Search Results (31,270)

Internal and external environmental changes have led to changes in the service value of plateau ecosystems. Plateau ecosystems are facing a risk of falling into “recession”. Meanwhile, climate change has become an important factor affecting the service value of plateau grassland ecosystems. In this paper, from the perspective of how changes in climate factors inhibit the value of ecosystem services of plateau grasslands, we adopt the equivalent factor method to measure the value of grassland ecosystem services in eight municipal levels in Qinghai Province from 2000 to 2021. We also construct a fixed utility model to test how changes in climate factors affect the value of ecosystem services and use the grass–animal balance as a mediating effect model for the test. The results of the study showed that (1) the increase in temperature and precipitation among the changes in climate factors significantly suppresses the ecosystem service value of grassland in the plateau. (2) The mediation test shows that the grass–livestock balance helped suppress the effects of climate factor changes on the ecological service value of plateau grassland. (3) The heterogeneity test shows that the area containing the Three-River-Source National Park is more resistant to climate factor changes. Climate factor changes have a greater impact on the ecosystem service value of plateau grassland in high altitude areas and have a significant positive effect on sustained low grassland carrying pressure index status. Therefore, in the protection of plateau grassland ecosystems, we should pay attention to the inputs in the ecosystems as well as appropriate grazing. At the same time, this study can provide a reference value for the decision-making with respect to ecological natural resources protection or restoration in plateau grassland under the effects of climate factors. Full article

Abstract: The horizontal joint is a critical component of the prefabricated shear wall structure, responsible for supporting both horizontal shear forces and vertical loads along with the wall, thereby influencing the overall structural performance. This study employs direct shear testing and finite element analysis to investigate the horizontal joint in walls with ring reinforcement. It examines the impact of various factors on joint shear performance, including the type of joint material, joint configuration, buckling length of ring reinforcement, strength of precast concrete, reinforcement ratio of ring reinforcement and dowel bars, and the effect of horizontal binding force. The findings indicate that the shear bearing capacity and stiffness of joints incorporating post-cast epoxy resin concrete and keyways are comparable or superior to those of integrally cast specimens. A larger buckling length in ring reinforcement may reduce shear strength, suggesting an optimal buckling length at approximately one-third of the joint width. As the strength of precast concrete increases, ductility decreases while bearing capacity increases, initially at an increasing rate that subsequently declines. Optimal results are achieved when the strength of precast concrete closely matches that of the post-cast epoxy concrete. Enhancing the reinforcement ratio of ring reinforcement improves shear capacity, but excessively high ratios significantly reduce ductility. It is recommended that the diameter of ring reinforcement be maintained between 10 mm and 12 mm, with a reinforcement ratio between 0.79% and 1.13%. Increasing horizontal restraint enhances stiffness and shear capacity but reduces ductility; thus, the axial compression ratio should not exceed 0.5. Full article

Forest fire is one of the dominant disturbances in the forests of Heilongjiang Province, China, and is one of the most rapid response predictors that indicate the impact of climate change on forests. This study calculated the Canadian FWI (Fire Weather Index) and its components from meteorological record over past years, and a linear model was built from the monthly mean FWI and monthly fire numbers. The significance test showed that fire numbers and FWI had a very pronounced correlation, and monthly mean FWI was suitable for predicting the monthly fire numbers in this region. Then FWI and its components were calculated from the SRES (IPCC Special Report on Emission Scenarios) A2 and B2 climatic scenarios, and the linear model was rebuilt to be suitable for the climatic scenarios. The results indicated that fire numbers would increase by 2.98%–129.97% and −2.86%–103.30% in the A2 and B2 climatic scenarios during 2020–2090, respectively. The monthly variation tendency of the FWI components is similar in the A2 and B2 climatic scenarios. The increasing fire risk is uneven across months in these two climatic scenarios. The monthly analysis showed that the FFMC (Fine Fuel Moisture Code) would increase dramatically in summer, and the decreasing precipitation in summer would contribute greatly to this tendency. The FWI would increase rapidly from the spring fire season to the autumn fire season, and the FWI would have the most rapid increase in speed in the spring fire season. DMC (Duff Moisture Code) and DC (Drought Code) have relatively balanced rates of increasing from spring to autumn. The change in the FWI in this region is uneven in space as well. In early 21st century, the FWI of the north of Heilongjiang Province would increase more rapidly than the south, whereas the FWI of the middle and south of Heilongjiang Province would gradually catch up with the increasing speed of the north from the middle of 21st century. The changes in the FWI across seasons and space would influence the fire management policy in this region, and the increasing fire numbers and variations in the FWI scross season and space suggest that suitable development of the management of fire sources and forest fuel should be conducted. Full article

