Focusing of acoustic waves by flat lenses made from negatively refracting two-dimensional phononic crystals
Bibliographic record
Abstract
"We investigate the phenomenon of imaging of elastic waves with flat lenses constituted of negatively refracting materials. We derive an analytical solution for the acoustic field produced by a point source near a flat lens composed of a homogeneous acoustic metamaterial (i.e. negative density and negative moduli) using the Green's function formalism of the Interface Response Theory. We then consider phononic crystals as a way of realizing negative refraction with materials possessing positive densities and moduli. The finite difference time domain (FDTD) simulation method is employed to investigate the properties of negative refraction and focusing of ultrasonic waves in a flat lens composed of a two-dimensional phononic crystal consisting of a triangular array of steel rods immersed in methanol. The flat lens is embedded in water. Focusing of the ultrasonic field emitted by a point source is analyzed with particular attention paid to the lateral resolution of the lens, i.e., the resolution along the direction parallel to the lens' surface. The FDTD image is compared to experimental measurements of the pressure amplitude field created by a similar source and lens. Agreements and differences between the calculated and measured images as well as resolutions are reported and discussed. The flow of energy in the phononic crystal lens is calculated and matched to a simple ray tracing analysis of negative refraction in a homogeneous negatively refracting medium."
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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 | 0.002 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| 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".