Search Results (468)

Fractures are widely developed in deep coal-mine surrounding rocks. They weaken the load-bearing capacity and energy-storage capacity of rock specimens, which may induce surrounding-rock deformation, roof collapse, and other hazards. Current studies on fractured rock masses mainly focus on a single parameter, such as fracture number or fracture dip angle. However, their coupled effects remain unclear. Integrated analyses of mechanical behavior, crack propagation, and energy evolution are also limited. In this study, uniaxial compression simulations of intact sandstone, single-fracture sandstone, and double-fracture sandstone were conducted using PFC^2D. The effects of fracture number and fracture dip angle on mechanical properties and failure characteristics were investigated. The results show that fractures reduced the peak stress and modulus of elasticity. A stronger weakening effect was observed with increasing fracture number. With increasing fracture dip angle, both peak stress and modulus of elasticity showed a V-shaped trend. The minimum peak stress occurred at 15°, while the minimum modulus of elasticity occurred at 45°. Sandstone failure was mainly dominated by tensile cracks. At 15°, the total crack number was the lowest, with 932 and 818 cracks for single-fracture and double-fracture specimens, respectively. Energy analysis showed that increasing fracture number reduced elastic strain energy and promoted dissipated energy. The weakest energy-storage capacity was observed at 30°. Overall, fracture number and fracture dip angle jointly controlled strength degradation, crack propagation, and energy evolution. This study provides a reference for fracture–damage assessment and disaster prevention in deep coal-bearing sandstone. Full article

Thermal overload in internal combustion engines may progressively destabilize lubricant-film integrity and promote severe tribological deterioration within highly stressed contact interfaces. This study investigates the thermo-tribological degradation sequence of a high-mileage gasoline engine subjected to prolonged idle operation under impaired cooling conditions, ultimately resulting in engine seizure. The investigated engine had accumulated 356,724 km, while the lubricant had remained in service for approximately 26,724 km prior to the experiment. The post-failure investigation combined teardown inspection, geometrical camshaft assessment, reverse gravimetric reconstruction, hydraulic tappet surface profiling, XRF surface characterization, laboratory oil analysis, and SEM/EDS evaluation of wear debris. The results demonstrated strongly localized degradation concentrated primarily within the cam–tappet interfaces. Severe non-uniform camshaft wear was accompanied by pronounced hydraulic tappet surface damage and evidence of unstable boundary-lubrication conditions. Laboratory oil analysis revealed elevated wear-metal concentrations, depletion of the alkaline reserve, increased oxidation indicators, and a final Class D oil condition assessment. SEM/EDS characterization identified Fe-bearing wear debris associated with sustained material removal and debris recirculation during the final degradation stage. The combined evidence supports a coupled thermo-tribological degradation mechanism involving lubricant deterioration, boundary-lubrication instability, adhesive wear acceleration, oxidative surface degradation, and debris-assisted surface damage preceding final engine seizure. The present case study provides experimentally documented evidence of lubrication collapse under real-engine thermal runaway conditions and highlights the critical role of lubricant condition in maintaining tribological stability under severe thermal loading. Full article

This paper presents a computational model of delirium in the Intensive Care Unit (ICU), in which delirium is defined as the endpoint of a self-reinforcing cycle of predictive failure between two bidirectionally coupled agents: the patient and the ICU room environment. Drawing on the active inference framework and the free energy principle, the paper proposes that delirium is not a property of the patient in isolation but a relational phenomenon that emerges when the environment persistently fails to predict the patient’s internal state. This failure triggers a causal feedback mechanism in which desynchronization pressure progressively sharpens the patient’s prior beliefs—implementing precision rigidity in the correct active inference sense: not a brain overwhelmed by noise but a brain locked into a state that incoming observations can no longer update. The model is implemented as a two-agent POMDP in which both agents maintain generative models and continuously attempt to predict each other’s states. The room agent (R)—understood as the environment-side sensing–inference–actuation loop, whether instantiated by clinical staff or by an automated monitoring system—infers the patient (P)’s latent parameters $({\theta }_{\mathrm{cog}},{\theta }_{\mathrm{emo}})$ over time and builds a progressively personalized generative model of the patient. Synchronization is operationalized via two commensurable directional surprisal metrics: $S_{R\to P}=-ln{Q}_R\left(s^{*}\right)$, the room’s surprisal at the patient’s true state, and $S_{P\to R}=-lnP(o_R\mid Q_P)$, the patient’s surprisal at the room’s observations. A systematic ablation study across four model variants shows that room inference is the architectural component necessary to reproduce the synchronization–delirium relationship: when the room infers, the association between synchronization and declared delirium is strong and stable, whereas a non-inferring room collapses to ceiling delirium rates and a weak association. $\theta$ learning and the prior-sharpening feedback do not increase the strength of this association; instead they shape the phenotypic gradient, reducing ceiling effects in vulnerable phenotypes and amplifying the separation between them. The model is presented as a computational hypothesis generator rather than a calibrated clinical predictor, and its implications for ICU design are discussed. Full article

