Search Results (55)

As one of the most catastrophic geological hazards globally, landslides exhibit heightened risks due to their increasing frequency, destructive potential, and extensive spatial distribution. The primary objective of this study is to develop an integrated analytical framework to quantitatively evaluate the stability of variably shaped slopes under rainfall infiltration. The core hypothesis is that slope curvature significantly alters infiltration behavior and stress distribution, leading to morphology-dependent failure mechanisms. Employing Green-Ampt infiltration theory coupled with limit equilibrium analysis, we establish stability prediction models for three fundamental slope geometries (linear, concave, convex) under contrasting rainfall regimes (high-intensity vs. low-intensity precipitation). The derived analytical solutions reveal two critical phenomena: (1) progressive downward migration of the saturation front maintaining parallelism with slope surfaces during infiltration and (2) time-dependent stability deterioration following hyperbolic decay patterns. The proposed models are rigorously validated through numerical simulations employing finite element methods, which demonstrate remarkable congruence with theoretical predictions, showing safety factor discrepancies below 5% (ΔFs < 0.05). Particularly, concave slopes exhibit 18–22% faster destabilization rates compared to convex counterparts under equivalent rainfall conditions. The validated models elucidate the spatiotemporal evolution of matric suction and pore pressure distributions, providing quantitative insights into morphology-dependent failure thresholds. These findings advance predictive capabilities for rainfall-induced landslides through physics-based stability criteria, offering critical guidance for terrain-specific early warning systems and mitigation strategies in geohazard-prone regions. Full article

Background: Inflammatory and metabolic risk factors are associated with adverse health outcomes among aging women. Physical activity may reduce these detrimental changes, helping to promote healthier aging. Methods: Seventy-nine non-obese women, aged 20–50 years, completed a supervised 4–8 week aerobic training program with measurements obtained before and after the intervention. The 20–30-year group (n = 29) completed a 4-week training program, with 13 participants fasting during training, while the 30–50-year group (n = 50) completed an 8-week program. Fasting blood sugar (FBS), lipid profile, insulin, Homeostatic Model Assessment for Insulin Resistance (HOMA IR), body composition, multiple cytokines, oxidative stress markers and leukocyte telomere length were assessed. Mixed-effects linear models were used to test age-by-activity (before versus after) interactions, adjusting for body mass index (BMI), fasting status and training duration. Results: Physical activity was associated with a higher superoxide dismutase (SOD) activity, lower tumor necrosis factor alpha (TNF α) concentrations, increased weekly Metabolic Equivalent of Task (METs) and a modest reduction in high-density lipoprotein (HDL) cholesterol. Significant age-by-activity interactions were identified for fat-free mass, total cholesterol, HDL cholesterol, FBS and TNF α, exhibiting attenuated or reversed age-related slopes for these traits after training. Specifically, older active women exhibited less age-related increases in FBS and TNF α and greater age-related reductions in total cholesterol, whereas the preservation of fat-free mass was more pronounced among younger participants. Conclusions: A short moderate-intensity aerobic program was sufficient to improve antioxidant defenses and inflammatory status and reshape age-group-specific responses to the training of selected glycemic, lipid, inflammatory and functional markers in healthy women, partly mitigating adverse age-associated changes, particularly in older participants. By modeling age-by-activity interactions across various metabolic and inflammatory risk factors, this study provides evidence that short-term moderate aerobic training can reshape age-group-specific cardiometabolic responses to training. Full article

Under random wave loading, the crack growth rate exhibits jump-like cycle-to-cycle variations, which limit the direct use of efficient integration schemes such as the Euler method. In addition, the crack growth life is highly sensitive to the initial crack size and aspect ratio, while the initial defects are often difficult to determine accurately in practice, leading to increased uncertainty in life assessment. To address these issues, a cycle-scaling-based crack size accumulation method for random loading is proposed. A predictor–corrector improved Euler method is then established, and a fourth-order Runge–Kutta scheme incorporating the cycle-scaling transformation is derived. Furthermore, based on spectral analysis theory, a mapping between the wave spectrum and the crack-tip stress intensity factor response spectrum is developed. A stress intensity factor range sequence is generated by concatenating short-term sea states, thereby providing a random loading input that preserves the required statistical characteristics. Finally, a 21,000-TEU container ship is analyzed as a case study to investigate crack growth evolution for different initial aspect ratios. The results show that the crack aspect ratio gradually converges to a particular trend during propagation. A convergent aspect ratio curve is fitted. And a unified life assessment curve is constructed. An equivalent transformation is used to map an arbitrary initial crack shape and size to an equivalent convergent aspect ratio crack. As a result, fatigue life can be rapidly estimated using a single “initial crack size–fatigue life” curve, providing support for crack growth life assessment and the definition of defect acceptance limits for ship hull structures. Full article

