1. a Department of Civil Engineering , University of Salford , Salford , M5 4WT , England
2. b Institut Laue Langevin , B.P. 156, 38042, Grenoble Cedex , France
3. c Department of Physics , Monash University , Clayton , Victoria , 3168 , Australia
4. d School of Electrical and Electronic Engineering, Preston Polytechnic , Preston , PR1 2TQ , England