Search Results (7,617)

Future lunar mining missions are expected to involve deeper geological conditions. Understanding the mechanical behaviors of the lunar subsurface regolith is essential to operational safety. Recent findings from the Chang’e-4 and Chang’e-5 missions revealed a marked increase in particle size and relative density of lunar regolith with depth. In addition, the geostatic stress naturally increases with depth. These three variables pose significant challenges for accurately predicting the shear strength. Existing predictive models, such as the Alshibli model, fail to account for the distinct conditions of lunar subsurface regolith. To address this, consolidated drained triaxial tests were conducted on the CUMT-1 lunar regolith simulants. The influences of confining pressure, relative density, and particle size distribution on shear strength were systematically analyzed. A novel indicator, named inter-particle void ratio, was introduced to capture the combined effects of relative density and particle size distribution. Based on this indicator, a new empirical model was proposed for predicting peak shear strength under varying subsurface conditions. The results suggest that deeper lunar regolith may have significantly lower shear strength than previously estimated, primarily due to the combined effect of increased inter-particle void ratio and geostatic stress. This finding has important implications for the assessment of excavation efficiency, underground construction stability, and the overall safety of lunar subsurface infrastructure. Full article

Water saturation is a key factor influencing the mechanical behavior and stability of tunnel rock masses in water-bearing strata. However, current research based on physical model tests has yet to systematically reveal its intrinsic relationship with rock failure modes. To address this gap, this study systematically investigated the effects of water saturation levels (0%, 33%, 58%, and 100%) on the failure mechanisms of four typical tunnel cross-section models: wall-arch, horseshoe, circular, and square. The results indicate the following: (1) Water saturation exerts a significant deteriorating effect on the mechanical properties of tunnel models. As saturation increases, peak stresses generally decrease across all models, but the extent of deterioration varies markedly by tunnel shape: at low saturation (≤58%), peak stress follows the order Wall-Arch > Horseshoe > Circular > Square; at high saturation (>58%), this relationship reverses to Circular > Square > Wall-Arch > Horseshoe. (2) The failure mechanism is significantly controlled by saturation, exhibiting distinct transition characteristics: At low saturation, capillary effects dominate, with matrix suction enhancing material strength, resulting in brittle failure with crack concentration. At high saturation, pore water pressure effects prevail, reducing effective stress and leading to plastic failure dominated by distributed shear slip. Notably, square tunnels consistently exhibit pronounced flexural failure characteristics across all saturation levels. (3) Energy evolution analysis indicates the following: as saturation increases, the total energy U of specimens decreases, the dissipation rate of dissipated energy U_d accelerates, the energy inflection point advances, and failure precursors manifest earlier. The energy dissipation factor n of high-saturation specimens decreases more significantly with increasing strain, confirming that moisture accelerates energy dissipation and promotes premature material instability. (4) Significant differences exist in the response characteristics to moisture effects among tunnel types: Square tunnels consistently exhibit pronounced flexural failure; Circular tunnels demonstrate optimal stress distribution properties under high water content conditions; Wall-arch and horseshoe-shaped tunnels are most sensitive to saturation changes, with their failure modes transitioning from tensile-dominated to shear failure as water content increases. This study reveals the coupled mechanism between water saturation and tunnel cross-sectional shape in influencing rock mass stability. Full article

Italy and the surrounding seas are recognised as one of the European hotspots for tornadoes and waterspouts. In recent years, the town of Rosignano Solvay (on the Northern Tyrrhenian coast) experienced repeated waterspouts affecting the same areas, raising local concern about the possible influence of heated wastewater discharged into the sea by a nearby industrial site. We reconstruct the mesoscale meteorological conditions of four intense waterspouts near Rosignano Solvay using a limited-area weather model at a high-to-very-high resolution (inner domain grid spacing of 500 m; sensitivity tests at 100 m). At the reported event times, the intensity of key mesoscale precursors (low-level wind shear, 1 km storm-relative helicity, maximum updraft intensity, and lifting condensation level) is consistent with the values typically associated with EF1 (or stronger) tornadoes and waterspouts. The model systematically predicts the peak of instability indices 2–3 h earlier than the reported event times. For one case study, we conduct two sea surface temperature sensitivity experiments to assess the potential atmospheric impact of heated wastewater discharge (temperature increases of +1.5 K and +5 K over a 10 km² area). The resulting changes in instability indices are marginal, with differences of at most 3% relative to the control run. A simple mass-balance estimate for the modified sea patch suggests that, given the reported discharge rates, a plausible impact of the warm water released from the industrial site could lead to an increase in the local sea surface temperature of approximately +0.7 °C over two months. We conclude that synoptic and mesoscale conditions primarily govern waterspout initiation in this region, while the direct effect of the small warm coastal plume from the industrial discharge appears to be minor. Full article

