Urban planning and electric fan: what they have in common

1. Step 1. Urban planning — uses — Sewerage. Infrastructure.
2. Step 2. Sewerage — has part — Sewage treatment plant. Treatment plants.
3. Step 3. Sewage treatment plant — has part — Compressor. Blowers supply oxygen to the microbes.
4. Step 4. Compressor — has part — Impeller. A centrifugal compressor is an impeller.
5. Step 5. Impeller — is part of — Electric fan. A fan's blades are an impeller that pushes the air.

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