Search Results (427)

Coal pillars are important safety structures for maintaining the stability of underground coal mine roadways. To address both coal resource loss from wide pillars and the need for safer, more sustainable underground building structures, this study proposes a framework for controlling the surrounding rock based on the narrow pillar. By establishing a load-bearing mechanical model for narrow coal pillars and a mechanical model for roof instability, the design principles of key parameters were clarified, including the optimal width, the required support strength for the pillar–roof system, and the height and angle of roof pre-splitting. In addition, zoning control measures and corresponding technical procedures for adjacent mining roadways were proposed. This technology was applied in Tashan Mine and, during the extraction of panel 8311, the surrounding rock stability of roadway 2312 was well maintained, with the maximum deformation of the solid coal rib measured at 135 mm, while that of the narrow pillar reached 386 mm. The proposed design method can effectively improve coal recovery in underground mining and provide theoretical and technical guidance for coal pillar stability control and wide pillar optimization under complex mining conditions. Full article

Inertial microfluidics has obtained attention for its good performance in microparticle manipulation. It has the advantages of simplicity, high throughput, and a lack of external fields. In this paper, a simple microfluidic device is described, which contains several split and recombination structures. The design takes advantage of microparticle migration based on inertial lift and the Dean drag force. Two forces drive microparticles to move laterally and arrive at equilibrium positions in a split–recombination microchannel. Based on the numerical and experimental analysis, the trajectories of microparticles are described, and microparticles are focused and form two narrow streams. In addition, the focusing of microparticles is enhanced significantly with the increase in angle. Finally, two sizes of microparticles are separated in experiments. The simple device and high throughput offered by this passive microfluidic approach make it attractive in biomedical and environmental applications. Full article

The Volume Bragg Grating (VBG) imaging technique provides a novel approach to gaze-type hyperspectral imaging. However, collimation constraints of the incident beam during narrow-band filtering and high-spatial-resolution imaging introduce system complexity, hindering miniaturization and modularization of the optical system. To address these limitations, this paper proposes a convex transmissive VBG structure with tunable design parameters to enhance the field of view (FOV), relax collimation requirements, improve imaging quality, narrow filter spectral bandwidth, and simplify the optical system design. For the precise analysis and optimization of convex VBG performance, we established a physical model for filtered imaging using a convex transmissive VBG with polychromatic extended sources. An evaluation metric termed the “Maximal Splitting Angle (MSA)” was introduced to quantify the dispersion extent of image spots. This approach was employed to investigate the intrinsic correlations between structural parameters (such as the radius of curvature, vector tilt angle, grating period, and thickness) and key system performance indicators (spatial resolution and spectral resolution). The necessity of optimizing these parameters was rigorously demonstrated. Theoretical analysis confirms that convex transmissive VBG achieves superior spatial and spectral resolution over planar VBG under reduced collimation constraints. The experimental results show a 58.5% enhancement in spatial resolution and a 63.6% improvement in spectral bandwidth for the convex transmissive VBG system. Crucially, while planar transmissive VBG suffers from stray fringe interference during wavelength tuning, its convex counterpart remains unaffected. This study proposes a novel device structure, offering new perspectives for optimizing VBG-filtered spectral imaging systems. Full article

In this paper, we present rigorous asymptotic componentwise perturbation bounds for regular Hermitian indefinite matrix eigendecompositions, obtained via the method of splitting operators. The asymptotic bounds are derived from exact nonlinear expressions for the perturbations and allow each entry of every matrix eigenvector to be bounded in the case of distinct eigenvalues. In contrast to the perturbation analysis of the Schur form of a nonsymmetric matrix, the bounds obtained here do not rely on the Kronecker product, which significantly reduces both memory requirements and computational cost. This enables efficient sensitivity analysis of high-order problems. The eigenvector perturbation bounds are further applied to estimate the angles between perturbed and unperturbed one-dimensional invariant subspaces spanned by the corresponding eigenvectors. To reduce conservatism in the case of high-order problems, we propose the use of probabilistic perturbation bounds based on the Markov inequality. The analysis is illustrated by two numerical experiments of order 5000. Full article

