Search Results (114)

The downwelling light sensor (DLS) is the industry-standard solution for generating UAV-based digital orthophoto maps (DOMs). Current mainstream DLS correction methods primarily rely on angle compensation. However, due to the temporal mismatch between the DLS sampling intervals and the exposure times of multispectral cameras, as well as external disturbances such as strong wind gusts and abrupt changes in flight attitude, DLS data often become unreliable, particularly at UAV turning points. Building upon traditional angle compensation methods, this study proposes an improved correction approach—FIM-DC (Fitting and Interpolation Model-based Data Correction)—specifically designed for data collection under clear-sky conditions and stable atmospheric illumination, with the goal of significantly enhancing the accuracy of reflectance retrieval. The method addresses three key issues: (1) field tests conducted in the Qingpu region show that FIM-DC markedly reduces the standard deviation of reflectance at tie points across multiple spectral bands and flight sessions, with the most substantial reduction from 15.07% to 0.58%; (2) it effectively mitigates inconsistencies in reflectance within image mosaics caused by anomalous DLS readings, thereby improving the uniformity of DOMs; and (3) FIM-DC accurately corrects the spectral curves of six land cover types in anomalous images, making them consistent with those from non-anomalous images. In summary, this study demonstrates that integrating FIM-DC into DLS data correction workflows for UAV-based multispectral imagery significantly enhances reflectance calculation accuracy and provides a robust solution for improving image quality under stable illumination conditions. Full article

The Black-winged Kite Optimization Algorithm (BKA) is likely to experience a sluggish convergence rate when confronted with the optimization of complex multimodal functions. The fundamental algorithm has a tendency to get stuck in local optima, thus rendering it arduous to identify the global optimal solution. When dealing with large-scale data or high-dimensional optimization challenges, the BKA algorithm entails significant computational expenses, which might lead to excessive memory usage or prolonged running durations. In order to enhance the BKA and tackle these problems, a revised Black-winged Kite Optimization Algorithm (TGBKA) that incorporates the Tent chaos mapping and Gaussian mutation strategies is put forward. The algorithm is simulated and analyzed alongside other swarm intelligence algorithms by utilizing the CEC2017 test function set. The optimization outcomes of the test functions and the function convergence curves indicate that the TGBKA demonstrates superior optimization precision, a quicker convergence speed, as well as robust anti-interference and environmental adaptability. It is also contrasted with numerous similar algorithms via simulation experiments in various scene models for Unmanned Aerial Vehicle (UAV) path planning. In comparison to other algorithms, the TGBKA produces a shorter flight route, a higher convergence speed, and stronger adaptability to complex environments. It is capable of efficiently addressing UAV path planning issues and improving the UAV’s path planning abilities. Full article

In response to the stalling fault of the solar array drive assembly (SADA) in an in-orbit MEO satellite, an analysis and research on the energy balance algorithm are conducted. This is performed under the continuous changes in the light period, shadow period, and the incident angle of the solar panels. An output energy model of the solar panels is presented. It is proven that this model is a continuous function, and the optimal stalling angle for energy output is deduced. By simulating and calculating the energy output under different stalling angles and taking into account the on-orbit performance degradation of the solar cell array, the energy output curve within one orbital period is obtained, which provides support for the on-orbit operation and maintenance of the satellite. Moreover, on-orbit verification was carried out in the case of a stalling fault of the -Y-wing SADA of a certain MEO-orbiting satellite. Full article

To improve the hydrodynamic performance of hydrofoils, this study combines the shape characteristics of flat and elliptical wings, uses parabolic function to fit the leading and trailing edges of hydrofoils, introduces the cross-section coefficient λ to characterize the cross-sectional size of hydrofoils along the spreading direction, and designs five hydrofoils with different cross-sections. The motion of the hydrofoil is simulated using the finite element analysis software Fluent to obtain the hydrodynamic performance curve of the hydrofoil and analyze the effect of different end face sizes on the performance of the hydrofoil. The results show that compared with the flat wing, the peak drag of the variable section hydrofoil with λ = 0.5 is reduced by 9.3%, the pitching moment is reduced by 23.1%, and the average power is raised by 17.4%. If the appropriate reduction in the cross-section coefficient is too small, it will exacerbate the wing tip vortex shedding, the hydrofoil surface pressure will be too concentrated, and the hydrofoil motion stability will be reduced. The lift coefficient, drag coefficient, and pitching moment coefficient of the hydrofoil are positively correlated with the cross-section coefficient λ, and positively correlated with the motion frequency. Full article

