Search Results (7,633)

This study presents a multi-platform airborne empirical evaluation of an engineered thermodynamic reactive seeding agent, Thai Formula8 (a CaO-based powder), for warm convective cloud modification under the Thai Royal Rainmaking patent framework. Laboratory XRD and laser diffraction confirmed the reactive seeding agent XRD identified CaO as the dominant crystalline phase, accounting for 75.51% of the normalized crystalline-phase composition with a median particle diameter of 17.62 µm and a specific surface area of 4971.77 cm²/g. Calibrating these mineralogical fractions under cloud-base conditions (20 °C, 850 hPa) establishes a theoretical composite reaction enthalpy (ΔH_{Formula8,composite}) of −1115.35 kJ/kg. Coordinated airborne campaigns deploying a Construcciones Aeronauticas S.A. (CASA) seeding aircraft at Cloud Base +2000 feet and a Super King Air profiling aircraft across three vertical layers investigated this thermodynamic mechanism across a 4-day dataset. In situ exothermic slaking at the mid-level core generated localized warming up to +0.92 °C, activating an artificial “thermodynamic pump”. This vertical suction conduit evacuated core liquid water content (ΔMLW down to −0.128 g/m³) and lofted moisture upward, accompanied by cloud-top accumulation (ΔTLW up to +0.145 g/m³) and a 2.4-fold (+140.5%) particle concentration surge. Rapid mass accumulation accelerated collision-coalescence, triggering warm-rain initiation via precipitation mass loading drag. This provides the first physics-based observational evidence for systematic, high-density thermodynamic cloud seeding. Full article

Fleet-level prognostics and health management (PHM) requires decisions that extend beyond diagnosis, remaining useful life estimation, and maintenance timing. Mission commitment, aircraft dispatch, maintenance, and spare-parts support consume the same finite sustainment capacity but operate at different temporal scales. This study investigates whether explicitly separating a mission-horizon commitment decision from day-to-day sustainment execution improves fleet-level decision quality, and under which operating regimes such a hierarchy is valuable. We develop a mission-horizon hierarchical reinforcement learning (MH-HRL) framework in which a learned weekly policy selects a portfolio of missions from a seven-day forecast and specifies a coarse sustainment posture, while a fixed daily executor implements aircraft assignment, maintenance prioritization, and replenishment decisions. Fleet evolution is represented by a next-event discrete-event simulator with stochastic mission arrivals, degradation/failure processes, repairs, and logistics lead times. Five decision policies—reactive rule-based control, rolling-horizon planning, flat PPO, a hierarchy without the learned posture signal, and the full MH-HRL policy—are evaluated over nine mission-load/support-capacity regimes using 10 paired common-random-number seeds (450 formal runs). The hierarchical policies consistently improve the composite mission-readiness-cost utility, with the full policy outperforming the rule baseline in all nine regimes after Holm correction. The benefit is not obtained by maximizing mission acceptance: the hierarchical policy accepts fewer missions but achieves higher accepted-mission success and fleet availability while substantially reducing failure-driven sustainment cost. Ablation further shows that approximately 97% of the Smart vs. Rule improvement is attributable to the weekly daily temporal decomposition rather than the additional posture signal. These results support that the principal value of hierarchy in the studied fleet-PHM setting is long-horizon commitment control, and its marginal value increases with mission pressure. Full article

A plant–controller co-design methodology is proposed in which the reference model dynamics are parameterized and incorporated directly into the optimization rather than prescribed a priori. Within an Explicit Model Following (EMF) architecture, plant-design variables and reference-model parameters are optimized simultaneously with the controller gains, subject to prescribed stability, performance, and maneuverability constraints. The framework accommodates $H_2$, $H_{\infty }$, and mixed $H_2/H_{\infty }$ state-feedback synthesis and can be extended to multiple design points. The bilinearities arising from the coupled plant–controller–reference model optimization are addressed through a perturbation-based iterative procedure that decomposes the resulting Bilinear Matrix Inequality (BMI) problem into sequential convex Linear Matrix Inequality (LMI) subproblems. The proposed framework is demonstrated and validated through an integrated sizing and control-design problem for a representative quad-wing tilt-rotor Vertical Take-Off and Landing (VTOL) air vehicle, where aircraft-specific maneuverability and handling-quality requirements are incorporated as design constraints. Compared with the initial controller design obtained for fixed plant parameters, the final co-designed plant–controller configuration achieves a substantial improvement in closed-loop performance, with the maximum control demand reduced by approximately $70\%$ in the directional control case. Further optimization of the reference-model parameters yields an additional 3–$5\%$ improvement in control effort metrics, indicating that the prescribed closed-loop dynamics can influence the overall co-design optimum while maintaining the required handling-quality constraints. Full article

