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On the antimicrobial properties and endurance of eugenol and 2-phenylphenol functionalized sol-gel coatings
Get PDFPublisher Copyright: © 2024 The AuthorsPreventing microbiological surface contamination in public spaces is nowadays of high priority. The proliferation of a microbial infection may arise through air, water, or direct contact with infected surfaces. Chemical sanitization is one of the most effective approaches to avoid the proliferation of microorganisms. However, extended contact with chemicals for cleaning purposes such as chlorine, hydrogen peroxide or ethanol may lead to long-term diseases as well as drowsiness or respiratory issues, not to mention environmental issues associated to their use. As a potentially safer alternative, in the present work, the efficacy and endurance of the antimicrobial activity of different sol-gel coatings were studied, where one or two biocides were added to the coating matrix resulting on active groups exposed on the surface. Specifically, the coating formulations were synthesized by the sol-gel method. Using the alkoxide route with acid catalysis a hybrid silica-titania-methacrylate matrix was obtained where aromatic liquid eugenol was added with a double function: as a complexing agent for the chelation of the reaction precursor titanium isopropoxide, and as a biocide. In addition, 2-Phenylphenol, ECHA approved biocide, has also been incorporated to the coating matrix. The antibacterial effect of these coatings was confirmed on Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli). Additionally, the coatings were non cyto-toxic and displayed virucidal activity. The coating chemical composition was characterized by 29Si NMR, and ATR-FTIR. Furthermore, the thickness and the mechanical properties were characterized by profilometry and nanoindentation, respectively. Finally, the durability of the coatings was studied with tribology tests. Overall, our data support the efficacy of the tested sol-gel coatings and suggest that added features may be required to improve endurance of the antimicrobial effects on operational conditions.Peer reviewe
Spatial Decision Making for Improvement of the Resilience of the Historic Areas: SHELTER DSS
No full textPublisher Copyright: © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.One of the challenges of Europe is how to adapt cultural heritage and historic areas to current climate change and natural disasters, these are causing irreversible losses on natural and historical heritage. The identification of the risk that heritage assets are suffering, and which are the best strategies or solutions to protect and conserve them is crucial. The article describes a decision support system that provides information in a GIS3D way, improving the analysis of the data and helps finding the best solutions for each heritage asset, working in an early-stage phase. The tool is divided in two components, on the one hand an interactive catalog of solutions, implementing multiple filters and multicriteria analysis methodology, making easier to find the solutions that better match each case. On the other hand, a risk assessment baseline visualization component that shows precalculated risk score for different hazards (Heat waves, wildfires, earthquakes, storms, flooding, and subsidence) in a table and in GIS 3D assets, and the same component allows the simulation of the impact of the solutions in the different capabilities of the assets. The tool allows saving the generated scenario for being loaded in the future. The components of the tool are flexible and can be used separately, accessing to visualization of solutions and their information, or making simulations.Peer reviewe
Towards measuring the aggregated debt of Trustworthiness level
No full textPublisher Copyright: © 2022 ACM.The management of technical debt related to non-functional properties such as security, reliability or other trustworthiness dimensions is of paramount importance for critical systems (e.g., safety-critical, systems with strong privacy constraints etc.). Unfortunately, diverse factors such as time pressure, resource limitations, organizational aspects, lack of skills, or the fast pace at which new risks appears, can result in an inferior level of trustworthiness than the desired or required one. In addition, there is increased interest in considering trustworthiness characteristics, not in isolation, but in an aggregated fashion, as well as using this knowledge for risk quantification. In this work, we propose a trustworthiness debt measurement approach using 1) established categories and subcategories of trustworthiness characteristics from SQuaRE, 2) a weighting approach for the characteristics based on an AHP method, 3) a composed indicator based on a Fuzzy method, and 4) a risk management and analysis support based on Monte Carlo simulations. Given the preliminary nature of this work, while we propose the general approach for all trustworthiness dimensions, we elaborate more on security and reliability. This initial proposal aims providing a practical approach to manage trustworthiness debt suitable for any life cycle phase and bringing the attention to aggregation methods.Thanks to the TRUSTIND project (Creating Trust in the Industrial Digital Transformation), an Elkartek project funded by the Basque Government.Peer reviewe
