Search Results (328)

Mismanagement of rural wastewater can lead to environmental contamination with the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Fungi with bioremediating potential constitute a sustainable alternative to decontaminate such wastewater before its reuse. This study evaluated the ability of Aspergillus oryzae pellets to remove 2,4-D from natural and sterile rural wastewater (i.e., with/without native microbiota). The pellets were produced by incubating conidial solutions of A. oryzae strains RCA2, RCA4, RCA5, and RCA10 in synthetic wastewater for 21 days at 25 °C. The wastewater samples were characterized physicochemically and microbiologically upon arrival at the laboratory. Afterwards, they were supplemented with 1, 2.5, or 5 mmol L⁻¹ of 2,4-D and inoculated with the pellets. Physicochemical characterization was repeated throughout the experiment. Herbicide removal and the presence of 2,4-D degradation intermediate, 2,4-dichlorophenol (2,4-DCP), were assessed through high-pressure liquid chromatography with UV/Vis detection (HPLC-UV) and mass spectrometry. At the beginning of the assay, the macro- and micronutrient content in the samples were suitable to sustain fungal growth. By the end, pH had increased and sodium and nitrate levels decreased in comparison with the control. RCA2, RCA4, and RCA10 removed over 80% of 2,4-D after 7 days of incubation, at the three herbicide concentrations tested. Moreover, wet fungal biomass had increased by the end of the assay. These findings demonstrate that RCA2, RCA4, and RCA10 can grow, form pellets, and remove 2,4-D in natural rural wastewater, which makes them potential candidates for bioremediation strategies aimed at improving the quality of water set to be reused. Full article

The growing disposal of used tyres and plastic waste in landfills poses a significant environmental challenge. This study investigates the potential of utilizing used tyre rubber and macro-synthetic fibres (MSFs) made from recycled plastics in fibre-reinforced rubberized concrete (RuFRC). Various percentages of tyre rubber shreds were used to replace coarse aggregates, calculated as 10%, 20%, and 30% of the volume of fine aggregates; fibre dosages (0%, 0.25%, 0.5%, 0.75%, and 1% by volume) were incorporated into the mix, and a series of physical, mechanical, and durability properties were evaluated. The results show that, as the fibre and rubber content increased, the slump of RuFRC decreased, with the lowest value obtained for concrete with 1% fibre and 30% rubber. The density of RuFRC decreases as the rubber percentage increases due to air voids and increased porosity caused by the rubber. The strength properties of RuFRC were found to decline with the increase in the rubber content, with mixes containing 30% rubber exhibiting reductions of about 60% in compressive strength, 27% in tensile strength, and 13% in flexural strength compared to the control specimen. Durability testing revealed that an increased rubber content led to higher water absorption, water penetration, and chloride ion permeability, with 30% rubber showing the highest values. However, lower rubber content (10%) and higher fibre dosages improved the durability characteristics, with water absorption reduced by up to 5% and shrinkage strains lowered by about 7%, indicating better compaction and bonding. These results indicate that RuFRC with moderate rubber and higher fibre content offers a promising balance between sustainability and performance. Full article

Fiber-reinforced resin matrix composites are generally composed of fibers and matrix with significantly different properties, which are non-uniform and anisotropic in nature. Macro-failure criteria generally view composite plies as a uniform whole and do not accurately reflect fiber- and matrix-scale failures. In this study, the interface phase effect between fiber and matrix has been introduced into the frame of trans-scale analysis to better model the failure process, and the equivalent mechanical property characterization model of the interface phase has also been established. Combined with the macro–micro-strain transfer method, the trans-scale correlation of the mechanical response of the composite laminates between the macro scale and the fiber, matrix and interface micro scale has been achieved. Based on the micro-scale failure criterion and the stiffness reduction strategy, the trans-scale failure analysis method of composite materials incorporating the interface phase effect has been developed, which can simultaneously predict the failure modes of the matrix, fiber and interface phase. A numerical implementation of the developed trans-scale failure analysis method considering interface phase was carried out using the Python and Abaqus 2020 joint simulation technique. Case studies were carried out for three material systems, and the prediction data of the developed trans-scale failure analysis methodology incorporating interface phase effects for composite materials, the prediction data of the Linde failure criterion and the experimental data were compared. The comparison with experimental data confirms that this method has good prediction accuracy, and compared with the Linde and Hashin failure methods, only it can predict the failure mode of the fiber–matrix interface. The case analysis shows that its prediction accuracy has been improved by about 2–3%. Full article