Composite materials, particularly carbon fiber-reinforced polymers (CFRPs), have become a cornerstone in industries requiring high-performance materials due to their exceptional mechanical properties, such as high strength-to-weight ratios, and their inherent lightweight nature. These attributes make CFRPs highly desirable in aerospace, automotive, and other advanced engineering applications. However, the compressive behavior of CFRP structures remains a challenge, primarily due to the material sensitivity to structural instability, leading to matrix cracking and premature failure under compressive loads. Isogrid structures, characterized by their unique geometric patterns, have shown promise in enhancing the compressive behavior of CFRP panels by providing additional support that mitigates these issues. Traditionally, these structures are manufactured using automated techniques like automated fiber placement (AFP) and automated tape laying (ATL), which, despite their efficacy, are often cost-prohibitive for small-scale or custom applications. Recent advancements in 3D-printing technology, particularly those involving continuous fiber reinforcement, present a cost-effective and flexible alternative for producing complex CFRP structures. This study investigates the compressive behavior of 3D-printed isogrid structures, fabricated using continuous carbon fiber reinforcement via an Anisoprint Composer A3 printer equipped with towpreg coextrusion technology. A total of eight isogrid panels with varying infill percentages were produced and subjected to buckling tests to assess their performance. The experimental results indicate a direct correlation between infill density and buckling resistance, with higher infill densities leading to increased buckling loads. Additionally, the failure modes were observed to shift from local to global buckling as the infill density increased, suggesting a more uniform distribution of compressive stresses. Post-test analyses using optical microscopy and scanning electron microscopy (SEM) revealed the presence of voids within the 3D-printed structures, which were found to negatively impact the mechanical performance of the isogrid panels. The findings of this study demonstrate that 3D-printed isogrid CFRP structures can achieve significant buckling resistance, making them a viable option for high-performance applications. However, the presence of voids remains a critical issue, highlighting the need for process optimizations in 3D-printing techniques to enhance the overall performance and reliability of these structures. Full article

Fractional vegetation cover (FVC) is a crucial indicator for measuring the growth of surface vegetation. The changes and predictions of FVC significantly impact biodiversity conservation, ecosystem health and stability, and climate change response and prediction. Southwest China (SWC) is characterized by complex topography, diverse climate types, and rich vegetation types. This study first analyzed the spatiotemporal variation of FVC at various timescales in SWC from 2000 to 2020 using FVC values derived from pixel dichotomy model. Next, we constructed four machine learning models—light gradient boosting machine (LightGBM), support vector regression (SVR), k-nearest neighbor (KNN), and ridge regression (RR)—along with a weighted average heterogeneous ensemble model (WAHEM) to predict growing-season FVC in SWC from 2000 to 2023. Finally, the performance of the different ML models was comprehensively evaluated using tenfold cross-validation and multiple performance metrics. The results indicated that the overall FVC in SWC predominantly increased from 2000 to 2020. Over the 21 years, the FVC spatial distribution in SWC generally showed a high east and low west pattern, with extremely low FVC in the western plateau of Tibet and higher FVC in parts of eastern Sichuan, Chongqing, Guizhou, and Yunnan. The determination coefficient R² scores from tenfold cross-validation for the four ML models indicated that LightGBM had the strongest predictive ability whereas RR had the weakest. WAHEM and LightGBM models performed the best overall in the training, validation, and test sets, with RR performing the worst. The predicted spatial change trends were consistent with the MODIS-MOD13A3-FVC and FY3D-MERSI-FVC, although the predicted FVC values were slightly higher but closer to the MODIS-MOD13A3-FVC. The feature importance scores from the LightGBM model indicated that digital elevation model (DEM) had the most significant influence on FVC among the six input features. In contrast, soil surface water retention capacity (SSWRC) was the most influential climate factor. The results of this study provided valuable insights and references for monitoring and predicting the vegetation cover in regions with complex topography, diverse climate types, and rich vegetation. Additionally, they offered guidance for selecting remote sensing products for vegetation cover and optimizing different ML models. Full article

