Search Results (2,168)

The mechanical behavior of fiber-reinforced concrete largely depends on the fiber morphology, geometry, and distribution. However, current numerical models do not take into account the stochastic properties of fibers with a spatial distribution, which limits their prediction accuracy and overlooks the critical impact of microstructural effects on macroscopic properties. To address this issue, a comprehensive numerical framework is developed using the Concrete Damage Plasticity (CDP) model for the concrete matrix, an elastoplastic model for steel fibers, and with cohesive zone elements applied to describe fiber–matrix interfacial debonding. Random fiber configurations are generated to represent statistical variability, and their effects on the elastic modulus, compressive strength, and tensile strength are systematically examined. A wide range of fiber parameters—including dimensions, volume fractions, stochastic orientation, and spatial distribution—is investigated to reveal microstructure-dependent mechanical behavior at the macroscale. The results highlight the critical roles of the fiber volume fraction and orientation control in enhancing mechanical behavior and provide practical guidelines for optimizing fiber incorporation strategies in concrete design. Full article

In cold regions, concrete is inevitably subjected to freeze–thaw (F–T) damage, where repeated water–ice phase transitions progressively erode its microstructure and shorten its service life. Compared with the abundant research focusing on macroscopic performance degradation, systematic summaries addressing the microstructural evolution of pores, cracks, and the interfacial transition zone (ITZ), as well as corresponding prevention measures, remain limited. This paper reviews studies from 2013 to 2025, outlining key deterioration mechanisms under F–T action, including pore coarsening, ITZ weakening, and microcrack propagation. Four frost resistance enhancement strategies are compared: introducing stable microbubbles, refining the pore structure with pozzolanic or nano admixtures, bridging cracks with fibers, and applying hydrophobic treatments to block water ingress. The findings indicate that combining multiple measures yields superior frost resistance. By integrating microstructural observations with engineering improvement approaches, this review provides a holistic perspective for the design of durable concrete in cold regions and highlights the need for further research on multi-factor coupling mechanisms, optimization of composite admixture systems, and the functional mechanisms of novel nanomaterials. Full article

Gel treatments have been widely applied to control water production in oil and gas reservoirs. However, for water shutoff in dense gas reservoirs, most gel-based treatments focus on individual wells rather than the entire reservoir, exhibiting limited treatment depth, poor durability, and inadequate repeatability Notably, formation damage is a primary consideration in treatment design—most dense gas reservoirs have a permeability of less than 1 mD, making them highly susceptible to damage by formation water, let alone viscous polymer gels. Constrained by well completion methods, gelant can only be bullheaded into deep gas wells in most scenarios. Due to the poor gas/water selective plugging capability of conventional gels, the injected gelant tends to enter both gas and water zones, simultaneously plugging fluid flow in both. Although several techniques have been developed to re-establish gas flow paths post-treatment, treating gas-producing zones remains risky when no effective barrier exists between water and gas strata. Additionally, most water/gas selective plugging materials lack sufficient thermal stability under high-temperature and high-salinity (HTHS) gas reservoir conditions, and their injectivity and field feasibility still require further optimization. To address these challenges, treatment design should be optimized using non-selective gel materials, shifting the focus from directly preventing formation water invasion into individual wells to mitigating or slowing water invasion across the entire gas reservoir. This approach can be achieved by placing large-volume gels along major water flow paths via fully watered-out wells located at structurally lower positions. Furthermore, the drainage capacity of these wells can be preserved by displacing the gel slug to the far-wellbore region, thereby dissipating water-driven energy. This study evaluates the viability of placing gels in fully watered-out wells at structurally lower positions in an edge-water drive gas reservoir to slow water invasion into structurally higher production wells interconnected via numerous microfractures and high-permeability streaks. The gel system primarily comprises polyethyleneimine (PEI), a terpolymer, and nanofibers. Key properties of the gel system are as follows: Static gelation time: 6 h; Elastic modulus of fully crosslinked gel: 8.6 Pa; Thermal stability: Stable in formation water at 130 °C for over 3 months; Injectivity: Easily placed in a 219 mD rock matrix with an injection pressure gradient of 0.8 MPa/m at an injection rate of 1 mL/min; and Plugging performance: Excellent sealing effect on microfractures, with a water breakthrough pressure gradient of 2.25 MPa/m in 0.1 mm fractures. During field implementation, cyclic gelant injections combined with over-displacement techniques were employed to push the gel slug deep into the reservoir while maintaining well drainage capacity. The total volumes of injected fluid and gelant were 2865 m³ and 1400 m³, respectively. Production data and tracer test results from adjacent wells confirmed that the water invasion rate was successfully reduced from 59 m/d to 35 m/d. The pilot test results validate that placing gels in fully watered-out wells at structurally lower positions is a viable strategy to protect the production of gas wells at structurally higher positions. Full article

