Search Results (3,921)

Gravel soil used as backfill behind rockfall barriers in mountainous roads can extend structural service life and support sustainable resource utilization. However, rainfall-induced erosion may cause soil loss and reduce its buffering capacity. The fibers are short discrete fibers with a length of approximately 12 mm and an average diameter of 32.7 μm, corresponding to an aspect ratio of approximately 367. Reinforcement is achieved through fiber–soil interaction mechanisms, including particle bridging, interfacial friction, and pull-out resistance. The effects of polyurethane and fiber contents on compressive strength, shear strength, and impact resistance were evaluated using response surface methodology. Scanning electron microscopy was used to examine the microstructural features associated with the reinforcement mechanisms, and engineering-scale model tests were conducted to assess erosion and impact resistance under representative service conditions. The results show that polyurethane and fibers produce significant nonlinear enhancement effects on the mechanical properties of gravel soil, mainly through their individual contributions, whereas their interaction is limited. Multi-objective optimization indicates that the optimal mixture contains 6.8% polyurethane and 0.19% fiber, with prediction errors below 5%. The unconfined compressive strength of the gravelly soil increased from 107.6 kPa to 931.5 kPa, representing a 765.7% increase. Cohesion increased from 23.4 kPa to 83.44 kPa, representing a 256.4% increase. The internal friction angle increased from 43.4° to 61.23°, corresponding to a 41.08% increase. Under 1 h of intense rainfall erosion, the stabilized soil exhibited only slight surface particle detachment and maintained overall integrity. In impact tests, the velocity attenuation rate reached 65.6–71.4%. The proposed material provides a sustainable solution for improving buffer layers in rockfall barriers. Full article

Industrial gear contacts operate under mixed-to-boundary lubrication where reliable antiwear protection is essential. This study assesses whether carbon nanomaterials can enhance the performance of zinc dialkyldithiophosphate (ZDDP) under severe conditions. A crossed-cylinder Reichert configuration (2 GPa, 75 °C, 1 m/s) with PAO6 was used to test ZDDP (1 wt%) and its blends with carbon nanotubes (CNT, 0.05 wt%), graphene nanoplatelets (GNP, 0.05 wt%), and few-layer graphene (FLG, 0.05 wt%) at 1, 10 and 60 min. The lubrication regime was boundary. Friction, specific wear rate (k), and tribofilm coverage were quantified. Oils containing only carbon nanoparticles could not sustain the test (seizure within minutes), confirming the necessity of ZDDP. After 60 min, average CoF remained similar across formulations and largely governed by ZDDP. By contrast, wear showed marked differences: relative to ZDDP alone (A), ZDDP + CNT (F) and ZDDP + GNP (G) reduced k by 52% and 48%, respectively, and exhibited higher tribofilm coverage (F = 68%, G = 72% vs. A = 57%). Time-resolved tests revealed that long-duration degradation was mitigated in F and G: from 10 to 60 min, k rose by 72% (F) and 58% (G) versus 159% for A; coverage decreased by only 8% (F) and 3% (G) versus 22% for A. SEM–EDS indicated no major differences in average elemental chemistry among formulations, suggesting an improvement on tribofilm coverage/stability rather than compositional change. Full article

Land-based airborne wind energy systems (LB-AWESs) offer a promising approach to harvesting high-altitude wind resources while significantly reducing costs. However, overall performance is heavily constrained by energy dissipation along the power chain, spanning from aerial traction to ground electromechanical conversion. While existing research and reviews predominantly focus on aircraft configurations or control strategies, comprehensive analyses of the energy transmission efficiency remain scarce. To fill this gap, this paper provides a holistic review of four critical stages: wind energy capture, tether transmission, ground mechanics, and electromechanical coupling. Distinct from traditional reviews centered on individual components, this study adopts a holistic perspective of the transmission chain to prioritize the analysis of loss mechanisms across different stages. In particular, it highlights that internal friction losses within multi-strand braided tethers under large-scale, cyclic loading conditions constitute a significant yet long-overlooked factor affecting energy transmission efficiency. Additionally, the stability and performance factors of umbrella-ladder configurations are qualitatively evaluated. By integrating existing theoretical studies, experimental findings and engineering practices, this paper identifies the key design factors affecting transmission efficiency, comprehensively elucidates the energy dissipation mechanisms of various subsystems, and proposes core efficiency enhancement methodologies, providing a foundational reference for the optimal design of next-generation LB-AWESs. Full article

