Search Results (2,595)

Thermal energy storage plays a crucial role in meeting human energy demands and is particularly essential for many solar energy applications. Among the various storage methods, phase change materials (PCMs) have attracted significant attention because their thermal performance can be greatly influenced by the material properties, physical characteristics, and the geometry of the encapsulating container. In this paper, the melting process of phase change materials (PCMs) within an elliptical enclosure using the finite volume method is analyzed. Gallium is selected as a PCM with a low Prandtl number. A physical model employing the enthalpy porosity formulation is elaborated to describe the coupling between natural convection and the melting process of PCMs. Numerical simulations are performed to examine the influence of the aspect ratio (n = b/a), ranging from 1 to 4, and inclination angles from 0° to 90° of the elliptical enclosure on the melting process. It has been found that the use of the elliptical capsule can reduce the melting process time. For a Rayleigh number of 10⁶, the melting time decreases as the aspect ratio increases from 1 (circle) to 4. The horizontal orientation (θ = 0°) is found to be the most efficient, with a melting rate higher than that observed for inclined positions (30°, 45°, 60°, and 90°). For a low Rayleigh number of 10⁴, the inclination angle has an imperceptible effect on the phase change. Empirical correlations are proposed to relate the Nusselt number to the Rayleigh number, with coefficients adapted to different Fourier numbers and geometric parameters. Full article

Wearable sensing has evolved from custom-built systems towards standardized research- and consumer-grade devices, improving accessibility and comparability in physiological data analysis. Wrist-worn sensors offer non-invasiveness, minimal setup, and suitability for everyday use, making them increasingly attractive for both research and real-world applications. However, it remains unclear how consumer-grade smartwatches compare with established research-grade wearables in physiological data quality and suitability for empirical studies. We present a mixed-methods study assessing the signal comparability and reliability of the research-grade Shimmer3 GSR+, Empatica E4, and the consumer-grade Pixel Watch 2 under controlled conditions including baseline, cognitive load (n-back), startle, relaxation and physical activity phases. A second study replicated key conditions to exploratorily compare the Empatica E4 with its successor, EmbracePlus. All wearables reliably captured pronounced physiological changes between distinct experimental conditions, but were less sensitive to subtle cognitive load differences and varied in absolute values and motion robustness. The Pixel Watch 2 effectively captured heart rate and skin temperature trends in dynamic settings, whereas research-grade devices remained preferable for analyses requiring raw data access, transparent data processing and advanced physiological metrics. Electrodermal activity provided the most consistent task differentiation under motion. Wrist-worn devices were perceived as more comfortable and less obtrusive than finger-based sensors. Full article

This study examines how key opinion consumers (KOCs) influence consumer behavior in social commerce, particularly under growing distrust toward traditional key opinion leaders (KOLs) and the resulting limitations in their influence. While prior research has primarily focused on trust-building, this study investigates how KOCs create perceived value through a distinct influence mechanism that distinguishes between the roles of trust and distrust. Using an explanatory sequential mixed-methods approach, this research integrates results from a quantitative study with findings from a qualitative study to arrive at robust meta-inferences. Following the PLS-SEM analysis (N = 582), qualitative interviews were conducted to corroborate these inferences and provide complementary insights into the psychological mechanisms underlying trust and distrust, identifying boundary conditions—such as the ineffectiveness of physical attractiveness—that redefine influence models in social commerce. The results indicate that a KOC’s expertise and recommendation cues significantly enhance perceived value, which serves as a key mediator influencing purchase behavior. This study conceptualizes the “invisible influence” effect as a distinct persuasion mechanism. KOCs construct utilitarian value through authentic, experience-based sharing. By identifying the mediating role of perceived value and mapping the evolutionary trajectories of influencer roles, this research extends social commerce strategy. Full article

