Search Results (98)

Reliable pack-level battery systems capable of safely handling instantaneous high-C-rate discharge above 10C during take-off, climb, and hovering are required for the commercialization of urban air mobility (UAM) aircraft. However, pack-level studies on wide-range C-rate characteristics of battery systems for UAM applications remain very limited, and most previous studies have been restricted to single-cell experiments or battery-pack simulations. In this study, a 24S1P test battery pack using nickel–cobalt–manganese (NCM) pouch cells, with a nominal voltage of 88.8 V and a capacity of 22 Ah, was designed and fabricated. A two-level battery management system (BMS) based on the LTC6803G-4 was also developed. To evaluate the charge–discharge characteristics of the battery system, constant-current discharge tests were conducted under five conditions ranging from 0.2C (4.4 A) to 10.68C (235 A), and charging tests were performed over the range of 0.2C–2C. The discharge test results showed that the capacity retention remained within 97.5–100.0% in the 1C–5C range, confirming excellent power capability. Continuous discharge operation was confirmed at 10.68C, the maximum discharge condition considered for vertical take-off and climb. Under this condition, the capacity decreased to 16.26 Ah, corresponding to 74.2% of the rated capacity, owing to internal-resistance-induced voltage drop, electrochemical polarization, and early attainment of the cut-off voltage. The Peukert exponent was estimated to be 1.113. An apparent pack-level direct-current internal resistance (DCIR) of approximately 40.3 mΩ was estimated from the initial voltage-drop analysis under different discharge-current conditions. In addition, the maximum temperature during 10.68C discharge was measured as 55.1 °C, providing a thermal margin of 4.9 °C relative to the operational temperature limit of 60 °C adopted in this study. Finally, a 24S4P battery system with a capacity of 88 Ah, consisting of four 24S1P battery packs connected in parallel, was installed in the VS-210, a 210 kg-class maximum take-off weight (MTOW) eVTOL aircraft. An in-flight test was conducted by repeating six take-off–hovering–landing cycles during a total test session of 15 min 20 s, and a stable propulsion power supply was maintained throughout all flight cycles. This study provides experimental baseline data for the design and preliminary safety assessment of high-power battery systems for UAM applications by presenting both the electrical and thermal characteristics of a 24S NCM battery pack over a wide discharge-rate range of 0.2C–10.68C and in-flight eVTOL data. Full article

Invasive species pose increasing threats, particularly in agriculture. Here we assess the open-field distribution, population density, and phenology of Tuta absoluta (Lepidoptera: Gelechiidae), an invasive pest rapidly expanding its range into open-field habitats in Hungary. Countrywide monitoring using sex pheromone traps was conducted at 23 sites in 2023, complemented with detailed seasonal monitoring at two locations. The results reveal a wide open-field distribution of the pest in Hungary, occurring at 21 of the 23 sampled sites. Population densities were significantly higher in highly urbanised areas, suggesting that warmer climatic conditions enhance colonisation and population growth. Continuous adult flight activity was recorded from May to December, indicating prolonged reproductive activity and overlapping generations. Based on the degree-day requirements (approx. 460 °C days per generation), five generations per year were expected and detected at two intensively sampled sites. These findings demonstrate a marked shift from the “greenhouse pest” status toward successful colonisation of open fields, supported by increased overwintering potential. The observed expansion and phenological changes indicate that the climatic conditions of temperate Hungary are increasingly suitable for the persistence of T. absoluta populations outdoors. This study underscores the growing agricultural risk posed by T. absoluta in temperate regions and highlights the importance of early detection and integrated pest management strategies for mitigating its impact. Full article

