Search Results (191)

AZ91D is a lightweight, representative commercial magnesium alloy known for its excellent castability and specific strength. However, the mechanical properties of as-cast AZ91D remain limited by inherent brittleness, relatively low strength, and microstructural inhomogeneity caused by enrichment of secondary phases at grain boundaries. In this study, AZ91D/Csf (short carbon fiber at 0, 2.5, and 5 wt.%) composites were prepared by gravity casting with mechanical stirring, followed by post-casting T4 heat treatment and equal-channel angular pressing (ECAP). Material characterization included optical microscopy (OM), field-emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), uniaxial tensile testing, and microhardness tests. The results demonstrate that T4 treatment reduced intermetallic β-Mg₁₇Al₁₂ segregation and homogenized the microstructure, whereas one-pass ECAP further refined the grains. Mechanically, these two processes enable the (AZ91D/5 wt.% Csf) composite to achieve higher ultimate tensile strength (280.7 MPa by T4/280.2 MPa by T4 + one-pass ECAP), larger maximum strain (12.1% by T4/5.4% by T4 + one-pass ECAP), and higher microhardness (63.9 HV by T4/78.1 HV by T4 + one-pass ECAP). Compared to as-cast AZ91D, these findings demonstrate that T4 treatment provides a better strength–ductility balance via solid solution, whereas one-pass ECAP preferentially enhances surface microhardness by plastic deformation. This study highlights the performance of AZ91D/Csf composites and their potential for lightweight, high-strength-demand applications. Full article

High-velocity oxy-fuel (HVOF)-sprayed NiCrBSi coatings containing 0, 10, 30, and 50 wt.% WC-Co were evaluated on AZ91D magnesium alloy to determine how the discrete reinforcement level affects surface topography, phase constitution, Vickers microhardness, dry-sliding friction, mass loss, and wear-track microchemistry. As-sprayed surfaces were characterized by three-dimensional profilometry; coating cross-sections and worn surfaces by optical microscopy and SEM/EDS; phase constitution by XRD; and mechanical response by HV_0.1 indentation. Dry-sliding tests were performed at 10, 30, and 50 N over 100–1000 m. Increasing WC-Co content raised Sa from 8.8 ± 0.3 to 13.0 ± 0.5 µm and Vickers microhardness from 776 ± 4 to 959 ± 5 HV_0.1. XRD indicated a γ-Ni-based matrix containing boride/carbide constituents, while WC, W₂C, and Co became increasingly prominent in the reinforced coatings. Boride assignments are based on diffraction evidence, whereas B and C EDS signals were treated semi-quantitatively. The 50 wt.% WC-Co coating exhibited the lowest mass loss and mean coefficient of friction at every load. Its mean friction coefficients were 0.31, 0.35, and 0.41 at 10, 30, and 50 N, corresponding to reductions of 40.1%, 38.9%, and 36.2% relative to AZ91D. At 1000 m, its mass-normalized wear rate indices were 9.0 × 10⁻⁴, 4.0 × 10⁻⁴, and 5.3 × 10⁻⁴ mg N⁻¹ m⁻¹, respectively. Post-wear mapping showed the largest field-scale W-Co-rich fraction in the 50 wt.% coating; however, isolated spectra containing more than 94 wt.% Mg are compatible with local coating penetration/substrate exposure and/or Mg-rich debris. The 50 wt.% composition therefore provided the best combined response among the four tested levels, while intermediate compositions are required to identify a continuous-composition optimum. Full article

