材料的主要分类为金属、高聚物，陶瓷，及合成材料。

The main classes of materials are metals, polymers, ceramics, and composites.

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同样，对于机器学习算法，一个通常的问题是过适合(原文为over - fitting，译者注)数据，以及主要记忆训练集，而不是学习过多的一般分类技术。

Similarly, with machine learning algorithms, a common problem is over-fitting the data and essentially memorizing the training set rather than learning a more general classification technique.

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海盗很少受到对抗的另一个主要原因似乎是他们被分类为罪犯而不是恐怖份子，因此被赋与多项权利。

Another major reason the pirates are rarely confronted seems to be that they are classified as criminals and not as terrorists and hence are accorded numerous rights.

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