In order to explore the influence of the temperature gradient on rock failure degree during freezing and thawing, freeze–thaw-cycle tests were carried out on saturated red sandstone under the conditions of all-directional freeze–thaw and unidirectional freeze–thaw. The results show that the deformation behavior of saturated red sandstone during freeze–thaw cycles is significantly affected by freeze–thaw direction, and the redistribution of water during freeze–thaw cycles leads to significant strain variations. Macro-cracks caused by all-directional freeze–thaw are located in the center of the sample and crack from the inside out, while macro-cracks caused by unidirectional freeze–thaw are perpendicular to the temperature gradient direction and located in the lower part of the sample. Unidirectional freeze–thaw cycles cause the vertical inhomogeneity of the sample to be more obvious, and the uniaxial compressive strength of the sample decreases more significantly in the early stage. After 30 freeze–thaw cycles, the uniaxial strength of all-directional freeze–thaw and unidirectional freeze–thaw samples tends to be stable and virtually identical. The freeze–thaw cycles have seriously damaged the micro-structure of the sample, but the extent of damage to the cementing agents between particles is weaker than that caused by the all-directional freeze–thaw, owing to the seepage path formed in the pore water under unidirectional freeze–thaw conditions. Full article

In order to solve various problems in traditional roads and extend their service life, new road materials have become a research hotspot. Polyurethane prepolymers (PUPs) and ceramic fibers (CFs), as materials with unique properties, were chosen due to their synergistic effect: PUPs provide elasticity and gel-like behavior, while CFs contribute to structural stability and high-temperature resistance, making them ideal for enhancing asphalt performance. PUPs, a thermoplastic and elastic polyurethane gel material, not only enhance the flexibility and adhesion properties of asphalt but also significantly improve the structural stability of composite materials when synergistically combined with CF. Using response surface methodology, an optimized preparation scheme for PUP/CF composite-modified asphalt was investigated. Through aging tests, dynamic shear rate (DSR) testing, bending rate (BBR) testing, microstructure scanning (MSCR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and infrared spectroscopy (IR), the aging performance, rheological properties, permanent deformation resistance, microstructure, and modification mechanism of PUP/CF composite-modified asphalt were investigated. The results indicate that the optimal preparation scheme is a PUP content of 7.4%, a CF content of 2.1%, and a shear time of 40 min. The addition of the PUP and CF significantly enhances the asphalt’s aging resistance, and compared with single-CF-modified asphalt and base asphalt, the PUP/CF composite-modified asphalt exhibits superior high- and low-temperature rheological properties, demonstrating stronger strain recovery capability. The PUP forms a gel network structure in the material, effectively filling the gaps between CF and asphalt, enhancing interfacial bonding strength, and making the overall performance more stable. AFM microscopic morphology shows that PUP/CF composite-modified asphalt has more “honeycomb structures” than matrix asphalt and CF-modified asphalt, forming more structural asphalt and enhancing overall structural stability. This study indicates that the synergistic effect of PUP gel and CF significantly improves the macro and micro properties of asphalt. The PUP forms a three-dimensional elastic gel network in asphalt, improving adhesion and deformation resistance. Using response surface methodology, the optimal formulation (7.4% PUP, 2.1% CF) improves penetration (↓41.5%), softening point (↑6.7 °C), and ductility (↑9%), demonstrating the relevance of gel-based composites for asphalt modification. Full article

To comprehensively investigate the compressive behavior of basalt fiber-reinforced concrete (BFRC) subjected to multiple freeze–thaw cycles, a series of quasi-static and dynamic compression tests were conducted on BFRC at various fiber volume fractions and a wide strain rate range of 1 × 10⁻³–420 s⁻¹. The freeze–thaw deterioration characteristics of BFRC were analyzed from macro and micro perspectives. The influence of freeze–thaw degradation, strain rate effect, and fiber reinforcement effect on the mechanical performance of BFRC was investigated. It was found that when the fiber volume fraction was 0.2%, the fiber reinforcement performance of basalt fiber was optimal. By incorporating the damage factor of freeze–thaw cycles and the dynamic increase factor of strength into the Ottosen nonlinear elastic constitutive model, a dynamic constitutive model that considers the fiber content, strain rate enhancing effect, and freeze–thaw degradation influence was established. Full article

