Search Results (1,196)

Studying the slumping disintegration, movement speed, impact intensity, accumulation characteristics, and energy conversion laws of tower-column unstable rock masses (TCURM) is crucial for high-altitude rockfall hazard risk evaluation. Existing PFC-based rockfall simulations rarely target the unique “top-hard-bottom-weak” structural characteristics of TCURM and lack in-depth integration of on-site monitoring videos to verify dynamic evolution processes. Taking the large-scale collapse of W12^# unstable rock mass at Zengziyan, Jinfo Mountain in Chongqing as an example, a combination method of orthogonal test and PFC^3D discrete element simulation is used. Mesoscopic parameters are calibrated via comparison with on-site video and investigation data, accurately reproducing the entire slumping disintegration process and revealing its dynamic characteristics. Results confirm the simulation is basically consistent with field data, verifying the model and parameter rationality. The total duration from instability to stagnation is 121 s (15 s to impact the secondary steep cliff base, 106 s for debris accumulation). Movement speed time-histories of deteriorated and non-deteriorated zones are generally consistent, both exhibiting a “double-peak” feature. Rockfall impact force first increases, stabilizes in the middle, and declines to stability afterward, with a maximum of 2.1 × 10⁹ N. The kinetic energy curve also shows a “double-peak” distribution, closely related to the on-site two-level steep cliff morphology. The findings provide important references for analyzing the dynamic evolution of such rockfalls and designing disaster prevention/mitigation engineering. Full article

This study investigates the complex relationship between fracture patterns and acoustic emission (AE) mechanisms during triaxial deformation experiments on Westerly granite under various confining pressures (5, 10, 20, and 40 MPa). Using numerical simulations with the Particle Flow Code (PFC2D, 6.0, Itasca Consulting Group Inc, Minneapolis, USA), this research emphasizes the significant influence of confining pressure on crack development, AE events, spatiotemporal distribution, energy dissipation, and peak stress in the samples. AE source mechanisms, categorized into T-Type, C-Type, and S-Type, show the dominance of T-Type fractures during post-peak unstable failure and the emergence of C-Type fractures as precursors to critical damage. Additionally, increasing confining pressure is found to correlate with changes in fracture dynamics, evidenced by an increase in big events and a decrease in small events. The analysis of b-values across different pressures reveals fluctuations that indicate change in fracture features. Fractures originate in the model center and propagate towards both ends as loading progresses, ultimately leading to failure. In summary, these findings provide important insights into the fracture patterns of granite and the underlying mechanisms of AE release. Moreover, they carry practical implications for identifying failure precursors and for the potential application of early warning systems in rock engineering. Full article

To address the current research gap where studies on the failure mechanisms of fissured tunnels mainly focus on single tunnels with insufficient research on double tunnels, and to provide a scientific basis for disaster prevention and control of the Jinan Tunnel on Jinan Ring Expressway, this study investigates the mechanical behavior and failure characteristics of tunnel structures containing fissure–hole composite systems using experimental tests and numerical simulations. The crack initiation, propagation, and coalescence mechanisms are systematically analyzed to provide engineering references for tunnel design and stability assessment. Sand-based 3D printing technology was used to fabricate double-tunnel models with prefabricated fissures of different inclination angles α. Uniaxial compression tests were conducted, and crack evolution was monitored using DIC technology. Meanwhile, numerical simulation verification was performed based on the parallel bond (PB) model of the Discrete Element Method (PFC). The results show that the mechanical response of sand-based 3D-printed models conforms to the brittle characteristics of engineering rock masses. For models without fissures, cracks are preferentially initiated at the top and bottom of the tunnels. For models with fissures, the peak strength is the highest when α = 30° and 60°, and the lowest when α = 45° and 90°. As the fissure inclination angle increases, the tensile stress concentration shifts from the top and bottom of the tunnels and the middle of the fissure to the two ends of the fissure. The numerical simulation results are consistent with the experimental results and can accurately reproduce crack evolution. This study verifies the effectiveness of combining sand-based 3D printing with discrete element simulation, providing a reference for fissure prevention and control as well as operation and maintenance optimization of similar double-tunnel projects. Full article