Wave erosion of slopes can easily trigger landslides into marine environments and pose severe threats to both the ecological environment and human activities. Therefore, near-shore slope monitoring becomes crucial for preventing and alerting people to these potential disasters. To achieve a comprehensive understanding, it is imperative to conduct a detailed investigation into the dynamics of wave erosion processes acting on slopes. This research is conducted through flume tests, using a wave maker to create waves of various heights and frequencies to erode the slope models. During the tests, seismic signals, acoustic signals, and pore pressure generated by wave erosion and slope failure are recorded. Seismic and acoustic signals are analyzed, and time-frequency spectra are calculated using the Hilbert–Huang Transform to identify the erosion events and signal frequency ranges. Arias Intensity is used to assess seismic energy and explore the relationship between the amount of erosion and energy. The results show that wave height has a more decisive influence on erosion behavior and retreat than wave frequency. Rapid drawdown may potentially cause the slope to slide during cyclic swash and backwash wave action. As wave erosion changes from swash to impact, there is a significant increase in the spectral magnitude and Power Spectral Density (PSD) of both seismic and acoustic signals. An increase in pore pressure is observed due to the rise in the run-up height of waves. The amplitude of pore pressure will increase as the slope undergoes further erosion. Understanding the results of this study can aid in predicting erosion and in planning effective management strategies for slopes subject to wave action. Full article

Due to their extraordinary qualities, including fire resistance, excellent crashworthiness, low thermal conductivity, permeability, non-toxicity, and reduced density, cellular materials have found extensive use in various engineering applications. This study uses a finite element analysis (FEA) to model the dynamic compressive behaviour of agglomerated cork to ascertain how its material density and stress relaxation behaviour are related. Adding the Mullins effect into the constitutive modelling of impact tests, its rebound phase and subsequent second impact were further examined and simulated. Quasi-static and dynamic compression tests were used to evaluate the mechanical properties of three distinct agglomerated cork composite samples to feed the numerical model. According to the results, agglomerated cork has a significant capacity for elastic rebound, especially under dynamic strain rates, with minimal permanent deformation. For instance, the minimum value of its bounce-back energy is 11.8% of the initial kinetic energy, and its maximum permanent plastic deformation is less than 10%. The material’s model simulation adequately depicts the agglomerated cork’s response to initial and follow-up impacts by accurately reproducing the material’s dynamic compressive behaviour. In terms of innovation, this work stands out since it tackles the rebounding phenomena, which was not previously investigated in this group’s prior publication, either numerically or experimentally. Thus, this group has expanded the research on cork materials’ attributes. Full article

Facial hyperpigmentation is a highly prevalent dermatological condition, characterized by dark spots on the skin resulting from excess melanin production. Hyperpigmentation significantly impacts patients’ quality of life and self-esteem. Current treatments often present disadvantages linked to poor product tolerability. A topical cosmetic approach combining three lightening active ingredients (tranexamic acid, niacinamide, vitamin C) offers a new option for treating dark spots on the skin. The present in-use test under dermatological control evaluated the clinical safety and efficacy of a cream and serum containing these three ingredients, formulated with hyaluronic acid for enhanced delivery, stability, and efficacy. A total of 22 Caucasian patients with facial hyperpigmentation, both male and female, aged between 45 and 67 years, applied the cream and serum for 8 weeks. Clinical assessments, colorimetric evaluations, standardized photography, and self-assessment questionnaires were used to measure outcomes. No serious adverse effects were recorded, and the incidence of local adverse effects was low, highlighting good tolerability of the investigated test items. In most participants, significant improvements in hyperpigmented areas were recorded. Clinical scoring by the dermatologist investigator indicated a statistically significant 13% reduction in color intensity and a 6% reduction in the size of dark spots after 8 weeks of treatment. Colorimetric evaluation showed a statistically significant 1% increase in luminosity (L* parameter) and an 8% improvement in the Individual Typological Angle (ITA°) in endpoint, indicating lighter skin spots. Subjective assessments reflected high user satisfaction, with 95% of participants noting improvements in skin hydration and luminosity, and 77% reporting a reduced appearance of dark spots. Overall, the present work supports the use of tranexamic acid, niacinamide, and vitamin C as an effective and well-tolerated combined topical management option for hyperpigmentation. This combination offers a viable alternative to classical whiteners for individuals seeking to reduce facial skin coloration imbalance and improve skin tone. Full article

