I can't remember if it's been pointed out already, but it should be noted that the name of the girl who built Nano is not "Hakase". Rather, that is her title: it's the honourific used for professors. She is Professor Shinonome, and is never at any point in the anime referred to by her given name. Just "Professor" or "the professor". I've no idea why the official subtitles treat "hakase" as her actual name. Yuuko is also almost universally called by either her nickname, Yukko, or by her surname, Aioi. Mio and Mai only ever call her Yukko, so while the subtitles aren't wrong to use "Yuuko" (it IS her actual name, after all), it's not what's actually being said.