This study theoretically investigates an optical fiber structure coated with a bilayer film of zinc oxide (ZnO) and lithium fluoride (LiF) for ethanol detection. The ZnO thin film exhibits lossy mode resonance (LMR) in the visible and near-infrared spectrum (400 – 1500nm), which serves as the basis for designing a refractive index (RI) sensor by appropriately selecting the ZnO thickness. To further enhance the resonance characteristics, a dielectric layer of LiF is introduced between the unclad fiber core and the ZnO coating. It Improves phase matching and generates sharper LMR dips with a narrower full width at half maximum. The proposed structure is also analyzed using two different core materials: pure silica and 4% Ge-doped silica. A comparative study of their sensing performance is also presented. Its sensing performance is examined by varying the thicknesses of the ZnO and LiF layers to identify the optimal structural parameters. The designed fiber-optic sensor is then evaluated for detecting ethanol concentrations in ethanol–water mixtures (RI =1.33 for 0% ethanol and RI =1.36 for pure ethanol) using both s- and p -polarized incident light. Calibration curves demonstrating the relationship between resonant wavelength shifts and the RI of the sample are presented. This sensor achieves excellent sensitivities of 1163 nm RIU ^−1 for s -polarization and 1475 nm RIU ^−1 for p -polarization, making it promising for the development of High-Figure of Merit biochemical sensors for potential applications.
Additive manufacturing of architected polymer reinforcements is an emerging geometry-driven approach to improve the mechanical performance of cementitious materials. In contrast to conventional methods, it enables controlled architectures where load transfer and crack propagation are governed by topology and spatial distribution. However, comparisons are difficult due to variability in architectures, materials, processes and testing conditions. This review covers advances in 3D-printed polymer reinforcements, such as discrete and graded lattices, TPMS, auxetic, and origami-inspired structures. The reported improvements are mainly related to ductility, post-cracking response, energy absorption (up to 853%) and flexural toughness (up to 23×), with some systems showing a transition toward strain-hardening behavior. However, these values are strongly influenced by the baseline reference conditions, reinforcement ratio, polymer type, architecture, specimen geometry and testing protocol, limiting direct quantitative comparison between studies. The effects of polymer selection and manufacturing processes are also discussed. The main challenges are geometric inaccuracies, limited interface characterization, insufficient durability assessment, and lack of standard protocols. To address these, better interface design, material selection, and consistent processing–structure–property analysis are needed, which would support a more rational design framework and broader applications.
Phosphate-induced eutrophication poses a critical water quality concern, and adsorption offers an effective remediation approach, yet conventional adsorbents suffer from limited capacity and poor reusability. In this study, a carboxyl-functionalized zirconium-based metal-organic framework (UiO-66-COOH) was synthesized through the hydrothermal method and deeply explored its phosphorus removal performance and potential mechanisms. Batch adsorption experiments were conducted to investigate the effects of initial solution pH, initial phosphate concentration, adsorbent dosage, and reaction temperature on the material’s phosphate adsorption behavior. Under the optimized conditions (pH = 3, dosage 0.2 g l ^−1 ), UiO-66-COOH exhibited a remarkable removal efficiency of 97.71%, with an equilibrium adsorption capacity of 48.86 mg g ^−1 . Adsorption kinetics followed the pseudo-second-order model, indicating chemisorption-dominated behavior, while thermodynamic analysis revealed a spontaneous and endothermic process. Comprehensive characterization (such as x-ray powder diffraction, x-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy) indicated that the efficient removal of phosphate by UiO-66-COOH was attributed to the synergistic effects of pore filling, carboxyl coordination chelation, and electrostatic interactions. This study not only provides an efficient adsorbent for phosphate pollution control but also offers theoretical and experimental support for the application of functionalized MOF materials in water environment remediation.
