Due to the import of cheap primary energy resources, the German domestic coal mining industry is forced to rationalize the organization and to reduce the production cost. Though the economical situation is stil severe, the new R & Ds and the improvement of practical technologies have been continued in a limited budget range. Many of them are remarkable technolgies to overcome the severe underground mining conditions and to increase productivity and to improve safety performance.
This report summarizes the recent R & Ds and practical technologies developed in German coal mining industries. It includes technologies on coal cutting, roadway drivage, material and man transportation, roadway maintenance, safety devices, utilization of mined-out space and safety management. The tndency of these technologies is described in conclusion.

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Two types of scale-model experiments were conducted to investigate the strata mechanics around the face with longwall face advance.For this study, three-dimensional 1/200 scale models with one and two longwall faces were fabricated to represent the typical longwall panels in the central district at-660 m sea level of Taiheiyo Coal Mine.During these scale-model experiments, the changes of vertical stress with face advance and the plofile of collapsed layers above coal seam was observed.Also the data obtained from the experiments were compared with the data from in-situ measurement at Taiheiyo Coal Mine.
Results were as follows:
The relative distribution of the peak abutment stress in longwall face was obtained.When the face advances equal to the longwall length, it is expected that the peak abutment stess becomes the largest at the center of the face line.Moreover, the peak position of the abutment stress exists within about 50 meters behind the face.
It seems that a vertical section of the collapsed area in the goaf will be approximated by a trapezoidal shape.
The coal pillar formed between adjacent two longwall panels suffers from the double large stress changes with the face approaching and passing.

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The purpose of this study is to clarify the mechanism of the cluster formation in a solid-liquid mixture vibrated by ultrasonic waves. This phenomenon has been explained by two different theories: one proposed by Rayleigh and Schlichting which concerns a steady secondary flow generated by a stationary wave in a tube, and the other by King which is based on sound pressure.
In the present study, the theory based on a steady secondary flow was examined theoretically and experimentally. The results showed that the secondary flow has no significant effect on cluster formation in a solid-liquid mixture. With this result, the upward lift force in highly concentrated particles and gas bubbles was derived theoretically based on the sound pressure and attenuation of the waves.

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Deposit velocities of gas-liquid-solid mixture flows with non-Newtonian fluids 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, the deposit velocity in non-Newtonian fluids is smaller than that in Newtonian fluids. On the other hand, when the volumetric flow rate of air is large, the deposit velocity in non-Newtonian fluids is approximately equal to that in Newtonian fluids.
(2) The effect of slurry density on the limit-deposit velocity is larger than that on the deposit velocity. That is, the limit-deposit velocity decreased with increasing the slurry density to a minimum at a certain slurry density. After that, the limit-deposit velocity increased with increasing the slurry density.
(3) The deposit velocity decreased with increasing the volumetric flow rate of air and showed a minimum at a certain air rate. After it showed a minimum, 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. At higher air rates, the limit deposit velocity was not observed. Furthermore, it was found that the deposit velocity was greater than the velocity at which the pressure loss shows a minimum for gas-liquid-solid mixture flows.

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To enhance the estimation rate of the SEEK (Switching mode Enhanced Extended Kalman) filter algorithm a recurrent neural network is embedded within the SEEK algorithm. The SEEK-FIND (SEEK For Initialisation of Neural Descriptor) algorithm is efficient to estimate state variables in multi-modal nonlinear systems with slowly varying states. When a nonlinear system has regularities, i.e. slowly varying states, and irregularities, i.e. quickly varying states such as bifurcations, the recurrent neural network is applied to estimate the regular states instead of the SEEK filter after trained by one-step delayed estimates of the state variables from the SEEK filter. The SEEK filter is activated again when the system shows irregularities such as bifurcations.The SEEK filter and the neural network are automatically switched by monitoring the maximum estimation error. As a demonstration here, we offer the dual-states Lorenz system with long regular states and the three vortices flow system with bifurcations after taking long term regularities. The latter is simulated by the discrete vortex method as a simple example of multi-modal transport processes in high Reynolds number flows. It has been confirmed that the state variables are accurately estimated by smoothly switching the SEEK filter to the trained neural network and vice versa. The estimation rate is enhanced in the SEEK-FIND algorithm by a few tens times compared with the original SEEK filter algorithm.

