| { |
| "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 |
| } |
