Search Results (4,207)

The SP Gas Storage is situated in the SP-Xingcheng structural belt, where volcanic gas reservoirs are widely distributed and characterized by abundant primary microfractures and pore structures. The developed pores and fractures degrade the petrophysical properties of reservoirs and render volcanic basement rocks highly abrasive. In addition, pore-fracture systems alter the internal stress field of formations, which substantially increases the risk of wellbore instability and the collapse of injection and production wells. This poses great challenges to drilling operations and the safe running of the gas storage in this block. To systematically clarify the wellbore instability mechanism of large-diameter wellbores and address the drilling engineering problems in the study area, a dedicated experimental scheme for large-diameter wellbore stability was designed in this work. Laboratory true triaxial tests were conducted on wellbore stability with different borehole sizes, and basic mechanical parameter tests of reservoir rocks were also completed. This study systematically investigates the evolution of rock mechanical parameters and the surrounding stress-reconstruction mechanism induced by pore-forming unloading and identifies the dominant internal mechanism of wellbore instability under large-diameter conditions. A clear distinction is made between the formation stress redistribution caused by stratum exposure and unloading during drilling and formation stress evolution during the subsequent injection and production of the gas storage. On this basis, the fracture initiation threshold, propagation paths, and morphological evolution in thin interbedded sandstone–mudstone reservoirs are further analyzed. Combined with rock mechanical parameters and in situ stress balance conditions, criteria and quantitative evaluation methods for wellbore instability discrimination are finally established. Full article

The reliance on a single evaluation parameter represents a major limitation in traditional geothermal reservoir assessment models, hindering accurate and effective evaluation of geothermal extraction performance. Moreover, mechanical deformation induced by cold fluid injection exerts a significant influence on both fluid flow behavior and geothermal energy recovery. In this study, a thermo-hydraulic–mechanical (THM)-coupled single-fracture model is developed based on the physical properties of the solid matrix and the seepage characteristics of the fluid, using a finite-element framework for heat and mass transfer. This model enables a multi-parameter evaluation of geothermal extraction efficiency as well as reservoir rock deformation. The simulation results indicate that reservoir temperature decreases progressively from the injection well to the production well, resulting in a gradual decline in the outlet temperature after an initial stable production period of approximately 200 days. The presence of a preferential “fastest flow path” between the injection and production wells plays a critical role in sustaining the stable production phase, whereas the development of a tongue-shaped isotherm pattern is a primary factor responsible for the reduction in outlet temperature during the later stages of extraction. In addition, thermally induced rock deformation further modifies geothermal extraction efficiency, mainly through its effects on reservoir permeability and top vertical displacement. Overall, this study provides reliable and effective fundamental data for geothermal exploitation in specific geological reservoirs, thereby supporting the role of geothermal energy as a viable supplement to fossil fuel resources. Full article

This study examines the evolving patterns and zoning characteristics of gas migration and storage zones during coal seam mining, taking the 215 fully mechanized longwall face at Huangling No. 2 Coal Mine as the engineering background. By integrating theoretical analysis, physical similarity simulation experiments, and field measurements, the research systematically explores the zonal linkage evolution mechanism of mining-induced depressurization gas migration and storage zones, together with the associated depressurization gas extraction technology. A flow regime determination equation, driven by the fracture expansion coefficient and permeability, is established on the basis of the fluid Reynolds number criterion. According to differences in gas flow states and medium morphology, the mining-induced fracture field is divided into five distinct zones: a high-permeability zone dominated by turbulent transport, a medium-to-high permeability zone with transitional flow as the secondary dominant region, a low-permeability zone featuring linear laminar flow with micro-permeability, an extremely low-permeability zone characterized by linear laminar flow in a locked state, and a zone of abrupt permeability change associated with gas enrichment. The dynamic evolution of depressurization gas migration and storage zones and their regional linkage mechanisms are clarified. On the basis of these findings, a dynamic targeted layout strategy for high-level boreholes is proposed that is consistent with the spatiotemporal evolution of the overburden permeability field. Field engineering practice shows that the optimized high-level borehole layout maintains the overall gas extraction rate at the drilling site stably above 70%, with a peak value of 93.7%, thereby ensuring safe and efficient mining of the working face. Full article

