Search Results (294)

Refractory metals typically exhibit limited room temperature ductility, hampering their widespread application. Recent advances in refractory high-entropy alloys have focused on finding optimum combinations of strength and ductility but require exploring vast compositional spaces. To facilitate such a search process, a method for fast assessment of intrinsic ductility would be highly advantageous. Herein, we propose a novel approach to screen for a refractory alloy’s ‘intrinsic ductility’ by leveraging the established technique of thin film fragmentation testing, which has been successfully used to evaluate stretchability of flexible electronics. We conducted in-depth investigations of sputtered tungsten thin films to identify the processing-induced extrinsic variables that can affect the crack onset strain (COS) under uniaxial loading. By tuning the process parameters for film deposition, Nb, Mo, Ta and W samples were fabricated with comparable thicknesses and residual stress levels. The films’ COS values were compared to the ductility levels of bulk counterpart materials, and the conditions for meaningful comparison are discussed. This approach offers a simple, inexpensive, and rapid means of screening based on relative intrinsic ductility of thin metal films and should also be applicable to the study of high-entropy alloy films. Full article

Gallium Nitride (GaN) is a wide-bandgap semiconductor that has revolutionized optoelectronic applications, enabling blue/white light-emitting devices and high-power electronics. Point defects in GaN strongly influence its optical and electronic properties, producing both beneficial and detrimental effects. This review provides a comprehensive update on the current understanding of point defects in GaN and their impact on photoluminescence (PL). Since our earlier review (Reshchikov and Morkoç, J. Appl. Phys. 2005, 97, 061301), substantial progress has been made in this field. PL bands associated with major intrinsic and extrinsic defects in GaN are now much better understood, and several defects in undoped GaN (arising from unintentional impurities or specific growth conditions) have been identified. Notably, the long-debated origin of the yellow luminescence band in GaN has been resolved, and the roles of Ga and N vacancies in the optical properties of GaN have been revised. Zero-phonon lines have been discovered for several defects. Key parameters, such as electron- and hole-capture coefficients, phonon energies, electron–phonon coupling strength, thermodynamic charge transition levels, and the presence of excited states, have been determined or refined. Despite these advances, several puzzles associated with PL remain unsolved, highlighting areas for future investigation. Full article

Introduction: Skin aging is a multifaceted process influenced by both intrinsic and extrinsic factors, resulting in visible changes such as wrinkles, loss of elasticity, uneven skin tone, and hyperpigmentation. Hyaluronic acid (HA) is widely recognized for its hydrating and structural support properties, while Vitamin C is known for its antioxidant and depigmenting effects. This study investigated the anti-aging efficacy of two topical formulations containing Jalubalance^® technology—HA delivered in Opuntia oil—with or without 1% Vitamin C. Background/Objectives: We conducted an 8-week, multicenter, randomized trial involving 91 women aged 30–50 years with mild-to-moderate photoaging. Participants were assigned to apply either HA-only cream (Group A) or a HA + Vitamin C cream (Group B) twice daily. The primary outcome was the percentage of subjects who achieved an improvement of at least one point in the hyperpigmentation score from baseline to week 8. Additionally, the study aimed to evaluate and compare the clinical and instrumental effects of both treatments, with a particular focus on improvements in wrinkles, elasticity, hydration, and pigmentation. Results: Both groups showed significant improvements across all measured parameters, including Glogau scores, wrinkle reduction, and skin elasticity. Instrumental analysis confirmed increased hydration and elasticity. Group B showed a significantly greater reduction in hyperpigmentation (−45%) compared to Group A (−31%, p < 0.05). At week 8, a ≥1-point reduction in hyperpigmentation score was observed in 56% of subjects in Group B and 30% in Group A (absolute difference: 26%; 95% CI: 5–43%; p < 0.05), highlighting the added benefit of Vitamin C on this parameter. Participant satisfaction was high, especially for the moisturization and brightening effects of both products. Conclusions: The topical application of Jalubalance-based creams effectively reduced signs of aging. The inclusion of Vitamin C provided enhanced benefits in reducing hyperpigmentation, suggesting its utility in personalized dermatological approaches for patients with pigmentation concerns. Full article

A Mg-Gd-Y alloy prepared by surface mechanical attrition treatment (SMAT) was annealed at 450 °C combined with peak aging. The deformation and fracture mechanisms were investigated using in situ tensile tests. Through quantitative calculations of the geometrically necessary dislocation (GND) densities, it was found that the fine-grained (FG) layer in the gradient structure carried greater plastic strain than the coarse-grained (CG) layer during tension. The calculation results of the geometric compatibility parameter (m’) and microstructure characterization during in situ tests showed that crack initiation and propagation were prone to occur between adjacent coarse grains. However, the hetero-deformation-induced (HDI) strengthening and strain hardening induced by the strain gradient between the FG and CG layers effectively improved the strength–ductility synergy of the gradient-structured (GS) alloy. In addition, the synergistic effect of intrinsic and extrinsic toughening mechanisms in the GS alloy played a significant role in delaying premature failure. Full article

