  Coupled grain boundary (GB) motion has been studied in a two-dimensional
tricrystal where a cylindrical grain is embedded at the center of the planar GB
of a large bicrystal. Kinetic relations for GB dynamics, grain orientations,
and junctions have been derived within the framework of Gibbs thermodynamics.
These are solved numerically to investigate the shrinkage of the embedded grain
while emphasizing the role of coupled motion as well as junction mobility in
the shape evolution.
