emitter    = scene.getEmitter("Circle02")
particle   = emitter.getFirstParticle()

while (particle):
emitterSpeed     = emitter.getParameter("Speed")

 if(emitterSpeed >= 200):
     new_velocity = Vector.new(0.0, 0.0, 0.0)
     particle.setVelocity(new_velocity)

 particle = particle.getNextParticle()