Search Results (3,351)

This study investigates the application of the Keyhole–Tungsten Inert Gas Welding (K-TIG) hot-wire filling welding technique with mechanical arc oscillation to weld a 95 mm-thick Ti-6Al-4V titanium alloy plate. The root layer thickness achieved with this technique reaches up to 17 mm, with an average filling thickness of 2.5 mm. The weld bead displays a smooth, shiny appearance, and no significant welding defects are observed in the cross-section of the welded joint. Experimental results show that the welded joint consists of the α phase in different forms, as well as fine α+β microstructures. Compared to the base material, both the weld metal and the heat-affected zone exhibit a lower crystallographic texture strength, with more complex texture types. The impact toughness of the welded joint is excellent, with no significant weaknesses. The impact toughness of the weld metal significantly surpasses that of both the base material and the heat-affected zone. The engagement strengthening effect induced by high-current filling plays a crucial role in enhancing the impact toughness of the weld metal. Full article

As a form of non-destructive testing, eddy current testing is widely used for detecting surface micro-damage on metal components in sectors such as aerospace. Conventional frequency-domain analysis techniques often fail to effectively extract defect-related features from non-stationary eddy current signals. This paper proposes an ECT system based on the Discrete Wavelet Transform to address this limitation. In hardware design, the system employs a DDS to generate a 1 MHz excitation signal for the probe. High-precision acquisition of defect response signals is achieved using an IQ demodulator and a 24-bit ADC. For signal processing, the Haar wavelet is applied for single-level decomposition. This method successfully isolates the defect response signal within the high-frequency detail coefficients. Experimental results demonstrate that for a metal surface notch with a depth of 1 mm, the system significantly improves the SNR, resulting in a ΔSNR improvement of 3.64 dB, which is 0.36 dB higher than that achieved using time-domain processing. Full article

Background: Congenital heart disease (CHD) is associated with an increased risk of anxiety and depression in adults. However, little is known about the mental health of children and adolescents with CHD. The aim of this study was to assess differences in anxiety and depression symptoms between children and adolescents with CHD and healthy controls. Methods: A total of 232 children and adolescents (age 7–18 years; mean age 13.5 ± 2.7 years, 50.9% female) were enrolled, consisting of 116 patients with CHD and 116 age- and sex-matched healthy controls. Participants were recruited during routine medical examinations at the German Heart Center and Munich schools, respectively. The Beck Anxiety Inventory (BAI) and the Depression Inventory for Youth (BDI-Y) were used to assess anxiety and depression symptoms. Results: The CHD cohort included patients with right heart obstruction (11.2%), left heart obstruction (19.8%), isolated shunts (15.5%), transposition of the great arteries (14.7%), univentricular heart (14.7%), and other defects (24.1%). According to published cut-off values, at least a mild form of anxiety was present in 46.5% CHD patients. However, no significant differences were observed between the CHD group and healthy controls in either the BDI-Y score (CHD: 7.9 ± 7.7 vs. controls: 8.6 ± 8.5; p = 0.569) or the BAI score (CHD: 9.3 ± 8.6 vs. controls: 9.3 ± 10.3; p = 0.429). The complexity of the heart defect was not associated with BAI scores (simple: 5.9 ± 5.7; moderate: 11.1 ± 8.1; complex: 9.3 ± 9.0; p = 0.073) or BDI-Y scores (simple: 7.4 ± 7.5; moderate: 9.0 ± 7.1; complex: 7.0 ± 7.7; p = 0.453). No significant differences in BAI (p = 0.141) or BDI-Y (p = 0.326) scores were found by type of heart defect. Conclusions: Children and adolescents with CHD did not exhibit significantly higher levels of depression or anxiety symptoms compared to healthy controls. Nevertheless, given the increased psychological risk observed in adults with CHD, ongoing mental health monitoring remains important to enable early identification and timely intervention. Further research, particularly through longitudinal studies, is needed to monitor mental health trajectories over time and to identify early predictors of psychological vulnerability in this population. Full article

This study investigated the influence of Cr, Mo, and W alloying elements incorporated into ferritic stainless steel on the characteristics of passive films formed under acidic chloride conditions. Electrochemical assessments demonstrated that increasing the amounts of Cr, Mo, and W reduces passive current density and enhances polarization resistance. Through XPS analysis, it was determined that the passive film exhibits a double-layer structure, consisting of an inner layer rich in metal oxides and an outer layer containing metal oxy-anions. Mott–Schottky analysis indicated the presence of both p-type and n-type semiconducting properties. To clarify the effect of these alloying elements on the passive films at the surface of stainless steel, this work introduces a new parameter termed the “Bipolar Index,” defined as |p-type slope| + |n-type slope|. With higher Cr, Mo, and W contents, the bipolar index increases, reflecting modifications in the semiconductive behavior. Consequently, the point defect concentration within the passive film decreases, causing a reduction in passive current density and a rise in polarization resistance. Full article

