Search Results (3,133)

Clay minerals in coal play a key role in controlling mineralogical composition, geochemical signatures, and the industrial behavior of coal and its combustion residues. This study investigates the occurrence, provenance, and potential applications of clay minerals in Carboniferous ash-rich coals from the Bogatyr, Lenin, and Saradyr coal mines in northeastern Kazakhstan. A total of 60 coal samples were analyzed using XRD, SEM–EDS/BSE, XRF, and ICP-OES following acid leaching. Based on ash yield, 52 samples were classified as coal (<50% ash), while 8 samples were classified as carbonaceous shale or mudstone (>50% ash). Mineralogical assemblages show clear variability among the studied mines. Saradyr samples are strongly quartz-dominated with lower clay proportions, Bogatyr samples exhibit highly heterogeneous quartz–clay–mica assemblages, whereas Lenin samples are relatively more clay-rich and dominated by kaolinite and illite-group minerals. Across all samples, kaolinite is the dominant clay mineral (16.6–46 wt.%), occurring mainly as authigenic pore- and cell-filling aggregates. Minor phases include illite–muscovite (7.1–29.9 wt.%), illite–smectite (up to 7.6 wt.% in Bogatyr), and smectite–montmorillonite (0.4–0.7 wt.%). Clay minerals occur as discrete particles, coatings, and pore fillings, contributing to ash formation; however, their correlation with ash yield is weak (R = 0.03–0.05), reflecting heterogeneous mineral inputs and diagenetic overprinting. All geochemical data are reported on a high-temperature coal ash (HTA) basis (815 °C). Geochemical indices (CIA, CIW, CIX) and Al₂O₃/TiO₂ ratios (1.8–17.4) indicate variable provenance and moderate to high weathering intensity, reflecting mixed mafic to intermediate source rocks. A total of 23 trace elements were identified. Au occurs at trace levels (up to 0.02 ppm), while selected rare earth elements (REE: Ce, Dy, Eu, La, Nd, Sm, Y, Yb) average 0.2–0.3 ppm, indicating negligible economic recovery potential. REEs show a strong positive correlation with clay minerals (r = 0.93), indicating adsorption and minor structural incorporation. In contrast, Au correlates with As, V, Zn, Cu, Ni, and Nb, suggesting sulfide association. HTA is enriched in SiO₂–Al₂O₃ phases dominated by kaolinite and quartz, indicating strong potential for cement, geopolymer, ceramic, and zeolite applications. Full article

Background: Head motion and variability in scan quality remain major methodological challenges in autism neuroimaging. Large multi-site datasets such as ABIDE-II provide a unique opportunity to systematically quantify diagnostic differences in MRI data quality and assess the influence of site-level heterogeneity. Methods: Functional MRI Quality Assessment Protocol (QAP) metrics were combined with phenotypic data from ABIDE-II. Participants were classified as autistic (ASD) or typically developing (TD). Key quality metrics—including mean framewise displacement (mFD), proportion of volumes exceeding 0.20 mm (FD > 0.20), signal-to-noise ratio (SNR), and entropy focus criterion (EFC)—were analyzed alongside age, sex, IQ, and site. Group differences were evaluated using non-parametric tests and linear mixed-effects models with site as a random factor. Additional analyses examined site-level heterogeneity and the impact of quality-control (QC) thresholds on sample composition. Results: The final sample included 1277 participants (579 ASD; 698 TD) across 14 sites. ASD participants exhibited significantly greater head motion (median mFD = 0.101 vs. 0.081 mm; p < 1 × 10⁻¹⁰) and modest reductions in signal quality (lower SNR, higher EFC). Elevated motion in ASD was observed in 12 of 14 sites, although effect sizes varied substantially. Mixed-effects models confirmed that diagnosis remained a significant predictor of motion after adjusting for covariates. In contrast, signal-quality differences were small and largely explained by site effects. Simulated QC procedures disproportionately excluded ASD participants, with exclusion rates up to 31% compared to 18% in TD. Conclusions: ASD participants show consistently higher head motion, while signal-quality differences are minimal and largely site-driven. Standard QC procedures disproportionately exclude ASD individuals, highlighting the need for improved motion handling and more balanced quality-control strategies in multi-site studies. Full article