This study investigates hydrogen embrittlement mechanisms at the interfaces of explosively welded joints between 304L austenitic stainless steel and carbon/low-alloy steels (St41k, 15HM), focusing on the unique properties of local melting zones (LMZs) formed during joining. Advanced microstructural characterization, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and microhardness testing, was combined with controlled electrochemical hydrogen charging. Results demonstrate that while base materials suffered substantial hydrogen-induced degradation—blistering in carbon steels and microcracking in stainless steel—the LMZ exhibited exceptional resistance to hydrogen damage. Compositional analyses revealed that the LMZ possessed intermediate chromium (4.8–8.8 wt.%) and nickel (1.7–3.6 wt.%) contents, reflecting mixing from both plates, and significantly higher microhardness compared to adjacent zones. The superior hydrogen resistance of the LMZ is attributed to their refined microstructure, increased density of hydrogen trapping sites, and non-equilibrium phase composition resulting from rapid solidification. These findings indicate that tailoring the process of the LMZ in clad steel joints can be an effective strategy to mitigate hydrogen embrittlement risks in critical hydrogen infrastructure. Full article

Background/Objectives: Neuroinflammation is a leading factor in secondary brain damage following a traumatic brain injury (TBI). Existing therapeutic approaches have limited efficacy against neuroinflammation. The bone marrow, the primary hematopoietic organ, is also a source of inflammatory cells. We propose that targeting the sympathetic regulation of inflammatory cell mobilization could reduce neuroinflammation after TBI. Methods: In ICR mice, we investigated the immune cell response in the blood, bone marrow, motor cortex, and the subventricular zone after TBI modeling and treatment with the sympatholytic agent reserpine. Results: TBI induced neutrophilia and lymphocytosis in the peripheral blood, activated hematopoiesis in the bone marrow, and triggered neuroinflammation and degenerative changes in the cerebral cortex (CC) and the subventricular zone (SVZ) of mice. Reserpine reduced leukocytosis in the blood and hematopoietic activity in the bone marrow of mice with TBI compared to untreated TBI mice. Furthermore, reserpine decreased neutrophilic and lymphocytic infiltration, as well as the number of Iba1⁺ microglial cells, including M1-polarized microglia, Caspase-3⁺ cells, and cells expressing myeloperoxidase (MPO) in the CC and SVZ of treated mice. The activity of degenerative processes was also reduced. Additionally, reserpine reduced the number of M2-polarized microglial cells in the SVZ. Conclusions: The sympatholytic drug reserpine may hold promise for the development of a novel approach to treating neuroinflammation and degeneration following a TBI. This is based on its ability to reduce hematopoiesis and mobilize inflammatory cells from the bone marrow into the bloodstream. Full article

The escalating scarcity of freshwater resources necessitates the utilization of alternative saline waters for sustainable aquaculture. Perca schrenkii, an endemic fish from the Ili River basin, demonstrates considerable potential for cultivation in chloride-type saline–alkaline waters: its 96 h acute salinity tolerance is higher than that of freshwater populations of its congeneric Perca fluviatilis. This study systematically investigated the histomorphological responses of its key osmoregulatory and metabolic organs—gill, kidney, intestine, and liver—under acute (12–14 ppt for 96 h) and chronic (3–7 ppt for 60 days) salinity stress. Acute exposure induced dose- and time-dependent structural damage, including lamellar fusion in gills, glomerular reduction in kidneys, mucosal atrophy in intestines, and hepatocellular swelling. In contrast, chronic acclimation revealed active remodeling, such as lamellar shortening, renal tubular dilation, intestinal muscularis thickening, and biphasic hepatocyte adjustments. A hierarchical framework of structural adaptation was proposed, delineating Safe (≤3 ppt), Acclimation (5 ppt), Tolerance (7 ppt), and Lethal (≥13 ppt) zones. These findings elucidate the structural basis of salinity tolerance in Perca schrenkii and provide practical morphological indicators for assessing fish health in saline aquaculture. Full article

