Search Results (119)

Hydrogen is being increasingly integrated into the international trade system as a clean and flexible energy carrier, motivated by the global energy transition and carbon neutrality objectives. The rapid expansion of the global hydrogen trade network has simultaneously exposed several sustainability challenges, including a centralized structure, overdependence on key countries, and limited resilience to external disruptions. Based on this, we develop a risk propagation model that incorporates the absorption capacity of nodes to simulate the propagation of supply shortage risks within the global hydrogen trade network. Furthermore, we propose a composite sustainability index constructed from structural, economic, and environmental resilience indicators, enabling a systematic assessment of the network’s sustainable development capacity under external shock scenarios. Findings indicate the following: (1) The global hydrogen trade network is undergoing a structural shift from a Western Europe-dominated unipolar configuration to a more polycentric pattern. Countries such as China and Singapore are emerging as key hubs linking Eurasian regions, with trade relationships among nations becoming increasingly dense and diversified. (2) Although supply shortage shocks trigger structural disturbances, economic losses, and risks of carbon rebound, their impacts are largely concentrated in a limited number of hub countries, with relatively limited disruption to the overall sustainability of the system. (3) Countries exhibit significant heterogeneity in structural, economic, and environmental resilience. Risk propagation demonstrates an uneven pattern characterized by hub-induced disruptions, chain-like transmission, and localized clustering. Accordingly, policy recommendations are proposed, including the establishment of a polycentric coordination mechanism, the enhancement of regional emergency coordination mechanisms, and the advancement of differentiated capacity-building efforts. Full article

Inspired by the active site of methane monooxygenase, we designed a Cu₂O cluster anchored in the six-membered nitrogen cavity of a C₂N monolayer (Cu₂O@C₂N) as a stable and efficient enzyme-like catalyst. Density functional theory (DFT) calculations reveal that the bridged Cu-O-Cu structure within C₂N exhibits strong electronic coupling, which is favorable for methanol formation. Two competing mechanisms—the concerted and radical-rebound pathways—were systematically investigated, with the former being energetically preferred due to lower energy barriers and more stable intermediate states. Furthermore, strain engineering was employed to tune the geometric and electronic structure of the Cu-O-Cu site. Biaxial strain modulates the Cu-O-Cu bond angle, adsorption properties, and d-band center alignment, thereby selectively enhancing the concerted pathway. A volcano-like trend was observed between the applied strain and the methanol formation barrier, with 1% tensile strain yielding the overall energy barrier to methanol formation (ΔG_overall) as low as 1.31 eV. N₂O effectively regenerated the active site and demonstrated strain-responsive kinetics. The electronic descriptor Δε (ε_d − ε_p) captured the structure–activity relationship, confirming the role of strain in regulating catalytic performance. This work highlights the synergy between geometric confinement and mechanical modulation, offering a rational design strategy for advanced C1 activation catalysts. Full article

To achieve regional sustainable development, the low-carbon transformation of agriculture is essential, as it serves both as a significant carbon source and as a potential carbon sink. This study calculated the agricultural carbon emissions in Liaocheng from 2010 to 2022 by analyzing processes including crop cultivation, animal husbandry, and agricultural input. Additionally, a simulation model of the water–energy–food–carbon nexus (WEFC-Nexus) for Liaocheng’s agricultural production process was developed. Using Vensim PLE 10.0.0 software, this study constructed a WEFC-Nexus model encompassing four major subsystems: economic development, agricultural production, agricultural inputs, and water use. The model explored four policy scenarios: business-as-usual scenario (S1), ideal agricultural development (S2), strengthening agricultural investment (S3), and reducing agricultural input costs (S4). It also forecast the trends in carbon emissions and primary sector GDP under these different scenarios from 2023 to 2030. The conclusions were as follows: (1) Total agricultural carbon emissions exhibited a three-phase trajectory, namely, “rapid growth (2010–2014)–sharp decline (2015–2020)–gradual rebound (2021–2022)”, with sectoral contributions ranked as livestock farming (50%) > agricultural inputs (27%) > crop cultivation (23%). (2) The carbon emissions per unit of primary sector GDP (CEAG) for S2, S3, and S4 decreased by 8.86%, 5.79%, and 7.72%, respectively, compared to S1. The relationship between the carbon emissions under the four scenarios is S3 > S1 > S2 > S4. The relationship between the four scenarios in the primary sector GDP is S3 > S2 > S4 > S1. S2 can both control carbon emissions and achieve growth in primary industry output. Policy recommendations emphasize reducing chemical fertilizer use, optimizing livestock management, enhancing agricultural technology efficiency, and adjusting agricultural structures to balance economic development with environmental sustainability. Full article

