Olympic bronze medallist Vijender Singh maintained his rampaging form to sail into the semi-finals and join six other Indians who have booked a medal each for themselves in the Asian Boxing Championships in Zhuhai, China, on Thursday. Vijender out-punched Kyrgyzstan's Karipov Ruslan for a 19-4 victory in the middleweight quarter-finals and assured himself at least a bronze in the event, in which he clinched a silver medal in the previous edition.