Search Results (2,308)

The shear-compression failure of key strata leads to stair-step collapse and severe mine pressure, posing significant safety risks in coal mines. Existing theories fail to account for the boundary conditions and breaking sizes of key strata, making accurate description of shear-compression failure difficult. A periodic breakage mechanics model for key strata was developed using Timoshenko Beam and Winkler Foundation Theory, incorporating transverse shear deformation. The deflection, rotation angle, bending moment, and shear force were calculated, and a shear-compression failure criterion function f(x) was derived. The main conclusions include the following: (1) shear-compression failure is influenced by the thickness–span ratio, cohesion, internal friction angle, and elastic modulus of the key strata, but not by the elastic foundation coefficient and shear modulus; (2) shear-compression failure occurs when the thickness–span ratio reaches 0.4; (3) when the internal friction angle is 25°, 30°, 35°, or 40°, shear-compression failure does not occur if cohesion exceeds 8.0, 7.5, 7.0, or 6.5 MPa, respectively, with a larger internal friction angle corresponding to a smaller critical cohesion; (4) when cohesion is 6 MPa, 8 MPa, 10 MPa, or 12 MPa, shear-compression failure does not occur if the internal friction angle exceeds 44°, 32°, 19°, or 8°, respectively, with larger cohesion correlating to a smaller critical internal friction angle; and (5) once cohesion or internal friction angle surpasses a critical value, the failure criterion approaches a constant value, preventing failure; the elastic modulus has a greater effect on shear-compression failure than the shear modulus, with higher elastic modulus increasing the likelihood of failure. Full article

Seeding depth is a critical factor influencing the uniformity and vigor of wheat seedlings. To address inconsistent seeding depth in wide-row uniform seeding agricultural practices, we performed parameter analysis and optimization experiments on the seeding depth device of a wheat wide-row uniform seeding machine. The structure and working principle of the device were described, soil movement during operation was analyzed, and the models of rotary tiller blades and soil retention plates were investigated, identifying three key factors affecting seeding quality. Using the discrete element method, a model of the seeding depth device was established, and experiments were conducted, yielding the following conclusions: 1. Single-factor experiments were conducted under different seeding rate conditions, and it was found that the effects of various factors on the two indicators, namely the seeding depth qualification rate and the coefficient of variation for seeding uniformity, were regular. 2. A quadratic orthogonal rotated combination experiment with three factors determined the optimal structural parameters: tillage device penetration depth of 120 mm, rotational speed of 310 rpm, and soil retention plate inclination angle of 27°. Under these parameters, the seed depth qualification rate exceeded 90%, and the coefficient of variation for seed distribution uniformity was below 25%. 3. Field validation tests under optimal parameters confirmed a seed depth qualification rate ≥90% and variation for seed distribution uniformity was below ≤20.69%. 4. The error between simulation and field tests was ≤5%, validating the reliability of the discrete element method-based optimization for the seeding depth device. Full article

The electronics industry has significantly contributed to the development of efficient heat dissipation systems. One widely used technique is pool boiling, a simple method requiring no moving parts or complex structures. It enables the removal of large amounts of heat at relatively low temperature differences. Enhancing pool boiling performance involves increasing the critical heat flux and the heat transfer coefficient, which defines how effectively a surface can transfer heat to a cooling fluid. This method is commonly applied in cooling electronic devices, digital circuits, and power systems. In this study, pool boiling at atmospheric pressure was investigated using copper surfaces. To validate the Rohsenow model used to estimate the maximum bubble departure diameter, a planimetric approach was applied. Measurements included average contact angle (CA), surface tension (σ), and droplet diameter for four working fluids: deionised water, ethanol, Novec-649, and FC-72. For each fluid, at least 15 measurements of CA and σ were conducted using the Young–Laplace model. This study provides a comprehensive analysis of the influence of contact angle and surface tension on nucleate boiling using four different fluids on copper surfaces. The novelty lies in combining high-precision experimental measurements with validation of the Rohsenow model, offering new insights into surface-fluid interactions critical for thermal system performance. Full article