The predictive modeling of concrete degradation under freeze–thaw cycling remains a challenge due to complex damage mechanisms and limited simulation accuracy. A plastic damage constitutive model for fly ash concrete under freeze–thaw conditions was established based on experimental data and implemented via the concrete damage plasticity (CDP) model in ABAQUS. A modified stress–strain relationship and damage factor were introduced to describe mechanical deterioration across various freeze–thaw stages. Macro- and mesoscale finite element simulations were applied to simulate the stress–strain evolution, plastic deformation, and damage development. A validation against experimental data indicated a relatively high accuracy, with prediction errors of 1.61% at the macroscale and 5.81% at the mesoscale. The macroscale model effectively captures global stiffness degradation and strength loss, while the mesoscale model reveals the internal freeze–thaw damage mechanisms, including crack initiation and propagation. The results demonstrate the applicability of the proposed model for assessing freeze–thaw-induced damage in concrete structures exposed to cold environments. Full article

Long-term vibrations from metro trains can cause liquefaction of water-rich sandy soil foundations, affecting the safety of operational tunnels. However, existing liquefaction studies mainly focus on seismic loads, and the macro-meso-mechanical mechanisms of liquefaction induced by train vibration loads remain unclear, which hinders the establishment of effective liquefaction prediction and evaluation methods. To investigate the microscopic mechanisms underlying sand liquefaction caused by train-induced vibrations, this study employs PFC3D discrete element software in conjunction with laboratory experiments to analyze the microscopic parameters of the unit cell. The findings indicate that the coordination number, mechanical coordination number, porosity, contact force chains, and strain energy all decrease with increasing vibration frequency. Conversely, the pore pressure, anisotropy, and energy exhibit opposite trends, continuing until the sample reaches a state of liquefaction failure. Notably, when the dynamic stress amplitude increases or the loading frequency decreases, the rate of reduction in coordination number, mechanical coordination number, porosity, contact force chains, and strain energy becomes more pronounced. Similarly, the rate of increase in pore pressure and anisotropy is more significant under these conditions. The research findings can provide a reference for the design of metro projects and liquefaction mitigation measures, thereby enhancing the safety and reliability of urban metro transportation systems. Full article

Different from general underground engineering, the micro-damage prior to failure of the surrounding rock has a significant influence on the geological disposal of high-level radioactive waste. However, the quantitative research on pre-failure dilatancy damage characteristics and stress path influence of hard brittle rocks under high stress levels is insufficient currently, and especially, the stress path under simultaneous unloading of axial and confining pressures is rarely discussed. Therefore, three representative mechanical experimental studies were conducted on the Beishan granite in the pre-selected area for high-level radioactive waste (HLW) geological disposal in China, including increasing axial pressure with constant confining pressure (path I), increasing axial pressure with unloading confining pressure (path II), and simultaneous unloading of axial and confining pressures (path III). Using the deviatoric stress ratio as a reference, the evolution laws and characteristics of stress–strain relationships, deformation modulus, generalized Poisson’s ratio, dilatancy index, and dilation angle during the path bifurcation stage were quantitatively analyzed and compared. The results indicate that macro-deformation and the plastic dilatancy process exhibit strong path dependency. The critical value and growth gradient of the dilatancy parameter for path I are both the smallest, and the suppressive effect of the initial confining pressure is the most significant. The dilation gradient of path II is the largest, but the degree of dilatancy before the critical point is the smallest due to its susceptibility to fracture. The critical values of the dilatancy parameters for path III are the highest and are minimally affected by the initial confining pressure, indicating the most significant dilatancy properties. Establish the relationship between the deformation parameters and the crack-induced volumetric strain and define the damage variable accordingly. The critical damage state and the damage accumulation process under various stress paths were examined in detail. The results show that the damage evolution is obviously differentiated with the bifurcation of the stress paths, and three different types of damage curve clusters are formed, indicating that the damage accumulation path is highly dependent on the stress path. The research findings quantitatively reveal the differences in deformation response and damage characteristics of Beishan granite under varying stress paths, providing a foundation for studying the nonlinear mechanical behavior and damage failure mechanisms of hard brittle rock under complex loading conditions. Full article

