Search Results (798)

Conventional cement-based grouts used to stabilize fractured rock slopes and fill large cavities are heavy, carbon-intensive, and can impose excessive dead load on weakened rock masses. This study addresses these limitations by integrating bio-based rigid polyurethane—particularly castor oil-based polyurethane—into a slag-based geopolymer mortar, producing a lightweight, low-permeability, rock-adherent alternative grouting system. Three formulations were evaluated: unmodified geopolymer grout (GG), geopolymer grout modified with petroleum-based polyurethane (G-PUG), and geopolymer grout modified with castor oil-based polyurethane (GCO-PUG). Materials were characterized using infrared spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction, and scanning electron microscopy with energy-dispersive X-ray spectroscopy, and tested for apparent density, permeability, unconfined compressive strength, and direct shear behavior—including at the grout–limestone interface using rock sourced from El-Mokattam plateau, Cairo. Polyurethane incorporation reduced apparent density by up to 24% (from 22.15 to 16.89 kN/m³) and permeability to as low as 2.3 × 10⁻⁸ m/s, at the cost of a substantial reduction in compressive strength (from 5564 to 139 kN/m²). The castor oil-based grout also showed improved rock adhesion, with interfacial cohesion increasing by 67% relative to its standalone state. Accordingly, unmodified GG is recommended for high-load structural applications, whereas GCO-PUG provides a lightweight, low-permeability, and strongly rock-adherent alternative for filling large cavities and stabilizing slopes under moisture-sensitive and weight-critical conditions, where reducing self-weight and limiting water ingress are more important than achieving maximum compressive strength. Full article

Bamboo is a renewable and mechanically robust bio-based material with potential for sand-barrier construction; however, its long-term outdoor use is limited by ultraviolet-induced photoaging, moisture uptake, wind-sand abrasion, and biological colonization. In this study, a fluorine-free EP/TiO₂/ODTMS superhydrophobic coating was deposited on moso bamboo using a simple spraying process. Rutile TiO₂ was incorporated as a roughness-building and ultraviolet-shielding filler, waterborne epoxy resin served as a film-forming binder to improve particle anchoring and coating cohesion, and octadecyltrimethoxysilane was used to reduce the surface energy. The formulation containing 50–100 nm rutile TiO₂ and 2 wt.% epoxy resin provided the best overall balance between surface wettability and mechanical durability, with a water contact angle of 156.4° and a sliding angle of 6.9°. SEM observations revealed a hierarchical surface composed of TiO₂ particles and microscale agglomerates immobilized within the epoxy matrix. EDS and FTIR results supported the incorporation of TiO₂- and ODTMS-derived components, while UV–Vis–NIR diffuse-reflectance measurements showed an improved optical response in the ultraviolet region. The coating retained superhydrophobicity after sandpaper abrasion, gravel impact, and tape-peeling tests. After 672 h of xenon-lamp aging, the coated bamboo maintained a water contact angle above 150°, exhibited a total color difference of approximately 7.65, and retained 91.1% of its initial flexural strength. In addition, qualitatively reduced visible mildew colonization was observed during 45 days of high-humidity exposure. These results demonstrate that the spray-deposited coating provides a fluorine-free and potentially scalable approach for improving the water repellency, mechanical durability, and accelerated-weathering resistance of bamboo sand-barrier materials. Full article

