A pair of propellers on concentric shafts, turning in opposite directions. 
A pair of propellers on concentric shafts, turning in opposite directions. 
Related Terms 
CELESTIAL SPHEREAn imaginary sphere of infinite radius concentric with the earth, on which all celestial bodies except the earth are imagined to be projected 
COAXIAL CABLEA transmission cable consisting of two concentric conductors insulated from each other 
CONCENTRICHaving the same center. 
COORDINATE PAPERPaper ruled with lines to aid in the plotting of coordinates. In its most common form, it has two sets of parallel lines, usually at right angles to each other, when it is also called CROSS SECTION PAPER. A type ruled with two sets of mutuallyperpendicular, parallel lines spaced according to the logarithms of consec utive numbers is called logarithmic coordinate papa or semilogarithmic coordinate paper as both or only one set of lines is spaced logarithmically. A type ruled with concentric circles and radial lines from the common center is called polar coordinate paper. Also called GRAPH PAPER. 
DISTANCE CIRCLESCircles concentric to the center of a formation of ships, designated by their radii in thousands of yards. 
MODIFIED LAMBERT CONFORMAL MAP PROJECTIONA modification of the Lambert conformal projection for use in polar regions, one of the standard parallels being at latitude 89°59'58' and the other at latitude 71° or 74°, and the parallels being expanded slightly to form complete concentric circles. Also called NEY’S MAP PROJECTION. 
ODESSEY PROTRACTORA device used in conjunction with a plotting sheet having equally spaced concentric circles (range circles) drawn about two or more stations of a radio determination system being operated in the ranging mode. 
RANGE RINGOne of a set of equally spaced concentric rings, centered on own ship’s position, providing a visual presentation of range on a radar display. 
SPHERE

CENTRIFUGAL EXTRACTORA device for separating components of a liquid solution, consisting of a series of perforated concentric rings in a cylindrical drum that rotates at 2000 5000 revolutions per minute around a cylindrical shaft; liquids enter and leave through the shaft; they flow radially and concurrently in the rotating drum. 
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