In deep coal mining, fault slip-type rockbursts occur frequently. Understanding the shear mechanical properties of bedded coal seams and their intrinsic mechanisms is crucial. This study used PFC^2D7.0 numerical simulation to systematically investigate the shear mechanical behavior and micro-mechanisms of bedded coal under different normal stresses (1, 2, 3, 4 MPa). The research results show that: (1) The shear stress-displacement curves of bedded coal show three stages: elastic rise, strain softening, and residual stability. Both peak and residual shear strengths increase with the rise in normal stress. The peak strength shows nonlinear growth, while the residual strength exhibits a good linear relationship. Higher normal stress significantly reduces the strength reduction rate and effectively inhibits the brittleness of coal. (2) The failure mode consistently manifests as shear failure along the preset weak bedding plane, forming a distinct shear zone. Crack evolution analysis shows that shear cracks within the bedding are the primary form of damage, with minimal contribution from tensile cracks. (3) Force chain analysis shows that an increase in normal stress significantly enhances the density and connectivity of compressive force chains within the shear zone. It also effectively inhibits tensile force chains, with the bedding plane consistently serving as the primary area for stress concentration and transfer. This study provides important theoretical references for understanding the shear instability mechanism of bedded coal, predicting its mechanical response, and preventing fault slip-type rockbursts in deep coal mines. Full article

The formation of hard coal seams is the outcome of multi-stage, complex transformations of organic matter that lead to an increase in carbon content, a decrease in volatile components, and a progressive evolution of the rock’s structure and texture. Diagenetic and metamorphic processes, which underpin coal formation, largely determine its petrographic and geochemical characteristics, but they are not the only factors controlling the final properties of coal. An equally important role is played by the tectonic history of the region in which the coal seams occur. In this study, we carried out an integrated analysis of coal rank, based on vitrinite reflectance measurements (R₀), and mechanical properties, using Vickers microhardness tests (Hv). Coal samples were collected from both sides of a fault plane within a single seam. The results show that the presence of the fault is clearly reflected in the measured parameters. Vitrinite reflectance generally increases towards the fault zone, but in the immediate vicinity of the fault, it exhibits a slight decrease. Subtle yet systematic changes are also observed in microhardness, particularly in the Hv values. The results show that vitrinite reflectance (R₀) and microhardness (Hv) vary in a very similar manner—both parameters decrease as the degree of structural degradation of coal increases within the fault zone. This consistent response of R₀ and Hv to local structural damage suggests that they may serve as sensitive indicators of the presence and extent of influence of small-scale tectonic dislocations. Their combined application provides additional information on the potential occurrence of a fault and on the degree of structural disturbance of coal in its vicinity. Full article

Polypropylene (PP) fibers, known for their high fracture strength, low density, and cost-effectiveness, can significantly enhance the impact resistance of concrete, making the material suitable for specialized engineering applications. This study combined Split Hopkinson Pressure Bar (SHPB) tests with a three-dimensional mesoscale numerical model to investigate the dynamic compressive behavior of PP fiber-reinforced concrete (PFRC). The model, developed using MATLAB, explicitly represented polyhedral aggregates, mortar, the interfacial transition zone (ITZ), and PP fibers. Numerical simulations of impact compression were then performed using LS-DYNA and validated against experimental results. The simulated results exhibit close agreement with the experimental data in terms of peak stress, peak strain, and failure characteristics. The incorporation of 0.1% polypropylene fibers significantly enhanced the dynamic compressive strength of the specimen by 24.45%, with a mere 2.10% deviation from the experimental measurement. When the impact velocity was increased to 8 m/s and 10 m/s, the peak stress showed increases of 6.14% and 22.62%, respectively, while the peak strain increased by 11.72% and 23.32%. Damage analysis revealed that the aggregates experienced minimal failure, with cracks primarily initiating from the mortar and the ITZ. The polypropylene fibers improved the dynamic mechanical performance by dissipating energy through both fiber fracture and pull-out mechanisms. Furthermore, as the impact velocity increased, the fibers absorbed more energy, leading to a progressive increase in their own damage. Full article

