http://www.k-wave.org/forum/topic/issue-with-the-function-kspacefirstorder2d Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 01:32:18 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/issue-with-the-function-kspacefirstorder2d#post-5034 Wed, 08 Apr 2015 16:05:42 +0000 bencox 5034@http://www.k-wave.org/forum/ <p>Hi Greg, </p> <p>Can you post your code, or put in somewhere I can download it, so I can take a closer look?</p> <p>Thanks,<br /> Ben </p> http://www.k-wave.org/forum/topic/issue-with-the-function-kspacefirstorder2d#post-5021 Thu, 26 Mar 2015 22:00:53 +0000 GreG 5021@http://www.k-wave.org/forum/ <p>Hi Ben,</p> <p>I tried with very low absorption values (see here below) and it crashes also...</p> <p>medium.alpha_coeff = 1e-6; for air and for concrete<br /> medium.alpha_power = 1.1</p> <p>The problem seems to come from the concrete's density value.</p> <p>Typically i set the density value to 2000 (kg/m3) and the simulation failed, when i decreased the value by 10, the simulation worked.</p> <p>Do you have any explanation ?</p> <p>Thanks.</p> <p>Greg. </p> http://www.k-wave.org/forum/topic/issue-with-the-function-kspacefirstorder2d#post-5014 Sun, 22 Mar 2015 18:39:39 +0000 bencox 5014@http://www.k-wave.org/forum/ <p>Hi GreG, </p> <p>What are your absorption values? Does it still fail if you make the absorption values very low?</p> <p>Ben </p> http://www.k-wave.org/forum/topic/issue-with-the-function-kspacefirstorder2d#post-5013 Sun, 22 Mar 2015 18:30:25 +0000 GreG 5013@http://www.k-wave.org/forum/ <p>Hi Ben,</p> <p>Thank you for your help.</p> <p>No, the simulation does not want to start. The process stops just before starting the time loop...<br /> It seems to be a display issue... I see briefly (less than 1 sec ) the wall displayed in greyscale, afterwards the error is generated.</p> <p>GreG. </p> http://www.k-wave.org/forum/topic/issue-with-the-function-kspacefirstorder2d#post-5009 Tue, 17 Mar 2015 23:41:56 +0000 bencox 5009@http://www.k-wave.org/forum/ <p>Hi GreG, </p> <p>When you watch the simulation does it look ok? I wonder if the simulation is blowing up and generating NaNs, perhaps because the absorption is too high. The simulations can become unstable for large values of absorption.</p> <p>Ben </p> http://www.k-wave.org/forum/topic/issue-with-the-function-kspacefirstorder2d#post-5006 Sun, 15 Mar 2015 18:44:01 +0000 GreG 5006@http://www.k-wave.org/forum/ <p>Hi,</p> <p>I tried to perform a 2 dimensions simulation (non homogeneous medium) and I got the following error message when i define the alpha_coeff, alpha_power and the medium density, (typically i was trying to simulate a part of a wall at audible frequencies) : </p> <p>Error using im2frame<br /> double-precision indexed CData values must be legal colormap indices: 1.0 &lt;= value &lt;=<br /> length(colormap)</p> <p>Error in kspaceFirstOrder2D (line 899)<br /> movie_frames(frame_index) = im2frame(p_plot, COLOR_MAP); %#ok&lt;AGROW&gt;</p> <p>Error in Grid_w_obstacles (line 157)<br /> sensor_data = kspaceFirstOrder2D(kgrid,medium,source,sensor,input_args{:}); </p> <p>When i don't define alpha and (or) medium density the simulation works perfectly.</p> <p>Does anyone have an idea how to fix this issue ?</p> <p>Thanks a lot ,</p> <p>GreG. </p>