In time-marching simulation of airborne wind energy systems (AWESs), the tether is usually discretised into a series of lumped masses (i.e., nodes) connected by spring and damper elements. There is no consensus on the appropriate number of nodes for AWES applications, although it is known that using more nodes than necessary is computationally costly. In this work, we examine the trim solutions of a fixed-wing aircraft connected to the ground by a 500 m tether. A successive difference metric is proposed to quantify the convergence rate of the trim solutions as more nodes are added. We then compare this gain in accuracy to the simulation time and memory usage by plotting their Pareto fronts. Results reveal that using 6–8 tether nodes (i.e., 7–9 segments) is sufficient. Compared to using 15 nodes, 8 nodes keep the successive difference metric below 2%, run over 13 times faster, and require less than a quarter of memories. Beyond 8 nodes, the differential equation solver appears to enter a new stiffness regime, resulting in rapid rises in computation time and memory usage. These findings suggest that the conservative choices of 10–20 nodes can be relaxed, promising significantly lower computation costs in future studies. Full article

The article examines and analyzes the use of composite materials, such as carbon fiber-reinforced plastic (CFRP) and glass fiber-reinforced plastic (GFRP), in new-generation aircraft. Comparative studies were conducted on these composite materials alongside aviation alloys based on aluminum, titanium, and steel. It was determined that contact interfaces in nominally stationary joints suffer significant damage due to vibrational loads—stemming from aircraft engines and normal operations—a phenomenon classified as fretting corrosion. The study found that Al-CFRP/GFRP contact leads to the catastrophic degradation of friction surfaces caused by the formation of hard Al₂O₃ oxides. Ti-CFRP/GFRP contact is the most common configuration in new-generation aircraft; notably, the wear resistance of the composite materials is 6–20 times higher than that of the titanium alloy, owing to the inherent properties of titanium and its susceptibility to wear. Furthermore, the article analyzes surface processing and protection methods for titanium components aimed at enhancing the durability and wear resistance of these contact pairs. Full article

An explicit finite element study examined the sensitivity of a rotating aircraft-engine fan to blade material and drone impact velocity. A complete 20-blade rotor and a deformable, equivalent-material quadcopter were modelled in ANSYS/LS-DYNA. Ti-6Al-4V, Ti-6242 and AA2024-T3 blades were assessed at 30, 60 and 100 m/s with an initial fan angular velocity of 283 rad/s. Nine frictional simulations and one Ti-6Al-4V frictionless case at 100 m/s were evaluated using stress, equivalent plastic strain, directional displacement, erosion and energy histories. Ti-6Al-4V produced the lowest maximum blade plastic strain at each velocity; AA2024-T3 values were 11.6–26.9 times greater despite lower equivalent stress. No fan elements were deleted, whereas drone deletion occurred in every case. The maximum-history reduction in surviving-drone kinetic energy increased with velocity, but the highest velocity did not produce the largest plastic strain in every material. Including friction increased maximum plastic strain by a factor of 6.46 in the sensitivity case. The results highlight multi-blade chronology and complementary response measures within the adopted model; local impact convergence and configuration-specific experimental validation were not established. Full article

