Search Results (59)

Historical buildings are highly prone to degradation because they are continuously exposed to the external environment, which represents an extremely aggressive factor. Globally, there are so many historical buildings that need urgent restoration. This paper focuses on finding a new consolidant for real oak old wood and presents a new recipe based on multi-walled carbon nanotubes (MWCNTs) decorated with zinc oxide (ZnO) nanoparticles dispersed in PHBHV solution, aimed at improving old wood properties. The research was conducted on Banloc Castle oak wood, which is predominant throughout the castle. The obtained treatment was applied by brushing onto the wood surface, while the retention and uniform application of the consolidation were confirmed by optical microscopy. One major advantage of the treatment is that the natural color of the wood is not affected, with the total color difference being very small. Another advantage gained after consolidation was the enhanced hydrophobic behavior of the old wood confirmed through water absorption, humidity and contact angle tests. In contrast, untreated wood exhibited hydrophilic behavior and high water and moisture absorption capacity, making aged wood extremely vulnerable to environmental degradation over time. Mechanical tests confirmed that the consolidant solution significantly improved the properties of the wooden material, due to the effective impregnation of the treatment into the wood structure. Furthermore, the MWCNT-based consolidant inhibited the growth of the Aspergillus niger strain, providing antifungal protection and preventing the colonization of microorganisms within the wood structure and its subsequent degradation. Through the methods investigated in this work, it was proven that the treatment is suitable for the consolidation of aged and degraded oak wood materials. Full article

Robust robotic autonomy remains challenging in complex environments, where loss of stability on uneven or slippery terrain can induce extreme accelerations and angular velocities. Such motions corrupt sensor measurements and degrade state estimation, motivating the need for improved algorithmic robustness. To investigate this issue, we introduce the Tumbling-Induced Gyroscope Saturation (TIGS) dataset, which consists of recordings from a mechanical lidar and an Inertial Measurement Unit (IMU) tumbling down a hill. The dataset contains angular speeds up to four times higher than those in similar datasets and is publicly available. We then propose two complementary methods to improve Simultaneous Localization And Mapping (SLAM) robustness and evaluate them on TIGS. First, Saturation-Aware Angular Velocity Estimation (SAAVE) estimates angular velocities when gyroscope measurements become saturated during aggressive motions, reducing angular speed estimation error by 83.4%. Second, Stretch-ICP, a novel registration and deskewing algorithm, enables reconstruction of smoother 6-Degrees Of Freedom (DOF) trajectories under aggressive motions compared to classical Iterative Closest Point (ICP). Stretch-ICP reduces linear and angular velocity errors by 95.2% and 94.8%, respectively, at scan boundaries. Together, these contributions improve the robustness and consistency of lidar-inertial state estimation under aggressive motions. Full article

Atmospheric corrosion of carbon and low-alloy steels causes direct economic losses that are estimated at around 3.4% of the global GDP, and its accurate multi-year prediction is essential for protective coating selection, service-life estimation, and infrastructure maintenance scheduling. In this study, machine learning (ML) algorithms, including gradient boosting regressor (GBR), eXtreme gradient boosting (XGBoost), random forest (RF), support vector regression (SVR), and ridge regression, were trained on a 600-sample physics-grounded dataset to predict the cumulative atmospheric corrosion loss (µm) of low-alloy steels over 1–10 years of exposure. The dataset was constructed using the exact ISO 9223:2012 dose–response function (DRF) for a first-year corrosion rate and the ISO 9224:2012 power-law multi-year kinetic model (C(t) = C₁·t0.5), spanning ISO 9223 corrosivity categories C2–CX across 11 environmental and material input features. All models were evaluated on the original (untransformed) corrosion scale under an 80/20 train/test split and five-fold cross-validation. Gradient boosting achieved the best overall performance with test set R² = 0.968, CV-R² = 0.969, RMSE = 10.58 µm, MAE = 5.99 µm, and MAPE = 12.6%. XGBoost was a close second (R² = 0.958, CV-R² = 0.960). RF achieved an R² of 0.944. SHAP (SHapley Additive exPlanations) analysis identified SO₂ deposition rate, exposure time, relative humidity, Cl⁻ deposition rate, and temperature as the five most influential predictors. The dominance of the SO₂ deposition rate (mean |SHAP| = 26.37 µm) and the high second-place ranking of exposure time (13.67 µm) are fully consistent with the ISO 9223:2012 dose–response function and ISO 9224:2012 power-law kinetics, respectively, while among the material features, Cu and Cr contents showed the strongest negative SHAP contributions, confirming their corrosion-inhibiting roles in weathering steels. These results establish a physics-consistent, interpretable ML benchmark exceeding R² = 0.90 for multi-year cumulative corrosion loss prediction and provide a quantitative tool for alloy screening, coating selection in aggressive atmospheric environments, and service-life planning. Full article

