In order to recover yttrium aluminum garnet (YAG) from slicing dust, flotation separation of YAG from green carborundum (GC) has been investigated by using cationic collector, dodecylammonium acetate (DAA) or anionic collector, Aero Promoter 845#(AP845#).
The point of zero charge of YAG existed at pH 7.5. The floatability of YAG with DAA was high in the alkaline pH range in which YAG surface was negatively charged and low in the acidic pH range in which YAG surface was positively charged. The floatability of YAG with DAA in the acidic pH range increased in the presence of sulfate or oxalate ions. The activation with oxalate ions is attributed to the reversal of the sign of zeta potential from positive to negative in acidic pH range by which DAA is electrostatically adsorbed. On the other hand, it is suggested that the activation with sulfate ions is mainly caused by a chemical interaction between sulfate ions specifically adsorbed on YAG and DAA. YAG was selectively floated from GC by using DAA as a collector, sulfuric acid or oxalic acid as an activator for YAG and corn starch as a depressor for GC. AP845# was specifically adsorbed on YAG surface and enabled YAG flotation in the acidic pH range. By using AP845# as a collector, YAG was floated from GC in the presence of corn starch at pH 2 to 3.

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Two kinds of uniaxial cyclic loading experiments of sandstone were conducted, together with measurements of AE (Acoustic Emission), in order to know the relation between the Kaiser effect of AE and microcracking in the rock. One loading pattern is the cyclic loading shown in Fig. 1, and the other loading pattern is the loading shown in Fig. 2. In these experiments, 8 AE sensors were attached to the surface of the rock in order to determine the spatial distribution of AE hypocenters.
The Kaiser effect of rock was closely related to the microcracking occurring in the rock during the loading of pre-stress. In the case of the loading shown in Fig. 1, Kaiser effect was not clear. This is because the microcracking region in the rock did not grow into the saturated microfractures' condition which was equivalent to the pre-stress. In the case of the loading shown in Fig. 2, however, the Kaiser effect was clearly observed during the loading up to 25 MPa. The result of the spatial distribution of AE hypocenters suggest that the rapid increase of AE over the pre-stress was regarded as the microcracking from the region where AE clusters were formed by the previous cyclic loading.

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Machine stiffness is regarded as one of the important factors in rock cutting, but its effects on cutting performance have scarcely been studied. In this study, a test rig with variable stiffness was designed and manufactured with which a series of cutting experiments were performed.
It was found that the horizontal-vertical (cross) component of compliance matrix has significant importance. If it is negative, the vertical component of cutting force increases and decreases harmonically with the horizontal component during a cutting process. If positive, however, the vertical component increases when the horizontal component decreases, and vice versa. It was also found that machine stiffness has effects on the mean, the mean peak and the maximum values of cutting force. The mean peak and the maximum values increase with stiffness against the force parallel to the bit axis, that is, stiffness corresponding to the sum of the cross and the vertical components of stiffness.

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Copper-nickel sulfide ores from Jinchuan mine in China contain pentlandite, chalcopyrite and pyrrhotite as major sulfide minerals with serpentine and olivine as gangue minerals. Since it is difficult to yield high grade copper and nickel concentrate with low content of magnesium oxide by present bulk flotation, researches for suitable processes to extract copper and nickel from the ores are required. In this study, bacterial leaching of copper-nickel sulfide ores was investigated by using Thiobacillus ferrooxidans isolated from acid mine water.
As copper-nickel sulfide ores have an acid buffering capacity, the optimum initial pH of the leach solution was about 1.0. At the initial stage of the leaching, pyrrhotite was dissolved rapidly by acid.
The extraction of nickel over 90 percent could be achieved, but the extraction of copper was about 30 percent for 34 days of the bacterial leaching. The dissolution of copper was improved by neither using an adapted strain on copper-nickel sulfide ores, nor a Cu-tolerant strain of T. ferrooxidans

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Slag foaming is one of the most important phenomena in bath smelting processes, not only for iron and steel making but also for non-ferrous metallurgy.Mukai, one of authors in the present paper, expected that slag foaming might be caused by high speed evolution of small gas bubbles at the reaction interface such as a slag-metal interface and the bubble size evolued at the interface depends on the interfacial properties such as wettability between both liquids.
Slag foaming behaviours have been directly observed in a carbon-iron silicate slag system and in a carboniron silicate slag-copper system using high temperature X-ray radiograph technique.CO gas evolution rates were also measured at the same time. Large bubbles at the interface between carbon and iron silicate slag were observed due to low wettability in the system, while relatively small bubbles were found in the carbon-iron silicate slag-copper system because CO gas was evolved at the interface between iron silicate slag and Fe-Cu-C alloy.It was also found that CO gas evolution rates in the carbon-slag system were slower than that in the carbon-slag-copper system.
Slag foaming in the latter system occurred in the earlier stage comparing with the fomer system.It is clearly suggested that slag foaming was strongly affected by the interfacical properties of the system.

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In order to investigate a useful application of serpentinite, hydrotalcite-like compounds [Mg_l-_x Al_x (OH) ₂] ^x+ [SO_4x/₂· m H₂O] ^x- were prepared using magnesium sulfate solution obtained from H₂SO₄-dissolution of the ore. The compounds with 0.16≤x≤0.33 were formed as a single phase by coprecipitation method at room temperature. Each recovery of Mg and Al from the starting materials was above 90% for the compounds with 0.22≤x≤0.33. To study the ion-exchange of SO₄^2- for CO₃^2-, the compound with x=0.25 was treated in 0.005-0.1 mol/l Na₂CO₃ solution at room temperature and 50°C for 4 hours. The amount of CO₃^2- in the compound reached 90% at room temperature and 95% at 50°C in 0.1 mol/l Na₂CO₃ solution, respectively.

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This paper deals with the effect of a damper on the dynamic stability and active control of cantilevered pipes conveying fluid. In order to control the response of the cantilevered pipe with a damper, an active control force is derived by the torque produced by a pair of tendons attached to the pipe. The problem is solved by means of the Galerkin method in conjunction with the optimal regulator theory. The combined effect of a damper and a tendon on the critical flow velocity in the uncontrolled system is clarified. Furthermore, the numerical simulation of the response of a pipe conveying fluid is carried out for various conditions, the effect of a damper on the active control of the pipe is also clarified.
The main results obtained are summarized as follows:
(1) The effect of the positions of a damper and a tendon on the dynamic stability of a pipe conveying fluid in the uncontrolled system is complex. In the stabilization of the pipe using a damper, the suitable position of a damper must be decided carefully together with that of a tendon.
(2) In the uncontrolled system, a damper is effective to stabilize the pipe conveying fluid only when the most suitable positions of a damper and a tendon are selected. A damper attached to the pipe at the unsuitable position destabilizes the pipe.
(3) The active control method using a tendon and a damper is effective to stabilize the pipe when they are set at the suitable position. The settling time of the response of the pipe decreases and a damper reduces the active control energy.
(4) The active tendon control method described in this paper is effective to stabilize the pipe, even if the pipe is lost its stability by selecting the unsuitable position of a damper. Therefore, the tendon-control pipe system is robust.

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