As a flagship city of China’s reform and opening-up policy and the core engine of the Guangdong–Hong Kong–Macao Greater Bay Area, Shenzhen faces dual challenges of economic development and ecological conservation during its rapid urbanization. This study systematically investigates the relationship between urbanization and ecological quality in this high-density megacity over the past three decades (1990–2020) using multi-temporal Landsat imagery, incorporating an enhanced Remote Sensing Ecological Index (RSEI), impervious surface extraction techniques, and a Coupling Coordination Degree (CCD) model. Key findings include: (1) Impervious surfaces expanded from 458.15 km² to 709.23 km², showing a tri-phase pattern of rapid expansion, steady infill, and slight contraction, with an annual growth rate of 1.47%; (2) Ecological quality exhibited a “decline-recovery” trajectory, with RSEI values decreasing from 0.477 (1990) to 0.429 (2000) before rebounding to 0.491 (2020), demonstrating phased ecological fluctuations and restoration; (3) The CCD between urbanization and ecological environment improved significantly from “marginal coordination” (0.548) to “primary coordination” (0.636), forming a distinct “west-high-east-low” spatial pattern with significant clustering effects. This study reveals a novel three-dimensional synergistic pathway (“industrial upgrading-spatial optimization-ecological restoration”) for sustainable development in megacities, establishing the “Shenzhen Paradigm” for ecological governance in rapidly urbanizing regions worldwide. Full article

As ecologically sensitive interfaces shaped by the interplay of land and sea, coastal zones demand close attention. Uncovering the spatiotemporal evolution of ecosystem service value (ESV) and the intricate interrelations among ecosystem service (ES) functions is imperative for the informed governance of human–land interactions and for fostering sustainable regional development. This study analyzes the spatiotemporal evolution of ESV based on the modified equivalent factor table, combining the Geo-information Tupu, Markov transfer model, and standard deviation ellipse. Additionally, we introduce an ecosystem service tradeoff degree (ESTD) to assess the tradeoffs and synergies among various ESs, and we utilize GeoDetector to elucidate the driving forces behind the spatial disparities in ESV. Our findings reveal that (1) Although the land use composite index in the Liaoning coastal economic belt (LCEB) increased, the pace of land use transformation demonstrated a trend toward stabilization over the study duration. (2) Between 2000 to2020, ESV initially declined but subsequently experienced an upward rebound, resulting in a net gain of approximately 48 billion yuan. Spatial analysis indicated continuous enlargement of the standard deviation ellipse, with its centroid consistently located within Yingkou City and a gradual directional shift toward the southwest. (3) The dominant relationship among ESs showed synergy, with notable tradeoffs between hydrological regulation and other services. (4) Topography and climate factors were the primary drivers of spatial heterogeneity of ESV in the LCEB. The research provides spatial decision support for optimizing the ecological security pattern of the coastal zone. Full article

Background: CrossFit^® aims to be equitable between both males and female athletes, supporting equal representation and equal prize money at international events. However, to date, limited information is known on CrossFit^® athletes’ performance in the countermovement jump (CMJ), countermovement rebound jump (CMR-J), and isometric mid-thigh pull (IMTP) when assessed using force plates, and if there are any differences between sexes. Therefore, the purpose of the present study was to observe whether any sex-based differences and relationships exist between performance within these assessments. Methods: A total of CrossFit athletes (43 male = 32.8 ± 9.0 years; height 1.78 ± 0.06 m; mass = 92.4 ± 10.6 kg; and 31 female = 31.0 ± 7.6 years, height = 1.64 ± 0.05 m; mass = 68.8 ± 6.0 kg) completed three trials of CMJ, CMR-J and IMTP using portable dual-system force-plate sampling at 1000 Hz. Results: Moderate–large relationships were observed between CMJ, CMR-J and IMTP outcome measures (r = 0.396–0.809, p < 0.001). Males demonstrated small to moderately greater performance outcomes than females for CMJ height (males = 0.35 ± 0.08 m; females 0.30 ± 0.06 m, d = 0.73), CMR-J height (males = 0.32 ± 0.08 m; females = 0.30 ± 0.06 m, d = 0.39) and IMTP peak net force (males = 30.62 ± 10.01 N·kg⁻¹; females = 27.49 ± 6.44 N·kg⁻¹, d = 0.29). Conclusions: Maximal relative strength in CrossFit^® athletes should be seen as imperative in both male and female athletes due to the meaningful relationship in ballistic and plyometric ability. Moreover, previous relationships with CrossFit^® performance and the injury risk reduction benefits of improving strength provide further support. The descriptive data presented could be used by CrossFit^® coaches to assess and compare the current performance of their own athletes in a battery of tests examining CMJ, CMR-J and IMTP, while also facilitating decisions upon prescription within training and competition. Full article

