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Production and Characterization of Fine-Grained Multielement AlCoxCrFeNi (x = 1, 0.75, 0.5) Alloys for High-Temperature Applications
Get PDFPublisher Copyright: © 2024 by the authors.In the present work, three different AlCoxCrFeNi (x = 1, 0.75, 0.5) alloys were produced through the mechanical milling of powders and spark plasma sintering. These alloys were characterized in terms of their microstructural, mechanical, and oxidation behaviors. Mechanical milling and spark plasma sintering were chosen to achieve a fine and homogeneous microstructure. Pore-free samples were produced by properly setting the sintering parameters. The unavoidable uptake of oxygen from the powders when exposed to air after milling was advantageously used as a source of oxides, which acted as reinforcing particles in the alloy. Oxidation behavior, studied through TGA tests, showed that decreasing the Co content promotes better oxidation protection due to the formation of a dense, compact Al2O3 layer. The alloy containing the lowest amount of Co is considered a good candidate for high-temperature structural applications.Peer reviewe
Guanylate Kinase 1 Deficiency: A Novel and Potentially Treatable Mitochondrial DNA Depletion/Deletions Disease
No full textPublisher Copyright: © 2024 The Author(s). Annals of Neurology published by Wiley Periodicals LLC on behalf of American Neurological Association.Objective: Mitochondrial DNA (mtDNA) depletion/deletions syndrome (MDDS) comprises a group of diseases caused by primary autosomal defects of mtDNA maintenance. Our objective was to study the etiology of MDDS in 4 patients who lack pathogenic variants in known genetic causes. Methods: Whole exome sequencing of the probands was performed to identify pathogenic variants. We validated the mitochondrial defect by analyzing mtDNA, mitochondrial dNTP pools, respiratory chain activities, and GUK1 activity. To confirm pathogenicity of GUK1 deficiency, we expressed 2 GUK1 isoforms in patient cells. Results: We identified biallelic GUK1 pathogenic variants in all 4 probands who presented with ptosis, ophthalmoparesis, and myopathic proximal limb weakness, as well as variable hepatopathy and altered T-lymphocyte profiles. Muscle biopsies from all probands showed mtDNA depletion, deletions, or both, as well as reduced activities of mitochondrial respiratory chain enzymes. GUK1 encodes guanylate kinase, originally identified as a cytosolic enzyme. Long and short isoforms of GUK1 exist. We observed that the long isoform is intramitochondrial and the short is cytosolic. In probands’ fibroblasts, we noted decreased GUK1 activity causing unbalanced mitochondrial dNTP pools and mtDNA depletion in both replicating and quiescent fibroblasts indicating that GUK1 deficiency impairs de novo and salvage nucleotide pathways. Proband fibroblasts treated with deoxyguanosine and/or forodesine, a purine phosphatase inhibitor, ameliorated mtDNA depletion, indicating potential pharmacological therapies. Interpretation: Primary GUK1 deficiency is a new and potentially treatable cause of MDDS. The cytosolic isoform of GUK1 may contribute to the T-lymphocyte abnormality, which has not been observed in other MDDS disorders. ANN NEUROL 2024;96:1209–1224.Peer reviewe
ON THE POSSIBILITY OF EXTENDING THE CRACK LENGTH CRITERION IN THE MASTER CURVE METHODOLOGY
No full textPublisher Copyright: Copyright © 2024 by ASME.The master curve methodology is a well-known approach utilized to characterize the ductile-to-brittle transition region of ferritic-pearlitic steels. This methodology was initially standardized in ASTM E1921 in 1997 and has undergone continuous evolution and improvement since its origin. However, the validity criterion for the crack aspect ratio (0.45 ≤ a0/W ≤ 0.55) has remained unchanged since its inception. It is worth noting that this criterion was originally established in accordance with standard ASTM E399, which characterizes fracture conditions under linear-elastic plane strain conditions, apparently for historical precedents rather than any scientific rationale. Furthermore, ASTM E1820, which is employed to characterize the fracture behavior of metallic materials in elastic-plastic conditions, permits a maximum crack length-to-width ratio of 0.70. In this context, and considering that ASTM E1921 measures KJc (elastic-plastic) values of the fracture toughness, our research seeks to empirically demonstrate that the crack length-to-width criteria established in ASTM E1921 can be increased up to 0.60, at the very least, without compromising the accuracy of the reference temperature calculations. Such a correction would offer significant advantages, especially when dealing with mini-C(T) specimens. Their tiny dimensions may result in the discarding of numerous specimens that could otherwise be effectively employed for reference temperature calculations.Peer reviewe
Real-time analysis of islanding detection scheme developed for AC microgrid system
