Search Results (2,935)

Carbon fiber-reinforced aluminum laminate (CARALL) has excellent properties such as strong impact resistance and fracture toughness. Lamb waves are expected to provide an efficient means for non-destructive testing of CARALL. However, the complex propagation characteristics of Lamb waves in CARALL with both anisotropic and isotropic materials between layers make it difficult to accurately identify and locate the damage. We proposed an integrated probabilistic imaging method to detect the damage localization considering Lamb waves propagation characteristics. First, the relationship between the propagation velocity and direction of Lamb waves was analyzed. It was found that, unlike CFRP laminates, where Lamb waves propagate fastest along the transverse direction, Lamb waves in CARALL exhibit the highest velocity along the 45° direction. Subsequently, a damage localization algorithm considering anisotropy and integrated probability imaging was proposed. Experimental and numerical results demonstrate that the damage localization algorithm proposed in this work accurately predicted the location of damage in CARALL, and the area of damage could be characterized by the direct wave correlation coefficient of Lamb waves. This study provides a useful framework for non-destructive testing of CARALL. Full article

To elucidate the structural evolution of fracture networks around gas drainage boreholes and their controlling mechanisms on grouting sealing performance, a coal seam in the Zhongmacun Mine (No. 2-1 coal seam) was selected as the engineering background. An integrated approach combining borehole camera observation, gray-level co-occurrence matrix (GLCM) texture analysis, and fractal theory was adopted to systematically characterize the development behavior, spatial heterogeneity, and fractal evolution of fracture networks under different stress zones surrounding the borehole. Furthermore, the quantitative relationship between fracture structure characteristics and grouting parameters was explored. Results indicate that three axial stress-related zones are formed, including a stress-relief zone (0–4 m), a post-peak stress concentration zone (4–20 m), and a pre-peak stress concentration zone (>20 m), with fracture development strongly dependent on stress state. Quantitative analysis based on GLCM parameters and their coefficients of variation reveals a progressive transition from highly complex and strongly heterogeneous fracture structures in the stress-relief zone to simpler and weakly heterogeneous characteristics in the pre-peak stress concentration zone. The fractal dimension (D) decreases from 1.847–1.907 to 1.676–1.713 across these zones, consistent with the evolution trends of GLCM metrics. Based on the relationship between fractal dimension and fracture connectivity, a prediction model for the equivalent permeability of fracture networks based on fractal dimension was established, and the quantitative relationship between grouting pressure and fractal dimension, slurry viscosity, and diffusion radius was derived, providing a theoretical method for analyzing the correlation between fracture structure characteristics and grouting parameters. On this basis, a zonal differentiated grouting sealing optimization scheme was proposed, and a theoretical calculation method for grouting pressure and sealing section length based on fractal parameters was established, providing theoretical references and technical support for precise sealing of gas drainage boreholes. Full article

Natural-fracture connectivity substantially influences hydraulic-fracture interaction with pre-existing discontinuities, but its quantitative role in fracture-network propagation remains insufficiently constrained. In this study, a coupled LEFM–cohesive-zone hydraulic-fracture propagation model was developed by combining crack-tip deflection criteria, traction-separation damage evolution and fluid–solid coupling. True triaxial hydraulic-fracturing experiments were conducted on artificial fracture networks with I-, V-, Y- and X-shaped connectivity elements to evaluate the model response. The results show that connected natural fractures redirect hydraulic fractures under low horizontal stress differences, producing deflection angles of 30–50 degrees. When the stress difference exceeds 4 MPa, fracture growth becomes more strongly aligned with the maximum principal stress direction. In the true triaxial tests, the total number of connected natural fractures increased from 14 in the I-shaped network to 17 and 21 in the Y- and X-shaped networks, corresponding to increases of 21.4% and 50.0%, respectively. X-shaped networks showed the strongest sensitivity to stress difference and injection rate, while higher elastic modulus reduced fracture width and promoted longer, narrower fractures. Scale-normalized comparisons based on image-derived experimental measurements showed that the predicted propagation length, fracture width and connected-fracture number followed the experimental trend from I-shaped to Y-shaped and X-shaped networks, with relative errors within 7.1% and a mean absolute percentage error of 4.8%. These findings suggest that fracture topology strongly influences pressure transmission and multidirectional activation in the tested models, whereas field-scale extrapolation requires three-dimensional validation and transport analysis. Full article

