[image: 1736961843959-327c9ace-0099-4e59-b102-4a34c31e609c-sim4life_fxfwepw8sg.gif] to extract the inner normal vector to the cortical surface mask the field (set NaN outside GM) using the Mask Filter available under "Field Data Tools" in the top ribbion. add the Grey Matter Surface in the post-pro interpolate the (masked) field to the grey matter surface using the "Interpolator" which is active when the masked field and surface is selected. get the normal component via the NormalFieldEvaluator under the "Field Data Tools"

@Sylvain Hi Sylvain! Thanks for sharing the method. I tried it in this very simple structure but get unexpected result for current density. Also available at my post here https://forum.zmt.swiss/post/2071. I use the following very simple structure to test whether I am using the LF Ohmic Quasi-Static Solver correctly. The voltage comes out as expected but the current (density) is incorrect. I have these three electrodes of the same radius (1mm) stacking together (touching each other) in an electrode-cylinder-electrode configuration. I want to apply to a 2V (+1V top, -1V bottom) to the two silver electrodes and achieve a 1 kA current through. So I chose the cylinder material (copper) and length such that the resistance is 2 mOhm. After running the simulation, where I place a line as voltage sensor (it runs from 2mm offset from the top electrode to 2mm offset from the bottom electrode, in the centre), it gives a value of -1.9786V as expected. When I combine the J(x,y,z,f0) from the overall field and a plane I created and use flux evaluator to measure total current density as described here, unexpected resutls occur. I tried two different planes and they gave different results:: A block with 0mm thickness and 1m x 1m in area in the middle of the cylinder parallel to the electrodes, result: 1 A/m^2, multiply by the area gives 1A A cylinder with 0mm thickness and 1mm in radius in the middle of the cylinder parallel to the elctrodes, resutls: 49.7369 A/m^2, multiply by the area gives 0.156mA (P.S. why the current density has a unit of [A/m^2 m^2]?) Model, Simulation and Analysis details are summaried in the screenshots attached. [image: 1736740622839-img_5162.jpg] [image: 1736740622913-img_5163.jpg] [image: 1736740622953-img_5164.jpg] [image: 1736740634276-screenshot-2025-01-12-at-21.26.50-resized.jpg] [image: 1736740634609-screenshot-2025-01-12-at-21.27.16-resized.jpg] [image: 1736740634957-screenshot-2025-01-12-at-21.27.32-resized.jpg] [image: 1736740635384-screenshot-2025-01-12-at-21.31.17-resized.jpg] [image: 1736740635771-screenshot-2025-01-12-at-21.34.49-resized.jpg] [image: 1736740636120-screenshot-2025-01-12-at-21.35.28-resized.jpg]

@bryn @gc00 @halder Thank you so much, You've been very helpful !

@ofli Can the conductivity map after head segmentation be exported?

Hi, you can get additional information by enabling the "Far Field" sensor and then choosing the "Radiation Report" evaluator (see for example the Phased Array Patch Antenna tutorial). It will not solve your problem, but might help you get a clearer picture. From what you describe, it's possible you have a very low mismatch efficiency (most of the energy is reflected). This could be addressed by improving the way you are modeling your source, or by just ignoring it if it is not important (i.e. if you are not actually simulating the real feed and are only interested in the antenna itself). You would do that by considering the Radiation Efficiency (ratio of Radiated Power to Accepted Power) instead.

Hello! Thank you for your quick answer :) I'll do that in the meantime

e.g. something like this def spherical_parametrization(theta: float, phi: float) -> Vec3 '''Parametrize head skin center and radius computed from head, e.g. using: p1, p2 = XCoreModeling.GetBoundingBox(skin) center = 0.5 * (p1 + p2) radius = 0.51 * (p2-p1).Length() ''' point_on_sphere = center + Vec3(radius * sin(theta) * cos(phi), radius * sin(theta) * sin(phi), radius * cos(theta)) r = XCoreModeling.GetEntityPointDistance(skin, point_on_sphere) return r.ClosestPosition This should work quite well, except for the concave regions, e.g. behind the ears.

