Design and Demonstration of Insect Mimicking Foldable Artificial Wing Using Four-Bar Linkage Systems

In this work, we develop an artificial foldable wing that mimics the hind wing of a beetle （Allomyrina dichotoma）. In real flight, the beetle unfolds forewings and hind wings, and maintains the unfolded configuration unless it is exhausted. The artificial wing has to be able to maintain a fully unfolded configuration while flapping at a desirable flapping frequency. The artificial foldable hind wing developed in this work is based on two four-bar linkages which adapt the behaviors of the beetle＇s hind wing. The four-bar-linkages are designed to mimic rotational motion of the wing base and the vein folding/unfolding motion of the beetle＇s hind wing. The behavior of the artificial wings, which are installed in a flapping-wing system, is observed using a high-speed camera. The observation shows that the wing could maintain a fully unfolded configuration during flapping motion. A series of thrust measurements are also conducted to estimate the force generated by the flapping-wing system with foldable artificial wings. Although the artificial foldable wings give added burden to the flapping-wing system because of its weight, the thrust measurement results show that the flapping-wing system could still generate reasonable thrust.     

Aerodynamic Ground Effect in Fruitfly Sized Insect Takeoff

Aerodynamic ground effect in flapping-wing insect flight is of importance to comparative morphologies and of interest to the micro-air-vehicle (MAV) community. Recent studies, however, show apparently contradictory results of either some significant extra lift or power savings, or zero ground effect. Here we present a numerical study of fruitfly sized insect takeoff with a specific focus on the significance of leg thrust and wing kinematics. Flapping-wing takeoff is studied using numerical modelling and high performance computing. The aerodynamic forces are calculated using a three-dimensional Navier–Stokes solver based on a pseudo-spectral method with volume penalization. It is coupled with a flight dynamics solver that accounts for the body weight, inertia and the leg thrust, while only having two degrees of freedom: the vertical and the longitudinal horizontal displacement. The natural voluntary takeoff of a fruitfly is considered as reference. The parameters of the model are then varied to explore possible effects of interaction between the flapping-wing model and the ground plane. These modified takeoffs include cases with decreased leg thrust parameter, and/or with periodic wing kinematics, constant body pitch angle. The results show that the ground effect during natural voluntary takeoff is negligible. In the modified takeoffs, when the rate of climb is slow, the difference in the aerodynamic forces due to the interaction with the ground is up to 6%. Surprisingly, depending on the kinematics, the difference is either positive or negative, in contrast to the intuition based on the helicopter theory, which suggests positive excess lift. This effect is attributed to unsteady wing-wake interactions. A similar effect is found during hovering.     

Investigation of Unsteady Aerodynamic Characteristics of a Seagull Wing in Level Flight

Unsteady aerodynamic characteristics of a seagull wing in level flight are investigated using a boundary element method.Anew no-penetration boundary condition is imposed on the surface of the wing by considering its deformation.The geometry andkinematics of the seagull wing are reproduced using the functions and data in the previously published literature.The proposedmethod is validated by comparing the computed results with the published data in the literature.The unsteady aerodynamicscharacteristics of the seagull wing are investigated by changing flapping frequency and advance ratio.It is found that the peakvalues of aerodynamic coefficients increase with the flapping frequency.The thrust and drag generations are complicatedfunctions of frequency and wing stroke motions.The lift is inversely proportional to the advance ratio.The effects of severalflapping modes on the lift and induced drag(or thrust)generation are also investigated.Among three single modes(flapping,folding and lead & lag),flapping generates the largest lift and can produce thrust alone.For three combined modes,both flapping/foldingand flapping/lead & lag can produce lift and thrust larger than the flapping-alone mode can.Folding is shown toincrease thrust when combined with flapping,whereas lead & lag has an effect of increasing the lift when also combined withflapping.When three modes are combined together,the bird can obtain the largest lift among the investigated modes.Eventhough the proposed method is limited to the inviscid flow assumption,it is believed that this method can be used to the designof flapping micro aerial vehicle.     

