Search Results (2,671)

High rock slopes are extensively distributed in areas of major engineering constructions, such as transportation infrastructure, hydraulic projects, and mining operations. The stability and failure evolution mechanism during their multi-stage excavation process have consistently been a crucial research topic in geotechnical engineering. In this paper, a series of two-dimensional rock slope models, incorporating various combinations of slope height and slope angle, were established utilizing the Discrete Element Method (DEM) software PFC2D. This systematic investigation delves into the meso-mechanical response of the slopes during multi-stage excavation. The Parallel Bond Model (PBM) was employed to simulate the contact and fracture behavior between particles. Parameter calibration was performed to ensure that the simulation results align with the actual mechanical properties of the rock mass. The research primarily focuses on analyzing the evolution of displacement, the failure modes, and the changing characteristics of the force chain structure under different geometric conditions. The results indicate that as both the slope height and slope angle increase, the inter-particle deformation of the slope intensifies significantly, and the shear band progressively extends deeper into the slope mass. The failure mode transitions from shallow localized sliding to deep-seated overall failure. Prior to instability, the force chain system exhibits an evolutionary pattern characterized by “bundling–reconfiguration–fracturing,” serving as a critical indicator for characterizing the micro-scale failure mechanism of the slope body. Full article

In response to the growing need for efficient, stable, and non-destructive gripping in apple harvesting robots, this study proposes a novel rigid–flexible coupled end-effector. The design integrates an underactuated mechanism with a real-time force feedback control system. First, compression tests on ‘Red Fuji’ apples determined the minimum damage threshold to be 24.33 N. A genetic algorithm (GA) was employed to optimize the geometric parameters of the finger mechanism for uniform force distribution. Subsequently, a rigid–flexible coupled multibody dynamics model was established to simulate the grasping of small (70 mm), medium (80 mm), and large (90 mm) apples. Additionally, a harvesting experimental platform was constructed to verify the performance. Results demonstrated that by limiting the contact force of the distal phalange region silicone (DPRS) to 24 N via active feedback, the peak contact forces on the proximal phalange region silicone (PPRS) and middle phalange region silicone (MPRS) were effectively maintained below the damage threshold across all three sizes. The maximum equivalent stress remained significantly below the fruit’s yield limit, ensuring no mechanical damage occurred, with an average enveloping time of approximately 1.30 s. The experimental data showed strong agreement with the simulation, with a mean absolute percentage error (MAPE) of 5.98% for contact force and 5.40% for enveloping time. These results confirm that the proposed end-effector successfully achieves high adaptability and reliability in non-destructive harvesting, offering a valuable reference for agricultural robotics. Full article

To address the inefficiency and high labor intensity associated with traditional manual mussel seedling unloading, this study proposes an automated traction-rope mussel unloading machine. This study focuses on the thick-shelled mussel (Mytilus coruscus) as the research subject. Furthermore, the key mussel unloading processes were simulated using the EDEM software to analyze mechanical interactions during detachment. A breakable mussel discrete element model was developed, and its Bonding V2 model parameters were systematically calibrated. Using the ultimate crushing displacement (2.25 mm) and ultimate crushing load (552 N) as response variables, the model was optimized through a sequential experimental design comprising Plackett–Burman screening, the steepest ascent method, and the Box–Behnken response surface methodology. The results demonstrate that the optimal parameter combination consists of unit area normal stiffness (2.48 × 10¹¹ N/m³), unit area tangential stiffness (3.80 × 10⁸ N/m³), critical normal stress (3.15 × 10⁶ Pa), critical tangential stress (2.90 × 10⁷ Pa), and the contact radius (1.60 mm). The model’s accuracy was validated through integrated discrete element simulations and prototype testing. The equipment achieves an exceptionally low mussel damage rate of only 1.2%, effectively meeting the operational requirements for mussel unloading. This study provides both theoretical foundations and practical insights for the design of mechanized mussel unloading systems in China. Full article

