Sulfuric acid solution is the most common environment in various industrial processes and it is well known that the ion affect on the rate of corrosion of steels. In this paper, corrosion resistance of mild steels, low alloy steels, stainless steels and Ni-base alloys in such environment, are reviewed based on various studies. Types of stainless steels are developed for the environment and the evaluation of these steels is reported for both laboratory scale and field tests.

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The instability in metal price is a very serious problem in the metal industry. There are many factors such as depletion of mineral deposits and exogenous shocks represented by wars and worldwide business fluctuations determining the phases of price increases or decreases. Resource economists have mainly focused on theoretical models which often ignore unexpected shocks on demand, while mining engineers have regarded exogenous shocks as an important factor to explain metal prices. In this study, a combined model is propos ed. This model was examined by using the actual trends in copper prices between 1945 and 1993. This model predicts that the price of copper will fall in the near future.

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If mine fire occurred underground of a coal mine, some materials would barn at the same time. Therefore, we attempted to measure the mixture smells generated from two different samples using multi-smell detector. We carried out the tests on three combinations of two samples, which were coal-machine oil, coal-belt and beltmachine oil. The results of the Experiment are as follows. The shape of output curves of each smell sensors on mixture smells is similar to the shape of output curve on the smell generated from one of two samples at a certain interval of the temperature of sample.
From the relation between the weight of sample and the output of each smell sensor at 190°C, there are two types of the output value change with the change of the weight of the mixture samples. One is the type which indicates the highest output value at a certain weight of the mixture samples. The other is the type which the output value of smell sensors value decreases or increases with the decrease or increase of the weight of the mixture samples. In this type, the output value of smell sensors indicates the character of the sample of which weight ratio is a bigger one.
Using neural network system, the source of generated gases was distinguished. Thus, this system enables the identification of the source of mixture smells, whether it be generated from the samples of coal-oil, belt-oil and belt-coal, but this system does not enable the identification of the weight of combinaSion samples accurately.

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In this study, drained creep tests under uni-axial compressive load were carried out on Kimachi-sandstone to clarify the creep process and mechanism of the soft sedimentary rock.
During these experiments, axial strain, lateral strain and the Acoustic Emission (AE) activity were observed in the loading time intervals of several minutes to one month.
Furthermore, thin sections for microscope were made of the tested specimens and micro-photographs on these sections were taken by a microscope. On these micro-photographs, using an image processing technique of a micro-computer, numerical data for the changes of pores and micro-cracks at controlled creep time or at prescribed creep region were acquired.
The main results obtained from these tests are as follows; 1) In loading process of the creep load on a rock specimen, firstly the axial strain rate is shown to decrease gradually to a minimum value, after it increases gradually and finally it increases rapidly, and then the specimen is going to fail, 2) In the process of decreasing the axial strain rate, closure of pores in the rock occurs and the compacting of the rock takes place. But, the compressive strength of the specimen, which is unloaded in this loading process, is not affected by the loading time and is almost the same as that of the intact rock, 3) In the process of increasing the axial strain rate, that is after passing through the minimum point of the axial strain rate, cracks in the specimen develop toward the direction parallel to the loading axis. And also, the compressive strength of the specimen, from which load is removed in this process, decreases as compared with that of intact rock.

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Knowledge of the rock stress is one of keys to design and construct rock structures. Thein-situstresses, therefore, have to be accurately measured. Since rock stress measurement is generally time consuming task, the new technique development is being expected to determine the complete stress state from a measurement in a single borehole. Thus, the stress relief method should be improved to meet its demand.
Many stress relief methods to determine the complete state of stress have been proposed and developed. Among these methods, the CSIRO hollow inclusion stress cell has been most popular in the world, since it enables us to accurately measurein-situstresses. The eight-elements strain gauge, the hemispherical shaped strain cell and the conical shaped strain cell have been used in Japan. In these three methods, the conical-ended borehole technique with sixteen-elements conical shaped strain cell has an advantage to reduce the time, effort and cost for a series of rock stress measurements, combining the compact overcoring, the diameter of which equals to that of the pilot borehole.
In the present study, the conical shaped strain cell has been modified and refined to improve the accuracy in rock stress measurement, increasing the number of strain measured on the conical bottom surface of the borehole with a cross typed strain gauge. This paper, firstly, shows how the stress tensor can be determined from the strains on a conical bottom surface of a single borehole. Then the accuracy of the proposed method was compared with that of existing method to confirm that the proposed method gives us more accurate results. Secondly, based on an in-siturock stress measurement, this paper indicates that the proposed method can be more effectively used forin-siturock stress measurements than the existing one. Also, process simulation of the strains and stresses on the conical bottom surface during the stress relieving gave well consistent results with measured data, which indicates that the proposed method is quite reliable forin-siturock stress measurements.

