Extraction of PEM fuel cell variables based on modified hippopotamus optimization algorithm. - Aldakheel, Eman Abdullah; Ismaeel, Alaa A. K.; El-Rifaie, Ali M.; Khafaga, Doaa Sami; Houssein, Essam H.; Bouaouda, Anas; Hashim, Fatma A.; Said, Mokhtar (Scientific Reports, 2025)