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Flash reduction smelting for zinc oxide materials was investigated by using a pilot scale furnace with a smelting capacity of 0.4t/h. At first, a new coke combustion burner was developed to obtain high gasification performance of powdery coke, and then the burner was slightly modified to be suitable for the implementation of the flash reduction smelting tests. The results obtained in this study are summarized as follows.
(1) Gasification of powdery coke was improved by reducing the dimensions of the burner and equipping with sub-mixing pipes for the promotion of the Boudouard reaction.
(2) Zinc content of the final slag was decreased to approximately 1 mass % without the formation of iron metal by use of the burner developed in this study.
(3) Combination of the flash reduction smelting and settler injection technologies resolved such difficulties encountered in this study as poor slag tapping and large thermal load to the reaction shaft lining, resulting in a successful furnace operation.

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Cobalt precipitation by zinc dust with co-addition of arsenious oxide and copper ion in a practical operation was simulated by the experiments using a galvanic cell with a diaphragm and this mechanism for removal of cobalt was explained as follows; a galvanic cell was formed between zinc dust and copper particles, which were precipitated first by zinc dust, and cobalt is deposited on copper particles by this galvanic cell and arsenious oxide in a solution accelerated the rate of precipitation of cobalt by co-deposition of As-Co. The anode side reaction of this galvanic cell is Zn=Zn²⁺+2e^-and a main cathode reaction is 2H⁺+2e^-=H₂ (g). Cobalt is difficult to be precipitated on copper without arsenious oxide. The galvanic current between zinc and copper becomes higher by addition of arsenious oxide. The over potential of the cathode reaction sifts the cathode potential to belower potential than the deposition potential of Co-As, and this C_o-A_seasily deposits on copper cathode with hydrogen.

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A Pb-Ag alloy has been used for an insoluble anode in zinc electrolytic winning. In this investigation, the effect of the Ag content on lowering anode potential in a sulfuric acid solution was examined. Pb-Agand Pb-Snalloys having various compositions, α-PbO₂and β-PbO₂film, Pb-Ag and Pb-Sn cladding materials were produced for use as specimen anode. The potential of α-PbO₂film anode is hardly different from that of β-PbO₂. In other words, the crystal structure of PbO₂has not a great affect on the potential of Pb base alloy anode. In the Pb-Ag cladding anodes oxygen generation occurs on Ag wire in preference to on Pb host metal, although the electrochemical reaction occurs both on Sn wire and on Pb host metal in the Pb-Sn cladding anodes. So, we conclude that the oxygen generation occurs preferentially on the Ag rich portion in the cast structure for Pb-Ag alloy anodes and the territorial expansion leads to lowering the oxygen overpotential, or anode potential.

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The concept of particle assemblage is that intelligent and multi-functional materials can be made of various particles by arranging them at the prescribed positions. The arranging technique of particles on substrates was developed to create new materials by the particle assemblage.
Calcium titanate (CaTiO₃) substrates were scanned by the electron beam along patterns to make electrified marks. The substrates were immersed in an inert solvent in which SiO₂particles were dispersed. The particles were attracted to the electrified patterns by the electrostatic force and arranged along the patterns. We obtained relatively clear arrangement of the particles corresponding to the electrified images by controlling the drawing and the dipping conditions.
The electrification on the substrate, attractive force between the particles and the electrified patterns, and the movement of the particles in the solvent were discussed.

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To clarify the rate and mechanism of the formation of Ce-Fe intermetallic compounds by the reduction-diffusion process, two kinds of experiments were carried out;(1) reduction of pellets consisting of CeO₂and CaH₂and (2) reduction-diffusion reaction of pellets consisting of CeO₂, CaH₂and Fe (powder and wire) in the temperature range from 1, 073 to 1, 373 K. X-ray diffraction revealed that the reduction of CeO₂proceeded rapidly in the initial stage of the reaction and then its rate retarded. The reaction progress was not uniform at 1, 073 K; at this temperature Ca is in solid state. In the reduction-diffusion reaction, both compounds of Ce2Fe17 and CeFe2 were formed at 1, 073 and 1, 173 K, though the formation of CeFe₂was not observed in the long time reaction. At 1, 273 K, only Ce₂Fe₁₇was formed, as expected from the binary phase diagram. The thickness of Ce₂Fe₁₇layer was in a good agreement with that obtained by the reaction of Fe with a melt of which composition was on the F_e-side liquidus line of the Ce-Fe phase diagram and grew in accordance with a parabolic rate law; the activation energy was 265 kJ·Emol^-1.

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