The effect of sputtering gas, particularly the generation of energetic recoil particles, is crucial in determining interfaces and microstructural evolution of magnetron-sputtered thin films. This is especially critical for nanoscale Ni/Ti multilayers, which are core components in advanced neutron mirrors. In this work, the modulation of the interface and layer structure in Ni/Ti multilayers was comparatively investigated by varying the sputtering gas using Ar and Kr. TRIM simulations reveal that using a heavier sputtering gas (Kr) significantly reduces the energy and number of recoil particles. Comprehensive characterizations using GIXRR, diffuse scattering, XRD, and TEM demonstrate a physical trade-off: the Ar-sputtered multilayer is found to exhibit approximately 1.5 times lower interface roughness (RMS), while it shows stronger Ni (111) crystallization and larger interdiffusion. Conversely, replacing Ar with Kr reduced the crystallization and atomic intermixing, despite the relatively larger interface roughness. These findings provide useful guidance for mitigating interface defects and optimizing the fabrication of high-performance multilayer optics.
Abstract A magnetically recoverable Fe 3 O 4 /TiO 2 composite was synthesized and applied for the removal of Xylenol Orange, a dye widely used in industrial applications, via a peroxymonosulfate assisted photocatalytic process under UV irradiation. The structural and physicochemical properties of the composite were characterized using XRD, FTIR, and SEM–EDS. Complete color removal (100%) was achieved under the optimum conditions of pH 5.0, PMS concentration of 1.0 mM, catalyst dosage of 1 g l −1 , 30 min dark adsorption, and 60 min UV irradiation. An increase in the initial XO concentration (25–100 mg l −1 ) resulted in a decline in removal efficiency. Kinetic analysis revealed that XO degradation followed a pseudo-first-order Langmuir–Hinshelwood model. The composite maintained its activity up to the second cycle and exhibited dual catalytic behavior, involving both photocatalysis and PMS activation via Fe 3 O 4 . Life cycle assessment using the ReCiPe 2016 Midpoint (H) method indicated that energy consumption, mainly from UV irradiation, is the primary contributor to environmental impacts. These findings demonstrate an efficient and environmentally relevant approach for azo dye removal.
This study investigated the long-term release of bisphenol A-glycidyl methacrylate (Bis-GMA), ethoxylated bisphenol A dimethacrylate (Bis-EMA), and urethane dimethacrylate (UDMA) from conventional and bulk-fill resin composites polymerized using different light-curing units and curing times. Three bulk-fill composites and one conventional resin composite were evaluated. Eighty specimens were prepared using standardized metal molds (2 mm × 8 mm for the conventional composite and 4 mm × 8 mm for the bulk-fill composites) and polymerized using either a halogen (Optilux 501) or light-emitting diode (LED; Demi Ultra) curing unit for 20 s or 40 s ( n = 5). The specimens were stored in a 75% ethanol/water solution, and monomer release was analyzed after 24 h, 1 week, 1 month, and 6 months using liquid chromatography-tandem mass spectrometry. Data were analyzed using multivariate ANOVA, repeated-measures ANOVA, Tukey HSD, and Tamhane’s T2 tests ( α = 0.05). Both curing-unit type and curing time significantly influenced monomer release ( p < 0.001). The LED curing unit resulted in lower monomer release than the halogen unit under the tested experimental conditions, while extending curing time from 20 s to 40 s significantly reduced monomer elution. Monomer release remained detectable throughout the six-month observation period. When all experimental conditions were considered collectively, UDMA exhibited the highest overall release and Bis-EMA the lowest, although material- and time-dependent variations were observed. Tetric EvoCeram Bulk Fill released significantly higher amounts of UDMA and Bis-GMA than the other investigated composites ( p < 0.001). Within the limitations of this study, both curing conditions and material composition significantly influenced long-term monomer release. These findings highlight the combined contribution of composite formulation and curing protocol to the release behavior of major resin-matrix monomers from contemporary resin composites.
