A new flower-like Bi@MoP/NC composite is prepared using a two-step in situ polymerization process, followed by a phosphorization reaction. In this unique architecture, the MoP nanoparticles are embedded in an N-doped carbon layer and coated on the surface of the Bi core to form a flower-like structure. Similar to this MoP/C coating, MoP facilitates rapid ion diffusion and enhances the mechanical flexibility of the carbon layer. Therefore, the MoP/C composite layer can effectively improve the sodium storage reaction kinetics and buffer the volume change of Bi during sodiation/desodiation. Moreover, the flower-like structure can provide fast sodium ion diffusion channels and dissipate the inner stress during the sodiation/desodiation process. Accordingly, the Bi@MoP/NC composite shows outstanding sodium storage performance, including excellent long-term cycling stability (299.6 mAh g−1 after 1500 cycles at 2.0 A g−1) and superior rate capability (288.6 mAh g−1 even at 10.0 A g−1).
Deep backfill mining requires understanding the mechanical behavior and damage evolution of coal-based solid waste cemented paste backfill (CSW-CPB). This study investigated the effects of slurry concentration, coal gangue (CG) size, CG/cement (CG/C) ratio, and fly ash/cement (FA/C) ratio on strength, energy evolution, and constitutive modeling. The results show that slurry concentration and FA/C ratio positively regulate strength, while CG/C ratio and CG size are negative regulators. Strain energy evolution comprises four stages (non-damage, stable growth, accelerated growth, and failure), corresponding to the stress – strain phases. Peak energy indices reveal that high slurry concentration increases total energy and elastic energy ratio while reducing the brittleness index; optimizing FA/C ratio (4) and fine CG gradation prolongs the yield plateau, promotes progressive dissipation, and transforms failure from brittle to ductile. A moderate CG/C ratio (6) maximizes elastic energy ratio (81.4
Curved tunnels are critical weak points in seismic design due to geometric coupling and high dynamic sensitivity. While current seismic assessment methods mainly focus on transverse responses, simplified analytical models for longitudinal behavior, especially those accounting for deformation joints, remain limited. A dual-criterion vulnerable-zone identification method, based on a moment-capacity ratio and joint-opening displacement, is established and applied to quantitatively analyze the influence of tunnel curvature, joint stiffness, traveling-wave velocity, and foundation stiffness on the spatial distribution of vulnerable zones. The results show that the vicinity of deformation joints is an intrinsic weak region, whose extent shrinks with increasing foundation stiffness but never disappears. To address this gap, this study develops a longitudinal analytical model for curved tunnels with deformation joints. The tunnel is idealized as a finite-length, curved Euler-Bernoulli beam resting on a two-parameter Pasternak-type viscoelastic foundation. The governing equations are derived using viscoelastic foundation beam theory, with joint deformations (shear dislocation and flexural rotation) incorporated via a virtual force formulation. Closed-form dynamic solutions are obtained via modal superposition and validated through degeneration analysis and finite element simulations. A parametric study examines the effects of joint stiffness, tunnel curvature radius, traveling-wave velocity, and foundation stiffness, complemented by a quantitative sensitivity analysis that ranks the relative influence of parameter uncertainties on the peak dynamic response. The results reveal the governing mechanical mechanisms of these parameters and theoretically confirm the critical role of joints in inducing discontinuous dynamic responses. This work advances the understanding of soil-structure interaction in curved tunnel systems and provides a practical analytical framework for seismic design and vulnerability assessment of jointed curved tunnels under realistic engineering conditions.