No full textPublisher Copyright: © 2023 Elsevier B.V.In this study, a communication assisted passive islanding detection technique is proposed for microgrid having converter based distributed generation (DG) resources. In the proposed approach, the matrix pencil method is applied to reconstruct the voltage signal then both the raw signal and reconstructed signals are used to estimate phasor magnitudes using Discrete Fourier Transform (DFT). Full cycle DFT is unable to eliminate the decaying DC component completely in one cycle from the actual input signal, whereas the reconstructed signal is a filtered signal. Hence, subsequent to the application of DFT, the difference between actual and reconstructed signal becomes negligible during steady state condition but exists only if an event occurs in the microgrid. Utilizing the well-known fact presence of DC component in initial stage at the time of transient event, the magnitude difference of raw and reconstructed signals is computed at a given end. Accordingly, an index for each phase is calculated considering difference from both sides; point of common coupling (PCC) and DG. The target DG gets detected as being islanded from the main grid, if the indices of all the three phases remains positive i.e., greater than zero. The results obtained for tested conditions indicate that all the three indices of phases retain simultaneously positive sign only for islanding event. On other hand, non-islanding cases involve at least one or more phases indices being of negative sign. The proposed approach is tested on signals generated from simulation model. Also, the obtained results for signals from real-time test bed executed using Opal-RT, proves the superiority, robustness, and reliability of the proposed islanding detection algorithm.Peer reviewe
Novel Li-Fi Transceiver design based on Perovskite Photodiode Devices (PeLiFi)
No full textPublisher Copyright: © 2024 SPIE.Perovskite is an emerging low-cost and high-quality material, that show significant potential to revolutionize photovoltaic and lighting sectors in Organic and Large Area Electronics (OLAE) devices. Their simple and inexpensive processing methods, such as solution-based synthesis and printing, make them attractive for flexible and lightweight electronic devices. In this work, perovskite suitability has been tested for telecommunication applications, particularly Li-Fi links. The perovskite devices were integrated into a telecom system, including an FPGA handling signal processing, LED array, analog transmitter circuitry, and driving electronics for the perovskite photodiode. 4-PPM modulation format has been adopted due to resilience in low SNR. The purpose is to thoroughly characterize the setup to assess the suitability of perovskite devices for Li-Fi scenarios or combined PV and Li-Fi usage. This research aims to advance the application of perovskites in telecommunication and expand their potential in various electronic devices.Peer reviewe
Designing interactive, gamified learning environments: a methodological approach with a case study on statistical quality control
No full textPublisher Copyright: © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.Statistical Quality Control is a subject present in many engineering degrees. Literature identifies shortcomings in the application of Statistical Quality Control in industry. Some factors include a lack of training, misunderstandings or failures in implementing Statistical Quality Control. Many authors suggest following new methodologies (e.g. Problem-Based Learning) to improve the teaching of Statistical Quality Control, but, in general, universities continue applying the traditional methodology based on master classes. In this paper, we propose a methodology to design interactive gamified environments, and apply it to improve the Statistical Quality Control teaching-learning process. This methodology is based on two phases. The first one focuses on the design of the formative itinerary. For this, taking into account the competencies and learning objectives, the teacher applies a divide-and-conquer approach to break down the content into concepts, elaborates a graph of dependencies (which reflects the dependencies between the concepts, their complexity and the required cognitive level) and designs the formative itinerary to define the order in which the individual modules will be presented, together with a strategy of controlled content exposure. This process generates a stable structure that will support the second phase, consisting of selecting diverse learning activities for each module to promote active, self-paced, reflective, and engaged learning. We apply this methodology by dividing the Statistical Quality Control content into modules that comprise the key concepts, creating a formative itinerary. Given that structure, for each module, we select learning activities that encourage active learning and we translate it all into a game-like tool. This tool not only includes gamification elements like scoreboards, stars, and a map, but it further innovates by including as learning activities interactive serious games that help to visualize and understand the Statistical Quality Control process, by performing real-life tasks, resulting in significant learning. It also incorporates other educational strategies to promote active learning, such as flipped classroom and the inclusion of formative assessment. The content exposure control is implemented through tests on quality control to ensure students’ assimilation of the concepts before allowing them to move on to activities or problems that require higher cognitive levels. We evaluate the methodology’s effectiveness through an experiment that shows that students who used the learning tool improved their knowledge (p-value < 0.001) in comparison to their peers who only attended a traditional master class. Students also thought that this type of application is a good complementary material for the course and that it helps to improve knowledge assimilation (score of 4.94 out of 5 points).Peer reviewe
Protection coatings for corrosion control of mild steel using phenolic polymeric deep eutectic solvents
