There is no scientific acronym or phrase that uses the letters "hy hi lo duh so." It's possible that you've misheard or misremembered something.

Could you please provide more context or information about where you encountered this phrase? Perhaps:

* Where did you hear it? (e.g., a book, a lecture, a conversation)

* What was the topic being discussed?

* Can you remember any other words or phrases that were used around it?

With more information, I might be able to help you figure out what it means.