File size: 9,398 Bytes
f9c02f1 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 | {
"body_sha256": "9fc77ca07928214342f44ade280e37f710d8b3a2e8f93a1569ffcab14431877b",
"caveats": {
"LV60A_crop": "Talabi's 0.377 porosity is not reachable on the released LV60A image: over all 3,442,951 possible 300^3 crops the porosity spans [0.3555, 0.3713]. The offset he used is not recorded in the thesis, and a central cube is what his other six samples' porosities support. That is the whole of LV60A's porosity gap, and it is not the walk.",
"band": "This is a RELAXATION pack. Its 200 us save grid is 22x coarser than the #143 rule asks of a Connectom, deliberately: the acquisition it reproduces carries no gradient at all. What keeps that honest is the pack's own band -- 21.33 Hz over the walk at K = 128, small and stated -- and a consumer replaying a gradient beyond it is refused by waveform_band rather than served a wrong number.",
"inversion": "The log-mean is the weakest link in this comparison, and every number here is on a 1 ms sampling of the decay. Measured on F42A, which still holds 3.3 % of its signal at 3 s: 674.4 ms at 1 ms sampling, 668.0 at 10 ms, 309.7 at 20 ms -- a truncated decay lets the regularised solve split amplitude between a short and a very long component. LV60A, down to 1.0 %, is 487.7 / 487.6 / 487.4 at the same three. Over lam in [0.003, 1] and five T2 grids the log-mean spans 3.1 % on LV60A and 4.2 % on Berea."
},
"crossref": {
"agency": "crossref",
"container": "Journal of Petroleum Science and Engineering",
"doi": "10.1016/j.petrol.2009.05.013",
"resolved": "2026-09-26T23:36:22Z",
"title": "Pore-scale simulation of NMR response",
"type": "journal-article"
},
"description": "Micro-CT sand packs and a sandstone walked on their own voxels through the label-volume producer: the surface-relaxation reference outside the brain, replayed as a CPMG decay. Relaxation is not in the walk -- one pack answers every relaxivity.",
"doi": "10.1016/j.petrol.2009.05.013",
"geometry_derivation": "the geometry is the released one when no free parameter marked 'ours' changes it; these do: crop",
"geometry_parameters_ours": [
"crop"
],
"inputs_sha256": "b3f46f15ee36e386e2c73d3262f79b8b72f1b4e1afcca701849b3cf6acb986d6",
"licence_note": "CC-BY-4.0 images; the thesis is CC-BY-ND and its numbers are cited, never redistributed; the packs are CC-BY-4.0",
"parameters": [
{
"changes_geometry": false,
"how": "fitted by him to his own LV60Y / F42Y CPMG; an effective value tied to his ~10 um voxel, because a segmentation's surface is the Manhattan area at that resolution, which is what both walks relax against",
"name": "rho",
"unit": "m/s",
"value": 4.1e-05,
"where": "thesis \u00a77.6.2",
"whose": "theirs"
},
{
"changes_geometry": false,
"how": "the brine's self-diffusion at 308 K, stated",
"name": "D0",
"unit": "m^2/s",
"value": 2.07e-09,
"where": "thesis eq. 7.1",
"whose": "theirs"
},
{
"changes_geometry": false,
"how": "the brine's bulk T2, stated; applied at replay, not in the walk",
"name": "T2B",
"unit": "s",
"value": 3.1,
"where": "thesis eq. 7.2",
"whose": "theirs"
},
{
"changes_geometry": true,
"how": "a central cube: over all 3,442,951 possible 300^3 crops of LV60A the porosity spans [0.3555, 0.3713] and his 0.377 is not reachable, so the offset is ours",
"name": "crop",
"unit": "voxels",
"value": "central 300^3",
"where": "thesis App. A-1 states the size, not the offset",
"whose": "ours"
},
{
"changes_geometry": false,
"how": "his is an unconstrained normal-equation solve with a fourth-derivative penalty on 100 points from 0.1 ms; ours is non-negative with a second-difference penalty on 60 points from 1 ms, so the log-mean is comparable to his Table 7-2 rather than computed the same way",
"name": "T2 inversion",
"unit": "-",
"value": "non-negative least squares with a second-difference penalty, lam = 0.1 (t2_distribution)",
"where": "thesis App. A-3 (after Chen et al. 1999)",
"whose": "ours"
},
{
"changes_geometry": false,
"how": "he kills a walker at an attempted move into a grain voxel with probability 2 rho s / (3 D); this walk weights it per specular reflection. The two agree in the continuum limit",
"name": "surface rule",
"unit": "-",
"value": "exp(-2 (rho/D) d_perp) per reflection",
"where": "thesis \u00a73.5 for his",
"whose": "ours"
}
],
"previous_sha256": "6de4bc05c509a8f61329eebb65d135e6c38c0c5a76c4a285cdc866b6cb18657c",
