SUMMARYDuring flapping flight, insect wings must withstand not only fluid-dynamic forces, but also inertial-elastic forces generated by the rapid acceleration and deceleration of their own mass. Estimates of overall aerodynamic and inertial forces vary widely, and the relative importance of these forces in determining passive wing deformations remains unknown. If aeroelastic interactions between a wing and the fluid-dynamic forces it generates are minor compared to the effects of wing inertia, models of insect flight that account for passive wing flexibility would be far simpler to develop. We used an experimental approach to examine the contributions of aerodynamic and inertial-elastic forces to wing bending in the hawkmoth Manduca sexta. We attached fresh Manduca wings to a motor and flapped them at a realistic wing-beat frequency and stroke amplitude. We compared wing bending in normal air versus helium (approx. 15% air density), in which the contribution of fluid-dynamic forces to wing deformations is significantly reduced. This 85% reduction in air density produced only slight changes in the pattern of Manduca wing deformations, suggesting that fluid-dynamic forces have a minimal effect on wing bending. We used a simplified finite element model of a wing to show that the differences observed between wings flapped in air versus helium are most likely due to fluid damping, rather than to aerodynamic forces. This suggests that damped finite element models of insect wings (with no fluid-dynamic forces included) may be able to predict overall patterns of wing deformation prior to calculations of aerodynamic force production, facilitating integrative models of insect flight.

It has been proposed that the mechanical flexibility of many wave-swept organisms reduces the hydrodynamic forces imposed on these plants and animals. For example, reorientation of the organism can render it more streamlined, and by "going with the flow" a flexible organism can reduce the relative velocity between itself and the surrounding water, thereby reducing drag and lift. Motion of the body allows the organism to gain momentum, however, and this momentum can apply an inertial force when the organism's motion is slowed by the deformation of the body's supporting structures. Through a series of mathematical models we show that the inertial forces imposed on flexible plants and animals can be large enough to increase the overall force on the organism, more than offsetting the advantages of moving with the flow. A dimensionless index, the jerk number, is proposed as a tool for predicting when inertial forces will be important, and the utility of this index is explored through an examination of the forces applied to kelps and mussels. The tendency for inertial loading to peak at certain frequencies raises the possibility that the structure of organisms can be tuned (either by evolution or physiological response) to avoid potentially damaging loads.-

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The Wave Glider TM wave-powered unmanned maritime vehicle represents a novel and unique approach to persistent ocean presence. Wave Glider is a hybrid seasurface and underwater vehicle in that it is comprised of a submerged "glider" attached via a tether to a surface float. The Wave Glider vehicle is propelled by the purely mechanical conversion of ocean wave energy into forward thrust, independent of wave direction. In this paper, we provide an overview of the design of this new platform and present results from the engineering sea trials conducted with several prototype and production versions of the vehicle. In addition to the Wave Glider technology, we present results from ongoing scientific demonstration programs. Results from test deployments of a conductivity-temperature-depth sensor and its applicability to oceanography are discussed.

Abstract-A 2.5 mW wireless flight control system for cyborg moths is presented, consisting of a 3-to-5 GHz non-coherent pulsed ultra-wideband receiver system-on-chip with an integrated 4-channel pulse-width modulation stimulator mounted on a 1.5 cm by 2.6 cm printed circuit board. The highly duty cycled, energy detection receiver requires 0.5-to-1.4 nJ/bit and achieves a sensitivity of 76 dBm at a data rate of 16 Mb/s (10 BER). A multi-stage inverter-based RF front end with resonant load and differential signal chain allow for robust, low energy operation. Digital calibration is used in the baseband amplifier, ADC and DLL to cancel voltage and timing offsets. Through the use of a flexible PCB and 3-D die stacking, the total weight of the electronics is kept to 1 g, within the carrying capacity of an adult Manduca sexta moth. Preliminary wireless flight control of a moth in a wind tunnel is demonstrated.