Events at Physics |
Events on Tuesday, October 28th, 2008
- Chaos & Complex Systems Seminar
- Chaos and its application in secure communication
- Time: 12:05 pm
- Place: 4274 Chamberlin (Refreshments will be served)
- Speaker: Kehui Sun, UW Department of Physics
- Abstract: Chaotic systems have several significant features favorable to secure communication, such as aperiodicity (useful for one-time pad cipher); sensitivity to initial conditions and parameters (useful for effective bit confusion and diffusion); and random behaviors (useful for producing output signals with satisfactory statistics). Thus, chaotic systems and their application in secure communication have received increasing attention. Up to now, four main secure communication schemes based on chaos synchronization have been investigated, such as chaos masking, chaos shifting key, chaos modulation, and chaos spread spectrum. In fact, chaos synchronization is one of the key technologies in the chaotic secure communication for its practical use. So I will focus on the chaos synchronization and chaos secure communication schemes in my talk.
- Astronomy Colloquium
- Understanding the Interstellar Neighborhood: Structure, Dynamics, and Quasar Scintillation"
- Time: 3:30 pm
- Place: 6515 Sterling Hall
- Speaker: Dr. Jeff Linsky, UC- Boulder
- Abstract: Absortion line spectroscopy provides a precise tool for understanding the properties of gas in the very local region of the Galactic disk and by implication interstellar media elsewhere in the universe. I will describe our recent studies of the dynamics and structure of local warm gas based on high-resolution HST and ground based Ca II spectra. Analysis of 157 sight lines shows that most velocity components can be modeled with 15 velocity vectors indicating the presence of 15 parcels of warm gas located within a few parsecs of the Sun. Cloud-cloud interactions may explain the morphologies and physical properties of these clouds.<br>
Large-amplitude intraday and annual variability of quasars can be simply explained as scintillation produced by nearby turbulent-scattering screens.<br>
I will show that the scattering screens are located near the edges of nearby warm clouds and that the turbulence responsible for the scattering could be explained by the interaction of clouds with large differences in radial and transverse velocities. - Host: Professor Blair Savage