For the impact-resistance evaluation of thermoplastics, the DuPont impact test is widely used to replicate multiaxial stress states inherent in actual product environments. However, conventional evaluation methods remain constrained by probabilistic pass/fail judgments or empirical calculations of absorbed energy. Consequently, quantifying the “material-specific fracture criterion,” which is indispensable for high-fidelity computer-aided engineering (CAE) analysis, persists as an important challenge. While our previous works established the derivation of CES from uniaxial tensile tests, the core originality of this study lies in extending this mechanical framework to the dynamic and multiaxial stress states of the DuPont impact test. By integrating a mathematical model with the probabilistic results of the staircase method, we enable for the first time the quantitative identification of material-specific fracture thresholds directly from standard drop-weight impact configurations. For this study, a novel mechanical model for deformation and fracture behavior in the DuPont impact test is constructed. Then a quantitative evaluation method is proposed for the “Critical Expansion Stress (CES),” a material-specific threshold triggering fracture under multiaxial stress. Specifically, using thermoplastic materials of five types and seven grades (including PP, POM, PS, ABS, and PC), the surface impact energy absorbed per unit volume was calculated via the DuPont impact test using the staircase method, accounting for size effects. Furthermore, microscopic parameters (shear modulus G and critical void volume fraction f0) were identified theoretically based on the mechanical properties obtained from short-beam shear tests. These parameters were integrated into a mathematical model to derive the CES. Comparing the derived CES with the true-stress-based uniaxial tensile strength, which incorporates the necking behavior during large deformations, revealed a distinct correlation governed by their mechanical relation (the 1:3 rule) based on the theoretical definition of hydrostatic stress. For the highly ductile polymer exhibiting significant strain hardening, this correlation holds universally when evaluated at the initial plastic flow stage prior to massive molecular orientation. The proposed method serves as a practical quantitative screening tool for evaluating the surface impact characteristics of plastic materials, providing an accessible framework for identifying material-specific fracture thresholds. Full article

Background: Osteoporotic vertebral compression fractures (OVCFs) are the most prevalent manifestation of osteoporotic skeletal disease, associated with severe pain, functional decline, and elevated risk of subsequent fractures. Conservative management remains the first-line approach for stable fractures, yet pain control is often suboptimal, and vertebral collapse progresses in up to 37% of patients. Bio-activated orthosilicic acid combined with vitamins D3 and K2 (BioSi-DK) may support fracture healing through complementary mechanisms acting on osteoblast differentiation, collagen synthesis, osteocalcin carboxylation, and mineralization, but its clinical efficacy in OVCFs has not previously been investigated. Methods: A retrospective, multi-center comparative cohort study was conducted in patients aged >50 years with DXA-confirmed osteoporosis and acute thoracolumbar OVCFs (AO Spine OF1-OF2) managed conservatively. Patients receiving BioSi-DK supplementation (two capsules daily for two months, then one capsule daily for four months) in addition to standard conservative treatment were compared with controls receiving conservative treatment alone. Propensity score matching (1:1, sex-exact constraint, caliper 0.3 SD) was applied across twelve pre-specified baseline covariates. The primary outcome was pain intensity at six months, assessed by numerical rating scale (NRS). Secondary outcomes included NRS change, analgesic use, Patient Global Impression of Change (PGIC), requirement for vertebral augmentation (kyphoplasty), MRI marrow edema score (MES), and Genant grade change. Results: After propensity score matching, 38 patients (19 per group) with balanced baseline characteristics were analyzed (mean age 71.2 ± 6.5 years; 89.5% female; mean T-score −2.61 ± 0.32; mean baseline NRS 8.26 ± 0.95). The BioSi-DK group achieved a significantly lower post-treatment NRS score compared with controls (2.05 ± 2.17 vs. 3.84 ± 2.83; p = 0.015; Cohen’s d = −0.71) and a significantly greater mean NRS reduction (−6.21 ± 1.90 vs. −4.42 ± 2.12 points; p = 0.005; d = −0.89). Analgesic discontinuation was more frequent in the BioSi-DK group (68.4% vs. 36.8%; p = 0.068). Kyphoplasty was required in 5.3% of BioSi-DK patients versus 21.1% of controls (p = 0.340; OR = 0.21), and vertebral compression grade remained stable in 100% of supplemented patients versus 84% of controls. At two months, MES improvement by at least one category was more frequently observed in the BioSi-DK group than in controls, suggesting an earlier edema resolution effect; at six months, MES distribution was comparable between groups (p = 0.620). Conclusions: BioSi-DK supplementation as an adjunct to conservative management was associated with a statistically significant and clinically large reduction in pain at six months, with favorable trends in analgesic burden, kyphoplasty requirement, and edema resolution. The safety profile was excellent. These findings support the conduct of prospective, randomized, placebo-controlled trials to confirm BioSi-DK as an effective adjunct therapy for OVCFs. Full article

