Feb 21 Tech giant Samsung Electronics Co Ltd unveiled the latest versions of its flagship Galaxy S series on Sunday, but the incremental upgrades they offer may not be enough to rejuvenate sales for the world's No.1 smartphone maker. Samsung once again launched two versions of its new premium phone: the 5.1-inch flat screen Galaxy S7 and the 5.5-inch curved screen Galaxy S7 edge in Barcelona, where the industry is gathered for the Mobile World Congress.