Search Results (218)

The rapid acquisition of spatial information over affected areas is critical for emergency decision-making and disaster assessment in complex environments. Unmanned aerial vehicles (UAVs) have become an important tool for disaster information acquisition due to their rapid deployment and flexible observation capabilities. However, multi-UAV remote sensing information acquisition in complex obstacle-laden environments still faces challenges such as insufficient coverage efficiency, limited obstacle avoidance capability, and weak cooperation. This paper proposes a multi-UAV cooperative remote sensing coverage method based on an improved rotational potential field (IRPF). A disaster area model is first constructed. The artificial potential field is then enhanced by integrating separation forces and rotational guidance mechanisms to improve obstacle avoidance and information acquisition capability in complex environments, while coverage feedback is incorporated to enable dynamic observation region allocation. The experimental results show that the proposed method achieves a multi-run success rate of 100.0% over 20 independent experiments, with a final coverage rate of 93.3% in the representative scenario. The UAV system reaches the predefined 85% coverage threshold at step 106 and maintains zero collisions throughout the entire process. This method provides an effective approach for multi-UAV cooperative coverage planning in simulated complex environments, providing a potential approach for cooperative coverage planning in simulated disaster environments. Full article

In recent years, hydrogen-fueled internal combustion engines offer significant potential for achieving high efficiency and near-zero carbon emissions. However, stable combustion remains challenging due to the limited time available for fuel–air mixing, particularly in direct-injection concepts. This study investigates the influence of injector orientation on in-cylinder charge preparation in a heavy-duty spark-ignition engine operating with a side-mounted hydrogen direct-injection strategy. Three-dimensional computational fluid dynamics (CFD) simulations are performed to evaluate the effects of injector blow-cap inclination and azimuthal alignment on hydrogen jet evolution, flow-field development, and mixture formation. Under high-pressure injection conditions, hydrogen enters the cylinder as a highly under-expanded jet with strong momentum, resulting in significant interaction with the in-cylinder flow field. The results show that injector inclination influences jet impingement behavior, wall-guided flow development, and subsequent vortex evolution, while injector rotation modifies the interaction between the jet trajectory and in-cylinder swirl motion, affecting aerodynamic shear and flow-field complexity. The resulting mixture formation is evaluated through local air–fuel ratio distribution together with flow-field analysis and streamline evolution, demonstrating strong sensitivity to injector orientation and its coupling with in-cylinder aerodynamic structures. Quantitatively, injector orientation produces significant changes in the local air–fuel ratio distribution, with up to 25% reduction in the standard deviation of local air–fuel ratio for inclination variations and up to 35% for azimuthal variations between the extreme configurations, indicating improved mixture uniformity. Configurations promoting earlier jet disruption and enhanced spatial dispersion achieve more homogeneous charge preparation, whereas stronger wall-guided jet attachment results in localized fuel-rich regions. The findings provide physical insight into the role of jet–wall interaction, aerodynamic shear, and vortex restructuring in governing hydrogen mixing processes. The simulation framework captures the relevant in-cylinder flow physics and provides trends consistent with available experimental observations in the literature, which report improved efficiency and reduced NOx emissions under enhanced mixture homogeneity conditions. Full article

