內(nèi)容回憶：

　　文章講了冰屋的一些特點，包括怎么建造的。然后一段時間屋頂化了就要打開門 refreeze。冰屋是錐形的，不是半球，因為半球不好建，需要 support。

　　參考閱讀：

　　An igloo (Inuit language: iglu,[1] Inuktitut syllabics ᐃᒡᓗ [iɣˈlu] (plural: igluit ᐃᒡᓗᐃᑦ [iɣluˈit])), also known as a snow house or snow hut, is a type of shelter built of snow, typically built when the snow can be easily compacted.

　　Although igloos are stereotypically associated with all Inuit,[2] they were traditionally associated with people of Canada's Central Arctic and Greenland's Thule area. Other Inuit people tended to use snow to insulate their houses, which were constructed from whalebone and hides. Snow is used because the air pockets trapped in it make it an insulator. On the outside, temperatures may be as low as -45 ° C (-49 ° F), but on the inside the temperature may range from -7 ° C (19 ° F) to 16 ° C (61 ° F) when warmed by body heat alone.

　　Snow igloos are built in the shape of a catenoid, which offers optimal ratios between the height and diameter of the structure to eliminate the structural tension which could otherwise cause it to implode or bulge. The stresses of snow as it ages and compresses against the igloo will not cause it to buckle because in an inverted paraboloid or catenoid the pressures are exclusively compressive.[10]

　　This design originates from the Central Inuit.[10] In applied mechanics, the equation for this type of structure is written y = a(cosh x/a- 1) where y is the height to any point in the surface, x is the horizontal distance to the same point, and a is a constant.[10]

　　Since stress is a force per unit area, if the walls are of uniform thickness the compressive stress is independent of wall thickness; thicker walls provide better insulation but do not strengthen the structure because of added weight.[12]