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airfoil

(Encyclopedia)airfoil, surface designed to develop a desired force by reaction with a fluid, especially air, that is flowing across the surface. For example, the fixed wing surfaces of an airplane produce lift, whi...

center of mass

(Encyclopedia)center of mass, the point at which all the mass of a body may be considered to be concentrated in analyzing its motion. The center of mass of a sphere of uniform density coincides with the center of t...

pound

(Encyclopedia)pound, abbr. lb, unit of either mass or force in the customary system of English units of measurement. Two different pounds of mass are defined, one in the avoirdupois system of units and one in the T...

neodymium

(Encyclopedia)neodymium nēˌōdĭmˈēəm [key], metallic chemical element; symbol Nd; at. no. 60; at. wt. 144.242; m.p. about 1,021℃; b.p. about 3,068℃; sp. gr. 7.004 at 20℃; valence +3. Neodymium is a lust...

Tz'u Hsi

(Encyclopedia)Tz'u Hsi, Tsu Hsi, Tse Hsi, or Cixi all: tso͝o shē [key], 1834–1908, dowager empress of China (1861–1908) and regent (1861–73, 1874–89, 1898–1908). Her failure to realize the gravity of ...

Struve

(Encyclopedia)Struve shtro͞oˈvə [key], family of astronomers. Friedrich Georg Wilhelm von Struve, 1793–1864, was born in Germany but later lived in Russia. While director (1817–39) of Dorpat Observatory he w...

moment

(Encyclopedia)moment, in physics and engineering, term designating the product of a quantity and a distance (or some power of the distance) to some point associated with that quantity. The most theoretically useful...

mineral

(Encyclopedia)mineral, inorganic substance occurring in nature, having a characteristic and homogeneous chemical composition, definite physical properties, and, usually, a definite crystalline form. A few of the mi...

Pynchon, Thomas

(Encyclopedia)Pynchon, Thomas pĭnˈchən [key], 1937–, American novelist, b. Glen Cove, N.Y., grad. Cornell, 1958. Pynchon is noted for his amazingly fertile imagination, his wild sense of humor, and the teeming...

lubrication

(Encyclopedia)lubrication, introduction of a substance between the contact surfaces of moving parts to reduce friction and to dissipate heat. A lubricant may be oil, grease, graphite, or any substance—gas, liquid...