Search Results (25,648)

The development of heterogeneous catalysts with suitable structural and physicochemical properties is important for catalytic processes involving renewable feedstocks. In this study, Nb₂O₅ and MoO₃/Nb₂O₅ composite catalysts were prepared by high-energy wet milling, systematically characterized, and subsequently evaluated in the transesterification of waste cottonseed oil. The effect of MoO₃ incorporation on the structural, morphological, thermal, and catalytic properties of the resulting materials was investigated. X-ray diffraction revealed the predominantly amorphous character of the hydrated Nb₂O₅ precursor, whereas increasing MoO₃ content promoted the formation and growth of orthorhombic α-MoO₃ crystalline domains. FTIR spectroscopy confirmed the presence of Nb-O-Nb vibrations and Mo-O/Mo=O species in the composite catalysts. SEM and SEM-EDS analyses revealed distinct morphologies and a homogeneous distribution of Nb, Mo, and O at the micrometric scale. The particle-size analysis showed changes in the particle-size distribution following MoO₃ incorporation. These structural and physicochemical modifications were accompanied by a substantial enhancement in catalytic performance compared with bare Nb₂O₅. At catalyst loadings of 4 and 6 wt.%, 35Mo/Nb achieved conversions of 88.34 ± 0.08% and 90.21 ± 0.14%, respectively. The 15Mo/Nb reached 69.50 ± 5.07% and 62.17 ± 0.21%. The 35Mo/Nb catalyst was further subjected to five reuse cycles, and XRD, FTIR, and TGA analyses indicated preservation of the oxide framework, along with the presence of adsorbed reaction-derived species after reuse. The results demonstrate that high-energy wet milling provides an effective route for preparing MoO₃/Nb₂O₅ composite catalysts with composition-dependent structural and physicochemical characteristics, whose catalytic applicability was demonstrated in biodiesel production. Full article

The polyunsaturated fatty acid (PUFA) content of phytoplankton determines the nutritional quality of aquatic basal food resources and influences food-web energy transfer. Field studies suggest that phytoplankton PUFA content is associated with taxonomic characteristics, with nutrient enrichment promoting cyanobacteria dominance to reduce phytoplankton PUFA content. Nevertheless, laboratory evidence indicates that nutrient enrichment can also alter the fatty acid composition of single algae species. The role of intraspecific physiological alterations has long been overlooked. To partition the relative importance of taxonomic and intraspecific physiological alterations on phytoplankton nutritional quality, nutrient-manipulated mesocosm experiments were conducted in spring and winter using natural plankton communities from a tropical eutrophic reservoir. Fatty acid analysis showed that the nutritional quality of the phytoplankton community declined in mesocosms after nutrient additions. Piecewise structural equation modeling (pSEM) was employed to disentangle direct effects (representing intraspecific physiological alterations) and indirect effects (via the Shannon–Wiener index, representing taxonomic alterations) of phosphorus enrichment on ω-3 PUFA. Within each season, phosphorus enrichment exerted a significant direct negative effect on ω-3 PUFA, regardless of whether cyanobacteria dominated in winter or chlorophytes dominated in spring. In the pooled cross-seasonal model, community diversity showed a significant positive effect on ω-3 PUFA, with a stronger standardized effect than that of phosphorus enrichment, whereas phosphorus enrichment still exerted a significant direct negative effect. Our results indicate that intraspecific physiological alterations in phytoplankton may play a crucial role in the changes in phytoplankton nutritional quality following additional nutrient loading, particularly in tropical, eutrophic waters. However, the underlying biochemical mechanisms remain uncertain because direct molecular or enzymatic evidence was not obtained in this study. Full article

A field-oriented, real-time implementation of the previously developed vision-based bridge weigh-in-motion (V-BWIM) framework is presented for vehicle-load monitoring under variable-speed and mixed-traffic conditions. Vehicle and wheel positions are obtained through YOLOv5-based object detection, binocular measurement, and coordinate transformation, whereas bridge responses are measured by strain gauges and synchronized with the vision-derived axle trajectories. A field-image dataset constructed from full-scale bridge experiments is used to compare object-detection performance, inference efficiency, and model complexity, and YOLOv5s is selected for field implementation. The calibrated bridge influence line is then combined with synchronized axle positions and structural responses for axle-load identification. Controlled field tests on a simply supported bridge quantitatively evaluate vehicle positioning and load identification under constant-speed, variable-speed, and two-vehicle car-following conditions. A further continuous-beam bridge experiment demonstrates vehicle-information estimation under random traffic. Because independent reference weights were unavailable for the randomly passing vehicles, the continuous-bridge results are interpreted as a field demonstration rather than an independent validation of load-identification accuracy. Full article

