to prevent an overseas outflow of talent (talented people)
to prevent talent people from going overseas for their study
to retain talent people domestically not to go overseas for their study.
そのまま直訳すると、
to prevent an overseas outflow of talented people
才能ある、優秀な人材の海外への流出を防ぐ。
to prevent talent people from going overseas for their study
才能ある、優秀な人材が研究のため海外へ行くのを妨げる。
to retain talent people domestically not to go overseas for their study
才能ある、優秀な人材が研究のため海外へ行かないように、国内へ留める。