这位副工程师负责协助总工程师完成桥梁设计的细节工作。

The ___sub-engineer is assisting the lead engineer with the detailed work of the bridge design.

这位助理工程师虽然还没取得正式资格，但在项目中发挥了重要作用。

The ___sub-engineer played a key role in the project despite not having full professional qualifications.