Search Results (1,646)

Diamond nanothreads (DNTs) represent a promising class of one-dimensional carbon nanomaterials for next-generation structural applications. However, exploring their mesoscale collective properties remains computationally prohibitive via all-atomistic molecular dynamics (MD) simulations. Here, we present a physically consistent coarse-grained model tailored for both zigzag (DNT-I) and tubular (DNT-II) nanothreads. By establishing an energy equivalence framework between all-atomistic MD simulations and molecular mechanics, the bonded potentials (stretching and bending) and non-bonded Lennard-Jones parameters were derived. Moreover, a degree of coarse-graining r₀ = 6 Å was determined, which well preserves the interfacial cohesive energy and axial sliding behavior of all-atomistic models. Using the established coarse-grained potentials of DNTs, a high glass transition temperature (T_g = 1485 K) was predicted, and a cooperative intermolecular sliding mechanism that governs the plastic deformation of crystalline DNT aggregates under uniaxial tension was revealed. Full article

Fully enclosed noise barriers (FENBs) are widely used in high-speed railway systems to mitigate environmental noise; however, the transient aerodynamic loads generated by train passage can induce complex structural responses. The relationship between the spatial–temporal evolution of these aerodynamic loads and the dynamic response of the complete FENB structural system remains insufficiently understood. To address this issue, this study develops a sequential computational fluid dynamics–finite element analysis (CFD–FEA) framework that directly relates the transient pressure evolution during the complete train-passage process to the deformation and stress responses of the principal FENB components. The unsteady aerodynamic field generated by high-speed train passage is simulated using a moving-mesh CFD model, and the resulting time-dependent pressure loads are subsequently applied to a finite-element structural model. Train speeds ranging from 250 to 330 km/h are considered. The results reveal strongly transient and spatially non-uniform pressure distributions inside the FENB, characterized by nose-induced compression, a middle negative-pressure region, and wake-induced pressure fluctuations. Both structural deformation and equivalent stress increase with train speed, and the exit stage produces the most pronounced structural response because of the strong negative-pressure effect. Different structural components exhibit distinct response characteristics, with localized stress concentrations occurring in the glass panels and H-section steel columns. By establishing the correspondence between transient aerodynamic pressure evolution, train-passage stages, and component-level structural responses, this study provides a more comprehensive understanding of the aerodynamic load–structural response mechanism of FENBs and provides a basis for structural design and engineering assessment under increasing train speeds. Full article

Vitrimers are covalent adaptable networks that combine the structural stability of thermosets with self-healing enabled by dynamic covalent bonds. However, the molecular-level interplay among polymerization, prescribed bond-exchange reactions (BERs), finite-time mechanical relaxation, and nanoscale interfacial recovery remains incompletely understood. Here, we employ all-atom molecular dynamics simulations with the REACTER template-based reaction algorithm to construct a Bis-GMA/2-HEMA methacrylate polymer assembly and to model temperature-dependent transesterification. The resulting structure exhibits heterogeneous connectivity and a simulated glass transition temperature consistent with reported trends. With the imposed BER-acceptance window centered near the simulated T_g, mechanical and self-healing analyses reveal a model-conditioned temperature crossover. Near the glass transition region, BERs cooperate with emerging segmental mobility to accelerate finite-time mechanical relaxation and early-stage healing. At higher temperatures, thermally activated chain mobility and physical interfacial reconsolidation dominate the apparent response, making the incremental contribution of BERs secondary. Because the glass transition temperature and the topology-freezing temperature are distinct and the latter is not calculated here, the near-transition crossover is interpreted as conditional on the adopted BER schedule rather than as a universal vitrimer rule. These results clarify how dynamic covalent chemistry and temperature-controlled relaxation jointly regulate nanoscale vitrimer mechanics and repair within the accessible simulation window. Full article

