From the series solutions  for the Helmholtz equation (1) and the harmonic equation
(2), the magnetic vector potential with any current ring in the spherical coordinates can be derived through the continuity of the magnetic vector potential and the tangential components of the magnetic field on the particle surface 10].
The Robin problem forinhomogeneous harmonic equation
is treated in [16,18,36].
These constants ate further substituted into the harmonic equation
to determine the tidal level.
is Laplace's operator; thus the above partial differential equation is called Laplace's equation or harmonic equation.
Accordingly, the task of the restoration is solving the above harmonic equation. We return to the previous example as shown in Figure 4, and the distorted image in Figure 4(b) can be approximated by harmonic transformation.
Another approach in  has used Colonial Competitive Algorithm to solve harmonic equations and to minimize low order harmonics.
Nonlinear harmonic equations required to obtain optimal switching angles can be stated by Fourier expansion of load voltage.
We should point out that the Dirac-harmonic equation is a kind of general equation which includes many existing harmonic equations
as special cases, such as the A-harmonic equation; see [18, 20, 21] for more information.