This is the 569th most frequent Arabic word.
برئاسة
"Under the presidency" or "headed by."
Here, 'برئاسة' indicates that the executive director is the leader or head of the meeting.
ترأس الاجتماع الجديد برئاسة المدير التنفيذي.
The new meeting was presided over by the executive director.
In this sentence, 'برئاسة' signifies that the new commander is in charge of the team.
تم تنظيم الفريق برئاسة القائد الجديد.
The team was organized under the leadership of the new commander.
The usage of 'برئاسة' in this context shows that Dr. Ahmed is the principal host or leader of the conference.