利用openbugs运算时，出现错误信息“sorry something went wrong in procedure power in module math”。能否帮忙解答下！谢谢！

model
{
  for (i in 1:N)
   {   
     x[i]<-1-exp(-b*d[i])
    pred[i]<-1.3+a*pow(x[i],c)
   
     h[i]~dnorm(pred[i],prec)
  }
  # Priors
  a   ~ dnorm(10.0,1.0E-6)
  b   ~ dnorm(0.05,1.0E-6)
  c   ~ dnorm(1.0, 1.0E-6)
  prec~dgamma(0.001,0.001) # prior for the precision
}