The aim of this work is to evaluate the influence of the surface deformations of an open inflatable wing section on aerodynamic performance and boundary layer separation phenomena. The inflation/deflation processes are allowed by an air intake placed on the bottom side of the model. Due to its low rigidity, non-contact measurements are required. Therefore, an infrared thermography technique was applied in order to detect local surface deformations and local separation phenomena. Additionally, the inflation and deflation of the whole wing were studied through an innovative approach, introduced by the authors, based on a piezoelectric sensor. It is important to note that open and closed wing sections exhibit very different aerodynamic behavior. For these reasons, both cases were investigated in the following research. The impact of deformation on the wing’s aerodynamic performance was assessed by means of wind tunnel tests. The inflatable wing presented lower lift and higher drag than the corresponding rigid wing due to the fabric’s deformations. Furthermore, the lift and moment coefficient curves were strongly related to the wing’s inflation. In particular, there was a change in the slope of the lift curve and a drop in the moment coefficient when the wing inflated. Lastly, the results provided evidence that a thermographic approach can be used to qualitatively detect local deformations of an inflatable wing and that a piezoelectric sensor can be used feasibly in detecting the inflation and deflation phases of a wing. Full article

The Italian Aerospace Research Centre (CIRA) is developing an unmanned stratospheric platform for Earth observation and telecommunications, known as a High-Altitude Pseudo-Satellite (HAPS). This paper presents an aerodynamic and stability analysis of a new closed-wing HAPS configuration. The design uses a hybrid approach, combining aerodynamic and aerostatic forces to achieve weight balance, with the stability analysis accounting for the buoyancy force applied at the center of volume of the structure. Following the initial design phase, which aims for an altitude of 20 km, a speed of 16 m/s, and a payload capacity of 20 kg, a suitable configuration using a NACA 0018 airfoil is selected. The aircraft lift–drag curve is evaluated using a stationary, incompressible Reynolds-Averaged Navier–Stokes (RANS) analysis with a k-$\omega$ SST turbulence model in OpenFoam. A detailed longitudinal and lateral-directional stability analysis is also conducted using OpenFOam and AVL software. Full article

Jointed soft-hard composite rocks are frequently encountered in nature, and this complex structure contributes to unpredictable fracturing mechanisms and failure behavior. In this study, soft-hard composite rocks with three joints were fabricated to conduct a uniaxial loading experiment, supplemented by Digital Image Correlation (DIC) and Acoustic Emission (AE) experiments. The results indicate that the mechanical parameters display a V-shape variation trend with the increase of joint angle, which minimized at 30°. The peak strength ranges from 33.48 MPa to 44.93 MPa. The failure characteristics change from tensile failure to shear failure and finally to intact failure. According to the displacement curves on both sides of the crack, the initiation of wing cracks is driven by the direct tensile displacement field and indirect tensile displacement field for specimens with joint angles of 0–30° and 75–90°, respectively. While the crack initiation from joint tips corresponding to specimens with a joint angle of 45–60° is controlled by direct and indirect tensile displacement fields. Wherein the cracks initiate from the coplanar joint in the hard layer, driven by the indirect tensile displacement field, and the cracks expanding upward from other joint tips are more susceptible to the indirect tensile displacement field. Full article

The tubercles on the flipper of humpback whales are beneficial for improving their locomotion performance. Based on biomimetic design, the bulge model was developed to mimic this function through cubic B-spline curve fitting, aiming to improve the stall performance of the two-element wingsail. The numerical calculation method was validated against experiments to ensure the reliability of the numerical results. Five models of the bulges of the main wing were developed, and the influence of different bulges on the stall performance of the two-element wingsail under logarithmic gradient wind conditions was examined. By analyzing its lift and drag characteristics, pressure load distribution, and flow field near the stall angle, the mechanism by which the bulges improved the stall characteristics of the two-element wingsail was revealed. The result indicated that the two-element wingsail in the Case 5 scheme has a maximum lift coefficient of 1.25, and that the lift reduction in the early stage of stall is only 8.8%, which is 43.6% less than the original wingsail lift reduction. As the bulge size increases the strength of the forward vortex created by the middle larger bulge increases, resulting in the absence of a symmetrical vortex structure on the suction surface of the wingsail, causing high fluid momentum band deflection. The energy of the boundary layer is supplemented by vorticity transport, promoting the formation of attached flow on the side of the smaller bulge and improving the lift coefficient. Full article

