China people have no hierarchical concept abroad, so they have no advanced concept. All names are called by their first names. In a sense, a senior can be a junior, but no one will call others "hi, junior". A freshman is called a freshman, a sophomore is called a sophomore, a junior is called a junior, and a senior is called a senior, but they are all general terms for others. You can't directly address each other, sophomore or junior. It's impolite.