An optoacoustic laser detector for gas chromatography

Journal of Applied Spectroscopy -     

Nonlinear absorption of sound by sound at the interaction of waves with multiple frequencies

The role of the phase-dependent nonlinear processes that accompany the interaction of a weak signal wave with an intense pump wave is investigated for the case of the pump frequency being a multiple of the signal frequency. Phase relations that provide the maximum absorption of sound by sound are determined. It is shown that, as the frequency ratio of the waves increases, the role of the phase-dependent absorption rapidly decreases and becomes negligible.     

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     

Mössbauer diffraction in perfect crystals undergoing ultrasonic excitation

The influence of the ultrasonic wave on the dynamic diffraction of the Mössbauer γ quanta in the perfect Si crystals has been studied. Both the scattering intensities and the diffractional Mössbauer spectra for different reflections and ultrasonic frequencesν _s have been measured. Some unusual results such as the enhancement of the elastic scattering at highν _s with ultrasound amplitude growing and non-exponential decrease of the Debye-Waller factor (connected with ultrasonic phonons) at lowν _s have been obtained. The experimental data are in good agreement with the theoretical calculations.     

Rheological characteristics and relaxation properties of polymer-nanodiamond composites

The effect of modifying additives of nanodispersed substances on rheological and relaxation properties of composite materials based on polydimethylsiloxane was examined. The effect of modifying additives on relaxation properties of polymeric composite materials was considered within the framework of elastic strain theory using the Mooney-Rivlin model.     

Application of new numerical algorithm for solving the Navier—Stokes equations for modelling the work of a viscometer of the physical pendulum type

A model is proposed, which describes the work of the viscometer sensor of the physical pendulum type. The model enables the obtaining of data on fluid viscosity directly from the measurement of the settling frequency of sensor oscillations or the amplitude of these oscillations. To describe the sensor operation a numerical computational algorithm is developed. This method enables the solution of a wide class of three-dimensional laminar fluid flow problems involving moving solids of arbitrary geometry. The results of testing the proposed numerical technique are presented.     

The infinitesimal 16th Hilbert problem in the quadratic case

Let H(x,y) be a real cubic polynomial with four distinct critical values (in a complex domain) and let X _H =H _y -H _x be the corresponding Hamiltonian vector field. We show that there is a neighborhood ? of X _H in the space of all quadratic plane vector fields, such that any X∈? has at most two limit cycles. Oblatum 23-III-2000 & 19-VI-2000?Published online: 11 October 2000     

Ion-Assisted α-Al2O3 Coating Deposition by Anodic Arc Evaporation at 500–550°С

Russian Physics Journal - The paper studies the α-phase formation and structure of Al2O3 coatings deposited by the anodic arc evaporation in the low temperature range of...     

Distribution of copper- and nickel-containing modifier components in the pore space of HZSM-5 zeolite

The distribution of copper- and nickel-containing components in the pore space of HZSM-5 zeolite was quantitatively studied. It was found that the detailed distribution of a modifier in the micropore and mesopore volumes of the zeolite depends on both the chemical nature of the modifier and the conditions of supporting and the regime of M²⁺ polycondensation in the pore space of the zeolite. The experimental data on the low-temperature adsorption of nitrogen on Cu(n)ZSM-5 catalysts can be interpreted as the result of the partial filling of the zeolite micropore space (10 vol %) and the finest mesopores with D < 3 nm with the modifier. In the case of Ni(n)ZSM-5 catalysts, the penetration of the modifier into zeolite channels (micropores) in detectable amounts was not found, and it was arranged in mesopores on the surface of zeolite crystallites. The reason for differences between modifier distributions in the pore structure of the zeolite was explained from the standpoint of different structures of copper and nickel polyhydroxo complexes in impregnating solutions after polycondensation. It was found that, in the Cu(n)ZSM-5 and Ni(n)ZSM-5 catalysts, the modifier component contained copper and nickel only in a doubly charged state and mainly octahedral oxygen environments. In this case, three-dimensional nanoparticles or coarsely dispersed particles of CuO were not detected in the pore space of the support, whereas the presence of a small amount of sufficiently large NiO crystals with a coherent-scattering region of 80–100 nm was detected in Ni(n)ZSM-5, and these crystals occurred on the surface of zeolite crystals. It was found that the apparent density of a copper-or nickel-containing component arranged in the pore space of the zeolite was lower than the density of the bulk CuO and NiO phases by a factor of ～3 and 4, respectively, because of the size effect.