AbstractAbstract
[en] We consider the dynamics of the slightly asymmetric heavy top, a non-integrable system obtained from the Lagrange top by breaking the symmetry of its inertia tensor. It shows signs of weak chaos, which we study numerically. We argue that it is a good example for introducing students to non-integrability and chaos. (author)
Primary Subject
Source
Available online at the Web site for the European Journal of Physics (ISSN 1361-6404) http://www.iop.org/; Country of input: International Atomic Energy Agency (IAEA)
Record Type
Journal Article
Journal
European Journal of Physics; ISSN 0143-0807;
; v. 16(3); p. 106-112

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Pastor, I.
Centro de Investigaciones Energeticas Medioambientales y Tecnologicas (CIEMAT), Madrid (Spain)1994
Centro de Investigaciones Energeticas Medioambientales y Tecnologicas (CIEMAT), Madrid (Spain)1994
AbstractAbstract
[en] A method for obtaining active control of a chaotic system based on the modulation of a control parameter by adding to it a small perturbation proportional to one output signal is proposed. From a theoretical point of view, chaos can be stabilized in the framework of this method because small modifications of the vector field controlling the dynamics are allowed, and thus some of the previously oxi sting unstable periodic trajectories can be made stable. The method is much inspired on recent treatments of some related problems, and i t is compared with them. One of its most attractive features is that is should be very easy to implement it on real experiments. The method is tested on a system of ordinary differential equations model ling the coupling of two se If - oscillating electronic circuits (van der Pol oscillators). Some brief comments are made on the no possibility that it could be applied to complex spatio-temporal systems where multiple chaotic structures can coexist for some values of the control parameters. (Author) 28 refs
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1994; 28 p
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Report
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Jovanovic, M.S.; Skoric, M.M.; Jovanovic, M.S.
Institute of Nuclear Sciences VINCA, Belgrade (Yugoslavia)1994
Institute of Nuclear Sciences VINCA, Belgrade (Yugoslavia)1994
AbstractAbstract
[en] Transition from regular to chaotic dynamics is studied for the case of stimulated Raman backscattering in a plasma corona induced by laser radiation in a typical controlled inertial confinement fusion experiment. Plasma is assumed bounded and homogeneous. The appropriate partial differential equations, with the nonlinear frequency shift taken into account, are solved numerically for typical laser plasma parameters. Variation of laser and plasma parameters drives the system towards the chaotic state, passing through quasiperiodic and intermittent regimes. Our results are qualitatively equivalent to those obtained by the other groups considering more complex physical and numerical models (author)
Original Title
Haoticni rezim stimulisanog Ramanovog rasejanja u laserski proizvedenoj fuzionoj plazmi
Primary Subject
Source
1994; 2 p; Society for Electronics,Telecommunications, Computers, Automation, and Nuclear Engineering, ETRAN; Beograd (Yugoslavia); 38. Conference - ETRAN '94: Society for Electronics, Telecommunications, Computers, Automation, and Nuclear Engineering; ETRAN 1994: 38. Konferencija za elektroniku, telekomunikacije, racunarstvo, automatiku i nuklearnu tehniku; Nis (Yugoslavia); 7-9 Jun 1994; ISBN--86-80509-10-8;
; Also available from Institute of Nuclear Sciences VINCA; 6 refs, 3 figs

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Miscellaneous
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Conference
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Jeffries, J.D.E.
ICONE-3: Proceedings of the 3rd JSME/ASME joint international conference on nuclear engineering. Volume 11995
ICONE-3: Proceedings of the 3rd JSME/ASME joint international conference on nuclear engineering. Volume 11995
AbstractAbstract
No abstract available
Primary Subject
Source
Japan Society of Mechanical Engineers, Tokyo (Japan); 701 p; 1995; p. 455-457; ICONE-3: 3. JSME/ASME joint international conference on nuclear engineering; Kyoto (Japan); 23-27 Apr 1995; Available from Japan Society of Mechanical Engineers, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-0016, Japan; 4 refs., 2 figs.
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Miscellaneous
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Conference
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Uchiyama, Junichi; Hayashi, Koji; Nabeshima, Kunihiko; Suzudo, Tomoaki; Suzuki, Katsuo
ICONE-3: Proceedings of the 3rd JSME/ASME joint international conference on nuclear engineering. Volume 31995
ICONE-3: Proceedings of the 3rd JSME/ASME joint international conference on nuclear engineering. Volume 31995
AbstractAbstract
[en] A framework for a PWR reactor noise diagnostic system using various signal processing methods has been investigated. Supposing to treat not only reactor noise data in a stationary linear system but also those in a nonstationary or nonlinear system, the study covers a third-order-correlation of bispectrum, cepstrum analysis, Group Method of Data Handling (GMDH), chaotic quantity, neural network, and wavelet, in addition to Multivariate AutoRegressive analysis and Signal Transmission Path Diagram analysis (MAR/STPD). This paper describes consideration about the methods from viewpoints of theories and applications to PWR reactor noise diagnostic system. The point at the issue in the application system is how to extract many characteristics from the signals whatever states (linear or nonlinear, stationary or nonstationary) may happen in order to get more information and more exact diagnose to support human judgment. From this viewpoint, the paper discusses several signal processing techniques for the PWR diagnostic system. (J.P.N.)
