Effect of fine structure on mechanical properties of hot-forged powder steels

Comparative analysis of the substructural parameters and mechanical properties of hot-forged steels reveals regular changes in the mechanical characteristics depending on the degree of imperfection. It is shown that higher imperfection at lower forging temperatures of porous billets can increase the strain hardening of particles. The maximum strain hardening of carbon steels is revealed at the maximal structural imperfection and a density of 7.77 g/cm³ after forging a billet heated to 1100°C. The high strain hardening of chromium steel results from high dispersion of coherent scattering regions. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 7–8 (456), pp. 91–99, 2007.     

Evaluation of Tribological Characteristics of Electric-Spark Coatings Prepared on Steel with Electrode Materials of the System TiN - Ni

The tribological and physicomechanical indices of electric-spark coatings of the system TiN - Ni are studied in relation to the phase and structural state of the electrode material. It is established that the optimum tribological properties are exhibited by TiN + (20–40)% Ni material due to forming a eutectic structure consisting of hard intermetallics and a ductile solid solution. It is shown that the ductile component (nickel) makes it possible to deform the coating material without embrittlement. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(443), pp. 43–48, May–June, 2005.     

Fluctuations of queuing processes with semi-Markov (impulse) flows

The problem of diffusion approximation of a queuing process with a semi-Markov flow is solved. In proving a theorem, the solution to a singular perturbation problem is used that is obtained for a compensative operator of a semi-Markov process.     

Dynamics of biometal distribution in breast milk

The results of 352 atomic-absorption measurements of the concentrations of 8 basic biometals in breast milk samples from women of different age were investigated by variation-statistical and correlative analysis. It was found that in all the cases the distribution patterns of biometals were asymmetric. K, Na, Fe and Mn were marked by logarithmic distributions, whereas Ca, Mg, Zn and Cu by power distributions with the index 1/2. That was determined most likely by the physicochemical nature of the mechanisms by which milk homeostasis was controlled. It was shown that in assumption about the normal distribution pattern, commonly accepted in practice, might lead to noticeable errors in quantitative assessments and to erroneous qualitative conclusions. The most probable concentrations of the metals and the width of their distribution showed alterations in time, dissimilar for different metals, including extremal alterations, with the concentrations of the test metals changing 1-5-fold and elementary relations up to 10-fold. For K-Na, Fe-Mn, Zn-Cu and Fe-Cu pairs the interelementary relations of the presumably biochemical nature were discovered, with the stability of those relations being dependent on the time of lactation. The data on variations in the balance of biometals can be used in the design of improved substitutes of breast milk and formula feeding adapted to babies of different age.     

Queuing system evolution in a diffusion approximation scheme

An asymptotic diffusion approximation scheme is investigated as applied to the requirement evolution in semi-Markov queuing systems. In proving the diffusion approximation theorem, the compensating operator of the corresponding extended Markov process is used. This problem is solved with the help of a phase merging procedure. Translated from Kibernetika i Sistemnyi Analiz, No. 3, pp. 136–145, May–June 2009. Original article submitted August 19, 2008.