Search Results (645)

This work introduces a compact multi-resonant metamaterial absorber designed to achieve efficient electromagnetic absorption over several microwave frequency bands. The proposed configuration is based on a hybrid resonator arrangement that promotes strong electromagnetic interaction and enables multiple resonant modes within a single unit cell. Consequently, six distinct absorption peaks are obtained at 2.4, 5.21, 6.88, 9.77, 12.61, and 14.99 GHz, covering S-, C-, X-, and Ku-band applications. The absorber exhibits high absorption performance, exceeding 97% across most operating frequencies and slightly lower value is observed of 91.13% at 12.61 GHz, which indicates effective impedance matching with free space and efficient energy dissipation mechanisms. The absorption characteristics are further examined through surface current distributions, electric field confinement, and effective medium analysis, demonstrating that the multi-band response originates from the interaction of multiple resonant elements and intrinsic material losses. Moreover, the proposed structure maintains stable performance for different polarization angles and oblique wave incidence, confirming its polarization-insensitive and angularly stable behavior. To validate the design, a prototype is fabricated and experimentally characterized using a free-space measurement setup, showing close agreement with the simulated results. The compact geometry, low fabrication cost, and scalability of the proposed absorber make it a promising candidate for applications such as electromagnetic interference mitigation, radar cross-section reduction, and modern wireless communication systems. Full article

This study evaluated how two commercial egg types (free-range and barn-laid) influence the physical, compositional, and rheological properties of egg white and yolk in raw and grilled states. Free-range eggs showed stronger correlations between external dimensions and internal composition, suggesting potential for nondestructive grading, whereas barn eggs exhibited heavier shells but weaker morphometric–composition relationships. Haugh units differentiated production systems, and yolk redness was the only color parameter clearly associated with free-range origin. Mechanical tests revealed that barn eggs had shells capable of absorbing more energy during rupture. Rheological measurements showed matrix-dependent behaviors: in raw samples, egg white behaved as a weakly structured viscoelastic fluid, while yolk exhibited characteristics of a concentrated lipoprotein emulsion. Stress, frequency, and temperature sweeps revealed contrasting behaviors between the two commercial egg types: barn-laid eggs displayed a stronger egg-white protein network, whereas free-range eggs showed a more reinforced yolk lipoprotein matrix under the conditions evaluated. Yolk behavior fitted the weak gel model with excellent accuracy (R² ≈ 1), while egg white did not. Steady shear and three-step tests confirmed pronounced shear thinning and thixotropic behavior in both matrices, with barn eggs showing higher viscosities but lower structural recovery. Thermal treatment reduced the strong rheological differences between raw egg white and yolk, yet production system effects persisted. All grilled samples behaved as weak gels, with barn egg whites forming stiffer networks and free-range yolks generating more elastic, cohesive, and energy-absorbing gels. A trend toward higher MUFA levels was observed in raw free-range yolks. Microscopy further clarified how production system shapes the structural and functional behavior of egg matrices. Full article

CuO thin layers were synthesized using the sol–gel method and deposited onto glass substrates through the dip-coating technique. The impact of annealing temperatures on the structural, optical, and electrical characteristics of the developed CuO thin layers was comprehensively assessed through X-ray diffraction, UV–visible spectrophotometry, and four-point techniques, respectively. X-ray diffraction analysis revealed the formation of CuO thin layers with a distinctive monoclinic tenorite phase structure. The UV–visible spectrophotometer results demonstrated a decrease in transmittance from approximately 30% to about 7% as the annealing temperature increased from 200 °C to 400 °C. The semiconducting properties exhibited temperature-dependent variations, with the band gap narrowing from 1.70 to 1.48 eV as the temperature increased from 200 to 400 °C. Additionally, the electrical conductivity of the CuO layers exhibited a significant increase from 48 to 61 S.m⁻¹ over the same temperature range. Collectively, the findings suggest that an annealing temperature of 400 °C is optimal for achieving well-crystallized CuO layers with desirable characteristics, including high absorbance, low transmittance, a reduced energy band gap, and enhanced electrical conductivity. These results underscore our ability to manipulate CuO properties, offering insights for tailoring them to meet specific requirements, particularly in the context of gas sensor applications. Full article

