It has been four years since I registered for WordPress.

Different people posted various kinds of blog. I did not quite explore this world a lot yet, but during the last year, when I was learning representation theory and compressed sensing, I found many useful blogs (maybe they should be called mini textbooks or mini papers) on this website. And the very first blog I followed should be that from Terence Tao. It is really nice that people could share whatever they want here, which others may find to be encouraging or useful.

At the end of my second 12 years, I guess it is time for me to record some of my thoughts. The main reason is to keep the memories, but hopefully some blogs I post will be useful for others.

Well, 1,2,3, go!