Search Results (98)

A rare-earth (RE)-segregation-assisted route combining mechanical alloying and hot extrusion was used to produce a WE43 alloy with an in situ network-like bimodal structure. Mechanical alloying fragmented and partially dissolved RE-containing phases produced a supersaturated Mg-RE solid solution, and dispersed oxygen-bearing surface films. During the pre-sintering stage before hot extrusion, defect-rich prior powder-particle boundaries (PPBs) acted as preferential sinks for RE solutes, establishing RE-enriched regions before extrusion, while some oxygen-bearing species remained near PPBs and grain boundaries. During subsequent hot extrusion, RE solute drag and pinning by RE-containing precipitates and retained oxides restricted grain-boundary migration near PPBs, whereas rotation-assisted grain coalescence and growth occurred within particle interiors. In the 350—extruded alloy, the relatively coarse and fine grains averaged 299 and 144 nm and occupied 71 and 29 vol.%, while the precipitates averaged 97.1 and 9.2 nm. The 400—extruded alloy achieved a yield strength of 396 MPa, an ultimate tensile strength of 432 MPa, and an elongation of 7.9%. For the 350—extruded alloy, Orowan-type, solid-solution, grain-boundary, and dislocation strengthening contributed approximately 118.5, 116.8, 84, and 67 MPa, respectively, leaving an unresolved residual difference of 63.7 MPa. Coupled RE redistribution and oxide dispersion therefore provide a route to a favorable strength–ductility balance in powder-metallurgy Mg alloys. Full article

Mechanized harvesting of subsurface crops has long been confronted with the critical engineering dilemmas of high damage rates and high impurity rates. Traditional taxonomic classification methods based on botanical families and genera fail to provide effective guidance for the engineering research and development of harvesting machinery. From an engineering perspective, this paper proposes a novel classification logic that categorizes subsurface crops into three major types based on their soil burial depth and physical distribution characteristics: shallow-soil clustered growth type (0–20 cm), mid-soil scattered growth type (20–40 cm), and deep-soil vertically rooted type (>40 cm). The harvesting bottlenecks of representative crops within these strata, including potato, onion, peanut, sweet potato, cassava, and yam, are systematically elucidated. Furthermore, this review provides an in-depth analysis of the current state of frontier core technologies, such as bionic drag reduction excavation, flexible multi-stage separation, microscopic discrete element method (DEM) simulation, kinematic optimization, and AI-based visual perception. This paper aims to reveal the common bottlenecks in subsurface crop harvesting and prospect future developmental trends centered on the deep integration of machinery and agronomy as well as intelligent perception and adaptation, thereby providing a solid theoretical foundation and engineering reference for the innovation of global agricultural machinery. Full article

Against the backdrop of the accelerating integration of the digital and real economies, exploring how digital-–real technology convergence enables corporate decarbonization and green upgrading represents a critical pathway. This development pathway is conducive to promoting the high-quality growth of industry while aligning with China’s strategic goals of carbon peaking and carbon neutrality. Based on panel data from Chinese A-share listed manufacturing enterprises during 2012–2023, and employing a fixed-effects model, this study empirically investigates how DRTC influences firms’ carbon performance, as well as the mechanisms through which this effect is transmitted. In addition, this research explores the intermediary function of green innovation and further investigates the contingent effects of R&D investment and financing constraints. The results show that DRTC contributes significantly to improving corporate carbon performance, with the validity of this conclusion supported by multiple robustness examinations. Green innovation acts as a partial mediator, channeling a portion of DRTC’s carbon-reduction benefits. R&D investment amplifies these positive effects, whereas financing constraints create a notable drag on DRTC’s effectiveness. Heterogeneity analysis adds nuance, showing that DRTC’s positive impact is substantially more pronounced in large-scale firms and asset-intensive enterprises. By clarifying the internal mechanisms and limiting conditions that underlie DRTC’s improvement of corporate carbon performance, this study enriches the interdisciplinary literature by linking research on the digital economy with discussions on green and low-carbon development. Full article