Canagliflozin (CFZ), a sodium–glucose cotransporter 2 (SGLT2) inhibitor, is extensively utilized in the management of type 2 diabetes. Among its various polymorphic forms, the hemi-hydrate (Hemi-CFZ) has been selected as the active pharmaceutical ingredient (API) for CFZ tablets due to its superior solubility. However, during the production, storage, and transportation of CFZ tablets, Hemi-CFZ can undergo transformations into anhydrous (An-CFZ) and monohydrate (Mono-CFZ) forms under the influence of environmental factors such as temperature, humidity, and pressure, which may adversely impact the bioavailability and clinical efficacy of CFZ tablets. Therefore, it is imperative to develop rapid, accurate, non-destructive, and non-contact methods for quantifying An-CFZ and Mono-CFZ content in CFZ tablets to control polymorphic impurity levels and ensure product quality. This research evaluated the feasibility and reliability of using near-infrared spectroscopy (NIR) combined with partial least squares regression (PLSR) for simultaneous quantitative analysis of An-CFZ and Mono-CFZ in CFZ tablets, elucidating the quantifying mechanisms of the quantitative analysis model. Orthogonal experiments were designed to investigate the effects of different pretreatment methods and ant colony optimization (ACO) algorithms on the performance of quantitative models. An optimal PLSR model for simultaneous quantification of An-CFZ and Mono-CFZ in CFZ tablets was established and validated over a concentration range of 0.0000 to 10.0000 w/w%. The resulting model, Y_{An-CFZ/Mono-CFZ} = 0.0207 + 0.9919 X, achieved an R² value of 0.9919. By analyzing the relationship between the NIR spectral signals selected by the ACO algorithm and the molecular structure information of An-CFZ and Mono-CFZ, we demonstrated the feasibility and reliability of the NIR-PLSR approach for quantifying these polymorphic forms. Additionally, the mechanism of PLSR quantitative analysis was further explained through the variance contribution rates of latent variables (LVs), the correlations between LVs loadings and tablets composition, and the relationships between LV scores and An-CFZ/Mono-CFZ content. This study not only provides a robust method and theoretical foundation for monitoring An-CFZ and Mono-CFZ content in CFZ tablets throughout production, processing, storage, and transportation, but also offers a reliable methodological reference for the simultaneous quantitative analysis and quality control of multiple polymorphic impurities in other similar drugs. Full article

Background: Rainfall-induced landslides are a widespread and destructive geological hazard that resist precise prediction. They pose serious threats to human lives and property, ecological stability, and socioeconomic development. Methods: To address the challenges in mitigating rainfall-induced landslides in high-altitude mountainous regions, this study proposes a digital twin framework that couples multiple physical fields and is based on the spherical discrete element method. Results: Two-dimensional simulations identify a trapezoidal stress distribution with inward-increasing stress. The stress increases uniformly from 0 kPa at the surface to 210 kPa in the interior. The crest stress remains constant at 1.8 kPa under gravity, whereas the toe stress rises from 6.5 to 14.8 kPa with the slope gradient. While the stress pattern persists post-failure, specific magnitudes alter significantly. This study pioneers a three-dimensional close-packed spherical discrete element method, achieving enhanced computational efficiency and stability through streamlined contact mechanics. Conclusions: The proposed framework utilizes point-contact mechanics to simplify friction modeling, enhancing computational efficiency and numerical stability. By integrating stress, rainfall, and seepage fields, we establish a coupled hydro-mechanical model that enables real-time digital twin mapping of landslide evolution through dynamic parameter adjustments. Full article

Low adhesion conditions can lead to significant wheel slip during braking for high-speed trains, resulting in severe wheel–rail rolling contact fatigue issues. The objective of this paper is to reproduce the dynamic wheel–rail adhesion characteristics of high-speed train braking with large creepage using the transient non-Hertzian ECF model under wet conditions and to clarify the underlying mechanisms. The Kik–Piotrowski (KP) model is used to solve the wheel–rail normal contact problem, and the corresponding non-elliptical adaptive method is adopted to modify the ECF model considering time-dependent effects for solving the tangential contact problem. The dynamic large creepage adhesion characteristics of high-speed trains under wet conditions during braking are analyzed. Furthermore, the effect of braking initial speeds and longitudinal creepage variation curves on dynamic adhesion characteristics is discussed. The results indicate that the large creepage adhesion characteristic curve of high-speed trains during braking exhibits a loading stable phase and an unloading stable phase, both of which effectively enhance the utilization of wheel–rail adhesion. Full article

