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Kazan, Russia

Bianchi M.,University of Milan | Konnov I.V.,Kazan University | Pini R.,University of Milan Bicocca
Journal of Global Optimization | Year: 2010

The aim of this work is to analyze lexicographic equilibrium problems on a topological Hausdorff vector space X, and their relationship with some other vector equilibrium problems. Existence results for the tangled lexicographic problem are proved via the study of a related sequential problem. This approach was already followed by the same authors in the case of variational inequalities. © 2009 Springer Science+Business Media, LLC. Source

Hennig J.,Albert Ludwigs University of Freiburg | Il'Yasov K.A.,Kazan University | Weigel M.,Albert Ludwigs University of Freiburg
Magnetic Resonance in Medicine | Year: 2012

This article presents the basic principles of the superstimulated echo mechanism and shows preliminary results of its application to T 1-weighted imaging with positive T 1-contrast. A superstimulated echo scheme uses a preparation of square-wave modulated, periodically inverted z-magnetization, which after signal evolution during the mixing time TM is fully converted into transverse magnetization. This avoids the 50% signal loss of a conventional stimulated echo. Furthermore, its implementation as a preparation module for standard turbo spin echo (TSE) imaging allows producing images with positive T 1-contrast. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc. Copyright © 2011 Wiley Periodicals, Inc. Source

Allevi E.,University of Brescia | Gnudi A.,University of Bergamo | Konnov I.V.,Kazan University | Schaible S.,Chung Yuan Christian University
Journal of Global Optimization | Year: 2012

We consider a problem of solution of a multi-valued inclusion on a cone segment. In the case where the underlying mapping possesses Z type properties we suggest an extension of Gauss-Seidel algorithms from nonlinear equations. We prove convergence of a modified double iteration process under rather mild additional assumptions. Some results of numerical experiments are also presented. © 2011 Springer Science+Business Media, LLC. Source

Mukhamedshin I.R.,University Paris - Sud | Mukhamedshin I.R.,Kazan University | Alloul H.,University Paris - Sud
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We report a complete set of 59Co NMR data taken on the x=2/3 phase of sodium cobaltates Na xCoO 2 for which we have formerly established the in-plane Na ordering and its three-dimensional stacking from a combination of symmetry arguments taken from Na and Co NQR/NMR data. Here, we resolve all the parameters of the Zeeman and quadrupolar Hamiltonians for all cobalt sites in the unit cell and report the temperature dependencies of the NMR shift and spin lattice relaxation T 1 data for these sites. We confirm that three nonmagnetic Co3 + (Co1) are in axially symmetric positions and that the doped holes are delocalized on the nine complementary magnetic cobalt sites (Co2) of the atomic unit cell. The moderately complicated atomic structure resumes then in a very simple electronic structure in which the electrons delocalize on the Co2 kagome sublattice of the triangular lattice of Co sites. The observation of a single temperature dependence of the spin susceptibilities indicates that a single band picture applies, and that the magnetic properties are dominated by the static and dynamic electronic properties at the Co2 sites. We evidence that they display a strong in-plane electronic anisotropy initially unexpected but which agrees perfectly with an orbital ordering along the kagome sublattice organization. These detailed data should now permit realistic calculations of the electronic properties of this compound in order to determine the incidence of electronic correlations. © 2011 American Physical Society. Source

Konnov I.V.,Kazan University
Journal of Global Optimization | Year: 2013

We consider vector models for complex systems with spatially distributed elements which arise in communication and transportation networks. In order to describe the flow distribution within such a network, we utilize the equilibrium approach, which extends the shortest path one. Being based on this approach, we investigate several networking control problems, with taking into account many factors. As a result, general vector equilibrium problems models with complex behavior of elements are suggested. In particular, they involve elastic demand functions. Due to the presence of many factors, we utilize multicriteria models with respect to different preference relations. The corresponding problems admit efficient solution methods within optimization and equilibrium frameworks. © 2011 Springer Science+Business Media, LLC. Source

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