Search Results (359)

As a core tenet of Green Urbanism, fostering social sustainability through restorative urban environments is essential for enhancing the psychological resilience of active urban generations. While urban parks are recognized as critical blue-green infrastructure, the micro-mechanisms through which their morphological configurations influence perceived restoration remain insufficiently understood. The aim of this study is to investigate how specific landscape element types and proportions in urban parks modulate the visual behavior and psychological restorative outcomes of young urban populations through a multimodal experimental approach. This study employs a novel assessment framework, integrating VR-based eye-tracking and physiological monitoring (HRV, EDA, EEG), with a sample of 77 young adults (aged 18–30) to investigate how landscape element types and proportions modulate visual behavior and restorative outcomes. The findings indicate that landscape components drive restoration through divergent visual cognitive pathways: natural elements promote recovery by fostering sustained visual engagement and exploratory saccades, whereas artificial elements function as cognitive stressors that fragment visual continuity. Mediation analysis further reveals a “quality-over-quantity” effect, demonstrating that restorative efficacy is governed by specific morphological configurations rather than mere green coverage. We identify critical restorative thresholds where the systematic reduction in artificial visibility, combined with the strategic prioritization of multi-layered vegetation and optimized sky openness, significantly maximizes restorative fascination and physiological relaxation. These evidence-based design strategies offer a precise toolkit for sustainable urban renewal, allowing urban planners to optimize the restorative quality of public spaces. By aligning micro-scale visual perception with macro-scale social sustainability goals, this research contributes to the development of resilient and health-promoting cities under the principles of Green Urbanism. Full article

Environmental concerns associated with the construction industry have drawn increasing attention worldwide. This study addresses the dual challenges of carbon emissions from cement production and construction waste disposal by developing and characterizing a fiber-modified geopolymer recycled aggregate porous concrete (GRAPC). An orthogonal experiment first optimized the GRAPC mix proportion (slag content = 40%, alkali modulus = 1.4, alkali content = 8%). Subsequently, the effects of coir, basalt, and steel fibers (0.25% and 0.5%) on its properties were investigated through laboratory experiments combined with scanning electron microscopy (SEM) analysis. The results show that steel fibers at 0.25% dosage enhanced compressive strength by approximately 25% due to their effective stress-bearing capacity. In contrast, 0.5% coir and basalt fibers reduced compressive strength by approximately 20.5% and 22.2%, respectively, due to low intrinsic strength and agglomeration. In addition, 0.25% coir and steel fibers increased effective porosity by 18.4% and 17.4%, respectively, owing to their uniform dispersion. All fibers promoted a more ductile-like failure mode, with coir fibers providing the best toughness improvement. This study elucidates how fiber type and dosage regulate the macro-properties and micro-mechanisms of GRAPC, providing a basis for designing sustainable eco-friendly concrete with great potential for non-primary load-bearing engineering fields. Full article

Geopolymer materials represent a novel green cementitious material characterized by excellent mechanical properties and unique microstructural features. This study developed geopolymer mortar using slag as the primary raw material by adjusting alkali content and water glass modulus. Characterization methods, including nanoindentation testing, mercury intrusion porosimetry (MIP), and X-ray diffraction (XRD), were employed to systematically analyze the influence mechanisms of alkali content and water glass modulus on the mechanical properties and microstructure of slag-based geopolymer mortar. Results demonstrated that compressive strength exhibited an initial increase followed by a decline with rising alkali content and water glass modulus, while flowability first increased and then decreased. When the water glass modulus was 1.4, and the alkali content reached 8%, the geopolymer mortar achieved a 28-day compressive strength of 86.5 MPa and flexural strength of 10.2 MPa. At 10% alkali content, flowability reached 240 mm. Compressive strength showed a trend of initial increase followed by a decrease with increasing alkali content, reaching a maximum value of 86.4 MPa at 8% alkali content after 28 days. Nanoindentation analysis revealed that the primary strength-forming phase in geopolymer mortar was C-A-S-H gel. Variations in alkali content and water glass modulus primarily affected the volume fractions of C-A-S-H gel, porous phases, and unreacted slag particles, with limited impact on micromechanical parameters of individual phases. These findings not only provide a theoretical basis for optimizing the mix design of slag-based geopolymer mortar but also offer practical guidance for its application in high-strength and workable construction materials. Full article

