Upcoming Seminars

TUESDAY, April 29, 2008

        MATHEMATICS AND COGNITION SEMINAR           PSA 206   12:15 p.m.
        Tom Taylor, Department of Mathematics and Statistics
          "A Probabilistic View of Dempster-Shafer Theory and It's
           Generalizations"
        ABSTRACT: Dempster-Shafer theory is a mathematical theory of
        evidence which aims to transcend the bounds of probability
        theory in the representation of uncertainty, based on the
        concept of a "belief function." Belief functions assigns
        probability to events for which there is a evidence to support
        the belief, and where there is no rational basis for assigning
        a probability, represents uncertainty in set theoretic terms.
        A feature of this theory which has been frequently criticized
        is the Dempster combination rule for combining independent
        beliefs, which has generated numerous attempts to construct an
        alternative combination rule, which include Smet's transferable
        belief theory.
          I will discuss a probabilistic model of the Dempster-Shafer
        theory, going so far as frequentism in the process. The
        Dempster rule is revealed as the combination of Bayes rule with
        simple set theory.  We extend this theory to the consideration
        of evidence which may be false or corrupted.
          Note: this talk will be an informal, black-board style talk.
          Reading:
        http://www.sandia.gov/epistemic/Reports/SAND2002-0835.pdf
        http://iridia.ulb.ac.be/Projects/trans.html
                Coffee and cookies will be served at 12:00 p.m.

        APPLIED ANALYSIS AND PDE READING SEMINAR     PSA 546   3:00 p.m.
          For more information, contact Svetlana Roudenko.

WEDNESDAY, April 30, 2008

        NUMBER THEORY SEMINAR                        PSA 230   1:40 p.m.
        Dong Quan Nguyen, Department of Mathematics and Statistics
          "On the Duffin-Schaeffer Conjecture, Part II"
        ABSTRACT: We will prove the Duffin-Schaeffer theorem, which
        motivates the formulation of the Duffin-Schaeffer conjecture.

THURSDAY, May 1, 2008

        APPLIED MATHEMATICS/ENVIRONMENTAL FLUID DYNAMICS
        SPECIAL SEMINAR                            ISTB2 299   2:00 p.m.
        Vanda Grubisic, National Center for Atmospheric Research
                        Boulder, Colorado
          "Terrain-induced Rotor Experiment:
           New Insights into Lee Waves and Atmospheric Rotors"
        ABSTRACT: Atmospheric rotors are three-dimensional anisotropic
        Atmospheric vortices that form parallel to and downwind of a
        mountain crest under conditions conducive to generation of
        large-amplitude lee waves. Intermittency, high-levels of
        turbulence, and complex small-scale internal structure are
        defining characteristics of rotors, which pose a known hazard
        to aviation. The central objective of the Terrain-induced Rotor
        Experiment (T-REX, March-April 2006, Sierra Nevada, CA) was to
        provide a comprehensive set of in situ and remotely-sensed
        meteorological observations from the ground to the upper
        tropospheric-lower stratospheric altitudes for the
        documentation of spatiotemporal characteristics of a tightly
        coupled system, consisting of an atmospheric rotor, terrain-
        induced internal gravity waves, and a complex-terrain boundary
        layer. Along with a concise overview of the entire project,
        presented will be new insights into the structure of
        atmospheric rotors and their relation to atmospheric lee waves
        that have emerged from our T-REX observational analyses to date
        and the related real-data and idealized numerical modeling
        studies of lee waves and, more generally, flow over complex
        terrain.