Radioactive particle tracking Fluidized beds 14 Radioactive tracers 14 Bubble columns 12 Radioactivity 8 Velocity 8 Atmospheric movements 6 Axially aligned detectors 6 Liquids 6 Solid motion 6 Solid motions 6 Axial dispersion coefficients 4 Calcium 4 Calcium alginate beads 4 Detectors 4 Dispersion coefficient 4 Dispersions 4 Flow regimes 4 Fluidization 4 Gamma rays 4 Gas foaming 4 Hydrodynamic stress 4 Mixing 4 Operating condition 4 Radioactive Particle Tracking 4 Trajectories 4 Turbulence 4 Alginate 2 Axial-velocity distribution 2 Bubble column hydrodynamics 2