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Repellence Effect of the New Sound for Underwater Speaker of Hydrofoil

Nakashima T., Kobayashi N., Yamada H., Katsumata T., Yoshida R., Kato H., Okabe H., Kawazu I., Yanase Y., Omine M., Terada M., Sugioka H., Kyo M.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2015

Vol. 9, no. 2

207--211

In order to prevent hydrofoil colliding with cetaceans, the underwater speaker (UWS) has been installed to repel cetaceans. Yamada et al. (2012) analyzed and devised the UWS sound as it fits the cetaceans' acoustic properties to prevent the collision furthermore. The new UWS sound was devised and synthesized by Yamada et al. (2015) with expectation of avoiding collision with large cetaceans (Patent applied for, JP2014-171411). In this research project, the new UWS sound was investigated by the playback experiment on humpback whale (Megaptera novaeangliae) and by sighting survey in the actual hydrofoil shipping service route. As a result, a physiological and behavioral change of the humpback whale was observed in the playback experiment of the new UWS sound, and the chance of hydrofoil encountering cetaceans of the new UWS sound was smaller than that of the previous UWS sound. Therefore, the improvement of the new UWS sound was confirmed. Lastly, we wish this research project would contribute toward the safer cruise of hydrofoil in the future.

Development of the Effective Underwater Speaker Sound Modulated by Audible Sound Frequency Range of Large Cetaceans for Avoidance with Ship Collision

Yamada H., Kobayashi N., Nakashima T., Kato H.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2015

Vol. 9, no. 2

213--217

The underwater speaker (UWS) has been installed on high speed vessels; hydrofoils (HF) with low-noise during their cruises, to avoid sudden collisions with large cetaceans, while its performance has remained uncertain because of the problem in quality of the produced sound. Thus, we developed a sound source for the UWS by modulating the sound based on the audible range of major large cetaceans so as to increase its utilities. To investigate the audible sound frequency range of cetacean, we tried two procedures, (1) indirect-estimation from relationship between cetaceans audibility and vocalization, and (2) indirect-estimation from measurements on the cochlear basal membrane. We also synthesized the two new sound sources which we can potentially expect an avoidance with large cetaceans. Through several field experiments with deploy the new sounds we reached a tentative conclusion that the new sound was effective in terms of inducing the cetaceans' avoidance reaction and would be also expected to be applied to other low-noise vessels.

Theoretical study of electron transport properties of an organic molecule

Nara J., Geng W. T., Kino H., Kobayashi N., Ohno T.

Materials Science Poland

2005

Vol. 23, No. 2

383--387

Electron transport properties of benzene-(1,4)-dithiolate sandwiched between two gold electrodes were investigated using first-principles calculations. It was found that the peak energies and the peak widths in the transmission spectra are strongly dependent on the contact structures. Furthermore, the contributions of MOs to the transmission coefficients also depend on the contact structures. Especially, only the channel related to HOMO-3, HOMO, and LUMO+1 contributes to the conductance at zero bias. These results suggest that the determination of the contact structure is essential for estimating the properties of molecular devices.