Tham khảo tài liệu 'biomimetics learning from nature part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Micro Swimming Robots Based on Small Aquatic Creatures 353 resultant velocity is shown in b . Sharp rising up of the velocity variation corresponds to the power stroke and gradual decreasing corresponds to the recovery stroke during swimming of the diving beetle. As stated above swimming legs of the diving beetle Hydroglyphus japonicas Sharp are also clothed in minute hairs. The hairs increase the hydrodynamic drag of the swimming leg. Scanning electron microscopic observation of the swimming legs of the diving beetle shows existence of fine hairs on the legs. Figure 12 shows scanning electron micrograph of the rowing appendages and fine hairs of the diving beetle Hydroglyphus japonicas Sharp. The thickness of the hair is about M m in . 4. Swimming of Dragonfly Nymph After the dragonfly nymph emerges from the egg it develops through a series of stages called instars. The dragonfly larvae are predatory and live in all types of freshwater. The younger nymph was selected as a test insect in the swimming experiment because the younger nymph swam actively. The tested nymph shown in Fig. 13 was a larva of dragonfly Sympetrum frequens. The swimming behavior of the nymph in water container was examined. shows a sequence of photographs showing the swimming behavior of dragonfly Fig. of a younger small dragonfly nymph used in the swimming experiment Fig. 14. A sequence of photographs showing the swimming behavior of the dragonfly nymph in water container 354 Biomimetics Learning from Nature nymph. The process of leg movement for the nymph swimming is clear. The fore- and middle-legs beat almost synchronously. During the power stroke they are stretched and move. On the other hand the hind-legs hardly move. The thrust-generating mechanism is related to the motion of the fore- and middle-legs. The dragonfly nymph expands and contracts its abdomen to move water during forward swimming. Figure 15 shows the change in the size of the nymph body
