Search Results (289)

To investigate the mechanical response and evolutionary mechanisms of shear-slip rockburst in fractured rock masses, intact, single-fracture, and double-fracture cubic specimens were fabricated using a self-developed synthetic material designed to reproduce pronounced elastic energy storage and rapid brittle failure. Shear-slip tests were conducted under normal stresses ranging from 0.9 to 3.6 MPa. The impact energy index, elastic energy index, and dynamic failure time of the material were 18.0, 9.2, and 140 ms, respectively. Shear stress, shear displacement, and normal displacement were monitored synchronously, while stress-drop events, shear-surface damage, and rock-powder mass were analyzed to clarify the controlling effects of normal stress and the fracture configuration. The results showed that, as the normal stress increased from 0.9 to 2.7 MPa, asperity interlocking along the shear surface was enhanced, resulting in overall increases in the peak and residual shear strengths and progressive suppression of dilation. At 3.6 MPa, all three specimen types exhibited pronounced stress drops, normal contraction, and complete loss of shear-bearing capacity, indicating a transition from stable frictional sliding to crushing collapse dominated brittle instability. The tested specimens suggest that increasing the number of prefabricated fractures may promote deformation localization and shorten the stable post-peak sliding process. At 3.6 MPa, the shear displacements corresponding to complete instability of the intact, single-fracture, and double-fracture specimens decreased from 9.0 to 7.8 and 6.5 mm, respectively, whereas the maximum stress drops increased from 0.28 to 0.62 and 0.90 MPa. These responses were characterized by earlier instability, increasingly concentrated stress-drop events, and larger individual stress drops. With increasing normal stress, the mass of rock powder increased from 11 to 56 g, indicating that shear surface damage evolved from localized fracturing to intensive crushing and grinding. The shear-slip process comprised four stages: compaction adjustment and load-bearing structure formation, elastic shearing and energy accumulation, damage accumulation and crack coalescence culminating in peak instability, and fragment reorganization with post-peak sliding. These findings provide experimental evidence for identifying shear-slip dynamic instability in fractured surrounding rock. Full article

Background and Objectives: The purpose of this study was to investigate the acute fatigue response to a standardized friendly football match in elite adolescent players and to describe the subsequent recovery of neuromuscular performance, biochemical markers, and subjective perceptions over a 72-h period. Methods: Thirty-seven elite male youth football players (16.3 ± 0.7 years) participated in this repeated-measures study. Neuromuscular function was assessed using the countermovement jump (CMJ) and repeated sprint ability (RSA) tests. Muscle damage was evaluated by measuring blood creatine kinase (CK) concentrations, while subjective recovery was monitored using a visual analog scale (VAS) for muscle soreness and the Well-Being Questionnaire (WBQ). Measurements were obtained before the match, immediately after the match, and again 24, 48, and 72 h later. Results: The friendly match induced significant neuromuscular, biochemical, and perceptual fatigue. CMJ height, reactive strength index, and repeated sprint performance decreased significantly immediately post-match (p < 0.001). Perceived muscle soreness increased markedly and remained elevated at 24 h. Neuromuscular performance largely recovered within 48 h, with 20-m sprint performance no longer significantly different from pre-match values at 48 h. In contrast, CK concentrations peaked at 24 h and remained significantly elevated throughout the 72-h recovery period. Significant correlations were observed between subjective soreness, CK concentrations, and neuromuscular performance during recovery. Recovery following match play differed depending on the marker used. Functional performance largely returned to baseline within 48 h, whereas CK concentrations remained elevated throughout the 72-h observation period. Conclusions: These findings emphasize the value of combining objective performance tests with subjective measures when monitoring post-match recovery in elite youth football players. Full article

Arterial stiffness is increasingly recognized as an important marker of vascular aging and an independent predictor of cardiovascular disease. Among the available methods for assessing arterial stiffness, brachial-ankle pulse wave velocity (baPWV) has gained widespread clinical acceptance because it is simple, noninvasive, highly reproducible, and suitable for routine practice and large-scale population screening. Accumulating evidence has demonstrated that baPWV is associated with hypertension-mediated target organ damage, coronary artery disease, cardiovascular events, and mortality. Beyond its prognostic value, baPWV has been investigated as a potential marker of vascular responses to pharmacological and lifestyle interventions. Emerging evidence also suggests that serial assessment and visit-to-visit variability of baPWV may provide additional prognostic information, although their clinical applicability requires further validation. Another advantage of baPWV is its simultaneous measurement of the ankle-brachial index, enabling comprehensive assessment of both arterial stiffness and peripheral artery disease without additional examination time. This review summarizes the physiological basis, measurement principles, strengths and limitations, and current clinical applications of baPWV, with particular emphasis on cardiovascular risk stratification, target organ damage, therapeutic monitoring, serial assessment, and combined ankle-brachial index evaluation. Finally, future perspectives for integrating baPWV into precision cardiovascular medicine are discussed. 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

