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.
Sound waves travel through air in much the same way as water waves travel through water. In fact, since water waves are easy to see and understand, they are often used as an analogy to illustrate how sound waves behave. Sound waves can also be shown in a standard x vs y graph, as shown here.