Thursday, September 12, 2002 (12.15 pm; Room 1207 Energy Research Building)
Michael Efroimsky, Univ of Minnesota
Inelastic Dissipation in a Freely Precessing Rotator. Applications to Interstellar-Dust Astrophysics, Tumbling Asteroids, Comets, Rotating Spacecraft, etc...
Abstract: Neutron stars, asteroids, comets, cosmic-dust granules, spacecraft, as well as whatever other freely spinnig body dissipate energy when they rotate about any axis different from principal. We study the internal-dissipation-caused relaxation of a freely precessing rotator to its minimal-energy mode (which corresponds to the spin about the maximal-inertia axis). We show that the internal dissipation takes place not so much at the frequency of body's precession but rather at the second and higher harmonics. In other words, this simple mechanical system provides an example of extreme non-linerity. Most surprisingly, lower frequencies also do come into play. The earlier estimates, that ignored this non-linearity, considerably underestimated the efficiency of the internal relaxation of wobbling asteroids and comets. At the same time, owing to the non-linearlity of inelastic relaxation, small-angle nutations can persist for very long time spans. The developed formalism has been applied, by me and by my colleagues, to description of cosmic-dust alignment and to analysis of asteroidal and cometary wobble These results are applicable also to the studies of damping of rotating spacecraft.
Atsushi Uchida, UMD
Dual synchronization of chaos in optical and electronic systems
Thursday, September 19, 2002 (12.15 pm; Room 1207 Energy Research Building)
Daniel Wojcik, IPST, UMD
Diffusive-ballistic crossover in 1D quantum multibaker walks
Aleksey Zimin, UMD
Efficient Local Ensemble Data Assimilation Technique
Thursday, September 26, 2002 (12.15 pm; Room 1207 Energy Research Building)
Eugenia Kalnay, UMD
Are Bred Vectors and Lyapunov Vectors the same?
Doug Armstead, UMD
Long Time Algebraic Relaxation in Chaotic Billiards
Thursday, October 3, 2002 (12.15 pm; Room 1207 Energy Research Building)
Jonathan Ozik, UMD
"Simulating Granular Coral Snake Patterns in Long Rotating Cylinders"
Sang-Yoon Kim,UMD
"Strange Nonchaotic Attractors in Quasiperiodically Forced Period-Doubling Systems."
Thursday, October 10, 2002 (12.15 pm; Room 1207 Energy Research Building)
Joerg Schumacher, Philipps-Universitaet, Germany
Clustering of Lagrangian tracers on free-surface flows.
Wayne Hayes, Univ. of Toronto
Shadowing the softened N-body problem
Thursday, October 17, 2002 (12.15 pm; Room 1207 Energy Research Building)
Richard Prange, UMD
Exotic quantum states in transiently integrable systems
no second speaker
Thursday, October 24, 2002 (12.15 pm; Room 1207 Energy Research Building)
Lou Pecora, NRL
Synchronization of oscillators in smallworld networks
Katepalli Sreenivasan, IPST, UMD
Asymmetry in the presence of intermittency
Thursday, October 31, 2002 (12.15 pm; Room 1207 Energy Research Building)
Victor Yakhot, Boston University
hydro-kinetic equation for description and simulation of strongly nonlinear fluids
(one talk only)
Thursday, November 7, 2002 (12.15 pm; Room 1207 Energy Research Building)
Tom Carroll, NRL
Regions of Period Doubling in the Diode Resonator
Moustafa Fofana, Department of Mechanical Engineering, Worcester Polytechnic Institute
Hopf Interactions in Machining Operations with Nonlinear Regenerative Chatter
Thursday, November 14, 2002 (12.15 pm; Room 1207 Energy Research Building)
Linda Moniz, NRL
Damage Assessment
Abstract: Analysis of data from experiments on dynamical systems often centers on the embedding of time series data to reconstruct an attractor. In our system, we consider output from (chaotic excitation of) a circuit designed to simulate a spring-mass system in both a damaged and an undamaged state. We employ a new version of the continuity statistic, first introduced by Pecora, Carroll and Heagy[1]. Here we use the statistic in the new setting of multiple time series embedding. We show the continuity statistic is an appropriate and sensitive tool for showing differences in the reconstructed attractors in the damaged and undamaged states.
