You'll typically notice less color while looking at the stone from the top down anyway (appraisers grade by looking at the side), and the metal of the setting further masks the tones.
The paper reviewed the mechanism, classification, corrosion prevention grade of metal pipelines as well as the corrosion features of the sea water pipeline.
本文阐述了金属材料腐蚀的机理、分类、耐腐蚀等级，以及海水管系腐蚀特点。
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The technical key to the dynamic optimization study of the rational mill feed grade of metal mines is the establishment of various mathematical models.