Graphene-based nanosheets (GNS), including graphene, graphene oxide (GO), reduced graphene oxide (rGO), and graphene nanoplatelets (GNPs), have attracted increasing attention for developing high-performance and sustainable cementitious composites. Compared with conventional dispersion strategies, graphene-based coating strategies enable the targeted localization of GNS at critical interfacial transition zones (ITZs), thereby maximizing their reinforcing efficiency while mitigating agglomeration issues. This review systematically summarizes recent advances in GNS coating technologies for cementitious composites, including physical adsorption, chemical assembly, electrophoretic deposition, and in situ growth. The effects of GNS coatings on interfacial engineering, mechanical performance, durability enhancement, and smart functionalities are critically discussed. Existing studies indicate that GNS coatings can improve strength, crack resistance, impermeability, and resistance to chloride ingress, freeze–thaw cycles, and other degradation processes mainly through ITZ densification and microstructure refinement. However, these benefits are strongly dependent on the coating method, substrate type, and stability of the graphene–substrate interface in calcium-rich alkaline pore solutions. In particular, physically adsorbed GO coatings may suffer from desorption or Ca²⁺-induced aggregation, chemically assembled coatings require further validation beyond laboratory-scale systems, and electrophoretic deposition is mainly applicable to electrically conductive substrates. In addition, localized conductive networks created by GNS coatings facilitate multifunctional properties such as self-sensing, electromagnetic shielding, and electrothermal performance. From a carbon-neutrality perspective, the improvements in mechanical properties and durability provide opportunities to reduce material consumption, extend service life, and lower life-cycle carbon emissions. Nevertheless, their carbon-neutral contribution should be verified through quantitative life-cycle assessment rather than inferred directly from strength or durability enhancement alone. Finally, the remaining challenges associated with large-scale implementation, long-term stability, cost-effectiveness, and field-scale validation are discussed. Particular attention is given to the fact that most existing evidence is derived from laboratory-scale specimens rather than real structural elements exposed to service environments. Full article

While traditional frameworks often simplify fluid dynamics, non-ideal thermodynamic characteristics, driven by intermolecular forces and spatial confinement, significantly alter bulk flow at the nanometer scale. To address this gap, we propose a novel transport model that rigorously couples nanoscale gas slippage with dynamic fluid properties. This approach uniquely integrates varying molecular interactions, seamlessly transitioning from attractive to repulsive regimes, alongside confinement-induced shifts in critical parameters. Taking the deep shale formation in the Sichuan Basin, China, as a representative geological context, accurately modeling methane transport is essential. Our analytical results reveal that incorporating non-ideal thermodynamics profoundly amplifies the predicted boundary slip. Specifically, the corrected mean free path is amplified by a factor of up to 4.7 relative to standard ideal gas assumptions. This enhancement scales strongly with elevated pressure but remains negligible near 1 MPa. Furthermore, we demonstrate that relying on ideal gas laws can inflate nanopore flow capacity estimates by more than 75%, an error primarily driven by density reductions and viscosity increases under high-pressure regimes. We also identify a specific thermodynamic window, sub-10 MPa pressures combined with temperatures below 290 K, where corrected transport metrics actually surpass conventional predictions, an anomaly governed predominantly by intensified slip dynamics. Ultimately, these findings highlight widespread inaccuracies in current permeability estimations, providing a more robust physical foundation for forecasting production and conducting numerical reservoir simulations. Full article

Snacking has become a routine part of how people eat today, with real potential to shape overall diet quality, food choices, and daily nutrient intake. This cross-sectional study aimed to investigate snack purchasing and consumption habits among Greek adults, examine consumers’ perceptions of the nutritional value of snacks, and assess their attitudes toward nutrition labelling, nutrition claims, and innovative snack products. A structured questionnaire was sent out electronically to 1039 Greek adults. Participants provided information on their sociodemographic background, health and lifestyle habits, snack consumption and purchasing behavior, perceptions of snack products, nutrition labelling, and interest in innovative and functional snacks. The data were analyzed using descriptive statistics and Chi-square tests of independence. The most common packaged snack for the average person in the study was a cereal bar, while the least popular non-packaged snack was a bakery cheese pie. Consumers viewed the appearance of the product’s packaging as a secondary consideration at the point of purchase, and the most prominent label elements that attracted consumer attention were nutrition, calories, and fat. The claims that consumers found most appealing were “no preservatives” and “sugar-free/no added sugars.” A clear preference was shown for snack products that relied mainly on naturally occurring nutrients rather than fortified ingredients, as well as a greater willingness to try new savory snack options that used familiar/demonstrable Greek ingredients, such as certain olives, nuts, and fruit. Statistically significant relationships have been identified between certain snacking behaviors, attitudes, and labelling preferences, with respect to age, gender, education level, employment status, Body Mass Index (BMI), health status, physical activity, and place of residence. Within this relatively highly educated and predominantly urban sample, sociodemographic, education level and lifestyle all have an influence on how Greek adult consumers view and use snacks. Interest in nutrition information varies widely between different types of consumers. These findings may be useful in guiding the future development of snacks that meet the nutritional requirements of the Mediterranean diet, as well as in creating more targeted nutrition information and consumer education programs. Full article

