The state of the art time-domain wavefield imaging using a discontinuous Galerkin forward-backward time-stepping method
| dc.contributor.author | Mahdinezhad Saraskanroud, Forouz | |
| dc.contributor.examiningcommittee | LoVetri, Joe (Electrical and Computer Engineering) | en_US |
| dc.contributor.examiningcommittee | Ormiston, Scott (Mechanical Engineering) | en_US |
| dc.contributor.examiningcommittee | Popovic, Milica (Electrical and Computer Engineering, McGill University) | en_US |
| dc.contributor.supervisor | Jeffrey, Ian | |
| dc.date.accessioned | 2022-06-17T20:42:49Z | |
| dc.date.available | 2022-06-17T20:42:49Z | |
| dc.date.copyright | 2022-06-07 | |
| dc.date.issued | 2022-06-07 | |
| dc.date.submitted | 2022-06-07T20:37:44Z | en_US |
| dc.degree.discipline | Electrical and Computer Engineering | en_US |
| dc.degree.level | Doctor of Philosophy (Ph.D.) | en_US |
| dc.description.abstract | In this thesis, an efficient wavefield imaging technique of Forward/Backward Time-Stepping (FBTS) in the Time Domain (TD) is developed, employing the Discontinuous Galerkin Method (DGM) as the spatial-discretization technique. The FBTS method is based on calculating gradients of a TD cost functional with respect to the constitutive parameters of the target, and updating the modeled target using Conjugate Gradient (CG) method. The DGM and Runge-Kutta method are used to solve the mentioned problem, respectively, in space and time. We call this TD - Microwave Imaging (MWI) technique DGM-FBTS and present it, for the first time, for dispersive media. The electromagnetic (EM) two-dimensional non-dispersive Transverse Magnetic (TM) DGM-FBTS is compared to Frequency Domain (FD) imaging algorithms for synthetic and experimental imaging targets in terms of computational cost, the quality of results, and robustness. For the first time, a direct comparison of TD and single-frequency FD MWI, DGM-Contrast Source Inversion (CSI) and DGM-Gauss Newton Inversion (GNI) schemes are used as the FD counterparts, all implemented in Matlab. For experimental data, the DGM-FBTS algorithm shows a robust noise performance, generating higher-resolution results than the two FD methods. The DGM-FBTS formulation is also modified for quantitative ultrasound imaging with preliminary results presented, as a foundation for future experimental work in this area. This ultrasound imaging technique is validated briefly in this work, and it shows to be promising in quantitative wavefield imaging. Finally, a novel development and investigation of quantitative hybrid time- and frequency-domain techniques is presented, focusing on enhancing the performance of both FD and TD schemes by improving the inversion speed and image resolution, respectively. These hybrid schemes are tested/validated on experimental data to study their accuracy in the presence of measurement noise and system modeling error. These results show improvement of image resolution compared to stand-alone FD algorithms (especially for complicated targets) and improvement in computational time by an average of 44% compared to stand-alone TD algorithm. | en_US |
| dc.description.note | October 2022 | en_US |
| dc.description.sponsorship | University of Manitoba GETS program, Canadian Foundation for Innovation Johns Evans Leader Fund, Mitacs Accelerate, 151 Research co. | en_US |
| dc.identifier.uri | http://hdl.handle.net/1993/36549 | |
| dc.language.iso | eng | en_US |
| dc.rights | open access | en_US |
| dc.subject | Wavefield Imaging, Microwave Imaging, TD Ultrasound Imaging, Time-Domain Imaging, Discontinuous Galerkin Method (DGM), Forward-Backward Time-Stepping Method (FBTS) | en_US |
| dc.title | The state of the art time-domain wavefield imaging using a discontinuous Galerkin forward-backward time-stepping method | en_US |
| dc.title.alternative | DGM-FBTS Imaging | en_US |
| dc.type | doctoral thesis | en_US |
| local.subject.manitoba | no | en_US |
| project.funder.identifier | https://doi.org/10.13039/501100000038 | en_US |
| project.funder.name | Natural Sciences and Engineering Research Council of Canada (NSERC) | en_US |