Prenatal stress (PNS) predisposes individuals to mental disorders later in life. Adolescence is a period of heightened brain plasticity and vulnerability, when many mental disorders emerge, yet pharmacological strategies remain largely underexplored. In adult PNS rats, lurasidone (LUR) has been shown to reduce PNS-induced risk; however, its effects following adolescent administration remain unclear. To investigate the long-lasting effects of PNS and their modulation following sub-chronic LUR adolescent treatment, a whole-genome expression analysis of the prefrontal cortex (PFC) of adult male PNS rats was performed. Twelve PNS and eleven control rats were randomly assigned to receive vehicle or LUR from postnatal day (PND) 35 to 49 and sacrificed at PND 50. Partek Genomics Suite and Ingenuity Pathway Analysis were used for differential expression and pathway analyses. Within the PFC, PNS induced an upregulation of pathways involved in environmental information processing and in immune system-related pathways, which was reduced after LUR, as observed by IL-8 signaling (z-scores before: 1.34 and after LUR: −2.65). In parallel, LUR administration itself modulated Inositol-related metabolic pathways. Overall, these findings suggest that LUR adolescent treatment may counteract some PNS-induced alterations, supporting adolescence as a critical window for early preventive strategies with translational relevance for stress-related neuropsychiatric disorders. Full article

To elucidate how pre-crack inclination affects the dynamic mechanical response, failure modes, and energy evolution of rocks, uniaxial impact compression tests were conducted on Φ50 mm Baima Iron Mine magnetite specimens with varying pre-crack angles using a split Hopkinson pressure bar (SHPB) system. The experiments were integrated with PFC2D discrete element simulations to investigate crack propagation and stress field characteristics. The results demonstrate that all specimens maintained dynamic stress equilibrium under impact loading. Crack inclination significantly influenced the dynamic stress–strain response: specimens with 0°~30°cracks exhibited gradual post-peak stress decay, indicating ductile behavior, while specimens with larger inclinations (≥45°) displayed pronounced brittle failure. Dynamic compressive strength followed a “U-shaped” trend with crack angle, reaching a minimum at 45°, whereas 0°and 90°specimens exhibited similar strength. Failure modes transitioned from axial splitting to wing-crack dominance, while anti-wing and shear cracks decreased significantly with increasing crack angle. Energy analysis indicated that reflected energy decreased and transmitted energy increased with increasing crack angle. Numerical simulations reproduced the experimental macroscopic failure patterns accurately, revealing the underlying mechanisms of crack-tip coalescence and stress concentration shifts as a function of crack inclination. These findings offer insights into the dynamic failure mechanisms of jointed rocks and provide guidance for engineering safety assessments. Full article

Premature skid resistance deterioration is a critical issue limiting the long-term performance of thin asphalt overlays. To elucidate the meso-scale degradation mechanisms, this study employs the Discrete Element Method (DEM) implemented in Particle Flow Code (PFC) to compare a conventional Stone Matrix Asphalt (SMA-10) mixture with an optimized skeleton-reinforced design, termed Optimized Gradation-10. The optimized gradation was developed by introducing supplementary sieve sizes of 5.6, 6.7, and 8.0 mm within the critical range of 4.75–9.5 mm following the V–S gradation framework. Cross-sectional images of actual mixtures were vectorized using Python (Version: 3.11.5) and MATLAB (Version: R2024a) to reconstruct irregular aggregate clump models that accurately capture particle morphology and spatial arrangement. Meso-scale parameters were calibrated and validated through uniaxial compression tests, and the evolution of contact number, contact force, and stress transmission was analyzed under 2.3 × 10⁵ wheel load cycles. Compared with SMA-10, the optimized mixture increased effective aggregate contacts by 41.8%, enhanced stress transfer efficiency by 19.8%, and reduced rut depth by 10%. These findings confirm that synergistic gradation optimization through supplementary sieves and the V–S method markedly improves structural stability and deformation resistance, providing a meso-mechanical foundation for prolonging skid resistance in thin overlays. Full article

In multi-module boost power factor correction (PFC) systems, current ripple is commonly mitigated by applying fixed 180° interleaving between modules; however, this approach relies on matched inductors and ideal symmetry. In practical implementations, inductor mismatch and duty-cycle variations prevent full cancellation, leading to residual ripple that increases losses and electromagnetic interference. To address this issue, several research works have proposed centralized coordination or high-speed communication among units. However, an explicit converter model is necessary, which makes the system more complicated and expensive. To resolve this problem, this paper presents an extremum seeking optimization method for reducing high-frequency ripple in multi-module PFC systems without requiring explicit converter models. The ripple minimization problem is formulated as a nonlinear, time-varying optimization task, where the relative switching phases of the modules are adaptively tuned. The proposed extremum seeking algorithm perturbs the phase shift, evaluates a ripple-based cost function, and updates the phases iteratively. A harmonic analysis is developed to characterize the dependence of ripple on duty ratio, inductor values, and phase displacement. Simulation results show that the method effectively reduces the RMS ripple current across balanced and mismatched operating conditions. In a three-unit system, applying the proposed technique lowered the current THD to 1.29% compared to 1.44% achieved with a fixed phase-shift approach. These findings demonstrate that extremum seeking optimization provides a mathematically rigorous and practically implementable solution for decentralized ripple minimization in multi-module boost PFC systems. Full article

