Regarding the "cyclic sighing" technique (called "Physiological sighing" in the graphic):

I have been doing it for a couple of years without knowing it was a thing. I have studied common Pranayama techniques, and I stumbled upon it via trial and error. I do it because I find it anxiety-reducing. I used to refer to it internally as "double inhale breathing".

After reading the OP article, and noting that they referred to "Yogic breathing", I decided to do a little research and discovered that this technique is called "Dirga Pranayama" or "three part breathing". The authors should have mentioned it in their article.