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<H3><A NAME="SECTION002031100000000000000">
Mexican Hat</A>
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The Mexican hat defined by Murenzi [<A
HREF="node370.html#murenzi">30</A>] is:
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<!-- MATH: \begin{eqnarray}
g(x) = (1 - x^2) e^{-\frac{1}{2}x^2}
\end{eqnarray} -->
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ALT="$\displaystyle g(x) = (1 - x^2) e^{-\frac{1}{2}x^2}$"></TD>
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(14.8)</TD></TR>
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it is the second derivative of a Gaussian (see figure <A HREF="node313.html#mexicain">14.2</A>).
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<DIV ALIGN="CENTER"><A NAME="mexicain"> </A><A NAME="14312"> </A>
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<CAPTION><STRONG>Figure 14.2:</STRONG>
Mexican Hat</CAPTION>
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\centerline{
\hbox{\psfig{figure=fig_mexicain.ps,bbllx=1cm,bblly=13.5cm,bburx=10.5cm,bbury=27cm,height=5cm,width=10cm,clip=}
}}
\end{figure}"></TD></TR>
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<ADDRESS>
<I>Petra Nass</I>
<BR><I>1999-06-15</I>
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