The double-concave shape of REE patterns of the alkali basalt show that the basalt melt had reached equilibrium or quasi-equilibrium with the garnet and clinopyroxene megacrysts.
碱性玄武岩的双凹型REE配分模式是熔体与单斜辉石、石榴石达到化学平衡或近于化学平衡的结果；
Just as a double convex lens enlarges so a double concave lens reduces.
正象双凸透镜可以放大那样，双凹透镜也可以缩小。
Spherical roller bearings are double-row, self-containing units that comprise solid outer rings with a concave raceway, solid inner rings and barrel rollers with cages.
球面滚子轴承是双列，自我包含的单位，包括坚实的外圈与凹面滚，固体和内圈与辊每桶笼。
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