Influence of the Structure of Cetyltrimethylammonium Bromide Based Microemulsions on Base Hydrolysis of Carboxylic Acid Esters

The structure of water/cetyltrimethylammonium bromide/n-butanol/hexane microemulsions was studied by conductometry, viscometry, and Fourier transform ¹H NMR spectroscopy with pulse magnetic field gradient. The regions of phase inversion from inverse micelles in hexane through a bicontinual structure to a dispersion of normal micelles in water were determined. The influence of the structure of the microemulsions on the rate of hydrolysis of carboxylic acid p-nitrophenyl esters was analyzed. The hydrolysis rate constants considerably increase in going from inverse to normal microemulsions.     

The self-similar problem of the diffusion mixing of vapour–gas–condensate systems

Self-similar solutions of the problem of the diffusion mixing of vapour–gas–condensate mixtures, which is a generalization of the Stefan problem, are constructed. It is established on the basis of the solution of the problem concerning the mixing a vapour with a gas that, depending on the initial temperatures, mixing can occur with the formation of an intermediate vapour–gas–condensate layer. A chart of the possible structures of the mixing zones of a vapour–gas–condensate system with a vapour-gas mixture is obtained.     

Approximation algorithm for the problem of partitioning a sequence into clusters

We consider the problem of partitioning a finite sequence of Euclidean points into a given number of clusters (subsequences) using the criterion of the minimal sum (over all clusters) of intercluster sums of squared distances from the elements of the clusters to their centers. It is assumed that the center of one of the desired clusters is at the origin, while the center of each of the other clusters is unknown and determined as the mean value over all elements in this cluster. Additionally, the partition obeys two structural constraints on the indices of sequence elements contained in the clusters with unknown centers: (1) the concatenation of the indices of elements in these clusters is an increasing sequence, and (2) the difference between an index and the preceding one is bounded above and below by prescribed constants. It is shown that this problem is strongly NP-hard. A 2-approximation algorithm is constructed that is polynomial-time for a fixed number of clusters.     

Structure and Mechanical Properties of a Dispersedly Filled Transparent Polycarbonate

Mechanics of Composite Materials - The structure and mechanical properties of a composition on the basic of polycarbonate filled with three types of dispersed particles (submicron corundum, micron...     

Self-organization of poly(methyl methacrylate) and polystyrene macromolecules functionalized by fullerene C60

Poly(methyl methacrylate) and polystyrene functionalized by fullerene C₆₀ tend to form micellar structures comprising a fullerene cluster as a core and a macromolecular shell. Films prepared from PMMA-C₆₀ and PS-C₆₀ micellar solutions are polymer matrices with fullerene-containing globular structures uniformly distributed in the polymer bulk.     

Fullerene-containing polymers: UV spectroscopic study

A spectral method is developed to determine the content of fullerene in polymers formed in its presence during the free-radical polymerization and copolymerization of methyl methacrylate, allyl methacrylate, allyl chloride, and styrene. The method is based on measurement of absorption coefficients for the ?Ц?*-excited transition of fullerene cores at 330 nm that is due to their insertion into a polymer chain and the related distortion of the closed polyene system of carbon-carbon bonds.     

Polyethylene glycol monomethyl ethers as the main component of brake fluid

The main physicochemical properties of polyethylene glycol monomethyl ethers in a wide temperature range were determined. The effect exerted on the main quality indices of brake fluids by the introduction of polyethylene glycol monomethyl ethers borates was studied. The use of these ethers as the main component of DOT-5.1 brake fluids was analyzed.     

A posteriori joint detection of a recurring tuple of reference fragments in a quasi-periodic sequence

The problem of joint detection of a recurring tuple of reference fragments in a noisy numerical quasi-periodic sequence is solved in the framework of the a posteriori (off-line) approach. It is assumed that (i) the total number of fragments in the sequence is known, (ii) the index of the sequence member corresponding to the beginning of a fragment is a deterministic (not random) value, and (iii) a sequence distorted by an additive uncorrelated Gaussian noise is available for observation. It is shown that the problem consists of testing a set of simple hypotheses about the mean of a random Gaussian vector. A specific feature of the problem is that the cardinality of the set grows exponentially as the vector dimension (i.e., the length of the observed sequence) and the number of fragments in the sequence increase. It is established that the search for a maximum-likelihood hypothesis is equivalent to the search for arguments that maximize a special auxiliary objective function with linear inequality constraints. It is shown that this function is maximized by solving the basic extremum problem. It is proved that this problem is solvable in polynomial time. An exact algorithm for its solution is substantiated that underlies an algorithm guaranteeing optimal (maximum-likelihood) detection of a recurring tuple of reference fragments. The results of numerical simulation demonstrate the noise stability of the detection algorithm.     

Estimation of kinetic parameters for curing of epoxy-anhydride compositions by DSC

The kinetics of the curing process of epoxy resin (ED-22) in the presence of the anhydride hardeners (iso-methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, and dodecylsuccinic anhydride) and accelerators (2-methyl imidazole and n-butyltriphenylphosphonium bromide) has been investigated by DSC method in the dynamic mode. Processing of experimental DSC thermograms recorded at different heating rates was carried out within the frameworks of isoconvertional analysis in two versions, namely "model-free" method of Friedman and the Ozawa—Flynn—Wall method. The possibility to describe the kinetics of epoxy compositions curing in the frameworks of one-step autocatalytic reaction model has been demonstrated. Obtained kinetic parameters were used to predict the curing kinetics under isothermal conditions and for comparative analysis of the compositions.     

A Randomized Algorithm for a Sequence 2-Clustering Problem

Computational Mathematics and Mathematical Physics - We consider a strongly NP-hard problem of partitioning a finite Euclidean sequence into two clusters of given cardinalities minimizing the sum...