Calcareous sands are widely distributed across the South China Sea’s continental shelf and coastlines. Understanding their mechanical behavior and microstructural evolution under cementation is critical for coastal engineering applications. While previous studies have investigated cemented calcareous sands, the comparative analyses of particle breakage and microstructural characteristics between cemented and pure sands remain limited. This study combines triaxial compression tests with X-ray CT scanning and Digital Volume Correlation analysis to systematically examine both material types. Pre- and post-loading CT scans enabled the detailed tracking of microstructural transformations. Results demonstrate that cemented specimens exhibit higher strength–stiffness properties with strain-softening behavior compared to pure sand under 200 kPa confining pressures. A quantitative analysis revealed greater particle breakage in cemented sand, while pure sand showed more pronounced increases in particle sphericity and the aspect ratio during deformation, accompanied by reduced porosity variation along specimen height (coefficient of variation decreased from 15.2% to 12.8% for pure sand. Microstructural analysis indicated moderate increases in pore sphericity and reduced anisotropy in both materials. Fractal dimension analysis demonstrated more significant structural reorganization in cemented sands. Both materials exhibited increases in key morphological parameters, including the throat equivalent radius, channel length, pore equivalent radius, and coordination number, with changes being more substantial in cemented sands. Within shear band regions, cemented sands displayed marked reductions in pore and throat quantities. These findings elucidate fundamental relationships between cementation effects and micro–macro mechanical responses, providing theoretical support for geotechnical applications involving calcareous sands. Full article

We present a comprehensive structural and thermomechanical investigation of N-salicylideneaniline, a Schiff base derivative that exhibits remarkable thermosalient phase transition behavior. By combining variable-temperature X-ray powder diffraction (VT-XRPD), differential scanning calorimetry (DSC), hot-stage microscopy, and Hirshfeld surface analysis, we reveal two distinct thermosalient mechanisms operating in different polymorphic forms. Form I displays pronounced anisotropic thermal expansion with negative strain along a principal axis, culminating in a sudden and explosive phase transition into Form IV. In contrast, Form III transforms more gradually through a microstrain accumulation mechanism. Fingerprint plots and contact evolution from Hirshfeld surface analysis further support this dual-mechanism model. These insights highlight the importance of integrating macro- and microscale structural descriptors to fully capture the mechanical behavior of responsive molecular solids. The findings not only enhance the fundamental understanding of thermosalience but also inform the rational design of functional materials for actuating and sensing applications. Full article

Edible mushrooms are macroscopic fungi that have been recognized as the “new superfoods” due to their high nutritional and medicinal values. The aim of this study was to develop and optimize a method for the wet digestion of edible mushrooms using a closed digestion block for the determination of macro- and micronutrients (Ca, Cr, Cu, Fe, K, Mg, Mn, Ni, and Zn) using microwave-induced plasma emission spectrometry (MIP OES). For the digestion of the samples, a 2³ factorial design was used to evaluate the amount of HNO₃ 65% (m m⁻¹), H₂O₂ 30% (m m⁻¹) and the digestion time, in 500 mg of the sample (dry and crushed) at 200° C. The method was applied to eleven species of edible or medicinal mushrooms (edible cultivated from wild strains, wild edible, and commercials medicinal). The average concentrations (in mg kg⁻¹) showed higher levels of K (1442.85–17,534.97), Mg (1295.40–13,550.72), Fe (11.33–27.38), Zn (28.86–36.09), and Mn (10.22–10.97). This study contributed to the determination of the multi-element composition and nutritional potential of edible mushrooms from Brazil. Full article

