Optimal Port Allocation for Nonlinear Distributed Parameter Systems**This work was supported by JSPS Grants-in-Aid for Scientific Research (C) No. 264204f 5, and JSPS Grants-in-Aid for Challenging Exploratory Research No. 26630197. N. Sakamoto was supported by Nanzan University Pache Research Subsidy I-A-2 for the 2015 academic year