Search Results (612)

The stability of shield tunnel segmental linings is highly sensitive to the lateral pressure coefficient, especially under weak, heterogeneous, and variable geological conditions. However, the mechanical behavior of steel plate-reinforced linings under such conditions remains insufficiently characterized. This study aims to investigate the effects of varying lateral pressures on the structural performance of reinforced tunnel linings. To achieve this, a custom-designed full-circumference loading and unloading self-balancing apparatus was developed for scaled-model testing of shield tunnels. The experimental methodology allowed for precise control of loading paths, enabling the simulation of realistic ground stress states and the assessment of internal force distribution, joint response, and load transfer mechanisms during the elastic stage of the structure. Results reveal that increased lateral pressure enhances the stiffness and bearing capacity of the reinforced lining. The presence and orientation of segment joints, as well as the bonding performance between epoxy resin and expansion bolts at the reinforcement interface, significantly influence stress redistribution in steel plate-reinforced zones. These findings not only deepen the understanding of tunnel behavior in complex geological environments but also offer practical guidance for optimizing reinforcement design and improving the durability and safety of shield tunnels. Full article

This study proposes a laser texturing method to optimize adhesion and minimize residual stresses in CVD diamond films deposited on tungsten carbide (WC-Co). WC-5.8 wt% Co substrates were textured with quadrangular pyramidal patterns (35 µm) using a 1064 nm nanosecond-pulsed laser, followed by chemical treatment (Murakami’s solution + aqua regia) to remove surface cobalt. Diamond films were grown via HFCVD and characterized by Raman spectroscopy, EDS, and Rockwell indentation. The results demonstrate that pyramidal texturing increased the surface area by a factor of 58, promoting effective mechanical interlocking and reducing compressive stresses to −1.4 GPa. Indentation tests revealed suppression of interfacial cracks, with propagation paths deflected toward textured regions. The pyramidal geometry exhibited superior cutting post-deposition cooling time for stress relief from 3 to 1 h. These findings highlight the potential of laser texturing for high-performance machining tool applications. Full article

This review will focus on how ethnic consumption of foods such as shiitake, ginseng, turmeric, black seeds, berries, rosemary, moringa and holy basil can help act as antioxidants and immune modulators in fighting many diseases. We will investigate how these foods act on pathways like Nrf2/Keap1 to increase endogenous antioxidant capacity and help in reducing ROS production, based on publications found in PubMed between 1994 and 2024. In addition, we will show how these plants can cause immune system shifts by changing the makeup of the ratio of Th1/Th2 cells, reduce inflammation, and have antiangiogenic effects on cancer. This review will also show how plants can alter the gut microbiota and lead to a further decrease in oxidative stress. Overall, it will show how plants and their metabolites can potentially create a path forward for creating novel therapeutic approaches and help lead to an improved redox balance, support immune function, and enhance long-term health outcomes. Full article

Accurate path tracking is crucial for greenhouse robots operating in complex environments. However, traditional curve tracking algorithms suffer from low tracking accuracy and large tracking errors. This study aim to develop a high precision greenhouse autonomous following robot, use ANSYS Workbench 19.2 to perform stress and deformation analysis on the robot, then propose a path tracking method based on Linear Quadratic Regulator (LQR) to optimize the pure tracking to ensure high precision curved path tracking for curved tracking, finally perform a comparative simulation analysis in MATLAB R2024a. The structural analysis shows that the maximum equivalent stress is 196 MPa and the maximum deformation is 1.73 mm under a load of 600 kg, which are within the yield limit of 45 steel. Simulation results demonstrate that at a speed of 2 m/s, the conventional Pure Pursuit algorithm incurs a maximum lateral error of 0.3418 m and a heading error of 0.2669 rad under high curvature conditions. By contrast, the LQR–Pure Pursuit algorithm reduces the peak lateral error to 0.0904 m and confines the heading error to approximately 0.0217 rad. Experimental validation yielded an RMSE of 0.018 m for lateral error and 0.016 m for heading error. These findings confirm that the designed robot can sustain its payload under most operating scenarios and that the proposed tracking strategy effectively suppresses deviations and improves path-following accuracy. Full article

