Anomalous transport of ultrasound in a strongly scattering inhomogeneous medium
Bibliographic record
Abstract
Investigating the propagation of multiply-scattered waves in disordered materials allows the characterization of heterogeneous media and may reveal anomalous wave properties. We study wave transport in a deceptively simple system consisting of closed packed aluminum beads surrounded by low viscosity silicone oil, in which ultrasonic waves undergo many scattering events without incurring significant dissipative losses. Using ultrasonic pulsed transmission experiments, the small ballistic pulse at short observation times was separated from the much larger multiple scattering coda that extends over a wide range of arrival times, enabling the scattering strength to be assessed as a function of frequency and giving values of kls (wave vector times scattering mean free path) between 4 and 10. Based on kls, the propagation of the multiply scattered waves is expected to be well described by the diffusion approximation. However, this is not the case, and the observed behaviour suggests the presence of two coupled modes of propagation: a fast component traveling through the liquid and a slower component traveling through the bead network. The results are interpreted by developing a model for the coupled propagation of a diffusive component and a “renormalized” component that is described using the self-consistent theory of localization.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".