No abstract

Acoustic underwater propulsion systems based on ultrasonic transducer have been studied. In previous research, the self-propelled acoustic swimmer using thickness-vibration-mode transducer is evaluated widely. The thickness-vibration-mode transducer is excited in the thickness and radial direction. Because the acoustic propulsion system is based on the acoustic driving force, the vibration in radial direction is hard to provide the propulsion thrust. In this study, a cylindrical transducer, the pure longitudinal vibrator, is evaluated for the acoustic underwater propulsion system. A prototype swimmer is designed and fabricated. The admittance difference of transducer in water and in air is investigated. The zero-speed propulsion (ZSP) force and no-load speed (NLS) are measured in water. Multi-degrees-of-freedom swimmer with the multiple cylindrical transducers is evaluated. Because of the small size, high power density, simple structure and multi-degrees-of-freedom, self-propelled acoustic swimmer is suitable for applications such as inspection and repairment robot in liquid environment.

In Matsuda's 1996 study, 4- to 11-yr.-old children (N = 133) watched two cars running on two parallel tracks on a CRT display and judged whether their durations and distances were equal and, if not, which was larger. In the present paper, the relative contributions of the four critical stimulus attributes (whether temporal starting points, temporal stopping points, spatial starting points, and spatial stopping points were the same or different between two cars) to the production of errors were quantitatively estimated based on the data for rates of errors obtained by Matsuda. The present analyses made it possible not only to understand numerically the findings about qualitative characteristics of the critical attributes described by Matsuda, but also to add more detailed findings about them.