Long-term crop rotation can improve soil function and crop performance, but it remains unclear whether rotation history can simultaneously alleviate drought-induced oxidative injury in spring wheat leaves and roots. To address this gap, we used a long-term field rotation experiment established in 2016 in the western foothills of the Greater Khingan Mountains. Four cropping systems were selected: spring wheat–potato rotation (R1), spring wheat–potato–rape rotation (R2), spring wheat–rape rotation (R3), and continuous spring wheat cropping (C1). In 2022, wheat occurred naturally in all rotation sequences, and all plots were planted with the same spring wheat cultivar (‘Longmai 36’) to enable comparison among different rotation histories. Drought stress was imposed from late jointing, and at anthesis, ROS-related levels, malondialdehyde (MDA), glutathione (GSH), and proline (Pro), as well as the activities of superoxide dismutase (SOD) and peroxidase (POD), were determined in the flag leaves and roots of spring wheat under normal-water (NC) and drought-stress (HC) conditions. Under drought stress, rotation significantly increased yield (R1 and R2 by 73.3% and 77.7% vs. C1, respectively, partly reflecting the low C1 baseline associated with continuous cropping) and reduced drought-induced accumulation of ROS-related levels and MDA, along with excessive antioxidant and osmotic responses. R1 better protected leaves, while R2 optimized root osmotic regulation. Two-way ANOVA revealed significant drought × rotation interactions for most leaf traits (p < 0.01) but not for root ROS-related levels, SOD, or POD, indicating organ-specific regulation. R1 and R2 show strong drought resilience potential, warranting multi-year, multi-site validation. Full article

High-quality and high-efficiency machining of film cooling holes (FCHs) is critical for enhancing the performance of gas turbines and aero-engines. Nanosecond fiber lasers offer advantages such as high stability, good beam quality, and ease of integration. However, when machining FCHs, issues including low drilling efficiency and significant thermal effects severely limit their industrial applications. In this study, a dual-rotary trepanning system was developed based on a nanosecond fiber laser, a galvanometer, and a five-axis cradle machine. High-quality FCHs with a diameter of 0.6 mm were efficiently machined in a 3-mm-thick DD6 superalloy plate within only 6.5 s. Compared with the method using machine tool rotation alone, the average recast layer thickness on the inner wall was reduced by 62.1% to 6.7 μm, and the average surface roughness was reduced by 61.1% to 0.35 μm. These improvements are primarily attributed to the galvanometer speed being two orders of magnitude higher than that of the machine tool, which significantly reduces the laser pulse overlap rate and the thermal accumulation effect. Moreover, the kerf widened by the galvanometer rotation allows the ablation products to expand more fully and be expelled efficiently, thereby reducing impact, scratching, and debris adhesion on the inner wall and improving the drilling efficiency. Furthermore, 10 × 10 FCH arrays were machined on both vertical and inclined plates, demonstrating high consistency and stability, indicating the potential for industrial applications in the field of FCH machining. Full article

Reliable obstacle avoidance is essential for bionic robotic fish operating in complex underwater environments. However, when a robotic fish performs depth-keeping cruising near U-shaped obstacles, the traditional artificial potential field (APF) method is prone to local minima, which can cause the vehicle to become trapped and lead to obstacle avoidance failure. To address this problem, this paper proposes a virtual sentinel obstacle strategy based on the APF method. Virtual sentinel obstacles are deployed near the entrance of U-shaped obstacles, and corresponding deployment rules are formulated to prevent the robotic fish from entering the local minimum region. To further improve path planning performance, a two-stage fuzzy controller is developed to adjust heading rotation and cruising step size. The proposed method is evaluated through numerical simulations and physical experiments using a self-developed bionic robotic fish prototype. The results show that the virtual sentinel obstacle strategy prevents entrapment around the tested U-shaped obstacles, while fuzzy control shortens the path and improves smoothness. The physical experiments further verify the feasibility of the proposed strategy in a two-dimensional underwater obstacle avoidance scenario. These results indicate that combining virtual sentinel obstacles with APF-based planning provides a feasible approach for U-shaped obstacle avoidance by bionic robotic fish. Full article