Solute transport in rock fractures is strongly influenced by hydrodynamic conditions, and clarifying the Péclet-number-controlled transition of transport regimes is important for understanding contaminant migration in fractured aquifers. Based on three-dimensional numerical simulations, this study investigates conservative solute transport in idealized rough fractures with perfectly mated walls and uniform aperture under a wide range of Péclet numbers (Pe). The evolution of concentration fields, breakthrough curves (BTCs), and diffusive and advective fluxes was analyzed to identify the dominant transport regimes. The results show that, as Pe increases, solute transport changes from a diffusion-dominated regime (Pe < 0.1), to a mixed macro-dispersion-dominated regime (0.1 < Pe < 1000), and finally to a high-Pe advection-controlled regime with Taylor-dispersion-like characteristics (Pe > 1000). Correspondingly, the concentration field evolves from rapid diffusion-driven spreading to a sharper advective front, while the BTCs change from early diffusion-breakthrough curves to step-like breakthrough behavior. Fracture aperture promotes solute spreading and broadens the mixing zone, especially under low-to-intermediate Pe conditions. In contrast, under the perfectly mated and uniform-aperture fracture conditions considered here, increasing roughness mainly induces local tortuosity of the concentration front and has limited influence on the overall BTCs. Flux decomposition further confirms that diffusive flux dominates at low Pe, whereas advective flux becomes increasingly dominant as Pe increases. These findings provide a mechanistic basis for interpreting Pe-controlled solute transport in idealized fracture channels and offer fracture-scale insights for classified groundwater contamination risk assessment. The implications should be interpreted within the assumptions of conservative transport without matrix diffusion, adsorption, or reactive processes. Full article

Lost circulation of wellbore fluids within fissured zones constitutes a primary factor contributing to increased non-productive time (NPT) and restricted rate of penetration (ROP). Conventional gel-based lost circulation materials (LCMs) inherently suffer from a tradeoff between pumpability and in situ fracture retention, and they lack a design methodology quantitatively correlated with drilling engineering parameters. In this study, a shear-responsive gel with a dual physically crosslinked network—combining hydrophobic association and Fe³⁺-mediated ionic coordination—was prepared through a single-step water-based radical polymerization process, utilizing commercially available monomers. By systematically tuning the hydrophobic monomer and Fe³⁺ contents, the gel’s fracture-sealing efficacy, autogenous healing ability, and shear rheological characteristics were evaluated, establishing a quantitative correlation between the critical shear rate and drilling parameters. The empirical data demonstrate that with an increase in the hydrophobic monomer dosage from 0.4 wt% to 1.2 wt%, the critical shear rate decreases from 22.5 s⁻¹ to 8.6 s⁻¹, exhibiting an exponential decay relationship. The optimized formulation, G0.8F0.5, demonstrates a low initial viscosity of 245 mPa·s under high shear conditions, which surges to 6180 mPa·s at a shear rate of 14.2 s⁻¹, achieving a thickening factor of 29.4. Upon incubation at 80 °C for a duration of 12 h, the formulated gel restores 94.9% of its mechanical tensile strength and 96.3% of its fracture strain, whereas the Fe³⁺-free control sample fails to heal. In dynamic plugging tests using a 3 mm fracture plate, G0.8F0.5 achieves a breakthrough pressure of 12.8 MPa with a minimal fluid loss of 98 mL. The LCM forms a monolithic gel block positioned at the middle-to-rear section of the fracture, outperforming conventional gel counterparts. Drilling hydraulics simulations reveal that deploying this gel reduces the annular equivalent circulating density (ECD) by 0.06 g/cm³. Furthermore, under idealized conditions, this approach is calculated to enhance the ROP by approximately 26%. The proposed molecular design of a shear-responsive, dual physically crosslinked network provides a viable technical pathway for quantitatively tailoring the shear-responsive properties of while-drilling LCMs. Full article

