The von Kármán–Gabrielli diagram (also Gabrielli–von Kármán diagram, GvK diagram) is a diagram which compares the efficiency of transportation methods by plotting specific tractive force, or specific resistance (ε = P/mgv = E/mgd) against velocity (v). It was first used by Theodore von Kármán and Giuseppe Gabrielli in their 1950 paper on this subject.
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Von Kármán–Gabrielli diagram Wikipedia(Text) CC BY-SA