The high levels of greenhouse gas emissions from energy-intensive industries have created an urgent need for decarbonization. As major sources of pollution, industries are increasingly being forced to reconsider the fuels they use in their processes. Interest in hydrogen combustion, particularly in high-temperature applications, has grown due to its physical properties and the absence of carbon dioxide emissions. Despite its potential, hydrogen combustion presents technical challenges, such as flame stability, burner adjustment requirements, control of nitrogen oxides (NO_x) emissions and material compatibility. This review examines the use of hydrogen as a fuel in industrial furnaces along three complementary axes. First, it analyzes combustion fundamentals, blending limits and mitigation strategies, including oxy-fuel and MILD combustion, and assesses their deployment maturity across the steel, cement, glass, ceramics, and refining and chemicals sectors, together with economic and regulatory constraints. Second, it reviews advances in Computational Fluid Dynamics (CFD) modeling of hydrogen flames, addressing turbulence-chemistry interaction, reaction kinetics, radiative heat transfer, NO_x formation and model validation. Third, it surveys camera-based diagnostics combined with Artificial Intelligence and computer vision for flame monitoring and combustion optimization. By synthesizing recent literature, the review identifies the principal knowledge gaps, notably standardized CFD validation datasets and robust monitoring under industrial conditions, providing a critical reference for researchers and industry. Full article

Hydrogel bio-adhesives have gained great attention in wound healing and tissue regeneration applications because conventional wound closures are often hindered by insufficient adhesion and poor biocompatibility. Considering that dynamic covalent interactions facilitate robust wet adhesion in hydrogels, we fabricated a Schiff base hydrogel bio-adhesive based on oxidized chondroitin sulfate (OCS) and polyethylenimine (PEI), and employed different degrees of OCS oxidation to regulate the physicochemical properties of the bio-adhesives. In this system, aldehyde groups of OCS react with amino groups of PEI to form covalent imine crosslinks, while physical hydrogen bonds also contribute as supplementary interactions. The fabricated hydrogel bio-adhesives demonstrated a three-dimensional interconnected microstructure and regulated equilibrium swelling ratios. The rheological tests also confirmed the typical viscoelasticity of the hydrogels and their shear-thinning behavior. The obtained hydrogel bio-adhesives demonstrated rapid and autonomous self-healing ability and strong adhesion to the surfaces of various matrices and wet organs, including wood, glass, metal, plastic, rubber, and heart, liver, spleen, stomach, and lung tissue. Furthermore, an ABTS radical scavenging assay confirmed their potent antioxidant activity. The hydrogels possessed effective antibacterial activities against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. The hydrogels exhibited good hemocompatibility, effective intracellular reactive oxygen species (ROS) scavenging activity, favorable cytocompatibility, and promoted cell proliferation. These results confirmed the fabricated hydrogels via Schiff base connections for biomedical applications and provided a facile design for biomedical hydrogel bio-adhesives. Full article

Non-isocyanate polyurethanes (NIPUs) incorporating dynamic imine linkages were developed via UV-induced photopolymerization of methacrylated monomers. The system combines a non-isocyanate urethane (NIU) precursor derived from cyclic carbonate chemistry with an imine-containing (Vit) monomer obtained via Schiff base formation, enabling compositionally tunable networks with a high gel content (90–97 wt%) and thermal stability up to >190 °C. The increase in NIU content enhances network rigidity, varying the glass transition temperatures from 29.3 °C to 73.4 °C. The dynamic imine chemistry imparts outstanding multifunctionality, including efficient shape memory behavior, thermally triggered reprogrammability, and rapid surface self-healing behavior, even at a low content of imine-containing precursor (30 wt%). The optimized composition further provides a proof-of-concept of selective chemical depolymerization for monomer recovery. These results establish NIU-Vit networks as versatile, having recyclability prospects, and a multifunctional platform for sustainable polymers as replacements for the traditional isocyanate-based polyurethanes. Full article