No full textPublisher Copyright: © 2024 RSC.The mitigation of corrosion, especially in coastal regions, stands as a significant social concern necessitating the exploration of environmentally friendly materials. This study introduces phenol-based ionic polymers as both coatings and solution corrosion inhibitors for mild steel. Three methacrylated phenolic deep eutectic monomers (DEMs) bearing catechol and gallol motifs were synthetized for this purpose, taking advantage of polyphenol chemistry. Both the polyphenol DEMs and the UV-photopolymerized ionic polymer coatings formed coordination complexes with iron ions on the surface of the mild steel, resulting in a distinctive colour evolution, transitioning from a non-coloured film to dark purple, characterized by optical imaging and UV-vis absorption analysis. The resulting interfacial complex layer demonstrated exceptional corrosion inhibition efficiency for tannic acid and protocatechuic acid based polymers, achieving efficiencies of 99.84% and 99.54% respectively. Further explanation of this phenomenon involves the investigation of phenolic deep eutectic monomers in solution as model compounds, revealing a purple hue in the solution arising from the complexation between the polyphenol chemistry and the iron ions leached from the steel surface.Peer reviewe
Inter-annual trends of ultrafine particles in urban Europe
No full textPublisher Copyright: © 2024 The AuthorsUltrafine particles (UFP, those with diameters ≤ 100 nm), have been reported to potentially penetrate deeply into the respiratory system, translocate through the alveoli, and affect various organs, potentially correlating with increased mortality. The aim of this study is to assess long-term trends (5–11 years) in mostly urban UFP concentrations based on measurements of particle number size distributions (PNSD). Additionally, concentrations of other pollutants and meteorological variables were evaluated to support the interpretations. PNSD datasets from 12 urban background (UB), 5 traffic (TR), 3 suburban background (SUB) and 1 regional background (RB) sites in 15 European cities and 1 in the USA were evaluated. The non-parametric Theil-Sen's method was used to detect monotonic trends. Meta-analyses were carried out to assess the overall trends and those for different environments. The results showed significant decreases in NO, NO2, BC, CO, and particle concentrations in the Aitken (25–100 nm) and the Accumulation (100–800 nm) modes, suggesting a positive impact of the implementation of EURO 5/V and 6/VI vehicle standards on European air quality. The growing use of Diesel Particle Filters (DPFs) might also have clearly reduced exhaust emissions of BC, PM, and the Aitken and Accumulation mode particles. However, as reported by prior studies, there remains an issue of poor control of Nucleation mode particles (smaller than 25 nm), which are not fully reduced with current DPFs, without emission controls for semi-volatile organic compounds, and might have different origins than road traffic. Thus, contrasting trends for Nucleation mode particles were obtained across the cities studied. This mode also affected the UFP and total PNC trends because of the high proportion of Nucleation mode particles in both concentration ranges. It was also found that the urban temperature increasing trends might have also influenced those of PNC, Nucleation and Aitken modes.Peer reviewe
Revisiting excitation force estimation in WECs: On the (mis)use of structure-based estimation approaches
No full textPublisher Copyright: © 2024 The Author(s)Wave excitation force (torque) estimators, vital in wave energy systems, generally combine the nominal representation of a wave energy converter (WEC) with an excitation force (perturbation) model. Thus, this model-based estimation approach, grounded in the internal model principle, often employs two perturbation models: (i) the harmonic oscillator structure, prevalent in literature, assuming sinusoidal signals; and (ii) the integrator (random walk) scheme, assuming unit step-like signals. These models comprehensively represent a specific family of estimators, as discussed in this study. However, both models may struggle to capture the irregular (stochastic) nature of ocean waves. This study challenges the prevailing assumption that the harmonic oscillator structure, selected for its resemblance to ocean wave oscillations, is inherently the optimal choice. This study provides a rigorous discussion on convergence conditions. Thus, is shown that, while the harmonic oscillator can be highly effective under specific conditions, the random walk structure, despite its simplicity, can surpass the performance of the harmonic oscillator scheme. Formal proofs support this argument, emphasising the effectiveness of the harmonic oscillator can be guaranteed with periodic signals.Peer reviewe
FUSeg: The Foot Ulcer Segmentation Challenge
No full textPublisher Copyright: © 2024 by the authors.Wound care professionals provide proper diagnosis and treatment with heavy reliance on images and image documentation. Segmentation of wound boundaries in images is a key component of the care and diagnosis protocol since it is important to estimate the area of the wound and provide quantitative measurement for the treatment. Unfortunately, this process is very time-consuming and requires a high level of expertise, hence the need for automatic wound measurement methods. Recently, automatic wound segmentation methods based on deep learning have shown promising performance; yet, they heavily rely on large training datasets. A few wound image datasets were published including the Diabetic Foot Ulcer Challenge dataset, the Medetec wound dataset, and WoundDB. Existing public wound image datasets suffer from small size and a lack of annotation. There is a need to build a fully annotated dataset to benchmark wound segmentation methods. To address these issues, we propose the Foot Ulcer Segmentation Challenge (FUSeg), organized in conjunction with the 2021 International Conference on Medical Image Computing and Computer-Assisted Intervention (MICCAI). It contains 1210 pixel-wise annotated foot ulcer images collected over 2 years from 889 patients. The submitted algorithms are reviewed in this paper and the dataset can be accessed through the Foot Ulcer Segmentation Challenge website.Peer reviewe