Background/Objectives: Empagliflozin (EMPA) was repurposed for Alzheimer’s disease (AD) treatment via buccal delivery, exploiting novel nanofibers (NFs) integrating chitosan (Cs), silk fibroin (Fb), and poly(lactic acid) (PLA). Methods: EMPA-loaded Cs/Fb/PLA NFs were electrospun in different formulations to optimize the formulation parameters. The optimized formulation was then investigated for its enhanced in vivo effect. Results: Optimized nanofiber diameters ranged from 459 ± 173 to 668 ± 148 nm, possessing bead-free morphology confirmed by SEM and satisfactory mechanical properties. EMPA was successfully well-dispersed in the polymer matrix as evidenced by FTIR, XRD, and drug content. The optimized NFs displayed a hydrophilic surface (contact angle < 90°), and biphasic drug release with sustained EMPA liberation (84.98% over 24 h). In vivo, buccal EMPA-Cs/Fb/PLA NFs in an AlCl₃-induced AD rat model significantly reduced brain-amyloid-β, phosphorylated tau, IL-1β, and AGER expression by 2.88-, 2.64-, 2.87-, and 2.50-fold, respectively, compared to positive controls, and improved locomotor activity (1.86-fold) and cognitive performance (T-maze) (4.17-fold). Compared to pure EMPA, the nanofiber formulation achieved further reductions in amyloid-β (1.78-fold), p-tau (1.42-fold), IL-1β (1.89-fold), and AGER (1.38-fold), with efficacy comparable to memantine. Histopathological examination revealed preservation of the hippocampal neuronal structure. Conclusions: The findings suggest EMPA-loaded Cs/Fb/PLA NFs as a promising non-invasive, sustained-release buccal delivery platform for AD therapy, offering multimodal neuroprotection through modulation of the Aβ–AGER–p-tau axis. Full article

Transient arcing often occurs as an electric locomotive traverses an electrical sectioning overlap (ESO), deteriorating current collection stability and reducing the durability of the pantograph–catenary (PC) system. In this study, the formation mechanism and electrical evolution characteristics of transient arcing in the ESO region are investigated through theoretical analysis and numerical simulations. First, based on the dynamic motion of the locomotive passing through the ESO, the transient arcing mechanism of the ESO is clarified, and the plasma characteristics of the arc are described. Then, the electromagnetic, airflow, and thermal field interactions within the PC contact gap during arc ignition are analyzed. A Multiphysics coupled PC arc model is developed, incorporating aerodynamic, electromagnetic, and heat transfer effects. Subsequently, finite element meshing and boundary conditions are applied to simulate the transient evolution of the ESO arc. Finally, the transient arcing characteristics of the ESO are analyzed. The results indicate that the current density is highly concentrated at the initial arcing stage and gradually forms an axially symmetric conductive channel (approximately 10⁷ A/m²), which shifts upward as the contact gap increases. Moreover, due to the geometric discontinuity of the ESO, a strong localized electric field develops near the wire edge, leading to arc root migration and reignition. Full article

The design of control systems for aircraft autonomous takeoff and landing, as well as full-flight-envelope operations—including taxiing, takeoff, climb, cruise, descent, and landing—presents significant challenges. These challenges arise from the strong nonlinear coupling between airframe dynamics and landing-gear–ground interactions, phase-specific disturbances (e.g., uneven runways and aerodynamic uncertainties), and the difficulty in coordinating trajectory tracking, attitude stability, and landing gear load management across all phases. To address these issues, this paper proposes a ground-contact-aware adaptive nonlinear dynamic inversion (GCA-ANDI) control system for fixed-wing UAVs with tricycle landing gear. Unlike conventional cascade PID or pure NDI methods, which lack phase awareness or explicit ground interaction modeling, GCA-ANDI integrates real-time ground contact perception and phase-adaptive mechanisms. This approach establishes a unified control system framework that synergizes high-level trajectory tracking, attitude stabilization, and landing gear load regulation. Simulation results demonstrate that the proposed GCA-ANDI control system outperforms benchmark methods across the full flight envelope. It achieves significant improvements in tracking accuracy, effectively suppresses attitude fluctuations induced by ground interactions or aerodynamic uncertainties, balances multi-wheel load distribution, and reduces structural impact during takeoff and landing. This study enhances robustness against phase-specific disturbances and provides a theoretical and technical foundation for high-precision, safe, and reliable full-flight-envelope autonomy in aircraft. Full article