During the last decades, the ever-growing evolution of the construction industry has led to a significant increase in demand for increasingly high-performing construction materials both in terms of mechanical characteristics and sustainability. Focusing on concrete, several researchers have designed different mixes to improve mechanical properties such as compressive strength, workability and durability, and in many of the proposed mixes, the use of industrial waste stands out both for their ability to improve the mechanical properties of concrete and for the importance of their reuse from a sustainability point of view. In this paper, the use of two waste materials, perlite and rhyolite, in concrete mix design was studied in detail, considering their influence on the compressive strength at 7 and 28 days of curing. The waste materials were introduced in the mix design as substitutes for cement in percentages of 15% and 30% in weight. In addition, perlite was micronized to two different particle sizes, 20 μm and 63 μm, respectively, according to what is already used in concrete within perlite in the mix design. The behavior of the structural concrete containing perlite and rhyolite was compared in terms of compressive strength, Young modulus and produced equivalent CO₂ with that of a standard C25/30 reference concrete, and with that of a mix design created using other waste materials, namely fly ash, metakaolin and silica fume, considering cement replacements that are always at 15% and 30% by weight. Moreover, ultrasonic testing and rebound hammer tests were run to evaluate a possible relationship between the physical-mechanical properties of the design mixes and their volumetric and surface characteristics. Full article

This study explores the application of predictive analytics in evaluating player performance in the National Basketball Association (NBA), focusing on rebounds per game (REB), an essential component for better performance and results in basketball. The research employs a comparative analysis of machine learning (ML) models by leveraging a detailed NBA dataset. A key novelty lies in integrating advanced hyperparameter tuning and feature selection, enabling these models to capture complex relationships within the dataset. The Gradient Boosting Regressor demonstrated superior predictive performance, achieving an R² score of 0.8749 after tuning, with Linear Regression following closely at 0.8668. This study also highlights the importance of model interpretability and scalability, emphasizing the balance between predictive accuracy and usability for real-world decision-making. By offering actionable insights for optimizing player strategies and team performance, this research contributes to the growing body of knowledge in data-driven sports analytics and paves the way for more advanced applications in professional basketball management. Full article

Fatigue among hospital nurses, resulting from demanding workloads and irregular shift schedules, presents significant risks to both healthcare workers and patient safety. This study developed a fatigue detection model using heart-rate variability (HRV) and investigated its relationship with the Swedish Occupational Fatigue Inventory (SOFI) among nurses. Sixty nurses from a hospital in Depok, Indonesia, participated with HRV data collected via Polar H10 monitors before and after shifts alongside SOFI questionnaires. A mixed ANOVA revealed no significant between-subjects differences in HRV across morning, afternoon, and night shifts. However, within-subjects analyses showed pronounced parasympathetic rebound (elevated Mean RR) and sympathetic withdrawal (reduced Mean HR) post-shift, particularly after afternoon and night shifts, contrasting with stable profiles in morning shifts. Correlation analysis showed significant associations between SOFI dimensions, specifically lack of motivation and sleepiness, with HRV measures, indicating autonomic dysfunction and elevated stress levels. Several machine-learning classifiers were used to develop a fatigue detection model and compare their accuracy. The Fine Gaussian Support Vector Machine (SVM) model achieved the highest performance with 81.48% accuracy and an 81% F1 score, outperforming other models. These findings suggest that HRV-based fatigue detection integrated with machine learning provides a promising approach for continuous nurse fatigue monitoring. Full article

This study explores the complex relationships among student cynicism, student–university identification, academic self-efficacy, and academic performance within the context of Turkish higher education. Drawing on social identity and social cognitive theories, student cynicism is examined through four dimensions: academic, policy-related, institutional, and social. Survey data were collected from 630 university students in Ankara, Türkiye, using a cross-sectional design and self-reported measures. The results indicate that institutional cynicism is the strongest negative predictor of student–university identification, while academic cynicism shows a curvilinear (U-shaped) relationship with academic performance, suggesting that extreme cynicism may paradoxically be linked to modest performance rebounds. Contrary to expectations, student–university identification does not significantly predict academic performance, nor does it mediate the relationship between cynicism and performance. However, academic self-efficacy moderates the relationship between identification and performance, amplifying the benefits of identification for students with higher levels of self-efficacy. These findings offer culturally grounded insights into student disengagement and highlight the importance of fostering trust, transparency, and self-efficacy to support student well-being and academic resilience, key elements in advancing Sustainable Development Goals 4 (Quality Education) and 8 (Decent Work and Economic Growth). Full article

In this paper, we focus on the internal structural characteristics of permutation tableaux and their correspondence with linked partitions. We begin by introducing new statistics for permutation tableaux, designed to thoroughly describe various positional relationships among the topmost 1s and the rightmost restricted 0s. Subsequently, we develop two marking algorithms for permutation tableaux, each from the perspective of columns and rows. Additionally, we introduce tugging and rebound transformations, which elucidate the generative relationship from original partitions to linked partitions. As a result, we demonstrate that the construction of these two marking algorithms in permutation tableaux provides a straightforward method for enumerating the crossing number and nesting number of the corresponding linked partitions. Full article

