Search Results (1,559)

This paper compares fixed-order (FO) and variable-order (VO) fuzzy fractional PID control in a reduced numerical benchmark for quadrotor altitude tracking. The study asks whether online order scheduling changes paired performance when the fuzzy gain structure, gain channels, fractional approximation, plant, reference, random realizations, and evaluation protocol are fixed. The benchmark comprises vertical double-integrator dynamics, a first-order actuator lag, and asymmetric clipping of an equivalent net-thrust command; it is not full-vehicle or hardware validation. Both controllers use the same two-input, five-output Sugeno structure. FO is optimized first, and VO then optimizes four scheduling parameters while retaining the FO gain channels. Evaluation uses a six-segment reference, a composite index, 100 pre-specified paired Monte Carlo seeds, paired effect estimates, two counterfactual order variants, and an existing stronger-disturbance test without retraining. At baseline, VO reduces mean J by 3.97%, ITAE by 7.06%, positive-upper-limit near-saturation exposure by 43.36%, and RMS input by 3.18% while increasing the total in-band ratio by 6.80%. Overshoot and robust settling time show no statistically supported improvement. The counterfactual results are more consistent with state-dependent variation than a fixed-order shift alone but do not form an additive causal decomposition. Within this benchmark, the results support a measurable role for online order scheduling but do not establish full-vehicle or hardware performance. Full article

Traditional target-oriented task allocation and path planning methods often struggle to balance real-time responsiveness to dynamic task alterations with multi-UAV cooperative operations in complex urban environments under meteorological disturbances. To address these challenges, this paper proposes a dynamic path planning method for low-altitude Unmanned Aerial Vehicles (UAVs) tailored for urban inspection missions. Integrating an improved Discrete Particle Swarm Optimization (DPSO) algorithm with a decoupled Soft Actor–Critic (SAC) and B-spline smoothing framework, the proposed approach optimizes upper-level task allocation and lower-level trajectory planning within a 3D joint meteorological-obstacle feasible region. For task scheduling, an improved DPSO algorithm embedded with a spatial topology guidance mechanism dynamically coordinates task flows governed by Poisson processes. effectively addressing the spatial blindness and fragmented route assignments typical of conventional discrete optimization. Concurrently, local trajectory replanning executes receding-horizon spatial exploration via SAC deep reinforcement learning, followed by B-spline refinement to strictly enforce UAV kinematic limits, systematically bridging continuous-space exploration with low-level flight compliance to overcome the kinematic infeasibility common in pure learning-based models. Validated through extensive Monte Carlo comparative simulations ($N=50$) and further verified by a high-fidelity AirSim dynamic physics engine, the results demonstrate that: (1) The improved DPSO constrains the average response latency for high-priority emergency tasks to within 40 s even under 50 concurrent dynamic tasks. (2) The lower-level replanning achieves an average execution time of $3.60\pm 0.18 \mathrm{s}$ and a path success rate of $95.8\pm 1.2\%$, in numerical tests, while maintaining a 96.2% kinematic feasibility rate under realistic rigid-body inertia and aerodynamic drag. While the current 3.60 s latency presents a potential bottleneck for millisecond-level dynamic emergency reactions, the developed framework offers a highly effective and safe closed-loop dynamic scheduling solution that lays a rigorous computational foundation for low-altitude urban inspections. Full article

Free-jet altitude simulation requires coordinated regulation of the intake thermodynamic states and flexible-nozzle geometry under time-varying Mach number commands and possible actuator faults. This study proposes a cooperative dual-loop active disturbance rejection control (ADRC) framework for a multi-pivot semi-flexible nozzle and a dual-valve intake system. In the inner loop, a constrained cooperative allocation method determines the pivot forces required to match the reference nozzle profile, while a dual-valve allocation mechanism redistributes the control demand when a valve loses effectiveness. ADRC is employed for hydraulic-actuator position tracking, and an SMC-LADRC controller regulates the intake pressure and temperature. An outer Mach number feedback loop compensates for the residual error of the integrated system. The convergence of the projected-gradient allocation algorithm and the ultimate boundedness of the observer and tracking errors are established under bounded disturbance variations. Simulation results under Mach number transitions, external disturbances, and progressive valve failure show that the proposed method effectively maintains stable intake pressure and temperature, improves nozzle-profile tracking accuracy, suppresses Mach number fluctuations, and enhances the fault tolerance and overall control performance of the integrated free-jet system. Full article