Apple (Malus domestica Borkh.) is a major fruit crop of global economic importance, and China ranks first worldwide in both apple cultivation area and total production. With the large-scale renewal of aging orchards, apple replant disease (ARD) has become increasingly prevalent in major apple-producing regions. ARD is typically characterized by severe growth suppression, impaired root development, increased incidence of soil-borne diseases, and, in severe cases, seedling mortality. These symptoms substantially constrain orchard renewal, limit improvements in fruit yield and quality, and threaten the sustainable development of the apple industry. The etiology of ARD is complex and involves the synergistic interaction of three factors: soil microbial dysbiosis characterized by pathogen enrichment and the depletion of beneficial microorganisms; allelopathic autotoxicity caused by the accumulation of phenolic acids, especially phloridzin; and degraded soil physicochemical properties, including acidification, compaction, and nutrient imbalance. Current management strategies mainly include the use of ARD-tolerant rootstocks, microbial regulation, chemical and physical soil disinfection, and agronomic practices such as crop rotation and organic amendment application. Among these approaches, biological regulation mediated by beneficial rhizosphere and endophytic microorganisms has attracted increasing attention because of its environmental compatibility and sustainability. This review summarizes the occurrence patterns, regional characteristics, core pathogenic mechanisms, and integrated management strategies of ARD, with particular emphasis on the functional roles of rhizosphere and endophytic microbiomes in disease alleviation. The review provides a theoretical basis and practical reference for the development of green, efficient, and sustainable strategies for ARD control and apple orchard management. Full article

Cr(VI) has become an urgent environmental concern due to its high toxicity. Adsorption is regarded as an effective technique for Cr(VI) removal, and high-performance adsorbents remain in great demand. In this study, waste-derived magnetic biochar (Fe⁰-Fe₃O₄ MB) was synthesized via synchronous pyrolysis combined with liquid-phase reduction, using Chinese medicinal residue as biomass feedstock and iron-based sludge as the sole iron source instead of traditional chemical agents. Mössbauer spectroscopy (MS) results confirmed the feasibility and high efficiency of synthesizing Fe⁰ using iron sludge as the iron source; meanwhile, in situ generated Fe₃O₄ and biochar effectively restrained particle aggregation and the surface passivation of Fe⁰. Cr(VI) adsorption fitted well with pseudo-second-order kinetics and Langmuir isotherm models, which suggests a predominant monolayer chemisorption process. The Fe⁰-Fe₃O₄ MB possessed excellent superparamagnetism, with a saturation magnetization of 66.74 emu/g. Rapid Cr(VI) adsorption was achieved within 30 min at pH 2 and 35 °C, with a maximum adsorption capacity of 128.36 mg/g. The main adsorption mechanisms may involve multiple pathways, including physical adsorption, electrostatic attraction, chemical reduction, and surface complexation. This study provides a feasible strategy for solid waste resource utilization and the fabrication of stabilized functional zero-valent iron materials, realizing the efficient adsorption treatment of Cr(VI)-containing wastewater. Full article

The growing adoption of additive manufacturing (AM) has increased the demand for efficient and sustainable powder management, particularly for aluminum alloys used in lightweight and high-performance applications. Despite their attractive strength-to-weight ratio, corrosion resistance, and recyclability, aluminum powders are highly sensitive to degradation during repeated reuse. This review examines the main physical and chemical changes occurring in aluminum alloy powders during AM, including oxidation, morphological evolution, agglomeration, moisture uptake, contamination, and porosity-related effects. Their influence on powder flowability, spreadability, packing behavior, laser absorption, and final part quality is critically discussed. The study also reviews current and emerging powder recycling and reconditioning strategies, including sieving, top-up blending, Hydride–Dehydride processing, plasma spheroidization, annealing, and chemical surface treatments. In addition, best practices for powder handling, storage, and quality assessment are summarized to support reliable reuse. Particular attention is given to aluminum powders used in laser powder bed fusion. Unlike earlier reviews that address powder degradation, recycling, or aluminum AM separately, this review provides an integrated framework connecting degradation mechanisms, reconditioning strategies, and qualification methods for reused aluminum powders. It also highlights key knowledge gaps and future directions for developing more reliable and sustainable powder lifecycle management in aluminum-based AM. Full article