This paper presents an analysis of the physicochemical and biological properties of the developed composite zinc phosphate cement modified with bismuth oxide and phosphorus slag additives. The powder phase was synthesized by sintering a frit with an optimal composition (ZnO, MgO, SiO₂, Bi₂O₃) using phosphorus slag as the active component. The study included an assessment of the microstructure, chemical resistance in aggressive environments (5% NaCl solution, 10% lactic acid, carbonated water), solubility in artificial saliva, and cytotoxicity in human fibroblasts. The addition of phosphorus slag was found to promote the formation of low-melting eutectics, which reduces the sintering temperature by 100 °C and increases the material’s whiteness to 97.8%. X-ray diffraction analysis confirmed the presence of zincite, quartz, and periclase phases, forming a dense microstructure without pronounced pores or cracks. The experimental cement demonstrated high acid resistance: the maximum weight loss in lactic acid was 8%, while the leaching of toxic elements (Pb, As, Cr, etc.) remained extremely low (10–67 ppm), confirming the material’s environmental safety. Testing of the composite zinc phosphate cement in artificial saliva revealed minimal weight loss compared to similar products. Biological testing showed that the cement’s cytotoxicity is dose-dependent; at a 0.3 g dose and a 1:4 dilution, the material loses its toxic properties and becomes safe for living tissue. The developed zinc phosphate composite cement composition offers improved aesthetic and mechanical properties, high chemical stability, and biocompatibility at working concentrations, making it promising for use in clinical dentistry. Full article

Ceramic materials are indispensable to aerospace and defence technologies, where structural and functional components are required to withstand extreme thermal, mechanical, and chemically aggressive environments. Traditionally valued for their exceptional thermal stability, oxidation resistance, and corrosion resistance, ceramics have nonetheless been constrained by their inherent brittleness, which has limited their widespread adoption in load-bearing structural applications. This review surveys the principal tough ceramic systems currently employed in aerospace and defence, including SiC, Al₂O₃, ZrO₂, Si₃N₄, SiC/SiC composites, and ultra-high-temperature ceramics (UHTCs) such as ZrB₂ and HfB₂. In parallel, it outlines advanced processing and manufacturing routes that enable enhanced microstructural control, improved reliability, and scalability for industrial deployment. Special attention is devoted to thermal and environmental barrier coatings (TBCs and EBCs), which provide critical protection against oxidation, corrosion, and severe thermal cycling in propulsion, power-generation, and hypersonic systems. Finally, the review highlights key material selection criteria for aerospace and defence platforms and discusses emerging trends that integrate tough ceramics with next-generation manufacturing technologies, underscoring their pivotal role in enabling high-performance, durable, and resilient systems for future extreme-environment applications. Full article

Background: In multicultural healthcare systems such as the Italian one, migrant children may experience dental care as particularly stressful because linguistic and cultural barriers can limit communication, emotional expression, and understanding of the clinical setting. Aim: Understanding the emotional experience of migrant children during dental visits is essential for improving clinical management in pediatric dentistry and orthodontics within multicultural contexts. Because linguistic barriers often limit verbal communication, this study aimed to explore children’s mental representations, emotional states, and perceptions of the dental environment through drawing and to evaluate the clinical implications for communication and therapeutic collaboration. Methods: This qualitative study was conducted in Italy between 2016 and 2025 and analyzed 50 drawings produced by 50 foreign-born migrant children aged 6–13 years, recruited through an educational cooperative in Piacenza. Most participants originated from developing countries and had limited proficiency in Italian, frequently showing a marked “experience gap” in drawing ability that interfered with normative developmental stages described by Lowenfeld. The analysis focused on spatial organization, line quality, color use, posture, interpersonal distance, and representation of the clinical environment, integrating graphic competence assessment with emotional interpretation. Results: Younger children commonly depicted rigid lines, essential settings, and oversized dental unit lamps, whereas older children increasingly represented threatening or disproportionate instruments, aggressive dentists, and omission of the patient figure. Around age 10, drawings became more detailed and colorful, although symbols of closure, such as locked doors, persisted. In adolescents, representations polarized between rich, coherent scenes and extremely essential drawings dominated by fear, rigidity, minimal environments, and symbols of constraint. The findings suggest that drawing may represent a valuable non-verbal clinical and communicative resource for exploring migrant children’s emotional experience of dental care and for identifying signs of anxiety and vulnerability that may not emerge through verbal interaction alone. Conclusions: These findings support the value of a culturally sensitive dental approach integrating drawing, visual aids, multilingual educational materials, and play-based strategies to reduce communication barriers and improve cooperation in migrant children receiving pediatric dental and orthodontic care. Full article

