set emission amount by surface speed?

[Saca]

hi,
can you tell me how to set emission amount by surface speed?

the scene is, some papers are flying, somes are stopped, somes are slow moving, somes are fast moving.
and they are emit particles like 'tinker bells'.

property_Test(velocity magnitude) is not work in this case, velMag=0 broken?
and one-zero switch is not match in this case.

thanks