19世纪，人类成功从石油中提炼出煤油，煤油代替了鲸油，使得许多鲸类免受灭绝的厄运。
Kerosene refined from such petroleum helped displace the whale oil that lit lamps in the 19th century and led to the near extinction of many whale species.
从1769年开始，胆固醇就开始困扰研究者们，当时法国化学家Poulletier de la Salle第一次提炼出了这种具脂类的黄白物体。
Cholesterol has been perplexing researchers since 1769, when French Chemist Poulletier DE la Salle first purified the soapy-looking yellow-white substance.
用主成份分析法和聚类技术提炼这些运动学片段的特征。
Principal component analysis and cluster analysis are performed to refine the features of these sequences.
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