The transfer of heavy metals (HMs) from industrial park soils to edible crops is strongly crop-specific; however, these differences have not been considered in probabilistic dietary health risk assessments. This study examined agricultural fields surrounding a high-altitude industrial park in southwestern China, where paired samples of surface soil, Chinese cabbage, and maize were collected and analyzed for Cd, Pb, Cr, Ni, Cu, Zn, Hg, and As. Spearman rank correlation and principal component analysis (PCA) were applied to identify elemental associations and probable sources; bioaccumulation factors (BAFs) were calculated to compare HM transfer and accumulation across the two crops; and Monte Carlo simulation was used to estimate probabilistic dietary health risks across age groups. The results showed that soil HMs in the study area displayed mixed-source characteristics, with marked enrichment of Pb, Cd, and Hg. After multiple comparison correction, only soil Ni showed a significant positive correlation with Ni in maize. Chinese cabbage had a relatively high accumulation capacity for Cd, whereas maize grains showed relatively limited transfer of most HMs, indicating pronounced crop-specific differences. Cd, Pb, Cr, Hg, and As concentrations in Chinese cabbage remained within permissible limits. For health risk, P95 hazard index (HI) values stayed below 1 across all age groups, indicating that non-carcinogenic risk was generally acceptable under the exposure scenarios evaluated; adults, however, carried higher estimated lifetime carcinogenic risk than other age groups. Sensitivity analysis revealed that As and Cd in Chinese cabbage were the dominant contributors to non-carcinogenic and carcinogenic risks, respectively, while the contribution of Cr to risk estimates was highly dependent on its speciation and toxicological parameter assumptions. By combining soil–crop monitoring, bioaccumulation analysis, and probabilistic risk assessment, this study characterizes crop-specific HM transfer patterns and identifies the principal drivers of health risk in industrially influenced agricultural systems, providing a scientific basis for risk-oriented monitoring, food safety management, and the long-term sustainable use of agricultural land in industrial–agricultural interface regions. Full article

Water deficit severely limits rice productivity. The elite Dian (D1)-type hybrid japonica rice ‘Dianheyou 615 (ZH1)’ exhibits exceptional drought adaptation in high-altitude rainfed uplands of the Yungui Plateau, yet the underlying molecular mechanisms remain unknown. We compared phenotypic and transcriptomic responses of ZH1 and six other japonica cultivars under well-watered and water-deficit conditions. Water-deficit stress significantly impaired agronomic traits across all cultivars; however, ZH1 uniquely maintained relatively stable flag leaf morphology and seed-setting rate, and displayed distinctive stomatal traits, in stark contrast to its parental lines and other cultivars. Transcriptomic profiling at the jointing-to-booting stage defined a core drought response module of 174 conserved genes across all cultivars. Critically, by intersecting 1097 ZH1-specific genes with drought-responsive elements, we pinpointed 15 core, cultivar-specific regulatory genes. These candidates are enriched in functions related to cuticle formation, carbohydrate metabolism, and stress signaling; among them, a DREB transcription factor (LOC4347618) is a prime candidate. qRT-PCR validated their expression. Using CRISPR/Cas9-mediated gene editing, we generated homozygous knockout mutants for LOC4333842, LOC4347618, and LOC4328441. Under 20% PEG-6000-simulated drought stress, all three mutant lines showed significantly increased drought susceptibility relative to wild-type controls, confirming the positive regulatory roles of these genes in drought stress tolerance in japonica rice. These results establish these three genes as promising targets for molecular breeding aimed at enhancing drought resistance in rice. Full article