The development of deep coalbed methane is hindered by the strong heterogeneity of coal mechanical properties and complex hydraulic fracturing behavior. To identify the key factors controlling fracture geometry and permeability enhancement, this study developed a thermo-hydro-mechanical-damage coupled model within a COMSOL Multiphysics 6.3-MATLAB R2022b co-simulation framework, incorporating a Weibull random field to characterize mechanical heterogeneity. Sensitivity analysis demonstrates that tensile strength is the predominant factor governing both the fracturing damage zone and permeability-enhanced area, with its damage area extreme difference (10.094) and coefficient of variation (0.85) significantly surpassing those of other parameters. Poisson’s ratio and elastic modulus emerge as key secondary parameters, while compressive strength shows the lowest sensitivity. The parametric influences exhibit distinct patterns: tensile strength shows a strong negative correlation with damage and permeability-enhanced areas (up to 85% reduction), whereas the maximum permeability enhancement rate follows a non-monotonic trend, peaking at 215 when tensile strength reaches 3.33 MPa. Compressive strength minimally affects the damage area (~15%) but steadily improves the maximum permeability enhancement rate (7.5% increase). Elastic modulus exhibits an optimal value (8.93 GPa) for maximizing damage area, while negatively correlating with maximum permeability enhancement rate (9.1% decrease). Fracture morphology is differentially controlled by multiple parameters: low compressive strength promotes fracture deflection and branching, elastic modulus regulates fracture network complexity, and low Poisson’s ratio enhances coal brittleness to effectively activate natural fractures, thereby facilitating complex fracture network formation. Full article

Understanding the influence of strike–slip faulting on deep carbonate reservoirs remains challenging. This study integrates core observations, well logging, and seismic interpretation to investigate fracture diagenesis and evaluate the impact of strike–slip faulting on Upper Permian reef–shoal reservoirs in the northern Sichuan Basin. Within the platform margin reef–shoal microfacies, transtensional faulting during the Late Permian was later overprinted by transpressional deformation in the Early–Middle Triassic. Although individual fault displacements are generally less than 200 m, the associated damage zones may extend over 1000 m in width. Strong compaction and cementation eliminated most primary porosity in the reef–shoal carbonates, whereas dissolution enhanced porosity preferentially developed along fault damage zones. The most productive of fracture–vug reservoirs (“sweet spots”) are mainly distributed adjacent to strike–slip fault zones within the reef–shoal bodies. Reservoir quality is controlled by syn-sedimentary faults, moldic vugs, karstic argillaceous fills, and U-Pb ages of fracture cements that indicate multi-stage diagenesis. Contemporaneous fracturing and dissolution during the Late Permian played a dominant role in enhancing reservoir porosity, while burial-stage cementation had a detrimental effect. This case study demonstrates that even small-scale strike–slip faulting can significantly improve reservoir quality in deep tight reef–shoal carbonates. Full article

Invasive alien species pose escalating threats to global biodiversity and ecosystems, which may be exacerbated by climate change, potentially leading to range expansions and intensified impacts. In China, Mikania micrantha Kunth, a fast-growing tropical vine listed among the world’s 100 worst invasive species, has proliferated since its introduction in the mid-20th century, causing severe ecological damage through the smothering of vegetation, suppression of allelopathy, and economic losses in agriculture and forestry. This study aimed to predict its current and future distributions to guide management. Using 205 stringently filtered occurrence records from databases, surveys, and literature, combined with bioclimatic variables from WorldClim and MaxEnt modeling—optimized via ENMeval and evaluated by AUC (>0.97)—projected habitats under current (1970–2000) conditions and future SSP1-2.6, SSP2-4.5, and SSP3-7.0 scenarios for the 2050s and 2070s via the BCC-CSM2-HR model. Temperature factors dominated predictions, with current excellent suitability (3.6 × 10⁴ km²) concentrated in Hainan and southern Guangdong, expanding to good and moderate zones in Guangxi, Fujian, and Yunnan. Future averages showed expansions in excellent (21.3%), good (10.0%), and moderate (14.0%) habitats, with some northward shifts into Jiangxi and Hunan under higher emissions. In situ augmentation of habitat suitability and spatial containment overshadows the northward range expansion. The high-emission scenario is projected to lead to temperature overshoots, which will dampen habitat suitability. The findings underscore M. micrantha’s resilience to warming, necessitating integrated strategies such as guarding critical biodiversity sites, early detection, biocontrol, and habitat restoration to mitigate risks in both core and emerging zones. Full article