Government data governance has become an important institutional mechanism for reducing information frictions, improving data-resource allocation, and supporting firm innovation in the digital economy. However, whether government data governance can promote firms’ technological catch-up remains insufficiently understood. Based on the quasi-natural experiment of the establishment of Big Data Administrations, this study constructs a multi-period difference-in-differences model to examine the impact of government data governance on firms’ technological catch-up. Using panel data from Chinese A-share listed firms from 2011 to 2021, the DID estimates indicate that the establishment of Big Data Administrations significantly improves firms’ technological catch-up. This estimated effect remains robust across placebo tests, specifications controlling for differential trends associated with pre-treatment city characteristics, and double/debiased machine learning estimation. Mechanism analyses provide evidence consistent with three channels: technology stimulation, digital-ecosystem optimization, and competition strengthening. Heterogeneity analyses further show that the effect is evident among non-state-owned enterprises, firms with higher information asymmetry, and larger firms. Additional spatial analyses suggest that neighboring cities’ data governance capacity does not generate stable positive spillovers; instead, it may be associated with negative spatial externalities, potentially reflecting siphoning or competitive crowding-out pressures. These findings highlight government data governance as an institutional driver of firm technological progress and provide policy implications for improving digital governance capacity, optimizing digital ecosystems, and promoting high-quality development. Full article

Friction stir welding (FSW) began as a fairly specialized joining method, but over the past three decades it has evolved into something considerably more versatile, a manufacturing platform that now handles complex multi-material assemblies and solid-state additive processes with reasonable reliability. This review follows this evolution, paying particular attention to friction stir additive manufacturing (FSAM) and the persistent difficulties that arise when joining dissimilar systems, such as aluminum to steel or metals to polymers, where the fate of the joint is largely decided by how well the intermetallic compounds are kept under control. Machine learning, artificial intelligence, and high-fidelity numerical models are reducing the reliance on trial-and-error that once dominated parameter selection and defect prediction, bringing FSW closer to the operating principles of Industry 4.0. Hybrid variants, including ultrasonically assisted and underwater FSW, also receive attention here, as they offer researchers finer control over heat generation and plastic flow than the standard process allows. Throughout the study, microstructural observations are directly connected to mechanical results, with the aim of analyzing the current state of solid-state manufacturing and identifying the questions that most urgently need answering. Full article

Despite its excellent impact toughness and work-hardening capacity, high-manganese steel (HMS) suffers from low initial hardness, limiting its wear resistance under low-stress conditions. Conventional surface hardening methods for HMS involve high cost and intensive energy consumption and produce only shallow hardened layers; moreover, the understanding of laser transformation hardening in HMS remains insufficient. To address these gaps, this study employs a high-energy-density laser for rapid and precise surface modification of Mn13 HMS. The studied Mn13 steel contains 1.98 wt.% Cr, which contributes to solid-solution strengthening and influences the phase transformation behavior during laser transformation hardening. By optimizing the laser power, a well-defined laser-quenched layer with a gradient microstructure along the thickness direction is obtained. Microhardness at the surface treated by laser transformation hardening at 1.5 kW improved significantly, primarily due to grain refinement and a dense dislocation network. The small fraction of martensite contributes indirectly by generating geometrically necessary dislocations and acting as local barriers to dislocation glide. Along the depth direction, the microhardness varies with the gradient microstructure: coarse columnar grains at intermediate depths cause a slight decrease in microhardness, while the substrate restores it. Correspondingly, the laser-quenched surface exhibits improved wear resistance, as indicated by reduced friction coefficient, wear depth, and wear volume, and the dominant wear mechanism shifts from adhesive to abrasive wear. Importantly, this gradient configuration maintains a mechanically compatible transition between the quenched layer and the substrate, preserving impact toughness comparable to that of the untreated material. Full article

