AUTHORS CONTRIBUTION
Minh Le Nguyen, suggested the idea and methods, conducted the
experiment, and prepared the manuscript.
Doan My Ngoc Nguyen: conducted the experiment and prepared the
manuscript.
Hoang Van Nguyen: suggested the idea and methods, edited and submitted
the manuscript.
Minh Kha Le, Man Van Tran and Phung My Loan Le: lecture contribution to
complete the manuscript.