Under high-Mach-number flight conditions, the combustion chambers of hypersonic vehicles encounter extreme thermal environments marked by unilateral heating, high-heat-flux density, and supercritical pressure. Traditional hydrocarbon fuel cooling often suffers from insufficient heat sinks, high-temperature cracking and coking blockages, making it difficult to meet long-endurance thermal protection requirements. Liquid metal, due to its extremely high thermal conductivity, wide liquid phase temperature range, low Prandtl number and electromagnetic pump driving capability, has become a key technology for breaking through the bottleneck of high-heat-flux thermal protection. Apart from the magnitude of heat flux, the heat-transfer time scale (such as the characteristic thermal response time of the wall and the fluid) is also crucial. During hypersonic flight, transient thermal loads can change within milliseconds, requiring rapid thermal response. Liquid metals, due to their high thermal diffusivity, have a shorter thermal diffusion time compared to hydrocarbon fuels. This review employs a systematic literature review of approaches using gallium-indium-tin alloy, GaInSn, focusing on three core directions: the flow and heat-transfer characteristics of liquid metals, the optimization of cooling micro-channels, and the application of thermal protection systems. It summarizes the research progress at home and abroad, compares and analyzes the performance differences and applicable scenarios of typical liquid-metal working fluids, and summarizes the advantages and disadvantages of existing models, structural designs, and system schemes. The research shows that liquid metals can significantly alleviate thermal stratification and eliminate coking, and deep, narrow, tree-shaped, and biomimetic micro-channels can effectively enhance heat transfer. The liquid-metal-fuel dual-channel waste heat recovery and thermoelectric power generation system has demonstrated engineering application potential. Currently, the field still faces key challenges, such as unclear heat-transfer mechanisms under extreme conditions, the lack of general heat-transfer correlation formulas, insufficient compatibility with high-temperature materials, poor miniaturization and vibration resistance of electromagnetic pumps, and low system integration. In the future, efforts should be focused on developing multi-field coupled heat-transfer models under extreme thermal environments using engineered micro-channel structures, corrosion-resistant materials, and lightweight electromagnetic pumps, promoting the research and development of integrated thermal protection, heating and power generation systems, and providing support for the development of advanced thermal management systems for hypersonic aircraft and aviation engines. Full article

Flying-wing aircraft are more susceptible to wind disturbance due to their smaller wing loading, making gust alleviation critical for flight performance and safety. Conventional control surfaces may exhibit insufficient manipulation efficiency on such configurations, motivating the adoption of active flow control, particularly circulation control (CC) due to its favorable control efficiency. This paper presents an Active Disturbance Rejection Control (ADRC) framework for gust load alleviation (GLA) of flying-wing aircraft equipped with CC actuators, which enables real-time estimation and compensation of both gust disturbance and practical uncertainties and is validated through closed-loop wind-tunnel experiments under various sinusoidal gust conditions. An unsteady aerodynamic model with experimental data is established and simulations are performed for further investigation of alleviation performance and response characteristics under a wide range of gust conditions. Results show that both ADRC and PID exhibit degraded performance at higher gust frequencies and larger gust ratios, but ADRC achieves higher alleviation efficiency across the tested conditions. Furthermore, ADRC maintains satisfactory performance with actuator delays up to 0.04 s and outperforms PID under measurement noise and Dryden turbulence. These findings validate the effectiveness and robustness of ADRC for GLA, underscoring its practical potential for active flow control systems. Full article

Remote sensing is widely recognized as a key technology across a wide range of technical and scientific domains, especially in agriculture. Although satellite data have long supported crop monitoring, their limitations in spatial resolution, revisit frequency and cloud coverage have often constrained their applications. High-resolution satellites, available from the beginning of the 2000s, have improved performance, particularly in the field of precision agriculture, but they remain expensive and inflexible. Unmanned Aerial Vehicles perform better in precision agriculture, offering flexibility and high levels of detail; however, their limited operational areas and short endurance flight times constrain their effectiveness. In this evolving landscape, High Altitude Pseudo Satellites (HAPSs), particularly high-altitude balloons, are emerging as a promising new technology that could fill the gaps between satellite and drone remote sensing. These platforms provide large area coverage with high-resolution imagery and long endurance flights at low operational expenses and ease of deployment. This study investigates the operational characteristics, strengths, and geometric limitations of data acquired by the CubeHAPS^® platform, a high-altitude pseudo-satellite system, as a prerequisite for its application in precision agriculture. Focusing on experimental campaigns conducted in northern Italy in summer 2024 and 2025, the research characterizes platform stability, image block consistency, and photogrammetric quality through internal metrics. The results demonstrate measurable improvements between the two campaigns, attributed to the introduction of a stabilization system in 2025 and establishing the conditions under which the platform can support reliable photogrammetric reconstruction. Full article