The rapid expansion of sub-6 GHz 5G and Internet of Things (IoT) networks demands highly miniaturized Multiple-Input Multiple-Output (MIMO) antennas. However, balancing extreme physical compactness with rigorous inter-port isolation introduces severe computational bottlenecks for conventional optimization algorithms. To overcome these multidimensional challenges, this paper proposes a novel Deep Surrogate Active Learning framework for the autonomous design and empirical validation of an ultra-compact dual-band MIMO antenna. By using a surrogate-assisted closed-loop strategy to reduce reliance on repeated full-wave evaluations, the methodology combined a custom-penalized Deep Neural Network with dynamic boundary reduction. After training the initial surrogate model with 440 valid full-wave responses obtained from the offline design-of-experiments (DOE) stage, the best CST-validated candidate was identified at the 83rd active learning cycle. The optimized nested-loop geometry, incorporating a partial defected ground structure (DGS), occupies an extremely confined footprint of only 1634 mm² on a Rogers RO4350B substrate (Rogers Corporation, Chandler, AZ, USA). The selected geometry provided simulated −10 dB impedance bands of 3.35–3.88 GHz and 4.34–5.05 GHz, while the complete two-port model maintained inter-port isolation better than 13.8 dB and 14.9 dB across the lower and upper target passbands, respectively. Measurements of the fabricated prototype showed the intended dual-band behavior, a maximum measured gain of 4.54 dBi, and total radiation efficiencies of approximately 51–63% across both ports at the evaluated frequencies. The simulated Envelope Correlation Coefficient (ECC) remained below 0.035 across the target passbands, supporting the suitability of the compact geometry for the investigated sub-6 GHz MIMO bands. Full article

This study presents the design, development, and evaluation of iSign, an Android-based educational mobile application developed to support sign language learning among deaf and hard-of-hearing individuals in rural communities. The project was conducted using a research and development (R&D) approach guided by the ADDIE instructional design framework. A preliminary needs assessment, based on municipal records and field validation, revealed limited access to structured sign language education and assistive learning resources in selected barangays of Odiongan, Romblon. The iSign application was designed as a user-centered and accessible mobile learning tool incorporating alphabet learning (A–Z), number recognition (0–9), a dictionary containing 160 commonly used vocabulary words with definitions and corresponding sign language video demonstrations, and multimedia content such as nursery rhyme songs interpreted in sign language. The system was developed using Android Studio and structured to support offline accessibility to accommodate low-connectivity environments. The application was evaluated in terms of functional suitability, performance efficiency, compatibility, usability, reliability, security, maintainability, and portability. Twenty-one community participants and four information technology experts assessed the system using a five-point Likert scale. The overall weighted mean rating of 4.0 (“Agree”) indicates that the developed application met acceptable software quality standards and user satisfaction levels. The findings demonstrate that iSign is a functional and accessible mobile learning application that can serve as a supplementary tool for sign language education in underserved communities. Full article

Driven by the automotive industry’s strategies for energy conservation, emission reduction, and lightweighting, magnesium alloy wheels have emerged as a key focus of research and industrialization efforts, owing to their high specific strength, excellent vibration-damping properties, and superior heat dissipation performance. This paper provides a systematic review of the performance advantages, material systems, forming processes, applications, and industrialization challenges of magnesium alloy automotive wheels. The core advantages of magnesium alloy wheels in terms of weight reduction, vibration damping, and thermal management are elaborated. The compositional characteristics, suitable processes, and performance differences between cast magnesium alloys (e.g., AZ91D, AM60B) and wrought magnesium alloys (e.g., AZ80, ZK61-Y) are outlined. The technical characteristics, microstructural and property evolution, and limitations of casting processes (gravity, high-pressure, low-pressure, and semi-solid casting), plastic forming processes (isothermal extrusion forging, backward extrusion forging, and spin forming), and hybrid processes are discussed. Combined with the case studies of magnesium alloy wheel applications in the automotive sector, this paper analyzes the core bottlenecks of magnesium alloy wheels in terms of corrosion resistance, production cost, and industrial consistency, and outlines future research directions. This paper aims to provide theoretical references and technical support for the design, manufacturing, and large-scale application of lightweight, high-performance magnesium alloy wheels. Full article

In this work, 2.0 wt.% SiCp/AZ91D magnesium matrix composite was fabricated by stir casting, and its microstructure and properties were optimized through a coupled process of parallel equal-channel angular combined extrusion (PC-ECAP) and T6 heat treatment. The results indicate that the extrusion temperature has a significant influence on the microstructure and mechanical properties of the material. At an extrusion temperature of 350 °C followed by T6 heat treatment, the 2.0 wt.% SiCp/AZ91D composite exhibits a tensile strength of 221 MPa, an elongation of 19.2%, and a product of tensile strength and elongation (PSE) of 4.24 GPa%, which represent increases of 14.5%, 128.6%, and 161.7%, respectively, compared with the as-cast specimen. To elucidate the microscopic mechanism of the enhanced ductility, first-principles calculations were further performed. It is found that Al solute atoms can reduce the electron localization in the Mg–Mg bond region, causing a downward shift of the d-band center, thereby weakening the interatomic bonding strength on the slip plane. This effect is equivalent to reducing the stacking fault energy of non-basal slip. The finding provides a theoretical explanation for the activation of multiple slip systems and the suppression of twinning observed in the experiments. By combining experiments with calculations, this study systematically reveals the mechanism underlying the synergistic regulation of strength and ductility in the composite by PC-ECAP coupled with T6 heat treatment, offering a theoretical basis and process reference for the fabrication of high-performance magnesium matrix composites. Full article

