Search Results (22,584)

Magnesium alloys with a high volume fraction of secondary phases exhibit inferior formability. Therefore, investigating their thermal deformation characteristics is critical for optimizing thermal processing techniques. In this work, isothermal compression experiments were performed on a Mg-15Gd-8Y-6Al-0.3Mn alloy with an elastic modulus of 51.3 GPa with a substantial volume of aluminum-rare earth (Al₂RE) phases. The rheological behavior and microstructural evolution of the material were systematically investigated at varying temperatures (350–500 °C) and strain rates (0.001–1.000 s⁻¹). The calculated thermal processing diagram indicates that the unstable region gradually enlarges with increased strain, and all unstable regions appear within the high-strain-rate, low-temperature domain. The ideal thermal processing range of the alloy is 350–500 °C at strain rates ranging from 0.001 to 0.016 s⁻¹. Particle-stimulated nucleation and discontinuous dynamic recrystallization are both verified to be responsible for the recrystallized microstructure of the alloy. The recrystallized grains exhibit a relatively random crystallographic orientation. As recrystallization proceeds, the texture gradually transitions from a typical [0001] texture in the compression direction to a random texture accompanied by decreased texture intensity. This work sheds new light on the thermo-mechanical processing of high-modulus Mg alloys, which could help design suitable processing techniques for related materials. Full article

Aiming at the problem of random environment interference in the process of strategy interaction and the behavioral evolution of an aerial attack–defense game, this paper considers the influence of the difference in the performance and value between both game players in terms of strategy evolution; explores the randomness of the complex battlefield environment, the uncertainty of the behavioral state of game players, and the limitations of the emergent situation; constructs a mathematical model of the stochastic evolution of an aerial-coordinated attack–defense game in uncertain environments; and studies the stability of the strategy interaction and behavioral decision-making process of both players of the aerial attack–defense game. Simulation results show that many factors of the performance and value between both game players have a greater impact on the strategy evolution trend in both game players, which not only causes changes in the results of the strategy selection but also affects the rate of strategy evolution for the game players. In addition, random environmental factors cause a certain degree of interference to the strategy evolution process of the game players, which usually accelerates the game players’ strategy evolution rate and greatly affects the evolution process of the game players’ strategy. This study can provide a theoretical basis and feasible reference for improving mission decision-making, response mechanisms, and system modeling of an aerial attack–defense game, which has important theoretical value and practical significance. 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

In the digital age, personalized recommendation systems have become crucial for information dissemination and user experience. While traditional systems focus on accuracy, they often overlook diversity, novelty, and serendipity. This study introduces an innovative recommendation system model, Time-based Outlier Aware Recommender (TOAR), designed to address the challenges of content homogenization and information bubbles in personalized recommendations. TOAR integrates Neural Matrix Factorization (NeuMF), Bidirectional Long Short-Term Memory Networks (Bi-LSTM), and Mean Shift clustering to enhance recommendation accuracy, novelty, and diversity. The model analyzes temporal dynamics of user behavior and facilitates cross-domain knowledge exchange through feature sharing and transfer learning mechanisms. By incorporating an attention mechanism and unsupervised clustering, TOAR effectively captures important time-series information and ensures recommendation diversity. Experimental results on a news recommendation dataset demonstrate TOAR’s superior performance across multiple metrics, including AUC, precision, NDCG, and novelty, compared to traditional and deep learning-based recommendation models. This research provides a foundation for developing more intelligent and personalized recommendation services that balance accuracy with content diversity. Full article

Recycling’s value in conserving scarce resources, avoiding environmental damage to the land, and reducing energy consumption is well known. This research aims to develop a composite that uses recycled reinforcement that was formed through an in situ method to build confidence in the usage of recycled materials. Thus, in connection with defense and aerospace industry applications, aluminum composite alloys receive more interest due to their light weight and high strength with improved mechanical properties; therefore, this research focuses on the fabrication of in situ-developed recycled TiC (r-TiC)-reinforced AlZnMgCu composites, i.e., new recycled materials. Experiments were conducted to determine the synthesized composites’ microstructural, mechanical, tribological, and corrosion properties. The microstructural study showed that r-TiC was distributed uniformly along the grain boundaries until the addition of 12% r-TiC. However, the accumulation of reinforcements began at 14% r-TiC addition and became more aggregated with subsequent increases in the percentage addition of r-TiC. The mechanical and tribological tests showed that the composite with 14% r-TiC was superior to all other compositions, with 60% improved mechanical qualities and the lowest wear rate of 0.0007 mm3/m. Composites containing 2% r-TiC showed the best corrosion resistance, an increase of 22% over AlZnMgCu, without reinforcement. Full article

