Search Results (48,262)

The performance of conventional bentonite-based drilling fluids is severely compromised in high-salinity and high-hardness brines, creating a need for salt-tolerant viscosifiers. This work provides a comprehensive performance evaluation of an activated palygorskite sourced from the Ventzia basin in Greece to be used as a high-performance additive for water-based drilling fluids. Six raw clay samples were mechanically processed and activated via extrusion and chemically treated with 2.25% MgO. Their rheological behavior and filtration properties were systematically investigated in three aqueous environments, (i) deionized water, (ii) API-standard salt water, and (iii) API-standard high-hardness salt water. The performance was benchmarked against that of commercial palygorskite products. The results demonstrated that the selected activated Greek samples exhibited excellent rheological properties, including higher viscosity, yield point, and thixotropic gel strength, comparable to those of the commercial benchmark. While the fluid’s rheology was suppressed by increasing salinity due to the flocculation of co-existing smectite, the best-performing Greek clays maintained a significant advantage, developing exceptionally robust gel structures critical for solid suspension in harsh conditions. Crucially, the same smectite flocculation mechanism proved highly beneficial for filtration control, leading to a significant reduction in fluid loss and the formation of a thin filter cake, particularly with the high-hardness brine. The findings confirm that activated Greek palygorskite is a technically viable, high-performance alternative to imported commercial materials, offering a sustainable solution for formulating resilient drilling fluids for challenging environments. Full article

Joining high-strength, cold-drawn Cu-Mg alloy conductors is a critical challenge for ensuring the reliability of high-speed railway catenary systems. This study investigates the evolution of mechanical properties and microstructure in Cu-0.43 wt% Mg alloy wires joined by multi-pass butt-upset cold welding without special surface preparation. High-integrity joints were achieved, exhibiting a peak tensile strength of 624 MPa (~96% of the base material’s strength). After four upsetting processes, the tensile strength of the weld can reach 90% of the original strength, and the gains from subsequent upsetting processes are negligible. Microstructural analysis revealed the joining process is governed by localized severe shear deformation, which forges a distinct gradient microstructure. This includes a transition zone of fine, equiaxed-like grains formed by dynamic recrystallization/recovery, and a central zone featuring a nano-laminar structure, high dislocation density, and deformation twins. A multi-stage dynamic bonding mechanism is proposed. It progresses from initial contact via thin film theory to bond consolidation through a “mechanical self-cleaning” process, where extensive radial plastic flow effectively expels surface contaminants. This work clarifies the fundamental bonding principles for pre-strained, high-strength alloys under multi-pass cold welding, providing a scientific basis to optimize this heat-free joining technology for industrial applications. Full article

Recent advances in agricultural biotechnology and sustainable farming have drawn attention to biochar as a multifunctional material for environmental remediation. Among its emerging applications, biochar has demonstrated remarkable potential in wastewater treatment, particularly as an efficient and sustainable adsorbent for pollutant removal. Numerous studies over the past decades have highlighted its effectiveness in eliminating a wide range of contaminants. This efficiency is mainly due to its abundant feedstock availability, simple production processes, and favorable surface and structural properties. This review summarizes current developments in biochar use for wastewater treatment, emphasizing its adsorption capabilities and the underlying mechanisms responsible for pollutant removal. Key modification strategies, physical, chemical, and biological, are discussed in detail to illustrate how biochar performance can be optimized for specific treatment goals. Furthermore, the prospects of biochar-based technologies are explored, with a focus on their role in addressing both inorganic and organic pollutants. This review also describes the use of biochar in adsorbing metals, organic contaminants, and industrial waste. The integration of biochar into sustainable water management systems presents a promising pathway toward achieving long-term environmental and agricultural resilience. Full article

The exploration of chalcogenides is on the rise owing to their desirable optical, electronic, thermoelectric, and thermal properties. Chalcogenide materials have been investigated for possible applications in areas such as non-linear optics and solar cells. Among these materials are BaTiS₃ and BaTiSe₃. BaTiS₃ has shown promise in the above-mentioned applications due to its low thermal conductivity. However, neither the thermal properties of BaTiSe₃ nor the mechanical properties of both BaTiS₃ and BaTiSe₃ have been reported. In this work, we performed a computational study of the mechanical and thermal properties of both materials within the density functional theory using Quantum Espresso and BoltzTrap2 codes, employing generalized gradient approximation. The results showed that the computed thermal conductivity of BaTiS₃ at 0.43 W/m/K is comparable to the literature values. The computed elastic constants of BaTiS₃ (bulk modulus of 44.7 GPa, shear modulus of 11.2 GPa, Young’s modulus of 29.6 GPa, and Vickers hardness of 1.053 GPa) were higher than those of BaTiSe₃. The calculated properties obtained in this work add to the literature on the properties of BaTiS₃ and BaTiSe₃. However, since the work was computational, the results can be verified by an experimental investigation. Full article

