Lefschetz Center for Dynamical Systems Seminar
Rapidly Oscillating Coefficients | |
CHANGE OF TIME FOR TODAY |
Brown University -
Joint Materials/Solid Mechanics Seminar Series
Arizona State University | |
Abstract: Growth of several Ge atomic layers onto Si(100) forms nonoscale coherent (defect-free) 3-D islands. These islands `self-assemble' into relatively uniformly sized but spatially random ensembles. Eventual technological application of these quantum dots requires improved control over size and composition uniformity as well as spatial periodicity. The self-assembly process is driven by the competition between elastic and surface energies. During growth, the island free energy is minimized by shape and composition evolution subject to kinetic constraints. In this talk I will discuss how controlling the system the system kinetics through variations in substrate temperature and deposition rate influence island morphology and composition. Since islands may grow by strain-enhanced interdiffusion of Si from the substrate or by Ge surface diffusion, island composition, and thus size, may be kinetically controlled. Strain-relief mechanisms such as island dislocation and formation of trenches at the island perimeters are also dependent on growth kinetics.
Scientific Computing Seminar
Old Dominion University, Norfolk, VA & Visiting Member Faculty, National Institute of Aerospace, Hampton, VA | |
Abstract: In this presentation I shall first provide a brief review on what we know about the lattice Boltzmann equation, i.e., the mathematical theory behind the lattice Boltzmann equation (LBE). It can be demonstrated that the lattice Boltzmann equation is a "coherent" finite-difference equation derived from linearized Boltzmann equation. (The phrase "coherent" is used to describe the coupled discretization of phase space and time.) The lattice Boltzmann equation can also be shown as a system of moments on discrete lattice space with discrete time. In the diffusive limit, one can show that the LBE system simulate the incompressible Navier-Stokes equations. The second part of my presentation I shall attempt to show the audience about what we can do with the LBE method. I shall demonstrate a few examples: (1) direct numerical simulations (DNS) of isotropic turbulence and large-eddy simulations by the LBE method; (2) suspensions in fluids; and (3) flow through porous media and free-surface flows. Through these examples I shall discuss pros and cons of the LBE method. More importantly, we hope to show that the lattice Boltzmann equation, as a mesoscopic method, could be an effective means to smoothly extend continuum/macroscopic methods (e.g., Navier-Stokes equations) into non-continuum regions which have to be dealt with by particle methods (e.g., DSMC or molecular dynamics), and it can be applicable to bio- and nano-fluid systems.
PDE Seminar
Abstract: It is well-known that the first order term in the Chapman-Enskog expansion to a rescaled Boltzmann equation leads to the incompressible Navier-Stokes- Fourier system in fluid dynamics. We establish global validity of such an expansion up to any order. In particular, we obtain error estimates for the Navier- Stokes-Fourier approximation and beyond.
JOINT BROWN UNIVERSITY -
Special Applied Mathematics and BioMedicine Colloquium
Coffee to be served from 4:00 to 4:30 p.m. at 182 George Street, Room 110 Professor Wen-Hsiung Li will be awarded The Horace Mann Medal from the Brown University Graduate School on Saturday, October 2nd, 2004
Check the Applied Mathematics Seminar Page -- |
Announcement: Horace Mann Award to W.-H. Li on October 2
Each year the Brown Graduate School awards The Horace Mann Medal to a distinguished former graduate student. This year the recipient is Wen-Hsiung Li, who received the PhD in Applied Mathematics in 1972. His PhD thesis concerned stochastic modelling in population genetics theory. Since then he has become a leader in the field of molecular evolution, and is especially known for his discoveries about molecular clocks. Recently, his interests have turned toward evolutionary genomics and bioinformatics. Professor Li is George Beadle Professor at the University of Chicago. He is a member of the National Academy of Sciences, and in 2003 received the prestigious Balzan Prize in Genetics and Evolution.
Professor Li will give two lectures, as follows:
Special Applied Math-BioMed Colloquium, Friday,
October 1, at 4:30 PM in Barus & Holley 190
Title: Some Topics in Evolutionary and Computational Genomics
Coffee and Cookies at 4 PM in Room 110, 182 George Street, (Applied Mathematics)
Horace Mann Award Lecture (intended for a broader audience). Saturday, October 2 at 2:45 PM in the List Art Center Auditorium
Title: From a Mathematician to a Bona Fide Biologist
A wine and cheese reception will follow this lecture.
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