Abstract: The effect of Raman scattering (RLS) signal amplification by carbon nanotubes (CNTs) was studied. Single-layered nanotubes were synthesized by the chemical vapor deposition (CVD) method using methane as a carbon-containing gas. The object of study used was water, the Raman spectrum of which is rather well known. Amplification of the Raman scattering signal by several hundred percent was attained in our work. The maximum amplification of a Raman scattering signal was shown to be achieved at an optimal density of nanotubes on a substrate. This effect was due to the scattering and screening of plasmons excited in CNTs by neighboring nanotubes. The amplification mechanism and the possibilities of optimization for this effect were discussed on the basis of the theory of plasmon resonance in carbon nanotubes. PubDate: 2018-12-01

Abstract: In this paper, we determined the main regularities of suppression of combustion and thermal decomposition of typical forest combustible materials (leaves and needles as an example) when they are exposed to droplet aerosol with a variable specific water consumption. The conditions for suppressing the thermal decomposition in the material layer were controlled using low-inertia thermocouples. The size and concentration of water droplets in the aerosol were determined by using the cross-correlation complex and optical recording methods while the density of irrigation was calculated. The typical suppression times of combustion and thermal decomposition of the materials under study are determined. For the dependence of the suppression times on the specific water consumption, two typical ranges illustrating the necessary and sufficient conditions for effective combustion suppression are established. Based on an analysis of the experimental data, we formulated a hypothesis on the dominant heat and mass exchange in the suppression of combustion and the thermal decomposition of typical forest combustible materials with water. PubDate: 2018-12-01

Abstract: Complex results in experimental and numerical flow dynamics research and spectra signals of gas pressure pulsations in annular and linear dual slotted nozzles are presented. Experiments are performed in a pulsed aerodynamic facility using acetylene-air mixture combustion products as working gas. Viscous flow calculations are based on the Navier-Stokes equations for multicomponent reactive gaseous medium using single-temperature chemical nonequilibrium model. As a result, the frequency Fourier spectrum of pressure pulsation at the thrust wall center is determined. Typical pulsed pressure signals obtained in the calculations and detected in the experiments are presented. PubDate: 2018-12-01

Abstract: The vorticity on the surface of an axially symmetric body streamlined by a steady unswirling homogeneous ideal gas supersonic flow with a detached shock wave has been studied. The formula for estimating the vorticity at any point on the body through its distance to the symmetry axis, the pressure at this point, the incident flow parameters, and the shock wave curvature radius at the point of its intersection with the symmetry axis has been derived. From this formula it follows that the vorticity on the surface of a body in axially symmetric flows differs from zero everywhere except for the point on the symmetry axis in contrast to two-dimensional symmetric flows. PubDate: 2018-12-01

Abstract: The limits of applicability of terahertz band radiowaves for creating communication lines in the Earth’s atmosphere have been shown in a well-argued manner for the first time. It has been shown that the extension of the lines for near-ground paths will be comparatively small due to the properties of the atmosphere. PubDate: 2018-12-01

Abstract: The trinomial asymptotic expansions of potential flow kinetic energy in an ideal fluid are constructed for the motion of two spheres of variable radii in the vicinity of their contact. Based on these expansions, it is possible to study the process of two pulsating gas bubbles approaching up to their contact. PubDate: 2018-12-01

Abstract: High temperature behavior of sodium–aluminum fluorophosphate glass—a potential matrix for immobilisation of waste salt electrolyte from pyrochemical reprocessing of irradiated nuclear fuel (INF) has been studied. The glass crystallizes between 430 and 640°C with formation of phosphate phases, which dissolve above 640°C leading to homogenization of the glass. Similar transformations of the glass matrix due to heating from the decay of short-lived fission products may have a negative effect on properties of vitrified radioactive chloride wastes during storage in a repository. PubDate: 2018-12-01

Abstract: The existence of a symmetric mode in an elastic solid wedge for all allowable values of the Poisson ratio and arbitrary openings close to π has been proven. A radically new effect—the presence of a wave localized in a vicinity of the edge of a wedge with an opening larger than a flat angle—has been found. PubDate: 2018-12-01

Abstract: The results of numerical molecular dynamics simulation of the synthesis and fracture of a Ti–Al intermetallic nanocrystal under uniaxial tension are reported. It is shown that, at temperatures higher than 1000 K, fracture is preceded by the phase transition of a nanocrystal from the crystalline to amorphous state. PubDate: 2018-12-01

Abstract: This article presents a description and comparative analysis of an integrated natural gas utilization technology for concurrently producing electricity and synthetic liquid engine fuel and partially sequestering carbon dioxide. In the daytime, the installation produces electricity, heat, and methanol. In the night-time hours of minimum load, CO2 is partially captured from flue gases and is converted in a plasmatron to obtain H2 + CO by adding natural gas and steam. The produced synthesis gas is forwarded to a catalytic synthesis reactor for boosting the operation of the methanol producing installation. In comparison with state-of-the-art installations for separate production of electricity, heat, and methanol, the proposed installation makes it possible to save about 20% of natural gas and decrease the amount of CO2 emissions into the atmosphere by as much as 30%. PubDate: 2018-12-01

