Continuum description of anomalous diffusion on a comb structure

1998 ◽  
Vol 87 (4) ◽  
pp. 700-713 ◽  
Author(s):  
I. A. Lubashevskii ◽  
A. A. Zemlyanov
Author(s):  
Lin Liu ◽  
Shuo Yang ◽  
Libo Feng ◽  
Qian Xu ◽  
Liancun Zheng ◽  
...  

This paper considers a novel distributed order time fractional dual-phase-lag model to analyze the anomalous diffusion in a comb structure, which has a widespread application in medicine and biology. The newly proposed constitution model is a generalization of the dual-phase-lag model, in which a spectrum of the time fractional derivatives with the memory characteristic governed by the weight coefficient is considered and the formulated governing equation contains both the diffusion and wave characteristics. With the L1-formula to discrete the time Caputo fractional derivatives, the finite difference method is used to discretize the model and the related numerical results are plotted graphically. By adding a source term, an exact solution is defined to verify the correctness of the numerical scheme and the convergence order of the error in spatial direction is presented. Finally, the dynamic characteristics of the particle distributions and the effects of involved parameters on the total number of particles in the [Formula: see text]-direction are analyzed in detail.


2020 ◽  
Vol 4 (2) ◽  
pp. 28 ◽  
Author(s):  
Maike Antonio Faustino dos Santos

Nowadays, the stochastic resetting process is an attractive research topic in stochastic process. At the same time, a series of researches on stochastic diffusion in complex structures introduced ways to understand the anomalous diffusion in complex systems. In this work, we propose a non-static stochastic resetting model in the context of comb structure that consists of a structure formed by backbone in x axis and branches in y axis. Then, we find the exact analytical solutions for marginal distribution concerning x and y axis. Moreover, we show the time evolution behavior to mean square displacements (MSD) in both directions. As a consequence, the model revels that until the system reaches the equilibrium, i.e., constant MSD, there is a Brownian diffusion in y direction, i.e., ⟨ ( Δ y ) 2 ⟩ ∝ t , and a crossover between sub and ballistic diffusion behaviors in x direction, i.e., ⟨ ( Δ x ) 2 ⟩ ∝ t 1 2 and ⟨ ( Δ x ) 2 ⟩ ∝ t 2 respectively. For static stochastic resetting, the ballistic regime vanishes. Also, we consider the idealized model according to the memory kernels to investigate the exponential and tempered power-law memory kernels effects on diffusive behaviors. In this way, we expose a rich class of anomalous diffusion process with crossovers among them. The proposal and the techniques applied in this work are useful to describe random walkers with non-static stochastic resetting on comb structure.


2020 ◽  
pp. 153-153
Author(s):  
Zhaoyang Wang ◽  
Liancun Zheng ◽  
Lianxi Ma ◽  
Goong Chen

A kind of anomalous diffusion and heat transfer on a comb structure with anisotropic relaxation are studied, which can be used to model many problems in Biologic and Nature in fractal porous media. The Hausdorff derivative is introduced and new governing equations is formulated in view of fractal dimension. Numerical solutions are obtained and the Fox H-function analytical solutions is given for special cases. The particles spatial-temporal evolution(STE)and the mean square displacement(MSD)versus time are presented. The effects of back bone and finger relaxation parameters, and the time fractal parameter are discussed. Results show that the MSD decreases with the increase of back bone parameter or the decrease of finger relaxation parameter in a short of time, but they have little effect on MSD in a long period. Particularly, the MSD has time dependence in the form of t?/2 (0 < ? ? 1)when t>?, which indicates that the diffusion is an anomalous sub-diffusion and heat transfer.


1990 ◽  
Vol 51 (13) ◽  
pp. 1387-1402 ◽  
Author(s):  
A. Giacometti ◽  
A. Maritan

2012 ◽  
Vol 9 (2) ◽  
pp. 65-70
Author(s):  
E.V. Karachurina ◽  
S.Yu. Lukashchuk

An inverse coefficient problem is considered for time-fractional anomalous diffusion equations with the Riemann-Liouville and Caputo fractional derivatives. A numerical algorithm is proposed for identification of anomalous diffusivity which is considered as a function of concentration. The algorithm is based on transformation of inverse coefficient problem to extremum problem for the residual functional. The steepest descent method is used for numerical solving of this extremum problem. Necessary expressions for calculating gradient of residual functional are presented. The efficiency of the proposed algorithm is illustrated by several test examples.


2021 ◽  
Vol 28 (8) ◽  
pp. 083703
Author(s):  
Biswajit Dutta ◽  
Pratikshya Bezbaruah ◽  
Nilakshi Das

2001 ◽  
Vol 280 (1-2) ◽  
pp. 97-103 ◽  
Author(s):  
V.B. Kokshenev ◽  
N.S. Sullivan

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