To address the challenges associated with operational ventilation in high-altitude tunnels, this study investigates the distribution patterns of ventilation flow fields and optimizes the spatial layout parameters of jet fans to determine the most effective configuration. Using a case study from the Zhuohe Expressway tunnel, numerical simulations were conducted to analyze four key design parameters: the lateral clear distance (L) between two jet fans in a single group, the vertical distance (H) from the fan center to the tunnel lining, the axial distance (T) from the fan to the tunnel entrance, and the longitudinal spacing (S) between two groups of fans. The results indicate that for a single-fan group, when the parameter L is 1.25D (D is the fan diameter), pressure rise and comprehensive influence coefficients reach peak values of 20.090 Pa and 0.886, respectively. As well as the parameter H between 1.20 m and 1.25 m, the diffusion of the vertical wind field velocity is continuously reduced due to the constraint of the tunnel lining on Section BB of the tunnel fan’s symmetry axis, and the interference of the tunnel lining on the stable flow state of the fan’s outlet airflow is relatively small. Moreover, parameter T has a relatively low sensitivity impact on the increase in pressure and the variation of the influence coefficient. When the parameter T is within the range of 50 m to 100 m, the airflow at the entrance of the tunnel is smoothly connected with the airflow at the suction section of the fan. Additionally, the pressure rise and the influence coefficient increase by the parameter T. Both the fan’s pressure rise and the influence coefficient reach their maximum values when the parameter T is 100 m. Furthermore, in the case of two-fan groups, the gas is fully mixed in the tunnel when the parameter S is 150 m, and the fan pressure rise and the influence coefficient increase as well as parameter S. The gas between the two sets of fans has been fully mixed in the parameter S at 175 m, and the pressure rise and the coefficient influence reach their maximum values of 40.231 Pa and 0.887, respectively. In light of these findings, the following optimal parameters ranges are recommended for similar tunnel ventilation designs: parameter L is 1.25D for two jet fans within a single group, parameter H is between 1.20 m and 1.25 m, parameter T is 100 m from the tunnel entrance, and parameter S is between 150 m and 175 m for two groups of fans. Full article

Unauthorized low-altitude UAVs can challenge conventional fixed-parameter interception algorithms through agile maneuvers. This study develops a three-dimensional one-on-one terminal-interception simulation environment that incorporates protected-zone penetration, a within-step geometric interception criterion, and kinematic constraints. The intruder, denoted as the red UAV, combines six physically interpretable maneuver templates to generate structured evasive penetration behavior. The defender, denoted as the blue UAV, augments blended generalized proportional navigation (B-GPN) with a bounded residual corrective acceleration produced by deep reinforcement learning, thereby forming a hybrid architecture that combines a geometry-based nominal guidance command with reward-driven bounded compensation. In standardized tests on 1000 unseen scenarios, the implemented residual PPO pipeline increased the interception rate from 63.8% for nominal guidance to 94.1% (95% Wilson interval: 92.46–95.40%) and maintained at least 88.0% interception under the tested control-delay, kinematic, and noise perturbations. It also achieved the highest interception rate among the evaluated residual-learning implementations under both the stable-configuration comparison and the auxiliary task-side-controlled check; this result is limited to the reported implementations and is not a general ranking of algorithm families. These findings indicate that bounded residual learning can compensate for structural limitations of conventional guidance under the evaluated conditions. Full article

