http://biblioteca.universia.net/verColeccion.do?id=8464 Mostrando recursos 1 - 20 de 13,166 es http://biblioteca.universia.net/img/logotipo.jpg http://biblioteca.universia.net/ http://biblioteca.universia.net/ficha.do?id=20858751 Using the Riemann-Hilbert approach, the $\Psi$-function corresponding to the solution of the first Painleve equation, $y_{xx}=6y^2+x$, with the asymptotic behavior $y\sim\pm\sqrt{-x/6}$ as $|x|\to\infty$ is constructed. The exponentially small jump in the dominant solution and the coefficient asymptotics in the power-like expansion to the latter are found. Kapaev, Andrei A. http://biblioteca.universia.net/ficha.do?id=20858821 A two-dimensional earthquake model that consists of a single block resting upon a slowly moving rough surface and connected by two springs to rigid supports is studied. Depending on the elastic anisotropy and the friction force three generic regimes are possible: i) pure creep; ii) pure stick-slip motion; and iii) a mixed regime. In all cases the long-time dynamics (fixed point, periodic orbit or chaos) is determined by the direction of the pulling velocity. The possible relevance of our find... Montagne, Raul; Vasconcelos, G. L. http://biblioteca.universia.net/ficha.do?id=20858884 Using group theory arguments, we demonstrate that, unlike in homogeneous media, no symmetric vortices of arbitrary order can be generated in two-dimensional (2D) nonlinear systems possessing a discrete-point symmetry. The only condition needed is that the non-linearity term exclusively depends on the modulus of the field. In the particular case of 2D periodic systems, such as nonlinear photonic crystals or Bose-Einstein condensates in periodic potentials, it is shown that the realization of d... Ferrando, Albert; Zacares, Mario; Garcia-March, Miguel-Angel http://biblioteca.universia.net/ficha.do?id=20858885 We investigate the behaviour of the two-point correlation function in the context of passive scalars for non homogeneous, non isotropic forcing ensembles. Exact analytical computations can be carried out in the framework of the Kraichnan model for each anisotropic sector. It is shown how the homogeneous solution is recovered at separations smaller than an intrinsic typical lengthscale induced by inhomogeneities, and how the different Fourier modes in the centre-of-mass variable recombine them... Afonso, M. Martins; Sbragaglia, M. http://biblioteca.universia.net/ficha.do?id=20858886 We derive model equations for optical pulse propagation in a medium described by a two-level Hamiltonian, without the use of the slowly varying envelope approximation. Assuming that the resonance frequency of the two-level atoms is either well above or well below the inverse of the characteristic duration of the pulse, we reduce the propagation problem to a modified Korteweg-de Vries or a sine-Gordon equation. We exhibit analytical solutions of these equations which are rather close in shape ... Leblond, Herve; Sanchez, Francois http://biblioteca.universia.net/ficha.do?id=20858887 We report structure formation in submonolayers of magnetic microparticles subjected to periodic electrostatic and magnetic excitations. Depending on the excitation parameters, we observe the formation of a rich variety of structures: clusters, rings, chains, and networks. The growth dynamics and shapes of the structures are strongly dependent on the amplitude and frequency of the external magnetic field. We find that for pure ac magnetic driving at low densities of particles, the low-frequenc... Snezhko, A.; Aranson, I. S.; Kwok, W. -K. http://biblioteca.universia.net/ficha.do?id=20858888 Computational anatomy (CA) has introduced the idea of anatomical structures being transformed by geodesic deformations on groups of diffeomorphisms. Among these geometric structures, landmarks and image outlines in CA are shown to be singular solutions of a partial differential equation that is called the geodesic EPDiff equation. A recently discovered momentum map for singular solutions of EPDiff yields their canonical Hamiltonian formulation, which in turn provides a complete parameterizati... Holm, Darryl D.; Ratnanather, J. Tilak; Trouvé, Alain; Younes, Laurent http://biblioteca.universia.net/ficha.do?id=20858889 In this paper, we use a series of small world networks to simulate the epidemic spreading in the real world. To make our model more similar to the real world, we employ a parameter $p_{move}$ to denote its moving probability, which corresponds with the general mobility of individuals in realistic social network. The networks keep the same small world properties when they are varying. And the SIRS model is used to simulate the disease propagation. From these simulations we see the moving proba... Li, Sheng; Meng, Meng; Ma, Hongru http://biblioteca.universia.net/ficha.do?id=20858890 At the short times, the enstrophy $\Omega$ of a two-dimensional flow, generated by a random Gaussian initial condition decays as $\Omega(t)\propto t^{-\gamma}$ with $\gamma\approx 0.7$. After that, the flow undergoes transition to a different state characterized by the magnitude of the decay exponent $\gamma\approx 0.4$ (Yakhot, Wanderer, Phys.Rev.Lett.