To examine how grain-size distribution affects the mechanical response and fracture behavior of Lac du Bonnet (LdB) granite under uniaxial compression, numerical simulations were conducted using the particle flow code (PFC) with a grain-based model. By displacing grain centroids in different directions along the y-axis, four LdB granite models with distinct grain sizes were generated, with grains delineated by Voronoi tessellation. The main findings are as follows: (1) The flat-jointed constitutive model reproduces the experimental response well, and introducing unbonded contacts (micrometer-scale gaps) improves the simulation of crack-closure behavior during loading. (2) Secondary cracks initiate predominantly at grain boundaries, and the yield stress is strongly associated with the evolution of intragranular tensile cracks. (3) Grain size governs the sequence of crack accumulation (tensile vs. shear), the growth rate and spatial correlation of damage, and the distribution and intensity of local failures; smaller grains hinder macroscopic damage, whereas larger grains are more readily penetrated and filled by microcracks. (4) Mechanical cutting tests show that grain-size combinations produce several dominant secondary-failure modes; the failure thickness is controlled by the penetration depth of the subsequent cutting head, and the stress concentration near the cutting head is sensitive to grain size. Full article

In contemporary educational spaces, circulation spaces such as corridors and stairwells are central to students’ daily experience, yet their capacity to serve as therapeutic environments remains underexplored. This study quantitatively evaluated the physiological and neurocognitive impacts of Biophilic Design (BD) in these circulation spaces. Thirty university students experienced immersive virtual scenarios of corridors and stairwells that integrated four BD elements—weather & view, plants & landscape, material & texture, and forms & shapes—while prefrontal cortex (PFC) activity and stress responses were simultaneously captured using functional Near-Infrared Spectroscopy (fNIRS) and Galvanic Skin Response (GSR). Results showed that BD conditions produced significantly greater stress reduction, reflected in lower GSR, compared with non-BD conditions. fNIRS analyses further indicated enhanced PFC activation, with spatially differentiated patterns that varied by circulation space type and by specific BD elements. Collectively, these findings offer empirical neurophysiological evidence that applying BD to educational circulation spaces can mitigate stress and foster psychological stability, thereby providing a robust basis for evidence-based strategies to create healthier, cognitively supportive learning environments. Full article

Based on true triaxial loading experiments and particle flow numerical simulations (PFC3D), this study systematically analyzes the mechanical behavior and failure mechanisms of granite under the influence of stress difference (deviatoric stress). The experimental results indicate that increasing deviatoric stress reduces peak strength, axial strain, and lateral strain, promoting rock failure with less deformation and dilatancy. An energy analysis reveals that higher deviatoric stress suppresses peak energy accumulation, with a greater proportion of energy being dissipated through crack initiation and propagation. Macroscopic observations show that failure surfaces develop combined tensile-shear cracks, evolving into distinct “V” shapes as deviatoric stresses increase. Numerical simulations demonstrate that intermediate principal stress plays a dual role, initially facilitating, then inhibiting, and finally promoting rock failure with its continuous increase. Microscopically, tensile cracks dominate during pre-peak stages, while rapid crack coalescence in the post-peak stage leads to the formation of throughgoing V-shaped failure zones. Particle displacement analysis reveals that deformation concentrates along the minimum principal stress direction, with the displacement vectors ultimately forming a V-shaped boundary that delineates the failure zone. The research provides comprehensive insights into the macro-meso failure characteristics of hard rock under true triaxial conditions, offering valuable guidance for stability prediction and control in underground rock engineering projects such as water-sealed storage caverns. Full article