The growing demand for large, lightweight, heat-resistant, and multifunctional aerospace structures has raised the requirements for metal matrix composites in terms of defect minimization, performance enhancement, and near-net-shape manufacturing. Additive friction stir deposition of composites enables feedstock delivery, reinforcement mixing, and layer-by-layer consolidation in a thermoplastic state below the melting point of the matrix, thereby mitigating porosity, hot cracking, elemental segregation, reinforcement degradation, and excessive interfacial reactions commonly encountered in fusion-based additive manufacturing. This review summarizes recent advances in the application of this technology to the fabrication of metal matrix composites, elucidates the mechanisms of material flow, interlayer bonding, microstructural evolution, and defect formation during deposition, and discusses the effects of tool design, process parameters, and reinforcement characteristics on interfacial bonding, microstructure control, and mechanical properties. Remaining challenges include the uniform delivery and quantitative control of reinforcements, characterization of interfacial bonding and load transfer, forming stability of complex components, and evaluation of in-service performance; accordingly, thermo-mechanical-flow multiphysics models, multisensor closed-loop control systems, and unified quality-assessment methods should be developed to promote the engineering application of large-scale, multimaterial graded aerospace components. Full article

Shipborne photoelectric telescopes must consider the influence of the ship on structural stability during offshore operations. In this study, a 1.2 m shipborne photoelectric telescope tracking frame was investigated, and the inertial acceleration induced by hull motion was analyzed. Three ship motion modes were simplified as independent harmonic motions, and their motion equations and parameters were derived. The structural deformation under combined ship motions was evaluated by applying inertial loads through finite element analysis. The maximum deformations along the altitude axis parallel and perpendicular to the bow-stern line were both less than 0.09 mm, indicating negligible structural impact. A ship motion simulation system was developed and validated using an LMS modal analyzer. Modal analysis was performed to obtain the first six mode shapes, and sensor locations were optimized accordingly. The measured frequencies of the first six modes were 43.10, 47.47, 62.76, 74.52, 126.84, and 146.32 Hz, respectively, with the fundamental frequency exceeding the simulated value of 34.32 Hz. Full article

While predefined cambering is widely implemented in prestressed concrete (PSC) girder bridges to counterbalance dead load deflections, the literature addressing its direct influence on structural behavior remains limited. Existing research focuses primarily on providing the required camber during fabrication and accidental deflections, with sparse attention dedicated to the interactive effects of diverse predefined initial profiles on structural performance. In this paper, an experimental investigation on the effect of predefined camber and accidental deflection on the structural behavior of both reinforced and prestressed rectangular concrete girders under four-point bending loading is presented. Fourteen large-scale beam specimens were tested, including eleven prestressed and three conventional reinforced concrete (RC) girders having concrete compressive strengths of 30, 40, and 80 MPa with predefined initial profiles ranging from −30 mm to +30 mm on key structural parameters, including cracking propagation, stiffness degradation, structural efficiency, displacement ductility, and total energy absorption. Test results have shown that all girders failed in a ductile manner via progressive cracking. It has been observed that positive predefined cambers could positively affect the performance of prestressed girders to a large extent, as the +30 mm predefined camber improved the ultimate load capacity by 19.3%. Full article

