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SUNMONTUEWEDTHUFRISAT
Events for January 29, 2008
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Pulsed-laser processing of ferromagnetic semiconductors
Tue, Jan 29, 2008 @ 01:00 PM
Mork Family Department of Chemical Engineering and Materials Science
Conferences, Lectures, & Seminars
Graduate SeminarbyOscar D. Dubón, Jr.Department of Materials Science and Engineering
University of California Berkeley and Lawrence Berkeley National Laboratory
Berkley, CAAbstract:Because of their unique combination of magnetic and semiconducting properties and their potential as both injection sources and filters for spin-polarized carriers, ferromagnetic semiconductors have attracted much attention for spin-based electronics, or spintronics. These novel materials are formed by the substitution of a relatively small fraction of host atoms—a few atomic percent—with a magnetic species such as Mn. In the prototypical ferromagnetic semiconductor Ga1-xMnxAs, inter-Mn exchange is known to be mediated by holes in extended or weakly localized states; however, the fundamental nature of exchange across the Ga-Mn-pnictide series is less clear. Unfortunately, challenges in materials synthesis have obstructed both the further understanding of these materials and their application in practical devices. Even the relatively low alloying levels necessary for ferromagnetism require the application of non-equilibrium growth strategies, in particular low-temperature molecular beam epitaxy (LT-MBE).At Berkeley we have undertaken investigations on the synthesis of ferromagnetic semiconductors using a combination of Mn ion implantation and pulsed-laser melting (II-PLM). By this simple process we have produced epitaxial, single crystalline films of ferromagnetic GaxMn1-xAs. These epilayers display the essential magnetic and electrical properties observed in films grown by LT-MBE. We have used II-PLM to produce new Ga-Mn-pnictide alloys including ferromagnetic Ga1-xMnxP. This material represents an intriguing system in which strongly localized carriers in a detached impurity band stabilize ferromagnetism. The possibility of introducing more than one species by ion implantation into a semiconductor host opens further opportunities to study quaternary alloys and probe chemical trend in the ferromagnetic Curie temperature. I will present results from our studies of these novel ferromagnetic semiconductors as well as efforts to develop laser patterning techniques for the realization of planar spintronic structures.Tuesday, January 29, 2008
Seminar at 1:00p.m.
OHE 122
The Scientific Community is Cordially Invited
Location: Olin Hall of Engineering (OHE) - 122
Audiences: Everyone Is Invited
Contact: Petra Pearce Sapir
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Torsional Effects on the Inelastic Seismic Response of Structures
Tue, Jan 29, 2008 @ 01:00 PM - 03:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Oral Defense by: Mehran Mansuri,
Sonny Astani Department of Civil and Environmental EngineeringABSTRACT:
To evaluate inelastic torsional response of buildings due to different parameters such as unsymmetrical distribution of mass or lateral load resisting elements in the plan of the structure or yielding and inelastic behavior of resisting elements and loss of the resistance of such an element during an earthquake, a full three-dimensional nonlinear dynamic analysis is a powerful tool to evaluate such a nonlinear response.
The results of nonlinear dynamic analyses of two actual steel moment frame buildings that were damaged during the 1994 Northridge earthquake subjected to couple of different recorded ground motions from Northridge and Loma Prieta earthquakes are presented and the importance of different parameters such as discontinuity of lateral resisting elements, unsymmetrical distribution of mass or resistance in the plan of structure, intensity and frequency content of earthquake ground motions, accidental eccentricity as prescribed by code and the effect of geometric nonlinearity (P-Delta) on the inelastic lateral-torsional response of structures is discussed. Response parameters considered include lateral story displacement, Interstory drift index, plastic hinge rotation demand and torsional rotation of each floor.
The analysis procedures use three-dimensional nonlinear dynamic analytical models developed for the PERFORM 3-D computer program.
Study of the results for different models with different eccentricities clearly shows the effect of inelastic torsion in comparison with elastic torsion on the response of structures. The torsional rotation of floors considered as a main parameter of torsional response of the building has an average increase of 30 to 60 percent for material nonlinearity. By adding geometric nonlinearity (P-Delta), this increases 70 to 100 percent of elastic torsional rotation. This clearly shows the inelastic torsional response of structures may be significantly underestimated by a linear dynamic analysis, especially for large value of mass or stiffness eccentricity and intensity of the ground motion.
Location: Kaprielian Hall (KAP) - 209
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
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Approximation Algorithms for Combinatorial Allocation Problems
Tue, Jan 29, 2008 @ 03:30 PM - 05:00 PM
Daniel J. Epstein Department of Industrial and Systems Engineering
University Calendar
Computer Science Colloquium: Approximation Algorithms for Combinatorial Allocation ProblemsSpeaker: Dr. Jan Vondrak (Princeton)Time: 3:30 pm - 5:00 pmDate: Jan 29, 2008Location: SSL 150Host: Prof. David KempeABSTRACT: Combinatorial allocation problems arise in situations where a set of items should be distributed among n players in order to maximize a certain social utility function. Such problems have been subject to recent interest due to their applications in combinatorial auctions and electronic commerce. Since allocation problems are typically NP-hard to solve optimally, we seek approximation algorithms that find a solution of value at least c * OPTwhere OPT is the optimum and cA particular case of interest is the Submodular Welfare Problem where utility functions are assumed to be monotone and submodular. It has been known since 1978 that a greedy algorithm gives a 1/2-approximation [Nemhauser,Wolsey,Fisher] for a more general problem of submodular maximization subject to a matroid constraint. I will show how this can be improved to a (1-1/e)-approximation - an approximation factor which is known to be optimal. A new technique that we use is the approximate solution of a non-linear optimization problem using a "continuous greedy algorithm".(partly joint work with G. Calinescu, C. Chekuri and M. Pal)BIO: Jan Vondrak grew up in the Czech republic and received a Master's degree in computerscience from Charles University in Prague. He attended graduate school at MIT where he received a PhD in applied math in 2005. His advisor was Michel Goemans. He spent a year as a postdoctoral researcher at Microsoft Reserch (2005-06) and is currently a postdoctoral researcher at Princeton University.