Real Time Selective Harmonic Control - PWM Based on Artificial Neural Networks
No full textPublisher Copyright: © 1986-2012 IEEE.Selective harmonic elimination-pulse width modulation (SHE-PWM) is a widely used low switching frequency modulation technique for medium-voltage high-power converters. This approach is able to adjust the converter fundamental component while eliminating low-order harmonics. However, some applications such as active power filters (APFs) require regulating simultaneously, both the fundamental and low-order harmonics in amplitude and phase. This article presents a novel selective harmonic control-PWM (SHC-PWM) modulator, valid for APFs, based on artificial neural networks (ANNs) and sequential quadratic programming (SQP). A new offline search methodology, based on a hybrid metaheuristic-numerical algorithm, is defined to calculate the solution space when both the fundamental and a low-order harmonic are controlled in phase and amplitude. The solutions obtained are used to train the ANNs offline. Afterwards, the ANN + SQP calculation method is used to solve the SHC-PWM problem in real-time (RT). Experimental results are provided for a three-level converter to verify the effectiveness of the proposed RT control method.Peer reviewe
Defense Strategy against Byzantine Attacks in Federated Machine Learning: Developments towards Explainability
No full textPublisher Copyright: © 2024 IEEE.The rise of high-risk AI systems has led to escalating concerns, prompting regulatory efforts such as the recently approved EU AI Act. In this context, the development of responsible AI systems is crucial. To this end, trustworthy AI techniques aim at requirements (including transparency, privacy awareness and fairness) that contribute to the development of responsible, robust and safe AI systems. Among them, Federated Learning (FL) has emerged as a key approach to safeguarding data privacy while enabling the collaborative training of AI models. However, FL is prone to adversarial attacks, particularly byzantine attacks, which aim to modify the behavior of the model. This work addresses this issue by proposing an eXplainable and Impartial Dynamic Defense against Byzantine Attacks (XI-DDaBA). This defense mechanism relies on robust aggregation operators and filtering techniques to mitigate the effects of adversarial attacks in FL, while providing explanations for its decisions and ensuring that clients with poor data quality are not discriminated. Experimental simulations are discussed to assess the performance of XI-DDaBA against other baselines from the literature, and to showcase its provided explanations. Overall, XI-DDaBA aligns with the need for responsible AI systems in high-risk collaborative learning scenarios through the explainable and impartial provision of robustness against attacks.Peer reviewe
Effects of 3D-printing on the tensile splitting strength of concrete structures
Get PDFPublisher Copyright: © 2024 The AuthorsConcrete and mortar are widely used construction materials that when processed with new 3D-printing techniques can be used to produce lighter structures with freeform shapes. Both conventional cast-moulded and 3D-printed concrete components can withstand high compressive though limited tensile stress, so reliable material data are required for correct dimensioning of those components. The indirect tensile test, or Brazilian test, as per EN 12390–6 A, is used to perform a tensile strength characterization of hardened concrete. In this study, Brazilian test results for both cast-moulded and 3D-printed specimens were examined, checking the inherent deviations produced during the printing process. The results reflected the tensile strength differences between cast and printed components, proposing a reduction coefficient applicable to cast specimen test results, to assist with the dimensioning of printed components at the design stage.Peer reviewe
Development of Flame-Retardant Polylactic Acid Formulations for Additive Manufacturing
