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The ongoing climate crisis requires innovative methods to maximize renewable and sustainable energy resources. There have been advancements in harvesting energy from ambient motions such as wind, ocean waves, and human movements. Dielectric elastomer generators (DEGs) are a promising option for energy harvesting due to their high energy density and compatibility with low‐frequency oscillations. This review provides an in‐depth overview of DEGs, including electroactive materials, electromechanical characterization, electronics for harvesting, interfacing circuits, prototypes, and challenges. DEGs have the potential to play a significant role in decarbonizing energy for both small‐ and large‐scale applications using ambient energy sources.

This paper studies the aeroelastic behavior of a rectangular, cantilever wing equipped with the spanwise morphing trailing edge (SMTE) concept. The SMTE consists of multiple trailing edge flaps that allow controlling the spanwise camber distribution of a wing. The flaps are attached at the wing’s trailing edge using torsional springs. The Rayleigh–Ritz method is used to develop the equations of motion of the wing-flap system. The use of shape functions allows for representing the wing as an equivalent 2D airfoil with generalized coordinates that are defined at the wingtip. Strip theory, based on Theodorsen’s unsteady aerodynamic model, is used to compute the aerodynamic loads acting on the wing. A representative Padé approximation for Theodorsen’s function is utilized to model the aerodynamic behaviors in a state-space form allowing time-domain simulation and analysis. The model is validated using a rectangular cantilever wing and the data are available in the literature. A comprehensive parametric comparison study is conducted to assess the impact of flap stiffness on the aeroelastic boundary. In addition, the potential of the SMTE to provide load alleviation and flutter suppression is assessed for a wide range of flight conditions, using a discrete (1-cosine) gust. Finally, the implementation and validation of a controller for a wing with SMTE for gust load alleviation are studied and controller parameters are tuned for a specific gust model.

There is an emerging trend in the morphing aircraft research where two or more morphing degrees of freedom are used on a wing which leads to the concept of polymorphing. The skin of the morphing wing must be flexible in the morphing direction but stiff in other directions to withstand the aerodynamic loads and maintain the airfoil shape. Polymorphing changes the loadings profile (from uniaxial to biaxial) and increases the complexity of designing suitable morphing skins. Furthermore, elastomeric materials used on morphing wings are usually prestretched to prevent wrinkling and to increase their out-of-plane stiffness. This paper focuses on elastomeric morphing skins and it studies the effect of biaxial strain rates and prestretch ratios on important mechanical properties such as stiffness, hysteresis losses (%), and stress relaxations (%) from an experimental perspective. Three polymeric materials are considered: Latex, Oppo, and Ecoflex. This study provides a mechanical comparative understanding of the three polymers used in the morphing wing under biaxial loading (two morphing degrees of freedom).

This paper investigates the effectiveness of a resonance avoidance concept for composite rotor blades featuring extension–twist elastic coupling. The concept uses a tendon, attached to the tip of the blade, to apply a proper amount of compressive force to tune the vibration behavior of the blade actively. The tendon is simulated by applying a non-conservative axial compressive force applied to the blade tip. The main load carrying part of the structure is the composite spar box, which has an antisymmetric layup configuration. The nonlinear dynamic behavior of the composite blade is modelled by using the geometrically exact fully intrinsic beam equations. The resulting nonlinear differential equations are discretized using a time–space scheme, and the stationary and rotating frequencies of the blade are obtained. It is observed that the proposed resonance avoidance mechanism is effective for tuning the vibration behavior of composite blades. The applied compressive force can shift the frequencies and the location at which the frequency veering take place. Furthermore, the compressive force can also cause the composite blade to get unstable depending on the layup ply angle. Finally, the results, highlighting the importance of compressive force and ply angle on the dynamic behavior of composite blades, are presented and discussed.

A morphing aircraft continuously adjusts its wing geometry to achieve optimal flight characteristics for a wide range of flight conditions. Research on morphing aircraft has focused on developing wings with 1 morphing degree of freedom “monomorphing”. However, nowadays the focus is on developing wings with multiple morphing degrees of freedom “polymorphing”. One of the key design challenges for morphing aircraft technology is the development of skin capable of facilitating morphing whilst maintaining the aerodynamic shape of the wing. Soft polymeric materials represent a potential candidate to act as morphing skin because of their ability to undergo large deformation in multiaxial directions. In this study, latex skin is characterized under all possible deformation modes such as uniaxial, pure shear, biaxial, and equibiaxial to account for monomorphing and polymorphing applications. The effects of strain rate, thickness, and aspect ratio on hysteresis loss, stress relaxation and, stiffness are also studied. The outcomes of this study provide a comprehensive understanding of the mechanical viscoelastic behavior of latex skin under various deformation modes.

