  We present two of our efforts directed toward the numerical analysis of
neutron star mergers, which are the most plausible sources for gravitational
wave detectors that should begin operating in the near future. First we present
Newtonian 3D simulations including radiation reaction (2.5PN) effects. We
discuss the gravitational wave signals and luminosity from the merger
with/without radiation reaction effects. Second we present the matching problem
between post-Newtonian formulations and general relativity in numerical
treatments. We prepare a spherical, static neutron star in a post-Newtonian
matched spacetime, and find that discontinuities at the matching surface become
smoothed out during fully relativistic evolution if we use a proper slicing
condition.