Mental health difficulties in university students are an increasing concern, especially after the COVID-19 global crisis. This study used a cross-sectional design to analyze the effect of psychological factors on students’ psychological well-being. Participants were 190 university students enrolled in undergraduate or graduate programs at a public university. Based on previous research and grounded theoretical models, a conceptual model was proposed to analyze the influence of affect states/experiences (emotion regulation difficulties, anxiety and depression, perceived stress, self-compassion, gratitude, and satisfaction with life) on psychological well-being, including the indirect effect of emotions (negative emotions, positive activation emotions, self-efficacy emotions, prosocial emotions, and serenity emotions), using a path analysis. Multigroup analyses were also performed to test the moderating effect of gender and education level. Findings indicated that self-efficacy emotions had an indirect effect on the relationship between anxiety and depression, self-compassion, and psychological well-being. Both prosocial and self-efficacy emotions indirectly impacted the relationship between gratitude, satisfaction with life, and psychological well-being. Being a female and a bachelor student played a moderating role in the final model. The findings suggest that psychological interventions focused on self-efficacy and prosocial emotions are needed to increase psychological well-being in university students. Full article

Background/Objectives: Both traumatic and stressful events, including major life changes, may contribute to post-traumatic stress symptoms (PTS), often associated with anxiety and depression. Feelings of loneliness may influence these relationships, whilst social support seems to mitigate the effects of stressful events on mental health. Our study thus aimed to evaluate the mediating role of loneliness in the relationships between PTS and both anxiety and depressive symptoms among university students. Methods: The data were from the CAMPUS study (0058642/21; FHMS 20-21 157), a survey on university students’ mental health in Italy and the UK. Using a logit model, mediation analyses were carried out to test whether the relationships between PTS and both anxiety and depressive symptoms might be mediated by loneliness. A path analysis was then performed to jointly test the associations between the Impact of Event Scale—Revised (IES-R)’s subscales and clinical domains. Results: Positive associations were found between PTS and both anxiety (p < 0.001) and depressive symptoms (p < 0.001). However, loneliness mediated approximately 22% of the effect of the PTS on anxiety symptoms (indirect effect: 1.04, 95% CI: 0.59; 1.48, p < 0.001) and approximately 33% of the effect of the PTS on depressive symptoms (indirect effect: 1.81, 95% CI: 1.22; 2.39, p < 0.001). Furthermore, the path analysis indicated associations between the IES-R’s hyperarousal subscale and both anxiety (coeff.: 0.34, p < 0.001) and depressive symptoms (coeff.: 0.27, p < 0.001). Conclusions: Along with the associations between PTS and both anxiety and depressive symptoms, our findings highlight the key role of loneliness in both these associations. Targeted interventions to reduce loneliness, especially for students exposed to traumatic events, may ultimately improve their mental health. Full article

Background/Objectives: The COVID-19 pandemic introduced various stressors for families, including changes to daily routines, work, and schooling. Studies have linked these stressors to increased mental health challenges for parents and children. Sleep difficulties were also common during the pandemic, with some children and parents experiencing poorer sleep quality and shorter sleep duration. However, it remains unclear whether the effects of COVID-19 stress on mental health challenges are explained, at least in part, by effects of COVID-19 stress on child and/or parent sleep challenges. This study examined the impacts of COVID-19 stress on sleep and, in turn, mental health difficulties in school-aged children and their parents in Canada and the United States. Methods: Parents (N = 961) completed validated measures of COVID-19 stress, and of their own and their child’s sleep and mental health. Path analyses tested direct and indirect effects of COVID-19 stress on mental health outcomes with sleep problems as the potential mediator. Results: Child sleep problems partially mediated COVID-19 stress effects on both parent (β = 0.33) and child (β = 0.20) mental health difficulties, while parent sleep problems contributed significantly but to a lesser degree (parent mental health: β = 0.07; child mental health: β = 0.03). There also remained significant direct effects of COVID-19 stress on both child and parent mental health difficulties that were not mediated through sleep difficulties. Conclusions: Our findings underscore the interconnected nature of sleep and mental health, demonstrating that stress-related disruptions in sleep (particularly children’s sleep) can exacerbate mental health difficulties for both parents and children during crises like the COVID-19 pandemic. Full article

