Plastic Strain Localization in Polycrystalline Titanium. Numerical Simulation

Russian Physics Journal - The paper presents numerical simulation of polycrystalline titanium deformation in terms of the crystal plasticity theory. Based on the experimental data, a...     

Singlet-triplet splitting of geminate electron-hole pairs in conjugated polymers

The singlet-triplet splitting of geminate polaron pairs in a ladder-type conjugated polymer has been studied by the thermally stimulated luminescence technique. The energy gap separating the singlet and triplet states of the geminate pairs is measured to be in the range of 3-6 meV, depending on the polymer morphology. The results of correlated quantum-chemical calculations on a long ladder-type oligomer are fully consistent with the observed values of the geminate polaron pair singlet-triplet gap. Such low splitting values have important implications for the spin-dependent exciton formation in conjugated polymers.     

A tandem mechanism of charge-carrier photogeneration in disordered organic materials

A model of tandem charge-carrier photogeneration in disordered organic materials at low excess photon energies above the absorption edge is formulated. It suggests that relaxed singlet excitons dissociate into strongly bound metastable short off-chain geminate pairs. In parallel, triplet excitons can be generated from both primary singlets and short geminate pairs. Owing to a long intrinsic lifetime of triplets, most of them are quenched by geminate pairs and the latter can gain additional energy that facilitates transformation of short pairs into longer ones. This reduces the Coulomb binding energy such that field-assisted full dissociation into free carriers becomes feasible.     

One-step synthesis of substituted 2-amino-5,6,7,8-tetrahydro-4H-benzo[b]pyrans. Molecular and crystal structure of 2-amino-3-(2-methoxyethoxycarbonyl)-4-(2-nitrophenyl)-5-oxo-5,6,7,8-tetrahydro-4H-benzo[b]pyran

Substituted 2-aminobenzo[b]pyrans were synthesized by three-component condensation of aromatic aldehydes, cyanoacetic acid derivatives, and cyclic 1,3-diketones. The molecular and crystal structure of 2-amino-3-(2-methoxyethoxycarbonyl)-4-(2-nitrophenyl)-5-oxo-5,6,7,8-tetrahydro-4H-benzo[b]pyran was established by X-ray diffraction analysis.     

Quasi-periodic bifurcations and “amplitude death” in low-dimensional ensemble of van der Pol oscillators

The dynamics of the four dissipatively coupled van der Pol oscillators is considered. Lyapunov chart is presented in the parameter plane. Its arrangement is discussed. We discuss the bifurcations of tori in the system at large frequency detuning of the oscillators. Here are quasi-periodic saddle-node, Hopf and Neimark–Sacker bifurcations. The effect of increase of the threshold for the “amplitude death” regime and the possibilities of complete and partial broadband synchronization are revealed.     

Influence of Polycrystalline Structure on Dynamic Strength and Fracture Character of an Aluminum Alloy in Different Welding Joint Zones

Russian Physics Journal - Plastic strain localization and fracture in the nugget and thermo-mechanically affected zone of a friction stir welded Al6061-T6 alloy are numerically investigated....     

Application of Information Technologies and Programming Methods of Embedded Systems for Complex Intellectual Analysis

An information model is outlined, which represents an intelligent system of metallographic analysis in the form of a set of subsystems, the interaction of which ensures the performance of metallographic analysis functions. The structure of the information storage subsystem for metallographic analysis is presented. The deployment model of an intelligent metallographic analysis system is proposed and described. The paper outlines the approach to the presentation of an expert subsystem for metallographic quality control of metals based on a neural network. The process of finding a close precedent in metallographic analysis with reference to a multilayer neural network is described. An intelligent metallographic analysis system is described, which based on proposed information model. A specialized software of an intelligent metallographic analysis system is presented. The functioning results of the developed system for processing images of steel microstructures to determine the steel quantitative parameters is presented.     

Hopping approach towards exciton dissociation in conjugated polymers

By employing random walk an analytic theory for the dissociation of singlet excitons in a random organic solid, for instance, a conjugated polymer, has been developed. At variance of conventional three-dimensional Onsager theory, it is assumed that an exciton with finite lifetime can first transfer endothermically an electron to an adjacent site, thereby generating a charge transfer state whose energy is above the energy of that of the initial exciton. In a second step the latter can fully dissociate in accordance with Onsager's concept Brownian motion. The results indicate that, depending of the energy required for the first jump, the first jump contributes significantly to the field dependence of the dissociation yield. Disorder weakens the temperature dependence of the yield dramatically and precludes extracting information on the exciton binding energy from it.     

The mutual synchronization of coupled delayed feedback klystron oscillators

We report on the results of a numerical investigation of the synchronization of two coupled klystron oscillators with an external feedback circuit. Simulation has been carried out using the particle-in-cell method. We have also considered the results of a numerical analysis of an amplifier klystron and an isolated klystron oscillator, which make it possible to choose the optimal values of parameters of coupled klystrons. The structure of the synchronization domain for various parameters has been analyzed. The possibility of increasing the total output power with an appropriate choice of parameter of coupling between the oscillators has been revealed.     

Synthesis of α-tocopherol analogs with unsaturated side chain and their transformation into the corresponding chromans with ω-functionalized side chain

-Tocopherol analogs with double bond-containing side chains were synthesized by condensation of trimethylhydroquinone with optically active (3R/S,4S)-3,4,8-trimethylnona-1,7-dien-3-ol and linalool in the presence of the zeolite-containing Tseokar-10 aluminosilicate. Ozonolysis of these compounds gave the corresponding chromans with -formyl or (after hydride reduction) -hydroxyl groups in the side chain.