Electrochemical analysis of the structure and formation kinetics of a porous anodic aluminum oxide

A technique is proposed for an electrochemical study of the morphology of porous anodic aluminum oxide films. The technique involves an analysis of anodic polarization curves recorded while linearly increasing potential. A phenomenological model describing the experimental curves is developed. The method may be used for studying the film formation kinetics     

Features of the motion of a 180° domain boundary in a thin ferromagnetic film with defects

For a thin ferromagnetic film, the braking process of a 180° domain boundary in a field of randomly distributed point defects is studied using perturbation theory. It is established that, for low velocities, the motion of the boundary is nonsteady-state. It is shown that the critical velocity of steady-state motion depends substantially on film thickness and the defect concentration. Fiz. Tverd. Tela (St. Petersburg) 41, 1231–1235 (July 1999)     

Polar properties of Langmuir-Blodgett films of copper phthalocyanines

Langmuir-Blodgett films of amphiphilic copper phthalocyanines are obtained. The Stark effect spectra and the spectra of pyro-and photosensitivity of these films are investigated. The following molecular parameters are determined: changes in the polarizability and the dipole moment for individual absorption bands in the Langmuir-Blodgett films and in an isotropic polymer solution. It is shown that the films obtained have photosensitivity due to the charge transfer in the spectral range 600–900 nm. The pyroelectric effect was observed, which indicates that the films have a polar structure.     

Transitions in three-dimensional XY magnets with two chiral order parameters

Two models of classic XY antiferromagnets in three dimensions are studied by Monte Carlo simulation: the model on a simple cubic lattice with two extra intralayer exchanges and the model on a stackedtriangular lattice with an extra interlayer exchange. In suggested models, the order parameters are magnetization and two chiral parameters. A transition corresponds to breaking ℤ₂ ⊗ ℤ₂ ⊗ SO(2) symmetry. A distinct first order transition is found in both models.     

Construction of an anechoic chamber for aeroacoustic experiments and examination of its acoustic parameters

The acoustic parameters of a new anechoic chamber constructed at Perm National Research Polytechnic University (PNRPU) are presented. This chamber is designed to be used, among other things, for measuring noise from aerodynamic sources. Sound-absorbing wedges lining the walls of the chamber were studied in an interferometer with normal wave incidence. The results are compared to the characteristics of sound-absorbing wedges of existing anechoic facilities. Metrological examination of the acoustic parameters of the PNRPU anechoic chamber demonstrates that free field conditions are established in it, which will make it possible to conduct quantitative acoustic experiments.     

Generation of a strong magnetic field inside a dielectric tube

Experiments on compression of an axial magnetic flux by a plasma liner are conducted with the MIG high-current generator. It is shown that, when the current passing through the liner is about 1 MA, a magnetic field with a strength of up to 50 T and a duration of 300 ns (in the steady state) can be achieved in a dielectric tube 3–4 mm in diameter that is placed on the axis. The physics of magnetic field evolution in the tube is discussed.     

Radiative characteristics of nitrogen upon excitation by volume discharge initiated by runaway electron beam

The amplitude, time, spectral, and energetic characteristics of a volume (diffuse) discharge at an elevated pressure (up to 5 atm) in a gap with an inhomogeneous electric field without an additional preionization source are studied. The concentration and temperature of electrons in the discharge plasma are mea-sured by spectral methods. The effective lifetime of the C ³Π _u state of the nitrogen molecule at the trailing edge of the radiation pulse is shown to be determined by radiative and collisional quenchings. For transitions of the second positive system of nitrogen, a plasma discharge radiation power into the complete solid angle is obtained to be ～120 kW, with a specific radiation power of up to ～50 kW/cm³.     

Superionic fluoride ceramics RF<Subscript>3</Subscript> and R<Subscript>0.95</Subscript>Sr<Subscript>0.05</Subscript>F<Subscript>2.95</Subscript> (R = La,Ce, Pr,Nd) prepared by hot pressing

RF₃ and R_0.95Sr_0.05F_2.95 (R = La, Ce, Pr, Nd) ceramic specimens were prepared by hot pressing at 1173 K under pressure of 3 × 10⁸ Pa for 20 min. The ionic conductivity value was determined by means of impedance spectroscopy in vacuum from 293 to 823 K. For LaF₃ at 350 K, the single crystal / ceramics conductivity ratio is about 5. The difference decreases at higher temperature and disappears about 500 K. The ionic conductivity activation energy is 0.30 ± 0.05 eV. For La_0.95Sr_0.05F_2.95, the conductivity of ceramics below 500 K is slightly lower that of single crystals. At T > 500 K, the conductivity values of ceramic and single crystal specimens practically coincide. The ionic conductivity of hot pressed ceramics is about 10^?2 S/cm at 500 K and activation energy is 0.25 ± 0.02 eV.     

Two-velocity flow containing surfactant

A hydrodynamic theory of two-velocity fluid with surfactant is constructed in the present paper. The model takes into account both surface effects and impact of the concentration gradient on relative velocity of the components. The dependence of the nonstationary two-phase flow regimes on the surface tension gradient and the dependence of the relative drop velocity on the gradient of the surfactant concentration are investigated numerically on the base of volume control method.