Acoustic emission (AE)/microseismic technique is employed in every modern geothermal development as the only means by which direct information about the state of the reservoir can be obtained at locations distant from the wellbores.
The past few years has seen considerable improvement in their ability to analyze and interpret data obtained by the AE/microseismic measurements.But progress must still be made if the technique is to contribute characterizing geothermal reservoirs, providing usable information for borehole physics, rock mechanics and reservoir engineering.

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It is considered that accumulation of the data related with horizontal traveling distance from the foot of a slope of fallen rocks is insufficient, although the data are basically important to determine the positions of concreate structures or net fences for the prevention of rock fall disasters in open pit mines and other places. Relation between kinetic energy of rock falls and the horizontal travelling distances has been given from video analyses on rock fall behaviors in a quarry. Then an evaluation method of the probability value of upper range of optional horizontal travelling disrance is proposed, in which the relations between kinetic energy, and mean value and standard deviation of the distribution of horizontal travelling distances are used.

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Based upon the assumption that core discing results from tensile stresses within and below a core during boring, the direction of the principal tensile stress was analyzed in detail for the stress conditions where core discing is likely to occur to investigate the relationship between the shape of a disced core and in-situ stresses for the case of a long disced core. Main results obtained in this study are summarized as follows:
1) In the central parts of the end surfaces, a relatively flat plane is formed. The azimuth of the normal direction of the plane coincides with that of the minimum principal stress, σ₃ The inclination, φ_m of the normal direction from the core axis is approximately one thirds of that, φ₃ of φ₃. By using the two equations, (1) and (3), a method for estimating more accurate φ₃ (±23%) was proposed.
2) By combining the additional equation, (1) on the magnitudes of σ₃, the mean stress, um and the stress in the direction of the core axis, σ_Z with the previously proposed equation, (2), which is the condition of core discing, two of the above stresses can be determined if φ_m is measured and if one of them is determined independently. For the vertical borehole, by assuming σ_z to be an overburden pressure, um and σ₃ can be determined from the two equations.
2) By combining the additional equation, (1) on the magnitudes of σ₃, the mean stress, and the stress in the direction of the core axis, σ_Z with the previously proposed equation, (2), which is the condition of core discing, two of the above stresses can be determined if is measured and if one of them is determined independently. For the vertical borehole, by assuming to be an overburden pressure, um and σ₃ can be determined from the two equations.
4) When the difference between σ₁ and σ₂ is small, the disced core has almost flat end surfaces.
5) The symmetry in the shape of a disced core coincides with that of in-situ stresses with respect to the axes on the core.
6) A method was proposed to estimate all of the directions of the principal stresses from the symmetry of the disc shape, the normal direction of the central plane and the azimuth of the concave axis or the convex axis when one of the principal stresses is in one of the directions of the core axis and the axes perpendicular to the core axis.

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The paper describes a fundamental investigation of the abrasive wear in rock drilling and cutting. Three laboratory tests of rock abrasivity were carried out and the results were compared with those obtained in fullscale field drilling tests.
The laboratory tests were comprised of drilling test, Taber abrasive test and turning-operation (facing) test developed in the study. The Taber abrasive test was found to be not feasible because of its difficulty in specimen preparation. The modified drilling test and the turning-operation test gave reasonable results. A correlation was demonstrated between abrasivity and unconfined compressive strength for more than fifty rock samples. There was also a rough correlation between the results of the modified drilling test and the turning-operation test.
The field drilling tests were performed measuring height-loss and gauge-loss of a worn bit. The best correlation exists between results of the turning-operation test and the field drilling test.