The presence of bubbles severely threatens the insulation safety of power transformers. Understanding bubble accumulation characteristics is essential for predicting potential insulation weaknesses. In this study, we propose a Euler–Lagrange two-phase flow model, combined with an experimental platform, to investigate the accumulation and growth characteristics of bubbles in typical oil channels. The continuous phase flow field is solved within the Eulerian framework, while discrete bubble trajectories are tracked using the Lagrangian approach, simultaneously accounting for drag, buoyancy, and friction forces. The results indicate that bubbles primarily accumulate on the top insulating paper surfaces within horizontal and corner oil channels. In horizontal channels, the accumulation rate correlates positively with flow velocity and bubble concentration; furthermore, paper overlapping gaps intercept sliding bubbles, promoting their coalescence into larger ones. Conversely, at channel corners, the accumulation length and rate decrease as flow velocity increases, with accumulation weakening significantly when the velocity exceeds 0.6 m/s. Additionally, bubble growth is highly sensitive to flow velocity and temperature: higher velocities inhibit bubble coalescence, whereas elevated temperatures accelerate both coalescence and growth. Ultimately, this research reveals the fundamental accumulation laws of bubbles in transformer oil channels, providing a reliable analytical tool and theoretical reference for assessing bubble-induced insulation risks. Full article

Bubble-assisted drag reduction is a promising strategy for improving the energy efficiency of underwater bodies, but its effectiveness depends not only on air injection but also on the ability of the body geometry to retain bubbles close to the surface. Drawing inspiration from the air retention and bubble release mechanisms of penguin plumage, this study examines whether a simplified penguin-inspired geometry can enhance bubble coverage compared to a conventional axisymmetric body. Prototypes featuring a penguin-inspired shape and a torpedo shape, each equipped with an air diffuser and injection holes, were designed and evaluated in a dedicated towing tank. At low air pressure, the penguin-inspired body demonstrated a 31.5% reduction in drag coefficient compared to the condition without bubbles. In contrast, the torpedo-shaped body did not exhibit a reduction in drag coefficient under identical air-injection conditions. Both geometries showed diminished performance at higher pressures, likely due to bubble growth, coalescence, and decreased near-wall retention. These findings indicate that the effectiveness of bubble-assisted drag reduction is highly dependent on body geometry and that bioinspired body morphology may play a critical role in sustaining a layer rich in air bubbles near the surface. This study offers a preliminary experimental assessment of penguin-inspired air lubrication and identifies bubble size, air-flow control, and quantification of surface coverage as key areas for future research. Full article

Hydrophobic and superhydrophobic surfaces have emerged as key solutions for fluid transport, biofouling prevention, and energy efficiency, with market forecasts projecting a compound annual growth rate (CAGR) of over 15% through 2030 due to their broad range of applications. This review critically examines the principles of natural hydrophobicity, as exemplified by lotus leaves and shark skin, and their translation into engineered surfaces via micro/nanofabrication techniques, such as laser patterning, etching, and self-assembly. Recent advances in hybrid nanomaterials have demonstrated WCAs in the range of 140–160°, along with enhanced mechanical strength and chemical stability, enabling applications in self-cleaning, anti-corrosion, and oil–water separation technologies. Superhydrophobic coatings are particularly important for reducing ice adhesion by more than 80%, while drag reduction in pipelines can reach up to 30%, contributing to energy savings. Despite these advances, challenges remain in achieving long-term stability under harsh environmental conditions, minimizing environmental impact, and developing cost-effective, scalable fabrication techniques. Future directions focus on environmentally friendly, multifunctional nanocomposites with switchable wettability, including pH- and light-responsive coatings capable of reversibly transitioning between superhydrophilic (<5°) and superhydrophobic (>150°) states, paving the way for sustainable and adaptable surface technologies. Full article