In this paper, the austenite grains growth behavior in the austenitizing process of Nb–Ti micro-alloyed medium manganese steel was studied through in situ observation by high temperature laser confocal microscope. The results show that the average austenite grain sizes change from about 3 μm at 1050 °C to over 50 μm at 1250 °C. When the grain boundary is a small-angle grain boundary, one grain boundary will split into several dislocations. With the extension of heating time, the lattice orientation difference further decreases, and the remaining dislocations may merge into new grain boundaries. The most suitable heating temperature for the medium manganese steel in this paper is from 1100 °C to 1150 °C, taking into account influences such as grain size, grain boundary damage, and deformation resistance. Full article

Slope stability prediction is a critical task in geotechnical engineering, but machine learning (ML) models require large datasets, which are often costly and time-consuming to obtain. This study proposes a domain-driven teacher–student framework to overcome data limitations for predicting the dry factor of safety (FS dry). The teacher model, XGBoost, was trained on the original dataset to capture nonlinear relationships among key site-specific features (unit weight, cohesion, friction angle) and assign pseudo-labels to synthetic samples generated via domain-driven simulations. Six student models, random forest (RF), decision tree (DT), shallow artificial neural network (SNN), linear regression (LR), support vector regression (SVR), and K-nearest neighbors (KNN), were trained on the augmented dataset to approximate the teacher’s predictions. Models were evaluated using a train–test split and five-fold cross-validation. RF achieved the highest predictive accuracy, with an R² of up to 0.9663 and low error metrics (MAE = 0.0233, RMSE = 0.0531), outperforming other student models. Integrating domain knowledge and synthetic data improved prediction reliability despite limited experimental datasets. The framework provides a robust and interpretable tool for slope stability assessment, supporting infrastructure safety in regions with sparse geotechnical data. Future work will expand the dataset with additional field and laboratory tests to further improve model performance. Full article

Feedthrough interference is inevitably introduced in MEMS gyroscopes due to non-ideal factors such as circuit layout design and fabrication processes, exerting non-negligible impacts on gyroscope performance. This study proposes a feedthrough suppression scheme for MEMS gyroscopes based on mixed-frequency excitation signals. Leveraging the quadratic relationship between excitation voltage and electrostatic force in capacitive resonators, the resonator is excited with a modulated signal at a non-resonant frequency while sensing vibration signals at the resonant frequency. This approach achieves linear excitation without requiring backend demodulation circuits, effectively separating desired signals from feedthrough interference in the frequency domain. A mixed-frequency excitation-based measurement and control system for MEMS gyroscopes is constructed. The influence of mismatch phenomena under non-ideal conditions on the control system is analyzed with corresponding solutions provided. Simulations and experiments validate the scheme’s effectiveness, demonstrating feedthrough suppression through both amplitude-frequency characteristics and scale factor perspectives. Test results confirm the scheme eliminates the zero introduced by feedthrough interference in the gyroscope’s amplitude-frequency response curve and reduces force-to-rebalanced detection scale factor fluctuations caused by frequency split variations by a factor of 21. Under this scheme, the gyroscope achieves zero-bias stability of 0.3118 °/h and angle random walk of 0.2443 °/h/√Hz. Full article

