alpha稳定分布的函数。该分布是一种连续概率分布，其概率密度比高斯分布概率密度有更厚的拖尾，是一类适用范围很宽的随机信号模型，比高斯分布有更广泛的适用性。-Alpha stable distribution function. This distribution is a continuous probability distribution, the probability density are thicker than gaussian probability density trailing, random signal model is a kind of very wide application scope, has wider applicability than gaussian distribution.