Assessing whether existing lattice towers can survive extreme wind when they are located on ridgelines or at saddle points requires three questions to be answered simultaneously: how the local wind field is modified by the surrounding topography, how the structural geometry recorded in legacy computer-aided design (CAD) drawings can be recovered accurately, and which member fails first and by what mechanism. This paper couples a Physics-Informed Neural Network (PINN) wind solver, jointly constrained by mass and momentum conservation, with a graph-theory-based Drawing Exchange Format (DXF) parser and a closed-loop vulnerability screening module, so that all three questions are answered in a single automated pass. The PINN reconstructs the three-dimensional steady-state wind field over irregular topography in approximately 0.12 s, holding the root-mean-square (RMS) velocity divergence below 2.1 × 10⁻³ (more than two orders of magnitude lower than that of linear interpolation) while recovering the pressure-gradient-driven acceleration that mass-consistent variational solvers cannot represent. On the CAD side, k-dimensional tree (KD-Tree) spatial indexing combined with breadth-first search (BFS) connected-component analysis resolves the pseudo-disconnections, spurious intersections, and multi-level nested block references that are common in production DXF files, achieving 100% node-merging accuracy across fifteen tower drawings. A unified Vulnerability Index (VI) that combines strength, member stability, and plate buckling into a single scalar, updated through Sherman–Morrison rank-one perturbation at a millisecond cost, closes the diagnose–strengthen–verify loop without re-solving the full stiffness system. Applied to a 220 kV line struck by Super Typhoon Meranti, the pipeline identified seven at-risk members that code-based checking had missed, a result consistent with the recorded field damage, and completed the full assessment in 34.4 s, over three orders of magnitude faster than conventional practice. Full article

Fine-aggregate source can alter both the load-bearing response and surface scaling of mortar under freezing and thawing, but these responses are often reduced to a single durability ranking. This study compared coal gangue sand mortar (CGM), river sand mortar (RSM), desert sand mortar (DSM), and standard sand mortar (StSM) after 0, 25, and 50 freeze–thaw cycles (FTCs). Compressive strength and mass loss were measured using three replicate specimens per quantitative condition, while post-compression fragments were examined by scanning electron microscopy (SEM). The primary integrative analysis was a parameter-free two-dimensional damage-trajectory map that retained absolute compressive strength and mass loss as separate measured axes; a weighted coupled index was retained only as an auxiliary sensitivity check. Before cycling, the compressive strengths of StSM, RSM, DSM, and CGM were $68.13\pm 0.48$, $53.90\pm 0.39$, $19.47\pm 0.33$, and $6.49\pm 0.07$ MPa, respectively. After 50 FTCs, StSM retained the highest absolute strength ($33.61\pm 0.39$ MPa) and the lowest mass loss ($0.21\pm 0.02\%$), whereas DSM retained $9.91\pm 0.19$ MPa and exhibited the highest mass loss ($17.46\pm 0.05\%$). The StSM trajectory moved primarily toward lower strength with negligible surface-material loss, while DSM moved toward both low residual strength and severe scaling. RSM showed substantial strength reduction followed by later-stage surface loss. CGM followed an atypical trajectory in which measured strength increased to $11.13\pm 0.13$ MPa while mass loss reached $9.67\pm 0.04\%$; because age-matched non-frozen controls were unavailable, this apparent gain cannot be separated from continued hydration and specimen-age effects. The SEM images suggested pores, interfacial discontinuities, cracking, and matrix loosening, although some defects may have been induced or widened by compression. The trajectory representation exposed distinct deterioration modes without arbitrary weighting, whereas the calculated ordering of CGM and RSM in the auxiliary index changed with weighting and normalization choices. The results support reporting absolute residual strength and surface loss jointly when screening alternative fine aggregates for cold-region mortar. Full article