Accurate and non-contact identification of individual sheep is important for intelligent livestock management, but remains challenging due to subtle inter-individual differences, breed-dependent facial morphology, and complex farm environments. This study proposes a lightweight sheep face detection and keypoint recognition framework based on an improved YOLO11 architecture, termed SAMS-KLA-YOLO11. The model incorporates a Sheep Adaptive Multi-Scale Convolution (SAMSConv) module to enhance feature extraction across breed-dependent facial scales, a Keypoint-Aware Lightweight Attention (KLAttention) mechanism to emphasize biologically discriminative facial landmarks, and the Efficient IoU (EIoU) loss to stabilize bounding box regression. A dataset of 3860 images from 68 individuals belonging to three breeds (Hu, Dorper, and Dorper × Hu crossbreeds) was collected under unconstrained farm conditions and annotated with five facial keypoints. On this dataset, the proposed model achieves higher precision, recall, and mAP than several mainstream YOLO-based baselines, while reducing FLOPs and parameter count compared with the original YOLO11. Additional ablation experiments confirm that each proposed module provides complementary benefits, and OKS-based evaluation shows accurate facial keypoint localization. All results are obtained on a single, site-specific dataset without external validation or on-device deployment benchmarks, so the findings should be viewed as an initial step toward practical sheep face recognition rather than definitive evidence of large-scale deployment readiness. Full article

This article presents the results of the first stage of a four-phase research program aimed at the comprehensive evaluation and enhancement in the functional properties of polymeric packaging films intended for active food packaging systems through their modification with detonative nanodiamonds (DND). Stage I involved the characterization of ten commercial single- and multi-layer films without the addition of DND, differing in structure, base material, thickness, and intended application. The scope of analyses included the assessment of biological and physicochemical properties relevant to food contact, such as surface wettability (contact angle), thermal stability (TGA, DSC), antimicrobial and antiviral activity (using E. coli and M. luteus models), as well as the quality of thermal seals examined by SEM. Biological activity was assessed in accordance with ISO 22196:2011. The results revealed significant differences among the tested samples in terms of microbiological resistance, surface properties, and thermal stability. Films with printed layers exhibited the highest antimicrobial activity, whereas some polypropylene samples showed no activity at all or even supported microbial survival. Cross-sectional analysis of welds indicated that the quality of thermal seals is strongly dependent on the surface properties of the base material. The obtained results provide a reference point for subsequent research stages, in which DND-modified films will be analyzed regarding their effects on mechanical, barrier, and biological properties. Preliminary trials with nanodiamonds confirmed their high application potential and the possibility of producing films with increased hydrophilicity or hydrophobicity and durability, which are crucial for the development of modern active food packaging systems. Full article

In complex mechanical systems involving multiple parts and contact interfaces, failure modes are not only statistically correlated but may also interact through underlying physical mechanisms. These interactions, often neglected in current reliability analysis, can lead to significant deviations in failure predictions, especially in rotor systems and actuators. Taking aeroengine turbine rotor assemblies as an example, multiple failure modes, such as wear, fatigue and slip at contact interfaces, affect key mechanical property parameters including assembly preload, cylindrical interference fit and cooling performance. These variations lead to evolving stress/strain and temperature fields with increasing load cycles, thereby inducing physical interactions among different failure modes. This study systematically analyzes the interaction mechanisms among multiple failure modes within a turbine rotor assembly. A mechanics model is established to quantify these interactions and their effects on failure evolution. Furthermore, a time-dependent reliability evaluation method is proposed based on Monte Carlo simulation and the Probability Network Evaluation Technique. A case study illustrates that both continuous-type and trigger-type interactions significantly affect the failure probabilities of wear and low-cycle fatigue. The results emphasize the necessity of accounting for interaction of multi-failure modes to improve the accuracy of failure prediction and enhance the design reliability of turbine rotor assemblies. Full article

Studying surface energy and permeability offers insights into the relationship between temporary polymers and the oral environment. Variations in contact angle and surface free energy may signify modifications in surface polarity and tendency for plaque buildup, staining, or microcrack formation. Objectives: The present study aims to evaluate the influence of simulated salivary and chemical aging conditions on the surface and mechanical properties of 3D-printed PMMA provisional materials. Methods: Two 3D-printed polymethyl methacrylate (PMMA) resins were investigated, namely Anycubic White (Anycubic, Shenzhen, China) and NextDent Creo (NextDent, 3D Systems, Soesterberg, The Netherlands), using two aging protocols. Protocol A consisted of chemical aging in an alcohol-based mouthwash, while Protocol B involved thermal aging in artificial saliva. After aging, surface properties (wettability and SFE) and compressive behaviour were analyzed. Statistical analysis was conducted to assess the influence of temperature, immersion duration, and aging medium, with significance established at p < 0.05. Results: In Protocol A, mechanical properties showed a time-dependent decrease, with material-specific stabilization trends. In Protocol B, thermal aging resulted in elastic modulus reductions ranging from 35% to 46% relative to the reference. The yield strength exhibited similar tendencies. In Protocol A, X samples exhibited a consistent decline, while C samples stabilized after 14 days. For Protocol B, the fitted model produced residuals under 2%, confirming temperature as the primary variable. Conclusions: Chemical and thermal aging influence the physical and mechanical properties of the analyzed 3D-printed PMMA. Among the two protocols, thermal aging in artificial saliva resulted in more pronounced material degradation. After chemical aging in mouthwash, the surface free energy remained almost constant. After thermal aging, all samples demonstrated a gradual rise in SFE with prolonged immersion duration. The current study offers valuable insights into the environmental stability of printed PMMA; however, it is an in vitro evaluation. The findings indicate that temperature exposure and prolonged contact with oral hygiene products may affect the mechanical reliability of 3D-printed provisional restorations, which must be considered during material selection for longer temporary usage. Additionally, spectroscopic and microscopic analyses might better clarify the molecular-level chemical alterations linked to aging. Full article