The process mineralogy and oxidative alkaline leaching kinetics of copper smelting dust were studied. Mineralogical analysis showed that Cu, Pb, and Zn mainly exist as sulfates, while most As is present as As2O3. The metals and As are uniformly distributed and intermingled, with acid-soluble and acid-insoluble phases intricately embedded, which may impact leaching and separation. Under the condition of particle size of 53–74 µm, leaching temperature of 90 µC, leaching time of 60 min, NaOH concentration of 3.5 mol/L, a liquid-solid ratio of 8:1, the molar mass ratio of H2O2 to As2O3 being 1.2, and a constant stirring speed of 300 r·min−1, the leaching efficiencies of the As, Pb and Zn can reach 97.27
To address the challenges of complex preparation procedures, high organic solvent consumption, and poor environmental stability of products in conventional phosphor synthesis, this study proposes a simple, low-cost, solventfree one-step melt synthesis strategy, by which a series of Zn2+-doped manganese-based coordination polymer phosphors, Mn1−xZnx(OAc)2 (OAc=acetate), were prepared. During heating, Mn(OAc)2·4H2O releases its crystallization water to form a homogeneous molten phase, thereby yielding octahedrally coordinated anhydrous Mn(OAc)2. Systematic investigations reveal that the optimal Zn2+ doping concentration (x=0.2) significantly enhances luminescence performance by suppressing defect-related non-radiative decay pathways and mitigating energy transfer between Mn2+ ions. The optimized Mn0.8Zn0.2(OAc)2 phosphor achieves a photoluminescence quantum yield of 28.7
Based on the typical meteorological characteristics of the Sichuan-Tibet Railway, the three-dimensional compressible SST k- ω turbulence model and overset mesh technology were adopted to investigate the pressure characteristics of a full-scale eight-carriage train passing through a single-track tunnel. The rationality of the simulation method was verified through comparison with experimental results from the reference. A method combining the improved Hilbert-Huang Transform (HHT) with Proper Orthogonal Decomposition (POD) was proposed to study the pressure field structures at the head and tail trains. Finally, the sliding window-based permutation entropy (SWPE) was introduced to quantify the disorder degree of the flow field. The results indicate that when a train is traveling through a tunnel, for the head train, the pressure wave dominates the primary mode and stimulates a strong response in the bogie; for the tail train, it couples with and amplifies the serpentine motion of the airflow around the bogie. From a dynamic perspective, the pressure waves promote the flow transformation into a more ordered and low-entropy state.
Rock mass discontinuity characterization is essential for stability evaluation and discrete fracture network (DFN) modeling, but conventional field measurements are labor-intensive and hazardous, while many point-cloud-based methods still rely on handcrafted descriptors and lack a direct pathway for converting recognition results into engineering parameters. To address these limitations, this study proposes a Rock Mass Discontinuity (RMD) framework for automated engineering-oriented discontinuity characterization from point clouds. The framework is a task-decoupled pipeline with three stages: sparse voxel-based discontinuity-set segmentation, instance-level geometric partitioning, and geometry-constrained parameter extraction. In the segmentation stage, a point – voxel – point feature learning strategy is adopted to identify discontinuity sets from XYZ-only point cloud input. Based on the segmented discontinuity sets, PCA-based plane normal estimation and DBSCAN-based intra-set clustering are further performed to derive key engineering parameters, including dip direction, dip angle, trace length, normal spacing, and DFN-style geometric representations. Tests on a road-cut slope and an underground mine face show improved semantic segmentation over PointNet++ in the road-cut case and feasible application under more fragmented underground conditions. The extracted dominant orientations are broadly consistent with DSE or field references, indicating that RMD offers a practical pathway from point-cloud recognition to engineering discontinuity parameters and preliminary DFN-style representation.
Developing high-efficiency, stable electrocatalysts for the oxygen evolution reaction (OER) is pivotal for enabling next-generation energy technologies. NiAl alloys demonstrate potential application value in electrochemical field. However, their intrinsic electrocatalytic activity is limited. Reports indicate that elemental doping and CV activation may enhance electrocatalytic activity. Based on this, this study investigates the electrochemical properties of NiAl and NiCuAl alloys, elucidating the synergistic mechanism between Cu doping and CV activation. Porous NiAl and NiCuAl alloy samples were prepared using powder metallurgy. CV activation was performed on the samples in a 1 mol/L KOH solution under a three-electrode system. The results indicate that: 1) CV activation drives surface rearrangement of the NiCuAl samples, promoting uniform elemental distribution and forming an active Ni-oxyhydroxide layer; 2) Compared to the activated NiAl catalyst, the activated NiCuAl catalyst exhibits superior oxygen evolution reaction kinetics, achieving a lower overpotential (310 mV) and a smaller Tafel slope (96.88 mV/dec) at a current density of 50 mA/cm2. Moreover, it maintains its activity for up to 72 hours in alkaline media; 3) The NiCuAl alloy forms more Ni oxyhydroxides due to the doping regulation effect of Cu.