Given the widespread application of multi-story modular container building structures, this article proposes a new seismic isolation system called the “sliding friction isolation system (IS)” that utilizes friction energy dissipation between containers. Firstly, lateral stiffness tests were conducted on a 20 ft container, a 40 ft container, and 20 ft connected containers. The constraint consists of four fixed-bottom corner pieces, and the load is achieved using a symmetrical longitudinal concentrated loading method. Their stiffness values were 58.07 kN/mm, 33.41 kN/mm, and 60.03 kN/mm, respectively, providing the necessary parameters for IS. Secondly, an IS model was established, and based on the theory of random vibration, the relationship between c_ei (the equivalent damping of i layer of the structure) and μ (the inter-layer friction coefficient) of the system was obtained. Thirdly, a nonlinear finite element model of a six-story container building was established. Namely, the non-isolation system with standard damping ratios (NIS-sdr), the non-isolation system with equivalent damping ratio (NIS-edr), and the IS. Elastic-plastic nonlinear time-history analyses were then conducted to study the dynamic responses of three systems under strong earthquakes. The analyses yielded the top displacement of the structure, each structural layer’s maximum displacement and displacement angle, the slip of each layer, the hysteresis loops, and the cumulative dissipated energy of IS. The results show that compared to NIS sdr and NIS edr, IS can effectively reduce the maximum interlayer displacement. The largest angular displacement between the structural layer of IS and NIS-edr is far less than that of NIS-sdr. The spectral characteristics of seismic waves (the EL-Centro wave, Taft wave, and artificial wave) can significantly affect the dynamic response of IS. Additionally, the length of the sliding hole on the corner piece can be set to 35 mm based on the displacement of each layer under the Taft wave to meet the standards for container houses (T/CECS 1932-2025). Full article

The influence of BN particle size on lithium grease performance was systematically compared among a base grease (Li), a micro-BN (3 µm, 0.1 wt%) modified grease (Li + 0.1% mBN), and a nano-BN (50 nm, 0.1 wt%) modified grease (Li + 0.1% nBN). SEM shows that addition nano-BN leads to a more compact soap fiber networks, whereas micro-BN tends to agglomerate and provides limited reinforcement, leaving the base grease with a loose, porous network. Consequently, Li + 0.1% nBN outperforms both Li and Li + 0.1% mBN in dropping point (199.5 °C vs. 194.9 °C and 198.6 °C), oil separation (0.39% vs. 0.64% and 0.44%), and flow point (49% vs. 45% and 47%). Its plateau modulus is significantly higher, reflecting stronger network entanglement. However, Li + 0.1% nBN shows lower structural recovery (61.0%) than Li (65.8%) and Li + 0.1% mBN (67.2%) due to rigid particle–fiber junctions. Notably, Li + 0.1% mBN exhibits a unique frequency-dependent viscoelasticity: higher tanδ at low frequencies but lower tanδ at high frequencies relative to Li. Tribologically, Li + 0.1% nBN reduces friction coefficient by 35% and wear scar diameter by 12.7% compared with Li, outperforming Li + 0.1% mBN. XPS confirms a protective hybrid tribofilm (BN + organic nitrogen species + iron oxides) on the nano-BN lubricated surface. Particle size critically governs BN–fiber interactions and the resulting rheological and tribological performance. Full article

Alfalfa densification is a critical step in feed utilization and biomass energy conversion because it directly affects the transport efficiency, storage stability, and energy consumption of biomass processing systems. However, the thermodynamic behavior of the densification process remains poorly understood, especially under open-die conditions without external heating. This study investigated the thermo-mechanical characteristics of alfalfa pellet open-die densification without external heating by combining experimental measurements with ANSYS macro-continuum simulation. Stress transmission and temperature field distributions were analyzed. The results showed that the pellet quality index under different process conditions remained above 800, meeting the requirements for pelleted feed. Moisture content had a more significant effect on forming pressure than other factors; as moisture content increased, the forming pressure decreased. At an aspect ratio of 5.0, the forming pressure was below 45 kN. Simulation results further indicated that aspect ratio had a stronger influence on frictional behavior during densification. Under an aspect ratio of 5.0, the energy consumption was 888.53 J, and the heat flux reached 0.0062 W/mm². These results indicate that frictional dissipation driven by radial force is the dominant mechanism governing thermo-mechanical coupling. Moisture content and aspect ratio significantly affected both peak compression force and coupling intensity. Although reducing moisture content or increasing aspect ratio improved pellet quality, it also increased die load due to enhanced radial force. The coupling intensity followed the order: peak pressure stage > moving stage > compression stage. These findings reveal the evolution of stress and temperature fields during alfalfa densification, offering critical theoretical guidance for optimizing densification process parameters. Full article

