Search Results (1,411)

Crop leaves naturally exhibit a curved morphology and primarily display bending deformation and vibrational responses under wind load. The curved surface structure of leaves plays a critical role in the deposition and retention of pesticide droplets. In this study, wind tunnel experiments combined with high-speed photography and digital image analysis were conducted to systematically investigate the curvature and flexibility distributions of three typical crop leaves: walnut, peach, and pepper, across a range of wind speeds. The results indicate that with increasing wind speed, all three types of leaves gradually transition from smooth, uniform bending to a multi-peak pattern of pronounced local curvature, with increasingly prominent nonlinear deformation characteristics. Moreover, once the wind speed exceeds the critical threshold of 6 m/s, the primary deformation region generally shifts from the leaf base to the tip. For example, the maximum curvature of walnut leaves increased from 0.018 mm⁻¹ to 0.047 mm⁻¹, and that of pepper leaves from 0.031 mm⁻¹ to 0.101 mm⁻¹, both more than double their original values. In addition, all three types of leaves demonstrated a distinct structural gradient characterized by strong basal rigidity and high apical flexibility. The tip flexibility values exceeded 1.5 × 10⁻⁵, 4 × 10⁻⁴, and 5.6 × 10⁻⁴ mm⁻²·mN⁻¹ for walnut, peach, and pepper leaves, respectively. These findings elucidate the mechanical response mechanisms of non-uniform flexible crop leaves under wind-induced bending and provide a theoretical basis and data support for the optimization of air-assisted spraying parameters. 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

Powder metallurgy tool steels, such as Vanadis 4 Extra (1.2210), are increasingly used in cold-work applications due to their superior hardness, wear resistance, and microstructural uniformity. Despite their growing popularity, there is limited data regarding their machinability, especially in milling processes. In this study, experimental milling tests were performed on Vanadis 4 Extra steel using AlCrN-coated carbide tools. A full factorial experimental design (3⁴) was applied to investigate the effects of cutting speed, depth of cut, width of cut, and feed per tooth on cutting forces (Fx, Fy, Fz, Fc), surface roughness parameters (Ra, Rz), and tool wear. Cutting forces were measured using a Kistler dynamometer, and surface roughness was evaluated using a contact profilometer. Regression models were developed and statistically validated. The results indicate that depth of cut had the most significant influence on cutting force, while cutting speed had the greatest impact on surface roughness. Moderate correlation between cutting forces and roughness was observed, particularly under low-load conditions. SEM analysis revealed abrasive wear and chipping of the coating layer. The findings provide insights into the machinability of Vanadis 4 Extra and offer guidelines for optimizing milling parameters to enhance tool life and surface integrity. Full article

Slurry-based additive manufacturing (AM) enables the fabrication of dense and complex ceramic components through the layer-by-layer deposition of high-solid-content slurries. However, the reliable formation of uniform, defect-free slurry layers remains a bottleneck for process stability and final part quality. In this study, the slot-die coating window for alumina slurry (50 wt%, viscosity = 34 Pa·s) was systematically investigated using volume-of-fluid simulations and experiments, with coating speed (0.7–2.8 mm/s), flow rate (0.6–0.8 mL/min), and coating gap (200–400 μm) as key variables. The coating process exhibited three distinct regimes, namely overflow, stable, and unstable, depending on process conditions. For a coating gap of 200 μm on a glass substrate, stable bead formation was observed over the widest coating speed range without overflow or air entrainment. At higher speeds, dynamic wetting failure induced air entrainment and bead breakage, while lower speeds led to overflow defects. When coating on a dried alumina layer (contact angle, CA = 137$°$), the stable window narrowed significantly compared to the glass substrate (CA = 66.7$°)$, highlighting the substantial influence of substrate wettability on coating stability and defect formation. The results derived in this work offer practical guidance for optimizing process parameters to achieve uniform, defect-free films in multilayer ceramic AM. Full article

In this study, pressure gradient effects on heat transfer from block-like electronic chips are investigated computationally. The pressure gradient is provided by the slope given to the upper plate and starts just before the first block. Tilt angles of −2°, 0°, 2°, 4° and 6° have been used. Air is used as the fluid, and it enters the duct at a constant speed with a uniform velocity profile. Calculations were made for Re numbers (Re = 6000, 9015, and 11,993) defined according to the channel height. For this purpose, conservation and SST k-ω turbulence model equations are solved by using ANSYS-Fluent 20.1 software for two-dimensional, incompressible, and turbulent flow conditions. Velocity, temperature, pressure, and turbulence kinetic energy distributions were obtained and compared for the considered slope angles. The effects of all changing conditions on heat transfer were discussed by calculating local and average Nusselt values, the reattachment lengths after the last block were calculated by plotting, and a comparison was made by plotting the pressure values on the block in the middle of the channel and at the top of the channel. Full article

