<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue-Light, Helvetica Neue Light, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:13px"><div id="yui_3_16_0_ym19_1_1468998012223_3079"><span id="yui_3_16_0_ym19_1_1468998012223_3153">Hi Ane,</span></div><div id="yui_3_16_0_ym19_1_1468998012223_3079"><span><br></span></div><div id="yui_3_16_0_ym19_1_1468998012223_3079" dir="ltr">Yes, an extra volume exists it the trapezoid. I had faced this problem a couple of months ago. Hopefully, Ricardo's suggestion should tackle the problem, please have a look at: <a href="http://article.gmane.org/gmane.comp.science.opengate.user/3383/match=problem+modeling+trapezoid" id="yui_3_16_0_ym19_1_1468998012223_3497">http://article.gmane.org/gmane.comp.science.opengate.user/3383/match=problem+modeling+trapezoid</a></div><div id="yui_3_16_0_ym19_1_1468998012223_3079" dir="ltr"><br></div><div id="yui_3_16_0_ym19_1_1468998012223_3079" dir="ltr">Good luck,</div><div></div><div id="yui_3_16_0_ym19_1_1468998012223_3081"> </div><div class="signature" id="yui_3_16_0_ym19_1_1468998012223_3048"><div id="yui_3_16_0_ym19_1_1468998012223_3082"><span style="font-size: small;" id="yui_3_16_0_ym19_1_1468998012223_3089">Hojjat</span><span style="font-size:small;font-weight:bold;" id="yui_3_16_0_ym19_1_1468998012223_3143"> </span></div><div id="yui_3_16_0_ym19_1_1468998012223_3102"><u style="color:rgb(34, 34, 34);font-family:arial, helvetica, sans-serif;font-size:small;background-color:rgb(255, 255, 255);"></u></div></div></div></body></html>