This paper studies the effect of morphing rate on the aeroelasticity of a polymorphing wing capable of active span extension and passive twist/pitch. A variable domain size finite element model is developed to capture the dynamic effects due to the presence of a variable span in the Euler–Bernoulli beam model, which introduces a structural damping term in the equations of motion. The effect of various morphing rates on the aeroelastic boundaries of the system, namely, flutter velocity and flutter frequency, is examined for a beam undergoing span extension and retraction, from baseline span to 25% span extension and vice versa, respectively. Three points of interest are analyzed: at the start of the span morphing, at the mid-point of morphing, and just before the morphing process ends. The parametric analysis is carried out to determine the effect of varying critical parameters, such as the elastic axis location of the outboard wing section and adjoining spring torsional rigidity on the aeroelastic boundaries of the polymorphing wing.

The main aim of this research is to introduce the relationship between the topic of coding theory and the projective plane of order four. The maximum value of size code M over the finite field of order four and an incidence matrix with the parameters, n (length of code), d (minimum distance of code) and e (error-correcting of code) have been constructed. Some examples and theorems have been given.

This paper presents the reverse hinge spoiler, a novel spoiler concept, for flight load control. The reverse hinge spoiler is a control surface mounted on the upper surface of the wing. Unlike conventional hinged spoilers that are hinged at their front and rotate forward toward the leading edge of the wing, the proposed spoiler concept is hinged at its rear and rotates backward toward the trailing edge of the wing. The aerodynamic performance of the proposed spoiler is compared and contrasted with that of a conventional hinged spoiler for different flight conditions and hinge locations using the two-dimensional Reynolds-Averaged Navier–Stokes (RANS) with the k-omega SST turbulence model-based computational fluid dynamic solver. The results show that the proposed spoiler results in a larger increase in drag and a sharper reduction in the lift for a wide range of spoiler angles and flight conditions. Reversing the spoiler is found to cause a higher adverse pressure gradient in front of the spoiler compared to a conventional spoiler, as it ‘traps’ more flow, thereby increasing drag and reducing lift.

This paper presents an aeroelastic analysis of a polymorphing wing capable of active span extension and passive pitch variation. The wing is split into two segments: an inboard segment responsible for span extension/retraction and an outboard segment capable of pitch variation. The two segments are connected through an overlapping spar and a torsional spring. A finite element aeroelastic model is developed where the wing structure is discretized into Euler–Bernoulli beam elements and the aerodynamic loads are calculated using Theodorsen’s unsteady model. A comprehensive parametric analysis is carried out with and without span extension to analyze the effect of varying critical design parameters, such as elastic axis position of outboard section and torsional spring rigidity, and conditions for aeroelastic phenomena of flutter and divergence are studied. A gust load analysis is carried out to quantify the capability of the outboard wing passive twist mechanism to alleviate loads. Finally, a nonlinear analysis is carried out by replacing the linear torsional spring with a nonlinear cubic spring to study the effects of cubic hardening and softening on the aeroelasticity of the polymorphing wing.

This paper presents the development of a novel polymorphing wing capable of Active Span morphing And Passive Pitching (ASAPP) for small UAVs. The span of an ASAPP wing can be actively extended by up to 25% to enhance aerodynamic efficiency, whilst its pitch near the wingtip can be passively adjusted to alleviate gust loads. To integrate these two morphing mechanisms into one single wing design, each side of the wing is split into two segments (e.g., inboard and outboard segments). The inboard segment is used for span extension whilst the outboard segment is used for passive pitch. The inboard segment consists of a main spar that can translate in the spanwise direction. Flexible skin is used to cover the inboard segment and maintain its aerodynamic shape. The skin transfers the aerodynamic loads to the main spar through a number of ribs that can slide on the main spar through linear plain bearings. A linear actuator located within the fuselage is used for span morphing. The inboard and outboard segments are connected by an overlapping spar surrounded by a torsional spring. The overlapping spar is located ahead of the aerodynamic center of the outboard segment to facilitate passive pitch. The aero-structural design, analysis, and sizing of the ASAPP wing are detailed here. The study shows that the ASAPP wing can be superior to the baseline wing (without morphing) in terms of aerodynamic efficiency, especially when the deformation of the flexible skin is minimal. Moreover, the passive pitching near the wingtip can reduce the root loads significantly, minimizing the weight penalty usually associated with morphing.