Drilling fluids are essential in oil and gas operations for wellbore stability, cuttings transport, pressure control, and fluid-loss reduction. Water-based drilling fluids (WBDFs) are widely used because of their cost-effectiveness and lower environmental impact compared with oil-based systems; however, they often suffer from fluid loss into the formation and lower rheological performance. This laboratory-scale study investigates the feasibility of using rice and bread waste powders as bio-based additives for WBDFs to mitigate fluid loss. The collected food wastes were dried, milled, and sieved into three particle sizes of fine (150 µm), very fine (75 µm), and ultrafine (45 µm). The prepared powders were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). A total of 18 drilling-fluid formulations were prepared using rice and bread powders at concentrations of 1 wt%, 2 wt%, and 3 wt%. Filtration tests were conducted under low-pressure low-temperature (LPLT) conditions of 100 psi and 25 °C and high-pressure high-temperature (HPHT) conditions of 1500 psi and 70 °C, while rheological properties were measured using a rotational viscometer. The results showed that additive type, particle size, and concentration strongly influenced WBDF performance. The best-performing formulation was WBDF with added rice powder at 45 µm and 3 wt% (RC45-3), which reduced fluid loss from 19.5 mL to 6.1 mL, corresponding to a reduction of approximately 68.7% at LPLT. Under HPHT conditions, the same formulation reduced fluid loss from 36.5 mL to 11.4 mL, corresponding to a reduction of approximately 68.8%. RC45-3 also produced the thinnest measured filter cake, reducing filter-cake thickness from 5.0 mm for the base mud to 0.52 mm. The formulation maintained shear-thinning behavior and produced suitable gel strength values, indicating improved suspension capacity. The improved performance of rice powder is attributed to its fine particle size, favorable morphology, and ability to form a compact, low-permeability filter cake. Overall, the findings indicate that processed rice waste powder has potential as a low-cost, bio-based fluid-loss-control agent for WBDFs, although further testing in field-representative mud systems is required before practical application. Full article

Soil salinity is a major constraint to agricultural productivity, causing osmotic stress, ion toxicity, nutrient imbalance, and progressive deterioration of soil biological functions. Beyond its direct effects on plant performance, salinity also generates persistent soil legacies that influence subsequent plant growth through plant-soil feedback (PSF) processes. PSF provides an ecological framework for understanding how plants modify the physicochemical and biological properties of soil and how these altered soil conditions subsequently affect plant growth, health, and resilience. Salinity research has predominantly emphasized soil microorganisms as promoters of plant growth, while their broader role in regulating soil legacy effects remains comparatively underexplored. This review examines whether soil microorganisms may contribute to a transition from salt-amplified negative PSF toward more favorable feedback outcomes by reshaping rhizosphere chemistry, nutrient cycling, pathogen pressure, ion homeostasis, stress signaling, and soil structural stability. However, conditioned-soil bioassays and multi-season saline field trials remain scarce, these proposed pathways are treated as potential mechanisms or testable hypotheses rather than as established evidence of PSF regulation. We first summarize the mechanisms underlying PSF in non-saline systems and then describe how salinity alters plant-, soil-, and microbe-mediated feedback pathways. We further evaluate the potential of halotolerant plant growth-promoting rhizobacteria, arbuscular mycorrhizal fungi, actinobacteria, disease-suppressive microbial communities, and synthetic microbial consortia as regulators of PSF, while distinguishing direct salt-tolerance effects from evidence of genuine feedback modulation. Specifically, improved salt tolerance in the inoculated plant is interpreted as direct stress mitigation, whereas demonstrated PSF regulation additionally requires measurable soil conditioning and an effect on a subsequent crop. The novelty of this review lies in organizing studies of salinity-microbiome interactions within an evidence-based PSF framework that differentiates immediate plant responses from rhizosphere modification, conditioned-soil effects, and subsequent-crop performance. The review concludes that microbial strategies for saline agriculture are most likely to succeed when developed as integrated PSF interventions that combine crop traits, indigenous microbiomes, optimized inoculant design, organic matter management, diversified rotations, and multi-season field validation. Full article

