Fibrous inorganic compounds are mainly devided compositionaly into oxide and non-oxide compounds. In the former, silicates including various glasses and optical quartz-fiber, aluminates, zirconia and potassiu hexatitanate, while, in the latter, carbon, silicon carbide and silicon nitride as the typical fiber materials are described for the fabrication processes, properties and apllications.
Although the inorganic fibers are fabricated by various methods, recently, many of them are synthesized as the polycrystal fibers by sintering the precursor fibers obtained from various organic polymers including indispensable metals.
Especial coil-form fibers of carbon and silicon nitride are described, and a new fabrication process of silicon carbide and a new fiber of Si-Ti-C-O composition are also introduced.

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The new mining method named the drawhole-less method, has been adopted recently in Toyoha Mine. The rate of recovery may increase by the new mining method to 84 percent while it was 70 percent by the old mining method in which the drawholes were made every 50 meters upward. However, it was anticipated that an increase of stress concentration in the rock around the openings may have caused fall of hanging rock and failure of rock around the driftsnear the mined area. Hence, before the use of the drawwhole-less system, the authors investigated the mechanical properties of the rock / ore and the deformation characteristic of the material for back-fill and carried out numerical analyses by the Displacement Discontinuity Method, taking the mechanical characteristic investigated into account. Stability ofexcavated the openings by the new mining method was studied. The influence of the new method on rock behaviour around the drifts under the openings was compared to those with the results obtained from the model for the old mining system. In this paper, the results investigated by numerical analyses and behaviour of rock around the mined area, which was observed after mining by the new method completed, are described.

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The subject of underground utilization has enhanced the importance of investigating water flow characteristics of fractured rock masses. The properties of the joints affect not only the normal stress but also the shear stress. However, the study of the water flow characteristic on joints subjected to shear stresses is seldom found.
From this point of view, we designed and developped a new testing apparatus and as well as some systems which areable to test the shear-flow coupling properties up to the residual region of the rock joints. In this paper, the mechanism and characteristics of the new testing apparatus are discribed.
Futhermore, some shear-flow coupling tests are carried out for the application of this apparatus. Artificially fractured granite and sandstone are used for those couplingtests. The hydraulic conductivity of both the rock joints decreases with the normal stressand increases greatly with the shear displacement. The dependence of the hydraulic conductivity is different quantitatively in both the rock joints, since the uniaxial compressive strength of sandstone is smaller than that of granite. Finally, the validity of the coupling tests is checked through a comparison with the model proposed by Barton et al.

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Coarse particles in liquid-solid freight pipelines form a highly concentrated zone or moving bed near the bottom of the pipe and a large part of the energy seems to be dissipated by the particles coming into contact with each other. The DEM (Distinct Element Method) mayprovide some insight into the mechanisms governing dense phase solid-liquid flows. This method can deal with collisions of many bodies and long time contact. The aim of the presentpaper is to apply this method to solid-liquid flows. As preliminary work for simulating solid-liquid flows in a freight pipeline, the motion of descending glass beads (10mm in meandiameter) in water was simulated in an hourglass-like tube. The selection of the DEM modeland the coefficients of interparticle and particle-wall friction are also discussed in this paper. Although there are some slight differences between the simulation and the measurement, the simulation satisfactorily represents the overall motion of descending particles.The DEM proved to be an effective tool for providing an inside view of highly concentrated solidliquid flows.

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In order to diagnose and predict the contaminant transport process in large scale geosystems using a nonlinear filtering strategy the state space model has been derived from simulating horizontal contaminant dispersion by extending the discrete vortex method. The dispersion area S and the dispersion rate S have been taken into account for evolving the state space model of the horizontal contaminant transport process. Eventually, S/S has been found to be represented by a function composed of exponential decay terms, which is transformed to the autonomous state equation and serves as the state space model accompanied with the observation equation. The state equation is extended to involve a noise process corresponding to disturbances such as viscous diffusion and inhomogeneity of the vortex strength as observed in real systems. The parameters involved in the state equation are adaptively estimated from the current state observations using a non-linear filtering algorithm. The state space model has been verified by a series of numerical demonstrations carried out using the discrete vortex method.

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The effects of cations including alkaline, alkaline earth, and transition metal ions on the pyrite dissolution with Fe (III) ions near pH 2 were studied by solution analysis and X-ray photoelectron spectroscopy (XPS). The results showed that Na⁺, K⁺, Ca (II), Mg (I), Ni (II), Zn (II), and Cd (II) ions had no effect, whereas Pb (II), and Ba (II) ions precipitated sulfate ions released from the pyrite; Cu (I) ions suppressed the release of Fe and S species from the pyrite. Pyrite is a soft base by HSAB theory but soft and moderate acids such as Cd (II), Ni (II), and Zn (II) did not adsorb significantly, leading to the absence of suppression. This suggests that the effect of other cations on pyrite dissolution with Fe (III) ions is not always explained by HSAB theory. After dissolutionin the presence of Cu (II) ions, Cu (I) species, very similar to Cu (I) in Cu₂Se, were formed on pyrite. It was presumed that Cu (II) ions were preferentially adsorbed at active sites of pyrite-S over Fe (III) ions and reduced to Cu (I) species becoming stabilized on the pyrite, and leading to the suppression of pyrite dissolution