Polyethylene terephthalate (PET) waste was depolymerized by microwave-assisted alkaline hydrolysis in two separate reagent systems, one based on NaOH and one on KOH, with the aim of recovering terephthalic acid (TPA) and characterizing each system at the process level. The two systems were optimized independently, each within its own operating window, using a Taguchi L9 (3 ^4 ) orthogonal array of four factors at three levels, with four replicates per run (36 runs per system). Because the two campaigns used different catalyst variables, TiO _2 loading in the NaOH system and catalyst type (none, zinc acetate, zinc oxide) in the KOH system, the results are reported as process-oriented characterizations of each system rather than as a catalyst-matched comparison of the two cations. Analysis of variance, signal-to-noise ( S / N ) analysis, main-effect analysis and general linear model (GLM) regression all identified temperature as the controlling factor in both systems, followed by alkali concentration and reaction time. PET conversion approached completion at 195 °C/30 min/12 wt.% NaOH and at 200 °C/36 min/18 wt.% KOH. The GLM models were predictive ( R ^2 ⩾ 98%; leave-one-out predicted R ^2 within 1.6% of R ^2 ), and residual analysis supported the model assumptions. The main methodological contribution is a pair of severity-normalized descriptors, a performance index and an apparent rate index adapted from the combined severity factor of biomass pretreatment, which read efficiency per unit of applied thermal and temporal severity rather than by conversion alone. A preliminary process assessment quantified the alkali stoichiometric excess (≈4.3–4.6-fold) and the inorganic salt by-product stream, both of which identify reagent efficiency as the main obstacle to scale-up. TPA recovery was confirmed by Fourier-transform infrared spectroscopy and ^1 H NMR, and product morphology was examined by scanning electron microscopy.
Abstract In this work, Mo, S, and carbon co-doped Co3O4 nanocube (MoSC@Co3O4) was prepared based on ZIF-67 and used to degrade levofloxacin (LEVO) via activating peroxymonosulfate (PMS). The doped Mo and S could promote the cyclic transformation of Co2+ and Co3+, and were participated in PMS activation. 96.0% of LEVO (initial concentration of 10 mg L–1) was degraded in 15 min with apparent rate constant of 0.206 min–1, which was 1.8 times larger than that of C@Co3O4 (0.113 min–1). 76.3% total organic carbon was removed in 30 min. The LEVO removal ratio nearly unchanged in consecutive five cyclic tests, in solution with pH of 5-10, or co-existing of Cl–, NO3–, H2PO4– and HA species. The possible PMS activation and LEVO degradation pathways were proposed. This study provides light on the synergism of Co-based species in activation of PMS.
In this in vitro study, the mechanical and optical properties of a conventional multi-shade resin composite, Charisma Topaz, were compared with a single-shade resin composite, Charisma Topaz ONE, over a period of 12 months. This investigation isolates the effect of adaptive light-matching filler technology by keeping the monomer matrix nearly constant. Vickers microhardness, flexural strength, and color stability (Δ E _00 ) were evaluated at baseline and after aging in distilled water. Charisma Topaz exhibited significantly higher Vickers microhardness than Charisma Topaz ONE at both baseline ( p = 0.042) and after 12 months ( p = 0.045). No statistically significant difference was found between the two materials in flexural strength at any time point ( p > 0.05). For color stability (Δ E _00 ), both resin composites exhibited clinically unacceptable color changes (Δ E _00 > 1.8). Notably, Charisma Topaz ONE exhibited significantly greater discoloration after 6 months than Charisma Topaz ( p = 0.006). The study concludes that although both materials maintain stable flexural strength, the conventional multi-shade resin composite Charisma Topaz demonstrates superior Vickers microhardness and medium-term color stability after long-term water aging under laboratory conditions. In contrast, although the optical benefits of ‘shade matching’ in Charisma Topaz ONE are evident, it may be more appropriate for less demanding scenarios where esthetic simplicity is more important.
