Polyurethane (PU) is widely used in nuclear environment as an indispensable engineering material but faces performance degradation under long-term low dose rate irradiation. However, the radiation mechanism of PU remains incompletely understood at the molecular level. In this study, three aromatic hard-segment PUs based on PPDI, MPDI, and NDI were designed and compared. We reveal that their radiation response is governed by the competition among chain scission, soft-segment cross-linking, and hard-segment structural reorganization, the dominance of which is strongly regulated by the isocyanate structure and the corresponding local energy deposition and dissipation pathway. For instance, NDI, by virtue of the energy delocalization capability of its extended it-conjugated naphthalene ring system, not only promotes intermolecular packing and a strong hydrogen-bonding network, but also avoids localized energy deposition, thereby exhibiting exceptional radiation tolerance. In contrast, the mechanical enhancement of EM is strongly influenced by post-irradiation structural reorganization, while the performance degradation of EP is dominated by irreversible hard segment destruction. The degradation of EP and EM at low dose rate was also enhanced by diffusion-limited oxidation (DLO) effect. This work elucidates the structure-mechanism-property relationship of segmented PU under gamma irradiation and offers guidance for designing radiation-tolerant polyurethane materials.

Super-tough poly-(lactic acid) (PLA) composites with an excellent balance between stiffness and toughness were successfully developed by incorporating core-shell particles comprising a rigid silica (SiO2) core and an elastomeric poly-(ether-block-amide) grafted with a glycidyl methacrylate (PEBA-GMA) shell. Morphological observations confirmed the formation of a well-defined core-shell structure within the PLA matrix. The effects of SiO2 particle size (100-800 nm) and core-shell mass ratio (1:3 to 3:1) on mechanical properties were systematically investigated. The results indicate that smaller SiO2 core particles (100 nm) led to severe agglomeration and poor dispersion, resulting in ineffective toughening. The optimal performance was achieved with PLA composites containing 500 nm SiO2 at a core-shell ratio of 1:3 and a total modifier content of 20 wt %, which exhibited a notched Izod impact strength of 70.6 kJ/m2a significant enhancement over binary PLA/PEBA-GMA composites. Furthermore, this composite maintained ductile fracture behavior even at a high SiO2 content, with an impact strength of 33.9 kJ/m2 at a SiO2:PEBA-GMA core-shell ratio of 3:1. The flexural modulus of this optimized composite was retained at 87% of that of pure PLA, demonstrating an excellent balance between stiffness and toughness. This work presents an effective strategy for developing high-performance PLA materials with tailored mechanical properties, offering promising potential for advanced biodegradable applications.

This study developed a copper-doped nanoscale zero-valent iron (Cu-nZVI) catalyst to synergistically enrich perfluorooctanoic acid (PFOA) and activate persulfate (PS) for enhanced degradation and defluorination. The system was evaluated under environmentally relevant PFOA concentrations (initial 1.0 mu M), with performance quantified via degradation kinetics, reactive species identification, intermediate analysis, and activation energy calculations. The optimized Cu-nZVI/PS system rapidly enriches PFOA within 1 min and achieves 90.0 % degradation and 49.8 % defluorination, even in complex water matrices with 1000-fold coexisting ions interference. Cu-nZVI accelerates defluorination by accelerating the rate-limiting step of perfluoroalkyl radical (CF3(CF2)6COO center dot) formation. Combined with intermediates analysis, a stepwise pathway was elucidated that SO4 center dot- initiates sulfonation/decarboxylation followed by center dot OH-mediated hydrolysis defluorination to F-. This work demonstrates that targeted Cu doping overcomes the inherent limitations of nZVI, establishing Cu-nZVI/PS as an efficient and robust technology for remediating PFOA contaminants in complex water environments.

Stainless steel components often face corrosion and tribocorrosion in various halide environments, as seen in applications like seawater plunger pumps, chemical agitators, and valves. Chloride (Cl-) and bromide (Br-) ions both degrade the corrosion and tribocorrosion resistance of stainless steel, yet their relative aggressiveness remains debated. Therefore, this study systematically compared the damage behavior of stainless steel in different halide environments using combined electrochemical and tribological techniques. Electrochemical corrosion analysis revealed Cl- exhibited greater propensity than Br- to displace oxygen within the Cr2O3 passive film and had a stronger penetration ability (smaller radius), rendering stainless steel more susceptible to pitting corrosion in Cl- solutions. Resultant pits were larger, deeper, and more densely distributed. However, accumulated corrosion products such as FexOy inhibited Cl- penetration, yielding a lower Icorr in Cl- (3.58 x10(-9) A/cm(2)) versus Br- solutions (8.87 x10(-9) A/cm(2)). Under tribocorrosion, copious Cl--derived corrosion products acted as abrasive third bodies, exacerbating material loss versus Br- environments, while wear-induced surface activation concurrently accelerated corrosion rates. This synergistic wear-corrosion interaction significantly elevated degradation, with corrosion-enhanced wear dominating material removal. Thus, while Cl- more readily disrupted the Cr2O3 passive film, static corrosion products conferred protection via a "corrosion-product barrier" effect; under tribocorrosion, however, these protective oxides transformed into abrasive particles, amplifying degradation through mechano-electrochemical synergy.