Tailored flax-reinforced composites (TFRC) are being investigated as a sustainable alternative to conventional glass- and carbon-fiber-reinforced composites, having a lower fiber volume than these and the structure of the laminate with two plies (two identical layers of alkali-treated flax yarns) is unidirectional, weakly twisted, oriented at ±45°, and reinforced by stitching; it is also impregnated with bio-resin and has robust reinforcement through controlled lamination. TFRC has shear-dominated behavior under both tensile and compressive loading, due to the off-axis orientation of the fibers, but the damage evolution differs significantly. Under tensile loading, the material exhibits a lower strength (55.2 MPa), whereas under compression loading, the composite achieves a higher apparent strength (99.1 MPa). The paper provides a comprehensive analysis for structural and mechanical characterization using the following: nondestructive evaluation using ultrasound to detect internal discontinuities and assess homogeneity; optical microscopy to evaluate fiber–matrix integration and porosity reduction; and Dynamic Mechanical Analysis to assess thermomechanical transitions and storage modulus stability. Finite element simulations have been used to determine elastic properties and validate the matrix-dominated shear response. The results confirm that the [±45°]_4S sequences of TFRC optimize mechanical response and interfacial adhesion, promoting TFRC as an ecological solution for structural systems where progressive energy dissipation is preferred. Full article

We present a nonlinear dynamical model for vehicular traffic jams and their dissolution based on the noise-perturbed onset of chaos. The model makes use of the bifurcation gap generated by addition of noise to quadratic iterated maps. The gap results from the elimination by noise of periodic and chaotic attractors with large periods and large numbers of chaotic bands, respectively. The bifurcation gap is recapitulated at the transition to chaos (vanishing Lyapunov exponent) as a crossover from noiseless to irregular, chaotic-like regimes at an iteration time $t_{cross}$ with value dependent on the noise amplitude. This behavior is employed in a model (with variants) that we design for multilane road congested traffic. We highlight four main model properties that are also present in the dynamics of glass formation: (i) plateau interrupted relaxation; (ii) Adam–Gibbs empirical law; (iii) aging; and (iv) diffusion arrest. The model bridges previous studies that have indicated analogies between glassy dynamics and vehicular traffic as well as nonlinear dynamics and same-name traffic. We also discuss the connection of the model with urban multilane road networks. Full article

The development of sustainable coatings that combine reprocessability with active functionalities remains a central challenge for the composites sector. In this work, a healable, electrically conductive coating was formulated using epoxidized castor oil (ECO) as a bio-based matrix, dibutyl phosphate (DBP) as a transesterification catalyst, and short recycled carbon fibres (RCFs, 2 mm in length) as a conductive filler at loadings of 10 and 20 phr. Formulations were UV-cured via cationic photopolymerization and characterized across the full liquid-to-solid processing chain. FT-IR and photo-DSC showed that increasing RCF content progressively reduced curing rate and conversion, an effect attributed to light scattering/absorption by the fibres and restricted chain mobility, although gel content remained above 98% in all cases. DMTA showed that RCF did significantly affect the glass transition temperature but markedly increased the rubbery storage modulus and apparent crosslink density, consistent with a physical reinforcement mechanism. Stress relaxation tests confirmed the dynamic bond exchange behaviour in all formulations, with the apparent activation energy decreasing from 112 kJ/mol for the neat resin to 33–34 kJ/mol upon RCF incorporation. This significant reduction suggests that the presence of RCF facilitates the bond-exchange process, potentially through interfacial interactions between the polymer network and the fibre surface. However, the specific molecular mechanism responsible for this effect cannot be established from the present data. Electrical conductivity peaked at 10 phr RCF (3.6 × 10⁻³ S/m), enabling measurable Joule heating, while the 20 phr formulation showed reduced conductivity linked to voids and lower conversion. Thermally triggered healing at 120 °C for 6 h restored mechanical integrity, which is higher than reference values, demonstrating the coating’s capacity for repeated repair through its dynamic covalent network. Full article

