{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/23644"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/23644","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Forward and inverse scattering problems in the time domain","abstract":"An efficient method of solving the 2${1\\over 2}$-dimensional electromagnetic forward scattering problem in the time domain is developed, which circumvents the use of three-dimensional arrays to solve the vector wave problem. The method is based on calculating the three-dimensional fields as a summation of Fourier-transformed two-dimensional fields. Each 2D problem is solved via the finite-difference time-domain algorithm. The solution is used to develop a realistic model of the subsurface interface radar.","abstract_html":"An efficient method of solving the 2${1\\over 2}$-dimensional electromagnetic forward scattering problem in the time domain is developed, which circumvents the use of three-dimensional arrays to solve the vector wave problem. The method is based on calculating the three-dimensional fields as a summation of Fourier-transformed two-dimensional fields. Each 2D problem is solved via the finite-difference time-domain algorithm. The solution is used to develop a realistic model of the subsurface interface radar.","abstract_has_math":true,"creators":["Moghaddam, Mahta"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Engineering, Electronics and Electrical","degree_department":null,"school":null,"contributors":["Chew, Weng Cho"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-05-07T14:21:45Z","date_published":"2011-05-07T14:21:45Z","updated_at":"2026-07-22T22:25:22Z","subjects":["Engineering, Electronics and Electrical"],"languages":["eng"],"rights":["Copyright 1991 Moghaddam, Mahta"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9210921","(UMI)AAI9210921"],"render_values":[{"text":"AAI9210921","href":null,"code":true},{"text":"(UMI)AAI9210921","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/23644","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Chew, Weng Cho"]},{"key":"dc:creator","label":"Author","values":["Moghaddam, Mahta"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-05-07T14:21:45Z","10000-01-01","1991"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Engineering, Electronics and Electrical"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Engineering, Electronics and Electrical"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 1991 Moghaddam, Mahta"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9210921","(UMI)AAI9210921","http://hdl.handle.net/2142/23644"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["An efficient method of solving the 2${1\\over 2}$-dimensional electromagnetic forward scattering problem in the time domain is developed, which circumvents the use of three-dimensional arrays to solve the vector wave problem. The method is based on calculating the three-dimensional fields as a summation of Fourier-transformed two-dimensional fields. Each 2D problem is solved via the finite-difference time-domain algorithm. The solution is used to develop a realistic model of the subsurface interface radar.","The nonlinear two-dimensional electromagnetic inverse scattering problem is solved using spatially-sparse transient data with TM incidence. The method uses Born-type iterations on a volume integral equation for the scattered field. We call this the Born iterative method. Both the full-angle and the limited-angle inverse problems are solved. In each case, resconstructions are obtained when the linear Born approximation is severely violated. It is shown that the permittivity and conductivity profiles can be reconstructed simultaneously. The effect of noise is considered, and it is shown that the algorithm has a robust noise performance. The high-resolution capability of the algorithm is demonstrated and discussed.","The nonlinear two-dimensional electromagnetic TE inverse problem is formulated and solved using the Born iterative method. Although a very important problem, the TE inverse problem has rarely been considered before, due to the more complex form of the wave equation: The unknown is acted upon by a derivative operator, rendering the solution prone to numerical error. Here, several profiles are successfully inverted, but it is shown that the resolution limit is degraded by a factor of two compared to the TM inverse problem. This is attributed to the high level of noise arising from numerical differentiations.","The two-unknown linear acoustic inverse problem is solved using a diffraction tomography-type method. Having established the limits of applicability of the linear solution, the nonlinear problem is formulated and solved via the Born iterative algorithm using a double-criterion optimization. The acoustic problem also involves the differentiation of one of the unknown profiles and the field inside the scatterer. Therefore, while the algorithm is able to invert smooth profiles, the resolution in this case is also deteriorated compared to the TM case because of numerical noise.","Made available in DSpace on 2011-05-07T14:21:45Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9210921.pdf: 6283696 bytes, checksum: fcac00a211d1edf6ad7d151caaab2cc7 (MD5) Previous issue date: 1991","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T15:05:52Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:31:36-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission","ETDs are only available to UIUC Users without author permission","U of I Only"]},{"key":"dc:title","label":"Title","values":["Forward and inverse scattering problems in the time domain"]}]}],"canonical_facts":{"dc:contributor":["Chew, Weng Cho"],"dc:creator":["Moghaddam, Mahta"],"dc:date":["2011-05-07T14:21:45Z","10000-01-01","1991"],"dc:description":["An efficient method of solving the 2${1\\over 2}$-dimensional electromagnetic forward scattering problem in the time domain is developed, which circumvents the use of three-dimensional arrays to solve the vector wave problem. The method is based on calculating the three-dimensional fields as a summation of Fourier-transformed two-dimensional fields. Each 2D problem is solved via the finite-difference time-domain algorithm. The solution is used to develop a realistic model of the subsurface interface radar.","The nonlinear two-dimensional electromagnetic inverse scattering problem is solved using spatially-sparse transient data with TM incidence. The method uses Born-type iterations on a volume integral equation for the scattered field. We call this the Born iterative method. Both the full-angle and the limited-angle inverse problems are solved. In each case, resconstructions are obtained when the linear Born approximation is severely violated. It is shown that the permittivity and conductivity profiles can be reconstructed simultaneously. The effect of noise is considered, and it is shown that the algorithm has a robust noise performance. The high-resolution capability of the algorithm is demonstrated and discussed.","The nonlinear two-dimensional electromagnetic TE inverse problem is formulated and solved using the Born iterative method. Although a very important problem, the TE inverse problem has rarely been considered before, due to the more complex form of the wave equation: The unknown is acted upon by a derivative operator, rendering the solution prone to numerical error. Here, several profiles are successfully inverted, but it is shown that the resolution limit is degraded by a factor of two compared to the TM inverse problem. This is attributed to the high level of noise arising from numerical differentiations.","The two-unknown linear acoustic inverse problem is solved using a diffraction tomography-type method. Having established the limits of applicability of the linear solution, the nonlinear problem is formulated and solved via the Born iterative algorithm using a double-criterion optimization. The acoustic problem also involves the differentiation of one of the unknown profiles and the field inside the scatterer. Therefore, while the algorithm is able to invert smooth profiles, the resolution in this case is also deteriorated compared to the TM case because of numerical noise.","Made available in DSpace on 2011-05-07T14:21:45Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9210921.pdf: 6283696 bytes, checksum: fcac00a211d1edf6ad7d151caaab2cc7 (MD5) Previous issue date: 1991","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T15:05:52Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:31:36-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission","ETDs are only available to UIUC Users without author permission","U of I Only"],"dc:identifier":["AAI9210921","(UMI)AAI9210921","http://hdl.handle.net/2142/23644"],"dc:language":["eng"],"dc:rights":["Copyright 1991 Moghaddam, Mahta"],"dc:subject":["Engineering, Electronics and Electrical"],"dc:title":["Forward and inverse scattering problems in the time domain"],"dc:type":["text"],"thesis:degree_discipline":["Engineering, Electronics and Electrical"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:25:22Z"}