An elastoplastic analytical solution is developed for excavation-induced disturbances in shallow-buried shield tunnels under the coupled constraints of segmental lining and synchronous grouting. A virtual columnar structure model is established, and an equivalent unloading ratio is formulated based on an excavation – grouting interface model. Based on static equilibrium, load transfer, and boundary conditions, analytical expressions are derived for the plastic zone radius and the elastoplastic stress and displacement fields in the initial geostatic stress field. The proposed solution is validated against classical analytical solutions and FEM results. Case analyses demonstrate that the constrained unloading ratio significantly affects the spatial distribution and evolution of excavation-induced stress and displacement fields. The proposed framework applies to different tunnel cross-sections and grouting conditions, providing a theoretical basis for evaluating construction-induced disturbances and engineering risks in shallow-buried shield tunnels.
The TiCp/Q690E composite offers excellent strength, toughness, and corrosion resistance, making it promising for marine engineering and shipbuilding. Investigating its hot deformation behavior and microstructure evolution is crucial for optimizing hot working processes and improving the material’s performance. In this study, isothermal compression tests were performed at temperatures ranging from 1000 to 1150 °C and at strain rates from 0.001 to 10 s−1 to investigate the influence of titanium carbide (TiC) particles on flow behavior, microstructure evolution, and dynamic recrystallization (DRX) mechanisms. The results indicate that the peak stress increases with the addition of TiC particles. The flow curves show DRX characteristics at strain rates ⩽1 s−1, whereas dynamic recovery (DRV) dominates at 10 s−1. A strain-compensated Arrhenius constitutive model was developed, which demonstrated high prediction accuracy with a correlation coefficient (R) of 0.9784 and an average absolute error (AARE) of 5.44
The migration of acidic and alkaline mine water significantly compromises rock structural integrity, posing risks to safe coal extraction. This study investigated the chemo-mechanical damage mechanism of sandstone subjected to 50 dry-wet cycles under varying pH conditions (pH 3–11). The experiments revealed that the fundamental cause of deterioration is the ionic dissolution of constituent minerals (e.g., feldspar and calcite) and the subsequent alteration of the microstructure. This chemical erosion drives surface roughening, mass loss, and the progressive evolution of micropores into mesopores and macropores. The damage severity followed the order: Acidic > Alkaline > Neutral. Quantitatively, porosity growth reached 4
The micro-pressure waves (MPWs) generated by a high-speed train entering a tunnel are a significant noise source affecting the acoustic environment near tunnel exits. Accurate prediction of MPW noise strongly depends on the selection of turbulence models and the treatment of transient impulsive sources. In this study, the generation of MPWs induced by a high-speed metro train was numerically simulated using delayed detached eddy simulation (DDES), based on the k-epsilon (k-ε), Shear stress transport k-omega (SST k-ω), Spalart-Allmaras (S-A) turbulence models, and large eddy simulation (LES). The comparison indicates that the DDES (SST k-ω) model achieves an appropriate balance between computational accuracy and efficiency, accurately reproducing the waveform and pressure gradient characteristics of MPWs. Furthermore, based on these results, the far-field radiation from MPW noise was computed using the acoustic finite element method (FEM). In the MPW noise, dipole noise dominated, with its energy concentrated below 20 Hz and a peak frequency of 4 Hz. An optimal time window method was also proposed, encompassing 95
Understanding the intrinsic relationship between microstructure and macroscopic properties under freeze-thaw (F–T) cycles is of great significance for advancing knowledge of soil-rock mixtures (SRM) in low-temperature environments. This study conducted F–T cycles, electrochemical impedance spectroscopy (EIS), and uniaxial compression mechanical tests on SRM with varying moisture contents. An equivalent circuit model of conductive paths was proposed, and the microstructure was characterized using the parameters of these paths. The paper examined the effects of varying moisture contents and F–T cycles on the characteristics of conductive paths and mechanical properties, exploring the underlying mechanisms. The results indicated that the increasing moisture content enlarged the cross-sectional area of CP and DSRP and enhanced the double-layer effect, while simultaneously reducing the ion concentration within DSRP. F–T cycling induced pore expansion and interconnection, resulting in increased contact areas and shortened lengths of CPP and CP, as well as increased contact areas and numbers of DSRP. The uniaxial strength degradation model based on ΔCDSRP(t) can be used to evaluate the peak strength after different cycles. Under F–T cycling, the expansion of DSRP exerted a deleterious effect on peak strength. Water – ice phase transitions increased the contact area of soil – rock cemented interfaces of DSRP and enhanced the double-layer effect.