Aiming at the problem of poor autonomy and weak time performance of reentry trajectory planning for Reusable Launch Vehicle (RLV), an online reentry trajectory planning and guidance method based on Twin Delayed Deep Deterministic Policy Gradient (TD3) is proposed. In view of the advantage that the drag acceleration can be quickly measured by the airborne inertial navigation equipment, the reference profile adopts the design of the drag acceleration–velocity profile in the reentry corridor. In order to prevent the problem of trajectory angle jump caused by the unsmooth turning point of the section, the section form adopts the form of four multiple functions to ensure the smooth connection of the turning point. Secondly, considering the advantages of the TD3 dual Critic network structure and delay update mechanism to suppress strategy overestimation, the TD3 algorithm framework is used to train multiple strategy networks offline and output profile parameters. Finally, considering the reentry uncertainty and the guidance error caused by the limitation of the bank angle reversal amplitude during lateral guidance, the networks are invoked online many times to solve the profile parameters in real time and update the profile periodically to ensure the rapidity and autonomy of the guidance command generation. The TD3 strategy networks are trained offline and invoked online many times so that the cumulative error in the previous guidance period can be eliminated when the algorithm is called again each time, and the online rapid generation and update of the reentry trajectory is realized, which effectively improves the accuracy and computational efficiency of the landing point. Full article

Ice accretion on critical transportation infrastructure presents serious operational risks and economic challenges, highlighting the need for sustainable anti-icing solutions. This study develops a strong PDMS-based composite coating on aluminum by incorporating carbon nanotubes (CNTs) and carbon powder, effectively merging passive superhydrophobicity with photothermal capabilities. We systematically assess how different ratios of CNTs to carbon powder (3:1, 1:1, 1:3) influence surface morphology, wettability, anti-icing performance, mechanical durability, and corrosion resistance. The morphological analysis shows the formation of hierarchical micro/nano-structures, with the optimal 1:3 ratio (designated as P13) resulting in dense, porous agglomerates of intertwined CNTs and carbon powder. P13 demonstrates high-performing superhydrophobicity, with a contact angle of 139.7° and a sliding angle of 9.4°, alongside a significantly extended freezing delay of 180 s at −20 °C. This performance is attributed to reduced water–surface interaction and inhibited ice nucleation. Mechanical abrasion tests indicate remarkable durability, as P13 retains a contact angle of 132.5° and consistent anti-icing properties after enduring 100 abrasion cycles. Electrochemical analysis reveals exceptional corrosion resistance, particularly for P13, which achieves a notable 99.66% corrosion inhibition efficiency by creating a highly tortuous diffusion barrier that protects against corrosive agents. This multifunctional coating effectively utilizes the photothermal properties of CNTs, the affordability of carbon powder, the low surface energy of PDMS, and the thermal conductivity of aluminum, presenting a robust and high-performance solution for anti-icing applications in challenging environments. Full article

Dynamic line rating (DLR) is an effective technique for real-time assessments on current-carrying capacities of overhead lines (OHLs), improving efficiencies and preventing overloads of transmission networks. Most research related to DLR forecasting mainly translates predictions of weather conditions into DLR forecasts or directly trains artificial intelligence models from DLR observations. Less attention has been given to the predictability of effective wind speeds (EWS) that describe overall convective cooling effects of varying weather conditions along OHLs, which could increase the reliability of DLR forecasts. To assess the effectiveness of EWS concepts in improving DLR predictions, this paper develops an EWS-based method for convective cooling predictions which are critical parameters dominating DLRs of overhead conductors. The EWS is first calculated from actual measurements of wind speeds and directions relative to OHL orientation based on the thermal model of overhead conductors. Then, an autoregressive model along with the Fourier series is employed to predict ultra-short-term EWS variations for up to three 10-min steps ahead, which are eventually converted into predictions of convective cooling effects along OHLs. The proposed EWS-based method is tested based on wind condition measurements in proximity to an OHL. Furthermore, to examine the impacts of angles between wind directions and line orientation on EWS estimation and thus EWS-based convective cooling predictions, the forecasting performance is assessed in the context of different line orientations. Results demonstrate that EWS-based ultra-short-term convective cooling predictions consistently outperform traditional forecasts from original wind conditions across all the tested line orientations. This highlights the significance of the EWS concept in reducing the complexity of DLR forecasting caused by the circular nature of wind directions, and in enhancing the accuracy of convective cooling predictions. Full article