"published_kind": "number",
"quantities": [
{
"direct": {
"grid": {
"from_s": 0.001,
"kind": "log",
"n": 60,
"sample_ms": 1.0,
"solver": "non-negative least squares with a second-difference penalty, lam = 0.1 (t2_distribution)",
"to_s": 10.0
},
"n_walkers": 200000,
"se": 0.0019517411744048516,
"se_derivation": "the delta method over walkers on the log-mean (talabi_micro_ct_rocks.log_mean_gradient), MEASURED here at record time on this family's own lv60a.rpk -- 0.004115 over 45,000 walkers at the same rho, channel and grid -- and scaled to the direct walk's 200,000 by 1/sqrt(N) (x 0.474342). The direct walk's own per-walker decays were not retained; the relative per-echo spread is a property of the substrate and the estimator, not of the pack.",
"se_kind": "delta_method",
"solver": "non-negative least squares with a second-difference penalty, lam = 0.1 (t2_distribution)",
"source": "examples/validation/talabi_micro_ct_rocks.py (run_rock), asserted by tests/validation/test_talabi_rocks.py",
"unit": "ms",
"value": 487.6
},
"documents": {
"10.25560/4261": {
"agency": "datacite",
"container": "Imperial College London",
"doi": "10.25560/4261",
"resolved": "2026-09-26T23:36:23Z",
"title": "Pore Scale Simulation of NMR Response in Porous Media",
"type": "Text"
}
},
"name": "T2_log_mean",
"published": {
"data_sha256": null,
"data_url": null,
"document": "10.25560/4261",
"locator": "Table 7-2, p. 63, the 'Micro-CT' column of Mean T2 (ms)",
"printed_in": "Talabi O (2008), Pore Scale Simulation of NMR Response in Porous Media, Imperial College London PhD thesis",
"uncertainty": 0.0,
"uncertainty_is": "none stated: Table 7-2 prints one figure per sample with no error bar and the thesis quotes none, so the gate's budget rests on our own standard error alone",
"unit": "ms",
"value": 512.0,
"verbatim": "LV60A 496 512 565 32.2 35.3 27.2 4.8 4.9 3.8"
},
"substrate": "LV60A"
},
{
"direct": {
"grid": {
"from_s": 0.001,
"kind": "log",
"n": 60,
"sample_ms": 1.0,
"solver": "non-negative least squares with a second-difference penalty, lam = 0.1 (t2_distribution)",
"to_s": 10.0
},
"n_walkers": 200000,
"se": 0.0020167727296136247,
"se_derivation": "the delta method over walkers on the log-mean (talabi_micro_ct_rocks.log_mean_gradient), MEASURED here at record time on this family's own f42a.rpk -- 0.004252 over 45,000 walkers at the same rho, channel and grid -- and scaled to the direct walk's 200,000 by 1/sqrt(N) (x 0.474342). The direct walk's own per-walker decays were not retained; the relative per-echo spread is a property of the substrate and the estimator, not of the pack.",
"se_kind": "delta_method",
"solver": "non-negative least squares with a second-difference penalty, lam = 0.1 (t2_distribution)",
"source": "examples/validation/talabi_micro_ct_rocks.py (run_rock), asserted by tests/validation/test_talabi_rocks.py",
"unit": "ms",
"value": 679.0
},
"documents": {
"10.25560/4261": {
"agency": "datacite",
"container": "Imperial College London",
"doi": "10.25560/4261",
"resolved": "2026-09-26T23:36:23Z",
"title": "Pore Scale Simulation of NMR Response in Porous Media",
"type": "Text"
}
},
"name": "T2_log_mean",
"published": {
"data_sha256": null,
"data_url": null,
"document": "10.25560/4261",
"locator": "Table 7-2, p. 63, the 'Micro-CT' column of Mean T2 (ms)",
"printed_in": "Talabi O (2008), Pore Scale Simulation of NMR Response in Porous Media, Imperial College London PhD thesis",
"uncertainty": 0.0,
"uncertainty_is": "none stated: Table 7-2 prints one figure per sample with no error bar and the thesis quotes none, so the gate's budget rests on our own standard error alone",
"unit": "ms",
"value": 677.0,
"verbatim": "F42A 668 677 756 42.0 59.0 61.5 5.2 5.8 3.6"
},
"substrate": "F42A"
}
],
"same_released_geometry": false,
"sample": "the same released micro-CT images: his 'Micro-CT' column is a random walk on these very volumes, on the central 300^3 section (App. A-1), and his 'Experiment' column is a CPMG measured on the sand the images are of",
"sample_relation": "the same object",
"source_note": "Dong & Blunt 2009 (Phys Rev E 80:036307) images, Imperial College 2007 collection on Figshare; Talabi 2008 (Imperial College PhD thesis) for the reference random walk and the measured CPMG, published as Talabi et al., J. Pet. Sci. Eng. 2009.",
"stage": "reference",
"title": "Pore-scale simulation of NMR response",
"title_matches": true
} |