Macroporous polymer gels were synthesized from bio-derived, linalool-based high internal phase emulsions (HIPEs). For this purpose, two types of water-in-oil (w/o) HIPEs were prepared. In the first approach, aqueous phases were dispersed into continuous phases containing varying amounts of linalool and ethylene glycol dimethacrylate (EGDMA). In the second approach, aqueous solutions of 2-hydroxyethyl methacrylate (HEMA), prepared at different volume ratios, were used as the internal phase and dispersed into continuous oil phases composed of linalool/EGDMA mixtures at various ratios. Following polymerization of HIPEs, polyHIPE and bicontinuous polyHIPE gels were obtained, with pore morphology varying from open to closed. Chemical structure analyses using Fourier transform infrared and ^1 H-nuclear magnetic resonance confirmed the presence of linalool, EGDMA, and HEMA units in the polymer chains forming the obtained polyHIPE network structures. The physicochemical parameters of the obtained polyHIPE gels, calculated using the Flory–Rehner equation, were found to be in high agreement with the void size variation of the macroporous gels determined by scanning electron microscope, as well as with the results obtained from thermogravimetric analysis analysis and mechanical tests. The controlled release, antibacterial efficacy, and cytocompatibility of polyHIPE gels were investigated. Kinetin was used to enhance the regenerative potential of the obtained polyHIPE gels. The kinetin-loaded polyHIPE gel sample exhibited antibacterial activity, displaying 17 mm inhibition zones against E. coli and S. aureus due to the presence of linalool units in the polymer network and its macroporous structure. Cytotoxicity tests showed that kinetin loading supported biocompatibility, maintaining over 90% cell viability in both MTT and neutral red uptake tests.
Laser cladding of aluminum alloys faces dual challenges of insufficient surface hardness and residual stress-induced cracking. This study presents an integrated experimental-numerical framework addressing both issues through material design and process optimization. AlSi10Mg/3 wt.%TiN composite powder with a core–shell architecture was prepared using a metal injection molding feedstock-inspired technique, ensuring uniform dispersion of nano-TiN particles on AlSi10Mg powder surfaces. Single-track cladding layers of AlSi10Mg and AlSi10Mg/3 wt.%TiN were deposited on 6061 aluminum alloy substrates via coaxial laser cladding. Microstructural characterization revealed that nano-TiN particles served as potent heterogeneous nucleation sites, promoting a pronounced columnar-to-equiaxed transition throughout the cladding layer. The TiN nanoparticles were distributed uniformly along grain boundaries via Marangoni convection-assisted transport, generating an Orowan dispersion strengthening effect. Combined with Hall–Petch grain refinement strengthening and Mg _2 Si precipitation strengthening, this effect constituted a triple synergistic strengthening mechanism. The average microhardness of the composite cladding layer reached 106.5 HV _0.01 , representing a 33.1% improvement over the 6061 substrate. A three-dimensional transient multi-physics finite element model incorporating Marangoni convection, recoil pressure, and solidification dynamics was established and validated against experimental melt pool depths across 20 parameter combinations, with most errors below 10%. Systematic parametric studies revealed that the volumetric average thermal stress increased by up to 105.1% with laser power and decreased by up to 48.2% with scanning speed. Response surface methodology was employed to establish second-order polynomial correlations ( R ^2 > 0.98) between process parameters and cladding performance indicators. A Non-dominated Sorting Genetic Algorithm II coupled with technique for order preference by similarity to an ideal solution was applied for multi-objective optimization, yielding optimal parameters of P = 3365 W and V _S = 11.28 mm s ^–1 , which simultaneously achieved low residual thermal stress and favorable geometric quality. This integrated framework provides both fundamental insights into nanoparticle-reinforced aluminum additive manufacturing and practical guidelines for process design.