The auxetic reentrant structure, one of the most widely studied negative Poisson’s ratio structures for its geometric simplicity, has long seen limited applications due to challenges emanating from its inherent design when built from a single rigid or flexible material. This paper aims to address these challenges by taking advantage of dual-material extrusion technology and density gradient design strategy. Two density gradient reentrant auxetic structures are proposed and fabricated using material extrusion additive manufacturing in single-material (flexible) and dual-material (rigid/flexible) modes, with the introduction of a novel dual-material interface design. In-plane compression tests are carried out to assess the energy absorption characteristics of the structures. The results show that dual-material structures exhibit higher yield stress, mean crushing force, peak crushing force, and maximum crushing force, as well as superior specific energy, energy dissipation, and energy release compared to single-material structures. Dual-material structures also demonstrate high lateral stiffness, minimizing elastic instability, a highly desirable feature for reusable energy-absorbing structures with high shape recovery capability. The results substantiate the significance of the synergy between the dual-material and density gradient designs proposed in this study. Overall, the key findings of the study may serve as a reliable reference for the design of future lightweight energy-absorbing structures. Full article

The continuous monoculture in Populus × euramericana ‘Neva’ plantations is closely related to the accumulation of phenolic acids in the soil, and these phenolic compounds exert a certain influence on plant nitrogen uptake. Leguminous plants can replenish soil nitrogen through biological nitrogen fixation, which is of great significance for enhancing plant productivity. This study employed different concentrations of phenolic acid treatments (0T, 0.5T, 1.0T, 1.5T, 2.0T) to analyze the photosynthetic characteristics of five phenolic compounds in a poplar–soybean (Glycine max (L.) Merr.) intercropping system, thereby providing a basis for biological management strategies aimed at increasing the yield of poplar monoculture stands. The results indicate that (1) P_n in poplar monoculture, soybean monoculture, and soybean intercropping all decreased as phenolic acid concentration increased, whereas P_n in poplar intercropping increased with rising phenolic acid concentration. Under treatments ranging from 0T to 1.5T, the decrease in P_n in the pure poplar, pure soybean, and intercropped soybean systems was primarily due to stomatal limitations, whereas under treatments ranging from 1.5T to 2.0T, it was primarily due to non-stomatal limitations. (2) Poplar, soybean, and soybean-intercropped poplar adapted to environmental stress by dissipating excess light energy absorbed by PS II as heat. The intercropping system effectively optimized poplar fluorescence parameters and mitigated the damage caused by phenolic acid stress to its photosynthetic machinery. (3) Chlorophyll A, chlorophyll B, and total chlorophyll in poplar and soybean leaves were significantly inhibited. (4) The biomass of poplars grown in monoculture decreased as phenolic acid concentration increased, whereas the biomass of poplars in intercropping showed the opposite trend. It is evident that, under phenolic acid conditions, poplar–soybean intercropping can mitigate the effects of phenolic acid stress to a certain extent. Full article

Truss-like and minimal surface-based cells are among the promising candidates for novel impact-resistant structural designs. However, the influence of cell configurations on impact resistance performance remains unclear. In this paper, the energy absorption characteristics of three truss-like cells (BCC, Fluorite, and Diamond) and three minimal surface cells (Gyroid, Primitive, Diamond) are systematically compared using quasi-static compression experiments and refined numerical models. Experimental results indicate that minimal surface cells possess clearly superior specific energy absorption performance. Specifically, the Gyroid (G-surface) exhibits a specific energy absorption (25 kJ/kg) approximately 2.3 times greater than the highest value among truss-like cells (11 kJ/kg), accompanied by an extended plateau strain by about 20%. Additionally, due to stress concentration at joints, truss-like cells show notably lower plateau forces compared to minimal surface cells. However, truss-like cells demonstrate better manufacturing precision and quality control, as evidenced by a relatively small average weight deviation (about 1.2%). Furthermore, numerical simulations were conducted to explore differences in deformation mechanisms between two representative cells. Results reveal that the BCC structure absorbs energy through localized shear band formation induced by point plastic hinges, whereas the Primitive (P-surface) minimal surface structure achieves more uniform plastic deformation via distributed line plastic hinges. Finally, impact simulations of protective structures show that the maximum stress in the P-surface-filled structure is reduced by 4.6% compared to the BCC-filled structure, and stress distribution uniformity is improved by 37%. The findings from this study provide valuable references and data support for future anti-impact structural designs. Full article