To overcome the limitation of the Paris law in capturing stress-ratio (R) effects, a modification of the Goodman model is introduced to account for the nonlinear variation of the fatigue limit with mean stress in this study. Based on the modified formulation, an equivalent crack driving force model incorporating R-effects is subsequently derived for fatigue-crack growth (FCG). The model unifies the stress-intensity factor ranges at different values of R into an equivalent value at R = 0 without introducing fitting parameters other than the Paris constants, relying solely on basic material properties (fatigue limit and tensile strength). This feature facilitates practical application and avoids extensive experimental calibration. Validation using FCG test results of Q345qD steel and 23 datasets show that the model outperforms classical models, achieving a goodness of fit up to 0.98 and demonstrating strong robustness and practical value for FCG prediction and residual-life assessment in engineering structures. Full article

To obtain fatigue crack propagation properties of ordinary concrete commonly employed in bridge construction, 48 replicate single-edge notched beam specimens were fabricated using C50 plain concrete. Twelve of these were subjected to monotonic loading to determine their static capacity; the remaining 36 were fatigue-loaded with various combinations of maximum stress level and stress ratio under three-point bending. Visual observation, strain gauges, and the compliance method were used to determine the evolution of crack length during fatigue loading. The fatigue crack growth rates were then evaluated for each specimen using linear regression. This study shows that the fracture surface under fatigue loading exhibits greater zigzagging than under monotonic loading, with multiple microcracks coalescing. The elastic compliance method captures the three-stage development of fatigue crack well, and the derived equivalent crack size is consistently smaller than surface measurements. Significant scatter exists in the test data; however, the crack growth rate and stress intensity factor range follow a straight line on logarithmic scales, indicating that the Paris Law applies to plain concrete. The slope and intercept of C50 concrete, based on 27 fatigue-failed specimens, follow a Normal distribution, with means of 16.46 and −24.81 (in N-mm units), and coefficients of variation of 0.38 and −0.38, respectively. The corresponding mean and coefficient of variation for slope and intercept by the Forman Equation are 14.80 and 0.42 and −21.18 and −0.44, respectively. The fatigue crack in C50 concrete of this study shows a faster growth rate (46.7% larger slope) than that in lower-strength concrete in the literature. With further research needs identified, this study contributes to a better understanding of the fatigue crack growth properties of ordinary structural concrete, providing valuable information for fatigue assessment and service-life extension of existing concrete bridges. Full article

The evolution characteristics of multi-source-fatigue-crack propagation in the subsurface of a high-speed wheel’s tread and its influence on tread peeling life are the basis for accurately evaluating wheel service lifetime. This study explores the influence of morphology distribution and the size of cracks in the tread on peeling life. The results show that the crack propagation mode in the wheel is mainly mode II and mode III composite propagation caused by shear stress. A fatigue crack inside the wheel with an angle of 45° represents the most dangerous situation. The maximum value of the von Mises stress inside the wheel increases with the increase in the number of multi-source cracks. The equivalent stress intensity factor (SIF) for multi-source cracks is higher than for a single crack. Also, mode III propagation has higher sensitivity to the number of cracks. The existence of multi-source cracks also increases the initial driving force ΔK_eq of crack propagation. The results are useful for the evaluation of the service life of high-speed wheels. Full article

This paper establishes the Brain Booster Buildings framework, the first model to demonstrate how daily stair use can elevate brain-derived neurotrophic factor (BDNF), a vital molecule for lifelong neurogenesis and brain health in humans. Through a novel framework of the associations between metabolic equivalents (METs) data and BDNF response studies, we establish that stairs are generally higher in METs than any indoor activity. We further explain how architectural parameters (riser height, floor number, pace) predictably modulate exercise intensity during stair use. We identify two implementable patterns: moderate-intensity continuous use (≥20 min, 1–3 floors) and high-intensity interval training (6 min, carrying loads while using stairs in a building with three floors or less, or using stairs in a building with ≥3 floors, load-free). Based on BDNF responses to comparable exercise intensities, 6 min of high-intensity stair climbing is predicted to increase serum BDNF by up to 40%. Since people spend ~90% of their time indoors while neurogenesis declines fourfold throughout the adult lifespan, affecting mood, stress resilience, and memory, vertical architecture emerges as a vital, accessible, and cost-effective infrastructure that boosts BDNF for neurogenesis, plasticity, and brain health. We conducted scenario-based modelling using the Brain Booster Buildings framework to estimate how the use of stairs in residential, office, educational, hospital, and commercial buildings may boost BDNF levels based on established intensity–BDNF relationships. The framework provides architects, policymakers, and clinicians with evidence-based estimated specifications to use buildings as daily brain boosters. Full article

