Search Results (811)

Silts are generally unsuitable for direct use as subgrade fill material due to their low shear strength and deformation resistance. In this study, a novel technique for strengthening silt using enzyme-induced calcium carbonate precipitation (EICP) with the addition of non-fat milk powder is proposed to improve the mechanical properties of silt for use as subgrade fill material. The effect of EICP on the mechanical properties of silt, in terms of internal friction angle and shear strength, was examined through consolidated undrained (CU) triaxial shear tests. The results showed that, with the EICP technique involving non-fat milk powder, the mechanical behaviors of silts were significantly enhanced due to the improved bonding ability of the silt particles. Furthermore, an optimum content of non-fat milk powder of 6 g/L is proposed to increase the mechanical properties. Compared with EICP treatment alone, under the optimum condition of 6 g/L non-fat milk powder and 14 days of curing, the shear strength, cohesion, and internal friction angle increased by 44.1%, 51.86%, and 31.4%, respectively. Finally, microstructural analyses were conducted using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) to provide insight into the mechanisms underlying the improvement of silt. The findings of this study can provide guidance for the application of silt improvement through the EICP technique involving non-fat milk powder. Full article

Heat-treatable aluminum alloys are widely used in aerospace and automotive industries for high-performance structural applications. However, their processing through conventional fusion-based additive manufacturing is limited by solidification-related defects, such as hot cracking, porosity, and elemental segregation. To overcome these limitations, friction-based additive manufacturing (FBAM) has emerged as a promising solid-state alternative. FBAM primarily includes friction stir additive manufacturing (FSAM), additive friction stir deposition (AFSD), friction screw extrusion additive manufacturing (FSEAM), and friction rolling additive manufacturing (FRAM), which differ in feedstock form and process configuration. In these processes, feed material is consolidated through frictional heat generated below the melting temperature, enabling the formation of refined equiaxed microstructures while minimizing solidification defects. Despite these advantages, significant challenges persist in processing heat-treatable aluminum alloys, particularly the 2xxx, 6xxx, and 7xxx series. These include non-uniform microstructure and mechanical properties along the build direction; precipitation instability; process-induced defects, such as tunnel formation; and mechanical properties that are often inferior to those of the corresponding base materials (BMs). Reported FBAM builds generally exhibit equiaxed ultrafine grains below 1 μm; however, the strength and microhardness of heat-treated alloy builds commonly remain around 70–75% of the corresponding BM. Following post-heat treatment, microhardness can be nearly fully recovered, whereas UTS typically reaches about 80–85% of BMs, often with an associated ductility reduction of nearly 50%. This review critically analyzes research reported over the past decade on FBAM processing of heat-treatable aluminum alloys, covering FSAM, AFSD, FSEAM, and FRAM. The key challenges related to microstructural evolution and mechanical performance are systematically discussed for each alloy series. Furthermore, mitigation strategies proposed in the literature, including process parameter optimization, in-process cooling, post-heat treatment, and nanoparticle reinforcement (e.g., SiC, TiC, Ni and ZrO₂), are evaluated. Finally, existing research gaps are identified, and future directions are proposed to support the development of robust, scalable, and high-performance FBAM processes for heat-treatable aluminum alloys. Full article

The present work reports on the microstructural and micro-mechanical characterization of Ti-Nb-HA-based composites. The composites were prepared via a spark plasma sintering (SPS) consolidation process. The effect of two distinct levels of hydroxyapatite (HA) content (e.g., 10 and 20 wt.%) on the microstructural and micro-mechanical properties were investigated via in situ micro-pillar compression, and the results were compared against a sole Ti-Nb composite. The microstructure of the composites was composed of parent Ti and Nb grains, together with the reaction products; due to the decomposition of HA, there was a rise in different biocompatible phases. The Vickers hardness of the composite was sensitive to applied loads due to the presence of pores and voids, which was foreseen to be beneficial when the composite was used as an implant, according to the literature. The addition of 20 wt.% HA causes a decrease in hardness to 990 HV, compared to 1109 HV for 10 wt.% HA and 1275 HV for sole Ti-Nb. The addition of HA into Ti-Nb also lowers the compressive strength from 553 MPa for Ti-Nb to 189 MPa for Ti-30Nb-20HA. This was accompanied by a reduction in the elastic modulus, from 130 GPa for Ti-Nb to 29 GPa for Ti-30Nb-20HA. The deformation mechanism was ductile-dominated in all cases, with the presence of a quasi-brittle nature for HA-containing composites. Full article