Thanks, the simulation file is from sim4life V7.2, so I'm not able to see the convergence in the analysis window. Fortunately, I have found the "x_Output.log" in my Results file, but I can't understand it. Could you please explain the meaning of each row in the results file? Take an example like this: Sensor 'Capacitor_L 1 (Current L)' Exponential moving average factor 0.894427, Harmonic steady state detector: time step 3.08414e-10s, frequency 64MHz, approximate quarter period 3.70097e-09s, target convergence level -50 dB Iteration number and conventional convergence level in dB <raw> <ema> [<raw> <ema> ...]: 16800 13.9358 1.47124 8.4181 0.888723 18816 7.67597 2.12629 15.5107 2.43241 20832 14.0806 3.38834 13.5789 3.60917 22848 1.26816 3.16451 7.74689 4.046 24864 4.59394 3.31542 3.89595 4.03016 26880 -2.64392 2.68627 0.958616 3.70589 28896 0.107048 2.41398 -1.53674 3.15241 30912 -4.9591 1.63558 -3.76506 2.42211 32928 -2.79052 1.1683 -6.11092 1.52126 34944 -5.90745 0.421296 -8.34643 0.479498 36960 -4.81187 -0.131184 -10.7496 -0.705992 38976 -5.89793 -0.739996 -13.7845 -2.08673 40992 -6.1714 -1.3134 -17.1553 -3.67755 43008 -5.32482 -1.7369 -21.5846 -5.56806 45024 -6.82203 -2.27375 -32.324 -8.39276 47040 -2.12306 -2.25784 -15.5315 -9.14641 49056 -0.278664 -2.0489 -3.5348 -8.55398 51072 -6.34679 -2.50264 -2.30536 -7.8943 53088 -0.399402 -2.28059 -2.38639 -7.31281 55104 -9.37643 -3.02972 -4.00497 -6.96359 57120 -29.014 -5.77295 -18.2975 -8.16015 59136 -55.4153 -11.0138 -31.9566 -10.6724 61152 -57.6383 -15.9361 -37.9006 -13.547 63168 -58.9883 -20.4813 -26.9761 -14.9647 65184 -58.6026 -24.5058 -39.9291 -17.6003 67200 -57.9518 -28.0368 -37.4931 -19.7004 69216 -59.1574 -31.3223 -36.9919 -21.5259 71232 -59.0974 -34.2546 -28.7893 -22.2927 73248 -59.633 -36.9339 -25.1269 -22.592 75264 -59.2213 -39.2868 -31.2338 -23.5043 77280 -59.5994 -41.4313 -27.1446 -23.8886 79296 -59.9846 -43.39 -25.5704 -24.0662 81312 -61.3968 -45.291 -28.9199 -24.5786 83328 -61.7502 -47.0287 -26.6773 -24.8002 85344 -61.0201 -48.5058 -30.0321 -25.3525 87360 -61.1226 -49.8378 -25.216 -25.3381 89376 -63.0251 -51.23 -33.6491 -26.2155 91392 -66.6494 -52.8579 -33.5 -26.9845 93408 -67.4893 -54.4026 -29.6102 -27.2617 95424 -70.0935 -56.0591 -29.03 -27.4484 97440 -71.562 -57.6958 -27.7633 -27.4817 99456 -69.5748 -58.9499 -26.854 -27.4154 101472 -78.6 -61.0244 -28.1287 -27.4907 103488 -67.7923 -61.7389 -25.6139 -27.2926 105504 -68.4293 -62.4452 -23.2911 -26.8701 107520 -65.0311 -62.7182 -24.074 -26.5749 109536 -65.161 -62.9761 -31.2989 -27.0737 111552 -65.5676 -63.2497 -29.642 -27.3448 113568 -61.3018 -63.0441 -27.2672 -27.3366 115584 -60.839 -62.8113 -26.1289 -27.2091 117600 -60.3076 -62.5469 -27.3216 -27.221 119616 -61.3064 -62.416 -26.3063 -27.1244 121632 -62.103 -62.3829 -28.0492 -27.2221 123648 -61.1791 -62.2558 -34.3984 -27.9797 125664 -61.6997 -62.1971 -24.1963 -27.5803 127680 -60.7142 -62.0406 -27.5361 -27.5756 129696 -62.5137 -62.0905 -28.7848 -27.7033 131712 -62.9527 -62.1815 -28.8431 -27.8236 133728 -63.5879 -62.33 -27.4008 -27.779 135744 -63.518 -62.4554 -27.3935 -27.7383 137760 -66.5672 -62.8895 -37.3044 -28.7482 139776 -66.7306 -63.295 -28.7205 -28.7453 141792 -66.0728 -63.5883 -24.7314 -28.3215 143808 -67.7974 -64.0327 -24.6679 -27.9358 145824 -69.0101 -64.5581 -25.0781 -27.6341 147840 -67.3162 -64.8493 -16.4316 -26.4514 149856 -66.9178 -65.0677 -21.271 -25.9045 151872 -72.7687 -65.8807 -28.3618 -26.1639 153888 -69.2686 -66.2384 -21.0304 -25.622 155904 -68.7916 -66.5079 -17.7813 -24.7942 157920 -65.0066 -66.3494 -19.2192 -24.2056 159936 -68.1325 -66.5377 -26.2937 -24.4261 161952 -64.7744 -66.3515 -23.2103 -24.2977 163968 -68.9681 -66.6278 -21.4553 -23.9976 165984 -67.3859 -66.7078 -18.5064 -23.4179 168000 -66.1211 -66.6459 -23.847 -23.4632 170016 -67.4045 -66.726 -19.9166 -23.0888 172032 -65.1708 -66.5618 -25.465 -23.3397 174048 -68.6925 -66.7867 -22.8274 -23.2856 176064 -67.0903 -66.8188 -25.4394 -23.513 178080 -64.5303 -66.5772 -19.6368 -23.1038 180096 -64.284 -66.3351 -20.7205 -22.8522 182112 -64.9833 -66.1924 -22.9353 -22.8609 184128 -64.2102 -65.9831 -17.2516 -22.2687 186144 -61.8411 -65.5458 -18.5849 -21.8798 188160 -67.4312 -65.7449 -22.0218 -21.8948 190176 -63.0463 -65.46 -29.3056 -22.6772 192192 -73.1833 -66.2753 -18.072 -22.191 194208 -62.5461 -65.8816 -17.785 -21.7259 196224 -66.6467 -65.9624 -21.6314 -21.7159 198240 -63.3296 -65.6845 -23.0527 -21.857 200256 -66.4044 -65.7605 -26.6222 -22.3601 202272 -66.1052 -65.7969 -25.6971 -22.7124 204288 -63.9959 -65.6067 -19.0422 -22.3249 206304 -67.4349 -65.7997 -26.79 -22.7963 208320 -65.1095 -65.7269 -26.0593 -23.1408 210336 -68.519 -66.0216 -24.4157 -23.2754 212352 -65.3768 -65.9536 -18.3469 -22.7551 By the way, what's the meaning of "convergence", and which value or formula do we use to express this variable? Thank you very much for your prompt response!

