Final purpose of this study is to develop a subsystem which constructs three-dimensional numerical system in order to contribute to predictive calculation of output and life of Hot Dry Rock geothermal energy generation. The authors have developed the two kind of the systems for 3D non-steady heat conduction by the direct boundary element methods, the TIME INTEGRAL method and the STEP WISE method. They have carried out numerical calculations by using the system developed and have shown applicability of the system, especially in aiming to high precision and high speed computation. In this report, the outline of the unique procedure of the numerical system developed by the authors is described first, the calculated results on heat conduction in a sphere solid is compared with the corresponding strict solution and accuracy of numerical solution is demonstrated next. Finally, the strict solution of heat conduction in infinite medium around a spherical cavity is originally presented and the numerical solution of it is compared with the strict solution.

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A heading face is usually ventilated by a forcing auxiliary ventilation system with an auxiliary fan and duct, because more heat, gases and dust produced by blasting or machines are liberated in the heading place rather than in other working places. In particular, because the explosive gases such as the methane gas are likely to cause serious disaster, appropriate countermeasures are required in such a heading face. Although a number of studies about the gas diffusion by ventilation at a heading face have been reported, methodical studies are not seen because most of the results are based on assumptions, due to difficulties in measurement of experiments and in theoretical analysis. From this point of view, a theoretical study on the profile of gas concentration at a heading face has been performed by using the CFD code `LASA 96' which is also used overseas based on SIMPLE algorithm. It is shown that the results of simulation coincide with the actual phenomena and can be available to estimate of ventilation including gas in a heading face.

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In order to reduce the longitudinal vibration and axial stress of the pipe string for mining manganese nodules from deep-sea floors by a pump-lift system, the string is assumed to be a two-stepped pipe string with larger diameter in the upper part. Moreover, a buffer and two pump-modules attached to the string are equipped with a vibration absorber. Then, the longitudinal vibration and axial stress caused in the string by the heave-motion of the mining ship are analyzed theoretically for practical cases. The result indicates that the maximum amplitude and axial stress in the uniform pipe string could be reduced by about 55 % and 42 %, respectively if the string were replaced by the two-stepped pipe string with the same mass and with the buffer having a vibration absorber.

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Waste water from mineral processing factories and organic chemical factories usually includes fine solids such as minerals, organic particles and microorganisms which can be removed fastening their settling velocities through flocculation. Generally organic flocculants have been used to treat the fine solids, but it is hard to deal with the obtained sediment because of the moisture including in it. The use of inorganic flocculants is limited because of the tendency of flocculant ions to remain into the clarified water. To cope with these problems, authors have been studying the development of a new method of waste water treatment by hetero-flocculation with fluorite. From the previous study on the treatment of two types of waste water (fluorite flotation tailing and bauxite residue from an alumina refining factory), it is found that artificial fluorite suspension in small quantity is more effective. In this study, the effect of artificial fluorite suspension as flocculant has been investigated using fluorite flotation tailing, organic matter after processing acrylic resin and microorganism after C. O. D treatment. It is noticed that the supernatant concentration of fluorite flotation tailing (height of 32 mm) reduces by hetero-flocculation for a few minutes when a small quantity of artificial fluorite suspension is added. The diluted waste water of organic maters and microorganism on the other hand are flocculated by the addition of a little of an artificial fluorite suspension and each supernatant concentration decreases.

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The authors have already constructed the transfer function model and proposed the control strategy for the cement grinding process. This paper presents the design of multivariable controller for the control systems considered, where the mill grinding property depends on its hold up and the mill dynamics vary with change of clinker grindability. Therefore applicability of the H∞ robust control to this process was investigated. The simplified model at a certain set-point was used as a nominal model of the process. The model deviation was determined based on the variation of coefficient ks of the model obtained by some plant data. The results showed that these transient responses in MIMO system were faster than those of conventional SISO systems. There was no remarkable difference in control performance between the two systems of type？ and type？. It was useful to apply a hierarchy control system in order to prevent the decrease of the product quantity, when clinker grindability decreases. Furthermore the authors studied applicability of a two-degree-of freedom method to type？ and that of a decoupling method to type？ respectively. As a result the transient characteristics in product quality could be improved by the two-degree-of-freedom method. The type？ system could be handled as a group of non interacting SISO systems by the decoupling method and the controller for each loop could be tuned independently.

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Leaching of fluorescent powder containing rare earths using 1N HCl solution at room temperature was conducted to extract the rare earths, followed by dry grinding of the powder using a planetary ball mill. The dry mechanochemical treatment of the powder causes the structural change of the crystals in the powder into a disordered system. This mechanochemical treatment leads to easy extraction of the rare earths. Only 3 minutes of grinding enables us to extract Y and Eu at above 70-80 % yield. More than 80 % of the other rare earths can be extracted from the powder ground for 2-hours. The mechanochemical treatment to the fluorescent powder before leaching would be an effective operation to be able to extract the rare earths at high yield in room temperature leaching even by low concentration HCl solution.

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Thermodynamic consideration of melting of copper based alloys with lanthanum in graphite crucible was carried out at 1,623 ∼ 1,873 K. Solubilities of lanthanum and carbon in liquid copper in the presence of C-LaC2 were determined： Lanthanum solubility in liquid copper under C-LaC2 equilibrium log(CLa/mass %) = 0.476 + 2.17 × 10-4 T (1,623 ∼ 1,873 K) Carbon solubility in liquid copper under C-LaC2 equilibrium log(CC/mass ppm) = 5.14 - 5.80 × 103/T (1,623 ∼ 1,823 K) Based on the result of lanthanum solubility, activity coefficient of lanthanum in liquid copper was calculated： logγLa = -0.306 - 2.25 × 10-4 T - 3.10 × 103/T (1,623 ∼ 1,873 K)

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