  In this paper, unmanned aerial vehicles (UAVs) and intelligent reflective
surface (IRS) are utilized to support terahertz (THz) communications.
  To this end, the joint optimization of UAV's trajectory, the phase shift of
IRS, the allocation of THz sub-bands, and the power control is investigated to
maximize the minimum average achievable rate of all the users.
  An iteration algorithm based on successive Convex Approximation with the Rate
constraint penalty (CAR) is developed to obtain UAV's trajectory, and the IRS
phase shift is formulated as a closed-form expression with introduced pricing
factors.
  Simulation results show that the proposed scheme significantly enhances the
rate performance of the whole system.
