fPersevalFactor = perseval()
  fPersevalFactor = perseval(sDimStr)
  m_mGrid multiplied by fPersevalFactor
  gives proper values of power of energy upon
  integration in all (or some) dimensions in Fourier Space
 
  Example:
  fER = trapz(vR, vR.*abs(transform.fromFS(A.m_mGrid)).^2) ;
  fEKR = trapz(vKR, vKR.*abs(fPersevalFactor*A.m_mGrid).^2);
  (fEKR/fER) gives 1
 
  fET = sum(abs(ifft(A.m_mGrid)).^2) * DT;
  fEAF = sum(abs((fPersevalFactor *A.m_mGrid)).^2) *DAF;
  (fEAF/fET) gives 1