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The mechanisms of pyrite depression by potassium salts of dichromate and permanganate havebeen inverstigated through flotation tests, measurements of reagent uptake and measurements of redox potential, etc. Both depressants had similar depressing effects and effectivelydepressed pyrite flotation at pH 9. At pH 6, pyrite depression with permanganate was insufficient, while dichromate strongly depressed. Collector (KAX) was found to be mostly consumed irrespective of flotation pH or depressant used. Both depressants oxidized pyrite surface in flotation pulp, resulting in precipitates on the surface of pyrite, which composed of the oxidation-reduction reaction products. When dichromate was used, the amounts precipitated of Cr species at pH 6 where pyrite flotation was significantly depressed was largerthan that at pH 9 where pyrite depression was inferior to pH 6. Also, in the case of permanganate the amounts precipitated of Mn species at pH 9 where significant depression occurred was much larger than that at pH 6 where insufficient depression occurred. Accordingly, it is considered that mechanisms of depression with both depressants were related to the formation of precipitates on the pyrite surface. It was concluded from material balance andEh-value that the precipitates by which pyrite flotation was depressed were basic chromiumsulfate and Mn₂O₃ or Mn₃O₄ in the case of dichromate and permanganate, respectively.

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A direct reduction and distillation of zinc sulfide with metallic iron, which is a new zinc distillation process, is expected to realize both the unnecessary oxidizing roasting andsintering steps and the fixation of sulfur as pyrrhotite, that is, not sulfuric acid. Fromthis point of view, reaction experiments of zinc sulfide reduction with metallic iron under vacuum and kinetic analysis were carried out.
A shrinking unreacted-core model was applied to analyze the reaction data based on the observation of the cross section of partially reacted sample. In the shrinking unreacted-core model, the following steps areconsidered. The first step is the chemical reaction step at the reaction interface, and the permeation step of zinc vapor through the pores of the product layer. The rate parameters such as the chemical reaction rate constant kc at the reaction interface and the specific permeability kp of zinc vapor through the pores of the product layer were determined by numerical solution by means of Runge-Kutta-Gill's method so that the calculated reaction curve could represent the experimental results. The rate parameters are expressed by the following equations
kc=exp {-138.4×10³/(RT) +10.533}
kp=exp {-304.9×10³/(RT) +7.337}
The zinc sulfide could be reduced and distilled with metallic iron, the reaction proceeded faster as the temperature increased. The overall reaction rate is controlled by the permeation step at the lower temperature, while at the higher temperature the chemical reaction step determines the overall reaction rate

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The Kroll process consists of the reduction process in which TiCl₄ is reduced by Mg and the distillation process in which residual Mg and MgCl₂ in the titanium sponge are removed by evacuation. It is well known that the higher the feeding rate of TiCl₄ in the reduction process, the higher the chlorine content in the titanium sponge after the distillation process.
Microscopic study on the residual chlorine in titanium sponge was conducted usingEPMA and EDX. It was found that there were three types ofresidual chlorine: 1) MgCl₂ in micro-cavities in the titanium grains, 2) MgCl₂ in the closed space between the titanium particles and 3) TiCl₂ on the titanium particle surface. Among them, the second type MgCl₂ is ascribed the residual chlorine content. Two routes to from such MgCl₂ in the Kroll process were discussed. One was trapping of MgCl₂ produced by the reduction of TiCl₄ and the other one was MgCl₂ formation via TiCl₂. The correlation between the residual chlorinecontent and the ratio of the TiCl₄ feeding rate to amount of Mg in the reduction vessel could be explained by the both hypothetical mechanisms. It was concluded that theamount of Mg in the vessel is one of the key factors for producing low chlorine content titanium sponge.

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The vacuum distillation process in the Kroll process has been developed to remove residualchlorine from titanium sponge. Despite the efforts to improve the productivity of the process, it takes more than a couple of days to produce desirable quality of the titanium sponge in a commercial scale operation. Though it is important to understand the nature of this process, it is quite difficult because of the complexity of non-linearity in heat transfer and vaporization. The temperature inside the titanium sponge during the distillation process was successfully measured. It revealed that there are two temperature stagnant periods which correspond to the vaporization of Mg and MgCl₂, respectively. It was also found that the penetration of the heat to the center of the sponge cake is a very slowprocess and that it takes more than 30hours.
A mathematical model to describe the heat transfer and vaporization kinetic has been developed. The model can regenerate the temperature measurement data successfully. The model calculation results show that topochemical vaporization of Mg and MgCl₂ and that the vaporization rate is mainly controlledby the heat transferin the titanium sponge. The effect of the operation parameters on the process performance was investigated using the model calculation. It indicates that the reduction in the amount of residual Mg and MgCl₂ would be effective to reduce thedistillation processing time

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Purification of iron oxide obtained from iron precipitation of the Zinc leaching residues with Na₂B₄O₇ flux by use of the recrystallization method and measurement of magnetization characteristics of purified iron oxide have been investigated.
Effects of iron oxide/flux ratio on removal of S, As, Zn and yield of the purified iron oxide crystal, and effectsof S, As, Zn on the magnetization characteristics, that is, saturation magnetization (σ), coercive force (iH_c) and magnetization sensbility (X) were tested.
The main results obtained are as follow:
1) S, As, Zn are removed from 4.45% to 2-30 ppm, from 0.51% to 30-44 ppm, from 0.60 % to about 247-257 ppm by purified treatment, respectively.
2) The yieldof purified iron oxide crystal is about 73 %.
3) S appears to increase σ and x, and to lower iHc. As appears to lower σ and x, and to increase iH_c. Zn appears to increase σ, and to lower iH_c and x.
4) It was recognized that As is large as compared with S and Zn in the effect on magnetization characteristics of iron oxide crystal, and governs magnetization characteristics of iron oxide.

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