Cytotoxicity is a critical parameter for materials intended for biological applications, such as food packaging. Shape-memory polyurethanes (SMPUs) have garnered significant interest due to their versatile properties and adaptability in synthesis. However, their suitability for biological applications is limited by the use of aromatic isocyanates, such as methylene diphenyl 4,4′-diisocyanate (MDI) and toluene diisocyanate (TDI), which are commonly used in SMPU synthesis but can generate carcinogenic compounds upon degradation. In this study, thermo-responsive shape-memory polyurethanes (SMPUs) were synthesized using poly(tetramethylene ether) glycol (PTMG) and castor oil (CO) as a chain extender with four different isocyanates—aromatic (MDI and TDI), aliphatic (hexamethylene diisocyanate [HDI] and isophorone diisocyanate [IPDI])—to evaluate their impact on polyurethane cytotoxicity. Cytotoxicity assays were conducted on the synthesized SMPU samples before and after exposure to light-induced degradation. The results showed that prior to degradation, all samples exhibited cell proliferation rates above 90%. However, after degradation, the SMPUs containing aromatic isocyanates demonstrated a drastic reduction in cell proliferation to values below 10%, whereas the samples with aliphatic isocyanates maintained cell proliferation above 70%. Subsequently, the influence of polyol chain length was assessed using PTMG, with molecular weights of 1000, 650, and 250 g·mol⁻¹. The results indicated that the SMPUs with longer chain lengths exhibited higher cell proliferation rates both before and after degradation. The thermal and mechanical properties of the SMPUs were further characterized using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermomechanical analysis (TMA), providing comprehensive insights into the behavior of these materials. Full article

Grouting technology in overburden separation is recognized as an effective method to prevent surface subsidence and reuse solid waste. This study used mechanical analysis to explore deflection characteristics of key strata and accurately predict and control surface subsidence. Conceptualizing the coal–rock mass beneath the key strata as an elastic foundation, we developed a method to calculate the elastic foundation coefficients for various regions and established an equation for key strata deflection, validated through discrete element numerical simulations. This simulation also examined subsidence behavior under different grout injection–extraction ratios. Additionally, combining the equivalent mining height theory with the probability integral method, we formulated a predictive model for surface subsidence during grouting. Applied to the 8006 working face of the Wuyang Coal Mine, this model was supported by numerical simulations and field data, which showed a maximum surface subsidence of 546 mm at a 33% injection–extraction ratio, closely matching the theoretical value of 557 mm and demonstrating a nominal error of 2%. Post-grouting, the surface tilt was reduced to below 3 mm/m, meeting regulatory standards and eliminating the need for ongoing surface structure maintenance. These results confirm the model’s effectiveness in forecasting and controlling surface subsidence with grouting. The study can provide a basis for determining the grouting injection–extraction ratios and evaluating the effectiveness of surface subsidence control in grouting into overburden separation projects. Full article

The profession of airline pilots is characterized by high levels of stress and a significant risk of burnout. The health emergency period has exacerbated these challenges to health and well-being, with long COVID adding further strain to aviation professionals even in the post-pandemic scenario. In this context, it is essential to promote positive organizational behaviors to reconcile individual well-being with work performance. This study aimed to explore the mechanisms linking burnout to work performance behaviors (i.e., proficiency, adaptivity, and proactivity) among pilots, hypothesizing the mediating role of continuous learning behaviors. Based on the Conservation of Resources theory, we posited that burnout depletes pilots’ resources, thereby hindering continuous learning and reducing performance behaviors. Moreover, this study examined the work-related stress factors that could affect burnout and the consequences of performance behaviors on actual performance measured by a flight simulator. Data were collected from 123 pilots through an online survey and analyzed using path analysis. The results revealed that continuous learning mediated the relationship between burnout and work performance behaviors. Furthermore, work-related stress factors were significantly related to burnout, and work performance behaviors were linked to flight simulator performance. Our findings underscored the critical role of continuous learning in explaining the adverse effects of burnout on performance. These insights could inform targeted interventions to promote continuous learning and stress management among aviation professionals, ensuring sustained performance and well-being in the long term. Full article

