著者
Toshitake ARAMAKI Takemi ABE Jun YAMASHITA
出版者
The Japanese Society of Agricultural Machinery and Food Engineers
雑誌
JOURNAL of the JAPANESE SOCIETY of AGRICULTURAL MACHINERY (ISSN:02852543)
巻号頁・発行日
vol.44, no.1, pp.45-51, 1982 (Released:2010-04-30)
参考文献数
15

ピアノ線刃を装着した刈払い作業では, 切込刃装着の場合に比し, 刈刃重量に関係なく, 心拍数及び表面筋電図がともに小さい。この一因として, ピアノ線刃では刈払物が飛散しやすく, 従って刈払い抵抗力が小さいことが考えられる。また, 石なとの障害物に刈刃が当たったときの作業者の精神負担度についても, ピアノ線刃の場合は切込刃に比し小さい。このように, 刈刃の違いによって作業者の受ける生体負担度が相違することを実験的に明らかにした。
著者
Jun YAMASHITA Hironori OKI Telhisa HASEGAWA Takeshi HONDA Tetsuro NOMURA
出版者
Japanese Society of Equine Science
雑誌
Journal of Equine Science (ISSN:13403516)
巻号頁・発行日
vol.21, no.2, pp.11-16, 2010 (Released:2010-07-16)
参考文献数
12
被引用文献数
3 2

To investigate the breeding structure in the Japanese Thoroughbred population, we applied a demographic analysis to the populations of foals produced from 1978 to 2005. The migration rate estimated from the proportion of foals produced by imported breeding horses was around 40% over the investigated period. After early 1990s, the migration rate through stallions imported from USA sharply increased. The average generation interval was within range of 10.5-11.5 years. The longer generation interval of Thoroughbred was considered to be a reflection of the fact that Thoroughbred horses begin breeding only after completing their performance in races. After the peak of 729 in 1993, the number of sires of foals progressively declined to 358 in 2005. Although the coefficient of variation of the progeny number of sires was within range of 1.0-1.2 until early 1990s, it gradually increased and reached the value of 1.6-1.7 in recent years. The effective number of sires consistently decreased after the peak of 302.6 in 1992, and reached 120-130 in recent years, which is 25-30% of the actual number of sires. In parallel, the demographic estimate of the effective population size declined after early 1990s. The main cause of the observed change in the breeding structure was inferred to be the intensive use of a limited number of stallions for breeding.