Artificial Cambered-Wing for a Beetle-Mimicking Flapper

In this paper, we have attempted to improve the aerodynamic force generation ability of an artificial wing by implementing initial wing camber in the flexible artificial wing. This initial camber is used to create passive wing camber during flapping motion. We modified original artificial wing by removing many minor vein structures in the wing and then placed the initial camber between two major veins. Stiffness measurements for the original artificial wing and the present wing with initial camber were conducted to compare the stiffnesses of the two artificial wings, and the similarities of the two wings are discussed. A flapping test was carried out using a previously-built flapper that can flap at higher than 25 Hz flapping frequency to verify the wing camber effect. Finally, a performance comparison between uncambered- and cambered-wings was also undertaken based on observations using a high-speed camera and force measurements from wired-flight tests and swing tests. The comparison showed that the cambered-wing could produce about 10% higher thrust than the uncambered-wing.     

Does hydraulic lift or nighttime transpiration facilitate nitrogen acquisition?

Water movement from roots to soil at night in the process of hydraulic lift (redistribution) rehydrates the rhizosphere and has been proposed to improve plant nutrient acquisition. Another process that has now been found in many plant species is nighttime transpiration and this could also affect nutrient relations by influencing supply of mobile nutrients to roots at night. The effects of these soil/root water relations interactions have not been adequately tested. We chose ten Sarcobatus vermiculatus (Hook.) Torrey shrubs with different magnitudes of hydraulic lift (i.e. diel range in soil water potential) to test the hypothesis that the magnitude of lift would be positively related to the amount of nitrogen (N) uptake over a period of days. A ¹⁵N tracer was injected in the 20–30 cm soil layer at locations with hydraulic lift to determine plant ¹⁵N acquisition by shallow roots conducting hydraulic lift. Half of the plants were also placed in large humidified tents (i.e. “bagged”), which suppressed nighttime transpiration, and thus were expected to have greater magnitudes of hydraulic lift, although they did not. All plants took up the ¹⁵N tracer, but contrary to our hypothesis the magnitude of hydraulic lift had no significant effect on the amount of ¹⁵N acquired over a 9-day period following labeling. However, plants that were bagged tended to have lower ¹⁵N acquisition (P = 0.07). These data indicate that decreased nighttime transpirational water loss or some other effect of bagging may decrease nutrient acquisition by these nutrient-limited phreatophytic shrubs and more generally suggests a possible nutritional benefit of nighttime transpiration by plants. This suggestion needs more thorough testing to elucidate an important potential link between plant water and nutrient relations.     

Flapping tail membrane in bats produces potentially important thrust during horizontal takeoffs and very slow flight

Historically, studies concerning bat flight have focused primarily on the wings. By analyzing high-speed video taken on 48 individuals of five species of vespertilionid bats, we show that the capacity to flap the tail-membrane (uropatagium) in order to generate thrust and lift during takeoffs and minimal-speed flight (<1 m ^s−1) was largely underestimated. Indeed, bats flapped the tail-membrane by extensive dorso-ventral fanning motions covering as much as 135 degrees of arc consistent with thrust generation by air displacement. The degree of dorsal extension of the tail-membrane, and thus the potential amount of thrust generated during platform launches, was significantly correlated with body mass (P = 0.02). Adduction of the hind limbs during upstrokes collapsed the tail-membrane thereby reducing its surface area and minimizing negative lift forces. Abduction of the hind limbs during the downstroke fully expanded the tail-membrane as it was swept ventrally. The flapping kinematics of the tail-membrane is thus consistent with expectations for an airfoil. Timing offsets between the wings and tail-membrane during downstrokes was as much as 50%, suggesting that the tail-membrane was providing thrust and perhaps lift when the wings were retracting through the upstoke phase of the wing-beat cycle. The extent to which the tail-membrane was used during takeoffs differed significantly among four vespertilionid species (P = 0.01) and aligned with predictions derived from bat ecomorphology. The extensive fanning motion of the tail membrane by vespertilionid bats has not been reported for other flying vertebrates.     