Perforation, a common well completion method in oil and gas exploitation, introduces structural defects in casings that alter their mechanical properties. Based on engineering specifications, this study calculates critical loads (i.e., collapse pressure and yield pressure) and the triaxial equivalent stress for casings. Four load cases were selected for analysis: uniform external pressure, uniform internal pressure, external pressure with axial compression, and internal pressure with axial tension. The equivalent stresses around circular, elliptical, pentagonal, and hexagonal perforation defects were computed. A self-defined perforation influence coefficient was used to evaluate changes in mechanical performance. Results show that circular defects have the least effect on the mechanical properties of the casing. Maximum equivalent stress occurs along the hole centerline parallel to the casing axis and increases with greater disparity between ellipse axes or smaller polygon angles. High shot density (>24 holes/m) and large phase angle (60°) generally enhance safety, but an optimal combination exists. Under tensile loads near cracked defects, crack propagation may lead to fracture. For elliptical defects with cracks, the Mode I stress intensity factor grows faster with greater axis disparity, accelerating crack tip stress and deformation, and raising fracture risk. Cracks perpendicular to tensile stress influence the stress intensity factor more significantly than parallel ones. Full article

This study compared physical activity (PA) intensity during leisure and recreation between youth with chronic pain with and without (overweight, obesity) healthy weight. Thirty youth with chronic pain, 11–19 years old, completed the Children’s Assessment of Participation and Enjoyment (CAPE), Functional Disability Inventory (FDI), and a Demographic and Participation Questionnaire. Metabolic equivalent of task (MET) values for CAPE activities were estimated. Youth in both groups reported moderate perceived disability in physical functioning due to pain and mostly participated in leisure and recreation at a low PA intensity. Mann–Whitney U and t-tests indicated that the number of activities performed at high, moderate, and low MET intensity levels did not differ between the two groups (p > 0.05). Perceived disability in physical functioning due to pain was not related to PA intensity (p > 0.05). Youth reported that pain, anxiety/stress, and not having time limited their PA intensity. The findings suggest that multiple factors are potential barriers to PA participation and intensity during leisure and recreation activities. Engagement with youth is encouraged to identify preferred PA at moderate to high intensity and integrate them into interventions and daily routines to promote a physically active lifestyle and reduce disability in physical functioning due to pain. Full article

This study presents a comparative analysis of fatigue crack growth (FCG) in four high-performance crystalline metallic alloys: Inconel 718, Ti-6Al-4V, Aluminum 7075-T6, and ASTM A514 Steel. The Finite Element Method was utilized to simulate crack propagation and quantify the individual and synergistic effects of key material properties, including Paris Law constants (C and m), yield strength, and modulus of elasticity, on FCG behavior. The analysis integrates simulation-driven parametric studies to quantify the impact on performance indicators (fatigue life cycles, equivalent stress intensity factors, safety factors, von Mises stress, and strain energy), and provides a quantitative analysis of secondary parameters. The results provide a robust, data-driven framework for material selection in aerospace, industrial, and structural applications where fatigue life is a paramount design consideration. Key findings reveal that Inconel 718 exhibits vastly superior fatigue life which is approximately 15 times greater than the next best-performing material, ASTM A514 Steel. Conversely, Ti-6Al-4V demonstrated the lowest fatigue resistance. Full article

This study presents a unique and comprehensive application of ANSYS Mechanical R19.2’s SMART crack growth feature, leveraging its capabilities to conduct an unprecedented parametric investigation into fatigue crack propagation behavior under a wide range of positive and negative stress ratios, and to provide detailed insights into the influence of hole positioning on crack trajectory. By uniquely employing an unstructured mesh method that significantly reduces computational overhead and automates mesh updates, this research overcomes traditional fracture simulation limitations. The investigation breaks new ground by comprehensively examining an unprecedented range of both positive (R = 0.1 to 0.5) and negative (R = −0.1 to −0.5) stress ratios, revealing previously unexplored relationships in fracture mechanics. Through rigorous and extensive numerical simulations on two distinct specimen configurations, i.e., a notched plate with a strategically positioned hole under fatigue loading and a cracked rectangular plate with dual holes under static loading, this work establishes groundbreaking correlations between stress parameters and fatigue behavior. The research reveals a novel inverse relationship between the equivalent stress intensity factor and stress ratio, alongside a previously uncharacterized inverse correlation between stress ratio and von Mises stress. Notably, a direct, accelerating relationship between stress ratio and fatigue life is demonstrated, where higher R-values non-linearly increase fatigue resistance by mitigating stress concentration, challenging conventional linear approximations. This investigation makes a substantial contribution to fracture mechanics by elucidating the fundamental role of hole positioning in controlling crack propagation paths. The research uniquely demonstrates that depending on precise hole location, cracks will either deviate toward the hole or maintain their original trajectory, a phenomenon attributed to the asymmetric stress distribution at the crack tip induced by the hole’s presence. These novel findings, validated against existing literature, represent a significant advancement in predictive modeling for fatigue life assessment, offering critical new insights for engineering design and maintenance strategies in high-stakes industries. Full article