Predicting compressive–shear fracture in rock masses containing complex flaw distributions remains a major challenge in rock engineering. We propose an improved non-ordinary state-based peridynamics (NOSB-PD) model to simulate rock fracture behavior in this work. A stabilized NOSB-PD formulation is developed by incorporating a bond-level deformation gradient strategy to effectively suppress the zero-energy mode inherent in conventional NOSB-PD formulations, thereby ensuring deformation compatibility and numerical robustness. More importantly, the triple-shear energy criterion is introduced into the PD framework for the first time, enabling a more accurate characterization of shear fracture in rocks under complex stress states. The proposed NOSB-PD model is validated using two examples, demonstrating its excellent capability in suppressing the zero-energy mode and capturing fracture behavior in rock under compressive–shear conditions. Subsequently, the proposed model is used to systematically investigate the influence of flaw distribution on crack propagation and failure modes in rocks. The results indicate that variations in flaw distribution alter the local stress field, leading to a change in the rock fracture mode. Consequently, the rock bridge failure mode transitions from shear-dominated direct coalescence to mixed tensile-shear failure, and finally to tension-dominated indirect failure. The overall rock specimen is more prone to tensile–shear-mixed failure under conditions of shorter rock bridges with larger inclinations, or longer rock bridges with smaller inclinations. These findings provide new insights into the role of flaw distribution on rock fracture behavior. Full article

Understanding the anisotropic mechanical behavior and pore–fracture structure (PFS) evolution of bedded coal under mining disturbance is critical for gas extraction and hazard prevention in deep coal mining. This study employed low-field nuclear magnetic resonance (NMR) and fractal analysis to characterize the PFS of water-saturated coal samples with bedding angles of 0°, 30°, 45°, 60°, and 90°. The pore system was classified into adsorption and seepage pores according to pore size distribution. Real-time triaxial NMR tests were further conducted to reveal the coupled evolution of mechanical responses and PFS under different bedding orientations. Results show that bedding inclination controls pore distribution, connectivity, and structural complexity, while influencing coal strength, deformation, and failure through stress redistribution and bedding-plane activation. The mechanical response and PFS evolution exhibit strong anisotropic coupling during loading. A fractional-order porosity model was established by incorporating bedding orientation, anisotropy, and stress memory based on pore geometry and stress decomposition. Model verification confirms its effectiveness in describing anisotropic porosity and PFS evolution under varying bedding angles. This study provides theoretical support for permeability prediction, stability assessment, and hazard control in deep-bedded coal seams. Full article