Material considerations are often neglected when developing digital twins, particularly at the relevant length scales that drive material and structural performance. For reinforced composite materials, the microscale has the largest impact on nonlinear material behavior and progressive damage, and thus accurately representing the disordered microstructure of a composite due to processing and manufacturing is critical to developing the material digital twin in the multiscale hierarchy. Automating microstructure characterization is typically done by either training convolutional neural network models using a pretrained encoder or using prompt-based segmentation tools. In this work, a toolset for developing segmentation models is presented, combining these two methods to enable rapid annotation, training, and deployment of microscopy segmentation models for automated material digital twin development without user knowledge of machine learning. Additionally, a Bayesian optimization framework is developed for generating statistically equivalent representative volume elements (SRVE) to a segmented microstructure using a random microstructure generator that implements soft body dynamics. Progressive failure analysis of random, statistically equivalent, and ordered microstructures is compared to the segmented microstructure subject to transverse loading to demonstrate the importance of accurately representing the driving material length scale of a composite digital twin. Ordered microstructures over-predicted crack initiation and ultimate strength and strain. Random and optimized RVE microstructures better agreed with the segmented simulation results, with no significant difference observed between the two methodologies. The improvement in predicted macroscale behavior for models that capture disordered microstructures due to manufacturing processes demonstrates the importance of capturing microstructure features in composites modeling and indicates that SRVEs that capture microstructural features of the physical material can be used in material digital twin development. Further, the toolsets provided in this work allow for rapid development of composite material digital twins without user expertise in machine learning. This has enabled the development of an integrated workflow to automatically characterize and idealize composite microstructures and generate representative geometric models for efficient micromechanics analysis. Full article

In this study, a composite powder explosion suppressant (MVTS–NaHCO₃) was prepared via the wet coating method of the solution–crystallization (WCSC) process, using modified vanadium–titanium slag (VTS) as the carrier and NaHCO₃ as the active suppressive component. A 20 L spherical explosion apparatus and a transparent pipeline explosion propagation test system were employed to investigate the effects of the composite powder explosion suppressant with different mass fractions (0%, 10%, 20%, 30%, 40%, 50%) on the explosion pressure and micro-mechanism of polyacrylonitrile (PAN) dust. The experimental results indicated that the MVTS–NaHCO₃ composite powder exhibited a significant suppression effect on PAN dust explosions. In the confined 20 L vessel, complete suppression was achieved when the mass fraction of the composite powder explosion suppressant exceeded 30%, with a maximum explosion pressure reduction of 53.2%. In the semi-open pipeline, 40% composite powder explosion suppressant reduced the maximum explosion pressure to 0.08 MPa (a reduction rate of 82.6%), and complete suppression was achieved at a mass fraction of 50%. Microstructural analysis revealed that the suppression performance of the composite powder explosion suppressant is attributed to the synergetic effects of physical and chemical mechanisms. Physically, NaHCO₃ decomposes endothermically (100 kJ/mol), releasing CO₂ and H₂O and thereby diluting the oxygen concentration, while the porous structure of MVTS enhances dispersibility. Chemically, the hydroxyl groups on the surface of MVTS bond with NaHCO₃, delaying its decomposition, while metal hydroxides (e.g., Al(OH)₃) decompose thermally to form Al₂O₃, which adsorbs and quenches free radicals (e.g., ·OH, ·H), thereby inhibiting chain reactions. This study provides new insights for the resource utilization of VTS and the prevention and control of industrial dust explosions. The findings have important reference value for optimizing explosion suppressant formulations and improving the intrinsic safety. Full article

This study presents a calibrated analytical micromechanical framework for predicting the linear elastic behavior of unidirectional glass fiber/epoxy and carbon fiber/epoxy composites over a wide range of fiber volume fractions. The approach combines the classical rule of mixtures for the longitudinal Young’s modulus with the semi empirical Halpin–Tsai equations to estimate the transverse Young’s modulus and the in-plane shear modulus. The framework is specifically formulated to support durability-oriented composite design through rapid and physically consistent estimation of elastic properties governing load transfer and stress distribution. Material parameters, including fiber and matrix Young’s moduli (Ef, Em), shear moduli (Gf, Gm), Poisson’s ratios (νf, νm), and fiber volume fraction (Vf up to 0.80), are taken from established material property databases and implemented within a literature-informed modeling scheme. To preserve physical realism at high fiber contents, a shear correction factor is introduced for Vf > 0.50 to account for microstructural interaction and fiber clustering effects. The predicted effective elastic constants (E₁, E₂, G₁₂, ν₁₂) exhibit consistent and physically meaningful trends across the full fiber volume fraction range. The model predictions were evaluated against trends widely reported in the composite micromechanics literature, and the results showed overall agreement in the nonlinear reduction in stiffness gains at elevated fiber volume fractions. Comparative results indicate that carbon fiber/epoxy composites achieve up to approximately 30% higher stiffness than glass fiber/epoxy systems at equivalent fiber contents, reflecting the influence of stiffness contrast on composite response. The analysis further indicates that stiffness saturation begins approximately in the Vf = 0.60–0.70 range, where the incremental gains in E2 and G12 become noticeably smaller for both composite systems. This behavior provides design-relevant guidance by showing that, beyond this range, further increases in fiber content may offer limited stiffness improvement relative to the associated manufacturing complexity. Overall, the calibrated Halpin–Tsai methodology offers a practical and computationally efficient tool for preliminary evaluation and design-stage optimization of the elastic performance of high-performance composite structures. Full article

