Pipe length
Water treatment
Kinesthetic sense
http://en.wikipedia.org/wiki/Digital_watermarking
Antenna
Reflection analysis
Color design
http://en.wikipedia.org/wiki/Optical_isolator
http://en.wikipedia.org/wiki/Electric_field
Air conditioner
Walking assistance
Mixer
Measuring pipe
http://en.wikipedia.org/wiki/Pulse_(signal_processing)