Human pose estimation (HPE) in privacy-sensitive environments such as healthcare facilities and smart homes demands non-visual sensing solutions. Millimeter-wave (mmWave) radar emerges as a promising alternative, yet its development is hindered by the scarcity of high-fidelity datasets with accurate annotations. This paper introduces mmFree-Pose, the first dedicated mmWave radar dataset specifically designed for privacy-preserving HPE. Collected through a novel visual-free framework that synchronizes mmWave radar with VDSuit-Full motion-capture sensors, our dataset covers 10+ actions, from basic gestures to complex falls. Each sample provides (i) raw 3D point clouds with Doppler velocity and intensity, (ii) precise 23-joint skeletal annotations, and (iii) full-body motion sequences in privacy-critical scenarios. Crucially, all data is captured without the use of visual sensors, ensuring fundamental privacy protection by design. Unlike conventional approaches that rely on RGB or depth cameras, our framework eliminates the risk of visual data leakage while maintaining high annotation fidelity. The dataset also incorporates scenarios involving occlusions, different viewing angles, and multiple subject variations to enhance generalization in real-world applications. By providing a high-quality and privacy-compliant dataset, mmFree-Pose bridges the gap between RF sensing and home monitoring applications, where safeguarding personal identity and behavior remains a critical concern. Full article

Bifacial photovoltaic panels are preferred over monofacial panels due to the ability of their back surfaces to absorb radiation and generate electricity. However, optimizing the rear-side energy contribution remains a critical area of research. This study systematically investigates how four key parameters (albedo, tilt angle, panel height, and mounting configuration) affect rear-side energy generation and overall panel efficiency. In the first scenario, the impact of surface reflectivity was evaluated. High-reflectivity materials such as aluminum (21.2%) and fresh snow (20.5%) significantly increased rear-side energy yield. The second scenario examined tilt angle, showing that increasing the tilt up to 50° enhanced back-side generation, reaching a gain of 5.5%. The third scenario focused on the effect of panel height, revealing a linear relationship with energy generation. The fourth assessed orientation, comparing horizontal and vertical installations. Horizontal mounting provided a higher rear-side energy yield (4.5%) due to increased exposure to ground-reflected radiation. The findings of this study provide important information for the optimization of bifacial photovoltaic panels and the information will provide guidance for easier and more efficient installation of solar power plants. Full article

This study analyzes the stability of embankment slopes with inclined interlayers and vertical tensile cracks at the crest under saturated conditions. This study first establishes a composite failure mechanism based on a finite element limit analysis; then, it derives an upper-bound solution formula for stability considering pore water pressure; and finally, it verifies the rationality of the method through case comparisons. This study finds that an increase in crack depth (H_c) causes the crack initiation position to approach the crest edge, while increases in the slope angle (β), pore water pressure coefficient (r_u), and interlayer embedment depth (d) lead to the opposite trend. Both the stability number (γH/c₁) and safety factor (F_s) decrease with the increase in the slope angle, pore water pressure coefficient, and crack depth, and they increase with the enhancement of relative soil strength and the increase in interlayer embedment depth. When cracks exist at the crest, the influence of pore water pressure on the sliding surface is diminished, while decreasing the cohesion ratio of interlayer to embankment slope soil (c₂/c₁) expands the range of the critical sliding surface. Full article

