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A commercial or industrial large city often develops at the hinterland of a deep bay owing to its high defensibility against stormy sea. However, the exchange rate of sea-water between the inside and the outside of the bay is very low, so that the water is much polluted by industrial and domestic waste water in many cases. The Dokai Bay has also the same social problem. In order to solve the problem we propose an idea of improvement of water quality in this paper, which is that clean sea water of Hibiki open sea is introduced into Dokai Bay. Various conditions for water purifications have been attempted by using the diffusion simulations of COD. It has been clear that introduction of clean sea water (3m3/sec.) into the innerpart of Dokai Bay is very effective for purification.

Columbite series and disordered mossite series minerals were synthesized by solid state reaction. In addition, its properties on are dressing were measured. The results are as follows.(1) Disordered mossite series minerals (FeNbxTai-xO4) were formed by solid state reaction of Fe2O3-Nb2O5-Ta2O5 series

In order to investigate the effects of ore grade and pulp density on the on-stream analysis of" Kuroko" pulp density.Several results obtained from the experiment and theoretical consideration are as follows:1) The characteristic X-ray intensities vary with the change of both grade and pulp density. The intensity is proportional to the amount of element in question present. If the variation in pulp density is in enough small range, the calibration curve can be considered to move parallel.2) The decrease of characteristic X-ray intensities is proportional to the amounts of co-existent elements, if the other conditions remained same. This effect can be calculated from the amounts of co-existent elements, mass absorption coefficients and pulp density.3) The intensity of Sb-Ka(pulp density monitor) is affected with a change of ore grade as well as pulp density.

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