Maritime safety is crucial as vessels underpin global trade, but engine room explosions threaten crew safety, the environment, and assets. With modern ship designs growing more complex, numerical simulation has become vital for analyzing and preventing such events. This study examines safety risks from alternative fuel explosions in ship engine rooms, using the Trinitrotoluene (TNT)-equivalent method. A finite element model of a double-layer cabin explosion is developed, and simulations using blastFOAM in OpenFOAM v9 analyze shock wave propagation and stress distribution. Four explosion locations and five scales were tested, revealing that explosion scale is the most influential factor on shock wave intensity and structural stress, followed by equipment layout, with location having the least—though still notable—impact. Near the control room, an initial explosion caused a peak overpressure of 2.4 × 10⁶ Pa. Increasing the charge mass from 10 kg to 50 kg raised overpressure to 3.9 × 10⁶ Pa, showing strong dependence of blast intensity on explosive mass. Equipment absorbs and reflects shock waves, amplifying localized stresses. The findings aid in optimizing engine room layouts and improving explosion resistance, particularly for alternative fuels like liquefied natural gas (LNG), enhancing maritime safety and sustainability. Full article

As the operating conditions of metro vehicles become more complex, the fatigue damage of metro bogie frames under actual operating conditions becomes increasingly difficult to evaluate realistically. After a period of operation of metro trains, the load excitation on the frame and its vibrations become more intense, which causes elastic resonance and leads to fatigue damage. Therefore, it is of high importance to establish test load conditions that match the actual operating environment to conduct fatigue reliability research on frames. To address this problem, in this study, we developed a high-precision force measurement frame and performed a long-term field test. The load optimization factor was used to quantify the load amplitude amplification near the modal frequency caused by the frame elastic resonance. The real load conditions and damage conditions of the fatigued weak position were obtained. Additionally, the square of the difference between the damage calculated via the load spectrum and the measured damage was used as the objective function; the calibrated test load spectrum fully covered the fatigued weak position damage as the constraint condition. The load spectrum calibration coefficient was obtained via multi-objective optimization through a genetic algorithm. The results showed that the damage calculated using the calibrated load agreed well with the real damage, and the ratio of the equivalent stress amplitude between the two was in the range of 1–2. The calibrated test load spectrum obtained in this study can be used for the structural optimization and fatigue reliability design of the later frame. The findings reported here can also be applied to other dynamic systems where fatigue failure is a critical issue. Full article

Kluyveromyces marxianus is a yeast that can be used as a microbial factory. However, little is known about its response to stress conditions. This work evaluated the response of this yeast against ethanol, acetic acid, isoamyl alcohol, and hydrogen peroxide as stress agents. Cytotoxicity assays were performed to assess the residual viability using a direct method (CFU counting) and an indirect method based on the reduction in MTT. Then, fermentation kinetics were performed at IC30 and IC50 for each stress factor to evaluate the effect of moderate and intense stress. This work is the first report presenting IC50 values for ethanol (21.82 g/L), acetic acid (1.19 g/L), isoamyl alcohol (2.74 g/L), and hydrogen peroxide (0.09 g/L) in K. marxianus. The IC50 values for the indirect method are between 3.7 and 68% higher than those for the direct method. Hydrogen peroxide and ethanol were the stress agents showing the highest overestimations. The results presented here demonstrated the overestimation of cell viability by the indirect method. Direct CFU counting is an adequate method to determine yeast viability during toxicity studies of chemical compounds. It was also established that ethanol and hydrogen peroxide have the highest toxicity against K. marxianus ITD-01005 during fermentation at concentrations equivalent to IC30 and IC50 of each stress agent. Full article

Cylindrical shells are extensively employed in fluid transport, pressure vessels, and aerospace structures, where they endure mechanical and environmental stresses. However, under high pressure or external loading, circumferential cracks may develop, threatening structural integrity. Composite patch reinforcement is an effective method to mitigate crack propagation and restore structural performance. This study presents a finite element model using p-refinement techniques to analyze cylindrical shells with circumferential cracks reinforced by composite patches. The approach integrates equivalent single-layer (ESL) and layer-wise (LW) theories within a unified single-element mesh, significantly reducing the degrees of freedom compared to conventional LW models. Fracture analysis is conducted using the virtual crack closure technique (VCCT) to evaluate stress intensity factors. The model’s accuracy and efficiency are verified through benchmark and patch reinforcement simulations. Additionally, a parametric study examines how patch material, thickness, and adhesive properties affect reinforcement efficiency across varying crack angles. This study provides an effective methodology for analyzing composite-reinforced thin-walled cylindrical shells, offering valuable insights for aerospace, marine, and pipeline engineering. Full article