Investigation of Ionospheric Electron Density Change During Two Partial Solar Eclipses and Its Comparison with Predictions of NeQuick 2 and IRI-2016 Models

Wireless Personal Communications - In the present study, the results obtained by incoherent scatter radar (ISR) and empirical models (NeQuick2 and IRI-2016) of the variations in mid-latitude...     

Effect of melting on the acoustic response of CdTe and GaAs subjected to the pulsed laser irradiation

The effect of a threshold process of surface melting on the acoustic response in CdTe and GaAs subjected to pulsed laser radiation is considered and the mechanisms of excitation of sonic signals are analyzed. Melting thresholds of the surface of binary compounds CdTe and GaAs are established under irradiation by pulses of nanosecond duration of ruby and neodymium lasers from measurements of the amplitude of the acoustic response.     

Reduction of Edge Effect in the Adhesive Joint of Pyroceramics

It has been shown that the stress concentration at the joint edges increases with rigidity of adhesive joints of pyroceramics. In view of the fact that the traditional methods are unsuitable for the reduction of stresses at the edges of joints of pyroceramics, we propose a new approach, which ensures reduction of the stress concentration in the edge region. The approach is based on the choice of a law of adhesion interlayer elastic modulus variation which would be a “mirror reflection” of the stress distribution function. The variation of elastic modulus makes it possible to maintain the joint rigidity at the level that is ensured by the constant elastic modulus of the interlayer. A model experiment performed confirms the proposed approach to be effective. __________ Translated from Problemy Prochnosti, No. 6, pp. 79 – 88, November – December, 2005     

Composite materials of diamond−(Co–Cu–Sn) system with improved mechanical characteristics. Part 1. The influence of hot re-pressing on the structure and properties of diamond−(Co–Cu–Sn) composite

We have studied the structure and tribological behavior of composite materials of the diamond–(Co–Cu–Sn) system, which were produced by sintering in molds at 800°C for 1 hour with subsequent hot re-pressing. It is shown that a change of hot re-pressing conditions makes it possible to produce nanocarbide Co₃C in the diamond–metal binder transition zone, instead of particles of structurally free graphite arising during graphitization of the diamond grain surface. The presence of nanocarbide provides an essential improvement of wear resistance of the composites.     

A model of discontinuous precipitation based on the balance and maximum production of the entropy

A model of discontinuous precipitation in supercooled binary polycrystalline alloys at reduced temperatures, taking place as a result of the diffusion-induced grain boundary migration, is constructed with allowance of grain boundary diffusion. The proposed approach allows independent determination of the main parameters, including the interlamellar distance, the maximum velocity of the phase transformation front, and the concentration jump at this boundary. This is achieved by using a set of equations for the (i) mass transfer in the moving interphase boundary, (ii) balance of the entropy fluxes at the phase transformation front, and (iii) maximum rate of the free energy release. The model uses a minimum of thermodynamic information on the two-phase system: the curvature of the Gibbs potential surface in the decomposing phase and the free energy of the interface between the new phases. Theoretical results are compared to the available experimental data.