#flux.rate  the rate of flow of energy or particles across a given surface
  supertype:  rate  a magnitude or frequency relative to a time unit; "they traveled at a rate of 55 miles per hour"; "the rate of change was faster than expected"
  subtype:  neutron_flux__neutronflux  the rate of flow of neutrons; the number of neutrons passing through a unit area in unit time
  subtype:  radiant_flux__radiantflux  the rate of flow of radiant energy (electromagnetic waves)
     subtype:  luminous_flux  the rate of flow of light energy

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