The artificial lighting demand of buildings is a controllable sustainability lever, whereas metalized food-packaging waste (i.e., multilayer polymer-aluminum films used for barrier protection) is difficult to recycle and routinely landfilled or incinerated, representing an underexplored circular-economy opportunity. This simulation-based feasibility study connected both objectives by investigating whether metalized snack-packaging waste can function as a daylight-redirecting surface on a faceted interior light shelf. Five configurations were simulated in VELUX Daylight Visualizer 3 using Ankara’s EnergyPlus Weather climate file (39.93° N): a no-shelf baseline (S1), white (ρ = 0.80) and metalized (ρ = 0.80–0.88) flat shelves (S2, S3), and faceted equivalents (S4, S5). None of the five scenarios met the EN 17037:2018 sufficiency threshold (DA300 ≥ 50%); the best configuration, S5 (faceted, metalized), reached DA300 = 40.23%. Within this limitation, S5 outperformed all comparators, averaging 3116 lux (9.6× baseline) and achieving a uniformity ratio of 0.823. Faceted geometry increased illuminance by 1.74–1.78× over an equivalent flat metalized shelf; metalized flat shelves outperformed the white ones by 1.44–1.54×, except in September, when high solar altitude caused a 0.83–0.89× reversal, eliminated by faceting. S5 reduced artificial lighting dependency from 78.42% to 59.77% of occupied hours (~101 kWh/yr, first-year estimate) and nearly halved critical daylighting-deficit hours (49%). However, it exceeded the 2000 lux useful-daylight ceiling in ~55% of occupied hours, indicating that glare mitigation is necessary for deployment. These preliminary results warrant further experimental and life-cycle work before the sustainability benefits of the circular economy pathway can be established. A sensitivity analysis confirms that S5’s daylighting advantage persists, though at reduced magnitude, under both a conservative reflectance assumption (ρ = 0.80) and a more energy-representative window-to-wall ratio (47.5%). Full article

Large-scale maritime activity, persistent shipping incidents, and complex marine environments continue to place substantial demands on maritime search and rescue (MSAR). Current MSAR systems do not fully capitalize on the complementary strengths of unmanned aerial vehicles (UAVs) and satellites for collaborative tracking and rescue support. Existing air-space collaboration technologies suffer from two critical limitations: (1) rigid processes, including fixed task allocation, pre-determined path planning without real-time environmental adaptation, and isolated satellite–UAV decision-making, and (2) long task completion cycles, mainly because many methods are adapted to wide-area, long-duration military tracking scenarios. They therefore provide limited support for the dynamic flexibility required in MSAR. This study proposes a Proximal Policy Optimization (PPO)-based air-space collaborative tracking method for maritime moving targets to address these shortcomings and enhance air-space cooperation in MSAR operations. The core implementation of the method includes: (1) integration of target drift forecasting, satellite orbit prediction, UAV task allocation, and path planning into a unified reinforcement learning framework to reduce isolated single-platform decision-making; (2) the adoption of PPO to generate dynamic and flexible air-space collaborative tracking strategies that adjust satellite observation angles and scanning ranges, as well as UAV altitude, speed, and heading according to real-time target, environmental, and platform states; and (3) the design of a multi-dimensional reward function that balances target proximity, energy efficiency, coverage overlap, and inter-platform cooperation to guide strategy optimization. Simulation experiments include system-feasibility verification, baseline-controller comparison, PPO hyperparameter screening, and cross-scenario evaluation. Under idealized communication and payload-matching assumptions, the method enables coordinated tracking of maritime moving targets in simulated MSAR scenarios. In the standardized evaluation, PPO achieved an 11.9% higher mean evaluation episode return, 11.2% lower aggregate UAV energy consumption, and a 9.92-percentage-point greater endurance margin than DDPG. Hyperparameter screening compared candidate learning rates, discount factors, and training budgets, informing the PPO configuration for the subsequent six-scenario evaluation. Across the six controlled scenarios, rewards stabilized after approximately 1400 steps, while action magnitudes varied among regions. These results indicate that the proposed method has potential to enhance air-space collaborative tracking for MSAR decision support. Full article

