ckquote>
<div><p>argument of the exponential function is 
normalised between [0 1]. When <code class="docutils literal notranslate"><span class="pre">r</span> <span class="pre">==</span> <span class="pre">1</span></code>,
the minimuum value of the exponential 
argument is set to 0.</p>
</div></blockquote>
</dd>
<dt>triangular:  </dt><dd><ul class="simple">
<li><p>r = a positive scalar whose value is the threshold 
(corner point) of the triangular function.</p></li>
</ul>
</dd>
<dt>trapezoidal1:  </dt><dd><u