Background/Objectives: The long-term clinical success of dental luting cements largely depends on their mechanical performance. This study systematically compared six commonly used definitive dental cements by assessing key mechanical characteristics such as compressive strength and fatigue resistance. Methods: The tested materials included Adhesor Zinc Phosphate (AphC), Harvard Zinc Phosphate (HphC), polycarboxylate cement (CaC), glass ionomer cement (GIC), resin-modified glass ionomer cement (RMGIC), and resin cement (ReC). Both static and dynamic compressive load tests were performed using an Instron ElectroPuls E3000 dynamic testing instrument. During static testing, 77 samples were subjected to an increasing load up to 1500 N. Dynamic tests on 78 samples involved cyclic loading over seven phases from 50 N to 1600 N, with 1500 cycles per phase at 10 Hz. Results: Static load results indicated that GIC, CaC, and phosphate cements exhibited similar performance and were significantly weaker compared to RMGIC and ReC. In the dynamic fatigue tests, most ReC and RMGIC samples maintained integrity throughout the entire protocol, demonstrating markedly superior mechanical reliability. Finite element analysis (FEA) further confirmed the experimental observations, revealing more homogenous stress distribution and lower peak stresses in ReC and RMGIC compared with the conventional cements. Conclusions: Overall, the resin-based and resin-modified glass ionomer cements showed the highest compressive strength and fatigue resistance, indicating superior long-term mechanical stability compared to the conventional cements. These findings support the clinical use of resin-based cements as reliable luting agents for definitive fixation in high-load prosthodontic applications. Full article

Wind power is a major source of renewable energy, yet turbine performance is strongly influenced by atmospheric conditions and surrounding terrain. Several meteorological phenomena can hinder energy production, disrupt operations, and accelerate structural deterioration. This paper reviews three key atmospheric hazards affecting wind turbine systems: lightning, icing, and rain. For each phenomenon, the formation mechanisms, operational effects, and mitigation approaches are examined, with offshore-specific processes and conditions integrated directly into each hazard discussion. Building on this foundation, the review then analyses interactions between the hazards, their combined implications for turbine performance and maintenance, and the associated economic impacts. Comparisons of material behaviour across lightning, icing, and rain-erosion conditions are also incorporated. Finally, future research directions are proposed. Full article

This work addresses computational inefficiency in ultra-wide-area remote sensing image (RSI) object detection. Traditional homogeneous tiling strategies enforce computational symmetry by processing all image regions uniformly, ignoring the intrinsic spatial asymmetry of target distribution where target-dense coexist with vast target-sparse areas (e.g., deserts, farmlands), thereby wasting computational resources. To overcome symmetry mismatch, we propose a heat-guided adaptive blocking and dual-model collaboration (HAB-DMC) framework. First, a lightweight EfficientNetV2 classifies initial 1024 × 1024 tiles into semantic scenes (e.g., airports, forests). A target-scene relevance metric converts scene probabilities into a heatmap, identifying high-attention regions (HARs, e.g., airports) and low-attention regions (LARs, e.g., forests). HARs undergo fine-grained tiling (640 × 640 with 20% overlap) to preserve small targets, while LARs use coarse tiling (1024 × 1024) to minimize processing. Crucially, a dual-model strategy deploys: (1) a high-precision LSK-RTDETR-base detector (with Large Selective Kernel backbone) for HARs to capture multi-scale features, and (2) a streamlined LSK-RTDETR-lite detector for LARs to accelerate inference. Experiments show 23.9% faster inference on 30k-pixel images and reduction in invalid computations by 72.8% (from 50% to 13.6%) versus traditional methods, while maintaining competitive mAP (74.2%). The key innovation lies in repurposing heatmaps from localization tools to dynamic computation schedulers, enabling system-level efficiency for Ultra-Wide-Area RSIs. Full article

This review critically examines photoresponsive supercapacitors based on TiO₂/graphene hybrids, with a particular focus on their emerging dual role as energy-storage devices and environmental sensors. We first provide a concise overview of the electronic structure of TiO₂ and the key attributes of graphene and related nanocarbons that enable efficient charge separation, transport, and interfacial engineering. We then summarize and compare reported device architectures and electrode designs, highlighting how morphology, graphene integration strategies, and illumination conditions govern specific capacitance, cycling stability, rate capability, and light-induced enhancement in performance. Particular attention is given to the underlying mechanisms of photo-induced capacitance enhancement—including photocarrier generation, interfacial polarization, and photodoping—and to how these processes can be exploited to embed sensing functionality in working supercapacitors. We review representative studies in which TiO₂/graphene systems operate as capacitive sensors for humidity, gases, and volatile organic compounds, emphasizing quantitative figures of merit such as sensitivity, response/recovery times, and stability under repeated cycling. Finally, we outline current challenges in materials integration, device reliability, and benchmarking, and propose future research directions toward scalable, multifunctional TiO₂/graphene platforms for self-powered and environmentally aware electronics. This work is intended as a state-of-the-art summary and critical guide for researchers developing next-generation photoresponsive supercapacitors with integrated sensing capability. Full article

