Queueing problems are often found in mining operation.
In the open-pit limestone quarry which produces 6200 tons of limestone each day by using the Caterpillar 988 (bucket capacity 4.59 m³)and 15 ton dump-trucks haulage system, queueing technique was applied to analyze the haulage operation and to decide the dump-truck capacity for the system.
Suitable number of trucks for a 1000 meter haulage distance to the crusher from the working face of the quarry was decided 3 to 4 trucks, for the reason of obtaining the lowest haulage cost per ton of limestone.

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Characteristics of aftergases of coal dust explosions were investigated for three high volatile bituminous coals. The apparatus used was a closed-type experimental one (Combustion and Flame 21, 2). Figure 1 shows the schematic diagram of the equipment and Fig. 2 the explosion chamber.
The composition of aftergas is shown on dry base in Fig. 4 to 6. Tars were not analyzed. The trends of H₂, CO, CH₄, and other hydrocarbons are similar to that of the explosion pressure shown in Fig. 3, that is, these gases have the peak near the optimum dust concentration at which the explosion pressure is the highest. Among these gases, CO is the most having the maximum value of about 8%. The concentration of hydrocarbons except CH₄ is less than 1%. In general the descending order of hydrocarbon is CH₄, C₂H₄, C₂H₂, C₂H₆, C₃H₆, C₃H₈, i-C₄H₁₀, and n-C₄H₁₀, and the amount of hydrocarbon decreases by one figure as number of carbon increases by one number. In hydrocarbons of the same carbon number unsaturated compounds predominate.
Regarding the effect of volatile content on the composition, no significant difference was found, although the amount of gases increases with increasing volatile content for increasing aftergas pressure as shown in Fig. 8. The effect of particle size is shown in Fig. 7.
Explosibility of aftergases was analyzed with a computer. The computation program used was the one developed by Yamao and Umezu. Figure 10 is an example of the diagram printed out by the computer. It was found that some aftergas-air mixture were explosive. Results for Ponbetsu coal are shown in Fig. 11. Also, it was experimentally confirmed that some aftergas-air mixtures were really explosive.

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The breakup of turbulent water jets in air is especially of technical importance. A familiar example of application is the effective jet length for the hydraulic fracturing in coal mining. In spite of this importance, there is little understanding of the breakup mechanism, no general theory, nor even a reasonably successful method of correlation in the jet cutting technology.
In this paper, the authors gave theoretical analysis of the breakup characteristics of the water jet atomizer and verified their results by high-speed photography, electric device and laser velocimeter. From the results of such a investigation, the authors proved the relationship between the characteristics of water jets in air and the hydraulic fracturing mechanism.

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The interfacial characteristics of rhodochrosite, which is one of the salt type minerals, were studied mainly in the view point of electrokinetics.
H⁺ and OH^-demand in a rhodochrosite-aqueous solution system was measured by potentiometric titration method. The pH value at the zero H⁺and OH^-demand was pH 7.8 (Fig. 2), and MnCO₃(chemicals) powder also showed the same pH value (Fig. 3).
Rhodochrosite powder was suspended in an aqueous solution adjusted the initial pH value to 4.6, 5.3 or 9.1. And, while stirring, change in pH with time was measured. The results indicated that in any initial pH, after enough time pH would be converging on an equilibrium pH value between pH 7.5 and 7.7. MnCO₃(chemicals) powder suspensions also showed the same result (Fig. 4).
Isoelectric point, indicated by a pH value, was pH 7.6, which was measured by the streaming potential method (Fig. 5).
On the rhodochrosite-aqueous solution system, activities of chemical species at various pH values were calculated on the basis of thermodynamic data (Fig. 6). In Fig. 6 IEP (aq) denotes the condition at zero point of total electric charge of chemical species concerning constituent ions of the mineral. This IEP (aq) was pH 7.8.
Accordingly, on the rhodochrosite-aqueous solution system it became clear that there was a good agreement among pH values at zero H⁺and OH^-demand, equilibrium pH value of the suspension, isoelectric point indicated by teh pH value and IEP (aq).
In determining the potential of rhodochrosite, chemical species playing an important role are Mn⁺⁺and HCO₃^-, and CO₃^--above pH 10, too. H⁺and 0H^-also make an important contribution to determining the potential.
Using sodium dodecylsulphate (SDS) and dodecyl ammonium chloride (DAC) as collectors, Hallimond tube flotation test of rhodochrosite was carried out (Fig. 7). Since the isoelectric point indicated by pH value is pH 7.6, below pH 7.6 rhodochrosite is positively charged, and as shown in Fig. 7, within this pH range SDS, anionic collector, is effective. On the other hand, above pH 7.6 DAC, cationic collector, is effective. Therefore, the adsorption mechanism of this type of collector on rhodochrosite is mainly electrostatic.

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The reduction of right cylindrical pellet of NiO and (Nix Mgr-x) O with CO gas has been studied in terms of kinetic consideration. The experimental data were analysed by the methods based on the unreacted core shrinking model. The observation through scanning electron microscope indicates that number and size of pores or grain form depend upon the reduction temperature. The values of rate parameters Kg' for the NiO pellet are in good agreement with those derived from naphthalene sublimation method. The temperature dependence of effective diffusion coefficient Ds for NiO will be expressed as follows; In Ds (NiO) =-7.59/R.T10³+0.87
The equation is also in good agreement with the equation Ds=DCO-CO₂ εvζ. In case of NiO-MgO pellets, the appearance of reduced layer is different from that of NiO, but the values Ds seems to show similar temperature dependence to the above mentioned. The activation energy for the reduction reaction in case of NiO is about 9.63 kcal/mole. whereas in NiO-MgO system the activation energy is about 70-80 kcal/mole.

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Thermodynamic properties of In, Tl, Cd, Zn, Sn or Pb in their amalgams were analyzed by the potentiometric measurements at high temperatures 150 to 200°C. In the cases of Zn, Pb, and Sn amalgams, their activity coefficients increased rapidly with temperature, but those of In, Tl and Cd amalgams decreased gradually. A difference between a normal amalgam potential for an amalgam and a standard electrode potential for a metal, E*, was studied. It was known that the value of E*indicated a deviation from a value calculated by Raoult's law. A temperature dependence of activity, partial molar enthalpy change, and a concentration dependence of temperature coefficient of e. m. f., partial molar entropy change, were discussed in relation to types of amalgam. It was seen that the potential difference between the metal and its saturated amalgam, Es, for In and Tl was zero while -8 to-2mV for Cd, Zn and Sn. Therefore, In and Ti amalgams were considered as a simple mixture of mercury and each of the metals. On the other hand, Zn, Cd, Sn and Pb amalgams were regarded as a complex such as Hg_xM_ywhich was dissolved in a mercury or a simple mixture of mercury and each of the metals.

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