Hyperspectral imagery (HSI) offers rich spectral signatures and fine-grained spatial structures for remote sensing, but practical HSI classification is often constrained by scarce labels and complex geometric disturbances, including translation, rotation, scaling, and shear. Existing deep models are typically developed under Euclidean assumptions and rely on data-hungry training pipelines, which makes them brittle in the few-shot regime. To address this challenge, we propose EMNet, a Lie-group-based Equivariant Manifold Network for few-shot HSI classification that explicitly encodes geometric invariance and improves discriminative accuracy. EMNet couples an SE(2)-based Equivariance-Guided Module (EGM) to enforce equivariance to translations and rotations with an affine Lie-group-based Characteristic Filtering Convolution (CFC) that models scaling and shearing on the feature manifold while adaptively suppressing redundant responses. Extensive experiments on WHU-Hi-HongHu, Houston2013, and Indian Pines demonstrate state-of-the-art performance with competitive complexity, achieving OAs of 95.77% (50 samples/class), 97.37% (50 samples/class), and 96.09% (5% labeled samples), respectively, and yielding up to +3.34% OA, +6.01% AA, and +4.14% Kappa over the strong DGPF-RENet baseline. Under a stricter 25-samples-per-class protocol with 10 repeated random hold-out splits, EMNet consistently improves the mean accuracy while exhibiting lower variance, indicating better stability to sampling uncertainty. On the city-scale Xiongan New Area dataset with extreme long-tail imbalance (1580 × 3750 pixels, 256 bands, and 5.925 M labeled pixels), EMNet further boosts OA from 85.89% to 93.77% under the 1% labeled-sample protocol, highlighting robust generalization for large-area mapping. Beyond point estimates, we report mean ± SD/SE across repeated splits and provide rigorous statistical validation by computing Yule’s Q statistic for class-wise behavior similarity, performing the Friedman test with Nemenyi post hoc comparisons for multi-method ranking significance, and presenting 95% confidence intervals together with Cohen’s d effect sizes to quantify practical improvement. Full article

The objective was to investigate the effect of an adhesive-enhancing primer (AEP) on the shear bond strength (SBS) between fresh resin composite and aged resin composite interface, specifically considering the presence or absence of saliva contamination on the aged resin composites. One hundred fifty-three resin composite blocks underwent thermocycling to replicate aging. Nine groups (n = 15) formed: Group 1: no saliva + no surface treatment; Group 2: no saliva + AEP; Group 3: no saliva + bonding agent; Group 4: no saliva + AEP + bonding agent; Group 5: saliva + no surface treatment; Group 6: saliva + AEP; Group 7: saliva + bonding agent; Group 8: saliva + AEP + bonding agent; and Group 9: saliva + phosphoric acid + bonding agent. Fresh resin composite was applied to the surface of each sample and then light-cured. All specimens were stored for 24 h in distilled water at 37 °C. The SBS testing and failure modes were assessed next. One-way ANOVA and the Tukey test (α = 0.05) were used. Group 9 had the highest SBS (15.42 ± 1.37 MPa) but did not significantly differ from Groups 3, 4, 7, and 8 (p > 0.05). Group 5 showed the lowest SBS (3.08 ± 0.41 MPa). Additionally, group 1 demonstrated significantly lower SBS than all other groups except group 5 (p < 0.001). Groups 2 and 6 exhibited comparable SBS (p > 0.05). Groups 3, 4, 7, 8, and 9 displayed both adhesive and mixed failure, whereas the other groups demonstrated a complete adhesive failure. Regardless of saliva contamination, AEP improved the bond strength at the interface between the fresh resin composite and the aged resin composite. Full article