Wide-area building-structure mapping from long-range airborne LiDAR requires image products that can represent building footprints, roof-height variations, and structural discontinuities with low computational latency. Airborne streak-tube imaging LiDAR (ASTIL) records a spatial–temporal echo image for each laser pulse, where the detector row corresponds to the fan-beam spatial angle, the detector column encodes echo arrival time, and the frame sequence represents the scanning process. This row–column–frame topology makes it possible to generate image-domain structural products directly from raw streak-tube echo sequences. In this paper, a relative-height image generation method is proposed for long-range ASTIL. The method constructs slant-range matrices from raw echo images, suppresses row-wise ground-related range trends, maps the residuals into relative-height values, and generates scan-geometry-calibrated swath-level relative-height images using lightweight calibration rather than rigorous point-wise POS/IMU trajectory reconstruction. Airborne experiments at 2 km, 3 km, and 6 km flight heights show that the proposed workflow can generate relative-height images with spatial sampling intervals of 0.30 m, 0.45 m, and 0.90 m, respectively, within a 0.5 s acquisition window. The generated cropped image products occupy less than 0.3% of the raw streak-image sequence volume, reflecting a compact image-domain representation for rapid preliminary mapping rather than lossless data compression. Building-scale comparisons with UAV LiDAR reference data indicate that the generated images preserve the main building footprints, boundary orientations, and roof-height discontinuities. For nine flat-roof targets, the mean absolute roof-to-ground height errors range from 0.24 m to 0.30 m across the three flight heights. These results suggest that ASTIL relative-height imaging can provide an efficient image-domain representation for wide-area building-structure mapping under long-range airborne observation conditions. Full article

Longitudinal mapping of the superficial peripheral vascular network is clinically relevant for conditions such as venous insufficiency, superficial venous thrombosis, and localized hemorrhagic injury; yet existing modalities are either operator-dependent, costly, or unable to provide wide-field coverage. We designed and demonstrated the feasibility of a relatively quick, cost-effective, automated panoramic near-infrared (NIR) imaging system operating at 850 nm, with a total acquisition time of 30 s. The prototype integrates a motorized rotational acquisition frame, co-localized illumination, lateral mirror enhancement, and a time-of-flight ranging sensor. A custom image processing pipeline combining contrast-limited adaptive histogram equalization (CLAHE), black-hat morphological filtering, Otsu binarization, structure-tensor-based diameter quantification, and photogrammetric 3D reconstruction was applied to data from five healthy volunteers. Optimal acquisition parameters (30 ms exposure, analog gain 3.5) were identified via systematic characterization. The pipeline reliably isolated venous structures of the 35 cm field of view, yielding a mean superficial vein diameter of 2.69 ± 1.48 mm, consistent with published anatomical references. A panoramic texture-mapped 3D surface reconstruction of the limb was generated for each participant. The system provides a rapid, operator-independent panoramic view of superficial veins suitable for future longitudinal monitoring, offering a compelling complementary tool to duplex ultrasound for tracking morphological and volumetric vascular changes. Full article

Centrifugal spraying systems are widely used in plant protection unmanned aerial vehicles (UAVs) due to their flexible droplet size adjustment and low-volume application capabilities. These systems can typically generate a wide range of volume median diameters from 50 to over 300 micrometers depending on rotational speed and disc structure. However, field performance is governed by a complex multi-physics coupling process rather than atomizer performance alone. Droplets released from the atomizer undergo near-field expansion and are subsequently entrained by rotor downwash. While strong downwash significantly improves deep canopy penetration compared to traditional application methods, it also dynamically reshapes droplet trajectories and size spectra through high-shear wake vortices. A critical comparative gap identified in this review is the severe discrepancy between static indoor atomization models and dynamic field transport. Current research lacks continuous spatial-temporal tracking of droplet size spectra under these complex field conditions. To address this, this review synthesizes the continuous mapping among droplet generation, spray plume transport, and canopy deposition. Precision application requires coordinated matching of flight parameters, aerodynamic downwash, and canopy architecture rather than single-parameter optimization. Future research must focus on the dynamic reconstruction of droplet size spectra and multisource perception-based feedback to shift centrifugal spraying systems from empirical parameter adjustment to mechanism-driven, closed-loop coordinated control. Full article