Digital transformation is portrayed both as a lever of territorial convergence and as a driver of polarisation between urban cores and peripheries, yet its effect on regional economic resilience has rarely been measured systematically. This study transposes the Economic Resilience Index framework from the national to the regional scale, building a Regional Resilience Index (R-ERI) for 236 NUTS2 regions of the EU-27 from Eurostat indicators, anchored in the capacities of absorption, recovery, and adaptation and measuring resilience as a capacity rather than as a realised shock trajectory. Two complementary models are estimated: a spatial Durbin panel with two-way fixed effects (2018–2023), spanning the COVID-19 pandemic and 2022 energy shocks, and an exploratory cross-sectional difference model exploiting regional artificial intelligence (AI) adoption data disaggregated by NACE branch (2023–2025). The results show that resilience is strongly spatially autocorrelated (Moran’s I between 0.66 and 0.74; p = 0.001); that digital connectivity generates a positive indirect effect on neighbouring regions despite a negative own-region effect; and that the synergy hypothesis—that digitalisation yields more resilience when combined with traditional sectors—does not hold robustly, the interaction being null in the panel and only marginally positive in the AI layer (p = 0.10). We conclude that digital connectivity is not, on its own, an automatic convergence mechanism, and that cohesion policy should account for each region’s sectoral structure and peripheral position. Full article

Group III-nitride semiconductors (GaN, AlN, InN) serve as foundational materials for modern optoelectronics, high-frequency microelectronics, and next-generation energy harvesting devices. However, traditional high-temperature epitaxy (>700 °C) introduces severe thermal stress, high dislocation densities, and fundamental incompatibility with flexible substrates or CMOS back-end-of-line (BEOL) processes. Plasma-enhanced atomic layer deposition (PEALD) provides a disruptive, ultra-low thermal budget (<300 °C) pathway for atomic-scale precision growth and conformal coating. This review systematically summarizes recent frontiers in PEALD-synthesized Group III-nitrides and 2D/3D polar heterostructures. First, we dissect the microscopic nucleation kinetics, surface bond reconstruction, and impurity suppression mechanisms across diverse substrates, including Si, sapphire, quartz, metals, and flexible polymers. Next, we highlight 2D template-assisted van der Waals epitaxy on graphene and MoS2, and elucidate polarization-driven dipole interactions and band alignment engineering at 2D/3D polar interfaces (e.g., α-In₂Se₃, Janus MoSSe). Furthermore, we comprehensively discuss innovative applications in advanced photovoltaics (as electron transport and passivation layers in perovskite and quantum dot-sensitized solar cells), silicon-based microcavity lasers, high-electron-mobility transistors (HEMTs), and flexible multimodal sensors. Finally, key technological challenges—including the low-thermal-budget paradox, wafer-scale uniformity, and deposition throughput—are addressed alongside future perspectives in area-selective ALD and neuromorphic computing, presenting a cohesive blueprint from underlying physics to macroscopic system integration. Full article

Fischer–Tropsch (FT) wax is widely used as an organic warm-mix asphalt (WMA) additive, lowering binder viscosity during construction while improving high-temperature deformation resistance in service; however, the comparative responses of SBS-modified asphalt to different FT wax grades remain insufficiently understood. Sasobit and three FT waxes with different carbon-chain ranges (FT 80, FT 90, FT 100) were incorporated into SBS-modified asphalt at about 7.0 wt%, and their effects on macroscopic performance, rheology, molecular packing, and diffusion were evaluated using physical-property tests, rotational viscosity, dynamic shear rheometer (DSR) testing, and molecular dynamics (MD) simulation. In the MD analysis, the wax additives were represented by linear alkane molecules with different chain lengths, and the systems were subjected to structural optimization, annealing, and NPT equilibration using the COMPASS III force field before the molecular descriptors were evaluated. The experimental results showed that all four additives produced a trade-off between increased high-temperature stiffness and reduced low-temperature ductility. Sasobit gave the strongest viscosity reduction (>70% above 165 °C), while FT 90 and FT 100 showed more stable, predictable viscosity–temperature behavior favorable for a wider construction window. DSR results showed higher complex modulus and lower phase angle for all modified binders at low frequencies, suggesting an increased elastic contribution and greater resistance to deformation under the tested rheological conditions; FT 80 produced the greatest stiffening but also the largest free volume and loosest molecular packing, whereas FT 100 increased cohesive energy density and reduced free volume, reflecting denser packing and stronger intermolecular cohesion. MD simulations revealed that FT wax enhanced short-time local molecular mobility and segment diffusion in its molten state (explaining the warm-mix viscosity reduction), whereas macroscopic stiffening and ductility loss at ambient temperatures were dictated by wax microcrystallization and physical network constraints that restricted long-range chain relaxation. By comparing three FT wax grades and Sasobit under the same experimental dosage and testing framework, this study provides a controlled assessment of the relationships among wax-grade characteristics, binder-scale rheological responses, and MD-derived molecular descriptors. Full article

