There exist research works on studying time-dependent integer-order and time-fractional constant-order geometric inverse source problems in the literature. The time-fractional variable-order geometric inverse source problems although also have important physical applications have not been studied mathematically and numerically in literature. The aim of this work is to study an inverse source problem associated with a variable-order time-fractional subdiffusion equation. We first build a mathematical model and show existence of the optimal shape for shape reconstruction of the source support. Then, shape sensitivity analysis is performed to propose a shape gradient optimization algorithm allowing deformations for numerically solving the model problem. In order to reconstruct the source support with topology unknown a priori, moreover, we build a phase-field model and propose a gradient algorithm allowing both shape and topological changes by a phase-field method. A variety of numerical examples are presented to demonstrate effectiveness of the two algorithms.
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Illustration of domain settings
Illustration of a phase-field function and its implicit representation
Reconstruction process of source (black region on the first row) and results of computed
Reconstruction comparisons with
Comparisons on the observed
Convergence histories of the objectives of Example 1:
Comparisons on
Convergence history of the objective for Example 2
Comparisons on
Evolution process of the source for Case 1 of Example 4: square initial (The region with red color represents
Evolution process of the source for Case 1 of Example 4: random initial
Convergence histories of the objective for Case 1 of Example 4: square initial (left) and random initial (right)
Reconstructed sources with random initial: Case 2 of Example 4
Convergence histories of the objective of Case 2 of Example 4
Comparisons of numerical and exact source of Example 5
Convergence histories of the objective of Example 5
Comparisons of numerical and exact sources of Example 6
Convergence histories of the objective of Example 6
Comparison of numerical and exact sources of Example 7
Convergence histories of the objective of Example 7
Comparison of numerical and exact sources of Example 8