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           COLLOQUIUM OF THE COMPUTATIONAL MATERIALS SCIENCE CENTER
                              College of Science
                       (CDS Department CSI 898-Sec 001)
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           Using Multivariate Analysis to Extract Chemical 
           Fluctuation Information from Energy Filtered 
                       TEM (EFTEM) Images

                             Xiang Li

          National Institute of Standards and Technology and
          Computational Materials Science Center, George Mason University
                         
In some Al_rare earth transition metal (Al_RE_TM) glasses, nucleation processes
are featured with nucleation rates orders of magnitude higher than predicted by
classical nucleation theory. Kinetics of nucleation in these metallic glasses 
is poorly understood, partly due to the difficulties in direct characterization
of chemical fluctuation at the nanometric scale. The objective of this work is 
to advance quantitative techniques using Energy Filtered Transmission Electron 
Microscopy (EFTEM) to the study of local chemical fluctuations associated with 
the nucleation phenomena in metallic glasses. Elemental maps and EFTEM image 
series were used as the multi-variate database. By applying histogram analysis 
and Principal Component Analysis (PCA) on this multivariate database, detailed 
compositional distribution information was able to be extracted from the 
database. The computational procedures for conducting a principal component 
analysis are described, which result in the establishment of a "chemical image"
showing possible fluctuations and clustering of chemistry within the 
microstructure. The implications of the work extend beyond the specific 
research testbed used in this work, and the existing problems and future 
directions are also discussed.

                        Monday , September 10, 2007
                                  4:30 pm
                     Room 301, Research I, Fairfax Campus

Refreshments will be served at 4:15 PM.
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Find the schedule at www.cmasc.gmu.edu/seminar/schedule.html
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