Cord-rubber composites are subjected to a wide range of loads in various applications. However, their fatigue behavior remains relatively under-researched. To address this gap, a set of representative specimens was developed, and a validated numerical model was employed to assess fatigue-relevant parameters. In this study, we present the results from two series of tests with different strain ratios (R values). One series was subjected to a pure pulsating tensile strain (R ~0), while the second series experienced an increased mean strain with an R ratio between 0.2 and 0.3. A direct comparison of the two series demonstrated that a higher strain ratio results in a longer service life. This is reflected in an increase in the slope (k) from 13 to 23, as well as an increase in the ultimate fiber strain from 8% to 11% at N_d = 50,000 load cycles for a survival probability of 50%. Both series indicate a comparable scatter in the test results. This comparative analysis shows that the strain ratio significantly impacts the fatigue behavior of cord-rubber composite materials based on cyclic tests under different loading conditions. The findings of this study demonstrate the necessity of considering different load situations when evaluating or designing components. Full article

Objective: Milk production during lactation places a high demand for calcium that is fulfilled both from maternal bone resorption and diet. While it is known that mammary gland-derived PTHrP drives bone resorption during lactation, the impact of postpartum estrogen loss on bone has been unclear. Methods: We used a case-control study design to test the effect of estrogen loss in lactating mice. Results: In the present study, we show for the first time that estrogen loss during lactation activates memory T-cells (T_M) to produce TNFα and IL-17A to aid in bone resorption and calcium release. Our studies reveal a new mechanism for the release of calcium from bone postpartum. The findings provide several new insights. First, the immune system plays a critical role in milk production postpartum. Second, evolutionarily, the pathway serves the physiological purpose of increasing bone resorption to release calcium for breastmilk production postpartum but becomes maladaptive postmenopause, leading to osteoporosis. Finally, these results highlight the crosstalk between the brain–bone–breast–endocrine axis and the immune system during lactation. Full article

The rising demand for açaí berries in Amazonian Brazil and French Guiana generates a significant amount of waste, namely the fruit’s stone, which accounts for 80% of the dry fruit’s mass. Recently, various studies have explored the potential valorization of açaí waste in the civil engineering sector, including the functionalization of the fibers surrounding the stone and the multiphysics testing of composite materials based on açaí fibers and/or stones, treated or untreated. This literature review aims to provide an overview of the technology readiness levels (TRLs) of the existing techniques capable of reducing the environmental impact of both the cultivation and management of naturally occurring açaí. While the research to date is promising, it remains at the prototype stage, and the mass ratio of waste in composites, regardless of their type, limits addressing the underlying ecological problem of açaí waste processing. Further experimental investigations are required to improve the functionalization processes, enabling the use of higher proportions of fibers and/or stones in cementitious composites and their large-scale production. Full article