Background/Objectives: Identifying geriatric hip fracture patients who will require postoperative intensive care unit (ICU) admission remains a clinical challenge. The American Society of Anesthesiologists Physical Status (ASA-PS) classification and the Clinical Frailty Scale (CFS) are both used in preoperative risk stratification, yet their comparative utility for this purpose has not been well characterized. Methods: This single-center, retrospectively designed study included 243 patients aged 65 years or older who underwent hip fracture surgery between January 2023 and December 2025. The primary outcome was determined as postoperative ICU admission, while the secondary outcomes were in-hospital mortality and postoperative complications. Discriminative performance was assessed by ROC analysis with DeLong pairwise comparison. Multivariable logistic regression analysis was performed to identify independent predictors of ICU admission. Results: Postoperative ICU admission occurred in 72.8% of patients. On multivariable analysis, neither ASA-PS nor CFS independently predicted ICU admission. Age (OR 1.052, 95% CI 1.009–1.096; p = 0.017), coronary artery disease (OR 3.992, 95% CI 1.581–10.083; p = 0.003), and spinal anesthesia (OR 0.363, 95% CI 0.161–0.823; p = 0.015) were found to be independent determinants. The addition of either scoring system to this clinical model did not improve discriminative performance (AUC 0.712 vs. 0.709 for both). For in-hospital mortality, CFS demonstrated a markedly superior discriminative ability compared to ASA-PS (AUC 0.801 vs. 0.623; DeLong p = 0.047). Conclusions: In this study, ASA-PS and CFS demonstrated comparable performance in predicting ICU admission; however, neither scale retained independent predictive value after adjustment for age, coronary artery disease, and type of anesthesia. Moreover, incorporating either score into the existing clinical risk model did not meaningfully improve discriminative performance (AUC: 0.709 vs. 0.712). Conversely, CFS exhibited superior discriminative ability compared to ASA-PS for in-hospital mortality. Given the low number of mortality events (n = 13), this finding should be interpreted cautiously as exploratory and warrants confirmation in larger, prospective, multicenter studies. Full article

Upper-loss and lower-kick (UL–LK) events may occur in ultra-deep fractured carbonate formations when gas enters from a lower high-pressure zone while drilling fluid is lost to an upper low-pressure fracture. Because both flows can continue after shut-in, the wellbore remains incompletely closed. This study develops a transient wellbore-formation pressure model based on phase mass conservation and global volume balance, and introduces an effective gas–liquid partition coefficient to represent phase separation at the fracture inlet. The model shows that circulation loss limits bottomhole-pressure recovery, allowing gas influx to persist after shut-in. Relative to kick-only conditions, UL–LK conditions have a lower initial shut-in casing pressure (SICP) but a steeper subsequent buildup. A smaller partition coefficient, corresponding to preferential liquid loss, leaves more free gas in the wellbore and further increases the SICP buildup rate. A surface-pressure-based screening method was developed from contrasting SICP and shut-in drillpipe pressure (SIDPP) responses. When applied to five field cases, the method correctly identified three UL–LK cases and two kick-only cases. Its outcomes for five field cases agreed with the field interpretations. This framework supports post-shut-in pressure prediction and rapid screening without dedicated downhole measurements. Full article

To address the challenge of fatigue life prediction caused by multiple-crack interactions in ship and offshore structures, this study proposes a dynamic Bayesian network (DBN)-based method for predicting the fatigue life of structures with multiple cracks, which is systematically validated through physical experiments. First, a numerical model of a representative structure containing a central hole and multiple initial cracks was established based on the coupled simulation platform of ABAQUS and Franc3D. The nonlinear interaction behavior among multiple cracks under different geometric configurations was systematically investigated. Subsequently, a neural network surrogate model was developed, in which geometric features and crack lengths were employed as inputs and key fracture mechanics parameters were taken as outputs, enabling efficient prediction of complex stress intensity factor (SIF) fields. On this basis, fatigue crack growth experiments were conducted on DH36 high-strength steel specimens containing multiple cracks, and crack evolution data under realistic cyclic loading conditions were obtained. Finally, by coupling the surrogate model with the Paris law as the state transition equation and incorporating sparse experimental observations as dynamic updating information, a dynamic Bayesian network framework based on the particle filtering algorithm was established. This framework enables posterior probability tracking of multiple-crack fatigue states and rolling prediction of the remaining fatigue life. The results demonstrate that the proposed method can effectively mitigate the error accumulation associated with deterministic simulation models during long-term open-loop prediction while relying only on a limited number of discrete observation anchors. Consequently, the prediction accuracy of the fatigue life of multiple-crack systems is significantly improved. Furthermore, under crack co-propagation conditions, the proposed framework exhibits a strong capability to capture the propagation retardation of secondary cracks induced by shielding effects. The proposed method provides a theoretical foundation and technical support for the dynamic assessment of fatigue damage and the development of digital twins for complex structures containing multiple cracks. Full article