Get PDFPublisher Copyright: © 2024 by the authors.Polymeric materials, renowned for their lightweight attributes and design adaptability, play a pivotal role in augmenting fuel efficiency and cost-effectiveness in railway vehicle development. The tailored formulation of compounds, specifically designed for additive manufacturing, holds significant promise in expanding the use of these materials. This study centers on poly(lactic acid) (PLA), a natural-based biodegradable polymeric material incorporating diverse halogen-free flame retardants (FRs). Our investigation scrutinizes the printability and fire performance of these formulations, aligning with the European railway standard EN 45545-2. The findings underscore that FR in the condensed phase, including ammonium polyphosphate (APP), expandable graphite (EG), and intumescent systems, exhibit superior fire performance. Notably, FR-inducing hydrolytic degradation, such as aluminum hydroxide (ATH) or EG, reduces polymer molecular weight, significantly impacting PLA’s mechanical performance. Achieving a delicate balance between fire resistance and mechanical properties, formulations with APP as the flame retardant emerge as optimal. This research contributes to understanding the fire performance and printability of 3D-printed PLA compounds, offering vital insights for the rail industry’s adoption of polymeric materials.Peer reviewe
Collaborative credentials for the Internet of Things
Get PDFPublisher Copyright: © 2024The Self-Sovereign Identity (SSI) paradigm has emerged as a decentralized Identity Management model with interesting capabilities for the Internet of Things (IoT). However, current standard SSI protocols and procedures only consider that individuals store their own identity, failing to provide an accurate solution for the identity management of groups where participants might use credentials from different identities and collaborate to meet a set of verifier´s requirements. The present work introduces the concept of Collaborative Credentials (CCs) to formalize identity management procedures that model the collaboration within a group of participants. CCs allow to leverage use cases requiring collaboration that cannot be solved with standard SSI verifiable credentials, increase the privacy of group participants and enable the development of a software framework that any verifier/holder could use to generate a generic application. In the paper, a generic model for CCs is presented, together with an implementation example that is subsequently evaluated in an experimental testbed.Peer reviewe
Low-Pressure Steam Generation with Concentrating Solar Energy and Different Heat Upgrade Technologies: Potential in the European Industry
Get PDFPublisher Copyright: © 2024 by the authors.The industry is currently responsible for around 21% of the total CO2 emissions, mainly due to heat production with fossil fuel burners. There are already different technologies on the market that can potentially reduce CO2 emissions. Nevertheless, the first step for their introduction is to analyze their potential on a global scale by detecting in which countries each of them is more attractive, given their energy prices and resources. The present work involves a techno-economic analysis of different alternatives to replace industrial gas boilers for low-pressure steam production at 120 °C and 150 °C. Solar Heat for Industrial Processes (SHIP) was compared with Electric Boilers (EBs), High-Temperature Heat Pumps (HTHPs), and Absorption Heat Transformers (AHTs). SHIP systems have the potential to reach payback periods in the range of 4 to 5 years in countries with Direct Normal Irradiance (DNI) values above 1400 kWh/m2/year, which is reached in Spain, Italy, Greece, Portugal, and Romania. HTHPs and AHTs lead to the lowest payback periods, Levelized Cost of Heat (LCOH), and highest CO2 emission savings. For both AHTs and HTHPs, payback periods of below 1.5 years can be reached, particularly in countries with electricity-to-gas price ratios below 2.0.Peer reviewe
Exploring Sustainable Coating Solutions for Applications in Highly Corrosive Environments
Get PDFPublisher Copyright: © 2024 by the authors.To protect carbon steel from degradation via corrosion, it is usually coated using a multilayer system of paints composed of petroleum-based polymers. The chemical industry is currently moving towards more sustainable chemistry, in which one of the main objectives is to reduce fossil fuel use and the derived raw materials. However, the replacement of petroleum-based raw materials with those that are bio-based is not straightforward since the properties of these new materials are often inferior to the traditional ones. One of the most used resins in primer paints is Diglycidyl ether bisphenol A (DGEBA). This is an epoxy resin synthesized from bisphenol A (BPA), a toxic and carcinogenic petroleum-based compound. This study investigates the substitution of the primer coating in a three-layer coating system with two different types of primer coating formulations, one which is partially bio-based and another that is BPA-free. The corrosion protection effectiveness of these sustainable coatings is assessed not only at the laboratory scale but also in real offshore conditions. Moreover, the adhesion of the different coating systems is evaluated before and after each ageing test. The results reveal that these novel coatings exhibit comparable performance to conventional paints while providing a more sustainable corrosion protection alternative.Peer reviewe