where Δ Δ V ≥ ≥ 0 , and Δ Δ V ( t = t 1 ) = 0 , Δ Δ V ( t → → ∞ ∞ ) = 0 . Δ Δ V is also referred as the “ Kovacs hump ”. Kovacs also found that the hump displayed some general features: Δ Δ V ≥ ≥ 0 with only one maximum of height Δ Δ V M at a certain time t M ; as the temperature T 1 is lowered, the hump becomes larger, Δ Δ V M increases, and moves to shorter times, t M decreases.