1. Department of Applied Mathematics and Statistics, University of Sao Paulo, Sao Carlos, Sao Paulo, CEP 13566-590, Brazil
2. Combustion and Propulsion Laboratory, National Institute for Space Research, Cachoeira Paulista, Sao Paulo, CEP 12630-000, Brazil
3. Department of Mathematics and Computer Science, Sao Paulo State University, Presidente Prudente, Sao Paulo, CEP 19060-900, Brazil