The coupled effects of Ni and Ti additions on amorphization, spark plasma sintering (SPS) response, and hardness evolution were investigated in Al-rich Al–Fe–Nb-based metastable alloys. Mechanically alloyed Al₈₂Fe₁₄Nb₂Ni₂, Al₈₂Fe₁₄Nb₂Ti₂, and Al₈₂Fe₁₂Nb₂Ni₂Ti₂ powders showed progressive loss of long-range order, with the quinary alloy exhibiting the strongest amorphization tendency, consistent with its higher configurational entropy (5.420 J·mol⁻¹·K⁻¹) and more negative mixing enthalpy (−9.36 kJ·mol⁻¹). SPS displacement analysis revealed that primary displacement contribution occurs during heating and is progressively limited by crystallization-induced stiffening. Consolidation at 500 °C produced amorphous–nanocrystalline composites containing Al₁₃Fe₄ and Al₃Nb, whereas increasing the temperature to 550 °C promoted further devitrification. The highest hardness, 445.4 HV, was obtained for Al₈₂Fe₁₄Nb₂Ni₂, despite its lower amorphous-forming ability than the quinary alloy. This demonstrates that hardness is controlled not by maximum amorphization, but by the kinetic balance between amorphous retention, fine intermetallic precipitation, and densification efficiency. The results identify SPS as a coupled densification–transformation route for designing high-strength Al-based amorphous–nanocrystalline alloys. Full article

Ground improvement for foundations supported on soft soils is traditionally problematic because of low bearing capacity and a large magnitude of settlement. One sustainable method for mitigating these problems is the use of stone columns (SCs), particularly geosynthetic-encased stone columns (GESCs), to improve load transfer, confinement, and consolidation. This review critically synthesizes recent advances in the analysis and design of SC systems using experimental investigations, numerical simulations, and machine learning (ML)-based methodologies. The article indicates that GESCs, when integrated with modern data-driven techniques, especially hybrid metaheuristic ML models, represent a reliable and sustainable solution for soft soil stabilization. Traditional analytical and empirical methods remain useful; however, they are often inadequate for very soft soils (Undrained shear strength (c_u) < 15 kPa), where excessive bulging and large deformations dominate system behavior. Consequently, intelligent hybrid modeling approaches are emerging as the next generation of optimized, data-driven design tools in geotechnical engineering. Different failure mechanisms of SCs, including bulging, punching shear, and general shear failure, are critically discussed along with the governing design parameters. Previous studies consistently indicate that spacing ratios within the range of s/D = 2–3 can improve the bearing capacity ratio (BCR) by approximately 50–100%. Numerical and experimental studies further demonstrate that SC systems can transfer nearly 60–80% of the applied load through stress concentration and soil arching mechanisms. Furthermore, the application of geosynthetic encasement enhances the performance of SCs in very soft soils by increasing confinement, reducing lateral deformation, and enhancing bearing capacity by nearly 3–6 times compared with ordinary SCs. The review also evaluates the growing role of artificial intelligence techniques in forecasting settlement and bearing capacity behavior. ML techniques such as artificial neural networks (ANN), support vector regression (SVR), random forest (RF), XGBoost, and hybrid metaheuristic–ML models have shown high predictive capability, often achieving prediction errors below 5%. Despite these advancements, many existing ML studies still suffer from limited datasets, a lack of generalization, and insufficient incorporation of physical mechanisms. Full article

Against the background of blast furnace burden optimization and the low-carbon transition of the steel industry, the development of high-quality Mg-bearing fluxed pellets is of great significance for the efficient utilization of medium-high silica iron ore concentrates. In this study, Mg-bearing medium-high silica fluxed pellets with a fixed SiO₂ content of 5.5% were prepared, and the effect of basicity in the range of R = 1.0–1.4 on compressive strength, liquid phase behavior, slag phase composition, and pore structure evolution was systematically investigated. The results showed that the compressive strength of the pellets decreased from 2527 N/pellet to 2079 N/pellet as the basicity increased from 1.0 to 1.4. At 1250 °C, the liquid phase content first decreased from 2.66% to 1.30% and then increased to 7.38%, while the liquid phase viscosity decreased continuously. Meanwhile, the liquid phase composition evolved from a SiO₂-rich calcium–iron silicate system to a Fe₂O₃⁻ and CaO-rich system. XRD results indicated that Fe₂O₃ was the dominant crystalline phase in the pellets, accompanied by a small amount of Fe₃O₄, whereas no distinct highly crystalline slag phase was detected. The slag phase was mainly a Fe-Ca-Si composite slag, in which the Fe₂O₃ content increased and the SiO₂ content decreased with increasing basicity. At higher basicity, the number and size of pores increased, and the pore morphology evolved from dispersed fine pores to irregular large pores and locally connected pores. Meanwhile, the slag phase became more widely distributed and locally enriched, weakening the continuity of the iron oxide load-bearing skeleton, which was the main reason for the decrease in compressive strength. This study provides a theoretical basis for preparing high-quality Mg-bearing fluxed pellets from medium-high silica iron ore concentrates. Full article