Marine concrete is often exposed to multiple aggressive ions, so mechanical deterioration cannot be reliably interpreted using single-ion durability concepts. This study investigates ocean-oriented concretes incorporating high contents of mineral admixtures under coupled sulfate/chloride/carbonate/magnesium actions and develops a pore-structure-based D–P dual-parameter framework linking microstructural descriptors to macroscopic peak stress and peak strain. Three binder systems were designed: ordinary Portland cement concrete (OPC), cement–silica fume concrete (CSC, 20% silica fume), and cement–silica fume–fly ash concrete (CSFC, 20% silica fume + 50% fly ash). Specimens were immersed for 12 and 24 months in four representative binary-salt solutions. Porosity evolution and pore-size-class distributions were quantified by low-field NMR, while pore complexity was characterized using multi-scale fractal dimensions. The results show that mineral admixtures generally refine the pore system and improve the integrity of fine pores; CSFC exhibits the most robust microstructural stability across the tested environments, whereas CSC shows a pronounced degradation of fine-pore structure under CE4. A second-order response surface model built on Z-score normalized fractal dimension (D) and porosity (P) achieves reliable predictability for peak strain (R² = 0.85) and peak stress (R² = 0.79). Global Sobol sensitivity analysis reveals distinct controlling mechanisms: peak strain is predominantly governed by porosity (S_P = 85.9%), whereas peak stress is controlled by the combined effects of porosity, pore complexity, and their interaction (S_P = 42.4%, S_D = 19.8%, S_{D × P} = 37.8%). Local sensitivity mapping further identifies high-sensitivity regimes at extreme pore states, providing mechanistic guidance for mixture optimization. Overall, the proposed D–P framework quantitatively bridges pore volume/geometry evolution and mechanical degradation, offering a practical predictive tool for durability-oriented design of marine concretes under multi-ionic attack. Full article

The degradation of building foundations, underground structures, and historical fabrics in sulfate-laden environments poses a persistent threat to the durability and safety of the built environment. Developing effective, sustainable repair materials is of paramount importance. This study presents the development, systematic optimization, and performance validation of a novel micro-expansive grout designed for high durability in aggressive sulfate conditions. The grout formulation utilizes industrial by-product fly ash, quicklime, and site-compatible soils, emphasizing sustainability. Nine chemical admixtures were screened for sulfate resistance enhancement. Laboratory experiments rigorously characterized the effects of water-to-solid ratio and admixture dosage on fresh-state properties (fluidity, setting time) and hardened-state performance (volumetric stability). To resolve a multi-objective optimization problem balancing injectability, dimensional compatibility, and cost-effectiveness, an integrated multi-criteria decision-making (MCDM) framework combining FAHP, MII, CRITIC, and TOPSIS was employed. This data-driven methodology identified an optimal formulation incorporating 3% disodium hydrogen phosphate (DSP) at a 0.58 water-to-solid ratio. The optimized grout exhibited a flow value of 75 mm, ensuring excellent injectability within the target range (40–120 mm), and an expansion rate of 7.67%, which falls within the safe range (0%–10%) to ensure dimensional compatibility. Accelerated durability tests via cyclic immersion in sodium sulfate solution demonstrated the optimized grout’s exceptional resistance to sulfate attack, retaining approximately 88% of its compressive strength after 15 aggressive cycles. The balanced properties and validated durability indicate strong potential for this grout in demanding repair scenarios. One key example is the repair of fissures in earthen heritage structures, which requires extreme material compatibility and long-term performance. Full article

