Dolphins swim by vertical oscillation of their tail fins which have been considered to play an important role for generating thrust. The propulsive performance of the tail fin relates with the structure and the mechanical properties of the tail fin. Our objectives are to investigate the structure and the bending properties of the central part of the tail fin of a dolphin. A sample of the tail fin was anatomized to investigate the vertebrae structure and tendons insertions, and the bending tests were carried out on the central part of the tail fin at the state with tensions on the tendons. Our results demonstrated that there were three kinds of tendons in the tail fin, that is, the epaxial tendon I, the epaxial tendon II and the hypaxial tendon. The epaxial tendons Is inserted into each tail vertebra, the epaxial tendon IIs inserted into five tip tail vertebrae, and the hypaxial tendons inserted on the chevron bones and tail vertebrae. In the bending test, it was found the tension which was acted on the epaxial tendon IIs produced larger bending deformation and made the central part of the tail fin stiffer than the same tension which was acted on the epaxial tendon Is or hypaxial tendons.
The mechanical properties of the tissues relates with the propulsive performance of the tail fins of dolphins. In this study, the tensile properties of the main two tissues in the tail flukes of a dolphin, that is, the ligamentous layer and dense connective tissue are investigated. As a result, the tissues all showed the effect of the strain rate which weakened gradually as the strain increased. The moduli obtained at different strain rates tend to converge.
We studied the application of the dilatant compound, which is the polymer-based material with dilatancy properties, to the matrix of the fiber composite material. The basic mechanical properties of the dilatant compounds have been studied, but no research has been done on fiber composite dilatant compound. In this paper, the tensile test and the three-point flexural test of fiber composite dilatant compound were performed. We discussed the influence of fiber orientation, fiber length, and fiber diameter on tensile load and flexural load by changing the deformation speed.
La station de Mizuho, dans l'Antarctique Est (a 250 km de la cote; alt. 2230 m) a son climat caracterise par un vent catabatique fort (11 m/s) soufflant continuellement et par une t moyenne au-dessous de −32°C. Description des enregistrements obtenus avec un sondeur acoustique et des caracteristiques des ondes de gravite engendrees par l'instabilite du cisaillement de vent dans la couche de vent catabatique
This paper presents a study of the relationship between the contraction on the sole surface, the shape and the forces generated by muscle for locomotion of snail (Gastropod). We observed sole surface of a moving snail to investigate the state of contraction when a sole wave is passing. Then we measured the vertical and horizontal forces generated by sole to investigate the relationship between the forces and the shape of sole surface. Based on these results observed, we proposed a model of the shape of snail's sole section. The mechanism of snail's locomotion will have a possibility to be applied to the mobility equipment which has flexibility for ground conditions and can easily turn in a house.
This paper describes the generation of motion pattern of a multi-link propulsion mechanism in fluid. To generate the motion pattern that has higher thrust force, a simple system imitating the oscillation of neurons and the Monte Carlo method for updating weights between adjacent neurons are employed. A bending motion similar to the bending of fish is generated for higher thrust force.
