Search Results (4,288)

In this study, commercial Ospray-2507 super-duplex stainless steel powder was investigated for the first time as a potential metal support material for solid oxide cells. Initially, metal supports were fabricated and processed in air using various sintering profiles, followed by comprehensive mechanical, structural and electrochemical characterization. The optimal sintering condition was identified as 900 °C for 5 h. Subsequently, sintering under a H₂ atmosphere was explored, and its effects on the microstructural and functional properties of the metal supports were systematically to assessed to evaluate the influence of the sintering atmosphere on material performance. Although X-ray diffraction patterns showed no phase changes between the two sintering atmospheres, notable improvements were observed in mechanical, electrochemical, and microstructural properties under H₂ sintering. XPS spectra reveal that both air- and hydrogen-treated surfaces remain rich in chromium (Cr) and Manganese (Mn), which together dominate the surface and consequently attenuate the signal from the underlying iron. The thickness of the Cr- and Mn-based oxide layer decreases when sintering MS in H₂ atmosphere. Specifically, mechanical strength, as measured by three-point bending tests, increased by a factor of 12.5, and hardness rose from 500.3 to 523.5 HV. Furthermore, electrical conductivity also improved significantly, exhibiting an approximately 2.3–2.4 fold increase under H₂-sintered conditions. Full article

High-speed operation is a key pathway to higher power density in modern EV traction systems, and multi-parameter optimization is essential for enhancing its high-speed performance. This study investigates a 20,000 r/min interior double-V permanent-magnet flat-wire motor via finite-element simulations to systematically examine the effects of multiple interacting parameters—including flat-wire layer number, stator slot geometry, magnet grade, and rotor magnetic barrier angle—on the electromagnetic performance under high-speed operating conditions. The results indicate that increasing winding layers significantly reduces high-speed torque; an eight-layer design decreases torque by about 50% compared to a four-layer one, while a six-layer arrangement offers a favorable torque-loss trade-off. Wider slots lower the average torque but reduce torque ripple by approximately 27%, whereas deeper slots increase tooth flux density and reduce efficiency. Higher-grade magnets enhance air-gap flux and torque at elevated cost. Rotor magnet angle optimization reveals a trade-off between peak torque and ripple, with a symmetric 100°/100° design achieving balanced performance. These findings clarify structural–control interactions and support the multi-objective design of high-speed flat-wire permanent-magnet motors. Full article

Recent studies have shown that a new family of Ni-based superalloys with high Ta and high Hf contents exhibits a promising property profile and may be able to fill the gap between creep-resistant alloys and those processable by PBF-LB/M. The effect of simultaneously high Ta and Hf contents on oxidation resistance has not yet been investigated and is addressed qualitatively in this study. Isothermal oxidation tests were conducted in air at 950 °C for 100 h, 300 h, and 500 h. After cooling, the weight change and cross-sections of the specimens were examined. The study shows that the Hf-free alloy exhibits severe spallation of the Al-oxide and Cr-/Ni-oxide layer. The Hf-containing alloys exhibit improved oxide layer adhesion and a promoted formation of a continuous Al-oxide layer, which is attributed to the early formation of Hf-oxide particles. Furthermore, the addition of Hf influences the morphology of internally oxidized Al, which grows preferentially parallel to the surface rather than perpendicular to it. This behavior leads to effective protection of the alloys by an Al-oxide layer, either external or internal, which is remarkable considering the moderate Al content of only 3 wt.%. Full article

The snow module of the HYDROTEL (version 2.8.x-078-00-4.1.15.5551) hydrological model was modified to incorporate a multilayer structure composed of ice and air layers within the snowpack, as well as to account for the impact of freezing rain on snow cover. This study examines whether this enhanced physical representation of snow processes improves the accuracy of streamflow simulations. The analysis was conducted across ten watersheds in Quebec, Canada. The multilayer snow model consistently improved low-flow simulations during both calibration and validation periods and enhanced the representation of the falling limb during the calibration period. However, the monolayer snow model performs slightly better during the rising limb of the freshet season for the calibration phase. In addition, the multilayer configuration reduced the bias of the cumulative freshet volumes and annual maximum freshet discharge. Overall, the multilayer snow model achieved comparable performance to the monolayer model for high-flow simulations while outperforming it for low-flow conditions, leading to a more accurate representation of freshet volumes and falling limb dynamics. Full article

