A few examples from different periods show that the simple design of Egyptian doorways conforms to a harmonic analysis.
It is your mother's hope that while you are studying overseas, you can write to her once a week; even if there is nothing to say, you can just scribble a few words. In these few days, she has not heard from you and she worries about you every day. A few days ago, she heard Li Bo-wen say that his son has written to say that he had met you. She was very happy. The last two postal parcels that were sent to you comprised three sports shirt, two pairs of shorts, a pair of shoes, socks and a harmonica. The latest parcel was sent on April and comprised three pairs of trousers. When you receive them, you should note down the date of receipt in your reply.
The next year she was given a harmonica and she took to it right away.
The cyclo converter station can be considered as a harmonic source with characters of voltage source.
We can work out positions of a harmonic oscillator by numerical methods.