[1] Pecora, L.M., Carroll, T.L. and Heagy, J.F. [1995] Statistics for mathematical properties between time-series embeddings,
Physical Review E 52(4),3420.
Thursday, November 21, 2002 (12.15 pm; Room 1207 Energy Research Building)
Cristel Chandre, Georgia Tech
Time-frequency analysis of chaotic systems
ABSTRACT: We describe a method for analyzing the phase space structures of Hamiltonian systems. This method is based on a time-frequency decomposition of a trajectory using wavelets. This method detects resonance trappings and transitions and allows a characterization of the notion of weak and strong chaos. It provides dynamical properties of the system. We illustrate this method using examples from atomic physics, celestial mechanics and chemical physics.
Guocheng Yuan, Brown University
Cross-jet transport and mixing in a meandering jet
ABSTRACT: An f-plane, quasi-geostrophic, 2 1/2 layer model is used to examine whether cross-jet transport can be enhanced at depth in a surface-intensified ocean jet, similar to the Gulf Stream. By using dynamical systems techniques, we find that cross-jet transport can be enhanced in the lower layer, but only when the vertical shear is sufficiently strong. Some preliminary results for understanding the role of transport barriers in controlling potential vorticity mixing will also be presented.
Special Seminar (NOTE DAY: FRIDAY, November 22, 2002 (12.15 pm; Room 1207 Energy Research Building)
Detlef Lohse, Univeristy of Twente
Rayleigh-Benard convection
Informal Statistical Physics seminar (due to a scheduling mistake, this talk was originally also scheduled for Dec 5):
Tuesday, November 26, 2002 (1.15 pm; Room 1116 IPST building)
Steven Schiff, Krasnow Institute, George Mason University
Relating Bad Brains, Rocks, and Gases -- Are Seizures Phase
Transitions?Special seminar (NOTE DAY+TIME): WEDNESDAY, November 27, 2002 (2 pm; Room 1207 Energy Research Building)
Tomas Bohr, Technical University of Denmark
Structure formation in laminar fluid flow: the creation of corners, cusps and needles
Thursday, December 5, 2002 (12.15 pm; Room 1207 Energy Research Building)
Romulus Breban, UMCP
Scaling Properties of the Indeterminate Saddle-Node Bifurcation
Thursday, December 12, 2002 (12.15 pm; Room 1207 Energy Research Building)
Bob Behringer, Duke University
Fluctuations, rate-dependence, and jamming in dense granular materials.
ABSTRACT: Granular materials exist in states that are roughly equivalent to those of ordinary molecular materials. Models for granular gases are at least moderately successful. However, models for dense granular phases, the subject of this talk, are still very much an open subject. Dense systems are typically characterized by enduring contacts between particles. In addition, forces are carried preferentially along a filamentary network known as force chains.
Recent work has focused on the statistical properties of these phases, and in particular on the transition that occurs from solid-like to fluid-like behavior as the shear stress is increased or more random energy is provided to the system. In engineering parlance, this transition is associated with Reynolds dilatancy, and in newer physics parlance, it is associated with jamming. Particularly intriguing is the possibility that the jamming transition of granular materials is representative of behavior in a much broader class of materials that includes colloids, foams, glasses and other systems.
We have carried out a number of experiments to characterize the statistical properties of dense granular materials. I will briefly outline issues associated with force propagation. In the remainder of the talk, I will present results on sheared systems. We have shown experimentally that there is a well-defined transition where the force-chain structure disappears. In MD simulations (with Lou Kondic--NJIT) this transition is associated with a major change in the partitioning of energy between kinetic and elastic modes. We have also investigated a long-standing tenet of continuum models: that stresses for sheared granular materials are rate-independent. We find that this is not the case, but rather that there is a logarithmic strengthening of the force network with shear rate.
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Note the different day and time for theses talks. Lunch will NOT be served for summer seminars unless otherwise posted.
Tuesday, July 9, 2002 (11am; Room 1207 Energy Research Building)Bhaskar Khubchandani, UMCP
The Influence of Stochasticity on Four-Wave-Mixing in an Optical FiberWing-Shun Lam, UMCP
Nature of Power Dropouts of Semiconductor Laser with Optical Feedback: Deterministic or Stochastic?Tuesday, July 16, 2002 (11am; Room 1207 Energy Research Building)
Hinke Osinga, University of Bristol
The geometry of optimal control
We study the value function and the existence and regularity of optimal trajectories to determine the structure of the solution set of a class of infinite-horizon optimal control problems. Optimal trajectories are always images of Hamiltonian trajectories on a global stable manifold. These ideas are illustrated with the example of an inverted pendulum on a cart. This is joint work with John Hauser (Colorado).