This paper proposes a two-stage probabilistic robust controller design framework based on Pareto optimization (TSPO) for aircraft longitudinal short-period motion subject to aerodynamic parameter uncertainties. Unlike conventional robust control approaches such as LQR, $H_{\infty }$, and LMI-based design, which require engineers to translate intuitive performance specifications into abstract tuning parameters, TSPO formulates the design in terms of explicit time-domain performance targets and actuator constraints. In Stage I, multi-objective Pareto optimization generates an approximate set of candidate controllers by balancing nominal tracking performance and sample-based performance variability. The elevator-deflection limit is imposed as a hard constraint under nominal parameter values. In Stage II, Monte Carlo simulation with uniform parameter sampling estimates the rates at which candidates satisfy the time-domain requirements and elevator-deflection constraint under parameter uncertainty, and these estimates are used to select a final controller. The selected controller is then evaluated on a unit-step acceleration tracking task under three parametric uncertainty distributions: truncated Gaussian, uniform, and skewed beta. Comparative results against LQR, $H_{\infty }$, and LMI controllers for the considered model and uncertainty cases show favorable time-domain requirement satisfaction and elevator-deflection behavior for TSPO. The proposed framework provides a practical, heuristic, and interpretable methodology for robust flight-controller design in engineering applications. Full article

A component health indicator does not directly establish whether an aircraft electrical power system (EPS) can sustain its required functions. This study evaluates a digital-twin-conditioned compact ordinal recognizer (DT-COR) for four ordered service states in a normalized EPS. Measured battery, insulated-gate bipolar-transistor, and bearing trajectories are synchronized through a declared network twin; system labels are produced by its priority-service and N − 1 rules. Testing holds out source assets across 32 episodes and 4800 operating points. The DT-COR emission head contains 108 learned coefficients (3 × 36); three intercepts, three validation offsets, one temperature term, and the temporal-mixing parameter are reported separately, while gate parameters, priors, unusable-zone values, and transition matrices are external configuration. DT-COR attains 90.8% four-state accuracy, 0.107 ordinal mean absolute error, and 0.024 expected calibration error on the reported asset-disjoint test set. Collapsing S2 and S3 yields 93.0% three-state accuracy from the reported confusion counts, while only 37 of 157 S2 points are identified as S2 in the four-state task and 103 are assigned to S3. The directional constraint applies only to directly constrained pre-filter emissions under fixed context; it does not guarantee monotonicity of the temporally filtered posterior. Under the reported 40% random masking protocol, DT-COR has an 11.8% false-safe proportion, but the baselines were not trained with identical masking augmentation, so this result is retained only as a descriptive unequal-training stress test. A separate state-contract sensitivity study over 27 prespecified threshold perturbations gives DT-COR severe-state AUROC in the range 0.988–0.990 and AUPRC in the range 0.811–0.825. The study therefore supports a compact research interface under twin-generated labels, not an aircraft-qualified recognizer. Full article

This paper proposes a frequency-integrated electromagnetic vulnerability index (FI-EVI), which is a reference-weighted susceptibility-screening metric for shielded electronic enclosures rather than a direct measure of functional failure. The frequency-resolved vulnerability is defined as the internal-to-reference RMS field ratio, V_E(f) = E_int,rms(f)/E_ref,rms(f), and FI-EVI is its log-frequency average from 10 MHz to 18 GHz. All cases use a swept-frequency incident plane wave of 1 V/m RMS and, as a common normalization benchmark, the MIL-STD-461G RS103 aircraft-internal limit (20 V/m up to 1 GHz and 60 V/m above). The internal field is obtained from an aperture-dominant reduced-order transfer function with parameters fixed in advance. A worst-case spectrum is derived under a fixed incident power-density budget and a peak power spectral density cap αS_flat; the amplification factor is bounded by $\sqrt{\alpha }$. For three UAV-scale apertures (15, 60, and 150 mm), FI-EVI is 0.0056, 0.0094, and 0.0159, and the amplification factor at α = 10 is 1.27, 1.58, and 2.23. For one similitude-scaled family of a controlled loaded enclosure simulated with openEMS, the band-limited reduced-order FI-EVI is 9.4–21.5% below the full-wave envelope and within −11.0% to +7.3% of the maximum among the prescribed probe locations and polarizations, although the enclosure resonances are not reproduced. Full article

