1,149 research outputs found

    Preparation, characterization, physical testing and performance of fluorocarbon membranes and separators

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    The direct fluorination method of converting carefully selected hydrocarbon substrates to fluorinated membranes was successfully applied to produce promising, novel membranes for electrochemical devices. A family of polymer blends was identified which permits wide latitude in the concentration of both crosslinks and carboxyl groups in hydrocarbon membranes. These membranes were successfully fluorinated and are potentially competitive with commercial membranes in performance, and potentially much cheaper in price

    Preparation, characterization, physical testing and performance of flurocarbon membranes and separators

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    The direct fluorination method of converting carefully selected hydrocarbon substrates to fluorinated membranes was successfully applied to produce promising, novel membranes for electrochemical devices. A family of polymer blends was identified which permits wide latitude in the concentration of both crosslinks and carboxyl groups in hydrocarbon membranes. The membranes of paragraph two were successfully fluorinated

    Fractional Curve Flows and Solitonic Hierarchies in Gravity and Geometric Mechanics

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    Methods from the geometry of nonholonomic manifolds and Lagrange-Finsler spaces are applied in fractional calculus with Caputo derivatives and for elaborating models of fractional gravity and fractional Lagrange mechanics. The geometric data for such models are encoded into (fractional) bi-Hamiltonian structures and associated solitonic hierarchies. The constructions yield horizontal/vertical pairs of fractional vector sine-Gordon equations and fractional vector mKdV equations when the hierarchies for corresponding curve fractional flows are described in explicit forms by fractional wave maps and analogs of Schrodinger maps.Comment: latex2e, 11pt, 21 pages; the variant accepted to J. Math. Phys.; new and up--dated reference

    Lax Tensors, Killing Tensors and Geometric Duality

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    The solution of the Lax tensor equations in the case Lαβγ=LβαγL_{\alpha\beta\gamma}=-L_{\beta\alpha\gamma} was analyzed. The Lax tensors on the dual metrics were investigated. We classified all two dimensional metrics having the symmetric Lax tensor LαβγL_{\alpha\beta\gamma}. The Lax tensors of the flat space, Rindler system and its dual were found.Comment: 9 pages LATE

    Extraction of reliable information from time-domain pressure and flow signals measured by means of forced oscillation techniques

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    This paper aims to give a proof-of-concept for the possible application of the forced oscillation lung function test to assess the viscoelastic properties of the airways and tissue. In particular, a novel signal processing algorithm is employed on non-stationary, noisy, (relatively) short time series of respiratory pressure and flow signals. This novel technique is employed to filter the useful information from the signals acquired under two measurement conditions: pseudo-functional residual capacity (PFRC) and pseudo-total lung capacity (PTLC). The PFRC is the measurement performed at lowest lung volume with maximum deflation, and the PTLC is measurement performed at the maximum lung volume under maximum inflation. The results suggest that the proposed technique is able to extract information on the viscoelastic properties of the lung tissue at a macroscopic level. The conclusion of this preliminary study is that the proposed combination of signal processing method and lung function test is suited to be employed on a large database in order to deliver reference values and perform further statistical analysis

    Note on counterterms in asymptotically flat spacetimes

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    We consider in more detail the covariant counterterm proposed by Mann and Marolf in asymptotically flat spacetimes. With an eye to specific practical computations using this counterterm, we present explicit expressions in general dd dimensions that can be used in the so-called `cylindrical cut-off' to compute the action and the associated conserved quantities for an asymptotically flat spacetime. As applications, we show how to compute the action and the conserved quantities for the NUT-charged spacetime and for the Kerr black hole in four dimensions.Comment: 13 pages, v. 2 added reference

    Vortex stability in nearly two-dimensional Bose-Einstein condensates with attraction

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    We perform accurate investigation of stability of localized vortices in an effectively two-dimensional ("pancake-shaped") trapped BEC with negative scattering length. The analysis combines computation of the stability eigenvalues and direct simulations. The states with vorticity S=1 are stable in a third of their existence region, 0<N<(1/3)Nmax(S=1)0<N<(1/3)N_{\max}^{(S=1)}, where NN is the number of atoms, and Nmax(S=1)N_{\max}^{(S=1)} is the corresponding collapse threshold. Stable vortices easily self-trap from arbitrary initial configurations with embedded vorticity. In an adjacent interval, (1/3)Nmax(S=1)<N<(1/3)N_{\max }^{(S=1)}<N< 0.43Nmax(S=1)\allowbreak 0.43N_{\max}^{(S=1)}, the unstable vortex periodically splits in two fragments and recombines. At N>N> 0.43Nmax(S=1)\allowbreak 0.43N_{\max}^{(S=1)}, the fragments do not recombine, as each one collapses by itself. The results are compared with those in the full 3D Gross-Pitaevskii equation. In a moderately anisotropic 3D configuration, with the aspect ratio 10\sqrt{10}, the stability interval of the S=1 vortices occupies 40\approx 40% of their existence region, hence the 2D limit provides for a reasonable approximation in this case. For the isotropic 3D configuration, the stability interval expands to 65% of the existence domain. Overall, the vorticity heightens the actual collapse threshold by a factor of up to 2. All vortices with S2S\geq 2 are unstable.Comment: 21 pages, 8 figures, to appear in Physical Review

    A Weibel Instability in the Melting Color Glass Condensate

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    Based on hep-ph/0510121, we discuss further the numerical study of classical SU(2) 3+1-D Yang-Mills equations for matter produced in a high energy heavy ion collision. The growth of the amplitude of fluctuations as exp(Γg2μτ)\exp{(\Gamma \sqrt{g^2\mu \tau})} (where g2μg^2\mu is a scale arising from the saturation of gluons in the nuclear wavefunction) is shown to be robust over a wide range of initial amplitudes that violate boost invariance. We argue that this growth is due to a non-Abelian Weibel instability, the scale of which is set by a dynamically generated plasmon mass. We find good agreement when we relate Γ\Gamma to the prediction from kinetic theory.Comment: 8 pages, invited talk at Workshop on Quark Gluon Plasma Thermalization, Vienna, August 10th-12th, 200
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