This study investigates the properties of WC–10Ni cermet coatings deposited by plasma spraying using two different plasma torches: a conventional A60 torch (APS) and an advanced Axial III torch (HV-APS). The aim of the work was to compare the microstructure, porosity, surface roughness, phase composition, and mechanical properties (hardness and instrumented indentation), as well as erosion, scratch response, and resistance to tribological wear of the obtained coatings. The coatings were deposited onto S235 steel substrates using WC–10Ni (WOKA 3302) powder. The results revealed that both coatings exhibit a typical lamellar structure characteristic of plasma-sprayed materials; however, distinct differences in surface roughness, porosity, and mechanical response were observed. The coating produced using the Axial III torch showed lower porosity (~6%) and higher hardness (~1000 HV) compared to the coating deposited with the A60 torch (~12% porosity and ~831 HV). Phase analysis confirmed the presence of WC, W₂C, and Ni in both coatings, indicating partial decarburization of carbides during the spraying process. Erosion resistance tests did not reveal significant differences between the coatings. Erosion testing revealed comparable performance for both coatings, with erosion rates of approximately 0.7 mg/min. Scratch testing showed significantly lower acoustic emission activity for the Axial III coating, indicating less intensive fracture-related events during loading and confirming its more compact microstructure. In contrast, ball-on-disk tribological tests demonstrated comparable wear rates for both coatings (≈9 × 10⁻⁵ mm³·N⁻¹·m⁻¹), despite the substantially higher hardness of the Axial III coating (1010 HV0.2 compared with 792 HV0.2 for the A60 coating). These results indicate that the improvements in hardness and coating densification achieved by the HV-APS process did not result in a measurable reduction in steady-state sliding wear under the applied test conditions. Full article

This systematic review aimed to investigate the effect of titanium dioxide (TiO₂) incorporation on the mechanical, physicochemical, and biological properties of conventional glass ionomer cements (GICs). A systematic search was conducted in June 2026 in PubMed, Scopus, Embase, Web of Science and WorldCat databases. Search terms included combinations of glass ionomer AND titanium dioxide OR TiO₂ OR titanium oxide OR titanium nanotubes OR titanium nanoparticles. The study selection process followed the PRISMA guideline and was organized according to the PECO framework. The search yielded the identification of 475 articles, of which 34 met the eligibility criteria. The included studies investigated different TiO₂ forms, concentrations, and commercial GIC formulations. Many studies reported improvements in compressive strength, surface microhardness, fracture toughness, and antibacterial activity following TiO₂ incorporation. However, the findings were heterogeneous. Several studies reported no statistically significant differences or contradictory outcomes, particularly regarding flexural strength, fluoride release, cytocompatibility, and antibacterial performance. Beneficial effects were most frequently observed at TiO₂ concentrations between 3 and 5 wt%, whereas higher concentrations were occasionally associated with nanoparticle agglomeration and reduced material performance. Variability among studies was likely influenced by differences in TiO₂ characteristics, concentration, testing protocols, and GIC formulation. Overall, TiO₂ incorporation appears to be a promising approach for enhancing selected properties of conventional GICs. However, further standardized studies are required to confirm the consistency and clinical relevance of these effects. Full article