CuIn₅Se₈ is reported as a remarkable copper-deficient layer that contains ordered vacancy compounds (OVCs) for high-efficiency chalcopyrite-based solar cells; however, the understanding of its carrier characteristics has remained limited. OVCs could naturally form on the surface of chalcopyrite absorber. In this study, the carrier dynamics characteristics of OVCs were investigated by constructing a junction consisting of chalcopyrite absorber and CdS buffer layer. At first, the band structure of CuIn₅Se₈ was studied to determine the bandgap properties. Then, thermodynamic stability, defect formation energy, defects and carrier concentration, defect transition energy level of CuIn₅Se₈ and its Cd doping state (caused by CdS) were comparatively studied. The results suggest that Cd doping has different effects on the defect and carrier characteristics of OVCs with various chemical potentials. However, the OVC always remains n-type under the whole thermodynamically stable region, with contribution from the hallow-level In_Cu donor defect. Finally, the OVC’s carrier dynamics characteristics were assessed using the collected defect and carrier data. It is indicated that the OVC layer may contribute to the formation of a p-n homojunction in solar cells. Under selenium-rich conditions, the OVC layer increases the carrier density on the n-type side of p-n junction nearly 30-fold, which helps reduce the difference in carrier density and minority current density between two sides of the p-n junction. The conversion efficiency of the solar cell with OVC shows a 7.25% improvement when compared to the control. The distinct behavior of OVCs may serve as a valuable reference for the creation or improvement of a related functional film layer or device. Full article

Conventional uniform-thickness expansion-tube energy-absorbing structures suffer from excessively high initial peak crushing forces (IPCFs) and sub-optimal energy absorption efficiency. Inspired by the gradient stiffness characteristics of the inter node-to-node structure in Buddha’s Belly Bamboo, this study proposed an expansion-tube energy-absorbing structure design featuring a gradient stiffness. An LS-DYNA finite element simulation model was first established, validated through experimental results, and subsequently subjected to multi-objective optimization. The analysis results demonstrate that the stiffness-gradient expansion-type energy-absorbing structure designed in this study not only effectively reduces the IPCF during energy absorption but also further enhances its buffering and specific energy absorption (SEA). Full article

When ground transportation is disrupted by natural disasters, airdropped rescue vehicles require energy-absorbing cushioning devices to prevent landing impact damage. Thin-walled circular tubes are preferred for their high energy absorption capacity and structural efficiency. However, to reduce platform force fluctuations and decrease residual stroke after compression, thereby avoiding unbalanced loading and ensuring post-landing mobility, slots are introduced into the tube wall, which renders the mean crushing force (MCF) difficult to predict accurately using conventional methods. To address this issue, this paper proposes a physics–data-driven method for predicting the energy absorption characteristics of slotted thin-walled circular tubes. The engineering scenario is introduced, followed by comparative validation via drop weight tests and impact simulations to obtain a sample set via design of experiments (DOE). A multi-layer perceptron (MLP) neural network then augments the samples to generate a dataset. Dimensional analysis yields candidate MCF prediction equations, whose forms and coefficients are determined via a physics–data-driven approach. Weighted graph encoding transforms the equation-solving problem into a graph optimization problem to reduce the computational complexity, and an improved differential evolution (DE) algorithm with a dual-adaptive mutation operator (DSADE) adjusts the parameters and accelerates convergence. The resulting MCF prediction formula, combined with drop test requirements as the optimization objective, achieves a simulation relative error below 5%. These parameters also satisfy engineering requirements in actual airdrop tests, confirming the method’s effectiveness in predicting the energy absorption characteristics of slotted thin-walled tubes. Full article

In the extraction of shale gas and oil, the vibration characteristics of the drill string significantly influence wellbore quality, potentially leading to wellbore instability, excessive tool wear, and diminished drilling efficiency. This study tackles the challenges associated with drill string vibrations by developing an integrated technical framework of multi-field coupled dynamic modeling, Sobol-based key parameter identification, and NSGA-II-driven multi-objective structural optimization, and proposes a synergistic vibration suppression strategy combining structural parameter adjustment and hydraulic damper configuration based on multibody dynamics and finite element analysis. Initially, a dynamic model that accounts for the coupling between the wellbore and the drill string is developed to scrutinize the impact of various vibration modes on wellbore quality. Subsequently, detrimental vibrations are mitigated through the optimization of structural parameters, including but not limited to stiffness distribution and the strategic placement of vibration absorbers. Finally, the efficacy of the optimized design is substantiated through numerical simulations and field experiments. The results demonstrate that the optimized drill string achieves a simulation average reduction of 30% in lateral vibration amplitude across the rotational speed range of 60–120 RPM and a simulation average improvement of 25% in the attenuation of axial vibration energy. These enhancements notably bolster drilling stability and elevate wellbore quality. This research furnishes both theoretical and technical underpinnings for the efficient development of shale gas and oil resources. Full article