This study takes limestone crushed stone concrete as the research object and systematically investigates its mechanical property changes and microstructural damage characteristics under different confining pressures using triaxial compression tests, scanning electron microscope (SEM) tests, and digital image processing techniques. The results show that, in terms of macro-mechanical properties, as the confining pressure increases, the peak strength increases by 192.66%, the axial peak strain increases by 143.66%, the elastic modulus increases by 133.98%, and the ductility coefficient increases by 54.61%. In terms of microstructure, the porosity decreases by 64.35%, the maximum pore diameter decreases by 75.69%, the fractal dimension decreases by 19.56%, and the interfacial transition zone cracks gradually extend into the aggregate interior. The optimization of the microstructure makes the concrete more compact, reduces stress concentration, and thereby enhances the macro-mechanical properties. Additionally, the failure characteristics of the specimens shift from diagonal shear failure to compressive flow failure. According to the Mohr–Coulomb strength criterion, the calculated cohesion is 6.96 MPa, the internal friction angle is 38.89°, and the breakage angle is 25.53°. A regression analysis established a quantitative relationship between microstructural characteristics and macro-mechanical properties, revealing the significant impact of microstructural characteristics on macro-mechanical properties. Under low confining pressure, early volumetric expansion and rapid volumetric strain occur, with microcracks mainly concentrated at the aggregate interface that are relatively wide. Under high confining pressure, volumetric expansion is delayed, volumetric strain increases slowly, and microcracks extend into the interior of the aggregate, becoming finer and more dispersed. Full article

To investigate the effects of the strain rate and confinement on characteristic stresses and strength criterion in granite under static to quasi-static loading, triaxial compression tests were systematically conducted across strain rates of 10⁻⁶ to 10⁻² s⁻¹ and confining pressures of 0–40 MPa. Stress–strain curves, characteristic stresses, macro-fracture patterns, and dynamic strength criterion were analyzed. The experimental results indicate the following: (1) crack damage stress (σ_cd) and peak stress (σ_p) show strong linear correlations with logarithmic strain rate, while crack initiation stress (σ_ci) exhibits weaker rate dependence; (2) linear regression establishes characteristic stress ratios σ_ci = 0.58σ_p and σ_cd = 0.85σ_p; (3) macroscopic fractures transition from Y-shaped shear patterns under low confinement and strain rate conditions to X-shaped shear failures at higher confinement and strain rate; (4) the Mohr–Coulomb criterion effectively characterizes dynamic strength evolution in granite, with cohesion increasing 22% across tested strain rates while internal friction angle remains stable at around 50°; (5) variations in microcrack activity intensity during rock deformation stages result in the dynamic increase factor for characteristic stresses (CSDIF) of σ_ci being lower than σ_cd and σ_p. More importantly, σ_cd and σ_p exhibit CSDIF reductions as confining pressure increases. This differential behavior is explained by confinement-enhanced shear fracturing dominance during crack propagation stages, combined with the lower strain rate sensitivity of shear versus tensile fracture toughness. Full article

Urban transportation systems are increasingly strained by population growth, changing mobility patterns, and the need for sustainable infrastructure planning. The accurate modeling of urban trip generation is critical for effective and sustainable transportation planning, especially in the context of rapidly growing urban populations and evolving travel behaviors. This study investigated the application of advanced statistical methods and artificial intelligence-based techniques for forecasting urban travel demand. Erzincan, with a population of approximately 200,000, serves as a representative mid-sized city, offering valuable insights for transportation planning and traffic management. Data collected from various user groups, including households and university students, provide a comprehensive understanding of local travel behavior. Four predictive modeling techniques, linear regression, Poisson regression, negative binomial regression, and artificial neural networks (ANNs), were applied to the dataset, followed by a comparative performance evaluation. Additionally, a macro-level simulation was conducted using VISUM (Release 18.2.22) software to evaluate the current transportation network and assess the potential impacts of proposed improvement scenarios. The results show that the ANN model provided the highest predictive accuracy for household-based data (R² = 0.62), while the linear regression model yielded the best results for dormitory-based data (R² = 0.95). Furthermore, Poisson regression proved most effective in estimating the minimum trip generation time, which was estimated to be 22.77 min under simulated conditions. The study offers practical insights for transport planners and policymakers by demonstrating how predictive analytics and simulation tools can be integrated to address urban mobility challenges. Full article