Carbon-based nanocomposites coated with iron oxides were synthesized using a wet impregnation method with thermally annealed coal and an iron nitrate precursor. The influence of the thermal treatment atmosphere (air, vacuum, or nitrogen) on the morphology, structure, and magnetic properties of the nanocomposites was examined by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. It was found that the vacuum thermal treatment produced carbon-based nanocomposite containing iron oxide with the highest crystallinity, according to XRD analysis, while also inducing the greatest degree of structural defects in the carbon matrix, as evidenced by Raman analysis. Mössbauer spectroscopy confirmed that all thermal treatment methods promote the formation of the hematite phase, which was found to be the only phase formed in the air-treated nanocomposites, whereas traces of magnetite and the formation of Fe(OH)₃ were detected in the vacuum- and nitrogen-treated nanocomposites, respectively. Magnetic characterization revealed that all nanocomposites exhibit ferromagnetic-like behavior, attributed to the weak ferromagnetic nature of hematite. The best magnetic response (highest saturation magnetization with the widest hysteresis loop) was observed in the vacuum-treated nanocomposites. These findings collectively demonstrate that the synthesis atmosphere plays a crucial role in tailoring the structural and magnetic characteristics of carbon-based iron oxide nanocomposites, offering pathways for their optimization in applications such as catalysis, environmental remediation, or sensing technologies. Full article

Silicon carbide (SiC) is widely utilized in semiconductors, microelectronics, optoelectronics, and other advanced technologies. However, its inherent characteristics, such as its hardness, brittleness, and high chemical stability, limit the processing efficiency and application of SiC wafers. This study explores the use of plasma etching as a pre-treatment step before chemical mechanical polishing (CMP) to enhance the material removal rate and improve CMP efficiency. Experiments were designed based on the Taguchi method to investigate the etching rate of plasma under various processing parameters, including applied power, nozzle-to-substrate distance, and etching time. The experimental results indicate that the etching rate is directly proportional to the applied power and increases with nozzle-to-substrate distance within 3–5 mm, while it is independent of etching time. A maximum etching rate of 5.99 μm/min is achieved under optimal conditions. And the etching mechanism and microstructural changes in SiC during plasma etching were analyzed using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), white light interferometry, and ultra-depth-of-field microscopy. XPS confirmed the formation of a softened SiO₂ layer, which reduces hardness and enhances CMP efficiency; SEM revealed that etching pits form in relation to distance; and white light interferometry demonstrated that etching causes a smooth surface to become rough. Additionally, surface defects resulting from the etching process were analyzed to reveal the underlying reaction mechanism. Full article

Internal conductive defects in composite insulators severely degrade their insulation performance and are considered concealed defects, posing a significant threat to the safe and stable operation of the power grid. Focusing on this issue, this study develops an electro-thermal multi-physical field simulation model and uses finite element analysis to investigate the electric field distribution and temperature rise characteristics. Composite insulator specimens with varying defect lengths were fabricated using the electrical erosion test. Charged tests were then conducted on these defective specimens, as well as on field-decommissioned specimens. The impact of internal conductive defects on the infrared, ultraviolet, and electric field distribution characteristics of composite insulators during operation was analyzed. The results indicate that the surface electric field of composite insulators with internal conductive defects becomes highly concentrated along the defect path, with a significant increase in electric field strength at the defect’s end. The maximum field strength migrates toward the grounded end as the defect length increases. Conductive defects lead to partial discharge and abnormal temperature rise at the defect’s end and the bending points of the composite insulator. The temperature rise predominantly manifests as “bar-form temperature rise,” with temperature rise regions correlating well with discharge areas. Conductive defects accelerate the decay-like degradation process of composite insulators through a positive feedback loop formed by the coupling of electric field distortion, Joule heating, material degradation, and discharge activity. This study identifies the key characteristics of electrical and temperature rise changes in insulators with conductive defects, reveals the deterioration evolution process and degradation mechanisms of insulators, and provides effective criteria for on-site diagnosis of conductive defects. Full article

