ρ(t)
Q > 1 c(t)
(1 − ρ
3
) ˙c = −3b(t)c
2
+ 3k(t)(1 − c)ρ
2
, c(0) = c
0
∈ [0, 1] ≤ 1,
(Q − c) ˙ρ = −k(t)(1 − c) ρ > 0, ρ(0) = ρ
0
∈ (0, 1),
˙ρ = 0 ρ = 0, t
∗
= min{t : ρ(t) = 0}.
b(t) k(t)
t
∗
b(t)
k(t) t
∗
[0, T ] f (t)
°
°
bc
2
− f(t)
°
°
2
L
2
([0,T ])
→ min .
b(t) k(t)
b(t) k(t)
c(t) ρ(t)
k(t)