Separating G_2-invariants of several octonions

We describe separating G_2-invariants of several copies of the algebra of octonions over an algebraically closed field of characteristic two. We also obtain a minimal separating and a minimal generating set for G_2-invariants of several copies of the algebra of octonions in case of a field of odd characteristic.Comment: 20 page

Classification of G_2-orbits for pairs of octonions

Over an algebraically closed field, we described a minimal set of representatives for G_2-orbits on the set of pairs of octonions. As an application, the case of traceless octonions is considered.Comment: 16 pages. Version 2 contains essential extension of the results obtained in version

Effect of microstructure state of titanium alloy Ti-6Al-4V on structure and mechanical properties of joints produced by diffusion bonding process

The studies of diffusion bonded samples of Ti-6Al-4V and Nitinol alloys were carried out considering the titanium alloy in two states: ultra-fine grained and bi-modal microstructures, the last one consisted of small and large a-phase grains. Depending on microstructure and chemical composition of the alloys, the diffusion bonding had been made at temperatures from 600°C to 850°C. The microstructures of joints was studied by scanning electron microscope using detector of backscattering electron diffraction. The shear strengths of joints were measured. It was concluded that the ultra-fine grained Ti-6Al-4V alloy could be applied for joints manufactured at a temperature lower than 750°C. The bi-modal Ti-6Al-4V alloy is an effective material for producing the joints at the temperature larger that 750°

Low temperature magnetoresistance of dirty thin films and quantum wires near a parallel-field-tuned superconducting quantum phase transition

We study the low temperature magnetoresistance of dirty thin films and quantum wires close to a quantum phase transition from a superconducting to normal state, induced by applying a parallel magnetic field. We find that the different corrections (Aslamazov-Larkin, density of states and Maki-Thompson) to the normal state conductivity, coming from the superconducting pair fluctuations, are of the same order at zero temperature. There are three regimes at finite temperatures. In the "quantum" regime, which essentially shows a zero-temperature-like behavior we find a negative magnetoresistance. Since in the "classical" regime the correction is positive, we predict a non-monotonic magnetoresistance at higher temperatures.Comment: Proceedings for SCES conference (2004

Generation of low-temperature plasma by low-pressure arcs for synthesis of nitride coatings

Experiments were performed to study gas, metal, and mixed metal-gas plasmas. The plasmas were generated with the use of an arc evaporator and a gas-plasma source with a hot filament and hollow cathode that were operated independently or simultaneously. It has been revealed that the arc current of gas-plasma source affects the parameters of the metal-gas plasma and the element concentrations in the coatings. It has been demonstrated that the characteristics of the nitride coatings produced by plasma-assisted vacuum-arc deposition can be controlled by varying the parameters of the arc in the gas-plasma source