著者
近藤 卓哉 阪田 和弘 竹下 直彦 中園 明信 木村 清朗
出版者
The Ichthyological Society of Japan
雑誌
魚類学雑誌 (ISSN:00215090)
巻号頁・発行日
vol.46, no.2, pp.121-125, 1999-11-30 (Released:2010-06-28)
参考文献数
16

Iwana-charr, Salvelinus leucomaenis is not indigenous to Kyushu Island western Japan. In 1971, this species was transplanted to a commercial hatchery by the Haki River (32°32'N, 130°57'E), a tributary of the upper reaches of the Kuma River System. Some of the charr individuals escaped from the hatchery's holding pond and came into the stream. Fifty-one were collected in the lower reaches near the hatchery but none in the upper reaches during 1994-1996. The collected sample consisted of individuals belonging to plural age classes. In addition, we observed some spawning activities of the charr in November every year during 1994-1997 and found some eggs in the redd. Our findings suggest that reproduction of the charr occurs in some tributaries of the upper reaches of the Kuma River and their distribution is expanding downstream. They also suggest that dams without fishways prevent the charr from migrating upstream.
著者
近藤 卓 飯尾 秀一 昼間 勝 古濱 庄一
出版者
一般社団法人日本機械学会
雑誌
日本機械学会論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.63, no.610, pp.2209-2214, 1997-06-25
参考文献数
4
被引用文献数
1

In order to facilitate practical application of hydrogen fueled engines with external mixture formations. it is necessary to determine the cause of backfire and to identify appropriate countermeasures. It has been found in our study that one of the causes of backfire is attributed to the electric discharge which occurs after the ignition of the spark plug when the pressure in the cylinder becomes low enough to discharge the electric charge remaining in the ignition system. The electric charge in the plug cable remains much longer when hydrogen is used as the fuel than when gasoline is used. In other words, the number of ions produced from hydrogen-air combustion after the ignition of the spark plug is less than that from gasoline-air combustion, so it is difficult for the ion current to flow out through the gap of the spark plug. It has been found in our experiments that backfire takes place when the electric discharge occurs during the intake stroke and that engine operation could be performed up to an excess air ratio of λ=1 without any backfire at a low engine speed when the ignition system was modified such that no electric charge remained in the spark plug cable.