One of the significant causes of failure in aerospace engine components is high-temperature oxidation. Therefore, it is necessary to investigate the high-temperature oxidation behavior of newly fabricated structural materials for aerospace components. From this perspective, the isothermal oxidation behavior and kinetics of newly developed stainless steel (SS) 08X14H were investigated at 750, 950 and 1050 °C for up to 100 h in an air environment. The weight results demonstrate that oxidation in 08X14H increases with time and temperature and follows a parabolic rate law. Major spallation was observed in samples oxidized for 100 and 24 h at 950 °C and 1050 °C, respectively. Structural and morphological analysis of oxidized samples through X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) of the surface and cross section reveal the phases present and their distribution. The structural results confirm the formation of Fe₂O₃, Cr₂O₃, FeCr₂O₄ and intermediate (Cr, Fe)₂O₃ oxides in the oxidized samples. Surface morphologies reveal that the formation of a Cr₂O₃ layer effectively protects the material from further oxidation. At higher temperatures, the coarsening of Fe₂O₃ oxides takes place, which leads to the formation of loose and porous oxide scale with stress-induced cracks. The spallation of the outermost Fe₂O₃-rich oxide scale was observed, and the matrix is exposed during the extreme oxidation at 950 and 1050 °C for 100 and 50 h, respectively. The cross-sectional morphologies and elemental mapping results reveal a duplex oxide layer with an outermost Fe₂O₃ layer followed by an underlying layer of Cr₂O₃, (Cr, Fe)₂O₃ and FeCr₂O₄ spinel beneath the Fe₂O₃ layer. Full article

The present study investigates the morphology, chemical composition, and phase constitution of oxide scales formed on the Fe40Al5Cr0.2TiB intermetallic alloy after long-term oxidation at 700 °C for 2000 h in air and water vapor environments. The results demonstrate the formation of an extremely thin oxide scale (≈300 nm), composed predominantly of α-Al₂O₃, which provides effective protection against further oxidation. The oxide layer exhibits locally heterogeneous morphology, including whisker-like structures and fine crystallites. Due to the very limited thickness of the oxide scale, significant challenges arise in the interpretation of microanalytical data. It is shown that the accelerating voltage strongly influences the effective information depth in SEM-EDS analysis, leading to a substantial contribution from the substrate even at low voltages. Monte Carlo simulations were used to support the interpretation of electron–matter interactions and to explain the observed discrepancies in chemical analysis. The study demonstrates that reliable characterization of ultrathin oxide scales requires careful optimization of SEM parameters and the combined use of complementary techniques, including EDS/WDS, XRD, and EBSD. The findings highlight the importance of methodological considerations in the analysis of thin oxide layers and provide guidance for the correct interpretation of experimental data in similar systems. Full article

To meet the need for global coverage, space–air–ground integrated networks (SAGINs) are crucial, but the openness of wireless links makes communications vulnerable to eavesdropping. This paper investigates the physical layer security (PLS) of uplink transmissions in a cooperative dual-hop SAGIN. The system comprises a ground source with a directional antenna, an unmanned aerial vehicle (UAV) relay cluster, and a low Earth orbit (LEO) satellite. Utilizing stochastic geometry, we model the spatial randomness of terrestrial eavesdroppers and the multi-layered dual-orbital LEO destination. To combat mixed radio-frequency (RF) and free-space optical (FSO) fading, multiple relay selection and maximum ratio combining (MRC) are integrated into the UAV cluster. We analytically derive the piecewise probability density function for the FSO link distance, obtaining exact closed-form expressions for the end-to-end secrecy outage probability (SOP). Monte Carlo simulations strictly validate the derivations. The results demonstrate that while increasing available relays and antennas enhances PLS via spatial diversity, a security bottleneck restricts the RF-FSO architecture under high-transmit power regimes, generating asymptotic secrecy floors. These findings provide explicit theoretical guidelines for the secure design and parameter optimization of future SAGINs. Full article

Thick-film organic photovoltaics (OPVs) are key for scalable manufacturing, but increasing active-layer thickness usually lowers power conversion efficiency (PCE) due to charge recombination and limited carrier extraction. We report high-efficiency thick-film OPVs fully processed in air by doctor blading using non-halogenated solvents (o-xylene with 3.5% tetralin) for two non-fullerene acceptor systems: PM6:ITIC-4F and PTQ-10:ITIC-4F. Active layers (100–500 nm) were fabricated by adjusting the coating speed while keeping the ink concentration and gap constant. Under mild drying (40 °C, 2 min), both systems exhibited significant efficiency losses at 1 sun (AM1.5G) as the thickness increased, whereas performance was largely preserved under indoor LED illumination (200 lx and 1000 lx), enabling high performance for thick films. Short thermal post-annealing (80–140 °C, 2 min) further improved PCE by reducing bimolecular recombination and enhancing nanostructure. Optimized PM6:ITIC-4F devices reached 10.2% (300 nm) under 1 sun and 14.78% at 200 lx; PTQ-10:ITIC-4F achieved 11.3% (500 nm) under 1 sun and up to 15.71% at 200 lx. Morphological and structural analysis indicates that the superior thick-film performance of PTQ-10:ITIC-4F is linked to favorable phase behavior, polymer-rich surface composition, and preferential face-on molecular orientation, promoting charge collection. These results demonstrate that low-cost PTQ-10 and non-halogenated air processing can enable industrially relevant, high-performance thick-film OPVs. Full article