Hydrogels are attractive biomaterials for skin replacement and tissue regeneration, offering advantages over split-skin grafts for large or irregular wounds. Honey-containing hydrogels are of particular interest, combining honey’s natural healing properties with the versatility of hydrogel matrices. This study aimed to develop a biocompatible, biodegradable, and mechanically stable hydrogel as a cutaneous substitute. To achieve this, different formulations were prepared using gelatin (GE), polyvinyl alcohol (PVA), and Kelulut honey (KH). The formulations were designated as: GE-PVA (6% (w/v) GE: 5% (w/v) PVA, without KH), GE-PVA-H1 (containing 1% (v/v) KH), GE-PVA-H5 (containing 5% (v/v) KH), and GE-PVA-H10 (containing 10% (v/v) KH). All formulations were crosslinked with 0.1% (w/v) genipin (GNP). GE-PVA-H1 and GE-PVA-H1-GNP showed swelling ratios of 110.18 ± 20.14% and 86.31 ± 14.27%, lower than GE-PVA-H5 (125.79 ± 23.76%), GE-PVA-H10 (132.79 ± 20.86%), and their crosslinked counterparts. All formulations had WVTR <1500 g/m⁻²h⁻¹, with GE-PVA-H1-GNP at 501.21 ± 41.35 g/m⁻²h⁻¹, GE-PVA-H5-GNP at 473.77 ± 44.10 g/m⁻²h⁻¹, and GE-PVA-H10-GNP at 467.51 ± 73.59 g/m⁻²h⁻¹. GE-PVA-H1-GNP exhibited the slowest biodegradation (0.0036 ± 0.0003 g/h vs. 0.0096–0.0206 g/h for other groups). Contact angle was lowest for GE-PVA-H1-GNP (38.46° ± 3.89°), confirming higher hydrophilicity compared with GE-PVA-H5/H10 groups. Resilience (98.85% ± 1.03%) and compression strength (77.42% ± 7.17%) of GE-PVA-H1-GNP were comparable to GE-PVA-H5-GNP and GE-PVA-H10-GNP. MTT assays confirmed cytocompatibility across all groups. Collectively, GE-PVA-H1-GNP emerged as the optimal formulation, combining mechanical stability, hydrophilicity, and biocompatibility for wound healing applications. Full article

The low-altitude economy represents an important facet of emerging productive forces, and flying cars serve as key vehicles driving its development. This paper proposes an aerodynamic design for the aerial vehicle module of split-type flying cars, which meets the functional requirements for vertical takeoff, climb, and cruising, and provides a reference solution for urban air mobility. A multidisciplinary constraint-based approach was employed to define the design requirements of the aerial vehicle module, ensuring its capability to operate in various complex environments. Through theoretical analysis and Computer-Aided Design (CAD) methods, key geometric, aerodynamic, and stability parameters were developed and evaluated. After finalizing the design concept of the aerial vehicle module, aerodynamic analysis was conducted, and aerodynamic coefficients were assessed using Computational Fluid Dynamics (CFD) simulations across angles of attack ranging from −5° to 20°. The results indicated that the aerial vehicle module achieved a maximum lift-to-drag ratio of 13.40 at an angle of attack of 2°, and entered a stall condition at 13°. The aerodynamic design enhances the module’s stability under various operating conditions, thereby improving handling performance. Overall, the aerial vehicle module demonstrates favorable aerodynamic characteristics during low-altitude flight and low-speed cruising, satisfying the design requirements and constraints. Full article

Argillaceous slate (AS) is a typical metamorphic rock with well-developed bedding, widely distributed globally. Its bedding structure significantly impacts slope stability assessment, and the challenges associated with slope anchoring and support arising from bedding characteristics have become a focal point in the engineering field. In this study, with bedding dip angle as the key variable, mechanical tests such as uniaxial compression, triaxial compression, direct shear, and Brazilian splitting tests were conducted on AS. Additionally, field anchoring grouting diffusion tests on AS slopes were carried out. The aim is to investigate the basic mechanical properties of AS and the grout diffusion law under different bedding dip angles. The research results indicate that the bedding dip angle has a remarkable influence on the failure mode, stress–strain curve, and mechanical indices such as compressive strength and elastic modulus of AS specimens. The stress–strain curves in uniaxial and triaxial tests, as well as the stress-displacement curve in the Brazilian splitting test, all undergo four stages: crack closure, elastic deformation, crack propagation, and post-peak failure. As the bedding dip angle increases, the uniaxial and triaxial compressive strengths and elastic modulus first decrease and then increase, while the splitting tensile strength continuously decreases. The consistency of the bedding in AS causes the grout to diffuse in a near-circular pattern on the bedding plane centered around the borehole. Among the factors affecting the diffusion range of the grout, the bedding dip angle and grouting angle have a relatively minor impact, while the grouting pressure has a significant impact. A correct understanding and grasp of the anisotropic characteristics of AS and the anchoring grouting diffusion law are of great significance for slope stability assessment and anchoring design in AS areas. Full article

