Operating condition Fluidized beds 6 Axially aligned detectors 4 Bubble columns 4 Liquids 4 Radioactive particle tracking 4 Radioactive tracers 4 Atmospheric movements 2 Axial dispersion coefficients 2 Axial-velocity distribution 2 Bed expansion 2 Binary mixtures 2 Biobleaching 2 Bleaching 2 Bubble column hydrodynamics 2 Buffer pH 2 Calcium alginate beads 2 Carboxymethyl cellulose 2 Chlorine 2 Cleaning 2 Detectors 2 Different densities 2 Doehlert 2 Enzymes 2 Expansion 2 Experimental design 2 Experimental procedure 2 Flow regime transition 2 Flow regimes 2 Fluidization 2