SEARCH Articles Figures Tables Fulcher Hessing Vogel Vogel-Fulcher Vogel-Fulcher-Tammann-Hesse VFTH) equation Vogel-Fulcher-Tammann-Hesse equation Vogel-Fulcher-Tammann-Hesse equation temperature Vogel-Fulcher-Tammann-Hesse segmental relaxation Vogel-Tammann-Hesse-Fulcher temperature-time dependence