https://askubuntu.com/questions/861416/changing-refresh-rate-for-specific-monitor (실패)
https://askubuntu.com/questions/1231441/ubuntu-screen-flickering (실패)
https://askubuntu.com/questions/945895/solution-to-intel-graphics-screen-tearing-flickering-causes-excessive-fan-use (실패)
NVIDIA 외장 그래픽 카드를 설치하여 해결 하였음. -_-;;
