{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/19767"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/19767","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Derivative free methods in covariance components estimation","abstract":"The downhill simplex (DS), Powell's (PO), and Rosenbrock's (RO) algorithm were optimized and applied to estimation of dispersion parameters. The optimization is independent of the log-likelihood function and thus, from the model. The model can accommodate two additive genetic effects and genetic groups for unknown ancestors.","abstract_html":"The downhill simplex (DS), Powell's (PO), and Rosenbrock's (RO) algorithm were optimized and applied to estimation of dispersion parameters. The optimization is independent of the log-likelihood function and thus, from the model. The model can accommodate two additive genetic effects and genetic groups for unknown ancestors.","abstract_has_math":false,"creators":["Kovac, Milena"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Animal Sciences","degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-05-07T12:17:54Z","date_published":"2011-05-07T12:17:54Z","updated_at":"2026-07-22T22:25:14Z","subjects":["Agriculture, Animal Culture and Nutrition","Engineering, Agricultural"],"languages":["eng"],"rights":["Copyright 1992 Kovac, Milena"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9236509","(UMI)AAI9236509"],"render_values":[{"text":"AAI9236509","href":null,"code":true},{"text":"(UMI)AAI9236509","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/19767","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Kovac, Milena"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-05-07T12:17:54Z","10000-01-01","1992"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Animal Sciences"]},{"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":["Agriculture, Animal Culture and Nutrition","Engineering, Agricultural"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 1992 Kovac, Milena"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9236509","(UMI)AAI9236509","http://hdl.handle.net/2142/19767"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["The downhill simplex (DS), Powell's (PO), and Rosenbrock's (RO) algorithm were optimized and applied to estimation of dispersion parameters. The optimization is independent of the log-likelihood function and thus, from the model. The model can accommodate two additive genetic effects and genetic groups for unknown ancestors.","Memory requirements and CPU time are determined by the size of equation system. While memory requirements of optimization algorithms are negligible, the CPU time depends on the number of evaluations. Convergence rate is linear for the three algorithms. Numerical stability was increased by scaling and by elimination of dependent equations. Robustness was increased by scaling and by minimum optimization steps. Frequent restarts improved robustness in DS. PO and RO are sensitive to linearly dependent directions. In addition, they fail more often with severe restrictions within linear search.","DS performed more efficiently with frequent restarts which were triggered by an allowance step and a lower decreasing rate. Contrary, the other two algorithms were less affected by the allowance step. PO and RO were efficient if started in the middle of parameter space, i.e. correlations close to zero and equal ratios for variances. The efficiency of the two algorithms was also affected by restrictions on the number of evaluations per linear search, the order of optimization and scaling.","In addition, covariances were estimated for daily gain on three growing intervals of boars and the post-birth daily gain and backfat of gilts. Records on boars contained missing values due to multiple stage selection. Heritability estimates were.17,.16,.20,.24, and.23 for daily gain in boars from birth to 30, 30 to 60, and 60 to 100 kg and for post-birth daily gain and backfat in gilts, respectively. The corresponding proportions for common litter effects were.26,.18,.11,.12, and.04. Correlations between adjacent intervals for daily gain were higher than estimates between nonadjacent intervals for both random effects. In gilts, the correlations were.11 and $-$.14 for genetic and litter effect. Correlations between daily gain in boars and post-birth daily gain in gilts were high for genetic and moderate for litter effects.","Made available in DSpace on 2011-05-07T12:17:54Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9236509.pdf: 6264933 bytes, checksum: 8a9f4e84d766feac3814f30864f648db (MD5) Previous issue date: 1992","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:39:18Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:16:30-05:00 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":["Derivative free methods in covariance components estimation"]}]}],"canonical_facts":{"dc:creator":["Kovac, Milena"],"dc:date":["2011-05-07T12:17:54Z","10000-01-01","1992"],"dc:description":["The downhill simplex (DS), Powell's (PO), and Rosenbrock's (RO) algorithm were optimized and applied to estimation of dispersion parameters. The optimization is independent of the log-likelihood function and thus, from the model. The model can accommodate two additive genetic effects and genetic groups for unknown ancestors.","Memory requirements and CPU time are determined by the size of equation system. While memory requirements of optimization algorithms are negligible, the CPU time depends on the number of evaluations. Convergence rate is linear for the three algorithms. Numerical stability was increased by scaling and by elimination of dependent equations. Robustness was increased by scaling and by minimum optimization steps. Frequent restarts improved robustness in DS. PO and RO are sensitive to linearly dependent directions. In addition, they fail more often with severe restrictions within linear search.","DS performed more efficiently with frequent restarts which were triggered by an allowance step and a lower decreasing rate. Contrary, the other two algorithms were less affected by the allowance step. PO and RO were efficient if started in the middle of parameter space, i.e. correlations close to zero and equal ratios for variances. The efficiency of the two algorithms was also affected by restrictions on the number of evaluations per linear search, the order of optimization and scaling.","In addition, covariances were estimated for daily gain on three growing intervals of boars and the post-birth daily gain and backfat of gilts. Records on boars contained missing values due to multiple stage selection. Heritability estimates were.17,.16,.20,.24, and.23 for daily gain in boars from birth to 30, 30 to 60, and 60 to 100 kg and for post-birth daily gain and backfat in gilts, respectively. The corresponding proportions for common litter effects were.26,.18,.11,.12, and.04. Correlations between adjacent intervals for daily gain were higher than estimates between nonadjacent intervals for both random effects. In gilts, the correlations were.11 and $-$.14 for genetic and litter effect. Correlations between daily gain in boars and post-birth daily gain in gilts were high for genetic and moderate for litter effects.","Made available in DSpace on 2011-05-07T12:17:54Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9236509.pdf: 6264933 bytes, checksum: 8a9f4e84d766feac3814f30864f648db (MD5) Previous issue date: 1992","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:39:18Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:16:30-05:00 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":["AAI9236509","(UMI)AAI9236509","http://hdl.handle.net/2142/19767"],"dc:language":["eng"],"dc:rights":["Copyright 1992 Kovac, Milena"],"dc:subject":["Agriculture, Animal Culture and Nutrition","Engineering, Agricultural"],"dc:title":["Derivative free methods in covariance components estimation"],"dc:type":["text"],"thesis:degree_discipline":["Animal Sciences"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:25:14Z"}