Spinodal decomposition both complete one cycle per second—but they represent different frequencies in the Fourier transform. Hence, frequency no longer measures the number of cycles per unit time, but is closely related.) If A(β) is the amplitude of a Fourier component of wavelength λ and wavenumber β = 2π/λ the spatial variation in composition can be expressed by the Fourier integral: in which the coefficients are defined by the inverse relationship: Substituting, we obtain on equating coefficients: This is an ordinary differential equation that has the solution: in which "A(β)" is the initial amplitude of the Fourier component of wave wavenumber β
Per-unit system use the nominal voltage 138 kV as the base voltage formula_23. We then have: If, for example, the actual voltage at one of the buses is measured to be 136 kV, we have: The following tabulation of per-unit system formulas is adapted from Beeman's "Industrial Power Systems Handbook". It can be shown that voltages, currents, and impedances in a per-unit system will have the same values whether they are referred to primary or secondary of a transformer. For instance, for voltage, we can prove that the per unit voltages of two sides of the transformer, side 1 and side 2,