The prebiological anomeric selectivity of ribonucleosides is a key phenomenon in the understanding of the RNA world hypothesis and the origin of life. While each ribonucleoside can have two anomers (α or β), ribonucleosides naturally occur in the β form, while α anomers are extremely rare. Guanosine, a canonical ribonucleoside, binds to borate and self-assembles into G4-quartets, enabling the formation of borate–guanosine hydrogels. These macrostructures, exhibiting elevated thermal robustness and self-healing properties, have been suggested as plausible frameworks for the syntheses of prebiological molecules. Moreover, their external layers could have prevented degradation of compounds by aggressive primitive radiation and reduced molecular dispersion. Herein it is proposed that anomeric selectivity may have occurred due to the different 3D organization and stereochemical environment formed by each borate–guanosine anomer and subsequent formation of borate–guanosine hydrogels. DFT was applied to the optimization of α and β anomeric structures in four steps, from borate–guanosine diesters to G4 structures. The results obtained suggest that β-syn-guanosine (the most stable structure) is the only anomer that forms a planar G4-quartet with borate, capable of self-assembling into a hydrogel. Given the properties of borate–guanosine hydrogels, this could explain why β-guanosine is currently the sole anomer present in living organisms. Full article

This qualitative study examines the impact of societal violence on the school climate in Arab society in Israel, focusing on teachers’ perspectives. Violence is conceptualized as an extreme, intentional form of aggression aimed at causing physical, psychological, or emotional harm. In the Israeli context, Arab society, constituting about 21% of the population, experiences disproportionately high rates of violent crime, reflecting historical marginalization, structural inequality, under-policing, and sociocultural transformations. Within schools, these societal dynamics are reported to negatively affect the learning environment, including diminished teacher motivation, concerns about teaching quality, heightened perceptions of unsafety, strained parent–school relationships, and increased parental aggression. Sixteen teachers participated in semi-structured interviews. Thematic analysis of the data revealed that financial pressures, emphasis on personal honor, and erosion of family values are perceived as key drivers of violence in the community. Teachers also reported adverse effects on students’ emotional, social, and behavioral functioning, as well as academic performance. These findings underscore the urgent need for interventions that enhance school safety, provide trauma-informed teacher training, expand psychological services, and strengthen parental collaboration. Future research should include students’ and parents’ perspectives, examine geographically diverse schools, and explore cross-cultural comparisons to better understand the educational consequences of societal violence. Full article

This study focuses on the susceptibility and surface degradation of low-alloy carbon steel 42CrMo4 to corrosion and cavitation erosion, as this steel is widely used in marine environments with aggressive chemical species and harsh conditions. Due to its high strength and fatigue resistance, 42CrMo4 steel is often employed in offshore mechanical components such as shafts and fasteners as well as crane parts in ports and harbors. Various experimental methods, including corrosion and cavitation tests, were used to assess the steel’s surface integrity under extreme conditions. Surface changes were monitored using modern analytical tools for precise assessments, including image and morphological analyses, to quantify degradation levels and specific parameters of defects induced by corrosion and cavitation. Non-destructive techniques such as optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and image analysis software were employed for the quantitative assessment of morphological parameters and elemental analysis. EDS analysis revealed changes in elemental composition, indicating corrosion products that caused significant mass loss and defect formation, with degradation increasing over time. The average corrosion rate of 42CrMo4 steel in a 3.5% NaCl solution reached a peak value of 0.846 mm/year after 120 days of exposure. Cavitation erosion behavior was measured based on mass loss, indicating the occurrence of different cavitation periods, with the steady-state period achieved after 60 min. The number of formed pits increased until 120 min, after which it decreased slightly. This indicates that a time frame of 120 min was identified as significant for changes in the mechanism of pit formation. Specifically, up to 120 min, pit formation was the dominant mechanism of cavitation erosion, while after that, as the number of pits slightly declined, the growth and merging of formed pits became the dominant mechanism. The cavitation erosion tests showed mass loss and mechanical damage, characterized by the formation of pits and cavities. The findings indicate that the levels of surface degradation were higher for corrosion than for cavitation. The presented approach also provides an assessment of the degradation mechanisms of 42CrMo4 steel exposed to corrosive and cavitation conditions. Full article