Background and Objectives: Malnutrition is highly prevalent among older adults with hip fracture and is associated with poorer surgical outcomes, yet its prognostic relevance is often under-recognized in routine orthopaedic practice. The Controlling Nutritional Status (CONUT) score is an objective laboratory-based screening tool; however, evidence regarding its value for predicting long-term mortality after hip fracture remains limited. This study aimed to evaluate whether nutritional status assessed by the CONUT score independently predicts mortality in older patients with hip fracture. Materials and Methods: This retrospective observational cohort study included consecutive patients aged ≥70 years admitted for hip fracture to a tertiary hospital between 2014 and 2021. Nutritional status was assessed at admission using the CONUT score and categorized as no, mild, moderate, or severe nutritional risk. Demographic characteristics, comorbidity burden, perioperative variables, postoperative morbidity, and mortality up to five years were recorded. Survival was evaluated using Kaplan–Meier methods, and independent predictors of mortality were identified using multivariable Cox proportional hazards models adjusted for clinically relevant confounders. Results: A total of 2798 patients were included (mean age [SD] 84.3 [6.3] years; 26.4% male), of whom 79.2% presented some degree of nutritional risk at admission. Mortality increased overall with worsening nutritional status (p < 0.001). After comprehensive multivariable adjustment, higher CONUT scores remained independently associated with mortality, with each one-point increase associated with an approximately 22% higher risk of long-term death. Poorer nutritional status was also associated with higher postoperative complication rates, greater transfusion requirements, and longer hospital stay. Conclusions: Nutritional status assessed using the CONUT score is an independent predictor of short-, mid-, and long-term mortality in older patients undergoing surgery for hip fracture. Incorporation of objective nutritional screening into orthogeriatric pathways may improve perioperative risk stratification and support targeted multidisciplinary management. Full article

Progressive stamping is a high-efficiency sheet metal forming method in the automotive and mass production industries, where material characteristics significantly influence process stability, cutting force, tool life, and final part quality. Herein, we report the effects of the chemical composition and mechanical properties of DD11 low-carbon steel on punching force during progressive stamping. Ten DD11 material batches with varying chemical compositions and mechanical properties were subjected to experimental investigation. Material characterization involved spectroscopic chemical analysis, tensile testing in accordance with ISO 6892-1, and hardness measurement. Punching tests were performed with a Zwick BZ2-MMAG100.SH01 universal testing machine that incorporates a punch–die assembly to study force–displacement behavior under controlled conditions. The cutting curves of these materials were analyzed to determine the maximum cutting and fracture loads, which were then statistically correlated with the materials’ chemical and mechanical parameters. The results indicated that tensile strength and yield strength are the strongest statistically significant contributors to the maximum cutting load and the fracture point, and that the correlation coefficients for these measurements were +0.866 and +0.869, respectively. Carbon, chromium, and silicon showed the most positive effect on cutting resistance; whereas, titanium was negatively associated with each of the tested responses among chemical composition measures. But none of the chemical factors were statistically significant. The analysis also showed that material hardness yields the highest predictive performance for cutting force behavior (Pearson correlation coefficients up to 0.935 and a regression coefficient of R² = 0.875). Results of this study show that DD11 cutting behavior at progressive stamping is controlled primarily by strength-dependent mechanical characteristics rather than chemical composition variations. Full article