It is difficult to achieve ultra-precision machining (UPM) on semiconductor materials like single-crystal silicon because of their hardness and brittleness. To solve this issue, numerous field-assisted machining systems and their combinations have been suggested and developed. However, the difficulty in directly observing the physical variables limits our comprehension of the in-depth machining mechanisms of field-assisted machining. In this work, we investigated the machining mechanism of single-crystal silicon under the combination of laser heating and tool vibration using molecular dynamics (MD) simulations. The effect of tool vibration trajectory determined by different tool edge radii is discussed under the condition of raising temperature. The simulation results indicate that the surface morphology is closely related to vibration and heating parameters. Raising the cutting temperature causes a reversed relation between tool edge radius and surface roughness. While the subsurface damage and internal stress are also determined by the tool edge radius and cutting temperature. The findings in this simulation could help to improve the understanding of machining mechanics in multi-field-assisted machining. Full article

Economic and technological factors necessitate the use of alternative fuels during oil shale combustion, a process that generates substantial amounts of solid waste with varying ash compositions. This study evaluates the potential of two such waste materials: (i) fly ash derived from the combustion of oil shale (a fine particulate residue from burning crushed shale rock, sometimes combined with biomass), and (ii) short carbon fibres recovered from the pyrolysis (a process of decomposing materials at high temperatures in the absence of oxygen) of waste wind turbine blades. Oil shale ash from two different sources was investigated as a partial cement replacement, while recycled short carbon fibres (rCFs) were incorporated to enhance the functional properties of mortar composites. Results showed that carbonate-rich ash promoted the formation of higher amounts of monocarboaluminate (a crystalline hydration product in cement chemistry), leading to a refined pore structure and increased volumes of reaction products—primarily calcium silicate hydrates (C–S–H, critical compounds for cement strength). The findings indicate that the mineralogical composition of the modified binder (the mixture that holds solid particles together in mortar), rather than the fibre content, is the dominant factor in achieving a dense microstructure. This, in turn, enhances resistance to water ingress and improves mechanical performance under long-term hydration and freeze–thaw exposure. Life cycle assessment (LCA, a method to evaluate environmental impacts across a product’s lifespan) further demonstrated that combining complex binders with rCFs can significantly reduce the environmental impacts of cement production, particularly in terms of global warming potential (−4225 kg CO₂ eq), terrestrial ecotoxicity (−1651 kg 1,4-DCB), human non-carcinogenic toxicity (−2280 kg 1,4-DCB), and fossil resource scarcity (−422 kg oil eq). Overall, the integrative use of OSA and rCF presents a sustainable alternative to conventional cement, aligning with principles of waste recovery and reuse, while providing a foundation for the development of next-generation binder systems. Full article

To advance “bamboo-as-plastic-substitute” initiatives and the sustainable use of furniture materials, this study investigates flattened bamboo sheets by determining their principal-direction elastic constants and evaluating two common furniture T-joints—dowel-jointed panel-type and right-angle mortise-and-tenon frame-type—through tensile and bending load-bearing tests alongside finite element (FE) comparisons. The results show a pronounced anisotropy, with the longitudinal elastic modulus markedly higher than in other directions. At the joint level, the average ultimate load-bearing capacities were 4.06 kN (panel-type tension), 3.70 kN (frame-type tension), 0.264 kN (panel-type bending), and 0.589 kN (frame-type bending). Under identical structural configurations and boundary conditions, the tensile and bending capacities of flattened bamboo sheets were comparable to or exceeded those of the comparator materials (MDF, cherry wood, bamboo-based composites), and failures predominantly occurred in the adhesive layer rather than the bamboo substrate. Across four representative cases, FE predictions achieved a mean absolute percentage error (MAPE) of 6.5% with a maximum relative error of 12.5%; the regression correlation was R² ≈ 0.999 based on four paired observations, which should be interpreted with caution due to the small sample size. The study validates that FE models driven by experimentally measured anisotropic parameters can effectively reproduce the mechanical response of flattened bamboo T-joints, providing a basis for structural design, lightweighting, and parameter optimization in furniture applications. Further work should characterize adhesive systems, environmental durability, and interfacial failure mechanisms to enhance the model’s general applicability. Full article

