Is putting a baby in a "duyan" effective in putting them to sleep?

Gladly yes. When my child was 3-8 mons old we usually put her in duyan wherein she can 'find more her sleep'. We figure out that when at home and she's very sleepy, she doesn't sleep right away in our arms after hele. But the swing always do the trick! Just be careful though as baby has tendency to switch positions so never miss an eye to them when sleeping (or most of the time! ^^)