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Events for December 06, 2007
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CS Colloquia: Next Generation Dynamic Spectrum Systems
Thu, Dec 06, 2007 @ 11:00 AM - 12:30 AM
Thomas Lord Department of Computer Science
Conferences, Lectures, & Seminars
Title: Next Generation Dynamic Spectrum SystemsSpeaker: Prof. Heather Zheng(UCSB)ABSTRACT:
Today's static spectrum assignment policy has led to a critical spectrum
shortage. While innovative wireless networks such as WiMAX are denied
from spectrum access, the majority of existing networks use only 10-15%
of their assigned spectrum. To reuse "wasted" spectrum, the recent
proposal on dynamic spectrum access allows unlicensed (secondary) users
to opportunistically utilize unused licensed spectrum on a
non-interfering basis. This "creates" new capacity and commercial value
from existing under-utilized spectrum.While it shows great promise, the technology underlying dynamic spectrum
systems is still in its infancy. Issues in wireless communications and
networking, once addressed in the context of fixed spectrum assignment,
offer new research challenges in the realm of dynamic spectrum systems.
In this talk, we describe some existing and on-going efforts on
dynamic spectrum systems. We begin by describing distributed algorithms
for secondary users to access spectrum fairly and efficiently. We
introduce (1) a distributed coordination approach where devices
coordinate to adapt spectrum assignment over topology variations, and
(2) a light-weight rule-based solution that requires minimum
communication overhead. We then present a dynamic spectrum auction
framework that addresses the impact of economic issues. We conclude by
summarizing this work in context, and discussing current and future
directions in combining these results with higher layer mechanisms, and
applying cross-layer design to produce an end-to-end programmable and
adaptive network.Additional information about this research can be found at
http://link.cs.ucsb.edu.BIO:
Since August 2005, Heather Zheng has been an assistant professor at
Department of Computer Science, University of California, Santa Barbara.
Her research area includes wireless networking and communications, and
multimedia computing. She currently focuses on Cognitive Radios and
dynamic spectrum networks. Her research on Cognitive Radios was selected
as one of the 10 Emerging Technologies of 2006 by MIT Technology Review
Magazine, and the Best Student Paper in IEEE DySPAN 2007. Dr. Zheng was
named as the MIT Technology Review's Top 35 Innovators under the age of
35 in 2005. She also received 2006 World Technology Award (top 5 in
communication), 2002 Bell-Labs President's Gold Award, 1998-99 George
Harhalakis Outstanding Graduate Student Award from University of
Maryland, College Park. Dr. Zheng received her Ph.D. from University of
Maryland, College Park in 1999 and then joined wireless research lab,
Bell-Labs, Lucent Technologies. She then moved to Microsoft Research
Asia as a project lead in March 2004 and later joined UCSB.Location: Seaver Science Library (SSL) - 150
Audiences: Everyone Is Invited
Contact: CS Colloquia
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Lyman Handy Colloquium Series
Thu, Dec 06, 2007 @ 12:45 PM - 01:50 PM
Mork Family Department of Chemical Engineering and Materials Science
Conferences, Lectures, & Seminars
Speaker: Rakesh Agrawal
School Of Chemical Engineering
Purdue University
West Lafayette, IN, USAhttps://engineering.purdue.edu/ChE/Directory/Faculty/Agrawal.htmlEnvironmentally Friendly Energy SolutionsThe recent rise in oil prices again reminds us that the world's supply of fossil fuels is finite. Roughly 85% of current energy use is being met by fossil fuels. Alternate primary energy sources are being identified and developed to permit the continued functioning of the world economy. The first part of this presentation will survey some of these alternative sustainable primary energy sources: solar, wind, nuclear, and bio-based sources. It will also review the particular challenges associated with various end uses of energy.Common energy carriers, such as electricity, are used to move energy from several primary sources to many different end uses. Recently, the possibility of an alternate energy system using H2 as a common energy carrier has been proposed and widely debated. In such a system, H2 would first have to be produced from a primary source. It would then need to be transported, delivered and stored at the point of end use. The second part of this presentation will briefly highlight the challenges associated with H2 supply chain that is currently being considered for fuel cell vehicles. Finally, some new and novel solutions to sustain the current transportation sector will be presented. These solutions provide a feasible framework for a fossil fuel-free world. Also they provide exciting possibilities for chemical engineers to apply their expertise and contribute to the grand challenge of energy.
Location: Olin Hall of Engineering (OHE) - 122
Audiences: Everyone Is Invited
Contact: Petra Pearce Sapir
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Vibration Mitigation of Nonlinear Structures using Nonlinear Energy Sinks
Thu, Dec 06, 2007 @ 02:00 PM - 03:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker:
Mr. Régis Viguié,
Ph.D. Candidate,
Aerospace and Mechanical Engineering Department,
University of Liège,
Liège, BelgiumAbstract:The tuned mass damper (TMD) is a simple and efficient device but it is only effective when it is precisely tuned to the frequency of a particular vibration mode. Because nonlinear vibrating structures have resonant frequencies that vary with the total energy in the system, the efficiency of a TMD is questionable in this case. In order to overcome this limitation, the nonlinear energy pumping phenomenon from the main mechanical structure to a coupled, local, passive nonlinear energy sink (NES) is investigated. It is shown that, unlike the TMD, an NES has no preferential resonant frequency, which makes it a good candidate for vibration mitigation of MDOF linear or nonlinear vibrating structures. In this presentation, the essential features of an NES will be described. Some potential applications of nonlinear energy pumping, including vibration absorption in drill-string systems and aeroelastic instability suppression, will be presented. Finally, the determination of a suitable design for the NES will also be discussed as well as some possible realizations of this nonlinear absorber.
Location: Kaprielian Hall (KAP) - 209
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