Corrosion remains a critical limitation in advanced engineering materials, particularly under aggressive and multi-environment conditions. High-entropy alloys (HEAs) have emerged as promising candidates for corrosion applications due to their multi-principal-element design and their ability to form chemically complex passive films. However, a unified, mechanism-driven understanding of passive film behavior in HEAs remains lacking. This review systematically examines passive film formation, stability, and breakdown in HEAs. It further evaluates electrochemical characterization methods, identifies corrosion mechanisms in aggressive environments, and proposes design strategies to enhance corrosion resistance. A systematic review was conducted using the Scopus database following Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines. A total of 487 records were identified, of which 369 met the inclusion criteria. Bibliometric analysis using VOSviewer and thematic classification was applied to identify dominant research clusters, mechanisms, and emerging trends. The findings show that corrosion resistance in HEAs is governed by multi-component passive films with complex chemistry and layered structures. Their performance is strongly dependent on composition, microstructure, and environment. Cr plays a dominant role in film formation, while Mo significantly enhances pitting resistance and stability in chloride- and acidic-environments. Electrochemical characterization consistently links low corrosion current density and high charge transfer resistance to stable passive films. Microstructural uniformity is also critical. Under aggressive conditions, including mixed-ion environments and tribocorrosion, degradation mechanisms shift from passivation-controlled behavior to dynamic film breakdown and repassivation. The ability of HEAs to rapidly reform passive films emerges as a key performance advantage. Future research should focus on multi-environment corrosion mechanisms, tribocorrosion behavior, and in-situ characterization of passive film evolution.
Abstract Bacterial biofilms, particularly those associated with urinary catheters and neurogenic bladder, present a formidable challenge due to their tolerance to conventional antibiotics and the acidic microenvironment they create. Here, we developed an injectable, self healing, pH responsive composite hydrogel (BTO@DG) by incorporating piezoelectric barium titanate nanoparticles into a dynamic network of oxidized starch and gelatin. This hydrogel rapidly forms under mild conditions, adheres well to tissues, and can be injected through a needle. Upon ultrasound stimulation, the embedded BTO nanoparticles generate reactive oxygen species via a piezoelectric effect, achieving over 98% killing of E. coli and effective disruption of pre formed biofilms. Notably, the hydrogel degrades faster in the acidic biofilm environment (pH 5.5), enabling targeted drug release. Importantly, BTO@DG plus ultrasound treatment not only eradicates bacteria but also reduces excessive inflammation by suppressing the JAK1/STAT-1 pathway in macrophages, decreasing pro inflammatory cytokines. This dual action—direct antibacterial activity combined with anti inflammatory immunomodulation—positions BTO@DG as a promising non antibiotic platform for biofilm associated infections, particularly for minimally invasive bladder instillation therapy.
Recent progress in magnonics has increased the demand for high-precision microfabrication techniques to realize complex spin wave devices. In this work, we investigate the propagation of magnetostatic surface spin waves (MSSWs) in one-dimensional magnonic crystals fabricated on epitaxial yttrium iron garnet (YIG) thin films by femtosecond pulsed laser ablation (fs-PLA). The effects of laser fluence on spin wave transmission are systematically studied. Transmission measurements in frequency and wavenumber space reveal well-defined magnonic bandgaps for structures fabricated at moderate fluences, whereas samples processed at higher fluence exhibit strong attenuation of MSSWs. Scanning electron microscopy and atomic force microscopy show that increasing fluence leads to a reduction of the effective YIG thickness within the grooves and enhanced surface roughness, introducing structural inhomogeneities that degrade spin wave propagation. Raman spectroscopy confirms that the crystalline structure of the remaining YIG film is preserved after fs-PLA processing. The experimental results are analyzed using a transmission matrix model that incorporates the geometric parameters and a wavenumber-dependent phenomenological damping, reproducing the observed transmission trends. These findings identify an optimal fluence window for the fabrication of low-loss YIG-based magnonic crystals by fs-PLA.