Recent advancements in rice breeding have significantly increased production in China. However, high-yielding varieties require strong airflow for effective cleaning. Longitudinal-flow rice combine harvesters equipped with a centrifugal fan with four blades are widely used in China; however, these fans exhibit fluctuating cleaning performance and airflow maldistribution. To address these limitations, this study developed an innovative multi-blade cleaning fan design by incorporating the blade clocking effect, a concept not previously applied in centrifugal fans. To support the design process, the required airflow rates and reduction in static pressure were first analyzed. Based on these findings and fundamental fan design theory, three fan models were designed with blade clocking angles of 0°, 5.5°, and 10.5°, respectively. Three fan models were evaluated through computational fluid dynamics (CFD) simulations using a design of experiments approach based on Box–Behnken design response surface methodology to identify the optimal fan. The fan features a 10.5° clocking angle, meeting the airflow requirements for effective cleaning. In the test bench measurements, the setup with guide plate angles No. 1 and No. 2 at 32° and a fan speed of 1200 rpm was identified as optimal. The newly designed multi-blade cleaning fan overcomes the limitations of conventional four-blade designs, significantly enhancing airflow uniformity. Full article

This study compares the Eddy current technique and optical microscopy for measuring the anodized layer thickness in a 6063 aluminum alloy with the aim of establishing an efficient and accurate methodology capable of delivering optimal results in a time-efficient manner. Optical microscopy was used as the reference method, with five measurements taken in different fields for each specimen. The Eddy current method was applied using two calibration strategies: one calibration before each measurement and another after every ten specimens. The Bland–Altman analysis was employed to compare both measurement techniques. The results indicated that the calibration before each measurement strategy using Eddy current showed higher agreement with the reference method, suggesting that both techniques can be considered equivalent and interchangeable. Furthermore, the Eddy current method demonstrated significant advantages in detecting thickness variations along the specimen, revealing non-uniform distribution of the anodized layer. This method also proved to be faster and eliminated the need for metallographic preparation required by optical microscopy, thus significantly reducing analysis time and cost. In conclusion, the Eddy current method with calibration before each measurement strategy is proposed as an effective alternative for measuring anodized layer thickness in applications where speed and precision are critical. Full article

To enhance the wear resistance of laser-clad coatings, this study investigates the underlying modulation mechanisms of scanning speed on the microstructure and properties of TiC-TiB₂-reinforced 316L stainless steel composite coatings. TiC/TiB₂ particle-reinforced 316L stainless steel composite coatings were fabricated on 45# steel substrates via laser cladding. Our analysis reveals that scanning speed critically governs the thermal cycle of the melt pool, thereby modulating the coating’s microstructure and properties: Lower scanning speeds prolong melt pool duration, consequently intensifying ceramic particle dissolution, coarsening, and tendencies toward agglomeration and settling. Conversely, higher scanning speeds promote rapid solidification, which both preserves ceramic particles and refines the matrix grains. With increasing scanning speed, accelerated melt pool cooling rates drive a microstructural transition from coarse dendrites to refined equiaxed grains, accompanied by dramatically enhanced uniformity in ceramic particle distribution. Coatings deposited at higher scanning speeds exhibit a 22% increase in hardness compared to those at lower speeds. Wear resistance evolution parallels this hardness trend: at 480 mm/min scanning speed, wear reduction can be expected, with the wear volume decreasing by 58.60% and the friction coefficient reducing by 42.1% relative to 120 mm/min. Full article

The jet fan system is a widely adopted form of longitudinal ventilation due to its cost-effectiveness, operational flexibility, and high reliability. However, in large-section highway tunnels with a low height-to-span ratio, the limited clearance between the tunnel ceiling and surrounding structural boundaries imposes significant constraints on improving ventilation performance by adjusting the installation height or pitch angle of the jet fan. To address this limitation, this study proposes a deflector shield system to enhance the aerodynamic efficiency of jet fans. A total of thirteen test cases, including a control group, three deflector plate quantities, and four deflector pitch angles, were tested in a full-scale field test conducted in a large-section tunnel. The objective of this study was to evaluate the influence of the number and pitch angle of deflector plates on tunnel ventilation efficiency and to identify the optimal parameter combination for application in large-section tunnels. The results show that static pressure along the tunnel initially rises with distance from the fan, peaks, and then declines sharply. The pressure rise coefficient is significantly enhanced under several configurations, particularly with four deflector plates at 8° and 10° pitches, and with five plates at 4° to 10° pitches. When the number of deflector plates is five, a sharp drop in average wind speed is observed 15 m downstream of the fan, and extensive low-velocity regions appear further downstream. In contrast, the configurations with four deflector plates at 8° and 10° exhibit better wind speed uniformity in the downstream flow field. Considering both the pressure rise coefficient and wind speed uniformity, the optimal ventilation performance of the jet fan system is achieved with four deflector plates at a pitch angle of 8°. Full article