Against the backdrop of global carbon neutrality, the cross-regional allocation of green electricity is pivotal for energy transition, yet its impact on inclusive economic growth and regional equity remains contentious. This study addresses the spatial welfare mismatch arising from large-scale power transmission in China. Utilizing provincial panel data from 2006 to 2022 and employing the staggered rollout of Ultra-High Voltage (UHV) lines as a quasi-natural experiment, we apply advanced econometric models, including CS-DID and Bartik instrumental variables, to identify causal effects. Empirical results reveal an asymmetric “cost-benefit separation” effect: while green electricity imports significantly bolster high-quality development (HQD) in eastern recipient regions, exports exert a drag on western provinces by triggering capital outflow, profit deprivation, and ecological load. Consequently, regional HQD gaps exhibit divergence rather than convergence. However, we find that fiscal ecological compensation acts as a critical moderating buffer, effectively reversing this trend and driving conditional convergence and sustainable regional development. Heterogeneity analysis further indicates that market-oriented electricity reforms and “East Data, West Computing” infrastructure mitigate these negative externalities. These findings underscore the necessity of shifting from a purely engineering-focused transmission model to an institutional framework centered on energy justice, offering actionable insights for achieving SDG 7 and SDG 10 synergies. Full article

Brush seals, as a fundamental dynamic sealing technology in the aerospace and energy propulsion industries, require performance enhancement through instantaneous adjustment of the friction coefficient and force analysis of brush filaments. This paper establishes an instantaneous friction coefficient correction method based on the open volume between bristles and the backing plate. The downstream section of the double-row brush wire (2.6 mm) was quantitatively identified as the maximum leakage point, and it was found that the vortex characteristic length in the downstream area is approximately 1–3 times the bristle gap, with an increasing pressure ratio enhancing downstream turbulence and reducing gas leakage. A cantilever beam structural model was developed to assess the motion, force, and hysteresis properties of a single filament. Additionally, a porous medium model was utilized to elucidate the flow field and temperature distribution within the seal. The results suggest that the lag angle increases linearly over the first one-third of the brush wire’s length from the free end to the fixed end and is directly proportional to the pressure difference ΔP, reaching a maximum of 10.18°. The viscous drag causes the radial force y-component F_xy to increase and then decrease near the free end. The rear baffle contact force, F_b, shows variable peaks at two-thirds of the filament length. The displacement at the brush filament’s free end, the deflection angle, and the bending moment are directly proportional to the pressure differential. As pressure increases, the deformed region propagates toward the fixed end, and the maximum displacement at the free end of the brush wire reaches 13.04 mm. The leakage rate increases nearly linearly with ΔP and its deformation, reaching a maximum of 0.00849 m²/s. The pressure gradient growth rates of 164%, 73%, and 29% at the front baffle corner demonstrate that adding pressure chambers on front and rear baffles is optimal for high-pressure scenarios (ΔP > 0.3 MPa), while the formation of vortices between bristles and rotor reduces tip friction force and front-row turbulent disturbance, providing design guidance for extending seal service life. Full article

Gondolas are a useful mode of transportation in the mountainous regions. In regions located at high altitudes, atmospheric icing is a significant safety hazard to gondola infrastructure. In this study, multiphase numerical simulations of ice accretion on the monopole gondola tower were performed and validated against experimental and analytical model results. An analytical model has limitations for calculating ice loads on large cylinder diameters, and conducting experiments on large cylinders is also challenging due to practical constraints. Ansys FENSAP-ICE 2025 R2, as the primary numerical simulation tool, appears to be an attractive alternative for better estimation of ice loads on structures with larger diameters. The numerical analysis demonstrates that the ice accretion on the access ladder of the gondola tower is more critical than its main structure. This is because the ice growth on the smaller components is higher than on the larger components. A solution based on passive structural design is suggested, in which a semi-circle-shaped wind shield is introduced along the windward side of the tower which successfully diverts the flow by creating a protective droplet shadow on the trailing components, significantly reducing the accreted ice loads. It can also serve as a safety barrier for maintenance personnel. The study also showed that increasing the shield diameter ultimately reduced overall ice accretion, due to the dominant droplet drag forces over inertial forces. Full article

