Discussion:Two points are proposed in here to explain the result.1. cut-off distribution (FJI-1 filter is shallower than BSI-1 filter)From the cross-sectional image, the obvious two dark layers can be found in BSI-1filter (red line); however, there is no obvious dark layer but just performed uniformgray in FJI-I filter. Dark layer meant that the a lot of dust is filled in this region. Theresult indicated that the cut-off (pore sized) distribution is more uniform in FJI-1filter than in BSI-1.2. The differences of the cut-off layer (BSI-1 filter is larger than FJI-1 filter)However, only cut-off distribution cannot be used to fully explain the resultbetween flow-differential pressure and filtration efficiency. Again, the cross-sectionalimage is used. The white layer is found in BSI-1 filter and indicated that there’s noenough dust accumulate in this region. It meant much larger difference of cut-offlayer in BSI-1 filter than FJI-1 filter (as shown in fig. 1). In theory, high pressure losswill be performed when the pore sizes in membrane have dramatic change. That’slikely why FJI-1 filter has better efficiency and lower differential pressure at the sametime.