The integration of bio-based constituents into cementitious materials requires robust predictive models capable of describing mechanical degradation while supporting sustainability-driven material design. This study presents a macro-constitutive damage modelling framework for biomass-modified cement mortars subjected to monotonic compressive loading, combining experimental characterisation, continuum damage mechanics (CDM), and life-cycle assessment (LCA). The calibrated parameters are interpreted in terms of meso-scale mechanisms, but the study does not constitute a direct imaging-based multiscale characterisation. Mortars containing 0–10% dried microalgal biomass as a partial replacement for binder mass were investigated through their complete compressive stress–strain response. A scalar damage variable was employed to model stiffness degradation and progressive microcrack evolution, enabling the identification of elastic-modulus reduction, damage-initiation thresholds, softening behaviour, and residual load-bearing capacity. A thermodynamically consistent Mazars-type damage model was calibrated against the measured envelopes and internally verified by reproducing the same pre-peak and post-peak responses, with coefficients of determination ranging from 0.979 to 0.996. Increasing biomass content reduced the 28-day compressive strength from 47.8 to 23.7 MPa and the elastic modulus from 27.5 to 14.9 GPa, while increasing the damage level at peak load from 0.26 to 0.46 and promoting a more gradual post-peak softening response. The calibrated law provides a compact constitutive representation within the tested replacement range; independent external validation is still required before extrapolation to other biomass types, mixture proportions, or curing regimes. In parallel, a cradle-to-gate LCA quantified global warming, acidification, eutrophication, ozone depletion, and abiotic depletion potentials. An integrated carbon-efficiency index was used to relate mechanical performance to environmental impact. Biomass replacement reduced global warming potential by up to 7.7% but increased eutrophication potential, highlighting a clear performance–environment trade-off. Despite the reduction in mechanical properties, all mixtures satisfied masonry-unit strength requirements, supporting the application of biomass-modified mortars in low-carbon concrete masonry units. The proposed framework demonstrates how experimentally calibrated damage models can support the structural assessment and sustainable development of emerging bio-based cementitious materials. Full article

Soil salinity is a major environmental constraint that threatens global food security by significantly inhibiting seed germination and early seedling establishment. Salinity disrupts all three phases of seed germination: Phase I (imbibition), where reduced water absorption capacity reduces seed hydration and delays metabolic reactivation; Phase II (lag phase), where ionic toxicity and oxidative stress impair enzyme activity, reserve mobilization, and cellular metabolism; and Phase III (radicle protrusion), where limited cell division and length prevent radicle emergence and seedling establishment. These disturbances reduce germination percentage, germination rate, germination index, germination energy, and plant vigor, while increasing average germination time. At the morpho-physiological level, salinity impairs water absorption, membrane stability, photosynthetic pigment accumulation, and root–shoot development. Biochemically, excessive accumulation of reactive oxygen species (ROS), hydrogen peroxide (H₂O₂), and malondialdehyde (MDA) causes cellular damage and metabolic dysfunction. At the molecular level, salinity alters the expression of the aquaporin gene family (PIPs, TIPs, NIPs, and SIPs), suppresses starch mobilization by reducing α-amylase, enhances abscisic acid (ABA) signaling, and inhibits gibberellic acid (GA) biosynthesis, all of which cause inhibition of germination and early growth. As a result, an effective strategy is needed to improve seed germination under saline conditions. Therefore, the second focus of this review is to critically evaluate the potential of nanoparticles (NPs) and nanobiochar (NBC) as emerging tools to mitigate salinity stress during seed germination. Current evidence suggests that NPs and NBC enhance water absorption, maintain membrane strength, improve nutrient availability, promote antioxidant defense systems, and regulate osmotic adjustment in saline environments. Furthermore, these nanomaterials alter key molecular pathways involved in aquaporin expression, hormonal homeostasis, and reserve mobilization, thereby promoting successful germination and seedling establishment. By combining recent advances in physiological, biochemical, and molecular research, this review provides a comprehensive understanding of salinity-induced germination disruption and highlights the potential of NP- and NBC-based approaches to improve crop establishment under saline conditions. Full article

Functional decline in older adults represents a major challenge in geriatric rehabilitation, and machine learning (ML) clustering techniques may help identify functional recovery profiles and support personalized rehabilitation strategies. This study characterizes functional recovery profiles in older adults admitted for rehabilitation using unsupervised clustering techniques. A retrospective longitudinal study was conducted including 957 older adults admitted to a geriatric rehabilitation unit between 2019 and 2025. Clinical and functional variables, including the Modified Barthel Index (MBI), Daniels and Worthingham’s Muscle Testing, and Functional Ambulation Category, were collected from medical records. Considering the baseline functional status and the temporal changes in MBI scores, a clustering of the functional trajectories has been performed using a k-means algorithm based on the silhouette score. The robustness of the resulting segmentation has been evaluated by comparing alternative partitions obtained from bootstrap-sampling, hierarchical clustering, and the centroids of Gaussian Mixture Models. Four distinct functional recovery profiles were identified, showing different trajectories of independence, ambulation, and muscle strength during rehabilitation. Two clusters demonstrated favorable recovery and higher functional resilience, whereas the remaining profiles were characterized by chronic impairment or severe damage with limited recovery. These findings support the usefulness of unsupervised ML clustering techniques for identifying clinically meaningful recovery profiles and may facilitate patient stratification and individualized intervention planning in geriatric rehabilitation. Full article