Primary Subject
Source
Japan Society of Mechanical Engineers, Tokyo (Japan); 534 p; 1995; p. 1629-1634; ICONE-3: 3. JSME/ASME joint international conference on nuclear engineering; Kyoto (Japan); 23-27 Apr 1995; Available from Japan Society of Mechanical Engineers, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-0016, Japan; 28 refs., 3 figs.
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Miscellaneous
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Conference
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Maitre, Agnes
Ecole Polytechnique (France); Ecole Normale Superieure, Departement de Physique, Laboratoire Kastler-Brossel, ENS, UPMC, CNRS, 24 rue Lhomond, 75005 Paris (France)1994
Ecole Polytechnique (France); Ecole Normale Superieure, Departement de Physique, Laboratoire Kastler-Brossel, ENS, UPMC, CNRS, 24 rue Lhomond, 75005 Paris (France)1994
AbstractAbstract
[en] The interaction of two counterpropagating electromagnetic waves of same frequency and same linear polarisation induces the generation of new waves when the intensity of these pump beams exceeds a threshold value. These new waves are called instabilities and are emitted in directions different from the direction of propagation of the pump beams. In this PhD work, the instabilities generated by two counterpropagating beams in a Rubidium vapor are studied in two different experiments. In the first experiment, an intense beam propagates in the nonlinear medium and is reflected on a feedback mirror so that the reflected field propagates also in the nonlinear medium. When the intensity exceeds a threshold value and the frequency of the beam is tuned near the D1 transition of Rubidium 85, off-axis instabilities are emitted. They propagate between the nonlinear medium and the feedback mirror and are reflected by this mirror. Their transverse pattern in far field consists of concentric rings, double spots or of 'Flowers' consisting of an odd number of spots ('petals') distributed on a circle. The theoretical and experimental study of such instabilities makes it possible to predict and observe the number of petals versus the different parameters of the system In particular, these studies show also that the intensity of the instabilities could be either static, periodic or chaotic. In the second experiment, the laser beam is divided in two pump beams counterpropagating in the nonlinear medium. No feedback mirror is used. The far field patterns consist of rings, double spots or hexagons. This experiment shows important analogies with hydrodynamics. (author)
[fr]
Deux ondes electromagnetiques intenses de meme frequence et de meme polarisation se propageant dans des sens opposes dans un milieu non-lineaire generent au-dessus d'une certaine intensite seuil, des nouvelles ondes appelees instabilites qui sont emises spontanement dans des directions differentes de celles des pompes. Ce travail de these a consiste en l'etude des instabilites generees dans une vapeur de Rubidium dans deux situations experimentales differentes. Dans la premiere experience, une onde pompe intense se propage dans le milieu non-lineaire, se reflechit sur un miroir de retroaction et est alors reinjectee dans le milieu non-lineaire. Pour une intensite suffisante et une frequence adaptee de l'onde pompe, des instabilites sont emises. Elles pourront se reflechir sur le miroir de retroaction et etre reinjectees dans le milieu non-lineaire. Leur structure transverse en champ lointain est alors constituee de diverses figures telles que des anneaux concentriques, deux points diametralement opposes ou des figures comportant un nombre pair de taches reparties sur un cercle et appelees 'marguerites'. L'etude theorique de ces instabilites associee a une etude experimentale a permis de predire et de decrire le comportement des differentes instabilites emises en fonction des differents parametres du systeme. En particulier ces etudes ont montre que l'intensite des instabilites pouvait etre statique, periodique ou chaotique. La deuxieme experience ne comporte pas de miroir de retroaction et le faisceau laser est separe en deux ondes pompes se contrepropageant dans le milieu non-lineaire. En champ lointain, les instabilites transverses sont constituees par un seul anneau, deux points diametralement opposes ou des hexagones. L'intensite de ces instabilites peut etre chaotique et l'etude de ce chaos ete realisee. (auteur)Original Title
Instabilites crees par melange a quatre ondes dans une vapeur atomique. Chaos et morphogenese
Primary Subject
Source
30 Jun 1994; 272 p; 120 refs.; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses; These Docteur de l'Ecole polytechnique, Specialite: Optique non-lineaire
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Miscellaneous
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Thesis/Dissertation
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Michel-Lours, Laurence
