{"id":116,"date":"2015-07-04T16:44:32","date_gmt":"2015-07-04T14:44:32","guid":{"rendered":"http:\/\/project.inria.fr\/rencontresljll\/?p=72"},"modified":"2016-08-27T13:05:57","modified_gmt":"2016-08-27T11:05:57","slug":"new-ljll-2","status":"publish","type":"post","link":"https:\/\/project.inria.fr\/rencontresljll\/new-ljll-2\/","title":{"rendered":"<font color=\"red\"><strong>Monday, July 4<\/strong><\/font><br><strong>Alexandre JANON<\/strong>, Universit\u00e9 Paris-Sud"},"content":{"rendered":"<p><span style=\"font-size: small;\"><em>Sensitivity analysis and dimension reduction<\/em><\/span><\/p>\n<p>Mathematical models seldom represent perfectly the reality of studied<br \/>\nsystems, due to, for instance, uncertainties on the parameters that<br \/>\ndefine the system. For instance, in geophysical fluids modelling, these<br \/>\nparameters can be, e.g., the domain geometry, the initial state, the<br \/>\nwind stress, the friction or viscosity coefficients.<\/p>\n<p>Sensitivity analysis aims at measuring the impact of each input<br \/>\nparameter uncertainty on the model solution and, more specifically, to<br \/>\nidentify the &#8220;sensitive&#8221; parameters (or groups of parameters). Amongst<br \/>\nthe sensitivity analysis methods, we will focus on the Sobol indices method.<\/p>\n<p>The numerical computation of these indices require numerical solutions<br \/>\nof the model for a large number of parameters&#8217; instances. However, many<br \/>\nmodels (such as typical geophysical fluid models) require a large amount<br \/>\nof computational time just to perform one run. In these cases, it is<br \/>\nimpossible (or at least not practical) to perform the number of runs<br \/>\nrequired to estimate Sobol indices with the required precision.<\/p>\n<p>This leads to the replacement of the initial model by a <em>metamodel<\/em><br \/>\n(also called <em>response surface<\/em> or <em>surrogate model<\/em>), which<br \/>\nis a model that approximates the original model, while having a<br \/>\nsignificantly smaller time per run, compared to the original model.<\/p>\n<p>We will focus on the use of metamodel to compute Sobol indices. More<br \/>\nspecifically, our main topic is the quantification of the metamodeling<br \/>\nimpact, in terms of Sobol indices estimation error. We also consider a<br \/>\nmethod of metamodeling which leads to an efficient and rigorous metamodel.<\/p>\n<p>11:00 a.m. to 12:00 p.m., <strong>LJLL<\/strong>, University Paris 6 (UPMC), Jussieu campus, seminar room 15-16-309. Coffee from 10:45 a.m.<\/p>","protected":false},"excerpt":{"rendered":"<p>Sensitivity analysis and dimension reduction Mathematical models seldom represent perfectly the reality of studied systems, due to, for instance, uncertainties on the parameters that define the system. For instance, in geophysical fluids modelling, these parameters can be, e.g., the domain geometry, the initial state, the wind stress, the friction or\u2026<\/p>\n<p> <a class=\"continue-reading-link\" href=\"https:\/\/project.inria.fr\/rencontresljll\/new-ljll-2\/\"><span>more<\/span><i class=\"crycon-right-dir\"><\/i><\/a> <\/p>\n","protected":false},"author":932,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[],"class_list":["post-116","post","type-post","status-publish","format-standard","hentry","category-seminar-15"],"_links":{"self":[{"href":"https:\/\/project.inria.fr\/rencontresljll\/wp-json\/wp\/v2\/posts\/116","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/project.inria.fr\/rencontresljll\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/project.inria.fr\/rencontresljll\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/project.inria.fr\/rencontresljll\/wp-json\/wp\/v2\/users\/932"}],"replies":[{"embeddable":true,"href":"https:\/\/project.inria.fr\/rencontresljll\/wp-json\/wp\/v2\/comments?post=116"}],"version-history":[{"count":21,"href":"https:\/\/project.inria.fr\/rencontresljll\/wp-json\/wp\/v2\/posts\/116\/revisions"}],"predecessor-version":[{"id":253,"href":"https:\/\/project.inria.fr\/rencontresljll\/wp-json\/wp\/v2\/posts\/116\/revisions\/253"}],"wp:attachment":[{"href":"https:\/\/project.inria.fr\/rencontresljll\/wp-json\/wp\/v2\/media?parent=116"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/project.inria.fr\/rencontresljll\/wp-json\/wp\/v2\/categories?post=116"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/project.inria.fr\/rencontresljll\/wp-json\/wp\/v2\/tags?post=116"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}