The initial stress exerted by bulk solids in the vertical-wall section of a bunker depends on the filling rate of solids. The flow stress is independent of the discharge rate of solids, The initial stress is ordinarily smaller than the flow stress. In the range of high filling rate of solids, however, the initial stress is similar to the flow stress. As a result, the upper bound of stresses can be established only and is estimated from the Janssen equation. In this case, the ratio of the horizontal to vertical stress, k, is represented by the equation k=(1-sin²φ)/(1+sin²φ) where φ is the frictional angle between solids and the vertical bunker walls. The stress ratio is therefore smaller than unity in the vertical-wall section of the bunker. The estimated stresses agree with the present data and early data of other sources. The wall coefficient of friction is the most important of the flow properties of bulk solids.

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In order to study the technique of blending gas-atomized steel powders, being liable to size-segregation, the determination of particle size distribution was carried out by using a radioactive tracer. A fraction of 10% cobalt high speed steel powder was activated by neutron in the Hitachi Training Reactor, thus yielding Co-60 to be traced. The activated powder as the tracer was admixed to the remainder by two different mixers, i.e. a ball mill and a static mixer; the composition of the mixtures could be analysed radiometrically.
The static mixer proved to have better blending effect compared with the ball mill, irrespective of local segregation observed during handling of the static mixer.

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The authors derived basic equations which express density current between parallel planes in a settling tank, where the phenomena are treated as two dimensional Problems.
Nondimensional parameters which characterize the phenomena are given, and some applications of these equations are also investigated by numerical calculations after examining this mathematical model by experiments.

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