Effect of outer wing separation on lift and thrust generation in a flapping wing system

We explore the implementation of wing feather separation and lead-lagging motion to a flapping wing. A biomimetic flapping wing system with separated outer wings is designed and demonstrated. The artificial wing feather separation is implemented in the biomimetic wing by dividing the wing into inner and outer wings. The features of flapping, lead-lagging, and outer wing separation of the flapping wing system are captured by a high-speed camera for evaluation. The performance of the flapping wing system with separated outer wings is compared to that of a flapping wing system with closed outer wings in terms of forward force and downward force production. For a low flapping frequency ranging from 2.47 to 3.90 Hz, the proposed biomimetic flapping wing system shows a higher thrust and lift generation capability as demonstrated by a series of experiments. For 1.6 V application (lower frequency operation), the flapping wing system with separated wings could generate about 56% higher forward force and about 61% less downward force compared to that with closed wings, which is enough to demonstrate larger thrust and lift production capability of the separated outer wings. The experiments show that the outer parts of the separated wings are able to deform, resulting in a smaller amount of drag production during the upstroke, while still producing relatively greater lift and thrust during the downstroke.     

In vivo sun protection factor and UVA protection factor determination using (hybrid) diffuse reflectance spectroscopy and a multi-lambda-LED light source

The sun protection factor (SPF) values are currently determined using an invasive procedure, in which the volunteers are irradiated with ultraviolet (UV) light. Non-invasive approaches based on hybrid diffuse reflectance spectroscopy (HDRS) have shown a good correlation with conventional SPF testing. Here, we present a novel compact and adjustable DRS test system. The in vivo measurements were performed using a multi-lambda-LED light source and an 84-channel imaging spectrograph with a fiber optic probe for detection. A transmission spectrum was calculated based on the reflectance measured with sunscreen and the reflectance measured without sunscreen. The preexposure in vitro spectrum was fitted to the in vivo spectrum. Each of the 11 test products was investigated on 10 volunteers. The SPF and UVA-PF values obtained by this new approach were compared with in vivo SPF results determined by certified test institutes. A correlation coefficient R² = 0.86 for SPF, and R² = 0.92 for UVA-PF were calculated. Having examined various approaches to apply the HDRS principle, the method we present was found to produce valid and reproducible results, suggesting that the multi-lambda-LED device is suitable for in-vivo SPF testing based on the HDRS principle as well as for in-vivo UVA-PF measurements.     

Tests for Genetic Differentiation

When testing for genetic differentiation the joint null hypothesis that there is no allele frequency difference at any locus is of interest. Common approaches to test this hypothesis are based on the summation of χ² statistics over loci and on the Bonferroni correction, respectively. Here, we also consider the Simes adjustment and a recently proposed truncated product method (TPM) to combine P‐values. The summation and the TPM (using a relatively large truncation point) are powerful when there are differences in many or all loci. The Simes adjustment, however, is powerful when there are differences regarding one or a few loci only. As a compromise between the different approaches we introduce a combination between the Simes adjustment and the TPM, i.e. the joint null hypothesis is rejected if at least one of the two methods, Simes and TPM, is significant at the α/2‐level. Simulation results indicate that this combination is a robust procedure with high power over the different types of alternatives.     

Dynamic Modeling, Testing, and Stability Analysis of an Ornithoptic Blimp

In order to study omithopter flight and to improve a dynamic model of flapping propulsion,a series of tests are conducted on a flapping-wing blimp.The blimp is designed and constructed from mylar plastic and balsa wood as a test platform for aerodynamics and flight dynamics.The blimp,2.3 meters long and 420 gram mass,is propelled by its flapping wings.Due to buoyancy the wings have no lift requirement so that the distinction between lift and propulsion can be analyzed in a flight platform at low flight speeds.The blimp is tested using a Vicon motion tracking system and various initial conditions are tested including accelerating flight from standstill,decelerating from an initial speed higher than its steady state,and from its steady-state speed but disturbed in pitch angle.Test results are used to estimate parameters in a coupled quasi-steady aerodynamics/Newtonian flight dynamics model.This model is then analyzed using Floquet theory to determine local dynamic modes and stability.It is concluded that the dynamic model adequately describes the vehicle's nonlinear behavior near the steady-state velocity and that the vehicle's linearized modes are akin to those of a fixed-wing aircraft.     

