Definitions - u

U-value applies the factor of time to the heat-loss measurement. U-values measure heat that escapes per hour through a window. Windows typically have two U-values: one for the glass and one for the window, including the frame.

Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. There are three naturally occurring isotopes, with 12C and 13C being stable, while 14C is radioactive, decaying with a half-life of about 5730 years. Carbon is one of the few elements known since antiquity. The name "carbon" comes from Latin language carbo, coal.

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A method of land disposal in which liquid wastes are injected into known geological formations, generally at great depths.

All oils requiring further refinery processing, except those requiring only mechanical blending. Includes naphtha and lighter oils, kerosene and light gas oils, heavy gas oils, and residuum.

A territory with one or more features present throughout and absent or unimportant elsewhere.

The ability to increase a product’s performance or features without replacing the product.

The upward flow of cold, nutrient-rich water toward the ocean surface as currents or seasonal winds draw warmer water away from a coast. Phytoplankton that feed in upwellings often support huge fish populations.