Search Results (812)

To address severe stress concentration, excessive convergence, and instability of the roadside backfill body (RBB) in gob-side entry retaining (GER) under thick and hard roof conditions, this study investigates the control mechanism of main roof fracture position on surrounding rock stability, using the 3⁻¹01 working face of Huoluowan Coal Mine as a case study. A combined approach integrating theoretical analysis, numerical simulation, and field investigation is adopted. A statically indeterminate mechanical model based on masonry beam theory is established to characterize the lateral roof fracture behavior. The deflection and bending moment distributions are derived, and a criterion for fracture position determination is developed based on the maximum bending moment condition. The theoretical results indicate that the natural fracture position is located approximately 9.4–11.2 m inside the gob boundary. Numerical simulations using UDEC Trigon under different fracture positions (−2 m, 1 m, 5 m, and 9 m) show that fracture location significantly affects the mechanical response of GER. Fractures occurring above the roadway or RBB induce large deformation levels and more extensive plastic zones, while gob-side fracture conditions correspond to relatively lower disturbance levels and improved structural stability. The RBB exhibits shear-dominated failure characteristics, and the displacement distribution is non-uniform along height, with larger deformation in the middle-to-upper region. To improve stability, a coordinated control strategy combining anchor cable reinforcement and directional long-distance hydraulic fracturing (HF) is proposed to regulate the main roof fracture position through the formation of artificial weak planes. Field monitoring results show that the maximum displacements of the roof, floor, and ribs are 558 mm, 233.5 mm, and 71.3 mm, respectively, with a convergence ratio of 19.8%. Borehole imaging confirms the development of hydraulic fractures within the designed roof stratum, supporting the effectiveness of the proposed control approach. These results demonstrate that the fracture position of the main roof plays a key role in controlling GER stability, and its regulation provides an effective means for improving roadway performance under complex geological conditions. Full article

As extreme weather events increasingly threaten global food systems, accurately assessing climate risks and predicting regional crop yields remains a critical challenge. Conventional prediction models often rely on direct weather-to-yield relationships, bypassing continuous crop physiological responses and limiting their capacity to capture fine-grained temporal impacts of meteorological anomalies. To address this, we propose a novel two-stage spatiotemporal functional framework that integrates high-resolution daily weather trajectories with satellite-derived indicators, utilizing the Enhanced Vegetation Index (EVI) and Land Surface Water Index (LSWI) to represent canopy structural vigor and hydraulic status, respectively. In the first stage, a Historical Functional Linear Model (HFLM) dynamically maps daily meteorological trajectories (temperature, precipitation, and solar radiation) onto continuous physiological curves under strict temporal causality constraints. This generates bivariate coefficient surfaces that reveal dynamic windows of vulnerability and capture divergent, lagged physiological responses to climate stress. In the second stage, a spatially heterogeneous functional additive model integrates these weather-shaped physiological trajectories alongside raw meteorological dynamics as joint predictors for county-level yields. By extracting functional principal components and modeling flexible non-linear biological responses while accounting for continuous spatial heterogeneity, this dual-channel frameworkcaptures key aspects of both chronic physiological stress and acute meteorological shocks. Validated across a 25-year (2000–2024) U.S. Corn Belt panel, the proposed DC-FAM achieves a mean weighted mean squared prediction error (WMSPE) of 242.33 (bu/acre)² and a median out-of-sample $R_{\mathrm{cv}}^2$ of 0.422, outperforming all benchmarks including a random forest. Attribution of the 2012 flash drought further demonstrates the framework’s capacity to mechanistically trace the complete disaster propagation chain from anomalous spring warming to mid-summer hydraulic failure. The proposed framework provides a transparent, biophysically grounded tool for decoding dynamic climate stress trajectories and disaster propagation chains, offering potential implications for adaptive farm management and precision agricultural insurance. Full article