Lateral femoral neck and peritrochanteric fractures are common and clinically challenging injuries, particularly in the elderly population, with significant implications for morbidity, mortality, and functional recovery. Traditional classification systems are widely used to guide treatment, yet their reproducibility and clinical applicability remain debated. Increasing attention has been directed toward trabecular architecture and its role in fracture behavior and reduction strategies. This review aims to summarize current evidence on classification systems, trabecular-based fracture patterns, pre-operative reduction techniques, and fixation strategies. A narrative review was conducted using PubMed/MEDLINE, Embase, and Scopus databases up to May 2026. Original studies, reviews, and biomechanical investigations focusing on proximal femur fracture classification, reliability, trabecular alignment, reduction techniques, and fixation methods were included. Data were qualitatively analyzed, with emphasis on interobserver reliability, biomechanical implications, and clinical outcomes. Conventional classification systems, including anatomical, Evans–Jensen, and AO/OTA frameworks, demonstrated variable and generally moderate reproducibility, with reported interobserver agreement ranging from approximately κ = 0.30 to 0.60. Emerging evidence highlights the importance of trabecular architecture, distinguishing intradigital fractures—confined within trabecular pathways and relatively stable—from extradigital fractures, which disrupt load-bearing structures and are associated with increased mechanical instability and higher failure rates. Biomechanical and clinical studies indicate that inadequate reduction with trabecular misalignment significantly increases the risk of varus collapse and implant cut-out. Reduction strategies tailored to fracture pattern, such as internal rotation for intradigital fractures and external or combined maneuvers for extradigital patterns, improve alignment and load transfer. In terms of fixation, dynamic hip screws remain effective in stable fractures, whereas cephalomedullary nails demonstrate superior performance in unstable patterns, with lower reoperation rates reported (approximately 5–8% vs. 10–15%). Management of lateral femoral neck and peritrochanteric fractures should extend beyond traditional classification systems to incorporate trabecular biomechanics. Restoration of trabecular alignment, alongside established parameters such as neck–shaft angle and tip–apex distance, is critical for optimizing outcomes. Further prospective studies are needed to validate trabecular-based classifications and standardize reduction strategies. Full article

In order to improve the poor wear resistance and adhesive wear of 7075 aluminum alloy under dry friction conditions, a nanosecond pulse laser was used to prepare surface micro-textures with different shapes, surface densities, and feature sizes. Subsequently, their friction and wear behavior, as well as the corresponding failure mechanisms, were systematically investigated. Circular, square, and hexagonal micro-pit textures were selected as the research objects. Combined with surface morphology characterization, ball-on-disk dry wear tests, reciprocating friction tests, and contact stress and wear model analyses, the effects of texture parameters on tribological performance were systematically revealed. The results indicate that laser microtexturing can reduce the coefficient of friction on the surface of 7075 aluminum alloy to a certain extent and improve its wear resistance, with the friction-reducing effect closely related to the texture shape, areal density, and feature size. Among these, hexagonal texturing exhibited the best friction-reducing effect, while circular texturing demonstrated superior formation quality and friction stability. Compared to other specimens, the T8 group with a 7.5% areal density and a feature size of 100 µm exhibited the lowest average coefficient of friction. During the friction process, the microstructures gradually fail due to plastic flow filling, wear debris accumulation, and edge collapse. The research findings provide a reference for the optimized design and engineering applications of surface microstructures on aluminum alloys. Full article