This paper presents a parametric study on the aeroelasticity of cantilever wings equipped with Flared Hinge Folding Wingtips (FHFWTs). The finite element method is utilized to develop a computational, low-fidelity aeroelastic model. The wing structure is modelled using Euler–Bernoulli beam elements, and unsteady Theodorsen’s aerodynamic strip Theory is used for aerodynamic load predictions. The PK method is used to estimate the aeroelastic boundaries. The model is validated using three rectangular, cantilever wings whose properties are available in literature. Then, a rectangular, cantilever wing is used to study the effect of folding wingtips on the aeroelastic response and stability boundaries. Two scenarios are considered for the aeroelastic analysis. In the first scenario, the baseline, rectangular wing is split into inboard and outboard segments connected by a flared hinge that allows the outboard segment to fold. In the second scenario, a folding wingtip is added to the baseline wing. For both scenarios, the influence of fold angle, hinge-line angle (flare angle), hinge stiffness, tip mass and geometry are assessed. In addition, the load alleviation capability of FHFWT is evaluated when the wing encounters discrete (1-cosine) gusts. Finally, the hinge is assumed to exhibit cubic nonlinear behavior in torsion, and the effect of nonlinearity on the aeroelastic response is assessed and analyzed for three different cases.

Background: Fractures of acrylic resin dentures are a common occurrence in clinical dentistry. The denture may be fractured accidentally when dropped or while in service in the mouth due to flexural fatigue. Objectives: The aim of this study was to compare the elastic modulus and the flexural strength between two heat-cured acrylic resins used in denture bases: a high-impact resin (Lucitone 199) and a traditional resin (Rodex). Materials and methods: Rectangular strips of Lucitone 199 and Rodex (10 samples each) were fabricated and stored in artificial saliva at 37 °C for 2 weeks. The specimens were subjected to a three-point flexural test. The data were statistically analysed with Student’s t-test (p ⩽ .05). Results: The high-impact acrylic resin had a lower elastic modulus (p = .000) and higher flexural strength (p = .001) compared to the traditional acrylic resin. Conclusion: Within the limitations of this study, it can be concluded that the high-impact acrylic resin is a suitable denture base material for patients with clinical fracture of the acrylic denture. Keywords: Denture, Acrylic resin, Fracture, High-impact, Elastic modulus, Flexural strength

Objective: To assess the performance of a test for breast cancer utilizing synchrotron x-ray diffraction analysis of scalp hair from women undergoing diagnostic radiology assessment. Design and Setting: A double-blinded clinical trial of women who attended diagnostic radiology clinics in Australia. Patients: 1796 women referred for diagnostic radiology, with no previous history of cancer. Main Outcome Measures: Sensitivity, specificity and accuracy of the hair test analysis compared to the gold standard of imaging followed by biopsy where indicated. Results: The hair-based assay had an overall accuracy of >77% and a negative predictive value of 99%. For all women, the sensitivity of both mammography and x-ray diffraction alone was 64%, but when used together the sensitivity rose to 86%. The sensitivity of the hair test for women under the age of 70 was 74%. Conclusion: In this large population trial the association between the presence of breast cancer and an altered hair fibre X-ray diffraction pattern previously reported has been confirmed. It appears that mammography and X-ray diffraction of hair detect different populations of breast cancers, and are synergistic when used together.

A low-fidelity aeroelastic model is developed to study the dynamic behaviour of uniform, cantilever span morphing wings. The wing structure is modelled using the shape functions of the bending and torsional modes of a uniform cantilever wing according to the Rayleigh–Ritz method. Theodorsen’s unsteady aerodynamic theory is used to model the aerodynamic loads. A Padé approximation for the Theodorsen’s transfer function is utilised to allow time-domain simulation and analysis. The sensitivity of the aeroelastic behaviour of span morphing wings to different geometric parameters and mechanical properties is considered. Furthermore, the impact of morphing rate on the aeroelastic behaviour is studied. Finally, the use of two novel span morphing concepts for flutter suppression is assessed. [ABSTRACT FROM AUTHOR]