Designing arrival routes in terminal airspace requires deciding how inbound streams should be grouped and where the resulting merge points should be placed. This paper searches convergence topology, merge-point positions and population-aware path decoding jointly at the network scale, treating the three as a single design problem. The problem is formulated as a bilevel optimization: an outer simulated annealing loop searches convergence topologies and merge-point locations, while an inner A* algorithm with population density embedded in its edge cost generates the track segments between structural nodes. Sound energy is accumulated once per unique structural segment, independently of how many arrival routes traverse it. The method is demonstrated as a single-case proof of concept on the north-landing configuration of Runway 35 at Shanghai Pudong International Airport. Over a preference sweep from distance-only to noise-only weighting, the optimized networks outperform the published procedures in both metrics for $w_N\in [0.0,0.6]$; at higher weights the proxy value falls further but the route length exceeds the baseline. The noise reduction forms a statistically flat plateau rather than a single working point: at $w_N=0.3$ the model-based, population-weighted noise proxy (the modelled population above a 65 dB single-event $L_{\mathrm{AE}}$ threshold) is reduced by 69.3% and the total route length by 3.4%, and the differences between neighbouring weights within the plateau are smaller than their run-to-run scatter. Attributing the reduction sequentially, a 3${}^{\circ }$ continuous-descent profile alone lowers the proxy value by 29.1%, and the horizontal redesign of the convergence structure accounts for the remainder at 3${}^{\circ }$ CDO. A sensitivity study across structural, algorithmic, population and acoustic assumptions shows that the reduction in the proxy is robust, whereas the route-length reduction holds only while the structural constraints are not substantially tightened. Full article

Accurate simulation of repetitive aircraft shock is needed to assess the environmental adaptability of aircraft equipment, especially at locations close to the excitation source. Conventional narrowband random-on-random (NOR) testing generates a stationary, approximately Gaussian waveform. Although its power spectral density (PSD) can satisfy the prescribed spectrum, it does not reproduce the high peaks, repeated pulse shape, and high kurtosis observed in near-field aircraft shock. This paper presents a time-domain windowed pulse (TDWP) synthesis method with a time-frequency joint optimization procedure. A stationary random carrier is generated from the initial PSD, and a physically motivated exponential window is used to impose the firing-rate-related pulse pattern. Windowing changes the spectrum, so a regularized spectral equalization is applied in a closed loop to bring the PSD of the final waveform back to the target spectrum. The window decay exponent is selected by minimizing errors in peak and kurtosis while enforcing PSD consistency. One set of field measurements and three laboratory tests were used for validation. Relative to the conventional method, TDWP reduced the absolute error in maximum peak, kurtosis, and fatigue-damage-equivalent response by 46.4, 51.2, and 53.9 percentage points, respectively. The results indicate that preserving the transient pulse sequence can improve the representation of near-source repetitive aircraft shock while maintaining the prescribed spectral requirement under the investigated conditions. Full article

Reliable aircraft-door perception is essential for automatic passenger-boarding-bridge (PBB) docking, where small sill-localization errors can affect alignment safety. We formulate aircraft-door perception as cross-scene joint detection and contour extraction using abundant boxes and limited contour annotations. Unlike conventional region segmentation, the target is a thin, often open door-frame contour. CS-DoorContour combines box-supervised detection, soft-contour supervision, selectively valid region assistance, box projection, and uncertainty-aware cross-scene consistency. A versioned label pipeline converts antialiased annotations into one-pixel centerlines, soft distance targets, fixed-width bands, and region masks only when safe closure is possible. Capture-sequence-disjoint protocols evaluate in-domain, cross-camera, day-to-night, and leave-one-aircraft-instance-out generalization using boundary, distance, and docking-oriented geometry metrics. Across three seeds with 20 contour labels, the in-domain model obtains $93.92\pm 3.23$ Box AP, $0.876\pm 0.002$ BF1@2, $0.233\pm 0.006$ Boundary AP, and $1.47\pm 0.22$-pixel mean sill error. Across held-out-camera folds, Box AP ranges from 91.09 to 95.87 and BF1@2 from 0.829 to 0.855; held-out-aircraft folds obtain 72.30–86.43 Box AP and 0.755–0.865 BF1@2. The method reduces dense annotation requirements while preserving contour and sill geometry for practical docking. Full article

