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 travels fastest in solids because the constituent particles (atoms/molecues/ions) are most closely/tightly packed. Sound is a longitudinal wave, which means that sound waves travel through the vibrations of individual particles of matter (compressions and rarefactions) which are along the direction on propogation. Only the disturbance is transmitted forward, without requiring the particles to actually move themselves.