Background/Objectives: Latent fingerprints are routinely recovered from conventional porous and non-porous substrates; however, biologically active surfaces such as plant leaves are generally regarded as unsuitable for dactyloscopic evidence. Because vegetation is frequently present at crime scenes, this study aimed to systematically evaluate whether plant leaves can retain usable friction ridge detail and to determine the durability and forensic value of such traces under laboratory and outdoor conditions. Methods: Latent fingerprints were deposited on leaves of multiple plant species (maple, ash, dandelion, bird cherry, chestnut, climbing ivy, and five-leaved ivy) under dry and hydrated conditions and at defined time intervals after deposition. Visualization was performed using several powders, with SupraNano Fluorescent Green magnetic powder providing the best performance. Developed impressions were photographed using controlled illumination and evaluated using automated quality assessment (NFIQ 2.0) and comparison software (Innovatrics IDkit 9.1.7.1004). Additional experiments examined living, growing leaves exposed to natural weather conditions for extended periods. Results: Usable ridge detail was successfully visualized on all tested species. Bottom leaf surfaces and hydrated samples generally provided better preservation and contrast. Identifiable traces persisted for up to 20 h on detached leaves and for up to 35 days on living leaves despite growth-related deformation. Under outdoor exposure, fingerprints on ivy remained visible and comparable for up to 60 days. Although overall automated quality scores were reduced by background venation, selected impressions achieved measurable comparison scores and successful matches. Conclusions: Plant leaves can serve as unconventional yet viable carriers of latent fingerprints. Magnetic fluorescent powder development combined with careful documentation enables recovery of forensically useful ridge detail even after prolonged environmental exposure. These findings expand the range of substrates that should be considered during crime scene processing and provide practical guidance for evidence collection on vegetation. Full article

This study focuses on a novel three-span hybrid continuous beam bridge, analyzing the force performance and key design parameters of the non-cellular post-support plate joint. A finite element model and parametric analysis were used to reveal the stress distribution patterns, the load-bearing characteristics of the connectors, and the load transfer path under negative bending moments. The study shows that the axial force within the joint is equitably shared among three load paths: the top slab concrete (20.7%), the bearing plate (40.1%), and the shear connectors (39.2%). Although interfacial friction contributes approximately 27.1% to the total shear resistance, it is conservatively recommended to neglect this effect in design due to inherent uncertainties. Parametric analysis reveals distinct marginal effects and efficiency thresholds: increasing the bearing plate thickness from 20 mm to 100 mm results in a mere 1.0 MPa reduction in the peak concrete stress, while extending the joint length beyond 1.0 times the beam height renders the central connectors ineffective. Furthermore, reducing the connector stiffness effectively lowers the non-uniformity coefficient from 2.3 to below 2.0. Notably, the first row of web PBLs carries 34.8% to 47.2% of the total shear force, with a stable non-uniformity coefficient of 1.05–1.06, establishing it as the critical control section for simplified design. These findings provide a theoretical basis and practical guidance for the design of similar joints in hybrid girder bridges. Full article

The frictional behavior and stability of skid shoe systems are critical to the safety and controllability of walking-type incremental launching for long-span steel truss bridges. Therefore, this study investigates friction control mechanisms and multilayer pad stability through two tests: (1) skid shoe tests to evaluate low-friction performance, sliding stiffness, and the stability of stacked pad assemblies, and (2) interface friction tests to examine the frictional behavior of different material combinations intended to provide high-friction restraint. The results show that Modified Graphene-Enhanced (MGE) plates, when combined with grease and stainless steel, reduce the friction coefficient to 0.017–0.074. High-stack pad assemblies (6–16 layers) exhibited a progressive interlayer slip, with cumulative displacements exceeding the allowable limit, leading to instability; anti-slip measures such as shear keys and segmented restraints were recommended. A load-dependent sliding stiffness relationship, y = 57.46 + 0.00886x, was established to characterize the variation in nominal sliding stiffness with vertical load. The findings provide experimental data and engineering recommendations for the design and operation of skid shoe systems in heavy-load incremental launching applications. The proposed criteria and regression model are applicable to the tested pad geometry, interface configuration, and loading conditions investigated in this study. Full article

