
34 Friction-Induced Vibration and Self-Organization
Therefore, T
1
> T
2
—in other words, heat ows from the hotter body to the
colder body.
Suppose now that there is no heat ow (dU = 0); however, the mass ow
dN exists between two parts of the system (Figure3.4). The temperatures of
these two sub-systems are equal T
1
= T
2
= T. Then, from the second law,
=
µ
−
µ
>dS
TT
dN 0
12
(3.20)
Therefore, μ
1
> μ
2
and the mass ows from a system with higher chemical
potential to that with a lower chemical potential. Chemical potentials are
widely used to study whether a chemical reaction or a phase transition is
energetically protable.
The rate of entropy p ...