.In my active research days, I supervise no more than five students at any one time. To teach research and explore new topics, you need working with students in one-on-one setting in hour long session at least once or twice a week. I have been retired since 2007 and wrote my last paper in 2009. If I were to advise research student again as a volunteer but with the same devotion, I can do it at most with one student nowadays if I want to do a honest job and not misled the students. Some people can supervise 40 to 50 students at once. I do not have such superhuman power to do it even if I am paid to do so. Besides in well established topics, there are plenty of qualified and paid professors to do the job. 

Thus, let me be brutually honest. If yolu wanted me to be your volunteer unpaid adviser to explore a new research topic, you have to compete for it. Write me a research proposal and convince me that your proposal is worth my time. Many other Chinese students wish to do the same. I must ration my time and energy. Even though I do't need the money in retirement, I like to be paid back in excitement and push back frontiers in new areas. Better yet see if you can get someone I know to recommend you. Their words are worth more than gold. As the saying goes, "No pain, no gain" . Otherwise, how does one draw the line among tens or hundreds similar requests? Remember, when you want something don't be self-centered but giver-centered. Yes you want something but why should the giver grant you your request among many other similar requests?  I want you as a partner in adventure not as someone just wanting some free advise. Remember FREE advise are probably worth the same. Than you will stand out..