Aluminium alloyAn aluminium alloy (or aluminum alloy; see spelling differences) is an alloy in which aluminium (Al) is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon, tin, nickel and zinc. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories heat-treatable and non-heat-treatable. About 85% of aluminium is used for wrought products, for example rolled plate, foils and extrusions.
Alloy steelAlloy steel is steel that is alloyed with a variety of elements in total amounts between 1.0% and 50% by weight to improve its mechanical properties. Alloy steels are broken down into two groups: low alloy steels and high alloy steels. The difference between the two is disputed. Smith and Hashemi define the difference at 4.0%, while Degarmo, et al., define it at 8.0%. Most commonly, the phrase "alloy steel" refers to low-alloy steels. Strictly speaking, every steel is an alloy, but not all steels are called "alloy steels".
Orographievignette|droite|redresse=1.2|Une carte orographique de l'Est Sibérie réalisée par Pierre Kropotkine en 1875. L'orographie (du grec ancien ὄρος, « montagne », et γραφή, « écrit ») est le domaine de la géomorphologie et de la géographie physique concernant la description des montagnes et par extension, plus généralement du relief (topographie), y compris sous-marin avec l'orographie sous-marine. Pour le cartographe, et dans les systèmes d'information géographique (SIG), l'orographie décrit des ruptures de pentes artificielles, et les toponymes relatifs au relief (dits oronymes).
Norwegian cyclone modelThe older of the models of extratropical cyclone development is known as the Norwegian cyclone model, developed during and shortly after World War I within the Bergen School of Meteorology. In this theory, cyclones develop as they move up and along a frontal boundary, eventually occluding and reaching a barotropically cold environment. It was developed completely from surface-based weather observations, including descriptions of clouds found near frontal boundaries.
