Who did more ring theory, Cahit Arf or Sind ibn Ali?
Cahit Arf:  He is known for the Arf invariant of a quadratic form in characteristic 2 (applied in knot theory and surgery theory) in topology, the Hasse–Arf theorem in ramification theory, Arf semigroups, and Arf rings. Sind ibn Ali:  The Zij al-Sindhind was the first astronomical table ever introduced in the Muslim World. Sind ibn Ali:  As a mathematician Sind ibn ʿAlī was a colleague of al-Khwarizmi and worked closely with Yaqūb ibn Tāriq together they calculated the diameter of the Earth and other astronomical bodies. Sind ibn Ali:  He also wrote a commentary on "Kitāb al-ğabr wa-l-muqābala" and helped prove the works of al-Khwarizmi.
i don't know