The deep to ultra-deep sandstone reservoirs of the Cretaceous Bashijiqike Formation in the Kelasu structural belt of the Kuqa Depression exhibit strong heterogeneity. This study integrates single-well stress calculation, image log fracture interpretation, thin-section petrographic analysis, and porosity–permeability testing to compare stress, fracture, and reservoir characteristics across the Dabei–Bozi cross-section. The results show that the northern stress release zone is characterized by low S_H (98 to 148 MPa) and E (9220 to 23,420 MPa), indicating weak cumulative stress, low effective fracture density (0.09 fractures/m), and primary-pore dominated reservoirs. The central stress transition zone has progressively increasing S_H (136 to 187 MPa) and E (27,450 to 33,210 MPa) from north to south, indicating strong cumulative stress, high effective fracture density (0.31 fractures/m), and mixed primary–secondary pore-fracture reservoirs. The southern stress accumulation zone shows increasing S_H but decreasing E to the south, indicating that the late-stage high stress results in low effective fracture density (0.08 fractures/m) and preserving primary pores. These results demonstrate that reservoir quality is governed by the cumulative effect of the stress field, rather than by present-day stress or peak paleo-stress alone. This reservoir distribution model could provide a theoretical basis for reservoir prediction in the foreland basin. Full article

Serial presepsin measurements were evaluated for their prognostic value compared with conventional laboratory markers in predicting in-hospital mortality among older adults with hip fractures. This prospective observational study included 85 patients aged ≥65 years admitted with acute hip fractures between December 2025 and May 2026. Residual serum remaining after routine clinical laboratory sampling was obtained on admission (Day 1), Day 3, and Day 5; serum presepsin was measured by commercial ELISA, and routine parameters (C-reactive protein [CRP], white blood cell count, lymphocytes, monocytes, platelets, and liver enzymes) were analysed in the hospital laboratory. Renal function was assessed by serial creatinine and estimated glomerular filtration rate (eGFR). Patients were classified as survivors or non-survivors according to in-hospital outcome. Temporal trajectories were modelled with a linear mixed-effects model fitted to log-transformed presepsin, receiver operating characteristic (ROC) analysis assessed predictive performance, and internal validity was examined by bootstrap resampling. Of the 85 patients, 68 survived and 17 died during hospitalization; all deaths occurred between hospital days 5 and 12. Presepsin diverged progressively between groups, reaching significantly higher concentrations in non-survivors by Day 5 (median 207.70 vs. 147.21 ng/L; p < 0.001), with a Day 5 group-by-time interaction ratio of 1.76 (95% CI 1.38–2.25; p < 0.001). Day 5 presepsin showed the highest predictive accuracy (AUC = 0.868, 95% CI 0.774–0.945; optimism-corrected AUC 0.866), significantly outperforming CRP (AUC = 0.606; p = 0.003) and platelet count (AUC = 0.485; p < 0.001). The association persisted after adjustment for age, ASA class, fracture type, and eGFR, and Day 5 presepsin added discrimination to a baseline clinical model (ΔAUC 0.125; p = 0.015). The Youden-derived cutoff of 169.54 ng/L was unstable across bootstrap resamples (95% range 169.5–207.7 ng/L). Serial presepsin measurement, particularly on Day 5, is associated with in-hospital mortality in this population; these exploratory findings require external validation before any clinical application can be considered. Full article

