Iwao'sm-m model m = α + βm is liner. But in nature, m-m is often notlinear,so that the model of Iwao has obvious limitations.Xu Rumei et al.have improved the model.The improving of Iwao 's m-mmodel is m = α' + β'm + rm2.We treat β as a function of m,β = β' + ym + dm2.Thus,the farther improvedmodel becomes:m = α'+β'm+r'm2 + m3.This farther improved model is more generalized.It can be used in descri-bing the relationships between m and m under both linear and third degree nonlinear condition.Each of the four ...