A modified blade element theory for estimation of forces generated by a beetle-mimicking flapping wing system

We present an unsteady blade element theory (BET) model to estimate the aerodynamic forces produced by a freely flying beetle and a beetle-mimicking flapping wing system. Added mass and rotational forces are included to accommodate the unsteady force. In addition to the aerodynamic forces needed to accurately estimate the time history of the forces, the inertial forces of the wings are also calculated. All of the force components are considered based on the full three-dimensional (3D) motion of the wing. The result obtained by the present BET model is validated with the data which were presented in a reference paper. The difference between the averages of the estimated forces (lift and drag) and the measured forces in the reference is about 5.7%. The BET model is also used to estimate the force produced by a freely flying beetle and a beetle-mimicking flapping wing system. The wing kinematics used in the BET calculation of a real beetle and the flapping wing system are captured using high-speed cameras. The results show that the average estimated vertical force of the beetle is reasonably close to the weight of the beetle, and the average estimated thrust of the beetle-mimicking flapping wing system is in good agreement with the measured value. Our results show that the unsteady lift and drag coefficients measured by Dickinson et al are still useful for relatively higher Reynolds number cases, and the proposed BET can be a good way to estimate the force produced by a flapping wing system.     

The three-dimensional optomotor torque system ofDrosophila melanogaster

Summary The well known optomotor yaw torque response in flies is part of a 3-dimensional system. Optomotor responses around the longitudinal and transversal body axes (roll and pitch) with strinkingly similar properties to the optomotor yaw response are described here forDrosophila melanogaster. Stimulated by visual motion from a striped drum rotating around an axis aligned with the measuring axis, a fly responds with torque of the same polarity as that of the rotation of the pattern. In this stimulus situation the optomotor responses for yaw, pitch and roll torque have about the same amplitudes and dynamic properties (Fig. 2). Pronounced negative responses are measured with periodic gratings of low pattern wavelengths due to geometrical interference (Fig. 3). The responses depend upon the contrast frequency rather than the angular velocity of the pattern (Fig. 4). Like the optomotor yaw response, roll and pitch responses can be elicited by small field motion in most parts of the visual field; only for motion below and behind the fly roll and pitch responses have low sensitivity.The mutantoptomotor-blind ^H31 (omb ^H31) in which the giant neurones of the lobula plate are missing or severely reduced, is impaired in all 3 optomotor torque responses (Fig. 5) whereas other visual responses like the optomotor lift/thrust response and the landing response (elicited by horizontal front-to-back motion) are not affected (Heisenberg et al. 1978).We propose that the lobula plate giant neurons mediate optomotor torque responses and that the VS-cells in particular are involved in roll and pitch but not in lift/thrust control. This hypothesis accommodates various electrophysiological and anatomical observations about these neurons in large flies.Abbreviation EMD elementary movement detector     

Flow visualization and unsteady aerodynamics in the flight of the hawkmoth,Manduca sexta

The aerodynamic mechanisms employed durng the flight of the hawkmoth, Manduca sexta, have been investigated through smoke visualization studies with tethered moths. Details of the flow around the wings and of the overall wake structure were recorded as stereophotographs and high-speed video sequences. The changes in flow which accompanied increases in flight speed from 0.4 to 5.7 m s^-1 were analysed. The wake consists of an alternating series of horizontal and vertical vortex rings which are generated by successive down- and upstrokes, respectively. The downstroke produces significantly more lift than the upstroke due to a leading-edge vortex which is stabilized by a radia flow moving out towards the wingtip. The leading-edge vortex grew in size with increasing forward flight velocity. Such a phenomenon is proposed as a likely mechanism for lift enhancement in many insect groups. During supination, vorticity is shed from the leading edge as postulated in the ''flex'' mechanism. This vorticity would enhance upstroke lift if it was recaptured diring subsequent translation, but it is not. Instead, the vorticity is left behind and the upstroke circulation builds up slowly. A small jet provides additional thrust as the trailing edges approach at the end of the upstroke. The stereophotographs also suggest that the bound circulation may not be reversed between half strokes at the fastest flight speeds.     

