Observation of hydrogen induced intermediate borides in PrFeB based alloys by Mössbauer effect spectroscopy

In the present work, a quantitative analysis of the phase compositions by Mössbauer effect spectroscopy of solid and conventional hydrogen disproportionated Pr_13.7Fe_80.3B_6.0 and Pr_13.7Fe_63.5Co_16.7Zr_0.1B_6.0 alloys was carried out. Significant amounts of intermediate borides t-Fe₃B and Pr(Fe, Co)₁₂B₆ were detected after solid hydrogen disproportionation treatment in Pr_13.7Fe_80.3B_6.0 and Pr_13.7Fe_63.5Co_16.7Zr_0.1B_6.0 alloys, respectively. After conventional hydrogenation–disproportionation–desorption–recombination treatment these phases were not detected and in no case residual Pr₂Fe₁₄B-phase was found. It was observed that the amount of intermediate borides after disproportionation can be correlated with the degree of texture after recombination at various temperatures.     

Relaxation dynamics of a broadband nanosecond acoustic pulse in a bubbly medium

The first experimental observation of the propagation dynamics of a short broadband acoustic pulse in a resonance medium with gas bubbles is carried out. The probing pulse is generated using the optoacoustic effect. It is shown that the theory of short pulse propagation in media with generalized resonance relaxation adequately and accurately describes the dynamics of short pulse dispersion. A possibility to determine the relaxation and resonance parameters of media by the pulsed testing technique is demonstrated.     

The analysis of thermal stresses in thermopiezoelastic semi-infinite body with an edge crack

Summary  Thermopiezoelastic materials have recently attracted considerable attention because of their potential use in intelligent or smart structural systems. The governing equations of a thermopiezoelastic medium are more complex due to the intrinsic coupling effects that take place among mechanical, electrical and thermal fields. In this analysis, we deal with the problem of a crack in a semi-infinite, transversely isotropic, thermopiezoelastic material by means of potential functions and Fourier transforms under steady heat-flux loading conditions. The problem is reduced to a singular integral equation that is solved. The thermal stress intensity factor for a crack situated in a cadmium selenide material is calculated. Received 20 March 2001; accepted for publication 18 October 2001     

Aminomethylation of 1-R-Tetrazoles

The reaction of tetrazole and a series of its 1-substituted derivatives with formaldehyde and alkylamines under mild conditions results in aminomethylation of the heterocyclic ring at the carbon atom with the formation of the corresponding Mannich bases. It was found that strong acids (HCl and CF₃COOH) have an activating action during the process. An ylide mechanism of the reaction was proposed from the data obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 66–71, January, 1991.     

Method of fictitious regions for one class of fourth-order quasilinear elliptical equations

We investigate the application of the fictitious region method to fourth-order quasilinear elliptical equations with Dirichlet and Neumann conditions. Convergence bounds are established for two versions of the fictitious region method.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 56, pp. 21–29, 1985     

New representation of Dirac-Yang-Mills equations

With the help of the apparatus of tensors with values in the Atiyah-Kähler algebra (the apparatus of lambda tensors), a new representation for the relativistic equation of field theory is proposed. The circle of questions under consideration is standard for investigations concerning the theory of the Dirac equation (in this paper, we treat no problems dealing with second quantization).