Deep placement of nitrogen fertilizer (DPN) is an effective fertilization strategy for improving nitrogen use efficiency in rice systems, but its effects on methane (CH₄) emissions and the associated microbial mechanisms remain insufficiently understood. This study aimed to determine whether DPN mitigates CH₄ emissions in a rice–wheat rotation system and to clarify how it regulates methanogenic and methanotrophic communities. A two-year field experiment was conducted in East China with two nitrogen management practices, i.e., conventional surface application and DPN. Compared with surface application, DPN significantly reduced cumulative CH₄ emissions by 22.9% in 2023 and 17.0% in 2024, while tending to increase rice grain yield. During the tillering stage, DPN decreased soil dissolved organic carbon by 19.0% and increased NH₄⁺-N and NO₃⁻-N concentrations by 35.8% and 44.1%, respectively. These changes were accompanied by a 24.7% reduction in methanogen abundance and a 26.9% decrease in methanogenic activity. Although total methanotroph abundance was not significantly affected, DPN increased methanotrophic activity by 24.6%. Amplicon sequencing further showed that DPN shifted the methanogenic community from acetoclastic taxa toward hydrogenotrophic taxa, as indicated by the decline in Methanosarcina and Methanothrix and the enrichment of Methanobacterium and Methanoregula. In parallel, DPN promoted Type I methanotrophs, especially Methylomonas, while suppressing the Type II methanotroph Methylocystis. These results demonstrate that DPN mitigates CH₄ emissions by reducing labile carbon availability, suppressing methanogenic abundance and activity, and enhancing the functional potential of methane oxidation through methanotrophic community restructuring. Overall, this study indicates that DPN mitigates CH₄ emissions through coordinated regulation of carbon substrate availability and functional microbial community restructuring, suggesting that DPN is a promising strategy for sustainable rice production and greenhouse gas mitigation. Full article

This paper investigates the dynamic characteristics of rotating functionally graded material (FGM) micro-beams based on Euler–Bernoulli beam theory, Euler–Bernoulli beam theory incorporating shear deformation, and Timoshenko theory. The deformation field of the micro-beam is described within a floating coordinate system using the meshless point interpolation method (PIM/RPIM). The couple stress tensor and curvature tensor, which capture the size effect, are incorporated into the potential energy formulation. Employing Lagrange’s equations of the second kind, a higher-order rigid-flexible coupled dynamic model for rotating FGM micro-beams is established under various beam theories. Simulation results obtained from the Euler–Bernoulli theory with shear correction and the Timoshenko model are compared with those from the classical beam model and previous literature. The influences of material gradient index, material characteristic length parameter, and rotational speed profiles on the transient dynamic response and steady-state free vibration of rotating micro-beams are systematically examined. The results show that increasing the material gradient index reduces the structural stiffness, resulting in lower natural frequencies and larger vibration amplitudes, whereas increasing the characteristic length parameter enhances the size effect and improves system stiffness. Full article

Mediterranean agricultural systems are highly vulnerable to increased climatic variability, which threatens soil water availability and the functionality of the soil carbon (C) cycle. Soil management practices strongly influence water dynamics and C-substrate quality, thus potentially affecting the temperature sensitivity of soil respiration. We evaluated the combined effects of tillage (traditional tillage, TT; reduced tillage, RT), fertilization (mineral, MF; addition of biosolid compost, BC), and rainfall inputs (ambient conditions, C; reduction of 30% rainfall inputs, EX) on soil water content (SWC) and storage (SWS), and in situ soil respiration (Resp) dynamics over three agricultural seasons in a Mediterranean legume–wheat rotation, using a factorial field experiment. We also evaluated how the sensitivity of soil respiration to temperature could be affected by tillage and fertilization types in a complementary laboratory experiment under controlled moisture and temperature conditions. RT was effective in improving SWS and mitigating surface desiccation, although this advantage was attenuated in wet years due to homogenization of moisture along the soil profile. Soil Resp was primarily controlled by SWC. BC stimulated soil respiration mainly during the first crop season, with a residual non-significant trend in the third season. This effect appeared constrained under dry periods, although no significant fertilization × rainfall exclusion interaction was detected. The diurnal cycle of Resp showed a clear decoupling from diurnal soil temperature. Crucially, the intrinsic thermal sensitivity of respiration (Q₁₀) remained stable across all tillage and fertilization treatments, suggesting that field variability is driven by water dynamics and crop phenology and not by microbial responses to changes in substrate availability. Our results confirmed the hierarchical role of climate on C-cycling processes. Full article