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In deep-sea mining conditions, abrasion on periphery units of the outlet is predicted at large flow rates of supplied air, because the velocity of solid-phase becomes very large toward the outlet of the conveying pipe owing to very great expansion of the air and corresponding velocities. In this paper, we present flow characteristics of air-lift pumps for deep-sea mining and discuss methods of the countermeasure. That is, some numerical simulations are performed for the flow conditions of air-lift pumps applied one-stepped enlargement pipe in the end part of conveying pipe and/or added excess pressure using back-pressure device at the outlet of conveying pipe. Consequently, it is found to reduce the velocity of solid-phase at the outlet considerably, almost remaining flow rate of lifting slurry. And we demonstrate most appropriate length of enlargement conveying pipe that maximum velocities of solid-phase became equal in main conveying pipe section and enlargement conveying pipe section. As a result, a guideline and fundamental data to design air-lift pumps for deep-sea mining more practically could be shown.

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Cement grinding process control recently requires not only to reduce the specific energy consumption and to stabilize the process but also to improve the final product quality. To achieve these requirements, detailed modelling of the process becomes necessary. However, in most cases the identification model (‘black-box’ model), derived from input/output behaviors of the process, has been used because of complexity of the process.
The authors have carried out the construction of transfer function models based on population balance model of the process. Firstly, the exact transfer function model based on these dynamic model was proposed by using computer software, MATLAB. Secondly, to consider the reduction of the exact model's order and the construction of the transfer function introducing the cut size as an input variable, the simplified model was proposed for the exact one. As the transfer function model of specific surface area as an output variable, the approximated model was obtained by taking account of simulation results and steady-state conditions.
The responses obtained by these simplified models coincided well with those by exact model.

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Decrease of clay resource demands to synthesize clay minerals especially for fine ceramics industry. We therfore have tried to convert Ca-rich plagioclase (An 66-72) from San Chung District, Korea, to kaolin minerals by a hydrothermal reaction with HCl-solution. The plagioclase bearing rocks is known as the mother rock of halloysitic kaolin deposit in Korea.
Relatively low crystalline kaolin mineral was synthesized by hydrothermal conditions such as 0.14mol/l of HCl, below 200°C and at 1.5 MPa. Addition of aluminum chloride is effective to supply aluminum to the sample of plagioclase which is deficient in aluminum component and to accelerate the conversion reaction by the aid of HCl by-product of the conversion reaction.
Electron micrographs showed that kaolin minerals with the crystal size about 1.1μm could be obtained by the hydrothermal reaction for 5 days under those conditions.

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Among nearly thirty types of calcium silicate hydrates, hydrothermally synthesized porous xonotlite is being used as fire resistant building material and heat resister. The molded body can be synthesized to have the necessary bulk density, strength and low thermal conductivity. When the porous amorphous silica (silica balloon) is synthesized through the removal of calcium from calcium silicate, the volume of ultrafine pores increases and the heat conductivity is further reduced. But, during the above process beside silica balloon, the needle shaped aragonite is also obtained. Since the aragonite not porous, the thermal conductivity of the slurry becomes five times that of silica glass. Therefore, to improve the thermal insulation aragonite has to dissolved using hydrochloric acid, a method that is costly and also the reuse of aragonite becomes impossible. In this study, we have examined the viability of separating aragonite and silica balloon using flotation and have arrived at the following conclusions.
(1) When silica balloon and aragonite were floated separately with sodium oleate as collector, the floatability of aragonite was low and silica balloon did not float at all. But, in the flotation of aragonite-silica ballon mixture increment in floatability was observed in the case of aragonite due to large average diameter of the particle and the floatability of silica ballon also increased due to calcium ion activated surface and consequently the separation became difficult.
(2) In the flotation of aragonite only, beside the collector sodium oleate, frother alcohol also was added. The floatability improved when the number of carbon atoms in the alkyl group was more than three. But, in the case of aragonite-silica mixture, silica balloon also floated due to the presence of dissolved calcium ions and the separation was difficult.
(3) At the elevated temperatures the solubility of aragonite decreases leading to a decrease in the calcium ion concentration in the suspension. As a result the separation of aragonite and silica balloon becomes possible at temperatures higher than 353 K using sodium oleate as collector.