Bernd Krauskopf, University of BristolUnstable manifolds in lasers with delay
We show how a new method for computing unstable manifolds of periodic orbits in delay differential equations can be used to study transitions to chaos in lasers with delay. This is joint work with Kirk Green (Bristol).
Tuesday, August 27, 2002 (11am; Room 1207 Energy Research Building)Jordi Garcia-Ojalvo, Technical University of Catalonia, Spain
Entrainment and synchronization in delay-coupled lasersJose M. Sancho, University of Barcelona, Spain
Order out of noise
Stephan Koehler, Harvard University
Foams: Drainage through single plateau borders. Direct observation of rigid and mobil interfaces.Thursday, January 31, 2002 (12.15pm; Room 1207 Energy Research Building)
Istvan Szunyosh, UMCP
On the relationship between the quality of weather forecasts and the resolution of the forecast modelsNicholas Weber, NRL
Adaptation to the Edge of Chaos via Low-Pass Filtered FeedbackThursday, February 7, 2002 (12.15pm; Room 1207 Energy Research Building)
Hydrodynamic Instabilities of Wormlike Micellar FluidsJordi Garcia-Ojalvo, Technical Univ. of Catalonia
Communicating with optical spatio-temporal chaosThursday, February 14, 2002 (12.15pm; Room 1207 Energy Research Building)
Arshad Kudrolli, Clark University
Vortices in vibrated granular rodsThursday, February 21, 2002 (12.15pm; Room 1207 Energy Research Building)
Katepalli Sreenivasan, UMCP
An informal discussion of atmospheric predictabilityThursday, February 28, 2002 (12.15pm; Room 1207 Energy Research Building)
Horst Meyer, Duke University
Heat Transfer and Convection Onset in a Compressible Fluid: 3He Near the Critical PointThursday, March 7, 2002 (12.15pm; Room 1207 Energy Research Building)
Peter Schiffer, Penn State
Jamming and drag in granular media***SECOND TALK POSTPONED***
Ron Skupsky, NIH
Mathematical modelling of gradient sensing in eukaryotic cellsJonathan Aurnou, Carnegie Institute of Washington
Effects of shell geometry on planetary dynamosThursday, April 4, 2002 (12:15pm; Room 1207 Energy Research Building)
Paulo Arratia, Rutgers University
Spontaneous Chaos in non-Newtonian FluidsJustin Lacombe, Rutgers University
Mixing in 3-D Dynamical SystemsThursday, April 11, 2002 (12:15pm; Room 1207 Energy Research Building)
Wayne Hayes, University of Toronto TALK POSTPONED -- seminar will proceed with 1 talk
Shadowing the gravitational N-body problemJulio Friedman, UMCP
Sandstone injectites: a geological record of granular fluidization, dynamic crack propogation, and seismic shakingThursday, April 18, 2002 (12:15pm; Room 1207 Energy Research Building)
Crystal Cooper, UMCP
A Reaction-Diffusion Model for Experimentally Altered Visual Function in Xenopus FrogsDhanurjay Patil, UMCP
Using Large Member Ensembles to Study Regions of Local Low Dimensionality in the AtmosphereThursday, April 25, 2002 (12:15pm; Room 1207 Energy Research Building)
Allen Hunt, CIRES, University of Colorado, Boulder
Why percolation theory is necessary to understand water retention, unsaturated flow, and solute diffusion in porous mediaRyan McAllister, UMCP
Competition between two frequencies for phase synchronization of a chaotic laserThursday, May 2, 2002 (12:15pm; Room 1207 Energy Research Building)
Robert Leheny, Johns Hopkins University
Memory in an Aging Structural GlassKyuyong Lee, UMCP
(Cell-Dendrite transition)Thursday, May 9, 2002 (12:15pm; Room 1207 Energy Research Building)
No seminarThursday, May 16, 2002 (12:15pm; Room 1207 Energy Research Building)
David DeShazer, UMCP
Noise Induced Burst Synchronization in Fiber Ring LasersWayne Hayes, University of Toronto
Shadowing the gravitational N-body problem