Poor consolidations and the strength–conductivity trade-off limit the performance of copper alloys fabricated by laser powder bed fusion (LPBF). To address this, this study developed a strategy combining the response surface methodology (RSM) with direct ageing treatment (DAT) to achieve a favorable strength–conductivity synergy. The results showed that under the optimal process parameters, a high relative density of 99.25% (8.95 g/cm³ for theoretical density) was obtained. After direct ageing treatment at 490 °C for 60 min, the CuCrZr exhibited an ultimate tensile strength of 399.31 MPa and a thermal conductivity of 326.53 W/(m·K). To reveal the underlying mechanisms, this study employed a combination of systematic characterization via high-resolution transmission electron microscopy (HRTEM) and quantitative modeling. HRTEM characterized the uniformly dispersed nanoscale body-centered cubic (BCC) Cr precipitates that form semi-coherent interfaces with the face-centered cubic (FCC) Cu matrix, showing a crystallographic misorientation of approximately 10.5° intermediate between the classic Nishiyama–Wassermann and Kurdjumov–Sachs orientation relationships. Quantitative modeling indicates that the high strength arises from a synergistic effect: coherent strain fields exerted by the precipitates effectively pin retained dislocations, coupling Orowan and dislocation strengthening. Meanwhile, solute precipitation reduces lattice distortion, restoring notable thermal conductivity. Full article

The DMD gene is best known for its product dystrophin, a large rod-shaped protein that plays a critical role in muscular membrane strength and integrity. Mutations affecting dystrophin lead to Duchenne muscular dystrophy, a fatal X-linked disease characterized by muscular weakness and breakdown. In addition to the full-length dystrophin product that is most often associated with disease, the DMD gene also encodes multiple shorter isoforms of dystrophin with diverse functions. One isoform in particular, Dp71, has been increasingly found to play a wide variety of roles throughout the body. In this narrative review, we consolidate the numerous studies on Dp71 to provide a comprehensive foundation for future work. We outline and summarize the current state of knowledge on the role of Dp71 in the brain, the retina, and skeletal muscles, identifying current knowns and unknowns in the field. We also explore Dp71-based therapies currently being tested in the pre-clinical landscape and identify potential limitations for clinical translation. Full article

Recent advances in three-dimensional (3D)-bioprinted hydrogels show promise for overcoming the limitations of conventional techniques for dental tissue regeneration. This scoping review systematically analyses the physical, mechanical, and rheological properties of these hydrogels in dental applications, aiming to identify knowledge gaps, limitations, and current and future directions for advancing and translating hydrogel-based 3D bioprinting in dentistry. In accordance with PRISMA-ScR guidelines, a comprehensive literature search was conducted across Ovid, PubMed, EBSCOhost, and Web of Science up to January 2026. Included studies focused on (i) 3D-bioprinted hydrogels, (ii) quantitative characterisation, and (iii) dental tissue engineering. A total of twenty-one studies met the inclusion criteria. The findings revealed substantial variability in formulations and properties. Gelatine-based hydrogels reinforced with β-tricalcium phosphate demonstrated the highest compressive strength within the range of cancellous bone, whereas GelMA/PEGDA composites exhibited tunable stiffness suitable for soft tissue applications. Extrusion-based bioprinting emerged as the predominant method, with photocrosslinking and ionic crosslinking as the primary gelation techniques. Biodegradation rates varied notably with composition and regenerative objectives. This review uniquely consolidates the physical, mechanical, and rheological evaluations of 3D-bioprinted hydrogels for dental applications. The review highlights critical gaps in methodological standardisation and validation, emphasising the importance of biomaterial selection to optimise scaffolds and regenerative outcomes in periodontal, bone, and pulp tissue engineering. Full article

