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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

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2015

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Vol. 9, no. 2

207--211

EN

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.

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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

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2015

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Vol. 9, no. 2

213--217

EN

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.

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Design of multi-layer sputter-deposited anode to reduce catalyst loading for liquid DMFC

Saito H., Nakashima T., Nakase K., Sudoh M.

Journal of Automation Mobile Robotics and Intelligent Systems

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2009

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Vol. 3, No. 4

175-178

EN

Superior catalyst utilization of direct methanol fuel cells (DMFCs) may be obtained by localized catalyst loading on reaction sites. The objective of this work is to improve the catalyst utilization by multi-layer structure and reduction of loading catalyst. Multi-layer anode consisted of sputter-deposited Pt-Ru catalyst layer and the support layer of Nafion-carbon-Isopropanol ink (NCI). Single layer anode consisted of sputter-deposited Pt-Ru catalyst layer and the layer of carbon-glycerin ink (CG). Multi-layer (1~4 layers) and single-layer (0.04, 0.10 and 0.24 mg cm-2) were evaluated by using electrochemical measurement and SEM images. Three-layer anode provided 50.9 W g-1, 3.4 times as mass activity of conventional paste method anode. Methanol residues stripping voltammetry revealed that electrochemical surface area (ECSA) was increased with the number of layers. Additionally, single-layer anode (0.04 mg cm-2) provided over 150 W g-1. These results suggested that reduction of loading catalyst per unit layer and multilayer structure enhanced catalyst utilization.

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Effects of particle spacing and void nucleation characteristics on the toughness of high strength steels.

Wojcieszynski A.L., Garrison W.M., Iorio L.E., Nakashima T.

Inżynieria Materiałowa

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1998

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R. XIX, nr 3

299-302

EN

In this work we have examined the effects of inclusion spacing and inclusion void nucleation resistance on toughness for several fine scale microstructures for the case of ductile fracture. It was found for high strength fine-scale microstructures that the crack tip opening displacement at fracture can increase almost linearly with increasing inclusion spacing. However, as the strength of the fine-scale microstructure decreases to about 850 MPa the toughness of the fine scale microstructure becomes essentially independent of inclusion spacing, at least over the range of inclusion spacings which could be obtained experimentally. It has also been found that exceptional increases in toughness can be achieved by gettering sulphur as titanium carbosulfide rather than as manganese sulfide. These improvements in toughness have been observed in steels having yield strengths ranging from 850 MPa to 1500 MPa. The improvement in toughness associated with gettering sulfur as titanium carbosulfide has been attributed to particles of titanium carbosulfide being more resistant to void nucleation than particles of manganese sulfide or lanthanum oxy-sulfides.