) are the vectors of discretized DRTs and experimental impedances, respectively. Each vector 𝒙 𝑘 and 𝒁 𝑘 (for 𝑘 = 1,2, … , 𝑁 𝜓 ) can be defined in an identical way as above. As in the fGP model , the distribution of 𝒙 conditioned to the experimental data 𝒁 exp is a truncated multivariate normal such that 𝒙|𝒁 exp ∼ 𝒯𝒩(𝝁, 𝚺, 0, ∞)