Applied Dynamics seminars - 2002


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

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.





Previous Seminars  - Summer 2002

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 Fiber
Wing-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 Bristol
Unstable 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 lasers
Jose M. Sancho, University of Barcelona, Spain
Order out of noise

Spring 2002

Thursday, January 24, 2002  (12.15pm; Room 1207 Energy Research Building) (one short seminar)

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 models
Nicholas Weber, NRL
Adaptation to the Edge of Chaos via Low-Pass Filtered Feedback
Thursday, February 7, 2002  (12.15pm; Room 1207 Energy Research Building)
Note (2/4/02):  New second speaker!!
Andrew Belmonte, Penn State
Hydrodynamic Instabilities of Wormlike Micellar Fluids
Jordi Garcia-Ojalvo, Technical Univ. of Catalonia
Communicating with optical spatio-temporal chaos
Thursday, February 14, 2002  (12.15pm; Room 1207 Energy Research Building)

Arshad Kudrolli, Clark University

Vortices in vibrated granular rods
Thursday, February 21, 2002  (12.15pm; Room 1207 Energy Research Building)
(One 1 hour talk)

Katepalli Sreenivasan, UMCP

An informal discussion of atmospheric predictability
Thursday, February 28, 2002  (12.15pm; Room 1207 Energy Research Building)
(One 1 hour talk)

Horst Meyer, Duke University

Heat Transfer and Convection Onset in a Compressible Fluid: 3He Near the Critical Point
Thursday, March 7, 2002  (12.15pm; Room 1207 Energy Research Building)

Peter Schiffer, Penn State

Jamming and drag in granular media
Thursday, March 14, 2002  (12.15pm; Room 1207 Energy Research Building)

Ron Skupsky, NIH

Mathematical modelling of gradient sensing in eukaryotic cells
Jonathan Aurnou, Carnegie Institute of Washington
Effects of shell geometry on planetary dynamos
Thursday, April 4, 2002  (12:15pm; Room 1207 Energy Research Building)

Paulo Arratia, Rutgers University

Spontaneous Chaos in non-Newtonian Fluids
Justin Lacombe, Rutgers University
Mixing in 3-D Dynamical Systems
Thursday, 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 problem
Julio Friedman, UMCP
Sandstone injectites: a geological record of granular fluidization, dynamic crack propogation, and seismic shaking
Thursday, April 18, 2002  (12:15pm; Room 1207 Energy Research Building)

Crystal Cooper, UMCP

A Reaction-Diffusion Model for Experimentally Altered Visual Function in Xenopus Frogs
Dhanurjay Patil, UMCP
Using Large Member Ensembles to Study Regions of Local Low Dimensionality in the Atmosphere
Thursday, 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 media
Ryan McAllister, UMCP
Competition between two frequencies for phase synchronization of a chaotic laser
Thursday, May 2, 2002  (12:15pm; Room 1207 Energy Research Building)

Robert Leheny, Johns Hopkins University

Memory in an Aging Structural Glass
Kyuyong Lee, UMCP
(Cell-Dendrite transition)
Thursday, May 9, 2002  (12:15pm; Room 1207 Energy Research Building)
No seminar
Thursday, May 16, 2002  (12:15pm; Room 1207 Energy Research Building)

David DeShazer, UMCP

Noise Induced Burst Synchronization in Fiber Ring Lasers
Wayne Hayes, University of Toronto
Shadowing the gravitational N-body problem