Short-pulse method for acoustic backscatter amplitude calibration at MHz frequencies
Bibliographic record
Abstract
The short-pulse acoustic backscatter amplitude calibration technique of Dragonette, Numrich, and Frank [(1981), J. Acoust. Soc. Am. 69, 1186-1189] is evaluated for MHz frequency systems, as are used to measure environmental suspended sediment concentration. The technique involves measuring backscatter from a short transmit pulse reflected by a solid spherical target, and treating the first received reflection as equivalent to that from a perfectly rigid sphere. In this implementation, the target sphere is 16 mm diameter tungsten carbide. The target is mounted on a stiff support rod rather than being suspended on a filament, enabling precise positioning of the sphere relative to the transducer. That the support rod does not significantly influence the calibration is demonstrated by reconstructing the backscatter time series, including the sequence of pulses from surface (Rayleigh) waves, using elastic scattering theory. Calibration results are verified in a separate experiment in which the backscatter from dilute aqueous suspensions of 400-600 μm diameter polystyrene beads in water is measured within the 1-2 MHz frequency band. After correcting for the additional attenuation within the scatterers, the resulting values of the backscatter form factor are within 20% of the theoretical predictions.
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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 | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
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".