As global focus on energy transition and carbon reduction grows, energy efficiency and renewable energy investment have become key policy tools. This study explores the nonlinear relationship between energy efficiency and fossil fuel consumption, emphasizing the threshold effect of renewable energy investment. Using panel data from 71 countries and a dynamic panel threshold model, the analysis reveals that at low renewable energy investment levels, energy efficiency improvements may be limited by the rebound effect, failing to significantly reduce fossil fuel consumption. However, once investment surpasses a critical threshold, energy efficiency begins to play a stronger role in reducing fossil fuel use. A heterogeneity analysis further shows that developed countries and those with carbon trading systems are more effective in leveraging energy efficiency for emission reduction. The findings highlight the need for synergistic policies combining renewable energy investment, carbon markets, and environmental regulations to accelerate the energy transition and achieve carbon neutrality. Full article

Concrete median barriers are prone to damage from low-velocity impacts. However, there is a limited understanding of how damage from initial impacts affects barriers’ long-term performance and whether they maintain safe continued service or must be replaced. Therefore, this paper evaluates the performance of the concrete barriers under sequential low-velocity impact using finite-element analysis. Crash test simulations were performed by impacting the concrete barrier twice with an 80,000 lb (36-ton) tractor-trailer at a target impact velocity and angle. The first impact’s velocities varied between 30 mph (48 kmph) and 54 mph (87 kmph) at 10°, 15°, and 20° crash angles, and the damaged barrier was subsequently subjected to the second impact conforming to the American Association of State Highway and Transportation Officials’ (AASHTO) Manual for Assessing Safety Hardware (MASH) for Test Level 5 criteria (i.e., representative velocity of 52.7 mph (85 kmph) at 15°). Therefore, a total of 78 impact simulations were conducted, and statistical analysis was performed to investigate the relationship between the peak impact forces of the first and second impacts and the crash angle and velocity across distinct phases of the crash simulation and over the entire crash history. The results show that while the peak impact force of the first impact was linearly related to both velocity and angle, the maximum impact force at the second impact did not follow the same trend. However, when considering the localized peak forces in each phase of the crash, the peak forces from the later stages of the second impact (i.e., rebound and final interaction phases) were highly correlated with the initial impact’s velocity and angle, substantially reducing the barrier’s capability to resist vehicular impact loads. In particular, for initial velocities above 46 mph (74 kmph) at angles of 15° and 20°, barriers formed shear cracks traversing across their cross-section, which resulted in excessive fragmentation during the second impact and consequent failure to meet the MASH criteria in terms of structural adequacy. Full article

This study investigated the mechanical properties of concrete specimens produced with a limestone aggregate through laboratory testing. Destructive tests, specifically concrete compressive strength and splitting tensile strength tests, were conducted. Additionally, the Schmidt hammer rebound hardness test, a non-destructive method, was performed on the same specimens. The experimental results, obtained from varying water-to-cement and limestone aggregate-to-cement ratios, yielded the following ranges: compressive strength from 23.6 to 42.6 MPa, splitting tensile strength from 3.2 to 5.1 MPa, and Schmidt hammer rebound values from 18 to 43 N. The correlation between the non-destructive and destructive test results was analyzed experimentally and statistically. Utilizing the experimental data, statistical models were developed, resulting in equations with a high determination coefficient (R² > 0.95) for accurately predicting concrete compressive and splitting tensile strengths. This approach offers the potential for significant labor and time savings in the production of sustainable conventional concrete that meets relevant standards. Furthermore, it aims to facilitate the estimation of concrete strength in existing structures. Full article

The objective of this study is to analyze the piston rebound energy storage characteristics of the nitrogen-hydraulic combined impact hammer and to investigate the manner in which the piston rebound energy is converted and utilized. The kinetic equation of the impact hammer system is established. A numerical calculation model is constructed based on AMEsim, which incorporates the piston, cylinders, reversing valve, accumulator, power source, drill rod, and impacted device. The performance experiment system is designed, the oil pressure experiment and the piston motion experiment are constructed, and the accuracy of the numerical calculation model is verified by comparing the numerical calculation results with the experimental results. This paper investigates the fundamental principles of the piston rebound energy storage and analyzes the relationship between the opening percentage of the reversing valve high-pressure port and the piston rebound energy storage at the outset of the rebound stage. Furthermore, the influence of the length of the piston middle section and the number of high-pressure grooves in the signal chamber on the piston rebound energy storage is investigated. Finally, the experimental comparison allows for an analysis of the influence of the piston rebound energy storage on the performance of the nitrogen-hydraulic combined impact hammer. Full article