1 1 1 1 σ 0 <σ< 1 T t t =1,...,T s(t) ˙ s(t)= γu(t)[m - s(t)] - δs(t), s(t 0 )= s 0 , u(t) m γ δ x(t) ˙ x(t)= ρu(t) √ 1 - x(t) - δx(t), x(t 0 )= x 0 .