The principle and method for testing surface crack through directcurrentpotential difference are introduced.
首先介绍了直流电位法——裂纹扩展片检测裂纹的方法和原理。
2
Trade fairs offer direct contact with current and potential customers and a venue to launch products that will reach opinion-formers (such as journalists).
展销会提供了与现有及潜在客户的直接接触，上市会则可以让媒体了解（例如记者）。
3
Through electrostatics and examples of low-frequency alternating current and direct-current circuit, the problem of zero potential point is queried and clarified.