The M_w7.7 Pazarcık–Kahramanmaraş and M_w7.5 Elbistan–Kahramanmaraş earthquakes on 6 February 2023 caused the collapse of 11 buildings in Adana’s city centre—predominantly 15-storey RC structures in a narrow zone—despite peak ground accelerations of only 0.05 g; most collapses occurred during the M_w7.7 event. Two-dimensional seismic site response analyses at the site of interest with bedrock input from station TK0118 yielded topographic amplification factors of 2.37 (EW) and 2.09 (NS) for homogeneous conditions; with stratigraphic heterogeneity, NS increased to 2.66 and EW remained at 2.27, reaching above 3.0 at the slope crest. Spectral amplification factors reached 4.53 (NS, T = 0.90 s) and 3.21 (EW, T = 0.68 s), indicating amplification in the short-to-intermediate period range. These amplified records were applied to idealised 15-storey RC models—from code-compliant to deliberately deficient—with C16 and C8 concrete classes through nonlinear performance analyses. Under unamplified TK0118 records, no model reached collapse-level damage. Under amplified records, only the most deficient model exhibited widespread shear and strain failures in the lower storeys. A detected velocity pulse (T_p = 13.496 s) was excluded as a collapse mechanism, as its period far exceeds structural periods (1.2–1.9 s). The collapses are attributable to the compounding of topographic and stratigraphic amplification with pre-existing structural deficiencies. Full article

Rockfall from slope unstable rock masses is a typical geological hazard induced by brittle failure, with abrupt occurrence, limited macroscopic deformation before failure, and a short warning lead time. Conventional static analysis methods are useful for design-stage stability checks, but they cannot continuously capture structural-plane damage or update the stability state in real time. Dynamic evaluation based on structural dynamics links measurable parameters such as natural frequency, damping ratio, mode shape, vibration trajectory, wave velocity, and energy dissipation to the degradation of structural planes. This review synthesizes the dynamic behavior mechanism, parameter system, theoretical models, sensing technologies, and engineering applications for slope unstable rock masses. Different from previous reviews that mainly summarize rockfall monitoring or conventional slope stability analysis, this paper organizes the literature by failure mode, monitoring scale, model assumptions, field validation, uncertainty sources, and engineering applicability. The single-degree-of-freedom models for sliding-, toppling-, and falling-type rock masses, multi-block chain-collapse models, and data-physics dual-driven surrogate models are compared critically. Contact monitoring based on MEMS sensors, non-contact LDV monitoring, acoustic emission, microseismic monitoring, coda wave interferometry, and cloud-edge early-warning architectures are further reviewed. Key challenges include field-scale validation under heterogeneous and anisotropic geological conditions, environmental compensation, robust threshold calibration, and probabilistic linkage between dynamic indicators and failure probability. The review provides guidance for selecting dynamic evaluation models, designing field monitoring systems, and developing full-life-cycle digital-twin platforms for rockfall risk mitigation. Full article

Whether Kaldor’s three growth laws still operate in commodity-dependent middle-income economies—and through what transmission mechanism—is an open empirical question after three decades of trade liberalisation, financial opening, and the 2002–2014 commodity super-cycle. This paper provides the first bloc-level panel test of the three laws for the Andean Community of Nations (ACN—Bolivia, Colombia, Ecuador, and Peru) over 1993–2019, combining static feasible generalised regressions with dynamic Arellano–Bond difference-GMM and long-run multipliers. The predictions are as follows: manufacturing growth is positively associated with aggregate output (long-run multiplier 0.91), the Verdoorn coefficient is positive and significant at 0.42, and labour reallocation from non-manufacturing activities is associated with rising aggregate productivity over the time. The headline finding, however, is a decomposition failure: the Verdoorn and employment elasticities coefficients sum up to 0.35 rather than 1 as required by the accounting identity, leaving a residual of 0.65. We term this “jobless manufacturing growth” (capital-deepening). This suggests that the Kaldorian regime in the ACN has neither collapsed nor remained intact, but has mutated into a capital-intensive, labour-saving form consistent with Dutch-disease. Thus, industrial policy alone would deepen the jobless pattern: structural transformation in these economies requires pairing subsidy plans with the macroeconomic management of commodity-dependent exchange rates. Full article