To meet the higher requirements of high-speed trains operational stability under crosswind and improve the train’s resistance to overturning, this study investigated the effects of various side-airfoil (SA) configurations installed on the train leeward side wall (LWS). The Shear Stress Transfer k −ω (SST k − ω) turbulence model was used to simulate the aerodynamic performance of the train and the surrounding flow field. And there are four numerical side-airfoil configurations: Baseline (the original train model), N10 (the train with ten SAs), N9 (that with nine SAs), and N7 (that with seven SAs). The results reveal that the various side-airfoil configurations effectively enhance the anti-overturning performance of the train by decreasing both the lateral force and overturning moment; the lightweight configuration of the side-airfoils (SAs) expands the space for airflow development on the leeward side, thereby simultaneously altering the pressure distribution over the train and promoting a more gradual variation of the surrounding flow field; and the head and tail car configurations play a more dominant role in enhancing operational stability compared to the middle. Compared with the original train model (Case Baseline), Case N10 and Case N9 exhibit comparable performance, with the lateral force reductions of 5.7
In high contact ratio gearboxes, incipient vibration features induced by tooth broken faults may be masked by multi-tooth meshing characteristics. To address this challenge, the stiffness reduction caused by tooth broken faults is quantitatively evaluated, and the corresponding vibration characteristic evolution is systematically investigated in the high contact ratio double-helical star gear transmission system (HCR-DHSGTS). When tooth broken faults are introduced separately into the sun gear, planet gear, and ring, an analytical-finite element method is employed to calculate the time-varying meshing stiffness. By incorporating the time-varying meshing stiffness, a rigid-flexible coupling dynamic model is established. The component mode synthesis method is then applied to enhance computational efficiency. The proposed stiffness calculation method is verified by finite element analysis, and the proposed dynamic model is verified against the multibody dynamics simulations in ADAMS software. The results indicate that under tooth broken fault conditions, a progressive stiffness reduction is observed, accompanied by modulation sidebands around the gear meshing frequency and its harmonics. Under the same fault severity, the stiffness reduction is found to be more pronounced for the sun gear and ring gear than for the planet gear. Furthermore, two indicators of sideband energy ratio and sideband level factor are proposed. Subsequent analyses reveal that both indicators monotonically increase with the severity for all fault locations considered in this paper. These findings provide theoretical support and quantitative guidance for early warning and condition monitoring of high contact ratio gearboxes.