Meeting the rigorous performance standards of modern electrified transit necessitates the deployment of high-performance outer rotor PMSMs with elevated power-to-volume ratios. However, their unique internal heat source topology inherently restricts heat dissipation. This limitation risks permanent magnet demagnetization and winding insulation failure. To address these thermal bottlenecks, this paper proposes internal bio-inspired cooling channels. These channels feature micro-scale V-shaped ribs. This design targets a 60 kW outer rotor PMSM. The motor uses a fractional-slot concentrated winding. The analytical procedure commences with the formulation of a transient 2D numerical model utilizing the Time-Stepping Finite Element approach (TS-FEM). It is coupled with the Bertotti model to compute electromagnetic losses. This approach accurately determines losses under high-frequency rated conditions. Results reveal that stator iron loss constitutes the dominant heat source. It accounts for 76.4 percent of the total electromagnetic loss. Furthermore, these losses show severe spatial concentration at the stator teeth. Subsequently, a three-dimensional fluid-solid coupled CFD model is developed. This model evaluates the proposed internal cooling channels. The design integrates bio-inspired vein networks and V-shaped ribs. These internal ribs disrupt the near-wall thermal boundary layer. This disruption enhances the local convective heat transfer. Comparative multiphysics analyses indicate improved hydraulic and thermal performance of the bio-inspired design under the same numerical boundary conditions. The bio-inspired channel achieves a more uniform static pressure distribution and reduces severe fluid stagnation zones. In the numerical model, the maximum stator and permanent magnet temperatures are reduced to 48 °C and 42 °C, respectively. This work provides a numerical design reference for thermal management in high-performance electric aviation. 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

To address the risks of cross-border transmission of pathogenic microorganisms posed by the failure or non-compliance of shipboard ballast water treatment systems, ports urgently require efficient and flexible emergency response solutions. This study presents a novel, containerized, integrated ship-to-shore emergency response system specifically designed for the rapid inactivation of pathogenic microorganisms in ballast water. The core innovation lies in the integration of a three-degree-of-freedom (3-DOF) hydraulic robotic arm, a vision and positioning system, and a dynamic inflatable sealing structure designed for rapid, automated docking with a ship’s ballast water discharge outlet (DN250), thereby enhancing operational safety and efficiency. The system employs a purely physical treatment process of “ultrasound (US) pre-treatment + dual-stage ultraviolet (UV) disinfection,” allowing for reception and treatment without secondary chemical pollution. The integrated treatment train, consisting of US (30 kHz, 7.6–12 kW, minimum acoustic energy density ≥ 0.45 J/cm²) followed by dual-stage UV disinfection (minimum UV dose: 147 mJ/cm²), maintained effective microbial inactivation at turbidity levels of 15, 125, 250, and 500 NTU. US alone showed little direct bactericidal effect, whereas the first UV stage achieved log reduction values (LRVs) of 3.31–4.13, and the complete US + UV + UV process achieved total LRVs of 5.07–7.34 for Escherichia coli. The results showed that dual-stage UV disinfection was key to achieving high inactivation efficacy (p < 0.001), while ultrasound, despite its limited direct bactericidal effect, may have facilitated downstream UV disinfection within the sequential treatment train. This system not only fills a critical gap in port biosecurity emergency infrastructure but also provides an experimentally validated, efficient, environmentally friendly, and flexibly deployable shore-based solution. Full article

To investigate the three-dimensional seepage response and safety implications of high concrete-face rockfill dams (CFRDs) under waterstop failure scenarios, this study establishes a refined three-dimensional finite element model for a high CFRD at the JD Hydropower Station using COMSOL (version 6.1) Multiphysics. A comparative analysis is conducted for six representative scenarios, including peripheral joint failure, single vertical joint failure, overall vertical joint failure, and combined failures. The seepage safety assessment is based on the phreatic surface, seepage discharge, hydraulic gradients in key zones, and left- and right-bank abutment bypass seepage. The results show that waterstop failure significantly changes the seepage field, phreatic surface, leakage discharge, and hydraulic gradients. Among the six scenarios, S5, representing overall vertical joint failure with an aperture of 0.5 mm for each of the 41 vertical joints, produces the most unfavorable leakage response, with the total seepage discharge reaching 3010.46 L/s and the water level behind the face slab reaching 3888.23 m. In contrast, peripheral joint failure mainly induces local hydraulic-gradient concentration in the special cushion zone. Under S1, the maximum hydraulic gradient in the special cushion zone reaches 2.72, exceeding the allowable value of 0.72. The results also reveal asymmetric bypass seepage around the dam abutments, with the right-bank foundation leakage being 90.4–137.7% higher than that on the left bank. These findings clarify the distinct seepage risk mechanisms of different waterstop failures and provide support for waterstop design, construction quality control, targeted monitoring, and operation-stage safety assessment of high CFRDs. Full article