Portable low-field magnetic resonance imaging (MRI) holds great promise for point-of-care and resource-limited settings; however, its clinical translation is hindered by insufficient signal-to-noise ratio (SNR) resulting from low-inductance transceiver coils, particularly for complex neck imaging. To address this limitation, we developed a hybrid coil architecture by integrating a two-turn solenoid with a conformal bilayer mirrored rotationally symmetric spiral metasurface (BMRSM). This design functionally compensates for the performance degradation caused by turn crowding in conventional multi-turn coils, enabling the hybrid system to achieve imaging performance comparable to that of a three-turn design in the target region, while retaining the low inductance characteristic of the original two-turn structure. Full-wave electromagnetic simulations at 0.2 T (8.5 MHz) were conducted using dielectric phantoms and multi-layer anatomical neck models. Key metrics—including SNR, B₁ field uniformity, specific absorption rate (SAR), and resonant stability under bending—were benchmarked against a conventional three-turn solenoid coil. Results demonstrate that the BMRSM-integrated coil decouples SNR from inductance, achieving more than a 16-fold local SNR enhancement in the laryngeal cartilages (5–30 mm depth), more uniform B₁ fields, and nearly an order-of-magnitude reduction in maximum local SAR compared to the three-turn coil. Resonance remained stable under bending, with a frequency shift of less than 0.2 MHz. This work advances RF coil design by engineering metasurfaces as integral functional components, overcoming traditional performance trade-offs and providing a practical, retrofittable solution to enhance the diagnostic capabilities of portable low-field MRI systems for dynamic anatomical imaging.

Zero-valent iron is a ductile metal and tends to be deformed into flake shape after mechanical milling. The milled flake ZVI (MF), despite its high chemical reactivity, was considered to be undesirable for ZVI applications. In this work, a new perspective is provided that the MF also possesses favorable hydrodynamics properties for water treatment, via the study of the MF at four typical hydrodynamic conditions using computational fluid dynamics simulation (CFD), real experimental test, and theoretical calculation, respectively. The simulation shows that the MF is subject to a higher drag force (4 times at the relative velocity of 1.0 m/s) from the surrounding water than the unmilled bulk ZVI (UB) and the MF can be better moved with the flow. The results are verified via the study of the particle suspension during mechanical mixing using the three methods, all of which show that the MF is easier to be suspended than the UB. The study also finds that (1) when packed together in the concentrated slurry, the MF is lower in packing density and less viscous, which means that the handling of the MF slurry is easier; (2) when attached to the carrier media, the MF has a higher capillary force between the flake and carrier surface, resulting in a higher attachment efficiency and showing its advantage in forming ZVI composite. These advantages are attributed to the high viscous force exerted on the MF due to its flake morphology and large surface area. The study helps to revitalize the environmental application of the flake ZVI; it also provides quantitative information and the knowledge about ZVI flake that can guide its practical applications. The applied methodology is equally applicable to the hydrodynamic study of other particles for water treatment use.

Knock detection is crucial for ensuring engine reliability and performance. Conventional approaches, such as the maximum amplitude of pressure oscillations (MAPO), face limitations including poor noise robustness, low sensitivity to incipient knock, and reliance on empirically defined thresholds. This study proposes a knock detection and diagnosis framework WPKNN based on weighted PCA and k-nearest neighbors. By constructing a time-sensitive weighted principal component score sequence, the method effectively captures weak incipient knock features, significantly enhancing detection sensitivity and accuracy. Furthermore, a novel statistic KNNp is introduced that integrates local neighborhood variations and global principal component information, enabling precise identification of knock. It overcomes the limitations of the MAPO method, which relies solely on a single-peak indicator. In addition, kernel density estimation (KDE) is employed to adaptively determine dual thresholds for slight and severe knock, thereby improving the knock risk management. To support knock tracing, an advanced contribution-based diagnostic mechanism is established. It combines enhanced complete decomposition contribution (ECDC) and enhanced partial decomposition contribution (EPDC) methods, which accurately identify the key parameters most responsible for knock evolution. Experiments on a turbocharged gasoline engine under various knock conditions confirm that the WPKNN framework improves detection reliability, and provides robust support for intelligent combustion control and active knock suppression strategies.

