Journal of Central South University最新文献

This study aims to evaluate the solar and wind energy potential across Razavi Khorasan Province, Iran, with a specific focus on the Khaf region. A preliminary assessment of mean solar radiation, mean wind speeds, and Weibull distribution parameters was conducted for different towns and zones within the province. The findings showed that Khaf has favorable characteristics for further analysis. The solar and wind energy metrics examined include global horizontal irradiance, clearness index, wind rose patterns, and turbulence intensity. At a height of 40 m, Khaf’s wind power density reached 1650 W/m², indicating exceptional wind energy generation potential. Additionally, Khaf received an average annual solar radiation of 2046 kW·h/m², representing significant solar energy potential. Harnessing these substantial renewable resources in Khaf could allow Razavi Khorasan Province to reduce reliance on fossil fuels, improve energy sustainability, and mitigate climate change impacts. This research contributes an in-depth assessment of Razavi Khorasan’s solar and wind energy potential, particularly for the promising Khaf region. Further work may examine optimal sites for renewable energy projects and grid integration strategies to leverage these resources.

Dilatancy is a fundamental volumetric growth behavior observed during loading and serves as a key index to comprehending the intricate nonlinear behavior and constitutive equation structure of rock. This study focuses on Jinping marble obtained from the Jinping Underground Laboratory in China at a depth of 2400 m. Various uniaxial and triaxial tests at different strain rates, along with constant confining pressure tests and reduced confining pressure tests under different confining pressures were conducted to analyze the mechanical response and dilatancy characteristics of the marble under four stress paths. Subsequently, a new empirical dilatancy coefficient is proposed based on the energy dissipation method. The results show that brittle failure characteristics of marble under uniaxial compression are more obvious with the strain rate increasing, and plastic failure characteristics of marble under triaxial compression are gradually strengthened. Furthermore, compared to the constant confining pressure, the volume expansion is relatively lower under unloading condition. The energy dissipation is closely linked to the process of dilatancy, with a rapid increase of dissipated energy coinciding with the beginning of dilatancy. A new empirical dilatancy coefficient is defined according to the change trend of energy dissipation rate curve, of which change trend is consistent with the actual dilatancy response in marble under different stress paths. The existing empirical and theoretical dilatancy models are analyzed, which shows that the empirical dilatancy coefficient based on the energy background is more universal.

The long-term storage of phosphate tailings will occupy a large amount of land, pollute soil and groundwater, thus, it is crucial to achieve the harmless disposal of phosphate tailings. In this study, high-performance geopolymers with compressive strength of 38.8 MPa were prepared by using phosphate tailings as the main raw material, fly ash as the active silicon-aluminum material, and water glass as the alkaline activator. The solid content of phosphate tailings and fly ash was 60% and 40%, respectively, and the water-cement ratio was 0.22. The results of XRD, FTIR, SEM-EDS and XPS show that the reactivity of phosphate tailings with alkaline activator is weak, and the silicon-aluminum material can react with alkaline activator to form zeolite and gel, and encapsulate/cover the phosphate tailings to form a dense phosphate tailings-based geopolymer. During the formation of geopolymers, part of the aluminum-oxygen tetrahedron replaced the silicon-oxygen tetrahedron, causing the polycondensation reaction between geopolymers and increasing the strength of geopolymers. The leaching toxicity test results show that the geopolymer has a good solid sealing effect on heavy metal ions. The preparation of geopolymer from phosphate tailings is an important way to alleviate the storage pressure and realize the resource utilization of phosphate tailings.