Turbofan engine performance is critically sensitive to operating conditions, yet comprehensive frameworks that simultaneously assess exergo-economic, exergo-environmental, and lifecycle cost performance across realistic flight envelopes remain limited, particularly for Gulf-region climates. In this study, we present a comprehensive analysis of the exergo-economic, exergo-environmental, and lifecycle costings of five different configurations of two-spool and triple-spool turbofan engines. The analysis was carried out for a wide range of four operating conditions, namely ambient temperature, flight altitude, Mach number, and % relative humidity, with emphasis on the climate conditions likely to be found in the Gulf region. The computational models developed were validated against published data to confirm their reliability. It was found that fuel consumption was the most significant contributor to total lifecycle ownership cost, between 60 and 75% of hourly operating cost over a 20-year service period. Ambient temperature, Mach number, and Cruise altitude represented the most significant drivers of long-term economic performance, with % relative humidity having little effect. Exergo-economic analysis showed that the major cost mechanisms changed dramatically with operating conditions. Exergy destruction and component inefficiencies determined the costs at Takeoff, with capital investment being the dominant factor when cruising. Increase in both or either ambient temperature and altitude was shown to reduce cost rates but simultaneously reduced thermo-economic efficiency via higher specific exergy costs. However, increase in Mach number enhances both exergy output and cost-effectiveness, confirming that specific exergy cost is a more reliable indicator of true system performance than cost rate alone. The two-spool configurations show superior specific CO₂ emissions, with Case 3 recording the lowest emissions at Takeoff and Case 2 at Cruise. For exergy-based environmental indicators, Case 3 performs best at both Takeoff and Cruise, achieving the lowest environmental destruction coefficient and index, as well as the highest environmental benign index among all five configurations. These findings provide actionable guidance for engine selection, operational optimization, and sustainable propulsion system design. Full article

Professional UAV thermal imaging systems are widely used for inspection, environmental monitoring, search and rescue, agriculture, and technical diagnostics. However, their cost limits their use in education, preliminary field screening, rapid prototyping, and low-resource applications. This study evaluates a minimum-cost indirect UAV thermal sensing workflow based on a DJI Mini 4K consumer drone, a lightweight Servo King9000 smartphone, and a UTi260M smartphone-connected infrared thermal camera. In the proposed configuration, the smartphone displayed and recorded the thermal stream, while the onboard RGB camera of the UAV recorded the smartphone-displayed infrared video during flight. The aim was not to develop a radiometric UAV thermal imaging platform, but to determine whether such a low-cost configuration can provide qualitative presence/absence indication of clear thermal hotspots and to identify its operational limits. The system was experimentally assessed under no-payload and payload conditions, daylight and nighttime illumination, and several low-altitude operating heights. Additional motor-region thermal observations were performed using a UTi260T handheld thermal camera under loaded and unloaded operating conditions. The complete UAV–payload configuration had a measured mass of approximately 340 g, corresponding to an effective added payload of 91 g and a payload-to-UAV mass ratio of 36.5%. Payload operation reduced near-ground flight endurance from approximately 25 min to 14 min 40 s. The maximum observed motor-region temperature increased from 24.9 °C under unloaded operation to 42.0 °C under loaded operation, while motor thermal asymmetry increased from 4.8 °C to 7.6 °C. Nighttime and low-glare operation improved the readability of the smartphone-displayed thermal stream, with the most practical usability observed at approximately 10–20 m. The results show that the proposed workflow is feasible only for short-range qualitative thermal screening and clear hotspot presence/absence indication. The UAV-recorded video should not be interpreted as direct thermal data, but as an RGB recording of a smartphone display showing thermal information. Therefore, the workflow is not suitable for quantitative temperature measurement, radiometric thermal mapping, or accurate thermal shape delineation. The main operational limits are payload mass, suspended-load oscillation, display readability, reduced endurance, motor-region thermal loading, sensitivity to payload alignment, and the absence of raw radiometric data. Direct UTi260M smartphone-recorded thermal frames were additionally used for pixel-size-assisted qualitative verification of practical reference thermal targets, including a human-sized target and a vehicle-sized target, at selected low-altitude operating heights. Full article