Background: The aesthetic performance of single-shade polymer-based restorative materials (SPRs) can be compromised by extrinsic stains. Understanding the effects of novel whitening interventions on SPRs is crucial. Objective: This in vitro study aimed to evaluate the effects of different whitening interventions, including a novel purple tooth serum and charcoal-based whitening toothpaste with and without in-office bleaching, on the color of a new coffee-stained SPR. Materials and Methods: Seventy disc-shaped SPR specimens were prepared, stained, and then divided into seven groups (n = 10). Three groups were subjected directly to 2500 cycles of brushing simulation with regular toothpaste (control), charcoal toothpaste, or purple tooth serum. The rest were divided into bleaching groups, and the four groups underwent a simulation of bleaching and then brushing with the three products. The color parameters were recorded at the stained baseline, after brushing, after bleaching, and after post-bleaching brushing. The color change (ΔE00) was calculated, and the data were analyzed statistically using the Kruskal–Wallis test and Dunn–Bonferroni pairwise comparisons (p < 0.05). Results: In-office bleaching without brushing had a statistically significantly higher ΔE00 value than all other groups (p < 0.001). Post hoc tests indicated that the ΔE00 values of the brushed specimens were not significantly different from each other when assessed with and without bleaching (p > 0.05). When using the charcoal toothpaste, the post-bleaching brushed specimens had a noticeable color change above the PT. Conclusions: Bleaching improved the stained SPR color initially, but other treatments may offer longer-lasting aesthetics. The charcoal toothpaste showed promising results when combined with bleaching. The purple serum showed limited effectiveness. Full article

This study examines the performance of a GaN HEMT with a 150 nm gate length, fabricated on silicon carbide, across various operational modes, including direct current (DC), radio frequency (RF), and small-signal parameters. The evaluation of DC, RF, and small-signal performance under diverse bias conditions remains a relatively unexplored area of study for this specific technology. The DC characteristics revealed relatively little I_ds at zero gate and drain voltages, and the current grew as V_gs increased. Essential measurements include I_dss at 109 mA and I_dssm at 26 mA, while the peak g_m was 62 mS. Because transconductance is sensitive to variations in V_gs and V_ds, it shows “Vth _roll-off,” where Vth decreases as V_ds increases. The transfer characteristics corroborated this trend, illustrating the impact of drain-induced barrier lowering (DIBL) on threshold voltage (Vth) values, which spanned from −5.06 V to −5.71 V across varying drain-source voltages (V_ds). The equivalent-circuit technique revealed substantial non-linear behaviors in capacitances such as C_gs and C_gd concerning V_gs and V_ds, while also identifying extrinsic factors including parasitic capacitances and resistances. Series resistances (R_gs and R_gd) decreased as V_gs increased, thereby enhancing device conductivity. As V_gs approached neutrality, particularly at elevated V_ds levels, the intrinsic transconductance (g_mo) and time constants (τ_gm, τ_gs, and τ_gd) exhibited enhanced performance. f_t and f_max, which are essential for high-frequency applications, rose with decreasing V_gs and increasing V_ds. When V_gs approached −3 V, the S₂₁ and Y₂₁ readings demonstrated improved signal transmission, with peak S₂₁ values of approximately 11.2 dB. The stability factor (K), which increased with V_ds, highlighted the device’s operational limits. The robust correlation between simulation and experimental data validated the equivalent-circuit model, which is essential for enhancing design and creating RF circuits. Further examination of bias conditions would enhance understanding of the device’s performance. Full article

Robust perception of road surface conditions is a critical challenge for the safe deployment of autonomous vehicles and the efficient management of transportation infrastructure. This paper introduces a synthetic data-driven deep learning framework designed to address this challenge. We present a large-scale, procedurally generated 3D synthetic dataset created in Blender, featuring a diverse range of road defects—including cracks, potholes, and puddles—alongside crucial road features like manhole covers and patches. Crucially, our dataset provides dense, pixel-perfect annotations for segmentation masks, depth maps, and camera parameters (intrinsic and extrinsic). Our proposed model leverages these rich annotations in a multi-task learning framework that jointly performs road defect segmentation and depth estimation, enabling a comprehensive geometric and semantic understanding of the road environment. A core contribution is a two-stage domain adaptation strategy to bridge the synthetic-to-real gap. First, we employ a modified CycleGAN with a segmentation-aware loss to translate synthetic images into a realistic domain while preserving defect fidelity. Second, during model training, we utilize a dual-discriminator adversarial approach, applying alignment at both the feature and output levels to minimize domain shift. Benchmarking experiments validate our approach, demonstrating high accuracy and computational efficiency. Our model excels in detecting subtle or occluded defects, attributed to an occlusion-aware loss formulation. The proposed system shows significant promise for real-time deployment in autonomous navigation, automated infrastructure assessment and Advanced Driver-Assistance Systems (ADAS). Full article