Fused deposition modeling (FDM) 3D printing is characterized as a technology for manufacturing three-dimensional objects through the deposition of successive layers of molten material onto a build platform, based on a user-defined design. The development of non-conventional polymer-based filaments incorporating carbon-based semiconducting materials represents an open field of research in both academia and industry, with applications in emerging areas such as supercapacitors, photocatalysts, and sensors. This paper investigates the development of non-conventional filaments for FDM 3D printing based on polylactic acid (PLA) and reduced graphene oxide (rGO) nanoparticles, aiming to obtain electrically conductive properties for emerging applications in nanoelectronics. The composites were prepared by dispersing rGO in a PLA solution using chloroform as solvent, followed by controlled evaporation, oven drying, and hot melt extrusion of filaments with different rGO mass concentrations (0%–15% w w ^−1 ), all showing good reproducibility. Sample characterization was carried out using scanning electron microscopy, x-ray diffraction, differential scanning calorimetry, mechanical strength tests, and electrical resistivity measurements. The results revealed a typical electrical percolation behavior with a reduction in resistivity by 6 orders of magnitude (∼200 MΩ cm to ∼300 Ω cm), with a percolation threshold around 3.95% rGO. The rate of change in resistivity became less evident for the samples containing 9.1% or more of rGO, while filament processability was maintained up to 15% rGO, above which excessive stiffness was observed. Additional tests demonstrated the feasibility of printing three-dimensional structures with low electrical resistance, with potential for use in personalized functional devices.
Water hyacinth (WH) ( Eichhornia crassipes ) is a highly invasive aquatic plant whose uncontrolled proliferation causes significant ecological and economic damage worldwide. However, its lignocellulosic biomass remains an underutilized resource for the development of biobased polymer composites. This study investigates the use of WH waste as a natural filler in polylactic acid (PLA) composites, using different plant fractions: petiole (WHP), leaf (WHL), and their mixture (WHM). The composites were produced by solvent casting. The effects of filler content (1–10 wt.%) and biomass fraction on the thermal, mechanical, and structural properties of the films were systematically evaluated. Morphological analysis confirmed good dispersion of PLA and lignocellulosic fillers. Mechanical tests showed that the petiole fraction was the most effective reinforcement. The tensile strength of pure PLA increased from 5.3 MPa to 7.3, 7.0, and 7.8 MPa. Meanwhile, its modulus ( E ) increased from 291.0 MPa to 578.5, 743.6, and 734.2 MPa in the PLA/WHP composites containing 1%, 3%, and 5% reinforcement, respectively. However, at higher filler contents (⩾10 wt.%), performance dropped due to particle agglomeration and limited stress transfer. Thermal analysis showed a slight decrease in thermal stability compared to pure PLA. The glass transition ( T _g ) and melting ( T _m ) temperatures stayed nearly the same (±2 °C), indicating the polymer’s crystalline structure was preserved. This study demonstrates that WH waste can serve as a lignocellulosic filler in PLA-based biocomposites. The petiole fraction, at moderate loading, best balances stiffness and mechanical integrity. This strategy helps valorize invasive biomass for use in biobased polymer materials. These PLA/WHP biocomposites are proposed as candidates for packaging and single-use plastic applications, supporting the development of renewable, sustainable alternatives to fossil-based polymers.
Six machine learning algorithms were employed to construct artificial intelligence models for the precise prediction of self-compacting concrete (SCC) flow properties, using a total of 158 sets of experimental data samples. A sensitivity analysis examining the relationships between feature parameters and flow properties was performed using Shapley additive explanations (SHAP). The mix proportion of SCC involved key feature parameters: the water-to-binder ratio, along with the proportions of cement, silica fume, slag, fly ash, fine aggregate, coarse aggregate, and water reducer. The flowability of SCC was quantitatively characterized by the results of the slump test. Based on the analysis of prediction errors and outcomes, the extreme gradient boosting (XGB) model was identified as exhibiting superior predictive accuracy and generalization performance, with the coefficient of determination ( R ^2 ) reaching 0.927, and the explained variance of 0.936. Building upon the XGB intelligent algorithm, a graphical user interface-based interactive program was successfully developed to predict flowability using SCC mix proportions. The results of SHAP analysis indicated that the content of cement and silica fume exhibited a negative correlation with SCC flowability, while the content of fly ash and slag showed a positive correlation with SCC flowability. Compared to coarse aggregates, fine aggregates exerted a less pronounced effect on the flow characteristics of SCC. The dosage of water-reducing agent was the most significant positive factor affecting the flow properties of SCC.
