We dont want no Thoughts Control??

My background is in engineering and Separation Processes in production of all chemicals can be considered to be my specialty. So , I was thinking of Separation Processes in daily life. How I wish I had some filtration device for my mind. Just take out/separate thoughts or people that you don't want or deserve your mindspace and dump them outside. Can thoughts be controlled? Is it possible to pinpoint just relevant thoughts, possible to change the frequency of stray thoughts? That certainly would be a great subject of research. Yogis have been known to master this art by meditating. So what exactly are they doing technically? Are they steering their thoughts in such a way that blood flow reaches just one particular region of brain and other regions face subdued activity? How can you block out impulses to certain regions of the brain though? I am really curious about their art/skill now. When doctors/scientists try to explain miracles, some strong believers rubbish them saying that man is too low a being to explain supernatural phenomena. But weren't the yogis exceeding that limit too? By not just being able to fathom the deep secrets, but by using them and having the power to tweak thoughts? Why doesn't anyone blame them..?