This study aims to investigate the influence of clay mineral content on the rheological properties and long-term deformation stability of clays, and to establish a unified model capable of quantitatively describing the nonlinear rheological behavior of clays with different mineral compositions. Direct shear rheological tests were conducted on specimens prepared with different mixing ratios of bentonite, kaolin, and quartz. Combined with micro-mechanism analysis, the controlling factors of clay rheological behavior were explored. The experimental results show that the creep stress threshold, elastic viscosity, and average plastic viscosity decrease significantly with increasing clay mineral content. The rheological deformation exhibits distinct nonlinear characteristics, and clay mineral content plays a controlling role in the rheological behavior. Based on experimental and mechanistic analysis, a unified rheological model was established, which reflects the material origin of rheology and captures nonlinear rheological characteristics. This model can predict the entire time-history mechanical behavior of clays with different mineral compositions across the three stages of instantaneous deformation, decay rheology, and steady-state rheology under different shear stress levels using a single set of parameters. Validation was performed through direct shear rheological tests under 50 working conditions for five types of clay specimens, demonstrating good consistency between the model calculations and experimental results. The unified rheological model reveals the material origin and physical essence of clay rheology, demonstrates high universality, and advances the understanding of the influence of mineral composition on rheology from the current phenomenological qualitative description to quantitative calculation for the first time, significantly enhancing its engineering application value. This provides a more reliable tool for predicting long-term deformation and assessing the stability of clay foundations. Full article

Granite is widely used in buildings, stone carvings, and sculptures, where long-term durability is strongly influenced by the micromechanical behavior of its constituent minerals and mineral interfaces. However, conventional rock mechanics tests cannot resolve the mechanical heterogeneity at the mineral scale, particularly at mineral interfaces. To address this limitation, a systematic nanoindentation study was conducted to quantitatively characterize the elastic modulus, hardness, creep behavior, residual deformation, and fracture toughness of both individual minerals and mineral interfaces in granite, and to clarify their mechanical contrasts and interrelationships. The results show that the constituent minerals quartz, feldspar, and biotite exhibit elastic modulus of 121.9 GPa, 115.6 GPa, and 66.3 GPa, respectively. Quartz and feldspar show relatively better mechanical properties, whereas biotite exhibits the weakest mechanical behavior. Hardness shows the same trend. In contrast, creep displacement and residual indentation depth follow the opposite order, i.e., quartz < feldspar < biotite. In addition, the elastic modulus and hardness of mineral interfaces are lower than those of the adjacent minerals, whereas their creep displacement and residual indentation depth are higher. The dispersion of these micromechanical parameters for mineral interfaces is generally greater than that of the adjacent minerals. The fracture toughness values of both minerals and mineral interfaces were also obtained: mineral fracture toughness ranges from 3.1 to 6.2 MPa·m^0.5, while mineral interfaces range from 0.7 to 4.3 MPa·m^0.5. Further analysis of the micromechanical parameters indicates that elastic modulus, hardness, and fracture toughness exhibit clear positive correlations among minerals, mineral interfaces, and the mineral aggregate. Comparatively, the correlations are strongest for minerals and weakest for mineral interfaces. Full article

To enhance the rheological properties and engineering applicability of fully solid waste filling slurry, this study uses iron tailings sand as aggregate and slag, steel slag, and desulfurization ash as cementing materials. Through a central composite design experiment, the synergistic regulatory effects of steel slag (10~30%) and desulfurization ash (10~30%) on the slurry’s rheological and strength properties were systematically investigated. The yield stress and plastic viscosity of the slurry were quantified based on the Bingham fluid model, using expansion tests and L-tube models, while isothermal calorimetry analysis and microscopic image processing revealed the underlying micro-mechanisms. The results show that when both steel slag and desulfurization ash contents are 20%, the cured specimen prepared from the slurry achieves an optimal 28-day uniaxial compressive strength of 5.90 MPa at 28 days, with yield stress and plastic viscosity of 146.71 Pa and 3.04 Pa·s, respectively. Micro-mechanistic analysis revealed that desulfurization ash effectively reduced the yield stress by up to 38% (from 196.04 Pa to 90.01 Pa) and increased the fractal dimension of flocculated structures to 1.906, thereby optimizing initial flowability. Conversely, steel slag increased the yield stress but decreased plastic viscosity, enhancing structural stability, and regulating the later hydration process. The loop tests confirmed the good transport performance and engineering adaptability of the optimized mix, achieving a cost reduction of up to 65% compared to cement-based systems. Full article