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The purpose of the present investigation is to theoretically analyze the flow characteristics of the air-lift pump for the case where a transitional process from the solid-liquid two-phase mixture flow to the solid-gasliquid three-phase mixture flow by injecting gas-phase into the upriser through a gas-injector is present. The system of equations governing the liquid-solid two-phase mixture flow consists of two mass conservation equations, two momentum conservation equations and an equation for two-phase volume fractions. Again, the gasliquid-solid three-phase flow field after the position of gas injection is solved by three mass conservation equations, three momentum equations, a gas equation of state and an equation for the individual phase volume fractions. The transitions of the flow pattern of gas phase from the bubbly flow to the slug flow and from the slug flow to the churn flow are taken into account in the system of governing equations of three-phase flow. In order to verify the validity of the system of governing equations accounting for the transition of the flow patterns, the flow characteristics calculated on the basis of the present theoretical model have been compared with experimental data by several other investigators. As a result, we have found that the present theoretical model built up in this study gives good fit to the experimental data obtained by several investigators.

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In the few studies devoted to increase the grinding efficiency of a Tower Mill Pulverizer, it has been possible to produce particles finer than 10μm. The problem now is to increase effectively the weight of fine particles in the products. To achieve this goal the weight and particle size distribution of products, and also the electric consumption of the Tower Mill KD-3 were investigated by varying the speed of the stirring screw from 1.08 s^-1to 1.58 s^-1.
The results of the tests can be summerized as follows:
(1) The weight of products in the classifying column and the cyclone, and the electric consumption of the stirring motor increase with the speed of the stirring screw, while the specific energy (J/kg) remains constant.
(2) The particle size distribution of the products in the classifying column and the cyclone are not influenced by the stirring screw speed.

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Leaching characteristics of iron bearing impurities contained in clay mineral, have been investigated by using oxalic acid (OxA). Two types of samples with different particle size fractions (J-A;-16/+100 mesh and J-B;-100 mesh) were prepared for the experiment. The main components of the clay sample were identified to be sericite, α-quartz, and hydrated iron oxides as main contaminants of iron and iron aluminum silicate hydroxide [K (Fe, Al) ₂ (Si, Al) ₄O₁₀ (OH) ₂] as a second phase of Fe-contamination. With a reaction temperature 100°C, aL/S ratio 5: 1, a spin rate of 500 rpm, a reaction time of 120 min., the optimum leaching percentage was obtained at 0.38 mol/l oxalic acid concentration for J-A and at 0.19 mol/l for J-B. Leaching percentages for J-A and J-B were then 83%and 96%, respectively. The substantial removal of iron reached to 86.2% and 89.6% as Fe₂O₃, respectively. Instead of high leaching efficiency of iron from the J-B, it is limited to wash out the leached iron species because of a little adsorption of iron species on the surface of clay. The whiteness of the leached clay with oxalic acid decreased with the higher content of iron in the product. The small amount of magnetic materials remained after oxalic acid leaching, could be removed by weakly magnetic separator and identified a mixture of ferrous oxalate by XRD pattern.

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The extraction of rhodium (III) from hydrochloric acid solutions has been investigated by using a trioctylmethylammonium chloride (TOMAC; R₃R'NCl) under various conditions.
The extraction curve shows a minimum value at about 4 mol dm^-3 in initial aqueous hydrochloric acid solution. The extraction efficiency is promoted in chlorobenzene, nitrobenzene and 1, 2-dichloroethane as diluent and suppressed in carbon tetrachloride and chloroform. At low acidity (≤4 mol dm^-3HCl) both origomer bridged by hydroxyl group and chloro species are extracted, while at higher acidity (≥4 mol dm^-3HCl) the origomer species is principally extracted. The stoichiometric composition of the origomer complex formed in the organic phase was found to be (R₃R'N) ₂Rh₃ (OH) ₄Cl₇ (H₂0) ₃.
The distribution ratio increases with increasing temperature.
In the examination of separation between rhodium (III) and ruthenium (III), the separation factor in the extraction of rhodium chloro species becomes about sixteen times greater than that from the solution containing origomer and chloro species.

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After leaching cobalt crusts in an ammoniacal solution using sulfur dioxide gas as a reductant, the extraction of cobalt was held down in the solvent extraction process. The effects of sulfite ion on cobalt were studied by using nitroso R salt which forms a complex with cobalt. As a result, formation of cobalt complex salt was negligible in the solution of ammonium sulfite and sodium sulfite. It is supposed that sulfite ion acts as a masking reagent for cobalt.
Solvent extraction of cobalt and nickel was carried out using LIX84-I as an extractant for the solution of ammonium sulfite. The effects of the ammonium sulfite concentration and retention time on the extraction of cobalt were investigated. Cobalt (10 ppm) was not extracted from the ammonium sulfite solution of concentration more than 0.5 M and the pH over 10.5. In the same condition, nickel (10 ppm) was extracted completely. Same studies were carried out by using PC-88A and D2EHPA, but superior separation of cobalt and nickel was not attained.
An EDTA titration was carried out by addition of sodium sulfite or ammonium sulfite to the solution including cobalt and nickel. As a result, only nickel was titrated quantitatively inthe mixed solution containing up to 1 mg (20 ppm) of cobalt

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