As far as cultural assimilation is concerned, if you take the example of the Tibetan language, at the university level, let's say in Tibet University in Lhasa, the capital city, the medium of instruction is Chinese, not Tibetan. At the high school and middle school level, the medium of instruction is Chinese, not Tibetan. Now even at the primary school level they're introducing Chinese as the medium of instruction.
In some areas of Tibet, even students are coming into the street and protesting and saying they want their language to be used in the classroom, because they are Tibetan after all and their language is very important. It's part of their identity, and to preserve their identity, language is very important. It's not just as the official language in offices, but even at school the Tibetan language is discouraged, and, for all practical purposes, even in government offices.
I have some friends who worked in the Chinese government in the Tibet Autonomous Region. If there are 20 staff members in one office, and if two of them are Chinese and 18 are Tibetans, when they convene their meeting they have to converse in Chinese. If a postman, let's say a nomad, wants to send a letter to his relatives in another village, he would have to write in Chinese, not in Tibetan.
When you impose that kind of system, discouraging your own identity, even language, you can clearly see the assimilation drive to essentially first dilute and then destroy the Tibetan culture is very much a part of the practice of the Chinese government.