To address the problem of insufficient shear bearing capacity of highway reinforced concrete (RC) T-beams, this paper systematically conducts a comparative study on the shear performance of RC T-beams strengthened with UHPC-CFP toughened composite plates of different configurations, and proposes a shear strengthening method using UHPC-CFP toughened composite plates. Comparative tests on different strengthening configurations are carried out. Meanwhile, a finite element numerical model is established to compare with the experimental results, analyze the influences of different strengthening schemes on the shear bearing capacity and mechanical properties of the beams, reveal the shear strengthening mechanism, and put forward a recommended formula for calculating the shear bearing capacity. The results show that after the diagonal cracks appeared in Beam T-0, they propagated rapidly from the support to the loading point. Beam T-1 had more diagonal cracks in the concrete between the UHPC-CFP toughened composite strips, while Beam T-2 had fewer. Fine cracks occurred in the UHPC-CFP toughened composite strips of Beams T-1 and T-2, whereas no cracking was observed in the UHPC composite rectangular plate of Beam T-3. The shear capacity of all strengthened beams was improved, with increases of 27.0%, 40.5%, and 43.2% for Beams T-1, T-2, and T-3, respectively. Beam T-3 exhibited the maximum deflection, and the strengthening configuration of Beam T-2 was determined to be the optimal. The carbon fiber strips embedded in UHPC effectively delayed the propagation of cracks in the UHPC plate and played the role of “reinforcement”. The truss–arch model theory is also applicable to the shear mechanism of concrete T-beams strengthened with UHPC-CFP toughened composite plates. Verification of Beams T-2 and T-3 using the proposed formula for shear design of strengthened beams showed that the average ratio of the calculated shear capacity to the experimental value was 0.87, indicating the reliability of the calculation results. Full article

To address the challenge of detecting internal defects in medium-thick titanium alloy laser welds, a combined simulation and experimental study on ultrasonic testing was conducted. A finite element model employing a 5 MHz shear wave angle transducer for inspecting titanium alloy welds was established. An ultrasonic testing system was developed, incorporating a DPR300 pulser-receiver (JSR Ultrasonics, Pittsford, NY, USA) and an MSO5204 oscilloscope (RIGOL, Suzhou, China), and was calibrated using standard reference blocks. The inspection results for four prefabricated internal defects at various depths demonstrated that all defects were effectively detected, with the minimum detectable equivalent defect size reaching 1 mm. The measured signal-to-noise ratio (SNR) averaged 17.6 dB, validating the high sensitivity of the proposed system. The mean absolute error for defect localization was 0.438 mm, achieving a positioning accuracy better than 0.5 mm. This study indicates that the pro-posed method enables effective detection and accurate localization of internal defects in titanium alloy laser welds, providing critical technical support for laser welding quality assessment. Full article

This study aimed to prepare and characterize nanoemulsions containing eugenol and 1,8-cineole using the emulsification method and to investigate their anesthetic effects on guppy fish. The optimized formulation comprised a 5–10% mixture of eugenol and 1,8-cineole in a 1:2 ratio, stabilized with 15–20% Tween 80. The selected formulations displayed mean particle sizes below 15 nm, a low polydispersity index (PDI) (<0.5), and a zeta potential that was more negative than −40 millivolts (mV), indicating stable emulsions. Their pH ranged from 6.50 to 6.63, indicating slight acidity. The formulations exhibited non-Newtonian rheology, as well as thinning under shear stress. Three formulations (F2, F6, and F12) remained stable after both accelerated and long-term stability testing. All nanoemulsions were able to induce guppy fish to the third stage of anesthesia. The nanoemulsions with concentrations of 50 mg/L and 100 mg/L eugenol effectively induced sedation and anesthesia in both sexes and reduced the induction and recovery times compared with the ethanol solution. In conclusion, this study highlights nanoemulsions as a promising drug delivery system for alternative anesthetics in aquaculture. Full article