Accurate geolocalization of ground targets from unmanned aerial vehicles (UAVs) is critically limited by pose estimation errors and the scarcity of active ranging sensors. To address these challenges, we propose a pipeline that integrates reference image cropping, robust cross-view matching, and geographic projection to estimate real-world coordinates using 2.5D reference maps. For evaluation, we introduce SkyPin, the first large-scale benchmark of its kind, designed to comprehensively test UAV-based localization methods. It comprises UAV imagery from eight diverse environments, featuring both visible and thermal infrared modalities under a wide range of conditions, including variations in weather, time of day, flight altitude, and camera perspective. All ground targets are annotated with centimeter-accuracy Real-Time Kinematic (RTK) coordinates. We establish a comprehensive benchmark by evaluating a series of feature matching methods combined with different projection strategies, allowing systematic comparison of algorithm performance. Representative results show that RoMa combined with PnP-based raytracing achieves the best overall performance, reaching a median 2D error of 0.87 m and Recall@5m values of 0.94 and 0.98 on RGB and thermal infrared UAV-map settings, respectively. Further analysis reveals that performance degrades in challenging mountainous scenes and under large viewing-angle variations, highlighting terrain relief and UAV perspective changes as remaining critical challenges for robust target geo-localization. The full dataset and implementation code will be made publicly available to facilitate future research in UAV-based geolocalization. Full article

A screening method based on dispersive solid-phase extraction (DSPE) coupled with ultra-performance liquid chromatography–quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF-MS) was established for the analysis of non-edible substances in food. This method is applicable to a wide range of non-edible substances, including but not limited to antihypertensive, hypoglycemic, weight-loss, antimicrobial, antipyretic–analgesic, sedative–hypnotic, and antifatigue agents. Through systematic optimization of sample pretreatment and UPLC-Q-TOF-MS conditions, ultrasonic extraction with methanol followed by cleanup using 25 mg Primary Secondary Amine (PSA) and 50 mg C₁₈ was identified as the optimal procedure. The methodological validation demonstrated that all 38 quality control compounds exhibited excellent linear correlation coefficients (R² > 0.99) across a concentration range of 0.005~5.0 mg/kg. At three spiking levels, the mean recoveries and relative standard deviations (RSDs) in four matrices ranged from 67.79% to 110.93% and from 0.23% to 9.37%, respectively. The screening detection limits (SDLs) and limits of quantification (LOQs) were within the range of 0.003~0.5 mg/kg. A screening database comprising 390 substances was constructed. In addition, an identification strategy for the unknown structural analogues was established by summarizing the mass spectrometric fragmentation patterns of the phosphodiesterase-5 (PDE-5) inhibitor analogues. Applied to 110 batches of samples, the method screened 12 known non-edible substances and identified a new PDE-5 inhibitor analogue, phenyl 3-desethyl 3-propyl carbodenafil. The workflow integrates suspected screening using a comprehensive database with a non-targeted identification strategy for unknown analogues. Overall, this strategy is efficient, sensitive and accurate, providing a robust analytical platform for high-throughput screening and discovery of illegally added unknown substances in food. Full article

Shock buffet is one of the critical issues affecting the aerodynamic performance, flight quality, and flight safety of large aircraft. To overcome the limitations of traditional experimental measurement methods, such as insufficient capability in capturing flow features and high cost, an integrated experimental system tailored for extreme cryogenic and high-Reynolds-number conditions is developed based on the conventional tuft technique. This system comprises “preparation of low-flow-disturbance fluorescent mini-tufts, high-efficiency large-area tuft taping, automatic generation of digital streamline, and flow topology analysis”. Furthermore, a technique for assessing the transonic shock buffet onset using dynamic flow visualization with fluorescent mini-tufts is proposed. This paper takes a typical supercritical airfoil as the research object. First, through high-precision numerical simulations, it reveals that low-energy, unstable boundary-layer separation is the core driving force for the development and maintenance of shock buffet, and that flow separation characteristics serve as an important basis for determining the shock buffet onset. Subsequently, experimental validation is conducted in a 0.3 m high-Reynolds-number transonic wind tunnel. Using a dual-excitation-band composite light source, simultaneous measurements of pressure-sensitive paint (PSP) and fluorescent mini-tuft patterns are realized. The experimental results show that under extreme conditions, characterized by a wide total temperature range of 110 K to 280 K and strong scouring at Mach numbers from 0.6 to 0.9, the fluorescent mini-tufts (approximately 0.05 mm in diameter) exhibit excellent flow-following capability without any detachment. The digitized flow patterns of the fluorescent mini-tufts, obtained via computer image recognition algorithms, clearly reveal the location and area of boundary-layer separation. The trends show good agreement with the cryogenic PSP results, providing an important reference for determining the shock buffet onset. Full article

