Search Results (20)

In psychology, small sample sizes are a frequent challenge—particularly when studying specific expert populations or using complex and cost-intensive methods like human scoring of creative answers—as they reduce statistical power, bias results, and limit generalizability. They also hinder the use of frequentist confirmatory factor analysis (CFA), which depends on larger samples for reliable estimation. Problems such as non-convergence, inadmissible parameters, and poor model fit are more likely. In contrast, Bayesian methods offer a robust alternative, being less sensitive to sample size and allowing the integration of prior knowledge through parameter priors. In the present study, we introduce small-sample-size structural equation modeling to creativity research by investigating the relationship between creative fluency and nested creative cleverness with right-wing authoritarianism, starting with a sample size of N = 198. We compare the stability of results in frequentist and Bayesian SEM while gradually reducing the sample by n = 25. We find that common frequentist fit indexes degrade below N = 100, while Bayesian multivariate Rhat values indicate stable convergence down to N = 50. Standard errors for fluency loadings inflate 40–50% faster in frequentist SEM compared to Bayesian estimation, and regression coefficients linking RWA to cleverness remain significant across all reductions. Based on these findings, we discuss (1) the critical role of Bayesian priors in stabilizing small-sample SEM, (2) the robustness of the RWA-cleverness relationship despite sample constraints, and (3) practical guidelines for minimum sample sizes in bifactor modeling. Full article

In this research, two inflatable-winged Unmanned Aerial Vehicles (UAVs) in distinct configurations, a single-fuselage layout with external trailing-edge control surfaces and a twin-fuselage layout with fully movable control surfaces were designed, developed, and flight tested to investigate the flight characteristics of inflatable-winged aircraft. Initially, inflatable wings were designed and fabricated from various materials, followed by rigorous ground testing, including structural characteristics tests, pressure retention and resistance tests, and low-speed wind-tunnel evaluations. Following this, two methods for controlling the inflatable wings were proposed, and their roll control effectiveness was thoroughly investigated. Subsequently, two inflatable-winged UAV prototypes, each employing a different configuration and manipulation method, were designed, assembled, and subjected to basic low-altitude flight tests to assess the feasibility of their aerodynamic layouts and control characteristics. The results demonstrated that a segmented wing design with a multi-boom configuration is particularly well-suited for inflatable wings. Additionally, both proposed control methods were tested and shown to be effective in flight. The findings provide valuable insights into the properties of inflatable wings and offer substantial guidance for the development of inflatable-winged aircraft. Full article

Flexible inflatable film wings have many functional advantages that traditional fixed rigid wings do not possess, such as foldability, small size, light weight, convenient storage, transportation, and so on. More and more scholars and engineers are paying attention to flexible inflatable wings, which have gradually become a new hot research topic. However, flexible wings rely on inflation pressure to maintain the shape and rigidity of the skin film, and the inflation pressure has a significant influence on the strain deformation and wing bearing characteristics of flexible wing skin film. Here, based on the flexible mechanics theory and balance principle of flexible inflatable film, a theoretical model of structural deformation and internal inflation pressure was constructed, and finite element simulation analysis under different internal inflation pressure conditions was carried out as well. The results demonstrate that the biaxial deformation of flexible wing skin film is closely related to internal inflation pressure, local size, configuration, and film material properties. However, strain deformation along the wingspan direction is quite distinguishing, skin films work under the condition of biaxial plane deformation, and the strain deformation of the spanning direction is obviously higher than that of the chord direction, which all increases with internal inflation pressure. Therefore, it is necessary to pay more attention to bearing strain deformation characteristics to meet the bearing stiffness requirements, which could effectively provide a theoretical reference for the structural optimization design and inflation scheme setting of flexible inflatable wings. 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