The tunnel subjected to strike-slip fault dislocation exhibits severe and catastrophic damage. The existing analysis models frequently assume uniform fault displacement and fixed fault plane position. In contrast, post-earthquake observations indicate that the displacement near the fault zone is typically nonuniform, and the fault plane position is uncertain. In this study, we first established a series of improved governing equations to analyze the mechanical response of tunnels under strike-slip fault dislocation. The proposed methodology incorporated key factors such as nonuniform fault displacement and uncertain fault plane position into the governing equations, thereby significantly enhancing the applicability range and accuracy of the model. In contrast to previous analytical models, the maximum computational error has decreased from 57.1% to 1.1%. Subsequently, we conducted a rigorous validation of the proposed methodology by undertaking a comparative analysis with a 3D finite element numerical model, and the results from both approaches exhibited a high degree of qualitative and quantitative agreement with a maximum error of 9.9%. Finally, the proposed methodology was utilized to perform a parametric analysis to explore the effects of various parameters, such as fault displacement, fault zone width, fault zone strength, the ratio of maximum fault displacement of the hanging wall to the footwall, and fault plane position, on the response of tunnels subjected to strike-slip fault dislocation. The findings indicate a progressive increase in the peak internal forces of the tunnel with the rise in fault displacement and fault zone strength. Conversely, an augmentation in fault zone width is found to contribute to a decrease in the peak internal forces. For example, for a fault zone width of 10 m, the peak values of bending moment, shear force, and axial force are approximately 46.9%, 102.4%, and 28.7% higher, respectively, compared to those observed for a fault zone width of 50 m. Furthermore, the position of the peak internal forces is influenced by variations in the ratio of maximum fault displacement of the hanging wall to footwall and the fault plane location, while the peak values of shear force and axial force always align with the fault plane. The maximum peak internal forces are observed when the footwall exclusively bears the entirety of the fault displacement, corresponding to a ratio of 0: 1. The peak values of bending moment, shear force, and axial force for the ratio of 0:1 amount to approximately 123.8%, 148.6%, and 111.1% of those for the ratio of 0.5:0.5, respectively.

This study considers an MHD Jeffery-Hamel nanofluid flow with distinct nanoparticles such as copper, Al₂O₃ and SiO₂ between two rigid non-parallel plane walls with the fuzzy extension of the generalized dual parametric homotopy algorithm. The nanofluids have been formulated to enhance the thermophysical characteristics of fluids, including thermal diffusivity, conductivity, convective heat transfer coefficients and viscosity. Due to the presence of distinct nanofluids, a change in the value of volume fraction occurs that influences the velocity profiles of the flow. The short value of nanoparticles volume fraction is considered an uncertain parameter and represented in a triangular fuzzy number range among [0.0, 0.1, 0.2]. A novel generalized dual parametric homotopy algorithm with fuzzy extension is used here to study the fuzzy velocities at various channel positions. Finally, the effectiveness of the proposed approach has been demonstrated through a comparison with the available results in the crisp case.

In this study, the Mg-3Zn-0.5Zr-χNd (χ=0, 0.6) alloys were subjected to final rolling treatment with large deformation of 50%. The impact of annealing temperatures on the microstructure and mechanical properties was investigated. The rolled Mg-3Zn-0.5Zr-0.6Nd alloy exhibited an ultimate tensile strength of 386 MPa, a yield strength of 361 MPa, and an elongation of 7.1%. Annealing at different temperatures resulted in reduced strength and obviously increased elongation for both alloys. Optimal mechanical properties for the Mg-3Zn-0.5Zr-0.6Nd alloy were achieved after annealing at 200 °C, with an ultimate tensile strength of 287 MPa, a yield strength of 235 MPa, and an elongation of 26.1%. The numerous deformed microstructures, twins, and precipitated phases in the rolled alloy could impede the deformation at room temperature and increase the work hardening rate. After annealing, a decrease in the work hardening effect and an increase in the dynamic recovery effect were obtained due to the formation of fine equiaxed grains, and the increased volume fraction of precipitated phases, which significantly improved the elongation of the alloy. Additionally, the addition of Nd element could enhance the annealing recrystallization rate, reduce the Schmid factor difference between basal and prismatic slip systems, facilitate multi-system slip initiation and improve the alloy plasticity.