Asphalt pavements at high-altitude airports endure prolonged extreme low temperatures and large diurnal swings, imposing stringent demands on crack sealants, whose multi-scale adhesion failure mechanism remains unclear. Three SBS and crumb-rubber-composite-modified sealants, designated A, B and C, were characterized through surface free energy tests, pull-off and shear tests, fluorescence microscopy, FTIR and molecular dynamics simulations. Cross-scale correlation analysis and CRITIC-TOPSIS were applied to link and rank the sealants across scales. Work of cohesion, work of adhesion, pull-off strength and shear strength all rose monotonically with modifier content, and sealant C exhibited a 38.5% higher work of cohesion and a 52.4% lower CV_φ than sealant A. Molecular dynamics simulations showed that electrostatic forces drove sealant–aggregate adhesion while van der Waals forces governed sealant–asphalt adhesion, with a simulation–experiment deviation of only 2.88–5.74%. A level-by-level transmission linked phase-morphology uniformity, intermolecular interaction, interfacial energy and macroscopic mechanical performance. Sealant C achieved a CRITIC-TOPSIS index of 1.000, far above 0.271 for B and 0.000 for A, and is recommended as the preferred material for crack sealing of high-altitude airport asphalt pavements. Full article

The structural performance of reinforced concrete (RC) columns can be substantially improved by using advanced confinement systems and sustainable cementitious materials. This study presents an integrated experimental, numerical, and analytical investigation of RC columns strengthened with self-compacting geopolymer concrete (SCGC) and carbon fiber-reinforced polymer (CFRP) under axial compression. Twelve column specimens were tested across four groups: conventional RC columns, unconfined SCGC columns, SCGC-jacketed columns (CONF. SCGC), and CFRP-wrapped columns (CONF. FRP), in three cross-sectional geometries: square (177 × 177 mm), rectangular (265 × 177 mm), and circular (Ø200 mm). Experimental results demonstrated that replacing conventional concrete with SCGC improved deformation capacity, increasing the ultimate axial displacement from 2.07 mm in the reference square RC column (RC C1) to 3.21 mm in the corresponding square SCGC specimen (SCGC C1). On a normalized stress basis, the unconfined SCGC specimens achieved ultimate axial stress values of 56–64 MPa compared to 41–49 MPa for the RC reference columns of the same geometry, representing material-level strength gains of 1.30–1.49×. The application of external confinement further enhanced column behaviour. The CFRP-wrapped specimens achieved the highest material-level strength efficiency, with normalized ultimate axial stress values of 98–108 MPa for the square and rectangular geometries, representing gains of 2.01–2.41× over the corresponding unconfined RC columns of identical cross-section. The SCGC-jacketed specimens achieved the highest absolute load capacities, with CONF. SCGC C2 reaching 8270 kN and a maximum stiffness of 5531 kN/mm and energy absorption of 19,740 kN·mm. However, on a normalized stress basis, the SCGC-jacketed square and rectangular specimens achieved 45–47 MPa, comparable to the RC reference columns, confirming that their absolute load gains are primarily attributable to section enlargement rather than intrinsic material strength enhancement. The circular SCGC-jacketed specimen achieved a normalized stress of 43 MPa, consistent with the same trend. A three-dimensional nonlinear finite element model developed in ABAQUS using the Concrete Damaged Plasticity model and cohesive zone interactions showed close agreement with experimental results, with mean prediction ratios of 1.03 for ultimate load and 0.96 for displacement. An analytical model provided conservative estimates of axial capacity. The findings demonstrate that CFRP wrapping offers superior material-level confinement efficiency, while SCGC jacketing provides the highest absolute load capacity through combined section enlargement and passive confinement, representing a potentially more environmentally friendly strengthening strategy for existing RC columns. Full article