The performance of resin anchoring agents in deep coal mine roadways is significantly compromised by water-bearing and chemically aggressive conditions, posing a major threat to support system reliability. This study aims to systematically quantify this performance deterioration and develop a more resilient material solution for these challenging environments. A comprehensive experimental program was conducted, including uniaxial compression, pull-out, and interface shear tests, accompanied by the systematic improvement of the resin formulation and microstructural analysis via Scanning Electron Microscopy (SEM). The results showed that increasing borehole water content to 30% reduced the compressive strength of conventional resin by over 40%, while acidic environments (pH = 5) caused a 70% drop in its interfacial shear strength. In contrast, an improved formulation incorporating hydroxypropyl acrylate and a super absorbent polymer (SAP) exhibited a 20% higher initial strength, maintained over 85% of its strength under water saturation, and retained functional residual strength in acidic conditions. SEM analysis confirmed that the improved resin’s denser microstructure suppressed interfacial microcrack formation. The findings demonstrate that the improved formulation provides a robust material basis for enhancing the long-term durability and safety of anchorage support systems in extreme underground engineering environments. Full article

Ensuring the long-term integrity of structural materials in extreme environments is a critical challenge in the design of equipment for nuclear fuel cycle operations. In particular, the durability of materials exposed to high temperatures and chemically aggressive environments during the processing of irradiated reactor components remains a key concern. This study investigates the high-temperature corrosion behavior of 12Cr18Ni10Ti austenitic stainless steel in the reaction chamber of a beryllium chlorination plant developed for recycling irradiated beryllium reflectors from the JMTR (Japan Materials Testing Reactor). The chlorination process was conducted at temperatures ranging from 500 °C to 1000 °C in a chlorine-rich atmosphere. Post-operation analysis of steel samples extracted from the chamber revealed that uniform wall thinning was the predominant degradation mechanism. However, in high-temperature regions near the heating element, localized forms of damage, specifically pitting and intergranular corrosion, were detected, indicating that thermal stresses exacerbated localized attack. These findings contribute to the assessment of the service life of structural components under extreme conditions and offer practical guidance for material selection and design optimization in high-temperature chlorination systems used in nuclear applications. Full article

As a kind of novel binderless composite, WC-cBN-SiC_w composite possesses significant potential value in special sealing components and high-pressure medium nozzles. However, under severe wear and corrosion conditions, the surface defects caused by friction will be accelerated to become a crack source in aggressive environments. Because of the intrinsic brittleness of WC cemented carbide, its strength is extremely sensitive to local surface damage. Therefore, the influence of applied load (10 N, 20 N, 40 N and 60 N) on its tribological behavior was studied. Meanwhile, the impact of corrosion resistance of WC-cBN-SiC_w composite on surface damage induced by friction was further investigated. Full article

Tribological processes in extreme environments pose serious material challenges, requiring coatings that resist both wear and corrosion. This review summarizes recent advances in protective coatings engineered for extreme environments such as high temperatures, chemically aggressive media, and high-pressure and abrasive domains, as well as cryogenic and space applications. A comprehensive overview of promising coating materials is provided, including ceramic-based coatings, metallic and alloy coatings, and polymer and composite systems, as well as nanostructured and multilayered architectures. These materials are deployed using advanced coating technologies such as thermal spraying (plasma spray, high-velocity oxygen fuel (HVOF), and cold spray), chemical and physical vapor deposition (CVD and PVD), electrochemical methods (electrodeposition), additive manufacturing, and in situ coating approaches. Key degradation mechanisms such as adhesive and abrasive wear, oxidation, hot corrosion, stress corrosion cracking, and tribocorrosion are examined with coating performance. The review also explores application-specific needs in aerospace, marine, energy, biomedical, and mining sectors operating in aggressive physiological environments. Emerging trends in the field are highlighted, including self-healing and smart coatings, environmentally friendly coating technologies, functionally graded and nanostructured coatings, and the integration of machine learning in coating design and optimization. Finally, the review addresses broader considerations such as scalability, cost-effectiveness, long-term durability, maintenance requirements, and environmental regulations. This comprehensive analysis aims to synthesize current knowledge while identifying future directions for innovation in protective coatings for extreme environments. Full article