Magnetic recording medias, e. g. tapes and disks for video and audio, has been making a remarkable advance for these 30 years.
Now, magnetic recording medias are daily commodities, becouse of remarkable improvement of property and cost reduction. Required performance for magnetic tapes are electromagnetic properties and physical properties.
Magnetic recording media gets 1 dB higher output every year. This pace of development has continued over 20 years. This depends on both magnetic materials and process technology of tape.
Dowa Mining Co., Ltd. has started research and development of metal particle from 1978. We filed an application for a patent of metal particle in 1980. 15t/month plant was established in 1983.
Our metal particle was applied for 8mm video tape in 1984. And now, we have a overwhelming share of world market, with 125t/month plant.
We give thanks to our customers who found merits of our metal particle, pointed out its faults, and launched for various metal tapes.

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Complex sinter structure of iron ore was analyzed and characterized with use of high-power and high-resolusion computerized tomography scanner newly developed. Image analysis system for CT figures was enabled (1) to visualize and observe three dimensional structure of inner portion of sinter, (2) to quantify densification degree of sintered parts, (3) to quantify geometric characteristic from the view point of topology and fractal as well as porosity by size, and (4) to simulate gas flow through pores in sintered body. Distinct relationship between pore size and pore type, that means the difference between open and closed pore, was found. By measuring densification degree distribution of inner sintered body, homogeneity of sintering and ratio of insufficiently sintered portion were evaluated.
By analyses of cluster or pore size distribution, structure of iron ore sinter was found to be fractal. Structural changes in cluster and pore size, and densification degree of solid portion, which occur simultaneously during sintering were quantified. These structural changes were found to be ruled by bonding percolation theory. The theory suggests that sintering condition corresponding to the critical point of percolation theory is the best for both gas flow through sintering layer and product yield. Based on the foundings, by checking the fundamentals of experience-based DL process, a new type of feeder, Intensified Sifting Feeder, which ennable to make idealized raw-packed structure was developed, and furthermore reduction of sinter cake load was found to improve permeability with change of pore network.

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This paper describes the optimum control of a ventilation network considering the total cost of the ventilation. Firstly, a basic theory to minimize the total cost of the ventilation is proposed. It leads to a conclusion, that is, the resistance changes required for the control of the network should be minimize to minimize the total cost. Then a practical method to calculate the resistance changes developed by the theory is described. Finally, some examples about the optimum control of a ventilation network are shown. The main features of the method are as follows;
(1) The specified factor of the control model is the total cost of the ventilation that consists of the energy cost for the ventilation and the construction cost for the control.
(2) The required air quantity for a roadway is not a fixed value but a value within some range.
(3) The combination of the roadways to be controled can be selected regardless of the cotree of the ventilation network.

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Landscape evaluation of mined-out quarry becomes necessary from the view point of environmental protection. Computer graphics is useful to simulate landscape changes caused by open-cut mining. We have used a wire frame model and a polygon model to predict changes in the geographical feature of quarry. In this study, we examined the composition of the photomontage of mined-out quarry using an color image processing technology with personal computer. It became possible to present changes in the scene more realistically.
Two psychometrical evaluation tests, rating-scale and selection method, using monochrome and color photomontages as variable stimulus were conducted. The allowable limit of the apparent height of mining slope was revealed to be lower in the evaluation test with color photomontages as compared to the one with monochrome photomontages. This is because mined-out area stood out in respect of color against the surrounding greens. It was considered that the results obtained using color photomontages were more reliable than those using monochrome photomontages.
Cluster analysis was performed using the evaluation results of semantic differential method, which clarified that the factor of landscape evaluation of mined-out quarry changed in distance. Size scale and beauty scale were important when it was seen at a short distance, whereas impression impact was important when it was seen at a long distance.

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Two methods have been applied to investigate the crack behaviors of Inada granite under constant stress and cyclic stress conditions. One method is to analyze the photomicrographs of thin sections prepared from the specimen unloaded at the several loading stages under two confining pressures (0 and 25 MPa). The following results have been obtained. New cracks mainly yield in the initial stage of loading under the creep test and the fatigue test, most of which are parallel to the maximum principal stress direction. In the succeeding stage of loading, new cracks rarely yield. Instead, existing cracks propagate with elapsed time of loading frequently passing through quartz grains.
Another method is to observe directly, with the aid of CCD-camera, the surface of the specimen under uniaxial loading condition. In the fatigue test, opening and closing of the crack in accordance with the loading and unloading are confirmed. During the creep test, stable growth of the open crack toward the loading direction is identified.

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Recently, the oil hydraulic control system has been widely applied to the mining industry, civil engineering and construction industry. Especially, robotized machines have been required to improve laborsaving, safety and production in mining and construction works. The problem of a vibration technique, that is vibration drilling, vibration shearing and vibration pile driver, has been the subject of a great deal of interest in the past few decades. The need to improve efficiency, and maintain economy has prompted the development of new techniques to mining industry and civil engineering such that the cutting or the digging forces are reduced without sacrificing the cost and the size for the oil hydraulic system.
The aim of this study is to design the oil hydraulic vibration cylinder as to a part of the robotized machines. This paper is to investigate the performance efficiency of vibration digging in case that the oil hydraulic vibration cylinder is applied to the hydraulic hoe, and the digging factors of the bucket with by the vibration cylinder are compared with no-vibration cylinder.

