Figure 11

Penetration resistance contour plot after treatment (a) S1 (pure electroosmotic flow) (b) S2 (electroosmotic flow with injection through the anode) (c) S3 (electroosmotic flow with simultaneous injection through both the anode and central tube) and (d) S4 (electroosmotic flow with injection through the anode followed by injection through the central tube with a 12.5-h interval between injections).