qt(.95, 18)
[1] 1.734064

n = 10; df = 18;  cv = qt(.95, df); cv
[1] 1.734064
sg = 4;  dlt = 5;  lam = dlt/(sg*sqrt(2/n)); ncp
[1] 2.795085
pwr = 1-pt(cv, df, lam);  pwr
[1] 0.8514775