Background: Congenital anomalies impact 52 million infants worldwide with an estimated 94% living in low- and middle-income countries (LMICs). Approximately 200,000 children are born with a neural tube defect (NTD) in LMICs annually. Zambia is an LMIC with a high burden of myelomeningocele (MMC; a severe form of NTD). This study sought to characterize the barriers influencing access to healthcare for children born with MMC in Zambia. Methods: Two cross-sectional surveys were administered to healthcare providers at referring public health facilities and mothers of infants born with MMC undergoing surgical closure. The survey among mothers was nested in a longitudinal study evaluating surgical closure in Lusaka, Zambia from 28 May 2024 to 21 January 2025. Results: Sixty-nine mother–MMC baby dyads and 123 providers from 21 facilities were enrolled in the study. The median age at presentation for MMC was 7.5 (range 0–244) days old. Most patients were referred from rural district hospitals (51%; n = 35) and travelled greater than 250 km to access care (80%; n = 55). Seventy-seven percent (n = 53) of mothers reported receiving at least one antenatal ultrasound, with 62% (n = 43) undergoing an ultrasound after 20 weeks estimated gestational age. Of these, only 3% (n = 2) received an MMC diagnosis prior to delivery. Referring patients with MMC for further care greater than six hours after birth was reported by 59% providers (n = 73). Hospitals further away from the tertiary center were more likely to report late referrals (p < 0.001). Conclusions: There is a delay in the diagnosis and referral of infants with MMC to specialized care in Zambia, which may be attributed to inadequate in utero diagnosis capabilities and distance from the tertiary facility. Improving the accuracy of prenatal diagnosis and strengthening referral pathways to facilitate access to care among infants with MMC in Zambia are important for improving incidence and outcomes. Full article

Metal halide perovskites have appeared as a promising semiconductor for high-efficiency and low-cost photovoltaic technologies. However, their performance and long-term stability are dramatically constrained by defects at the surface and grain boundaries of polycrystalline perovskite films formed during the processing. Herein, we propose a defect-targeted passivation strategy using 2-chlorocinnamic acid (2-Cl) to simultaneously enhance the efficiency and stability of perovskite solar cells (PSCs). The crystallization kinetics, film morphology, and optical and electronic properties of the used formamidinium–cesium lead halide (FA_0.85Cs_0.15Pb(I_0.95Br_0.05)₃, FACs) absorber were modulated and systematically investigated by various characterizations. Mechanistically, the carbonyl group in 2-Cl coordinates with undercoordinated Pb²⁺ ions, while the chlorine atom forms Pb–Cl bonds, effectively passivating the surface and interfacial defects. The optimized FACs perovskite film was incorporated into inverted (p-i-n) PSCs with a typical architecture of ITO/NiO_x/PTAA/Al₂O₃/FACs/PEAI/PCBM/BCP/Ag. The optimal device delivers a champion power conversion efficiency (PCE) of 22.58% with an open-circuit voltage of 1.14 V and a fill factor of 82.8%. Furthermore, the unencapsulated devices retain 90% of their initial efficiency after storage in ambient air for 30 days and 83% of their original PCE after stress under 1 sun illumination with maximum power point tracking at 50 °C in a N₂ environment, demonstrating the practical potential of dual-site molecular passivation for durable perovskite photovoltaics. Full article

Grid-stiffened panels are indispensable in aerospace applications, valued for their lightweight nature, high strength, and excellent deformation resistance. However, the roll-bending forming process of these panels is plagued by critical defects such as rib buckling and uneven skin deformation, which undermine structural quality and performance. Fillers are commonly employed to mitigate these issues, yet there remains a lack of systematic guidance for optimizing filler parameters—particularly the elastic modulus—that is tailored to high-rib thin-web configurations. This study focuses on high-rib thin-web grid-stiffened panels, aiming to address this gap by exploring the optimization of filler elastic modulus. By delving into this critical parameter, the research seeks to lay the groundwork for enhancing forming precision in roll bending, offering valuable insights for advancing high-quality manufacturing of aerospace components. Full article

This study investigates the critical influence of oxidation temperature on the intrinsic characteristics and surface properties of thermally oxidized Zr2.5Nb alloy. The resulting oxide layers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), surface hardness, and nanoindentation. The tribological behavior of the untreated and thermally oxidized Zr2.5Nb alloy was evaluated via reciprocating ball-on-disc wear tests under a load of 29.4 N. MC3T3-E1 cells were employed to assess the biocompatibility. The results show that oxide layers primarily composed of m-ZrO₂ formed on the alloy surface, with thickness increasing from 2.43 µm to 13.59 µm as the oxidation temperature rose from 500 °C to 700 °C. However, this thickness increase was accompanied by elevated defect density. Compared to the untreated alloy, thermally oxidized samples exhibited significantly enhanced hardness and wear resistance. Notably, oxidation at 600 °C produced a dense 5.31 µm oxide layer with optimal structural integrity, achieving an 85% reduction in wear rate and a superior MC3T3-E1 cell relative activity of 123.07 ± 6.02%. These findings provide foundational data for developing zirconium-based implants with improved stability. Full article

