Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, Kyoto, 610-0394, Japan.
Faculty of Biology-Oriented Science and Technology, Kindai University, Kinokawa, Wakayama, 649-6493, Japan.
Sci Rep. 2018 Jan 11;8(1):437. doi: 10.1038/s41598-017-18728-6.
We report the collective behavior of numerous plastic bolt-like particles exhibiting one of two distinct states, either standing stationary or horizontal accompanied by tumbling motion, when placed on a horizontal plate undergoing sinusoidal vertical vibration. Experimentally, we prepared an initial state in which all of the particles were standing except for a single particle that was placed at the center of the plate. Under continuous vertical vibration, the initially horizontal particle triggers neighboring particles to fall over into a horizontal state through tumbling-induced collision, and this effect gradually spreads to all of the particles, i.e., the number of horizontal particles is increased. Interestingly, within a certain range of vibration intensity, almost all of the horizontal particles revert back to standing in association with the formation of apparent 2D hexagonal dense-packing. Thus, phase segregation between high and low densities, or crystalline and disperse domains, of standing particles is generated as a result of the reentrant transition. The essential features of such cooperative dynamics through the reentrant transition are elucidated with a simple kinetic model. We also demonstrate that an excitable wave with the reentrant transition is observed when particles are situated in a quasi-one-dimensional confinement on a vibrating plate.
我们报告了大量塑料螺栓状粒子的集体行为，这些粒子表现出两种截然不同的状态之一，要么静止站立，要么在水平方向上伴随翻滚运动，当它们放置在水平板上并经历正弦垂直振动时。在实验中，我们制备了一个初始状态，其中除了放置在板中心的单个粒子外，所有粒子都处于站立状态。在连续的垂直振动下，最初处于水平状态的粒子通过翻滚诱导的碰撞触发相邻粒子倒下进入水平状态，这种效应逐渐传播到所有粒子，即水平粒子的数量增加。有趣的是，在一定的振动强度范围内，几乎所有的水平粒子都会重新回到站立状态，同时形成明显的二维六方密堆积。因此，由于再进入转变，站立粒子的高低密度或结晶和弥散域之间发生了相分离。通过再进入转变的这种协同动力学的基本特征通过一个简单的动力学模型得到了阐明。我们还证明了当粒子在振动板上的准一维约束中时，会观察到具有再进入转变的可激发波。