Shield tunnels are inherently discontinuous structures, whereas conventional longitudinal beam models generally idealize them as continuous systems and therefore cannot adequately capture the mechanical interactions at segment joints. To address this limitation, this paper proposes an improved longitudinal Timoshenko short beam spring model, LTSBSM, for shield tunnels. In the proposed model, each segment ring is represented by a Timoshenko short beam to account for shear deformation within the ring, while rotational, tensile, compressive, and shear springs are introduced at the inter-ring joints to characterize the coupled tension, compression, bending, and shear behavior, as well as the associated deformation discontinuities. Based on this framework, governing equations are established for overcrossing, undercrossing, and asymmetric thrust conditions, and a 10-point hybrid finite difference template is developed for the discontinuous tunnel joint system. The proposed model is then validated using three representative engineering cases. In the case studies, the joint-related parameters are first calibrated using a reference foundation elastic coefficient expression, and alternative empirical expressions are then compared on the same basis. The results show that the proposed model can capture both global tunnel deformation and local joint opening and dislocation under different loading conditions, while preserving the discontinuous longitudinal response of segmental shield tunnels. Different foundation elastic coefficient expressions generally produce similar spatial response patterns but noticeable differences in peak magnitude and influence range. Within the investigated range, increasing the soil elastic modulus Es, from 15 MPa to 60 MPa, reduces the peak tunnel heave from approximately 4.29 mm to 0.98 mm, whereas the scaling coefficients for joint rotational and shear stiffnesses mainly regulate the distribution of local joint opening and dislocation through rotational and shear restraint.
The cryogenic multi-directional forging (Cryo-MDF) technique enables aluminum alloys to achieve a remarkable strength-ductility synergy through unique microstructural evolution. The Cryo-MDF processed T6-6061 aluminum alloy attains a high tensile strength of 412 MPa while retaining an elongation of 10.5
Surrounding rock control of a withdrawal roadway (WR) in longwall mining is essential for ensuring equipment safety and completing equipment withdrawal. Under deep and complex geomechanical conditions, conventional support systems often fail to withstand the strong disturbance induced by hydraulic support (HS) withdrawal during the withdrawal stage (WS). In this study, the instability mechanism of the WR and the corresponding control technology were investigated through theoretical analysis, numerical simulation, and a physical model experiment monitored using digital image correlation (DIC). Based on the masonry-beam (MB) mechanical model of the key roof block, WR instability is attributed to the disruption of the original moment equilibrium of key block-B as HS restraint decreases during the WS, which drives block-B from a stable state to rotational instability. Therefore, effective regulation of the rotational motion of block-B is identified as the key requirement for maintaining surrounding rock stability. To control this failure mode, a coupled control strategy integrating directional pre-splitting roof cutting and pressure relief (DP-RCPR) and Negative Poisson’s Ratio(NPR) cable active support (NPRC-AS) is proposed. The experimental and numerical results indicate that directional pre-splitting cuts off the lateral mechanical linkage between adjacent key blocks and promotes stable contact between the main roof in the goaf and the caved gangue, so that the goaf evolves from a load source into a load-bearing structure. In addition, the NPR cables, characterized by constant resistance and large deformation capacity, provide high-resistance support for both the immediate roof and the main roof, thereby enhancing the integrity of the roof-bearing system. Field implementation demonstrates that the proposed core technologies effectively control WR deformation. The developed approach provides theoretical support and technical guidance for HS retreat under deep dynamic ground-pressure conditions.
This study systematically investigated the leaching efficacy and mechanisms of La3+ and Y3+ from the clay minerals kaolinite and halloysite by Aspergillus niger, Acidithiobacillus ferrooxidans, and typical metabolites (citric acid and protease). The results indicated that nearly complete leaching of rare earth ions was achieved by A. niger, A. ferrooxidans, their fermentation broths, and citric acid. A. niger dissolves rare earth ions mainly by secreting organic acids, which form soluble complexes to promote mineral dissolution and increase ion-exchange release. In contrast, A. ferrooxidans oxidizes elemental sulfur to generate sulfuric acid, significantly reducing the system’s pH and enhancing the leaching process. However, both microorganisms adsorbed free rare earth ions during the later stages of leaching, leading to a decrease in their concentrations in the solution. Citric acid significantly improved the solubility of rare earth elements through complexation, whereas proteases showed relatively poor leaching efficiency for clay minerals. Phase composition and surface functional group analyses revealed notable changes in the O-H and C=O groups of kaolinite and halloysite after treatment with microbes and their metabolites, which increased mineral reactivity. This research provides a theoretical basis and technical support for the green and efficient recovery of rare earth resources from clay minerals.