Glass fiber-reinforced polymer (GFRP) and carbon/glass hybrid fiber-reinforced polymer (HFRP) laminates with two vinyl ester resin systems were investigated to evaluate their early environmental response, residual mechanical performance, and damage behavior after moisture-assisted low-temperature exposure and freeze–thaw cycling (FTC). After 150 days of moisture preconditioning, the conditioned specimens were exposed to −50 °C or subjected to FTC between −50 °C and 22 °C. Tensile, compressive, flexural, in-plane shear, interlaminar shear, and compression-after-impact (CAI) tests were conducted. Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM) were used to examine chemical structure, thermomechanical response, and damage morphology. FTIR spectra showed no obvious changes in the characteristic absorption bands of the vinyl ester matrix. DMA showed condition-dependent changes in thermomechanical behavior, with the largest decrease in glass transition temperature reaching 5.5 °C after Condition 3. Tensile and in-plane shear properties were largely retained, whereas compressive, flexural, interlaminar shear, and CAI properties were more sensitive; the largest CAI strength loss was 19.1%. Hybrid stacking affected the property retention and damage tolerance of the laminates under the designed FTC condition. SEM observations identified interfacial debonding, matrix microcracking, and interlaminar crack growth as the main damage features. Full article

This experimental work aims at the study by non-destructive and destructive testing of the mechanical and acoustical properties of cold-setting epoxy resins plasticized with amounts of plasticizer and of PMMA (Plexiglas), both belonging to the two basic categories (thermosetting and thermoplastics respectively) of polymeric materials, which usually can be modified because of polymerization rate and curing, change in temperature and frequency, by the addition of plasticizers and/or inclusions as well as due to discontinuities (defects, voids and porosity) where stress concentration exists. On the other hand, ultrasound is a mechanical, elastic wave of very high frequency, and can be used for material testing. Using ultrasounds, defects, discontinuities, and damage can be detected, and moduli can be evaluated accurately. It should be noted that the moduli determined in this way are the dynamic moduli and differ from the static ones for any material. Here, the authors focus their study on plasticized epoxy resins and PMMA and apply this NDT method to estimate mechanical properties and correlate the results with those from destructive tests. Finally, the glass-transition temperature of plasticized epoxies was also evaluated from thermal experiments to determine the effect of the plasticizer. Full article

Hybrid composites combining natural and synthetic fibers offer a pathway to sustainable structural materials, yet their performance is often limited by weak interfacial bonding and mechanical mismatches between constituents. Here, we address these challenges in bamboo/glass fiber hybrid epoxy composites through a sequential alkali and silane surface modification strategy. Alkali treatment removes amorphous lignin and hemicellulose, creating a roughened, cellulose-rich surface; subsequent grafting with (3-aminopropyl) triethoxysilane introduces an amino-functionalized interphase that covalently bonds with the epoxy matrix. This combined treatment increases the tensile strength of bamboo fibers by 51.2% and the interfacial shear strength by 136.6%, reaching values comparable to those of commercial glass fibers. The resulting hybrid composite exhibits a tensile strength of 485 MPa and a flexural modulus of 30.2 GPa, corresponding to improvements of 39.4% and 98.3%, respectively, over the unmodified hybrid system. Dynamic mechanical analysis further confirms an enhanced storage modulus across a wide temperature range. This work demonstrates that rational interfacial design via sequential functionalization offers a viable route to high-performance, lightweight, and structurally stable bamboo/glass fiber hybrid composites for sustainable engineering applications, such as reusable concrete formwork. Full article

