1. Process Engineering Group, IIM-CSIC, Spanish Council for Scientific Research, Eduardo Cabello 6, 36280 Vigo, Spain
2. Departamento Matemáticas del Área Industrial ETSII, Universidad Politécnica de Madrid, José Gutierrez Abascal 2, 28006 Madrid, Spain
3. Department of Mathematics, University of A Coruña, CITIC and ITMATI, Campus Elviña s/n, 15071 A Coruña, Spain