In an effort to explore the influence mechanism of expanded polystyrene (EPS) foam particle content on the freeze–thaw resistance of geopolymer EPS concrete (GEPSC) and realize the synergistic optimization of freeze–thaw durability and low-carbon performance, systematic tests on the apparent morphology, mass loss rate, and relative dynamic elastic modulus (RDEM) of GEPSC with different EPS contents (30%, 35%, 40%, 45%, 50%, 55%) were conducted via freeze–thaw cycle tests. A parabolic damage model was established based on the theory of damage mechanics, and comparisons were made between GEPSC and conventional EPS concrete (EPSC) in terms of microstructure and carbon emission effect. Results indicate that the freeze–thaw resistance of GEPSC exhibits a nonlinear negative correlation with EPS content, which clarifies the applicable scope of GEPSC with different EPS dosages. The fitting correlation coefficient R² of the established parabolic damage model is all higher than 0.98, which can accurately predict the evolution law of freeze–thaw damage of GEPSC. The interfacial transition zone of GEPSC is indistinct and the geopolymer matrix presents a denser structure. Compared with EPSC of the same density, the carbon emission of GEPSC is reduced by 45.3%, demonstrating that GEPSC integrates favorable freeze–thaw resistance with prominent environmental benefits. This study provides a scientific basis for the mixed proportion design and engineering application of low-carbon concrete materials in cold regions. Full article

This study aimed to reveal the rhizosphere microbial community structure, carbon–nitrogen–phosphorus (C-N-P) nutrient cycling processes, and functional gene characteristics of Pinus massoniana and Schima superba in mixed forests. Furthermore, we sought to elucidate the microbial mechanisms by which mixed-species afforestation enhances soil quality improvement, providing a theoretical basis in soil microbiology for the cultivation of these mixed forests. The research subjects included pure P. massoniana plantations (CLPs), pure S. superba plantations (CLSs), and individual P. massoniana (HJP) and S. superba (HJS) trees within mixed plantations (HJLs). We collected rhizosphere and bulk soil samples to analyze their physicochemical properties and enzyme activities. Metagenomic sequencing was employed to profile the rhizosphere microbial communities and functional genes involved in C-N-P cycling. Furthermore, by integrating a functional gene co-occurrence network analysis with structural equation modeling (SEM), we systematically elucidated the coupling relationships among the stand types, soil properties, microbial communities, and nutrient cycling. Mixed planting significantly improved soil quality; compared to the CLP and CLS forests, the nitrate nitrogen (NO₃⁻-N) content in the mixed forest soils increased by 121.01% and 120.10% (p < 0.05), and the activity of urease (URE) also significantly increased by 123.99% and 49.56%, respectively. Mixing significantly altered the microbial community structure. In the bacterial community of the mixed forests, the abundance of nitrogen-fixing and potentially phosphorus-solubilizing bacteria from the genera Paraburkholderia and Burkholderia increased. In the fungal community, the arbuscular mycorrhizal fungus Rhizophagus, which possesses a nutrient absorption advantage, exhibited absolute dominance, with its relative abundance ranging from 14.84% to 88.81%. The abundances of genes associated with denitrification and phosphorus starvation regulation were significantly upregulated in the mixed forests; notably, the abundance of phosphorus starvation regulation genes in the HJSs was 18.84% higher than that in the CLSs. A co-occurrence network analysis demonstrated that the proportion of positive correlation edges in the HJP nitrogen cycling network reached as high as 75.0%, and the average degree of the HJS phosphorus cycling network (2.691) surpassed that of the CLSs. The structural equation modeling further revealed that the association strength between the fungi and phosphorus cycling genes in the mixed forests increased to R² = 0.915 (p < 0.01) from R² = 0.213 in the pure forests. This mixed planting practice transforms nutrient cycling from a resource-competitive mode to a microbially synergized mode, thereby forming an efficient endogenous nutrient cycling system. This synergistic rhizosphere microbial effect is a key internal mechanism for overcoming nutrient bottlenecks and should serve as a diagnostic indicator of soil recovery in the ecological restoration of degraded pine forests. Full article