Katydids employ acoustic signals to communicate with others of their species and have evolved to generate sounds by coupling the anatomical structures of their forewings. However, some species have evolved to implement an additional resonance mechanism that enhances the transmission and sound pressure of the acoustic signals produced by the primary resonators. Secondary resonators, such as burrow cavities or horn-shaped structures, are found in the surrounding environment but could also occur as anatomical modifications of their bodies. Chamber-like structures have been described in species of katydids with modified pronota or wings. It has been shown that these modified structures directly affect the transmission and filtering of acoustic signals and can function as a Helmholtz resonator that encapsulates the primary sound source. By morphological and acoustic analysis, we describe a new genus of Conocephalinae and investigate the physical properties of their sound production structures for three new species from the Andes of Colombia and Ecuador. Males of the new genus, here described as Tectucantus n. gen., have a characteristic inflated pronotum enclosing the reduced first pair of wings and extending rearward over the first abdominal segments. We test the hypothesis that the pronotal cavity volume correlates with the carrier frequency of specific calls. The cavity of the pronotal chamber acts as a Helmholtz resonator in all three Tectucantus species and, potentially, in other distantly related species, which use similar secondary body resonators. Full article

This study is aimed at assessing the feasibility of employing an innovative, smart-material-based control effector for an inflatable wing. A shape memory alloy (SMA) actuator is primarily investigated as a control effector in this work for its advantages of a simple actuation mechanism and a high force-to-weight ratio. This paper presents the design, control strategy and simulation results of the SMA actuator used as a stability augmentation system for a small-scale prototype kite. Stable flight of the kite is achieved during open wind tunnel tests using the SMA actuator. Based on experimental and simulation analyses, it is evident that the current SMA actuator is better for low-frequency actuations rather than stability augmentation purposes, as its performance is sensitive to practical conditions. The study also discusses potential improvements and applications of the SMA actuator. Full article

Airborne wind energy systems using flexible membrane wings have the advantages of a low weight, small packing volume, high mobility and rapid deployability. This paper investigates the aero-structural deformation of a leading edge inflatable kite for airborne wind energy harvesting. In the first step, a triangular two-plate representation of the wing is introduced, leading to an analytical description of the wing geometry depending on the symmetric actuation state. In the second step, this geometric constraint-based model is refined to a multi-segment wing representation using a particle system approach. Each wing segment consists of four point masses kept at a constant distance along the tubular frame by linear spring-damper elements. An empirical correlation is used to model the billowing of the wing’s trailing edge. The linear spring-damper elements also the model line segments of the bridle line system, with each connecting two point masses. Three line segments can also be connected by a pulley model. The aerodynamic force acting on each wing segment is determined individually using the lift equation with a constant lift coefficient. The particle system model can predict the symmetric deformation of the wing in response to a symmetric actuation of the bridle lines used for depowering the kite (i.e., changing the pitch angle). The model also reproduces the typical twist deformation of the wing in response to an asymmetric line actuation used for steering the kite. The simulated wing geometries are compared with photogrammetric information taken by the onboard video camera of the kite control unit, focusing on the wing during flight. The results demonstrate that a particle system model can accurately predict the geometry of a soft wing at a low computational cost, making it an ideal structural building block for the next generation of soft wing kite models. Full article

The conceptual design of a hybrid aerial vehicle for the exploration of the upper Venus atmosphere is presented. The vehicle will float like a balloon and harvest solar energy which is stored in batteries. The neutral buoyancy reduces the energy consumption and makes the vehicle robust and durable. Energy stored in the batteries can be used for powered flight with good horizontal and vertical mobility to explore aspects of the atmosphere. The vehicle is intended to operate near 55.3 km altitude and to explore the cloud layer of the planet. The vehicle takes its inspiration from the Stingray inflatable wing by Prospective Concepts. Based on a trade study, the wing span was set to 25 m. Equations are developed for the altitude, gas and skin temperature, and skin stress during neutrally buoyant flight. To keep the equations in a simplified analytical form, the complex compartmentalized gas pockets of the vehicle are lumped into a single gas sphere. The equations take into account the volumetric expansion of the structure and the requirement that the differential pressure needs to be large enough to allow for brief periods of powered flight without significant structural deformation. An aerodynamic analysis provides the lift and drag coefficient curves and indicates that the vehicle is pitch-stable. A powered flight analysis shows that an airspeed of 30 m/s can be maintained for 31 min at 55 km and 69 min at 69 km altitude. Full article