To address the poor vertical vibration reduction in laminated rubber bearings, the high cost and low practicality of combined three-dimensional isolation bearings, and the low load-bearing capacity of thick-layer rubber bearings, this paper proposes a stiffness-reduced rubber isolation bearing. Based on the deformation coordination principle and the incompressibility of thick-layer rubber, theoretical formulas for the horizontal and vertical stiffness of the proposed bearing are established. Compression–shear tests and finite element simulations are then conducted to investigate its mechanical properties under vertical compressive stress. The results show that the theoretical predictions agree well with the simulation and experimental results. The maximum error of horizontal stiffness is no more than 5.6% relative to the finite element simulation and no more than 3.3% relative to the experimental results, while the maximum error of vertical stiffness is no more than 7.9% and 2.3%, respectively. Compared with the traditional laminated rubber bearing, the stiffness-reduced rubber isolation bearing reduces the average vertical stiffness by 35.8% while maintaining stable horizontal mechanical performance and overall integrity within the tested range. Furthermore, parametric analysis indicates that the stiffness can be effectively adjusted by changing the inner-diameter/outer-diameter ratio. A case study based on measured metro-induced vibration time-history curves further shows that the proposed bearing has potential for achieving the dual objective of horizontal isolation and vertical vibration reduction. Full article

Groundwater fluctuations in bedrock affect the mechanical behavior of rock masses hosting geo-energy recovery systems utilizing borehole heat exchangers. To investigate the combined influencing mechanism of changes in groundwater saturation and fracture dip angle on mechanical properties of typical fractured rock masses, triaxial compressive tests were conducted using specimens containing fissures at different angles (15° and 75°) under three conditions: conventional dry, water-immersed, and immersed-dried. The results reveal a combined influencing mechanism of groundwater saturation and fracture dip angle on mechanical properties of typical fractured rock mass. Since specimens with gentle fissure angles tend to fail through fracturing of the intact rock, while those with steeper fissure angles are more prone to failure via slippage along fissure planes, the stress–strain response exhibits greater variability among samples with gentle fissures, attributable to the material heterogeneity of the rock matrix; an increase in water saturation reduces the strength of steeper fissures more pronouncedly due to the relatively homogeneous properties of these fissures, and gravitational water present along fissure planes reduces effective stress and weakens interfacial bonding. Therefore, rock masses with steeper fissures are more susceptible to water-induced weakening and pose a higher risk of shear slippage by fissure reactivation. The findings have a practical value in offering theoretical support for assessing stability risks in geo-energy structures in shallow bedrocks. Full article

This study evaluated eleven resin cements used as core build-up materials by examining the following properties: (a) push-out force between root dentin and the fiber post; (b) pull-out force between the fiber post and the core build-up material; (c) shear bond strength of the resin cement to root dentin; (d) flexural strength of the resin cement; and (e) flexural modulus of elasticity of the resin cement. The purpose of this investigation was to clarify the relationships between recently available universal adhesives, core build-up materials, resin cements, and fiber posts. All experiments were performed at two evaluation periods: after 1 day of water storage (Base) and after 20,000 thermocycles (TC 20k). For the push-out test, simulated post spaces were prepared in single-rooted human premolars. The specimens were sectioned perpendicular to the long axis into 2 mm-thick slices and then subjected to push-out testing to assess the bond strength of the dentin–resin cement–fiber post complex. No significant differences in bonding performance were found between Base and TC 20k. These findings suggest that universal adhesives used for pretreatment of multiple substrates in fiber post cementation can provide not only strong but also durable adhesion over time. Full article

This study presents an analytical and numerical framework to describe the debonding behavior of fiber-reinforced cementitious matrix (FRCM)-reinforced flat masonry elements under direct shear tests. A sawtooth shear stress–slip law, initially proposed for Steel Reinforced Grout (SRG) systems by two of the authors, is calibrated for a PBO-FRCM system based on the experimental results available in the literature. These recent experimental outcomes on flat masonry pillars serve to validate the model by capturing essential interface behaviors, including residual strength and pseudo-linear hardening. Furthermore, a finite element (FE) model of the specimens has been developed to simulate the interface response, allowing for a comparison between numerical predictions and experimental results. The sawtooth law is implemented directly in commercial FE software without the need for custom coding. Additionally, a mesh sensitivity analysis was performed to verify numerical stability and identify the optimal discretization parameters for consistent model response. Results show good agreement among experimental observations, the sawtooth analytical model, and FE simulations. The analytical model slightly underestimates the experimental peak load by about 4–6%, while the FE predictions differ from the experimental results by less than 10%, confirming the reliability of the proposed modeling framework. Full article

