We introduce the standard distribution width of fitness to characterize the global and individual features of a ecosystem in the Bak-Sneppen evolution model. Through tracking this quantity in evolution, a different hierarchy of avalanche dynamics, w0 avalanche is observed. The corresponding gap equation and the self-organized threshold wc are obtained. The critical exponents τ, γ and ρ, which d...

雪崩の流動・停止プロセスの理解及び予測は防災上重要である．雪崩到達範囲を物理法則に基づき定量的に予測するために，数値シミュレーションを活用する動きが近年活発化している．それらの数値計算では，計算のコストや現象の再現性の観点から，三次元の流れを厚さ方向に平均化した二次元流として近似する理論（浅水流理論）に基づくモデルが主に用いられる．本稿では，浅水流理論に基づく雪崩動力学シミュレータの1つfaSavageHutterFOAMについて解説する．faSavageHutterFOAMは，高濃度粒子流（流れ型雪崩）の基礎方程式を解くオープンソース数値コードであり，OpenFOAMをプラットフォームとして開発された．本解説では，faSavageHutterFOAMの基礎方程式，ファイル構成，計算条件の設定方法，任意の地形上での雪崩計算の実行方法，地理情報システム（GIS）による数値計算結果の可視...

We introduce the standard distribution width of fitness in the Bak-Sneppen evolution model. Through observing the fluctuation of this quantity in evolution, we find a different hierarchy of avalanche dynamics, w0 avalanche. We also obtain the corresponding gap equation and the self-organized threshold wc. The critical exponents (τ, γ and ρ), which describe the behavior of avalanche size distrib...

By molecular-dynamics simulations, we have studied the devitrification (or crystallization) of aged hard-sphere glasses. First, we find that the dynamics of the particles are intermittent: Quiescent periods, when the particles simply "rattle" in their nearest-neighbor cages, are interrupted by abrupt "avalanches," where a subset of particles undergo large rearrangements. Second, we find that cr...