In this paper, the molecular dynamics simulation method was adopted to systematically study the microstructure evolution behavior of TiAl alloys under impact compression under three typical crystal orientations ([001], [110], [111]). By analyzing the characteristics of structural phase transition, defect type evolution, dislocation expansion, and radial distribution function, the anisotropic response mechanism under the joint regulation of crystal orientation and impact velocity was revealed. The results show that the [111] crystal orientation is most prone to local amorphous transformation at high strain rates, and its structural collapse is due to the rapid accumulation and limited reconstruction of dislocations/faults. The [001] crystal orientation is prone to forming staggered stacking of layers and local HCP phase transformation, presenting as a medium-strength structural disorder. Under the strain regulation mechanism dominated by twinning, the [110] orientation exhibits superior structural stability and anti-disorder ability. With increases in the impact velocity, the defect type gradually changes from isolated dislocations to large-scale HCP regions and amorphous bands, and there are significant differences in the critical velocities of amorphous transformation corresponding to different crystal orientations. Further analysis indicates that the HCP structure and the formation of layering faults are important precursor states of amorphous transformation. The evolution of the g(r) function verifies the stepwise disintegration process of medium and long-range ordered structures under shock induction. It provides a new theoretical basis and microscopic perspective for the microstructure regulation, damage tolerance improvement, and impact resistance design of TiAl alloys under extreme stress conditions. Full article

Folate is an essential vitamin involved in one-carbon metabolism. It can be acquired from many food sources or in synthetic form. A wide range of processing methods have been studied to improve the bioaccessibility and bioavailability of folate in foods, yet this is often accompanied by a decrease in stability. Encapsulation technology has emerged as an effective solution for protecting folate from degradation and liberation while also improving its bioavailability. Folate deficiency is a prevalent phenomenon worldwide, particularly in underprivileged countries, leading to various health problems, such as neural tube defects. Thus, folate was fortified through both exogenous addition and biofortification. Gene editing technology, especially CRISPR-Cas9, has great promise in this field when compared to transgenic engineering, because transgenic engineering may pose safety concerns and environmental risks. While ongoing research has identified additional potential effects of folate, the dosage and duration remain important factors to consider for optimal health outcomes. The mechanisms of how folate promotes the production of neurotransmitters associated with the gut microbiota–brain axis and reduces depression are not well understood. In addition to folate alone, there may be synergistic effects of combined supplementation of folate and other nutrients or medications, but this is not yet fully clarified and requires further examination. This review summarizes the food sources, enrichment, bioaccessibility, and bioavailability of folate. Furthermore, the health benefits of folate, including neural tube protection, cardiovascular protection, neuroprotection, anti-cancer, immune response augmentation, and gut homeostasis maintenance, with their potential bioactivity mechanisms, are discussed. Full article

Reliable, non-destructive grading of fresh fruit requires simultaneous assessment of external morphology and hidden internal defects. Camera-based grading of fresh fruit using colorimetric (RGB) and near-infrared (NIR) imaging often misses subsurface bruising and cannot capture the fruit’s true shape, leading to inconsistent quality assessment and increased waste. To address this, we developed a 4D-grading pipeline that fuses visible and near-infrared (VNIR) and short-wave infrared (SWIR) hyperspectral imaging with structured-light 3D scanning to non-destructively evaluate both internal defects and external form. Our contributions are (1) flagging the defects in fruits based on the reflectance information, (2) accurate shape and defect measurement based on the 3D data of fruits, and (3) an interpretable, decision-tree framework that assigns USDA-style quality (Premium, Grade 1/2, Reject) and size (Small–Extra Large) labels. We demonstrate this approach through preliminary results, suggesting that 4D hyperspectral imaging may offer advantages over single-modality methods by providing clear, interpretable decision rules and the potential for adaptation to other produce types. Full article

The interface between high-performance thermoelectric materials and electrodes critically governs the conversion efficiency and long-term reliability of thermoelectric generators under high-temperature operation. Here, we propose Al_xCoCrFeNi high-entropy alloys (HEA) as barrier layers to bond Cu-W electrodes with p-type skutterudite (p-SKD) thermoelectric materials. The HEA/p-SKD interface exhibited excellent chemical bonding with a stable and controllable reaction layer, forming a dense, defect-free (Fe,Ni,Co,Cr)Sb phase (thickness of ~2.5 μm) at the skutterudites side. The interfacial resistivity achieved a low value of 0.26 μΩ·cm² and remained at 7.15 μΩ·cm² after aging at 773 K for 16 days. Moreover, the interface demonstrated remarkable mechanical stability, with an initial shear strength of 88 MPa. After long-term aging for 16 days at 773 K, the shear strength retained 74 MPa (only 16% degradation), ranking among the highest reported for thermoelectric materials/metal joints. Remarkably, the joint maintained a shear strength of 29 MPa even after 100 continuous thermal cycles (623–773 K), highlighting its outstanding thermo-mechanical stability. These results validate the Al_xCoCrFeNi high-entropy alloys as an ideal interfacial material for thermoelectric generators, enabling simultaneous optimization of electrical and mechanical performance in harsh environments. Full article