LoRaWAN’s role in global maritime logistics has allowed for efficient monitoring of ships and cargo, but it also comes with critical cybersecurity vulnerabilities. Experimental validation of three attack vectors—replay attacks, narrowband jamming and metadata inference—is conducted using a reproducible digital-twin LoRaWAN dataset reflecting Rotterdam port-like operational patterns (N = 20,000 baseline transmissions). Using controlled simulations and Kolmogorov–Smirnov statistical analysis, we show that: (1) replay attacks are feasible under Activation by Personalization (ABP) configurations lacking enforced frame-counter validation and exhibit no univariate separation from legitimate traffic under Kolmogorov–Smirnov analysis (p > 0.46 for all evaluated radio features); (2) narrowband jamming leads to significant SNR degradation (p = 2.36 × 10⁻⁵) on targeted channels without inducing broad distributional anomalies across other radio features; and (3) metadata-only analysis supports elevated metadata-based re-identification susceptibility (median $R_d=0.834$), indicating high predictability under passive observation which can reveal operationally relevant signals even when AES-128 is employed. Our proposed layered mitigation framework consists of mandatory Over-the-Air Activation (OTAA), cryptographic key rotation, channel diversity incorporating Adaptive Data Rate (ADR), gateway hardening, and protocol-level enforcement considerations, customized for maritime LPWAN scenarios. We provide experiment-backed evidence and actionable recommendations to connect academic LPWAN security research to that of industrial maritime practice. Full article

Photothermal superhydrophobic surfaces represent a promising solution for passive anti-icing; however, the persistent high solar absorption of static black coatings often leads to undesirable overheating under non-icing conditions. To address this limitation, we developed a smart superhydrophobic polydimethylsiloxane (PDMS) surface embedded with thermochromic capsules (TC) (S-PDMS/TC) featuring reversible thermochromic capability via a facile combination of spin-coating and femtosecond laser ablation. The resulting hierarchical micro-grid structure acts as a sacrificial layer, shielding fragile nanostructures against mechanical abrasion, while endowing the surface with robust superhydrophobicity (contact angle > 155°). Uniquely, S-PDMS/TC exhibits an adaptive color transition from pale yellow to deep black when the temperature drops below 5 °C. This response enables on-demand photothermal enhancement, significantly boosting solar absorption in freezing environments while minimizing heat absorption at room temperature. Consequently, S-PDMS/TC demonstrates superior anti-icing performance, extending the freezing time to 310 s and reducing ice adhesion strength to 40.4 kPa. Notably, during photothermal de-icing, the meltwater exhibits spontaneous dewetting behavior driven by the replenishment of the air cushion, effectively preventing secondary icing. This work presents a mechanically durable and intelligent strategy for ice protection, successfully balancing efficient de-icing with thermal management. Full article

This study investigated thermal insulation in layered suit systems by systematically varying air-layer thickness and structure (single vs. sandwiched), fabric air permeability, and ambient airflow. A hot plate based apparatus equipped with air-layer spacers and an airflow-generation system was developed, and suit fabrics with different air permeability but similar thickness were fabricated. Heat flux from the heated plate and air-layer temperature were measured in three experimental series. Under no-airflow conditions, insulation was maximized at a 20 mm air layer, whereas a 30 mm air layer increased heat flux, suggesting buoyancy-driven convection. Under airflow conditions, thinner air-layers allowed airflow to influence the hot plate region more directly, while thicker-layers attenuated this effect. The sandwich-structured air layer reduced heat flux compared with a single air layer of the same total thickness, and its effect depended on the thickness distribution between the upper and lower air-layers. Fabric air permeability increased heat flux mainly under airflow, indicating that permeability effects should be evaluated under combined conditions of ambient airflow and controlled air-layer configurations. Full article