This study aims to explore the development characteristics and evolutionary patterns of strike–slip fault zones in carbonate rocks, through quantitative characterization of fault elements and their interrelationships. Taking three strike–slip fault zones in the Daniudi Block of the northeastern Ordos Basin, China, as examples, we analyzed the distribution of fault damage zone width and throw along the strike of the fault zones at equal intervals, based on data derived from 3D seismic interpretation. The relationship between damage zone width and throw was also explored. The results indicate the following: (1) The throw–distance curve of strike–slip fault zones exhibits bimodal or multimodal patterns. As the peak of the curve is located near the overlap zone of the fault, this signifies that the fault is in the independent stage, whereas a peak situated in the middle of a fault segment suggests that the strike–slip fault has achieved integrity through “hard linkage”. (2) The width of the fault damage zone is controlled by the scale of the fault zone and its associated structures. (3) A strong power–law relationship exists between the damage zone width and throw, with a more pronounced positive correlation observed in the Taigemiao Fault Zone. (4) The strike–slip fault zone is primarily composed of a “ternary” structure, including fault core, damage zone, and fracture zone, and has undergone three evolutionary stages. Analyzing the relationships among fault elements contributes to understanding the interaction and evolutionary history of subsurface strike–slip faults in the study area. Full article

High-temperature superconductor (HTS) magnet systems, especially those designed for fusion reactors, require effective and reliable monitoring to avoid damaging anomalies. In tokamaks, some of the magnetic coils are time-dependent, which causes strain and large inductive voltages within the magnet, rendering detection of incipient quench challenging. Ionizing radiation can also create material defects and lead to non-uniform degradation of conductors. The resulting decrease in critical current uniformity across the magnet, along with manufacturing defects, such as failure of structural materials or cooling systems, can all potentially initiate a quench. HTS magnets have a lower normal zone propagation velocity than low-temperature superconductors, and this causes normal zones to be localized, increasing the risk of permanent damage. Fiber optic sensors have several qualities that are essential in fusion systems. Unlike traditional voltage-based sensors, fiber optic cables are immune to the large electromagnetic fields present. This study presents and validates a fiber optic interrogation technique for monitoring magnetic confinement fusion and other high-temperature superconducting magnet systems. Coherent-phase optical time domain reflectometry (OTDR) allows for the high sampling rates (tens of kHz) necessary to quickly detect and mitigate quench events over the long distances required to monitor fusion magnet systems. This technique was demonstrated to successfully detect localized thermal transients at cryogenic temperatures as low as 6 K. These outcomes were also demonstrated using fibers embedded in HTS magnet coils at 77 K, verifying the potential for this interrogation technique’s use for failure detection in HTS coils. Full article

Urban infrastructure in seismic zones demands efficient and scalable tools for damage prediction. This study introduces an attention-integrated progressive transfer learning (PTL) framework for the seismic vulnerability assessment (SVA) of reinforced concrete (RC) frame buildings. Traditional simulation-based vulnerability models are computationally expensive and dataset-specific, limiting their adaptability. To address this, we leverage a pretrained artificial neural network (ANN) model based on nonlinear static pushover analysis (NSPA) and Monte Carlo simulations for a 4-story RC frame, and extended its applicability to 2-, 8-, and 12-story configurations via PTL. An attention mechanism is incorporated to prioritize critical features, enhancing interpretability and classification accuracy. The model achieves 95.64% accuracy across five damage categories and an R² of 0.98 for regression-based damage index predictions. Comparative evaluation against classical and deep learning models demonstrates superior generalization and computational efficiency. The proposed framework reduced retraining requirements across varying building heights, shows potential adaptability to other structural typologies, and maintains high predictive fidelity, making it a practical AI solution for structural risk evaluation in seismically active regions. Full article