α μe = ( μ e ) θ − ( μ e ) ref ( μ e ) ref ( θ− θ ref ) MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHXgaruavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeaaciWacmGadaGadeaabaGaaqaaaOqaaiabeg7aHnaaBaaaleaacqaH8oqBciGGLbaabeaakiabg2da9maalaaabaWaaeWaaeaacqaH8oqBdaWgaaWcbaGaciyzaaqabaaakiaawIcacaGLPaaadaWgaaWcbaGaeqiUdehabeaakiabgkHiTmaabmaabaGaeqiVd02aaSbaaSqaaiGacwgaaeqaaaGccaGLOaGaayzkaaWaaSbaaSqaaiaabkhacaqGLbGaaeOzaaqabaaakeaadaqadaqaaiabeY7aTnaaBaaaleaaciGGLbaabeaaaOGaayjkaiaawMcaamaaBaaaleaacaqGYbGaaeyzaiaabAgaaeqaaOWaaeWaaeaacqaH4oqCcqGHsislcqaH4oqCdaWgaaWcbaGaaeOCaiaabwgacaqGMbaabeaaaOGaayjkaiaawMcaaaaaaaa@59A9@
where (µe)θ and (µe)ref are the effective permeabilities at temperatures θ and θref respectively