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A study on the recovery of metallic components from the spent printed circuit boards (PCBs) was conducted using a shape separation technique. PCBs were pulverized to under 1 mm by a swing hammer type impact mill to liberate vairous metallic components after all electronic parts were removed in advance. The milled PCBs were subjected to the shape separation process using an inclined vibrating plate (IVP) to separate metal particles from nonmetallic components. The effect of vibration intensity and inclined angle on the metal separation efficiency were investigated. The optimum operation conditions for IVP were at the vibration intensity (Kv) of 1.40 and the inclin. ed angle of 10°C. By optimizing the operatiop conditions, it was possible to obtain the recovery and grade of the metallic components over 90%.

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In the hot galvanizing process of steel pipe, so-called zinc dust, contaminated with small amounts of impurities like Fe, Pb and Cd, is generated as a by-product. Ammonia leaching is one of successful processes for recycling zinc dust. In order to improve productivity of the ammonia leaching process, dissolution behaviors of zinc have been investigated in the presence of amminecopper (II) oxidant with OCAL (Oxygen Circulating Ammonia Leaching) method.
The experiments were carried out at 30-40°C and IONL/min oxygen in a 2-litter glass flask with leaching solution of 0-24g/L Cu (II), 0.5mol/L (NH₄) ₂CO₃ and 1.0 mol/L NH₃. It has been found that the dissolution rate of zinc remarkably increases with increasing Cu (II) concentration. Compared with the case in the absence of Cu (II), dissolution rate is speeded up more than 40 times for sheet zinc and more than 10 times for zinc dust in the presence of Cu (II). Further, it has found that the optimum molar ratio of zinc dust to Cu (II) in leaching solution is 1 to 1 for leaching of zinc dust and leaching rate remarkably decreases below or above this value. The dissolution reactions of zinc are proposed as follows.
Zn+[Cu(NH³)₄]²⁺→[Zn(NH₃)₄]²⁺+Cu
Cu+Cu[(NH₃)₄]²⁺→2Cu[(NH₃)2]+4Cu[(NH₃)₂]⁺+4NH₃+4NH₄⁺+O₂→4Cu[(NH₃)₄]²⁺+2H₂O
From the results of this study, it has been proved that combing Cu (II) oxidant with OCAL method is very effective for improving the ammonia leaching process of zinc dust.

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Anode slime formed in the nickel matte electrorefining, which contains elemental sulfur, gives great influences to the anode potential. In this study, the effect of copper content in the nickel matte on the morphology of the anode slime was investigated by measurements of polarization and the electrolysis using the nickel mattes with different copper contents. The following results were obtained.
1) Ni₃S₂ as well as metallic nickel in the nickel matte with high copper content starts dissolution in the beginning of the electrolysis, becaus copper in the matte increases the potential for dissolution of the metallic nickel.
2) Anode potential changes according to the porosity of the anode slime. Since nickel matte with high copper content produces the porous slime, the anode potential increases more gradually compared with the matte with low copper content.
3) Orientation index of Ni₃S₂ in the nickel matte with high copper content is kept at about one during the electrolysis and it means that Ni₃S₂ dissolves uniformly. It is concluded that the uniform dissolution of matte makes the slime layer porous, which suppresses the increase in the anode potential.

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Removal of copper from acidic nickel chloride solution was investigated using nickel matte with different compositions in various conditions. The following results were obtained.
1) Cupric ion in the solution is reduced to cuprous ion by metallic nickel or Ni₃S₂ in matte at the early stage after addition of nickel matte into the solution. Consequently metallic copper or copper sulfide; Cu₂S is formed by the reaction with the matte.
2) Copper is removed as metallic copper when the solution is reduced to below-50 mV of oxidationreduction potential, while as Cu₂S above 150mV.
3) These types of copper removed from the solution change according to the R value, defined as ratio of content of metallic nickel and Ni₃S₂ to amount of copper ion in the solution.
4) The reaction for metallic copper formation is faster than that for the formation of Cu₂S. The difference between the reaction constants for both reactions at 75°C, is approximately ten times.
5) Copper is removed to a lower concentration with addition of both matte and elemental sulfur.

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