Recent advancements in structural engineering have driven the development of sophisticated damping mechanisms aimed at reducing the detrimental effects of structural vibrations. As a result, accurate numerical modeling and analytical evaluation have become essential for assessing structural stability and enhancing seismic resilience. This study introduces a model-updating framework to develop analytical constitutive models for structural damping systems. The proposed approach employs a genetic algorithm (GA) to calibrate model parameters by minimizing the discrepancy between analytical predictions and experimental responses. Experimental force–displacement hysteresis data and displacement time-history records are used at both the element and system levels for model calibration. The methodology is applied to a rubber isolator, a 10-story structure equipped with Pall friction dampers, and a 6-story structure with friction dampers to evaluate its performance under different dynamic characteristics and damping mechanisms. The results indicate that the proposed approach achieves very high accuracy, with prediction errors reduced to negligible levels for both force and displacement responses in all cases. Consistent performance is observed using both global and local displacement measures in friction-damped systems, indicating the robustness of the proposed method. Overall, the findings indicate that the GA-based model-updating framework provides an efficient and reliable tool for improving the predictive capability of analytical models of structures with nonlinear damping devices and is suitable for practical structural engineering applications. Full article

Mobility hubs promise to reduce car dependence and make multimodal travel work in practice, yet behavioural evidence remains limited when hub improvements coexist with easier car access. This article examines the tension at Rome Trastevere, an urban rail node that gradually acquires mobility-hub functions while facing improved parking access near Piazza della Radio. The empirical analysis combines a pilot survey of 83 users with an on-site stated preference survey of 204 valid respondents. The stated preference instrument uses a route-based feasible-choice design with nine choice sets per experiment: respondents evaluate alternatives among bikes, walking, e-scooters, e-mopeds, public transport, private cars, and shared cars under variations in travel time, travel cost, and search time. The paper estimates a multinomial logit model in Apollo and uses sample enumeration, supported by Monte Carlo simulation, to assess four parking and shared-mobility scenarios and produce confidence intervals around predicted probabilities. Results show that users respond to time, monetary cost, and search friction in coherent and policy-relevant ways. Setting the car parking search time to zero increases predicted car probability only marginally, by about 0.9% relative to the baseline. By contrast, a EUR 1/h increase in parking cost reduces predicted car probability by about 14.7%, while a EUR 1.5/h increase reduces it by about 22.4%. A coordinated scenario combining higher parking cost and lower shared-mode search time produces the lowest predicted car probability and strengthens e-scooter and e-moped alternatives, while public transport remains the dominant option. Findings indicate that parking pricing steers behaviour more clearly than parking convenience destabilizes it in the tested range. The paper shows that mobility-hub performance depends on coordinated access management, including parking regulation, shared-service reliability, and legible multimodal transfer. Full article

The acceleration and deceleration of high-speed gas flow within a pipeline, induced by the action of flow-restriction devices, frequently result in the emergence of unsteady flow phenomena. Consequently, the generated excitation forces provoke intense vibrations in the pipeline, thereby substantially elevating the operational risks of the pipeline system. To mitigate such risks, the pipeline is typically subjected to fixed constraints to reduce vibration. A pipeline designed to simulate unsteady airflow was developed for the purpose of validating the vibration attenuation effect. Within this context, the effects of binding and friction constraints were compared through fluid–structure interaction simulation, and their respective mechanisms of action were analyzed individually. The results demonstrate that the constraints, in conjunction with the original pipeline, will result in a higher first-order natural frequency, which constitutes one of the primary methods for mitigating resonance effects. Both friction constraints and binding constraints significantly elevate the first-order natural frequency of the pipeline system, with binding constraints demonstrating higher efficiency. This phenomenon is attributable to the arch-like bending deformation observed in such experimental pipelines during first-order resonance, as binding constraints effectively maximize the restriction on pipeline strain. Through a comparative analysis of the time-domain and frequency-domain results of outlet pipe 1 before and after constraint application, it was observed that the axial RMS value of the constrained pipe decreased by 21.8%, while the radial value diminished by 33%. This finding further substantiates that imposing binding constraints at the location of maximum strain can elevate the pipe’s natural frequency by reducing both strain and the effective length of the “beam”, thereby significantly alleviating pipe vibrations induced by unsteady flow. Full article