Sludge-conditioning strategies are commonly optimized for filtration performance, with less attention paid to the rheological and textural properties of concentrated sludge and their relevance to low-temperature drying. Here, thermally modified drinking-water sludge (HDWS) was evaluated as a waste-derived mineral conditioner for filtration dewatering and low-temperature drying. The specific resistance to filtration (SRF) was lowest at 30% DS, whereas the 60% DS treatment reduced the moisture content to 35.66% after drying at 60 °C for 30 min, indicating that the optimum filtration condition did not deliver the best drying performance. Increasing the HDWS dosage from 0 to 60% DS reduced the Jenike shear stress from approximately 565 to 490 Pa and the apparent yield stress from approximately 670 to 380 Pa, while also decreasing adhesiveness and cohesiveness. At higher dosages, the sludge retained relatively high small-strain stiffness but exhibited lower nonlinear elastic and viscous resistance. These responses were consistent with weakened macroscopic bonding and altered deformation-dependent energy dissipation after HDWS addition. A possible contribution from mineral-particle contacts is suggested, although the underlying microstructural mechanism was not directly resolved. The 60% DS treatment shortened the time required to reach 20% water content to approximately two-thirds of that for raw sludge but reduced the cake calorific value from approximately 9.6 to 4.3 kJ g⁻¹. HDWS, therefore, exhibited process-specific trade-offs, and its dosage should be selected according to the targeted unit operation and downstream management route rather than regarded as a single overall optimum. Full article

The pursuit of energy efficiency has dominated sustainable housing policy and research, yet growing evidence suggests that technical performance alone cannot guarantee positive outcomes, particularly in rural contexts where housing is embedded within complex socio-economic systems. This study addresses this gap by developing and applying a context-specific analytical framework for evaluating the socio-economic sustainability of rural housing in Scotland. Through a structured literature review of 43 peer-reviewed articles and thematic coding, four core sustainability dimensions were identified: People and Community, Land and Site, House, and Energy and Infrastructure. The framework was developed and tested through four contemporary rural housing case studies in Scotland, spanning private and social tenures across Aberdeenshire, Moray, Dumfries & Galloway, and Shetland Islands. Data were collected through semi-structured interviews, on-site observations, and documentary evidence. A multi-evidence traffic-light evaluation system was developed to cross-check assessment results across distinct data sources. The findings reveal that sustainability outcomes are conditional, sometimes uneven, and shaped by multiple factors. While all cases demonstrated strong performance in community cohesion, affordability, and non-speculative land access, some persistent challenges emerged around energy resilience, fuel poverty mitigation, transport accessibility, and participatory practices for social-house design. The study contributes a replicable analytical framework to develop and evaluate rural housing sustainability beyond energy-efficiency assessments, providing empirical insights for policy and practice in Scotland. Full article

Mixed mode I–III fracture commonly occurs in rock masses under complex three-dimensional stress states, yet the combined effects of loading conditions and fracture mode remain unclear. In this study, a heterogeneous sandstone disc model is developed in ABAQUS by coupling the Drucker–Prager elastoplastic model, an equivalent-strain damage model, and cohesive elements. The model is validated against static Brazilian splitting tests and dynamic SHPB tests. ENDB specimens are then employed to investigate mode I, mode III, and mixed mode I–III fracture under static and dynamic loading with offset angles ranging from 0° to 62.5°. As the offset angle increases, crack propagation evolves from straight tensile extension to deflected, twisted, and fragmented patterns dominated by anti-plane shear. Dynamic loading intensifies crack segmentation, localized damage, and transient instability while increasing the peak load, fracture toughness, and fracture energy. In contrast, the effective fracture toughness and fracture energy decrease monotonically with increasing offset angle under both loading conditions. A linear trend consistent with R² > 0.99 is observed between the mode I–III mixing coefficient and the effective fracture toughness based on single-realization simulations, the effective fracture toughness under dynamic loading is approximately 2.22 times that under static loading based on direct comparison of calculated values. These findings improve the understanding of loading-dependent mixed mode I–III fracture in sandstone and provide guidance for rock mass stability assessment. Full article