Hopeite (Zn₃(PO₄)₂·4H₂O) coatings, obtained via zinc phosphate chemical conversion (ZPCC), have gained increasing attention in the biomedical field. Such coatings are particularly appealing owing to their combined capability of excellent corrosion resistance and biocompatibility. This study investigates the influence of processing time on the formation of hopeite coatings on AZ91D magnesium alloy by zinc phosphate chemical conversion (ZPCC). X-ray diffraction (XRD) analysis confirmed that the coatings primarily consisted of hopeite, with trace amounts of phosphophyllite. The maximum coating mass and thickness were achieved after a 30 min treatment at 55 °C. Electrochemical measurements demonstrated superior corrosion resistance for coatings formed within 15–30 min. Additionally, coating self-adhesion tests revealed strong bonding between the coating and the substrate. Full article

Background: Maxillary sinus lift is among the most common preprosthetic procedures in the posterior maxilla due to alveolar ridge resorption and the maxillary sinus pneumatization. It often extends treatment duration, significantly increases costs, and is not without complications. Objective: To explore the prevalence and morphology of the palatal bone reservoir as a viable site for dental implant insertion, offering a conservative alternative to avoid maxillary sinus lift. Methods: DICOM data sets from helical CT of maxillofacial trauma patients aged 50 years and older were used to perform virtual dental implant positioning in the edentulous second premolar, first molar, or second molar areas using ImplaStation software (version 5.3.2; ProDigiDent, Inc., Scottsdale, AZ, USA). A 3D Slicer software (version 5.3.2; ProDigiDent, Inc., Scottsdale, AZ, USA) was used to calculate the volume of the palatal bone reservoir and identify its mean density. The density of the residual alveolar process was also identified and compared with that of the previous one. Results: A total of 1822 maxillofacial trauma cases with helical CT between 2015 and 2025 were retrieved. After exclusion, 305 cases were analyzed. A total of 65 implants were virtually positioned in 50 patients. The mean volume of the palatal bone reservoir was 229 ± 139.2 mm³ with a mean radiodensity of 546.7 ± 159.6 HU. The mean radiodensity of the residual alveolar process was 286.3 ± 118.0 HU. The palatal bone reservoir was significantly denser than the residual alveolar process (95% CI [184.2, 336.6]; p < 0.01). Conclusions: The presence of a palatal bone reservoir is not uncommon and can offer a more conservative alternative for implant placement, potentially increasing primary stability and facilitating immediate loading. Full article

Breast cancer is classified into distinct molecular subtypes, including Luminal A, Luminal B, HER2-enriched, Basal-like, and Claudin-low. While traditional studies mostly use 2D cell cultures, 3D models better mimic in vivo tumor conditions. In this study, we generated and characterized 3D spheroids from breast cancer cell lines representing different molecular subtypes. Morphologically, spheroids were either compact (MCF-7/AZ, T47D, BT474, MDA-IBC-3, BT-20, SUM149PT) or loosely adhered (MDA-MB-468, SK-BR-3, MDA-MB-231), while retaining key parental subtype biomarkers. Cell viability decreased with increasing spheroid size, but apoptotic cCasp3 staining was restricted to Basal-like spheroids. Compact spheroids expressed E- and/or P-cadherin, indicating epithelial or epithelial–mesenchymal transition (EMT) hybrid traits, while loose spheroids showed vimentin expression linked to a mesenchymal phenotype. In conclusion, EMT-associated features, rather than intrinsic molecular subtype, may contribute to 3D spheroid architecture of breast cancer cell lines. Full article

