its diameter up to 200 m and depth up to 20 m
61Protection of exposed concrete — is necessary to prolong its service life. A 120 year design life for concrete infrastructure has become increasingly common. Without early preventive maintenance this design life target may be optimistic. The design service life of reinforced… …
62Gramophone record — A 12 inch (30 cm) 33⅓ rpm record (left), a 7 inch 45 rpm record (right), and a CD (above) A gramophone record, commonly known as a phonograph record (in American English), vinyl record (in reference to vinyl, the material most commonly used after …
63comet — cometary /kom i ter ee/, cometic /keuh met ik/, cometical, adj. cometlike, adj. /kom it/, n. Astron. a celestial body moving about the sun, usually in a highly eccentric orbit, consisting of a central mass surrounded by an envelope of dust and… …
64North America — North American. the northern continent of the Western Hemisphere, extending from Central America to the Arctic Ocean. Highest point, Mt. McKinley, 20,300 ft. (6187 m); lowest, Death Valley, 276 ft. (84 m) below sea level. 400,000,000 including… …
65permafrost — /perr meuh frawst , frost /, n. (in arctic or subarctic regions) perennially frozen subsoil. Also called pergelisol. [1943; PERMA(NENT) + FROST] * * * Perennially frozen earth, with a temperature below 32 °F (0 °C) continuously for two years or… …
66Comet Shoemaker-Levy 9 — Shoemaker Levy redirects here. For other Shoemaker Levy comets see List of periodic comets. Infobox Comet name=SL9 (Shoemaker Levy) caption=Image of Comet Shoemaker Levy 9 fragments (total: 21), taken on May 17, 1994 discoverer= Carolyn Shoemaker …
67Ganymede (moon) — Ganymede Image of Ganymede s anti Jovian hemisphere taken by the Galileo probe. Lighter surfaces, such as in recent impacts, grooved terrain and the whitish north polar cap at upper right, are enriched in water ice. Discovery …
68Plastics extrusion — Cross section of a plastic extruder to show the screw Plastics extrusion is a high volume manufacturing process in which raw plastic material is melted and formed into a continuous profile. Extrusion produces items such as pipe/tubing, weather… …
69Tropical cyclone — Hurricane redirects here. For other uses, see Hurricane (disambiguation). Hurricane Isabel (2003) as seen from orbit during Expedition 7 of the International Space Station. The eye, eyewall and surrounding rainbands that are characteristics of… …
70Moon — /moohn/, n. Sun Myung /sun myung/, born 1920, Korean religious leader: founder of the Unification Church. * * * Sole natural satellite of Earth, which it orbits from west to east at a mean distance of about 238,900 mi (384,400 km). It is less… …