Autonomous subterranean mobility remains one of the least unified domains in robotics because locomotion emerges from coupled interactions among deformable geomaterials, structural mechanics, energy dissipation, and environment-dependent sensing constraints. This foundational pioneer technical review synthesizes 35 years of research on burrowing and underground robotic systems through a terradynamic and multiphysics perspective. Following PRISMA guidelines, 143 peer-reviewed studies were analyzed across granular soils, cohesive sediments, saturated media, fractured geomaterials, and extraterrestrial regolith analogs. The review evaluates six dominant locomotion classes, including peristaltic, undulatory, fluidization-assisted, excavation-based, tip-extension, and hybrid architectures. Results demonstrate that locomotion performance is governed primarily by regulation of substrate response rather than propulsion generation alone. Across all architectures, mobility depends on the coupled evolution of confinement-dependent stress redistribution, yielding mechanics, pore-pressure dynamics, fracture propagation, structural stability, thermomechanical loading, and energy partitioning. The analysis further reveals a convergence toward stress-regulated locomotion, where successful systems minimize drag accumulation, control force-chain evolution, and adapt to changing terradynamic conditions. Major unresolved challenges include the absence of transferable scaling laws, standardized benchmarking methodologies, predictive terradynamic models, and multi-medium autonomy. The review concludes by proposing the foundations of a unified multiphysics terradynamic robotics paradigm capable of linking robot design, substrate mechanics, control, and deployment across terrestrial and planetary subsurface environments. Full article

This study investigates the effect of selective z-pinning on the tensile strength of single step-lap composite joints through a combined experimental and numerical investigation. Uniaxial tensile tests were performed on unpinned and z-pinned samples to assess the effect of z-pins on the strength and failure of joints. Unpinned and pinned joints exhibited an initial linear load–strain response, followed by stiffness degradation due to the onset and propagation of interfacial delamination. However, z-pinned joints exhibit increased strength and ultimate strain, indicating enhanced energy absorption and damage tolerance without compromising joint stiffness. The damage of single step-lap joints was mainly governed by matrix cracking and delamination. In order to identify and investigate the toughening mechanisms specifically induced by z-pins, a three-dimensional finite element (FE) model was developed in ABAQUS/Explicit to simulate the mechanical response of the joints. Both the bonding and the pin-laminate interface were modeled as a cohesive contact interface modeled with a bilinear traction–separation law, using a quadratic nominal stress criterion to initiate damage and the Benzeggagh–Kenane criterion to control damage evolution. The numerical results exhibited a relatively good agreement with the experimental data in terms of load-bearing capacity, ultimate strain, and damage evolution. Full article