Abstract: Modification of a steel surface by coating with fullerenes C60 and subsequent treatment by intense laser radiation has been investigated. The initial samples are made of low-carbon steel. The laser source is a commercial LTA4-1 laser with a wavelength of 1.064 µm, pulse energy up to 12 J, and pulse width of 2 ms. The obtained dependences of the surface microhardness on the specific laser energy are nonmonotonic with a maximum in the range of 100–150 J/cm2. An eight-fold increase in the surface microhardness can be reached under optimal treatment conditions. There is an increasing dependence of the degree of surface strengthening on the fullerene-coating thickness. In addition, the laser irradiation of the treated surface is accompanied by a decrease in the friction coefficient by several tens of percent. The experimental results are compared with the data of similar measurements for nanocarbon soot used as the coating, which was obtained by the electric-arc sputtering of graphite with subsequent extraction of fullerenes. PubDate: 2018-12-01

Abstract: A general covariance variational model of reversible thermodynamics is developed in which the kinematic and force variables are the components of unified tensor objects in the space−time continuum, and the resolving equations of the dynamic thermoelasticity and heat-conduction of an ideal (defect-free) media are described by the 4D-vector equation. It is shown that the formulations of relations of the generalized Duhamel−Neumann representation and the Maxwell−Cattaneo law follow directly from the constitutive relations of the space−time-continuum model without additional hypotheses and assumptions. It is proved that the Maxwell−Cattaneo and Fourier generalized heat-conduction laws are unambiguously characterized by well-known thermomechanical parameters determined under isothermal and adiabatic conditions for reversible coupled deformation processes and heat-conduction despite the fact that one usually relates both the Fourier law and the relaxation time in the Maxwell−Cattaneo law with the dissipative processes. PubDate: 2018-12-01

Abstract: The processes of ultrasonically-assisted drilling (UAD) and the dynamic tests on split Hopkinson pressure bar (SHPB), fracture in which is implemented at various structural-scale levels, are considered. The simulation of UAD based on the Hertz contact problem and the structural−time criterion is presented. The problem of using the value of the fracture incubation time and its linear size obtained from the tests on SHPB in the simulation is considered. A principle of equal power is used for converting the strength parameters into another structural−scale level. The theoretical curve obtained in the simulation is compared with the results of experiments on conventional drilling (CD) and UAD. PubDate: 2018-11-01

Abstract: Preferential orientation of erythrocytes along the flow lines in the vertical plane was observed in the acceleration zone at the entry to the narrow part of the cell and inside this part when whole blood flow in a canal with stenosis was analyzed. An area where the erythrocyte orientation changed was observed in the deceleration zone; erythrocytes assumed an orientation perpendicular to the flow lines in the vertical plane after they passed through this zone. The flow of erythrocytes at a concentration of 1 vol % was studied under the same hydrodynamic conditions in order to characterize the behavior of individual erythrocytes. PubDate: 2018-11-01

Abstract: Hypersonic flow past a yawed plate of finite length is considered in the regime of strong interaction for the case when an additional condition at its trailing edge varies in span instead of being constant. It is shown that, in this case, the form of expansion of the stream functions in the vicinity of the leading edge changes significantly and, consequently, the character of the propagation of disturbances changes principally in the boundary layer on the plate. PubDate: 2018-11-01

Abstract: Extreme fluctuations have been modeled based on point nonpotential and potential systems of stochastic equations, in which white noise induces random processes with a power-law frequency dependence of the power spectra. The distribution of extreme fluctuations corresponds to the maximum of statistical entropy, which indicates their stability. The stability of fluctuation processes with 1/f α power spectra has been analyzed based on the principle of maximum information entropy. PubDate: 2018-11-01

Abstract: Magma flow in a volcanic conduit is traditionally described within one-dimensional or quasi-one-dimensional models taking into account the dependence of the viscosity on the crystal concentration. The velocity profile is assumed to be parabolic, and the parameters are averaged across the conduit. The results of calculations based on the quasi-two-dimensional model are compared with those for the one-dimensional model. It is shown that the velocity profile differs significantly from parabolic and that the magma flow rate depends on the pressure at the magma chamber. PubDate: 2018-11-01

Abstract: The results of numerical and experimental study of the effect of the Earth’s magnetic field on the electric-vortex flow of liquid metal in a hemispherical container are presented. It is found that the combination of toroidal flow and azimuthal force caused by the interaction of an electric current flowing through the liquid metal with a relatively weak external magnetic field leads to an intense twist of the fluid. This effect can be observed, for example, in electrometallurgical aggregates. PubDate: 2018-11-01

Abstract: The problem of propagation of acoustic waves in a liquid with gas bubbles covered by a viscoelastic shell has been considered. The dependence of the wave number on the perturbation frequency has been found. The low-frequency asymptotes for the phase velocity and the attenuation coefficient have been deduced. The dependence of the equilibrium sound velocity on the perturbation frequency and size of covered bubbles has been established and illustrated. A comparison of the theory with the known experimental data is presented. PubDate: 2018-11-01

Abstract: In the present paper, we established the conditions and the main characteristics of the stable boiling and subsequent explosive disintegration of emulsion droplets based on water and oil products under high-temperature (from 350 to 1100 K) heating using high-speed video recording (up to 105 frames per second). The studies were carried out under various conditions of energy supply to the droplet: on a massive substrate, in contact with a heated rod (local heating), and in a heated air flow. The times of heating up the emulsion droplets before the explosive decay are determined. The scale of the effect of the ambient temperature (up to 1100 K), the heat flux density (up to 104 kW/m2), and the oil product concentration (up to 70%) in the emulsion on these characteristics is established. Using high-speed video tracking, the main characteristics of the emulsion droplet decay are determined: the duration, surface transformation stages, and the number of liquid fragments formed (up to 300) and their total area (7–8 times higher than the initial one). The conditions for the emulsion drop decay both before and after its ignition were studied. PubDate: 2018-11-01