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by irreversible cognitive decline and synaptic dysfunction and represents the most prevalent etiology of dementia, accounting for an estimated 60–70% of all clinically diagnosed cases worldwide. The growing focus on microglia–neuron interactions in AD research highlights their diverse, region-specific responses, which are driven by the functional and pathological heterogeneity across different brain regions. Therefore, investigating the interactions between microglia and neurons is of crucial importance. To explore the regional heterogeneity of microglia–neuron crosstalk in AD, we integrated human single-nucleus RNA sequencing data from the prefrontal cortex (PFC), hippocampus (HPC), and occipital lobe (OL) provided by the ssREAD database. Our study delineated four microglial subtypes and uncovered a pseudotime trajectory activation trajectory leading to the disease-associated microglia (DAM) phenotype. The transition along this trajectory is driven and stabilized by a key molecular switch: the coordinated downregulation of inhibitory factors (e.g., LINGO1) and upregulation of immune-effector and antigen-presentation programs, which collectively establish the pro-inflammatory DAM state. Furthermore, we observed that each brain region displayed unique microglia–neuron communication patterns in response to AD pathology. The PFC and OL engage a THY1-ITGAX/ITGB2 signaling axis; the HPC predominantly utilizes the PTPRM pathway. Notably, THY1 dysregulation strongly correlates with pathology in the PFC, HPC, and OL, suggesting that microglia–neuron crosstalk in AD possesses both heterogeneity and commonality. The main contribution of this study is the systematic characterization of region-specific microglia-neuron interactions and the identification of THY1 as a potential mediator that may be targeted therapeutically to modulate microglial function in affected brain regions. Full article

Geogrids significantly enhance the soil matrix stability and foundation bearing capacity. Despite the development of numerous geogrid configurations, their geometric design has not yet been systematically optimized. The design of geogrid aperture geometry aims to maximize geogrid performance while maintaining material efficiency. Nevertheless, topology optimized geogrid designs remain underexplored, particularly regarding the influence of aperture shape on interface shear behavior. To address this gap, this study developed SIMP-based variable density topology optimization models for three types of tensile geogrid structures: uniaxial, biaxial, and triaxial geogrid. The effects of key model parameters on the optimization results are examined, resulting in new geogrid geometries optimized primarily to minimize compliance, achieving weight reductions of 7%, 10%, and 12%, respectively. Subsequently, FLAC3D was used for tensile performance analysis, while coupled PFC3D–FLAC3D was employed for interfacial friction performance analysis. In FLAC3D, numerical simulations demonstrated that the topologically optimized geogrid outperformed conventional ones in both tensile resistance and strain distribution. Consequently, conventional biaxial and triaxial geogrids, along with their topologically optimized versions, were chosen for further analysis. Pull-out interface simulations of these geogrids were conducted using the coupled discrete element–finite difference method (PFC3D–FLAC3D) to investigate the influence of geogrid aperture shape and aperture ratio on the soil–geogrid interface. The results indicate that the reinforcement efficiency of the topologically optimized biaxial and triaxial geogrids was 10% and 8% higher, respectively, than that of the conventional geogrids. Taking the biaxial geogrid as an example, a comprehensive comparison of performance parameters between the conventional and topology-optimized versions revealed that the optimized design achieved a 10% reduction in weight. Simultaneously, it reduced stress concentration at critical locations by approximately 60% and increased the interface pull-out resistance by 20%. These findings demonstrate that the new topologically optimized geogrid exhibits significant potential for further promotion and application in practical engineering. Full article

Instability in dump slopes frequently induces landslides, a process governed by complex factors. To investigate the impact of gradation composition on dump slope stability, four distinct gradations were designed, and large-scale laboratory triaxial tests were conducted to characterize their strength and deformation behaviors under varying confining pressures. Concurrently, numerical models of dump slopes with these four gradations were established using Particle Flow Code (PFC) to simulate rainfall infiltration processes. Through a comparative analysis of particle contact force chains, pore water pressure evolution, particle displacement under varying rainfall durations, and safety factors under natural and rainfall conditions, the mechanisms governing the influence of gradation composition on slope stability were elucidated from both macroscopic and microscopic perspectives. Results indicate the following: (1) Gradation composition significantly affects the strength and deformation characteristics of dump materials. Sample group 3 (with a fine-to-coarse particle ratio of 4:6) exhibited the highest strength among the four test samples, with peak deviatoric stresses of 610 kPa, 1075 kPa, and 1539 kPa under confining pressures of 200 kPa, 400 kPa, and 600 kPa, respectively. Its corresponding shear strength parameters were a cohesion of 38.45 kPa and an internal friction angle of 32.55°. In contrast, sample group 4 (fine-to-coarse ratio of 6:4) showed the lowest strength, with peak deviatoric stresses of 489 kPa, 840 kPa, and 1290 kPa under the same confining pressures, and shear strength parameters of c = 25.35 kPa and φ = 30.02°. (2) Gradation modulates contact forces and failure modes via a “skeleton-filling” mechanism. (3) Gradation plays a critical role in controlling pore water pressure evolution and the seepage characteristics of the dump slope model. Among the four designed gradations and their corresponding numerical models, Model 3 was characterized by the highest contact forces and the lowest pore water pressure. It exhibited the highest stability under both natural and rainfall conditions, with safety factors of 1.70 and 1.22, respectively. Conversely, Model 4 showed weak particle contact forces and high pore pressure, demonstrating the poorest stability. It yielded safety factors of only 1.25 and 1.02 under natural and rainfall-saturated conditions, indicating that it represents the least favorable gradation composition. These findings provide valuable references for the optimization of dumping processes and stability control in similar engineering projects. Full article

