A Fractional Structural Derivative Model for Ultra-Slow Diffusion
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摘要: 自然界和工程中存在很多比幂率慢扩散(sub-diffusion)过程更慢的扩散,即特慢扩散(ultra-slow diffusion).特慢扩散难以用传统的反常扩散建模方法来描述.Sinai(西奈)随机模型描述了一种特殊的对数关系特慢扩散.运用Mittag-Leffler(米塔格-累夫勒)函数的反函数,将Sinai扩散拓展为一般的特慢扩散.此外,该文的模型引入初始状态参量,解决了Sinai对数扩散不适用于初始时刻附近的问题.作为分数阶导数的一般情况,该文也引入了分数阶结构导数的概念,并用来建立特慢扩散的控制微分方程.
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关键词:
- 特慢扩散 /
- Sinai随机模型 /
- Mittag-Leffler反函数 /
- 分数阶结构导数 /
- 扩散方程
Abstract: The ultra-slow diffusion is even more slow than the power-law sub-diffusion and is widely observed in a variety of natural and engineering fields. The ultra-slow diffusion cannot be well described with the traditional anomalous diffusion models. The Sinai’s law of diffusion depicts a special type of ultra-slow diffusion which is characterized by a logarithmic stochastic relationship. In this study, the Sinai diffusion was extended to a general ultra-slow diffusion. In addition, in the proposed model the initial parameters were introduced to remedy the perplexing issue that the Sinai diffusion was not feasible around the initial period of the ultra-slow diffusion. As a generalized fractional-order derivative, the concept of the fractional structural derivative was also presented to establish the partial differential equation governing the ultra-slow diffusion. -
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