Heat and mass transfer of a circular-shaped porous moist object inside a two-dimensional triangle cavity is investigated by using finite element method. The porous object is considered to be a moist food sample, located in the middle of the cavity with inlet and outlet ports with different configurations of inlet/outlet ports. Convective drying performance is numerically assessed for different values of Reynolds numbers (between 50 and 250), dry air inlet temperature (between 40 and 80 °C) and different locations of the port. It is observed that changing the port locations has significant impacts on the flow recirculaitons inside the triangular chamber while convective drying performance is highly affected. The moisture content reduces with longer time and for higher Reynolds number (Re) values. Case P4 where inlet and outlet ports are in the middle of the walls provides the most effective configuration in terms of convective drying performance while the worst case is seen for P1 case where inlet and outlet are closer to the corners of the chamber. There is a 192% difference between the moisture reduction of these two cases at Re=250, T=80 °C and t=120 min.

Manganese ferrite (MnFe₂O₄) has the advantages of simple preparation, high resistivity, and high crystal symmetry. Herein, we have developed an electrochemical sensor utilizing graphene and MnFe₂O₄ nanocomposites modified glassy carbon electrode (GCE), which is very efficient and sensitive to detect bisphenol A (BPA). MnFe₂O₄/graphene (GR) was synthesized by immobilizing the MnFe₂O₄ microspheres on the graphene nanosheets via a simple one-pot solvothermal method. The morphology and structure of the MnFe₂O₄/GR nanocomposite have been characterized through scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). In addition, electrochemical properties of the modified materials are comparably explored by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). Under the optimal conditions, the proposed electrochemical sensor for the detection of BPA has a linear range of 0.8–400 µmol/L and a detection limit of 0.0235 µmol/L (S/N=3) with high sensitivity, good selectivity and high stability. In addition, the proposed sensor was used to measure the content of BPA in real water samples with a recovery rate of 97.94%–104.56%. At present, the synthesis of MnFe₂O₄/GR provides more opportunities for the electrochemical detection of BPA in practical applications.

The evolution of mechanical properties, localized corrosion resistance of a high purity Al-Zn-Mg-Cu alloy during non-isothermal aging (NIA) was investigated by hardness test, electrical conductivity test, tensile test, intergranular corrosion test, exfoliation corrosion test, slow strain rate tensile test and electrochemical test, and the mechanism has been discussed based on microstructure examination by optical microscopy, electron back scattered diffraction, scanning electron microscopy and scanning transmission electron microscopy. The NIA treatment includes a heating stage from 40 °C to 180 °C with a rate of 20 °C/h and a cooling stage from 180 °C to 40 °C with a rate of 10 °C/h. The results show that the hardness and strength increase rapidly during the heating stage of NIA since the increasing temperature favors the nucleation and the growth of strengthening precipitates and promotes the transformation of Guinier-Preston (GPI) zones to η′ phase. During the cooling stage, the sizes of η′ phase increase with a little change in the number density, leading to a further slight increase of the hardness and strength. As NIA proceeds, the corroded morphology in the alloy changes from a layering feature to a wavy feature, the maximum corrosion depth decreases, and the reason has been analyzed based on the microstructural and microchemical feature of precipitates at grain boundaries and subgrain boundaries.

The low-cost Fe-Cu, Fe-Ni, and Cu-based high-entropy alloys exhibit a widespread utilization prospect. However, these potential applications have been limited by their low strength. In this study, a novel Fe₃₁Cu₃₁Ni₂₈Al₄Ti₃Co₃ immiscible high-entropy alloy (HEA) was developed. After vacuum arc melting and copper mold suction casting, this HEA exhibits a unique phase separation microstructure, which consists of striped Cu-rich regions and Fe-rich region. Further magnification of the striped Cu-rich region reveals that it is composed of a Cu-rich dot-like phase and a Fe-rich region. The aging alloy is further strengthened by a L1₂-Ni₃(AlTi) nanoprecipitates, achieving excellent yield strength (1185 MPa) and uniform ductility (∼8.8%). The differential distribution of the L1₂ nanoprecipitate in the striped Cu-rich region and the external Fe-rich region increased the strength difference between these two regions, which increased the strain gradient and thus improved hetero-deformation induced (HDI) hardening. This work provides a new route to improve the HDI hardening of Fe-Cu alloys.