¥(When an elastic flat sheet of elastic thickness h is
constrained by normal forces that are unbalanced except over distances
R >> h, the shape converges pointwise as h/R¨0 to an a developable surface with an uncurved director through every point. For certain choices of constraint forces, the directors converge to a point,
thus forming a developable cone.)
¥If part of a d-cone is constrained (with nonzero normal
force) to follow a curve that imposes
nonzero curvature perpendicular to the director lines, then the Àmean
curvature averaged over this curve vanishes when h/R¨0
? .