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5.2
Establishing a "transport formula"
(1) The net number of particles j flowing out of the volume
∆
V :
dA
j,in-out
j,E,
d
d
d d d
S
N
A E
Ω
= ΩΦ Ω
∫
ur
ur
∆
V
∆
S
j,in-out
j,E,
d
d
dVd d
v
N
E
Ω
= Ω∇Φ Ω
∫
ur
therefore the surface
integral can be
written as a
volume integral:
33