Hello Minh Thanh, and Thank you.
Sometimes, when I show my engines to family or friends, someone asks "so what does it do?" Building this fan was partially in response to that, to build something with a "function". A couple of days ago I put that into practice. It was an unseasonably warm evening, so I had the fan running on the table while we ate dinner. It gave a very nice, soft little breeze, made almost no noise, and took up little table space. Pleasant and unobtrusive.