Background/Objectives: Our previous study demonstrated that while the third SARS-CoV-2 booster effectively enhanced immunity against the Delta subvariant, its protection declined over time. This study aimed to evaluate and compare the humoral and cellular immune responses, as well as reactogenicity, of the mRNA-1273 vaccine administered as a fourth booster in healthy Thai adults previously vaccinated with two doses of CoronaVac (CV) followed by a third dose of either AZD1222 (AZ) or BNT162b2 (BNT). Methods: Participants received a single 100 µg (0.5 mL) intramuscular dose of mRNA-1273. Blood samples were collected at baseline (D0), D14, D90, and D180 to assess anti-RBD IgG, conduct a surrogate virus neutralization test (sVNT) against the Delta and Omicron variants, and assess IFN-γ levels and reactogenicity. Results: Both 2CV/AZ- and 2CV/BNT-primed groups exhibited comparable local and systemic reactogenicity. The fourth mRNA-1273 dose markedly increased Delta variant inhibition within 14 days in both groups and remained at high levels at Days 90 and 180. sVNT inhibition against Omicron rose similarly in both groups at Day 14; it declined sharply by Days 90 and 180, with the 2CV/AZ-primed group showing significantly lower levels than the 2CV/BNT-primed group. Baseline anti-RBD IgG levels were lower in the 2CV/AZ group (p = 0.003) but surpassed those of the 2CV/BNT group by Day 14, with no significant differences at later time points. IFN-γ responses followed a similar pattern to anti-RBD IgG Conclusions: A heterologous fourth mRNA-1273 booster in both 2CV/AZ- and 2CV/BNT-primed groups effectively enhances B-cell and T-cell responses against SARS-CoV-2. However, emerging variants such as Omicron may still pose challenges. The trial was registered with the Thai Clinical Trials Registry: the name of the registry: “The comparison of immune response to the 4th dose booster with mRNA-1273 COVID-19 vaccine in individuals who had received 2 doses of CoronaVac and booster with ChAdOx-1 or BNT162b2 COVID-19 vaccine”, TCTR20220205002 on 5 February 2022. Full article

The rapid advancement and widespread application of telecommunication technologies have significantly increased human exposure to electromagnetic waves, thereby intensifying the demand for effective electromagnetic shielding materials. Beyond potential health concerns, ensuring the stable performance of highly integrated electronic devices also necessitates protection against electromagnetic interference (EMI). In this study, the effects of processing conditions on the EMI shielding effectiveness (SE) of AZ61 magnesium alloy sheets were systematically investigated. Aging treatment of rolled AZ61 alloy promoted the formation of Mg₁₇Al₁₂ lamellae. Transmission Kikuchi diffraction analysis revealed that plate-like Mg₁₇Al₁₂ precipitates preferentially formed on the (0001) planes of the Mg matrix, contributing to improved EMI shielding. The rolled AZ61 sheet exhibited the highest SE in both the as-rolled state (83.1 dB at 900 MHz) and after aging for 131 h at 250 °C (76.2 dB at 900 MHz). The superior shielding performance of the as-rolled sheet is attributed to its high density of deformation-induced defects such as dislocations and twins, which induce lattice distortions and impede wave propagation. Meanwhile, the enhanced SE from the 131 h-aged condition results from multiple reflections of incident electromagnetic waves facilitated by the matrix–precipitate lamellar microstructure. Full article

The accuracy of digital impressions in fully edentulous cases is limited by the lack of anatomical reference structures, potentially affecting passive fit. The effects of scanner type, impression level, and scan body splinting on accuracy remain insufficiently elucidated. This in vitro study aimed to evaluate the effects of different intraoral scanners, scanning levels, and scan body splinting methods on digital impression accuracy. A fully edentulous mandibular model with four implants (All-on-4) was fabricated, and scan bodies were connected at either the implant or multi-unit abutment level. Five splinting methods (nonsplinted, floss, orthodontic elastomeric, chain attachments, and single attachments) were applied, creating 10 experimental groups. Each group was scanned using three intraoral scanners: iTero Lumina (Align Technology, Tempe, AZ, USA), TRIOS 3 (3Shape A/S, Copenhagen, Denmark), and Medit i700 (Medit Corp, Seoul, Republic of Korea), with four repeated scans per scanner (120 scans total). Trueness and precision were assessed based on linear and angular deviations using Geomagic Control X (3D Systems, Rock Hill, SC, USA). Scanner type and scanning level significantly affected accuracy (p < 0.05), with TRIOS 3 showing higher deviations, while multi-unit abutments reduced deviations. Splinting methods showed no significant effect on accuracy, and precision did not differ among groups. Scanner type and scanning level significantly influenced digital impression accuracy; however, splinting methods yielded no significant effect. Precision remained comparable among groups. Full article

