Direct measurement of shear modulus at low frequencies and small strains
Bibliographic record
Abstract
In many applications, one needs to measure elastic moduli of materials at low frequencies and small strains. With most techniques, such as ultrasonic pulse transmission or acoustic resonance, measurements are limited to a few discrete frequencies. These sound speed measurements are also indirect, since they involve density as well as elastic constants. We have developed a direct, quasi-static method to measure the shear modulus of solid 4 He. A 4 He crystal is grown in a narrow gap (0.2 to 0.5 mm) between two rigidly mounted lead zirconium titanate (PZT) piezoelectric transducers. A voltage applied to one transducer generates a shear displacement at its surface and a corresponding shear strain in the sample. The resulting shear stress at the surface of the second transducer generates a piezoelectric charge which is measured using a low noise current amplifier. The ratio between the measured stress and the applied strain gives the sample's shear modulus. Measurements can be made at any frequency between the mechanical resonances of the sample holder and cell (around 8 kHz in our arrangement) and a few Hz (a limit set by our current amplifier). At 2000 Hz, the minimum detectable stress is about 10 -5 Pa, corresponding to a strain of order 10 -12 .
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 0.001 |
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".