Some theorems in gravitational and electromagnetic fields
  The paper discusses the influences of velocity curl and field strength on some theorems in the electromagnetic field and gravitational field. With the characteristics of the algebra of quaternions, the theorem of linear momentum, conservation of linear momentum, and conservation of angular momentum etc. can be deduced from the quaternionic definitions of physical quantities. And the strength of gravitational field and electromagnetic field have an influence on some theorems directly. While the velocity curl has an effect on some theorems also. 
Zihua Weng