Coordination polymerization of 2,3-dimethyl-1,3-butadiene (DMB) has been investigated by using rare-earth metal catalysts. Of which the ligand-free gadolinium dibenzyl chloride precursor exhibits the highest activity and perfect cis-1,4 selectivity for...

This study employs Higher-Order Dynamic Mode Decomposition (HODMD) and Proper Orthogonal Decomposition (POD) to analyze turbulent flow noise characteristics of a Clark-Y airfoil at Rec = 105. By decomposing sound pressure signals, different frequency, direction, and amplitude components of sound waves are extracted for in-depth acoustic analysis. CFD simulations using LES with the WALE model reveal that laminar separation bubbles form at x/c = 0.28 and reattach at x/c = 0.45, generating a turbulent boundary layer and strong pressure fluctuations, identified as the primary source of low-frequency discrete noise. Modal decomposition and reconstruction of experimental sound pressure data across various angles of attack compare HODMD and POD in handling flow-induced noise. Results indicate HODMD effectively extracts dominant frequencies and high-frequency modal structures, while POD, though efficient in energy decomposition, suffers from mode mixing and lacks interpretability in high-frequency noise scenarios. By integrating Sound Pressure Level (SPL) analysis with HODMD, key frequencies associated with boundary layer transition noise are identified, revealing their time-evolution characteristics. The study highlights HODMD's superiority in capturing dynamic evolution and stable modes of airfoil noise, providing valuable insights for aeroacoustic noise prediction and control strategies.

Coordination polymerization of 2,3-dimethyl-1,3-butadiene (DMB) has been investigated by using rare-earth metal catalysts. Of which, the ligand-free gadolinium dibenzyl chloride precursor exhibits the highest activity and perfect cis-1,4 selectivity for DMB homopolymerization and copolymerization with butadiene (BD) to afford plastic poly(2,3-dimethyl-1,3-butadiene) (PDMB) and the plastic-rubber diblock copolymer PDMB-b-PBD, respectively. In solution, PDMB-b-PBD self-assembles into a "core-shell" morphology with the crystalline cis-1,4 regulated PDMB segment as the core and the amorphous cis-1,4 stereoregular PBD unit as the shell, while in the melt state, the PDMB block forms physical cross-linking in the PBD rubbery matrix, endowing the material with unusually high stress accompanied by excellent elongation.

Low-field magnetic resonance imaging (MRI) systems (<0.5 T) have emerged as increasingly valuable tools for emergency and bedside imaging due to their cost-effectiveness and portability, but their adoption is limited by low signal-to-noise ratio (SNR). Conventional optimization methods offer limited improvements, while current metasurface technologies face challenges related to clinical integration, such as excessive dimensionality, and inadequate SNR enhancement at low magnetic field strengths. Addressing these challenges, we present an ultrathin (0.136 mm) flexible open-ring spiral metasurface (ORSM) engineered via subwavelength resonator optimization. Through rigorous theoretical modeling (equivalent circuit analysis) and comprehensive electromagnetic simulations (0.2 T full-wave analysis), we demonstrate concurrent achievement of: (i) unprecedented 137.1-fold surface field enhancement, (ii) deep-tissue penetration reaching 140 mm, and (iii) exceptional mechanical stability (<0.05 MHz frequency shift under deformation). Experimental validation on a 0.2 T MRI scanner quantitatively confirmed the clinical impact of the ORSM. Testing on a large-volume phantom (180 mm in diameter) demonstrated 97.4-133.2 % SNR enhancement across various regions, resulting in an increase in mean SNR by over 2.3 times. Importantly, the ORSM also optimized field homogeneity, reducing the spatial coefficient of variation from 18.9 % to 3.8 % and the relative SNR variation from 58.3 % to 24.6 %, all while ensuring full compliance with safety standards. This technology uniquely combines clinical-grade flexibility, deep penetration, and substantial SNR amplification with field uniformity, creating a practical pathway for advancing portable MRI in critical care.