Modified PES ultrafiltration membranes containing Ag-MBene nanoparticles were developed via the non-solvent-induced phase separation (NIPS) technique and evaluated for tertiary-treated sewage (TSE) filtration applications. This study aims to establish an integrated understanding of membrane structure, properties, and performance by correlating morphology, roughness, hydrophilicity, porosity, permeability, antifouling properties, and pollutant rejection capabilities. Ag-MBene nanomaterials were incorporated into the PES membrane at various loading concentrations to increase the membrane hydrophilicity and antifouling characteristics. The detailed characterization of membrane samples was performed using SEM, AFM, EDS, FTIR, contact angle analysis, and porosity evaluation. The membranes exhibited distinct structural features after the addition of Ag-MBene nanomaterials. SEM analysis revealed enhanced macropore formation and increased pore interconnectivity at a relatively moderate loading concentration of nanoparticles. AFM analysis further confirmed progressive membrane roughness enhancement after incorporating Ag-MBene particles. The contact angle decreased from 81.2° (UF00) to 47.3° (UF1.5), indicating enhanced hydrophilicity of the modified membranes. UF0.5 exhibited the most balanced overall performance due to optimized pore morphology, improved wettability, and uniform nanoparticle dispersion. The modified membranes also exhibited enhanced flux performance, more reversible fouling behavior, and improved chemical oxygen demand (COD)/total suspended solids (TSS) removal efficiency than pristine membranes. ANOVA revealed significant differences among various membranes (p < 0.05), and the UF0.5 configuration was identified as the optimal membrane based on its balanced structural and performance characteristics. These findings demonstrate that balanced optimization of membrane morphology, hydrophilicity, and nanoparticle dispersion is essential for maximizing ultrafiltration performance. Full article

Cuminaldehyde (CA), a major bioactive constituent of cumin essential oil, was incorporated into gelatin/konjac glucomannan (Gel/KGM) composite films at different levels, expressed relative to the polymer content (mL/g polymer), to investigate its effects on film structure, physicochemical properties, and antioxidant activity. Structural characteristics of the films were examined using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Mechanical properties, surface wettability, optical properties, water sensitivity, and antioxidant activity were also determined. Spectroscopic analyses indicated changes in the molecular interactions of the Gel/KGM matrix following CA incorporation, while XRD and SEM analyses showed reduced structural order and a more heterogeneous microstructure at higher CA levels. Representative contact-angle observations showed an initial angle of 40.2° for the Control and 58.0° for CA-10, suggesting a tendency toward reduced surface wettability after CA incorporation. The addition of CA also improved UV-shielding properties and enhanced antioxidant responses, although the magnitude and trend of the antioxidant effect depended on the assay. In contrast, higher CA levels significantly reduced tensile strength and increased water solubility, whereas the tensile strength of films containing 1 mL CA did not differ significantly from that of the control (p > 0.05). These results demonstrate that the structural, physicochemical, and functional responses of Gel/KGM composite films varied with the nominal CA loading. Among the tested formulations, CA-3 represented a possible compromise between structural integrity and functional performance. Further studies using real food matrices are required to validate its practical applicability under actual food-packaging conditions. Full article

Lithium–sulfur (Li–S) batteries offer high theoretical specific energy and low-cost sulfur chemistry, but their practical application is limited by polysulfide shuttle, the electronic insulation of sulfur and Li₂S, and sluggish liquid–solid and solid–liquid conversion. Covalent triazine frameworks (CTFs) combine nitrogen-rich pore walls, tunable porosity, chemical robustness, and molecular designability, making them promising platforms for regulating sulfur species. This review focuses on strictly defined CTFs and closely related CTF-derived systems used in Li–S batteries. Rather than treating polysulfide adsorption or improved cycling as evidence of catalysis, the functional roles of CTFs are separated into confinement, catalysis, and redox mediation, while the strength of mechanistic evidence is evaluated independently. Representative sulfur hosts, conductive hybrids, functional separators, and redox-active CTFs are compared with emphasis on Li₂S nucleation and growth, deposition morphology, sulfur-conversion kinetics, direct Li₂S precipitation/decomposition tests, and practical cell parameters. The analysis identifies balanced polysulfide affinity, electronic connectivity, wet-state pore accessibility, active-site attribution, and framework stability as key structure–activity descriptors. Future progress requires rigorous mechanistic controls, scalable and sustainable synthesis, and testing under high-sulfur-loading and lean-electrolyte conditions. CTFs are therefore best regarded as molecularly tunable platforms for verifiable sulfur-redox regulation rather than universal catalysts. Full article