Hybrid steel–PVA fiber-reinforced concrete offers promise for enhancing both load-bearing capacity and deformation capacity. However, the coupled effects of fiber parameters and volume-fraction combinations on compressive strength (σc) and peak strain (εc) are still not fully understood. A unified, interpretable, and engineering-oriented quantitative framework is still lacking. This study compiled experimental data from 26 published literature, building a multi-source database consisting of 397 datasets for σc and 203 datasets for εc. Based on this database, a comprehensive analytical framework was proposed, including model prediction, SHAP-based interpretation, Monte Carlo marginalization, synergy-gain window determination, and dual-objective mix-proportion optimization. For σc prediction, LightGBM achieved the highest test-set R² (0.9783), whereas CatBoost showed more robust error control (MAE = 2.7409 MPa). CatBoost was therefore selected as the base model for the subsequent interpretation analysis. For εc prediction, Bayesian-optimized CatBoost achieved the best test performance (R² = 0.9659, MAE = 0.0218, RMSE = 0.0358), while the transfer-learning model reached a comparable accuracy level (R² = 0.9650). SHAP analysis revealed that σc is mainly governed by matrix mix-proportion factors and steel fiber volume fraction, whereas εc is more sensitive to S/B and PVA-related variables. The mean synergy-gain maps generated via Monte Carlo marginalization and two-dimensional grid evaluation further showed clear differences between the two targets. Positive synergy in σc was highly localized. Its maximum mean synergy gain was 4.7949 MPa at (Steel, PVA) = (1.875%, 2.000%). By contrast, εc exhibited a wider positive-synergy region, with a peak value of 0.0141629 at (0.38%, 1.62%). Therefore, the engineering output of this study is not a single optimal mix point. Instead, it is a set of candidate windows for different performance targets, together with boundary-risk identification and priorities for experimental validation. Full article

To promote the practical application of metakaolin-slag geopolymer materials in engineering repair, it is essential to clarify the influence of mix proportion parameters on macroscopic properties, given their inherent deficiencies of inferior toughness and volume stability. In this study, a five-factor and four-level orthogonal experimental design was adopted to systematically investigate the effects of slag content, water glass modulus, alkali equivalent, water–binder ratio, and sand–binder ratio on the fluidity, compressive strength, flexural strength, compressive-to-flexural strength ratio (toughness indicator), and drying shrinkage rate (volume stability indicator) of geopolymer mortar. Range analysis and variance analysis were conducted to clarify the primary and secondary order of influencing factors for each performance index, and the optimal mix proportion balancing multiple performance demands was determined. The results indicate that alkali equivalent is the core factor governing compressive and flexural strength, whereas slag content dominates the compressive-to-flexural ratio, fluidity and drying shrinkage. The geopolymer mortar achieves relatively optimal comprehensive performance when the slag content is 20%, the sodium silicate modulus is 1.6, the alkali equivalent is 12%, the water-to-binder ratio is 0.49, and the sand-to-binder ratio is 2:1, and all indicators meet the specification requirements for rigid repair mortar. Combined with SEM-EDS and XRD microstructural analysis, the main products of the metakaolin-slag system are amorphous N-A-S-H gel and C-(A)-S-H gel. Appropriate alkali equivalent and slag content can promote the dissolution of aluminosilicate raw materials and facilitate the formation of both gel products, providing microstructural support for the improvement of macroscopic performance. Full article

This study experimentally evaluates the mechanical healing performance of precast concrete incorporating hybrid capsules under load reapplication conditions. Hybrid capsule systems are defined as self-healing systems that combine solid capsules (SCs) and liquid capsules (LCs), to enable multi-scale crack healing. In this study, four mix proportions (HC-0, HC-1, HC-3, and HC-5), corresponding to 0%, 1%, 3%, and 5% replacement of fine aggregate by volume with hybrid capsules, were prepared. The hybrid capsules consisted of SCs and LCs in a fixed ratio of 7:3. Among the mixtures, a representative intermediate content (3%) was selected to examine the feasibility of mechanical recovery compared to plain concrete, rather than to determine an optimal dosage. Mechanical recovery was evaluated through compressive and flexural strength tests after preloading and healing periods. The results confirm that the incorporation of hybrid capsules enables partial recovery of mechanical properties after damage. These findings provide preliminary experimental evidence of the feasibility of hybrid capsule systems in precast concrete. Further studies are required to investigate the influence of capsule content and to establish optimal mixture conditions. Full article

