of;
Mechanical;
and;
Automotive;
Engineering,;
College;
of;
Engineerifig,;
Kongju;
National;
University,;
Chungnam;
330-717,;
Korea;
of;
Electrical;
&;
Electric;
Engineering,;
Daewon;
University;
College,;
Chungbuk;
390-702,;
Korea;