Background/Objectives: Tissue bio-adhesives have gained significant attention as efficient alternatives to conventional wound closures, which are often hindered by insufficient adhesion and poor biocompatibility. Methods: Inspired by nature’s robust wet-adhesion strategies that use dynamic covalent interactions, we have reported a facilely fabricated hydrogel bio-adhesive based on lactobionic acid-conjugated polyethylenimine (LA-PEI) and oxidized dextran (ODex) via Schiff base linkages. Results: The prepared hydrogels exhibited three-dimensional interconnected porous networks, regulated swelling ratios, typical viscoelasticity, shear-thinning behavior, and self-healing ability. Notably, the swelling ratios of the hydrogels depended on composition, and OLP11 displayed the highest swelling ratio of over 1500%. The hydrogel bio-adhesives exhibited strong adhesion to various surfaces, including glass, metal, plastic, rubber, and wood, as well as to different chicken organs, including the heart, liver, spleen, and stomach. Furthermore, the hydrogels exhibited excellent ABTS radical-scavenging activity, effective intracellular reactive oxygen species (ROS) scavenging, and good hemocompatibility, with hemolysis ratios of all hydrogels close to 0%, below the threshold of 5%. After culturing with NIH 3T3 fibroblasts, the hydrogels demonstrated good cytocompatibility and promoted cell proliferation, with cell viabilities on day 3 reaching over 90%. Conclusions: This design yields multifunctional hydrogel bio-adhesives, showing strong promise for wound care and tissue repair applications. Full article

Vibration monitoring of glass substrate transfer systems is crucial for ensuring the stable operation of Flat Panel Display (FPD) manufacturing equipment. Fabrication defects in the functional nanofiber membrane of flexible vibration sensors can significantly degrade sensing performance and lead to inaccurate monitoring results. To address the challenge of achieving an effective balance between detection accuracy and inference efficiency in such defect-dense scenarios characterized by large variations in defect scale, this paper proposes a novel defect detection model, termed MA-YOLO. The proposed model incorporates four key architectural enhancements: the Multi-level Bidirectional Feature Aggregation Network (MLBAN), the Multi-Receptive Field Adaptive Fusion Module (MRAF), the Morphology-Adaptive Feature Extraction Module (MA-C2f), and the Interactive Dynamic Decoupling Head (IDDH). These components collaboratively improve defect feature extraction, multi-scale feature fusion, and localization performance while maintaining a lightweight architecture and high inference speed. Experimental results on a self-constructed defect dataset demonstrate that MA-YOLO achieves a mean Average Precision (mAP@0.5) of 91.9%, which is a 3.1 percentage point improvement over the baseline model. Moreover, with only 9.15 million parameters and an inference speed of 119.05 FPS, the proposed model exhibits superior overall performance compared with several mainstream and state-of-the-art object detection methods. Full article

This study investigates the flow and economic valuation of recyclable materials across fifteen Secondary Transfer Stations (STSs) in Dhaka North City Corporation (DNCC), Bangladesh, with the aim of understanding how market dynamics influence material recovery and circular economy potential. Primary data were collected through field surveys, structured questionnaires administered to 50 waste workers, five waste dealers and five local traders. Recovered materials were classified into six major categories, paper, plastic, metal, glass, electronic waste (e-waste), and other materials with further sub-categorization, to capture price variations and material characteristics. The results reveal a highly differentiated recycling market, with prices varying by more than an order of magnitude across materials. High-value materials, including copper wire, scrap aluminum, scrap metal, and electrical wire, are consistently recovered, whereas medium-value materials such as HDPE, PET, polypropylene, PVC, LDPE, Styrofoam, plastic crates, and mixed plastics are recovered selectively depending on market demand. In contrast, low-value materials, including packaging cartons, white paper, glass items, mixed LDPE, damaged LED lights, and mixed wastepaper, are frequently discarded due to weak economic incentives. Despite spatial and socioeconomic differences across STSs, price variability remains relatively low, indicating an integrated city-wide recycling market driven by active trader networks and broader commodity trends. To the best of our knowledge, this is one of the first studies to integrate recyclable material flow with economic valuation across multiple STSs in Dhaka. The findings highlight that recovery efficiency is strongly governed by economic value and informal practices, with limited segregation efficiency and inadequate occupational safety conditions. Enhancing source segregation, improving storage infrastructure, and introducing targeted market and policy interventions for low-value materials are critical for advancing Dhaka’s transition toward a circular and resource-efficient urban waste management system. Full article