Location: Seaver Science Library (SSL) - 150
Audiences: Everyone Is Invited
Contact: Georgia Lum
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CS Colloquia: Approximation algorithms for combinatorial allocation problems
Tue, Jan 29, 2008 @ 03:30 PM - 05:00 PM
Thomas Lord Department of Computer Science
Conferences, Lectures, & Seminars
Title: Approximation algorithms for combinatorial allocation problemsSpeaker: Dr. Jan Vondrak (Princeton)ABSTRACT:
Combinatorial allocation problems arise in situations where a set of items
should be distributed among n players in order to maximize a certain social
utility function. Such problems have been subject to recent interest due to
their applications in combinatorial auctions and electronic commerce. Since
allocation problems are typically NP-hard to solve optimally, we seek
approximation algorithms that find a solution of value at least c * OPT where
OPT is the optimum and cA particular case of interest is the Submodular Welfare Problem where utility
functions are assumed to be monotone and submodular. It has been known since
1978 that a greedy algorithm gives a 1/2-approximation [Nemhauser, Wolsey,
Fisher] for a more general problem of submodular maximization subject to a
matroid constraint. I will show how this can be improved to a
(1-1/e)-approximation - an approximation factor which is known to be optimal.
A new technique that we use is the approximate solution of a non-linear
optimization problem using a "continuous greedy algorithm".(partly joint work with G. Calinescu, C. Chekuri and M. Pal)BIO:
I grew up in the Czech republic and I got a Master's degree in computer
science from Charles University in Prague. Then I went to grad school at MIT
where I got a PhD in applied math in 2005. My advisor was Michel Goemans. I
spent a year as a postdoc at Microsoft Reserch (2005-06) and currently I'm a
postdoc at Princeton University.
~Location: Seaver Science Library (SSL) - 150
Audiences: Everyone Is Invited
Contact: CS Colloquia
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Approximation algorithms for combinatorial allocation problems
Tue, Jan 29, 2008 @ 03:30 PM - 05:00 PM
Thomas Lord Department of Computer Science
Conferences, Lectures, & Seminars
ABSTRACT:
Combinatorial allocation problems arise in situations where a set of items should be distributed among n players in order to maximize a certain social utility function. Such problems have been subject to recent interest due to their applications in combinatorial auctions and electronic commerce. Since allocation problems are typically NP-hard to solve optimally, we seek approximation algorithms that find a solution of value at least c * OPT where OPT is the optimum and cA particular case of interest is the Submodular Welfare Problem where utility functions are assumed to be monotone and submodular. It has been known since
1978 that a greedy algorithm gives a 1/2-approximation [Nemhauser, Wolsey, Fisher] for a more general problem of submodular maximization subject to a matroid constraint. I will show how this can be improved to a (1-1/e)-approximation - an approximation factor which is known to be optimal.
A new technique that we use is the approximate solution of a non-linear optimization problem using a "continuous greedy algorithm".(partly joint work with G. Calinescu, C. Chekuri and M. Pal)BIO:
I grew up in the Czech republic and I got a Master's degree in computer science from Charles University in Prague. Then I went to grad school at MIT where I got a PhD in applied math in 2005. My advisor was Michel Goemans. I spent a year as a postdoc at Microsoft Reserch (2005-06) and currently I'm a postdoc at Princeton University.
Location: Seaver Science Library (SSL) - 150
Audiences: Everyone Is Invited
Contact: CS Front Desk
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KIUEL Book Club
Tue, Jan 29, 2008 @ 05:00 PM
Viterbi School of Engineering Student Affairs
Workshops & Infosessions
The KIUEL Book Club will hold its first meetings of the spring semester on Monday, January 28 and Tuesday, January 29 at 5pm in RTH 110. We will be discussing "The Kite Runner" by Khaled Hosseini. If you are interested in participating in the Book Club, please send an email to viterbi.kiuel@usc.edu.
Location: Ronald Tutor Hall of Engineering (RTH) - 110
Audiences: Undergrad
Contact: Viterbi Admission & Student Affairs
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Recruitment - Spring 08
Tue, Jan 29, 2008 @ 07:00 PM - 09:00 PM
Viterbi School of Engineering Student Organizations
Student Activity
CALLING ALL WOMEN ENGINEERS!!!
-Need help with that killer homework?
-Want to make friendships and memories to last a lifetime? Join AOE! USC's only professional and social ENGINEERING SORORITY! To find out more come to our events: 1/23: Info Night
1/24: Games and Pinkberry!
1/25: Bowling!
1/28: Professional Night Dinner
1/29: Frame Painting & Ice Cream ***All events FREE! meet @ 7pm in front of Tommy Trojan. Visit our website:www-scf.usc.edu/~aoeLocation: Meet In Front of Tommy Trojan
Audiences: All Women in Engineering (undergrad and graduate)
Contact: Alpha Omega Epsilon
