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Author
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Kathleen
Cao
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Chemistry
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Before
embarking on this project, Kathleen Cao wasnt certain
about what to pursue in graduate school. Now thats clearer,
after immersing herself in chemistry research with Professor
Shaka. Kathleen advises others who have an interest in research
not to hesitate in getting started, explaining that professors
and other students provide all the necessary guidance and training
on projects. In May 2002, she presented her findings at the
UCI Undergraduate Research Symposium. She plans to attend graduate
school in physical chemistry and hopes to continue research
in NMR spectroscopy, a topic that now fascinates her. When Kathleen
is not in the lab, she enjoys reading and tutoring high school
students.
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Abstract
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Two parametric fitting
methods for spectrum analysis, the filter diagonalization method
(FDM) and decimated signal diagonalization (DSD) method, are
compared for processing one-dimensional nuclear magnetic resonance
(NMR) spectroscopy time signals. These methods are alternatives
to the discrete Fourier transform (DFT) for processing time
domain data for NMR. FDM and DSD use pure linear algebra to
diagonalize small matrices generated from an NMR time signal
in order to extract the inherent spectral parameters, the characteristic
frequencies and amplitudes. These techniques have advantages
over DFT because they can use smaller data sets and the resolution
is not restricted by the Fourier transform time-frequency uncertainty
principle. The main difference between FDM and DSD is the method
of generating small matrices from a single long signal; FDM
filters basis functions whereas DSD filters the time signal.
This comparative study shows that the development of DSD is
not yet at the level of FDM, particularly for one-dimensional
NMR data processing.
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Faculty
Mentor
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There has never been
any acceptable alternative to Fourier transform for frequency
analysis of the time-dependent signal obtained in nuclear magnetic
resonance. Kathleen Caos work on alternative linear algebraic
methods of making the connection between the time and frequency
domains shows why this is so. Two very closely related approaches,
both of which may seem to be equivalent on paper, give markedly
different results. The decimated signal diagonalization method
(DSD) is obtained by first decimating or reducing
the signal size and then extracting frequencies. The filter
diagonalization method (FDM) is obtained by constructing a filtered
local frequency-domain signal matrix, and then diagonalizing.
Rather surprisingly, the latter is far more effective, and now,
based on Kathleens careful investigation, we know exactly
why. Making a discovery can be one of the most exciting events
in ones life, therefore, it is very important for undergraduates
to conduct research and get a taste of the unknown.
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If
you wish to view the paper in its entirety, please select
the link given to the PDF file. [Kathleen
Cao.pdf]
If you wish to download the Adobe Acrobat Reader,
please go to Adobes website (www.adobe.com).
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© 2002
by the Regents of the University of California. All rights reserved.
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