Hydraulic fracture height growth in thin sandstone–mudstone interbeds is often limited by bedding interface failure and multi-cluster stress interference. In this study, a coupled fracture–matrix interface finite element model was developed for the He-8 sandstone–mudstone interbeds in the Sulige Gas Field and validated against previously published true triaxial hydraulic fracturing experiments. The simulations indicate that vertical–horizontal stress difference (VSD; the difference between overburden stress and minimum horizontal stress within a layer) promotes fracture-height growth, whereas interlayer stress difference (ISD; the minimum horizontal stress contrast between adjacent layers) acts as a stress barrier that promotes bedding interface shear failure and arrests vertical growth. For the investigated reservoir configuration, each 4 MPa increase in VSD increased fracture height by approximately 1.5 m in the three-cluster case and 1.8 m in the four-cluster case, whereas each 2 MPa increase in ISD reduced the average fracture height by approximately 4.0 m in the three-cluster case and 3.5 m in the four-cluster case. Under moderate ISD, increasing the fluid viscosity was more effective than increasing the injection rate alone, although the benefit depended on cluster number and interface failure state. These results clarify how stress contrast, interface strength, and multi-cluster stress shadows jointly control cross-layer fracture propagation in thin interbedded reservoirs. Full article

With deep coal mining in China, high in situ stress frequently causes severe floor deformation, bolt-cable support failure, and excessive floor heave, which critically threaten mine safety. In this study, we use physical experiments, numerical simulation, and theoretical analysis to explore how hydraulic fractures with different azimuth angles affect stress transfer in roadways under floor dynamic pressure. Prefabricated fractures simulate weak planes induced by hydraulic fracturing. Uniaxial compression tests and PFC2D fluid–solid coupling simulations analyze mechanical properties, failure modes, acoustic emission behavior, and stress distribution. Results show that fracture azimuth significantly controls rock damage and failure modes. As the angle increases from 0° to 90°, failure changes from gradual degradation to sudden instability. Peak strength first decreases then increases, reaching the minimum at 22.5°, while roadway damage is minimal at 45°. Small-angle fractures lead to shear failure with clear precursors, and large-angle fractures cause sudden tensile failure. Hydraulic fractures form directional stress-relief zones and enable effective stress transfer and pressure relief. The results support parameter optimization of hydraulic fracturing and stability control for deep roadways under floor dynamic pressure. Full article

Deep gas emissions in volcanic and tectonic environments are commonly interpreted as the surface expression of localized deep emitters. This representation is adequate for first-order description, but it is not physically complete. Deep degassing is more appropriately represented as a coupled source–storage–pathway system in which volatile generation, compressible accumulation, phase change, hydraulic communication, and permeability evolution are dynamically linked. Starting from phase-wise mass conservation in deformable porous–fractured media, reduced equations for gas migration, pore-pressure diffusion, and thermo-poro-mechanical coupling are derived, showing how the distinction between gas-mass transport and pressure propagation provides a unified framework for volcanic and tectonic degassing. Deep pressure gradients are shown to arise from the competition between volatile supply and pathway leakance, while episodic discharge can occur when permeability evolves under effective stress, sealing, and failure. A minimal analytical source–storage–pathway model is further derived, yielding explicit criteria for valve onset, source charging and discharge times, and the distinction between pressure-led and mass-led responses. The framework is then applied to the published Campi Flegrei carbon dioxide (${\mathrm{CO}}_2$) diffuse total output record, providing a real-data illustration of slow storage loading and rapid transient discharge. The analysis considers magmatic exsolution, hydrothermal mediation, metamorphic devolatilization, advective–diffusive near-surface filtering, and the inverse problem through which surface fluxes and gas compositions are used to infer deep source properties. The formulation links magmatic degassing, hydrothermal pressurization, tectonic fluid ascent, and fault-valve behavior within a common continuum-physics perspective and identifies the constitutive assumptions that most strongly control interpretation. Full article