Machine Learning Prediction of Cancer Cell Sensitivity to Drugs Based on Genomic and Chemical Properties

Predicting the response of a specific cancer to a therapy is a major goal in modern oncology that should ultimately lead to a personalised treatment. High-throughput screenings of potentially active compounds against a panel of genomically heterogeneous cancer cell lines have unveiled multiple relationships between genomic alterations and drug responses. Various computational approaches have been proposed to predict sensitivity based on genomic features, while others have used the chemical properties of the drugs to ascertain their effect. In an effort to integrate these complementary approaches, we developed machine learning models to predict the response of cancer cell lines to drug treatment, quantified through IC₅₀ values, based on both the genomic features of the cell lines and the chemical properties of the considered drugs. Models predicted IC₅₀ values in a 8-fold cross-validation and an independent blind test with coefficient of determination R² of 0.72 and 0.64 respectively. Furthermore, models were able to predict with comparable accuracy (R² of 0.61) IC50s of cell lines from a tissue not used in the training stage. Our in silico models can be used to optimise the experimental design of drug-cell screenings by estimating a large proportion of missing IC₅₀ values rather than experimentally measuring them. The implications of our results go beyond virtual drug screening design: potentially thousands of drugs could be probed in silico to systematically test their potential efficacy as anti-tumour agents based on their structure, thus providing a computational framework to identify new drug repositioning opportunities as well as ultimately be useful for personalized medicine by linking the genomic traits of patients to drug sensitivity.     

Pitching Moment Generation in an Insect-Mimicking Flapping-Wing System

Unlike birds, insects lack control surfaces at the tail and hence most insects modify their wing kinematics to produce control forces or moments while flapping their wings. Change of the flapping angle range is one of the ways to modify wing kinematics, resulting in relocation of the mean Aerodynamic force Center （mean AC） and finally creating control moments. In an attempt to mimic this feature, we developed a flapping-wing system that generates a desired pitching moment during flap- ping-wing motion. The system comprises a flapping mechanism that creates a large and symmetric flapping motion in a pair of wings, a flapping angle change mechanism that modifies the flapping angle range, artificial wings, and a power source. From the measured wing kinematics, we have found that the flapping-wing system can properly modify the flapping angle ranges. The measured pitching moments show that the flapping-wing system generates a pitching moment in a desired direction by shifting the flapping angle range. We also demonstrated that the system can in practice change the longitudinal attitude by generating a nonzero pitching moment.     

Ornithopter Flight Simulation Based on Flexible Multi-Body Dynamics

This paper introduces a flight simulation of an ornithopter (flapping-wing air vehicle) based on the flexible multi-body dynamics, a refined flapping-wing aerodynamic model and the fluid-structure interaction approach. A simulated ornithopter was modeled using the multi-body dynamics software, MSC.ADAMS, where the flexible parts can be included by importing a finite element model built in the finite element analysis software, ANSYS. To model the complex aerodynamics of flapping-wing, an improved version of modified strip theory was chosen. The proposed integrative simulation framework of ornithopter was validated by the wind tunnel test data reported in the literature. A magpie-sized model oruithopter was numerically designed and simulated to have the longitudinal trim flight condition. We observed a limit-cycle-oscillation of flight state variables, such as pitch attitude, altitude, flight speed, during the trimmed flight of the model ornithopter. Under the trimmed condition of free flight of the model omithopter, we fixed all the degrees of freedom at the center of gravity to measure the constraint forces and moment. The concept of the "zero moment point" is introduced to explain the physics of ornithopter trimmed longitudinal flight.     

