Photochromic properties of 1,3,3-trimethyl-6′-nitrospiro (indolino-2,2′-[2H-1]benzothiopyran) in polymeric films

Conclusions An indolinobenzothiopyran with an electron-acceptor substituent- the NO₂ group- in position 6 has been synthesized, and its photochromic behavior in various polymeric matrices has been investigated.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1509–1512, July, 1985.     

Mathematical model of acoustic speech production with mobile walls of the vocal tract

A mathematical speech production model is considered that describes acoustic oscillation propagation in a vocal tract with mobile walls. The wave field function satisfies the Helmholtz equation with boundary conditions of the third kind (impedance type). The impedance mode corresponds to a threeparameter pendulum oscillation model. The experimental research demonstrates the nonlinear character of how the mobility of the vocal tract walls influence the spectral envelope of a speech signal.     

Interface instability of methane hydrate stability zone in permafrost deposits

The method of linear stability analysis is applied to determine the necessary conditions of existence of natural hydrate deposits under Arctic permafrost. It is found that the existence is limited to relatively small thicknesses of the hydrate stability zone and the underlying methane-saturated layer, low-to-moderate permeability of the deposits, and low-to-moderate hydrate saturation. At larger thicknesses, higher permeability, or higher saturation, the interface between the two layers is unstable to small-amplitude perturbations. The results do not support the hypothesis that the interface instability may lead to accelerating meltdown of natural methane hydrates in response to increase in global temperature.     

Modeling of Three-Dimensional Turbulent Jet and Boundary-Layer Flows

New anisotropic algebraic constitutive relations for the Reynolds stress tensor are formulated. These relations make it possible to model correctly three-dimensional turbulent flows which cannot be described on the basis of traditional modern semi-empirical models of turbulence. Along with the well-known nonlinear Saffman term, these relations contain new nonlinear terms which take the wall effect into account. Several two- and three-dimensional turbulent flows are calculated nu\-merically using the averaged Navier-Stokes equations. The calculation results are compared with known experimental data.     

Resonant and Conversion Reflections of Electromagnetic Waves from a Crystal-Metal Interface

The exact dispersion equations describing the resonant excitation of a polariton-plasmon at the crystal-metal interface, which were previously analytically studied within the approximate impedance approach, have been numerically analyzed. The results of an exact numerical analysis and an approximate analytical consideration almost coincide in the long-wave limit (IR region). Conversion arises simultaneously with the resonance: the incident pump wave is completely converted into a polariton of the other polarization branch, which is localized at the crystal boundary, while the amplitude of the reflected bulk wave of the same branch is zero. When passing from the IR range to the visible region, the decrease in the wavelength leads to an increasing difference in the conditions for the existence of resonance and conversion reflections and the height of the resonance peak becomes distinctly smaller than the value predicted by the approximate theory. The parameters of the resonant and conversion reflections have been calculated for optically uniaxial saltpe- ter and calomel crystals with an aluminum coating for the wavelength range of 0.4–5.0 μm.