Anemometer beam exits reflect, or backscatter, the light back into a detector, where it is measured relative to the original laser beam. When the particles are in great motion, they produce a Doppler shift for measuring wind speed in the laser light, which is used to calculate the speed of the particles, and therefore the air around the anemometer. Ultrasonic anemometers, first developed in the 1950s, use ultrasonic sound waves to measure wind velocity. They measure wind speed based on the time of flight of sonic pulses between pairs of transducers. Measurements from pairs of transducers can be combined to yield
P.S.K. What Does It Mean? P.S.K. What Does It Mean? "P.S.K. What Does It Mean?" (also written as "P.S.K. (What Does It Mean?)") is a song released in 1985 by Philadelphia rapper Schoolly D on his independent label Schoolly D Records. P.S.K. is the abbreviation for Park Side Killas, a street gang with which Schoolly D was affiliated. The highly influential song is considered the first hardcore rap song and features incidents of graphic sex, gunplay, drug references and one of the first uses of the word "nigga" in a rap song (earlier uses include "Scoopy Rap" and "Family Rap" in 1979, and "New York