How to determine a regional species pool: a study in two Swedish regions

The species pool hypothesis has been proposed as one of the possible explanations for the local species richness of plant communities. For testing and validating this theory, it is of crucial importance to determine the dimension of the regional pool, which is the reservoir of species that are potentially able to exist in a community. The main purpose of this study was to develop and test different methods for the determination of the regional species pool. Two regions in Sweden served as study areas, Öland and Uppland. In both regions, three different vegetation types were treated: dry calcareous grasslands, coastal meadows and deciduous forests. For the determination of the regional pool two main groups of methods are proposed: 1) six ecological approaches, based on Ellenberg species indicator values, and 2) two phytosociological approaches, based on the occurrence of species in different syntaxa in the framework of the Braun-Blanquet system. The different screening methods were tested using Sørensen's index expressing the similarity between the community species pool and the regional species pool. Two types of error were recognized which may result in low index values. For the six ecological methods Sørensen's index values were below 50%. The methods differed considerably from each other in accuracy, due to large differences in errors of both types. The phytosociological methods resulted in higher similarity values of up to almost 70%. The two approaches differed in error type but gave similar results.     

Testing Hardy-Weinberg proportions in a frequency-matched case-control genetic association study

In case-control genetic association studies, cases are subjects with the disease and controls are subjects without the disease. At the time of case-control data collection, information about secondary phenotypes is also collected. In addition to studies of primary diseases, there has been some interest in studying genetic variants associated with secondary phenotypes. In genetic association studies, the deviation from Hardy-Weinberg proportion (HWP) of each genetic marker is assessed as an initial quality check to identify questionable genotypes. Generally, HWP tests are performed based on the controls for the primary disease or secondary phenotype. However, when the disease or phenotype of interest is common, the controls do not represent the general population. Therefore, using only controls for testing HWP can result in a highly inflated type I error rate for the disease- and/or phenotype-associated variants. Recently, two approaches, the likelihood ratio test (LRT) approach and the mixture HWP (mHWP) exact test were proposed for testing HWP in samples from case-control studies. Here, we show that these two approaches result in inflated type I error rates and could lead to the removal from further analysis of potential causal genetic variants associated with the primary disease and/or secondary phenotype when the study of primary disease is frequency-matched on the secondary phenotype. Therefore, we proposed alternative approaches, which extend the LRT and mHWP approaches, for assessing HWP that account for frequency matching. The goal was to maintain more (possible causative) single-nucleotide polymorphisms in the sample for further analysis. Our simulation results showed that both extended approaches could control type I error probabilities. We also applied the proposed approaches to test HWP for SNPs from a genome-wide association study of lung cancer that was frequency-matched on smoking status and found that the proposed approaches can keep more genetic variants for association studies.     

Kinetic comparison of free weight and machine power cleans

The purpose of this investigation was to compare the kinetic characteristics of the power clean exercise using either free weight or machine resistance. After familiarization, 14 resistance trained men (mean +/- SD; age = 24.9 +/- 6.2 years) participated in two testing sessions. During the initial testing session, one-repetition maximum performance (1RM) was assessed in either the free weight or machine power clean from the midthigh. This was followed by kinetic assessment of either the free weight or the machine power clean at 85% of 1RM. One week after the initial testing session, 1RM performance, as well as the subsequent kinetic evaluation, were performed for the alternate exercise modality. All performance measures were obtained using a computer-interfaced FiTROdyne dynamometer (Fitronic; Bratislava, Slovakia). Maximum strength (1RM) and average power were significantly greater for the free weight condition, whereas peak velocity and average velocity were greater for the machine condition (p < 0.05). Although peak power was not different between modalities, force at peak power (free weights = 1445 +/- 266 N, machine = 1231 +/- 194 N) and velocity at peak power (free weights = 1.77 +/- 0.28 m x s(-1), machine = 2.20 +/- 0.24 m x s(-1)) were different (p < 0.05). It seems that mechanical limitations of the machine modality (i.e., lift trajectory) result in different load capacities that produce different kinetic characteristics for these two lifting modalities.