Timber structures constitute the primary form of ancient architecture in China and possess immense historical, artistic and scientific value. Having withstood the ravages of time over hundreds or even thousands of years, timber beams—one of the main load-bearing components in such structures—have largely sustained varying degrees of damage and require repair and reinforcement. Superelastic shape memory alloy (SMA) wires offer numerous advantages, including high strength, corrosion resistance, and stable recovery stress via stress-induced martensitic transformation, and are currently widely used in the field of concrete; however, research into their application for reinforcing timber beams remains limited. This study experimentally investigated the flexural performance of diagonally cracked Korean pine beams reinforced with prestressed Ni–Ti SMA wires. The results demonstrate that SMA reinforcement significantly enhances ultimate load-bearing capacity, with prestressing proving substantially more effective than simply increasing the number of wires. The optimal configuration—two SMA wires at 3% prestress—yielded the greatest improvement of 38.02% in ultimate capacity. Additionally, SMA reinforcement improved flexural stiffness, reduced compressive strain under equivalent loads, and lowered the neutral axis position, thereby enlarging the compression zone. These findings confirm that prestressed superelastic SMA wires offer a highly effective solution for strengthening diagonally cracked timber beams in existing structures. Full article

Modern distribution networks increasingly face reverse power flow, heavy loading or overloading, and voltage violations as distributed generation and flexible demand introduce large spatiotemporal variations in active-power injections and withdrawals. This paper proposes a planning-operation consistent DC-AC time-series optimal power flow (OPF) method for flexible-resource planning and operation optimization to mitigate these problems. The DC module optimizes investment decisions with embedded DG curtailment and flexible-load regulation to improve the operational relevance. The AC module further considers resource reactive-power flexibility and optimizes their operation under voltage constraints. The consistent design of the two modules in objective structure, operating constraints, and flexible-resource representation allows the planning results to be parsed as the initial schedule for AC operation refinement, improving operation-optimization efficiency. Furthermore, the model introduces discrete type-and-number BESS planning, endogenous initial state of charge (SOC) optimization, and a unified flexible-load model to improve operability and economic relevance. The method is implemented in a CloudPSS-based DSLab environment and tested on a real distribution feeder and the IEEE 123-node benchmark. The real-feeder case demonstrates coordinated mitigation of reverse-power export, branch overloads, and voltage violations. In the IEEE 123-node benchmark, the 8760 h AC operation case converges in 376.31 s, confirming tractability for long-horizon time-series optimization. Full article

Accurate modeling of the tooth friction coefficient is central to analyses of efficiency, vibration, and durability in enclosed gear drives. Physics-based models describe these contacts using a large set of coupled thermal, contact, and lubrication laws whose individual parameters have uncertainties that are difficult to propagate. This study proposes a compact alternative: the HAF model, a three-parameter phenomenological description of the friction coefficient as a function of the slide-to-roll ratio (SRR). The three parameters have distinct tribological interpretations: h (hysteresis) governs the steepness of the sigmoidal transition, a (attrition) governs the slope of the plateau, and ν (friction level) governs the overall magnitude. The model is calibrated using nonlinear regression with fourteen two-disc traction curves acquired with a one-factor-at-a-time (star) design around a reference operating point (1.6 GPa, 80 °C, and 20 m/s): the contact pressure (1.2, 1.6, and 1.9 GPa), the injection temperature (40, 80, and 100 °C), and the mean speed (10, 20, and 30 m/s) are each varied in turn, for both smooth and rough discs. Parameter uncertainty is quantified using the residual-resampling bootstrap (BIG) established in a companion paper and applied over 10⁵ iterations; it yields near-Gaussian, weakly correlated parameter distributions. The three HAF parameters are then expressed as linear functions of load, temperature, speed, and roughness; least-squares inference across the fourteen conditions shows that eleven of the fifteen regression coefficients differ significantly from zero at the 5% level, with roughness having the strongest effect on the friction level (t = 7.98). Substituting these laws into the HAF equation and reoptimizing the resulting expression globally yields a single closed-form model that reproduces the measured friction coefficient with a residual spread of σ ≈ 0.001 in friction-coefficient units (R² ≈ 0.996) and approximately Gaussian, zero-mean, and homoscedastic residuals with no evident systematic structure. Being differentiable and equipped with bootstrap confidence intervals, the model predicts friction throughout the tested operating envelope—across which the maximum friction coefficient varies by a factor of eight, from 0.0049 to 0.0388—and supports gradient-based optimization of low-friction operating conditions. The contribution of this study is a compact, interpretable, and statistically characterized predictive law for tooth friction, expressed in closed form as a function of the operating conditions and of the surface state. Full article