Automating system-level nuclear thermal-hydraulic (T-H) model construction remains challenging because platform-specific API syntax, graph connectivity, parameter dependency ordering, and solver admissibility must be satisfied simultaneously. This study develops a closed-loop modeling framework on the SAFRI platform by combining supervised fine-tuning (SFT), a Plan-and-Act agent with retrieval-grounded parameter completion, and reinforcement learning based on group relative policy optimization (GRPO). The SFT stage uses a 6003-record domain corpus derived from expert-authored or expert-verified SAFRI modeling exemplars, while system-level generalization is evaluated on a held-out 50-case in-house evaluation set separated at the case-template level. At the component level, LoRA-adapted Qwen3-8B achieves 100% code accuracy, compared with 50% for zero-shot and 74% for one-shot prompting. At the system level, the SFT agent attains a 100% syntax success rate (SSR), 90% topology success rate (TSR), and 72.4% physical convergence rate (PCR), showing that local API correctness is insufficient for solver-valid model assembly. After GRPO training with schema, topology, physics, and sequence rewards, the full SAFRI-SFT-RL agent reaches a 100% SSR, 100% TSR, and 88.8% PCR on the in-house evaluation set, while an error self-healing loop resolves execution-time failures in an average of 2.3 corrective iterations. These results show that solver-grounded reinforcement learning is effective for closing the gap between syntactically correct script generation and physically convergent nuclear T-H model construction. Full article

The localized high hydraulic gradient at the bottom of concrete cutoff walls in deep overburden foundations poses a significant seepage failure risk. This stability is heavily influenced by the high-stress state, a critical factor often overlooked in conventional evaluations. Taking a specific engineering project as the research background, this study investigates the seepage stability of gravelly medium-coarse sand by simulating the coefficient of earth pressure at rest (K₀) condition. A comprehensive series of triaxial seepage tests was conducted across burial depths from 120 m to 260 m, supplemented by conventional zero-stress permeability tests as a baseline. The results indicate that the seepage failure mode is characterized by overall soil flow. For soil deeply buried at the wall bottom, the risk of seepage failure is relatively low, provided there are no significant geological defects or internal seepage outlets nearby. Compared to conventional tests, the K₀ stress condition significantly increases the failure gradient and reduces the permeability coefficient. Under the same gradation, variations in burial depth have a negligible influence on these parameters. However, at the same burial depth, particle gradation has a major effect; the mean envelope line is the most sensitive to stress, followed by the upper and lower envelope lines. Based on these findings, an allowable hydraulic gradient of 3.0 is proposed—approximately five times the traditional design value (0.6–0.65). This study provides a critical scientific basis for the seepage-control design and stability assessment of high dams on deep overburden foundations. Full article

To address the large deformation and instability of gob-side entry roofs in soft, thick coal seams induced by residual cavities left by hydraulic flushing, the 1609 working face of Jiulishan Coal Mine was selected as the engineering background. Field investigation, numerical simulation, and industrial field testing were combined to investigate the deformation and failure characteristics of surrounding rock and the corresponding control technology for gob-side entries with cavity-bearing roofs. The results indicate that residual cavities created by hydraulic flushing disrupt the stress transfer path within the roof, causing stress field distortion and expansion of tensile stress zones, thereby significantly weakening the roof load-bearing capacity. As the cavity size increases, the surrounding rock deformation and plastic zone continuously expand. When the cavity size exceeds 1.0 m, roof subsidence exhibits a nonlinear increase, and the fractured zone around the cavity connects with the roof plastic zone, forming a continuous failure band that serves as the key factor leading to surrounding rock instability. Based on the deformation characteristics of the cavity-bearing roof, namely shallow fragmentation, deep-seated separation, and structural instability, a collaborative control technology consisting of multi-level cable bolts, steel-beam reinforcement, and grouting through injection pipes was proposed. By establishing a shallow–intermediate–deep hierarchical load-bearing structure and reinforcing the fractured cavity zone through grouting, the technology reconstructs the surrounding rock load-bearing system and optimizes the stress environment. Field application results show that, for a roof containing a 1.5 m cavity, the maximum roof subsidence and separation were controlled within 102 mm and 55 mm, respectively, and the roadway maintained a stable condition throughout the monitoring period. The findings provide both a theoretical basis and engineering guidance for surrounding rock control of gob-side entries with cavity-bearing roofs in soft, thick coal seams. Full article

