Thermal ignition revisited with two-dimensional molecular dynamics: role\n of fluctuations in activated collisions
Bibliographic record
Abstract
The problem of thermal ignition in a homogeneous gas is revisited from a\nmolecular dynamics perspective. A two-dimensional model is adopted, which\nassumes reactive disks of type A and B in a fixed area that react to form type\nC products if an activation threshold for impact is surpassed. Such a reaction\nliberates kinetic energy to the product particles, representative of the heat\nrelease. The results for the ignition delay are compared with those obtained\nfrom the continuum description assuming local thermodynamic equilibrium, in\norder to assess the role played by molecular fluctuations. Results show two\nregimes of non-equilibrium ignition whereby ignition occurs at different times\nas compared to that from the continuum description. The first regime is at low\nactivation energies, where the ignition time is found to be higher than that\nexpected from theory for all values of heat release, in agreement with\npredictions from Prigogine and Xhrouet who attribute this departure to\nnon-equilibrium effects. Results suggest the ignition is spatially homogeneous\nin this regime. The second regime occurs at high activation energies and\nsufficiently large heat release values. In this regime, ignition times are\nfound to be dependent on domain size, with larger domains yielding shorter\nignition delays than expected. Results for larger systems agree with the\nexpectations by Prigogine and Mahieu, who predict a non-equilibrium reaction\nrate larger than expected for a homogeneous system in equilibrium. Results\nyield a large variance for ignition times under these conditions, suggesting a\ndeparture from homogeneous combustion. The results obtained are in qualitative\nagreement with experimental observations of auto-ignition at relatively low\ntemperatures, where hot-spot ignition and associated ignition delays lower than\npredicted are generally observed.\n
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".