Background/Objectives: Pulp necrosis in immature permanent teeth arrests root development, leaving an open apex, thin, divergent dentinal walls, and an unfavorable crown-to-root ratio that predisposes the tooth to fracture and complicates endodontic management. An apical barrier using hydraulic calcium silicate cements has become the first-line orthograde approach for these teeth when regenerative procedures are not indicated or feasible. This narrative review synthesizes current evidence on the complete clinical pathway for apical barrier placement in immature permanent teeth, with particular emphasis on the procedural determinants of barrier formation. It also critically appraises where the evidence is robust and where it remains uncertain. Methods: The relevant English-language literature on root development, the etiology of pulp necrosis in immature teeth, diagnosis, isolation, apical barrier methods, calcium silicate materials, and treatment outcomes was reviewed through targeted searches of PubMed/MEDLINE, Scopus, Web of Science, the Cochrane Library, and Google Scholar through June 2026. The literature search was completed in June 2026; therefore, studies published after this date were not included. Evidence was narratively synthesized according to the clinical sequence of diagnosis, treatment selection, isolation, disinfection, barrier formation, restoration, follow-up, and evidence gaps. Throughout, an explicit distinction was maintained between clinical and laboratory evidence. Results: Sensibility testing is widely considered unreliable in immature teeth, complicating diagnosis. Isolation is often challenging because of traumatic crown loss. Successful treatment depends on adequate chemical disinfection, judicious minimal instrumentation, a well-condensed apical barrier of at least 4–5 mm, and a definitive coronal seal that also addresses the weak cervical dentin. Calcium silicate cements—principally MTA, Biodentine, and pre-mixed bioceramic putties—achieve high clinical success. Observational evidence further suggests, as a hypothesis requiring prospective confirmation, that material choice may be less decisive than operator experience and the quality of the coronal restoration. Conclusions: Apical barrier placement with hydraulic calcium silicate cements is a predictable orthograde preservation approach for non-vital immature permanent teeth, particularly when regenerative endodontic procedures are not indicated, not feasible, or unlikely to yield predictable clinical outcomes. Well-designed randomized clinical trials with standardized reporting are needed. Full article

Azimuthal traveltime analysis provides comparatively stable fracture-orientation estimates but limited information on fracture-related elastic changes, whereas amplitude variation with offset (AVO) inversion is sensitive to residual azimuthal moveout. We propose a sequential offset vector tile (OVT)-domain azimuthal traveltime-constrained AVO inversion workflow for reservoir-scale fracture characterization. Traveltime responses are first used to estimate the locally dominant fracture orientation and reduce azimuth-dependent event misalignment. Prestack AVO inversion is then applied separately to representative fracture-parallel and fracture-perpendicular gathers to obtain two sets of apparent elastic parameters, from which a relative tangential-weakness attribute ($\Delta e$) and Poisson’s ratio ratio ($R_{\nu }$) are derived. Synthetic tests show that the mean fracture-orientation error is no greater than 1.1° for prescribed noise levels of 0–50%, and that varying the maximum incidence angle from 20° to 40° causes no systematic deterioration in the recovered attributes. In the field application, the predicted dominant orientation of N 45° E–N 60° E agrees with the approximately N 50° E fracture trend identified from an independent structure-tensor-based seismic interpretation near ZT3. Compared with the uncorrected results, the corrected $\Delta e$ and $R_{\nu }$ maps exhibit improved continuity and better spatial correspondence with the independently interpreted fracture pattern. These results demonstrate that the proposed workflow effectively integrates the stable directional constraint provided by azimuthal traveltime analysis with the fracture-related elastic information obtained from directional AVO inversion, enabling reservoir-scale characterization of the dominant fracture orientation, relative fracture-related weakness variation, and possible fluid sensitivity. Within the stated assumptions and applicability conditions, the method provides a practical seismic framework for fractured-reservoir characterization and evaluation. Full article

