Some experiments with the measurement of viscous resistance in rotating liquid helium II show nonlinear dissipation effect at certain critical velocity of rotating cylinder.
Recently S.M.Bhaget and R.K.Pathria have analysed this phenomena on the basis of London's stratifical model.
We attempt to explain the onset of this effect on the basis of Feynman's vortex model.This phenomena would happen at a certain velocity corresponding to which the mean distance among each vortex becomes of the order of correlation length.

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Based on a similar method which was used in a preceding paper a general treatment is given of a system of two interacting different species of spin, one of them being saturated by applying a strong radio-frequency field and the other being detected by a weak radiofrequency field. Two rather different extreme cases are classified according to the relative magnitude of the static strength of interaction to and the characteristic frequency of fluctuation φ0 of the relevant environment.
A) when the fluctuation of the environment dominates (φ0>>σ0), then we are lead to a general “Overhauser effect”, the process of saturation working as a energy pump. B) If, on the other hand, the static strength of interaction dominates (σ0>>φ0), then there results the phenomenon called “saturational narrowing”, the process of saturation working as a local field moderator. The latter case was illustrated with an application to the double resonance in TIF.

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