To meet the growing demand for reliable space–air–sea-integrated communications and underwater information backhaul, this paper proposes and analyzes a three-hop heterogeneous space–air–sea communication system consisting of a satellite, a high-altitude platform (HAP), a sea-surface buoy, and an autonomous underwater vehicle (AUV). Specifically, the satellite-to-HAP link employs free-space optical (FSO) transmission, the HAP-to-sea-surface buoy link adopts mixed FSO/radio-frequency (RF) transmission, and the sea-surface buoy-to-AUV link utilizes underwater wireless optical communication (UWOC). To enhance the reliability of the HAP-to-sea-surface buoy link in complex atmospheric and maritime environments, a threshold-based adaptive combining scheme for mixed FSO/RF transmission is designed. Meanwhile, nonzero-boresight pointing error models are incorporated into the FSO and UWOC links to characterize practical link misalignment. Based on the proposed system model, analytical expressions for the end-to-end bit error rate (BER) are derived and validated through Monte Carlo simulations. The numerical results show that the proposed adaptive combining scheme achieves better BER performance than conventional dual-hop and hard-switching schemes. In addition, the effects of pointing errors, underwater turbulence, underwater transmission distance, shadowed fading, detection techniques, and modulation schemes on the system BER performance are further investigated. This work provides theoretical guidance for reliable cross-domain heterogeneous transmission in future space–air–sea integrated communication systems. Full article

Tomographic synthetic aperture radar (TomoSAR) effectively characterizes forest vertical structure, while baseline configuration strongly affects forest height retrieval accuracy. However, systematic baseline analysis is limited by the lack of real multi-baseline datasets with controllable configurations. In this study, the landscape-scale canopy backscatter model (LandSAR) is used to simulate airborne P-band SAR data under different baseline configurations. LandSAR performance is first evaluated against real P-band InSAR data and lidar canopy height. Forest height is then retrieved under a known-ground assumption, and the effects of inter-track baseline spacing, track number, and total aperture length on forest height retrieval are analyzed at different flight altitudes. The results show that retrieval accuracy is governed by the coupled effects of baseline spacing and track number. For small baseline spacings, accuracy improves with increasing track number, but the improvement remains limited. Larger spacings improve retrieval performance, whereas overly large spacing or aperture may reduce the height ambiguity margin and reconstruction stability. The optimal accuracies are 4.72 m, 4.58 m, 4.52 m and 4.48 m at flight altitudes of 3000 m, 3500 m, 4000 m and 4500 m, respectively. This study provides a physically interpretable reference for airborne P-band TomoSAR configuration design. Full article

Predefined low-altitude corridors create a coupled routing–scheduling problem when multiple drone routes enter the same controlled segment. This study separates an upstream control hub from its scarce directed hub–segment resource and develops an event-expanded continuous-time mixed-integer linear programming model with optional fleet activation, complete-route energy and capacity checks, release precedence, minimum entry headway, holding, and downstream delay propagation. A headway-aware large neighborhood search (HA-LNS) combines route neighborhoods with a finite serial event decoder. Gurobi proves optimality on three small instances, and fixed-route timing MILPs exactly match the decoder, including for a repeated physical-hub visit. Across ten matched networks per scale, HA-LNS changes the mean objective relative to route-only LNS by 0.01%, 0.90%, and 2.33% at nominal scales 30, 50, and 100. Under high conflict-resource density, the reduction reaches 5.77%, while mean holding falls from 2.054 to 0.025 min. Simulated annealing is 1.04% better at scale 50 and statistically indistinguishable at scales 30 and 100, showing that the contribution is conflict-aware integration rather than universal heuristic dominance. The framework identifies directed-resource density as the main condition under which temporal coordination materially improves route decisions. Full article