This paper presents the technical barriers and an analysis to advance the conceptual development of novel robotic ground-aerial vehicles (RGAVs) for exploration missions to Mars prior to human arrival and the establishment of a base. The concept for RGAVs for Mars planetary exploration is novel, and will require innovations that are at various stages of development or use by the aerospace community. The RGAV concept will utilize inflatable wing technology, which increases the flexibility of the wing, and thus the possibility of structural dynamic instabilities that must be studied in the context of the Martian atmosphere. An aeroelastic model for wing bending is proposed, which considers wind gusts where the change in wind direction is up to ±6° from the mean, and a turbulence intensity of up to 20%. Their effect on the bending displacement of a semi-elastic wing is quantified, resulting in a maximum wing tip displacement of 16.2 cm. Low-fidelity computational aerodynamic analysis is performed using OpenVSP (3.31.1, NASA, Washington, DC, USA) to compute mean aerodynamic loads during cruise conditions at a cruise Mach number of 0.70. Finally, a non-linear adaptive control system is proposed for the longitudinal aerial dynamics and a proportional integral derivative (PID) controller is outlined for the ground roving lateral dynamics. Full article

Soft-wing kites for airborne wind-energy harvesting function as flying tensile membrane structures, each of whose shape depends on the aerodynamic load distribution and vice versa. The strong two-way coupling between shape and loading poses a complex fluid-structure interaction problem. Since computational models for such problems do not yet meet the requirements of being accurate and at the same time fast, kite designers usually work on the basis of intuition and experience, combined with extensive iterative flight testing. This paper presents a fast aero-structural model of leading-edge inflatable kites for the design phase of airborne wind-energy systems. The fluid-structure interaction solver couples two fast and modular models: a particle system model to capture the deformation of the wing and bridle-line system and a 3D nonlinear vortex step method coupled with viscous 2D airfoil polars to describe the aerodynamics. The flow solver was validated with several wing geometries and proved to be accurate and computationally inexpensive for pre-stall angles of attack. The coupled aero-structural model was validated using experimental data, showing good agreement in the deformations and aerodynamic forces. Therefore, the speed and accuracy of this model make it an excellent foundation for a kite design tool. Full article

Inflatable wings are of interest for applications where low weight, compact transport volume, and easy set-up are important. Examples are unmanned aerial vehicles with inflatable wings, paragliders and softkites for sport or airborne wind-energy applications. In this paper, a new method of designing and fabricating conformable inflatable wings by Jacquard three-dimensional weaving is presented. Depending on the weaving pattern, plane-parallel, tapered, or even curved structures can be produced. An analytical framework was developed to determine the shapes of pressurized structures produced by Jacquard weaving. Based on this theory, several design patterns suitable for inflatable wings are proposed. It is shown that the structural efficiency of the woven structure is identical to the structural efficiency of a cylinder. To validate the concept, different wing prototypes were built with the methods used for the mass production of airbags. The new method allows for the cost-efficient fabrication of inflatable structures, pressure vessels, and liquid containers with applications in the automotive, aerospace, and leisure industries. Full article