Global food security and climate mitigation goals are placing unprecedented demands on agricultural systems to simultaneously improve soil productivity and reduce carbon emissions. Spent mushroom substrate (SMS), the mushroom industry’s principal waste stream, offers considerable recycling potential, yet its influence on dissolved organic carbon (DOC) chemistry and soil aggregate stability remains unclear. We tested four SMS return regimes on a medium-textured fluvo-aquic soil: CK, 0 t·ha⁻¹; ORS, 22.5 t/ha; ERS, 22.5 t/ha; and SRS, 45 t/ha in total, with 22.5 t/ha applied per SMS return event. It was found that SMS improved soil structural stability across all regimes, with SRS delivering the strongest effects. Compared with CK, SRS raised the proportions of >2 mm and 0.25–2 mm aggregates by 31.62% and 33.42%, while the mean weight diameter (MWD) and geometric mean diameter (GMD) increased by 23.25% and 22.68%. SMS also elevated aromatic carbon abundance, DOC concentration, UV254, and SUVA254. Fluorescence EEM-PARAFAC resolved DOC into three component: namely, two humic-like and one protein-like, and SMS expanded the relative contribution of the humic-like C1 fraction. Overall, under the tested fluvo-aquic soil and wheat–maize rotation conditions, SMS return was associated with changes in DOC composition, higher aggregate stability, and greater aggregate-associated carbon accumulation. These findings suggest that SMS return may be a promising strategy for improving soil structure and recycling agricultural waste under similar field conditions, but its broader applicability requires further validation. Full article

Collision detection is the core of collision analysis which is a vital fundamental work in computational particle mechanics. Collision detection algorithms can be divided into direct and indirect algorithms. Among them, the indirect algorithms transform the collision detection between two 2D objects into the position judgment of a reference point and a 2D object by constructing the no-fit polygon (NFP). However, the existing NFP algorithms are either not suitable for concave objects, or their time complexity is too high. This has hindered the development of indirect algorithms. Almost unknown to researchers interested in NFP, in the field of discontinuous mechanics calculation, there exists an ‘entrance block’ in Contact theory. Since NFP is the outline of the entrance block, the entrance block also has the potential to develop into a collision detection algorithm like NFP. The entrance block is suitable for arbitrary objects but ignores the rotation in each time step, which restricts it from becoming a collision detection algorithm. In this study, we improve this limitation and propose a 2D collision detection algorithm that is suitable for arbitrary objects. This algorithm can distinguish collision and contact, which reduces the calculation of late collision response. In addition, the algorithm has the potential to be transformed into a continuous algorithm and a new narrow-phase 3D collision detection algorithm. Finally, we propose a potential NFP algorithm that can be applied to arbitrary objects, which has an important influence on many NFP-related fields like computer graphics, operations research, computational mechanics, etc. Full article

