<html><head></head><body><div style="color:#000; background-color:#fff; font-family:lucida console, sans-serif;font-size:13px"><div id="yui_3_16_0_ym19_1_1511818070417_13417">
</div>I have what that
appears to be computational error in the HarmonicToTime plug-in.
This happened while using onelab to demonstrate EM fields in
waveguides.
<div style="margin-bottom: 0in; line-height: 100%" id="yui_3_16_0_ym19_1_1511818070417_13537">Set up:</div>
<ul id="yui_3_16_0_ym19_1_1511818070417_13538"><li id="yui_3_16_0_ym19_1_1511818070417_13539">
<div style="margin-bottom: 0in; line-height: 100%" id="yui_3_16_0_ym19_1_1511818070417_13540">In gmsh, open
models/waveguides/main.pro</div>
</li><li id="yui_3_16_0_ym19_1_1511818070417_13541">
<div style="margin-bottom: 0in; line-height: 100%" id="yui_3_16_0_ym19_1_1511818070417_13542">In the dialog
for Input > Problem, use the pull-down menu and select
Rectangular waveguide [3D].
</div>
</li><li id="yui_3_16_0_ym19_1_1511818070417_13543">
<div style="margin-bottom: 0in; line-height: 100%" id="yui_3_16_0_ym19_1_1511818070417_13544">Run</div>
</li><li id="yui_3_16_0_ym19_1_1511818070417_13545">
<div style="margin-bottom: 0in; line-height: 100%" id="yui_3_16_0_ym19_1_1511818070417_13546">Under
Post-processing, select [0] e. This is the electric field.</div>
</li><li id="yui_3_16_0_ym19_1_1511818070417_13547">
<div style="margin-bottom: 0in; line-height: 100%" id="yui_3_16_0_ym19_1_1511818070417_13548">Adjust the
view to see the long (Y) axis. On any of the long sides, you should
see 3 places with a maximum E field alternating with 3 minimums of
the E field.
</div>
</li><li id="yui_3_16_0_ym19_1_1511818070417_13549">
<div style="margin-bottom: 0in; line-height: 100%" id="yui_3_16_0_ym19_1_1511818070417_13550">Use the Step
Forward from the animation icons in the bottom left border. The
display alternates between “e - real part” and “e –
imaginary part”. The locations of field maximums change;
amplitudes stay the same. The scale is 0 to 502.</div>
</li></ul>
<div style="margin-bottom: 0in; line-height: 100%" id="yui_3_16_0_ym19_1_1511818070417_13551"><br id="yui_3_16_0_ym19_1_1511818070417_13552">
</div>
<div style="margin-bottom: 0in; line-height: 100%" id="yui_3_16_0_ym19_1_1511818070417_13553">Now run the
HarmonicToTime plug-in with the default settings. The step function
causes the peaks to move in smaller increments, as expected. However
the amplitude changes during the cycle. It is maximum at step 9 and
minimum at step 0. And the scale has changed to be 0 to 542.</div>
<div style="margin-bottom: 0in; line-height: 100%" id="yui_3_16_0_ym19_1_1511818070417_13554"><br id="yui_3_16_0_ym19_1_1511818070417_13555">
</div>
<div style="margin-bottom: 0in; line-height: 100%" id="yui_3_16_0_ym19_1_1511818070417_13556">Further experiments
were done with various numbers of steps. With NumSteps =4, everything
appears as expected. Full scale is 502. Step 0 and Step 1 look
identical to the real and imaginary parts of e, as is expected.
Steps 2 and 3 continue the cycle with the same amplitude.</div>
<div style="margin-bottom: 0in; line-height: 100%" id="yui_3_16_0_ym19_1_1511818070417_13557"><br id="yui_3_16_0_ym19_1_1511818070417_13558">
</div>
<div style="margin-bottom: 0in; line-height: 100%" id="yui_3_16_0_ym19_1_1511818070417_13559">Minor problem: the
default time step is -1, aka going back in time.</div>
<div style="margin-bottom: 0in; line-height: 100%" id="yui_3_16_0_ym19_1_1511818070417_13560"><br id="yui_3_16_0_ym19_1_1511818070417_13561">
</div>
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</div>
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