Achieving adequate load capacity and ensuring ductile behavior are crucial for reinforced-concrete knee joints to prevent a complete structural collapse if an adjacent member fails. The reinforcement detailing plays a critical role in achieving these factors. In this study, the performance of a knee joint under closing moments was analyzed using innovative truss-shaped reinforcement and simplified mechanical joints, in comparison to traditional reinforcement detailing, through four large-scale specimens. The findings showed that incorporating a truss-shaped reinforcement system with the suggested detailing effectively redistributed stresses in the knee-joint area and decreased stress concentration at the bent-bar zone, thus helping to prevent premature joint failure when compared to conventional specimens. Overall, the proposed system shifted the failure mode towards a highly ductile response. Furthermore, the suggested specimen experienced significant increases in both the yield load and the ultimate load, with the yield-load boost ranging from around 29.5% to 70.5%, and the ultimate-load increase ranging from 20% to 81%. Additionally, the proposed reinforcement system exhibited notably higher displacement capacity, with increases ranging from 88% to 347%. The proposed specimen also showed a considerable enhancement in displacement ductility, with an increase of roughly 160% to 382% relative to traditional specimens. The results matched well with the created analytical models confirming the effectiveness of the proposed load-transfer system. Full article

Cascading failures in complex networks occur when local node or edge failures propagate to trigger large-scale collapse. Traditional pairwise network models cannot adequately capture group coordination and multi-agent higher-order interactions. Higher-order networks incorporating simplicial structures more accurately represent group and multi-node interactions, providing a new framework to study cascading failures and network robustness. The paper proposes a higher-order coupled map lattice (CML) model to characterize cascading failures in simplicial complex networks and analyze the influence of higher-order structures on network robustness. Further experiments on fourth-order simplicial networks investigate robustness differences under various topologies and attack strategies. Results indicate that fourth-order simplicial networks are vulnerable to targeted attacks but robust against random failures, regardless of network type. Furthermore in single-order networks, the higher simplex dimensions, the greater robustness. The theoretical perturbation thresholds for third-order networks show a negative correlation between the critical perturbation and the sum of network coupling parameters. These results are validated by analysis of simplices added to ordinary networks, destructive experiments, and empirical networks. This study deepens the understanding of cascading failure mechanisms and robustness in higher-order networks, and provides theoretical guidance for designing resilient networks based on higher-order structures. Full article

Progressive collapse represents a catastrophic failure mode for reinforced concrete (RC) structures, yet the use of architected materials to mitigate this risk remains largely unexplored. This study presents a numerical feasibility investigation of RC beam–column sub-assemblages with auxetic metamaterial inserts embedded in critical joint regions. A hierarchical multiscale framework is developed to link the effective behavior of auxetic metamaterials with structure-scale collapse response. The framework couples macroscale structural analysis with mesoscale fracture simulations through a hybrid voxel–Voronoi discretization strategy. Baseline finite element models are validated against published experimental results for conventional RC specimens, while the auxetic-enhanced configurations are evaluated numerically. Under high tensile strain, the auxetic insert expands laterally because of its negative Poisson’s ratio and generates a localized confining stress field within the surrounding concrete. The simulations suggest that this mechanism may promote crack bifurcation, redistribute localized cracking into a more distributed damage pattern, and delay compressive crushing and crack coalescence. Compared with the corresponding conventional RC configurations, the auxetic-enhanced models predict a 25% increase in load redistribution capacity and a 20% enhancement in deformation ductility. These predicted improvements require future experimental validation using physical auxetic-enhanced RC specimens. The findings provide a computational basis for exploring material-by-design strategies aimed at improving the robustness of critical RC joint regions under progressive collapse demands. Full article

Rainfall-induced instability of gravelly silt slopes is strongly affected by infiltration, runoff erosion, pore water pressure evolution, and particle-scale degradation. In this study, laboratory rainfall model tests were conducted on gravelly silt slopes under three extreme rainfall intensities of 80, 120, and 160 mm/h, and an FVM-DEM coupled model was developed to investigate the associated hydromechanical response and failure mechanism. The tested soil was obtained from the Shanghai East Railway Station project, and the 30% gravel content was selected to represent the typical field condition. Pore water pressure gauges and laser displacement sensors were used to monitor the infiltration response and slope deformation. The results show that all three slopes developed shallow instability, but the deformation rate and failure mode changed with rainfall intensity. Under the tested infiltration-excess conditions, the additional rainfall mainly increased surface runoff, toe erosion, and failed mass mobility rather than proportionally increasing the infiltration depth. The numerical results further indicate that failure evolved through equivalent fine matrix mobilization, gravel destabilization, skeleton collapse, and matrix-entrained gravel movement. These findings clarify the progressive instability mechanism of gravelly silt model slopes under extreme rainfall and provide experimental evidence for slope protection under short-duration, high-intensity rainfall. Full article