This study systematically investigates the effects of solution temperature ranging from 1060 to 1150 °C on grain growth kinetics, microstructural evolution, and tensile properties of GH4698 superalloys. The results indicate that grain size coarsens parabolically with increasing solution temperature. Based on the Sellars model, the grain growth time exponent n is determined to be 3.4 and the activation energy Q is 478.7 kJ·mol⁻¹. This confirms that the grain growth process is significantly influenced by both MC carbide pinning and alloying element drag effects. Additionally, due to the coarsening of grains, the precipitation density of M₂₃C₆ carbides per unit grain boundary length increased from 0.26 μm⁻¹ to 0.39 μm⁻¹. The ultimate tensile strength at room temperature decreased from 1268 MPa to 1226 MPa, and the yield strength decreased from 840 MPa to 807 MPa, while the elongation remained at 28–32%. At 700 °C, the ultimate tensile strength decreases from 974 MPa to 904 MPa, and the yield strength decreases from 755 MPa to 696 MPa, with the elongation remaining at ~6%. Quantitative analysis reveals that the decrease in strength is primarily due to the weakening of grain boundary strengthening caused by grain coarsening. At 700 °C, the deformation mechanism transitions from dislocation shearing at room temperature to stacking fault shearing. This not only leads to a reduction in strength but also, accompanied by grain boundary weakening, results in a decrease in elongation. Full article

Riparian vegetation plays an important role in the morphological evolution of rivers; here, an alternative numerical methodology for modeling river morphodynamics influenced by vegetation is presented. The approach integrates a vegetation growth and flow-resistance submodule coupled with the TELEMAC–MASCARET system. Vegetation is represented at the patch scale, and its hydraulic effect is incorporated through an additional drag force in the momentum equation, while stem obstruction is accounted for using the porosity formulation in TELEMAC-2D. Vegetation dynamics consider water depth variability, interspecific competition, and nutrient availability. The model is applied to a braided river reach in southeastern Mexico. The results indicate that riparian vegetation promotes more organized flow paths, enhances bar development, and plays a significant role in modulating bar stability. These findings highlight the importance of explicitly representing flow–sediment–vegetation feedback in river hydro-morphological modeling. Full article

Marine renewable energy (MRE) systems operate in harsh marine environments where long-term exposure to seawater leads to biofouling, resulting in increased surface roughness, hydrodynamic drag, added mass, structural loading, sensor degradation, and reduced energy production. Despite its significant operational and economic impact, biofouling management in MRE devices has traditionally relied on manual inspections and empirical growth models, which offer limited predictive capability. This review provides a structured, data-centric synthesis of recent advances in machine learning (ML) and bioinformatics approaches for biofouling modeling, performance prediction, and maintenance planning in offshore wind turbines, tidal turbines, and wave energy converters. The study systematically examines key fouling locations and associated engineering impacts, and analyzes the major data streams used for predictive modeling, including SCADA and condition-monitoring time series, metocean variables, inspection imagery, laboratory and field experiments, and environmental DNA (eDNA) sequencing outputs. We compare modeling strategies ranging from physics-based simulations to classical ML, deep learning, computer vision, and hybrid physics-informed frameworks, and discuss how biological indicators such as microbial community profiles and eDNA-derived taxa abundances can be integrated as predictive features. The review further outlines emerging digital twin architectures for fouling-aware performance forecasting and maintenance decision support. Finally, we identify key challenges including data scarcity, cross-site generalization, validation practices, and uncertainty quantification, and propose future research directions toward integrated, proactive biofouling management systems in marine renewable energy infrastructure. Full article