Tesla valves are passive hydraulic devices capable of producing directional flow resistance without moving components, making them attractive for applications in microfluidics, thermal systems, and high-reliability hydraulic circuits. Despite extensive experimental and numerical studies, an analytical formulation capable of describing the hydrodynamic behavior of Tesla valves under varying operating and geometric conditions remains limited. In this work, a comprehensive analytical model is developed to describe the pressure losses, flow redistribution, and diodicity behavior of Tesla valves through a physics-based formulation derived from conservation laws, dimensional analysis, and inertial scaling principles. The proposed model incorporates the influence of Reynolds number, flow partition, geometric ratios, branch inclination angle, and number of diode stages within a unified nonlinear framework. A closed structural equation is obtained that relates hydraulic losses and directional asymmetry to the internal geometry of the valve. The formulation reveals the existence of geometric and energetic constraints governing rectification efficiency, including bounds associated with stage number, channel scaling, and angular momentum exchange. The results show that Tesla valve performance emerges from a delicate balance between inertial amplification and dissipative mechanisms, providing an analytical framework for the design and optimization of Tesla-type hydraulic systems across multiple scales. Full article

With the rapid development of networked cyber-physical systems, the coordinated control of heterogeneous multi-agent systems has attracted increasing attention in applications such as autonomous vehicles, robotic arms, and distributed sensor networks. This paper investigates the leader-following cluster consensus problem for heterogeneous multi-agent systems over weighted cooperative–competitive networks with matched disturbances generated by linear exosystems. Unlike purely cooperative or binary signed networks, the considered network allows interaction weights to take arbitrary positive or negative values, thereby describing both the type and intensity of cooperative or competitive interactions. To handle heterogeneous agent dynamics and matched disturbances, a disturbance-observer-based distributed control protocol is developed for both first-order and second-order followers. Based on path-product-based coordinate transformations and Lyapunov stability analysis, sufficient conditions are derived to guarantee topology-dependent scaled leader-following cluster consensus under interactively balanced and interactively sub-balanced topologies. For interactively unbalanced topologies, a structurally selected pinning control strategy is introduced to compensate for sign conflicts caused by unbalanced directed cycles and ensure global asymptotic convergence. Numerical simulations verify the effectiveness of the proposed protocol under heterogeneous dynamics, weighted cooperative–competitive interactions, and matched disturbances. Full article

Background: Artemisia absinthium (A. absinthium) is a perennial plant valued for its antibacterial, antioxidant, and anti-inflammatory properties, exhibiting broader therapeutic potential. Given the need to deliver low doses of A. absinthium extract, mesoporous silica nanoparticles have attracted considerable attention as promising nanocarriers due to their distinctive physical and chemical properties. Methods: Physicochemical characterization of the materials was performed and biological assays were conducted to investigate the ROS, antibacterial and antioxidant activity of A. absinthium extract encapsulated within cerium- and calcium-doped mesoporous silica nanoparticles (MNSiCaCe) against both aerobic and anaerobic bacteria. Results: FTIR, SEM, and BET analysis confirmed successful synthesis of the MNSiCaCe. Phytochemical profiling of Artemisia absinthium extract using HPLC revealed the presence of artemisinin and a rich composition of phenolic and flavonoid constituents, with a total phenolic content of 182 ± 3.6 mg GAE/100 g dry plant material and a total flavonoid content of 42.5 ± 0.6 mg QE/100 g. Quantitative drug loading profiling demonstrated that while plain MNSi nanocarriers achieved a loading capacity of 16.96%, the MNSiCaCe enhanced this threshold to 43.11%. The in vitro controlled-release kinetics exhibited a highly prolonged and slow-release profile of the MNSiCaCe. The materials demonstrated excellent hemocompatibility and high mitochondrial activity with human periodontal ligament cells (hPDLCs). Elevated ROS generation was observed under conditions where antibacterial activity was most pronounced. While the artemisinin-doped nanoparticles showed notable antibacterial effects, the complete Artemisia absinthium-loaded nanoparticles achieved a significantly greater reduction in bacterial viability probably due to the synergistic interaction between artemisinin and the extract’s rich polyphenol profile. Conclusions: These findings highlight MNSiCaCe as a promising and safe nanocarrier system for drug delivery, with strong antibacterial potential, offering valuable applications in antibacterial therapies. Full article

