A current-mode analog computational circuit can be controlled to produce multiplying, squaring, divider and inverse functions and corresponding current outputs. The carbon regeneration circuit may include a dedicated regeneration vessel, or the regeneration process may proceed within a GACwater contactor of the process water circuit. The inserts each include two sets of milling teeth. The outer layer may include a number of contact sections that confront the body layer through the adhesive layer, as well as a number of raised sections that are spaced from the body layer and increase or otherwise improve the stiffness of the metal panel assembly.