D8 = fft(d8,2048);
energyD8 = abs(D8).^2;
energies = energyD8(k);

% Results are:
% energies =
%    1.0e+05 *
%     0.0000    0.0020    2.5049    0.0005    0.0005    2.5022    0.0001
%
% Interpretation:
%  d8 has high energy at frequencies roughly 0.6565 and 1.0278.
%  This is as expected.