The adsorption characteristics of CH₄ have an important influence on gas content prediction, gas extraction, and hazard prevention. Therefore, we explored the mechanism of CH₄ adsorption under the action of water and temperature to grasp the influence of water and temperature on the adsorption characteristics of CH₄. In this paper, a giant, regular-system Monte Carlo method is used to simulate the CH₄ adsorption behavior at the molecular level under different temperatures, water contents, and the coupling of both. The results indicate that an empirical formula for the coupling effect of temperature and water content on CH₄ adsorption was obtained. The impact of different effects on CH₄ adsorption is as follows: coupling effect > single temperature effect > single water content effect. The optimal combination is at a temperature of 363 K and a water content of 8.31%. Compared with the CH₄ adsorption capacity without water at room temperature, the CH₄ adsorption capacity is reduced by 68.04% under the coupling effect of the optimal combination. Temperature has a negative effect on the adsorption of CH₄, and temperature changes the adsorption capacity by changing the average molecular kinetic energy of CH₄. The reason why the increase in H₂O reduces the adsorption capacity of CH₄ is that the interaction between H₂O and the oxygen-containing functional groups of coal is stronger than that of CH₄. As the water content increases, the adsorption heat decreases, thereby inhibiting the adsorption of CH₄. In addition, H₂O has a smaller molecular dynamics radius as compared to CH₄; the larger the free volume and surface area in the pore structure, the more adsorption pores it occupies, resulting in a more significant reduction in the adsorption of CH₄. Full article

Designing a wound dressing with controlled uptake, antibacterial, and proper biocompatibility is crucial for the appropriate wound healing process. In this study, alginate/tetracycline (Alg/TC) beads were produced and embedded into chitosan/pluronic/agarose semi-interpenetrating polymer network hydrogel, which serves as a potential biocompatible dressing for treating skin wounds. The effect of pluronic content on the porosity, swelling, mechanical characteristics, and degradation of the hydrogel was investigated. Furthermore, the impact of Alg beads on TC release was subsequently examined. In the absence of Alg beads, faster release was observed. However, after incorporating beads into the hydrogels, the release was sustained. Particularly, the hydrogel containing Alg beads exhibited a nearly linear release, reaching 74% after 2 days in acidic media. The antimicrobial activity and biocompatibility of the hydrogel were also evaluated to assess the capability of the TC-loaded hydrogels for wound dressing applications. The hydrogel demonstrated efficient antibacterial features against Gram-positive and Gram-negative bacteria. Additionally, the sample behavior was evaluated against exposure to yeast. Furthermore, based on biocompatibility studies using HFF2 cells, the TC-loaded hydrogel exhibited remarkable biocompatibility. Overall, this novel composite hydrogel shows remarkable biocompatibility and antibacterial activities which can be used as a great potential wound dressing to prevent wound infections due to its effective inhibition of bacterial growth. Full article

A foundation pit’s excavation area, which is determined by its radius in a circular foundation pit, exerts a considerable influence on the pit’s behavior. Using a full-scale experiment on a circular foundation pit retained by a prefabricated recyclable supporting structure (PRSS), this study develops a series of axisymmetric numerical models to systematically investigate the influence of excavation radius on the pit’s deformation, stress, and stability. Furthermore, simulation results from axisymmetric models are compared with those from plane strain models to illustrate the influence mechanism. The results show that at a given excavation depth, the deflection and bending moments of the supporting piles, the earth pressure on the non-excavation side, and ground surface settlement increase with the enlarged excavation radius, but the increase rate progressively decreases. However, the foundation pit’s safety factor decreases with an increasing excavation radius and gradually stabilizes. When the excavation radius exceeds 50 m, its influence on the foundation pit’s behavior significantly diminishes. The axisymmetric model results closely approximate those from the plane strain models, suggesting that the spatial arching effects of the circular foundation pit can be disregarded. Full article

In this study, bentonite clay was modified through silane treatment and calcination to enhance its compatibility with basalt fiber (BF) and epoxy in multiscale composites. The as-received bentonite (ARB) was subjected to silane treatment using APTES, producing silane-modified bentonite (STB), while calcination yielded calcined bentonite (CB). The modified clays were incorporated into basalt fiber-reinforced epoxy (BFRP) composites, which were fabricated using the vacuum-assisted resin transfer method (VARTM). Analytical techniques, including X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy, confirmed the structural changes in the clays. BET surface area analysis revealed a 314% increase in the surface area of STB and a 176% increase for CB. The modified clays also demonstrated reduced hydrophilicity and swelling behavior. Thermogravimetric analysis (TGA) indicated a minimal improvement in thermal stability, with the degradation onset temperatures increasing by less than 3 °C. However, tensile tests showed significant gains, with CB- and STB-reinforced composites achieving 48% and 21% higher tensile strength than ARB-reinforced composites. Tribological tests revealed substantial reductions in wear, with CB- and STB-reinforced composites showing 90% and 84% decreases in the wear volume, respectively. These findings highlight the potential of modified bentonite clays to improve the mechanical and wear properties of basalt fiber–epoxy composites. Full article

