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New semimagnetic semiconductor Hg0.91Mn0.09Te-MnSe mixture, grown by Bridgman method, was investigate by Atomic Force Microscopy, X-ray and far-infrared spectroscopy, in order to obtain the necessary feedback information to determine the optimal conditions for crystal growth. The investigated mixture consists of MnSe nanoclasters randomly distributed in Hg0.91Mn0.09Te matrix. Far-infrared reflectivity spectrum of the Hg0.91Mn0.09Te-MnSe mixture was measured in the 80-500 cm(-1) range at a room temperature. The analysis of the far-infrared spectrum was made by the fitting procedure. The Maxwell-Garnett effective medium theory is used for modeling an effective dielectric function, and on that way calculating both electron and phonon response.

Ultrafine nickel-ferrite materials were prepared from complex compounds with acetylacetonato-ligands, according to a previously developed method. The influence of different atmospheres (air, oxygen and nitrogen) applied during thermal decomposition of precursors was studied. Thermal decomposition was carried out with the heating rate of 10 degrees C/min and the cooling rate of 20 degrees C/min. Characterization of the final products was performed by X-ray and TEM analysis. Reviewing the products, we concluded that the optimal temperatures for the preparation of pure ultrafine ferrite materials were 400 degrees C for air atmosphere, and 500 degrees C for O-2 and N-2 atmospheres. All samples prepared at lower temperatures show the presence of the nickel-phase, while all samples prepared at higher temperatures show the presence of the hematite-phase.

Nickel and nickel-zinc ferrites are ones of the most abundant members of the soft magnetic materials. In the last few years, the interest in new methods of their preparation increases, because it is well known that the physical and chemical properties of these materials strongly depend on the preparing conditions. Powder samples of soft ferrites of NiFe2O4 and NixZn1-xFC2O4 were synthesized by a classical sintering procedure, planetary mill synthesis, and by a chemical procedure from complex compounds with acetylacetonato-ligands. Average particle sizes were 1 mum, 40 nm and 20x20x4 nm (slabs), respectively. All of the obtained materials were measured ill the frequency range of 7 - 12 GHz for the real and the imaginary part of permittivity and permeability, and the absorption coefficients were calculated. A concurrent analysis of the obtained values showed the influence of the method of synthesis, as well as the particle size on the absorption coefficients in the applied frequency range.

Reserves of several million tons have been found at the deposit, in Yugoslavia. Mn flotation was carried out from the deslimed tailings of the collective flotation of the sulphide minerals, using emulsions of oleic acid and emigol as collectors. A sample of ore containing 0.36% Pb, 1.71% Zn, 18.84% Mn and 9.40% Fe was used for laboratory testing of flotation of Zn, Fe and Mn minerals, heavy media separation and high intensity magnetic separation of Mn- and Fe-carbonates. A concentrate was obtained grading 26.37% Mn, 8.80% Fe and 0.28% Zn with Mn recovery of 78.76% and total Fe of 60%. Heating this concentrate at 950 degrees C gave a product containing 36.97% Mn, 13.18% Fe, 0.50% Zn, 0.15% Pb and 0.97% S. From the nonmagnetic fraction by flotation (with one cleaning stage) the Zn concentrate had 51.43% Zn, and from the magnetic fraction 45.23% Zn (with two cleaning stages) was obtained. The combined Zn concentrate contained 46.70% Zn., Reserves of several million tons have been found at the deposit, in Yugoslavia. Mn flotation was carried out from the deslimed tailings of the collective flotation of the sulphide minerals, using emulsions of oleic acid and emigol as collectors. A sample of ore containing 0.36% Pb, 1.71% Zn, 18.84% Mn and 9.40% Fe was used for laboratory testing of flotation of Zn, Fe and Mn minerals, heavy media separation and high intensity magnetic separation of Mn- and Fe-carbonates. A concentrate was obtained grading 26.37% Mn, 8.80% Fe and 0.28% Zn with Mn recovery of 78.76% and total Fe of 60%. Heating this concentrate at 950 degrees C gave a product containing 36.97% Mn, 13.18% Fe, 0.50% Zn, 0.15% Pb and 0.97% S. From the nonmagnetic fraction by flotation (with one cleaning stage) the Zn concentrate had 51.43% Zn, and from the magnetic fraction 45.23% Zn (with two cleaning stages) was obtained. The combined Zn concentrate contained 46.70% Zn.