The development of the straddle-type monorail tour-transit system (MTTS) has received keen attention. Regarding the unspecified regulations on the lateral stiffness limit of steel substructures, which is essential for the design of MTTSs, this work presents a comprehensive assessment of the issue. Firstly, a wind–vehicle–bridge coupling model was established, integrating multibody dynamics and finite element methods. This model was then validated against field test results, considering measured track irregularities and simulated wind loadings as the excitations. Afterwards, a trend analysis and a variance-based sensitivity analysis was performed to investigate the effect of various factors on the dynamic response of the MTTS. Results indicate that the pier height significantly impacts the lateral displacement of the pier top, accounting for 87% of the first-order sensitivity index and 75% of the total sensitivity index. In comparison, the lateral stiffness of track beams contributes over 70% to the maximum responses at the mid-span. Based on this, two responses, the lateral displacement of the pier top and the lateral deflection–span ratio of the track beam, were utilized as evaluation indicators. With the analysis of indicators in terms of lateral acceleration, Sperling index, and lateral wheel force, the limited values for the two indicators were determined as 8.04 mm and L/4200, respectively. These findings can serve as valuable references for future research and designs in this field. Full article

Effective communication networks are crucial for ensuring reliable and stable operation and control in smart microgrids (MGs). This paper proposes a comprehensive analysis of the interdependence between power and communication networks in the real-time control of a standalone AC microgrid to address this vital need. Thus, the role of communication network design is emphasized in facilitating an effective centralized secondary control to regulate the voltage and frequency of an MG. Consequently, voltage and frequency deviations from the droop-based primary control should be eliminated. This study employs a real-time co-simulation testbed setup that integrates OPAL-RT and network simulator (ns-3), supporting a rigorous evaluation of the interplay between the communication networks and control within the MG. Experiments have been conducted to demonstrate the effectiveness of the designed communication infrastructure in seamlessly enabling real-time data exchange among the primary and secondary control layers. Testing scenarios have been implemented, encompassing low-traffic patterns with minimal load variations and high traffic characterized by more frequent and severe load changes. The experimental results highlight the significant impact of traffic variations on communication network performance. Despite the increase in traffic, the effectiveness and reliability of the designed communication network have been validated, underscoring the vital role of communication in ensuring the resilient and stable operation of cyber–physical standalone AC microgrids. Full article

Intumescent fireproof coatings protect steel structures and cables by forming a thick, fire-resistant layer under high temperatures. These coatings can deteriorate over time, impacting their fire resistance. Current testing methods are largely lab-based, lacking in-service evaluation platforms. Laser-Induced Breakdown Spectroscopy (LIBS) is emerging as a promising in situ detection technology but is influenced by low air pressure in high-altitude areas. This study investigates how air pressure affects LIBS signals in intumescent coatings on galvanized steel. Using pressures between 35 and 101 kPa, a linear model was developed to correlate laser pulses to ablation depth for characterizing coating thickness. Results show that spectral intensity decreases with lower air pressure. However, a strong linear relationship persists between laser pulses and ablation depth, with a fitting accuracy above 0.9. The coating thickness is identified by the number of laser pulses required to detect the Zn spectral line from the underlying galvanized steel. As air pressure decreases, the ablation depth increases. The study effectively models and corrects for air pressure effects on LIBS data, enabling its application for field detection of fireproof coatings. This advancement enhances the reliability of LIBS technology in assessing the fire performance of these materials, providing a reference for their in situ evaluation and ensuring better fire safety standards for building steel structures and cables. Full article

The synthetic peptide TAT-I24 (GRKKRRQRRRPPQCLAFYACFC) exerts antiviral activity against several double-stranded (ds) DNA viruses, including herpes simplex viruses, cytomegalovirus, some adenoviruses, vaccinia virus and SV40 polyomavirus. In the present study, in vitro profiling of this peptide was performed with the aim of characterizing and improving its properties for further development. As TAT-I24 contains three free cysteine residues, a potential disadvantageous feature, peptide variants with replacements or deletions of specific residues were generated and tested in various cell systems and by biochemical analyses. Some cysteine replacements had no impact on the antiviral activity, such as the deletion of cysteine 14, which also showed improved biochemical properties, while the cyclization of cysteines 14 and 20 had the most detrimental effect on antiviral activity. At concentrations below 20 µM, TAT-I24 and selected variants did not induce hemolysis in red blood cells (RBCs) nor modulated lipopolysaccharide (LPS)-induced release of cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), in human peripheral blood mononuclear cells (PBMCs). These data indicate that TAT-I24 or its peptide variants are not expected to cause unwanted effects on blood cells. Full article