Double-component convection due to different boundary conditions in an infinite slot diversely oriented to the gravity

Onset of small-amplitude oscillatory and both small- and finite-amplitude steady double-component convection arising due to component different boundary conditions in an infinite slot is studied for various slot orientations to the gravity. The main focus is on two compensating background gradients of the components. The physical mechanisms underlying steady and oscillatory convection are analyzed from the perspective of a universally consistent understanding of the effects of different boundary conditions.Comment: V2: Submitted to and published in Annals of Physics. 59 manuscript pages, 15 figures (occupying 21 pages). The full abstract is on the first page. Nonessential modifications/enhancements in the presentation (more compact presentation of the text and figure data, some style improvements, etc.

Amplitude equations for a system with thermohaline convection

The multiple scale expansion method is used to derive amplitude equations for a system with thermohaline convection in the neighborhood of Hopf and Taylor bifurcation points and at the double zero point of the dispersion relation. A complex Ginzburg-Landau equation, a Newell-Whitehead-type equation, and an equation of the $\phi^4$ type, respectively, were obtained. Analytic expressions for the coefficients of these equations and their various asymptotic forms are presented. In the case of Hopf bifurcation for low and high frequencies, the amplitude equation reduces to a perturbed nonlinear Schr\"odinger equation. In the high-frequency limit, structures of the type of "dark" solitons are characteristic of the examined physical system.Comment: 21 pages, 8 figure

A simple high-performance matrix-free biomass molten carbonate fuel cell without CO2 recirculation

In previous reports, flowing CO2 at the cathode is essential for either conventional molten carbonate fuel cells (MCFCs) based on molten carbonate/LiAlO2 electrolytes or matrix-free MCFCs. For the first time, we demonstrate a high-performance matrix-free MCFC without CO2 recirculation. At 800°C, power densities of 430 and 410 mW/cm2 are achieved when biomass—bamboo charcoal and wood, respectively–is used as fuel. At 600°C, a stable performance is observed during the measured 90 hours after the initial degradation. In this MCFC, CO2 is produced at the anode when carbon-containing fuels are used. The produced CO2 then dissolves and diffuses to the cathode to react with oxygen in open air, forming the required Embedded Image or Embedded Image ions for continuous operation. The dissolved Embedded Image ions may also take part in the cell reactions. This provides a simple new fuel cell technology to directly convert carbon-containing fuels such as carbon and biomass into electricity with high efficiency

Global stability properties of a hyperbolic system arising in pattern formation

Global stability properties of a hyperbolic system arising in pattern formatio

EFFECT OF CARBON NANOTUBES ON THE ELECTRICAL PROPERTIES OF THE POLYMERIC COMPOSITES

Experimental study of single-wall carbon nabotubes (CNT) effect on the electrical properties of polymeric composite materials based on epoxy matrix has been carried out. Direct-current (DC) as well as alternating-current (AC) electrical conductivity of nanocomposites with different CNT concentrations have been investigated in the temperature interval from 293 K to 373 K. Measurements of Seebeck coefficient confirm n-type conductivity of composite with CNTs. Percolation threshold of the composite material under study has been estimated. It has been found that addition of single-wall CNT at low concentration causes hysteresis of current-voltage characteristics and the temperature dependences of electrical conductivity as well as its anisotropy in the samples under study. No noticeable frequency dependence of the AC electrical conductivity has been found in the frequency range from 100 Hz to 300 kHz

Influencia de las condiciones de crecimiento de monocristales de molibdeno en la perfección de su estructura.

The method of monocrystal obtaining from refractory metals by the method of zone melting with the use of electron beam heating is considered. The main factors affecting the number of dislocations in grown monocrystals are determined. Using the example of Mo monocrystals, the optimal conditions for the growth of monocrystals with a reduced dislocation density were established.Se considera el método de obtención de monocristales a partir de metales refractarios por el método de fusión por zona con el uso de calentamiento por haz de electrones. Se determinan los principales factores que afectan el número de dislocaciones en monocristales crecidos, utilizando el ejemplo de monocristales de Mo, y se establecieron las condiciones óptimas para el crecimiento de monocristales con densidad de dislocación reducida.&nbsp

Absorption of microdroplets by layered porous media

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.The subject of this paper is the sequential absorption of two droplets at its arbitrary location on the surface of single- and double-layer porous media. The consideration is based on simultaneous solution of the equations describing liquid flow in the droplet and equations of unsteady filtration in the porous medium. The layers of porous medium were characterized by effective permeability coefficients dependent on porosity and pore size. The change in the droplet shape during absorption and the propagation of absorbed fluid in a porous medium are the output data of the problem. The effect of porous medium structure parameters and relative location of droplets on the rate of absorption and distribution of absorbed liquids is analyzed using the numerical experiment. It is shown that the presence of the second layer can significantly affect the duration and result of droplet absorption. The ratio of the pore size in the layers is found to be the main parameter that governs the effect of the second layer.vk201

Structural, transport and microwave properties of 123/sapphire films: Thickness effect

The effect of thickness and growth conditions on the structure and microwave properties has been investigated for the 123/sapphire films. It has been shown that in the conditions of epitaxial growth the Al atoms do not diffuse from substrate into the film and the films with thickness up to 100 nm exhibit the excellent direct current (DC) properties. The increase of thickness of GdBaCuO films causes the formation of extended line-mesh defects and the increase of the surface resistance (R(sub S)). The low value of surface resistance R(sub S)(75 GHz, 77K) = 20 mOhm has been obtained for the two layer YBaCuO/CdBaCuO/sapphire films