  We analyze eleven NuSTAR and Swift observations of the black hole X-ray
binary GX 339-4 in the hard state, six of which were taken during the end of
the 2015 outburst, five during a failed outburst in 2013. These observations
cover luminosities from 0.5%-5% of the Eddington luminosity. Implementing the
most recent version of the reflection model relxillCp, we perform simultaneous
spectral fits on both datasets to track the evolution of the properties in the
accretion disk including the inner edge radius, the ionization, and temperature
of the thermal emission. We also constrain the photon index and electron
temperature of the primary source (the "corona"). We find the disk becomes more
truncated when the luminosity decreases, and observe a maximum truncation
radius of $37R_g$. We also explore a self-consistent model under the framework
of coronal Comptonization, and find consistent results regarding the disk
truncation in the 2015 data, providing a more physical preferred fit for the
2013 observations.
