<qa>  What is the purpose of the study?The purpose of the study is to compare strut coverage and neointimal thickness between everolimus eluting XIENCE-V or PROMUS stent and biolimus A9 eluting NOBORI Stent 14 months after stent implantation and to determine the coronary endothelial function after everolimus eluting XIENCE-V or PROMUS stent and biolimus A9 eluting NOBORI Stent 14 months after stent implantation by using supine bicycle exercise testing to assess coronary vasomotor response to exercise. 