NOTICE: this is the author’s version of a work that was accepted for publication in Communications in Nonlinear Science & Numerical Simulation. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in COMMUNICATIONS IN NONLINEAR SCIENCE & NUMERICAL SIMULATION, [VOL 18, ISSUE 8, (2013)] DOI: 10.1016/j.cnsns.2012.12.030