High-Andean grasslands in the Central Andes of Peru are severely degraded by Lepidium meyenii (maca) cultivation, compromising pasture structure and forage availability for sustainable livestock production. A factorial field experiment evaluated restoration timing and pasture-oriented seed mixtures by manipulating resting time after abandonment (0, 1, 2, and 3 years) and restoration treatment (control; Festuca dolichophylla monoculture; full mixture of Dactylis glomerata + Lolium spp. + Trifolium repens + F. dolichophylla; and mixture without F. dolichophylla) across 64 plots. Vegetation was assessed eight months after seeding, and responses were analysed with ordination, PERMANOVA with restricted permutations, PERMDISP, and generalised linear models and mixed-effects models for diversity metrics. Community composition differed significantly among resting times and seed treatments, with resting time explaining the largest proportion of variance (R² = 0.353), followed by treatment (R² = 0.236), while the interaction was significant but smaller (R² = 0.102, p = 0.002). PERMDISP detected significant differences in multivariate dispersion for both Resting Time and Treatment, indicating that compositional differences may reflect both centroid shifts and heterogeneity among groups. Passive recovery and Festuca-only plots showed slower, more variable compositional change, whereas productive mixtures produced clearer, treatment-specific trajectories over time, suggesting possible divergence in community development patterns, rather than providing formal evidence of distinct alternative stable states. Establishment was consistently high for D. glomerata and Lolium spp., supporting rapid ground cover, which may be associated with short-term forage potential, while F. dolichophylla showed chronically low establishment consistent with limited germination performance. The invasive Pennisetum clandestinum was most pronounced under passive recovery and was reduced under seeded mixtures, suggesting a potential competitive suppression effect. Overall, early seeding with productive mixtures appeared to influence community assembly trajectories, while resting time remained the dominant driver of compositional variation, suggesting potential implications for restoration management in maca-degraded landscapes, although outcomes related to sustainable grazing systems were not directly evaluated. Full article

To address underground shotcrete support scenarios with potential radiation-protection requirements, a bismuth oxide/clay functional filler was incorporated into a baseline shotcrete formulation. Functional filler dosage, calcium formate dosage, and PCE dosage were selected as variables, and Box–Behnken response surface methodology was used to establish quadratic regression models for 28 d compressive strength, fluidity, and bond strength. Representative optimized mixtures were further evaluated by MCNP5 simulation, gamma-ray air-kerma attenuation tests, and SEM. The models showed good fitting and predictive performance within the investigated design space. Functional filler dosage mainly controlled compressive strength and bond strength, whereas PCE dosage dominated fluidity. Under the constraints of compressive strength ≥ 25 MPa, fluidity of 160–170 mm, and bond strength ≥ 0.8 MPa, three representative mixtures were selected for shielding-, strength-, and interface-priority strategies. Simulated and measured results showed consistent shielding-performance rankings, and the optimized mixtures exhibited higher gamma-ray attenuation than the blank mixture. BBD26 achieved the highest shielding performance, with measured shielding rates of 65.51% and 51.54% at 661.7 keV and 1.25 MeV, respectively. Thickness-gradient tests indicated exponential attenuation, while SEM revealed differences in Bi-bearing particle distribution and matrix continuity. Full article

Heritage rammed earth is a special soil material formed by manually selecting and ramming locally available Quaternary surface deposits layer by layer. However, the quantitative influence of material sourcing and rammed technology on the compressive properties of heritage rammed earth remains insufficiently understood, which limits the mechanical assessment and conservation planning of rammed earth sites. In this study, undisturbed rammed earth from 15 Ming Great Wall sites in Northwest China was investigated. Field 3D scanning, particle-size analysis, uniaxial compression testing, mesoscopic structural observation, and DEM analysis were combined to evaluate the effects of material characteristics and rammed technology on the compressive properties of heritage rammed earth. The results show clear regional differences in material characteristics and rammed technology parameters across the 15 sites. Across the five occurrence regions from the Extremely Arid Area to the Semi-Humid Area, dry density, silt fraction, curvature coefficient, and ramming pit distribution area ratio generally decreased, whereas clay and colloidal particle fraction, $d_{60}$, $C_u$, and rammed modulus generally increased. These variations were accompanied by changes in internal fabric, including aggregate proportion, coordination-number difference, high-stress particle proportion, and force-chain particle proportion. The peak stress and failure strain ranged from 0.48 to 1.01 MPa and from 0.03 to 0.07, respectively. Both parameters showed a decreasing regional trend from the extremely arid area to the semi-humid area, following the sequence: extremely arid area, arid area, semi-arid area, cold and humid area, and semi-humid area. From the Extremely Arid Area to the Semi-Humid Area, the shear failure mode changed from single-fork to mixed double-fork and then to intersecting double-fork. Regression analysis further showed that material and rammed technology parameters were closely related to mesoscopic structural parameters, with R² values generally greater than 0.75. These findings suggest that the regional differences in compressive behavior were closely associated with variations in material sourcing, rammed technology, internal fabric, and the load-bearing structure of rammed earth. Full article

