{"id":{"repo_id":"manitoba","oai_identifier":"oai:mspace.lib.umanitoba.ca:1993/36549"},"canonical_url":"https://search.dev.ndltd.org/etd/manitoba/oai:mspace.lib.umanitoba.ca:1993/36549","repository":{"repo_id":"manitoba","name":"University of Manitoba","base_url":"https://mspace.lib.umanitoba.ca/oai/request"},"display":{"title":"The state of the art time-domain wavefield imaging using a discontinuous Galerkin forward-backward time-stepping method","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.","abstract_html":"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.","abstract_has_math":false,"creators":["Mahdinezhad Saraskanroud, Forouz"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Jeffrey, Ian"],"committee_chairs":[],"committee_members":[],"year":2022,"date_issued":"2022-06-07","date_published":"2022-06-07","updated_at":"2026-07-24T03:02:01Z","subjects":["Wavefield Imaging, Microwave Imaging, TD Ultrasound Imaging, Time-Domain Imaging, Discontinuous Galerkin Method (DGM), Forward-Backward Time-Stepping Method (FBTS)"],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/1993/36549","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.supervisor","label":"Supervisor","values":["Jeffrey, Ian"]},{"key":"dc:creator","label":"Author","values":["Mahdinezhad Saraskanroud, Forouz"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2022-06-17T20:42:49Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2022-06-17T20:42:49Z"]},{"key":"dc:date.issued","label":"Date","values":["2022-06-07"]},{"key":"dc:type","label":"Dc Type","values":["doctoral thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Wavefield Imaging, Microwave Imaging, TD Ultrasound Imaging, Time-Domain Imaging, Discontinuous Galerkin Method (DGM), Forward-Backward Time-Stepping Method (FBTS)"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/1993/36549"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["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."]},{"key":"dc:title","label":"Title","values":["The state of the art time-domain wavefield imaging using a discontinuous Galerkin forward-backward time-stepping method"]}]}],"canonical_facts":{"dc:contributor.supervisor":["Jeffrey, Ian"],"dc:creator":["Mahdinezhad Saraskanroud, Forouz"],"dc:date.accessioned":["2022-06-17T20:42:49Z"],"dc:date.available":["2022-06-17T20:42:49Z"],"dc:date.issued":["2022-06-07"],"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."],"dc:identifier.uri":["http://hdl.handle.net/1993/36549"],"dc:language.iso":["eng"],"dc:subject":["Wavefield Imaging, Microwave Imaging, TD Ultrasound Imaging, Time-Domain Imaging, Discontinuous Galerkin Method (DGM), Forward-Backward Time-Stepping Method (FBTS)"],"dc:title":["The state of the art time-domain wavefield imaging using a discontinuous Galerkin forward-backward time-stepping method"],"dc:type":["doctoral thesis"]},"updated_at":"2026-07-24T03:02:01Z"}