The development of innovative wound dressings capable of accelerating diabetic wound healing while simultaneously reducing scar formation is a significant clinical challenge. In this study, we designed and fabricated a multifunctional nanofibrous scaffold PCL/Az-CS/dECM/NAC by incorporating decellularized extracellular matrix (dECM) and N-acetylcysteine (NAC) into a composite backbone of polycaprolactone (PCL) and azidobenzoic acid-modified chitosan (AZCS). The scaffold exhibited ideal hydrophilicity and swelling capacity, and demonstrated excellent biocompatibility. In vitro studies demonstrated that the scaffold effectively scavenged reactive oxygen species (ROS) and promoted the polarization of macrophages from the M1 phenotype to the M2 phenotype; in vivo studies confirmed that the PCL/AZ-CS/dECM/NAC scaffold significantly accelerated wound closure, promoted mature angiogenesis, and facilitated orderly collagen deposition. The PCL/AZ-CS/dECM/NAC scaffold mitigated scar formation by increasing the proportion of regenerative type III collagen, optimizing the collagen I/III ratio. Our findings suggest that the PCL/AZ-CS/dECM/NAC scaffold is a highly promising candidate for a multifunctional dressing designed to treat recalcitrant diabetic wounds and prevent excessive scarring. Full article

Polyhydroxybutyrate (PHB) is considered a coating material capable of limiting the corrosion of biodegradable metallic implants due to its biocompatibility and ability to form a physical barrier. In this study, PHB was deposited on commercial AZ91D magnesium alloy using the spin coating technique. To improve adhesion at the polymer–substrate interface, the magnesium substrates were subjected to atmospheric pressure plasma treatment for different exposure times (5, 10, or 15 min) before coating. The optimal treatment time of 5 min significantly increased substrate wettability and surface free energy, facilitating stronger PHB adhesion. In addition, the PHB coatings were subjected to atmospheric pressure plasma treatment for 5, 10, or 15 s to evaluate potential surface modifications. Corrosion behavior under simulated physiological conditions was assessed via potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in HANK’s solution at 37 °C. Pull-off tests were used to evaluate the adhesion strength between the coating and the substrate under each treatment condition. The results showed a significant decrease in the corrosion rate (V_corr), from 4.083 mm/year for bare Mg-AZ91D to 0.001 mm/year when both the substrate and the polymer received plasma treatment. This indicates that the treatment modifies surfaces and improves interfacial bonding, enhancing polymer–metal interaction and producing durable, biocompatible coatings for medical implants. Full article

Simplex-centroid mixture design (SCMD) is applied to change the combination of Na₂SiO₃, KF, NaOH and NaAlO₂ to examine the influences of electrolyte components and their interactions on the thickness and corrosion resistance of micro-arc oxidation (MAO) coating of AZ91D magnesium alloy. The results indicate that the obtained regression equations are very significant (p-value < 0.01) and have high prediction accuracy (R² = 0.9893, 0.9989). Pareto analysis shows that the interactions effect between Na₂SiO₃, KF and NaAlO₂ on the coating thickness and corrosion resistance are 70.03% and 92.35%, respectively, which quantitatively confirms that there are interactions among electrolytes. The analysis of response surface methodology (RSM) demonstrates that the optimum formula is high concentration of Na₂SiO₃, high concentration of KF and low concentration of NaAlO₂. When Na₂SiO₃ is compounded with NaAlO₂, the two will react to form aluminosilicate colloids, resulting in increased viscosity of the electrolyte, and the coating corrosion resistance is poor. When the main salt of electrolyte is single Na₂SiO₃ or NaAlO₂, the corrosion resistance is better. KF can significantly improve the coating thickness and corrosion resistance. Pearson correlation coefficient (PCC) reveals that there is a remarkable relationship between thickness and the corrosion resistance in acidic media (r = 0.88927), which was determined by the corrosion mechanism of the latter. Full article