Background and objectives: Articular cartilage provides low-friction articulation across joint surfaces, distributes loads, and absorbs stress, all of which are crucial mechanical functions of joints. Changes in the mechanical characteristics of cartilage are among the first signs of degenerative joint disease, and they are especially important for athletes who are subjected to high-impact, high-magnitude loading on a regular basis. The objective of this study was to: (i) compare the mechanical characteristics of tibiofemoral cartilage in healthy and osteoarthritic conditions across medial and lateral anatomical compartments; and (ii) use nonlinear phenomenological viscoelastic modeling in conjunction with unconfined compression testing to characterize compartment-specific viscoelastic behavior. Materials and Methods: Forty-six human tibiofemoral cartilage samples were collected during knee surgeries and classified as healthy (n = 17) or osteoarthritic (n = 29) and as medial (n = 26) or lateral (n = 20). Quasi-static unconfined compression tests were performed at 1 mm/min to obtain stress–strain responses, Young’s modulus, maximum compressive stress, and energy absorption. Viscoelastic behavior was analyzed using a nonlinear phenomenological viscoelastic model. Appropriate parametric or non-parametric statistical tests and effect size measures were applied. Results: Osteoarthritic cartilage’s stiffness and energy absorption were significantly higher than those of healthy tissue (p < 0.05). Medial cartilage exhibited significantly greater stiffness and stress than lateral cartilage (p < 0.001). The nonlinear phenomenological viscoelastic model provided an excellent fit (R² > 0.999). Conclusions: The mechanical profile of osteoarthritic tibiofemoral cartilage is characterized by pathological mechanical remodeling and increased stiffness. Greater mechanical susceptibility in the medial compartment supports the significance of cartilage biomechanical properties as sensitive indicators of early degeneration and osteoarthritis risk in athletic populations. Full article

An eco-friendly green synthesis approach was employed to produce copper nanoparticles (CuNPs) using a polyherbal extract derived from two medicinally important plant species, Hygrophila auriculata (Schumach.) Heine and Leucas aspera (Willd.) Link. The plant extracts were initially subjected to phytochemical screening to identify bioactive constituents potentially involved in nanoparticle synthesis. The synthesized CuNPs were characterized using UV-visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), gas chromatography–mass spectrometry (GC-MS), field-emission scanning electron microscopy coupled with energy-dispersive X-ray analysis (FESEM-EDAX), X-ray diffraction (XRD), and thin-layer chromatography (TLC). UV-visible spectroscopy revealed a characteristic absorption peak at 233.6 nm. FTIR analysis indicated the presence of functional groups associated with nanoparticle reduction and stabilization, whereas FESEM imaging showed predominantly spherical particles with sizes ranging 63–68 nm. Elemental composition was confirmed using EDAX analysis. XRD analysis demonstrated polycrystalline nature of the CuNPs, with an average crystallite size of 11.5 nm. GC-MS analysis and phytochemical screening further confirmed the presence of bioactive compounds, whereas TLC analysis revealed differences in mobility between the plant extract and synthesized CuNPs. Antibacterial activity of the synthesized CuNPs was evaluated using the agar well diffusion method against clinically relevant bacterial strains, including those of Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Streptococcus pyogenes. The polyherbal-derived CuNPs produced larger inhibition zones than the individual plant extracts, particularly against multidrug-resistant pathogens such as P. aeruginosa and S. aureus. Additionally, the nanoparticles exhibited concentration-dependent antioxidant activity in the 2,2-diphenyl-1-picrylhydrazyl assay at concentrations ranging 10–50 mg/mL, with radical scavenging activity increasing from 29.9% to 76.5% and a corresponding decrease in absorbance from 0.698 to 0.234 (p < 0.05). Cytotoxic evaluation in HepG2 cells after 48 h of exposure demonstrated dose-dependent morphological changes and reduced cell viability. These findings suggest that polyherbal-derived CuNPs possess antibacterial, antioxidant, and cytotoxic properties with potential relevance for biomedical applications. Full article