As an emerging energy-saving approach, bio-inspired drag reduction technology has become a key research direction for reducing energy consumption and greenhouse gas emissions. This study introduces the latest research progress on bio-inspired microstructured surfaces in the field of underwater drag reduction, focusing on analyzing the drag reduction mechanism, preparation process, and application effect of the three major technological paths; namely, bio-inspired non-smooth surfaces, bio-inspired superhydrophobic surfaces, and bio-inspired modified coatings. Bio-inspired non-smooth surfaces can significantly reduce the wall shear stress by regulating the flow characteristics of the turbulent boundary layer through microstructure design. Bio-inspired superhydrophobic surfaces form stable gas–liquid interfaces through the construction of micro-nanostructures and reduce frictional resistance by utilizing the slip boundary effect. Bio-inspired modified coatings, on the other hand, realize the synergistic function of drag reduction and antifouling through targeted chemical modification of materials and design of micro-nanostructures. Although these technologies have made significant progress in drag reduction performance, their engineering applications still face bottlenecks such as manufacturing process complexity, gas layer stability, and durability. Future research should focus on the analysis of drag reduction mechanisms and optimization of material properties under multi-physical field coupling conditions, the development of efficient and low-cost manufacturing processes, and the enhancement of surface stability and adaptability through dynamic self-healing coatings and smart response materials. It is hoped that the latest research status of bio-inspired drag reduction technology reviewed in this study provides a theoretical basis and technical reference for the sustainable development and energy-saving design of ships and underwater vehicles. Full article

This study systematically investigates the effect of steel fiber content on the fractal evolution characteristics of bending cracks in alkali-activated slag concrete (AASC) beams. A four-point bending test on simply supported beams, combined with digital image correlation (DIC) technology, was employed to quantitatively analyze the fractal dimension of crack propagation paths in AASC beams with steel fiber contents ranging from 0% to 1.4%, using the box-counting method. The relationship between fracture energy and fractal dimension was examined, along with the fractal control mechanisms of mid-span deflection, crack width, and the fractal evolution of fracture toughness parameters. The results revealed that as the steel fiber content increased, the crack fractal dimension decreased from 1.287 to 1.155, while the critical fracture energy of AASC beams increased by approximately 75%. Both mid-span deflection and maximum crack width were positively correlated with the crack fractal dimension, whereas the fractal dimension showed a negative correlation with critical cracking stress and fracture toughness and a positive correlation with the energy release rate. When the steel fiber content exceeded 1.2%, the performance gains began to diminish due to fiber agglomeration effects. Overall, the findings suggest that an optimal steel fiber content range of 1.0% to 1.2% provides the best crack control and mechanical performance, offering a theoretical basis for the design of AASC structures. Full article

In this study, the effects of post-weld heat treatment (PWHT) on residual stress distribution and fatigue crack propagation (FCP) behavior in linear friction welded (LFW) Ti-6Al-4V joints were investigated. Microstructural evolution in the weld center zone (WCZ), thermomechanically affected zone (TMAZ), heat-affected zone (HAZ), and base metal (BM) was characterized using scanning electron microscropy (SEM) and electron backscatter diffraction (EBSD). Mechanical properties were evaluated via Vickers hardness testing and digital image correlation (DIC)-based tensile testing. Residual stresses before and after PWHT were measured using the contour method. The LFW process introduced significant residual stresses, with tensile stresses up to 709.2 MPa in the WCZ, resulting in non-uniform fatigue crack growth behavior. PWHT at 650 °C and 750 °C effectively reduced these stresses. After PWHT, fatigue cracks propagated uniformly across the weld region, enabling reliable determination of crack growth rates. The average crack growth rates of the heat-treated specimens were comparable to those of the base metal, confirming that PWHT, particularly at 750 °C, stabilizes the fatigue crack path and relieves internal stress. Full article