The cyclic material properties are crucial for accurate assessment of structural response; however, conventional numerical methods often fail to replicate the mechanical degradation caused by ultra-low cycle fatigue (ULCF) damage accumulation. This paper focuses on a novel constitutive model characterizing the continuous degradation in yield stress and stiffness under large-strain tension–compression cyclic loads. A series of 32 cyclic tests on circular notched specimens covering a range of stress triaxialities are first revisited to systematically identify the cyclic softening behavior. The corresponding limitations of the widely applied classical Chaboche theory are examined, and an enhanced elastoplastic constitutive framework is proposed accordingly. On this basis, the stress-weighted ductile fracture model (SWDFM), which is developed from micro-damage mechanics, is then employed as the internal damage criterion of the proposed constitutive model. Explicit functional relationships linking the evolved yield stress and Young’s modulus to the imposed damage index are established and calibrated against the test data. Based on these findings, a new cyclic ductile constitutive model is developed, which is programmed into the UMAT subroutine compatible with ABAQUS/Standard. Numerical validations against the experimental cyclic responses exhibit good agreement, as indicated by the considerably low average errors of 5% for both strength and stiffness, demonstrating its validity in terms of the hysteretic behavior simulation for metals subjected to progressive ULCF damage. Full article

The probability estimation of agrometeorological damage risk is the core technical support for consolidating the agricultural disaster prevention and reduction system and ensuring the sustainable development of national agriculture. It has been widely applied in agricultural production and agricultural insurance. Based on the crop planting area data, as well as the damaged crop area data (damage-affected, damage-stricken, and dead harvest) of 31 provinces and municipalities from 1980 to 2018, this study creatively builds a comprehensive damage strength index. After that, this study obtains accurate risk probability estimation results of five meteorological damage types by using the parameters of the nonparametric normal information diffusion model. The results show that the risk probability of comprehensive meteorological damage is the largest, followed by drought, flood, wind and hail, and freezing. Flood in Hubei, drought in NeiMenggol, windstorm and hailstorm in Qinghai, freezing damage in Hainan, and comprehensive meteorological damage in NeiMenggol have the highest risk probability. The regions where various meteorological damage occur show different distribution characteristics, which is closely related to the latitude and longitude and topography of China. These findings indicate that it is necessary to understand the overall patterns of agrometeorological damage risks and consider their internal heterogeneity, in order to take targeted prevention and control measures to avoid systemic risks in agricultural production and safeguard sustainable and high-quality agricultural development. Full article

Through-going faults represent critical geological hazards that threaten the long-term operational safety of arch dams. Conventional studies predominantly rely on homogeneous material assumptions and static analysis, neglecting two essential characteristics of natural faults: (1) the discrete, localized distribution of intact rock blocks within fractured zones, and (2) degradation of the mechanical properties of faults with time during the service life of arch dams. These limitations will unavoidably introduce systematic errors into the safety state judgment of operating arch dams. To address these limitations, this paper develops an enhanced constitutive model that couples three key mechanisms: confining pressure strengthening with burial depth, local reinforcement from discrete random rock blocks, and fatigue damage accumulation under cyclic water level fluctuations. The model is implemented via ABAQUS UMAT subroutine development, enabling three-dimensional spatiotemporal evolution simulation of fault mechanical parameters. Furthermore, a multi-index comprehensive evaluation framework is established by integrating normalized dam stress state and abutment strength reduction stability, providing a holistic assessment of arch dam performance throughout its service life. Applied to a practical pumped storage arch dam project, the results demonstrate that: (1) Fault damage evolution is characterized by prominent spatial heterogeneity. The results reveal that the fault damage coefficient at a burial depth of 0 m after 40,000 days of service is nearly twice that of the fault at a burial depth of 270 m. (2) The abutment safety factor decreases from 2.36 to 1.17 after 40,000 days of cyclic operation, entering a critical warning state at approximately 28,000 days. This study provides refined characterization methods and quantitative assessment tools for the long-term safety evaluation of fault-controlled arch dams, with direct implications for engineering risk prevention and reinforcement design. Full article