Marine hydraulic components (e.g., seawater piston pumps) continuously endure coupled high hydrostatic pressure, electrochemical corrosion, and tribological degradation during prolonged operation, significantly compromising equipment stability and longevity. While WC-20Cr3C2-7Ni/W-DLC (WC/W-DLC) duplex coatings demonstrate improved tribocorrosion resistance for metal substrates, their long-term performance under extreme deep-sea conditions remains insufficiently characterized, particularly regarding high-pressure tribocorrosion mechanisms. In this work, the long-term corrosion and tribocorrosion properties of the coatings were evaluated using an autoclave equipped with an in-situ electrochemical monitoring system in a 20 MPa alternating hydrostatic pressure (AHP) environment. The results showed that the corrosion resistance of the WC/W-DLC coating was always superior to that of the WC-based coating during AHP cyclic immersion. It was attributed to the barrier of the structurally stable W-DLC layer against the corrosive solution and Cl-adsorption. The tribocorrosion results after AHP cycling revealed that the bonding between WC grains was weakened due to the corrosion of the Ni binder phase. Therefore, WC grains were pulled out and exfoliated during the sliding process, causing relatively severe failure of the WC-based coating. In contrast, the duplex coating, featuring a structurally stable and strongly bonded W-DLC layer, exhibited a coefficient of friction (COF) and wear rate of only 0.067 and 4.71 x 10- 8 mm3/N & sdot;m after sliding for 1200 m. Additionally, the potential drop induced by sliding was only 5 mV, significantly lower than that of the WC-based coating (down arrow 159 mV). In short, the optimized WC/W-DLC duplex coating can provide excellent and consistent surface protection for metal parts in deep-sea environments.

Zero-valent iron (ZVI) is a solid reductant that can react with a wide array of contaminants; however, its effectiveness is significantly reduced by the surface passivation layer formed on its surface. This study introduces mechanochemical depassivation to revitalize passivated ZVI and restore its reactivity. The method is exemplified through mechanical milling to depassivate ZVI with different passivation layers formed in solutions containing Cr(VI), Ni(II), and/or trichloroethylene, as well as in a complex water matrix. The results demonstrate rapid restoration of ZVI reactivity within 10 min of milling, achieving a 7-fold increase in contaminant removal capacity after eight cycles. The method universally outperforms acid pickling and ultrasonication across all of the tested passivation scenarios. Mechanistic analysis attributes its efficacy to the ductile-brittle disparity between the metallic iron and the passivation layers: brittle passivation layers fragment under mechanical stress, while ductile iron resists structural damage. Discrete element method simulations provide further mechanical insights into the milling dynamics and identify the contact frequency as the key factor determining depassivation efficiency. The study provides a versatile, environmentally benign, and effective depassivation method for ZVI reactions that can be integrated into ZVI reuse processes for water treatment applications.

This study aims to develop a mechanochemical reactor (MCR) integrated with persulfate-based advanced oxidation processes (SR-AOPs) to overcome zerovalent iron (ZVI) passivation for efficient degradation of high-concentration Rhodamine B (RhB) in textile wastewater. By employing high shear and mechanical collisions, the MCR continuously refreshes ZVI surfaces, enhancing Fe2+ release and persulfate activation. The MCR achieves 96.3% RhB degradation (500 mg·L-1), 68.3% COD reduction, and 74% TOC removal in 60 min, significantly outperforming the traditional stirred reactor (TSR: 22.7%, 17.8%, 9%). SO4·- and ·OH radicals drive Csp3-N/Csp2-N bond cleavage and aromatic ring hydroxylation, ensuring rapid decolorization and mineralization. The MCR maintains high performance across pH 3-11, RhB concentrations of 50-1000 mg·L-1, and anionic interferences, with degradation rates of 66.5%-99.0%. Simulated wastewater tests and economic-environmental assessments confirm its scalability and sustainability, establishing the MCR as a transformative solution for high-load dye wastewater treatment.

Bidirectional axial-flow turbomachines are used in a wide range of applications. Despite this, little research has been conducted to understand the flow characteristics of bidirectional airfoils, particularly S-shaped airfoils, which are likely the most commonly used type of bidirectional airfoil. This paper presents a direct description of the flow features of a typical S-shaped airfoil, which is based on a combination of the two front parts of the standard Clark-Y airfoil. A comparison between the flow fields for the S-shaped airfoil and those of the Clark-Y airfoil reveals why the aerodynamic performance of S-shaped airfoils differs from that of the standard airfoils. It is shown that S-shaped airfoils can improve the aerodynamic performance under high angles of attack (AoAs), while they degrade the aerodynamic performance under low AoAs. The decline in performance for S-shaped airfoils should be caused by a reduction of the effective AoA or incidence at the leading edge and the outward pressure gradient caused by the curved streamlines along the bulge of the rear half of the pressure surface. The reason for the performance improvement at high AoAs should be that the upwarp in the rear half of S-shaped airfoils alleviates the local flow deceleration, and thus diminishes the flow separation on the suction surface. This study can help deepen our understanding of the flow behaviors of bidirectional S-shaped airfoils, and hence offer guidance for enhancing the performance of bidirectional turbomachines.