Vegetable sweet potato shoot tips are harvested repeatedly for fresh markets, but harvest timing and cut length are still determined largely by experience, limiting their translation into mechanized design parameters and control thresholds. We conducted a two-factor shear-mechanics experiment using three cultivars (‘Fu 23’, ‘Fu 18’, and ‘HD-V4’) and five shoot-tip length levels (10–30 cm), while also measuring stem diameter and moisture content. Because shear tests were performed on short stem segments sampled from a fixed internodal position relative to the apex, the length factor is interpreted mainly as a field-operable harvest criterion and only secondarily as a variable partly associated with tissue position. Moisture content was uniformly high and did not differ among cultivars (p > 0.05). In a pooled two-way ANOVA, length significantly affected maximum shear force (p < 0.01), cultivar was also significant (p < 0.05), and the interaction was not significant (p > 0.05). After including stem diameter as a covariate, both diameter and length remained significant, whereas cultivar became non-significant, indicating that stem diameter explains much of the apparent cultivar difference in absolute load. The reported stress is nominal shear stress. Laboratory-based 95th percentile design loads with γ = 1.3 provide conservative engineering thresholds for preliminary design and harvest-window back-calculation. Full article

This study investigates the shear performance of reinforced concrete (RC) beams strengthened with near-surface-mounted (NSM) carbon fiber-reinforced polymer (CFRP) ropes under ambient and elevated temperature conditions. An experimental program comprising twelve RC beams was conducted, including both normal- and high-strength concrete specimens. The beams were strengthened using CFRP ropes installed at two orientations (45° and 90°) and two spacing configurations (150 mm and 200 mm). Ten specimens were exposed to a temperature of 600 °C prior to shear testing. The experimental results were evaluated against finite element (FE) simulations and shear strength predictions obtained from ACI 440.2R provisions. The FE models demonstrated close agreement with the observed experimental response, whereas ACI 440.2R consistently yielded conservative shear strength estimates, particularly for high-strength concrete beams. The results confirm that inclined CFRP configurations and reduced rope spacing significantly enhance shear capacity, even after severe thermal exposure, with measured strength gains reaching approximately 75% relative to unheated control beams and up to 135% compared to heated control specimen. The findings emphasize the sensitivity of NSM CFRP in terms of strengthening effectiveness to elevated temperature and highlight the limitations of existing design provisions when applied to fire-damaged RC members. Full article

Wetting–air-drying cycling significantly alters the internal damage evolution and failure behavior of sandstone, and identifying reliable acoustic-emission (AE) precursors during loading is important for understanding the rupture mechanism of water-affected rock. In this study, uniaxial compression tests with AE monitoring were conducted on green sandstone subjected to different numbers of wetting–air-drying cycles. Ringing counts, RA–AF parameters, b-value evolution, AE spatial localization, and the correlation dimension D₂ were jointly used to characterize mechanical deterioration, failure-mode transition, and fractal dynamic evolution. The results show that increasing cycling causes a progressive decrease in peak stress and elastic modulus, while AE activity evolves from a relatively dispersed state to stronger pre-peak concentration. The RA–AF distributions indicate that the dominant AE population gradually shifts from tensile-feature dominance toward mixed/shear-involved behavior, suggesting increasing shear participation during failure. The b-value captures stage-dependent damage evolution but exhibits relatively strong fluctuations under increasingly nonstationary event distributions. In contrast, D₂ shows a clearer pre-peak turning feature, and the corresponding stress level remains relatively consistent among different cycling groups. These results indicate that wetting–air-drying cycling not only accelerates the mechanical degradation of green sandstone, but also substantially modifies its rupture dynamics. The D₂ feature may therefore serve as a potential precursor parameter for characterizing pre-peak complexity transition in water-affected sandstone. Full article