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Amaziane B.,University of Pau and Pays de lAdour | Antontsev S.,University of Lisbon | Pankratov L.,University of Pau and Pays de lAdour | Pankratov L.,Bverkin Institute For Low Temperature Physics And Engineering
Nonlinear Analysis: Real World Applications | Year: 2012

A system of evolutionary partial differential equations (PDEs) describing the two-phase flow of immiscible fluids, such as watergas, through porous media is studied. In this formulation, the wetting and nonwetting phases are treated to be incompressible and compressible, respectively. This treatment is indeed necessary when a compressible nonwetting phase is subjected to compression during confinement. The system of PDEs consists of an evolution equation for the wetting-phase saturation and an evolution equation for the pressure in the nonwetting phase. This system is applied to the problem of unsaturated flows to assess gas migration and two-phase flow through engineered and geological barriers for a deep repository for radioactive waste. This paper is primarily concerned with the large time behavior of solutions of this system. Under some realistic assumptions on the data, we derive estimates of the speed of propagation of the gas by water in porous media. Namely, we establish estimates of time stabilization for the water saturation to a constant limit profile. The analysis is based on the energy methods whose main idea involves deriving and studying suitable ordinary differential inequalities. We show that the time of complete displacement of a gas by water may be at most infinite or finite depending essentially on the power parameters defining the capillary pressure and the relative permeabilities. This result is then illustrated with two examples in the context of gas migration in a deep nuclear waste repository. We consider Van Genuchten's and BrooksCorey's models for a two-phase watergas system. © 2012 Elsevier Ltd. All rights reserved. Source


Evstigneev M.P.,Kharkiv Polytechnic Institute | Buchelnikov A.S.,Kharkiv Polytechnic Institute | Voronin D.P.,Kharkiv Polytechnic Institute | Rubin Y.V.,Bverkin Institute For Low Temperature Physics And Engineering | And 3 more authors.
ChemPhysChem | Year: 2013

The contributions of various physical factors to the energetics of complexation of aromatic drug molecules with C60 fullerene are investigated in terms of the calculated magnitudes of equilibrium complexation constants and the components of the net Gibbs free energy. Models of complexation are developed taking into account the polydisperse nature of fullerene solutions in terms of the continuous or discrete (fractal) aggregation of C60 molecules. Analysis of the energetics has shown that stabilization of the ligand-fullerene complexes in aqueous solution is mainly determined by intermolecular van der Waals interactions and, to lesser extent, by hydrophobic interactions. The results provide a physicochemical basis for a potentially new biotechnological application of fullerenes as modulators of biological activity of aromatic drugs. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Amaziane B.,University of Pau and Pays de lAdour | Antontsev S.,University of Lisbon | Pankratov L.,University of Pau and Pays de lAdour | Pankratov L.,Bverkin Institute For Low Temperature Physics And Engineering | And 2 more authors.
Multiscale Modeling and Simulation | Year: 2010

This paper is devoted to the homogenization of a coupled system of diffusionconvection equations in a domain with periodic microstructure, modeling the flow and transport of immiscible compressible, such as water-gas, fluids through porous media. The problem is formulated in terms of a nonlinear parabolic equation for the nonwetting phase pressure and a nonlinear degenerate parabolic diffusion-convection equation for the wetting saturation phase with rapidly oscillating porosity function and absolute permeability tensor. We obtain a nonlinear homogenized problem with effective coefficients which are computed via a cell problem. We rigorously justify this homogenization process for the problem by using two-scale convergence. In order to pass to the limit in nonlinear terms, we also obtain compactness results which are nontrivial due to the degeneracy of the system. © 2010 Society for Industrial and Applied Mathematics. Source


Gonzalez-Zalba M.F.,Hitachi Cambridge Laboratory | Shevchenko S.N.,Bverkin Institute For Low Temperature Physics And Engineering | Shevchenko S.N.,University of Kharkiv | Shevchenko S.N.,RIKEN | And 6 more authors.
Nano Letters | Year: 2016

Quantum mechanical effects induced by the miniaturization of complementary metal-oxide-semiconductor (CMOS) technology hamper the performance and scalability prospects of field-effect transistors. However, those quantum effects, such as tunneling and coherence, can be harnessed to use existing CMOS technology for quantum information processing. Here, we report the observation of coherent charge oscillations in a double quantum dot formed in a silicon nanowire transistor detected via its dispersive interaction with a radio frequency resonant circuit coupled via the gate. Differential capacitance changes at the interdot charge transitions allow us to monitor the state of the system in the strong-driving regime where we observe the emergence of Landau-Zener-Stückelberg-Majorana interference on the phase response of the resonator. A theoretical analysis of the dispersive signal demonstrates that quantum and tunneling capacitance changes must be included to describe the qubit-resonator interaction. Furthermore, a Fourier analysis of the interference pattern reveals a charge coherence time, T2 ≈ 100 ps. Our results demonstrate charge coherent control and readout in a simple silicon transistor and open up the possibility to implement charge and spin qubits in existing CMOS technology. © 2016 American Chemical Society. Source


Pyshkin O.,Bverkin Institute For Low Temperature Physics And Engineering | Kamarchuk G.,Bverkin Institute For Low Temperature Physics And Engineering | Yeremenko A.,Bverkin Institute For Low Temperature Physics And Engineering | Kravchenko A.,University of Kharkiv | And 3 more authors.
Journal of Breath Research | Year: 2011

This work describes the gas-sensitive properties of a one-dimensional organic conductor before and after exposure to carbon monoxide and human breath. A sensitive material, an anion-radical salt of tetracyanoquinodimethane, has been investigated by infrared spectroscopy and electrical resistivity measurements. Drastic spectral and electrical changes are found after gas exposure showing that the compound interacts strongly with human breath, carbon monoxide, and ammonia. Under breath action the resistance changes by more than three orders of magnitude while the adsorption of CO, one of the components of breath, results in a decrease in both IR absorption and electrical conductivity. The intensity of the IR absorption spectrum of the material in the CO medium decreases down to 30% in the 2180-2500 cm-1 range. This absorption varies by about 10% between 750 and 2500 cm-1 after breath action. Direct electrical measurements show that actions of donor or acceptor gas result in opposite changes of electric resistance. The electrical resistance of the sample can drop down to 0.4 MΩ due to the pulse action of ammonia at 4 ppm concentration, while it increases upon exposure to carbon monoxide media at concentrations of 6-25 ppm. The response signal of the investigated samples changes proportionally to the concentration of the acting gas. The results substantiate prominent gas sensitivity of the investigated material, which might find applications for breath analysis, in particular, for the development of noninvasive diagnosis of gastric diseases. © 2011 IOP Publishing Ltd. Source

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