crack coalescence in rock, but their coupled effects on mechanical degradation and acoustic emission signatures remain incompletely understood. We conducted uniaxial compression tests with synchronous acoustic emission monitoring on prismatic sandstone specimens containing five intersecting-fissure configurations and on intact controls. The specimens measured 50 mm × 50 mm × 100 mm, and each prefabricated fissure was 30 mm long and 2 mm wide. The central 0–90° configuration produced the greatest degradation: its peak stress, peak strain, and elastic modulus were about 70%, 36%, and 50% lower, respectively, than those of the intact specimen. Acoustic emission ring-down counts captured the transition from early crack activation to unstable coalescence and increased sharply near macroscopic failure. Low-inclination configurations generated predominantly intermediate- and high-frequency signals, consistent with the activation of numerous small tensile cracks. Gaussian mixture model clustering of rise angle and average frequency values further showed that tensile microcracking dominated all fissured specimens, whereas the shear-crack fraction increased with fissure angle α. These findings link fissure geometry, macroscopic weakening, and acoustic emission source characteristics under uniaxial loading, providing a laboratory basis for identifying potentially hazardous intersecting-fissure configurations in underground rock engineering. Full article

Growing environmental concerns and the need to replace fossil-based plastics have accelerated the development of biodegradable foamed materials for lightweight packaging. However, the limited melt strength and poor foamability of biodegradable polymers remain major challenges. This work proposes and systematically investigates novel multiphase biodegradable blend compositions based on PBAT, PLA, PBSA, and thermoplastic starch (TPS), specifically engineered to exploit the complementary properties of each component and improve foamability without compromising processability. The formulations were compounded by co-rotating twin-screw extrusion, processed into films by cast extrusion, and foamed using nitrogen as the blowing agent. Rheological, thermal, mechanical, and morphological characterizations were performed to evaluate the effect of polymer composition. F2 exhibited the highest melt flow rate (5.42 ± 0.10 g/10 min), whereas F1 showed superior melt stability and ductility. Foaming experiments revealed that blend composition significantly affected the cellular structure. F1 produced the most homogeneous cellular structure, exhibiting the highest cell circularity (0.826 ± 0.04). Independent density measurements also showed that F1 exhibited the lowest foam density (0.786 ± 0.02 g/cm³), whereas the TPS-containing formulation (F3) exhibited greater cell coalescence and partial cell collapse. The findings demonstrate that tailoring biodegradable blend composition, in combination with nucleating and chain-extending masterbatches, is an effective strategy to control foam morphology and enhance processing performance. The proposed formulation represents a promising alternative to expanded polystyrene for sustainable lightweight packaging applications. Full article

Flutter constrains the design of modern high-aspect-ratio wings, yet the combined influence of planform geometry, aspect ratio (AR) and structural flexibility is rarely assessed within a single consistent framework. This work presents a unified, physics-based reduced-order comparison of rectangular, trapezoidal and elliptical planforms under both rigid and flexible representations, intended as a screening tool for preliminary design rather than as a quantitatively predictive methodology for specific aircraft. A two-degree-of-freedom plunge–pitch typical section with quasi-steady (Theodorsen-based) aerodynamics is cast in state-space form, and flutter is identified through eigenvalue continuation by combined frequency coalescence and damping sign change. For rectangular and trapezoidal wings, increasing AR or reducing stiffness consistently advances flutter onset: at a fixed AR of 7.1, stiffening alone raises the critical speed by approximately 43 m/s (from 105 to 148 m/s, ≈+41%). In contrast, within the reduced-order model the elliptical planform inverts this trend: with sufficient stiffness, frequency coalescence is suppressed, and from the stiffened baseline (AR ≈ 4.75) raising AR to 5.6 keeps the wing flutter-free across the investigated velocity range, whereas lowering AR to 3.9 reintroduces hard flutter at 155 m/s. These model-based comparative tendencies indicate that AR and structural flexibility are strongly coupled design drivers and that elliptical loading is comparatively flutter-resistant, providing an efficient basis for early-stage configuration screening. Full article

Hydrophilic sucrose esters are widely used in whipped cream, but the relationship between their molecular structure, interfacial behavior, and whipping performance remains unclear. This study investigated three hydrophilic sucrose esters, S1170, S1570, and P1570, in sodium caseinate-stabilized cream systems. Interfacial measurements showed that sucrose ester concentration strongly affected the adsorption behavior and viscoelasticity of the oil/water interface. Low concentrations produced rheological responses consistent with the formation of a more elastic mixed interface, whereas excessive addition was associated with competitive adsorption, reduced interfacial protein coverage, and weakened interfacial viscoelasticity. The molecular structure of sucrose esters further influenced this process: S1170, with a higher polyester content, showed behavior consistent with stronger interfacial interactions, while P1570 showed a greater decrease in interfacial modulus. These interfacial differences were associated with changes in whipping behavior. At 0.10 wt%, sucrose esters slowed fat partial coalescence, prolonged the optimal whipping time, and increased overrun. At 0.50 wt%, they accelerated early-stage coalescence and increased serum loss, especially for P1570. These findings suggest that selecting appropriate sucrose ester type and dosage is essential for balancing interfacial stability, fat partial coalescence, and whipped cream quality. Full article