{\bf 93}, 154502 \~(2004)). It is shown that the very existence of this transition and various characteristics of evolving flow crucially depe... Yakhot, Victor; Wanderer, John http://biblioteca.universia.net/ficha.do?id=20858891 We predict theoretically and verify experimentally the suppression of chaos in the Lorenz system driven by a high-frequency periodic or stochastic parametric force. We derive the theoretical criteria for chaos suppression and verify that they are in a good agreement with the results of numerical simulations and the experimental data obtained for an analog electronic circuit. Choe, Chol-Ung; Benner, Hartmut; Kivshar, Yuri S. http://biblioteca.universia.net/ficha.do?id=20858892 This contribution is relative to the opening lectures of the ISSAOS 2001 summer school and it has the aim to provide the reader with some concepts and techniques concerning chaotic dynamics and transport processes in fluids. Our intention is twofold: to give a self-consistent introduction to chaos and diffusion, and to offer a guide for the reading of the rest of this volume. Boffetta, G.; Lacorata, G.; Vulpiani, A. http://biblioteca.universia.net/ficha.do?id=20858893 We reveal that spatially localized vortex solitons become stable in self-focusing nonlinear media when the vortex symmetry-breaking azimuthal instability is eliminated by a nonlocal nonlinear response. We study the main properties of different types of vortex beams and discuss the physical mechanism of the vortex stabilization in spatially nonlocal nonlinear media. Yakimenko, Alexander; Zaliznyak, Yuri; Kivshar, Yuri http://biblioteca.universia.net/ficha.do?id=20858894 Experiments observing the liquid surface in a vertically oscillating container have indicated that modeling the dynamics of such systems require maps that admit states at infinity. In this paper we investigate the bifurcations in such a map. We show that though such maps in general fall in the category of piecewise smooth maps, the mechanisms of bifurcations are quite different from those in other piecewise smooth maps. We obtain the conditions of occurrence of infinite states, and show that ... Kumar, Aloke; Banerjee, Soumitro; Lathrop, Daniel P. http://biblioteca.universia.net/ficha.do?id=20858895 The propagation of a front connecting a stable homogeneous state with a stable periodic state in the presence of additive noise is studied. The mean velocity was computed both numerically and analitically. The numerics are in good agreement with the analitical prediction. Clerc, M. G.; Falcon, C.; Tirapegui, E. http://biblioteca.universia.net/ficha.do?id=20858896 Using a nonperturbative weak noise approach we investigate the interference of noise and chaos in simple 1D maps. We replace the noise-driven 1D map by an area-preserving 2D map modelling the Poincare sections of a conserved dynamical system with unbounded energy manifolds. We analyze the properties of the 2D map and draw conclusions concerning the interference of noise on the nonlinear time evolution. We apply this technique to the standard period-doubling sequence in the logistic map. From ... Fogedby, Hans C.; Jensen, Mogens H. http://biblioteca.universia.net/ficha.do?id=20858897 We consider the algebraic Bethe ansatz solution of the integrable and isotropic XXX-S Heisenberg chain with non-diagonal open boundaries. We show that the corresponding K-matrices are similar to diagonal matrices with the help of suitable transformations independent of the spectral parameter. When the boundary parameters satisfy certain constraints we are able to formulate the diagonalization of the associated double-row transfer matrix by means of the quantum inverse scattering method. This ... Melo, C. S.; Ribeiro, G. A. P.; Martins, M. J. http://biblioteca.universia.net/ficha.do?id=20858898 In this work the open-plus-closed-loop (OPCL) method of synchronization is used in order to synchronize the systems from the Sprott's collection of the simplest chaotic systems. The method is general and we were looking for the simplest coupling between master and slave system. The interval of parameters were synchronization is achieved are obtained analytically using Routh-Hurwitz conditions. Detailed calculations and numerical simulation are given for the system I from the Sprott's collecti... Lerescu, A. I.; Constandache, N.; Oancea, S.; Grosu, I. http://biblioteca.universia.net/ficha.do?id=20858899 This paper studies bifurcations in a three node power system when excitation limits are considered. This is done by approximating the limiter by a smooth function to facilitate bifurcation analysis. Spectacular qualitative changes in the system behavior induced by the limiter are illustrated by two case studies. Period doubling bifurcations and multiple attractors are shown to result due to the limiter. Detailed numerical simulations are presented to verify the results and illustrate the natu... Kavasseri, Rajesh G.; Padiyar, K. R. http://biblioteca.universia.net/ficha.do?id=20858900 Integrable dispersionless Kadomtsev-Petviashvili (KP) hierarchy of B type is considered. Addition formula for the $\tau$-function and conformally invariant equations for the dispersionless BKP (dBKP) hierarchy are derived. Symmetry constraints for the dBKP hierarchy are studied. Bogdanov, L. V.; Konopelchenko, B. G. http://biblioteca.universia.net/ficha.do?id=20858901 We investigate the dynamics of an array of logistic maps coupled with random delay times. We report that for adequate coupling strength the array is able to synchronize, in spite of the random delays. Specifically, we find that the synchronized state is a homogeneous steady-state, where the chaotic dynamics of the individual maps is suppressed. This differs drastically from the synchronization with instantaneous and fixed-delay coupling, as in those cases the dynamics is chaotic. Also in cont... Masoller, Cristina; Marti, Arturo C.