Solution of the problem of identifying structures of discrete stochastic objects based on the minimum posterior error criterion of distribution densities

The importance of studying methods for solving the problem of identifying structures of discrete stochastic objects has been shown. The general structure of an identification algorithm based on the use of generalized probabilistic criteria has been proposed. The structural identification algorithm is synthesized based on the minimum posterior error criterion of distribution densities. A numerical example that makes it possible to assess the effectiveness of the proposed approach has been considered.     

Oxysulfonation of coke coal by nitrosylsulfuric acid

The interaction of coke coal with nitrosylsulfuric acid NOHSO₄ in acetonitrile at 20–25°C, times to 24 h, and the NOHSO₄/coal ratio R ≤ 50 mmol/g was studied. The process leads to the formation of oxysulfonated coal accompanied by an increase in the weight (to 46%), a decrease (by a factor of 3.8–7.3) in the concentration of radicals, and the formation of the following O-, S-, and N-containing groups in the coal structure: carboxyl, phenol, sulfo groups (≤1.9 mmol/g), and nitroso groups (≤0.9 mmol/g). Changes in the characteristics of oxysulfonated coal under varying R and upon hydrolysis were established by IR and EPR spectroscopy and elemental analysis. The results were interpreted within the framework of a mechanism that included the formation of coal radical cations as a result of electron transfer from coal to the nitronium cation, the intercalation of the bisulfate anion into the coal structure, and the nitrosation and sulfonation of coal arenes. Side oxidation reactions occurred simultaneously with the formation of carboxyl, phenol, and quinoid groups.     

Stress-strain state in the hydrostatic pressing of tubular parts from powder materials and method of calculating mold assembly elements

Conclusions An analysis is made of the mechanism of deformation of sizing shells in mold assemblies during the hydrostatic pressing of tubular parts from powder materials by the radial expansion technique. A plot has been obtained showing the distribution of pressure across the thickness of a part being pressed. A method is proposed for calculating the elements of mold assemblies for the hydrostatic pressing of tubular parts from powder materials by the radial expansion technique.Translated from Poroshkovaya Metallurgiya, No. 12(228), pp. 17–21, December, 1981.     

Alkaline activation of the donbass coals of different ranks

The effect of the rank of coal (C ^daf = 80?95.2%) on the yield and characteristics of activated carbons prepared under the conditions of alkaline activation (800°C, 1 h, Ar) at KOH/coal ratios of 1 g/g was studied. Under these conditions, the ability of coals to form porous materials decreased in the metamorphic series. Grade D coal (C ^daf = 80%) exhibited a maximum activation ability to form a material with S _BET = 1560 m²/g, V _Σ = 0.71 cm³/g, and V _mi = 0.51 cm³/g. A minimum activation ability was found in anthracite (C ^daf = 95.2%), which forms activated carbon with poorly developed porosity (S _BET = 306 m²/g, V _Σ = 0.15 cm³/g, and V _mi = 0.11 cm³/g).     

The T-P-H effects on the magnetoresistance of La0.7Ca0.3Mn1.0O3−δ ceramics and films

Effects of the temperature (T=77–325 K), high hydrostatic pressures (P=0–2.1 GPa), and magnetic fields (H=0–8 kOe) on the electric resistance (R) and magnetoresistance (ΔR/R ₀) were studied in La_0.7Ca_0.3Mn_1.0O_3−δ based ceramics and single crystal films. A significant difference between the magnetoresistance peak temperatures (T _P) observed in the ceramic and film samples is explained by their different deviations from the stoichiometry with respect to oxygen, that is, by a greater concentration of anion vacancies in the film perovskite structure. An increase in the magnetic field strength H and the pressure P leads to a decrease in the electric resistance R. The magnetoresistance grows with increasing field strength H and decreasing pressure P. A growth in the hydrostatic pressure leads to an increase in the T _P value by 12 K for the ceramics and by 40 K for the films.     

Monte Carlo evaluation of derivative-based global sensitivity measures

A novel approach for evaluation of derivative-based global sensitivity measures (DGSM) is presented. It is compared with the Morris and the Sobol’ sensitivity indices methods. It is shown that there is a link between DGSM and Sobol’ sensitivity indices. DGSM are very easy to implement and evaluate numerically. The computational time required for numerical evaluation of DGSM is many orders of magnitude lower than that for estimation of the Sobol’ sensitivity indices. It is also lower than that for the Morris method. Efficiencies of Monte Carlo (MC) and quasi-Monte Carlo (QMC) sampling methods for calculation of DGSM are compared. It is shown that the superiority of QMC over MC depends on the problem's effective dimension, which can also be estimated using DGSM.