The pursuit of greater efficiency in agricultural operations, particularly in input application, has led producers to adopt strategies aimed at minimizing production costs. Aerial fertilizer application has emerged as a viable alternative due to its high operational efficiency and its ability to operate in conditions where ground-based application is not feasible. However, few studies have evaluated its efficiency, resulting in limited technical guidelines for calibration and adjustment. In this context, the present study aimed to evaluate the quality of broadcast application of solid potassium fertilizer via aircraft. The experiment was conducted using a split-plot design in a factorial arrangement with three flight altitudes (10, 15 and 20 m) and four application rates (50, 75, 100 and 125 kg ha⁻¹), each with three replications. Longitudinal and transverse distributions were evaluated, as well as the correlation between wind speed and applied doses. The longitudinal analysis showed that flight altitude influenced both the uniformity of distribution and the effective dose applied, with a significant interaction between factors. In the transverse analysis, the overall transverse deposition pattern was predominantly governed by the 4.0–2.0 mm particle-size fraction, which represented approximately 90% of the recovered fertilizer mass across all flight heights. Although the granulometric composition remained consistent, the spatial distribution of individual particle-size classes varied with flight height, particularly for the finer fractions. Overall performance was achieved and the best results were observed at a 25 m swath width with flight heights between altitudes of 10 and 15 m. While the 10 m flight height resulted in lower eccentricity and greater fertilizer deposition, the 15 m flight height provided lower coefficients of variation after overlap simulation across most application rates, indicating more uniform transverse distribution. Full article

Vineyard monitoring requires efficient methods for detecting plant stress and disease while limiting flight time, data volume, and labour effort. This paper presents a satellite-enabled two-tier UAV workflow for semi-automated vineyard inspection. The proposed approach combines high-altitude multispectral scanning, NDVI-based point-of-interest identification, adaptive flight path planning, low-altitude RGB inspection, and downstream vision-based disease analysis. Processing tasks are offloaded to a remote server accessed through an emulated Low Earth Orbit satellite communication environment, allowing the UAV-side system to remain lightweight while receiving multispectral analysis results during the mission. A simulation framework was developed to evaluate mission behaviour under controlled and repeatable conditions, using both pseudo-random point generation and real multispectral vineyard images processed through the satellite emulation testbed. A flight with a real drone was also conducted to validate adaptive flight optimisation. Experimental results focus on the impact of path-adaptation strategies and communication bandwidth on mission efficiency. The results show that route optimisation can reduce mission time by up to $15\%$ when new low-altitude waypoints emerge, while bandwidth bottlenecks affect performance once image transmission can no longer keep pace with acquisition. The findings highlight the need to consider sensing, communication, and mission planning jointly in adaptive UAV-based crop monitoring. Full article

Abandoned, lost, or otherwise discarded fishing gear (ALDFG) is a persistent form of marine pollution requiring survey approaches capable of resolving individual items across large spatial extents. While uncrewed aerial vehicles (UAVs) can capture imagery at resolutions sufficient to resolve individual debris items, their use remains largely constrained to visual line-of-sight (VLOS) operations, limiting large-scale coastal monitoring. This case study develops and field-tests an operational framework for low-altitude beyond visual line-of-sight (BVLOS) UAV surveys, in which DEM-based communication viewshed modelling incorporating first Fresnel zone clearance is used to plan BVLOS missions. A lightweight fixed-wing UAV flown at 60 m AGL completed 20 missions across 210 km of remote northern Australian coastline. Communication viewshed modelling reliably guided mission planning with 90.5% of waypoints placed within predicted high-clearance zones maintaining moderate-to-strong command-and-control (C2) link quality in flight. Manual screening confirmed that the resulting imagery was of sufficient quality, with 291 derelict fishing nets detected. In a simulated VLOS operational scenario, 76.3% of these detections fell beyond VLOS range, and equivalent coverage would require an estimated 8.8-fold increase in mission count. These findings demonstrate that fixed-wing UAVs operating under low-altitude BVLOS conditions can support large-scale image acquisition in remote coastal areas, particularly when enabled by communication-aware mission planning. Full article