def bed(d, alpha_beta)
      # FIXME: Perhaps better to use number of fractions instead of fraction dose?!
      raise ArgumentError, "A positive alpha_beta factor is required (got: #{alpha_beta})." unless alpha_beta.to_f > 0.0
      @value * (1 + d.to_f/alpha_beta.to_f)
    end
def bed(d, alpha_beta)
      # FIXME: Perhaps better to use number of fractions instead of fraction dose?!
      raise ArgumentError, "A positive alpha_beta factor is required (got: #{alpha_beta})." unless alpha_beta.to_f > 0.0
      @value * (1 + d.to_f/alpha_beta.to_f)
    end
Calculates the biologically equivalent dose, BED. This is the theoretical
 limit of the equivalent dose delivered in small fractions, i.e. when
 complete repair takes place.

 @param [#to_f] d fraction dose
 @param [#to_f] alpha_beta the alpha/beta tissue factor to be used
 @return [Float] the biologically equivalent dose