Experimental and theoretical investigations of focusing of ultrasonic waves by two-dimensional flat phononic crystals
Bibliographic record
Abstract
We compare experimental and theoretical results demonstrating focusing of sound fields emitted by subwavelength sources using two-dimensional flat phononic crystals. Our phononic crystals are made of stainless steel rods assembled in a triangular crystal lattice and immersed in a liquid. Focusing is achieved due to negative refraction of ultrasonic waves propagating through the crystal, which is realized at the frequencies corresponding to the 2nd band, where the group velocity and wave vector are antiparallel. High quality images are obtained experimentally with a methanol-filled phononic crystal surrounded by water, in which the source and detecting transducers are located. Excellent resolution approaching the diffraction limit is achieved for the frequency at which the equifrequency contours inside the crystal match those in water. Our experimental results are compared with theoretical predictions by the Finite Difference Time Domain (FDTD) method. Good agreement is observed for the width of the focal spot in the direction parallel to the crystal surface, while along the perpendicular direction, we find experimentally that the focal spot is narrower and closer to the crystal surface than in the theoretical predictions.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| 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 | 0.004 |
| Scholarly communication | 0.000 | 0.000 |
| 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 teacher head, 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".