Mature thin oil reservoirs remain pivotal to maintaining reserves, sustaining production, and enhancing profitability due to their substantial annual output and untapped recovery potential. However, prolonged development leads to compromised fracturing efficacy, manifesting as severe formation-energy depletion, rapid production decline, and short effective periods of stimulation measures. Energy-storage fracturing technology addresses these challenges through fluid-injection energization and imbibition displacement, thereby replenishing formation energy and mobilizing residual oil. Leveraging a geo-engineering integrated platform, this study establishes an inverted seven-spot well-pattern energization model to systematically investigate pore pressure–stress field evolution and dynamic responses under varying energization parameters, including energy-storage injection rate, energy-storage volume, and energy-storage sequence. Key findings include: (1) increasing the energy-storage injection rate from 1.5 m³/min to 3.5 m³/min elevates average pore pressure by 7.8 MPa, with minimum and maximum horizontal principal stresses increasing by 1.4 MPa and 1.7 MPa, respectively; (2) raising the energy-storage volume from 2800 m³ to 4200 m³ enhances pore pressure by 5.5 MPa, accompanied by 2.5 MPa and 2.6 MPa increments in minimum and maximum horizontal principal stresses; (3) simultaneous energizing of all injection wells (1–6) is identified as the optimal injection sequence, yielding the highest average pore pressure of 40.3 MPa at equivalent monitoring positions within the well group, with corresponding average minimum and maximum horizontal principal stresses of 55.3 MPa and 60.3 MPa, respectively. The results provide theoretical and technical support for optimizing energy-storage fracturing strategies in mature thin oil reservoirs. Full article

The progressive development of microscopic fractures within rock masses is a primary mechanism of macroscopic failure, threatening the structural integrity of rock engineering systems. In this paper, a novel deep learning model, Principal Component Analysis (PCA)-Visual Geometry Group 16 (VGG16), is developed to accurately identify spectrogram features associated with limestone fractures. In this architecture, a PCA-based convolution encoder is seamlessly integrated as a foundational preprocessing layer before feedforwarding into the deep neural network to execute linear feature purification. The model is first validated on standard image datasets comprising handwritten digits and facial images to evaluate classification performance. Subsequently, acoustic emission signals are acquired during triaxial compression tests on limestone specimens pretreated with cyclic acid–alkali exposure. The PCA-VGG16 framework is then employed to classify the corresponding acoustic spectrograms, and its performance is quantitatively compared with a conventional convolutional neural network (CNN) and the standard VGG16 model. The results indicate that the PCA-VGG16 model achieves classification accuracies that are 19.19% and 10.77% higher than the conventional CNN and standard VGG16 models, respectively. In terms of computational efficiency, the training time is reduced by 35.00% and 23.53% compared to CNN and VGG16. The superior classification performance of the proposed PCA-VGG16 model enables accurate identification of internal microscopic fracture characteristics in limestone. Furthermore, the integration of acoustic emission signals with deep learning models offers an effective approach for quantifying internal fracture levels and predicting the progressive failure of rocks. Full article

This study aimed to evaluate the influence of various 3D printing resins and post-processing cleaning protocols on the physical and mechanical characteristics of printed dental models. Specifically, the research compared the effects of water-based vs. isopropyl alcohol (IPA)-based cleaning on surface morphology, mass, color stability, and mechanical durability. The findings revealed that surface roughness and microstructure remained constant regardless of the solvent used, indicating that these properties are primarily driven by resin composition and curing protocols. However, specimens cleaned with water exhibited slightly higher mass values due to moisture retention or lower evaporation rates. Color stability remained unaffected by the post-processing method. Most notably, water-cleaned models demonstrated superior mechanical durability and structural integrity compared to those processed with IPA, which is often associated with micro-fractures and excessive dehydration. Full article

The effect of quenching rate combined with pre-tempering treatments on the mechanical properties of H13 steel was systematically investigated in this study. Tensile testing, electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and X-ray diffraction analysis (XRD) were employed to study the structure–property relationships associated with different heat treatment conditions. The results showed that the specimen subjected to pre-tempering at 680 °C exhibited optimal strength performance, and fractographic analysis revealed that the specimen exhibited characteristic ductile fracture features. Further analysis revealed that increasing the quenching cooling rate effectively refined the grain size of the matrix, thereby significantly enhancing the strength of the sample. Tensile tests demonstrated optimal comprehensive mechanical performance with a yield strength of ~1050.4 MPa and elongation after fracture of ~17.1% for the oil-quenched specimen subjected to 680 °C pre-tempering treatment. The findings provide valuable experimental evidence and theoretical guidance for optimizing the heat treatment process of H13 steel and improving its failure resistance. Full article