A study combining multiscale numerical simulation and low-velocity impact (LVI) experiments was performed to explore the comprehensive effects on the impact-resistance of EMAA filaments incorporated as thermoplastic healing agents into a plain woven composite. A multiscale micro–meso–macro modeling framework was established, sequentially propagating mechanical performance parameters among micro–meso–macro models. The equivalent mechanical parameters of the carbon fiber bundles were predicted based on the microscopic model. The mesoscopic representative volume element (RVE) model was crafted by extracting the actual architecture of the monolayer EMAA filaments encompassing the plain woven composite. Subsequently, the fiber and matrix of the mesoscopic model were transformed into a monolayer-equivalent cross-panel model containing monolayers aligned at 0° and 90° by local homogenization, which was extended into a macroscopic equivalent model to study the impact-resistance behavior. The predicted force–time curves, energy–time curves, and damage profile align closely with experimental measurements, confirming the reliability of the proposed multiscale modeling approach. The multiscale analysis reveals that the EMAA stitching network can effectively improve the impact-resistance of plain woven composite laminates. Furthermore, there exist positive correlations between EMAA content and both impact-resistance and self-healing efficiency, achieving a self-healing efficiency of up to 98.28%. Full article

The aim of the present in vitro comparative study is to validate a novel composite polymer, named “ONLY”, developed to overcome the mechanical drawbacks of conventional, metal-reinforced poly(methyl methacrylate) (PMMA) interim restoration. Ten interim restorations were designed and fabricated (five in the composite “ONLY” group, and five in the metal-reinforced PMMA group). All the samples were screwed into the prototype models, simulating a complete edentulous mandible rehabilitated with six straight implants. Outcome measures were break point (load, N) and displacement (mm) through a static compression test, and material behavior through a dynamic cyclic test method (fatigue test). A total of 20 samples were tested (10 for static and 10 for dynamic). In each group, five samples (test and control) were used. All the specimens completed the mechanical tests, as planned. There was no statistically significant difference between groups for any test. In the test group, the break point was 1953.19 ± 543.73 N, while it was 2031.10 ± 716.68 N in the control group (p = 0.775). The displacement was 1.89 ± 0.34 mm in the test group and 1.98 ± 0.75 mm in the control group (p = 0.763). Using the dynamic cyclic test method, in the control group the mean load was 2504.60 ± 972.15 N, while in the test group the mean load was 3382.00 ± 578.50 N. The difference between groups was 877.40 ± 579.30 N (p value = 0.121). Within the limitations of this in vitro study, the novel composite polymer can be used to immediately load dental implants. Further clinical research is needed to confirm these preliminary results. Full article

Using first-principles density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations, we performed this study on the phase stability, the intrinsic redox stability, and the Li⁺ conductivity of Li₁₀Ge_xMo_1-xP₂S₁₂ (x = 0~1) superionic conductors. Molybdenum (Mo) is expected to replace expensive germanium (Ge) to lower tmaterial costs, reduce sensitivity to ambient water and oxygen, and achieve acceptable Li⁺ conductivity. The ab initio first principle molecular dynamics simulations show that room-temperature Li⁺ conductivity is 1.12 mS·cm⁻¹ for the Li₁₀Ge_0.75Mo_0.25P₂S₁₂ compound, which is comparable to the theoretical value of 6.81 mS·cm⁻¹ and the experimental measured one of 12 mS·cm⁻¹ of the Li₁₀GeP₂S₁₂ (LGPS) structure. For Li₁₀Ge_xMo_1-xP₂S₁₂ (x = 0, 0.25, 0.5 and 1) compounds, the density of states and the projection fractional wave state density were calculated. It was found that when Ge atoms were partially replaced by Mo atoms, the band gap remained unchanged at 2.5 eV, but deep level defects appeared in Mo-substituted compounds. Fortunately, this deep level defect is difficult to ionize at room temperature, so it has no effect on the electronic conductivity of Mo substitute compounds, making Mo substitution a suitable solution for electrolyte materials. The projection fractional wave state density calculation shows that the covalent bond between Mo and S is stronger than that between Ge and S, which reduces the sensitivity of Mo-substituted compounds to water and oxygen contents in the air. In addition, the partial state density coincidence curve between Li and S elements disappears in the 25% Mo-substituted compound with energies of 4–5 eV, indicating that the Li₂S by-product is decreased. Full article