Background: The perioperative context is characterized by high complexity and a significant risk of adverse events, requiring highly developed technical and non-technical competencies. Structured clinical supervision has been identified as a relevant strategy for professional development and for promoting the quality and safety of care, although the specific evidence in this context remains dispersed. Objective: To analyze the available scientific evidence on the impact of structured clinical supervision on nurses’ professional development and on the quality and safety of care delivered in the perioperative setting. Methods: A systematic literature review was conducted in accordance with PRISMA 2020 recommendations. The search was performed in the PubMed, Web of Science, EBSCO, SciELO, BVS, and CONSENSUS databases and included studies published between January 2020 and October 2025 in Portuguese, English, or Spanish with full-text availability. The research question was structured according to the PICO strategy. Study selection was carried out in multiple stages (duplicate removal, screening by title and abstract, and full-text review), performed by two independent reviewers. Methodological quality was assessed using the Joanna Briggs Institute (JBI) checklists. Data synthesis was conducted through thematic narrative analysis, given the methodological heterogeneity of the included studies. Results: Twelve studies were included, predominantly qualitative and observational in nature, as well as psychometric validation studies, one Delphi study, and one quasi-experimental study. The findings show consistent convergence regarding the association between structured clinical supervision and the development of technical and non-technical competencies, namely communication, leadership, teamwork, situational awareness, and decision-making. The use of structured assessment instruments demonstrated good psychometric reliability and improved the quality of supervisory feedback. Organizational factors, such as protected time, specific training for supervisors, and role clarification, were identified as determinants of the effectiveness of the supervisory process. However, the predominance of non-experimental designs and the scarcity of objective clinical outcomes limit direct causal inference between structured supervision and measurable reduction in adverse events. Conclusions: The available evidence suggests that structured clinical supervision is a relevant component for the professional development of perioperative nurses and for strengthening the safety culture in the operating room. Despite the high conceptual consistency of the findings, the overall strength of evidence is moderate, and experimental and longitudinal studies are needed to consolidate the impact of supervision on objective clinical indicators of care quality and safety. Full article

Agricultural waste materials can serve as functional constituents in cement-based composites through three pathways: (i) organic bio-aggregates that lower density and alter thermal behavior, (ii) lignocellulosic fibers that control cracking and improve post-cracking resistance, and (iii) agro-ash supplementary cementitious materials (SCMs) that densify pore structure and reduce permeability when ash quality and curing are controlled. This review draws on 98 papers, with coconut shell aggregate and coir/coconut fibers as the core focus; agro-ash SCMs (notably palm oil fuel ash, POFA, and rice husk ash, RHA) enter where they clarify mechanisms or inform hybrid design. Rather than cataloging compressive-strength data, the synthesis is organized around controllable process inputs (feedstock conditioning, mix design, curing) and the interface-governed mechanisms that determine performance: interfacial transition zone (ITZ) character and pore connectivity. In coconut shell systems, density reductions come at a cost: elastic modulus drops and moisture sensitivity rises unless shell conditioning, particle packing, and matrix refinement are managed. In fiber systems, gains in toughness and residual capacity are bounded by mixing workability and by the long-term stability of the fiber–matrix bond under alkaline and wet–dry exposure. A mix must first meet strength, serviceability, and transport requirements before its embodied impact is compared with conventional alternatives. The contribution is to reframe these systems around controllable processing and interface mechanisms instead of tabulated strength values; preparation, treatment, and characterization data are consolidated into bounded design windows, an explicit core versus supporting evidence convention is applied, and sustainability is judged under functional equivalency rather than per-volume carbon. Full article

Additive manufacturing with soil–cement mixtures is emerging as a disruptive approach to advancing sustainable manufacturing processes. However, its industrial scalability remains limited by material brittleness and a lack of process standardization. This study presents an integrative literature review that critically evaluates the influence of fiber reinforcement on the 3D printing process and the mechanical performance of soil–cement mixtures within the context of sustainable construction and circular economy principles. The analysis integrates fresh-state rheological behavior with hardened-state performance, showing that an optimized fiber dosage (0.3–0.5% by volume) shifts the failure mode from brittle to quasi-ductile while reducing crack propagation by approximately 60%. Additionally, the study compares various fiber types, including synthetic and natural alternatives. The results show that synthetic fibers used at low dosages (0.5–1.0% by volume) provide the greatest improvements in tensile strength and post-cracking ductility. In contrast, natural fibers, typically used at higher dosages (8.0–13.0% by volume), mainly improve toughness and thermal performance, with more limited gains in strength. The review also identifies key gaps in the existing literature, such as a lack of standardized protocols for measuring process parameters and the need for studies that address long-term durability and comprehensive lifecycle assessments. These findings outline a clear research roadmap to support the consolidation of reinforced soil–cement as a resilient and sustainable material for next-generation additive manufacturing. Full article