Particle-based 3D printing shows great potential in high-performance composite fabrication due to high raw material utilization and flexible material compatibility. However, constrained by conventional extrusion system structures, critical issues (non-uniform melt conveying, insufficient mixing efficacy, poor extrusion stability, etc.) remain. To address these, this study proposes a novel separate-type pin screw integrating solid–liquid separation (from split screws) and high-efficiency mixing (from pin screws) to improve CF/PLA composite extrusion efficiency and mixing homogeneity in particle-based 3D printing. Three-dimensional modeling, static strength/stiffness analysis, and POLYFLOW-based numerical simulation of particle melt conveying/mixing in the screw channel were conducted to analyze structural parameter effects on pressure field, shear rate, and mixing. Experiments assessed printer extrusion rate (different screws) and printed specimen mechanical properties. The simulation and experiment confirmed the optimized screw has better pressure distribution and mixing at 20 rpm, with optimal pin parameters: diameter 2 mm, height 1.6 mm, radial angle 60°, and axial spacing 10 mm. This work offers theoretical/structural support for particle-based 3D printing extrusion system optimization. Full article

Clear aligners are increasingly used as an alternative to fixed appliances in orthognathic surgery, particularly for skeletal Class III malocclusions. This scoping review aimed to evaluate the effectiveness of clear aligners in the pre- and postoperative phases of surgical treatment and was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. Electronic searches were conducted in PubMed, Scopus, Embase, Web of Science, Cochrane Library, and OpenGrey. Data extraction considered study design, country, sample characteristics, surgical protocol, orthodontic biomechanics, use of auxiliaries, and cephalometric outcomes. Seven studies published between 2020 and 2024 were included. They involved 120 adult patients treated with Invisalign^® combined with Le Fort I osteotomy and bilateral sagittal split osteotomy. All studies reported skeletal improvements, particularly in ANB angle and Wits appraisal, with maintenance of vertical dimensions. Clear aligners facilitated presurgical dental decompensation, torque control, and postsurgical occlusal refinement, with auxiliaries and digital tools enhancing predictability. Despite variability in protocols and limited long-term follow-up, outcomes were comparable to those achieved with fixed appliances. Current evidence supports the clinical viability of integrating clear aligners into orthognathic surgery, although standardized protocols and further high-quality prospective studies are needed to confirm long-term stability. Full article

Waxy maize (Zea mays L. ceratina) is extensively cultivated and exhibits substantial market demand in China; however, its yield and quality improvement remain constrained by relatively underdeveloped cultivation techniques. Optimizing plant density and row spacing is critical to improving the yield and nutritional quality of waxy maize, yet their combined effects remain insufficiently explored. A split-plot design evaluated two plant densities, i.e., 5.25 × 10⁴ plants ha⁻¹ (PD_5.25) and 6.75 × 10⁴ plants ha⁻¹ (PD_6.75), and three row configurations, i.e., 80 + 40 cm wide–narrow rows (RS_8-4), 100 + 20 cm wide–narrow rows (RS_10-2) and conventional 60 + 60 cm equal rows (RS_6-6). This study aims to identify the optimal cultivation configuration for waxy maize in the Loess Plateau region. Results showed that the RS_8-4 configuration maximized agronomic traits, dry matter accumulation, and yield relative to RS_6-6 and RS_10-2 treatments. Specifically, RS_8-4 reduced the insertion angle of the lower ear leaf by 12.4% (p < 0.05) and ear height by 8.3% while increasing yield by 19.86–20.00% compared to RS_6-6 and RS_10-2 treatments. At fresh-market maturity, dry matter accumulation under RS_8-4 treatment increased significantly by 34.0% with higher plant density. Under PD_6.75, RS_8-4 boosted dry matter by 29.8% and 39.4% versus RS_6-6 and RS_10-2, respectively. Under the RS_8-4 and PD_6.5 configurations, dry matter accumulation reached 13.56 t ha⁻¹ and a yield of 9.94 t ha⁻¹ was achieved in 2022. In summary, the combination of the PD_6.75 density and the RS_8-4 row spacing configuration achieved the optimal yield for the ‘Jinnuo 20’ cultivar in the Loess Plateau region. This approach provides a scalable planting framework for high-yield waxy maize production in the area, while demonstrating that optimized plant density and row spacing represent not only a key technical measure for enhancing productivity but also a core agronomic strategy for improving resource-use efficiency. Full article