Addressing the challenges of multi-parameter interactions and unclear micro-mechanisms in poplar biomass panel manufacturing, this study employed a multi-scale approach integrating statistical optimization, microstructural characterization, and mechanism validation. A central composite design was used to investigate the effects of pressing time, pressure, and baking temperature (conditioning step) on modulus of rupture (MOR), modulus of elasticity (MOE), water absorption (WA), and thickness swelling (TS), establishing predictive models for multi-objective performance. Quantitative SEM analysis correlated macroscopic properties with microstructural parameters (porosity, pore size distribution, fiber–fiber contact ratio), elucidating how process conditions govern performance via interface quality and material densification. The optimized parameters yielded panels with MOR of 30.04 MPa, MOE of 10,716 MPa, WA of 4.98%, and TS of 1.75%. Modifier incorporation enhanced MOR and MOE by 23.10% and 26.38%, respectively, while reducing WA and TS by 50.59% and 29.89%. SEM confirmed an improvement in fiber–matrix interfacial bonding under optimized conditions. Environmental emission and combustion tests validated compliance with green development principles. This work establishes a cross-scale framework linking processing, microstructure, and performance, offering theoretical foundations for green manufacturing of high-performance biomass panels. Full article

To investigate the improvement effect of sodium polyacrylate on the shear strength of silty clay, this study explores the curing treatment of silty clay using sodium polyacrylate. Liquid-plastic limit tests and triaxial shear tests were conducted to examine the impact of sodium polyacrylate on the liquid-plastic limits and shear strength of silty clay, as well as to determine the optimal dosage. Additionally, low-field nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) tests were performed to further reveal the micro-mechanism of sodium polyacrylate’s action. The results show that as the sodium polyacrylate content increases, the liquid-plastic limits of silty clay increase significantly. Compared to untreated samples, when the sodium polyacrylate content is 7%, the liquid limit and plastic limit increase by 132.7% and 167.3%, respectively. Meanwhile, the cohesion of the modified samples increases with the sodium polyacrylate content, while the internal friction angle first increases and then decreases. When the sodium polyacrylate content rises from 0% to 7%, the cohesion and internal friction angles of the modified samples increase by 522.9% and 70.6%, respectively. Through comprehensive analysis of the experimental results, it was determined that the optimal dosage of sodium polyacrylate is 5%. Microstructural analysis indicates that sodium polyacrylate interacts with soil particles through hydrogen bonding and ion bridging, filling the pores between particles and encapsulating their surfaces. This improves the pore structure of the soil and enhances the bonding strength between particles. This study provides a theoretical basis for the application of sodium polyacrylate in soft soil improvement. Full article

Carbon fiber-reinforced thermoplastic composites (CFRTP) are widely used in automotive, aerospace, and other industries due to their lightweight, high specific strength, recyclability, and superior thermal properties. However, their non-homogeneity and anisotropy present challenging machining characteristics, often leading to damage that deteriorates component performance. It is imperative to conduct numerical simulation and experimental studies on CFRTP to systematically analyze the relationship between cutting mechanisms and the surface integrity of CFRTP. This study aimed to establish an innovative three-dimensional micro-scale cutting numerical model that integrates the differentiated constitutive behaviors and damage criteria of carbon fibers, matrices, and fiber–matrix interfaces—enabling precise characterization of micro-scale damage evolution during cutting. By combining simulation with experimental verification, it unveils the material removal mechanisms and processing damage causes of CF/PEEK, and further pioneers the quantification of the gradient correlation between fiber orientations (0°, 45°, 90°, and 135°) and fracture modes, cutting forces, and surface integrity, thereby addressing the gap of micro-mechanism and quantitative analysis in CFRTP machining. The micro-scale damage mechanisms revealed by the model directly reflect the intrinsic response of individual fibers in the tow, and the collective effect of these micro-behaviors determines the macro-scale machining performance observed in the experiments. A right-angle cutting experiment was conducted to validate the accuracy of the micro-scale numerical model. The mechanisms of fiber fracture, damage patterns, and chip morphology were systematically compared. The experimental results demonstrate good agreement with the outcomes of the numerical simulations. This study aims to bridge the gap between theoretical understanding and practical application of the cutting mechanisms in CFRTP, providing valuable insights for advancements in manufacturing processes. Full article

