Preparation, Structure, and Properties of (Bi,Pb)2Sr2Ca2Cu3O10 + δ Ceramics with Si3N4 Additions

The microstructure, phase composition, texture, and superconducting properties (T _c, T _c, j _c(T), and R(T) at H= 0 and 5 mT) of (Bi,Pb)₂Sr₂Ca₂Cu₃O_{10 +} ceramics (sintering at 840°C for 36 h) with ultrafine Si₃N₄ additions (0.05–0.2 wt %) are studied. The introduction of 0.05–0.1 wt % Si₃N₄ is shown to reduce the width of the superconducting transition by 2–3 K and to raise the critical current density at temperatures below 95 K.     

Temperature field of radioactive isotopes in a porous medium

The asymptotic method in zero and first approximations is used to find formulas for the calculation of temperature fields arising as a result of injection of fluid radioactive waste into porous deep-lying beds. A formula is derived for determining the critical value of Henry coefficient K _cr. It is demonstrated that, at K < K _cr, the contamination front leads the temperature front and, at K > K _cr, it lags behind the latter. Because in actual cases K > K _cr is observed, it is possible to monitor the contamination zone on the basis of temperature measurements in monitor wells.     

Charged Surface of Liquid Hydrogen at Near Zero Gravitation

The results of investigations of the evolution of the shape of the equipotentially charged surface of a liquid hydrogen layer in the external electric field in the case when the effective gravitation acceleration is near to zero are presented. The reconstruction phenomenon—the formation of a solitary wave at the flat charged surface of liquid hydrogen at some critical value of the external electric field—has been studied under the conditions of a total screening of the electric field in the bulk of a liquid by a surface charge. From the results obtained it follows that the transition of the flat surface into the reconstructed state is close to a second order phase transition. A voltage-temperature U–T phase diagram of the charged surface has been determined. The statement of a soft character of the transition has been confirmed also by the results of studies of the oscillations spectrum of the charged surface in electric fields lower and higher the critical value.     

Semantic clustering and affinity measure of subject-oriented language texts

The problem of semantic clustering of subject-oriented natural language texts is discussed. Based on the theory of Formal Concept Analysis, an approach is proposed to determine the measure of semantic affinity of texts.     

Influence of the hole in the blank on the quality and precision of the hole obtained by broaching

The dependence of the final macrogeometry and microgeometry of the machined hole surface on the surface quality of the blank in broaching is investigated by simulation.