Results of tests of improvements to the technology of lead-zinc flotation at the Blagodat plant are presented. The results were applied in the plant and gave a 10% increase in lead recovery, which was achieved by the introduction of an independent cell in the grinding process and flotation of oxide lead minerals in addition to higher lead recovery rates. The processing capacity was also increased by 16% with a reduced consumption of flotation reagents., Results of tests of improvements to the technology of lead-zinc flotation at the Blagodat plant are presented. The results were applied in the plant and gave a 10% increase in lead recovery, which was achieved by the introduction of an independent cell in the grinding process and flotation of oxide lead minerals in addition to higher lead recovery rates. The processing capacity was also increased by 16% with a reduced consumption of flotation reagents.

Flotation concentration yields lead, zinc and pyrite concentrates, and tailings may be successfully used for the production of silica bricks., Flotation concentration yields lead, zinc and pyrite concentrates, and tailings may be successfully used for the production of silica bricks.

The benefits are discussed of pressure grouting for the pres-stressing of the concrete linings in hydraulic tunnels with reference to its use in the supply-drainage tunnel at the Bajina Basta pumped storage plant in Serbia. The circular cross-section tunnel runs through the Tara Mountain massif and its overall length is 8 030 m. The tunnel was excavated using a 7 m diameter tunnel boring machine, and pressure grouting was employed along the first 5 700 m to ensure water impermeability, with backfill grouting used along the remaining 2 300 m. An analysis is presented of the state of stress of a concrete lining obtained by the superposition of normal stresses due to the internal effects of water and temperature changes and the external effects of the grouting pressure. Rock mass studies were carried out based on refractive seismic, geo-electrical and rock mass deformability tests. Pressure grouting was carried out using injection boreholes around the cross-section of the tunnel. Tests were conducted before and during grouting and during the relaxation period and after the tunnel was put into operation, and additional pressure grouting carried out at locations where the required level of pre-stressing had not been achieved. A water loss investigation method was developed based on a mathematical model for the effects of parameters including internal water pressure, piezometric head and the temperature of the concrete lining. Water losses have been reduced from 120 to the current 20 l/s., The benefits are discussed of pressure grouting for the pres-stressing of the concrete linings in hydraulic tunnels with reference to its use in the supply-drainage tunnel at the Bajina Basta pumped storage plant in Serbia. The circular cross-section tunnel runs through the Tara Mountain massif and its overall length is 8 030 m. The tunnel was excavated using a 7 m diameter tunnel boring machine, and pressure grouting was employed along the first 5 700 m to ensure water impermeability, with backfill grouting used along the remaining 2 300 m. An analysis is presented of the state of stress of a concrete lining obtained by the superposition of normal stresses due to the internal effects of water and temperature changes and the external effects of the grouting pressure. Rock mass studies were carried out based on refractive seismic, geo-electrical and rock mass deformability tests. Pressure grouting was carried out using injection boreholes around the cross-section of the tunnel. Tests were conducted before and during grouting and during the relaxation period and after the tunnel was put into operation, and additional pressure grouting carried out at locations where the required level of pre-stressing had not been achieved. A water loss investigation method was developed based on a mathematical model for the effects of parameters including internal water pressure, piezometric head and the temperature of the concrete lining. Water losses have been reduced from 120 to the current 20 l/s.

In the course of operation of Veliki Majdan flotation plant difficulties arose in selective flotation of zinc and pyrite minerals. After laboratory tests the plant was reconstructed and more satisfactory recovery rates and concentrate grades were achieved., In the course of operation of Veliki Majdan flotation plant difficulties arose in selective flotation of zinc and pyrite minerals. After laboratory tests the plant was reconstructed and more satisfactory recovery rates and concentrate grades were achieved.