High-speed permanent magnet synchronous motors (PMSMs) used in electric pump-fed liquid rocket engines require stator shielding sleeves to prevent corrosive propellants from causing harm under cyclic pressure. However, metallic sleeves suffer significant losses due to eddy currents. Conversely, pure carbon fiber reinforced polymer (CFRP) sleeves have failed when exposed to 98% H₂O₂. Micro-CT analysis of a failed pump sleeve reveals a four-stage failure mechanism. Manufacturing defects caused matrix cracking, which propagated under pressure and thermal cycling. This progression resulted in the formation of through-thickness leakage paths, which ultimately triggered catalytic decomposition and explosion. To address these issues, an improved dual-layer sleeve is proposed, featuring a 2.5 mm PEEK 450G liner and a 2.0 mm T700S/epoxy CFRP overwrap. Finite Element Analysis (FEA) indicates peak von-Mises stresses of 86.25 MPa and 112.16 MPa, yielding Tsai–Wu safety factors of 2.9 and 1.7. Furthermore, various tests, including immersion, fatigue, burst, hydraulic, and thermal evaluations, demonstrate a burst margin of 2.37× at 7.12 MPa, with only 0.19% increase in mass. This design effectively eliminates leakage pathways while preserving zero eddy-current loss and ensuring a low weight. Full article

Artificial muscles are an emerging class of actuators designed to mimic the compliant, efficient, and versatile behavior of biological muscles for fields including the following: soft robotics, prosthetics, wearable enhancements, haptic interfaces, and biomedical devices. These systems encompass various actuation mechanisms, including pneumatic, hydraulic, thermal, ionic, electrochemical, and electrostatic. Each with distinct tradeoffs in voltage, strain, output force, bandwidth, efficiency, and manufacturability. Among them, electrostatic actuators have attracted increased attention due to their fast response times, high energy densities, strong compatibility with soft materials, and scalability from microscale devices to large-area and stacked actuators. However, challenges such as dielectric breakdown, material fatigue, and fabrication complexity continue to limit widespread deployment. This review presents a structured classification of various artificial muscle technologies and an in-depth examination of electrostatic actuators including dielectric elastomers, electrostrictive and ferroelectric polymers, liquid crystal elastomers, electrostatic film motors, stacked architectures, and microscale/milliscale devices. In this review the operating principles, materials, architectures, performance characteristics, and failure modes of electrostatic actuators will be discussed. Additionally, a comparison will highlight tradeoffs across actuator families based on metrics such as voltage, force, strain, bandwidth, and manufacturability. Lastly, we outline future research directions in materials, physics-informed modeling, system integration, and scalable fabrication necessary to advance electrostatic artificial muscles toward practical, real-world deployment. Full article

Concentrated rear runoff is an important hydraulic factor that promotes slope instability and flow-like transport characteristics in mountainous landslides; however, the deformation–failure process of slopes and their response relationships under different runoff intensities remain unclear. In this study, the Shaziba landslide in Enshi, Hubei Province, China, was selected as the research object. Two-dimensional flume model tests were conducted under four runoff discharge conditions of 7, 15, 27, and 35 mL/s to investigate the effects of runoff intensity on the hydraulic response and failure mode of the slope. The results show that, as the runoff discharge increased from 7 to 35 mL/s, the initial response times of water content, pore water pressure, and earth pressure at the rear edge decreased from 1205, 1488, and 888 s to 160, 248, and 112 s, respectively. Meanwhile, the gully formation time shortened from 6810 to 336 s, and the time of the first evident collapse decreased from 5758 to 650 s. Under low-runoff conditions, slope deformation was dominated by infiltration-induced softening and progressive creep. Under moderate to high runoff conditions, gully incision and gully-wall collapse accelerated slope disintegration, resulting in soil–water mixed transport and enhanced mobility of failed materials. Concentrated rear runoff drives the slope through successive stages of initial deformation, structural disintegration of the slope, flow-like failure, and toe deposition. These findings provide experimental evidence for the identification and prevention of landslides controlled by rear runoff. Full article