Laser powder bed fusion (LPBF) of aluminum matrix tribological composites holds high potential for advanced bearing applications, yet its widespread implementation is often constrained by high porosity and severe residual stresses. In this work, the influence of hot pressing (HP) temperature (100–400 °C) on the microstructure, substructural evolution, mechanical properties, and fracture mechanisms of the LPBF Al-10Sn-10Pb alloy was investigated to achieve simultaneous densification and matrix optimization. Processing was carried out at 300 MPa with a 30 min holding time. It was established that at temperatures >200 °C, near-full consolidation is achieved through liquid-assisted pore closure. Increasing the temperature leads to the coarsening of Sn and Pb inclusions and the disruption of the initial dispersed network of soft phases. Williamson–Hall analysis revealed a transition from dislocation accumulation at 100 °C (~15 × 10¹³ m⁻²) to dynamic recovery at 200 °C, followed by matrix recrystallization at higher temperatures. A combination of strength (up to 127 MPa) and ductility (~11%) is realized at 200 °C due to the synergy between remaining substructural strengthening and pore healing. At 300–400 °C, the strength decreases to 108–113 MPa with a concomitant increase in ductility to 34–44%. A shift in fracture mechanisms from quasi-brittle to ductile is shown; at 400 °C, the development of intergranular fracture associated with the influence of liquid phases is possible. Full article

This study presents the development of an eco-friendly brick for mining, a sustainable composite material manufactured from gold mine tailings and used cooking oil (UCO) through a thermal oxypolymerization process. Unlike conventional stabilization methods, which often require additional materials beyond tailings or have a high carbon footprint in their production, this approach uses oxypolymerization to transform these two waste products into novel building materials. The use of various percentages of UCO at different heating temperatures was evaluated to identify the optimal mixture, determining that a 9% UCO content and a 9 h cycle are key conditions for inducing fatty acid crosslinking. This logical relationship between heat treatment and dosage allows the organic binder to consolidate the mineral matrix, giving the material a compressive strength of 19.12 MPa and a flexural strength of 8.24 MPa, exceeding the thresholds of the NTE INEN 297 standard. The low water absorption (2.86%) is attributed to the densification of the matrix and the hydrophobic nature of the polymerized oil, indicators of its structural durability. This work is the first to use Ecuadorian tailings as the sole mineral aggregate, validating a high-efficiency, low-impact product for sustainable construction under the principles of the circular economy. Full article

In oil-rich countries, petroleum contamination of soils frequently occurs during refining, transportation, and exploitation. Such contamination significantly alters soil behavior and properties from a geotechnical perspective. Given that some fine-grained soils exhibit insufficient bearing capacity or excessive settlement, soil improvement is often necessary. The selective use of nanoparticles offers a promising novel approach in this regard. This study investigates the effects of diesel contamination and nanosilica modification on the physical and mechanical properties of clayey sand and aims to interpret the variations in the mechanical properties and the permeability of the treated soil based on microstructural observations. Diesel (0–10% in 2% increments) and nanosilica (0%, 1%, 2%) were added to the soil, preparing a total of 18 mixtures for testing. The microstructural changes directly alter the physical parameters such as specific gravity, optimum moisture content (OMC), and maximum dry unit weight, consequently affecting the permeability and the mechanical behavior. The microstructural analysis via scanning electron microscopy revealed diesel-induced clay flocculation and increasing macroporosity, while the nanosilica at 1% improved the soil fabric through pore filling and interparticle bonding, whereas 2% nanosilica led to partial dispersion and agglomeration. The findings demonstrate that soil behavior is controlled by the interplay between diesel (lubrication, pore blocking, hydrophobicity) and nanosilica (surface activation, micro-bonding, agglomeration). Increasing the diesel content consistently reduces the specific gravity across all the mixtures, due to the replacement of heavier mineral particles by lighter hydrocarbon, diesel adsorption onto the soil grains, the formation of low-density organic films, and increased micro-voids. Diesel addition reduces the OMC but increases the maximum dry unit weight due to its lubrication effect. Mechanically, the unconfined compressive strength (UCS) peaked at approximately 4% diesel contamination, with the addition of 1% nanosilica yielding the highest strength overall. Conversely, the California Bearing Ratio (CBR) increased continuously with diesel due to improved packing and frictional resistance and was further improved by nanosilica. The results show that permeability decreases with increasing diesel content due to hydrophobic diesel molecules coating soil particles, filling micro-voids, and blocking pore channels, while the consolidation parameters exhibit non-monotonic trends, peaking at moderate contamination levels. An optimal nanosilica content effectively mitigated some of the adverse effects of diesel and enhanced the mechanical performance, providing valuable insights for managing hydrocarbon-contaminated soils. Full article