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Time delay in chemical exchange during an NMR pulse

Dan Gamliel (2014)

Mathematica Bohemica

Spin exchange with a time delay in NMR (nuclear magnetic resonance) was treated in a previous work. In the present work the idea is applied to a case where all magnetization components are relevant. The resulting DDE (delay differential equations) are formally solved by the Laplace transform. Then the stability of the system is studied using the real and imaginary parts of the determinant in the characteristic equation. Using typical parameter values for the DDE system, stability is shown for all...

Two shallow-water type models for viscoelastic flows from kinetic theory for polymers solutions

Gladys Narbona-Reina, Didier Bresch (2013)

ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique

In this work, depending on the relation between the Deborah, the Reynolds and the aspect ratio numbers, we formally derived shallow-water type systems starting from a micro-macro description for non-Newtonian fluids in a thin domain governed by an elastic dumbbell type model with a slip boundary condition at the bottom. The result has been announced by the authors in [G. Narbona-Reina, D. Bresch, Numer. Math. and Advanced Appl. Springer Verlag (2010)] and in the present paper, we provide a self-contained...

Un teorema de mecánica estadística relativista y los espacios de Hilbert-Lobatschewsky.

Darío Maravall Casesnoves (1985)

Trabajos de Estadística e Investigación Operativa

Se expone la geometría diferencial del espacio de las velocidades relativistas y se obtiene la función de distribución de velocidades de un gas de partículas relativistas, que modifica la función de Maxwell de Mecánica Estadística Clásica. Se introducen los espacios de Hilbert-Lobatschewsky.

Une méthode nodale appliquée à un problème de diffusion à coefficients généralisés

Abdelkader Laazizi, Nagib Guessous (2010)

ESAIM: Mathematical Modelling and Numerical Analysis

In this paper, we consider second order neutrons diffusion problem with coefficients in L∞(Ω). Nodal method of the lowest order is applied to approximate the problem's solution. The approximation uses special basis functions [1] in which the coefficients appear. The rate of convergence obtained is O(h2) in L2(Ω), with a free rectangular triangulation.

Upper bounds for a class of energies containing a non-local term

Arkady Poliakovsky (2010)

ESAIM: Control, Optimisation and Calculus of Variations

In this paper we construct upper bounds for families of functionals of the form E ε ( φ ) : = ∫ Ω ε | ∇ φ | 2 + 1 ε W ( φ ) d x + 1 ε ∫ ℝ N | ∇ H ¯ F ( φ ) | 2 d x where Δ H ¯ u = div { χ Ω u}. Particular cases of such functionals arise in Micromagnetics. We also use our technique to construct upper bounds for functionals that appear in a variational formulation of the method of vanishing viscosity for conservation laws.

Vortex motion and phase-vortex interaction in dissipative Ginzburg-Landau dynamics

F. Bethuel, G. Orlandi, D. Smets (2004)

Journées Équations aux dérivées partielles

We discuss the asymptotics of the parabolic Ginzburg-Landau equation in dimension N ≥ 2 . Our only asumption on the initial datum is a natural energy bound. Compared to the case of “well-prepared” initial datum, this induces possible new energy modes which we analyze, and in particular their mutual interaction. The two dimensional case is qualitatively different and requires a separate treatment.

Vortex rings for the Gross-Pitaevskii equation

Fabrice Bethuel, G. Orlandi, Didier Smets (2004)

Journal of the European Mathematical Society

We provide a mathematical proof of the existence of traveling vortex rings solutions to the Gross–Pitaevskii (GP) equation in dimension N ≥ 3 . We also extend the asymptotic analysis of the free field Ginzburg–Landau equation to a larger class of equations, including the Ginzburg–Landau equation for superconductivity as well as the traveling wave equation for GP. In particular we rigorously derive a curvature equation for the concentration set (i.e. line vortices if N = 3 ).

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