Two-dimensional transient electroluminescent devices have attracted considerable attention owing to their simple device architecture and reduced contact-barrier dependence. However, the influence of semiconductor transport polarity on transient electroluminescence (EL) remains unclear. Here, we compare four representative transition metal dichalcogenide (TMDC) semiconductors with different transport polarities and find that ambipolar WSe₂ exhibits a stronger transient EL signal under identical driving conditions, a trend that cannot be explained by relative photoluminescence quantum yield (PLQY) alone. Transfer characteristics and gate-modulated photoluminescence (PL) measurements were further used to analyze the gate-dependent carrier doping states and the local spectral response associated with interfacial carrier modulation near the metal/TMDC interface during abrupt gate-voltage switching. Based on these results, we propose a possible physical picture in which ambipolar WSe₂ is more likely to form a transient interfacial electron–hole distribution favorable for electron–hole radiative recombination, whereas predominantly n-type materials tend to form electron-rich interfacial carrier states. These findings suggest that semiconductor transport polarity is an important material factor for designing low-dimensional transient electroluminescent devices. Full article

The post-COVID-19 tourism recovery exposes a structural divergence between economic resilience and environmental sustainability. Traditional tourism planning metrics consistently fail to diagnose how macroeconomic growth dynamics decouple from environmental pressures, leaving policymakers without empirical tools to identify structural vulnerabilities or prevent carbon-intensive recoupling during post-crisis transitions. This study integrates macroeconomic, environmental, and digital data across a global panel to map actionable pathways for sustainable tourism transitions. Employing a multi-stage methodology, the analysis first utilizes K-Means clustering (n = 80) to isolate the structural fixed effects of baseline destination archetypes driving a K-shaped recovery. Second, using a synchronized environmental panel (n = 41), a Decoupling Index evaluates eco-efficiency elasticity to test the alignment between tourism value recovery and aviation-induced CO₂ emissions. Third, regression analysis of an elite digital cohort (n = 18) measures dynamic exogenous catalysts, revealing that digital attractiveness, proxied by the global digital nomad market share, is a significantly stronger accelerator of recovery (β = 55.59, p = 0.019) than traditional physical air connectivity (β = −46.48, p = 0.036). Synthesizing these insights, a 2 × 2 Strategic Decision Matrix (n = 41) classifies destinations into Sustainable Leaders, Mass-Market Traps, Value Pivoters, and Vulnerable Laggards. The empirical results demonstrate that pre-pandemic structures do not deterministically dictate recovery (p > 0.05, Partial η² ≤ 0.077), yet rapid financial recovery often masks deep atmospheric vulnerabilities, with specific absolute decoupling leaders achieving exceptional value expansion alongside strict carbon contraction (e.g., Saudi Arabia, DE = −0.35; El Salvador, DE = −0.26). This framework provides a data-driven roadmap for policymakers to utilize “soft” digital infrastructure to transition from carbon-intensive, volume-dependent models toward value-optimized, low-emission ecosystems. Full article

Chemical bonding is a fundamental concept in chemistry and is essential for understanding the chemical and physical properties of substances and their interactions. Despite its importance, students often hold alternative conceptions and exhibit poor conceptual understanding. This study examines the extent to which widely used textbooks in Turkey, Norway, and Czechia reflect key recommendations from science education research. We analysed textbook passages covering chemical bonding, assessing whether they: (1) focus on molecules and ions rather than atoms, (2) present bonds as electrical phenomena, (3) avoid anthropomorphic or magical language, and (4) take care with language, avoid mixing the macroscopic and submicroscopic levels. The findings reveal that most textbooks in the three countries do not fully incorporate these recommendations. Explanations frequently focus on individual atoms, combine electrical attraction with other models such as the octet rule, and employ anthropomorphic language. Additionally, linguistic precision regarding the macro–submicro-scale is often lacking. Notably, Turkish and Norwegian textbooks continue to rely heavily on the octet rule, whilst its use is minimal in Czech texts. The observed divergence highlights the persistent gap between science education research and textbook writing practices. We discuss potential reasons for this gap and outline implications for teaching, curriculum development, and future research. Full article