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Events for February 12, 2009
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Diffusion-Weighted and NMR Imaging of Porous Media
Thu, Feb 12, 2009 @ 11:00 AM
Mork Family Department of Chemical Engineering and Materials Science
Conferences, Lectures, & Seminars
A non-invasive study of translational dynamics requires a kind of "marking" or "labeling" of the traveling atoms or molecules for tracing their displacements. Magnetic field is a superb experimental tool for encoding the motion of spin-bearing particles. Moreover, since a geometrical confinement considerably affects diffusive motion, the geometry of porous media can be indirectly accessed by measuring the signal attenuation due to restricted diffusion in inhomogeneous magnetic fields. In this talk, we focus on some theoretical and numerical aspects of this problem. Starting from the classical Bloch-Torrey equation, we obtain the NMR signal in a compact matrix form. Each attenuation mechanism (restricted diffusion, gradient dephasing, surface or bulk relaxation) is represented by a matrix which is constructed from the Laplace operator eigenbasis and thus depending only on the geometry of the confinement. In turn, the physical parameters (free diffusion coefficient, gradient intensity, surface or bulk relaxivity) characterize the "strengths" of the underlying attenuation mechanisms and naturally appear as coefficients in front of these matrices. We illustrate the use of this matrix technique by considering restricted diffusion in simple domains: a slab, a cylinder, and a sphere. Further investigation of irregularly-shaped confinements is discussed.
Location: Hedco Pertroleum and Chemical Engineering Building (HED) - 116
Audiences: Everyone Is Invited
Contact: Petra Pearce Sapir
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Explaining Market Price Discovery as an Algorithmic Process
Thu, Feb 12, 2009 @ 04:00 PM
Thomas Lord Department of Computer Science
Conferences, Lectures, & Seminars
Speaker: Prof. Richard Cole, New York University
Host: Prof. David KempeAbstract:
Self-organizing behavior can often be characterized in terms of a distributed process. It is natural to ask when and why it arises.One instance of such a distributed process is pricing in markets. A basic tenet of well-functioning markets is that they discover (converge toward) prices that simultaneously balance supplies and demands of all goods; these are called equilibrium prices. Further, the markets are self-stabilizing, meaning that they converge toward new equilibria as conditions change. This talk will seek to explain why this might happen by taking an algorithmic approach.More specifically, we introduce the setting of Ongoing Markets (by contrast with the classic Fisher and Exchange markets). An Ongoing Market allows trade at non-equilibrium prices, and, as its name suggests, continues over time. The main task remaining is to specify and analyze a price update rule. We consider a (tatonnement-style) rule with the following characteristics:1. The procedure is distributed: (i) the price updates for each good are independent, and (ii) the update for each good uses only limited "local" information. 2. It is asynchronous: price updates do not have to be simultaneous. 3. It is simple.And for appropriate markets the rule enables:4. Fast convergence. 5. Robustness in the face of (somewhat) inaccurate data.This talk is intended for a general (Computer Science) audience; it is based on joint works with Lisa Fleischer and Ashish Rastogi.Biography:
Richard Cole is a professor of Computer Science in the Courant Institute at NYU, where he has been on the faculty since receiving his Ph.D. in 1982. His Ph.D. was from Cornell, supervised by John Hopcroft. He served as department chair from 1994-2000. He was a fellow of the Guggenheim Foundation in 1988-89, and was named an ACM Fellow in 1998. He is the author or coauthor of over 100 papers. Highlights include the Parallel Merge Sort algorithm, the proof of the Dynamic Finger Conjecture for Splay Trees, and a tight analysis of the Boyer-Moore string matching algorithm.Location: Seaver Science Library (SSL) - 150
Audiences: Everyone Is Invited
Contact: CS Colloquia
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Precision Castparts Corp. Information Session
Thu, Feb 12, 2009 @ 06:30 PM - 07:30 PM
Viterbi School of Engineering Career Connections
Workshops & Infosessions
Join representatives of this company as they share general company information and available opportunities.
Location: Grace Ford Salvatori (GFS) 106
Audiences: Current Engineering Undergraduate/Graduate Students
Contact: RTH 218 Viterbi Career Services
