A 15-day flow test (Exp. 8805) was conducted at the hot dry rock reservoir created by hydraulic fracturing at the bottom of injection well, SKG-2 at Hijiori test field in Yamagata Prefecture. The depth of SKG-2 well was about 1, 800m and the bottomhole temperature was about 250°C. Water was circulated at the flow rate of 0.5 t/min for first 10 days and then increased to 1.0 t/min. During the circulation test, fluid pressure, temperature and flow rate were measured at the wellheads of injection well, SKG-2 and production well, HDR-1. Production well temperature increased throughout the test and reached a maximum of 175°C, while the water recovery was about 40%.
To evaluate the reservoir performance during Exp. 8805, two models were introduced: one is applied above 1, 500m depth and the other below 1, 500m depth, because we can analyze the performance above 1, 500m as two wells model and must introduce three-dimensional model for the reservoir created in hot dry rock. First, we calculate water temperature in SKG-2 well at the depth of 1, 500m using WBHT (Wellbore Heat Transfer Code). Then, the reservoir performance was simulated by placing two wellbores, SKG-2 and HDR-1 in the finite element mesh of FEHM (Finite Element Heat and Mass Transfer Code) at their relative positions. After the data match to this circulation test, one year simulation was conducted to predict the reservoir performance. Finally, the temperature of production fluid at the wellhead of HDR-1 well was calculated by the WBHT. The results showed that the wellhead temperature of production well reached 180°C and kept almost constant at the flow rate of 0.5 t/min and the recovery of 40%, while it reached 202°C and decreased to 185°C when the flow rate was 1.0 t/min and recovery was 38%.

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All factors affecting the efficiency in hydraulic rockdrills and breakers were studied by using actual manufactured articles with help of PV-diagrams and piston velocity diagrams. Effects of these factors on efficiency were possible to be estimated, though among the factors there was some difference by the type of the drill and of the breaker for volumetric, hydraulic and mechanical efficiency. Hence conclusions obtained were as follows.
It is one of the most important factors for improvement of unavailable flow that kinetic energy of the returning piston is recovered. The recovery of this energy is prevented by fluid resistance for discharging hydraulic oil from the rear chamber of the rockdrill through the valve and by a restriction of the piston for sliding. The piston sliding resistance is mainly due to a tightning force of packing as to mechanical efficiency. The oil flow necessary for shifting the valve is unavailable flow, but may be relevant to the pressure loss in the drill. When we pay no heed to the other drill design requisite it may be the best valve for the efficiency that the sum of the above two losses is minimum.

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A new ball mill with the grinding chamber of V letter shape (V-type ball mill) was produced as an experiment to improve an ability on fine grinding in a ball mill. The ability and optimum operating conditions of the V-type ball mill were investigated. The V-type mill and balls were made of stainless steel. Sample of quartz was utilized to examine the specific surface area as a function of operating conditions.
The optimum revolution speed of the V-type mill was found to be smaller than that of a conventional ball mill, and to agree approximately with that of V-type mixer. Compared with the ability of the conventional ball mill under optimum operating conditions, the ability of V-type mill was superior to the conventional, the specific surface area by V-type mill was about 30% greater than that by the conventional at the same number of total revolution. The improvement on fine grinding is considered to be attributed to an increase in the effects of mixing and agitating in the V-type mill. We can estimate the effectiveness of the reciprocating motion in addition to the revolution motion of balls and sample for fine grinding by ball mill.

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We successfully synthesized ultrafine hydroxyapatite powders by dropping an (NH₄) ₂HPO₄ solution into a vigorously stirred Ca (CH₃COO) ₂ solution at 30°C. They consisted of particles of specific surface area of 293 m₂/g. The particles were rod-shaped and about 10 to 20nm in size. We made differential thermal, X-ray diffractive and infrared spectroscopic analyses of these powders. The presence of a small amount of CO₃^2- ion in the hydroxyapatite powders was detected by infrared spectroscopic analysis. We also examined gas desorption phenomena for the powders. H₂O and CO₂ gases were mainly detected while heating the powders at temperatures up to 800°C in a high vacuum.

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In order to elucidate the rate and mechanism in producing Nd-Fe-B magnetic materials by the R-D process, kinetic experiments in a temperature range between 1, 200K and 1, 400K were conducted for pellets composed of Nd₂O³ powder, Fe wire of 200μm in diameter and CaH₂.
The fractional reduction of Nd₂O₃ obtained by an X-ray intensity of diffraction increased with time nearly parabolically. The reduction proceeded slowly and it may take about 2 hours to complete the reaction even at 1400K. During the R-D process at 1, 300K, the Nd₂Fe₁₇ layer was formed on the surface of Fe wires and the layer thickness obeyed the parabolic rate law, showing that the diffusion of Nd in the Fe wire controlled the rate. However, the higher temperature of 1, 400K or longer reaction time caused dissolution of Fe in the Nd melt.

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Water-quenched samples were collected from the reaction shaft of a pilot scale flash furnace, in which copper concentrate was processed together with silicious sand. The samples were subjected to size distribution measurements and chemical analyses. Based on the results, the following conclusions have been obtained:
(1) The sampling method used in this study can collect not only coarse particles but fine ones equally.
(2) The desulfurization reaction of copper concentrate is not completed in the reaction shaft, but proceeds even in the settler to some extent.
(3) A copper concentrate particle impinges on other particles about 40 times while falling down 4m from the shaft roof to the bath, and its final diameter becomes more than 250μm or 5 times as large as the original diameter.
(4) Such increase in particle diameter is not brought about by the agglomeration of the particles during feeding nor difference in terminal velocity of the particles, but by turbulence in the reaction shaft.

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Floating behaviour of molten copper and matte droplets on slag surface has beeninvestigated using X-ray radio photograph technique in order to clarify the mechanism of the mechanical copper loss. It was experimently found that copper matte droplets of which density is higher than that of slag stably floated on surface of the slag by a surporting force of surface tension of the slag. About 1×10^-3kg of matte droplets floated on an fayalite slag and the profile of it was not spherical but flat because of low interfacial tension between the matte and slag.
The quantitative analysis of floating behaviour was carried out. The profile and amount of floating droplets were calculated using interfacial properties such as surface tensions of the slag and matte and interfacial tensions between the slag and matte. The floating model in this study could explain the floating behaviour of copper matte droplet on an fayalite slag and copper droplet on a sodium silicate slag.

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