Alginate-based materials are widely studied for biomedical use, but their limited mechanical properties and variable biocompatibility pose challenges. In this work, hybrid composites composed of alginate, calcium, and graphene oxide were fabricated using a freeze-drying method and cross-linked with calcium ions via calcium chloride at different concentrations. Structural and morphological features were assessed using SEM, EDS, ICP-MS, and BET analysis. The resulting composites exhibited a porous architecture, with calcium incorporation confirmed by elemental analysis. Surface characteristics and pore parameters were influenced by the presence of graphene oxide and the cross-linking process. The effects of the materials on haemostasis were evaluated through activated partial thromboplastin time (aPTT) and prothrombin time (PT) assays, revealing modulation of the intrinsic coagulation pathway without significant changes in the extrinsic pathway. In this study, we analysed the effect of alginate–graphene oxide composites on the viability of peripheral blood mononuclear (PBM) cells and human foreskin fibroblasts from the Hs68 cell line. We also assessed the genotoxic potential of alginate–graphene oxide composites on these cells. Our results showed no cyto- or genotoxic effects of the material on either cell type. These findings suggest the biocompatibility and safe character of alginate–graphene oxide composites for use with blood and skin cells. Full article

Computer vision techniques such as three-dimensional digital image correlation (3D-DIC) and three-dimensional point tracking (3D-PT) have demonstrated broad applicability for monitoring the conditions of large-scale engineering systems by reconstructing and tracking dynamic point clouds corresponding to the surface of a structure. Accurate stereophotogrammetry measurements require the stereo cameras to be calibrated to determine their intrinsic and extrinsic parameters by capturing multiple images of a calibration object. This image-based approach becomes cumbersome and time-consuming as the size of the tested object increases. To streamline the calibration and make it scale-insensitive, a multi-sensor system embedding inertial measurement units and a laser sensor is developed to compute the extrinsic parameters of the stereo cameras. In this research, the accuracy of the proposed sensor-based calibration method in performing stereophotogrammetry is validated experimentally and compared with traditional approaches. Tests conducted at various scales reveal that the proposed sensor-based calibration enables reconstructing both static and dynamic point clouds, measuring displacements with an accuracy higher than 95% compared to image-based traditional calibration, while being up to an order of magnitude faster and easier to deploy. The novel approach has broad applications for making static, dynamic, and deformation measurements to transform how large-scale structural health monitoring can be performed. Full article

To improve the accuracy of three-dimensional (3D) reconstruction under microscopic conditions for laser-induced breakdown spectroscopy (LIBS), this study developed a novel visual platform by integrating an industrial CCD camera with a microscope. A customized microscale calibration target was designed to calibrate intrinsic and extrinsic camera parameters accurately. Based on the pinhole imaging model, disparity maps were obtained via pixel matching to reconstruct high-precision 3D ablation morphology. A mathematical model was established to analyze how key imaging parameters—baseline distance, focal length, and depth of field—affect reconstruction accuracy in micro-imaging environments. Focusing on trace element detection in WC-Co alloy samples, the reconstructed ablation craters enabled the precise calculation of ablation volumes and revealed their correlations with laser parameters (energy, wavelength, pulse duration) and the physical-chemical properties of the samples. Multivariate regression analysis was employed to investigate how ablation morphology and plasma evolution jointly influence LIBS quantification. A nonlinear calibration model was proposed, significantly suppressing matrix effects, achieving R² = 0.987, and reducing RMSE to 0.1. This approach enhances micro-scale LIBS accuracy and provides a methodological reference for high-precision spectral analysis in environmental and materials applications. Full article

Introduction: Obstructive sleep apnea syndrome (OSAS) is caused by anatomical and non-anatomical factors which lead to upper airway (UA) obstruction during sleep. Intrinsic UA collapse is the most frequent determinant of OSA. In the era of personalized medicine, adopting a tailored diagnostic approach is essential to rule out secondary causes of UA collapse, particularly those stemming from extrinsic anatomical factors. Although being rarely considered in the differential diagnosis, space-occupying lesions of deep cervical spaces such as the parapharyngeal space (PPS) may be responsible for airway obstruction and lead to OSAS. Objective: This study aimed to present an atypical case of OSAS caused by extrinsic PPS compression, outlining the relevance of modern personalized medicine in the diagnostic and therapeutic protocols, and to enhance understanding through a comprehensive literature review. Methods: A 60-year-old female presented with sleep-disordered complaints and was diagnosed with severe OSAS after polysomnography. At physical examination, a swelling of the right posterior oropharyngeal mucosa was noticed. Imaging confirmed the suspicion of a PPS tumor, and transcervical resection was planned. Case presentation was adherent to the CARE checklist. A comprehensive literature review was conducted using the most reliable scientific databases. Results: Surgery was uneventful, and the patient made a full recovery. The histopathology report was consistent with the diagnosis of pleomorphic adenoma. Postoperative outcomes showed marked improvement in polysomnographic parameters and symptom burden. Conclusions: Parapharyngeal space tumors are a rare, often overlooked cause of OSA. This case highlights the role of a personalized head and neck assessment in OSA patients, particularly in identifying structural causes and offering definitive surgical management when indicated. Full article

