THE CLOSING OF RESONANCE HORNS FOR PERIODICALLY FORCED OSCIlLAmRS A THESIS SUBMlI'IED TO TIIEFACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA BY BRUCE BARTLETT PECKHAM IN P AR11AL FULFIl.LMENT OF THE REQUIREMENTS FOR THE DEGREE OF OCX::TOR OF PHILDSOPHY