Reducibility of nonlinear almost periodic systems of difference equations given on a torus

We establish sufficient conditions for a nonlinear system of difference equations x(t + 1) =x(t) + + P(x(t),t)+ to be reducible to the system y(t + 1) =y(t) + . Here, P(x, t) is a function 2-periodic in x_i(i = 1, ...,n) and almost periodic int with a frequency basis .Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 46, No. 4, pp. 404–412, April, 1994.This work was supported by Ukrainian State Committee on Science and Technology.     

Synthesis of an inorganic-organic polymer blend from orthoboric acid and caprolactam

The possibility of modifying boron polyoxide with an oligomeric amide upon thermal dehydration of orthoboric acid and oligomerization of caprolactam in a common melt is shown. The products obtained after thermal pretreatment of the initial blend containing 30 wt % caprolactam are investigated. It is shown that the main processes at T < 200°C are dehydration of orthoboric acid and hydrolysis of caprolactam with the formation of ε-aminocaproic acid. At temperatures of 225–260°C, the predominant process is the formation of boron polyoxide and a caprolactam-based oligomeric product. The data of ¹¹B NMR spectroscopy show that the chemical transformations of caprolactam occur against the background of the N:B donor-acceptor interaction. The two-dimensional [¹¹B-¹H] heteronuclear correlation spectrum indicates that the systems obtained upon thermal treatment are solid solutions.     

Allobetulin Ring A Contraction Effected by Sulfur Diethylaminotrifluoride

Russian Journal of General Chemistry - The action of sulfur diethylaminotrifluoride on 19β,28-epoxyoleanan-3-ol (allobetulin) causes dehydration of the terpenoid and isomerization of the ring...     

Method of delivery of methane from seafloor deposits of solid hydrates to the surface

A model of the process of methane delivery from seafloor deposits of solid hydrates to the surface has been developed and approved. The model considers methane delivery through a vertical pipe lowered from the sea surface to the seafloor deposit. The model allows to determine important characteristics of the flow through the pipe—the possibility of stationary self-sustained flow of the medium to the surface; the gushing character of the flow; medium velocity, pressure, and composition distribution along the pipe—and thus to optimize the process of gas production.     

Synthesis of isotactic polybutene-1 over titanium-magnesium catalysts with polydentate phosphine oxides as external electron donors

The polymerization of 1-butene over the TiCl₄/MgCl₂ (TMC) catalyst with the use of substituted phosphine oxides R _n P(O)(CH₂OR′)_{3 ? n} (R = alkyl, R′ = methyl or acyl, n = 0–2)—new external electron donors-has been investigated. The electron-donating (coordinating) centers in these compounds are the phosphoryl group (P=O) and the oxygen atoms of the substituents at the phosphorus atom. The dependence of the 1-butene polymerization activity of TMC on the nature of the substituents in the phosphine oxides has been studied. The microstructure, degree of crystallinity, molecular weight, and strain-strength characteristics of the synthesized polybutene-1 and the effect of hydrogen on these properties are reported. The most efficient external donor is Me₂P(O)CH₂OAc.     

Structure and Magnetoresistance of Co–Gd and Al–Co–Gd Alloy Films

Technical Physics - Structural data and dependences of the film resistance on magnetic field strength R(H) are presented for Co–Gd and Al–Co–Gd alloy films obtained by vacuum...     

Gas-phase autoignition of a spherical volume of fuel in an oxidative medium

A mathematical model of the ignition of unmixed of fuel and oxidizer (a finite spherical volume of fuel surrounded by an infinite oxidizer medium) was developed. The regularities of the autoignition of this system were examined. It was demonstrated that the temperature maximum arising at the fuel-oxidizer interface propagates with increasing amplitude and velocity toward the center of the spherical volume and that the time it takes to attain the maximum temperature (below the autoignition threshold) and the ignition delay time (above the threshold) depend on the parameter δ nonmonotonically, more specifically, exhibit well-pronounced maxima     

Thermal explosion in a batch reactor charged with a liquid–solid heterogeneous system

The characteristics of a thermal explosion in an ideal mixing batch reactor charged with a liquid–solid heterogeneous system are studied. The reactor initially contains both phases. The solid reagent dissolves and reacts in the liquid phase. A strong dependence of the critical value of the Semenov parameter on the dimensionless time of complete dissolution of the solid reagent is established. It is shown that, at short times of complete dissolution, the critical value of the Semenov parameter is practically independent on this time, and the thermal explosion occurs as in a homogeneous system, according to Semenov theory. The heterogeneous properties of the reaction system manifest themselves only at long times of complete dissolution.