In this work, an adaptive dynamic programming (ADP)-based event-triggered infinite-horizon ($H_{\infty }$) control algorithm is proposed for high-precision speed regulation of permanent magnet synchronous motors (PMSMs). The $H_{\infty }$ control problem of PMSM can be formulated as a two-player zero-sum differential game, and only a single critic neural network is needed to approximate the solution of the Hamilton–Jacobi–Isaacs (HJI) equations online, which significantly simplifies the control structure. Dynamically balancing control accuracy and update frequency through adaptive event-triggering mechanism significantly reduces the computational burden. Through theoretical analysis, the system state and critic weight estimation error are rigorously proved to be uniform ultimate boundedness, and the Zeno behavior is theoretically precluded. The simulation results verify the high accuracy tracking capability and the strong robustness of the algorithm under both load disturbance and shock load, and the event-triggering mechanism significantly reduces the computational resource consumption. Full article

During electron beam cold hearth melting (EBCHM) of Ti-6wt%Al-4wt%V titanium alloy, aluminum volatilization causes compositional segregation in the ingot, significantly degrading material performance. Traditional methods (e.g., the Langmuir equation) struggle to accurately predict aluminum diffusion and compensation behaviors, while computational fluid dynamics (CFD), although capable of resolving multiphysics fields in the molten pool, suffer from high computational costs and insufficient research on segregation control. To address these issues, this study proposes a CFD-machine learning (backpropagation neural network, CFD-ML(BP)) approach to achieve precise prediction and optimization of aluminum segregation. First, CFD simulations are performed to obtain the molten pool’s temperature field, flow field, and aluminum concentration distribution, with model reliability validated experimentally. Subsequently, a BP neural network is trained using large-scale CFD datasets to establish an aluminum concentration prediction model, capturing the nonlinear relationships between process parameters (e.g., casting speed, temperature) and compositional segregation. Finally, optimization algorithms are applied to determine optimal process parameters, which are validated via CFD multiphysics coupling simulations. The results demonstrate that this method predicts the average aluminum concentration in the ingot with an error of ≤3%, significantly reducing computational costs. It also elucidates the kinetic mechanisms of aluminum volatilization and diffusion, revealing that non-monotonic segregation trends arise from the dynamic balance of volatilization, diffusion, convection, and solidification. Moreover, the most uniform aluminum distribution (average 6.8 wt.%, R² = 0.002) is achieved in a double-overflow mold at a casting speed of 18 mm/min and a temperature of 2168 K. Full article

Uniform and graded BCC lattice cylindrical shells were proposed, and the corresponding structural specimens were fabricated with 316L stainless steel material. Experimental testing and numerical simulations were both utilized to investigate the quasi-static and dynamic compression behavior of the uniform and graded BCC lattice cylindrical shells. Finite element results were compared with the experimental results. Parametric studies were conducted to study the effects of relative density, gradient distribution, and loading velocity on the mechanical properties and deformation features. When the relative density increased from 9% to 25%, a 175% increase in SEA could be seen. Graded BCC lattice cylindrical shells almost exhibited the same mechanical performance. When compared with the SEA value under low-speed loading conditions, a 26.95% maximum increase could be witnessed in the graded-5 specimen under high-speed loading. Testing results indicated that the proposed uniform and graded BCC lattice cylindrical shells exhibited fascinating quasi-static and dynamic mechanical behavior, which provided guidance for the design and application of next-generation lightweight materials with excellent protective properties. Full article

