2019 Volume 48 Issue 3 Pages 85-94
The hybrid lognormal distribution (Kumazawa, Ohashi 1986) is a probability distribution generated by the existence of a mechanism that suppresses the frequency of occurrence of higher values predicted by lognormal. This is a distribution with a main body of lognormal and a right tail of normal distribution and was derived as a risk management model of a stochastic process that reasonably suppresses dose accumulation accompanying radiation work. Similar probability distributions are widely found in natural phenomena, engineering, economics, culture, sports and social statistics. In this paper, we premised that ``the rational adjustment of increase and suppression of quantity'' of the mechanism which generates the hybrid lognormal distribution is feasible to become a universal risk management formula and that the risk output from this management formula becomes a hybrid fluctuation (combining the logarithmic fluctuation and the linear fluctuation). Then we presented the concept and application examples in terms of identifying the hybrid fluctuation on a hybrid scale (an integration of logarithmic scale and linear scale) as well as on a two-dimensional graph paper having a hybrid scale on both axes. In the application example, a hybrid scale (HS) model that gives a bestlinear graph on hybrid-hybrid graph paper was applied to therelationship between protons and excess neutrons, where the strongCoulomb repulsion of protons in the stable isotopes of heavier nucleiis moderated by an excess of neutrons with strong attractiveinteractions. We have verified that the nuclear structural stabilitywith respect to neutron excess is the same as the risk managementformula derived from dose management.
