This calendar is your conduit to the events in Plan-It Purple that pertain specifically to the McCormick School of Engineering. If you would like to list an event on the calendar, please consult the list of department contacts.
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Event List
This list shows events for May 19 only. [Show all events]
2008 NICO Complexity Conference
Monday May 19, 2008 at 8:30 AM — Allen Center
AM Leg - "Connecting the Nets: Network Evolution" will feature the following:
Neo Martinez (PEaCE Lab)- "Dynamics and Robustness in Complex Network: How Does Nature Keep it Together and How Does it Fall Apart?"
Neil Johnson (U of Miami)- Complex Laws for Next-Generation Wars: from Iraq and Global Terrorism, to Street Gangs and Online Guilds"
Michelle Girvan (U of Maryland)- “Modularity: Mechanisms and Measurements”
PM Leg - "Outbreaks" will include:
James Fowler (UC San Diego)- “The Dynamic Spread of Happiness in a Large Social Network”
Alex Vespignani - “The Impact of Mobility Networks on the Worldwide Spread of Epidemics”
Vittoria Colizza - “Do the Rich Really Take it All?
A Student Poster Board presentation will close the day's activities. Please e-mail for entry information.
Event URL: http://www.northwestern.edu/nico/complexity-conference/
For more information, contact:
Tanya Stanfield
complexity-conference@northwestern.edu
847-467-1348
Northwestern Institute on Complex Systems (NICO)
[Show detail]
EECS SEMINAR: "Development of a High Power Sum-Frequency Sodium Laser for ‘Laser Guide Star’ Appl.
Monday May 19, 2008 at 11:00 AM — Technological Institute - Room L324
EECS Seminar
Dr. Renu Tripathi
Palomar Observatory at Caltech
“Development of a High Power Sum-Frequency Sodium Laser for ‘Laser Guide Star’ Application”
Adaptive optics (AO) systems require a reference source in order to correct for the atmospheric distortion of light. Sufficiently bright stars are not available in all parts of the sky, which limits the usefulness of natural guide star adaptive optics. However, one can create an artificial guide star by shining a laser into the atmosphere. Lasers that can excite the D2 line in sodium (Na) atoms present in the mesosphere (about 50 km to 80-90 km altitude above Earth's surface) are of significant interest to the astronomical scientific community. The return signal received from backscattering serves as an artificial bright star. When imaged through a ground-based telescope onto a wavefront sensor, this provides a dynamic map of the atmospheric distortion or turbulence. This information is then used to adaptively correct the phase errors through feedback onto deformable mirrors used in the telescope to significantly improve their resolution.
During the talk, I will discuss my efforts to develop a high power sum-frequency sodium laser system based on sum-frequency mixing of two (1064 nm and 1319 nm) diode-pumped, pulsed and mode-locked Nd:YAG lasers. I will describe my continued effort in improving the system to obtain higher average optical power by virtue of better cavity design, efficient mode-locking and nonlinear wave-mixing. Currently, the laser operates with an average power of 8W at 500 Hz repetition rate and with 10% duty cycle. I will show the critical component development in the laser system and briefly discuss the projection from the launch telescope, laser beam quality and the photon number density in the return signal. I will also show some early results obtained using the table-top laser system operating in conjunction with the adaptive optics (AO) system at the Caltech’s Palomar observator
Event URL: http://www.eecs.northwestern.edu/events/
For more information, contact:
Brooke Hildebrand
brooke@eecs.northwestern.edu
847-491-3451
Electrical Engineering & Computer Science
[Show detail]
Rinzel: Dynamics of perceptual bistability
Monday May 19, 2008 at 4:00 PM — Tech M416
Applied Math Colloquium
Title: Dynamics of perceptual bistability
Speaker: J. Rinzel, New York University (Courant Institute)
Abstract: When visualizing an ambiguous scene (such as the Necker cube) one may perceive ongoing random alternations between the possible interpretations. Dynamical models implement competition as reciprocal inhibition between neuronal populations; dominance alternates - while slow negative feedback, adaptation, sets the basic time scale (seconds) for switching. When adaptation is strong enough it overcomes dominance and alternations occur intrinsically and periodically; noise perturbs the regularity. In a different framework, attractor-based dynamics, adaptation is weak and switches are induced by noise operating on a bistable system. We find that statistics of the observed alternations provide constraints that favor an operating range near the transition zone between the parameter regimes for the two mechanisms. In some paradigms one can manipulate stimulus cues to bias the competition away from equal dominance. We have proposed that the percent of time dominant is a measure for the likelihood of valid interpretation of the scene.
For more information, contact:
Beth Siculan
b-siculan@northwestern.edu
847-491-3345
McCormick-Colloquia Engineering Sciences and Appli
[Show detail]
