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[en] In terms of kinetic equations based on the accounting for the temperature dependence of probabilities of multiphonon processes of radiationless relaxation and energy transfer, computer calculations have been made of the temperature dependence of the efficiency of transformation of IR radiation (lambda approximately equal to 1 μm) into visible luminescence of ions Ho³⁺ and Tm³⁺ in yttrium fluoride. The calculation results are in a good agreement with the known experimental data. It has been concluded that the temperature effects in anti-Stokes luminescence of holmium and thulium are due to the temperature dependence of probabilities of multiphonon processes of radiationless relaxation and energy transfer. It has been shown that in the case of Ho³⁺ and Tm³⁺ unlike the Er³⁺ ions, the temperature variations of cross-relaxation probabilities is essential

[en] The temperature effect on the efficiency of transforming infrared radiation into visible in the YF₃:Yb, Er system has been theoretically analyzed. It is shown that temperature dependence of the transformation efficiency is caused by temperature dependence of probabilities of multiphonon processes of radiationless relaxation and electron excitation energy transfer. A conclusion is made that optical modes with intermediate frequencies of the phonon spectrum of the base lattice and values of wave vectors in the vicinity of the Brillouin zone centers participate in multiphonon processes

[en] Numerical analysis of the effect of impurity rare earth elements on blue luminescence of thulium in different temperature ranges is conducted. Temperature dependences of highly excited G₄ level population at the presence of Pr, Nd, Sm, Eu, Tb, Dy, Er and Ho ions are calculated. Impurities essentially affecting the course of temperature dependence of intensity of thulium blue luminescence are determined based on comparison of the calculated results with present experimental data

[en] Computer calculations of the Er³⁺ energy level population in yttrium fluoride and yttrium oxychlorides as a function of the erbium and ytterbium concentration are performed. The calculations are made in the framework of the stepwise sensitization mechanism with account for the erbium cross-relaxation and ytterbium-erbium energy transfer for the pair interactions. The curves for the sup(4)Fsub(9/2) and sup(4)Ssub(3/2) population coincide with the experimental dependences of the red and green Er³⁺ luminescence intensities in oxychloride matrices for tihe dope total concentration of up to 15 mol. %. The population scheme of sup(4)Fsub(9/2) and sup(4)Ssub(3/2) levels is constructed. The red luminescence sensitization and green luminescence quenching effect by ytterbium are demonstrated

[en] This paper describes the effect of ytterbium on the luminescence of yttrium oxychloride with erbium ions at different temperatures. The intensity of the anti-Stokes luminescence was estimated from the integrated emission spectra of erbium. The spectra were recorded with a luminescence apparatus consisting of a grating monochromator with a reciprocal dispersion of 8 A.mm^-1 and an electrometric voltmeter. The authors conclude that over the whole temperature range, Yb³⁺ enhances the red anti-Stokes luminescence of erbium and has a weak quenching effect on the green component. Both enhancement and quenching effects can be described by a model based on cross-relation interactions between pairs of Er³⁺ ions, energy transfer between ytterbium and erbium, and the temperature dependence of the rate constants for all these processes. The authors also observed a strong attenuation of the green emission in the presence of ytterbium, which is caused by additional quenching due to impurities

[en] Numerical computations of the temperature dependence of the ⁵S₂ and ⁵F₅ holmium level populations at excitation in the ytterbium absorption band are performed. Based on the comparison of the experimental and theoretical results, the main channels of the ⁵S₂ and ⁵F₅ holmium levels population are determined

[en] The temperature dependences of the sup( 4)Ssub(3/2) and sup(4)Fsub(9/2) erbium level population in yttrium oxychloride during IR excitation with lambda approximately equal to 1.5 μm are calculated on the base of consideration of temperature changes in the rates of multiphonon processes of intra- and intercentral relaxation of Er³⁺ ions. Relative luminescence intensities of (Ysub(0.9)Crsub(0.1)OCl are measured within the 0.55 and 0.66 μm wavelength band. The behaviour of experimental curves is interpreted on the base of the analysis of different erbium cross-relaxation channel contributions to the luminescent level population

[en] The influence of erbium intercenter relaxation processes on the sup(4)Isub(13/2)-sup(4)Isub(15/2) luminescence in polycrystalline yttrium oxichloride at resonance excitation is investigated. The emission kinetics has been measured for samples with different concentration of impurity ions. The dependence of the sup(4)Isub(13/2) state duration on the erbium concentration for various powers of stationary excitation has been calculated. The values of the luminescence damping constant found from the kinetic measurement data quite satisfactorily fall on the calculated dependence. The calculation and experiment results are interpreted on the base of consideration of pair cross-relaxation inteAactions of Er³⁺ ions

[en] Description is given of mills for manufacturing cold-rolled pipes of large diameters with close diameter and wall thickness tolerances and with good surface quality. The rolling has been mastered of pipes of 08Kh18N10T, 12Kh18N10T, 15KhM, 45, 20, 10, 40Kh and other steels. The introduction of a new method for roll pass design based on mandrels with a parabolic generatrix has allowed to raise mill capacity by 10 to 20%, to prolong the service life of roll passes and to lower the consumption of metal