A piston device comprises a sleeve, a casing pipe, a first piston, a resilient member, and a second piston. Polymer-dispersed liquid crystals in accordance with the invention preferably comprise a homogeneous mixture of a nematic liquid crystal and a multifunctional pentaacrylate monomer in combination with photoinitiator, coinitiator and cross-linking agent. 5:1 and where the % are by weight based on the combined weights of, and. After correlation, the analysis may also further involve assigning a weight to individual photon emissions as a function of the correlation.