Similar to parafoils, ram-air kites are flexible membrane wings inflated by the apparent wind and supported by a bridle line system. A major challenge in estimating the performance of these wings using a computer model is the strong coupling between the airflow around the wing and the deformation of the membrane structure. In this paper, we introduce a staggered coupling scheme combining a structural finite element solver using a dynamic relaxation technique with a potential flow solver. The developed method proved numerically stable for determining the equilibrium shape of the wing under aerodynamic load and is thus suitable for performance measurement and load estimation. The method was validated with flight data provided by SkySails Power. Measured forces on the tether and steering belt of the robotic kite control pod showed good resemblance with the simulation results. As expected for a potential flow solver, the kite’s glide ratio was overestimated by 10–15%, and the measured tether elevation angle in a neutral flight scenario matched the simulations within 2 degrees. Based on the obtained results, it can be concluded that the proposed aero-structural model can be used for initial designs of ram-air kites with application to airborne wind energy. Full article

The flow structures and surface pressure distributions on corrugated airfoils significantly differed from those on a conventional, smooth airfoil. An unsteady, two-dimensional computational simulation was carried out to investigate the flow behavior and associated aerodynamic performance of a group of corrugated airfoils with different levels of waviness at angles of attack from 0° to 20° with an interval of 2° at a low Reynolds number regime (Re = 1.2 × 10⁵) and were quantitatively compared with those of its smooth counterpart. Time-averaged aerodynamic coefficients demonstrated that the corrugated airfoils have a lower lift and higher drag because of trapped vortices in the corrugations. The pressure drag of the corrugated airfoils was greater than that of the smooth airfoil. In contrast, the viscous drag of the corrugated airfoils was smaller than that of the smooth airfoil because the recirculation generated in the corrugation could reduce the viscous drag. The averaged velocity gradient in the boundary layer showed that the thickness of the boundary layer increased significantly for the corrugated airfoils because of recirculating flow caused by the small-standing vortices trapped in the valley of corrugations. The smoother the corrugated surface, the closer the aerodynamic characteristics are to those of the smooth airfoil. Full article

Leading-edge inflatable (LEI) kites use a pressurized tubular frame to structurally support a single skin membrane canopy. The presence of the tubes on the pressure side of the wing leads to characteristic flow phenomena for this type of kite. In this paper, we present steady-state Reynolds-Averaged Navier-Stokes (RANS) simulations for a LEI wing for airborne wind energy applications. Expanding on previous work where only the leading-edge tube was considered, eight additional strut tubes that support the wing canopy are now included. The shape of the wing is considered to be constant. The influence of the strut tubes on the aerodynamic performance of the wing and the local flow field is assessed, considering flow configurations with and without side-slip. The simulations show that the aerodynamic performance of the wing decreases with increasing side-slip component of the inflow. On the other hand, the chordwise struts have little influence on the integral lift and drag of the wing, irrespective of the side-slip component. The overall flow characteristics are in good agreement with previous studies. In particular, it is confirmed that at a low Reynolds number of $\mathrm{Re}={10}^5$, a laminar separation bubble exists on the suction side of this hypothetical rigid wing shape with perfectly smooth surface. The destruction of this bubble at low angles of attack impacts negatively on the aerodynamic performance. Full article

An instrumentation system for in-situ measurement of the inner-outer pressure differential at the upper and lower surfaces of dynamically inflatable wings is designed and tested, revealing important insights into the aerodynamic characteristics of inflatable airfoils. Wind tunnel tests demonstrated full capability of low-pressure differential readings in the range of 1.0–120 Pa, covering speeds from 3 to 10 m/s at angles of attack from −20 to +25°. Readings were stable, presenting coefficients of variation from 2% to 7% over the operational flight envelope. The experimental data confirmed the occurrence of a bottom leading-edge recirculation bubble, linked to the low Reynolds regime and the presence of an air intake. It supported the proposition of a novel approach to aerodynamic characterization based on local pressure differentials, which takes in account the confined airflow structure and provides lift forces estimations compatible with practical observation. The results were also compatible with data previously obtained following different strategies and were shown to be effective for parameterizing the inflation and stall phenomena. Overall, the instrumentation may be applied straightforwardly as a flight-test equipment, and it can be further converted into collapse alert and prevention systems. Full article