Piezoelectric actuators are essential for sub-millimeter robots and reconfigurable microstructures owing to their advantages, including the ability to operate in air and high-speed response. However, the substantial performance degradation observed in piezoelectric actuators with sub-micrometer thickness poses a critical challenge for the design of low-voltage microactuators capable of achieving large bending curvature. Here we develop a coupled analytical–numerical framework for designing multilayer lead zirconate titanate (PZT) nanofilm microactuators under a low voltage constraint (≤5 V). An analytical multilayer beam model is extended to incorporate thickness-dependent material properties and an interfacial dead layer that reduces the effective electric field at small thicknesses. This enables rapid exploration of curvature and the neutral-axis position as functions of the thicknesses of PZT, electrodes, and the dielectric layer. Two- and three-dimensional finite-element simulations provide complementary predictions of neutral-axis location, voltage-dependent curvature response, and eigenmode shapes. The resulting design maps reveal a non-monotonic optimum for PZT thickness in the few-hundred-nanometer range to maximize the curvature change at low voltages and identify ultrathin top electrodes as a key design lever that enhances bending by reducing parasitic stiffness while shifting the neutral axis favorably. These findings offer quantitative guidelines for designing low-voltage, high-curvature piezoelectric microactuators for microrobotic systems. Full article

Aim: Insertion of a chest drain in a newborn infant is a procedure commonly performed in an emergency setting. There are no commercially available neonatal chest drain insertion simulation models. We aim to build an inexpensive and realistic model. Methods: A discarded Laerdal Newborn manikin was modified with an internal rib cage, obtained from a decorative Halloween child skeleton. A synthetic silicone layer was used as a subcutaneous tissue and a resealable snack bag as lungs. This cost approximately $110 AUD. Medical staff were invited to use the manikin for chest drain insertion using a Safe-T centesis device. Results: Thirty medical officers (50% were registrars and the rest senior medical officers) participated in the study. Fidelity was rated high and there was no difference in the reported aesthetics, tactility, location of anatomy, ease of drainage of air or fluid amongst the registrars, fellows or neonatal consultants. Conclusions: It is feasible to build a realistic, high-fidelity manikin for newborn chest drain insertion. The use of a low-cost high-fidelity chest drain model needs to be evaluated in further studies. Full article

Industrial equipment data often exhibit high dimensionality and class imbalance, which make it difficult to achieve both accurate failure detection and identification of the factors contributing to failures. To address this issue, this study proposes an explainable failure classification framework, Feature-Wise Attention Graph Convolutional Network (FWA-GCN), which combines Feature-Wise Attention (FWA) with a Graph Convolutional Network (GCN) to provide both high classification performance and variable-level interpretability. In the proposed model, tabular sensor records are treated as nodes, and a similarity-based graph is constructed to capture relationships among samples. Feature-Wise Attention learns the importance of each feature and reweights node features accordingly, and the reweighted features are then used as input to the GCN to classify failure occurrences. To alleviate the class imbalance problem, a weighted loss function is applied during training by assigning a higher weight to the failure class. Experiments conducted on the Air Pressure System (APS) dataset demonstrate that the proposed FWA-GCN achieves Precision of 79.95%, Recall of 85.07%, and F1-score of 82.43%, outperforming conventional machine learning models including Random Forest, XGBoost, CatBoost, and Multi-Layer Perceptron, as well as a standard GCN model. Furthermore, an ablation study was conducted by removing the top features selected by the attention mechanism. The results show a significant decrease in recall, confirming the effectiveness of the attention-based feature importance and supporting the interpretability of the proposed framework. Full article

This study investigates the formation mechanism of lactic-acid-derived coatings produced by open-air atmospheric-pressure plasma polymerization. A comparison of nebulization and bubbling precursor-delivery methods using FT-IR and XPS showed that the bubbling method facilitated plasma-assisted chemical bonding, including the possible formation of copper(II) lactate-like interfacial species and the retention of carbonyl-containing functional groups. However, the present dataset does not provide direct, discriminating evidence for a specific metal-lactate interfacial species, and alternative interpretations such as adsorption, oxidation, hydroxylation, or generic oxygenated carbon deposition cannot be excluded. Time-dependent analysis revealed a transition from oxygen-rich functional layers at short plasma exposure to carbon-rich overlayers at longer exposure, suggesting a fragmentation-recombination mechanism that is consistent with the formation of a metal-lactate-like interfacial region and a carbon-rich overlayer, while alternative interpretations related to signal attenuation and non-uniform coverage remain possible. Antibacterial testing revealed that the observed bacterial responses were not attributable to an intrinsic antibacterial property of the deposited films, but were instead strongly dependent on the underlying substrate chemistry and exposure time. C1100 retained the inherent antibacterial activity of copper, SUS430 showed no activity due to the absence of film formation, and SPCC exhibited only a transient effect attributed to lactic-acid-induced local acidification. Overall, the study elucidates the plasma-assisted deposition mechanism of lactic-acid-derived coatings under open-air conditions and highlights the critical role of interface chemistry in achieving stable and substrate-independent functional properties. Full article