Fabrication of Fe-based ribbon with controlled permeability by Joule heating under tensile stress

We prepared an Fe-based ribbon with controlled permeability and low magnetic loss by Continuous Stress-Annealing by Joule Heating (CSA-JH) method. The shortest annealing time necessary for the obtaining of the ribbons with completely developed anisotropy was 1 sec, but in order to obtain the sufficiently crystallized ribbons with small saturation magnetostriction it is required to perform annealing longer than 2 sec. A toroidal core was prepared from a long ribbon with controlled permeability and small saturation magnetostriction, and the magnetic loss and relative permeability of the core were evaluated in the frequency range of 0.1 - 3 MHz. The permeability was kept constant up to 2 MHz, and the magnetic loss is lower than that for other types of core with a similar permeability value. These results suggest that the CSA-JH method is a promising method for realizing an Fe-based core with excellent magnetic properties.Proceedings of the 18th International Symposium on Soft Magnetic Material

26. The Small Earthquake Activity of May 1982 in the Northeast Part of the Izu Peninsula, Japan : Results of a Temporary Observation

1982年5月に伊豆半島北東部の川奈崎付近で起きた群発地震活動(M=2.0)について,現地で臨時観測を行った.観測期間は活動の最盛期を過ぎた5月12～14日で,2観測点は固定し,他の1観測点を次々に移動する方式をとった.川奈崎付近に集中して発生した一群の地震(ここではa型と呼ぶ)があり,計5ケ所のP時刻から平均的な震源の位置と観測点補正を求めた.今回のような移動多点観測も,ある場合には役に立つものと思われる.一方,川奈崎付近の活動は5月13日の朝に急速に低下したが,ちょうどその前に,約30km南方で群発活動が起きている.活動の低下はまずa型の地震群に現われ,数時間遅れて周辺も静かになった.A tail of the swarm activity (M=2.0) near Kawana-zaki in the northeastern part of the Izu Peninsula in May, 1982, was observed by a temporary microseismic network installed close to the epicentral region. During the observations on May 12-14th, two seismometers were fixed at the respective places and another was moved from place to place. Station corrections and the average location of the events which occurred within a small area near Kawana-zaki (they are called ""a-type"" in this paper) were obtained from P arrivals of the two fixed and three tentative stations, suggesting the utility of the moving installation of instruments in some cases. The observation also shows a distinct decrease in activity near Kawana-zaki in the morning of May 13th, following the earthquake swarm which occurred about 30km to the south. The decrease in activity occurred at fast in the hypocentral region of the a-type events, and in the adjacent areas several hours later