Iron ore mining requires the surrounding rock to be excavated, and the beneficiation process generates tailings. When used as construction aggregates, these materials can cause concrete to crack due to the presence of pyrite. Currently, there are no established technical methods to prevent damage caused by pyrite, which limits the resource recovery of such solid waste. In this study, we selected the surrounding rock and tailings to serve as coarse or fine aggregates for C50 concrete based on standard engineering mix proportions. We found that surface-exposed pyrite on aggregates oxidizes first to form ettringite, triggering expansion, with the expansion rate positively correlated with the surface-exposed pyrite content. The deformation process was quantitatively characterized using the Arrhenius equation and by analyzing the acceleration effect of temperature on expansion, yielding an apparent activation energy of 8.28–9.47 kJ/mol. Using a 0.04% expansion value as the failure criterion, the results indicate that at an annual average temperature of 20 °C, C50 concrete with surface-exposed pyrite introduced by concrete aggregates exceeding 20 kg/m³ will fail within its service life. Full article

This study presents a comparative evaluation of the structural performance of flexible pavements made from different hot mix asphalt (HMA). HMAs were proportioned using the conventional Marshall method and HMAs subjected to short-term aging were analyzed. Grades B (binder course) and C (surface course), according to DNIT specifications, were used. After determining the aggregate gradation and asphalt content using the Marshall method, test specimens were produced and tested in the laboratory to determine the mechanical parameters characteristic of each HMA (stability, tensile strength by diametral compression, resilient modulus, fatigue behavior, and permanent strain). The Elsym5 software was used to carry out a structural analysis of an assumed pavement, whereby only the mechanical properties of the surface course and the binder course were varied. The results showed that short-term aging significantly affected the mechanical behavior of HMA and the structural response of flexible pavements. Better structural performance was observed in HMAs subjected to short-term aging. The aged specimens showed an improvement in mechanical properties compared to specimens produced by the conventional method, indicating a promising approach for optimizing pavement performance. These results provided new parameters for investigation and development in the field of road engineering. Full article

Viscous fluid dampers are widely used for mechanical vibration reduction to ensure the stability and safety of structures and systems. However, when a small amount of air (less than 10%) is mixed into the fluid, the compressibility of the fluid increases, leading to a decrease in the physical series stiffness of the damper. Consequently, under dynamic excitation, the proportion of elastic force in the total output force rises, resulting in an increase in the equivalent parallel additional stiffness—a concept often conflated with the series stiffness in the literature. This paper aims to demonstrate these two aspects of stiffness change by investigating the dynamic characteristics of air-mixed viscous fluid dampers through nonlinear modeling, finite element simulation, and experimental validation. Starting from a nonlinear series model comprising nonlinear damping and a nonlinear fluid spring (series stiffness), the energy dissipation and physical series stiffness under different air mixtures are simulated using a finite element model. To further explore the influence of air, an equivalent linear parallel model is established based on the equal energy principle, yielding an equivalent parallel additional stiffness. The results reveal that the energy dissipation effectiveness and the dynamic stiffness of viscous fluid dampers decrease as the air mixture increases. Nevertheless, the additional stiffness is increased with the air content. When the amount of air mixing is the same, the energy dissipation characteristics of the viscous fluid damper under different excitation frequencies vary. Both the damper efficiency and the additional stiffness are increased with the increase of the excitation frequency. The proposed equivalent linear model effectively captures the coupled effects of air mixture and excitation conditions on damper performance. Full article