Intelligent perception of watermelon targets in complex field environments is a key prerequisite for automated harvesting and future collaborative decision-making with agricultural large models. To address severe leaf occlusion, large pose variation, dense adhesion among adjacent fruits, and the inability of conventional horizontal bounding boxes to accurately represent target orientation under natural cultivation conditions, this paper proposes an improved YOLO11n-OBB-based method for rotated watermelon detection. During data preparation, a semi-automatic annotation strategy combining segmentation-mask assistance with circumscribed rectangle fitting was adopted to efficiently construct a watermelon OBB dataset that closely matches the true physical boundaries of the fruits. On this basis, three structural improvements were introduced to the YOLO11n-OBB baseline: an LSK module was selectively embedded into the middle and later stages of the backbone to enhance adaptive receptive-field modeling and occlusion reasoning in complex bac kgrounds; the original neck structure was replaced with a lightweight BiFPN to strengthen bidirectional feature fusion for targets with large-scale variation in field scenes; and KFIoU Loss was incorporated into the rotated box regression branch to alleviate angle sensitivity and boundary discontinuity, thereby improving the convergence stability of orientation parameter learning. On the constructed watermelon OBB test set, the improved model raised mAP@0.5 (OBB) from 0.871 to 0.931, mAP@0.5:0.95 (OBB) from 0.670 to 0.736, Precision from 0.885 to 0.931, and Recall from 0.849 to 0.908 relative to the YOLO11n-OBB baseline (relative gains of 6.89%, 9.85%, 5.20%, and 6.95%, respectively), while keeping the inference speed at 100 FPS and the parameter count at only 2.71 M. While maintaining a compact model size and high real-time performance, the proposed method significantly improved rotated detection accuracy in crowded and overlapping scenes. In addition, the detection results were encapsulated into a structured JSON perception interface, preliminarily demonstrating the integration pathway of this lightweight front-end for task planning and human–machine collaborative operations with agricultural large models, and indicating its potential for future intelligent agricultural decision-making. Full article

Intensive rice–wheat (RW) rotations in the Yangtze River Basin often rely on excessive nitrogen (N) inputs, leading to low N use efficiency and environmental risks. To test whether high productivity can be sustained with lower N inputs, a two-year field experiment was conducted in the Upper Yangtze River Basin to evaluate seasonal N allocation strategies across the annual rotation. A moderately reduced annual N input of 315 kg ha⁻¹ maintained annual grain yields of 18.2–19.3 Mg ha⁻¹, statistically comparable to traditional high-input practices using 360 kg N ha⁻¹. Wheat yield was mainly determined by current-season N supply, and no significant yield carry-over effect of rice-season N input on subsequent wheat yield was detected. Instead, higher rice-season N input tended to increase nitrate accumulation in deeper soil layers, particularly at 40–60 cm. Optimized seasonal N allocation significantly improved the partial factor productivity of N while maintaining a positive apparent system N balance under full straw return. These results indicate that strategically limiting and reallocating seasonal N inputs according to crop demand can sustain high annual productivity, improve N use efficiency, and reduce potential N-related environmental risks in intensive RW rotations. Full article

Long-term reliance on mineral fertilizers may degrade soil structure and weaken carbon and nitrogen retention in rice–wheat rotation systems. Organic amendments combined with mineral fertilizers can provide organic substrates, promote aggregate formation, and improve soil C–N retention, but the contrasting effects of plant- and animal-derived amendments remain unclear. A long-term field experiment initiated in 2012 in Chaohu, China, compared no fertilization (CK), chemical fertilizer alone (CF), chemical fertilizer plus oil cake (OC), and chemical fertilizer plus cattle manure (CM). At wheat maturity in 2025, soil aggregate distribution, stability, aggregate-associated soil organic carbon (SOC) and total nitrogen (TN), C and N contribution rates, and yield components were determined; wheat yield was further evaluated using annual records from 2021 to 2025. Compared with CK, OC and CM increased water-stable macroaggregates (>0.25 mm) by 17.35% and 17.94% and reduced aggregate destruction by 54.61% and 53.57%, respectively. In large macroaggregates (>2 mm), OC and CM increased SOC by 58.30% and 84.83% and TN by 141.76% and 200.00%, respectively. Five-year mean yield increased by 208.09%, 240.78%, and 225.15% under CF, OC, and CM, respectively, relative to CK, but did not differ significantly among fertilized treatments. Overall, oil cake showed a numerical advantage in maintaining wheat yield, whereas cattle manure had greater potential to improve aggregate-scale C–N retention and soil structural stability. Full article