(1) Background: Soccer action recognition (SAR) is essential in modern sports analytics, supporting automated performance evaluation, tactical strategy analysis, and detailed player behavior modeling. Although recent advances in deep learning and computer vision have enhanced SAR capabilities, many existing methods remain limited to coarse-grained classifications, grouping actions into broad categories such as attacking, defending, or goalkeeping. These models often fall short in capturing fine-grained distinctions, contextual nuances, and long-range temporal dependencies. Transformer-based approaches offer potential improvements but are typically constrained by the need for large-scale datasets and high computational demands, limiting their practical applicability. Moreover, current SAR systems frequently encounter difficulties in handling occlusions, background clutter, and variable camera angles, which contribute to misclassifications and reduced accuracy. (2) Methods: To overcome these challenges, we propose TAT-SARNet, a structured framework designed for accurate and fine-grained SAR. The model begins by applying Sparse Dilated Attention (SDA) to emphasize relevant spatial dependencies while mitigating background noise. Refined spatial features are then processed through the Split-Stream Feature Processing Module (SSFPM), which separately extracts appearance-based (RGB) and motion-based (optical flow) features using ResNet and 3D CNNs. These features are temporally refined by the Multi-Granular Temporal Processing (MGTP) module, which integrates ResIncept Patch Consolidation (RIPC) and Progressive Scale Construction Module (PSCM) to capture both short- and long-range temporal patterns. The output is then fused via the Context-Guided Dual Transformer (CGDT), which models spatiotemporal interactions through a Bi-Transformer Connector (BTC) and Channel–Spatial Attention Block (CSAB); (3) Results: Finally, the Cascaded Temporal Classification (CTC) module maps these features to fine-grained action categories, enabling robust recognition even under challenging conditions such as occlusions and rapid movements. (4) Conclusions: This end-to-end architecture ensures high precision in complex real-world soccer scenarios. Full article

A polyurethane slurry was developed to simultaneously enhance the strength and permeability of geological formations, differing from the conventional fracture grouting used for soft-soil reinforcement. Injected via splitting grouting, the slurry cures to form high-strength, highly permeable channels that increase reservoir permeability while improving mechanical stability (dual-enhanced stimulation). To quantify its diffusion behavior and guide field application, we built a splitting-grouting model using the finite–discrete element method (FDEM), parameterized with the reservoir properties of coalbed methane (CBM) formations in the Ordos Basin and the slurry’s measured rheology and filtration characteristics. Considering the stratified structures within coal rock formed by geological deposition, this study utilizes Python code interacting with Abaqus to divide the coal seam into coal rock and natural bedding. We analyzed the effects of engineering parameters, geological factors, and bedding characteristics on slurry–vein propagation patterns, the stimulation extent, and fracturing pressure. The findings reveal that increasing the grouting rate from 1.2 to 3.6 m³/min enlarges the stimulated volume and the maximum fracture width and raises the fracturing pressure from 26.28 to 31.44 MPa. A lower slurry viscosity of 100 mPa·s promotes the propagation of slurry veins, making it easier to develop multiple veins. The bedding-to-coal rock strength ratio controls crossing versus layer-parallel growth: at 0.3, veins more readily penetrate bedding planes, whereas at 0.1 they preferentially spread along them. Raising the lateral pressure coefficient from 0.6 to 0.8 increases the likelihood of the slurry expanding along the beddings. Natural bedding structures guide directional flow; a higher bedding density (225 lines per 10,000 m³) yields greater directional deflection and a more intricate fracture network. As the angle of bedding increases from 10° to 60°, the slurry veins are more susceptible to directional changes. Throughout the grouting process, the slurry veins can undergo varying degrees of directional alteration. Under the studied conditions, both fracturing and compaction grouting modes are present, with fracturing grouting dominating in the initial stages, while compaction grouting becomes more prominent later on. These results provide quantitative guidance for designing dual-enhanced stimulation to jointly improve permeability and mechanical stability. Full article