In cold and arid regions, the durability of asphalt pavement materials is often inadequate, and the hot mixing process further accelerates pavement ageing and releases harmful gases. To address the high-viscosity of pavement materials in such regions, lower mixing temperatures, extend the construction duration, and enhance pavement durability, this study systematically investigates a warm-mix technology for rubber-composite-modified asphalt. First, the influence of processing conditions on the viscosity-reducing effect was examined, and the optimal warm-mix preparation process was determined. Second, the properties of warm-mix rubber-modified asphalt were optimised through high- and low-temperature rheological testing. Finally, the mechanism of warm-mix modification was elucidated using microscopic techniques such as scanning electron microscopy, fluorescence microscopy and infrared spectroscopy. The results show that the 40-mesh pelletised desulphurised rubber treated with activator at a 5:1 ratio of activator at 220 °C for 50 h exhibits the optimal viscosity reduction effect. As the proportion of cracked rubber increases, the viscosity-reducing effect first intensifies and then diminishes optimal results are achieved at a dosage of 5%; the optimal comprehensive performance is achieved at a 5% proportion, where the asphalt simultaneously exhibits excellent high-temperature stability and low-temperature crack resistance. The cracking process effectively disrupts the cross-linked network structure of rubber, significantly reducing viscosity while enhancing the compatibility and stability of the asphalt system. Notably, the proposed warm-mix process reduces the production temperature of rubber-modified asphalt by 40–60 °C and lowers its viscosity by approximately 30% compared to conventional asphalt. This improvement provides crucial support for low-temperature construction and viscosity control of rubber-modified asphalt in cold and arid regions. Full article

Background/Objectives: Sleep quality is a critical determinant of recovery after total joint arthroplasty (TJA), yet multidimensional trajectories of sleep health remain poorly defined. This study aimed to describe the trajectory of sleep health and sleep quality before and after hip or knee arthroplasty, and to examine the influence of sex and surgical site. Methods: A single-centre, prospective cohort study was conducted including 316 patients scheduled for primary hip or knee arthroplasty. Sleep was assessed two months before surgery and at one and six months postoperatively, using the Pittsburgh Sleep Quality Index (PSQI) and the RU-SATED scale. Statistical analyses used linear mixed-effects models with random intercepts for participants. Effect sizes (Cohen’s d) were derived from the residual variance of the mixed models. Results: At baseline, 40% of patients had poor sleep quality. Estimated marginal mean PSQI scores were 5.30 (95% CI: 4.87 to 5.73) preoperatively, 5.71 (5.27 to 6.15) at one month, and 4.19 (3.73 to 4.65) at six months, representing a reduction of 1.11 points (95% CI: 0.69 to 1.54; Cohen’s d = 0.49, 95% CI: 0.30 to 0.68; p < 0.001) from baseline to six months. The proportion of patients with poor sleep quality (PSQI > 5) fell from 40% to 28%, a 12 percentage-point absolute reduction reflecting individual-level transitions across the validated clinical threshold. Exploratory component analyses showed improvements in subjective sleep quality, sleep duration, sleep efficiency, and sleep disturbance. RU-SATED scores increased from 9.72 (95% CI: 9.46 to 9.98) to 10.45 (10.19 to 10.72) at six months, an improvement of 0.73 points (95% CI: 0.47 to 1.00; Cohen’s d = 0.44, 95% CI: 0.27 to 0.60; p < 0.001). Women undergoing knee arthroplasty had significantly worse sleep scores than men at baseline and one month postoperatively, though both sexes followed parallel recovery trajectories (time-by-sex interaction p > 0.30), with the absolute sex difference narrowing by six months. In hip arthroplasty, no significant sex differences or time-by-sex interactions were observed after adjusting for the age imbalance between sexes. Conclusions: Arthroplasty was associated with significant improvements in multidimensional sleep health by six months, though the first postoperative month represents a period of stagnation or slight decline. Women undergoing knee arthroplasty consistently reported worse sleep than men, although the recovery trajectory was parallel between sexes. These findings highlight the potential value of integrating sleep assessment into perioperative care, particularly for women scheduled for knee arthroplasty, though whether targeted sleep interventions improve clinical outcomes remains to be established through prospective intervention studies. Full article