Lightweight design of leaf springs is a key approach to reducing the operating costs of commercial vehicles. In recent years, a variety of new materials and manufacturing processes have created opportunities for the performance improvement of traditional automotive leaf springs. Leaf springs have complex stress characteristics that involve typical mechanical behaviors, including nonlinearity, large deformation, and friction between spring leaves. In the design of leaf springs for light-duty vehicles, 50SiMnCr ultra-high-strength spring steel with a tensile strength over 2000 MPa was innovatively adopted, and response surface optimization was carried out. The thickness and width of the leaf springs were taken as design variables, while equivalent stress, deformation, and mass were set as optimization objectives and constraints. After optimization, the maximum equivalent stress of the leaf springs was 1335.2 MPa. This value was lower than the yield strength of the material (1855 MPa), yielding a safety factor of 1.39 that satisfied the design specifications for automotive leaf springs. The maximum deformation reached 42.462 mm, which was within the allowable full-load deflection range of the suspension system. A weight reduction of 14% was achieved. The optimized leaf springs exhibited excellent fatigue life and overall reliability, meeting the design requirements for high-cycle fatigue performance. This study proposes a new method for the lightweight design of automotive leaf springs.
Common distresses in bridge expansion joints, such as rutting and interface debonding, often result in premature failure and frequent replacement. To address these issues, this study evaluates a custom-synthesized polyurethane (PU) modified bitumen for use in asphalt plug joints (APJ) against a commercial high-viscosity elastic (HVE) modified bitumen. The rheological properties of the binders were characterized using temperature sweep, frequency sweep, and stress relaxation tests. To optimize the APJ mixtures, four joint mixtures (P-Ⅰ, P-Ⅱ, H-Ⅰ, and H-Ⅲ) were prepared using two binder types (PU and HVE), three combined gradations (Ⅰ, Ⅱ, and Ⅲ), and varying binder-to-aggregate ratios (1:6, 1:7, and 1:8). Their mechanical performance was investigated through rutting, low-temperature bending, freeze–thaw splitting, and fatigue tests. Experimental results indicated that the PU modified bitumen exhibited high-temperature mixture performance comparable to that of the HVE bitumen, while maintaining similar low-temperature properties. Furthermore, PU-based mixtures exhibited higher flexural strength and elastic modulus, along with superior water stability and fatigue resistance. This study provides a reference for developing durable bridge joints that extend service life, thereby contributing to reduced maintenance needs and resource consumption.
A six-band polarization-insensitive terahertz metamaterial absorber based on a hybrid square-ring and circular-ring resonator is proposed for refractive-index sensing applications. Numerical simulations were carried out using the finite-difference time-domain method. The absorber consists of a patterned metallic resonator, a dielectric spacer, and a metallic ground plane. The results demonstrate six distinct absorption peaks within 0.4–4.5 THz, five of which exhibit absorption above 95%, while the sixth peak reaches 64.8%. The resonant frequencies can be effectively tuned by varying the structural parameters. Electric- and magnetic-field analyses indicate that the six absorption peaks arise from square-ring-dominated, circular-ring-dominated, and hybrid resonances with distinct field-localization characteristics. Refractive-index sensing analysis shows that the proposed absorber exhibits favorable sensing performance, with a maximum figure of merit of 5.71 at the f _4 resonance peak. In addition, stable polarization-insensitive absorption behavior is achieved owing to the symmetric resonator geometry. Benefiting from its simple structure, stable polarization response under normal incidence, and favorable refractive-index sensing performance, the proposed absorber shows potential for terahertz refractive-index sensing and related integrated terahertz sensing devices.