Structure-from-motion (SfM) is a foundational technology that facilitates 3D scene understanding and visual localization. However, bundle adjustment (BA)-based SfM is usually very time-consuming, especially when dealing with numerous unknown focal length cameras. To address these limitations, we proposed a novel SfM system based on pose-only adjustment (PA) for intrinsic and extrinsic joint optimization to accelerate computing. Firstly, we propose a base frame selection method based on depth uncertainty, which integrates the focal length and parallax angle under a multi-camera system to provide more stable depth estimation for subsequent optimization. We explicitly derive a global PA of joint intrinsic and extrinsic parameters to reduce the high dimensionality of the parameter space and deal with cameras with unknown focal lengths, improving the efficiency of optimization. Finally, a novel pose-only re-triangulation (PORT) mechanism is proposed for enhanced reconstruction completeness by recovering failed triangulations from incomplete point tracks. The proposed framework has been demonstrated to be both faster and comparable in accuracy to state-of-the-art SfM systems, as evidenced by public benchmarking and analysis of the visitor photo dataset. Full article

The accurate detection and precise spatial localization of rebar intersection points are essential for advancing automation in construction tasks, such as robotic rebar tying. This paper presents a vision-based methodology that integrates RGB-D sensing, camera calibration, and coordinate transformation techniques to robustly detect and localize rebar crossing points. A structured detection framework efficiently extracts intersection coordinates from RGB-D imagery, subsequently mapping these points to a global reference frame using extrinsic camera calibration parameters. To achieve comprehensive site coverage and optimize operational efficiency, the path planning challenge is reformulated as a sequencing optimization problem of the identified intersections. We propose a greedy optimization algorithm that generates smooth, snake-like traversal paths in an efficient manner. Experimental validation confirms the effectiveness of our approach, demonstrating detection accuracy exceeding 99%, an average processing time below 125 ms per intersection point, and a maximum coordinate transformation error under 2 mm. The presented solution offers a lightweight, precise, and scalable framework, significantly facilitating the integration of vision-based methods into automated construction workflows. Full article

Three-dimensional reconstruction using monocular camera images is a well-established research topic. While multi-image approaches like Structure from Motion produce sparse point clouds, single-image depth estimation via machine learning promises denser results. However, many models estimate relative depth, and even those providing metric depth often struggle with unseen data due to unfamiliar camera parameters or domain-specific challenges. Accurate metric 3D reconstruction is critical for railway applications, such as ensuring structural gauge clearance from vegetation to meet legal requirements. We propose a novel method to scale 3D point clouds using the track gauge, which typically only varies in very limited values between large areas or countries worldwide (e.g., $1.435$ m in Europe). Our approach leverages state-of-the-art image segmentation to detect rails and measure the track gauge from a train driver’s perspective. Additionally, we extend our method to estimate a reasonable railway-specific extrinsic camera calibration. Evaluations show that our method reduces the average Chamfer distance to LiDAR point clouds from $1.94$ m (benchmark UniDepth) to $0.41$ m for image-wise calibration and $0.71$ m for average calibration. Full article

The spatial distribution of equiaxed crystal zones during extra-thick slab solidification exerts a critical influence on the mechanical performance of the final product. This investigation establishes a dual-pathway control framework for solidification structure modulation, differentiating between intrinsic regulation through columnar-to-equiaxed transition (CET) positioning and extrinsic intervention via strand electromagnetic stirring (S-EMS) parameter adjustment. The aim is to improve the internal quality of extra-thick slabs, enabling further investigations into the material properties. To achieve this, a solidification heat transfer model along with a cellular automata–finite element model were developed to characterize the thermal conditions at CET initiation, with experimental validation conducted on a 475 mm extra-thick slab. The systematic analysis identified a significant correlation between continuous casting parameters, alloy concentrations, and CET positioning, while S-EMS experiments further elucidated the distribution patterns of the solidification structure and the formation mechanism of the white band in the mushy zone. This methodology bridges computational metallurgy with process engineering, offering systematic guidance for solidification structure control in extra-thick slabs. Full article