Rock shelters are important cultural and archaeological sites in Australia, often containing evidence of Aboriginal occupation and symbolic expression. While rock shelters have been investigated across Australia, locating them in rugged environments through pedestrian surveys remains challenging. This research contributes a methodology which integrates remote sensing, GIS analyses, and archaeological survey to locate rock shelters in the Blue Mountains. We produced models in ArcGIS Pro that analyse high-resolution, UAV-based LiDAR datasets and publicly available, low-resolution, aircraft-based LiDAR datasets from the New South Wales government. Our models yield locations of potential rock shelters, which can be visually evaluated in 3D LiDAR point clouds and ground-truthed through archaeological survey. Ground-truthing confirmed the successful detection of six known rock shelters on UAV and NSW LiDAR datasets, producing more accurate coordinates than the ones listed in online databases. Significantly, we identified three previously unregistered rock shelters that preserve rock art and lithics. These promising results indicate capacity to improve the spatial accuracy of legacy site records and locate unregistered archaeological rock shelters within, and potentially beyond, Australia. Our methodology promotes targeted and efficient survey of rock shelters that can produce regional datasets benefitting local communities, archaeology, and cultural heritage management. Full article

Quantitative evaluation of axial stress in small diameter thin-walled aircraft tubing is important for characterizing its mechanical state during assembly and service. However, restricted circumferential access necessitates a compact local excitation configuration, for which geometric mismatch between conventional planar acoustic sources and curved tube surfaces can lead to circumferentially nonuniform excitation and interfere with stable time of flight (TOF) estimation. This study proposes a reference-based axial stress measurement method using an L(0,2)-dominated guided wave response generated by a conformal oblique incidence probe. Based on acoustoelastic-guided wave analysis and transient response characteristics, 500 kHz was adopted as an appropriate operating frequency for the present sensing configuration. Three-dimensional finite element simulations showed that the conformal loading configuration produced a more regular circumferential wavefield distribution. Experimental comparisons showed that the amplitude of the strong subsequent response was approximately 91% of the target wave packet amplitude for the conventional planar probe but below 31% for the conformal probe, indicating greater time domain prominence of the target wave packet relative to subsequent responses and providing a more stable waveform basis for TOF estimation. Repeated calibration established an approximately linear relationship between TOF shift and axial tensile stress. Validation tests on tubes from the same batch, together with repeated measurements after probe reinstallation and recoupling, yielded an overall mean absolute deviation from the reference stress of 1.86 MPa and a mean absolute relative deviation of 3.17%. The results demonstrate the feasibility of reference based quantitative axial stress evaluation using an established zero-load reference state in small diameter thin-walled aluminum alloy tubes under restricted circumferential access. Full article

Urban air mobility path planning must account for objects that do not provide cooperative surveillance information, but their motion and avoidance responses vary by class, making a single extrapolated trajectory insufficient to inform every path decision. We propose PRISM to bring alternative futures and their uncertainty into path planning. Using current sensor tracks, PRISM predicts three 15 s trajectory branches with probabilities and time-varying positional uncertainty. Forecast positions are used to screen candidate paths for potential collisions, while a time-indexed risk field derived from the predictive distribution ranks the paths that remain. This allows different possible futures to inform path selection without being collapsed into one trajectory. While work to extend the method to three-dimensional motion continues, the present study evaluates this approach in a two-dimensional horizontal-plane simulation containing aircraft, birds, and drifting objects with different motion and avoidance rules, including classes absent from training. Prediction tests, repeated futures from saved simulator states, and paired closed-loop episodes assess forecast quality and planning outcomes against a constant-velocity forecast. In in-distribution (ID) tests, PRISM’s mixture-mean average displacement error was 72.54 m versus 122.53 m for constant velocity, about 41% lower without future-based branch selection; the closest of three branches gave a 62% reduction. With raw predictive scales, exploratory paired comparisons supported fewer screened severe union encounters (minimum separation below 45 m) and greater lower-tail separation in three of five settings. The nominal out-of-distribution (OOD) severe-encounter contrast was uncertain without screening, while both ID contrasts retained support. Nominal-OOD sampling was extended after initial outcomes were examined. Total encounter counts within 152.4 m showed no clear difference from constant velocity. In the recalibration control, improved predictive coverage did not yield a consistent planning gain. PRISM brings possible motion across object classes into a common planning interface without requiring the target’s class or intent in advance. Its contribution is to make those alternatives and their uncertainty usable for path selection without changing the planner’s structure, and to assess their value through closed-loop separation as well as trajectory accuracy. Full article