Cu₂ZnSn(S,Se)₄ (CZTSSe) is a candidate thin-film photovoltaic material; however, its performance is restricted by innate defect-induced nonradiative recombination. Low-concentration Ge doping has been identified as an efficient way to mitigate these defects, but the selenization temperature remains an important process parameter that governs the structure and optoelectronic characteristics of CZTSSe absorbers. In the present work, low-concentration Ge-doped Cu₂ZnSn_0.95Ge_0.05S₄ (CZTGS) precursor films were synthesized through a green, n-butylammonium butyrate-based solution approach. The effects of the selenization temperature (530–570 °C) on the microstructure, composition, and photovoltaic performance of Cu₂ZnSn_0.95Ge_0.05(S,Se)₄ (CZTGSSe) films and devices were comprehensively investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectrometer (EDS), atomic force microscopy (AFM) were performed to comprehensively characterize the synthesized samples, and the results suggested that the selenization temperature dramatically altered the film grain growth, crystallinity, elemental retention and surface roughness. Specifically, the film that underwent selenization at 550 °C presented the best crystallinity, which was accompanied by large-scale even grains, efficient Ge⁴⁺ addition to the kesterite lattice and the lowest surface roughness. These better properties in terms of structure and composition resulted in the lowest carrier transport resistance (R_s = 8.6 Ω∙cm²), improved recombination resistance (R_j = 5.9 kΩ∙cm²), inhibited nonradiative recombination, and prolonged carrier lifetime (τ_EIS = 35.8 μs). Therefore, the resulting CZTGSSe thin-film solar cell had an 8.69% better power conversion efficiency (PCE), while its open-circuit voltage (V_OC) was 0.42 V, the fill factor (FF) was 55.51%, and the short-circuit current density (J_SC) was 37.71 mA·cm⁻². Our results elucidate the mechanism by which the selenization temperature regulates low-concentration Ge-doped kesterite devices and provide more insights into the optimization of processes for cost-effective, high-performance, and green thin-film solar cells. Full article

We present a checkerboard metasurface integrating interleaved Helmholtz resonator arrays with distinct geometrical parameters, enabling decoupled dual-band coherent perfect absorption (CPA) in both in-phase and anti-phase excitation conditions. Full-wave simulations confirm that the proposed structure achieves absorption rates exceeding 99% at 2.904, 3.024, 3.788 and 3.856 THz, corresponding to two pairs of resonant modes enabled by the asymmetric transmission characteristics. Notably, by actively manipulating the relative phase difference between the two excitation modes, the absorption frequencies associated with each CPA channel can be independently and continuously tuned. Benefiting from the planar checkerboard configuration, which combines compact geometry, suppressed mutual coupling, and balanced energy distribution, the metasurface achieves stable and independent dual-band absorption characteristics. The proposed design provides a promising pathway for the development of terahertz coherent absorbers with enhanced frequency stability and spectral flexibility of dual-mode operations, offering strong potential for practical photonic and electromagnetic applications. Full article

Under severe ice and snow weather, ice-covered pantograph–catenary arcs affect the safe operation of high-speed trains. This study investigates the impact of ice-covered arc electrical characteristics, plasma parameters, and material ablation mechanisms. By constructing a comprehensive pantograph–catenary icing experimental platform, arc voltage, current signals, high-speed dynamic images, and emission spectra were synchronously collected under different icing thicknesses ranging from 0 to 15 mm. Research indicates that ice coverture causes frequent “extinction–reignition” phenomena during the arc initiation stage due to the latent heat absorbed by melting ice, significantly reducing the initial stability of arc combustion. Spectral analysis confirms that the arc excitation temperature and energy density are positively correlated with the concentration of hydrogen ions produced by water vapor ionization, reaching a peak under the 5 mm icing condition. Experimental results show that the average energy density of ice-covered arcs is approximately double that of the non-iced condition, causing the ablation pits on the carbon strip to exhibit characteristics of greater depth and wider copper deposition zones. This study reveals the unique mechanisms and damage characteristics of icing pantograph–catenary arcs, providing an important basis for the safe design and maintenance of pantograph–catenary systems in high-cold railway environments. Full article