Background: Hospitalization during the COVID-19 pandemic has been linked with increased psychological distress, cognitive impairment, and reduced quality of life (QoL). Posttraumatic stress symptoms (PTSS) and rumination may significantly influence QoL outcomes, yet the mechanisms underlying these effects remain poorly understood. Based on the Cognitive Aging Model, this study examines the mediating effects of cognitive and emotional functioning, loneliness, and posttraumatic growth (PTG) on the connection between PTSS/rumination and QoL among patients hospitalized with COVID-19, including the moderator effect of sex, time since discharge, and admission to the intensive care unit (ICU). Methods: A cohort of 258 patients previously hospitalized with COVID-19 as the primary or secondary diagnosis was assessed 6 to 24 months post-discharge. Participants completed validated self-report and neuropsychological assessments of PTSS, rumination, cognitive function, psychological morbidity (depression and anxiety), loneliness, PTG, and QoL. Path analysis and multigroup analysis were employed to assess mediating and moderating effects. Results: PTSS and rumination were associated with reduced physical and mental QoL, primarily via increased psychological morbidity, impaired cognitive functioning, loneliness, and reduced PTG. Rumination showed strong direct and indirect effects on multiple mediators. Only sex and time since discharge significantly moderated pathways, with women showing a strong association between rumination and cognitive impairment/loneliness, while the association between loneliness and mental QoL was significant only in men and in recently discharged patients. Conclusions: PTSS and rumination contribute negatively to QoL in post-discharged patients with COVID-19 through emotional, cognitive, and social pathways, influenced by sex and duration since discharge. The findings underscore the significance of comprehensive long-term care methods focused on cognitive rehabilitation, psychosocial sT, and social reintegration for COVID-19 survivors. Full article

Cyclic triaxial tests are frequently used in the laboratory to assess the liquefaction susceptibility of soils. This paper will serve a two-fold purpose: First, it will serve to explain how the mechanics of the tests represent the stresses that occur in the field. Topics covered include the differences in the stress paths for the soil in the field and in the lab, the differences in the actual stresses applied in the lab and the field, the differences between stress-controlled and strain-controlled tests, and the effects of other aspects of the testing methodology. The development of adjustment factors for converting the laboratory test results to the field is also briefly discussed. The second purpose of the paper is to serve as a guide to interpreting cyclic triaxial test results. The topics covered will include an examination of the two main liquefaction modes and the impact that the failure criteria selected have on the analysis, the differences between stress-controlled and strain-controlled test results, energy dissipation, and pore pressure generation. The author has run more than 1500 cyclic triaxial tests over the course of his career. He has found that, while the test is fairly straightforward to perform, it requires a much deeper understanding of the test mechanics and data interpretation in order to maximize the information gained from performing the test. This paper is intended as a guide, helping engineers to gain further insights into the test and its results. It has a target audience encompassing both those who are running their first tests and those who are looking to increase their understanding of the tests they have performed. Full article

COVID-19 school closures forced German high-school graduates (Abitur 2022 cohort) to prepare for their final examinations with lengthy learning times at home. Guided by transactional stress theory, we tested how personal resources—self-regulated learning (SRL) skills and academic self-efficacy—and contextual resources—perceived teacher support and teacher digital competence—jointly predicted perceived stress during exam preparation. A cross-sectional online survey (June–July 2022) yielded complete data from N = 2379 students (68% female; Mage = 18.3). Six latent constructs were measured with 23 items and showed adequate reliability (0.71 ≤ α/ω ≤ 0.89). A six-factor CFA fit the data acceptably (CFI = 0.909, RMSEA = 0.064). The structural equation model (CFI = 0.935, RMSEA = 0.064) explained 35% of the variance in stress and 23% of the variance in SRL—action. Academic self-efficacy (β = −0.31, p < 0.001), perceived support (β = −0.28, p < 0.001), teacher digital competence (β = −0.08, p < 0.001), COVID-19 learning disruptions (β = +0.13, p < 0.001), and gender (male = 0.32 SD lower stress, p < 0.001) had direct effects on stress. SRL—action’s direct path was small and non-significant (β = −0.02). Teacher digital competence also reduced stress indirectly through greater perceived support (standardized indirect β = −0.11, p < 0.001). The results highlight self-efficacy and perceived instructional support as the most potent buffers of pandemic-related stress, whereas cancelled lessons added strain. Boosting teachers’ digital pedagogical skills has a dual payoff—raising students’ sense of support and lowering their stress. Full article