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Deposit velocities of gas-liquid-solid mixture flows in a horizontal pipe were experimentally investigated in this study. The following conclusions were obtained through this experiment.
(1) When the volumetric flow rate of air is small, both the deposit velocity and the limit deposit velocity were observed in gas-liquid-solid mixture flows. On the other hand, when the volumetric flow rate of air is large, only the deposit velocity was observed and the limit deposit velocity was not observed.
(2) The velocity at which the pressure loss becomes minimum for gas-liquid-solid mixture flows was larger than the deposit velocity when the volumetric flow rate of air was small. However, when the volumetric flow rate of air was large, it was less than the deposit velocity.
(3) The deposit velocity decreased with increasing the volumetric flow rate of air and showed minimum at a certain air rate. After that, the deposit velocity was almost constant regardless of the volumetric flow rate of air. On the other hand, the limit deposit velocity decreased rapidly with increasing the volumetric flow rate and showed zero at a certain air rate. After that, the limit deposit velocity was not observed.

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In the enrichment culture of the sulfur-oxidizing bacteria collected from an acid mine drainage, we have confirmed protozoa that belongs to Bodo edax. This paper describes an interaction between the bacteria and the protozoa in the presence of cupric ion. The SO₄^2- produced by the bacteria from S0 and the cell numbers of the bacteria and the protozoa were measured as a function of time in the culture containing Cu²⁺ of 0, 1, 10, 100 and 1, 000mg dm^-3. The results obtained were as follow;
(1) the bacterial oxidation rate and the yield factor of the bacteria growth became small due to the protozoa;
(2) in the cultivation of the bacteria alone, the lag phase of the bacteria growth became long over 1 mg dm^-3 of Cu²⁺ concentration but the growth rate was not affected;
(3) in the culture coexisting the bacteria and the protozoa the bacteria grew, but the protozoa did not grow at Cu²⁺ concentration of 100mg dm^-3;
(4) preincupation in the culture containing Cu²⁺ gave the ability to resist Cu²⁺ to the bacteria, but did not to the protozoa.

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Codeposition behaviors of Cu, Cd, Pb, Sn, Ni, Co, Zn and Mo with Fe have been studied in chloride and sulfate baths. The results obtained are as follows:
(1) The single deposition of Fe proceeded with significant overvoltage, the degree of which depended on the type of electrolyte and temperature.
(2) The codeposition of Cu and Cd with Fe was found to be regular type, resulting in higher contents of these impurities in the deposits than in the baths.
(3) The codeposition behavior of Pb from chloride bath was similar to those of Cu and Cd. However, the content of the impurities in the deposits obtained from Pb-containing sulfate bath and Sn-containing chloride and sulfate baths was lowered by the precipitation of Pb sulfate and Sn hydroxide in the baths.
(4) The contents of Ni and Co in the deposits showed lower value. This indicates the anomalous codeposition of Ni and Co with Fe, i. e., the preferential deposition of Fe over the wide range of electrolysis condition.
(5) In the baths containing Zn²⁺, the anomalous codeposition in which less noble Zn deposits preferentially occurred. In this case, the codeposition of electrochemically less noble Zn should be considered to produce high purity Fe.
(6) Mo content in the deposits decreases with an increase in current density to become less than 1% at higher current densities.

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Solvent extraction applied to refining process for platinum group metals (PGMs) offers several advantages over the traditional precipitation methods.
Chloride is the only effective medium in which PGMs can be brought into a solution, thus chlorocomplexes are particularly important in the process chemistry of PGMs separations. Rh (III) chlorocomplex is poorly extracted into organic solvents, which is due to the charge of the complex as well as its labile character in a solution, that is, formation of RhCl₆-_n(H₂O)_n^(3-n)-(n=1-6). The problem of solvent extraction of Rh from chloride solutions has not yet been solved and there is no effective extractant for Rh.
In the present study, the extraction of Rh from hydrochloric acid solutions with substituted 8-hydroxyquinoline (LIX 26) was tested to clarify the effect of addition of SnCl₂ on the extraction and stripping of Rh.The results obtained in this study are summarised as follows:
(1) The extraction efficiency of Rh increased with an increase in the molar ratio of [Sn]:[Rh] and when the molar ratio of [Sn]:[Rh] was more than 10: 1, high extraction efficiency was obtained.
(2) The extraction mechanism of Rh from hydrochloric acid solutions containing SnCl₂ with LIX 26 was discussed and the following extraction reaction was considered.
3HL_o+4H⁺_a+Rh(SnCl₃)₅^4-, a=(H₂L)₃RhH(SnCl₃)_{5, o}
(3) The stripping efficiency of Rh from the organic phase by nitric acid solution was better than that by sulfuric acid solution.

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The platinum group metals (PGMs) are traditionally separated from one another and the other metals by a complex series of selective precipitation techniques. These are generally inefficient in terms of the degree of separation achieved. Solvent extraction applied to refining process for PGMs offers several advantages over the traditional precipitation methods. Adding SnCl₂ to a Rh feed is a good procedure which can be used to make Rh react more easily to extraction.
In the present study, the effect of addition of SnCl₂ on the solvent extraction behaviour of Rh was discussed. The extraction efficiency of Rh increased with increasing the molar ratio of [Sn]:[Rh] and the stripping efficiency of Rh from organic phase by nitric acid solution was better than that by sulfuric acid solution. When the molar ratio of [Sn]:[Rh] increased, the stripping efficiency of Rh became better. The extraction mechanism of Rh from hydrochloric acid solutions containing SnCl₂ was also discussed and the following extraction reaction was considered.
3R₃N_o+4H⁺_a+Rh(SnCl³)₅^4-, _a=(R₃NH)₃RhH(SnCl₃)_{5, o}

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