Industrial conveyor systems commonly use steel flight bars, which can account for nearly 50% of the total system mass and significantly affect energy consumption. This study investigates epoxy matrix composites reinforced with glass, carbon, and Kevlar fibers as lightweight alternatives to steel flight bars. A multiscale analytical approach combining micromechanics, Classical Laminate Theory (CLT), and ply-level failure criteria is applied to evaluate the structural response under an industrial bending moment of 342.02 N·m. Tensile tests on vacuum-infused woven glass/epoxy laminates are used to validate micromechanical assumptions and calibrate elastic properties. Ply-wise analysis shows that carbon/epoxy laminates exhibit the lowest longitudinal stresses (≈43 MPa), followed by Kevlar/epoxy (≈53 MPa) and glass/epoxy (≈95 MPa), all well below their respective strength limits. Replacing steel flight bars (4.64 t) with composite alternatives reduces the moving mass to 0.68–0.82 t, corresponding to an 82–85% reduction. This mass reduction significantly lowers the required mechanical power, resulting in an estimated annual energy saving of R$ 8812.80 under continuous operation. Overall, the results demonstrate that polymer-matrix composite flight bars are structurally safe and energetically advantageous, with carbon/epoxy providing the highest mechanical efficiency. Full article

Zinc(II) bis(8-hydroxyquinolinate) (Zn(HQ)₂) and 1,10-phenanthroline (phen) were combined to fabricate an organic semiconductor in a bulk heterojunction architecture and subsequently embedded in a poly 3,4-ethylene dioxythiophene–polystyrene sulfonate (PEDOT–PSS) matrix. The resulting Zn(HQ)₂-phen/PEDOT–PSS was deposited as a film upon tin-oxide-coated glass and graphite-covered Tetra Pak (TP)-recycled substrates for the manufacture of organic photoconductive devices. The topographical and micromechanical characteristics of the hybrid films were assessed by atomic force microscopy, with an average roughness of 5.6 nm, maximum tensile strength of 7.95 MPa, and Knoop microhardness of 14.7. The fundamental energy gap (E_g) was determined employing the Kubelka–Munk function, with E_g of 3.5–3.8 eV. These results were complemented with a computational DFT molecular orbital analysis of the species involved in the hybrid semiconductor. The devices were electrically characterized under UV irradiation conditions, obtaining the current–voltage and power–voltage relationships. The maximum current in the TP–graphite device is 1.8 × 10⁻² A and 1.1 × 10⁻² A in the device on glass–ITO. Zn(HQ)₂-phen/PEDOT–PSS film presents its own operating regimes relating to a photoconductor or flexible photoresistor. The power in the device on glass–ITO is 120 mW and 113 mW for shortwave and longwave, respectively, and in the device on TP–graphite, it is 198 mW and 139 mW. Full article

This study addresses the major engineering challenges of leaving roadways along the goaf in shallow-buried coal seam tunnels through water-bearing soft rock. It focuses on three core issues: the mechanism of rock mass softening upon water exposure, large-deformation control, and directional pressure relief technology. By integrating laboratory testing, theoretical analysis, numerical simulation, and field testing methods, the evolution of macro- and micro-mechanical properties of rock under water–rock interaction can be studied. The research developed constant-resistance large-deformation rock bolts with “yielding within resistance and resisting within yielding” characteristics, revealed the mechanism of directional fracturing through shaped charge blasting, and proposed a synergistic control technology for along-the-goal rib retention: “shaped charge blasting for roof fracturing and pressure relief + reinforced rib support + debris retention devices.” Research findings indicate: increased sandstone water content triggers dissolution of calcareous cement and expansion of clay minerals, leading to rock strength degradation and accelerated deformation, yet the failure mode remains uniaxial shear failure. The developed constant-resistance large-deformation anchor core device maintains a stable working resistance of approximately 350 kN within a 396–405 mm tensile deformation range, significantly enhancing the support system’s crack-resistant capacity under pressure. The focused jet directs cracks to penetrate along predetermined paths, forming planar damage zones and effectively suppressing vertical damage to the surrounding rock. Based on field monitoring, the tunnel was divided into advance support zones, temporary support zones, and stable tunnel sections, enabling a differentiated support scheme. The engineering application achieved stable tunnel retention and safe reuse. This study provides key theoretical foundations and technical approaches for controlling rock mass stability in similar tunnel conditions. Full article