This paper examines the effectiveness of deposit insurance in reducing bank run risk using an agent-based model with heterogeneous depositor behavior, including random withdrawals, risk-based responses, and peer-driven contagion. The results reveal a nonlinear stability pattern with a narrow transition region separating solvency from collapse. Within this region, deposit insurance mainly improves stability by shifting the critical threshold and extending time-to-failure. Across all scenarios, behavioral and structural factors, including wealth inequality, risk aversion, depositor awareness, and contagion, systematically affect the location and sharpness of this transition without removing it. Fragility rises sharply beyond moderate inequality (Gini ≈ 0.5), while depositor awareness and peer effects act as coordination mechanisms that accelerate collapse. Overall, deposit insurance is a powerful but limited stabilization tool: it strengthens resilience but does not alter the underlying dynamics of systemic risk. These findings suggest that effective policy must also address the behavioral and informational drivers of bank runs. Full article

Sepsis is a systemic disorder in which infection-induced inflammation progressively disrupts vascular homeostasis and drives organ dysfunction. This review reframes septic pathophysiology as a sequential and self-amplifying process centered on endothelial failure. Early activation of innate immune pathways by pathogen- and damage-associated molecular patterns promotes cytokine release, oxidative stress, and enzymatic degradation of the endothelial glycocalyx. Loss of this protective surface layer exposes endothelial cells to unbuffered inflammatory and mechanical injury, impairing mechanotransduction, increasing leukocyte and platelet adhesion, and destabilizing vascular barrier function. Subsequent disruption of intercellular junctions promotes capillary leakage, tissue edema, and impaired oxygen diffusion, while mitochondrial dysfunction and redox imbalance reduce endothelial repair capacity. In parallel, complement activation, neutrophil extracellular trap formation, platelet–leukocyte interactions, and loss of anticoagulant signaling shift the microvasculature toward a prothrombotic and proinflammatory state. These interconnected mechanisms culminate in microvascular incoherence, characterized by heterogeneous capillary flow, regional hypoxia, impaired oxygen extraction, and progressive organ failure despite apparent restoration of systemic hemodynamics. Within this framework, biomarkers such as syndecan-1, soluble thrombomodulin, angiopoietin-2, von Willebrand factor, and plasminogen activator inhibitor-1 are best interpreted as mechanistic readouts of glycocalyx shedding, endothelial injury, permeability imbalance, and thromboinflammatory activation. Understanding sepsis as an evolving endothelial pathophysiological process provides a coherent framework for integrating inflammation, vascular leakage, hypoxia, coagulation, and organ dysfunction while identifying mechanistic biomarkers that reflect distinct stages of microvascular collapse. Full article

The wide application of liquid hydrogen as a key energy carrier is severely limited by the reliability of high-pressure and low-temperature pumps. The traditional research on liquid hydrogen pumps relies on empirical analysis of isolated components, but fails to reveal the fundamental failure mechanism of these pumps. This review argues for a paradigm shift in the understanding and design of liquid hydrogen pumps. We systematically decomposed the failure of the liquid hydrogen pump into a thermodynamic-driven, cross-scale cascading process rather than the failure of isolated components. At the molecular level, the extreme thermal physical properties of liquid hydrogen (ultra-low latent heat and surface tension) can lead to widespread nucleation under slight thermal disturbances. At the mesoscopic scale, the initial perturbation is significantly amplified through the nonlinear dynamics of bubble clusters. This amplification is characterized by intense collapse and strong energy concentration due to the low density and low viscosity of liquid hydrogen. At the component level, this enhanced destructive energy will cause faults similar to phase transitions; namely, the liquid lubrication in the bearings will disappear, the seals will shift from viscous blockage to gas diffusion, and at the same time, the damage caused by low-temperature hydrogen cavitation and corrosion to the materials will also occur simultaneously. At the system level, the strong dynamic coupling among the subsystems has led to a nonlinear performance collapse. This cross-scale failure chain reveals the flaws in the classical cavitation theory, which is based on the assumptions of isothermal and inertia dominance. We have expounded the thermodynamic-dominated cavitation state in liquid hydrogen. This state is quantified by the Σ parameter and governs the multimodal behavior of low-temperature cavitation phenomena. To address this complexity, we have proposed a comprehensive framework that integrates multi-scale collaborative simulation and digital twin, combining molecular dynamics, CFD, system dynamics, and targeted experiments. This review proposes a candidate physical framework for addressing the reliability challenges of liquid hydrogen pumps. It also provides a clear roadmap for the next generation of inherently robust cryogenic fluid machinery, and offers a reference for the design of energy systems under other extreme conditions. Full article