Stratification

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Stratification is the building up of layers. Stratified is an adjective referring to the arranging of layers, and is also the past form of the verb stratify, to separate or become separated into layers. They may refer to:

in mathematics, statistics and applied science

• Stratified sampling, a method of variance reduction in Monte Carlo methods
• Stratified fuel charge, or ultra lean burn, the use of lean mixtures in an internal combustion engine with unequalized pressure in the cylinder
  • Fuel charge stratification, a internal combustion process using direct injection to reduce fuel consumption and emissions
    • Fuel Stratified Injection (FSI), the operation of a stratified fuel charge in an engine using direct injection

in the earth sciences

• Stratification, the layering (strata) of rocks
  • Stratification (archeology), the formation of layers (strata) in which objects are found
  • Stratigraphy, the study of geological (or archaeological) stratification and strata
• Atmospheric stratification, the dividing of the Earth's atmosphere into strata
• Stratification (water), the formation of water layers based on salinity and temperature
  • Lake stratification, the dividing of lake water

in architecture

Stratification is the formation of air at different densities filling a house or room. It occurs when the ceiling is warmer than the floor. This keeps the hotter, lighter (less dense) air at the ceiling and the colder, heavier (denser) air near the floor. When the ceiling is colder than the floor, stratification does not occur. This situation causes the colder, heavier to fall along the cold walls and cover the floor. The warmer air which was over the floor rises from the center of the house to the ceiling. This convection current keeps the air churning and prevents stratification from occurring.

Although stratification is often considered undesirable, this is not necessarily so. In a hot house, it's desirable to keep the hotter air away from the occupants on the floor level. Cathedral ceilings are blamed for stratification, however the real culprit is insufficient insulation which causes wide diurnal temperature swings.

in the social sciences and humanities

• Social stratification, the dividing of a society into levels based on power or socioeconomic status
• Stratification (music), the layering of musical texture
  • Stratification, the independent operating of more than one parameter simultaneously in auditory streams

in biology and medicine

• Stratification (botany), where seeds are pretreated to simulate winter conditions so that germination may occur.
• Stratified epithelial linings, several types of epithelium characterized by multiple layers
• Stratified medicine, where patients are grouped according to shared biological traits and diagnostic results
• Population stratification, the stratification of a genetic population based on allele frequencies

[edit] See also

• Destratification
• Strata (disambiguation)
• Stratum (disambiguation)
• Layer (disambiguation)
• Partition

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