Advanced High-Strength Steel (AHSS) exhibits stress-state-dependent competing shear–tensile fracture modes that limit the applicability of conventional ductile fracture criteria based solely on equivalent plastic strain accumulation, such as the Forming Limit Diagram (FLD) approach and the classical Gurson–Tvergaard–Needleman (GTN) model. This paper proposes an extended GTN damage model incorporating Hill’48 anisotropy and the Nahshon–Hutchinson shear mechanism, regulated by a stress-state-dependent weighting function. The experimental program comprised uniaxial tension tests for constitutive calibration, notched plate specimens with shear angles ranging from 0° to 90° (spanning pure shear to tensile–shear stress states), and tension-bending tests. The fracture initiation point was identified from the abrupt load drop on the experimental force–displacement curve and further located in the finite element simulation to extract the corresponding stress-state history. SEM fractography was employed to characterize the microscopic damage mechanisms, revealing a continuous transition from shear-dominated to void-dominated damage at a critical stress triaxiality of approximately 0.35. A weighting function dependent on both stress triaxiality and the normalized Lode angle was formulated to couple void evolution with shear band localization. Following calibration via finite element inverse fitting, the model, implemented as an ABAQUS VUMAT subroutine, successfully reproduced fracture strains and crack paths across stress states ranging from pure shear to high hydrostatic tension. Comparative simulations indicate that this approach yields improved prediction accuracy over the classical GTN model, particularly under mixed-mode conditions, thereby offering a practical numerical tool for analyzing AHSS formability. Full article

Objective: Commercial lip balm sticks are often selected based on brand popularity and marketing claims, which may not reflect formulation quality or mechanical reliability. This study investigated whether lipid matrix organization better predicts mechanical integrity and consumer acceptance than commercial positioning and introduced the Structural Lipid Architecture (SLA) concept. Materials and Methods: Seven best-selling commercial lip balm sticks were evaluated through consumer research, instrumental texture analysis, and compositional assessment. A validated questionnaire completed by 234 participants assessed product performance, fracture perception, purchasing behaviour, and willingness to pay for improved quality. Mechanical properties were determined using a Brookfield CT3 Texture Analyzer, while INCI compositions were analysed for structural wax diversity, lipid co-structuring agents, and melting point distribution within the SLA framework. Results: Overall, 76.9% of respondents reported having previously experienced stick fracture or deformation, while 94.4% expressed willingness to pay more for products offering superior performance and safety. Product fracture was strongly associated with reduced confidence in product quality (ρ = 0.672, p < 0.0001) and lower repurchase intention (ρ = 0.725, p < 0.0001). Hardness strongly correlated with mechanical work (r = 0.950, p = 0.001). Formulations combining complementary natural, mineral, and/or synthetic waxes with lipid co-structuring agents exhibited superior structural cohesion and fracture resistance, whereas simplified wax systems showed progressive mechanical failure. Conclusions: Best-selling status did not consistently predict superior mechanical performance. Optimized combinations of complementary structural waxes were key determinants of product integrity and fracture resistance. Full article

Hot dry rock (HDR) represents a highly promising sustainable clean energy resource for the future, with the fracture network induced by hydraulic fracturing serving as the cornerstone for thermal energy extraction efficiency. However, conventional numerical simulation tools are computationally expensive and fail to meet the requirements for real-time, dynamic on-site predictions. While machine learning models, such as traditional artificial neural network (ANN) and Long Short-Term Memory (LSTM), suffer from severe “black-box” limitations, they also lack the capability to capture the dynamic evolutionary characteristics of complex time series. To resolve these limitations, this study proposes a deep learning framework based on the Temporal Fusion Transformer (TFT) to dynamically predict the temporal evolution of fracture morphology. The research dataset was automatically generated in batches using GOHFER software (version 9.5.6), and feature selection was subsequently completed through parametric sensitivity analysis. A comparative analysis between the TFT model and traditional baseline models (ANN and LSTM) demonstrates that the TFT model achieves superior accuracy in capturing non-linear features that evolve dynamically over time, effectively overcoming the severe underfitting issues exhibited by conventional models under complex temporal constraints. Furthermore, leveraging the inherent attention mechanism of the TFT, this study elucidates the influence weights of injection rate, proppant concentration, and carrier fluid volume on fracture propagation across different fracturing stages, thereby enhancing the interpretability of the deep learning model. This research provides a novel decision-making tool that balances high efficiency with interpretability for the efficient and sustainable design of HDR. Full article