結合位相振動子系である蔵本モデルにおいて、素子数が有限の場合にはカオスが起こる[O. V. Popovych et al., 2005]。同様に、他の位相振動子、リミットサイクル振動子、カオス振動子のそれぞれの結合系においてもカオスが起こる。このように、結合振動子系におけるカオスは普遍的な現象である。
我々は、蔵本モデルにおけるカオスを調べる。同期現象の時刻tにおけるオーダーパラメータR(t)の時刻0からtまでの時間積分LR(t)は、区間[0, t]における同期の強さを表わす。LR(t)は拡散を示し、その拡散係数はクラスターの形成に伴いピークを持つことが分かった。
Tornadoes and dust devils are violent small-scale vortices in the atmosphere. Although they have affected human lives significantly, their smallness and short lifetime have prevented detailed investigations until re-cently. In the present talk, our current understandings of these vortices are reviewed and future subjects to be studied are proposed.
International Maritime Organization (IMO) had discussed for developing the harmonized requirements for ships navigating in ice covered waters from middle of 90’s and issued the “Guidance for Ships Operating in Arctic Ice Covered Waters” as MSC (Maritime Safety Committee) / Circ. 1056 and MEPC (Marine Environment Protection Committee) / Circ. 399, in 2002. After that, the International Association of Classification Society (IACS) issued the Unified Requirements (URs) for Polar Class Ships in 2006 in order to supplement the provisions regarding a hull structure and a machinery mentioned in the IMO Guidance. This paper describes the summaries of the IACS URs.
The sea ice begins to melt in the Arctic Ocean because of global warming. The possibility of the Commercial Navigation in the Arctic Ocean also has risen. The author considers the current state and the problem in this text.