Human development in the European Union remains uneven, and it is still unclear how economic, social, environmental, and institutional conditions jointly shape it. Understanding this question is essential for EU cohesion and sustainability policy, since Member States differ widely in governance capacity and development trajectories. This study proposes and empirically tests an extended Triple Bottom Line framework in which governance is treated as a fourth sustainability subsystem and examines its influence on the Human Development Index (HDI) in the 27 EU member states over 2000–2024 (675 country-year observations). Composite dimension indices are constructed through principal component analysis and validated with KMO and Bartlett diagnostics, and the analysis combines two-way fixed-effects models, Mundlak within–between decomposition, dynamic panels, a parsimonious system GMM estimator, and Driscoll–Kraay standard errors. The institutional dimension is the most robust positive correlate of HDI across all specifications, and its long-run effect remains significant. The environmental dimension is negatively and significantly associated with HDI, revealing a development–environment tension rather than a welfare effect, while CO₂ emissions display a positive coefficient in disaggregated models, reflecting development-stage and energy-structure effects. The economic dimension matters mainly as a long-run structural difference between countries, not as short-run within-country variation, and institutional and environmental effects are more pronounced in Central and Eastern Europe than in Western Europe. The findings imply that EU policies aimed at strengthening governance quality and supporting a just green transition—including the European Green Deal, the Recovery and Resilience Facility (RRF), and cohesion policy instruments—are central levers for sustaining human development. Full article

Developing sustainable lithium-ion batteries (LIBs) requires binder–carbon interfaces that combine mechanical compatibility, interfacial cohesion, and reduced environmental impact. In this work, density functional theory calculations were used to evaluate the interactions of representative binder monomers acrylonitrile (AN), pyrrole (PY), vinylidene fluoride (VDF), and tetrafluoroethylene (TFE) with pristine graphene and chitosan-functionalized graphene oxide (GO/chitosan). Structural, energetic, electronic, and topological features were analyzed using counterpoise-corrected interaction energies, frontier-orbital descriptors, molecular electrostatic potential maps, projected density of states, noncovalent interaction analysis, and quantum theory of atoms in molecules topology. Final interaction energies were obtained at the M06-2X/def2-TZVP level with Boys–Bernardi counterpoise correction to provide a more robust description of weak noncovalent adsorption. Most binder–surface interactions fall within a weak, near-thermoneutral adsorption regime. On pristine graphene, AN and PY exhibit weakly favorable adsorption, with minimum counterpoise-corrected interaction energies of −3.13 and −2.10 kcal mol⁻¹, respectively, whereas TFE and VDF show orientation-dependent, near-neutral behavior. GO/chitosan introduces oxygen-containing and amino functionalities that modify the adsorption balance, particularly for selected perpendicular configurations of fluorinated monomers, although the net stabilization remains modest. NCI, QTAIM, MEP, and PDOS analyses indicate that surface functionalization increases the chemical heterogeneity and directionality of local contacts; however, these local descriptors do not necessarily translate into strong global adsorption energies. Overall, the results identify GO/chitosan as a chemically tunable interface for binder–carbon compatibility in LIB electrodes and demonstrate the importance of triple-ζ, counterpoise-corrected calculations for evaluating weak binder–surface interactions. Full article

Conventional bond-slip models generally represent ribbed GFRP bars as equivalent smooth cylinders, limiting their ability to describe local rib-bearing, interface degradation, and non-uniform stress transfer. This study establishes a three-dimensional finite-element model for helically ribbed GFRP bars embedded in concrete, explicitly incorporating the helical rib geometry, cohesive-frictional interface interaction, and concrete damaged plasticity. Validation against independent pull-out tests yields minor peak bond-stress errors of −0.55% and −2.49% across different bar diameters, with numerical reliability confirmed through mesh and energy checks. The results indicate that bond resistance evolves from cohesive transfer to rib-bearing action, followed by localized concrete damage, frictional sliding, and residual interlocking. Stress transfer is highly non-uniform along the bonded length, and post-peak interface degradation causes the active transfer zone to migrate dynamically away from the loaded end. Parametric analyses reveal conditional main-effect trends within the investigated ranges, demonstrating that rib height has the strongest influence on residual resistance and energy dissipation, whereas the benefit of increasing concrete strength gradually diminishes. Increasing the bonded length or bar diameter raises the total pull-out force but reduces the nominal bond efficiency due to shear lag. Finally, a simplified four-stage bond-slip relationship is proposed, wherein each stage physically aligns with distinct interface degradation phases, to facilitate computationally efficient structural-scale simulations. Full article