The primary responsibilities of human resources are: 1  C - Compensation. 2  H - Human resource development. 3  E - Employee and labor relations. 4  S - Safety and health. 5  S - Staff.
A new technique uses sound waves to levitate objects and move them in mid-air. Credit: Dimos Poulikakos View full size image. View full size image. Hold on to your wand, Harry Potter: Science has outdone even your best Leviosa! levitation spell.
Note: The motion of a wave and the motion of the medium on which the wave moves are not the same: ocean waves, for example, move toward the beach, but the water itself merely moves up and down. Sound waves are spread by alternating compression and expansion of air.