Background: Malnutrition is a prevalent but underrecognized condition in cardiovascular disease (CVD) patients, associated with adverse outcomes including longer hospitalizations, higher readmission rates, and increased mortality. Traditional measures such as body mass index (BMI) often fail to detect malnutrition, especially in patients with fluid retention, sarcopenia, or obesity. Methods: This review critically examines current tools used to assess nutritional status in CVD populations. Screening instruments such as Nutritional Risk Screening 2002 (NRS 2002), Mini Nutritional Assessment (MNA, MNA-SF), Malnutrition Universal Screening Tool (MUST), Subjective Global Assessment (SGA), and the Controlling Nutritional Status (CONUT) score are discussed, alongside diagnostic frameworks including the Global Leadership Initiative on Malnutrition (GLIM) criteria. The role of body composition assessment, particularly bioelectrical impedance analysis (BIA) and phase angle (PA), is also highlighted. Results: These tools differ in diagnostic performance and applicability, with many influenced by the pathophysiological features of CVD, such as inflammation, altered fluid balance, and pharmacotherapy. GLIM criteria provide a standardized two-step approach, combining phenotypic and etiologic factors, but require further validation in cardiology settings. Conclusions: A tailored, multimodal approach could be recommended: initial screening followed by confirmatory assessment using GLIM criteria and objective measures of muscle mass or cellular integrity. Clinicians should be aware of tool-specific limitations and interpret findings in the context of CVD-specific challenges. Full article

With the continuous increase in mining activities, effective tailings management has become a critical concern in geotechnical and environmental engineering. This study systematically investigates the microstructural characteristics and 3D reconstruction behavior of copper tailings with different particle sizes using X-ray computed tomography (micro-CT), digital image processing, and 3D modeling techniques. Two particle size groups (fine: 0.075–0.15 mm; coarse: 0.15–0.3 mm) were analyzed to quantify differences in particle morphology, pore structure, and orientation anisotropy. Binary images and reconstructed models revealed that coarse particles tend to have more irregular and angular shapes, while fine particles exhibit more complex pore networks with higher fractal dimensions. The apparent porosity derived from CT data was consistently lower than laboratory measurements, likely due to internal agglomeration effects. Orientation analysis indicated that particle alignment and anisotropy vary systematically with section angle relative to the principal stress direction. These findings offer new insights into the particle-scale mechanisms affecting the packing, porosity, and anisotropy of tailings, providing a scientific basis for enhancing the structural evaluation and sustainable management of tailings storage facilities. Full article

Slotted roller buckets are energy dissipator structures designed to reduce the destructive power of high-velocity water flows in spillways, protecting downstream environments. This study aimed to estimate the critical role of slotted roller bucket design in downstream scour mitigation and hydraulic energy dissipation. The three-dimensional Navier–Stokes (N-St) equations were solved to simulate the jet flow over the roller bucket using CFD software. The free surface volume tracking using the volume of fluid (VOF) and non-equilibrium sediment transport equations was coupled with N-St to model the local scour downstream of the roller bucket system. Subsequently, the impact of bucket tooth lip angles, tailwater depth, and bucket radius on downstream scour were examined in a numerical 3D framework. The results showed that the 45- to 55-degree lip angle configuration significantly reduced the maximum scour depth by approximately 36%. Furthermore, the study quantified the effects of tailwater depth and bucket radius on scour dimensions and flow patterns. The optimal tailwater depth reduced scour depth by approximately 20% compared with the worst case, while variations in bucket radius led to more than a 50% difference in scour depth. We identified specific ranges for these parameters that further minimized erosion potential. The research also underscored the influence of transverse mixing on surging depth, revealing a crucial mechanism for energy dissipation. These findings contributed to a deeper understanding of the complex interplay between design parameters and scour. It offered practical insights for optimizing and operating hydraulic structures sustainably and understanding the scouring processes downstream of the dams. Full article