Indoor direct shear tests under different stress levels were conducted on sandstone–concrete samples to investigate the rock–concrete interfaces’ shear energy evolution features and fracture behaviors under different normal stresses, combined with acoustic emission (AE) and digital image correlation (DIC) techniques. The research results show that the growth of normal stress restricts the coalescence and failure of micro-cracks inside the sample and improves the bearing capacity. The shear strength of the sandstone–concrete cemented interface increases by 12.3–34.34% with increasing normal stress. The evolution behaviors of the total input energy, elastic strain energy and dissipated energy density are similar under different normal stress conditions, and the increase in normal stress raises the energy storage capacity of the sample, as well as the input external energy required for a sample’s failure, thereby enhancing the bearing capability of the sample. In addition, the AE count and b value characteristics indicate that crack propagation shows a three-stage variation trend. It can be seen from the RA (rise time/amplitude)-AF (AE count/duration time) curves that as the normal stress increases, the proportion of shear cracks in the sample progressively increases. When the final overall failure of the sample is imminent, the high-energy level fracture type changes from tensile fracture to shear fracture with increased normal stress, leading to an increasing percentage of shear fracture. Finally, the speckle results indicate that the nucleation and coalescence of tensile wing-shaped cracks are the main causes of sample failure. Under relatively high normal stress conditions, the damage degree of the serrated interface increases and the crack morphology becomes more intricate. Full article

Due to irregular hydrodynamic–aerodynamic coupling, the modeling and simulation of near-surface flight are extremely complex. For the present study, a practical dynamic model and a complete motion simulation method for the solution of such problems were established for engineering applications. A discrete non-linear time-varying dynamics model was employed in order to ensure the universality of the method; thereafter, force models—including gravity, aerodynamic, hydrodynamic, control, and thrust models—were established. It should be noted that a non-linear approach was adopted for the hydrodynamic model, which reflects the influences of waves in real-world situations; in addition, a Proportional–Integral–Derivative (PID) control law was added to realize closed-loop simulation of the motion. Considering a take-off flight as a study case, longitudinal three Degrees of Freedom (DoF) motion was simulated. The velocity, angle of attack, height, and angular velocity were selected as the state vectors in the state–space equations. The results show that, with the equilibrium state as the initial setting for the motion, reasonable time–history curves of the whole take-off phase can be obtained using the proposed approach. Furthermore, it is universally applicable for aircraft operating under hydrodynamic–aerodynamic coupling scenarios, including amphibious aircraft, seaplanes, Wing-in-Ground-Effect (WIGE) aircraft, and Hybrid Aerial–Underwater Vehicles (HAUVs). Full article

The optimization of the water-entry strategy for cross-wing underwater vehicles has become a research hotspot in the field of engineering, and its water-entry process is quite different from that of wedges and cylinders. In order to address this problem, a water-entry numerical model for the cross-wing underwater vehicle was first established based on the CFD method. The governing equations and boundary conditions of the dynamic model were defined, along with the basic principles of discretization and turbulent flow of the governing equations. The overset mesh and the VOF multiphase flow model were introduced, and a mesh size independence analysis of the numerical model was conducted. Furthermore, the numerical results were compared with the experimental results to ensure the accuracy of the numerical model. The research focused on the cross-wing underwater vehicle’s impact with calm water and regular waves, respectively. The results show that: (1) the numerical simulations are in good agreement with the experimental results (the maximum predictive error is less than 10%), which verifies the accuracy of the numerical model in this paper; (2) when the cross-wing underwater vehicle impacts calm water, the slamming pressure curve firstly shows a trend of increasing, reaching a peak, and then decreasing sharply, and finally stabilizes. As the water-entry velocity increases, the peak slamming pressure exhibits a gradual increase; (3) during the water entry of the cross-wing underwater vehicle into calm water, the acceleration profile demonstrates a trend of initial increase, followed by a decrease, another increase, and then a subsequent decrease as the entry velocity continues to rise. It should be noted that there are two peaks in the acceleration, with the first peak being significantly smaller than that of the second; (4) when the cross-wing underwater vehicle impacts a regular wave, the slamming pressure is lowest when impacting the crest and highest when impacting the trough. Full article

Mastering the dynamic mechanical behaviors of pre-stressed fractured rocks under repeated impact loads is crucial for safety management in rock engineering. To achieve this, repeated impact loading experiments were performed on produced fractured samples exposed to varying pre-applied axial and confining pressures using a split Hopkinson pressure bar test system in combination with a nuclear magnetic resonance imaging system, and the dynamic failure mechanism and fractal features were investigated. The results indicate that the dynamic stress–strain curves exemplify typical class II curves, and the strain rebound progressively diminishes with growing impact times. The impact times, axial pressure, and confining pressure all significantly affect the dynamic peak strength, average dynamic strength, dynamic deformation modulus, average dynamic deformation modulus, maximum strain, and impact resistance performance. Moreover, under low confining pressures, numerous shear cracks and tensile cracks develop, which are interconnected and converge to form large-scale macroscopic fracture surfaces. In contrast, specimens under a high confining pressure primarily experience tensile failure, accompanied by localized small-scale shear failure. Under low axial pressure, some shear cracks and tensile cracks emerge, while at high axial pressure, anti-wing cracks and secondary coplanar cracks occur, characterized predominantly by shear failure. In addition, as the confining pressure grows from 8 to 20 MPa, the fractal dimensions are 2.44, 2.32, 2.23, and 2.12, respectively. When the axial pressures are 8, 14, and 20 MPa, the fractal dimensions are 2.44, 2.46, and 2.52, respectively. Overall, the degree of fragmentation of the sample decreases with growing confining pressure and grows with rising axial pressure. Full article

