Imperial and US customary measurement systems the Troy units of weight—the troy ounce used to this day for weighting precious metals. Edward I (1272–1307) broke the link between a coin's value and its weight when he debased the English coinage by introducing a groat (four pence) which weighed of 89 grains rather than the expected 96 grains. The groat was further devalued in the 1350s when its weight was reduced to 72 grains. During Saxon times land was measured both in terms of its economic value and in terms of its size. The Domesday Book used the hide, an economic unit of measure. In other references
Refractory metals 1900 K. An environment must not interact with the material in question. Liquid alkali metals as the heat transfer fluids are used as well as the ultra-high vacuum. The high-temperature creep strain of alloys must be limited for them to be used. The creep strain should not exceed 1–2%. An additional complication in studying creep behavior of the refractory metals is interactions with environment, which can significantly influence the creep behavior. Refractory metals Refractory metals are a class of metals that are extraordinarily resistant to heat and wear. The expression is mostly used in the context of materials science, metallurgy