(Color online) The DBF potential energy for Pore01; solid blue: potential barrier when we use bulk relative permittivity of 80 inside the pore, dashed green: potential well, as a result of setting the axial relative permittivity to 600 inside the channel, while keeping 80 in either of x- or y-directions, solid black: potential barrier with axial relative permittivity of 600, and radial one of 3.5