Using deep learning-based techniques to overcome physical limitations and explore the potential performance of 0.2 T low-field unshielded MRI in terms of imaging quality and speed. First, fast and high-quality unshielded imaging is achieved using active electromagnetic shielding and basic super-resolution. Then, the speed of basic super-resolution imaging is further improved by reducing the number of excitations. Next, the feasibility of using cross-field super-resolution to map low-field low-resolution images to high-field ultra-high-resolution images is analyzed. Finally, by cascading basic and cross-field super-resolution, the quality of the low-field low-resolution image is improved to the level of the high-field ultra-high-resolution image. Under unshielded conditions, our 0.2 T scanner can achieve image quality comparable to that of a 1.5 T scanner (acquisition resolution of 512 × 512, spatial resolution of 0.45 mm2), and a single-orientation imaging time of less than 3.3 min. The proposed strategy overcomes the physical limitations of the hardware and rapidly acquires images close to the high-field level on a low-field unshielded MRI scanner. These findings have significant practical implications for the advances in MRI technology, supporting the shift from conventional scanners to point-of-care imaging systems.

Zero-valent iron (ZVI) mechanochemistry utilizes high-energy milling to activate ZVI for remediating persistent organic contaminants (e.g., PFAS, halogenated organics) and heavy metals across diverse environmental matrices-water, soil, sediment, and solid waste. This review synthesizes nearly two decades of advances of ZVI mechanochemistry to delineate two scalable technological pathways (i) green synthesis of reactive ZVI composites (e.g., sulfidated ZVI): and (ii) direct mechanochemical destruction via shear-induced electron transfer for cleaving recalcitrant bonds (C-F/C-Cl). Mechanistically, surface renewal, defect generation, and plasma-assisted redox are triggered by extreme shear (>105 s-1), transient local heating (∼700 K), and turbulence during the milling, overcoming ZVI passivation in complex matrices. Attritor mills emerge as the most viable reactor platform, offering wet-milling compatibility, continuous operation, enhanced energy efficiency, and inherent safety for field deployment. Critical scale-up strategies include sulfide-assisted wet milling for Fe(0) preservation, rheological monitoring of concentrated slurries, and stabilization protocols to balance material reactivity with energy demands. The technology demonstrates high efficacy for priority organics-including synergistic coupling with persulfate activation-and heavy metal sequestration in complex environmental systems. Future priorities encompass real-time process control, site-specific mechanistic validation, and safety-optimized reactor designs to advance sustainable remediation applications.

The persistent threat of emerging contaminants (ECs) in aquatic ecosystems necessitates advanced water purification strategies. Peroxymonosulfate (PMS)-activated advanced oxidation processes (AOPs) have emerged as promising solutions, where non-metallic heteroatom-doped carbon catalysts demonstrate enhanced PMS activation capabilities. However, reconciling high catalytic efficiency with long-term stability in metal-free systems remains challenging. Herein, we develop monodisperse nitrogen-doped carbon nanospheres (NCS) through a facile in situ doping strategy. This approach involves the synthesis of spherical resorcinol-formaldehyde resin via the Stober method using resorcinol as the carbon source and melamine as the nitrogen source, followed by controlled carbonization. By systematically adjusting the resorcinol/melamine ratio, we achieved precise regulation of nitrogen configurations, obtaining NCS-3 with optimal N content (5.3 at %). Remarkably, the NCS-3/PMS system exhibited ultrafast bisphenol A (BPA) degradation (100 % removal within 15 min, rate constant = 0.346 min(-1)) across a broad pH range (3.0-11.0), while maintaining exceptional tolerance to coexisting anions. Through multi-spectroscopic investigations and mechanistic analyses, we elucidated a dual-pathway activation mechanism: Dominant nonradical process mediated by singlet oxygen (O-1(2)) synergized with auxiliary radical pathway (O-2(center dot-)). Experimental and theoretical evidence confirmed that pyridinic N serves as the primary catalytic center, promoting PMS adsorption/activation through enhanced charge redistribution. This work provides critical insights for designing high-performance metal-free catalysts and advances the mechanistic understanding of active site engineering in carbon-based PMS activation systems.