Dear Arjama, Thanks a lot for your reply and for your very detailed example. The problem I was referring to is in the line where you add TIMAM to the mask. If I run: inputs = [TIMAM] field_masking_filter = analysis.core.FieldMaskingFilter(inputs=inputs) where TIMAM = modulation_envelope(e_field_1, e_field_2, dir_vector=None) I get the error: field_masking_filter = analysis.core.FieldMaskingFilter(inputs=[TImax]) File "C:\Program Files\Sim4Life_8.0.0.15165\Python\lib\site-packages\s4l_v1_api\analysiswrappers.py", line 231, in init self.Inputs[id].Connect(input) File "C:\Program Files\Sim4Life_8.0.0.15165\Python\lib\site-packages\s4l_v1_api\analysiswrappers.py", line 647, in Connect raise Exception("Can't connect ports") Exception: Can't connect ports So I think my problem is the creation of TIMAM. I Imagine it is not the TI envelope, but rather the TI Envelope inside some data structure that can be connected to the masking filter? Thanks again!

@halder Hi Arjama, thanks for your reply! I will send you an email!

It depends on what you mean by transmitting and receiving. If the port outputs of the antenna look like 50 ohms in both transmit and receive then the usual multiport simulation will work just fine. Then you just need to go into each port, say "port extract" then go to overall field, then extract that ports E field. This E field will be what is generated from exciting port n and "receiving" on all other antenna. Do this 8 times for all 8 ports and this should be what you want

Wow I can't believe I missed that. Thank you so much! The warning definitely threw me off

Note that the above is only true in the case of a harmonic signal, which is why Sim4Life does not provide the RMS by default. It is up to the user to calculate the RMS based on their knowledge of the signal. If you are interested in B1+/B1-, the rotational components of B1 are by definition constant in time and so their RMS magnitudes are equal to their absolute magnitudes.

When you used the Mask Filter, did you check the option 'Invalidate Masked Values'? This will set the Background to NaN, which should hide it. Otherwise, the Background value will be changed to a user-defined replacement value, which would still show up during visualization.