{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,5]],"date-time":"2026-06-05T15:47:20Z","timestamp":1780674440835,"version":"3.54.1"},"reference-count":35,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2022,2,18]],"date-time":"2022-02-18T00:00:00Z","timestamp":1645142400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100012331","name":"Flanders Innovation and Entrepreneurship","doi-asserted-by":"publisher","award":["Living Lab project Smart Maintenance"],"award-info":[{"award-number":["Living Lab project Smart Maintenance"]}],"id":[{"id":"10.13039\/100012331","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002913","name":"Flemish Government","doi-asserted-by":"publisher","award":["Onderzoeksprogramma Artifici\u00eble Intelligentie (AI) Vlaanderen"],"award-info":[{"award-number":["Onderzoeksprogramma Artifici\u00eble Intelligentie (AI) Vlaanderen"]}],"id":[{"id":"10.13039\/501100002913","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Remaining useful life is of great value in the industry and is a key component of Prognostics and Health Management (PHM) in the context of the Predictive Maintenance (PdM) strategy. Accurate estimation of the remaining useful life (RUL) is helpful for optimizing maintenance schedules, obtaining insights into the component degradation, and avoiding unexpected breakdowns. This paper presents a methodology for creating health index models with monotonicity in a semi-supervised approach. The health indexes are then used for enhancing remaining useful life estimation models. The methodology is evaluated on two bearing datasets. Results demonstrate the advantage of using the monotonic health index for obtaining insights into the bearing degradation and for remaining useful life estimation.<\/jats:p>","DOI":"10.3390\/s22041590","type":"journal-article","created":{"date-parts":[[2022,2,21]],"date-time":"2022-02-21T08:23:29Z","timestamp":1645431809000},"page":"1590","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":23,"title":["A Semi-Supervised Approach with Monotonic Constraints for Improved Remaining Useful Life Estimation"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6215-6439","authenticated-orcid":false,"given":"Diego","family":"Nieves Avendano","sequence":"first","affiliation":[{"name":"IDLab, Ghent University\u2014IMEC, 9052 Ghent, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nathan","family":"Vandermoortele","sequence":"additional","affiliation":[{"name":"IDLab, Ghent University\u2014IMEC, 9052 Ghent, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Colin","family":"Soete","sequence":"additional","affiliation":[{"name":"IDLab, Ghent University\u2014IMEC, 9052 Ghent, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2035-8766","authenticated-orcid":false,"given":"Pieter","family":"Moens","sequence":"additional","affiliation":[{"name":"IDLab, Ghent University\u2014IMEC, 9052 Ghent, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7153-8663","authenticated-orcid":false,"given":"Agusmian Partogi","family":"Ompusunggu","sequence":"additional","affiliation":[{"name":"Flanders Make\u2014Corelab Decision S, 3001 Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6600-1792","authenticated-orcid":false,"given":"Dirk","family":"Deschrijver","sequence":"additional","affiliation":[{"name":"IDLab, Ghent University\u2014IMEC, 9052 Ghent, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7865-6793","authenticated-orcid":false,"given":"Sofie","family":"Van Hoecke","sequence":"additional","affiliation":[{"name":"IDLab, Ghent University\u2014IMEC, 9052 Ghent, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,2,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"724","DOI":"10.1016\/j.ymssp.2008.06.009","article-title":"Rotating Machinery Prognostics: State of the Art, Challenges and Opportunities","volume":"23","author":"Heng","year":"2009","journal-title":"Mech. 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