Probabilistic models of glued laminated timber are a required input to structural reliability analysis, and the JCSS Probabilistic Model Code is the reference most analyses adopt without independent verification. This paper reports an experimental programme of 61 small clear-wood specimens of GL24h glulam produced in Croatia, cut from three parent elements from one producer, delivered together as a single lot, covering bending, tension and compression parallel to grain, shear of wood and of the adhesive line, compression perpendicular to grain, and finger joints in tension and bending. All eight strength properties are tested against the reference model with confidence intervals and a family-wise error correction across the eight comparisons. Exactly one deviation survives: the coefficient of variation (COV) of tensile strength parallel to grain is 0.339 against the reference 0.180, with a Holm-adjusted p = 0.0064; no other property is distinguishable from the reference. The measured density COV of 0.026, against a reference value of 0.10, shows directly that the specimens are a cluster sample from three parent elements rather than independent draws from the GL24h population, which makes the elevated tensile scatter the more notable, since clustering suppresses observed variability rather than inflating it. The reliability consequence is then shown to depend on an assumption usually left implicit. Holding the characteristic value at the declared 19.2 MPa, as grading enforces, the reliability index of a tension-critical element falls from 3.30 to 3.09; holding the mean constant, it falls to 2.41. The absolute values depend on the load-duration class assumed for snow, but the contrast between the two treatments does not. Carrying the sampling uncertainty of the COV estimate through the calculation lowers these to predictive values of 2.88 and 1.82. The conclusion is correspondingly narrow: elevated tensile variability matters for the assessment of existing structures, where the mean is measured rather than declared, and for reliability studies that adopt generic parameters and vary only dispersion; it matters little where grading against a fractile is active. Full article

Against the background of the global green transition, digitalization has become an important driver of energy-efficiency improvement and carbon mitigation, making its overall environmental effects worthy of further investigation. This study constructs a pollution and carbon mitigation pressure (PCMP) index covering emission load, governance support, and ecological carrying capacity to examine the effect of the digital economy on PCMP, its transmission mechanism, boundary conditions, and regional heterogeneity. Using panel data for 30 Chinese provinces from 2013 to 2024, we apply a two-way fixed-effects model, mechanism analysis, a moderation model, instrumental-variable estimation, and a spatial Durbin model. The results show that digital-economy development significantly reduces PCMP, and this conclusion remains stable across multiple robustness checks. The digital economy alleviates PCMP by promoting industrial structure upgrading, while urbanization significantly strengthens this effect. The effect is more pronounced in Northern China, with a statistically significant north–south difference. Spatial analysis further shows that higher digital-economy development in neighboring regions is significantly associated with lower local PCMP. These findings extend research on the environmental effects of the digital economy by showing how industrial upgrading, urban conditions, and cross-regional linkages shape its contribution to pollution control, low-carbon transition, and regional sustainable development, with implications for the broader goals of the 2030 Agenda. Given the limitations of provincial data and the identification strategy, future research could use city-level data to further examine the underlying mechanisms and causal effects. Full article

Piles are structural members subjected to combined compression and bending and are typically constructed in soil or underwater environments. As a result, they are exposed to moisture, chloride attack, and various chemical agents, which may lead to cross-sectional deterioration. These environmental effects can reduce structural durability and should be appropriately considered during the design stage. In practice, compression members are rarely subjected to pure axial loads because eccentricity and lateral loads generally induce combined compression and bending actions. Therefore, the interaction between compression and bending should be carefully considered in structural design. This study experimentally and analytically evaluated the load-carrying capacity of hybrid concrete-filled FRP piles subjected to combined compression and bending. Based on the findings, a P–M interaction diagram was developed to predict the strength and behavior of hybrid concrete-filled FRP piles. Full article