Microplastics (MPs) and cadmium (Cd) in the soil environment are expected to pose a serious threat to agricultural production. However, the effect of the interaction between them on the soil–plant system and the mechanism of MPs on plant Cd uptake are still unclear. Therefore, the effects of different concentrations of polyethylene (PE-MPs, 0, 1.0% and 2.0%), alone or combined with Cd, on soil properties, plant growth and Cd uptake were investigated through pot experiments. The results showed that the single contamination of MPs and Cd and their interaction (MPs + Cd) significantly decreased soil moisture and pH; however, it increased soil organic matter (SOM) and total nitrogen (TN). Soil urease and catalase activities were significantly decreased and sucrase and alkaline phosphatase activities were increased with or without Cd addition. The exposure of PE and Cd, alone or combined, significantly and negatively affected plant biomass, photosynthetic parameters, and caused oxidative damage to plants, and the overall toxicity to plants increases with the increase in PE concentration. Moreover, co-pollution causes greater plant toxicity than the individual pollution of PE or Cd. Plants can resist oxidative stress by increasing superoxide dismutase (SOD) and peroxidase (POD) activities. The heat map showed that soil environmental factors were significantly correlated with plant growth; and the results of redundancy analysis (RDA) indicated that for plant physiological characteristics, soil properties under PE, alone or co-contaminated with Cd, explained a total of 85.77% and 97.45%, respectively. This indicated that the alteration of the soil microenvironment is the key factor influencing plant growth. The results of the partial least squares path model (PLS-PM) indicated that plant oxidative damage and biomass had significant positive and negative direct effects on plant Cd uptake, respectively. The linear model of relative importance (%) further revealed in depth that soil moisture (relative importance: 33.60%) and plant biomass (relative importance: 20.23%) were, respectively, regarded as the most important soil environmental factors and plant indicators affecting their Cd uptake. This study provided theoretical support for assessing the risks of MPs and Cd co-pollution to agricultural ecosystems. Full article

Background: Caregiving can be a challenging experience, particularly for caregivers of people with Parkinson’s disease, given the array of motor and neuropsychiatric symptoms. Elevated care tasks and demands related to these symptoms may result in greater care burden, heightened caregiving-related strain, and, in turn, poorer health for Parkinson’s disease (PD) caregivers compared to non-PD caregivers. Guided by the Stress Process Model, the purpose of this study was to explore the pathways connecting PD caregiving and caregiver health, with attention to the role of care burden and caregiving-related strain. Methods: We applied path analysis in a structural equation modeling framework to data from 3116 PD and non-PD caregivers participating in the National Alliance for Caregiving and AARP’s Caregiving in the U.S. 2015 and 2020 surveys. We estimated pathways between PD caregiving, care burden, caregiving-related strain (i.e., emotional, physical, and financial), and caregiver self-reported health simultaneously, then decomposed these pathways into total, indirect, and direct effects. Results: Findings show PD caregiving is indirectly linked to poorer health among caregivers through increased care burden and heightened caregiving-related strain, with additional path analysis models pointing to physical strain as an important component of caregiving-related strain in mediating the associations between PD caregiving and overall health. Conclusions: Our findings suggest a need to be especially attentive to the accumulation of care burden and caregiving-related strain—particularly physical strain—among PD caregivers, given the potential consequences for caregiver health. Solutions are needed, such as caregiver screening and caregiver-specific care plans, to better support reductions in burden and strain among PD caregivers, thereby promoting their overall health. Full article