Reliable altitude and vertical speed estimation are fundamental for unmanned aerial vehicle (UAV) autonomous flight, especially during low-altitude operations such as takeoff and landing. Barometric altimeters are widely used due to their low cost, high availability, and good long-term stability, providing smooth altitude trends over a wide operating range. However, barometric measurements are indirectly inferred from static pressure and are therefore sensitive to local airflow disturbances. In particular, rotor downwash and ground effect-induced pressure perturbations near the surface can introduce significant biases and short-term fluctuations in barometric altitude, which propagate into erroneous vertical speed estimates during critical flight phases. Time-of-flight (TOF) altimeters, such as radar or laser sensors, provide direct above-ground-level (AGL) measurements and are largely insensitive to ground effect-related pressure disturbances. Within their limited operational range, TOF altimeters typically offer higher accuracy and lower short-term noise compared with barometric altitude. Nevertheless, TOF sensors are characterized by a restricted valid measurement range and frequently exhibit non-ideal behaviors in real-world UAV operations, including out-of-range outputs, frozen measurements, and in-range biased readings. These anomalies violate the nominal sensor assumptions used in conventional Kalman filter-based fusion and can significantly degrade estimation performance if not properly handled. This paper proposes a hybrid Kalman–rule-based altitude estimation framework that fuses barometric and TOF altitude measurements to exploit their complementary characteristics while mitigating their respective limitations. A vertical dynamic state-space model is formulated to jointly estimate altitude, vertical velocity, accelerometer bias, and ground height offset. A rule-based anomaly detection and classification module is developed to identify multiple TOF altimeter failure modes observed in operational UAV flights. The detected anomaly states are incorporated into the Kalman filter to adaptively weight, accept, or reject TOF measurements, thereby improving robustness against sensor non-idealities. The proposed approach is validated using 39 real UAV flight logs covering diverse flight regimes, including low-altitude maneuvers, cruise, and autonomous landing. Experimental results show that the proposed framework provides more stable and robust altitude and vertical speed estimation under practical sensor anomaly conditions compared with conventional barometer-only and standard Kalman fusion configurations. These results demonstrate the practical effectiveness of the proposed method for fault-aware altitude estimation in UAV autonomous flight. Full article

To compare hurdle-resisted sprint training (EGH), sled-resisted training (EGS), and hurdles-only training (CG) on performance and kinematics using a smallest-effect-size-of-interest (SESOI) framework, fifteen U18 female hurdlers (16.3 ± 1.3 years) were randomized to EGH, EGS, or CG (n = 5 each) for a 7-week intervention (7 microcycles). EGH used individualized resistance (10% velocity decrement), while EGS used fixed ~13% body-mass resistance. Outcomes included 30 m hurdle time (30 mH), Technique Index, and exploratory kinematics. Primary analysis used baseline-adjusted robust ANCOVA with permutation and linear mixed models (LMM) as sensitivity checks. A smallest-effect-size-of-interest (SESOI) of −0.066 s (~1.2%) was pre-specified. Adjusted ANCOVA favored EGH over CG (−0.19 s; 95% CI [−0.45, 0.06]; p = 0.11). The point estimate exceeded the SESOI, though the CI captured both meaningful and trivial effects. Sensitivity analyses maintained this directional pattern, but LMM estimates varied in magnitude, suggesting model dependence. The EGH–EGS contrast was smaller and uncertain (−0.15 s; p = 0.10). Exploratory baseline-adjusted kinematic contrasts showed no clear differences at the first hurdle, but highlighted nominal differences in the EGH group at the second hurdle (greater take-off distance, p = 0.030) and third hurdle (shorter flight and landing times, p < 0.05), which should be interpreted as hypothesis-generating. In this preliminary trial, the data are compatible with a range of effects from negligible to practically meaningful for hurdle-resisted sprint training relative to both control and sled-resisted conditions. All estimates are accompanied by wide compatibility intervals, precluding confirmatory conclusions. These findings establish protocol feasibility, provide estimation-based preliminary evidence with openly available individual-level data, and motivate adequately powered multi-center replication trials. Full article