This study presents the results of laser beam welding of dissimilar high-alloy super stainless steels. Differences in their thermal and mechanical properties pose significant challenges in manufacturing processes. The present work demonstrates the potential advantages of using 309L filler material in laser welding of high-alloy materials with different properties. The research focuses on a comparative evaluation of the effects of 309L filler metal on the TP904L—TP347 joint in terms of joint strength and microstructure. The analysis of the joints provides insight into the role of the filler metal in improving joint properties. The obtained results show that both welds exhibit a similar microstructure composed of pillar, cellular, and equiaxed dendrites; however, they differ in dendrite growth orientation, calculated ferrite number (FN), the G/R ratio, and dendrite arm spacing, indicating a lower thermal gradient in the joint welded with filler metal. The results also reveal the presence of precipitates in the welds near the TP904L steel fusion line, most likely Cr₂₃C₆ type. Mechanical properties evaluation, based on standard and miniaturized tensile tests as well as hardness measurement, shows that the use of 309L filler metal improves both the joint strength and ductility, although it does not significantly affect the material hardness. Full article

Although the dynamic response of orthotropic materials under uniaxial impact loading has been extensively studied, their behavior under multiaxial stress states, which more accurately represent real-world blast and impact scenarios, has received limited attention. To address this gap, this study employed a self-developed biaxial impact testing apparatus to systematically investigate the dynamic mechanical behavior of beech wood, a typical orthotropic material, under three biaxial loading configurations: radial-tangential, radial-longitudinal, and tangential-longitudinal. By combining theoretical derivation with experimental data, it systematically examines stress wave propagation characteristics, strain rate effects, and anisotropy evolution under different loading paths. The results reveal that beech wood exhibits significantly distinct dynamic responses along different material orientations, with a consistent strength hierarchy: longitudinal > radial > tangential. Biaxial loading notably enhances the equivalent stress–strain response and alters the deformation mechanisms and energy absorption behavior. Furthermore, lateral confinement and multiaxial stress coupling are identified as critical factors influencing the dynamic performance. This study provides the first systematic revelation of the strain rate strengthening mechanisms and wave propagation characteristics of orthotropic materials from the perspective of multiaxial dynamic loading, thereby offering theoretical and experimental foundations for developing advanced dynamic constitutive models suitable for complex impact conditions. These findings provide important guidance for the design and evaluation of lightweight impact-resistant structures in fields such as aerospace and protective engineering. Full article

Bioactive glasses (BGs) are promising materials for enamel remineralization and caries management due to their ion-releasing ability and capacity to promote apatite formation. However, their clinical translation remains limited. Conventional BGs, such as 45S5, exhibit excellent bioactivity but are mechanically weak, prone to rapid ion burst release, and lack long-term stability. Recent advances—including secondary oxide incorporation (e.g., B₂O₃, ZnO), polymer–glass hybrids, and nanostructured systems like mesoporous BGs and RegeSi have improved reactivity, mechanical performance, and remineralization depth, though their durability under oral conditions is not yet established. BGs also display antibacterial activity by elevating local pH and releasing ions that inhibit cariogenic bacteria, but their broader ecological impact on the oral microbiome remains poorly understood. Emerging approaches such as halogen-modified BGs, particularly fluoride- and chloride-doped formulations, show dual benefits for remineralization and antimicrobial action, though supporting evidence is largely confined to in vitro studies. The absence of standardized protocols for assessing remineralization, ion release, and biofilm interaction further complicates cross-study comparisons and slows clinical adoption. Future progress will require interdisciplinary collaboration, standardized evaluation methods, and rigorous clinical validation to ensure that next-generation BGs can be safely and effectively integrated into dental practice. Full article

Erosion of the leading edge is one of the most severe forms of damage in wind turbine blades, particularly in offshore wind farms. This degradation, mainly caused by rain, sand, and airborne particles through droplet impingement wear, significantly decreases blade aerodynamic efficiency and power output. Since blades, typically made of fiber-reinforced polymer composites, are the most expensive components of a turbine, developing protective coatings is essential. In this study, polyurethane (PU) composite coatings reinforced with titanium dioxide (TiO₂) particles were added on glass fiber substrates by spray coating. The incorporation of TiO₂ improved the mechanical and electrochemical performance of the PU coatings. FTIR and XRD confirmed that low TiO₂ loadings (1 and 3 wt%) were well dispersed within the PU matrix due to hydrogen bonding between TiO₂ –OH groups and PU –NH groups. The PU/TiO₂ 3% coating exhibited ~61% lower corrosion current density (I_corr) compared to neat PU, indicating superior corrosion resistance. Furthermore, uniform TiO₂ dispersion resulted in statistically significant improvements (p < 0.05) in hardness, yield strength, elastic modulus, and adhesion strength. Overall, the PU/TiO₂ coatings, particularly at 3 wt% loading, show strong potential as protective materials for wind turbine blades, given their enhanced mechanical integrity and corrosion resistance. Full article