Providing an on-board power supply is difficult, however, so he is investigating the use of external magnetic fields to power the device.

然而，倘若板载动力装置很难实现的话，他正在研究利用外部磁场给器件提供动力的途径。

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Lately, a new class of materials has emerged that manifests topological properties at room temperature and without the need of external magnetic fields.

最近，一类新的材料出现，号称不需要外磁场也能在室温下看到拓扑性质。

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When external magnetic fields are absent, there may be a competitive growth between (100) and (111) surfaces; and the final morphology of particles are irregular polyhedra.

而当外磁场不存在的时候，(111)面和(100)面可能存在竞争生长的关系，从而纳米粒子呈现不规则的多面体形。

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Most materials, including milk and water, are diamagnetic, which means they are repelled by external magnetic fields though this phenomenon is far too subtle to be observed in normal circumstances.

ECONOMIST: Monitor