Most studies on circular mineral-based materials report short-term mechanical properties without providing predictive frameworks that link chemical degradation to long-term mechanical performance. This study develops and validates a leaching-index-driven chemo-mechanical framework for predicting the degradation of a natural hydraulic lime (NHL)–pozzolan mortar exposed to sulfuric acid. A normalized ionic-release index was used to drive all parameters of a trilinear continuum damage mechanics (CDM) model, enabling the prediction of complete stress–strain responses from leachate chemistry alone. The framework was calibrated using an extensive experimental dataset comprising accelerated acidic exposure at pH 1.5, 2.0, and 3.0 for durations up to 6000 h. Iron release was identified as the most suitable degradation indicator based on its monotonic evolution and strong correlation with mechanical deterioration. Power-law relationships linking the normalized leaching index to elastic modulus, peak strength, transition strain, and post-peak energy were established and validated against independent exposure groups, yielding prediction errors generally below 20%. Validation was performed against three independent blind exposure groups withheld from calibration, yielding mean deviations of approximately 18% in the elastic modulus and 13% in the peak strength, so that the quantitative validation rests on this limited three-group set, whereas the extension to circular mineral binders is presented only on a prospective, non-validated basis. A kinetic sub-model was further introduced to relate exposure conditions to the leaching index, enabling a complete predictive chain from environmental exposure to mechanical response and service-life estimation. Sensitivity analysis showed that post-peak energy dissipation degrades approximately 1.3–1.5 times faster than stiffness and strength, indicating that ductility-related parameters govern long-term reliability. The methodological architecture is further discussed, on a prospective and non-validated basis, in relation to circular mineral binders relevant to Baltic industrial and municipal by-product streams, including municipal-waste bottom ash, slag, fly ash, and recycled glass. Although experimental validation is limited to the NHL–pozzolan system, the proposed framework provides a physically grounded and data-efficient pathway for durability assessment and future durability-oriented design of circular mineral binders in the Baltic region. Full article

Loess has a metastable microstructure and high water sensitivity. When exposed to water, it undergoes rapid structural damage and disintegration, posing significant risks to the stability and durability of geotechnical structures such as foundations and slopes. Unconfined compressive strength (UCS) tests, direct shear tests, uniaxial tensile strength tests, and slake durability tests were conducted to evaluate the treatment performance. Optical microscopy and SEM were used to characterize the changes in microstructure to explain the potential reinforcement mechanism. The results show that microbial-induced carbonate precipitation (MICP) treatment leads to substantial improvement. Compared with untreated loess, the UCS, cohesion, internal friction angle, and uniaxial tensile strength increased by 370%, 663%, 43.7%, and 480%, respectively. Empirical refinements to the Mohr-Coulomb criterion were established to relate the measured UCS and uniaxial tensile strength to their theoretical values predicted from cohesion and friction angle. Both correlation models achieved R² > 0.82, quantifying the additional structural strength contributed by bio-cementation. At the same time, the treatment significantly improved water stability, and the slaking index was reduced from 100% to less than 20%. Microstructural analysis shows that precipitated calcium carbonate crystals bond soil particles at contact points and fill inter-particle pores, constructing a bonding framework, which enhances the mechanical strength and water stability of the soil mass. These research results further illustrate the potential of MICP in enhancing the performance of loess in engineering projects. Full article

Conventional masonry infill walls can significantly alter the seismic response of framed buildings and often produce damage patterns incompatible with resilience-based seismic design. Dry-jointed sliding masonry wall systems have therefore emerged as deformation-tolerant alternatives that accommodate drift through controlled interface motion rather than damage accumulation. This study investigates the sequential in-plane (IP) and out-of-plane (OOP) behavior of such systems considering wall thickness, openings, and boundary detailing. Six full-scale specimens were tested, including thick- and thin-wall reference specimens, thick-wall specimens with window openings, and thin-wall specimens with door openings. IP performance was evaluated using global hysteretic and energy-based response parameters, whereas OOP behavior was assessed through load–displacement response, an equivalent acceleration index, and selected image-based displacement fields. The results show that IP drift was mainly accommodated through distributed sliding along horizontal interfaces and local block rotation, without diagonal compression strut formation or brittle cracking, even at drift ratios up to approximately 3.5%. Wall thickness improved IP strength, stiffness, shear resistance, and cumulative energy dissipation, while openings mainly affected deformation compatibility and load-transfer continuity. Under OOP loading, wall thickness and boundary continuity increased stiffness and capacity while enabling resistance mobilization at smaller displacement levels. As inertia-based comparison indicators, boundary-enhanced thick- and thin-wall specimens reached equivalent acceleration capacities of 3.41 g and 1.64 g, respectively. Overall, the system reduced IP damage accumulation, but adequate OOP stability requires appropriate wall thickness, unit geometry, and boundary detailing. Full article