矩,動差任意變量的正整數(shù)功效的期望值。第一個矩是分配的平均數(shù) The expected value of a positive integral power of a random variable. The first moment is the mean of the distribution.
人們使用軋機把材料加工成各種形狀,如圓棒材、方棒材和矩形棒材。 A rolling mill is used to form the material into various form such as round rod, square or rectangular bar.