Background: Aging is associated with reduced joint flexibility and balance, which increases the risk of falls, especially during stair descent where motor control is critical. Stretching has been shown to improve ankle range of motion and gait speed. This study investigated the effects of a 4-week training program combining stretching plus resistance training (RT) with elastic bands on functional capacity and ankle stability during stair descent in older women. Methods: Twenty-four active older women (mean age: 73.1 ± 0.97 years) were randomly assigned to static stretching (SS), dynamic stretching (DS) and control (CG) groups. All participants completed two weekly 60 min sessions consisting of progressive RT preceded by three different warm-ups. The SS and DS groups completed static or dynamic stretching, while the CG walked. Assessments included 30s-Chair Stand (30s-CS), Handgrip Strength (HGS), Time Up and Go (TUG), Chair Sit and Reach (CSR), Rating of Perceived Exertion (RPE), and ankle kinematics during stair descent. Results: All groups improved 30s-CS and TUG (p < 0.05). Only the SS group improved CSR in both legs and the ankle dorsiflexion angle during stair descent at final foot contact (p = 0.002). RPE increased over time across all groups (p < 0.0001); however, the SS and DS groups reported lower exertion than the CG group in first–second weeks (p = 0.0001–0.003). Conclusions: SS prior to progressive RT improved flexibility and ankle kinematics during stair descent, thus reducing the perception of effort particularly during the initial training phase. These findings indicate the effectiveness of SS as a warm-up strategy for increasing ROM and potentially reducing the risk of falls in this population. Full article

Capsule-based self-healing technologies offer a promising solution to extend pavement service life without requiring external activation. The effect of the capsule content on the mechanical behaviour of self-healing asphalt mixtures still needs to be understood. This study presents a numerical evaluation of the isolated effect of incorporating capsules containing encapsulated rejuvenators, at different volume contents, on the stiffness and strength of asphalt mixtures through a three-dimensional discrete-based programme (VirtualPM3DLab), which has been shown to predict well the experimental behaviour of asphalt mixtures. Uniaxial tension–compression cyclic and monotonic tensile tests on notched specimens are carried out for three capsule contents commonly adopted in experimental investigations (0.30, 0.75, and 1.25 wt.%). The results show that the effect on the stiffness modulus progressively increases as the capsule content grows in the asphalt mixture, with a reduction ranging from 4.3% to 12.3%. At the same time, the phase angle is marginally affected. The capsule continuum equivalent Young’s modulus has minimum influence on the overall rheological response, suggesting that the most critical parameter affecting asphalt mixture stiffness is the capsule content. Finally, while the peak tensile strength shows a maximum reduction of 12.4% at the highest capsule content, the stress–strain behaviour and damage evolution of the specimens remain largely unaffected. Most damaged contacts, which mainly include aggregate–mastic and mastic–mastic contacts, are highly localised around the notch tips. Contacts involving capsules remained intact during early and intermediate loading stages and only fractured during the final damage stage, suggesting a delayed activation consistent with the design of healing systems. The findings suggest that capsules within the studied contents may have a moderate impact on the mechanical properties of asphalt mixtures, especially for high-volume contents. For this reason, contents higher than 0.75 wt.% should be applied with caution. Full article

Accurate computation of external heat flux is critical for spacecraft thermal analysis and thermal control system design. The traditional method, which adopted the uniform planetary infrared radiation model (UPIRM), is inadequate for lunar orbital missions due to the extreme planetary surface temperature variations. This study proposes an external heat flux calculation method for lunar orbits by integrating a non-uniform lunar surface temperature model derived from Lunar Reconnaissance Orbiter (LRO) Diviner radiometric data. Specifically, the lunar surface temperature data were first fitted as functions of latitude ($\psi$) and position angles ($\zeta$) through data regression analysis. Then, a comprehensive mathematical framework is established to analyze solar radiation, lunar albedo, and lunar infrared radiation components, incorporating orbital parameters such as beta angle ($\beta$), orbital inclination ($i$) and so on. Coordinate transformations and numerical integration techniques are employed to evaluate heat flux distributions across cuboidal orbiter surfaces. It is found that the lunar infrared radiation heat flux manifests pronounced fluctuation, peaking at 1023 W/m² near the lunar noon region while plummeting to 20 W/m² near the midnight region under the orbital parameters investigated in this study. This study demonstrates the essential role of the non-uniform planetary infrared radiation model (NUPIRM) in enhancing prediction accuracy by contrast, offering foundational references for thermal management in future lunar and deep-space exploration spacecraft. Full article