This study utilized a dynamic cross-linking algorithm to formulate a chemical cross-linked hydrogel model of poly(N-isopropylacrylamide) (PNIPAM) with N, N’-methylenebisacrylamide (BIS). Molecular dynamics (MD) simulations were conducted to investigate the temperature sensitivity and ibuprofen release mechanism of this hydrogel under varying cross-linking degrees and water contents. The low critical solution temperature (LCST) of the hydrogel was determined based on changes in solvent-accessible surface area (SASA) and hydrogen bond count. The LCST was found to be between 300 and 310 K. As the temperature increased, both SASA and hydrogen bond counts generally exhibited a gradual decrease. However, near the LCST, polymer chain collapse temporarily exposed the hydrophilic groups of the PNIPAM, forming hydrophilic regions that increased the contact area with water. This led to a transient increase in SASA (8% higher than that before 300 K) and hydrogen bond counts (6.25% higher than that at 290 K). Concurrently, Young’s modulus of the PNIPAM hydrogel was found to decrease with increasing water content (from 3.11 GPa to 2.59 GPa, representing a 16.7% decrease when water content increased from 0% to 50% for 80% cross-linking degree) and increase with rising cross-linking density (from 2.02 GPa to 2.94 GPa, representing a 45.5% increase when the cross-linking degree increased from 0% to 80% for 20% water content). These findings indicate that enhancing cross-linking density is an effective strategy for improving the hydrogel’s mechanical properties. A PNIPAM–ibuprofen delivery model was constructed and molecular dynamics (MD) simulations were conducted, revealing temperature dependence release behavior. Below the LCST, the PNIPAM hydrogel remains in a highly swollen state (PNIPAM single-chain radius of gyration, Rg = 0.64 nm at 290 K), with ibuprofen molecules adsorbed within the PNIPAM polymer chain network. Conversely, above the LCST, PNIPAM undergoes phase separation (Rg decreases to 0.56 nm at 320 K, representing a 12.5% decrease), resulting in volume contraction (cavity volume reduced by 35%) and disruption of the hydrogen bond network. This process results in the release of ibuprofen molecules, accompanied by an increase in their diffusion coefficient from 1.3817 × 10⁻⁹ (280 K) to 4.2847 × 10⁻⁹ m²/s (320 K). Concurrently, the interaction energy with PNIPAM experiences a decline, from −126.72 kcal/mol to −108.69 kcal/mol. The findings of this study provide insights into the optimization of the structural stability of ibuprofen delivery carriers. Full article

Repeat-in-toxin (RTX) toxins are calcium-dependent exoproteins secreted by diverse Gram-negative bacteria and play central roles in cytotoxicity, immune modulation, and tissue colonization. While their structure and secretion mechanisms are well-characterized, the regulation of RTX toxin expression remains complex and species-specific. This review provides a comprehensive overview of the regulatory networks governing RTX gene expression, highlighting both conserved mechanisms and niche-specific adaptations. RTX genes are controlled by multilayered regulatory systems that integrate global transcriptional control, metabolic regulation, and environmental sensing. Expression is further shaped by host-derived signals, physical contact with host cells, and population-dependent cues. Quorum sensing, post-transcriptional regulation by small RNAs, and post-translational activation mechanisms contribute additional layers of control to ensure precise regulation of toxin production. We also explore how RTX regulation varies across anatomical niches, including the gut, lung, bloodstream, and biofilms, and how it is co-regulated with broader bacterial virulence. Finally, we discuss emerging insights from omics-based approaches and the potential of anti-virulence strategies targeting RTX regulatory pathways. Together, these topics underscore RTX regulation as a model for adaptive virulence control in bacterial pathogens. Full article