Blurb::
Aleatory uncertain variable - exponential
Description::
The exponential distribution is often used for modeling failure rates. 

The density function for the exponential distribution is given by: 
\f[f(x) = \frac{1}{\beta} \exp \left( \frac{-x}{\beta} \right)\f] 
where 
\f$\mu_{E} = \beta\f$ and \f$\sigma^2_{E} = \beta^2\f$. 


Note that 
this distribution is a special case of the more general gamma distribution.

Topics::	continuous_variables, aleatory_uncertain_variables
Examples::
Theory::

When used with some methods such as design of experiments and
multidimensional parameter studies, distribution bounds are inferred
to be [0, \f$\mu + 3 \sigma\f$].

For some methods, including vector and centered parameter studies, an
initial point is needed for the uncertain variables. When not given
explicitly, these variables are initialized to their means

Faq::
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