Background: The development of microsurgical techniques has enabled reconstructive versatility in various clinical scenarios. Supermicrosurgery is an advanced microsurgical technique ensuring precise reconstructions by operating on small-caliber vessels and nerves, with applications in reconstructive surgeries. Objectives: This study aims to compare the effectiveness of four low-cost training models, thereby improving surgical precision and reducing the learning curve for novice surgeons. Materials and Methods: We conducted a prospective non-randomized study comparing the classic anastomosis technique, the intravascular stenting (IVaS) technique, the color contrast (CC) technique, and our newly introduced double-contrast (DC) technique, which combines IVaS with CC. We used a non-living experimental model represented by chicken wings, analyzing the vessel preparation and anastomosis time, anastomosis patency, and back wall biting through a standardized protocol. We performed 120 end-to-end anastomoses in total, with vessel diameters ranging from 0.5 to 0.8 mm. Results: CC demonstrated superior time efficiency and success rates, reaffirming it as a reliable option in supermicrosurgery, while DC showed slightly better time efficiency and patency compared to both IVaS alone and the classic method. CC outperformed the others in anastomosis time, patency, and back wall catching, reaffirming its reliability in supermicrosurgery. Conclusions: Although DC did not significantly improve patency, it reduced back wall engagement. This makes the DC technique beneficial for trainees working on vessels under 0.5 mm in diameter, where stenting is often required, improving surgical precision and reducing the learning curve, leading to better outcomes in supermicrosurgery. Full article

Spotted wing drosophila (SWD) is a pest that causes damage due to the female laying eggs under the skin of ripe fruit, from which a larva emerges, causing its collapse and reducing its commercial value. Due to the importance of this pest, monitoring its population is the starting point for any control program; however, there is no early monitoring plan within management tasks, nor are there studies on behavior, the optimization of traps, or their baits. This research proposes the evaluation of a monitoring system with encapsulated baits and adhesive traps that allow effective control. The encapsulated bait was selected after evaluating three options in olfactometric tests in the laboratory; the most attractive bait was WVM, with 70% of visits to the stimulus and 30% to its control, unlike SAG I and SAG II, whose values did not exceed 40% attraction. Among the expected results is the availability of a new format of attractive bait for SWD with a better release rate over time, and the information obtained will allow the generation of SWD population curves for the area, which is essential for decision-making. This study will contribute from the perspective of nanomaterials, insect biology, agricultural entomology, and pest monitoring. Full article

The static aeroelastic characteristics of the distributed propulsion wing (DPW) were studied using the CFD/CSD loose coupling method in this study. The momentum source method of the Reynolds-averaged Navier–Stokes equation based on the k-ω SST turbulence model solution was used as the CFD solution module. The upper and lower surfaces of the DPW were established using the cubic B-spline basis function method, and the surfaces of the inlet and outlet were established using the fourth-order Bezier curve. Finally, a three-dimensional parametric model of the DPW was established. A structural finite-element model of the DPW was established, a multipoint array method program based on the three-dimensional radial basis function (RBF) was written as a data exchange module to realize the aerodynamic and structural data exchange of the DPW’s static aeroelastic analysis process, and, finally, an aeroelastic analysis of the DPW was achieved. The results show that the convergence rate of the CFD/CSD loosely coupled method is fast, and the structural static aeroelastic deformation is mainly manifested as bending deformation and positive torsion deformation, which are typical static aeroelastic phenomena of the straight wing. Under the influence of static aeroelastic deformation, the increase in the lift characteristics of the DPW is mainly caused by the slipstream region of the lower surface and the non-slipstream region of the upper and lower surface. Meanwhile, the increase in its nose-up moment and the increase in the longitudinal static stability margin may have an impact on the longitudinal stability of the UAV. To meet the requirements of engineering applications, a rapid simulation method of equivalent airfoil, which can be applied to commercial software for analysis, was developed, and the effectiveness of the method was verified via comparison with the CFD/CSD loose coupling method. On this basis, the static aeroelastic characteristics of the UAV with DPWs were studied. The research results reveal the static aeroelastic characteristics of the DPW, which hold some significance for engineering guidance for this kind of aircraft. Full article