Universite de Paris-Sud, Centre d'Orsay (France); Laboratoire de Physique des Milieux Ionises, Ecole Polytechnique, Palaiseau (France)1993
Universite de Paris-Sud, Centre d'Orsay (France); Laboratoire de Physique des Milieux Ionises, Ecole Polytechnique, Palaiseau (France)1993
AbstractAbstract
[en] It has been confirmed that the motion of an electron in a helical wiggler with guide field may be chaotic when taking into account the equilibrium self-fields of the beam. It is also found that the motion of an electron in a linearly polarized wiggler with an axial guide field is non-integrable. There is evidence of chaos from numerical calculations of non-zero Lyapunov exponents and Poincare maps. Efficient numerical tools allowing to find out of whether a trajectory is chaotic or not have been suggested. The calculation of Lyapunov exponents was performed and tested by comparing the results obtained by using different approaches of Benettin's method. The Poincare maps were calculated with a great accuracy. A very stringent condition on energy conservation was used. Local Lyapunov exponents were also calculated in order to find the mixing-time of the electron trajectories. We have shown that chaos can be a crucial problem in an experiment. (author)
[fr]
On confirme que le mouvement d'un electron peut etre chaotique lorsqu'il est soumis au champ d'un onduleur helicoidal, a un champ de guidage axial ainsi qu'aux champs propres lies a la charge d'espace du faisceau. D'autre part, on trouve que le mouvement d'un electron dans les seuls champs d'un onduleur lineaire et de guidage n'est pas integrable. L'existence de trajectoires chaotiques est montree par le calcul d'exposants de Liapunov et de sections de Poincare. Le calcul des exposants de Liapunov est teste en utilisant differentes approches de la methode de Benettin. Les sections de Poincare sont calculees avec une tres grande precision, verifiee sur la conservation des constantes du mouvement. On a de plus calcule des exposants de liapunov locaux afin de connaitre le temps de melange des trajectoires. Ces resultats nous permettent de dire que le chaos peut etre un probleme important dans certaines experiences. (auteur)Original Title
Etude de la dynamique hamiltonienne dans le laser a electrons libres
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Secondary Subject
Source
7 Jun 1993; 152 p; 33 refs.; Available from the INIS Liaison Officer for France, see the 'INIS contacts' section of the INIS website for current contact and E-mail addresses: http://www.iaea.org/inis/Contacts/; These Docteur en Sciences de l'Universite Paris XI Orsay
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Miscellaneous
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Thesis/Dissertation
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Besnard, D.; Dubois-Gance, M.; Manneville, P.; Grand, D.; Pomeau, Y.
Commissariat a l'energie atomique et aux energies alternatives - CEA, Centre d'Etudes de Limeil Valenton, Departement de Mathematiques Appliquees, Service Mathematiques et Codes Numeriques, 94195 Villeneuve Saint Georges Cedex (France)1992
Commissariat a l'energie atomique et aux energies alternatives - CEA, Centre d'Etudes de Limeil Valenton, Departement de Mathematiques Appliquees, Service Mathematiques et Codes Numeriques, 94195 Villeneuve Saint Georges Cedex (France)1992
AbstractAbstract
[en] This report summarizes a review of Research and Development on Turbulence in fluids. On top of a description of the major themes studied in CEA, one gives an overview of the needs in this domain, and proposals for expanding current efforts. In an Annex are gathered information on development in other French institutions. (authors)
[fr]
Ce document resume les resultats d'une enquete sur les etudes sur les ecoulements fluides turbulents faites au CEA. Outre une description des themes majeurs etudies au CEA, on y trouve un recensement des besoins, et des propositions pour favoriser l'effort fait dans ce domaine. Une annexe rassemble en outre quelques informations sur les efforts faits en turbulence dans d'autres institutions publiques et privees francaises. (auteurs)Original Title
Analyse et perspectives des etudes sur la turbulence au CEA
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Source
Jun 1992; 104 p; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses
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Report
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CEA, CHAOS THEORY, CLIMATE MODELS, COMPRESSIBLE FLOW, CONVECTION, DETONATION WAVES, FLAME PROPAGATION, FLUID-STRUCTURE INTERACTIONS, IMPLOSIONS, INERTIAL CONFINEMENT, ISOTOPE SEPARATION, LARGE-EDDY SIMULATION, NONLINEAR PROBLEMS, RAYLEIGH-TAYLOR INSTABILITY, RESEARCH PROGRAMS, REYNOLDS NUMBER, TURBULENCE, TURBULENT FLOW, TWO-PHASE FLOW
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