To address the issue in high-throughput longitudinal axial-flow grain combine harvester cleaning systems, in which the extended length of the cleaning chamber results in airflow velocity attenuation and makes it difficult to efficiently and rapidly remove light impurities, a front-blowing and rear-suction enhanced cleaning technology and device was developed. Based on the investigation of the movement characteristics of the cleaning airflow within the cleaning chamber, a theoretical model was established to describe the velocity variation of the front-blowing and rear-suction enhanced cleaning airflow. CFD simulation software was employed to conduct a comparative analysis of the airflow field structure before and after improvement, aiming to identify the influence patterns of key structural parameters on the airflow field distribution. An orthogonal experiment with three factors and three levels was conducted on the improved cleaning system, focusing on the suction fan speed, vertical installation height of the suction fan, and horizontal distance between the suction fan and the sieve surface. The influence of each factor on the airflow field was analyzed, and the optimal parameter combination was obtained. When the suction fan speed was 2275 r/min, the vertical installation height was 72.5 mm, the horizontal distance to the sieve surface was 385 mm, and the airflow non-uniformity coefficient at the rear part of the screen surface was 11.17%, with a relative error of 4.39% compared to the optimization result. Finally, bench tests were conducted to verify the accuracy of the simulation results. Compared to that before improvement, the airflow non-uniformity coefficient at the rear part of the screen surface in the cleaning chamber was reduced by 59.43%, significantly improving the uniformity of airflow distribution. These findings provide both theoretical and technical support for improving the cleaning efficiency and operational performance of high-throughput grain combine harvesters. Full article

In recent years, in situ blasting–leaching, in the stope has emerged as an economically viable and environmentally sustainable mining technique for low-grade ore deposits. While the leaching efficiency is influenced by factors such as ore type, solution composition, and spraying speed, the most significant factor is the effect of post-blasting crushed-stone particle size and gradation on the pore structure, which subsequently influences seepage and leaching performance. To investigate how particle size and gradation affect the pore structure of granular media, physical models of ore particles with varying sizes and gradations were constructed. These models were scanned and three-dimensionally reconstructed using CT scanning technology and Avizo software (Avizo, Version 2023.1; Thermo Fisher Scientific: Waltham, MA, USA, 2023) enabling quantitative analysis of pore structure parameters. The results indicate that the coefficient of uniformity (Cu) is approximately negatively correlated with porosity, while the vertical absolute permeability (kz) follows an attenuated exponential trend. When the fine-particle content (L8 > L3 > L1) increases by 1.5-fold and 9-fold, the number of pore throats increases by 8.71% and 30.91%, respectively, the average pore size decreases by 75.1% and 64.4%, the average throat size decreases by 66.3% and 60%, and the connectivity rate decreases by 92% and 77.8%. This study further evaluates permeability based on the aforementioned pore structure parameters. Multiple regression analysis reveals that the connectivity rate and throat size have the most significant influence on permeability. Accordingly, permeability analysis and prediction are conducted using the improved Purcell formula, which demonstrates a strong correlation with the experimentally measured results. Full article

China ranks as the world’s leading potato (Solanum tuberosum L.) producer, while the poor seeding machinery performance limited a higher input–output ratio in potato cultivation and impeded sustainable development. We developed an advanced air-suction mulai-arm potato planter (ASPP) that incorporated integrated side-deep fertilization, automated seed feeding, negative-pressure seed filling, seed transportation, positive-pressure seed delivery, soil covering, and compaction. The study proposes a Negative-pressure seed extraction mechanism that minimizes seed damage by precisely controlling suction pressure, and the near-zero-speed seed delivery mechanism synchronizes seed release with ground speed, reducing bounce-induced spacing errors. Furthermore, the structural configuration and operation principle of ASPP were systematically elucidated, and key performance parameters and optimal values were identified. We conducted a randomized complete block design plot trial comparing the spoon-belt potato planter (SBPP) and spoon-chain potato planter (SCPP), evaluating sowing quality, seedling emergence rate (ER), potato yield (PY), and comprehensive economic benefits. The results revealed that plant spacing index (PSI), missed-seeding index (MI), re-seeding index (RI), and coefficient of variation (CV) of ASPP were 90.05%, 3.78%, 2.32%, and 7.93%, respectively. The mean ER values for ASPP, SBPP, and SCPP were 94.76%, 85.42%, and 83.46%, respectively, with the ASPP showing improvements of 10.93% and 13.54% over SBPP and SCPP. However, the SBPP and SCPP exhibited greater emergence uniformity than ASPP. The mean PY value was 37,205.25, 32,973.75, and 34,620 kg·ha⁻¹ for ASPP, SBPP, and SCPP. The ASPP outperformed the SBPP and SCPP by 12.83% and 7.47%. Overall, ASPP demonstrated balanced and superior performance across the above-mentioned indicators, demonstrating its potential to enable precision agriculture in tuber crop cultivation. Full article