Rock mechanical parameters can provide fundamental data for the numerical simulation of hydraulic fracturing, aiding in the construction of hydraulic fracturing models. Due to the laminated nature of shale, constructing a hydraulic fracturing model requires obtaining the rock mechanical parameters of each lamina and the bedding planes. However, acquiring the mechanical parameters of individual shale laminas through physical experiments demands that, after rock mechanics testing, cracks propagate along the centre of the laminae without connecting additional bedding planes, which imposes extremely high requirements on shale samples. Current research on the rock mechanics of the Minfeng subsag shale is relatively limited. Therefore, to obtain the rock mechanical parameters of each lamina and the bedding planes in the Minfeng subsag shale, a numerical simulation approach can be employed. The model, built using PFC2D, is based on prior X-ray diffraction (XRD) analysis, conventional thin-section observation, scanning electron microscopy (SEM), Brazilian splitting tests, and triaxial compression tests. It replicates the processes of the Brazilian splitting and triaxial compression experiments, assigning initial parameters to different bedding planes based on lithology. A trial-and-error method is then used to adjust the parameters until the simulated curves match the physical experimental curves, with errors within 10%. The model parameters for each lamina at this stage are then applied to single-lithology Brazilian splitting, biaxial compression, and three-point bending models for simulation, ultimately obtaining the tensile strength, uniaxial compressive strength, Poisson’s ratio, Young’s modulus, brittleness index, and Mode I fracture toughness for each lamina. Simulation results show that the Minfeng subsag shale exhibits strong heterogeneity, with all obtained rock mechanical parameters spanning a wide range. Calculated brittleness indices for each lamina mostly fall within the “good” and “medium” ranges, with carbonate laminae generally demonstrating better brittleness than felsic laminae. Fracture toughness also clearly divides into two ranges: mixed carbonate shale laminae have overall higher fracture toughness than mixed felsic laminae. Full article

This research investigates the effects of corona plasma treatment on the mechanical properties of jute/epoxy-reinforced composites, particularly within biomedical application contexts. Plant Fibre Composites (PFCs) are attractive for medical devices and scaffolds due to their environmental friendliness, renewability, cost-effectiveness, low density, and high specific strength. However, their applications are often constrained by inferior mechanical performance arising from poor bonding between the plant fibre used as the reinforcement and the synthetic resin or polymer serving as the matrix. This study addresses the challenge of improving the weak interfacial bonding between plant fibre and synthetic resin in a 2/2 twill-weave-woven jute/epoxy composite material. The surface of the jute fibre is modified for better adhesion with the epoxy resin through plasma treatment, which exposes the jute fibre to controlled plasma energy and utilises dry air (plasma only), argon (Ar) (argon gas with plasma), and nitrogen (N₂) (nitrogen gas with plasma) at two different distances (25 mm and 35 mm) between the plasma nozzle and the fibre surface. In this context, “equilibrium” refers to the optimal combination of plasma power, treatment distance, and gas environment that collectively determines the degree of fibre surface modification. The results indicate that all plasma treatments improve the interlaminar shear strength in comparison to untreated samples, with treatments at 35 mm using N₂ gas showing a 35.4% increase in shear strength. Conversely, plasma treatment using dry air at 25 mm yields an 18.3% increase in tensile strength and a 35.7% increase in Young’s modulus. These findings highlight the importance of achieving an appropriate equilibrium among plasma intensity, treatment distance, and fibre–plasma interaction conditions to maximise the effectiveness of plasma treatment for jute/epoxy composites. This research advances sustainable innovation in biomedical materials, underscoring the potential for improved mechanical properties in environmentally friendly fibre-reinforced composites. Full article