With the growth of urban zones and the increasing need for energy, the use of renewable energy solutions in the built environment becomes a must. Due to their small size and the ability to capture wind from any direction, vertical-axis wind turbines are an alternative to conventional wind energy generators. However, the use of these turbines in the built environment faces difficulties due to performance inefficiencies, particularly because of the intricate aerodynamic characteristics of the blades. This work investigates a method for increasing the efficiency of VAWTs by addressing blade-to-blade interactions using Computational Fluid Dynamics simulations. The research aims to improve turbine design for urban locations, which motivates the application context of the study. The present numerical model employs a uniform inflow to isolate blade–blade interaction mechanisms under controlled conditions. The paper presents a design that minimizes aerodynamic losses, decreases turbulence-induced drag, and increases overall energy capture efficiency by modeling different blade configurations and their interactions. The performance of four asymmetric configurations of blade chord and radius was numerically studied and compared to a symmetric configuration. Full article

Laminar separation bubbles (LSBs) on low-Reynolds-number airfoils are sustained by intrinsic unsteadiness driven by Kelvin–Helmholtz (K-H) growth in the separated shear layer. Using incompressible 2D URANS with the SA-$\gamma$ transition model for a NACA 0012 airfoil at $Re=5.3\times {10}^4$, we reveal that numerical dissipation behaves as a critical bifurcation parameter. Validated against the recent Jardin (2025) experimental benchmark, the physical state correctly resolves the LSB-induced pressure plateau ($C_p$) and local negative skin friction ($C_f<0$). However, when numerical dissipation exceeds the K-H instability growth rate, the physical limit-cycle oscillation collapses into a spurious fixed-point attractor—a phenomenon defined as numerical quenching. This pseudo-convergence triggers a catastrophic ∼30% deficit in mean lift ($C_l$). Furthermore, at $\alpha =6^{\circ }$, a drag-mechanism inversion is identified: while the physical branch is dominated by LSB-induced pressure (form) drag, the quenched branch exhibits a non-physical drag surge that exceeds the fully turbulent baseline. Phase portraits and power spectral densities ($St\approx 0.2$) provide objective diagnostics, demonstrating that standard residual convergence is a deceptive indicator of physical fidelity in transitional separated aerodynamics. Full article

The two most severe cosmological tensions in the Hubble constant $H_0$ and the matter clustering amplitude $S_8$ have the same relative discrepancy of 8.3%, which suggests that they may have a common origin. Modifications of gravity and exotic dark fields with numerous free parameters introduced in the Einstein field equations often struggle to simultaneously alleviate both tensions; thus, we need to look for a common cause within the standard $\Lambda$CDM framework. At the same time, linear perturbation analyses of matter in the expanding $\Lambda$CDM universe have always neglected the impact of comoving peculiar velocities $\mathbf{v}$ (generally thought to be a second-order effect), the same velocities that, in physical space, cannot be fully accounted for in the observed late-time universe when the cosmic distance ladder is used to determine the local value of $H_0$. We have reworked the linear density perturbation equations in the conformal Newtonian gauge (sub-horizon limit) by introducing an additional drag force per unit mass $-\Gamma \left(t\right)\mathbf{v}$ in the Euler equation with $\Gamma \equiv \gamma \left(2H\right)$, where $\gamma \ll 1$ is a positive dimensionless constant and $2H\left(t\right)$ is the time-dependent Hubble friction. We find that a damping parameter of $\gamma =0.083$ is sufficient to resolve the $S_8$ tension by suppressing the growth of structure at low redshifts, starting at $z_{★}\simeq 3.5–6.5$ to achieve $S_8\simeq 0.78–0.76$, respectively. Furthermore, we argue that the physical source causing this additional friction (a tidal field generated by nonlinear structures in the late-time universe) is also responsible for a systematic error in the local determinations of $H_0$—the inability to subtract peculiar tidal velocities along the lines of sight when determining the Hubble flow via the cosmic distance ladder. Finally, the dual action of the tidal field on the expanding background—reducing both the matter and the dark energy sources of the squared Hubble rate $H^2$, thereby holding back the cosmic acceleration $\ddot{a}$—is of fundamental importance in resolving cosmological tensions and can also substantially alleviate the density coincidence problem. Full article