腐殖质是树叶被细菌和真菌迅速分解和根部表面循环过程的必需品。

Humus is necessary for rapid decomposition of leaves by bacteria and fungi and for recycling by surface roots.

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最后，给出了两个关于饱和土体受到表面循环荷载的计算实例来说明所提出有限元技术的有效性。

Finally, two numerical examples regarding saturated soils subject to a surface cyclic loading are presented to illustrate the effectiveness of the proposed techniques.

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海底的磷必须找到某种方式回到表面，以完成这个循环，从而重新开始这个循环。

The phosphorus at the bottom of the ocean has to somehow make its way back to the surface, to complete the cycle, to begin the cycle all over again.

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So, if you look in the blood of patients that are infected with Hepatitis B you find a lot of Hepatitis B surface subunits, proteins without the nucleic acid circulating in their blood.

因此,如果你观察一下,已经感染乙肝病毒患者的血液,你会发现许多乙肝病毒的表面亚基,以及血液循环中存在没有核酸的蛋白质

耶鲁公开课 - 生物医学工程探索课程节选